beta-MSCs: Successful fusion of bone marrow mesenchymal stromal cells with beta-cells results in a beta-cell like phenotype

Bone marrow mesenchymal stromal cells (MSC) have anti-inflammatory, anti-apoptotic and immunosuppressive properties and are a potent source for cell therapy. Cell fusion has been proposed for rapid generation of functional new reprogrammed cells. In this study, we aimed to establish a fusion protocol of bone marrow derived human MSCs with the rat beta-cell line (INS-1E) as well as isolated human pancreatic islets in order to generate functional insulin producing beta-MSCs as a cell-based treatment for diabetes. Human eGFP-puromycin MSCs were co-cultured with either stably mCherry-expressing rat INS-1E cells or human dispersed islet cells and treated with phytohemagglutinin (PHA-P) and polyethylene glycol (PEG) to induce fusion. MSCs and fused cells were selected by puromycin treatment. With an improved fusion protocol, 29.79 ± 2.92% of all MSCs generated beta-MSC heterokaryons based on double positivity for mCherry and eGFP. After fusion and puromycin selection, human NKX6.1 and insulin as well as rat Neurod1, Nkx2.2, MafA, Pdx1 and Ins1 mRNA were highly elevated in fused human MSC/INS-1E cells, compared to the mixed control population. Such induction of beta-cell markers was confirmed in fused human MSC/human dispersed islet cells, which showed elevated NEUROD1, NKX2.2, MAFA, PDX1 and insulin mRNA compared to mixed control. Fused cells had higher insulin content and insulin positive beta-MSCs also expressed nuclear PDX1. Our results show an efficient protocol for fusion of human MSCs and beta-cells, which resulted in a beta-cell like phenotype. This could be a novel tool for cell-based therapies of diabetes.