Background: We investigated the influence of exocrine tissue contamination on the process of vascularization of isolated pancreatic islets of Langerhans after free transplantation into Syrian golden hamsters.
Methods: After isolation by a modified collagenase digestion technique, a total of 45 individual islets contaminated with exocrine tissue were transplanted syngeneically into striated muscle of dorsal skinfold chambers of nine animals. Sixty-six purified islet grafts transplanted into nine additional animals served as controls. Islet engraftment as well as the process of angiogenesis and revascularization were analyzed at days 3, 5, 9, and 13 after transplantation using intravital fluorescent microscopic techniques.
Results: Islet grafts contaminated with exocrine tissue showed a significantly (P<0.05) lower take rate initially after transplantation when compared with purified islet grafts. In addition, functional capillary density, which served as an indicator of graft vascularization, was found significantly (P<0.05) decreased in contaminated compared with purified islets. Exocrine tissue contamination was further associated with marked leukocyte-endothelial cell interaction within the grafts' postcapillary venules, which finally resulted in six of nine animals in an overwhelming unspecific inflammation of the transplantation site with successive loss of the islet transplants.
Conclusions: These findings support the view that exocrine tissue contamination is detrimental for the process of angiogenesis and vascularization of freely transplanted pancreatic islets when grafted to a confined site such as striated muscle tissue.