U.S. patent application number 13/875043 was filed with the patent office on 2013-10-10 for compositions for regenerating defective or absent myocardium.
The applicant listed for this patent is Robert G. Matheny. Invention is credited to Robert G. Matheny.
Application Number | 20130266547 13/875043 |
Document ID | / |
Family ID | 37661866 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130266547 |
Kind Code |
A1 |
Matheny; Robert G. |
October 10, 2013 |
Compositions for Regenerating Defective or Absent Myocardium
Abstract
Compositions of the invention for regenerating defective or
absent myocardium comprise an emulsified or injectable
extracellular matrix composition. The composition may also include
an extracellular matrix scaffold component of any formulation, and
further include added cells, proteins, or other components to
optimize the regenerative process and restore cardiac function.
Inventors: |
Matheny; Robert G.;
(Norcross, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Matheny; Robert G. |
Norcross |
GA |
US |
|
|
Family ID: |
37661866 |
Appl. No.: |
13/875043 |
Filed: |
May 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11182551 |
Jul 15, 2005 |
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13875043 |
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Current U.S.
Class: |
424/93.7 |
Current CPC
Class: |
A61K 38/39 20130101;
A61K 48/00 20130101; A61K 38/1825 20130101; A61L 2300/45 20130101;
A61K 31/7088 20130101; A61K 38/1841 20130101; A61L 27/227 20130101;
A61L 2300/64 20130101; A61L 27/3873 20130101; A61L 27/3687
20130101; A61K 35/407 20130101; A61K 35/34 20130101; A61K 31/726
20130101; A61L 27/3629 20130101; A61L 27/3683 20130101; A61L 27/40
20130101; A61K 35/50 20130101; A61K 35/37 20130101; A61L 27/58
20130101; A61L 2300/426 20130101; A61K 9/0019 20130101; A61L 27/54
20130101; A61L 27/3633 20130101; A61K 35/22 20130101; A61K 35/545
20130101; A61L 27/3834 20130101; A61K 38/1741 20130101; A61L
2300/412 20130101; A61L 27/367 20130101; A61K 35/38 20130101; A61L
2400/06 20130101; A61L 2430/20 20130101; A61L 2430/30 20130101;
A61L 2300/414 20130101 |
Class at
Publication: |
424/93.7 |
International
Class: |
A61K 35/34 20060101
A61K035/34 |
Claims
1. An injectable composition for inducing cell differentiation into
cardiomyocytes comprising decellularized cardiac tissue and a
supplemental bioactive agent component, said bioactive agent
component comprising a myofibroblast.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional application of U.S.
application Ser. No. 11/182,551, filed on Jul. 15, 2005.
FIELD OF THE INVENTION
[0002] The invention relates to tissue engineering generally, and
more specifically to compositions and methods for regenerating
defective or absent myocardium.
BACKGROUND OF THE INVENTION
[0003] Heart failure occurs in nearly 5 million people a year in
the U.S. alone at a combined cost of about $40 billion annually for
hospitalization and treatment of these patients. The results of all
the effort and cost are disappointing with a 75% five year
mortality rate for the heart failure victims. Treatments for
chronic heart failure include medical management with
pharmaceutical drugs, diet and exercise, transplantation for a few
lucky recipients, and mechanical assist devices, which are costly
and risk failure and infection. Thus the landscape for cardiac
treatment is turning in recent years to transplantation of tissue
or cells.
[0004] Medical researchers have transplanted human hematopoetic
stem cells, mesenchymal stem cells, endothelial precursor cells,
cardiac stem cells, and skeletal myoblasts or bone marrow cells to
the myocardium, with however little or mixed success in
satisfactory regeneration of the myocardium. Another protocol
involved injecting transforming growth factor beta preprogrammed
bone marrow stem cells to the myocardium, with greater success than
transplantation of bone marrow stem cells alone, but without
generation of contractile myocardium.
[0005] After myocardial infarction, injured cardiomyocytes are
replaced by fibrotic tissue promoting the development of heart
failure. On the basis that embryonic stem cells may be directed to
differentiate into true cardiomyocytes, transplantation of
embryonic stem cells to a site of myocardial infarction may yield
success in myocardial tissue regeneration, though the experiments
have not yet so proven. For a related challenge, to induce
angiogenesis in ischemic myocardial tissue, transplanting
endothelial progenitor cells, with or without angiogenic protein
factors has been proposed to generate capillary blood vessels at
the site of ischemia in the myocardium. As yet, the experiments to
prove these theories have not worked sufficiently to be attempted
in humans.
[0006] Meanwhile, typical structural abnormalities or damage to the
heart that would lend itself to tissue regenerative therapies, were
they available, include atrial septal defects, ventricular septal
defects, right ventricular out flow stenosis, ventricular
aneurysms, ventricular infarcts, ischemia in the myocardium,
infarcted myocardium, conduction defects, conditions of aneurysmic
myocardium, ruptured myocardium, and congenitally defective
myocardium, and these defective conditions remain untreated in
humans by any current tissue regenerative techniques.
[0007] Although tissue regeneration has been accomplished by
transplantation in mammalian tissues such as the endocranium, the
esophagus, blood vessels, lower urinary tract structures, and
musculotendinous tissues, heart tissue regeneration by foreign
tissue explant has remained a challenge. Recently, myocardium has
been regenerated using xenogenic extracellular matrix patches in
pigs and dogs, and the contractility achieved was at 90% of
normal.
[0008] It would be beneficial for treatment of heart failure in
humans to develop myocardium regenerative strategies using matrices
and additives for optimizing the potential results. One problem
exists in the preparation of extracellular scaffolds in that they
must be non-immunogenic and thus acellular before implantation.
Getting rid of the cells in the matrix may also inadvertently strip
the scaffold of key bioactive proteins. In order to perform
procedures to regenerate human myocardium with fidelity,
compositions that mimic the function of extracellular matrices are
provided below.
[0009] No experimentation has been conducted to date on
regenerating mammalian myocardium using an emulsified or injectable
extracellular matrix formulation. The only known experimental use
of extracellular emulsions for tissue regeneration have been with
gastroesophageal repair to prevent reflux and urinary bladder
sphincter repair. Both of these experiments were conducted in
non-human animals. Some veterinary use of extracellular matrix
emulsions have been reported, but none of those uses were for the
repair of myocardium. The disadvantage of using intact,
non-emulsified extracellular matrix compositions such as patches or
strips is that placement of the material requires open surgery,
with its coordinate risk of infection, challenge of access to the
site, and longer recovery for the patient post-procedure.
[0010] The present invention pioneers compositions and alternatives
to prior art solutions for tissue regeneration to provide a
biomedical composition (and methods using the composition) for
regenerating defective or absent myocardium, particularly for use
in humans.
SUMMARY OF THE INVENTION
[0011] An object of the invention is to provide a composition for
regenerating defective or absent myocardium and restoring cardiac
function.
[0012] Accordingly, a composition for regenerating defective or
absent myocardium and restoring cardiac function comprising an
emulsified or injectable extracellular matrix composition from a
mammalian or synthetic source is provided.
[0013] Also, a composition for regenerating defective or absent
myocardium and restoring cardiac function is provided comprising an
extracellular matrix derived from a mammalian or synthetic source,
said composition further comprising an additional component
selected from the group of: a) a cell, b) a peptide, polypeptide,
or protein, c) a vector having a DNA capable of targeted expression
of a selected gene, and d) a nutrient, a sugar, a fat, a lipid, an
amino acid, a nucleic acid, a ribo-nucleic acid, an organic
molecule, an inorganic molecule, a small molecule, a drug, or a
bioactive molecule.
