U.S. patent application number 11/480711 was filed with the patent office on 2006-11-09 for muscle-based grafts/implants.
This patent application is currently assigned to Regeneration Technologies, Inc.. Invention is credited to John R. Bianchi, David T. Cheung, John W. JR. Howell, C. Randal Mills, Chandrasekaran Nataraj, Michael R. Roberts.
Application Number | 20060251629 11/480711 |
Document ID | / |
Family ID | 34811500 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060251629 |
Kind Code |
A1 |
Mills; C. Randal ; et
al. |
November 9, 2006 |
Muscle-based grafts/implants
Abstract
The present invention is directed to a composition comprising a
matrix suitable for implantation in humans, comprising defatted,
shredded, allogeneic human muscle tissue that has been combined
with an aqueous carrier and dried in a predetermined shape. Also
disclosed is a tissue graft or implant comprising a matrix suitable
for implantation in humans, comprising defatted, shredded,
allogeneic human muscle tissue that has been combined with an
aqueous carrier and dried in a predetermined shape. The composition
and/or tissue graft or implant of the invention is usable in
combination with seeded cells, a tissue growth factor, and/or a
chemotactic agent to attract a desired cell.
Inventors: |
Mills; C. Randal; (Tioga,
FL) ; Bianchi; John R.; (Gainesville, FL) ;
Roberts; Michael R.; (Gainesville, FL) ; Cheung;
David T.; (Arcadia, CA) ; Nataraj;
Chandrasekaran; (Gainesville, FL) ; Howell; John W.
JR.; (Gainesville, FL) |
Correspondence
Address: |
MCANDREWS HELD & MALLOY, LTD
500 WEST MADISON STREET
SUITE 3400
CHICAGO
IL
60661
US
|
Assignee: |
Regeneration Technologies,
Inc.
|
Family ID: |
34811500 |
Appl. No.: |
11/480711 |
Filed: |
July 3, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10793976 |
Mar 5, 2004 |
|
|
|
11480711 |
Jul 3, 2006 |
|
|
|
10754310 |
Jan 9, 2004 |
7001430 |
|
|
10793976 |
Mar 5, 2004 |
|
|
|
Current U.S.
Class: |
424/93.7 ;
514/16.5; 514/8.8; 514/8.9; 514/9.1; 623/1.11 |
Current CPC
Class: |
A61F 2/08 20130101; A61L
27/3604 20130101; A61L 27/54 20130101; B33Y 80/00 20141201; A61L
2400/06 20130101; A61L 2430/10 20130101; A61L 2430/02 20130101;
A61L 27/3687 20130101; A61L 27/56 20130101; A61F 2/105 20130101;
A61L 2300/414 20130101; A61L 2430/30 20130101; A61L 27/46 20130101;
A61L 27/38 20130101; A61L 27/3826 20130101; A61F 2002/0894
20130101; A61L 27/3608 20130101; A61L 27/3691 20130101 |
Class at
Publication: |
424/093.7 ;
514/012; 623/001.11 |
International
Class: |
A61K 38/17 20060101
A61K038/17; A61K 35/12 20060101 A61K035/12; A61F 2/06 20060101
A61F002/06 |
Claims
1. A composition comprising a matrix suitable for implantation in
humans, said matrix comprising a dried aqueous slurry of shredded,
allogeneic human muscle tissue.
2. The composition of claim 1, wherein said muscle tissue is
striated muscle tissue.
3. The composition of claim 2, wherein said striated muscle tissue
is skeletal muscle.
4. The composition of claim 1, wherein said shredded allogeneic
human muscle tissue is also defatted.
5. The composition of claim 1, wherein said shredded allogeneic
human muscle tissue was also lyophilized prior to shredding.
6. The composition of claim 1, further comprising a particulate
component selected from the group consisting of demineralized bone
matrix (DBM), mineralized bone matrix, cortical cancellous chips
(CCC), crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate and a combination
thereof.
7. The composition of claim 6, wherein the particulate component
constitutes from 50% to 99% of the dry weight of the
composition.
8. The composition of claim 7, wherein the particulate component
constitutes from 90% to 99% of the dry weight of the
composition.
9. The composition of claim 1, further comprising an effective
amount of a bone morphogenic protein (BMP), a LIM mineralization
protein, or RUNX-2 protein.
10. The composition of claim 9, wherein said BMP is selected from
the group consisting of BMP-2, BMP-4 and BMP-7.
11. The composition of claim 10, wherein said BMP is BMP-2.
12. The composition of claim 11, wherein said BMP-2 is a
recombinant human BMP-2.
13. An implant suitable for implantation in humans comprising a
matrix of defatted, shredded, allogeneic human muscle tissue that
has been combined with an aqueous carrier and dried into a
predetermined shape.
14. The implant of claim 13, wherein said muscle tissue is striated
muscle tissue.
15. The implant of claim 14, wherein said striated muscle tissue is
skeletal muscle.
16. The implant of claim 13, wherein said shredded allogeneic human
muscle tissue is also defatted.
17. The implant of claim 13, wherein said shredded allogeneic human
muscle tissue was also lyophilized prior to shredding.
18. The implant of claim 13, further comprising a particulate
component selected from the group consisting of DBM, mineralized
bone matrix, CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate and a combination
thereof.
19. The implant of claim 18, wherein the particulate component
constitutes from 50% to 99% of the dry weight of the implant.
20. The implant of claim 19, wherein the particulate component
constitutes from 90% to 99% of the dry weight of the implant.
21. The implant of claim 13, further comprising an effective amount
of a bone morphogenic protein (BMP), a LIM mineralization protein,
or RUNX-2 protein.
22. The implant of claim 21, wherein said BMP is selected from the
group consisting of BMP-2, BMP-4 and BMP-7.
23. The implant of claim 22, wherein said BMP is BMP-2.
24. The implant of claim 23, wherein said BMP-2 is a recombinant
human BMP-2.
25. The implant of claim 13, wherein said matrix of digested
allogeneic human muscle comprises from about 1% to about 100% of
the final weight of said implant.
26. The implant of claim 25, wherein said matrix of digested
allogeneic human muscle comprises from 25% to about 85% of the
weight of said tissue implant.
27. The implant of claim 18, wherein said particulate component is
DBM.
28. The implant of claim 27, wherein said DBM is uniformly
distributed throughout the matrix.
29. The implant of claim 27, wherein said DBM is layered within
said matrix.
30. The implant of claim 18, wherein said particulate component is
CCC.
31. The implant of claim 30, wherein said CCC is uniformly
distributed throughout the matrix.
32. The implant of claim 30, wherein said CCC is layered within
said matrix.
33. The implant of claim 13 further comprising digested allogeneic
human tendon.
34. A method for making an implantable tissue comprising the steps
of: i. removing the fat and soluble proteins from allogeneic or
xenogeneic mammalian muscle tissue; ii. lyophilizing the muscle
tissue from step (i); iii. shredding the lyophilized muscle tissue;
iv. mixing the shredded muscle tissue in an aqueous carrier to form
a muscle tissue slurry having a viscosity within the range of 1
centistoke to 20,000 centistokes; v. transferring the muscle tissue
slurry to an appropriate shaped mold: and vi. drying the slurry in
the mold to form the tissue implant having the corresponding shape
of said mold.
35. The method of claim 34, wherein the tissue implant is a shaped
sponge.
Description
BACKGROUND OF THE INVENTION
[0001] This application is a continuation of U.S. Ser. No.
10/793,976, filed Mar. 3, 2005, now pending, which is a
continuation-in-part of U.S. Ser. No. 10/754,310, filed Jan. 9,
2004, now U.S. Pat. No. 7,001,430.
[0002] The present invention is directed to the field of
biocompatible matrices for use in forming devices for implantation
in animals and humans. More particularly, the present invention is
directed to an implantable composition or a tissue graft/implant
formed from an allogeneic biocompatible human muscle matrix that is
capable of carrying other implantable materials or that can be
formed into a plurality of tissue implants or compositions having
different properties and different shapes. The present invention is
useful because it provides an implantable composition or device
that is versatile in its ability to be formulated into a variety of
implants or grafts that are useful in the treatment of a variety of
medical conditions in patients.
[0003] In the field of biomedical implants, devices have been made
that range far afield from the biological components found in the
human body. For example, many devices that are intended as bone
substitutes are made from metals such as titanium, or biocompatible
ceramics. A problem in such instances is that they have different
material properties than the host tissue causing the devices to
loosen at the interface between the host tissue and the device
itself.
