Therapeutic effect of human mesenchymal stem/stromal cells (hMSCs) in the context of beta cell engraftment. Human MSCs modulate the host immune systems, for example, by secreting various trophic factors. Therefore, they prevent rejection of allogenic beta cell grafts and improve the survival of the graft by promoting neoangiogenesis at the transplant site and prevent apoptosis and fibrosis. ┤ inhibition, → improvement. Abbreviations: VEGF: vascular endothelial growth factor; IGF-1: insulin-like growth factor 1; PDGF: platelet-derived growth factor; CCL2: monocyte chemoattractant protein-1; FGF-2: basic fibroblast growth factor; IL-5/6/10: interleukins 5, 6, and 10; HGF: hepatocyte growth factor; GM-CSF: granulocyte macrophage colony-stimulating factor; TGF-β: transforming growth factor beta; PGE2: prostaglandin E2; IDO: indoleamine 2,3-dioxygenase; HO-1: heme oxygenase 1; NO: nitrogen monoxide; HLA-G5: human leukocyte antigen-G5.