Drug – bio-affecting and body treating compositions – Whole live micro-organism – cell – or virus containing
Reexamination Certificate
1999-02-19
2001-06-05
Jones, Dwayne C. (Department: 1614)
Drug, bio-affecting and body treating compositions
Whole live micro-organism, cell, or virus containing
C435S335000
Reexamination Certificate
active
06241981
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to tissue graft constructs useful in promoting regrowth and healing of damaged or diseased neurological related tissue structures. More particularly this invention is directed to a method of inducing the formation of endogenous neurological structures at a site in need of endogenous neurological related tissue growth by contacting the site with a submucosal tissue graft construct.
BACKGROUND AND SUMMARY OF THE INVENTION
The neurosurgeon is frequently confronted with the necessity of repairing dural defects due to trauma, tumor resection, and decompressive procedures. Numerous materials have been investigated for use in the repair of the dura mater and underlying tissues. Current options include autologous materials (e.g. pericranium, temporalis fascia, and tensor fascia lata), lyophilized cadaveric materials (e.g. dura mater and tensor fascia lata) and synthetic materials (e.g. Silastic sheets, Dacron sheets, Vicryl mesh); however, each of these materials is associated with significant limitations.
One object of the present invention is to provide a biodegradable material that can serve as a dural substitute.
Many individuals have suffered injuries to their central nervous system that leave the individual partially paralyzed or result in reduced motor function. Repair strategies and graft material for repairing damage to the central nervous system do not currently exist. In particular nerve fibers within the brain and the spinal cord, which differ structurally from peripheral nerves, will not regenerate after they have been severed or crushed. For example there is no currently known treatment for humans that promotes functional regeneration across a complete spinal cord transection or a severed optic nerve.
An additional object of the present invention is to provide a composition and method that promotes the production of endogenous central nerve cells thus allowing the repair of damage to both central nervous system tissues and peripheral nerve tissues.
It is known that compositions comprising the tunica submucosa delaminated from both the tunica muscularis and at least the luminal portion of the tunica mucosa of the intestine of warm-blooded vertebrates can be used as tissue graft materials. See, for example, U.S. Pat. Nos. 4,902,508 and 5,281,422. The compositions described in those patents are characterized by excellent mechanical properties, including high compliance, a high burst pressure point, and an effective porosity index which allowed such compositions to be used beneficially for vascular graft constructs and in connective tissue replacement applications. When used in such applications the submucosal graft constructs appear to serve as a matrix for the regrowth of the tissues replaced by the graft constructs. Furthermore, as described in U.S. Pat. No. 5,275,826 fluidized forms of vertebrate submucosal tissues can also be used as injectable or implantable tissue grafts without loss of biotropic properties. Significantly, too, in over 600 cross-species implants, submucosa-derived graft compositions have never been shown to elucidate a tissue graft rejection reaction.
Applicants have discovered that submucosal tissue induces the growth and proliferation of neurological related tissues, including the dura mater and nerve cells of the central and peripheral nervous system. Accordingly, the present invention is directed to the use of submucosal tissue as a graft construct for promoting the repair of damaged or diseased neurological related tissues.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The submucosal tissue constructs of the present invention have been found to promote or induce the growth of neurological related tissues. In accordance with the present invention the term neurological related tissues includes neurons and glial cells, and dura mater, arachnoid and pia mater tissues. There is provided in accordance with this invention a method for utilizing compositions comprising warm-blooded vertebrate submucosal tissue to repair or to enhance the repair of damaged or diseased neurological related tissues in a warm-blooded vertebrate. The method comprises the step of contacting the site in need of repair with a composition comprising submucosal tissue.
Submucosal tissue suitable for use in accordance with the present invention comprises natural collagenous matrices that include highly conserved collagens, glycoproteins, proteoglycans, and glycosaminoglycans in their natural configuration and natural concentration. One source of submucosal tissue is the intestinal tissue of a warm-blooded vertebrate. Small intestinal tissue is a preferred source of submucosal tissue for use in this invention.
Submucosal tissue for use in this invention is derived from various warm-blooded vertebrate sources, including intestinal tissue harvested from animals raised for meat production, such as pigs, cattle and sheep or other warm-blooded vertebrates. This tissue can be used in either its natural configuration or in a comminuted or partially enzymatically digested fluidized form. Vertebrate submucosal tissue is a plentiful by-product of commercial meat production operations and is thus a low cost graft material, especially when the submucosal tissue is used in its native layer sheet configuration.
Suitable intestinal submucosal tissue typically comprises the tunica submucosa delaminated from both the tunica muscularis and at least the luminal portion of the tunica mucosa. In one embodiment of the present invention the intestinal submucosal tissue comprises the tunica submucosa and basilar portions of the tunica mucosa including the lamina muscularis mucosa and the stratum compactum. Those layers are known to vary in thickness and in definition dependent on the source vertebrate species.
The preparation of submucosal tissue for use in accordance with this invention is described in U.S. Pat. No. 4,902,508, the disclosure of which is expressly incorporated herein by reference. A segment of vertebrate intestine, preferably harvested from porcine, ovine or bovine species, but not excluding other species, is subjected to abrasion using a longitudinal wiping motion to remove the outer layers, comprising smooth muscle tissues, and the innermost layer, i.e., the luminal portion of the tunica mucosa. The submucosal tissue is rinsed with saline and optionally sterilized; it can be stored in a hydrated or dehydrated state. Lyophilized or air dried submucosa tissue can be rehydrated and used in accordance with this invention without significant loss of its biotropic and mechanical properties.
Submucosal tissue prepared from warm-blooded vertebrate organs typically has an abluminal and a luminal surface. The luminal surface is the submucosal surface facing the lumen of the organ source and typically adjacent to an inner mucosa layer in the organ source, whereas the abluminal surface is the submucosal surface facing away from the lumen of the organ source and typically in contact with smooth muscle tissue in the organ source.
The submucosal tissue graft compositions of the present invention can be preconditioned by stretching the material in a longitudinal or lateral direction as described in U.S. Pat. No. 5,275,826, the disclosure of which is expressly incorporated herein by reference. Multiple strips/pieces of submucosal tissue can also be fused together to form a unitary multi-layered submucosal tissue construct having a surface area greater than any to the individual strips/pieces of submucosal tissue. The process for forming large area/multilayered submucosal tissue constructs is described in U.S. patent application Ser. No. 08/418,515, the disclosure of which is expressly incorporated herein by reference. In summary, the process of forming large area sheets of submucosal tissue comprises overlapping at least a portion of one strip of submucosal tissue with at least a portion of another strip of submucosal tissue and applying pressure at least to said overlapped portions under conditions allowing dehydration of the submucosal tissue. Under th
Badylak Stephen F.
Cobb Mark A.
Isom Gary
Sharma Archana
Barnes & Thornburg
Jones Dwayne C.
Purdue Research Foundation
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