[0014] Also provided is a composition for regenerating defective or
absent myocardium and restoring cardiac function comprising at
least a portion of an extracellular matrix scaffold derived from a
mammalian source and also comprising an additional component
selected from the groups consisting of: a) a plurality of synthetic
extracellular matrix-like scaffold-forming molecules, b) a cell, c)
a peptide, polypeptide, or protein, and d) a vector having a DNA
capable of targeted expression of a selected gene, and e) a
nutrient, a sugar, a fat, a lipid, an amino acid, a nucleic acid, a
ribo-nucleic acid, an organic molecule, an inorganic molecule, a
small molecule, a drug, or a bioactive molecule.
[0015] The invention further provides a method of regenerating
defective myocardium and restoring cardiac function, comprising
contacting said defective myocardium with a composition of the
invention in an amount effective to regenerate the myocardium and
restore cardiac function.
[0016] The invention also provides a method of inducing
angiogenesis in myocardium at a site of ischemia, comprising
contacting said ischemic myocardium with a composition of the
invention in an amount effective to induce angiogenesis in the
myocardium at the site of ischemia.
[0017] Further embodiments of the invention are described
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 depicts cell-ECM interaction through the matrix
proteoglycans, glycoaminoglycans and growth factors.
[0019] FIG. 2 depicts cell-cell adhesions, and cell-matrix
adhesions through specific structural and functional molecules of
the ECM.
[0020] FIG. 3 depicts a model of matrix scaffold structure
including common collagen, proteoglycans, and glycoproteins.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The invention is a composition that regenerates defective or
absent myocardium and restores cardiac function. For this purpose,
an emulsified or injectable extracellular matrix composition can be
derived from a mammalian or synthetic source. The composition can
further include added cells or protein or both. An extracellular
matrix composition of any formulation can include also an
additional component such as: a) a cell, b) a peptide, polypeptide,
or protein, or c) a vector expressing a DNA of a bioactive
molecule, and d) other additives like nutrients or drug molecules.
One additional component can be used in the composition or several.
The composition can be placed in contact with the defective or
absent myocardium, resulting in myocardial tissue regeneration and
restoration of contractility, conductivity, or function to the
heart muscle. The invention appreciates the importance of the
presence of some amount and form of an extracellular matrix, or
extracellular matrix-like scaffold, as a framework for the
essential activities of cell-cell, matrix-cell, protein-cell, and
protein-protein interactions that form the dynamic tissue
regenerative process in vivo, potentially optimized by the presence
of added cells, proteins, or other bioactive components.
[0022] A composition to accomplish regeneration of myocardium needs
to induce complex dynamic interactions and activities at the site
of defect. The present invention provides a composition that
creates an environment in vivo to allow these processes to occur.
The processes needed to regenerate myocardium include specific
phenotypic changes in stem cells that are recruited to the
defective site, establishment of cell-cell connections,
establishment of vascular supply at the site, beginning of normal
tissue specific metabolism, limiting new growth once new tissue is
made, coupling electric conduction from new cells to existing cells
and pathways, and establishment of cell-extracellular matrix
connections by way of cell adhesions to the matrix proteins.
[0023] The expectations for the extracellular matrix scaffold are
that it will organize the cells into tissues, both by recruiting
endogenous cells and using cells that have been provided as
additional components in the composition. The extracellular matrix
scaffold then coordinates the function of the newly recruited or
added cells, allowing also for cell migration within the matrix.
The matrix allows and provides for normal metabolism to the cells
once the vascular supply delivering nutrients to the cells is
established. Additionally, signal transduction pathways for growth,
differentiation, proliferation and gene expression are
established.
[0024] The extracellular matrix of myocardium is complex. There is
a three-dimensional architecture established with proteoglycan
molecules, with available cytokines in the microenvironment. Cell
movement occurs using focal adhesions, and eventually permanent
cell adhesions occur called hemidesmosomes. Environmental signals
are transmitted, including specific cell signals from growth
factors on cell surfaces and disposed within the matrix framework
as well. The matrix itself has structural components and functional
components and the line between the two sometimes blurs because
some of the moieties of structural components signal and trigger
protein activation, and activation of nearby cells. See FIG. 1 for
an illustration of signaling, FIG. 2 for depiction of cell-cell,
protein-cell, and matrix-cell interactions, and FIG. 3 for a
diagrammatic view of three-dimensional ECM scaffold.
[0025] There has been much research recently to elucidate the
properties and function of the extracellular matrix: its protein
make-up, and its role in the body. The extracellular matrix (ECM)
is a scaffold matrix of polymerized "structural" proteins that fit
into three groups: collagens, glycoproteins, and proteoglycans
(which have glycosaminoglycan repeats throughout). These molecules
actually polymerize to form the scaffold or matrix of proteins that
exists in dynamic interaction with cells, and closely placed
functional proteins (either on the cells, or bound to a structural
protein).
[0026] Thus, the extracellular matrix also includes within its
matrix scaffold "functional" proteins that interact with the
structural proteins and with migrating or recruited cells,
particularly stem cells in tissue regeneration. The matrix
functional proteins also interact with protein expressing cells
during the life and maintenance of the matrix scaffold itself as it
rebuilds and maintains its components. Note that some proteins fall
into both a structural protein classification and a functional
protein classification, depending on the protein's configuration
and placement in the whole matrix.
[0027] The extracellular matrix of myocardium is made up of
collagen types I (which is predominant), III, IV, V, and VI,
combined which are 92% of the dry weight of the matrix.
Glycosaminoglycans (GAGs) include chondroitin sulfate A and B,
heparan, heparin, and hyaluronic acid. Glycoproteins such as
fibronectin and entactin, proteoglycans such as decorin and
perlecan, and growth factors such as transforming growth factor
beta (TGF-beta), fibroblast growth factor-2 (FGF-2) and vascular
endothelial growth factor (VEGF), are key players in the activity
of a myocardium regenerating matrix. Furthermore, the precise
chemical constitution of the matrix appears to play a role in its
function, including for example what collagen type is prevalent in
the matrix, the pore size established by the matrix scaffold, the
forces transmitted to adhesion molecules and mechanoreceptors in
the cell membranes of cells at the matrix, and the forces directed
from the three-dimensional environment (for example the gene
expression in the three-dimensional matrix scaffold environment is
very different than in a monolayer environment). Thus, the outcome
of any tissue regenerative processes is determined by the
structural and functional components of the matrix scaffold that
form the basis of the regenerative process.
[0028] More specifically, when in early regenerative processes,
circulating cells or added cells are directed, initial temporary
cell adhesion processes occur that result in embryogenesis of the
cells, morphogenesis of the cells, regeneration of cell form,
eventual maintenance of the cell, possible motility to another
site, and organogenesis that further differentiates the cell.
Facilitating these early cell adhesion functions are cell adhesion
molecules (CAMs). The CAMs are available either endogenously, or
added as an additional component of the composition. CAMs are
glycoproteins lodged in the surface of the cell membrane or
transmembrane connected to cytoskeletal components of the cell.
Specific CAMs include cadherins that are calcium dependent, and
more than 30 types are known.
[0029] Also working as CAMs are integrins, which are proteins that
link the cytoskeleton of the cell in which they are lodged to the
extracellular matrix or to other cells through alpha and beta
transmembrane subunits on the integrin protein. See FIG. 2 for an
illustration of these interactions. Cell migration, embryogenesis,
hemostatis, and wound healing are so facilitated by the integrins
in the matrix. Syndecans are proteoglycans that combine with
ligands for initiating cell motility and differentiation.
Immunoglobins provide any necessary immune and inflammatory
responses. Selectins promote cell-cell interactions.
