ANGIOGENESIS IN CULTURED AND CRYOPRESERVED PANCREATIC-ISLET GRAFTS

Background. The ability of rat pancreatic islets to revascularize afte r transplantation was examined via in vitro and in vivo imaging of the microvasculature using laser scanning confocal microscopy (LSCM). Met hods. Cultured or cryoprocessed islets were transplanted at the renal subcapsular site in rats. At various time intervals after transplantat ion, three-dimensional imaging of the graft was performed by LSCM. In vitro studies were conducted via microvascular corrosion casting of th e grafted kidney in situations where it was difficult to obtain in viv o confocal data due to surgical complications. The vascular morphology of the islet grafts was evaluated quantitatively via digital image an alysis algorithms to determine the morphology of the neovascular ingro wth and the rate of revascularization. Results. In cultured islet graf ts, the initiation of angiogenesis was observed within 1 week, charact erized by the presence of capillary sprouts, tortuous vessels, and blo od vessels with blind ends. The revascularization of the graft was typ ically completed within 2 weeks and could be distinguished as a networ k of completely perfused blood vessels consisting of intertwining capi llaries, with surrounding arterioles and venules. The angiogenesis pro cess in cryopreserved islet grafts required a longer time period to in itiate (similar to 2 weeks), and the revascularization was completed i n 1 week after the initiation. Conclusions. These results successfully demonstrate the potential of the described in vivo and in vitro LSCM techniques to measure the angiogenesis process in pancreatic islet gra fts.