Fluorescence lifetime metabolic mapping of hypoxia-induced damage in pancreatic pseudo-islets.

Pancreatic islet isolation from donor pancreases is an essential step for the transplantation of insulin-secreting ß-cells as a therapy to treat type 1 diabetes mellitus. This process however damages islet basement membranes, which can lead to islet dysfunction or death. Posttransplantation, islets are further stressed by a hypoxic environment and immune reactions that cause poor engraftment and graft failure. The current standards to assess islet quality before transplantation are destructive procedures, performed on a small islet population that does not reflect the heterogeneity of large isolated islet batches. In this study, we incorporated fluorescence lifetime imaging microscopy (FLIM) into a pancreas-on-chip system to establish a protocol to noninvasively assess the viability and functionality of pancreatic ß-cells in a three-dimensional in vitro model (= pseudo-islets). We demonstrate how (pre-) hypoxic ß-cell-composed pseudo-islets can be discriminated from healthy functional pseudo-islets according to their FLIM-based metabolic profiles. The use of FLIM during the pretransplantation pancreatic islet selection process has the potential to improve the outcome of ß-cell islet transplantation.