Nonfreezing cryopreservation--a possible means of improving long-term transplant function?

Improving organ preservation techniques for transplantation is one of the most important goals of transplantation research. We have established a new, nonfreezing cryopreservation method to optimize the viability of rat kidneys for transplantation with up to 4 M dimethylsulphoxide (DMSO) in EuroCollins solution (EC) at -5 degrees C to -15 degrees C. We have confirmed the occurrence of a tubular and glomerular defect pattern that mediates acute tubular necrosis (ATN) and that may be a cause of major histocompatibility complex (MHC) independent immunological components of chronic transplant rejection. The extent of this defect [transplant survival and function, 31P-NMR spectroscopy, histological defect index] in the nonfreezing cryopreserved groups (n = 22) is significantly (P = 0.017) lower than in the simple cold storage group (n = 12). Quality and localization of the lesions in kidney transplants can elucidate the context of organ preservation, progressive hyperfiltration defects, and the occurrence of graft failure without elevated frequency of acute rejection episodes. These results indicate that further efforts to provide higher pretransplant organ viability without using it to prolong cold storage intervals may provide better insight into MHC-independent factors of chronic transplant failure and may result in improved long-term transplant outcome.