U.S. patent application number 12/041435 was filed with the patent office on 2009-02-12 for process for decellularizing soft-tissue engineered medical implants, and decellularized soft-tissue medical implants produced.
This patent application is currently assigned to LifeNet Health. Invention is credited to Perry Lange, Alyce Linthurst Jones, Eric Moore, Barry Nolf, Lloyd Wolfinbarger, JR..
Application Number | 20090041729 12/041435 |
Document ID | / |
Family ID | 32095724 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090041729 |
Kind Code |
A1 |
Wolfinbarger, JR.; Lloyd ;
et al. |
February 12, 2009 |
Process for Decellularizing Soft-Tissue Engineered Medical
Implants, and Decellularized Soft-Tissue Medical Implants
Produced
Abstract
The invention provides methodologies and apparatus for producing
acellular soft-tissue implants, both in small quantities and in
commercializable quantities. Such soft-tissue implants include
vascular graft substitutes. An acellular graft is produced by
subjecting the tissue sample to an induced pressure mediated flow
of an extracting solution, followed by inducing a pressure mediated
flow of a treating solution, then washing the treated tissue to
produce the acellular graft. The acellular grafts produced are
uniform and non-immunogenic. The inventive method allows for the
production of multiple decellularized soft tissue implants, where
processing time is significantly less than prior art processes and
the number of implants produced per day is increased over prior art
processes. In clinical use, the decellularized grafts produced
exhibit significantly improved in long-term durability and
function.
Inventors: |
Wolfinbarger, JR.; Lloyd;
(Norforlk, VA) ; Lange; Perry; (Virginia Beach,
VA) ; Linthurst Jones; Alyce; (Virginia Beach,
VA) ; Moore; Eric; (Virginia Beach, VA) ;
Nolf; Barry; (Courtland, VA) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
LifeNet Health
Virginia Beach
VA
|
Family ID: |
32095724 |
Appl. No.: |
12/041435 |
Filed: |
March 3, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10624534 |
Jul 23, 2003 |
7338757 |
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12041435 |
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09528371 |
Mar 17, 2000 |
6734018 |
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10624534 |
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09327240 |
Jun 7, 1999 |
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09528371 |
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Current U.S.
Class: |
424/93.7 |
Current CPC
Class: |
A61K 35/36 20130101;
A61P 43/00 20180101; A61K 35/12 20130101; A61K 35/32 20130101; A61L
27/3625 20130101; A61L 27/3604 20130101; A61K 35/44 20130101; A61L
27/3633 20130101; A61L 27/3687 20130101; A61L 2430/40 20130101 |
Class at
Publication: |
424/93.7 |
International
Class: |
A61K 35/12 20060101
A61K035/12; A61P 43/00 20060101 A61P043/00 |
Claims
1. (canceled)
2: A process for preparing commercializable quantities of acellular
soft tissue grafts for implantation into mammalian systems,
comprising: obtaining tissue samples from an acceptable donor;
extracting said tissue samples with an extracting solution
comprising one or more nonionic detergents and one or more
endonucleases, to produce extracted tissue; treating said extracted
tissue with a treating solution comprising one or more anionic
detergents, to produce a treated tissue; washing said treated
tissue with a decontaminating solution comprising one or more
decontaminating agents; to produce said acellular soft tissue
graft; and storing said acellular soft tissue graft in a storage
solution comprising one or more decontaminating agents.
3-6. (canceled)
7: The process of claim 2, said one or more decontaminating agents
comprise one or more antimicrobial agents.
8: The process of claim 2, said extracting solution having an
alkaline pH.
9: The process of claim 2, said extracting solution further
comprises one or more organic or inorganic buffers, wherein an
alkaline pH is maintained, and an osmolality of the extracting
solution which is hypotonic to the cells in said soft tissue is
maintained.
10: The process of claim 2, wherein said nonionic detergent
comprise one or more detergents selected from the group consisting
of: polyxyethylene alcohol, polyoxyethylene isoalcohol,
polyoxyethylene p-t-octylphenol, polyoxyethylene nonylphenol,
polyoxyethylene esters of fatty acids, and polyoxyethylene sorbitol
esters.
11: The process of claim 2, said treating solution comprises one or
more buffers selected from the group consisting of: an organic
buffer and an inorganic buffer, wherein an alkaline pH is
maintained, and an osmolality of the treating solution which is
hypotonic to the cells in said soft tissue is maintained.
12: The process of claim 2, said one or more anionic detergents are
selected from the group consisting of: sodium dodecysulphate,
sodium dodecylsulphonate, sodium dodecyl-N-sarcosinate, and sodium
suramin.
13: The process of claim 2, said decontaminating solution comprises
ultrapure, endotoxin-free, water solutions of antimicrobial agents,
wherein said antimicrobial agents are non-reactive towards said one
or more anionic detergents.
14: The process of claim 2, said storage solution comprises
ultrapure, endotoxin-free, water.
15: The process of claim 14, wherein said storage solution further
comprises one or more antimicrobial agents.
16: The process of claim 15, wherein said one or more antimicrobial
agents comprise one or more members selected from the group
consisting of: chlorine dioxide, ethanol, isopropanol, methanol,
glycerol, and methylparaben.
17: The process of claim 16 wherein said chlorine dioxide or said
methylparaben are present in said storage solution at a
concentration in the range of from 0.001% to 0.1% (v:v).
18: The process of claim 16, wherein said ethanol, isopropanol,
methanol, or glycerol are present in said storage solution at a
concentration in the range of from 60% to 90% (v:v).
19: The process of claim 12, wherein said one or more anionic
detergents are present in said treating solution at a concentration
in the range of from 0.001% to 10% (w:v).
20: The process of claim 19, wherein said one or more anionic
detergents are present in said treating solution at a concentration
in the range of from about
21: The process of claim 2, said one or more endonucleases comprise
one or more broad spectrum endonucleases capable of degrading both
deoxyribonucleic acids and ribonucleic acids.
22: The process of claim 21, wherein said one or more
broad-spectrum endonucleases comprise one or more recombinant
endonucleases.
23: The process of claim 22, wherein said one or more recombinant
endonucleases comprise Benzonase.RTM..
24: The process of claim 21, said one or more endonucleases are
present in said extracting solution at a concentration sufficient
to degrade nucleic acids present in said tissue sample.
25: The process of claim 24, wherein said one or more endonucleases
are present in said extracting solution at a concentration of from
about 30 IU/ml tissue to about 70 IU ml tissue.
26-120. (canceled)
Description
[0001] This application is a continuation-in-part application of
U.S. patent application Ser. No. 09/327,240, filed Jun. 7, 1999,
hereby incorporated herein in its entirety.
FIELD OF THE INVENTION
[0002] The invention is directed toward methodologies and apparatus
for use in the preparation of acellular, i.e. essentially lacking
in living cells andi or non-living cells, soft-tissue implants, in
small quantities and commercializable quantities. Such soft-tissue
implants include vascular graft substitutes. These implants can be
derived from tissue engineered soft tissue devices, tissue products
derived from animal or human donors that contain or are devoid of
cells, and that contain or are devoid of valve structures useful in
directing the flow of fluids through tubular vascular devices,
and/or combinations of natural tissue products and tissue
engineered soft-tissue products. The invention includes
methodologies and apparatus for producing uniform, gently
processed, decellularized multiple soft tissue implants, where
processing time is significantly reduced and the number of implants
produced per day is increased. The decellularized grafts produced
are significantly improved in long-term durability and function
when used in clinical applications.
BACKGROUND OF THE INVENTION
[0003] Numerous types of vascular graft substitutes have been
produced in the last four decades. These vascular graft substitutes
have included large and small diameter vascular, blood carrying
tubular structures, grafts containing valvular structures (vein
substitutes, and heart valve substitutes) and lacking valvular
structures (artery substitutes). The materials out of which these
vascular grafts have been constructed have included man-made
polymers, notably Dacron and Teflon in both knitted and woven
configurations, and non-man-made polymers, notably tissue
engineered blood vessels such as described in U.S. Pat. Nos.
4,539,716; 4,546,500; 4,835,102; and blood vessels derived from
animal or human donors such as described in U.S. Pat. Nos.
4,776,853; 5,558,875; 5,855,617; 5,843,181; and 5,843,180.
[0004] The prior art processing methods are prohibitively time
consuming, easily requiring numerous days, for example anywhere
from eight to twenty-one days total processing time. Such long
processing times result in proteolytic degradation of the matrix
structures of the processed tissues. Over the past few decades
numerous efforts have been made to manage the large surgical use of
vascular prostheses in the treatment of vascular
dysfunctions/pathologies. While vascular prostheses are available
for clinical use, they have met with limited success due to
cellular and immunological complications, and the inability to
remain patent and function. These problems are especially
pronounced for small diameter prostheses, i.e. less than about 6
mm. Efforts have been directed at removing those aspects of
allograft and xenograft vascular prostheses that contribute to
immunological "rejection" and these efforts have focused primarily
on development of various "decellularization" processes, which
processes require unduly burdensome incubation times. In addition
the prior art methods involve using volumes of processing solutions
which do not lend themselves to the production of large numbers of
vascular grafts, which ability to "scale-up" is necessary for
economic clinical use.
[0005] The inventive process produces a cellular grafts including
but not limited to ligaments, tendons, menisci, cartilage, skin,
pericardium, dura mater, fascia, small and large intestine,
placenta, veins, arteries, and heart valves. The process is
advantageous over prior art processes in that processing times and
conditions have been optimized and reduced, and the economics of
production have been dramatically improved, resulting in large
numbers of uniform, non-immunogenic grafts being produced. The
grafts produced are non-immunogenic, are substantially free from
damage to the matrix, and are substantially free from contamination
including for example free from infectious agents.
