The role of autophagy in steroid necrosis of the femoral head: a comprehensive research review

Palliative effect of rotating magnetic field on glucocorticoid-induced osteonecrosis of the femoral head in rats by regulating osteoblast differentiation

With the substantial increase in the overuse of glucocorticoids (GCs) in clinical medicine, the prevalence of glucocorticoid-induced osteonecrosis of the femoral head (GC-ONFH) continues to rise in recent years. However, the optimal treatment for GC-ONFH remains elusive. Rotating magnetic field (RMF), considered as a non-invasive, safe and effective approach, has been proved to have multiple beneficial biological effects including improving bone diseases. To verify the effects of RMF on GC-ONFH, a lipopolysaccharide (LPS) and methylprednisolone (MPS)-induced invivo rat model, and an MPS-induced invitro cell model have been employed. The results demonstrate that RMF alleviated bone mineral loss and femoral head collapse in GC-ONFH rats. Meanwhile, RMF reduced serum lipid levels, attenuated cystic lesions, raised the expression of anti-apoptotic proteins and osteoprotegerin (OPG), while suppressed the expression of pro-apoptotic proteins and nuclear factor receptor activator-κB (RANK) in GC-ONFH rats. Besides, RMF also facilitated the generation of ALP, attenuated apoptosis and inhibits the expression of pro-apoptotic proteins, facilitated the expression of OPG, and inhibited the expression of RANK in MPS-stimulated MC3T3-E1 cells. Thus, this study indicates that RMF can improve GC-ONFH in rat and cell models, suggesting that RMF have the potential in the treatment of clinical GC-ONFH.

Omaveloxolone ameliorates glucocorticoid-induced osteonecrosis of the femoral head by promoting osteogenesis and angiogenesis

Steroid (glucocorticoid)-induced necrosis of the femoral head (SONFH) represents a prevalent, progressive, and challenging bone and joint disease characterized by diminished osteogenesis and angiogenesis. Omaveloxolone (OMA), a semi-synthetic oleanocarpane triterpenoid with antioxidant, anti-inflammatory, and osteogenic properties, emerges as a potential therapeutic agent for SONFH. This study investigates the therapeutic impact of OMA on SONFH and elucidates its underlying mechanism. The in vitro environment of SONFH cells was simulated by inducing human bone marrow mesenchymal stem cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs) using dexamethasone (DEX).Various assays, including CCK-8, alizarin red staining, Western blot, qPCR, immunofluorescence, flow cytometry, and TUNNEL, were employed to assess cell viability, STING/NF-κB signaling pathway-related proteins, hBMSCs osteogenesis, HUVECs migration, angiogenesis, and apoptosis. The results demonstrate that OMA promotes DEX-induced osteogenesis, HUVECs migration, angiogenesis, and anti-apoptosis in hBMSCs by inhibiting the STING/NF-κB signaling pathway. This experimental evidence underscores the potential of OMA in regulating DEX-induced osteogenesis, HUVECs migration, angiogenesis, and anti-apoptosis in hBMSCs through the STING/NF-κB pathway, thereby offering a promising avenue for improving the progression of SONFH.

Fibroblast growth factor 23 inhibition attenuates steroid-induced osteonecrosis of the femoral head through pyroptosis

Steroid-induced osteonecrosis of the femoral head (SONFH) is the predominant cause of non-traumatic osteonecrosis of the femoral head (ONFH). Impaired blood supply and reduced osteogenic activity of the femoral head are the key pathogenic mechanisms of SONFH. Fibroblast growth factor 23 (FGF23) levels are not only a biomarker for early vascular lesions caused by abnormal mineral metabolism, but can also act directly on the peripheral vascular system, leading to vascular pathology. The aim of this study was to observe the role of FGF23 on bone microarchitecture and vascular endothelium, and to investigate activation of pyroptosis in SONFH. Lipopolysaccharide (LPS) combined with methylprednisolone (MPS) was applied for SONFH mouse models, and adenovirus was used to increase or decrease the level of FGF23. Micro-CT and histopathological staining were used to observe the structure of the femoral head, and immunohistochemical staining was used to observe the vascular density. The cells were further cultured in vitro and placed in a hypoxic environment for 12 h to simulate the microenvironment of vascular injury during SONFH. The effect of FGF23 on osteogenic differentiation was evaluated using alkaline phosphatase staining, alizarin red S staining and expression of bone formation-related proteins. Matrigel tube formation assay in vitro and immunofluorescence were used to detect the ability of FGF23 to affect endothelial cell angiogenesis. Steroids activated the pyroptosis signaling pathway, promoted the secretion of inflammatory factors in SONFH models, led to vascular endothelial dysfunction and damaged the femoral head structure. In addition, FGF23 inhibited the HUVECs angiogenesis and BMSCs osteogenic differentiation. FGF23 silencing attenuated steroid-induced osteonecrosis of the femoral head by inhibiting the pyroptosis signaling pathway, and promoting osteogenic differentiation of BMSCs and angiogenesis of HUVECs in vitro.

Bioinformatics proved the existence of potential hub genes activating autophagy to participate in cartilage degeneration in osteonecrosis of the femoral head

The obvious degeneration of articular cartilage occurs in the late stage of osteonecrosis of the femoral head (ONFH), which aggravates the condition of ONFH. This study aimed to demonstrate aberrant activation of autophagy processes in ONFH chondrocytes through bioinformatics and to predict and identify relevant hub genes and pathways. Differentially expressed genes (DEGs) were identified using R software in the GSE74089 dataset from the GEO database. DEGs were crossed with the Human Autophagy Database (HADb) autophagy genes to screen out autophagy-related differential genes (AT-DEGs). GSEA, GSVA, GO, and KEGG pathway enrichment analyses of AT-DEGs were performed. The STRING database was used to analyze the protein-protein interaction (PPI) of the AT-DEGs network, and the MCODE and CytoHubba plugin in the Cytoscape software was used to analyze the key gene cluster module and screen the hub genes. The PPI network of hub genes was constructed using the GeneMANIA database, and functional enrichment and gene connectivity categories were analyzed. The expression levels of hub genes of related genes in the ONFH patients were verified in the dataset GSE123568, and the protein expression was verified by immunohistochemistry in tissues. The analysis of DEGs revealed abnormal autophagy in ONFH cartilage. AT-DEGs in ONFH have special enrichment in macroautophagy, autophagosome membrane, and phosphatidylinositol-3-phosphate binding. In the GSE123568 dataset, it was also found that ATG2B, ATG4B, and UVRAG were all significantly upregulated in ONFH patients. By immunohistochemistry, it was verified that ATG2B, ATG4B, and UVRAG were significantly overexpressed. These three genes regulate the occurrence and extension of autophagosomes through the PI3KC3C pathway. Finally, we determined that chondrocytes in ONFH undergo positive regulation of autophagy through the corresponding pathways involved in three genes: ATG2B, ATG4B, and UVRAG.

