Improved outcomes in islet isolation and transplantation by the use of a novel hemoglobin-based O₂ carrier

During isolation, islets are exposed to warm ischemia. In this study, intraductal administration of oxygenated polymerized, stroma-free hemoglobin-pyridoxalated (Poly SFH-P) was performed to improve O₂ delivery. Rat pancreata subjected to 30-min warm ischemia were perfused intraductally with collagenase in oxygenated Poly SFH-P/RPMI or RPMI (control). PO₂ was increased by Poly SFH-P (381.7 ± 35.3 mmHg vs. 202.3 ± 28.2, p = 0.01) and pH maintained within physiological range (7.4-7.2 vs. 7.1-6.6, p = 0.009). Islet viability (77% ± 4.6 vs. 63% ± 4.7, p = 0.04) was improved and apoptosis lower with Poly SFH-P (caspase-3: 34,714 ± 2167 vs. 45,985 ± 1382, respectively, p = 0.01). Poly SFH-P improved islet responsiveness to glucose as determined by increased intracellular Ca²⁺ levels and improved insulin secretion (SI 5.4 ± 0.1 vs. 3.1 ± 0.2, p = 0.03). Mitochondrial integrity was improved in Poly SFH-P-treated islets, which showed higher percentage change in membrane potential after glucose stimulation (14.7% ± 1.8 vs. 9.8 ± 1.4, respectively, p < 0.05). O₂ delivery by Poly SFH-P did not increase oxidative stress (GSH 7.1 ± 2.9 nm/mg protein for Poly SFH-P vs. 6.8 ± 2.4 control, p = 0.9) or oxidative injury (MDA 1.8 ± 0.9 nmol/mg protein vs. 6.2 ± 2.4, p = 0.19). Time to reach normoglycemia in transplanted diabetic nude mice was shorter (1.8 ± 0.4 vs. 7 ± 2.5 days, p = 0.02), and glucose tolerance improved in the Poly SFH-P group (AUC 8106 ± 590 vs. 10,863 ± 946, p = 0.03). Oxygenated Poly SFH-P improves islet isolation and transplantation outcomes by preserving mitochondrial integrity.