[0004] One solution to the problem was the use of allograft bone in
place of metal or ceramic implants. Under the proper conditions and
under the influence of osteogenic substances, implants made of
allograft bone can act as the scaffolding for remodeling by the
host. Such implants function by being both structurally and
biologically similar to the host tissue. Further, they allow
cellular recruitment through the natural openings in the matrix and
allow the graft to be replaced by natural host bone. While
allograft bone is very useful, it is limited by the intended
clinical use. Thus, it is particularly useful for spinal fusions
where the spacings between the vertebrae are relatively fixed and
well known. However, injuries come in a variety of shapes and sizes
that present a logical limitation on the availability of an ideal
graft to fill the defect. Moreover, availability, donor
demographics and cost further limit the usefulness of allograft
bone. Accordingly, there is a need in the art for an implantable
biocompatible matrix that can be formulated into a variety of
shapes and sizes and that can act as scaffolding to allow the
infiltration of native regenerative cells that will lay down a
natural replacement structure in the shape of the implant.
[0005] Another example area where biocompatible implants are
important is in replacement skin for burn victims.
Histocompatibility, remodeling and safety are considerable problems
in utilizing allograft skin. To avoid this problem and the shortage
of viable donor skin, a surgeon often removes skin from another
part of the patient and transplants it to the area of need. While
such skin is non-antigenic, it causes significant morbidity to the
patient at the site of removal. Moreover, depending upon the size
of the wound or burn, there may not be sufficient skin on the
patient to satisfy the need. To alleviate this problem, at least
one company will culture the patient's skin cells on a collagen
matrix to form a transplantable layer of skin. However, the culture
time is relatively extensive and the patient's wound or burn is
exposed while awaiting the graft. Moreover, the grafts generated in
this way do not mimic normal skin, which is composed of multiple
cell types and structures. Accordingly, there is a need in the art
for an implantable biocompatible matrix that can be formulated into
a sheet and cut to size and that can act as scaffolding to allow
the infiltration of a variety skin cells from adjacent tissue that
will lay down a compatible and natural replacement structure in the
shape of the implant, while absorbing the implant itself.
[0006] It is an object of the present invention to prepare a matrix
from biological tissue that has the ability to be formulated into a
variety of forms and shapes that can participate in the correction
of a variety of pathologies such as those described above.
SUMMARY OF THE INVENTION
[0007] The applicants have discovered a composition that provides a
biocompatible, non-antigenic matrix and scaffolding material for
tissue regeneration in humans. In its simplest form, the present
invention is directed to a composition comprising a matrix suitable
for implantation in humans, comprising defatted, shredded,
allogeneic human muscle tissue that has been combined with an
aqueous carrier and dried. Typically, the composition of the
present invention is sufficiently dried to so as to be able to be
handled. More typically, it is dried to a moisture content of about
3% or less.
[0008] In another aspect, the present invention is directed to a
tissue graft/implant suitable for implantation in humans comprising
a matrix of defatted, shredded, allogeneic human muscle tissue that
has been combined with an aqueous carrier and dried in a
predetermined shape. Typically, the shape of the tissue
graft/implant of the present invention includes a strip, a sheet, a
disc, a molded 3D shaped object, a plug, a sponge, and a gasket.
Typically, the composition of the present invention is sufficiently
dried to so as to be able to be handled. More typically, it is
dried to a moisture content of about 3% or less.
[0009] Any human muscle is suitable for use in the compositions or
tissue graft/implant of the present invention, including smooth
muscle and striated muscle. Preferably, the human muscle tissue
that is employed is striated muscle, such as skeletal muscle or
cardiac muscle. More preferably, the muscle tissue employed is
skeletal muscle tissue.
[0010] Any of the compositions of tissue graft/implants of the
present invention may include collagen fibers, growth factors,
antibiotics, cells, or particles such as demineralized bone matrix
(DBM), mineralized bone matrix, cortical cancellous chips (CCC),
crushed cancellous chips, tricalcium phosphate, hydroxyapatite, or
biphasic calcium phosphate (wherein the latter is the combination
of tricalcium phosphate and hydroxyapatite) or a combination
thereof.
[0011] A composition or tissue graft/implant of the present
invention that is particularly suited for treating bone trauma,
bone disease or bone defects, for providing artificial arthrodeses,
or for other treatment where new bone formation is desired, further
comprises particles of DBM, mineralized bone matrix, CCC, crushed
cancellous chips, tricalcium phosphate, hydroxyapatite, or biphasic
calcium phosphate dispersed in the matrix.
[0012] A preferred composition or tissue graft/implant of the
present invention that is particularly suited for treating bone
trauma, bone disease or bone defects, for providing artificial
arthrodeses, or for other treatment where new bone formation is
desired, further comprises particles of DBM, mineralized bone
matrix, CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate dispersed in the
matrix, in combination with a therapeutically effective amount of a
growth factor selected from the group consisting of bone
morphogenic protein (BMP), LIM mineralization protein (LMP) and
RUNX-2.
[0013] A preferred growth factor is BMP. BMP is a well-known
naturally occurring bone protein and may be obtained by extraction
from fresh bone. Methods for isolating BMP from bone are described
in U.S. Pat. No. 4,294,753 to Urist and Urist et al., PNAS 371,
1984. Often BMP is obtained by packing fresh fragments of bone into
a cavity in an implant that is designed for receiving such packing.
However, the amount of BMP in such packing is variable. Therefore,
it is preferred that the BMP be a recombinant human BMP such that
its activity is known. Recombinant human BMPs are commercially
available or prepared as described and known in the art, e.g., in
U.S. Pat. No. 5,187,076 to Wozney et al.; U.S. Pat. No. 5,366,875
to Wozney et al.; U.S. Pat. No. 4,877,864 to Wang et al.; U.S. Pat.
No. 5,108,932 to Wang et al.; U.S. Pat. No. 5,116,738 to Wang et
al.; U.S. Pat. No. 5,013,649 to Wang et al.; U.S. Pat. No.
5,106,748 to Wozney et al; and PCT Patent Nos. WO93/00432 to Wozney
et al.; WO94/2693 to Celeste et al.; and WO94/26892 to Celeste et
al., all of which are hereby incorporated herein by reference in
their entirety. Recombinant human BMP-2 (rhBMP-2), recombinant
human BMP-4 (rhBMP-4), recombinant human BMP-7 (rhBMP-7) or
heterodimers thereof are more preferred. rhBMP-2 is most
preferred.
[0014] The amino acid sequence of the RUNX-2 protein and vectors
suitable for expressing the protein are disclosed in co-pending
patent application U.S. Ser. No. 10/437,171, filed May 13, 2003,
and incorporated herein in its entirety.
[0015] Other suitable tissue growth factors for use in combination
with the composition and with the tissue graft/implant of the
present invention include transforming growth factor-.beta.
(TGF-.beta.), a fibroblast growth factor (FGF) such as FGF-1 to
FGF-12, platelet-derived growth factor (PDGF), and insulin-like
growth factor (ILGF). All of these factors are well known in the
art.
[0016] The composition and the tissue graft/implant of the present
invention comprise a matrix that is formed from the fibers of
defatted, shredded, allogeneic human muscle tissue. This fibrous
structure is advantageous because the resulting matrix that is
formed is porous and particularly well suited both for the
infiltration by colonizing cells (e.g., osteoconduction), and for
the storage and slow release of seeded cells, growth factors (as
described above), and chemotactic agents to attract desired cells
(e.g., osteoinduction).
[0017] Thus, it is also within the scope of the present invention
that the composition or implant/tissue graft of the present
invention be combined with seeded cells, a tissue growth factor, or
a chemotactic agent, or a combination thereof.
[0018] When the composition or tissue graft/implant of the present
invention is to be used as a tissue graft for skin, it is
optionally seeded with dermatocytes, more typically with
dermatocytes and melanocytes.
[0019] When the composition or tissue graft/implant of the present
invention is to be used to treat bone trauma, disease and defects,
for artificial arthrodeses and for other treatment where new bone
formation is desired, it is optionally seeded with osteogenic
cells. Preferably, the composition or tissue graft/implant of the
present invention is seeded with stem cells that will provide a
natural distribution of the native cells necessary for restoration
of the injury or defect at the site of implantation.
[0020] The tissue grafts and implants of the present invention
exhibit a great degree of tensile strength. They are readily
stitchable and retain a majority of their tensile strength even
when rehydrated. In addition, upon hydration, tissue grafts and
implants of the present invention are moldable and suitable for
filling in irregular gaps or holes in the tissue to be repaired.
Typically, the hydrated tissue is press fitted by the surgeon into
the defect or cavity to be filled.
[0021] It is also within the scope of the present invention that
the tissue graft/implant of the present invention be utilized with
a load-bearing member used in a spinal fusion. Suitable load
bearing members include hollow spinal cages, hollow dowels,
C-shaped and D-shaped spacers and other devices known in the art,
having a pocket, chamber or other mechanism for retaining the
tissue graft/implant of the present invention. Typically, the
load-bearing member has a compressive strength of at least about
1,000 N. More typically, when utilized between lumbar vertebrae,
the load-bearing member has a compressive strength of 3,000 to
11,000 N. When utilized between cervical vertebrae, the load
bearing member has a compressive strength of about 1,000 to 3,000
N. Suitable load bearing members are known in the art and described
in multiple U.S. patents, including, for example in U.S. Pat. Nos.
