Lentivirus-mediated Bcl-2 expression in βTC-tet cells improves resistance to hypoxia and cytokine-induced apoptosis while preserving in vitro and in vivo control of insulin secretion

Abstract

βTC-tet cells are conditionally immortalized pancreatic β cells which can confer long-term correction of hyperglycemia when transplanted in syngeneic streptozocin diabetic mice. The use of these cells for control of type I diabetes in humans will require their encapsulation and transplantation in non-native sites where relative hypoxia and cytokines may threaten their survival. In this study we genetically engineered βTC-tet cells with the anti-apoptotic gene Bcl-2 using new lentiviral vectors and showed that it protected this cell line against apoptosis induced by hypoxia, staurosporine and a mixture of cytokines (IL-1β, IFN-γ and TNF-α). We further demonstrated that Bcl-2 expression permitted growth at higher cell density and with shorter doubling time. Expression of Bcl-2, however, did not interfere either with the intrinsic mechanism of growth arrest present in the βTC-tet cells or with their normal glucose dose-dependent insulin secretory activity. Furthermore, Bcl-2 expressing βTC-tet cells retained their capacity to secrete insulin under mild hypoxia. Finally, transplantation of these cells under the kidney capsule of streptozocin diabetic C3H mice corrected hyperglycemia for several months. These results demonstrate that the murine βTC-tet cell line can be genetically modified to improve its resistance against different stress-induced apoptosis while preserving its normal physiological function. These modified cells represent an improved source for cell transplantation therapy of type I diabetes.