[0030] Specific requirements for the scaffold component of the
invention, whether a native scaffold prepared for introduction into
a mammal, or a synthetic scaffold formed by synthetic polymerizing
molecules, or a combination of the two, are that the scaffold must
be resorbable over time as the tissue regeneration ensues, and this
resorbtion is at an appropriate degradation rate for optimal tissue
regeneration and absence of scar tissue formation.
[0031] The extracellular matrix scaffold is preferably non-toxic
and provides a three-dimensional construction at the site of defect
in the myocardium (once delivered to the site). The matrix scaffold
is required to have a high surface area so that there is plenty of
room for the biological activities required of the tissue
regeneration process. The scaffold must be able to provide cellular
signals such as those mentioned herein that facilitate tissue
regeneration. Finally the scaffold needs to be non-immunogenic so
that it is not rejected by the host, and it needs to be
non-thrombogenic.
[0032] Particular study of the components of the native scaffolds
facilitates design of compositions well-suited for regeneration of
myocardium.
[0033] Collagens, the most abundant components of ECM, are homo- or
heterotrimeric molecules whose subunits, the alpha chains, are
distinct gene products. To date 34 different alpha chains have been
identified. The sequence of the alpha chains contains a variable
number of classical Gly-X-Y repetitive motifs which form the
collagenous domains and noncollagenous domains. The collagenous
portions of 3 homologous or heterologous alpha chains are folded
together into a helix with a coiled coil conformation that
constitutes the basic structure motif of collagens.
[0034] Characteristically, collagens form highly organized
polymers. Two main classes of molecules are formed by collagen
polymers: the fibril-forming collagens (collagens type I, II, III,
V, and XI) and the non-fibrillar collagens that are a more
heterogeneous class. Fibril collagen molecules usually have a
single collagenous domain repeated the entire length of the
molecule, and non-fibrillar collagen molecules have a mixture of
collagenous and noncollagenous domains. On this basis several more
subgroups of the collagen family are identified: e.g. the basement
membrane collagens (IV, VIII, and X). In addition, most all the
different types of collagen have a specific distribution. For
example, fibril forming collagens are expressed in the interstitial
connective tissue. The most abundant component of basement
membranes is collagen IV. The multiplexins, collagens XV and XVIII
are also localized to the basement membranes.
[0035] In the extracellular matrix of the heart, collagen types I
and III predominate, together forming fibrils and providing most of
the connective material for typing together myocytes and other
structures in the myocardium, and thus these molecule types are
involved in the transmission of developed mechanical force in the
heart. Only collagen types I, II, III, V, and XI self assemble into
fibrils, characterized by a triple helix in the collagen molecules.
Some collagens form networks, as with the basement membrane, formed
by collagen IV. Type III collagen dominates in the wall of blood
vessels and hollow intestinal organs and copolymerizes with type I
collagen.
[0036] Proteoglycans are grouped into several families, and all
have a protein core rich in glycosoaminoglycans. They control
proliferation, differentiation, and motility. The lecticans
interact with hyaluronan and include aggrecan, versican, neurocan,
and brevican. Versican stimulates proliferation of fibroblasts and
chondrocytes through the presence in the molecule of EGF-like
motifs. The second type of proteoglycans have a protein core with
leucine-rich repeats, which form a horse shaped protein good for
protein-protein interactions. Their glycosoaminoglycan side chains
are mostly chondroitin/dennatan sulphate or keratin sulphate.
Decorin, biglycan, fibromodulin, and keratocan are members of this
family. Decorin is involved in modulation and differentiation of
epithelial and endothelial cells. In addition, transforming growth
factor beta (TGF beta) interacts with members of this family.
[0037] There are part-time proteoglycans, comprising CD44 (a
receptor for hyaluronic acid), macrophage colony stimulating
factor, amyloid precursor protein and several collagens (IX, XII,
XIV, and XVIII).
[0038] The last family of proteoglycans is the heparan sulfate
proteoglycans, some of which are located in the matrix, and some of
which are on cell membranes. Perlecan and agrin are matrix heparan
sulfate proteoglycans found in basement membranes. The syndecans
and glypicans are membrane-associated heparan sulfate
proteoglycans. Syndecans have a heparan sulfate extracellular
moiety that binds with high affinity cytokines and growth factors,
including fibroblast growth factor (FGF), hepatocyte growth factor
(HGF), platelet-derived growth factor (PDGF), heparin-binding
epidermal growth factor (HB-EGF), and vascular endothelial growth
factor (VEGF). The heparan sulfate proteoglycans have been
implicated in modulation of cell migration, proliferation and
differentiation in wound healing.
[0039] Glycoproteins are also structural proteins of ECM scaffold.
The glycoprotein fibronectin (Fn) is a large dimer that attracts
stem cells, fibroblasts and endothelial cells to a site of newly
forming matrix. Tenascin is a glycoprotein that has Fn repeats and
appears during early embryogenesis then is switched off in mature
tissue. Tenascin reappears during wound healing. Other glycoprotein
components of ECM include elastin that forms the elastic fibers and
is a major structural component along with collagen; fibrillins
which are a family of proteins consisting almost entirely of
endothelial growth factor (EGF)-like domains. Small glycoproteins
present in ECM include nidogen/entactin and fibulins I and II.
[0040] The glycoprotein laminin is a large protein with three
distinct polypeptide chains. Together with type IV collagen,
nidogen, and perlecan, laminin is one of the main components of the
basement membrane. Laminin isoforms are synthesized by a wide
variety of cells in a tissue-specific manner. Laminin I contains
multiple binding sites to cellular proteins. Virtually all
epithelial cells synthesize laminin, as do small, skeletal, and
cardiac muscle, nerves, endothelial cells, bone marrow cells, and
neuroretina. Laminins affect nearby cells, by promoting adhesion,
cell migration, and cell differentiation. They exert their effects
mostly through binding to integrins on cell surfaces. Laminins 5
and 10 occur predominantly in the vascular basement membrane and
mediate adhesion of platelets, leukocytes, and endothelial
cells.
[0041] In addition to the structural matrix proteins just
discussed, specific interactions between cells and the ECM are
mediated by functional proteins of the ECM, including transmembrane
molecules, mainly integrins, some members of the collagen family,
some proteoglycans, glycosaminoglycan chains, and some cell-surface
associated proteins. These interactions lead to direct or indirect
control of cellular activities within the extracellular matrix
scaffold such as adhesion, migration, differentiation,
proliferation, and apoptosis.
[0042] Glycosaminoglycans (GAGs) are glycosylated
post-translational molecules derived from proteoglycans. Well known
GAGs include heparin, hyaluronic acid, heparan sulfate, and
chondroitin sulfate A, B, and C. Heparin chains stimulate
angiogenesis, and act as subunits in a proteoglycan to stimulate
the angiogenic effects of fibroblast growth factor-2 (FGF-2) (also
known as basic FGF or bFGF). Chondroitin sulfate B (dennatan
sulfate) interacts with TGF-beta to control matrix formation and
remodeling. The proteoglycan form of chondroitin sulfate B
regulates the structure of ECM by controlling collagen fibril size,
orientation and deposition. Hyaluronic acid is associated with
rapid wound healing and organized deposit of collagen molecules in
the matrix. It is believed that hyaluronic acid binds TGF-beta1 to
inhibit scar formation.
[0043] The ECM is also being remodeled constantly in the live
animal. The proteins of the ECM are broken down by matrix
metalloproteases, and new protein is made and deposited as
replacement protein. Collagens are mostly synthesized by the cells
comprising the ECM: fibroblasts, myofibroblasts, osteoblasts, and
chondrocytes. Some collagens are also synthesized by adjacent
parenchymal cells or also covering cells such as epithelial,
endothelial, or mesothelial cells.
[0044] The extracellular part of integrins bind fibronectin,
collagen and laminin, and act primarily as adhesion molecules.
