Drug – bio-affecting and body treating compositions – Extract – body fluid – or cellular material of undetermined... – Digestive system
Reexamination Certificate
2002-04-29
2004-09-21
Witz, Jean C. (Department: 1651)
Drug, bio-affecting and body treating compositions
Extract, body fluid, or cellular material of undetermined...
Digestive system
Reexamination Certificate
active
06793939
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a tissue graft composition and methods for its preparation and use. More particularly, the present invention is directed to non-immunogenic tissue graft compositions comprising the basement membrane of liver and the use of same to promote endogenous tissue growth in vivo and to support the growth and differentiation of eukaryotic cells cultured in vitro.
BACKGROUND AND SUMMARY OF THE INVENTION
There has been much research effort directed to finding natural and synthetic materials having the requisite properties for use as tissue grafts. Surprisingly, it has been found that basement membranes (stroma) prepared from liver tissue of warm-blooded vertebrates by removing cellular components of the liver tissue exhibit certain mechanical and biotropic properties similar to that which has been reported for intestinal submucosal tissue in U.S. Pat. Nos. 4,902,508; 5,281,422; and 5,275,826. It can be substituted for intestinal submucosa tissue in most, if not all, of the applications previously reported for intestinal submucosa, including enhancing wound healing, promoting endogenous tissue growth, stimulating cell proliferation and inducing cell differentiation.
The basement membrane of the liver is an extracellular matrix distinct from submucosal extracellular matrices. The liver basement membrane does not support an overlaying mucosa and is devoid of the laminate tissue structure in which submucosal extracellular matrices reside. The liver plays a central role in numerous regulatory processes in the body, including glucose metabolism, insulin regulation, anabolic processes for the musco-skeletal system and central nervous system, and the maintenance of appropriate levels of circulating proteins essential for day to day homeostasis.
In one embodiment of the present invention, liver basement membranes are used to manufacture a non-immunogenic tissue graft composition for use in the repair of damaged or diseased tissues. The tissue graft composition of the present invention comprises the basement membrane of organ tissue of a warm-blooded vertebrate, for example, liver tissue, substantially free, preferably devoid, of all cells (e.g., hepatocytes and bile ductal cells) of said warm-blooded vertebrate. The present tissue graft composition can be implanted, or fluidized and injected, into a vertebrate host to contact damaged or defective tissues and induce the repair or replacement of said tissues. The compositions of the present invention can also be applied as a component of a wound dressing (ointment or bandage) in fluidized or solid form for topical application to promote wound healing. Alternatively, the liver tissue derived extracellular matrix can be utilized as a cell growth substrate for growing eukaryotic cells in vitro.
DETAILED DESCRIPTION OF THE INVENTION
The tissue graft composition of the present invention comprises liver basement membrane prepared by separating same from the natively associated cellular components of liver tissue of a warm-blooded vertebrate. The preparative techniques described below provide an extracellular matrix composition consisting essentially of liver basement membrane substantially free of any cellular components. These compositions are referred to herein generically as liver basement membrane(s) (LBM). 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.
Basement membrane for use in the graft composition of this invention is typically prepared from liver tissue harvested from animals raised for meat production, including, for example, pigs, cattle and sheep or other warm-blooded vertebrates. Thus, there is an inexpensive commercial source of liver tissue for use in preparation of the tissue graft compositions in accordance with the present invention. In accordance with one embodiment, a composition comprising liver basement membranes is prepared from liver tissue of a warm-blooded vertebrate. This composition is useful as a non-immunogenic tissue graft capable of inducing endogenous tissue growth when implanted in warm-blooded vertebrates. In one embodiment, the composition comprises an extracellular matrix consisting essentially of liver basement membrane devoid of endogenous cells associated with the source vertebrate liver tissue used to prepared the composition.
The preparation of liver basement membrane from of liver tissue of a warm-blooded vertebrate in accordance with the present invention is carried out by removing the cellular components from liver tissue. Ideally the process is carried out to separate the cells from the basement membranes without damaging, or at least minimizing disruption or damage to, the basement membrane tissue. Removal of the cellular components from the liver extracellular matrix allows the preparation of a graft composition that is non-immunogenic, and thus does not induce a host immune response when the graft composition is implanted into a host. In general, the method for preparing a tissue graft composition from warm-blooded vertebrate liver tissue comprising the steps of treating the liver tissue with a cell dissociation solution for a period of time sufficient to release the cellular components of the liver tissue from the extracellular components without substantial disruption of the extracellular components, and separating the cellular components from said extracellular components. Typically the cell dissociation solution comprises a chaotropic agent or an enzyme or both.
The first step in preparing LBM in accordance to one embodiment of the present invention comprises slicing a segment of liver tissue into pieces (e.g., strips or sheets) to increase the surface area-to-volume ratio of the liver tissue. In one embodiment the liver tissue is sliced into a series of sheets each having a thickness of about 50 to about 500 microns, more preferably about 250 to about 300 microns. Freshly harvested liver tissue can be sliced using a standard meat slicer, or the tissue can be frozen and sliced with a cryomicrotone. The thin pieces of liver tissue are then treated with a solution that releases component liver cells from the associated extracellular basement membrane matrix.
In accordance with one embodiment the liver tissue is treated with a solution comprising an enzyme, for example, a protease, such as trypsin or pepsin. Because of the collagenous structure of the liver 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. In addition, the liver tissue is typically also treated with a calcium chelating agent or chaotropic agent such as a mild detergent such as Triton 100. Thus, in one embodiment of this invention liver tissue is treated by suspending slices or strips of the tissue in a cell-dissociation solution containing enzyme(s) and chaotropic agent(s). However, 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.
In one preferred embodiment the cell-dissociation step is 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.
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
Barnes & Thornburg
Purdue Research Foundation
Witz Jean C.
LandOfFree
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