Cryopreservation and the age of the allotransplant

Abstract

For centuries, reconstructive surgeons have restored form and function with autografts. These techniques are highly effective, but they are associated invariably with donor site morbidity. To avoid this, surgeons have long dreamed of using cadaveric sources for reconstructive material. However, allografts have two major limitations: rejection and limited donor tissue. In order to limit rejection, the allograft must be rendered more tolerable to the host or the host must be rendered more tolerant of the allograft. Both strategies have been used with considerable success in recent years. As understanding of the human immune response increases, clinical immunosuppressive regimens will undoubtedly become less morbid, and the indications for allotransplantation will broaden. This will place an even greater burden on the already small donor pool. One way to relieve this burden would be through the development of strategies for the long-term preservation of donated tissues and organs. Cryopreservation has been used clinically for decades, and recent advances in the field have allowed the preservation of an ever widening array of tissues and organs. As cold storage has been shown to reduce the antigenicity of parts, cryopreservation may actually serve to improve the survival rate of transplanted parts, as well as increase their availability. As the era of autotransplantation gives way to the age of allotransplantation, cryopreservation will play an increasingly important role.

Keywords: allograft; composite tissue allotransplantation; cryopreservation; cryoprotective agents; donor-specific tolerance.

Figure 1

(A) A 48 year old patient following free fibular osteocutaneous composite reconstruction of a defect involving mandible, chin, lower lip and oral mucosa. (B) The typical donor site defect. Today's indications for free tissue transfer will likely be tomorrow's indications for composite tissue allotransplantation.

Figure 2

(A) Experimental animal on postoperative day one following microsurgical transplantation of a cryopreserved and thawed composite flap. (B) Appearance of transplant on postoperative day seven, with a small area of peripheral necrosis. (C) Appearance of transplant on postoperative day 60, with full survival of the transplant and normal hair growth.