Integrin-ligand binding also triggers cascades of activity for cell
survival, cell proliferation, cell motility, and gene
transcription.
[0045] Tenascins include cytotactin (TN-C). Cell surface receptors
for tenascins include integrins, cell adhesion molecules of the Ig
superfamily, a transmembrane chrondroitin sulfate proteoglycan
(phosphacan) and annexin II. TN-C also interacts with extracellular
proteins such as fibronectin and the lecticans (the class of
extracellular chondroitin sulphate proteoglycans including
aggrecan, versican, and brevican).
[0046] In addition to direct knowledge of protein cell interaction
many of the proteins associated with the ECM can initiate binding
to proteins that then activate to bind other proteins or cells,
e.g. decorin binds Fn or thrombospondin and causes their cell
adhesion promoting activity. Other proteoglycans control the
hydration of the ECM and the spacing between the collagen fibrils
and network, which is believed to facilitate cell migration.
Proteoglycans regulate cell function by controlling growth factor
activity, e.g. decorin, biglycan, and fibromodulin bind to isoforms
of transforming growth factor beta (TGF beta) and heparin sulfate
proteoglycans bind and store fibroblast growth factor.
[0047] The matrix metalloproteases (MMPs) break down the collagen
molecules in the ECM so that new collagen can be used to remodel
and renew the ECM scaffold. It is also believed that the
proteolytic activity of MMPs augment the bioavailability of growth
factors sequestered within the ECM, and can activate latent
secreted growth factors like TGF-beta and IGF from IGFBPs and cell
surface growth factor precursors. MMPs can proteolytically cleave
cell surface growth factors, cytokines, chemokine receptors and
adhesion receptors, and thus participate in controlling responses
to growth factors, cytokines, chemokines, as well as cell-cell and
cell-ECM interactions.
[0048] Structural or functional matrix proteins that can comprise
the compositions herein disclosed to facilitate myocardial tissue
regeneration include, minimally, collagen I and III, elastin,
laminin, CD44, hyaluronan, syndecan, bFGF, HGF, PDGF, VEGF, Fn,
tenascin, heparin, heparan sulfate, chondroitin sulfate B,
integrins, decorin, and TGF-beta.
[0049] Native extracellular matrix scaffolds, and the proteins that
form them, are found in their natural environment, the
extracellular matrices of mammals. These materials are prepared for
use in mammals in tissue grafts procedures. Small intestine
submucosa (SIS) is described in U.S. Pat. No. 5,275,826, urinary
bladder submucosa (UBS) is described in U.S. Pat. No. 5,554,389,
stomach submucosa (SS) is described in U.S. Pat. No. 6,099,567, and
liver submucosa (LS) or liver basement membrane (LBM) is described
in U.S. Pat. No. 6,379,710, to name some of the extracellular
matrix scaffolds presently available for explanting procedures. In
addition, collagen from mammalian sources can be retrieved from
matrix containing tissues and used to form a matrix composition.
Extracellular matrices can be synthesized from cell cultures as in
the product manufactured by Matrigel.TM..
[0050] In addition, dermal extracellular matrix material,
subcutaneous extracellular matrix material, large intestine
extracellular matrix material, placental extracellular matrix
material, ornamentum extracellular matrix material, heart
extracellular matrix material, and lung extracellular matrix
material, may be used, derived and preserved similarly as described
herein for the SIS, SS, LBM, and UBM materials. Other organ tissue
sources of basement membrane for use in accordance with this
invention include spleen, lymph nodes, salivary glands, prostate,
pancreas and other secreting glands. In general, any tissue of a
mammal that has an extracellular matrix can be used for developing
an extracellular matrix component of the invention.
[0051] When using collagen-based synthetic ECMs, the collagenous
matrix can be selected from a variety of commercially available
collagen matrices or can be prepared from a wide variety of natural
sources of collagen. Collagenous matrix for use in accordance with
the present invention comprises highly conserved collagens,
glycoproteins, proteoglycans, and glycosaminoglycans in their
natural configuration and natural concentration. Collagens can be
from animal sources, from plant sources, or from synthetic sources,
all of which are available and standard in the art.
[0052] The proportion of scaffold material in the composition when
native scaffold used will be large, as the natural balance of
extracellular matrix proteins in the native scaffolds usually
represents greater than 90% of the extracellular matrix material by
dry weight. Accordingly, for a functional tissue regenerative
product, the scaffold component of the composition by weight will
be generally greater than 50% of the total dry weight of the
composition. Most typically, the scaffold will comprise an amount
of the composition by weight greater than 60%, greater than 70%,
greater than 80%, greater than 82%, greater than 84%, greater than
86%, greater than 88%, greater than 90%, greater than 92%, greater
than 94%, greater than 96%, and greater than 98% of the total
composition.
[0053] Native extracellular matrices are prepared with care that
their bioactivity for myocardial tissue regeneration is preserved
to the greatest extent possible. Key functions that may need to be
preserved include control or initiation of cell adhesion, cell
migration, cell differentiation, cell proliferation, cell death
(apoptosis), stimulation of angiogenesis, proteolytic activity,
enzymatic activity, cell motility, protein and cell modulation,
activation of transcriptional events, provision for translation
events, inhibition of some bioactivities, for example inhibition of
coagulation, stem cell attraction, and chemotaxis. Assays for
determining these activities are standard in the art. For example,
material analysis can be used to identify the molecules present in
the material composition. Also, in vitro cell adhesion tests can be
conducted to make sure that the fabric or composition is capable of
cell adhesion.
[0054] The matrices are generally decellularized in order to render
them non-immunogenic. A critical aspect of the decellularization
process is that the process be completed with some of the key
protein function retained, either by replacement of proteins
incidentally extracted with the cells, or by adding exogenous cells
to the matrix composition after cell extraction, which cells
produce or carry proteins needed for the function of tissue
regeneration in vivo.
[0055] Myocardial tissue has been regenerated in vivo in non-humans
using native xenogenic extracellular matrix scaffolds in the form
of intact patches derived and prepared from mammals, so it can be
presumed that at least some of the components required for
myocardial tissue regeneration are to be found in these xenogenic
patch matrices. Prudent practice may dictate that the cell extract
from the patches be tested for its protein make-up, so that if
necessary proteins are removed they can be place back into the
matrix composition, perhaps using exogenous proteins at
approximately the same amount as those detected in the extraction
solution. Replacing lost essential proteins may also be necessary
with emulsions or injectable solutions of extracellular matrix,
particularly those emulsified from mammalian sources. Another
option would be that the proteins extracted during the cell
extraction process can simply be added back after the cell
extraction is complete, thus preserving the desired bioactivity in
the material.
[0056] The bioactivity of extracellular matrix material can be
mimicked in tissue regeneration experiments with combinations of
native and synthetic extracellular matrices explanted together,
also optionally with additional components such as proteins or
cells, in order to provide an optimal myocardial tissue
regenerative composition and environment in vivo. What works as the
best composition for myocardial tissue regeneration in patients,
particularly humans can be tested first in other mammals by
standard explanting procedures to determine whether tissue
regeneration is accomplished and optimized by a particular
composition. See Badylak, et al, The Heart Surgery Forum,
Extracellular Matrix for Myocardial Repair, vol. 6(2), pp. 20-26
(2003).
[0057] When adding proteins to the extracellular matrix
composition, be it an emulsified composition, or another
formulation of matrix, the proteins may be simply added with the
composition, or each protein may be covalently linked to a molecule
in the matrix. Standard protein-molecule linking procedures may be
used to accomplish the covalent attachment.
[0058] For decellularization when starting with a whole organ,
whole organ perfusion process can be used. The organ is perfused
with a decellularization agent, for example 0.1% peractic acid
rendering the organ acellular. The organ can then be cut into
portions and stored (e.g. in aqueous environment, liguid nitrogen,
cold, freeze-dried, or vacuum-pressed) for later use. Any
appropriate decellularizing agent may be used in whole organ
perfusion process.
