Canine islet isolation, cryopreservation, and transplantation to nude mice.

Background: Successful human islet transplantation has led to insulin independence in type 1 diabetes. Dogs constitute an animal model for preclinical studies. We present our recent experience in canine islet isolation, cryopreservation and transplantation.

Methods: Twenty-seven pancreases from mongrel dogs, weighing 9-31 kg, were removed. Each pancreas was digested with collagenase, and then purified by density gradients. Islet number and purity were counted, and the viability of isolated islets was assessed in vitro by static incubation, perifusion study and in vivo transplantation into nondiabetic or diabetic nude mice. Additionally. freshly isolated islets were cryopreserved for 1 week, and then studied in vitro.

Results: The islet yield and purity were 121,000 +/- 135,000 IEQ per pancreas and 81.4 +/- 1.2%, respectively. The stimulation index (insulin release in 300 mg/dl glucose/insulin release in 100 mg/dl glucose) of the isolated islets was 6.6 +/- 1.9 (N = 7), and first and second phases of insulin secretion were demonstrated during perifusion study. After 1-week cryopreservation, the islet number decreased from 1,000 to 540 (N = 1) and insulin content decreased from 50.95 to 39.23 microg/150 islets (N = 1). These islets maintained their insulin response to high glucose. Four weeks after transplantation, the grafts showed abundant beta-cells and significant insulin content. Normoglycemia was achieved in 14 of 23 diabetic recipients after transplantation with 2,000 freshly isolated islets.

Conclusion: Canine islets isolated at our laboratory were viable and maintained their physiological function both in vitro and in vivo.