Primary isolation, culture expansion, and differentiation of human bone marrow-derived MSCs. (a) Net total cell expansion per flask for primary cultures grown in SFM for five continual passages. (b) (a) Morphology of passage 1 human bone marrow-derived MSCs in SFM. (b) Passage 5 MSCs in SFM were differentiated for 14 days and analyzed with (b) Oil Red O staining for adipocytes, (c) Alcian blue staining for chondrocytes, and (d) alkaline phosphatase staining for osteoblasts. a-d, 10× objective.