Transplantation of Langerhans islet into digestive organs of the diabetic rat

Kim, Byeong Moo; Min, Bon Hong; Park, In Sun

Abstract

Although replacement therapy with insulin can prevent acute metabolic disorder in patients with IDDM (insulin dependent diabetes mellitus), it does not permanently restore glucose homeostasis. Recently it has been reported that islet transplantation could completely correct the glucose metabolic abnormalities and prevent further progression of the secondary complications of IDDM. For successful transplantation, the isolated islets should be prepared without loss of viability, while their immunogenicity being suppressed to reduce graft rejection. The present study was aimed to determine the optimal condition of islet culture, and to transplant them into the digestive organs including gastroin-testinal wall and salivary gland. For islet culture, pancreatic islets were isolated by a modified collagenase digestion technique from rats and cultured for 24, 48 and 72 hours in RPMI-1640 containing 0, 5.6 and 16.7 mM glucose. The viability of islets was evaluated by detection of insulin mRNA expressed in islet beta-cells using the in-situ hybridization and northern blot analysis, while their insulin content was examined by immunocytochemistry. Insulin mRNA was significantly reduced after 48 hours of culture in the islets incubated with absence of glucose, while distinct immunoreaction for insulin remained in the same islet. On the other hand, the islets cultured with normoglycemic (5.6 mM glucose) and hyperglycemic (16.7 mM glucose) conditions showed a normal or excessive transcription of insulin gene after 72 hours, respectively. These results indicate that biosynthetic activity of islets could be maintained longer than 72 hours without alteration of viability when they were cultured in normoglycemic condition. Therefore, we used islets cultured for 72 hours with 5.6 mM glucose for transplantation. The islets were implanted into the submucosal wall of the stomach and duodenum as well as into the parenchyme of the submandibular gland of the streptozotocin-induced diabetic rats. The transplanted islets in the gastrointestinal wall were abolished in 72 hours, while the islets injected into the submandibular gland retained normal cellular structure with viability for longer period. The beta-cell in the submandibular gland showed similar immunoreactivity for insulin compared to that of normal islets. However, they showed gradual infiltration of lymphocytes and beta-cell destruction at 10~14 days after transplantation. We suggested that the submandibular gland could be recommended as an alternative site for islet transplantation, because it is very easy to access for transplantation and provides the structural and functional similarities to pancreas in which the islets spontaneously grow.