To further characterize the effect of metformin on endogenous MSCs, we recruited 10 T2DM patients without metformin medication history (T2DM, n = 10), 10 T2DM patients with metformin medication history (T2DM-M), and 10 healthy volunteers (Additional file 1: Table S1) to quantify the number of peripheral blood MSCs (CD34−/CD11b−/CD19−/CD45−/HLA-DR−/CD90+/CD73+/CD105+). Here, CD19 is linked to type 2 diabetes mellitus.