[0006] The invention involves the use of an anionic agent, for
example sodium dodecylsulfate (SDS), for the treatment of tissues
with the dual objective of decellularization and treatment of
tissues to restrict recellularization. Further, the invention
expands on the process of treating tissue(s) with SDS, describing
how the amount(s) of SDS deposited in the tissue(s) can be further
enhanced/reduced to either further inhibit recellularization of the
tissue OR enhance recellularization of the tissue. Treatment of
tissues with salt solutions prior to treatment with SDS results in
different patterns of SDS deposition/precipitation in the tissues
than treatment of tissues with SDS followed by treatment of tissues
with salt solutions. Treatment of tissues with SDS prior to salt
treatment can be expected to result in significant binding of SDS,
primarily via hydrophobic interactions, to matrix "proteins" with
further deposition of SDS in the tissues as salt precipitated
materials by salt precipitation post SDS treatment. Treatment of
tissues with salt solutions prior to treatment with SDS solutions
can be expected to result in significant precipitation of SDS as a
salt precipitated form and less SDS being bound to tissue matrix
structure(s) via hydrophobic interactions. It is further understood
that the particular salt solution used, either prior to or
following SDS treatment, can significantly alter the subsequent
solubility of the salt precipitated SDS and thus long-term
retention of SDS in the tissues post implantation. The observed
salt effects on both perceptibility of SDS and subsequent
resolubilization of the salt precipitated form of SDS indicate an
activity order of Ca>Mg>Mn>K>Na and calcium salts of
dodecylsulfate (CaDS) are less soluble and thus more slowly
released from treated tissues than, for example, sodium salts of
dodecylsulfate (SDS). The invention is directed at a process for
producing acellular soft-tissue implants including vascular grafts,
veins, arteries, and heart valves, where processing times and
conditions have been optimized to dramatically improve on the
economics of production as well as to produce a graft with minimum
damage to the matrix structure of the acellular graft. It is a
further objective of the present invention to describe how to
control the amount(s) of anionic detergents, for example sodium
dodecylsulfate (SDS), deposited in the tissue(s) with the objective
of enhancing or restricting subsequent recellularization.
SUMMARY OF THE INVENTION
[0007] The inventive process is a process for preparing biological
material(s) for implantation into a mammalian cardiovascular
system, musculoskeletal system, or soft tissue system. The process
removes cellular membranes, nucleic acids, lipids, and cytoplasmic
components and produces an implant having an extracellular matrix
including as major components collagens, elastins, proteoglycans,
and mucopolysaccharides.
[0008] The process provides for the production of commercializable
quantities of acellular soft tissue grafts for implantation into
mammalian systems by removing the cellular populations, cellular
remnants, nucleic acids, and small molecular weight proteins,
lipids, and polysaccharides forming an acellular nonsoluble matrix
having is major components collagens, elastins, hyaluronins, and
proteoglycans. The acellular tissue produced can be implanted into
a mammalian system, or recellularized in vitro and subsequently
implanted into a mammalian system.
[0009] An embodiment of the process includes the following steps:
[0010] isolating from a suitable donor a desired tissue sample of
the biological material; [0011] extracting the tissue with mildly
alkaline hypotonic buffered solution of an endonuclease such as
Benzonase.RTM. (a registered product of Merck KGaA, Darmstadt,
Germany) and a nonionic detergent formulation such as Allowash
Solution.TM. (a registered trademark product of LifeNet, Virginia
Beach, Va.); [0012] optionally treating the tissue with a
hypertonic buffered salt solution; [0013] extracting and treating
the tissue with a mildly alkaline hypotonic buffered solution of
sodium dodecylsulfate, optionally with 0.1 to 0.5 M sodium chloride
rendering the solution hypertonic; [0014] optionally treating the
tissue with a hypertonic buffered salt solution; [0015] washing the
tissue with ultrapure water followed by a water solution of
chlorine dioxide; and [0016] storage in a sealed container in
isotonic saline, chlorine dioxide or 70% isopropanol.
[0017] The invention provides a process for preparing an acellular
soft tissue graft for implantation into a mammalian system,
including extracting a soft tissue sample with an extracting
solution including one or more nonionic detergents and one or more
endonucleases, to produce extracted tissue; treating the extracted
tissue with a treating solution including one or more anionic
detergents, to produce a treated tissue; washing the treated tissue
with a decontaminating solution including one or more
decontaminating agents to produce the acellular soft tissue graft;
and storing the acellular soft tissue graft in a storage solution
comprising one or more decontaminating agents.
[0018] The invention further provides a process for preparing
commercializable quantities of acellular soft tissue grafts for
implantation into mammalian systems, including obtaining tissue
samples from an acceptable donor; extracting the tissue samples
with an extracting solution including one or more nonionic
detergents and one or more endonucleases, to produce extracted
tissue; treating the extracted tissue with a treating solution
including one or more anionic detergents, to produce a treated
tissue; washing the treated tissue with a decontaminating solution
including one or more decontaminating agents to produce the
acellular soft tissue graft; and storing the acellular soft tissue
graft in a storage solution including one or more decontaminating
agents.
[0019] The invention also provides a process for preparing an
acellular soft tissue graft for implantation into a mammalian
system, including inducing a pressure mediated flow of an
extracting solution including one or more nonionic detergents and
one or more endonucleases, through soft tissue, to produce
extracted tissue; inducing a pressure mediated flow of a treating
solution including one or more anionic detergents, through the
extracted tissue, to produce a treated tissue; inducing a pressure
mediated flow of a decontaminating solution including one or more
decontaminating agents through the treated tissue, to produce the
acellular soft tissue graft; and storing the acellular soft tissue
graft in a storage solution including one or more decontaminating
agents.
[0020] The invention provides a process where the extracting
solution is recirculated through the soft tissue graft.
[0021] The invention further provides a process where the treating
solution is recirculated through the soft tissue graft.
[0022] The invention also provides a process where the
decontaminating solution is recirculated through the soft tissue
graft.
[0023] The invention provides a process for producing an acellular
tissue graft and includes the use of calcium salts which use
results in the acellular tissue graft containing a significantly
more insoluble form of salt precipitated anionic detergent, which
results in retarded recellularization of the acellular tissue graft
in vivo or in vitro.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 illustrates a view of one embodiment of the
processing chamber showing flow mediated processing of long vein
segments.
[0025] FIG. 2 illustrates a view of an embodiment of the processing
chamber showing flow mediated processing of a heart valve.
[0026] FIG. 3 illustrates a view of an unprocessed human saphenous
vein examined with Hemoxylin and Eosin staining, magnified 20
times.
[0027] FIG. 4 illustrates a view of an unprocessed human saphenous
vein examined with Feulgen staining, magnified 20 times.
[0028] FIG. 5 illustrates a view of a decellularized human
saphenous vein examined with Hemoxylin and Eosin staining,
magnified 20 times.
[0029] FIG. 6 illustrates a view of a decellularized human
saphenous vein examined with Feulgen staining, magnified 20
times.
[0030] FIG. 7 is a bar graph illustrating the percent reduction in
nucleic acids extractable from human saphenous veins using the
inventive process.
[0031] FIGS. 8A & 8B are graphs illustrating the binding of a
nonionic detergent, tritiated Triton X-100, to human saphenous vein
versus time of incubation.
[0032] FIGS. 9A & 9B are graphs illustrating the release of a
nonionic detergent, tritiated Triton X-100, from human saphenous
vein versus time of incubation.
[0033] FIGS. 10A & 10B are graphs illustrating the binding of
an anionic detergent, tritiated sodium dodecylsulfate, to human
saphenous vein versus time of incubation.
[0034] FIGS. 11A & 11B are graphs illustrating the release of
an anionic detergent, tritiated sodium dodecylsulfate, from human
saphenous vein versus time of incubation.
[0035] FIGS. 12A & 12B are graphs illustrating the toxicity of
a nonionic detergent, Triton X-100, towards mammalian cells in in
vitro culture, on days 1 and 7, respectively.
[0036] FIGS. 13A & 13B are graphs illustrating the toxicity of
an anionic detergent, sodium dodecylsulfate, towards mammalian
cells in in vitro culture, on days 1 and 7, respectively.
[0037] FIG. 14 is a graph illustrating the ability of detergents to
disrupt and solubilize mammalian cells.
[0038] FIG. 15 is a graph illustrating the ability of Allowash
Solution to enhance the activity of Benzonase relative to the
ability of Triton X-100 to enhance the activity of Benzonase in the
degradation of deoxyribonucleic acid.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] Definitions. The below definitions serve to provide a clear
and consistent understanding of the specification and claims,
including the scope to be given such terms.
Allowash.TM. Solution.
[0040] By the term "Allowash.TM. solution" is intended those
compositions disclosed in U.S. Pat. No. 5,556,379 incorporated
herein by reference. Examples of suitable Allowash.TM. compositions
include: A cleaning composition containing about 0.06 wt %
polyoxyethylene-4-lauryl ether; about 0.02 wt % poly (ethylene
glycol)-p-nonyl-phenyl-ether; about 0.02 wt %
octylphenol-ethyleneoxide and endotoxin free deionized/distilled
water.
Decontaminating Agent.
[0041] By the term "decontaminating agent" is intended one or more
agents which remove or inactivate/destroy any infectious material
potentially present in a biological tissue sample, for example,
such agents include but are not limited to one or more of the
following: an antibacterial agent; an antiviral agent; an
antimycotic agent; an alcohol for example, methyl, ethyl, propyl,
isopropyl, butyl, and/or t-butyl; trisodium phosphate; a
preservative such as chlorine dioxide, isopropanol,
METHYLPARABIN.RTM. (Croda, Inc.), antimicrobials, antifungal
agents, sodium hydroxide; hydrogen peroxide; a detergent, and
ultrapure water, where the decontaminating agent or agents do not
chemically alter the matrix components of the soft tissue
grafts.