5,522,899, 5,785,710, 5,776,199 and 5,814,084, 6,033,438,
6,096,081, each of which is hereby incorporated by reference in its
entirety
[0022] It was unexpectedly discovered that the skeletal
muscle-based implantable devices and compositions of the present
invention have hemostatic action and cause platelet activation.
This is a particular advantage during surgical procedures wherein
patient bleeding is a well known problem.
[0023] In its second aspect, the present invention is directed to a
method for making a (muscle-based) composition or a tissue implant
suitable for treating an injury or a surgical or medical condition
in a human patient, wherein the tissue implant comprises a matrix
of allogeneic human muscle. In this embodiment, the method
comprises the steps of: [0024] i. removing the fat and soluble
proteins from allogeneic or xenogeneic mammalian muscle tissue;
[0025] ii. lyophilizing the muscle tissue from step (i); [0026]
iii. shredding the lyophilized muscle tissue; [0027] iv. mixing the
shredded muscle tissue in an aqueous carrier to form a muscle
tissue slurry having a viscosity within the range of 1 centistoke
to 20,000 centistokes; [0028] v. transferring the muscle tissue
slurry to an appropriate shaped mold; and [0029] vi. drying the
slurry in the mold to form the correspondingly shaped tissue
implant.
[0030] In the above method, the matrix of allogeneic human muscle
comprises from about 1% to about 100% of the final weight of the
composition or implant, more typically from 50% to about 99% of the
final weight of the implant, even more typically from 75% to about
99% of the final weight of the implant.
[0031] In another embodiment, the method of making a composition or
tissue implant of the present invention further comprises combining
the allogeneic human muscle with a demineralized bone matrix (DBM),
cortical cancellous chips (CCC), tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate and/or shredded
allogeneic human tendon. The addition of any of these components
increases the viscosity of the intermediate slurry. When the tissue
implant of the present invention contains DBM, mineralized bone
matrix, CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate or a combination
thereof, the resulting tissue implant is osteogenic and
particularly suited for repairing bone. The implant of this
embodiment also exhibits improved dimensional stability and ability
to hold shape during drying, rehydration and handling. In one
variation of the above embodiment, the DBM, mineralized bone
matrix, CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate or a combination
thereof are dispersed equally or randomly throughout the matrix. In
another variation, the DBM, mineralized bone matrix, CCC, crushed
cancellous chips, or a combination thereof are sandwiched between
layers of the matrix to form a laminate implant. In either of the
above referenced embodiments, the DBM, mineralized bone matrix,
CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate or a combination
thereof typically constitute from 1% to 99%, more typically 50% to
99%, most typically from 90% to 99% of the dry weight of the
composition or implant.
[0032] When the tissue implant contains tendon, it is tougher, and
stronger than the digested human muscle matrix alone and is
particularly suited as a dressing for a wound or burn that will
become infiltrated with skin cells and allow for development of a
replacement skin layer that will cover the wound or burn. The ratio
of tendon to intermediate composition ranges from 1:99 to 99:1 by
dry weight. Typically, the range is 10:90 to 90:10; more typically,
the range is 25:75 to 75:25. While the above discussion is in
relation to "tendon," which is a preferred source of collagen for
this invention, it is intended that any collagen source be used,
including fascia, ligament, or dermis.
[0033] After the mixing step, the resulting intermediate
composition (the digested allogeneic human muscle slurry) of the
present invention is optionally degassed, by pouring the slurry
into plates or tubes, and centrifuging them to eliminate any
entrapped air and produce a higher density slurry.
[0034] Alternatively, the slurry is poured into a mold for
formation of an implantable tissue matrix of any size or shape. As
noted above, the slurry can be combined with other agents, such as
DBM, CCC or a collagen (e.g., tendon, fascia) slurry before being
poured into the mold. To produce an implantable film, a thin layer
of the slurry is poured in a flat plate and the slurry is either
air dried, air dried with positive airflow, or dried in an oven,
preferably a convection oven. To produce a sponge, a gasket or an
implantable shape, the slurry (neat or amended) is poured into a
mold of the appropriate shape, frozen (to retain its size), and
lyophilized. The resulting dried implantable film or shape is then
ready for packaging and final sterilization.
[0035] Prior to implantation, the freeze dried composition, tissue
graft or implant of the present invention is removed from its
sterile packaging and rehydrated by contacting with water, saline,
blood, plasma, a buffered solution, or any other suitable liquid.
Preferably, the rehydrating liquid contains a growth factor or a
chemotactic agent as discussed above.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0036] FIG. 1 is a photograph showing the fluffy fibrous texture of
shredded, defatted allogeneic human muscle for use in making the
intermediate composition (muscle slurry) of the present
invention.
[0037] FIGS. 2A-2C are photographs of tissue implants in the form
of a sponge that were made from the muscle slurry of the present
invention.
[0038] FIGS. 3A-3B are photographs of a three-dimensional molded
tissue implant made from the muscle slurry of the present
invention. FIG. 3A. is a side view. In FIG. 3B, the implant is
rotated 90.degree. to show the hole that was molded in the
center.
[0039] FIGS. 4A and 4B are photographs of tissue implants/grafts in
the form of a thin film that were made from the muscle slurry of
the present invention. In FIG. 4A, the film was formed from the
muscle slurry without an additive. In FIG. 4B, the film was made
from a mixed slurry comprising a 50:50 ratio of muscle tissue to
tendon tissue.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The present invention has multiple embodiments. In its first
embodiment, the present invention is directed to a composition that
provides a biocompatible, non-antigenic matrix and scaffolding
material for tissue regeneration in humans. More specifically, the
present invention is directed to a composition comprising a matrix
suitable for implantation in humans, comprising defatted, shredded,
allogeneic human muscle tissue that has been combined with an
aqueous carrier and dried. Typically, the composition of the
present invention is sufficiently dried to so as to be able to be
handled. More typically, it is dried to a moisture content of about
3% or less.
[0041] To be suitable for implantation in humans, the composition
(and implants) of the present invention must be treated to remove
any antigenic proteins, which may generate a rejection of the
implant. It also must be treated to remove any bacteria and
viruses. Suitable processes for removing antigenic proteins and
sterilizing to neutralize any bacteria and viruses are known in the
art. See U.S. Pat. No. 5,846,484, entitled "Pressure flow system
and method for treating a fluid permeable workpiece such as a
bone," which issued to Scarborough, et al. on Dec. 8, 1998. In the
present case, the applicants utilized the assignees' well known
method for defatting tissue, which also has the added benefit of
removing blood, cellular debris, and soluble and antigenic
proteins, by subjecting the muscle tissue to alternating cycles of
pressure and vacuum in the sequential presence of solvents, such as
isopropyl alcohol, hydrogen peroxide and a detergent. These
assignee's processes also neutralize any bacteria and viruses.
These processes are disclosed in full detail in assignee's U.S.
Pat. No. 6,613,278, entitled "Tissue Pooling Process," which issued
to Mills et al., on Sep. 2, 2003; U.S. Pat. No. 6,482,584, entitled
"Cyclic implant perfusion cleaning and passivation process," which
issued to Mills, et al. on Nov. 19, 2002; and U.S. Pat. No.
6,652,818, entitled "Implant Sterilization Apparatus," which issued
to Mills et al., on Nov. 25, 2003, all of which are incorporated
herein by reference in their entirety.
[0042] In its second aspect, the present invention is directed to a
tissue graft/implant suitable for implantation in humans comprising
a matrix of defatted, shredded, allogeneic human muscle tissue that
has been combined with an aqueous carrier and dried in a
predetermined shape. The tissue graft/implant of the present
invention is made in various shapes including that of a strip, a
sheet, a disc, a molded 3D shaped object, a plug, a sponge, and a
gasket. A preferred shape is a sponge. Any of these objects may
include a cavity, a pouch, a hole, a post, a hook, or a suture. Any
of these objects may be made with or without the addition of
demineralized bone matrix (DBM), mineralized bone matrix, cortical
cancellous chips (CCC), crushed cancellous chips, lyophilized and
shredded muscle or collagen fibers, growth factors, antibiotics,
stem cells, or other additives.
[0043] Preferably, the human muscle tissue that is employed in the
composition and tissue graft/implant of the present invention is
striated muscle, such as skeletal muscle or cardiac muscle, more
preferably, skeletal muscle tissue.
[0044] A composition or tissue graft/implant of the present
invention that is particularly suited for treating bone trauma,
bone disease or bone defects, for providing artificial arthrodeses,
or for other treatment where new bone formation is desired, further
comprises particles of DBM, mineralized bone matrix, CCC, crushed
cancellous chips, tricalcium phosphate, hydroxyapatite, or biphasic
calcium phosphate dispersed in the matrix.
