High pancreatic islet sensitivity to hypoxia is an important issue in the field of pancreatic islet transplantation. A promising strategy to improve islet oxygenation in hypoxic conditions is to leverage the properties of hemoglobin as a natural carrier of oxygen. Studies using human or bovine hemoglobin have failed to demonstrate efficacy, probably due to the molecule being unstable in the absence of protective erythrocytes. Recently, marine worm hemoglobins have been shown to be more stable and to possess higher oxygen carrier potential, with 156 oxygen binding sites per molecule compared to four in humans. Previous studies have shown the beneficial effects of two marine worm hemoglobins, M101 and M201, on nonhuman pancreatic islets. However, their effects on human islets have not been tested or compared. In this study, we assessed the impact of both molecules during human islet culture in vitro under hypoxic conditions. Human islets were exposed to both molecules for 24 h in high islet density-induced hypoxia [600 islet equivalents (IEQ)/cm²]. M101 and M201 reduced the release of hypoxic (VEGF) and apoptotic (cyt c) markers in the medium after 24-h culture. Human islet function or viability was improved in vitro in the presence of these oxygen carriers. Thus, the utilization of M101 or M201 could be a safe and easy way to improve human islet oxygenation and survival in hypoxic conditions as observed during islet culture prior to transplantation or islet encapsulation.
Keywords: apoptosis; hypoxia; islet culture; islet transplantation; oxidative stress; oxygen carriers.