Sympathetic neuron can promote osteoblast differentiation through BMP signaling pathway

Communication between sympathetic neurons and osteoblasts through the adrenergic receptor pathway has already been reported. To investigate whether the sympathetic neurons have a direct effect on osteoblast differentiation, an in vitro Transwell coculture system was established in which osteoblasts were cocultured with sympathetic neurons with no cell-to-cell contact. The expression of osteogenesis-related genes was upregulated in osteoblasts cocultured with sympathetic neurons. Meanwhile, bone morphogenetic protein (BMP) mRNA and protein expressions were detected in sympathetic neurons, and BMP secretion from sympathetic neurons was also confirmed. However, transfection with BMP-2 and/or BMP-6 siRNA in sympathetic neurons caused a down-regulation of osteogenesis-related genes in the cocultured osteoblasts. Sympathetic neurons promoted osteoblast differentiation through BMP signaling pathway, implying that the integrity of sympathetic neurons was important for optimal bone formation and remodeling.

► Sympathetic neurons were cocultured with osteoblasts with no direct contact.
► Sympathetic neurons promoted osteogenic gene expressions in osteoblasts.
► Sympathetic neurons expressed and secreted BMPs.
► BMP gene-silenced sympathetic neurons could not promote osteoblast differentiation.
► The integrity of sympathetic neurons was important for bone metabolism.