Essentially Free From.
[0042] By the term "Essentially Free From" is intended for the
purposes of the present invention, a soft tissue graft where the
material removed (for example, cellular elements and infectious
materials) from the soft tissue graft is not detectable using
detection means known in the art at the time of filing of this
application.
Normal Tissue.
[0043] By the term "normal tissue" is intended for the purposes of
the present invention, a particular soft tissue, for example a
vein, artery, heart valve, ligament, tendon, fascia, dura mater,
pericardium or skin, present in a living animal, including for
example a human, a pig, and/or a cow. Tensile properties of a
particular decellularized soft tissue graft approximate, that is,
are not statistically significantly different from, the tensile
properties of that tissue in a living animal. Cellular components
of soft tissue graft biomaterials represent the major immunogenic
component of such grafts post implantation.
Acellular Soft Tissue Graft.
[0044] Bye the term "acellular tissue graft" is intended for the
purposes of the present invention, soft tissue including but not
limited to veins, arteries, heart valves, ligaments, tendons,
fascia, dura matter, pericardium, and skin, from any mammalian
source, including but not limited to, a human source, porcine
source, and a bovine source, where the acellular graft produced is
allogenic or xenogenic to the mammalian recipient.
[0045] The invention provides a process for removing these cellular
components from the tissue without resultant damage to the matrix
and/or tissue structure. Preferably, the tissue thickness does not
exceed about 8 mm, more preferably does not exceed about 6 mm, and
most preferably does not exceed about 4 mm, such that the time
intervals described herein are sufficient for the process solutions
to penetrate the tissue and solubilize the cellular components,
allowing for the extraction of extractable materials. Processing
times can be altered to accommodate thicker tissues. A quantity of
endonuclease is used for a given volume of tissue, such that the
quantity is sufficient to digest the DNA within that volume of
tissue.
[0046] The invention recognizes that the mechanical strength of
soft tissue graft biomaterials resides in the matrix structure of
the graft. The matrix structure of these biomaterials include
collagens, elastins, mucopolysaccharides and proteoglycan
components. The removal of cellular components from the graft does
not compromise the mechanical strength of the graft. The invention
further recognizes that vascular and nonvascular soft tissue grafts
do not need to be readily repopulated by recipient cells, post
implantation, to function long-term. The absence of an early and
rapid repopulation event(s) results in a graft having adequate
mechanical strength similar to the mechanical strength associated
with that particular normal tissue. This is because the subsequent
remodeling of a graft is associated with weakening of the
mechanical strength of the graft. That treatment of the graft with
a strongly anionic detergent, such as sodium dodecylsulfate, leaves
a strongly anionic charge distribution to the graft. This, in turn,
restricts recellularization of the graft post implantation.
Further, differences in anionic detergent binding to basement
membrane components of the graft allows early re-endothelialization
of vascular graft(s). That slow leaching of the anionic detergent
from the graft allows slow long-term repopulation and slow
long-term remodeling of the transplanted soft tissue graft
consistent with a durability and graft life, to be measured in
terms of decades. Although the description of the invention is
directed primarily at processing vascular graft materials, it
should be appreciated that this invention is not restricted to
processing of vascular graft materials and can also be directed to
processing non-vascular soft tissue grafts. Such tissue grafts
include, but are not limited to, tissues such as tendons, fascia,
ligaments, pericardium, intestine, skin, dura, and cartilage. Such
soft tissue can be processed by one of ordinary skill in the art to
which the present invention pertains by simple manipulation of the
inventive processing times, without undue experimentation. Tissue
is processed according to the invention by surgically removing
normal healthy tissues (for example, veins, arteries, heart valves)
from animals or humans. The removed tissue is then transported to a
processing facility where the tissue is cleaned of extraneous
matter and quickly submersed in the first processing (extracting)
solution which includes hypotonic buffered solutions containing an
endonuclease, for example Benzonas.RTM., and nonionic detergent(s)
including for example Allowash Solution.TM., TritonX-100, and/or
Tween 20, and MgCl.sub.2. Other suitable nonionic detergents can be
readily selected and employed by one of ordinary skill in the art
to which the present invention pertains, without undue
experimentation. Procurement and transport of tissue is preferably
carried out sterilely and is held in a sterile container on wet ice
in a solution iso-osmolar to the cellular population of the tissue
being procured and transported. Furthermore, antibiotics may be
added to the procurement and transport solution. The invention
includes the use of one or more decontaminating agents including
for example one or more antibiotics, anti-fungal agents or
anti-mycotic agents. Other such agents can be added during
processing if so desired to maintain sterility of the procured
tissues.
[0047] According to an aspect of the invention, a process for
preparing biological material for implantation into a mammalian
cardiovascular system, musculoskeletal system, or soft tissue
system, or for recellularization in vitro, is provided and includes
removing cellular membranes, nucleic acids, lipids, and cytoplasmic
components, and forms an extracellular matrix including collagens,
elastins, proteoglycans, and mucopolysaccharides, the process
includes, isolating from a suitable donor a desired tissue sample
of the biological material; extracting the tissue with mildly
alkaline hypotonic buffered solution of an endonuclease (including
for example Benzonase.RTM. (a registered product of Merck KGaA,
Darmstadt, Germany)) and a nonionic detergent formulation
(including for example Allowash Solution.TM. (a product of LifeNet,
Virginia Beach, Va.)); treating the tissue with a mildly alkaline
hypotonic buffered solution of an anionic detergent (including for
example sodium dodecylsulfate); washing the tissue with water
followed by a water or isotonic saline solution of chlorine dioxide
or alcohol wash; and storage in a sealed container in water (for
example, ultrapure water) or a dilute isotonic solution which may
contain low concentrations of chlorine dioxide or 70%
isopropanol.
[0048] The cellular components of soft tissue graft biomaterials
represent the major immunogenic component of such grafts post
implantation and the invention provides for the removal of these
cellular components without resultant damage to the matrix
structure in which the cells resided. Preferably, the soft tissue
sample thickness does not exceed about 4 mm such that the time
intervals described herein are sufficient for the solutions to
penetrate and affect the necessary solubilization and extraction of
extractable materials. The concentration of endonuclease utilized
is based on calculations designed at achieving a sufficient
quantity of endonuclease within a given volume of tissue which is
sufficient to digest the DNA within that volume of tissue and is
not arbitrarily chosen based on volume of processing solution. The
inventive process maintains the mechanical strength of the soft
tissue graft biomaterials because the process does not
detrimentally affect the matrix structure of the graft. The matrix
structure of these biomaterials include collagen, elastin,
mucopolysaccharide and proteoglycan components.
[0049] The inventive process provides for the modulation of
recellularization of the acellular soft tissue graft by adjusting
the amount of bound and/or precipitated anionic detergent left in
the acellular soft tissue graft produced.
[0050] This invention provides for the production of vascular and
tendenous grafts, which are not repopulated by recipient cells,
post implantation. The inventors discovered that these grafts do
not need to be repopulated to function long-term. That absence of
repopulation events reduce the possibility that subsequent
remodeling of the graft will occur along with the weakening of
mechanical strength of the graft which would be associated with
remodeling. That treatment of the graft with a strongly anionic
detergent, such as sodium dodecylsulfate, will leave a strongly
anionic charge distribution to the graft that will restrict
recellularization of the graft post implantation and that
differences in SDS binding to the basement membrane components will
allow reendothelialization of the vascular graft(s).
[0051] The inventors further discovered that the introduction of
high salt concentrations in the tissues prior to or following
treatment/extraction with an anionic detergent such as SDS results
in the precipitation of greater quantities of this anionic
detergent within the tissues and that this greater quantity of
anionic detergent significantly restricts recellularization of the
acellular tissue graft, than treatment of the tissue sample with an
anionic detergent without the use of high salt concentrations in
that tissue.
[0052] The invention provides a process that uses 0.001% to 0.024%
anionic detergent, for example, SDS in the treatment phase which
causes deposition of SDS in the tissues without the potentially
harmful effects of using 1% SDS in the treatment phase and can be
used preferentially with or without introduction of high salt
concentrations in the tissue when recellularization of that tissue
is desired. Although the description of this invention is directed
primarily at processing vascular graft materials, it should be
appreciated that this invention can also be directed to processing
non vascular soft tissue grafts such as tendons, fascia, ligaments,
pericardium, skin, dura, and cartilage by simple manipulation of
processing times and parameters, such manipulation can be readily
determined and employed by one of ordinary skill in the art,
without undue experimentation.
[0053] In the inventive process, normal healthy vessels (veins,
arteries, heart valves, tendons, ligaments, fascia, pericardium,
intestine, urethra, etc.) are surgically removed from animals or
humans, transported to the processing facility where they are
cleaned of extraneous matter and immediately submersed in an
extracting solution which contains a hypotonic buffered solution
containing one or more endonucleases including for example,
Benzonase, and one or more nonionic detergents including for
example, Allowash Solution, Triton X-1100, and Tween 20. In that
most such vessels are procured at sites distant from the processing
facility and that such vessels may ultimately either be
cryopreserved or made acellular, procurement and transport will
normally be in a sterile container on wet ice in a solution
isoosmolar to the cellular population of the tissue being procured
and transported. Furthermore, antibiotics are preferably added to
the procurement and transport solution. One or more decontaminating
agents, including for example, one or more antibiotics, can be
optionally employed in any step of the inventive process, to
maintain sterility of the procured tissues.
