PANCREAS

R. Oberhuber¹, M. Maglione², B. Cardini², M. Hermann³, P. Obrist⁴, S. Schneeberger⁵, R. Margreiter⁶, J. Pratschke¹, E. Werner⁷, G. Brandacher^1
1Department Of Visceral, Transplant And Thoracic Surgery, Innsbruck Medical University, Innsbruck/AUSTRIA, ²Center Of Operative Medicine, Department Of Visceral, Transplant And Thoracic Surgery, Innsbruck Medical University, Innsbruck/AUSTRIA, ³Department For Islet Cell Transplantation, Innsbruck Medical University, Innsbruck/AUSTRIA, ⁴Institute Of Pathology, St. Vinzenz KH, Zams/AUSTRIA, ⁵Transplant Surgery, University Hospital, Innsbruck/AUSTRIA, ⁶Department Of Visceral Transplant And Thoracic Surgery, Innsbruck Medical University, Innsbruck/AUSTRIA, ⁷Division Of Biological Chemistry, Biocenter, Innsbruck Medical University, Innsbruck/AUSTRIA

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Introduction: Ischemia-reperfusion injury (IRI) is a major cause of graft pancreatitis and a severe complication after pancreas transplantation (PTX). Recently, significantly reduced parenchymal damage after IRI was shown following treatment with tetrahydrobiopterin (H4B), an essential cofactor of nitric oxide synthases (NOS). Here we analyzed if H4B supplementation apart from tissue protection is also able to prolong survival and compared its efficacy with to strong antioxidants, vitamin C (VitC) and the pterin analog tetrahydroneopterin (H4N). Methods: Male syngeneic C57BL6 mice were used as size-matched donor and recipient pairs. Heterotopic PTX was performed with a modified no-touch technique. To induce graft pancreatitis grafts were subjected to 16h prolonged cold ischemia time (CIT) and to 45min warm ischemia. Treatment regimens included: H4B, H4N 50mg/kg, respectively and VitC 350mg/kg (all prior to organ retrieval). Untreated grafts served as controls. Graft microcirculation was analyzed by intravital fluorescence microscopy evaluating functional capillary density (FCD) and capillary diameters (CD). Parenchymal damage and peroxynitrite formation were assessed by H&E histology and by immunostaining. H4B tissue levels were determined by HPLC. In addition, recipient survival and endocrine graft function were studied. Results: Prolonged CIT resulted in significantly impaired microcirculation compared to non-ischemic controls. Pancreatic grafts treated with H4B displayed NOS stabilization and hence markedly improved microcirculation with significantly higher FCD as compared to untreated animals (p<0.01). In contrast, neither H4N nor the strong antioxidant VitC lead to enhanced FCD (p=ns). Compared to controls application of both pteridin analogues as well as VitC significantly attenuated intragraft peroxynitrite formation (p<0.05). However, reduction of IRI-related tissue damage was most pronounced following H4B pre-treatment (p<0.05). Finally, H4B treated pancreatic grafts showed significantly prolonged survival and improved endocrine function compared to non-treated animals (p<0.0001). In contrast, pretreatment with H4N and VitC did not improve recipient survival. Conclusion: Only H4B attenuates graft pancreatitis and significantly improves recipient survival and might therefore be a novel promising agent preventing IRI following PTX.

Disclosure: All authors have declared no conflicts of interest.