Method for processing and preserving collagen-based tissues for transplantation

Abstract

A method for processing and preserving an acellular collagen-based tissue matrix for transplantation is disclosed. The method includes the steps of processing biological tissues with a stabilizing solution to reduce procurement damage, treatment with a processing solution to remove cells, treatment with a cryoprotectant solution followed by freezing, drying, storage and rehydration under conditions that preclude functionally significant damage and reconstitution with viable cells.

Description

RELATED APPLICATION [0001] This application is a continuation-in-part of copending application Ser. No. 835,138 filed Feb. 12, 1992 which is a continuation-in-part of copending application Ser. No. 07 / 709,504 filed Jun. 3, 1991 which is a continuation-in-part of application Ser. No. 07 / 581,584 filed Sep. 12, 1990.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to methods for procuring decellularizing and further processing and dry preserving collagen-based tissues derived from humans and animals for transplantation into humans or other animals. These methods produce a tissue product that consists of a selectively preserved extracellular protein matrix that is devoid of certain viable cells which normally express major histocompatibility complex antigenic determinants and other antigens which would be recognized as foreign by the recipient. This extracellular protein matrix is made up of collagen and other proteins and provides a structural ...

AI Technical Summary

Benefits of technology

[0016] In its preferred form, the method of this invention includes the steps of processing biological tissues including treatment with a stabilizing solution to reduce procurement damage, treatment with a processing solution to remove cells and other antigenic tissue components, treatment with a cryoprotectant solution, freezing and storage under specific conditions to avoid functionally significant damaging ice crystal formation, drying under conditions to prevent damaging ice recrystallization, storage in the dry state at above freezing temperatures, rehydration under specific conditions and with a rehydration solution to minimize surface tension damage and further augment the selective preservation of the matrix, and reconstitution with viable cells that will not be rejected by the host.

Problems solved by technology

Despite major advancements in this field, modern tissue transplantation remains associated with complications including inflammation, degradation, scarring, contracture, calcification (hardening), occlusion and rejection.

Unfortunately, however, other complications can ensue with autologous transplants.

For example, significant damage can occur to several tissue components of transplanted veins during harvesting and prior to implantation.

This damage can include mechanical contraction of the smooth muscle cells in the vein wall leading to loss of endothelium and smooth muscle cell hypoxia and death.

Hypoxic damage can result in the release of cellular lysosomes, enzymes which can cause significant damage to the extracellular matrix.

Following implantation, such damage can lead to increased platelet adhesion, leucocyte and macrophage infiltration and subsequently further damage to the vessel wall.

The end result of such damage is thrombosis and occlusion in the early post implant period.

Even in the absence of such damage, transplanted autologous veins typically undergo thickening of the vessel wall and advancing atherosclerosis leading to late occlusion.

Dividing epidermal cells will ultimately grow into and cover the areas of the slits, however, the underlying dermal support matrix does not readily expand into these areas.

Absence of a dermal matrix results in scarring and contracture in the area of the slits.

This contracture can be severe and in cases of massively burned patients that undergo extensive split-skin grafting, can necessitate subsequent release surgical procedures to restore joint movement.

Synthetic materials can be made with low immunogenicity but are subject to other limitations.

Synthetic vascular conduits, often used in above-the-knee peripheral vascular bypass procedures, are subjected to an even higher incidence of occlusion than autologous grafts.

Glutaraldehyde-treated tissues, however, will not allow in-migration of host cells which are necessary for remodeling, and will gradually harden as a result of calcification.

Glutaraldehyde-treated bovine veins have been used in the past for vascular bypass bypass procedures, however, their use has been discontinued due to the unacceptable incidence of aneurysm formation and occlusion.

Despite this therapy, many allogeneic transplants, including heart valves and blood vessels, undergo an inflammatory response, and fail within 5-10 years.

Allogeneic skin is typically rejected within 1-5 weeks of application, and has never been demonstrated to be permanently accepted by the host, even with the use of immunosuppressive drugs.

When the freeze-drying process has been applied to more complex tissues such as heart valves, the results have been mixed but overall unsatisfactory.

Most of the freeze-dried valves failed due to mechanical causes in the early post-graft interval.

Chemical processing of more complex structures such as heart valves, vascular conduits and skin, however, has had only limited success in clinical applications.

Images