[0054] FIG. 1 illustrates the processing of a long vein grafts (1),
the distal end of the vein is cannulated onto the ribbed attachment
(2) of the inlet port (3) and a single suture (4) is used to secure
the vein. An additional suture line (5) is attached to the proximal
end of the vein for later use in maintaining the vein in an
extended state in the processing vessel (6). The vein (1) is then
removed from the first processing (extracting) solution and
transferred to the processing vessel (6) that has been temporarily
inverted. The second suture line (5) along with the vein (1) is
passed through the processing vessel (6) and secured to a point (7)
on the outlet port end (8) of the processing vessel (6). Prior to
closing the processing vessel, a portion of the first processing
(extracting) solution is gently added to the processing vessel and
the inlet port (3), with attached vein (1), is then secured. The
processing vessel (6) is turned such that the inlet port (3) is
down and the outlet port (8) is up and the vessel (6) is attached
to its support racking system via clamps (9). Sterile disposable
tubing (10) is attached to the inlet port (3) and to pump tubing in
a peristaltic pump (11). Further, sterile disposable tubing (12) is
attached to the inflow side (13) of the peristaltic pump (1) and to
the solution reservoir (14) which will contain all remaining first
processing (extracting) solution. Finally, sterile disposable
tubing (15) is attached between the top (outlet) port (8) of the
processing vessel (6) and the solution reservoir (14). Sterile,
in-line, filters (16) can optionally be added at appropriate
positions in the fluid flow to safeguard sterility during
processing. The first processing (extracting) solution is pumped
into, through and out of the processing vessel (6) such that flow
of fluids through the luminal part of the vein tubule passes into
the processing vessel (6) to affect constant solution change in the
processing vessel and out through the outlet port (8) to a solution
reservoir (14). By processing the vein in an inverted state, air
which may be trapped in the luminal space of the vein will be
induced to exit facilitating equal access of the processing
solutions to the vein tissue being processed. Processing of the
vein tissue with the first processing (extracting) solution is
preferably carried out at temperatures ranging from about 4.degree.
C. to about 37.degree. C. for time periods ranging from about one
hour to about 24 hours (overnight as necessary to accommodate
processing scheduling of processing staff). The endonuclease
(Benzonase) is optimally active between pH 6 and 10, and from
0.degree. C. to above 42.degree. C. (Merck literature describing
product) when provided with 1-2 mM Mg.sup.+2. Following processing
with the first processing (extracting) solution, the first
processing solution can optionally be replaced with water, for
example sterile ultrapure water, to preclude a possible
precipitation reaction between the nonionic detergents in the first
processing (extracting) solution and the anionic detergent in the
second processing (treating) solution, or the first processing
(extracting) solution can be replaced with an alkaline hypotonic
solution containing one or more detergents, including for example,
sodium dodecylsulfate (SDS) at a concentration, for example, of
about 1% by weight (second processing (treating) solution). Under
the optional processing procedure, only sufficient water need be
circulated through the processing vessel to affect one volume
change of solution in the processing vessel. During processing with
the second processing (treating) solution, this solution is
circulated through the tissue, preferably at a temperature of from
room temperature to about 37.degree. C., to avoid precipitation of
the detergent, for example SDS, at reduced temperatures, for a time
period not shorter than 3 hours. Following processing with the
second processing (treating) solution, water, for example ultrapure
sterile water, is circulated through the tissue and processing
vessel such that the available volume of washing solution
approximates a 1000-fold dilution of the detergent, for example
SDS, present in the second processing (treating) solution. The SDS
will exit from the tissues to a given amount of SDS/mg tissue wet
weight (protein concentration) provided the washing time is at
least 1 hour, preferably at least 2 hours and more preferably at
least 3 hours, at a flow rate sufficient to affect a volume change
in the processing vessel about every 30-40 minutes, suitable flow
rates including for example of from about 30 mls/min. to about 70
mls/min., more preferably from about 40 mls/min to about 60
mls/min., and most preferably about 50 mls/min. Following washing
in this final processing step, the vein is removed from the
processing vessel and transferred into storage solution, for
example phosphate buffered saline, 70% isopropanol, or 0.001% to
0.005% chlorine dioxide in sterile ultrapure water/isotonic saline,
and packaged in a volume of storage solution sufficient to cover
the tissue preventing dehydration. This packaged graft may then be
terminally sterilized, for example using gamma irradiation, if so
desired. Artery segments can be similarly processed, taking into
consideration that veins have valves and arteries do not, and that
veins generally have a smaller internal diameter than arteries,
thus dictating slower flow rates with veins.
[0055] FIG. 2 illustrates processing heart valve grafts. The heart
valve (1) is placed into the deformable processing device (2) such
that the valved end of the conduit is directed towards the inlet
port (3) and the nonvalved end of the conduit is directed towards
the outlet port (8). Prior to closing the processing vessel (2), a
portion of the first processing (extracting) solution is gently
added to the processing vessel. The processing vessel (2) is turned
such that the inlet port (3) is down and the outlet port (8) is up
to effect removal of air bubbles, and the vessel (2) attached to
its support racking system via clamps (9). Sterile disposable
tubing (10) is attached to the inlet port (3) and to pump tubing in
a peristaltic pump (1). Further, sterile disposable tubing (12) is
attached to the inflow side (13) of the peristaltic pump (11) and
to the solution reservoir (14) which will contain all remaining
first processing (extracting) solution. Finally, sterile disposable
tubing (15) is attached between the top (outlet) port (8) of the
processing vessel (2) and the solution reservoir (14). Sterile,
in-line, filters (16) can optionally be added at appropriate
positions in the fluid flow to safeguard sterility during
processing. The first processing (extracting) solution is pumped
into, through and out of the processing vessel (2) such that the
flow of fluids through the luminal part of the heart valve (1)
passes into the processing vessel (2) to affect constant solution
change in the processing vessel (2) and out through the outlet port
(8) to a solution reservoir (14). By processing the heart valve (1)
in this orientation, air which may be trapped in the luminal space
of the valve will be induced to exit facilitating equal access of
the processing solutions to the valve tissue being processed.
Processing of the heart valve (1) tissue with the first processing
(extracting) solution is performed at for example, a temperature of
from about 4.degree. C. to about 37.degree. C., for example for
time periods of from about one hour to about 24 hours (overnight as
necessary to accommodate processing scheduling of processing
staff). The endonuclease (Benzonase) is optimally active between pH
6 and 10, and from 0.degree. C. to above 42.degree. C. (Merck
literature describing product) when provided with 1-2 mM Mg.sup.+2.
Following processing with the first processing (extracting)
solution, the first processing (extracting) solution is optionally
be replaced with water, for example sterile ultrapure water, to
preclude a possible precipitation reaction between the nonionic
detergents in the first processing (extracting) solution and the
anionic detergent in the second processing (treating) solution, or
the first processing (extracting) solution can be replaced with an
alkaline hypotonic solution containing for example, about 1% by
weight of a detergent, for example, sodium dodecylsulfate (SDS)
(second processing (treating) solution). Under the optional
processing procedure, only sufficient water need be circulated
through the processing vessel to affect one volume change of
solution in the processing vessel. The second processing (treating)
solution is circulated through the tissue at a temperature for
example, of from about room temperature to about 37.degree. C., to
avoid precipitation of the detergent, for example SDS, at reduced
temperatures, for a time period of for example, not shorter than 3
hours. Following processing with the second processing (treating)
solution, water, for example ultrapure sterile water, is circulated
through the tissue and processing vessel such that the available
volume of washing solution approximates a 1000-fold dilution of the
SDS present in the second processing (treating) solution. The SDS
will exit from the tissues to a given amount of SDS/mg tissue wet
weight (protein concentration) provided the washing time preferably
exceeds 1 hour, more preferably exceeds 2 hours, and most
preferably exceeds about 3 hours, at a flow rate sufficient to
affect a volume change in the processing vessel about every 30-40
minutes, suitable flow rates including for example of from about 30
mls/min. to about 70 mls/min., more preferably from about 40
mls/min to about 60 mls/min., and most preferably about 50 mls/min.
Following washing, the heart valve may then be removed from the
processing vessel and transferred into storage solution of for
example, either 70% isopropanol or 0.001% chlorine dioxide in
sterile ultrapure water, and packaged in a volume of storage
solution sufficient to cover the tissue preventing dehydration.
Alternatively, the storage solutions can be pumped into the
processing vessel until the water wash solution has been adequately
exchanged and the whole processing vessel sealed and used as the
storage container for distribution.
[0056] For all other soft tissue grafts, the tissue is placed into
the deformable processing device such that the smaller portion is
directed towards the inlet port and the larger (bulkier) end of the
tissue is directed towards the outlet port. Preferably the
thickness of other soft tissue grafts does not exceed about 8 mm,
more preferable does not exceed 5 mm, and most preferably the
thickness does not exceed about 2-3 mm. If the thickness of the
tissue graft exceeds about 5 mm, incubation and processing times
need to be appropriately extended. Such incubation and processing
times can be readily selected and employed by one of ordinary skill
in the art to which the present invention pertains based on the
thickness of the tissue being processed, the type of tissue being
processed, and the volume of tissue being processed, without undue
experimentation. Prior to closing the processing vessel, a portion
of the first processing (extracting) solution is gently added to
the processing vessel. The processing vessel is then turned such
that the inlet port is down and the outlet port is up and the
vessel is attached to its support racking system for example, via
clamps. Sterile disposable tubing is attached to the inlet port and
to pump tubing in a peristaltic pump. Further, sterile disposable
tubing is attached to the inflow side of the peristaltic pump and
to the solution reservoir which will contain all remaining first
processing (extracting) solution. Finally, sterile disposable
tubing is attached between the top (outlet) port of the processing
vessel and the solution reservoir. Sterile, in-line, filters can
optionally be added at appropriate positions in the fluid flow to
safeguard sterility during processing. The first processing
(extracting) solution is pumped into, through and out of the
processing vessel such that flow of fluids occurs in close
proximity to the surfaces of the soft tissue grafts into the
processing vessel to affect constant solution change in the
processing vessel and out through the outlet port to a solution
reservoir. By processing the soft tissue graft in this orientation,
the bulkier portions of the soft tissue graft will receive the
greatest flow of fluids across the surfaces facilitating equal
access of the processing solutions to the tissue being processed.