[0045] Typically, particles of DBM or CCC or both are added to the
composition or to the tissue graft/implant of the present invention
when the composition or implant is being used as a scaffold to
obtain bone regeneration or remodeling at the site of implantation.
In this embodiment, the mean size of the particles of DBM and
mineralized bone matrix are typically from 150 microns to 900
microns, more typically from 250 microns to 800 microns, most
typically from 400 to 500 microns. The CCC and crushed cancellous
chips are utilized in a larger particle size than the DBM. The mean
particle size for CCC is typically 0.5 mm to 5 mm, more typically 1
mm to 3 mm, and even more typically from 1.5 mm to 2.5 mm.
[0046] A preferred composition or tissue graft/implant of the
present invention that is particularly suited for treating bone
trauma, bone disease or bone defects, for providing artificial
arthrodeses, or for other treatment where new bone formation is
desired, further comprises particles of DBM, mineralized bone
matrix, CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate dispersed in the
matrix, in combination with a therapeutically effective amount of a
growth factor selected from the group consisting of bone
morphogenic protein (BMP), LIM mineralization protein (LMP) and
RUNX-2.
[0047] A preferred growth factor is BMP. The term BMP encompasses a
family of well-known naturally occurring proteins (BMP-2, BMP-3,
BMP-4, BMP-5, BMP-6, BMP-7, BMP-13 and BMP-14) that are involved in
skeletal formation. BMP2 or BMP-2A is a 396 amino acid (aa) dimeric
protein in human (chr 20p12) that belongs to the TGF-beta
superfamily of structurally related signaling proteins. It is
involved in cartilage and bone formation during embryogenesis, but
may have additional functions in morphogenesis as implied by its
expression in various organs and embryonic tissues. It is abundant
in bone, lung, spleen, and colon. Recombinant human BMP-2 (rhBMP-2)
consists of two 115 amino acid chains that lack the natural
N-terminus and that are bonded by a disulfide bond into a
homodimeric protein with an apparent molecular weight of 26 kDa.
The rh-BMP-2, lacking the natural N-terminus, has 15-20 times
specific activity of the wild-type BMP-2. Methods for isolating BMP
from bone are described in U.S. Pat. No. 4,294,753 to Urist and
Urist et al., PNAS 371, 1984. Often BMP is obtained by packing
fresh fragments of bone into a cavity in an implant that is
designed for receiving such packing. However, the amount of BMP in
such packing is variable. Therefore, it is preferred that the BMP
be a recombinant human BMP such that its activity is known.
Recombinant human BMPs are commercially available as described
below or prepared as described and known in the art, e.g., in U.S.
Pat. No. 5,187,076 to Wozney et al.; U.S. Pat. No. 5,366,875 to
Wozney et al.; U.S. Pat. No. 4,877,864 to Wang et al.; U.S. Pat.
No. 5,108,932 to Wang et al.; U.S. Pat. No. 5,116,738 to Wang et
al.; U.S. Pat. No. 5,013,649 to Wang et al.; U.S. Pat. No.
5,106,748 to Wozney et al; and PCT Patent Nos. WO93/00432 to Wozney
et al.; WO94/2693 to Celeste et al.; WO94/26892 to Celeste et al.,
and Hogan et al., (1996) Gene Dev., 10:1580-1594; all of which are
hereby incorporated herein by reference in their entirety.
[0048] BMP3/Osteogenin/BMP-3A is a 472aa protein in human (chr
4p14-q21), highly expressed in lung, ovary and small intestine. Its
function is involved in the cartilage and bone formation. BMP3 and
BMP2 genes map to conserved regions between human and mouse.
Sequences or methods of isolating BMP-3 are disclosed in Kawabata,
M et al. (1998) Cytokine and Growth Factor Reviews 9: 49-61;
Ebendal, T et al. (1998), J. Neurosci. Res. 51: 139-146; Reddi, A.
H (1998), Nature Biotechnology 16: 247-252; Daluiski, A et al.
(2001), Nature Genetics 27: 84; and Bahamonde, M. E et al. (2001)
Bone and Joint Surgery 83-A (suppl 1): S156, each of which is
incorporated herein by reference.
[0049] BMP-3B/GDF-10, a 478aa protein in human (Chr 10q11.22),
belongs to a group of proteins that can induce endochondral bone
formation in adult animals, it, is closely related in sequence to
BMP3 with 44% homology. The amino acid sequences of human and rat
BMP-3b precursor proteins are 83% similar, whereas the mature
proteins show 98% identity. BMP-3B is mainly expressed in femur,
brain, lung, pancreas and testis. Sequences or methods of isolating
BMP-3 are disclosed in Hino. J et al. (1996) Biochem Biophysic.
Res. Commun. 223 (2), 304-310; Cunningham, N. S. et al. (1995)
Growth Factors 12 (2), 99-109; A. H (1998), Nature Biotechnology
16: 247-252; and Daluiski, A. et al. (2001), Nature Genetics 27: 8,
each of which is incorporated herein by reference.
[0050] BMP4/BMP-2B is a 408aa protein (Chr 14q22) and vital
regulatory molecule that functions throughout development in
mesoderm induction, tooth development, limb formation, bone
induction, and fracture repair. In human it is expressed in lungs,
kidney and is secreted into the extracellular matrix. Sequences or
methods of isolating BMP-4 are disclosed in Hogan et al., (1996)
Gene Dev., 10:1580-1594; Kawabata, M et al. (1998) Cytokine and
Growth Factor Reviews 9: 49-61; Ebendal, T et al. (1998), J.
Neurosci. Res. 51: 139-146; Reddi, A. H (1998), Nature
Biotechnology 16: 247-252; Daluiski, A et al. (2001), Nature
Genetics 27: 84; Bahamonde, M. E et al. (2001) Bone and Joint
Surgery 83-A (suppl 1): S156, each of which is incorporated herein
by reference.
[0051] BMP5 is a 454aa protein mainly expressed in lungs and liver.
(Chr 6). The Bmp5 gene is expressed at the earliest stages of
skeletal development in small, local patterns that prefigure the
shapes of future skeletal elements. Based upon a high degree of
amino acid sequence homology, BMP5, BMP6, and BMP7 constitute a
subfamily within the BMPs. Sequences or methods of isolating BMP-5
are disclosed in Kawabata, M et al. (1998) Cytokine and Growth
Factor Reviews 9: 49-61, Ebendal, T et al. (1998), J. Neurosci.
Res. 51: 139-146; Reddi, A. H (1998), Nature Biotechnology 16:
247-252, each of which is incorporated herein by reference.
[0052] BMP6 or VGR1 is a 57 kD protein with 513aa in human (chr
6p24). Increased production of BMP6 is mediated by the skeletal
effects of estrogen on bone and cartilage. BMP-6 differs from other
members of the BMP family by its concentration in cartilage of the
fetus. Sequences or methods of isolating BMP-6 are disclosed in
Kawabata, M et al. (1998) Cytokine and Growth Factor Reviews 9:
49-61; Ebendal, T et al. (1998), J. Neurosci. Res. 51: 139-146;
Reddi, A. H (1998), Nature Biotechnology 16: 247-252; and Celeste,
A et al. (1990) PNAS. 87: 9843-9847, each of which is incorporated
herein by reference.
[0053] BMP7 or OP1a 431-amino acid polypeptide (chr 20) that
includes a secretory signal sequence, expressed in kidney, bladder
and brain. BMP-7 induces cartilage and bone formation. It also
plays a role in calcium regulation and bone homeostasis. Sequences
or methods of isolating BMP-7 are disclosed in Sampath, T. K et al.
(1990) JBC 265: 13198-13205, Reddi, A. H et al. (1998), Nature
Biotechnology 16: 247-252; Helder, M. N et al (1995) J. Histochem.
Cytochem 43: 1035-1044; and Godin, R. E et al. (1998) Development
125: 3473-3482, each of which is incorporated herein by
reference.
[0054] BMP13/CDMP-2/GDF-6 is a cartilage derived morphogenetic
protein (CDMP) with 436aa precursor sequence, that is cleaved to a
120aa polypeptide mature chain. Like all BMPs, it exists as
homodimer subunits linked with a disulphide bond. This protein is
predominantly expressed in long bones during human embryonic
development. Sequences or methods of isolating BMP-13 are disclosed
in Chang, S. C et al. (1994) JBC Vol. 269 (45), 28227-28234;
Paralkar V. M et al. (1998) JBC 273 (22) 13760-13767; Tomaski S M
et al. (1999) Arch Otolaryngol Head Neck Surg. 125 (8) 901-906.
[0055] BMP14/CDMP-1/GDF-5 is a 501aa precursor protein (chr
20q11.2) with a 121aa mature chain. It is predominantly expressed
in long bones during embryonic development and is involved in bone
formation. Sequences or methods of isolating BMP-14 are disclosed
in Chang, S. C et al. (1994) JBC Vol. 269 (45), 28227-28234;
Paralkar V. M et al (1998) JBC 273 (22) 13760-13767; and Tomaski S
M et al. (1999) Arch Otolaryngol Head Neck Surg. 125 (8) 901-906,
each of which is incorporated herein by reference.
