Background:Steroid-induced avascular necrosis of the femoral head
(SANFH) is a typical refractory disease that often progresses irreversibly and has a high
disability rate. Numerous studies have confirmed that abnormal osteogenic-adipogenic
differentiation of bone marrow mesenchymal stem cells (BM-MSCs) is one of the major
factors of SANFH. However, the mechanism remains to be elucidated.Objectives:This study aimed to investigate the function of the IFT80/Hedgehog pathway
in the osteogenic-adipogenic differentiation of BM-MSCs.Methods:Femoral head specimens of SANFH patients and femoral neck fractures (FNFs)
patients were collected to detect the expression of IFT80, Shh and osteogenic-adipogenic
differentiation-related genes by immunohistochemistry (IHC), western blot (WB)
and Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR). Based
on the rabbit SANFH model, the mRNA expression and protein level of IFT80 and Shh
were detected by RT-qPCR and WB. After the osteogenic-adipogenic differentiation
based on rabbit BM-MSCs, the IFT80, Gli, PPAR-γ, and Runx2 expression were detected.
Differences in alkaline phosphodiesterase activity, calcium nodule, quantification/distribution
of lipid droplets, expression of IFT80/Hedgehog axis, and the level of osteogenic-
adipogenic associated factors were determined after IFT80 overexpression.Results:RT-qPCR, WB and IHC revealed that IFT80 was highly expressed in the osteoblasts
and intra-trabecular osteocytes at the edge of trabeculae and in the intercellular
matrix of the bone marrow lumen; Shh was highly expressed in the osteoblasts and intra-
trabecular osteocytes at the edge of trabeculae. The Runx2 expression was low,
while the PPAR-γ expression was high in both human specimens and animal models of
SANFH, suggesting that the balance of osteogenic-adipogenic differentiation was dysregulated.
Rabbit BM-MSCs with stable overexpression of IFT80 showed increased alkaline
phosphatase activity after induction of osteogenic differentiation, increased calcium
nodule production, and decreased adipogenesis after induction of adipogenic differentiation.Conclusion:There is a dysregulation of the balance of osteogenic-adipogenic differentiation
in SANFH. IFT80 may inhibit adipogenic differentiation while promoting osteogenic
differentiation in rabbit BM-MSCs by activating the Hedgehog pathway.