Processing of the soft tissue graft with the first processing
(extracting) solution is preferably performed at a temperature of
from about 4.degree. C. to about 37.degree. C., for a period of
time preferably of from about one hour to about 24 hours (overnight
as necessary to accommodate processing scheduling of processing
staff). The endonuclease (Benzonase) is optimally active between pH
6 and 10, and from 0.degree. C. to above 42.degree. C. (Merck
literature describing product) when provided with 1-2 mM Mg.sup.+2.
Following processing with the first processing (extracting)
solution, the first processing (extracting) solution is optionally
be replaced with water, for example sterile ultrapure water, to
preclude a possible precipitation reaction between the nonionic
detergents in the first processing (extracting) solution and the
anionic detergent in the second processing solution, or the first
processing (extracting) solution can be replaced with an alkaline
hypotonic solution containing for example, preferably about 1% by
weight of a detergent, for example, preferably sodium
dodecylsulfate (SDS) (second processing (treating) solution). Under
the optional processing procedure, only sufficient water need be
circulated through the processing vessel to affect one volume
change of solution in the processing vessel. The second processing
(treating) solution is circulated through and/or around the tissue
at a temperature of preferably form room temperature to about
37.degree. C., to avoid precipitation of the detergent, for example
SDS, at reduced temperatures, for a time period of preferably not
shorter than 3 hours. Following processing with the second
processing (treating) solution, water for example ultrapure sterile
water, is circulated through and/or around the tissue and
processing vessel such that the available volume of washing
solution approximates a 1000-fold dilution of the SDS present in
the second processing (treating) solution. The SDS will exit from
the tissues to a given amount of SDS/mg tissue wet weight (protein
concentration) provided the washing time preferably exceeds 1 hour,
more preferably exceeds 2 hours and most preferably exceeds 3
hours, at a flow rate sufficient to affect a volume change in the
processing vessel about every 30-40 minutes, suitable flow rates
including for example of from about 30 mls/min. to about 70
mls/min., more preferably from about 40 mls/min to about 60
mls/min., and most preferably about 50 mls/min. Following washing,
the soft tissue graft may be removed from the processing vessel and
transferred into storage solution containing for example, buffered
isotonic saline, 70% isopropanol, or 0.001% to 0.005% chlorine
dioxide in sterile ultrapure water/isotonic saline, and packaged in
a volume of storage solution sufficient to cover the tissue
preventing dehydration. Alternatively, the storage solutions can be
pumped into the processing vessel until the ultrapure water wash
solution has been adequately exchanged and the whole processing
vessel sealed, sterilized for example using gamma-irradiation, and
used as the storage container for distribution. Storage of
processed soft tissue grafts should be in a solution which covers
the graft and which is contained in a container that will prevent
evaporation and fluid loss or concentration of solutes. The
solution can be isotonic saline, isotonic saline or ultrapure water
containing a preservative such as chlorine dioxide, isopropanol,
METHYLPARABIN.RTM. (Croda, Inc.), antibiotics, antimicrobials,
antimycotic agents, antifungal agents, or ultrapure water, or
similar bacteriostatic or bacteriocidal agent which do not
chemically alter the matrix components of the soft tissue grafts.
Suitable storage solutions are well known to of ordinary skill in
the art to which the present invention applies, and such solutions
can be readily selected and employed by those of ordinary skill in
the art to which the present invention applies without undue
experimentation. The storage containers with solution and soft
tissue grafts can be terminally sterilized, for example using gamma
irradiation at doses up to 2.5 Mrads.
[0057] The following examples illustrate processing of soft tissue
grafts according to the invention.
EXAMPLE 1
[0058] Saphenous vein tissues (two) from each leg of an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and the side vessels were tied off
using nonresorbable suture materials such that the ties did not
occur in close proximity to the long run of the vessel. Sutures can
restrict the decellularization process and the tissues under the
sutures were removed following decellularization. For long vein
grafts (40-60 cm) (FIG. 1), the distal ends of the veins were
cannulated onto the ribbed attachment of the inlet port(s) and
single sutures used to secure each vein. Additional suture lines
were attached to the proximal ends of the veins. The veins were
then removed from the dissecting solution (ultrapure water
containing 50 mM Tris-HCl (pH 7.2), 5 .mu.m EDTA, and one or more
antibiotics) and transferred to the processing vessel which had
been temporarily inverted. The second suture line along with the
vein was passed through the processing vessel and secured to a
point on the outlet port end of the processing vessel. Prior to
closing the processing vessel, a portion of the first processing
solution was gently added to the processing vessel and the inlet
port, with attached vein, was then secured. The processing vessel
was then turned such that the inlet port was down and the outlet
port was up and the vessel attached to its support racking system
via clamps. Sterile disposable tubing was attached to the inlet
port and to pump tubing in a peristaltic pump. Further, sterile
disposable tubing was attached to the inflow side of the
peristaltic pump and to the solution reservoir which contained all
remaining first processing solution. Total processing solution
volume approximated 250 ml. Finally, sterile disposable tubing was
attached between the top (outlet) port of the processing vessel and
the solution reservoir. Sterile, in-line, filters were added at
appropriate positions in the fluid flow to safeguard sterility
during processing. The first processing solution was then pumped
into, through and out of the processing vessel such that flow of
fluids through the luminal part of the vein tubule passed into the
processing vessel to affect constant solution change in the
processing vessel and out through the outlet port to a solution
reservoir. By processing the vein in an inverted state, air which
had been "trapped" in the luminal space of the vein was induced to
exit facilitating equal access of the processing solutions to the
vein tissue being processed. Processing of the vein tissue with the
first processing solution was performed at 25.+-.5.degree. C. for
16 hours using a flow rate of the first processing solution of 60
mls/min. The first processing (extracting) solution consisted of 50
mM Tris-HCl (pH 7.2), 5 mM MgCl.sub.2, 1% (w:v) Allowash Solution
(as described in U.S. Pat. No. 5,556,379), and endonuclease
(Benzonase, a registered product of EM Industries, Inc.) (41.8
Units/ml). Following processing with the first processing solution,
the first processing solution was replaced with sterile ultrapure
water (250 mls at a pump rate of 90 mls/min.) which was then
replaced with an alkaline hypotonic solution containing about 1% by
weight sodium dodecylsulfate (SDS) in ultrapure water buffered with
50 mM Tris-HCl (pH 7.2) (second processing (treating) solution).
Under this processing procedure, only sufficient ultrapure water
was circulated through the processing vessel to affect one volume
change of solution in the processing vessel. Under the processing
with second processing (treating) solution, this second solution
was circulated (flow rate of 60 mls/min.) through the tissue at
room temperature (25.+-.5.degree. C.), to avoid precipitation of
the SDS at reduced temperatures, for a time period of about 3
hours. Following processing with the second processing solution,
ultrapure sterile water was circulated through the tissue and
processing vessel such that the available volume of washing
solution approximated a 1000-fold dilution of the SDS present in
the second processing solution with a flow rate of 2 ml/min. for
1.5 hours. Following washing in this final processing step, the
vein was removed from the processing vessel and transferred into
storage solution of 0.005% chlorine dioxide in sterile ultrapure
water and packaged in a volume of this solution sufficient to cover
the tissue.
EXAMPLE 2
[0059] Saphenous vein tissues (two) from each leg of an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and side vessels were tied off
using nonresorbable suture materials such that the ties did not
occur in close proximity to the long run of the vessel. Sutures can
restrict the decellularization process and the tissues under the
sutures were removed following decellularization. For these long
vein grafts (33 and 28 cm) (FIG. 1), the distal ends of the veins
were cannulated onto the ribbed attachment of the inlet port(s) and
single sutures used to secure each vein. Additional suture lines
were attached to the proximal ends of the veins. At this point, the
veins were removed from the dissecting solution (ultrapure water
containing 50 mM Tris-HCl (pH 7.2), 5 mM EDTA, and one or more
antibiotics and transferred to the processing vessel which had been
temporarily inverted. The second suture line along with the vein
was passed through the processing vessel and secured to a point on
the outlet port end of the processing vessel. Prior to closing the
processing vessel, a portion of the first processing (extracting)
solution was gently added to the processing vessel and the inlet
port, with attached vein, was then secured. The processing vessel
was then turned such that the inlet port was down and the outlet
port was up and the vessel attached to its support racking system
via clamps. Sterile disposable tubing was attached to the inlet
port and to pump tubing in a peristaltic pump. Further, sterile
disposable tubing was attached to the inflow side of the
peristaltic pump and to the solution reservoir which contained all
remaining first processing (extracting) solution. Total processing
solution volume approximated 250 ml. Finally, sterile disposable
tubing was attached between the top (outlet) port of the processing
vessel and the solution reservoir. Sterile, in-line, filters were
added at appropriate positions in the fluid flow to safeguard
sterility during processing. The first processing (extracting)
solution was pumped into, through and out of the processing vessel
such that flow of fluids through the luminal part of the vein
tubule passed into the processing vessel to affect constant
solution chance in the processing vessel and out through the outlet
port to a solution reservoir. By processing the vein in an inverted
state, air which had been "trapped" in the luminal space of the
vein was induced to exit facilitating equal access of the
processing solutions to the vein tissue being processed. Processing
of the vein tissue with the first processing (extracting) solution
was performed at 25.+-.5.degree. C. for 16 hours using a flow rate
of the first processing solution of 30 mls/min. The first
processing (treating) solution consisted of 50 mM Tris-HCl (pH
7.2), 5 mM MgCl.sub.2, 1% (w:v) Triton X-100, and endonuclease
(Benzonase, a registered product of EM Industries, Inc.) (41.8
Units/ml). Following processing with the first processing
(extracting) solution, the first processing (extracting) solution
was replaced with an alkaline hypotonic solution containing about
1% by weight sodium dodecylsulfate (SDS) in ultrapure water
buffered with 50 mM Tris-HCl (pH 7.2) (second processing (treating)
solution). Under the processing with second processing (treating)
solution, this second solution was circulated (flow rate of 120
mls/min.) through the tissue at room temperature (25.+-.5.degree.