[0056] Each of the above described BMP's is commercially available
from a variety of sources. Human recombinant BMP-2 is commercially
available from a plurality of sources, including Genetics
Institute, Inc., Andover, Mass., Abbott Laboratories, North Chicago
Ill., and Yamanouchi Pharmaceutical Co., Japan. Recombinant BMP-3
to rBMP-14 are commercially available from Alpha Diagnostics, San
Antonio Tex.
[0057] The preferred BMPs are recombinant human BMP-2 (rhBMP-2),
recombinant human BMP-4 (rhBMP-4), recombinant human BMP-7
(rhBMP-7) and heterodimers thereof. rhBMP-2 is most preferred.
[0058] The amino acid sequence of the RUNX-2 protein and vectors
suitable for expressing the protein are disclosed in co-pending
patent application U.S. Ser. No. 10/437,171, filed May 13, 2003,
and incorporated herein in its entirety.
[0059] Other suitable tissue growth factors for use in combination
with the composition and with the tissue graft/implant of the
present invention include transforming growth factor-.beta.
(TGF-.beta.), a fibroblast growth factor (FGF) such as FGF-1 to
FGF-12, platelet-derived growth factor (PDGF), and insulin-like
growth factor (ILGF). All of these factors are well known in the
art.
[0060] The composition and the tissue graft/implant of the present
invention comprise a matrix that is formed from the fibers of
defatted, shredded, allogeneic human muscle tissue. This fibrous
structure is advantageous because the resulting matrix that is
formed is porous and particularly well suited both for the
infiltration by colonizing cells, and for the storage and slow
release of seeded cells, tissue growth factors (as described
above), and chemotactic agents to attract desired cells.
[0061] Thus, it is also within the scope of the present invention
that the composition or implant/tissue graft of the present
invention be combined with seeded cells, a tissue growth factor, or
a chemotactic agent, or a combination thereof.
[0062] When the composition or tissue graft/implant of the present
invention is to be used as a tissue graft for skin, it is
optionally seeded with fibroblasts, more typically with
fibroblasts, and melanocytes. In this embodiment, it is preferred
that the composition or tissue graft further comprise a growth
factor suitable for inducing the growth of the fibroblasts and/or
melanocytes. Suitable growth factors include a fibroblast growth
factor (FGF), such as FGF-1 of FGF-2, epidermal growth factor,
transforming growth factor-.alpha. (TGF-.alpha.), transforming
growth factor-.beta. (TGF-.beta.), platelet derived growth factor
(PDGF) or a combination thereof. Each of these growth factors are
well known in the art and commercially available.
[0063] When the composition or tissue graft/implant of the present
invention is to be used to treat bone trauma, disease and defects,
for artificial arthrodeses and for other treatment where new bone
formation is desired, it is optionally seeded with osteogenic
cells. Preferably, the composition or tissue graft/implant of the
present invention is seeded with stem cells that will provide a
natural distribution of the native cells necessary for restoration
of the injury or defect at the site of implantation.
[0064] The implant/graft of the present invention comprising a
matrix of digested allogeneic human muscle was made in various
shapes including that of a strip, a sheet, a film, a disk, a molded
3D shaped object, a plug, a sponge, and a gasket. Any of these
objects may include a cavity, a pouch, a hole, a post, a hook, or a
suture. Any of these objects may be made with or without the
addition of DBM, CCC, lyophilized and shredded muscle tissue,
collagen fibers, growth factors, antibiotics, stem cells, or other
additives.
[0065] In making a strip, the dimensions are typically from about
10 mm to 500 mm long, by 10 mm to 200 mm wide and 1 mm to 10 mm
thick, more typically from about 15 mm to 200 mm long by 15 mm to
100 mm wide and 2 mm to 8 mm thick, even more typically from about
50 mm to 90 mm long by 15 mm to 35 mm wide and 2 mm to 5 mm thick.
The cross section of such a strip may take any shape including a
rectangle, square, triangle, other polygon, circle, half circle,
ellipse, or partial ellipse.
[0066] For a sheet in this embodiment, the dimensions are typically
from about 20 mm to 300 mm by 10 mm to 100 mm and 1 mm to 10 mm
thick, more typically from about 30 mm to 150 mm by 20 mm to 70 mm
and 1.5 mm to 8 mm thick, even more typically from about 50 mm to
100 mm by 25 mm to 50 mm and 2 mm to 5 mm thick.
[0067] For a film in this embodiment, the dimensions are typically
from about 20 mm to 300 mm by 10 mm to 100 mm and 0.1 mm to 5 mm
thick, more typically from about 30 mm to 150 mm by 20 mm to 70 mm
and 0.25 mm to 3 mm thick, even more typically from about 50 mm to
100 mm by 25 mm to 50 mm and 0.5 mm to 1 mm thick. A film is
characterized by removing most air bubbles prior to or while
molding a thin layer of material. The film shape may be flat or may
follow a 3D contoured shape. The film may be created in a single
layer or by laminating multiple layers of material.
[0068] For a disk in this embodiment, the dimensions are typically
from about 10 mm to 100 mm diameter and 1 mm to 10 mm thick, more
typically from about 30 mm to 80 mm diameter and 2 mm to 8 mm
thick, even more typically from about 55 mm to 65 mm diameter and
2.5 mm to 5 mm thick. A disk can be described as a cylinder with
nominal diameter greater than nominal height.
[0069] For a molded 3D shaped object in this embodiment, the
nominal outer body dimensions are typically up to about 100 mm by
100 mm and 25 mm thick, more typically up to about 50 mm by 70 mm
and 20 mm thick, even more typically up to about 30 mm by 50 mm and
15 mm thick. A molded 3D shape is typically defined so as to fit
into a particular anatomical feature or surgically created space,
such as a dental cavity, a drilled tunnel in a bone, or the space
between two vertebral bodies in the spine.
[0070] For a plug in this embodiment, the dimensions are typically
from about 10 mm to 100 mm diameter and 1 mm to 10 mm tall, more
typically from about 2 mm to 20 mm diameter and 5 mm to 50 mm tall,
even more typically from about 4 mm to 15 mm diameter and 7 mm to
40 mm tall. A plug may be described as a cylinder or extruded 2D
shape, such as a square, triangle, star, or polygon, with nominal
height greater than nominal diameter or characteristic width of the
2D shape.
[0071] For a sponge in this embodiment, the dimensions are
typically up to about 500 mm by 500 mm and 50 mm thick, more
typically up to about 100 mm by 100 mm and 20 mm thick, even more
typically up to about 50 mm by 50 mm and 10 mm thick.
[0072] For a gasket in this embodiment, the outside body dimensions
are typically up to about 100 mm by 100 mm and 15 mm thick, more
typically up to about 50 mm by 50 mm and 5 mm thick, even more
typically up to about 25 mm by 25 mm and 2.5 mm thick. The cross
section of such a gasket may take any shape including a rectangle,
square, triangle, other polygon, circle, half circle, ellipse, or
partial ellipse, tracing the entire periphery or some portion of
the outside body shape.
[0073] It was unexpectedly discovered that the muscle-based
implantable composition and tissue graft/implant of the present
invention have hemostatic action and cause platelet activation.
This is a particular advantage during surgical procedures wherein
patient bleeding is always a problem. Thus, the muscle-based
implantable composition and tissue graft/implant of the present
invention reduce the need for cauterization at the interface
between the patient's tissue and the implant.
[0074] The muscle-based composition and the tissue graft/implant of
the present invention comprise a matrix that is formed from the
fibers of defatted, shredded, allogeneic human muscle tissue. Due
to the fibrous nature of the muscle tissues, the matrix that is
formed is porous and particularly well suited both for the
infiltration by colonizing cells, and for the storage and slow
release of seeded cells, tissue growth factors, and chemotactic
agents that attract a desired cell.
[0075] Thus, it is also within the scope of the present invention
that the composition or implant/tissue graft of the present
invention be combined with a natural or recombinant growth factor
to stimulate tissue growth and healing, or a chemotactic agent to
attract a desired cell. It is also within the scope of the present
invention that the composition or tissue graft/implant of the
present invention be seeded with one or more cells prior to
implantation into the patient. When the composition or tissue
graft/implant of the present invention is to be used as a tissue
graft for skin, it is typically seeded with fibroblasts, preferably
with melanocytes. When the composition or tissue graft/implant of
the present invention is to be used to treat a defect or an injury
to a bone, it is seeded with osteogenic cells. Preferably, when the
composition or tissue graft/implant of the present invention is to
be used to treat any tissue defect or injury, it is seeded with
stem cells that will provide the native cells necessary for
restoration of the injury or defect.
