Phase-changing citrate macromolecule combats oxidative pancreatic islet damage, enables islet engraftment and function in the omentum

Abstract

Clinical outcomes for total-pancreatectomy followed by intraportal islet autotransplantation (TP-IAT) to treat chronic pancreatitis (CP) patients are suboptimal due to the inflammatory state of the patients pancreas, oxidative tissue damage during the isolation process, and the harsh engraftment conditions in the livers vasculature, which include ischemia-reperfusion injury, and instant blood-mediated inflammatory reactions. We describe the use of the thermoresponsive, antioxidant macromolecule poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN) to protect islet redox status and function in vitro and in vivo and to create a viable extrahepatic islet engraftment site in the abdomen. PPCN in aqueous media transitions from a liquid to an elastic hydrogel when exposed to body temperature via temperature-induced macromolecular self-assembly. Islets entrapped in the PPCN hydrogel and exposed to oxidative stress remain functional and support long-term euglycemia, in contrast to islets entrapped in a biologic scaffold (BS). When applied to the omentum of non-human primates (NHPs), PPCN is well-tolerated, safe, and mostly resorbed without fibrosis at 3 months post-implantation. To obtain autologous islets, a partial pancreatectomy was performed, followed by STZ administration to induce diabetes and destroy any remaining endogenous islets. Application of the autologous islets to the momentum using PPCN restored normoglycemia with minimal insulin requirements for over 100 days. These results support the use of PPCN as a scaffold for minimally invasive delivery of islets to the omentum of pancreatitis patients and highlight the importance of scaffold antioxidant properties as a new mechanism to protect islet function and maximize long-term autologous graft performance. One Sentence SummaryOmentum islet transplantation using a thermoresponsive, antioxidative polymer supports autologous islet viability and function in nonhuman primates.