C.), to avoid precipitation of the SDS at reduced temperatures, for
a time period of 3 hours. Following processing with the second
processing solution, ultrapure sterile water was circulated through
the tissue and processing vessel such that the available volume of
washing solution approximated a 1000-fold dilution of the SDS
present in the second processing solution with a flow rate of 1
ml/minute for 1.5 hours. Following washing in this final processing
step, the vein was removed from the processing vessel and
transferred into storage solution of 0.001% chlorine dioxide in
sterile ultrapure water and packaged in a volume of this solution
sufficient to cover the tissue.
EXAMPLE 3
[0060] Internal mammary artery tissues (two) from an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and side vessels were tied off
using nonresorbable suture materials such that the ties did not
occur in close proximity to the long run of the vessel. Sutures can
restrict the decellularization process and the tissues under the
sutures were removed following decellularization. For short artery
grafts (11 and 8 cm) (FIG. 1), one end of each artery were
cannulated onto the ribbed attachment of the inlet port(s) and
single sutures used to secure each arteries. The arteries were then
removed from the dissecting solution (ultrapure water containing 50
mM Tris-HCl (pH 7.2), 5 mM EDTA, and one or more antibiotics) and
transferred to the processing vessel which had been temporarily
inverted. Prior to closing the processing vessel, a portion of the
first processing (extracting) solution was gently added to the
processing vessel and the inlet port, with attached artery, was
then secured. At this point, the processing vessel was turned such
that the inlet port was down and the outlet port was up and the
vessel attached to its support racking system via clamps. Sterile
disposable tubing was attached to the inlet port and to pump tubing
in a peristaltic pump. Further, sterile disposable tubing was
attached to the inflow side of the peristaltic pump and to the
solution reservoir which contained all remaining first processing
solution. Total processing solution volume approximated 150 ml.
Finally, sterile disposable tubing was attached between the top
(outlet) port of the processing vessel and the solution reservoir.
Sterile, in-line, filters were added at appropriate positions in
the fluid flow to safeguard sterility during processing. The first
processing (extracting) solution was pumped into, through and out
of the processing vessel such that flow of fluids through the
luminal part of the artery tubule passed into the processing vessel
to affect constant solution change in the processing vessel and out
through the outlet port to a solution reservoir. By processing the
artery in an inverted state, air which had been "trapped" in the
luminal space of the vein was induced to exit facilitating equal
access of the processing solutions to the vein tissue being
processed. Processing of the artery tissue with the first
processing (extracting) solution was performed at 25.+-.5.degree.
C. for 16 hours using a flow rate of the first processing
(extracting) solution of 50 mls/min. The first processing
(extracting) solution consisted of 50 mM Tris-HCl (pH 7.2), 5 mM
MgCl.sub.2, 1% (w:v) Allowash Solution (as described in U.S. Pat.
No. 5,556,379), and endonuclease (Benzonase, a registered product
of EM Industries, Inc.) (41.8 Units/ml). Following processing with
the first processing (extracting) solution, the first processing
(extracting) solution was replaced with sterile ultrapure water
(250 mls at a pump rate of 60 mls/min.) which was then replaced
with an alkaline hypotonic solution containing about 1% by weight
sodium dodecylsulfate (SDS) in ultrapure water buffered with 50 mM
Tris-HCl (pH 7.2) (second processing (treating) solution). Under
this processing procedure, only sufficient ultrapure water was
circulated through the processing vessel to affect one volume
change of solution in the processing vessel. Under the processing
with second processing solution, this second solution was
circulated (flow rate of 30 mls/min.) through the tissue at room
temperature (25.+-.5.degree. C.), to avoid precipitation of the SDS
at reduced temperatures, for a time period of 3 hours. Following
processing with the second processing solution, ultrapure sterile
water was circulated through the tissue and processing vessel such
that the available volume of washing solution approximated a
1000-fold dilution of the SDS present in the second processing
solution with a flow rate of 2 ml/min. for 1.5 hours. Following
washing in this final processing step, the artery was removed from
the processing vessel and transferred into storage solution of 70%
(v:v) pharmaceutical grade isopropanol in sterile ultrapure water
and packaged in a volume of this solution sufficient to cover the
tissue.
EXAMPLE 4
[0061] Aortic and pulmonary tissues (one each) from a heart of an
acceptable human donor were carefully dissected under sterile
conditions to remove all visible fat deposits and cardiac muscle
tissue (leaving only a small but visible band of cardiac muscle
tissue around the proximal end of the conduit. The valves were then
removed from the dissecting solution (ultrapure water containing 50
mM Tris-HCl (pH 7.2), 5 mM EDTA, and one or more antibiotics) and
transferred to the deformable (plastic) processing vessel (FIG. 2).
Prior to closing the processing vessel, a portion of the first
processing (extracting) solution was gently added to the processing
vessel and the side access port closed using the clamping mechanism
illustrated in FIG. 2. The proximal end of the heart valve(s) was
placed towards the inlet port and the distal end(s) of the valve
was placed towards the outlet port. At this point, the processing
vessel was placed such that the inlet port was down and the outlet
port was up and the vessel attached to its support racking system
via clamps. Sterile disposable tubing was attached to the inlet
port and to pump tubing in a peristaltic pump. Further, sterile
disposable tubing was attached to the inflow side of the
peristaltic pump and to the solution reservoir which contained all
remaining first processing solution. Total processing solution
volume approximated 350 mm. Finally, sterile disposable tubing was
attached between the top (outlet) port of the processing vessel and
the solution reservoir. Sterile, in-line, filters were added at
appropriate positions in the fluid flow to safeguard sterility
during processing. The first processing (extracting) solution was
pumped into, through and out of the processing vessel such that
flow of fluids through the luminal part of the heart valve tubule
passed into the processing vessel to affect constant solution
change in the processing vessel and out through the outlet port to
a solution reservoir. By processing the heart valve in an
noninverted state, air which had been "trapped" in the luminal
spaces behind the leaflets of the heart valve was induced to exit
facilitating equal access of the processing solutions to the heart
valve tissue being processed. Processing of the valve and conduit
tissue with the first processing (extracting) solution was
performed at 25.+-.5.degree. C. for 16 hours using a flow rate of
the first processing (extracting) solution of 50 mls/min. The first
processing (extracting) solution consisted of 50 mM Tris-HCl (pH
7.2), 5 mM MgCl.sub.2, 1% (w:v) Allowash Solution (as described in
U.S. Pat. No. 5,556,379), and endonuclease (Benzonase, a registered
product of EM Industries, Inc.) (41.8 Units/ml). Following
processing with the first processing (extracting) solution, the
first processing (extracting) solution was replaced with sterile
ultrapure water (350 mls at a pump rate of 50 mls/min.) which was
then replaced with an alkaline hypotonic solution containing about
1% by weight sodium dodecylsulfate (SDS) in ultrapure water
buffered with 50 mM Tris-HCl (pH 7.2) (second processing (treating)
solution). Under this processing procedure, only sufficient
ultrapure water was circulated through the processing vessel to
affect one volume change of solution in the processing vessel.
Under the processing with second processing (treating) solution,
this second solution was circulated (flow rate of 30 mls/min.)
through the tissue at room temperature (25.+-.5.degree. C.), to
avoid precipitation of the SDS at reduced temperatures, for a time
period of 5 hours.
[0062] Following processing with the second processing solution,
ultrapure sterile water was circulated through the tissue and
processing vessel such that the available volume of washing
solution approximated a 1000-fold dilution of the SDS present in
the second processing solution with a flow rate of 1 ml/min. for
1.5 hours. Following washing in this final processing step, the
heart valve(s) was (were) removed from the processing vessel and
transferred into storage solution of 0.05% chlorine dioxide in
sterile ultrapure water and packaged in a volume of this solution
sufficient to cover the tissue.
