Regression of diabetic complications by islet transplantation in the rat.

AIMS/HYPOTHESIS: Type 1 diabetes is a chronic disease leading to complications such as peripheral neuropathies, nephropathy and cardiovascular disease. Pancreatic islet transplantation is being extensively investigated for blood glucose control in animals and in human type 1 diabetic patients, but the question of whether it can reverse long-term diabetic complications has not been fully explored. We investigated the effects of islet transplantation on diabetic complications in a rat model of streptozotocin-induced diabetes. METHODS: Three groups of rats were used: healthy controls, diabetic and diabetic rats transplanted with microencapsulated islets at 2 months after diabetes induction, when neuropathy was detectable by a decrease in tail nerve conduction velocity (NCV) and impaired nociceptive thresholds. Blood glucose levels and body weight were measured weekly. The variables considered were: thermal (hot plate test) and mechanical sensitivity (Randal-Selitto paw withdrawal test), NCV and Na+, K+-ATPase activity in the sciatic nerve. At the end of the experiments hearts were removed for morphometric determination and myocyte number, and kidneys removed for histological examination. RESULTS: Islet transplantation in diabetic rats induced normoglycaemia in a few days, accompanied by a rapid rise in body weight and amelioration of impaired nociceptive thresholds, as well as normalisation of NCV and Na(+), K(+)-ATPase, which were both about 25% below normal in diabetic rats. Myocyte loss was reduced (-34%) by islet transplantation and the observed mild kidney damage of diabetic rats was prevented. CONCLUSIONS/INTERPRETATION: Besides controlling glycaemia, transplantation of microencapsulated pancreatic islets induced almost complete regression of neuropathy and prevented cardiovascular alterations.

Bone marrow-derived mesenchymal stem cells improve islet graft function in diabetic rats.

Type 1 diabetes is associated with a progressive loss of beta cells and pancreatic islet transplantation could represent a cure for this disease. Herein we explored whether transplantation of bone marrow-derived mesenchymal stem cells (MSCs) allowed a reduced number of pancreatic islets to improve glycemic control in diabetic rats, by promoting islet vascularization. We transplanted 2000 syngenic islets alone or in combination with MSCs (10(6) cells) under the kidney capsules of diabetic Lewis rats. Animals transplanted with 2000 islets never reached normoglycemia. In contrast, rats transplanted with 2000 islets plus MSCs, showed a gradual fall in glycemia after transplantation, with normoglycemia maintained until killing. Comparable glycemic control was obtained with transplantation of 3000 islets alone. The MSC preparation used for in vivo experiments expressed high levels of vascular endothelial growth factor (VEGF(165)) and, at less extent, VEGF(189), as evaluated by reverse transcriptase polymerase chain reaction (RT-PCR). In transplanted animals, vascularization was quantified by morphometric analysis of islet grafts with anti-RECA and anti-insulin antibodies. MSCs were stained with PKH-26. Mean capillary density was 1002 +/- 55 capillaries/mm(2) in islets transplanted alone. Co-infusion of MSCs with islets significantly increased the number of capillaries to 1459 +/- 66 capillaries/mm(2). In conclusion, our study indicated that co-transplantation of MSCs with pancreatic islets improved islet graft function by promoting graft vascularization.