Cryopreservation of insulin-producing tissue in rats and dogs

Transplantation of frozen-thawed islets of Langerhans normalized urine volume, urine glucose, plasma glucose, and weight gain in diabetic rats. However, these animals had abnormal intravenous glucose tolerance tests (ivGTT) at 3 mo post-transplant. Modified cryopreservation protocols were extended to canine islet-containing tissue: a higher temperature was used during equilibration in the 2 M dimethyl sulfoxide. Recipients of frozen-thawed isografts had prolonged normoglycemia with plasma glucose <105 mg/100 ml for up to 18 mo. During ivGTT at 6 mo post-transplant, K values (decline in glucose concentration, %/min) were similar in dogs autotransplanted with fresh (K=1.22±0.37) or cryopreserved tissue (K=1.8±0.4). Because of the similar compactness of the pancreas in humans and dogs, this canine model should be useful for formulating an optimal cryopreservation technique for human islets.