Material and Methods for Nerve Grafting

Abstract

The subject invention pertains to compositions and methods for promoting repair of damaged nerve tissue using nerve grafts and preparation of nerve grafts. The compositions and methods of the subject invention can be employed to restore the continuity of nerve interrupted by disease, traumatic events or surgical procedures. Compositions of the subject invention comprise one or more chondroitin sulfate proteoglycan (CSPG)-degrading enzymes that promote axonal penetration into damaged nerve tissue and nerve graft. The invention also concerns methods for promoting repair of damaged nerve tissue using the present compositions and nerve tissue treated according to such methods. The invention also includes storage solutions for nerve tissue.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of provisional patent application Ser. No. 60 / 311,870, filed Aug. 13, 2001, which is hereby incorporated by reference in its entirety, including all figures, tables, and drawings.[0002]The subject invention was made with government support under a research project supported by National Institutes of Health Grant No. R01 NS37901. The government has certain rights in this invention.BACKGROUND OF THE INVENTION[0003]Peripheral nerve injuries are a major source of chronic disability. Poor management of nerve injuries is associated with muscle atrophy and can lead to painful neuroma when severed axons are unable to reestablish continuity with the distal nerve. Although nerves have the potential to regenerate after injury, this ability is strictly dependent upon the regenerating nerve fibers (and their axonal sprouts) making appropriate contact with the severed nerve segment (and the Schwann cell basal laminae ...

AI Technical Summary

Benefits of technology

The patent is about a new invention that promotes the repair of damaged nerve tissue. The invention involves using enzymes to break down a substance called chondroitin sulfate proteoglycan (CSPG), which can inhibit the growth of nerve cells. By removing this substance, the enzymes create a more favorable environment for nerve cells to grow and regenerate. The invention also includes methods for preparing nerve grafts by treating them with CSPG-degrading enzymes, as well as methods for culturing and providing nerve grafts for implantation. The technical effects of the invention include improving the ability of regenerating axons to traverse the nerve-nerve or nerve-graft interface, promoting axonal growth within the basal lamina scaffold, and increasing the number of axons that successfully penetrate damaged nerve tissue or implanted nerve grafts.

Problems solved by technology

Poor management of nerve injuries is associated with muscle atrophy and can lead to painful neuroma when severed axons are unable to reestablish continuity with the distal nerve.

Regenerating axons that fail to traverse the gap or injury site and enter the basal lamina of the severed distal nerve segment will deteriorate, resulting in neuronal death, muscle atrophy and permanent functional deficit (Fawcett J W et al.

Full restoration of function after repair of nerve transection remains an unobtainable ideal because of the fine microstructure of nerves and an inability to achieve precise axon-to-axon coaptation, despite the current state of the art in microsurgical techniques.

Nerve grafting is warranted with nerve ablation but presents several practical challenges.

While the availability of donor grafts suffers the difficulties of other organ replacement strategies, the importance of viable cellular elements in nerve grafts may be far less important.

However, while normal (uninjured) nerve is rich in laminin, normal nerve remains inhibitive or refractory to axonal growth.

Loss of function associated with nerve injury results from axon disruption.

Axons are very thin and fragile and the slightest injury (including compression) can cause a severing response (axotomy).

Transection injuries are those in which both axons and the nerve sheaths are severed, disrupting the continuity of the nerve and the guidance mechanisms required for axon regeneration.

In addition, axonal regrowth after nerve transection and repair is further complicated by the misalignment of proximal and distal elements.

Even in the instances of clean transection by a sharp instrument, the entire nerve structure is disrupted.

Swelling and axoplasmic outflow from the cut ends causes a mushrooming effect which interferes with accurate coaptation and realignment of the basal lamina scaffolding.

Consequently, any misalignment of nerve microstructure (after injury and repair) forces regenerating axonal sprouts to negotiate nonpermissive tissues which may severely limit their access to basal laminae in the distal nerve.

However, the procedure for creating pre-degenerated nerves in humans is impractical (i.e., nerve injury followed by a period of survival in vivo to allow tissue degeneration).

However, in vivo studies testing predegenerated nerve grafts have produced conflicting results, especially when using cellular (live) nerve grafts (Gordon et al.

Although not beneficial for optimizing the growth-promoting potential of nerve grafts, continued cold storage does further decrease cell viability, immunogenicity and the concerns of immunorejection of allogenic nerve grafts (Evans et al.

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