Cryopreservation of islets of Langerhans does not affect angiogenesis and revascularization after free transplantation

Abstract

Cryopreservation of isolated islets of Langerhans will be a necessary procedure if pancreatic islet transplantation crosses the threshold for clinical treatment of diabetes mellitus. Although successful cryopreservation of rodent, canine, porcine and human islets has been documented in the past few years, little is known about the influence of the freeze-thaw procedure on the islet's potential to induce angiogenesis and revascularization, a process which is of crucial importance after free transplantation. We have analyzed the process of revascularization of 1- and 10-week-cryopreserved hamster islet isografts using intravital fluorescence microscopy. First signs of angiogenesis of cryopreserved islet grafts were observed on day 2 after transplantation, characterized by the protrusion of capillary sprouts. During the following days these sprouts formed a microvascular network, and revascularization was completed on day 10 after transplantation. Quantitative analysis of functional capillary density, capillary red blood cell velocity, capillary diameter and flow of individual capillaries did neither show differences between 1- and 10-week-cryopreserved islets, nor differences between cryopreserved islets and islets transplanted without cryopreservation were observed. From these results we conclude that cryopreservation of isolated pancreatic islet grafts is an adequate technique for long-term storage prior to transplantation.