[0059] With regard to submucosal tissue, extractions may be carried
out a near neutral pH (in a range from about pH 5.5 to about pH
7.5) in order to preserve the presence of growth factor in the
matrices. Alternatively, acidic conditions (i.e. less than 5.5 pH)
can be used to preserve the presence of glycosaminoglycan
components, at a temperature in a range between 0 and 50 degrees
centrigrade. In order to regulate the acidic or basic environment
for these aqueous extractions, a buffer and chaotropic agent
(generally at a concentration from about 2M to about 8M) are
selected, such as urea (at a concentration from about 2M to 4M),
guanidine (at a concentration from about 2M to about 6M, most
typically about 4M), sodium chloride, magnesium chloride, and
non-ionic or ionic surfactants. Urea at 2M in pH 7.4 provides
extraction of basis FGF and the glycoprotein fibronectin. Using 4M
guanidine with pH 7.4 buffer yields a fraction having transforming
growth factor beta. (TGF-beta). Accordingly, it may behoove a
practitioner to decellularize one portion of a matrix, and extract
desired proteins to add back in from other different portions.
[0060] Because of the collagenous structure of basement membrane
and the desire to minimize degradation of the membrane structure
during cell dissociation, collagen specific enzyme activity should
be minimized in the enzyme solutions used in the cell-dissociation
step. For example, liver tissue is typically also treated with a
calcium chelating agent or chaotropic agent such as a mild
detergent such as Triton 100. The cell dissociation step can also
be conducted using a calcium chelating agent or chaotropic agent in
the absence of an enzymatic treatment of the tissue. The
cell-dissociation step can be carried out by suspending liver
tissue slices in an agitated solution containing about 0.05 to
about 2%, more typically about 0.1 to about 1% by weight protease,
optionally containing a chaotropic agent or a calcium chelating
agent in an amount effective to optimize release and separation of
cells from the basement membrane without substantial degradation of
the membrane matrix.
[0061] After contacting the liver tissue with the cell-dissociation
solution for a time sufficient to release all cells from the
matrix, the resulting liver basement membrane is rinsed one or more
times with saline and optionally stored in a frozen hydrated state
or a partially dehydrated state until used as described below. The
cell-dissociation step may require several treatments with the
cell-dissociation solution to release substantially all cells from
the basement membrane. The liver tissue can be treated with a
protease solution to remove the component cells, and the resulting
extracellular matrix material is further treated to remove or
inhibit any residual enzyme activity. For example, the resulting
basement membrane can be heated or treated with one or more
protease inhibitors.
[0062] Basement membrane or other native ECM scaffolds may be
sterilized using conventional sterilization techniques including
tanning with glutaraldehyde, formaldehyde tanning at acidic pH,
ethylene oxide treatment, propylene oxide treatment, gas plasma
sterilization, gamma radiation, and peracetic acid sterilization. A
sterilization technique which does not significantly weaken the
mechanical strength and biotropic properties of the material is
preferably used. For instance, it is believed that strong gamma
radiation may cause loss of strength in the graft material.
Preferred sterilization techniques include exposing the graft to
peracetic acid, low dose gamma irradiation and gas plasma
sterilization; peracetic acid sterilization being the most
preferred method.
[0063] Synthetic extracellular matrices can be formed using
synthetic molecules that polymerize much like native collagen and
which form a scaffold environment that mimics the native
environment of mammalian extracellular matrix scaffolds. According,
such materials as polyethylene terephthalate fiber (Dacron),
polytetrafluoroethylene (PTFE), glutaraldehyde-cross linked
pericardium, polylactate (PLA), polyglycol (PGA), hyaluronic acid,
polyethylene glycol (PEG), polyethelene, nitinol, and collagen from
non-animal sources (such as plants or synthetic collagens), can be
used as components of a synthetic extracellular matrix scaffold.
The synthetic materials listed are standard in the art, and forming
hydrogels and matrix-like materials with them is also standard.
Their effectiveness can be tested in vivo as sited earlier, by
testing in mammals, along with components that typically constitute
native ECMs, particularly the growth factors and cells responsive
to them.
[0064] The ECM-like materials are described generally in the review
article "From Cell-ECM Interactions to Tissue Engineering", Rosso,
et al., Journal of Cellular Physiology 199:174-180 (2004). In
addition, some ECM-like materials are listed here. Particularly
useful biodegradable and/or bioabsorbable polymers include
polylactides, poly-glycolides, polycarprolactone, polydioxane and
their random and block copolymers. Examples of specific polymers
include poly D,L-lactide, polylactide-co-glycolide (85:15) and
polylactide-co-glycolide (75:25).
[0065] Preferably, the biodegradable and/or bioabsorbable polymers
used in the fibrous matrix of the present invention will have a
molecular weight in the range of about 1,000 to about 8,000,000
g/mole, more preferably about 4,000 to about 250,000 g/mole. The
biodegradable and/or bioabsorbable fiberizable material is
preferably a biodegradable and bioabsorbable polymer. Examples of
suitable polymers can be found in Bezwada, et al. (1997)
Poly(p-Dioxanone) and its copolymers, in Handbook of Biodegradable
Polymers, A. J. Domb, J. Kost and D. M. Wiseman, editors, Hardwood
Academic Publishers, The Netherlands, pp. 29-61.
[0066] The biodegradable and/or bioabsorbable polymer can contain a
monomer selected from the group consisting of a glycolide, lactide,
dioxanone, caprolactone, trimethylene carbonate, ethylene glycol
and lysine. The material can be a random copolymer, block copolymer
or blend of monomers, homopolymers, copolymers, and/or
heteropolymers that contain these monomers.
[0067] The biodegradable and/or bioabsorbable polymers can contain
bioabsorbable and biodegradable linear aliphatic polyesters such as
polyglycolide (PGA) and its random copolymer
poly(glycolide-co-lactide-) (PGA-co-PLA). The FDA has approved
these polymers for use in surgical applications, including medical
sutures. An advantage of these synthetic absorbable materials is
their degradability by simple hydrolysis of the ester backbone in
aqueous environments, such as body fluids. The degradation products
are ultimately metabolized to carbon dioxide and water or can be
excreted via the kidney. These polymers are very different from
cellulose based materials, which cannot be absorbed by the
body.
[0068] Other examples of suitable biocompatible polymers are
polyhydroxyalkyl methacrylates including ethylmethacrylate, and
hydrogels such as polyvinylpyrrolidone, polyacrylamides, etc. Other
suitable bioabsorbable materials are biopolymers which include
collagen, gelatin, alginic acid, chitin, chitosan, fibrin,
hyaluronic acid, dextran, polyamino acids, polylysine and
copolymers of these materials. Any glycosaminoglycan (GAG) type
polymer can be used. GAGs can include, e.g., heparin, chondroitin
sulfate A or B, and hyaluronic acid, or their synthetic analogues.
Any combination, copolymer, polymer or blend thereof of the above
examples is contemplated for use according to the present
invention. Such bioabsorbable materials may be prepared by known
methods.
[0069] Nucleic acids from any source can be used as a polymeric
biomaterial. Sources include naturally occurring nucleic acids as
well as synthesized nucleic acids. Nucleic acids suitable for use
in the present invention include naturally occurring forms of
nucleic acids, such as DNA (including the A, B and Z structures),
RNA (including mRNA, tRNA, and rRNA together or separated) and
cDNA, as well as any synthetic or artificial forms of
polynucleotides.
