Low Temperature Condition Prevents Hypoxia-Induced Islet Cell Damage and HMGB1 Release in a Mouse Model

Abstract

One of the major issues in clinical islet transplantation is the poor efficacy of islet isolation. During pancreas preservation and islet isolation, islets suffer from hypoxia as islets are highly sensitive to hypoxic conditions. Cold preservation has been applied to minimize hypoxia-induced cell damage during organ preservation. However, the studies related to hypoxia-induced islet cell damage during islet isolation are limited. Recently, we demonstrated that mouse islets contain high levels of high-mobility group box 1 protein (HMGB1), and during proinflammatory cytokine-induced damage, islets release HMGB1 outside the cell. The released HMGB1 is involved in the initial events of early islet loss. In the present study, we hypothesize that low temperature conditions could prevent both hypoxia induced islet cell damage and HMGB1 release from islets in a mouse model. Isolated mouse islets underwent normoxic condition (95% air and 5% CO2) at 37°C or hypoxic conditions (1% O2, 5% CO2, and 94% N2) at 37°C (hypoxia-37°C islets), 22°C (hypoxia-22°C islets), or 4°C (hypoxia-4°C islets) for 12 h. In vitro and in vivo viability and functionality tests were performed. HMGB1, IL-6, G-CSF, KC, RANTES, MCP-1, and MIP-1 α levels in the medium were measured. Low temperature conditions substantially reduced hypoxia-induced necrosis ( p < 0.05) and apoptosis ( p < 0.05). In addition, low temperature islet culture significantly increased the insulin secretion from islets by high glucose stimulation ( p < 0.05). All of the recipient mice reversed diabetes after receiving the hypoxia-4°C islets but not after receipt of hypoxia-37°C or 22°C islets. The amounts of released HMGB1, IL-6, G-CSF, KC, RANTES, MCP-1, and MIP-1 α were significantly reduced in the hypoxia-4°C islets compared to those of the hypoxia-37°C islets ( p <0.05). In conclusion, low temperature conditions could prevent hypoxia-induced islet cell damage, inflammatory reactions in islets, and HMGB1 release and expression. Low temperature conditions should improve the efficacy of isolated islets.