CRYOPRESERVATION OF RAT PANCREATIC-ISLETS - EFFECT OF ETHYLENE-GLYCOLON ISLET FUNCTION AND CELLULAR COMPOSITION

Background. Inasmuch as cryopreservation can facilitate clinical islet transplantation by providing a means of storing supplemental islets i n order to augment marginally adequate grafts, protocols are needed to allow for a minimal loss in viable beta cells, By replacing the cryop rotectant dimethyl sulfoxide (DMSO) with ethylene glycol (EG), a more simplified cryopreservation protocol was developed, which resulted in improved survival and function of rat pancreatic islets, Methods, Nonf rozen islets, islets cryopreserved in DMSO, and EG-cryopreserved islet s were compared for percent recovery, cellular composition, in vitro v iability, and metabolic function after transplantation, Results, After cryopreservation in DMSO or EG, islet yield was similar to that of no nfrozen controls; however, islets cryopreserved in DMSO exhibited lowe r cellular DNA, insulin, and glucagon content, as well as an impaired insulin secretory capacity in vitro than the nonfrozen controls, When compared with controls, islets cryopreserved in DMSO contained a highe r proportion of beta cells but a lower number of glucagon-positive cel ls, whereas cryopreservation with EG resuited in similar DNA/hormone c ontents, in vitro viability, and cellular composition, Transplantation of islet grafts composed of comparable numbers of beta cells (2.1-2.3 million) corrected diabetes in 100% (6/6; nonfrozen controls), 92% (1 0/11; DMSO), and 100% (14/14; EG) of the recipients; however, those wh o received DMSO-treated islets took longer to achieve euglycemia and r emained glucose-intolerant. Conclusions, These results demonstrate tha t EG allows for the successful cryopreservation of rat islet beta and alpha cells with the same yield and quality as nonfrozen islets, The o bservation that alpha-cell survival was better after cryopreservation with EG may explain the improved functional viability of these grafts, Further studies are needed to assess whether this protocol provides a ny advantage for cryopreserving large numbers of human islets.