Hydroxyapatite nanocrystals stimulate osteogenic differentiation in primary human aortic smooth muscle cells by activation of oxidative stress and the ERK pathway

Hydroxyapatite nanocrystal (HN) deposition underlies the development of vascular calcification, which is an actively regulated process resembling bone formation. This study investigated the role of HNs in inducing osteogenic differentiation of primary human aortic smooth muscle cells (HASMCs).

These findings suggest that HNs stimulated osteogenic differentiation of vascular smooth muscle cells that build biomineralized deposits partly by activating oxidative stress and the ERK pathway.

Primary HASMCs were incubated with HNs, cell osteogenic differentiation was evaluated by von kossa staining and calcium content. The expressions of SM-α-actin and bone markers, including runt-related transcription factor 2 (Runx2), osteopontin (OPN), osterix, and collagen 1 (COL1) were also determined. Antioxidants, ERK-specific inhibitor were used to examine whether oxidative stress and the ERK pathway were required for this transition.

Stimulation of HASMCs with HNs increased calcium deposition, expression of bone markers and decreased SM-α-actin expression. HNs produced reactive oxygen species (ROS) in HASMCs, as evaluated by fluorescent probe. Antioxidants inhibited HN-induced osteogenic differentiation. Furthermore, the inhibitor of the ERK pathway, PD98059, suppressed the effect of HNs on bone marker expression. Conclusions: These findings suggest that HNs stimulated osteogenic differentiation of vascular smooth muscle cells that build biomineralized deposits partly by activating oxidative stress and the ERK pathway.