Lithium prevents glucocorticoid-induced osteonecrosis of the femoral head by regulating autophagy

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.

Gene expression profiling of peripheral blood in patients with steroid-induced osteonecrosis of the femoral head

Aim: Steroid-induced osteonecrosis of the femoral head (SONFH) is a severe complication following glucocorticoid therapy. This study aimed to identify the differential mRNA expression and investigate the molecular mechanisms of SONFH. Materials & methods: RNA sequencing was performed in eight SONFH patients, five non-SONFH patients and five healthy individuals. Results: A total of 1555, 3997 and 5276 differentially expressed mRNAs existed between the following combinations: SONFH versus non-SONFH, SONFH versus healthy subjects and non-SONFH versus healthy subjects. Increased ISM1 expression might contribute to a high risk of SONFH through antiangiogenesis. Decreased FOLR3 expression might affect the metabolism of homocysteine, leading to avascular necrosis of the femoral head. KCNJ2, which plays a pivotal role in regulating bone development, was also deregulated. Conclusion: ISM1, FOLR3 and KCNJ2 might be related to the occurrence of SONFH.

Mechanism of KDM5A-mediated H3K4me3 modification in the osteogenic differentiation of mesenchymal stem cells in steroid-induced osteonecrosis of the femoral head

OBJECTIVES

Steroid-induced osteonecrosis of the femoral head (SONFH) is characterized by impaired osteogenesis in bone marrow mesenchymal stem cells (BMSCs). This study investigates the role of lysine-specific demethylase 5A (KDM5A) in SONFH to identify potential therapeutic targets.

METHODS

Human BMSCs were isolated and characterized for cell surface markers and differentiation capacity. A SONFH cell model was established using dexamethasone treatment. BMSCs were transfected with KDM5A overexpression vectors or si-KDM5A, and the expression of KDM5A, miR-107, runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and osteopontin (OPN) was assessed. Alizarin red staining was used to observe mineralization nodules, while alkaline phosphatase activity and cell viability were measured. The enrichment of KDM5A and histone 3 lysine 4 trimethylation (H3K4me3) on the promoters of RUNX2, OCN, and OPN was analyzed. The binding between miR-107 and KDM5A 3'UTR was validated, and the combined effect of miR-107 overexpression and KDM5A overexpression on BMSC osteogenic differentiation was evaluated.

RESULTS

KDM5A was upregulated in BMSCs from SONFH. Inhibition of KDM5A promoted osteogenic differentiation of BMSCs, associated with increased RUNX2, OCN, and OPN promoters. KDM5A bound to the promoters of RUNX2, OCN, and OPN, leading to reduced H3K4me3 levels and downregulation of their expression. Overexpression of miR-107 inhibited KDM5A and enhanced BMSC osteogenic differentiation.

CONCLUSION

KDM5A negatively regulates BMSC osteogenic differentiation by modulating H3K4me3 levels on the promoters of key osteogenic genes. miR-107 overexpression counteracts the inhibitory effect of KDM5A on osteogenic differentiation. These findings highlight the potential of targeting the KDM5A/miR-107 axis for SONFH therapy.

Ursolic acid alleviates steroid-induced avascular necrosis of the femoral head in mouse by inhibiting apoptosis and rescuing osteogenic differentiation

Steroid-induced avascular necrosis of femoral head (SANFH) is a common disorder worldwide with high disability. Overdose of glucocorticoid (GC) is the most common non-traumatic cause of SANFH. Up until now, there are limited therapeutic strategies for curing SANFH, and the mechanisms underlying SANFH progression remain unclear. Nevertheless, Osteogenic dysfunction is considered to be one of the crucial pathobiological mechanisms in the development of SANFH, which involves mouse bone marrow mesenchymal stem cells (BMSCs) apoptosis and osteogenic differentiation disorder. Ursolic acid (UA), an important component of the Chinese medicine formula Yougui Yin, has a wide range of pharmacological properties such as anti-tumor, anti-inflammatory and bone remodeling. Due to the positive effect of Yougui Yin on bone remodeling, the purpose of this study was to investigate the effects of UA on dexamethasone (DEX)-induced SANFH in vitro and vivo. In vitro, we demonstrated that UA can promote mouse BMSCs proliferation and resist DEX-induced apoptosis by CCK8, Western blotting, TUNEL and so on. In addition, vitro experiments such as ALP and Alizarin red staining assay showed that UA had a beneficial effect on the osteogenic differentiation of mouse BMSCs. In vivo, the results of H&E staining, immunohistochemistry staining, Elisa and micro-CT analysis showed that UA had a bone repair-promoting effect in SANFH model. Moreover, the results of Western blot and TUNEL experiments showed that UA could delay the disease progression of SANFH in mice by inhibiting apoptosis. Overall, our study suggests that UA is a potential compound for the treatment of SANFH.

Pyroptosis -related potential diagnostic biomarkers in steroid-induced osteonecrosis of the femoral head

PURPOSE

Steroid-induced necrosis of the femoral head (SONFH) is a refractory orthopedic hip disease occurring in young and middle-aged people, with glucocorticoids being the most common cause. Previous experimental studies have shown that cell pyroptosis may be involved in the pathological process of SONFH, but its pathogenesis in SONFH is still unclear. This study aims to screen and validate potential pyroptosis-related genes in SONFH diagnosis by bioinformatics analysis to further elucidate the mechanism of pyroptosis in SONFH.

