Nanoparticle contrast-enhanced computed tomography and magnetic resonance imaging of vascularization of a subcutaneous niche for islet transplantation

Revascularization plays a critical role in the successful engraftment of transplanted pancreatic islets, which are inherently rich in capillaries to meet their high metabolic demands. Innovative islet encapsulation strategies such as the NICHE (neovascularized implantable cell homing and encapsulation), generate a prevascularized transplantation site that allows for direct integration of the graft with the systemic circulation. Timing the transplantation is key to maximizing islet engraftment and survival, especially in diabetic individuals, who exhibit impaired wound healing. Therefore, in this study, we explored different methods to assess vascular development within NICHE in vivo in a non-invasive fashion. We effectively tracked neoangiogenesis using nanoparticle contrast-enhanced computed tomography (nCECT), observing a steady increase in vascularization over an 8-week period, which was confirmed histologically. Next, we estimated relative vascularization changes via T2 mapping with magnetic resonance imaging (MRI) before and after islet transplantation. On the first day post-transplantation, we measured a slight decrease in T2 values followed by a significant increase by day 14 attributable to islet revascularization. Our findings underscore the potential of non-invasive imaging techniques to provide insightful information on the readiness of the transplant site within cell encapsulation systems to support cell graft transplantation.