Decreased survival of islet allografts in rats with advanced chronic complications of diabetes

Successful islet transplantation has been possible in experimental animals in contrast to humans. One difference between animal models of diabetes and human islet transplantation is the presence of advanced chronic complications in humans. Even longer-term follow-up of islet transplantation in humans according to the Edmonton protocol suggests that advanced chronic complications may adversely affect allograft survival with the glucocorticoid-free immunosuppressive regimen as well. We developed a rat model of chronic complications of diabetes and compared islet allograft survival in rats with advanced chronic complications to age-matched control rats with acute onset diabetes. Islets were transplanted at either the renal supcapsular, intrahepatic, or intramuscular location. The survival of islet allografts in rats with chronic complications was decreased at all sites compared with the age-matched controls. The best survival in the rats with advanced chronic complications occurred at the renal subcapsular site. Blood sugar measurements indicated impaired glucose tolerance in most of the rats with chronic complications and surviving renal subcapsular islet allograft. Histological and gross examination of the surviving renal subcapsular islet allografts indicated disordered angiogenesis in the rats with chronic complications. Rats with successful intrahepatic islet allografts and the respective age-matched controls had comparable blood sugars. Survival of islet allografts at the intramuscular site was poor in rats with chronic complications or acute onset diabetes. We conclude that the structural or metabolic abnormalities associated with chronic poor control of diabetes impair islet allograft survival and function. This should be considered as a possible explanation for failure of islet allograft survival in human islet transplantation.