METHODS

There were 33 pyroptosis-related genes obtained from the prior reviews. The mRNA expression was downloaded from GSE123568 dataset in the Gene Expression Omnibus (GEO) database, including 10 non-SONFH (following steroid administration) samples and 30 SONFH samples. The pyroptosis-related differentially expressed genes involved in SONFH were identified with "affy" and "limma" R package by intersecting the GSE123568 dataset with pyroptosis genes. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of the pyroptosis-related differentially expressed genes involved in SONFH were conducted by "clusterProfiler" R package and visualized by "GOplot" R package. Then, the correlations between the expression levels of the pyroptosis-related differentially expressed genes involved in SONFH were confirmed with "corrplot" R package. Moreover, the protein-protein interaction (PPI) network was analysed by using GeneMANIA database. Next, The ROC curve of pyroptosis-related differentially expressed genes were analyzed by "pROC" R package.

RESULTS

A total of 10 pyroptosis-related differentially expressed genes were identified between the peripheral blood samples of SONFH patients and non-SONFH patients based on the defined criteria, including 20 upregulated genes and 10 downregulated genes. The GO and KEGG pathway enrichment analyses revealed that these 10 pyroptosis-related differentially expressed genes involved in SONFH were particularly enriched in cysteine-type endopeptidase activity involved in apoptotic process, positive regulation of interleukin-1 beta secretion and NOD-like receptor signaling pathway. Correlation analysis revealed significant correlations among the 10 differentially expressed pyroptosis-related genes involved in SONFH. The PPI results demonstrated that the 10 pyroptosis-related differentially expressed genes interacted with each other. Compared to non-SONFH samples, these pyroptosis-related differentially expressed genes had good predictive diagnostic efficacy (AUC = 1.000, CI = 1.000-1.000) in the SONFH samples, and NLRP1 had the highest diagnostic value (AUC: 0.953) in the SONFH samples.

CONCLUSIONS

There were 10 potential pyroptosis-related differentially expressed genes involved in SONFH were identified via bioinformatics analysis, which might serve as potential diagnostic biomarkers because they regulated pyroptosis. These results expand the understanding of SONFH associated with pyroptosis and provide new insights to further explore the mechanism of action and diagnosis of pyroptosis associated in SONFH.

Construction of ceRNA network based on RNA-seq for identifying prognostic lncRNA biomarkers in Perthes disease

Introduction: Legg-Calvé-Perthes disease or Perthes disease is a condition that occurs in children aged 2 to 15 years, and is characterized by osteonecrosis of the femoral head, which results in physical limitations. Despite ongoing research, the pathogenesis and molecular mechanisms underlying the development of Perthes disease remain unclear. In order to obtain further insights, the expression patterns of long non-coding RNAs (lncRNAs), miRNAs, and mRNAs in a rabbit model of Perthes disease were analyzed in this study by transcriptome sequencing. Methods and results: The results of RNA-seq analyses revealed that 77 lncRNAs, 239 miRNAs, and 1027 mRNAs were differentially expressed in the rabbit model. This finding suggested that multiple genetic pathways are involved in the development of Perthes disease. A weighted gene co-expression network analysis (WGCNA) network was subsequently constructed using the differentially expressed mRNAs (DEmRNAs), and network analysis revealed that the genes associated with angiogenesis and platelet activation were downregulated, which was consistent with the findings of Perthes disease. A competing endogenous RNA (ceRNA) network was additionally constructed using 29 differentially expressed lncRNAs (including HIF3A and LOC103350994), 28 differentially expressed miRNAs (including ocu-miR-574-5p and ocu-miR-324-3p), and 76 DEmRNAs (including ALOX12 and PTGER2). Disscusion: The results obtained herein provide novel perspectives regarding the pathogenesis and molecular mechanisms underlying the development of Perthes disease. The findings of this study can pave the way for the development of effective therapeutic strategies for Perthes disease in future.

Astragalus polysaccharide ameliorates steroid-induced osteonecrosis of the femoral head by regulating miR-200b-3p-mediated Wnt/β-catenin signaling pathway via inhibiting SP1 expression : Astragalus polysaccharide regulates SONFH via SP1

BACKGROUND

Steroid-induced osteonecrosis of the femoral head (SONFH) is the necrosis of the femur bone caused by prolonged and massive use of corticosteroids. The present study probed into the significance of Astragalus polysaccharide (APS) in SONFH progression.

METHODS

SONFH cell model was constructed using murine long bone osteocyte Y4 (MLO-Y4) cells and then treated with APS. mRNA microarray analysis selected differentially expressed genes between control group and SONFH group. RT-qPCR determined SP1 and miR-200b-3p expression. Levels of SP1, β-catenin, autophagy-related proteins (LC3II/LC3I, Beclin1, p62) and apoptosis-related proteins (Bax, C-caspase3, C-caspase9, Bcl-2) were tested by Western blot. ChIP and luciferase reporter assays confirmed relationship between SP1 and miR-200b-3p. Fluorescence intensity of LC3 in cells was detected by immunofluorescence. Flow cytometry assessed cell apoptosis. Osteonecrosis tissues from SONFH mice were examined by HE and TRAP staining.

RESULTS

APS induced autophagy and suppressed apoptosis in SONFH cell model. APS inhibited SP1 expression and SP1 overexpression reversed effects of APS on SONFH cell model. Mechanistically, SP1 targeted miR-200b-3p to inhibit Wnt/β-catenin pathway. MiR-200b-3p depletion rescued the promoting effect of SP1 on SONFH cell model by activating Wnt/β-catenin pathway. HE staining showed that APS treatment reduced the empty lacunae and alleviated inflammation in trabecular bone of SONFH mice. TRAP staining revealed decreased osteoclasts number in SONFH mice after APS treatment.

