UPREGULATION OF ISLET-1 IN ISLETS CO-CULTURED WITH BONE MARROW MESENCHYMAL STEM CELLS PROMOTES ANGIOGENESIS THROUGH NF-ΚB PATHWAYS

Abstract

Purpose: Deficient angiogenesis in the early stage of islets transplantation is one of the main obstacles to its clinical application. Several studies have confirmed that co-transplantation of bone marrow mesenchymal stem cells (BMSCs) and islets can improve the angiogenesis in early transplanted islets, but the mechanism remaining further characterized. Islet-1 (Isl1) is a (LIM)-homeodomain transcription factor important for pancreatic islet cells development, maturation, and function.Importantly Isl1 can enhance the release of vascular endothelial growth factor-a (VEGF-A) in human umbilical vein endothelial cells and plays a vital role in angiogenesis. The aim of this study was to investigate whether upregulation of Isl1expression in islets co-cultured with BMSCs improved the poor angiogenesis in the early stage of islets transplantation. Methods: Primary islet cells isolated from Lewis rats and rat β cell line (INS-1) were cultured with or without BMSCs for 48 hours respectively, and then the islets function was detected by glucose-stimulated insulin secretion (GSIS). Viability of islets was measured using fluorescein diacetate and PI staining. The apoptosis assay of islets was performed by cytometry. Quantitative RT-PCR, immunoblot and immunofluorescence were enrolled to examine the mRNA and protein expression of Isl1 and VEGF-A of primary islet cells or INS-1 in co-culture and culture groups.Besides, we used lentiviral vector, GV358-Isl1, to increase Isl1 in INS-1 and corroborated the increase of Isl1,activator of the nuclear factor-kappa B (NF-κB) and VEGF protein levels by immunoblot analysis. Results: Co-culture of rat islet cells with BMSCs can improve rat survival rate and maintain glucose-induced insulin secretion. Though BMSCs cannot improve the loss of intraislet endothelial cells in early islet cells, it can reduce the early apoptosis rate of islet cells.Importantly, co-culture with BMSCs provoked both the mRNA and protein expressions of Isl1 and induced the expression of VEGF-A in islet cells.Our further study found that Isl1 overexpression of INS-1 greatly enhanced expression of NF-κB p65 and VEGF-A. Conclusion: Co-culture with BMSCs could induce the expression of ISL1 in islets, which promote angiogenesis by NF-κB pathways and ultimately ameliorate ischemia and hypoxia to improve the graft’s activity and survival rate. National Nature Science Foundation of China (grant no. 81970670).. National Nature Science Foundation of China (grant no. 81970688).. Correspondence to: Dr Xiaoming Ding, Department of Kidney Transplantation, Nephropathy Hospital, the First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, People’s Republic of China.