Fibrin supports subcutaneous neonatal porcine islet transplantation without the need for pre-vascularization.

Background Neonatal porcine islets (NPIs) are a promising tissue source for clinical islet xenotransplantation. To facilitate graft monitoring and recovery if needed, an extra-hepatic transplant site would be optimal. In addition, islet transplantation into the portal vein has been associated with life-threatening intraperitoneal bleeding, portal vein thrombosis, hepatic steatosis, and loss of islet graft function. Although it is hypoxic, the subcutaneous space is a potential extra-hepatic location for clinical islet transplantation. In this study, we explore the benefits of fibrin scaffolds in enhancing the engraftment and long-term function of NPI grafts in this ectopic site. Methods Diabetic immune-compromised mice were transplanted with 5000 NPIs under the kidney capsule (KC), and subcutaneously with or without fibrin (SC + F, SC, respectively). All mice were monitored for reversal of hyperglycemia and long-term metabolic function. Results All mice transplanted with NPI under the KC or SC + F (12/12 and 17/17, respectively) achieved normal fasting blood glucose levels between 5 and 22 weeks post-transplantation and displayed normal glucose tolerance during an intraperitoneal glucose tolerance test. In contrast, NPIs transplanted SC with no fibrin (n = 7) failed to obtain normoglycemia. Conclusion Fibrin matrix facilitates engraftment of NPIs in the subcutaneous site of diabetic mice. These data support further investigation of the subcutaneous site for clinical islet xenotransplantation.