[0070] The nucleic acids used in the present invention may be
modified in a variety of ways, including by cross linking,
intra-chain modifications such as methylation and capping, and by
copolymerization. Additionally, other beneficial molecules may be
attached to the nucleic acid chains. The nucleic acids may have
naturally occurring sequences or artificial sequences. The sequence
of the nucleic acid may be irrelevant for many aspects of the
present invention. However, special sequences may be used to
prevent any significant effects due to the information coding
properties of nucleic acids, to elicit particular cellular
responses or to govern the physical structure of the molecule.
[0071] Nucleic acids may be used in a variety of crystalline
structures both in finished biomaterials and during their
production processes. Nucleic acid crystalline structure may be
influenced by salts used with the nucleic acid. For example, Na, K,
Bi and Ca salts of DNA all have different precipitation rates and
different crystalline structures. Additionally, pH influences
crystalline structure of nucleic acids.
[0072] The physical properties of the nucleic acids may also be
influenced by the presence of other physical characteristics. For
instance, inclusion of hairpin loops may result in more elastic
biomaterials or may provide specific cleavage sites. The nucleic
acid polymers and copolymers produced may be used for a variety of
tissue engineering applications including to increase tissue
tensile strength, improve wound healing, speed up wound healing, as
templates for tissue formation, to guide tissue formation, to
stimulate nerve growth, to improve vascularization in tissues, as a
biodegradable adhesive, as device or implant coating, or to improve
the function of a tissue or body part. The polymers may also more
specifically be used as sutures, scaffolds and wound dressings. The
type of nucleic acid polymer or copolymer used may affect the
resulting chemical and physical structure of the polymeric
biomaterial.
[0073] The extracellular matrix can be emulsified for
administration to the defective or absent myocardium. The matrix
may also be otherwise liquefied or made into an injectable
solution, such as an emulsion, or a liquid, or injectable gel, or
semi-gel, other injectable formulation that can be administered
with a percutaneous catheter, or other device capable of delivering
an injectable formulation.
[0074] An emulsion of mammalian or synthetic extracellular matrix
material can be accomplished as is standard for tissue or polymer
emulsification in general. Generally, the emulsion will be
maintained in an emulsified state by control of some component of
the composition, for example the pH. Upon delivery of the emulsion
the pH is altered to allow the molecules of the matrix to
polymerize into a three-dimensional scaffold.
[0075] An emulsified extracellular matrix material comprising also
cells can have the cultured cells simply added into the matrix
emulsion, or the cells may be co-cultured with the matrix for a
time before administration to the patient. Standard procedures for
culturing or co-culturing cells can be used. In addition, where
proteins such as growth factors, or any other protein, including
protein forms such as peptides or polypeptides, or protein
fragments, are added into the extracellular matrix, the protein
molecules may be added into the matrix composition, or the protein
molecules may be covalently linked to a molecule in the matrix. The
covalent linking of protein to matrix molecules can be accomplished
by standard covalent protein linking procedures known in the art.
The protein may be covalently linked to one or more matrix
molecules. The covalent linking may result in an integration of the
protein molecules in the matrix scaffold formation once the
emulsion converts from the emulsified form to the scaffold form of
the extracellular matrix.
[0076] Unlike skeletal myocytes, cardiomyocytes withdraw from cell
cycle shortly after birth, and adult mammalian cardiomyocytes lack
the potential to proliferate. Therefore, in order to regenerate
myocardium, the right cells may have to be added to the
composition, or the site, or the right molecules to attract the
right cells will have to be added to the composition or the site.
Transplantation cell sources for the myocardium include allogenic,
xenogenic, or autogenic sources. Accordingly, human embryonic stem
cells, neonatal cardiomyocytes, myofibroblasts, mesenchymal cells,
autotransplanted expanded cardiomyocytes, and adipocytes can be
used as additive components to accompany the scaffold.
[0077] Embryonic stem cells begin as totipotent cells,
differentiate to pluripotent cells, and then further
specialization. They are cultured ex vivo and in the culture dish
environment differentiate either directly to heart muscle cells, or
to bone marrow cells that can become heart muscle cells. The
cultured cells are then transplanted into the mammal, either with
the composition or in contact with the scaffold and other
components.
[0078] Myoblasts are another type of cell that lend themselves to
transplantation into myocardium, however, they do not always
develop into cardiomyocytes in vivo. Adult stem cells are yet
another species of cell that work in the context of tissue
regeneration. Adult stem cells are thought to work by generating
other stem cells (for example those appropriate to myocardium) in a
new site, or they differentiate directly to a cardiomyocyte in
vivo. They may also differentiate into other lineages after
introduction to organs, such as the heart. The adult mammal
provides sources for adult stem cells in circulating endothelial
precursor cells, bone marrow-derived cells, adipose tissue, or
cells from a specific organ. It is known that mononuclear cells
isolated from bone marrow aspirate differentiate into endothelial
cells in vitro and are detected in newly formed blood vessels after
intramuscular injection. Thus, use of cells from bone marrow
aspirate may yield endothelial cells in vivo as a component of the
composition.
[0079] Other cells which may be employed with the invention are the
mesenchymal stem cells administered with activating cytokines.
Subpopulations of mesenchymal cells have been shown to
differentiate toward myogenic cell lines when exposed to cytokines
in vitro.
[0080] Once a type of cell is chosen, the number of cells needed is
determined. Their function and anticipated change upon
implantation, as well as their viability during the process of
transplantation need to be considered to determine the number of
cells to transplant. Also the mode of transplantation is to be
considered: several modes including intracoronary, retrograde
venous, transvascular injection, direct placement at the site,
thoracoscopic injection and intravenous injection can be used to
put the cells at the site or to incorporate them with the
composition either before delivery or after delivery to the
defective myocardium. In all cases, the mode of delivery and
whether the cells are first mixed with the other components of the
composition is a decision made based on what will provide the best
chance for viability of the cells, and the best opportunity for
their continued development into cells that can function in the
scaffold in vivo in order to signal and promote tissue
regeneration.
[0081] The following list includes some of the cells that may be
used as additional cellular components of the composition of the
invention: a human embryonic stem cell, a fetal cardiomyocyte, a
myofibroblast, a mesenchymal stem cell, an autotransplanted
expanded cardiomyocyte, an adipocyte, a totipotent cell, a
pluripotent cell, a blood stem cell, a myoblast, an adult stem
cell, a bone marrow cell, a mesenchymal cell, an embryonic stem
cell, a parenchymal cell, an epithelial cell, an endothelial cell,
a mesothelial cell, a fibroblast, a myofibroblast, an osteoblast, a
chondrocyte, an exogenous cell, an endogenous cell, a stem cell, a
hematopoetic stem cell, a pluripotent stem cell, a bone
marrow-derived progenitor cell, a progenitor cell, a myocardial
cell, a skeletal cell, a fetal cell, an embryonic cell, an
undifferentiated cell, a multi-potent progenitor cell, a unipotent
progenitor cell, a monocyte, a cardiomyocyte, a cardiac myoblast, a
skeletal myoblast, a macrophage, a capillary endothelial cell, a
xenogenic cell, an allogenic cell, an adult stem cell, and a
post-natal stem cell.
[0082] In particular, human embryonic stem cells, fetal
cardiomyoctes, mesenchymal stem cells, adipocytes, bone marrow
progenitor cells, embryonic stem cells, adult stem cells, or
post-natal stem cells together with growth factors or alone with
matrix scaffold optimize myocardium regeneration in vivo.
[0083] Cells can be seeded directly onto matrix scaffold sheets
under conditions conducive to eukaryotic cell proliferation. The
highly porous nature of extracellular matrices in particular will
allow diffusion of cell nutrients throughout the membrane matrix.
