FOLLOW-UP-STUDY OF THE REVASCULARIZATION PROCESS OF CRYOPRESERVED ISLETS OF LANGERHANS

Cryopreservation of islets of Langerhans is a necessary procedure sinc e human pancreatic islet transplantation has become a reality for the clinical treatment of Type I, insulin-dependent diabetes mellitus. Alt hough successful cryopreservation of rodent and human islets is a well -established technique for islet storage after isolation and purificat ion, little is known about the influence of the freeze-thaw procedure on the islets' potential to induce angiogenesis and revascularization, a major process necessary for the viability of grafted cells. In this study, the revascularization process of cryopreserved islets transpla nted in the liver and in the renal subcapsular space of diabetic and n ondiabetic rats is analyzed by a double indirect immunofluorescence te chnique. Frozen-thawed pancreatic islets were cooled slowly to -40 deg rees C, stored at -196 degrees C, and thawed rapidly. Lewis rats were grafted with either Lewis (isografts) or Wistar (allografts) overnight -cultured and frozen-thawed islets obtained by collagenase digestion. Rats were killed different days after implantation, and the livers and kidneys bearing the grafted islets were snap-frozen and immunohistoch emically stained with a double immunofluorescence technique using a ra bbit anti-factor VIII antiserum (which labels endothelial cells) and a guinea pig anti-insulin antibody. Overnight-cultured islet grafts com pleted revascularization by Days 4-7 after transplantation, as shown b y the detection of endothelial cells within and surrounding the islets . The identical staining pattern of revascularization was observed in islets frozen-thawed before transplantation. It is concluded that isle t cryopreservation is a suitable technique for long-term storage prior to transplantation since it does not interfere with the neovasculariz ation process of islet grafts. (C) 1996 Academic Press, Inc.