Dexamethasone induces osteogenesis via regulation of hedgehog signalling molecules in rat mesenchymal stem cells

Hedgehog signalling plays an important role during the development of tissues and organs, including bone and limb. Dexamethasone (DEX), a synthetic and widely used glucocorticoid, affects osteogenesis of bone marrow mesenchymal stem cells (MSCs), while the signalling pathway by which DEX affects osteoblast differentiation remains obscure. This study aimed to investigate expressions of hedgehog signalling molecules Shh, Ihh and Gli1 during DEX-induced osteogenesis of rat MSCs in vitro.

DEX promoted osteoblast differentiation of MSCs at 10(-8) mol/L from seven days to 21 days, demonstrated by enhancing alkaline phosphatase (ALP) activity and osteoblast-associated marker type I collagen expression during osteoblastic differentiation. Gene and protein expressions of hedgehog signalling molecules, Shh, Ihh and Gli1 were tested by RT-PCR and western blot analysis during osteoblast differentiation.

Shh expression was increased compared to the control while Ihh and Gli1 expressions were decreased on both mRNA and protein level during DEX-induced osteoblast differentiation of MSCs from seven days to 21 days. Altogether, these data demonstrate that DEX can enhance Shh expression via a Gli1-independent mechanism during osteoblast differentiation of MSCs.

These results indicate that different patterns of hedgehog signalling are involved in DEX-induced osteogenesis and these findings provide insights into the mechanistic link between glucocorticoid-induced osteogenesis and hedgehog signalling pathway.