Thus, cells can be cultured on or within the matrix scaffold
itself. With the emulsified extracellular matrix compositions, or
with some of the other formulations, the cells can be co-cultured
with the extracellular matrix material before administration of the
complete composition to the patient.
[0084] In addition to a native ECM scaffold, or a synthetic
scaffold, or a mixture of the two, peptides, polypeptides or
proteins can be added. Such components include extracellular
structural and functional proteins in admixture so as to mimic
either heart ECM, or other native ECMs that are capable of
regenerating at least some reasonable percentage of the defective
myocardium, for example at least 30%, preferably more than 50%.
Effective regeneration of the myocardium relies on the
extracellular matrix scaffold by its structure and components.
Mimicking the native explant material as closely as possible thus
optimizes the opportunity for regeneration using a composition
comprising some native ECM, albeit treated, but also with
additional components.
[0085] The peptides, polypeptides or proteins that can be added to
the scaffold are: a collagen, a proteoglycan, a glycosaminoglycan
(GAG) chain, a glycoprotein, a growth factor, a cytokine, a
cell-surface associated protein, a cell adhesion molecule (CAM), an
angiogenic growth factor, an endothelial ligand, a matrikine, a
matrix metalloprotease, a cadherin, an immunoglobin, a fibril
collagen, a non-fibrillar collagen, a basement membrane collagen, a
multiplexin, a small-leucine rich proteoglycan, decorin, biglycan,
a fibromodulin, keratocan, lumican, epiphycan, a heparan sulfate
proteoglycan, perlecan, agrin, testican, syndecan, glypican,
serglycin, selectin, a lectican, aggrecan, versican, nuerocan,
brevican, cytoplasmic domain-44 (CD-44), macrophage stimulating
factor, amyloid precursor protein, heparin, chondroitin sulfate B
(demaatan sulfate), chondroitin sulfate A, heparan sulfate,
hyaluronic acid, fibronectin (Fn), tenascin, elastin, fibrillin,
laminin, nidogen/entactin, fibulin I, fibulin II, integrin, a
transmembrane molecule, platelet derived growth factor (PDGF),
epidermal growth factor (EGF), transforming growth factor alpha
(TGF-alpha), transforming growth factor beta (TGF-beta), fibroblast
growth factor-2 (FGF-2) (also called basic fibroblast growth factor
(bFGF)), thrombospondin, osteopontin, angiotensin converting enzyme
(ACE), and vascular epithelial growth factor (VEGF).
[0086] Typically, the additional peptide, polypeptide, or protein
component will comprise an amount of the composition by weight
selected from the group consisting of greater than 0.1%, greater
than 0.5%, greater than 1%, greater than 1.5%, greater than 2%,
greater than 4%, greater than 5%, greater than 10%, greater than
12%, greater than 15%, and greater than 20%.
[0087] Evaluation of the effectiveness of a particular protein
component or combination of components for myocardial tissue
regeneration may be accomplished by contacting the composition with
defective myocardium in a test animal, for example a dog, pig, or
sheep, or other common test mammal. Myocardial tissue regeneration
and myocardium contractility are both indicia to measure the
success of the composition and procedure, by procedures standard in
the art. In addition, a small sampling of the regenerated tissue
can be made to determine that new extracellular matrix and new
tissue has been made. As to what balance between structural
extracellular matrix proteins and functional ones to use in a given
composition, nature provides direction. Most ECMs are predominantly
made up of structural proteins by dry weight. Thus only a small
portion of functional proteins by weight is needed for effective
myocardial tissue regeneration.
[0088] Peptides, polypeptides or proteins for the composition may
be formulated as is standard in the art for the particular class of
protein, and that formulation may be added to the extracellular
matrix material (of whatever formulation) for delivery into the
patient.
[0089] Alternatively, the protein molecules may be covalently
linked to an appropriate matrix molecule of any of the matrix
formulations. Covalent linking of the protein molecules to
molecules of the matrix may be accomplished by standard covalent
linking methods known in the art.
[0090] Some of the proteins required for the composition can be
genetically synthesized in vivo with DNA and vector constituents.
Thus a vector having a DNA capable of targeted expression of a
selected gene can contribute a bioactive peptide, polypeptide, or
protein to the composition. Standard in vivo vector gene expression
can be employed.
[0091] In addition, other additives such as a nutrient, a sugar, a
fat, a lipid, an amino acid, a nucleic acid, a ribo-nucleic acid,
may provide support to the regenerative process in vivo in the
composition. Finally, also a drug, such as a heart regenerating or
angiogenesis promoting drug may be also added to the composition,
in such a form as, for example, an organic molecule, an inorganic
molecule, a small molecule, a drug, or any other drug-like
bioactive molecule.
[0092] A formulation of extracellular matrix material can be an
emulsified or injectable material derived from mammalian or
synthetic sources. The extracellular matrix material can be
emulsified or made into an injectable formulation by standard
procedures in the art, and maintained as an emulsion or injectable
until delivered to the patient. Once delivered to the patient, an
environment is established (by some change such as a change in pH)
so that the extracellular matrix molecules (be they mammalian or
synthetic) polymerize to form a matrix scaffold.
[0093] Depending on the nature of the scaffold selected, and
depending on which additional components are used, the scaffold
component and the additional component can be formulated together
in the same way, or in different ways that are however but
delivery-compatible with each other for delivery purposes. Options
for formulation of the scaffold include a solid sheet,
multilaminate sheets, a gel, an emulsion, an injectable solution, a
fluid, a paste, a powder, a plug, a strand, a suture, a coil, a
cylinder, a weave, a strip, a spray, a vapor, a patch, a sponge, a
cream, a coating, a lyophilized material, or a vacuum pressed
material, all of which are standard in the art.
[0094] Formulation of the additional components, when they are not
scaffold-like is generally accomplished using some form of an
injectable, semi-gel, or emulsified material, although powdered
forms may also then be combined with a hydration-promoting solution
at delivery. Thus, formulations for the additional components will
generally comprise formulations of the nature of a gel, an
emulsion, an injectable solution, a fluid, a paste, a spray, a
vapor, a cream, and a coating. Dried materials that are hydrated
either at delivery or just before delivery are powders, such as
lyophilized materials.
[0095] Cells can be added in from a culture, or can be co-cultured
with the matrix component of the composition. Proteins can be added
into the composition, or covalently linked to matrix molecules. DNA
can be added in with their vectors for expressing proteins in vivo.
Other additives can be combined with the matrix component as is
practical for the delivery of the composition (for example, as an
injectable or a composition administered with a percutaneous
catheter) and as is practical for maintaining bioactivity of the
molecules or components in vivo.
[0096] Fluidized forms of native extracellular matrices are
described, e.g. in U.S. Pat. No. 5,275,826. The comminuted
fluidized tissue can be solubilized by enzymatic digestion
including the use of proteases, such as trypsin or pepsin, or other
appropriate enzymes such as a collagenase or a
glycosaminoglycanase, or the use of a mixture of enzymes, for a
period of time sufficient to solubilize said tissue and form a
substantially homogeneous solution.
[0097] The present invention also contemplates the use of powder
forms of extracellular matrix scaffolds. In one embodiment a powder
form is prepared by pulverizing basement membrane submucosa tissue
under liquid nitrogen to produce particles ranging in size from 0.1
to 1 mm.sup.2. The particulate composition is then lyophilized
overnight and sterilized to form a solid substantially anhydrous
particulate composite. Alternatively, a powder form of basement
membrane can be formed from fluidized basement membranes by drying
the suspensions or solutions of comminuted basement membrane. The
dehydrated forms have been rehydrated and used as cell culture
substrates without any apparent loss of their ability to support
cell growth.