CONCLUSION

APS regulated osteocyte autophagy and apoptosis via SP1/miR-200b-3p axis and activated Wnt/β-catenin signaling, thereby alleviating SONFH, shedding new insights for therapy of SONFH.

Microrna-206 induces hypoxic necrosis of femoral head by inhibiting VEGF/PI3K/AKT signaling pathway

The most common form of non-traumatic necrosis of the femoral head is anoxic necrosis of the femoral head, which is a metabolic disease, mainly involving young and middle-aged people. Apoptosis and its related signal regulation pathway play an important role in the occurrence and development of hypoxic necrosis of the femoral head. In order to investigate the possible pathological manifestations of miR-206 and VEGF/PI3K/AKT signal pathway genes and their interactions in hypoxic necrosis of the femoral head, this paper intended to systematically study the expression and regulation mechanism of miR-206 and VEGF/PI3K/AKT signal pathway genes. The interaction between miR-206 and VEGF/PI3K/AKT signaling pathway and its regulation on apoptosis, differentiation and proliferation of human osteoblast cell line hFOB1.19 (SV40 transfer of human osteoblasts) were studied by double luciferase reporter gene analysis, overexpression and inhibition of miR-206, and gene silencing of VEGF/PI3K/AKT signaling pathway. After 24 h and 48 h of intervention with MicroRNA 206 on osteoblasts, it was found that the fluorescence intensity of caspase-3 was higher than that of 0 h group (p < 0.05). This paper has provided an important research basis for the research of femoral head necrosis and the development of new diagnosis and therapeutic drugs for this kind of disease. It also has provided a reference for the further promotion of the chemotherapy drug delivery system.

Methylprednisolone Inhibits Autophagy of Vascular Endothelial Cells in Rat Femoral Head Via PI3K/Akt/mTOR Pathway

Objective

To study the relationship between vascular endothelial cells (VEC) and autophagy, and its regulatory mechanism in steroid‐induced avascular necrosis of the femoral head (SANFH).

Methods

In cell experiment, VEC were isolated and cultured from the femoral head of Sprague–Dawley rats and divided into three groups: blank control group (Ctrl), methylprednisolone group (MP), and methylprednisolone+mTOR‐shRNA group (MP + shmTOR). The autophagy formation was observed by transmission electron microscope. The mRNA expression of PI3K, Akt, mTOR, Beclin1 and MAP1LC3 was detected by RT‐PCR and the protein expression was detected by Western blot and immunofluorescence. Expression of the damage marker 6‐keto‐PGF1α was detected by the ELISA method. In vivo experiment, after establishing the model, the grouping method was the same as cell experiment. Autophagosomes were observed by same method, and the expression of related factors was detected by the same method in cell experiment.

Results

In the cell experiment, autophagosomes in the MP group were significantly lower than in the Ctrl group, and the autophagosomes in the MP + shmTOR group were intermediate between two groups (P < 0.05). The mRNA expression levels of PI3K, Akt and mTOR in the MP group were significantly higher than in the Ctrl group, while the MP+ shmTOR group presented intermediate levels between these groups (average gray value were 3837.90, 2996.30, 3005.60, F = 428.64, P < 0.05). MRNA expression levels of Beclin1 and MAP1LC3 in the MP group were significantly lower than that in Ctrl group (P < 0.05). The content of 6‐keto‐PGF1α in the MP + shmTOR group was higher than in the Ctrl group and lower than in the MP group at the evaluated time intervals (average absorbance value were 104.98, 206.83, 145.91, F = 352.83, P < 0.01). In vivo experiment, the content of 6‐Keto‐PGF1α in the hormone group increased as time went on; the mTOR‐si group was higher than that in control group, but lower than that in the hormone group (P < 0.01). The mRNA expressions of Beclin1 and MAP1LC3 in the control group were higher than those in the hormone group, while the mRNA expressions of PI3K, Akt and mTOR were lower than those in the mTOR‐si group (P < 0.05).

Conclusion

The steroid inhibited the physiological protective effect of autophagy on SANFH by increasing the expression of PI3K/Akt/mTOR signaling pathway related factors and decreasing the expression of Beclin1 and MAP1LC3 in the femoral head VEC.

Identification of potential autophagy-related genes in steroid-induced osteonecrosis of the femoral head via bioinformatics analysis and experimental verification

PURPOSE

Steroid-induced osteonecrosis of the femoral head (SONFH) is a refractory orthopaedic hip joint disease that occurs in young- and middle-aged people. Previous experimental studies have shown that autophagy might be involved in the pathological process of SONFH, but the pathogenesis of autophagy in SONFH remains unclear. We aimed to identify and validate the key potential autophagy-related genes involved in SONFH to further illustrate the mechanism of autophagy in SONFH through bioinformatics analysis.

METHODS

The GSE123568 mRNA expression profile dataset, including 10 non-SONFH (following steroid administration) samples and 30 SONFH samples, was downloaded from the Gene Expression Omnibus (GEO) database. Autophagy-related genes were obtained from the Human Autophagy Database (HADb). The autophagy-related genes involved in SONFH were screened by intersecting the GSE123568 dataset with the set of autophagy genes. The differentially expressed autophagy-related genes involved in SONFH were identified with R software. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of the differentially expressed autophagy-related genes involved in SONFH were conducted by using R software. Then, the correlations between the expression levels of the differentially expressed autophagy-related genes involved in SONFH were confirmed with R software. Moreover, the protein-protein interaction (PPI) network was analysed by using the Search Tool for the Retrieval of Interacting Genes (STRING), significant gene cluster modules were identified with the MCODE Cytoscape plugin, and hub genes among the differentially expressed autophagy-related genes involved in SONFH were screened by using the CytoHubba Cytoscape plugin. Finally, the expression levels of the hub genes of the differentially expressed autophagy-related genes involved in SONFH were validated in hip articular cartilage specimens from necrotic femur heads (NFHs) by using the GSE74089 dataset and further verification by qRT-PCR.

