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Autophagy may play an important role in the occurrence and development of glucocorticoid‐induced osteonecrosis of the femoral head (GC‐ONFH). Lithium is a classical autophagy regulator, and lithium can also activate osteogenic pathways, making it a highly promising therapeutic agent for GC‐ONFH. We aimed to evaluate the potential therapeutic effect of lithium on GC‐ONFH. For in vitro experiments, primary osteoblasts of rats were used for investigating the underlying mechanism of lithium's protective effect on GC‐induced autophagy levels and osteogenic activity dysfunction. For in vivo experiments, a rat model of GC‐ONFH was used for evaluating the therapeutic effect of oral lithium on GC‐ONFH and underlying mechanism. Findings demonstrated that GC over‐activated the autophagy of osteoblasts and reduced their osteogenic activity. Lithium reduced the over‐activated autophagy of GC‐treated osteoblasts through PI3K/AKT/mTOR signalling pathway and increased their osteogenic activity. Oral lithium reduced the osteonecrosis rates in a rat model of GC‐ONFH, and restrained the increased expression of autophagy related proteins in bone tissues through PI3K/AKT/mTOR signalling pathway. In conclusion, lithium can restrain over‐activated autophagy by activating PI3K/AKT/mTOR signalling pathway and up‐regulate the expression of genes for bone formation both in GC induced osteoblasts and in a rat model of GC‐ONFH. Lithium may be a promising therapeutic agent for GC‐ONFH. However, the role of autophagy in the pathogenesis of GC‐ONFH remains controversial. Studies are still needed to further explore the role of autophagy in the pathogenesis of GC‐ONFH, and the efficacy of lithium in the treatment of GC‐ONFH and its underlying mechanisms. [ABSTRACT FROM AUTHOR]

A high prevalence of osteoarthritis (OA) has been observed among individuals living at high altitudes, and hypobaric hypoxia (HH) can cause bone mass and strength deterioration. However, the effect of HH on OA remains unclear. In this study, we aimed to explore the impact of HH on OA and its potential mechanisms. A rat knee OA model was established by surgery, and the rats were bred in an HH chamber simulating a high‐altitude environment. Micro‐computed tomography (Micro‐CT), histological analysis, and RNA sequencing were performed to evaluate the effects of HH on OA in vivo. A hypoxic co‐culture model of osteoclasts and osteoblasts was also established to determine their effects on chondrogenesis in vitro. Cartilage degeneration significantly worsened in the HH‐OA group compared to that in the normoxia‐OA (N‐OA) group, 4 weeks after surgery. Micro‐CT analysis revealed more deteriorated bone mass in the HH‐OA group than in the N‐OA group. Decreased hypoxia levels in the cartilage and enhanced hypoxia levels in the subchondral bone were observed in the HH‐OA group. Furthermore, chondrocytes cultured in a conditioned medium from the hypoxic co‐culture model showed decreased anabolism and extracellular matrix compared to those in the normoxic model. RNA sequencing analysis of the subchondral bone indicated that the glycolytic signaling pathway was highly activated in the HH‐OA group. HH‐related OA progression was associated with alterations in the oxygen environment and bone remodeling in the subchondral zone, which provided new insights into the pathogenesis of OA. [ABSTRACT FROM AUTHOR]

Glucocorticoid-induced osteonecrosis of the femoral head (ONFH) is a hip disorder, and it threatens patients who require megadose of steroid therapies. Nowadays, no valid therapies can reverse the development of GC-induced ONFH once it occurs. Stem cell therapy to GC-induced ONFH would be a promising choice. Although the pathogenesis of GC-induced ONFH is not yet fully clear, Dickkopf-1 (Dkk-1) upregulated by excessive GC use, which hinders the canonical Wnt pathway, could be an explanation. Thus, the aim of the present work lies in investigating the efficiency of the allograft bone marrow stem cells (BMSCs) with Dkk-1 interference in preventing the progression of the GC-induced ONFH. Lentivirus-meditated Dkk-1 RNAi was introduced into BMSCs which was exposed to dexamethasone (10−6 mol/L) in vitro. This interference blocked Dkk-1 overexpression by GC and afterwards prompted the transduction of Wnt/β-catenin in which the Runx2 and PPARγ were upregulated and downregulated, respectively. Thus, the osteogenesis was promoted while adipogenesis was inhibited. In vivo, GC-induced ONFH rats were treated by allotransplantation of BMSCs with Dkk-1 interference, and the progression of the disease was prevented. However, the effects were not significantly superior to treatment with nongenetically modified or normal BMSCs.