Mitomycin-C Treatment Followed by Culture Produces Long-Term Survival of Islet Xenografts in a Rat-to Mouse Model

Abstract

One of the goals of islet transplantation is to transplant viable islets without host immunosuppression. The present study was designed to determine whether pretreatment of islets with mitomycin-C (MMC) followed by culture enhances islet survival in a rat-to-mouse xenogeneic combination. WS(RT1k) rat islets pretreated with various concentrations of MMC (0, 3.2, 10, 32, 100, 320, and 1000 μg/ml) were tested for viability by in vitro insulin secretory capacity and vital staining of islets. The MMC-treated islets (10 μg/ml) cultured for various periods (4, 20, or 40 h, 3 or 7 days) were transplanted into the renal subcapsular space of STZ-induced diabetic C57BL/6 (B6: H-2b) mice. MMC-treated or nontreated islets were subjected to microarray gene analysis and immunohistological study. Evaluation of in vitro insulin secretory capacity and vital staining of islets indicated that MMC at a dose ≤32 μg/ml is nontoxic and preserves islet function. Marked prolongation of graft survival was noted with half of islet grafts surviving indefinitely (>100 days) when 10 μg/ml of MMC-treated islets was transplanted after 40 h or 3 days in culture, but not when they were transplanted within 4 h following treatment or at 7 days following treatment, indicating that there is a critical culture period necessary for successful islet graft survival. Microarray analysis suggested possible genes for this prolongation with TGF-β highly expressed in MMC-treated islets subjected to culture for 3 days. Our results indicate that MMC treatment followed by a critical culture period induces marked prolongation of rat islet xenograft survival in nonimmunosuppressed recipient mice, offering a strategy for islet transplantation without immunosuppression.