EXAMPLE 5
[0063] Saphenous vein tissues (two) from each leg of an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and side vessels were tied off
using nonresorbable suture materials such that the ties did not
occur in close proximity to the long run of the vessel. Sutures can
restrict the decellularization process and the tissues under the
sutures were removed following decellularization. For long vein
grafts (40-60 cm) (FIG. 1), the distal ends of the veins were
cannulated onto the ribbed attachment of the inlet port(s) and
single sutures used to secure each vein. Additional suture lines
were attached to the proximal ends of the veins. The veins were
then removed from the dissecting solution (ultrapure water
containing 50 mM Tris-HCl (pH 7.2), 5 mM EDTA, and one or more
antibiotics) and transferred to the processing vessel which had
been temporarily inverted. The second suture line along with the
vein was passed through the processing vessel and secured to a
point on the outlet port end of the processing vessel. Prior to
closing the processing vessel, a portion of the first processing
(extracting) solution was gently added to the processing vessel and
the inlet port, with attached vein, was then secured. At this
point, the processing vessel was turned such that the inlet port
was down and the outlet port was up and the vessel attached to its
support racking system via clamps. Sterile disposable tubing was
attached to the inlet port and to pump tubing in a peristaltic
pump. Further, sterile disposable tubing was attached to the inflow
side of the peristaltic pump and to the solution reservoir which
contained all remaining first processing solution. Total processing
solution volume approximated 250 ml. Finally, sterile disposable
tubing was attached between the top (outlet) port of the processing
vessel and the solution reservoir. Sterile, in-line, filters were
added at appropriate positions in the fluid flow to safeguard
sterility during processing. The first processing (extracting)
solution was pumped into, through and out of the processing vessel
such that flow of fluids through the luminal part of the vein
tubule passed into the processing vessel to affect constant
solution change in the processing vessel and out through the outlet
port to a solution reservoir. By processing the vein in an inverted
state, air which had been "trapped" in the luminal space of the
vein was induced to exit facilitating equal access of the
processing solutions to the vein tissue being processed. Processing
of the vein tissue with the first processing (extracting) solution
was performed at 25.+-.5.degree. C. for 18 hours using a flow rate
of the first processing (extracting) solution of 30 mls/min. The
first processing (extracting) solution consisted of 50 mM Tris-HCl
(pH 7.2), 5 mM MgCl.sub.2, 1% (w:v) Allowash Solution (as described
in U.S. Pat. No. 5,556,379), and endonuclease (Benzonase, a
registered product of EM Industries, Inc.) (41.8 Units/ml).
Following processing with the first processing (extracting)
solution, the first processing (extracting) solution was replaced
with sterile ultrapure water (250 mls at a pump rate of 30
mls/min.) which was then replaced with an alkaline hypotonic
solution containing about 1% by weight sodium dodecylsulfate (SDS)
in ultrapure water buffered with 50 mM Tris-HCl (pH 7.2) (second
processing (treating) solution). Under this processing procedure,
only sufficient ultrapure water was circulated through the
processing vessel to affect one volume change of solution in the
processing vessel. Under the processing with second processing
solution, this second solution was circulated (flow rate of 30
mls/min.) through the tissue at room temperature (25.+-.5.degree.
C.), to avoid precipitation of the SDS at reduced temperatures, for
a time period of than 1.5 hours. Following processing with the
second processing solution, ultrapure sterile water was circulated
through the tissue and processing vessel such that the available
volume of washing solution approximated a 1000-fold dilution of the
SDS present in the second processing (treating) solution with a
flow rate of 1 ml/min. for 6 hours. Following washing in this final
processing step, the vein was removed from the processing vessel
and transferred into storage solution of isotonic saline in sterile
ultrapure water and packaged in a volume of this solution
sufficient to cover the tissue. The packaged tissue was
gamma-radiation sterilized at 2.5 Mrads and stored at room
temperature until use.
EXAMPLE 6
[0064] Saphenous vein tissues (two) from each leg of an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and side vessels tied off using
nonresorbable suture materials such that the ties did not occur in
close proximity to the long run of the vessel. Sutures can restrict
the decellularization process and the tissues under the sutures
will be removed following decellularization. For long vein grafts
(40-60 cm) (FIG. 1), the distal ends of the veins were cannulated
onto the ribbed attachment of the inlet port(s) and single sutures
used to secure each vein. Additional suture lines were attached to
the proximal ends of the veins. At this point, the veins were
removed from the dissecting solution (ultrapure water containing 50
mM Tris-HCl (pH 7.2), 5 mM EDTA, and antibiotic solution for
cardiovascular tissue procurement and transport) and transferred to
the processing vessel(s) which had been temporarily inverted. The
second suture line along with the vein was passed through the
processing vessel and secured to a point on the outlet port end of
the processing vessel. Prior to closing the processing vessel, a
portion of the First Processing Solution was gently added to the
processing vessel and the inlet port, with attached vein, was then
secured. At this point, the processing vessel was turned such that
the inlet port was down and the outlet port was up and the vessel
attached to its support racking system via clamps, respectively.
Sterile disposable tubing was attached to the inlet port and to
pump tubing in a peristaltic pump. Further, sterile disposable
tubing was attached to the inflow side of the peristaltic pump and
to the solution reservoir which contained all remaining first
processing solution. Total processing solution volume approximated
250 ml. Finally, sterile disposable tubing was attached between the
top (outlet) port of the processing vessel and the solution
reservoir. Sterile, in-line, filters were added at appropriate
positions in the fluid flow to safeguard sterility during
processing. First Processing Solution was pumped into, through and
out of the processing vessel such that flow of fluids through the
luminal part of the vein tubule passed into the processing vessel
to affect constant solution change in the processing vessel and out
through the outlet port to a solution reservoir. By processing the
vein in an inverted state, air which had been "trapped" in the
luminal space of the vein was induced to exit facilitating equal
access of the processing solutions to the vein tissue being
processed. Processing of the vein tissue with the First Processing
Solution was performed at temperatures approximating
25.+-.5.degree. C. for 16 hours using a flow rate of the First
Processing Solution of 50 mls/min. The First Processing Solution
consisted of 50 mM Tris-HCl (pH 8), 2 mM MgCl.sub.2, 1% (w:v)
Allowash Solution (as described in U.S. Pat. No. 5,556,379), and
endonuclease (Benzonase, a registered product of EM Industries,
Inc.) (41.8 Units/1 ml). Following processing with the First
Processing Solution, the First Processing Solution was replaced
with sterile ultrapure water containing 0.5 M NaCl (250 mls at a
pump rate of 50 mls/min.) over a period of 1 hour, which was then
replaced with an alkaline hypotonic solution containing about
0.001% by weight sodium dodecylsulfate (SDS) in ultrapure water
buffered with 50 mM Tris-HCl (pH 9) (Second Processing Solution).
Under this processing procedure, only sufficient ultrapure water
salt solution needed to be circulated through the processing vessel
to affect one volume change of solution in the processing vessel.
Under the processing with Second Processing Solution, this second
solution was circulated (flow rate of 50 mls/min.) through the
tissue at room temperature (25.+-.5.degree. C.), to allow
precipitation of the SDS at reduced temperatures, for a time period
of than 3 hours. Following processing with the Second Processing
Solution, ultrapure sterile water containing 0.01 M calcium
chloride was circulated through the tissue and processing vessel
such that the available volume of washing solution approximated a
1000-fold dilution of the SDS present in the Second Processing
Solution with a flow rate of 50 ml/min. for 1.5 hours. Following
washing in this final processing step, the vein was removed from
the processing vessel and transferred into storage solution of
0.001% chlorine dioxide in sterile ultrapure water and packaged in
a volume of this solution sufficient to cover the tissue.
EXAMPLE 7
[0065] Saphenous vein tissues (two) from each leg of an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and side vessels tied off using
nonriesorbable suture materials such that the ties did not occur in
close proximity to the long run of the vessel. Sutures can restrict
the decellularization process and the tissues under the sutures
will be removed following decellularization. For these long vein
grafts (33 and 28 cm) (FIG. 1), the distal ends of the veins were
cannulated onto the ribbed attachment of the inlet port(s) and
single sutures used to secure each vein. Additional suture lines
were attached to the proximal ends of the veins. At this point, the
veins were removed from the dissecting solution (ultrapure water
and antibiotic solution including: 100 mcg/ml polymyxin B sulfate,
240 mcg/ml cefoxitin, 50 mcg/ml vancomycin, 120 mcg/ml lincomycin
HCL, (for use with heart valves and arteries, when veins are
processed, 0.12 mg/ml papaverive is added) in RMI 1640 tissue
culture media, and transferred to the processing vessel(s) which
had been temporarily inverted. The second suture line along with
the vein was passed through the processing vessel and secured to a
point on the outlet port end of the processing vessel. Prior to
closing the processing vessel, a portion of the First Processing
Solution was gently added to the processing vessel and the inlet
port, with attached vein, was then secured. At this point, the
processing vessel was turned such that the inlet port was down and
the outlet port was up and the vessel attached to its support
racking system via clamps, respectively. Sterile disposable tubing
was attached to the inlet port and to pump tubing in a peristaltic
pump. Further, sterile disposable tubing was attached to the inflow
side of the peristaltic pump and to the solution reservoir which
contained all remaining first processing solution. Total processing
solution volume approximated 250 ml. Finally, sterile disposable
tubing was attached between the top (outlet) port of the processing
vessel and the solution reservoir. Sterile, in-line, filters were
optionally added at appropriate positions in the fluid flow to
safeguard sterility during processing. First Processing Solution
was pumped into, through and out of the processing vessel such that
flow of fluids through the luminal part of the vein tubule passed
into the processing vessel to affect constant solution change in
the processing vessel and out through the outlet port to a solution
reservoir. By processing the vein in an inverted state, air which
had been "trapped" in the luminal space of the vein was induced to
exit facilitating equal access of the processing solutions to the
vein tissue being processed. Processing of the vein tissue with the
First Processing Solution was performed at temperatures ranging
between 25.+-.5.degree. C. for 16 hours using a flow rate of the
First Processing Solution of 50 mls/minute. The First Processing
Solution consisted of 50 mM Tris-HCl (pH 8), 2 mM MgCl.sub.2, 1%
(w:v) Triton X-100, and endonuclease (Benzonase, a registered
product of EM Industries, Inc.) (41.8 Units/ml). Following
processing with the First Processing Solution, the First Processing
Solution was replaced with a sterile water solution of 1.0 M KCl
(50 mls/min. flow rate over 1.5 hours) and then by an alkaline
hypotonic solution containing about 1% by weight sodium
dodecylsulfate (SDS) in ultrapure water buffered with 50 mM
Tris-HCl (pH 9) (Second Processing Solution). Under the processing
with Second Processing Solution, this second solution was
circulated (flow rate of 50 mls/min.) through the tissue at room
temperature (25.+-.5.degree. C.), to allow deposition/precipitation
of the SDS at reduced temperatures, for a time period of 3 hours.