RESULTS

A total of 34 differentially expressed autophagy-related genes were identified between the peripheral blood samples of SONFH patients and non-SONFH patients based on the defined criteria, including 25 upregulated genes and 9 downregulated genes. The GO and KEGG pathway enrichment analyses revealed that these 34 differentially expressed autophagy-related genes involved in SONFH were particularly enriched in death domain receptors, the FOXO signalling pathway and apoptosis. Correlation analysis revealed significant correlations among the 34 differentially expressed autophagy-related genes involved in SONFH. The PPI results demonstrated that the 34 differentially expressed autophagy-related genes interacted with each other. Ten hub genes were identified by using the MCC algorithms of CytoHubba. The GSE74089 dataset showed that TNFSF10, PTEN and CFLAR were significantly upregulated while BCL2L1 was significantly downregulated in the hip cartilage specimens, which was consistent with the GSE123568 dataset. TNFSF10, PTEN and BCL2L1 were detected with consistent expression by qRT-PCR.

CONCLUSIONS

Thirty-four potential autophagy-related genes involved in SONFH were identified via bioinformatics analysis. TNFSF10, PTEN and BCL2L1 might serve as potential drug targets and biomarkers because they regulate autophagy. These results expand the autophagy-related understanding of SONFH and might be useful in the diagnosis and prognosis of SONFH.

IL-34 Aggravates Steroid-Induced Osteonecrosis of the Femoral Head via Promoting Osteoclast Differentiation

IL-34 can promote osteoclast differentiation and activation, which may contribute to steroid-induced osteonecrosis of the femoral head (ONFH). Animal model was constructed in both BALB/c and IL-34 deficient mice to detect the relative expression of inflammation cytokines. Micro-CT was utilized to reveal the internal structure. In vitro differentiated osteoclast was induced by culturing bone marrow-derived macrophages with IL-34 conditioned medium or M-CSF. The relative expression of pro-inflammation cytokines, osteoclast marker genes, and relevant pathways molecules was detected with quantitative real-time RT-PCR, ELISA, and Western blot. Up-regulated IL-34 expression could be detected in the serum of ONFH patients and femoral heads of ONFH mice. IL-34 deficient mice showed the resistance to ONFH induction with the up-regulated trabecular number, trabecular thickness, bone value fraction, and down-regulated trabecular separation. On the other hand, inflammatory cytokines, such as TNF-α, IFN-γ, IL-6, IL-12, IL-2, and IL-17A, showed diminished expression in IL-34 deficient ONFH induced mice. IL-34 alone or works in coordination with M-CSF to promote osteoclastogenesis and activate ERK, STAT3, and non-canonical NF-κB pathways. These data demonstrate that IL-34 can promote the differentiation of osteoclast through ERK, STAT3, and non-canonical NF-κB pathways to aggravate steroid-induced ONFH, and IL-34 can be considered as a treatment target.

Cell therapy for osteonecrosis of femoral head and joint preservation

Osteonecrosis of femoral head (ONFH) is a disease of the femoral head and can cause femoral head collapse and arthritis. This can lead to pain and gait disorders. ONFH has various risk factors, it is often progressive, and if untreated results in secondary osteo-arthritis. Biological therapy makes use of bone marrow concentrate, cultured osteoblast and mesenchymal stem cell (MSC) obtained from various sources. These are often used in conjunction with core decompression surgery. In this review article, we discuss the current status of cell therapy and its limitations. We also present the future development of biological approach to treat ONFH.

Comprehensive analysis of pivotal biomarkers, immune cell infiltration and therapeutic drugs for steroid-induced osteonecrosis of the femoral head

Steroid-induced osteonecrosis of the femoral head (SONFH) is a progressive disease that leads to an increased disability rate. This study aimed to ascertain biomarkers, infiltrating immune cells, and therapeutic drugs for SONFH. The gene expression profile of the GSE123568 dataset was downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified using the NetworkAnalyst platform. Functional enrichment, protein-protein interaction network (PPI), and module analyses were performed using Metascape tools. An immune cell abundance identifier was used to explore immune cell infiltration. Furthermore, hub genes were identified based on maximal clique centrality (MCC) evaluation using cytoHubba application and confirmed by qRT-PCR using clinical samples. Finally, the L1000 platform was used to determine potential drugs for SONFH treatment. The SONFH mouse model was used to determine the therapeutic effects of aspirin. In total, 429 DEGs were identified in SONFH samples. Functional enrichment analysis showed that these DEGs were enriched in myeloid leukocyte activation and osteoclast differentiation processes. A set of nine immune cell types was confirmed to be markedly different between the SONFH and control samples. All 10 hub genes were significantly highly expressed in the serum of SONFH patients, as shown by qRT-PCR. Finally, the therapeutic effect of aspirin on SONFH was examined in animal experiments. Taken together, our data revealed the hub genes and infiltrating immune cells in SONFH, and we also screened potential drugs for use in SONFH treatment.

Astragalus polysaccharide ameliorates steroid-induced osteonecrosis of femoral head through miR-206/HIF-1α/BNIP3 axis

Declining autophagy and rising apoptosis are the main factors driving the development of steroid-induced osteonecrosis of the femoral head (SONFH). Here, we showed that astragalus polysaccharide (APS) improved femoral head necrosis via regulation of cell autophagy and apoptosis through microRNA (miR)-206/hypoxia inducible factor-1 (HIF-1α)/BCL2 interacting protein 3 (BNIP3) axis. The expression of miR-206, HIF-1α, and BNIP3 in SONFH specimens and cell model were measured using qPCR. SONFH cell model was treated with APS. Cell autophagy was evaluated using LC3-immunofluorescence assays. Flow cytometry was conducted to assess cell apoptosis. Apoptosis-related proteins and autophagy-related proteins were determined using western blot. Besides, dual-luciferase reporter assay was employed to investigate the relationship between miR-206 and HIF-1α. Here we showed that miR-206 expression was upregulated in SONFH tissues and cell model. APS promoted autophagy and inhibited apoptosis in SONFH cell model via downregulating miR-206. What is more, HIF-1α was the target of miR-206. Knockdown of HIF-1α reversed the recovery effect of miR-206 inhibitor on SONFH cell model. Furthermore, BNIP3 was the target of HIF-1α. HIF-1α overexpression promoted autophagy and inhibited apoptosis, and knockdown of BNIP3 abolished the recovery effect of HIF-1α overexpression in SONFH cell model. These results provided evidence that APS reduced miR-206 expression, and the downregulated miR-206 increased BNIP3 expression by targeting HIF-1α to promote autophagy and inhibit bone cell apoptosis. Our research proved that APS effectively improved SONFH by regulating cell autophagy and apoptosis.

