Aging and Autophagic Phenotypic Changes in Bone Marrow Mesenchymal Stem Cells in Glucocorticoid-induced Osteonecrosis

Background: Glucocorticoid (GC) overuse is the main cause of osteonecrosis of the femoral head (ONFH). The dysfunction of bone marrow mesenchymal stem cells (BMSCs) plays an important role in ONFH pathogenesis. Physiological concentrations of GCs can induce the osteogenic differentiation of BMSCs; however, intervention with high concentrations of GC may lead to changes in aging and autophagy in certain cell types.

Methods: We generated an ONFH mouse model by injecting C57BL/6 J mice with MPS. BMSCs were harvested from the femora and tibiae of mice and were analyzed for osteogenesis, adipogenesis, senescence, and cell proliferation. In vitro, BMSCs were treated with different concentrations of GC for 48 h, followed by functional analyses to identify differentially expressed genes (DEGs) associated with ONFH. Additionally, various bioinformatics analyses were performed to identify differentially expressed genes in ONFH.

Results: BMSCs from ONFH mice showed signs of aging, as indicated by increased SA-β-gal positive cells (4.4-fold) and upregulated p53 (2.6-fold) and p21 (2.0-fold) protein expression. It is also accompanied by changes in osteogenic/lipogenic differentiation ability. Bioinformatics analysis further verified these findings. High-dose GC stimulation significantly induced cellular senescence of BMSCs, as indicated by an increase in SA-β-gal positive cells (6.2-fold) and a decrease in autophagy levels. GC stimulation changes the differentiation fate of BMSCs.

Conclusions: Our results indicated that GC-induced ONFH was associated with changes in aging and autophagy in BMSCs. GC not only directly affected the osteogenic differentiation of BMSCs but also indirectly affected their differentiation fate through aging and autophagy changes.