Characterization of α-smooth muscle actin positive cells during multilineage differentiation of dental pulp stem cells.

OBJECTIVES: Dental pulp tissue contains stem cells that can differentiate into multiple lineages under specific culture conditions; the origin of these dental pulp stem cells, however, is still unknown.
MATERIALS AND METHODS: Here we have utilized an α-SMA-GFP transgenic mouse model to characterize expression of a-smooth muscle actin (SMA)-GFP in subpassages of pulp-tissue-derived dental pulp cells, as perivascular cells express α-SMA.
RESULTS: During subculturing, percentages of cells expressing a-SMA increased significantly from passage 1 to 3. α-SMA-GFP-positive cells expanded faster than α-SMA-GFP-negative cells. The dental pulp cells at passage 3 were induced towards osteogenic, adipogenic or chondrogenic differentiation. All three differentiated cell lines expressed high levels of α-SMA (mineralized nodules, lipid droplets and chondrocyte pellets). GFP expression colocalized with differentiated osteoblasts, adipocytes and chondrocytes. Co-culturing the α-SMA-GFP-positive cells with human endothelial cells promoted formation of tube-like structures and robust vascular networks, in 3-D culture.
CONCLUSIONS: Taken together, the a-SMA-GFP-positive cells were shown to have multilieange differentiation ability and to promote vascularization in a co-culture system with endothelial cells.