The Amphiphilic Oxygen Carrier Perfluorohexyloctane Improves Oxygenation of Ischemic Pig Pancreases and Increases the Quality of Isolated Islets Compared to Perfluorodecalin

Abstract

Introduction: Ischemia is one of the most critical variables for success or failure of islet isolation and islet transplantation. Prolonged cold storage is associated with reduced yield and decreased viability of isolated islets. Technical equipment for continuous vascular oxygen supply during cold storage of retrieved organs is expensive and requires trained personnel for operation. In the present study we assessed the efficiency of the amphiphilic compound perfluorohexyloctane (F6H8) to provide oxygen during static cold storage of pancreases retrieved from adult non-heartbeating pigs for subsequent islet isolation. Methods: Pancreases (n=10) were explanted after 15 min of warm ischemia and dissected ex-situ into the connecting and spleenic lobe. After intraductal perfusion with cold UW-solution the pancreatic segments were immersed in oxygen-precharged F6H8 or perfluorodecalin (PFD) and stored on ice for 9-10 hours until processing for islet isolation and purification. After culture at 37°C for 2-3 days islets were subjected to extensive quality assessment. All data are presented as mean ± SEM and were analysed by Wilcoxon test. Results: Pancreatic segments stored in oxygen-precharged F6H8 had a significantly higher intrapancreatic pO2 compared to preoxygenated PFD (10.1±3.9 vs. 1.6±1.1 mm Hg, p< 0.05). This finding corresponds to the significantly increased ATP content in islets isolated from segments stored in F6H8 (290±60 vs 203±31 pg/ng DNA, p< 0.01). Although freshly isolated islet yield per gram trimmed tissue did not significantly differ between F6H8 and PFD (3020±330 vs. 2940±270 IEQ/g) significantly more islets were recovered after culture when isolated from F6H8-stored lobes (57±6 vs. 39±6%, p< 0.01). Lower viability (76±3 vs. 82±3%, p< 0.05) measured in islets after PFD storage correlated with their inability to downregulate insulin release after switching from high (20 mmol/L) to basal (2 mmol/L) glucose concentration during static glucose incubation (Fig. 1).[Figure 1]Figure 1. Insulin release of islets isolated from ischemic porcine pancreatic segments after 9-10 hours of cold storage in oxygenprecharged PFD or F6H8. Islets were sequentially stimulated by 2 (white bars), 20 (grey bars) and again 2 mmol/L of glucose. *p< 0.05, **p< 0.01 as indicated. Conclusions: In the case that pig races, suitable for successful islet isolation, are locally not available, pancreas preservation for subsequent islet isolation can be significantly improved utilizing oxygen-precharged F6H8 for organ shipment. The same applies if pathogen-free pig pancreases have to be processed in institutions highly experienced in pig islet isolation.