Parathyroid hormone and its related peptides in bone metabolism

Parathyroid hormone (PTH) is an 84-amino-acid peptide hormone that is secreted by the parathyroid gland. It has different administration modes in bone tissue through which it promotes bone formation (intermittent administration) and bone resorption (continuous administration) and has great potential for application in sbone defect repair. PTH regulates bone metabolism by binding to PTH1R. PTH plays an osteogenic role by acting directly on mesenchymal stem cells, cells with an osteoblastic lineage, osteocytes, and T cells. It also participates as an osteoclast by indirectly acting on osteoclast precursor cells and osteoclasts and directly acting on T cells. In these cells, PTH activates the Wnt signaling, cAMP/PKA, cAMP/PKC, and RANKL/RANK/OPG pathways and other signaling pathways. Although PTH(1-34), also known as teriparatide, has been used clinically, it still has some disadvantages. Developing improved PTH-related peptides is a potential solution to teriparatide's shortcomings. The action mechanism of these PTH-related peptides is not exactly the same as that of PTH. Thus, the mechanisms of PTH and PTH-related peptides in bone metabolism were reviewed in this paper.

Hyper-activated platelet lysates prevent glucocorticoid-associated femoral head necrosis by regulating autophagy

Platelet Rich Plasma (PRP) can activate angiogenic and osteogenic pathways, making it a highly promising therapeutic agent for bone growth. Super active platelet lysate (sPL) is derived from platelet-rich plasma (PRP) through ultra-low temperature freeze-thawing. The aim of this study was to evaluate the potential therapeutic effect of sPL on glucocorticoid (GC)-induced osteonecrosis of the femoral head (ONFH). sPL increased the proliferation of GC-treated osteoblasts and endothelial cells, and inhibited apoptosis in vitro. Furthermore, sPL promoted healing of necrotic bone tissues in a rat ONFH model by restraining GC-induced apoptosis and increase autophagy of the osteoblasts. Overall, the results of this study provide a theoretical basis for the clinical application of sPL in ONFH.

Atorvastatin Upregulates microRNA-186 and Inhibits the TLR4-Mediated MAPKs/NF-κB Pathway to Relieve Steroid-Induced Avascular Necrosis of the Femoral Head

Steroid-induced avascular necrosis of the femoral head (SANFH) is caused by the death of active components of the femoral head owing to hormone overdoses. The use of lipid-lowering drugs to prevent SANFH in animals inspired us to identify the mechanisms involving Atorvastatin (Ato) in SANFH. However, it is still not well understood how and to what extent Ato affects SANFH. This study aimed to figure out the efficacy of Ato in SANFH and the underlying molecular mechanisms. After establishment of the SANFH model, histological evaluation, lipid metabolism, inflammatory cytokines, oxidative stress, apoptosis, and autophagy of the femoral head were evaluated. The differentially expressed microRNAs (miRs) after Ato treatment were screened out using microarray analysis. The downstream gene and pathway of miR-186 were predicted and their involvement in SANFH rats was analyzed. OB-6 cells were selected to simulate SANFH in vitro. Cell viability, cell damage, inflammation responses, apoptosis, and autophagy were assessed. Ato alleviated SANFH, inhibited apoptosis, and promoted autophagy. miR-186 was significantly upregulated after Ato treatment. miR-186 targeted TLR4 and inactivated the MAPKs/NF-κB pathway. Inhibition of miR-186 reversed the protection of Ato on SANFH rats, while inhibition of TLR4 restored the protective effect of Ato. Ato reduced apoptosis and promoted autophagy of OB-6 cells by upregulating miR-186 and inhibiting the TLR4/MAPKs/NF-κB pathway. In conclusion, Ato reduced apoptosis and promoted autophagy, thus alleviating SANFH via miR-186 and the TLR4-mediated MAPKs/NF-κB pathway.

Astragaloside IV ameliorates steroid-induced osteonecrosis of the femoral head by repolarizing the phenotype of pro-inflammatory macrophages

Osteonecrosis of the femoral head (ON-FH) is a common complication of steroid use. Pro-inflammatory macrophages play a crucial role in the apoptosis of osteocytes. The objective of the study was to evaluate a plant extract astragaloside IV (AS-IV) in treating ON-FN. Bone-marrow-derived macrophages (BMDMs) were treated with lipopolysaccharides (LPS), IFN-γ or IL-4 to induce M1 and M2-like phenotypes. Quantitative real-time PCR and Western blot were used to examine M1 and M2 phenotypic markers. Flow cytometry was used to analyze MHC II, CD206, F4/80, and CD11b levels and cell apoptosis. Glucocorticoid was used to induce ON-FN in mice. TNF-α and IL-1β levels in femoral head were determined using enzyme-linked immunosorbent assay. AS-IV repolarized macrophages from M1 to M2 phenotypes. Culture medium from AS-IV treated M1 macrophages induced less cell apoptosis osteocytes compared to that from untreated M1 macrophages. In ON-FH mice, the ratio of M1 macrophages was decreased in the femoral head by AS-IV, concomitant with a decrease in TNF-α and IL-1β levels. AS-IV is effective in alleviating ON-FH through its effects in repolarizing macrophages from M1-like phenotype to M2-like phenotype, promoting survival of osteocytes, reducing arthritic symptoms, and decreasing inflammatory cytokines.