[0076] The tissue grafts and implants of the present invention
exhibit a great degree of tensile strength. They are readily
stitchable and retain a majority of their tensile strength even
when rehydrated. In addition, upon hydration, tissue grafts and
implants of the present invention are moldable and suitable for
filling in irregular gaps or holes in the tissue to be repaired.
Typically, the hydrated tissue is press fitted by the surgeon into
the defect or cavity to be filled.
[0077] The implantable compositions and tissue grafts/implants of
the present invention are formed from an intermediate composition
comprising a muscle tissue slurry that is poured into a mold for
formation into of a composition or tissue graft/implant of any size
or shape. As noted above, the muscle tissue slurry can be combined
with other agents, such as DBM, CCC or a collagen (e.g., tendon,
fascia) slurry before being poured into the mold. To produce an
implantable film, a thin layer of the slurry is poured in a flat
plate and the slurry is either air dried, air dried with positive
airflow, or dried in an oven, preferably a convection oven. To
produce a sponge, a gasket or an implantable shape, the slurry
(neat or amended) is poured into a mold of the appropriate shape,
frozen (to retain its size), and lyophilized. The resulting dried
implantable shape is then ready for packaging and final
sterilization.
[0078] In its second aspect, the present invention is directed to a
method for making a (muscle-based) composition or a tissue implant
suitable for treating an injury or a surgical or medical condition
in a human patient, wherein the tissue implant comprises a matrix
of digested allogeneic human muscle. In this embodiment, the method
comprises the steps of: [0079] i. removing the fat and soluble
proteins from allogeneic or xenogeneic mammalian muscle tissue;
[0080] ii. lyophilizing the muscle tissue from step (i); [0081]
iii. shredding the lyophilized muscle tissue; [0082] iv. mixing the
shredded muscle tissue in an aqueous carrier to form a muscle
tissue slurry having a viscosity within the range of 1 centistoke
to 20,000 centistokes; [0083] v. transferring the muscle tissue
slurry to an appropriate shaped mold; and [0084] vi. drying the
slurry in the mold to form the correspondingly shaped tissue
implant.
[0085] In the above method, the matrix of digested allogeneic human
muscle comprises from about 1% to about 100% of the final weight of
the composition or implant, more typically from 50% to about 99% of
the final weight of the implant, even more typically from 75% to
about 99% of the final weight of the implant.
[0086] The muscle tissue slurry that is used to make the
composition and implant of the present invention is the subject of
copending parent application, U.S. Ser. No. 10/754,310, filed Jan.
9, 2004, and incorporated herein by reference in its entirety. The
muscle tissue slurry has a viscosity within the range of 1
centistoke to 20,000 centistokes when measured at 25.degree. C.
Typically, the muscle tissue slurry has a viscosity within the
range of 1 centistoke to 10,000 centistokes when measured at
25.degree. C.; more typically, the muscle tissue slurry has a
viscosity within the range of 1 centistoke to 5,000 centistokes
when measured at 25.degree. C.
[0087] The muscle tissue slurry that is used to make the
composition and/or tissue graft/implants of the present invention
is also characterizable in terms other than viscosity.
Specifically, the muscle tissue slurry is characterized instead by
the ratio of the volume of aqueous carrier (milliliters) to dry
weight of muscle (grams). The aqueous carrier is acidic, basic or
neutral. Preferably, the aqueous carrier is an aqueous acidic
solution ("an acid"). Typically, the ratio of acid (volume) to dry
weight of muscle (grams) is within the range of 100:1 to 10:1; more
typically within the range of 80:1 to 20:1; most typically within
the range of 70:1 to 30:1. The choice of the ratio of acid to
protein determines the viscosity of the slurry and the choice is
based upon the ultimate application of the slurry. The muscle
tissue slurry of the present invention was used to make the various
tissue implants and grafts (collectively "implants") disclosed
further herein.
[0088] The viscosity of the muscle tissue slurry (i.e.,
intermediate composition) ranges between slightly greater than the
viscosity of water to almost solid.
[0089] Although autogeneic muscle can be used in the intermediate
composition of the present invention, the source of the muscle is
typically donor muscle that is obtained from cadavers and thus, the
muscle is allogeneic. While the present invention is discussed
herein in terms of an allogeneic human muscle source and being used
for preparing a tissue implant for humans, any non-human mammal may
be used as the muscle donor and the resulting slurry used to
prepare a xenogeneic implant for use in a human or in another
species of mammal. Preferred xenogeneic muscle sources are porcine
and bovine. Pigs are currently being used to generate minimally
antigenic hearts suitable for implantation as living heart
transplants in humans. In the examples herein, the applicants
disclose that they ectopically implanted into a rat a tissue matrix
(in the form of a sponge) that was derived from human donor muscle
and the tissue matrix was resorbed over a period of time without
inducing an inflammatory response. This establishes the
functionality of the tissue matrix as a biocompatible resorbable
tissue scaffold even when implanted (as a xenograft) in a different
species. Thus, there is evidence that the intermediate composition
of the present invention would produce an acceptable tissue matrix
even when made from xenograft muscle tissue.
[0090] In a preferred embodiment of the present invention, the
muscle tissue is defatted prior to or after being shredded.
Preferably, it is defatted prior to being shredded. In this
embodiment, the donor muscle is cut into chunks of sufficiently
small size (e.g., 20 mm.times.20 mm) to allow the tissue to be
easily defatted. Suitable methods for defatting tissue are well
known in the art. Typically, this involves treating the tissue with
a fat dissolving substance such as 60% to 90% alcohol in water. See
U.S. Pat. No. 5,846,484, entitled "Pressure flow system and method
for treating a fluid permeable workpiece such as a bone," which
issued to Scarborough, et al. on Dec. 8, 1998. In the present case,
the applicants utilized the assignees' well known method for
defatting tissue, which also has the added benefit of removing
blood, cellular debris, and soluble and antigenic proteins, by
subjecting the muscle tissue to alternating cycles of pressure and
vacuum in the sequential presence of solvents, such as isopropyl
alcohol, hydrogen peroxide and a detergent. These methods are
disclosed in full detail in assignee's U.S. Pat. No. 6,613,278,
entitled "Tissue Pooling Process," which issued to Mills et al., on
Sep. 2, 2003; U.S. Pat. No. 6,482,584, entitled "Cyclic implant
perfusion cleaning and passivation process," which issued to Mills,
et al. on Nov. 19, 2002; and U.S. Pat. No. 6,652,818, entitled
"Implant Sterilization Apparatus," which issued to Mills et al., on
Nov. 25, 2003, all of which are incorporated herein by reference in
their entirety.
[0091] In a more preferred embodiment, the defatted allogeneic
human muscle tissue was dried, more preferably by lyophilization,
to facilitate further processing, such as shredding. The
lyophilization process need not remove all of the water. While the
water content of the chopped allogeneic muscle can vary, it is
typically dried to about 3% moisture content by weight. It is
especially preferred that the allogeneic human muscle tissue be
defatted prior to lyophilization.
[0092] The defatted and dried muscle tissue was shredded to a
coarse fiber. Shredding is accomplished by any commercial shredder.
Suitable shredders include coffee grinders, food processors, and
the like.
[0093] The shredded muscle tissue was mixed vigorously with a
biocompatible acid to produce the muscle slurry that is the
intermediate composition of the present invention. On a small
scale, mixing was accomplished with a hand-held food processor.
Mixing takes from 15 seconds to over two minutes and is dependent
upon the amount of shredded protein and the volume of acid. Mixing
should continue until the slurry has uniform consistency. After
mixing, the slurry is preferably degassed. Degassing was
accomplished by centrifugation, or possibly vacuum
centrifugation.
[0094] The biocompatible acid is either a biocompatible organic
acid or a biocompatible inorganic acid. Preferably, a suitable
biocompatible acid is selected from the group consisting of acetic
acid, citric acid, formic acid, hydrochloric acid, lactic acid,
phosphoric acid, phosphorus acid and sulfuric acid. More
preferably, the biocompatible acid is an organic acid; most
preferably the organic acid is acetic acid. The function of the
acid is to partially digest the muscle tissue.
[0095] The intermediate composition employed in the present
invention is implantable in liquid form, such as by injecting into
the patient at a site in need of restoration. In another
embodiment, it is dried to a predetermined shape to prepare a
variety of tissue implants.
[0096] Thus, the present invention is directed to a tissue graft of
implant suitable for treating an injury or a surgical or medical
condition in a human patient, wherein the tissue implant comprises
a matrix of digested allogeneic human muscle. In this embodiment,
the matrix of digested allogeneic human muscle comprises from about
1% to about 100% of the dry weight of the implant, more typically
from 15% to about 95% of the dry weight of the implant, even more
typically from 25% to about 85% of the dry weight of the
implant.
