Implantation of rat insulinoma cell line into cyclosporine treated rats. Effect of the in vivo environment on beta-cell specific gene expression

Background. Transplantation of engineered beta cell-derived lines is a prom ising modality for cell-based therapy of diabetes mellitus. The in vivo env ironment and antirejection and other medications may have significant effec ts on the differentiation and proliferation of the transplanted beta cells, thus affecting their function. The effect of the in vivo environment on ex pression of genes encoding proteins involved in insulin production, secreti on, and glucose sensing were analyzed in the RIN 1046-38 cell line. Methods. RIN 1046-38 cells, were used for s.c. implantation in cyclosporine treated rats and for parallel in vitro culture. The differential expressio n of the insulin, PDX-1, GLUT-2, and glucokinase genes were assessed:by qua ntitative reverse transcription polymerase chain reaction. Results. The in vivo environment of cyclosporine-treated rats, preserved mo st of the differentiated characteristics of the implanted cells. Insulin an d glucokinase gene expression were maintained at high levels, although GLUT -2 expression decreased. This was in contrast to the substantial decrease o f all the three genes expression when cultured in vitro. Cyclosporine treat ment reduced insulin and GLUT-S gene expression in in vitro culture. Conclusions. beta cell implantation in cyclosporine-treated rats induces al teration in expression of genes pivotal to insulin production and secretion and the glucose sensing abilities. The normal in vivo environment improves the implanted b cell function by increasing the insulin gene expression an d content. Furthermore, it reverses some of the dedifferentiating changes c aused by the in vitro culture. This may have a positive effect on the thera peutic efficiency of this cell line.