[0098] The mode used for delivery of the compositions of the
invention to the defective myocardium may be critical in
establishing tissue regeneration in vivo. Standard delivery to
myocardial sites can be used for injectable, fluidized, emulsified,
gelled, or otherwise semi-fluid materials, such as direct injecting
(e.g. with a needle and syringe), or injecting with a percutaneous
catheter. For materials that have been rendered wholly or partially
vaporized, force-driven delivery of the material can be used, for
example, CO.sub.2 powering emission of fine emulsion, micronizing
an injectable solution, ink jet delivery, spray with a conventional
atomizer or spray unit, or other type of vaporized delivery. Some
of these vaporized formulations can be delivered using a
percutaneous catheter adapted for delivery of a vaporized
formulation.
[0099] For materials that are essentially solid, such as some of
the native or synthetic scaffolds, physically depositing the
material will be the most prudent mode of delivery. For example a
patch, sponge, strip, weave, or other geometrically defined
material form should be placed at the site of deposit either during
surgery, or with a percutaneous minimally invasive catheter capable
of depositing all or portions of solid material at the site.
Preferred modes of delivery will be minimally invasive delivery
procedures, which reduce the risk of infection and provide an
easier recovery for the patient.
[0100] Where the scaffold component is in a different material form
than the additional components, care must be taken to orchestrate
an effective delivery of both components to the site. For example,
where the scaffold is a solid sheet, and cells have been cultured
and proteins hydrolyzed, the cells and proteins may be added to the
scaffold prior to delivery and the composition is then delivered in
surgery. Alternatively, also in surgery, the solid sheet of
scaffold may be delivered and the emulsified agents deposited on
the sheet before closure. Where both the scaffold component and the
additional components can be emulsified, with complete retention of
functionality, the composition can be delivered together by direct
injection or percutaneous catheter delivery.
[0101] In all cases, before a mode is used to treat a patient, the
feasibility and effectiveness of any one delivery mode or
combination of modes can be tested in a test mammal prior to actual
use in humans.
[0102] A site of defective myocardium is identified and the
appropriate composition of a scaffold component and additional
components is made and formulated. The formulated composition is
delivered by an appropriate means to the site of defect. The site
and mammal are observed and tested for regeneration of the
defective myocardium to determine that an effective amount of the
composition has been delivered, particularly to observe new tissue
growth, and also to determine that the new tissue has the
contractility necessary for it to function usefully as myocardium.
Tissue growth and contractility can be tested and observed by
standard means, for example, as described in Badylak, et al.
referenced above.
[0103] Goals for contractility in the defective myocardium include
observed and measured contractility in an amount measured against
contractility of a normal heart selected from the group consisting
of greater than 10%, greater than 20%, greater than 30%, greater
than 40%, greater than 50%, greater than 60%, greater than 70%,
greater than 80%, greater than 90%, and greater than 95% of normal
myocardial contractility in vivo.
[0104] The method step of contacting the defective myocardium or
site of absent myocardium with a composition of the invention can
be accomplished by means discussed in the delivery section,
including, delivering the composition by injecting, suturing,
stapling, injecting with a percutaneous catheter, CO.sub.2 powering
emission of fine emulsion, micronizing an injectable solution,
inkjet delivery, physically depositing a sponge, physically
depositing a patch, physical depositing a strip, or physically
depositing a formed scaffold of any shape.
[0105] A complementary method of use of the compositions of the
invention include a method of inducing angiogenesis in myocardium
at a site of ischemia by similarly contacting said ischemic
myocardium with a composition of the invention in an amount
effective to induce angiogenesis in the myocardium at the site of
ischemia. Effectiveness can be measured by measuring
vascularization at the site, using standard biomedical procedures
for such analysis.
EXAMPLES
Example 1
[0106] An emulsion of urinary bladder submucosa (UBS) is prepared
using standard emulsifying techniques. The emulsion is free of
endogenous cells. This preparation is maintained as an emulsion by
controlling the pH during storage of the emulsion before it is
administered to the patient. In a minimally invasive procedure, a
percutaneous catheter device is loaded with sufficient quantity of
the emulsified UBS to address a defect in a human heart, the defect
having been identified previously by imaging. The catheter is
directed to the site of the myocardium in need of tissue
regeneration using sonographic or radiographic imaging. Upon
contact with the site, the emulsion is released and the catheter is
withdrawn. The tissue regeneration process is monitored by
sonography for several weeks or months post-delivery of the
emulsion.
Example 2
[0107] An emulsion of decellularized immunogenic liver basement
membrane (LBM) is prepared using standard known techniques. While
maintaining the emulsion state of the LBM, adult stem cells are
co-cultured with the emulsion using standard stem cell culturing
techniques. When the cells are ready, the entire composition is
loaded into a catheter for percutaneous delivery to a human patient
in need of tissue regeneration at a site of defective or absent
myocardium. The emulsion with the co-cultured cells is delivered to
the patient: a percutaneous catheter is loaded with the emulsion
and directed to the site of the myocardium in need of tissue
regeneration using sonographic or radiographic imaging. Upon
contact with the site, the emulsion is released and the catheter is
withdrawn. The tissue regeneration process is monitored by
sonography for several weeks or months post-delivery of the
emulsion.
Example 3
[0108] An injectable emulsion of decellularized immunogenic stomach
submucosa (SS) is prepared using standard known techniques. An
aliquot of glycoaminoglycan (GAG) protein is covalently linked to
some of the molecules of the matrix emulsion using standard
covalent linking procedures for proteins. While maintaining the
emulsive state of the SS, bone marrow progenitor cells are
co-cultured with the emulsion using standard progenitor cell
culturing techniques. An aliquot of transforming growth factor
protein is added to the co-culturing composition before delivery to
the human in need of myocardial tissue regeneration. The emulsion
complete with cells and proteins is loaded into a percutaneous
catheter which is directed to the site of the myocardium in need of
tissue regeneration using sonographic or radiographic imaging. Upon
contact with the site, the emulsion is released and the catheter is
withdrawn. The tissue regeneration process is monitored by
sonography for several weeks or months post-delivery of the
emulsion.
[0109] The preceding merely illustrates the principles of the
invention. It will be appreciated that those skilled in the art
will be able to devise various arrangements which, although not
explicitly described or shown herein, embody the principles of the
invention and are included within its spirit and scope.
[0110] Furthermore, all examples and conditional language recited
herein are principally intended to aid the reader in understanding
the principles of the invention and the concepts contributed by the
inventors to furthering the art, and are to be construed as being
without limitation to such specifically recited examples and
conditions.
[0111] Moreover, all statements herein reciting principles,
aspects, and embodiments of the invention as well as specific
examples thereof, are intended to encompass both structural and
functional equivalents thereof.
[0112] Additionally, it is intended that such equivalents include
both currently known equivalents and equivalents developed in the
future, i.e., any elements developed that perform the same
function, regardless of structure. The scope of the present
invention, therefore, is not intended to be limited to the
exemplary embodiments shown and described herein. Rather, the scope
and spirit of present invention is embodied by the appended
claims.
[0113] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed within the invention. The upper and
lower limits of these smaller ranges may independently be included
or excluded in the range, and each range where either, neither or
both limits are included in the smaller ranges is also encompassed
within the invention, subject to any specifically excluded limit in
the stated range. Where the stated range includes one or both of
the limits, ranges excluding either or both of those included
limits are also included in the invention.
[0114] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. It must
be noted that as used herein and in the appended claims, the
singular forms "a", "an", and "the" include plural referents unless
the context clearly dictates otherwise.
[0115] All publications cited are incorporated in their entirety.
Such publications are provided solely for their disclosure prior to
the filing date of the present application. Nothing herein is to be
construed as an admission that the present invention is not
entitled to antedate such publication by virtue of prior invention.
Further, the dates of publication provided may be different from
the actual publication dates which may need to be independently
confirmed.
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