CaO2/gelatin oxygen slow-releasing microspheres facilitate tissue engineering efficiency for the osteonecrosis of femoral head by enhancing the angiogenesis and survival of grafted bone marrow mesenchymal stem cells

The osteonecrosis of femoral head (ONFH), a common refractory disease, is still not fully understood today. Hypoxia caused by ischemia is not only an important pathogenic factor but also a critical challenge for the survival of seed cells in the tissue engineering therapy of ONFH. To explore an efficient strategy to treat ONFH by targeting hypoxia, newly designed CaO₂/gelatin microspheres were composited with 3D printed polycaprolactone/nano-hydroxyapatite (PCL/nHA) porous scaffold, sodium alginate/gelatin hydrogel, and bone marrow mesenchymal stem cells (BMSCs) to develop a novel tissue engineering scaffold and then transplanted into the core depression area of the ONFH rabbit model. The current data demonstrated that CaO₂/gelatin microspheres can constantly release oxygen for 19 days. In vitro assays with BMSCs illustrated that scaffolds have high biocompatibility and are favorable for cell proliferation in extreme hypoxia (1% O₂). The in vivo study demonstrated that the transplanted scaffold with oxygen-generating microspheres significantly enhanced the osteogenic and angiogenic effects compared to the scaffold without microspheres. Further assessments revealed that microspheres in the scaffold can reduce the local cell apoptosis and enhance the survival of grafted cells in the host. Collectively, the present study developed a novel oxygen slow-releasing composite scaffold, which can facilitate tissue engineering efficiency for treating the osteonecrosis of the femoral head by enhancing the angiogenesis and survival of grafted stem cells.

Effects of osteoblast autophagy on glucocorticoid-induced femoral head necrosis

Objectives

This study aims to explore the mechanism by which osteoblast autophagy participated in glucocorticoid-induced femoral head necrosis (FHN).

Materials and methods

Thirty male specific-pathogen-free C57 mice (age, one month; weighing 20-25 g) were randomly divided into blank control, dexamethasone and rapamycin-dexamethasone groups (n=10). After six weeks of intervention, right femoral head was obtained to observe morphology and to calculate percentage of empty lacunae. MC3T3-E1 cells were randomly divided into normal, dexamethasone, rapamycin and dexamethasone-rapamycin groups, and cultured for 24 h. Microtubule-associated protein 1 light chain 3 (LC3)-I, LC3-II, mammalian target of rapamycin (mTOR) and Beclin-1 protein expressions were detected by Western blot.

Results

In rapamycin-dexamethasone group, some bone trabeculae in medullary cavity ruptured and atrophied, and subchondral bone underwent local necrosis. The total apoptosis rates of dexamethasone and rapamycin-dexamethasone groups surpassed that of blank control group, and the former two groups had significantly different rates (p<0.001). LC3-II/LC3-I of dexamethasone group was lower than those of rapamycin and dexamethasone-rapamycin groups (p<0.001), and the ratio of rapamycin group surpassed that of dexamethasone-rapamycin group (p<0.001). Dexamethasone group had higher mTOR protein expression than those of rapamycin and dexamethasone- rapamycin groups (p<0.001), and the expression of rapamycin group was lower than that of dexamethasone-rapamycin group (p<0.001). The Beclin-1 protein expression of dexamethasone group was lower than those of rapamycin and dexamethasone- rapamycin groups (p<0.001), and the expression of rapamycin group exceeded that of dexamethasone-rapamycin group (p<0.05).

Conclusion

Osteoblast autophagy may play a crucial protective role in dexamethasone-induced FHN. The attenuation of autophagy may be related to the affected expressions of key autophagy regulators mTOR and Beclin-1.

Integrated analysis of transcriptome and proteome to explore the genes related to steroid-induced femoral head necrosis

PURPOSE

Femoral head necrosis (FHN) is a common disease of hip. However, the pathogenesis of FHN is not well understood. This study attempted to explore the potentially important genes and proteins involved in FHN.

METHODS

We integrated the transcriptomic and proteomic methods to quantitatively screen the differentially expressed genes (DEGs) and proteins (DEPs) between Control and FHN groups. Gene ontology (GO) terms and KEGG pathway enrichment analysis were used to assess the roles of DEGs and DEPs. qRT-PCR and western blot were performed to verify the key genes/proteins in FHN. CCK-8 assay was performed to measure cell viability. The protein expression of Bax and Bcl-2 were used to evaluate cell apoptosis.

RESULTS

Transcriptome and proteome studies indicated 758 DEGs and 1097 DEPs between Control and FHN groups, respectively. Cell division, extracellular exosome, and serine-type endopeptidase activity were the most common terms in biological process (BP), cellular component (CC), and molecular function (MF) enrichment, respectively. DEPs were mainly enriched in cellular process, cell, and binding for BP, CC, and MF categories, respectively. DEGs were mainly involved in PI3K-Akt pathway and DEPs were mainly focused in glycolysis/gluconeogenesis pathway. Notably, 14 down-regulated and 22 up-regulated genes/proteins were detected at both the transcript and protein level. LRG1, SERPINE2, STMN1, COL14A1, SLC37A2, and MMP2 were determined as the key genes/proteins in FHN. SERPINE2/STMN1 overexpression increased viability and decreased apoptosis of dexamethasone-treated MC3T3-E1 cells.

CONCLUSIONS

Our study investigated some pivotal regulatory genes/proteins in the pathogenesis of FHN, providing novel insight into the genes/proteins involved in FHN.