Following processing with the Second Processing Solution, ultrapure
sterile water was circulated through the tissue and processing
vessel such that the available volume of washing solution
approximated a 1000-fold dilution of the SDS present in the Second
Processing Solution with a flow rate of 50 ml/minute for 1.5 hours.
Following washing in this final processing step, the vein was
removed from the processing vessel and transferred into storage
solution of 0.001% chlorine dioxide in sterile ultrapure water and
packaged in a volume of this solution sufficient to cover the
tissue.
EXAMPLE 8
[0066] Internal mammary artery tissues (two) from an acceptable
human donor were carefully dissected under sterile conditions to
remove all visible fat deposits and side vessels tied off using
nonresorbable suture materials such that the ties did not occur in
close proximity to the long run of the vessel. Sutures can restrict
the decellularization process and the tissues under the sutures
will be removed following decellularization. For short artery
grafts (11 and 8 cm) (FIG. 1), one end of each artery were
cannulated onto the ribbed attachment of the inlet port(s) and
single sutures used to secure each arteries. At this point, the
arteries were removed from the dissecting solution (ultrapure water
containing 50 mM Tris-HCl (pH 7.2), 5 mM EDTA, and antibiotic
solution for cardiovascular tissue procurement and transport) and
transferred to the processing vessel(s) which had been temporarily
inverted. Prior to closing the processing vessel, a portion of the
First Processing Solution was gently added to the processing vessel
and the inlet port, with attached artery, was then secured. At this
point, the processing vessel was turned such that the inlet port
was down and the outlet port was up and the vessel attached to its
support racking system via clamps, respectively. Sterile disposable
tubing was attached to the inlet port and to pump tubing in a
peristaltic pump. Further, sterile disposable tubing was attached
to the inflow side of the peristaltic pump and to the solution
reservoir which contained all remaining first processing solution.
Total processing solution volume approximated 150 ml. Finally,
sterile disposable tubing was attached between the top (outlet)
port of the processing vessel and the solution reservoir. Sterile,
in-line, filters were added at appropriate positions in the fluid
flow to safeguard sterility during processing. First Processing
Solution was pumped into, through and out of the processing vessel
such that flow of fluids through the luminal part of the artery
tubule passed into the processing vessel to affect constant
solution change in the processing vessel and out through the outlet
port to a solution reservoir. By processing the artery in an
inverted state, air which had been "trapped" in the luminal space
of the vein was induced to exit facilitating equal access of the
processing solutions to the vein tissue being processed. Processing
of the artery tissue with the First Processing Solution was
performed at temperatures approximating 25.+-.5.degree. C. for 16
hours using a flow rate of the First Processing Solution of 50
mls/hour. The First Processing Solution consisted of 50 mM Tris-HCl
(pH 7.2), 5 mM MgCl.sub.2, 1% (w:v) Allowash Solution (as described
in U.S. Pat. No. 5,556,379), and endonuclease (Benzonase, a
registered product of EM Industries, Inc.) (41.8 Units/ml).
Following processing with the First Processing Solution, the First
Processing Solution was replaced with sterile ultrapure water
amended with 0.5 M CaCl.sub.2 (250 mls at a pump rate of 60
mls/minute) which was then replaced with an alkaline hypotonic
solution containing about 0.001% by weight sodium dodecylsulfate
(SDS) in ultrapure water buffered with 50 mM Tris-HCl (pH 8)
(Second Processing Solution). Under this processing procedure, only
sufficient ultrapure salt solution needed to be circulated through
the processing vessel to affect one volume change of solution in
the processing vessel. Under the processing with Second Processing
Solution, this second solution was circulated (flow rate of 30
mls/min.) through the tissue at room temperature (25.+-.5.degree.
C.), to allow precipitation of the SDS at reduced temperatures, for
a time period of 3 hours. Following processing with the Second
Processing Solution, ultrapure sterile water was circulated through
the tissue and processing vessel such that the available volume of
washing solution approximated a 1000-fold dilution of the SDS
present in the Second Processing Solution with a flow rate of 50
l/min. for 1.5 hours. Following washing in this final processing
step, the artery was removed from the processing vessel and
transferred into storage solution of 70% (v:v) pharmaceutical grade
isopropanol in sterile ultrapure water and packaged in a volume of
this solution sufficient to cover the tissue.
EXAMPLE 9
[0067] Aortic and pulmonary tissues (one each) from a heart of an
acceptable human donor were carefully dissected under sterile
conditions to remove all visible fat deposits and cardiac muscle
tissue (leaving only a small but visible band of cardiac muscle
tissue around the proximal end of the conduit. At this point, the
valves were removed from the dissecting solution (ultrapure water
and antibiotic solution for cardiovascular tissue procurement and
transport) and transferred to the deformable (plastic) processing
vessel(s). Prior to closing the processing vessel, a portion of the
First Processing Solution was gently added to the processing vessel
and the side access port closed using the clamping mechanism
illustrated in FIG. 2. The proximal end of the heart valve(s) was
placed towards the inlet port and the distal end(s) of the valve
was placed towards the outlet port. At this point, the processing
vessel was placed such that the inlet port was down and the outlet
port was up and the vessel attached to its support racking system
via clamps. Sterile disposable tubing was attached to the inlet
port and to pump tubing in a peristaltic pump. Further, sterile
disposable tubing was attached to the inflow side of the
peristaltic pump and to the solution reservoir which contained all
remaining first processing solution. Total processing solution
volume approximated 350 ml. Finally, sterile disposable tubing was
attached between the top (outlet) port of the processing vessel and
the solution reservoir. Sterile, in-line, filters were added at
appropriate positions in the fluid flow to safeguard sterility
during processing. First Processing Solution was pumped into,
through and out of the processing vessel such that flow of fluids
through the luminal part of the heart valve tubule passed into the
processing vessel to affect constant solution change in the
processing vessel and out through the outlet port to a solution
reservoir. By processing the heart valve in an noninverted state,
air which had been "trapped" in the luminal spaces behind the
leaflets of the heart valve was induced to exit facilitating equal
access of the processing solutions to the heart valve tissue being
processed. Processing of the valve and conduit tissue with the
First Processing Solution was performed at temperatures
approximating 25.+-.5.degree. C. for 16 hours using a flow rate of
the First Processing Solution of 50 mls/minute. The First
Processing Solution consisted of 50 mM Tris-HCl (pH 8), 2 mM
MgCl.sub.2, 1% (w:v) Allowash Solution (as described in U.S. Pat.
No. 5,556,379), and endonuclease (Benzonase, a registered product
of EM Industries, Inc.) (83 Units/ml). Following processing with
the First Processing Solution, the First Processing Solution was
replaced with sterile ultrapure water (350 mls at a pump rate of 50
mls/min. being recirculated over a period of 3 hours) which was
then replaced with an alkaline hypertonic solution containing about
024% by weight sodium dodecylsulfate (SDS) in ultrapure water
buffered with 50 mM Tris-HCl (pH 7.2) containing 0.5 M sodium
chloride (Second Processing Solution). This specific formulation of
SDS and sodium chloride is balanced so as not to precipitate the
SDS, the SDS concentration is minimized to lessen extension of the
tissue dimensions, the salt concentration is maximized so as to
facilitate limited contraction of the tissue dimensions-yet not be
so concentrated as to precipitate the anionic detergent, and the
whole processing solution facilitates decellularization and
treatment of the tissue yet promotes coaptation of the valve
leaflets post decellularization. Second Processing Solution was
replaced with a hypertonic solution of 0.005 M calcium hydroxide.
Under this processing procedure, only sufficient ultrapure water
salt solution needed to be circulated through the processing vessel
to affect one volume change of solution in the processing vessel.
Under the processing with Second Processing Solution, this second
solution was circulated (flow rate of 30 mls/minute) through the
tissue at room temperature (25.+-.5.degree. C.), to allow
precipitation of the SDS at reduced temperatures, for a time period
of 5 hours. Following processing with the Second Processing
Solution, ultrapure sterile water containing calcium ion was
circulated through the tissue and processing vessel such that the
available volume of washing/treatment solution approximated a
1000-fold dilution of the SDS present in the Second Processing
Solution with a flow rate of 50 ml/min. for 1.5 hours. Following
washing in this final processing step, the heart valve(s) was
(were) removed from the processing vessel and transferred into
storage solution of 0.05% chlorine dioxide in sterile ultrapure
water and packaged in a volume of this solution sufficient to cover
the tissue.
[0068] While the invention has been described in connection with
specific embodiments thereof, it will be understood that it is
capable of further modifications and this application is intended
to cover any variations, uses, or adaptations of the invention
following, in general, the principles of the invention and
including such departures from the present disclosure as come
hypotonic buffered within known or customary practice within the
art to which the invention pertains and as may be applied to the
essential features hereinbefore set forth as follows in the scope
of the appended claims. Any references including patents cited
herein are incorporated herein in their entirety.
* * * * *