These results suggested that hUC-MSCs could induce M2 macrophage polarization in pancreatic islets of T2D mice, and this was further supported by the results form flow cytometry analysis for CD11c and CD206 (a marker for M2) (Fig. 4a–d) as well as the immunostaining of iNOS+ (a marker for M1), CD163 and ARG1 (markers for M2) (Supplementary Fig 4a-c). This evidence concerns the gene ARG1 and type 2 diabetes mellitus.