Islet transplantation is becoming a potential cure for type 1 diabetes (T1D). However, the limited supply and significant islet loss in the peritransplant period are cast as the major limitations of this treatment strategy. This project is aimed to improve the therapeutic outcome of islet transplantation by introducing constitutively active Akt1 (CA-Akt1) into the insulin producing 2-cells ex vivo. The serine/threonine protein kinase Akt/PKB is the direct downstream target of PI3 Kinase pathway, and has been found to have dual functions of anti-apoptosis and induction of cell proliferation. Relevance of Akt on 2-cell survival and proliferation has been demonstrated in studies of transgenic and knockout mouse models, as well as using pharmacological methods. Nonetheless, in order to realize the therapeutic potential of CA-Akt1, a safe, efficient and specific vector is needed to deliver Akt1 into islet 2-cells ex vivo. In this regard, adenovirus serotype 5 (Ad5)-based vector is of great interest. Our previous studies have demonstrated the modified Ad5 vector, AdRGDpK7, exhibited significantly higher gene transfer efficiency for the human islet cells. We thus propose to employ Ad5RGDpK7 to deliver Akt1 into islet cells ex vivo. To further diminish the potential adverse effect of CA-Akt1, we will restrict exogenous Akt1 expression in 2-cells by employment of 2-cell specific promoter-rat insulin promoter (RIP) to drive Akt1 expression. In addition, we propose to co-express a dual functional modality, HSV-TK, with CA-Akt1 so that it can be used as both a non-invasive imaging modality to follow the transplanted islets and a suicide gene should malignancy occur.
Our specific aims are thus: 1) To develop a 2-cell specific, infectivity-enhanced Ad5 vector that allows efficient and specific CA-Akt1 and HSV-TK gene delivery into 2-cells ex vivo;2) To examine the capacity of the Ad5 vector developed above to promote islet survival and proliferation while minimizing transformation, thus enhancing the efficacy of islet transplantation;and 3) To evaluate the safety of the Ad5 vector developed above in the context of islet transplantation.
It is clear that islet transplantation holds great potential for the cure of Type 1 Diabetes. This study seeks to improve the therapeutic outcome of islet transplantation by modifying the islets with protective genes using a highly efficient, specific and safe gene delivery vector. Success of this study is expected to have significant impact in the field of islet transplantation treatment for type 1 diabetes.
