Project Summary: Total pancreatectomy and islet autotransplantation (TP-IAT) are currently performed in around 20 centers worldwide for the treatment of chronic pancreatitis (CP). Major problems associated with TP-IAT are poor islet engraftment and dysfunction after intraportal infusion. Because of these issues, only around 20% of the non- diabetic CP patients are insulin-independent after surgery. Currently, interventional protocols to increase the survival of the islet graft following transplantation are empiric. Thus, effective therapies that can facilitate islet cell engraftment and promote survival after transplantation are urgently needed. Multiple studies including our own demonstrate that islet co-transplantation with mesenchymal stem cells (MSCs) enhances islet engraftment, decreases number of islets needed to achieve normoglycemia in rodent and nonhuman primate islet transplantation models. MSCs exert such effects mainly via direct cell-cell contact and their paracrine secretion of protective molecules including insulin growth factor-1 (IGF-1), hepatocyte growth factor (HGF), transforming growth factor β (TGF- β) and others. We are the first group who performed a pilot NIH-funded clinical trial evaluating the feasibility of autologous bone marrow-derived ex vivo-expanded MSCs (BM-MSCS) and islet co-transplantation in CP patients. Although only three subjects received MSC and islet co- transplantation due to the pilot nature of the grant, our data showed that BM-MSCs and islet co-transplantation was a safe and promising strategy to improve islet engraftment after transplantation. Based on this unique clinical trial experience and animal studies, the goal of this study is to further evaluate the safety and efficacy of autologous MSCs and islet co-transplantation in a larger TP-IAT patient population. Our hypothesis is that co- transplantation of islets with autologous BM-MSCs can enhance islet survival and function after transplantation, resulting in more CP patients being diabetes free after TP-IAT. A critical part of this trial will be to define the mechanisms by which MSCs modulate β cell survival and explore cellular and molecular biomarkers that can be used as indicator(s) for β cell death and the potential response/efficacy of MSC therapy. Results from these studies are not only urgently needed for the prevention of post-surgical diabetes in CP patients, but also may offer useful information on which to address the more complex allogeneic islet cell transplantation for patients with type 1 diabetes.