HOST-GRAFT CIRCULATION AND VASCULAR MORPHOLOGY IN PANCREATIC TISSUE-TRANSPLANTS IN RATS

One of the most determining factors for the survival of tissue grafts is an intact vasculature. This vasculature must, however, be linked to the circulation of the host animals for survival and growth to occur. The mechanism(s) of revascularization of pancreatic tissue grafts is still unclear and more so the process by which the host blood vessels anastomose with those of the graft. The microvasculature and revascula rization of neonatal pancreatic tissue fragments transplanted into the anterior eye chamber of rats were investigated using conventional lig ht and electron microscopy as well as the india ink perfusion method. Light microscopy demonstrated that the blood vessels of the host iris revascularized the transplants within 24 h of transplantation. Sinusoi dal blood capillaries were observed to invade the peripheral parts of the grafts. The capillary encroachment from the iris into the graft co ntinued through the second day of transplantation. The host-graft anas tomosis developed completely and became prominent and conspicuous afte r the third day of transplantation. Many capillaries were observed to encroach into the graft from the iris. The vasculature of the graft wa s increased in comparison with that of normal pancreatic tissue. This increase was prominent especially around pancreatic islet and ductal c ells which survived after transplantation. Blood cells observed in the se vessels of the graft indicated a functional state. The ultrastructu re of the intrinsic blood vessels of the graft was intact and showed t he peculiar fenestrations normally seen in the blood Vessels of endocr ine tissues. These observations indicated that pancreatic tissue fragm ents transplanted into the anterior eye chamber of rats were revascula rized within 24 h. The revascularization was completed at the end of t he third day of transplantation when definitive blood vessels linked t he circulation of the graft with that of the iris. Anat. Rec. 251:448- 459, 1998. (C) 1998 Wiley-Liss, Inc.