Enhanced pancreatic islet cell engraftment by treatment with serpin B1

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PROJECT SUMMARY The number of people with diabetes worldwide is predicted to increase from 415 million in 2015 to 642 million in 2040. The health care costs of treating diabetes accounts for 12% of the global health expenditure of which Type 1 diabetes mellitus (T1DM) constitutes 10-15% of the disease burden (IDF World Atlas 2015). T1DM is an autoimmune disease triggered by genetic and/or environmental factors in early childhood, resulting in T-cell mediated destruction of insulin producing pancreatic β-cells causing life-threatening hyperglycemia. Pancreatic β-cell transplantation is a promising experimental therapy that reverses diabetes in both animals and humans but is limited by the availability of donors and immune-mediated graft rejection and thus used primarily to control diabetes in patients who do not respond well to insulin replacement therapy or who develop severe complications. The discovery of new ways to induce tolerance without compromising a patient's immune system would be a major step forward in allowing wider adoption of β-cell transplantation as an effective therapy. One such protein displaying profound immunoregulatory effects is the human plasma protein alpha 1-antitrypsin (AAT, serpin A1) which is currently in clinical trials to improve pancreatic islet survival in patients undergoing renal transplantation, total pancreatectomy, or with difficult-to-control T1DM. Recently, the Kulkarni lab identified Serpin B1 (sB1) as a β-cell growth and survival factor. Serpin B1 is structurally and functionally related to AAT, and like AAT, is an effective anti-inflammatory protease inhibitor with immunoregulatory activities. However, sB1 also induces β-cell proliferation in vitro, promotes the neogenesis of insulin + cells in pancreatic ductal lining epithelia in vivo, induces immuno-tolerance by altering the Th17/Treg ratio in vivo and inhibits programmed cell death pathways not regulated by AAT. Independently, the Pemberton lab discovered that the protease inhibitory activity of sB1 can be rapidly inactivated by reactive oxygen and nitrogen (ROS/RNS) species and has formulated the protein with N-acetylcysteine to protect against this inactivation and mitigate the oxidative stress-induced inflammation, and pro-coagulant activities that islets are subject to during transplantation. We have demonstrated this formulation to prevent and treat new onset diabetes in the NOD mouse via mechanisms directly relevant to islet cell transplantation. Thus, we propose that sB1 will restore and maintain euglycemia in syngeneic (C57BL/6) and xenogeneic (NOD-SCID) mouse models of islet transplantation by protecting functional marginal β-cell masses against oxidative stress, IBMIR and inflammation while inducing their proliferation and enhancing immune tolerance by altering the Th17/Treg ratio. The proposed research in phase I will focus on producing highly purified active recombinant proteins and providing proof-of-principle in animal models of β-cell transplantation. The outcome of these studies will guide the design of future efficacy studies in animals and humans.