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Influence of islet culture on angiogenic and inflammatory mechanisms

Allan Langlois¹, Kevin Vivot¹, Nathalie Jeandidier^2,3, Camille Dollinger¹, William Bietiger¹, Michel Pinget^1,2,3, Severine Sigrist¹

¹Centre europeen d’étude du Diabète; ²Service d’endocrinologie, diabète, maladies métaboliques, Pôle NUDE, Hôpitaux Universitaires de Strasbourg; ³Université de Strasbourg, Strasbourg, France

Introduction: The early events hampering islet engraftment may be related to IBMIR and to the insufficient revascularisationof islets inducing β cells death. However, the influence of time of culture of islets on cellular mechanisms involved in islet revascularization and IBMIR are not well understood and must be elucidated. The aim of this work was to study the influence of islet culture on angiogenesis and inflammatory reactions in vitro.

Materials and methods: Rat pancreatic islets were cultured for 0, 12, 24 and 48h. The identification of signaling pathways involved in angiogenesis and IBMIR was performed by PCR array. 84 genes were analyzed using the RT ² Profiler PCR Array Data Analysis Template v3.2. Insulin expression was evaluated using qPCR. The comparative study of gene expression has been made toward t=0h (n= 3).

Results: After 12h of culture, islets exhibit a significant decrease in gene expression of growth factors and their receptors such as IGF1, the kdr… with respectively -18.42 and -5.65 fold (p <0, 001) which is maintained for 48 hours. No significant modulation of the expression of VEGF A, B and C is observed during the study. Then, the metallopeptidase 9 (MMP9) is 16.1 times overexpressed at 12h while its inhibitor TIMP1, was 55.01 times overexpressed (p <0.001). This unfavorable environment for angiogenesis is confirmed since 48 h of culture, MMP9 is not overexpressed in contrast to TIMP1 (20.3 times, p <0.01). Then, only after 48 hours of culture, we observed a significant increase of the expression of extracellular matrix genes such as procollagen 18 α1 (5.61 times, p <0.05). Moreover, after 12h of culture, the islets have a significant overexpression of proinflammatory cytokine such as IL-6 and CXCL1 with respectively 597.9 (p <0.001) and 429.2 fold (p <0, 05). However, this overexpression of proinflammatory cytokines decreased after 12h. Finally, in association to these results, the insulin expression decrease after 12h of culture with 0.68 ± 0.323 fold overexpression after 24h of culture versus 2.059 ± 0.597 fold after 12h (p< 0,05).

Conclusion: This study showed that current conditions of culture are deleterious to a good implantation of islet after transplantation. These results may help finding different ways of islets protection, if they are confirmed by proteomic data.