Beneficial effects of hyperbaric oxygen therapy on islet transplantation

We envisage that hyperbaric oxygen (HBO) would ameliorate islet anoxia, preventing early graft failure. Thus, treatment of HBO to diabetic recipients should improve the outcome of islet transplantation. We tested this hypothesis by syngeneically transplanting insufficient number of islets (150 islets) into streptozotocindiabetic C57BL/6 mice, each followed by HBO (2.4 ATA, 100% O₂) therapy for 1.5 h from day 0 to 28, once daily (group A) or twice daily (group B), or from day 5 to 28, once daily (group C) or twice daily (group D), 6 days/week. Recipients without HBO treatment served as controls. At day 28 after transplantation, groups B, C, and D gained weight and had lower blood glucose compared with their baseline values. In addition, groups B and D had higher insulin content of the graft than the controls. To determine the optimal timing of HBO therapy, groups B and D were compared with recipients treated with HBO twice daily, 6 days/week, from day -14 to 0 (group E) and from day -14 to 28 (group F). At day 28 after transplantation, groups B, D, E, and F had significantly lower blood glucose than their individual baseline values and higher insulin content of the graft than controls. But only group F had more β-cell mass of the graft than controls. These findings lend credence to the expectation that peritransplant application of adequate frequency of HBO to diabetic recipients would enhance the performance and growth of the islet graft, resulting in an improvement of the outcome of the transplantation.