[0097] In another embodiment, the method of making a composition or
tissue implant of the present invention further comprises combining
the allogeneic human muscle with a demineralized bone matrix (DBM),
mineralized bone matrix, cortical cancellous chips (CCC), crushed
cancellous chips, tricalcium phosphate, hydroxyapatite, or biphasic
calcium phosphate and/or shredded allogeneic human tendon. The
addition of any of these components increases the viscosity of the
intermediate slurry. When the tissue implant of the present
invention contains DBM, mineralized bone matrix, CCC, crushed
cancellous chips, tricalcium phosphate, hydroxyapatite, or biphasic
calcium phosphate or a combination thereof, the resulting tissue
implant is osteogenic and particularly suited for repairing bone.
The implant of this embodiment also exhibits improved dimensional
stability and ability to hold shape during drying, rehydration and
handling. In one variation of the above embodiment, the DBM,
mineralized bone matrix, CCC, crushed cancellous chips, tricalcium
phosphate, hydroxyapatite, or biphasic calcium phosphate or a
combination thereof are dispersed equally or randomly throughout
the matrix. In another variation, the DBM, mineralized bone matrix,
CCC, crushed cancellous chips, or both are sandwiched between
layers of the matrix to form a laminate implant. In either of the
above referenced embodiments, the DBM, mineralized bone matrix,
CCC, crushed cancellous chips, tricalcium phosphate,
hydroxyapatite, or biphasic calcium phosphate or a combination
thereof typically constitute from 1% to 99%, more typically from
50% to 99%, most typically from 90% to 99% of the dry weight of the
composition or implant.
[0098] When the tissue implant contains tendon, it is tougher and
stronger than the digested human muscle matrix alone and is
particularly suited as a dressing for a wound or burn that will
become infiltrated with skin cells and allow for development of a
replacement skin layer that will cover the wound or burn. The ratio
of tendon to intermediate composition ranges from 1:99 to 99:1 by
dry weight. Typically, the range is 10:90 to 90:10; more typically,
the range is 25:75 to 75:25. While the above discussion is in
relation to "tendon," which is a preferred source of collagen for
this invention, it is intended that any collagen source be used,
including tendon, fascia and dermis.
[0099] After the mixing step, the resulting intermediate
composition (the digested allogeneic human muscle slurry) of the
present invention is optionally degassed, by pouring the slurry
into plates or tubes, and centrifuging them to eliminate any
entrapped air and produce a higher density slurry.
[0100] Alternatively, the slurry is poured into a mold for
formation of an implantable tissue matrix of any size or shape. As
noted above, the slurry can be combined with other agents, such as
DBM, CCC or a collagen (e.g., tendon, fascia) slurry before being
poured into the mold. To produce an implantable film, a thin layer
of the slurry is poured in a flat plate and the slurry is either
air dried, air dried with positive airflow, or dried in an oven,
preferably a convection oven. To produce a sponge, a gasket or an
implantable shape, the slurry (neat or amended) is poured into a
mold of the appropriate shape, frozen (to retain its size), and
lyophilized. The resulting dried implantable film or shape is then
ready for packaging and final sterilization.
[0101] Prior to implantation, the freeze dried composition, tissue
graft or implant of the present invention is removed from its
sterile packaging and rehydrated by contacting them with water,
saline, blood, plasma, a buffered solution, or any other suitable
liquid. Preferably, the rehydrating liquid contains a growth factor
or a chemotactic agent as discussed above.
[0102] In a pilot study, prototype implants were resorbed into an
ectopic site in an athymic nude rat model, without any signs of an
inflammatory response. Specifically, an implant of Example 2,
containing 20% DBM was implanted in abdominal muscle pouches of
athymic nude rats using a modified Urist model. Urist, M. R.,
"Bone: Formation by Autoinduction," Science 160:893-894 (1965). The
explants were retrieved four weeks later, processed, and evaluated
histologically for evidence of new bone formation. The control
implants containing only the sponge carrier were resorbed without
evidence of inflammation. More significantly, the implants
containing DBM demonstrated signs of new bone formation
(endochondral ossification). Hence, the muscle tissue matrix of the
present invention, under the influence of DBM, provided scaffolding
for colonization by native restorative cells and the laying down of
new bone.
[0103] Alternatively, the slurry is poured into a mold for
formation of an implantable tissue matrix of any size or shape. As
noted above, the slurry can be combined with other agents, such as
DBM, mineralized bone matrix, CCC, crushed cancellous chips, or a
collagen (e.g., tendon, fascia, or dermis) slurry before being
poured into the mold. To produce an implantable film, a thin layer
of the slurry is poured in a flat plate and the slurry is either
air dried, air dried with positive airflow, or dried in an oven,
preferably a convection oven. To produce a sponge, a gasket or an
implantable shape, the slurry (neat or amended) is poured into a
mold of the appropriate shape, frozen (to retain its size), and
lyophilized. The resulting dried implantable film or shape is then
ready for packaging and final sterilization.
[0104] Several parameters are controlled during the molding process
which impact the shape, composition, and material properties of the
finished grafts. Shrinkage of the material during drying is noted,
especially as characteristic thickness and bulk of the implant
increase. Shrinkage results in changes in shape, density,
uniformity, thickness, appearance, and residual stresses of the
implants. Shrinkage and its effects can be controlled and
manipulated by careful control of parameters including drying time,
thickness of implant sections, shape of implant, coring or
segmenting of thick sections, and shape and configuration of molds.
Other process parameters directly affecting the finished product
include order of process steps, spatial orientation of the graft
during processing, and method of application of the slurry into the
molds. For example, freezing before drying creates a thicker sponge
implant with porous structure, where drying without freezing
produces a compressed and much thinner film from a similar amount
of graft material. Gravitational effects can produce grafts with
material either concentrated in a particular area or spread more
evenly throughout the mold. Thus, rotational molding can produce
thin film grafts wrapped evenly around complex internal or external
3D molds, nominal drying under constant gravitational force can
produce grafts which are slightly thicker at the bottom due to slow
flowing of the slurry during drying, and drying in a vacuum
centrifuge can produce grafts with material strongly concentrated
in the direction of the centrifugal forces. Finally, different
graft properties can be created by introducing the slurry to a
given mold all at once in order to form a uniform implant, or by
introducing it in layers or stages and allowing for drying or
adding additional materials between layers to produce a layered
composite or fiberglass like structure.
[0105] Thus, in another embodiment, the present invention is
directed to a method for making the intermediate composition
(muscle tissue slurry) of the present invention comprising the
steps of: [0106] i. removing the fat and soluble proteins from
allogeneic or xenogeneic mammalian muscle tissue; [0107] ii.
lyophilizing the muscle tissue from step (i); [0108] iii. shredding
the lyophilized muscle tissue; and [0109] iv. mixing the shredded
muscle tissue in an aqueous carrier to form a muscle tissue slurry
having a viscosity within the range of 1 centistoke to 20,000
centistokes.
[0110] The tendon that is used in the tissue implants of the
present invention is processed the same as the allogeneic human
muscle. It is chopped into pieces, defatted, freeze dried
(lyophilized), shredded into a coarse fiber, and acid digested to
provide a viscous tendon digestate that is suitable for combining
with the acid digested allogeneic muscle (intermediate composition)
of the present invention. The ratio of tendon digestate to
intermediate composition ranges from 1:99 to 99:1. Typically, the
range is 10:90 to 90:10; more typically, the range is 25:75 to
75:25. While the above discussion is in relation to "tendon," which
is a preferred source of collagen for this invention, it is
intended that any collagen source be used, including fascia. The
collagen source is xenogeneic or allogeneic. Preferably, it is
allogeneic.
EXAMPLE 1
Preparation of a Slurry of Allogeneic Human Muscle
[0111] Skeletal muscle was removed from a donor cadaver and cut
into chunks (20 mm.times.20 mm). The chunks of skeletal muscle were
defatted, deantigenized and soluble protein was removed by
subjecting the muscle tissue to cyclically alternating pressure and
vacuum in the sequential presence of the isopropyl alcohol,
hydrogen peroxide and a detergent. The method is fully described in
assignee's U.S. Pat. No. 6,613,278, entitled "Tissue Pooling
Process," which issued to Mills et al., on Sep. 2, 2003; U.S. Pat.
No. 6,482,584, entitled "Cyclic implant perfusion cleaning and
passivation process," which issued to Mills, et al. on Nov. 19,
2002; and U.S. Pat. No. 6,652,818, entitled "Implant Sterilization
Apparatus," which issued to Mills et al., on Nov. 25, 2003, all of
which are incorporated herein by reference in their entirety. After
the above cleansing process, the defatted and non-antigenic muscle
tissue was lyophilized to remove the moisture. The lyophilization
procedure was a standard 17-hour program. The dried chunks were
shredded and chopped in a grinder. The processing time varied from
5 seconds to 2 minutes depending upon the amount of lyophilized
muscle being processed, dryness and starting size. At this stage,
the shredded muscle tissue looks like fluffed fibers. The shredded
muscle tissue were weighed and then combined with a predetermined
amount of 10% or 20% aqueous acetic acid according to the table
below: TABLE-US-00001 TABLE 1 Ratios of Acetic Acid (ml) to weight
of dry muscle (g) Muscle (g) Muscle (g) Muscle (g) Acid Acid:muscle
Acid:muscle Acid:muscle 10% acetic acid 0.5 g 0.75 g 1 g 46:1 34:1
22:1 20% acetic acid 0.5 g 0.75 g 1 g 46:1 34:1 22:1
[0112] The combined acid solution and muscle tissue were mixed with
a high speed mixer until a uniform gel (i.e., slurry) was formed.
Mixing took between 15 seconds to more than 2 minutes depending
upon the acid concentration, amount of muscle tissue and volume of
acid solution.
[0113] The above described slurry was used alone or combined with
another component to make a tissue implant of the present
invention. The lower viscosity (more dilute) slurries were
preferred when making pourable/flowable films. The lower to
intermediate viscosity slurries were more desirable when being
combined with DBM or CCC or tendon, each of which thickened the
slurry.
EXAMPLE 2
Formulation Comprising the Slurry of Example 1 and DBM
[0114] The slurry of Example 1 was degassed via centrifugation.
After the degassing, the slurry was transferred to a mixing bowl.
DBM was added and mixed to uniformity at ratios of 0.1%, 1%, 5%,
10%, 20% and 30% (DBM weight to slurry weight).
[0115] A portion of each of the above slurries containing the DBM
were poured into molds and allowed to dry at room temperature with
positive airflow. The dried products produced a series of muscle
based tissue implants in the form of films with the differing
amounts of DBM embedded therein.
[0116] A second portion of the slurries from above was poured into
molds, frozen, and lyophilized. The dried products produced a
series of sponge-like tissue implants having increasing amounts of
DBM therein.
EXAMPLE 3
Formulation Comprising the Slurry of Example 1 and CCC
[0117] The slurry of Example 1 was degassed via centrifugation.
After the degassing, the slurry was transferred to a mixing bowl.
CCC was added and mixed until uniform at a ratio of 50% (CCC volume
to slurry volume). The slurry containing CCC was poured into a
mold, frozen, and lyophilized. This dried product produced a tissue
implant in the form of a sponge with CCC imbedded therein.
[0118] The degassed slurry from above was transferred to a mixing
bowl, where 60% CCC (CCC volume to slurry volume) and 10% DBM (DBM
volume to slurry volume) were added to the degassed slurry with
mixing. Mixing continued until a uniform appearing mixture was
formed. The slurry was poured into a cube shaped mold, frozen, and
lyophilized. This dried product produced a cube shaped tissue
implant having CCC and DBM imbedded therein.
EXAMPLE 4
Formulation Comprising the Slurry of Example 1 and a Slurry of
Tendon
[0119] The slurry from Example 1 was degassed via centrifugation.
After degassing, the slurry was transferred to a series of three
(3) mixing bowls. Using allogeneic human tendon, a tendon slurry
was made in the exact same manner as the muscle slurry. After the
solubilized tendon slurry was degassed, a portion of it was added
to each of the three (3) mixing bowls. The ratio of muscle to
tendon in each of the three (3) bowls was 25:75, 50:50 and 75:25
(muscle volume:tendon volume), respectively. A portion of the
tendon/skeletal slurry mixtures were poured into flat molds and
allowed to dry at room temperature with positive airflow. Once
dried, the three dried materials each produced a tissue implant in
the form of a film.
[0120] Three identical tendon/skeletal muscle slurries were poured
into molds, frozen, and lyophilized. The lyophilized frozen
slurries produced tendon/skeletal muscle based implants in the form
of a sponge.
EXAMPLE 5
Preparation of an Implantable Strip
[0121] A series of implantable strips were created from the films
produced in Examples 1, 2, 3, and 4. Specifically, the dried films
were cut into implantable strips that were 0.5 mm thick, 20 mm
wide, and 70 mm long.
EXAMPLE 6
Preparation of an Implantable Sheet
[0122] An implantable sheet was created from the films produced in
Example 1, 2, 3, and 4. The dried films either were left in the
final shape of their molds, or were cut into sheets that were 0.5
mm thick, 70 mm wide and 70 mm long. Sheets were made that were
also three dimensional, such as convex and concave spherical
bodies. These implantable three dimensional films were made via
rotational molding, vacuum centrifugation drying, room temperature
drying, or room temperature drying with forced air, to a thin film
in a three dimensional mold. Thicker sheets were produced in both
two dimensional and three dimensional forms by successive
reapplication of muscle tissue slurry, after drying of the
preceding layer. In some cases DBM was added to the implant between
this application of successive layers, to create a laminated tissue
implant impregnated with DBM.
EXAMPLE 7
Preparation of an Implantable Sponge
[0123] A series of implantable sponges were made as specified in
Examples 1, 2, 3, and 4 above. Using appropriate molds, the sponges
were made in a square, circular, or hexagonal forms. The average
thickness was 5 mm. The squares were as large as 50 mm by 50 mm.
The circles had diameters as large as 90 mm. The hexagons were 40
mm per side.
EXAMPLE 8
Preparation of an Implantable Gasket
[0124] Using the slurry of Example 1, a gasket was made as a
thinner version (2.5 mm) of the sponge in Example 7. The gasket was
used in conjunction with a bone plate to tie together two model
vertebral bodies in the laboratory.
EXAMPLE 9
Preparation of a Graftable Wound Dressing
[0125] The films from Example 4 were suitable for use as a wound
dressing/skin graft. The films are hydrated before use with sterile
saline until soft and pliable and then applied to the wound. Any
excess film overhanging the wound is cut off with surgical
scissors.
EXAMPLE 10
Biological Activity of an Ectopically Implanted Sponge in a Rat
[0126] The implant of Example 2, containing 20% DBM, and measuring
about 5 mm diameter by about 25 mm length, was implanted in
abdominal muscle pouches of athymic nude rats using a modified
Urist model. Urist, M. R., "Bone: Formation by Autoinduction,"
Science 160:893-894 (1965). Explants were retrieved four weeks
later, processed, and evaluated histologically for evidence of new
bone formation. Whereas control implants containing only the sponge
carrier were resorbed without evidence of inflammation, those
containing DBM demonstrated signs of new bone formation
(endochondral ossification).
EXAMPLE 11
Composite Implants for Hip Replacement Applications
[0127] An implant following the method of Example 2, containing 20%
DBM, was poured into molds shaped to match an existing metal hip
replacement stem graft and an acetabular cup. The hip stem graft
was structurally enhanced with pieces of bone and bone fragments
placed into the material during molding. The acetabular cup graft
featured a two part construction, wherein a sponge implant section
was formed inside of and bonded to an earlier formed, shaped three
dimensional thin film mold. No attempt was made to quantify the
failure load or strength of the implants, but the proof of concept
objective was satisfied as the stem and cup implants both withstood
normal handling and manipulation.
EXAMPLE 12
Meniscus Replacement Implant
[0128] An implant following the method of Example 2, containing no
DBM or DBM added only to specific regions of the graft, is proposed
as meniscus replacement graft. The combination of precisely
controlled shaping and contouring with appropriate load bearing
capacity and appropriate remodeling response with or without the
application of specific growth factors to various parts of the
graft answers a unique need in the art.
EXAMPLE 13
Precise Anatomically Matched Implants
[0129] An implant following the method of Example 2, can be formed
in a mold created by known methods from digitized data of an area
in need of treatment. Methods of mold creation are known in the
art, and can include x-ray, ultrasound, or cat-scan imaging data
translated to a computer aided design (CAD) or computer aided
manufacturing (CAM) or computer numerical controlled (CNC)
machining center. The implants made from these methods could be
used to treat conditions where exact matching of the anatomical
structure is critical and where a biocompatible allograft implant
is beneficial. Applications can include facial reconstruction,
general orthopedic defects and bone segment replacements, and
vertebral body replacements.
EXAMPLE 14
Flowable Implants
[0130] An implant following the method of Example 2 was transferred
to a syringe after drying and full rehydration in sterile saline
solution. The rehydrated implant was found to be flowable under the
forces of the syringe, and could be placed in rows or used to fill
cavities similar to those found commonly in surgical sites. A
second flowable implant was created by transferring the slurry of
Example 1 directly into a syringe and then using the syringe to
flow the graft material into rows or into cavities similar to those
found commonly in surgical sites.
EXAMPLE 15
Moldable Implants
[0131] An implant following the method of Example 2 was partially
rehydrated with sterile saline solution after drying. The implant
was placed into a cavity and molded to the shape of the cavity
under manual manipulation. The implant molded to the shape of the
cavity and then retained that shape under minimal forces including
gravity and light rinsing.
* * * * *