Immunoexpression pattern of autophagy mediators in alveolar bone osteoclasts following estrogen withdrawal in female rats

It is known that estrogen deficiency increases osteoclast formation and activity. Autophagy, a cell survival pathway, has been shown to be crucial for osteoclast function. However, little is known about the effects of estrogen depletion on osteoclast autophagy. Here, we evaluated the effects of estrogen deficiency in the immunoexpression of autophagy mediators in alveolar bone osteoclasts of ovariectomized rats. Twelve adult female rats were ovariectomized (OVX-group) or SHAM-operated (SHAM-group). After three weeks, the rats were euthanized and maxillary fragments containing alveolar bone of the first molars were processed for light microscopy or transmission electron microscopy (TEM). Paraffin-sections were subjected to the TRAP method (osteoclast marker) or to the immunohistochemical detections of beclin-1, LC3α, and p62 (autophagy mediators); araldite-sections were processed for TEM. The number of TRAP-positive osteoclasts and the number of immunolabeled-multinucleated cells (MNCs) along the alveolar bone surface of the first molar were computed. The number of TRAP-positive osteoclasts and the number of beclin-1-, LC3α- and p62-immunolabelled osteoclasts were significantly higher in OVX-group than the SHAM-group. MNCs were frequently located juxtaposed to Howship lacunae along the alveolar bone surface, indicating that these cells are osteoclasts. TEM revealed osteoclasts exhibiting autophagosomes. Our data indicate that autophagy plays an important role during estrogen deficiency-induced osteoclastogenesis. Thus, our results contribute to a better understanding on the role of autophagy on osteoclasts under estrogenic deficiency, and reinforce the idea that modulation of autophagy may be a useful tool to inhibit excessive oral bone resorption in post-menopausal women.

Epidemiological Study Based on China Osteonecrosis of the Femoral Head Database

Objective

The aim of the present study was to reveal the case characteristics of osteonecrosis of the femoral head (ONFH) in Mainland China.

Methods

This cross‐sectional epidemiological study derived data for ONFH patients from July 2016 to December 2018 from the China Osteonecrosis of the Femoral Head Database (CONFHD). The derived data included gender, age, body mass index (BMI), height, occupation, region, and etiology of femoral head necrosis. A descriptive analysis was performed to summarize the epidemiological characteristics of the case data in the CONFHD.

Results

A total of 1844 ONFH patients (2945 hips) were included in this study, comprising 1302 men and 542 women. The age of patients ranged from 18 to 95 years, with a median of 50 years, and the male to female ratio was 2.4. Male patients are younger than female patients (48.26 ± 12.56 years old and 55.56 ± 14.94 years old, respectively). Among the 1844 patients (2945 hips), there were 528 (17.92%) hips at ARCO stage I, 941 (31.99%) hips at ARCO stage II, 873 (29.63%) hips at ARCO stage III, and 603 (20.46%) hips at ARCO stage IV. In the subclassification of ARCO stages I and II, the majority of cases were type C; type A comprised the majority in the subclassification of ARCO stage III. According to the Kellgren–Lawrence classification system, among the 603 ARCO stage IV hips, there were 178 (29.52%) grade 1 hips, 201 (33.34%) grade 2 hips, 176 (29.18%) grade 3 hips, and 48 (7.96%) grade 4 hips. Most were from three provinces: Henan (27.3%), Shanxi (13.9%), and Shandong (11.9%). Regarding BMI, 982 patients (53.25%) were overweight or obese. Among all patients, the largest proportion of patients engaged in level IV manual work. Of all the patients, there were 495 (26.84%) with steroid‐induced ONFH, 685 (37.15%) were alcoholics, and 290 (15.73%) had traumatic ONFH. The 495 patients with steroid‐induced ONFH included 278 men (56.16%) and 217 women (43.84 %), had a complete history of hormone use. Among the primary diseases, there were 195 cases (39.39%) of immune system diseases, followed by dermatological diseases, respiratory diseases, nephropathy, and other diseases. There were a total of 685 patients with alcoholic ONFH, 589 of these patients (85.99%) were men. A total of 188 (27.45%) patients had drunk alcohol for 6–10 years (comprising the highest proportion), and 280 patients (40.88%) consumed 3001–3500 mL of alcohol each week (the highest proportion).

Conclusion

Osteonecrosis of the femoral head most commonly occurs after the age of 40. Male patients have an earlier onset than female patients, and the number of male patients is approximately twice that of female patients. The BMI of patients was mainly in the overweight and obese range, and half of these patients engaged in level IV manual work. From the imaging findings, the numbers of hips at ARCO stages II and III were greatest, and the number at stage I was relatively small. Among all the causes of disease, alcohol, steroid use and trauma were the three most common reasons for ONFH.

Glucocorticoids decreased Cx43 expression in osteonecrosis of femoral head: The effect on proliferation and osteogenic differentiation of rat BMSCs

Glucocorticoid (GC)‐induced osteonecrosis of the femoral head (GC‐ONFH) is considered as one of the most serious side effects of long‐term or over‐dose steroid therapy. However, the underlying cause mechanisms are still not fully investigated. We firstly established a rat model of GC‐ONFH and injected lipopolysaccharide (LPS) and methylprednisolone (MPS). We found that the expressions of Cx43, Runx2, ALP and COLⅠ were more decreased than the normal group. Secondly, the isolated rat bone marrow stem cells (BMSCs) were treated with dexamethasone (Dex) in vitro, and the expressions of Cx43, Runx2, ALP and COLⅠ were decreased significantly. Moreover, the results of immunofluorescence staining, alizarin red staining, EdU assay and CCK8 showed that the osteogenic differentiation and the proliferation capacity of BMSCs were decreased after induced by Dex. A plasmid of lentivirus‐mediated Cx43 (Lv‐Cx43) gene overexpression was established to investigate the function of Cx43 in BMSCs under the Dex treatment. Findings demonstrated that the proliferation and osteogenic differentiation abilities were enhanced after Lv‐Cx43 transfected to BMSCs, and these beneficial effects of Lv‐Cx43 were significantly blocked when PD988059 (an inhibitor of ERK1/2) was used. In conclusion, the overexpression of Cx43 could promote the proliferation and osteogenic differentiation of BMSCs via activating the ERK1/2 signalling pathway, which provide a basic evidence for further study on the detailed function of Cx43 in GC‐ONFH.

[Experimental study on transplantation of microencapsulated transgenic bone marrow mesenchymal stem cells for early steroid-induced osteonecrosis of femoral head in rabbits]

Objective

To investigate the effect of microencapsulated transgenic bone marrow mesenchymal stem cells (BMSCs) transplantation on early steroid induced osteonecrosis of femoral head (SONFH) in rabbits.

Methods

Alginate poly- L-lysine-sodium alginate (APA) microencapsulated transgenic BMSCs with high expression of Foxc2 were prepared by high-voltage electrostatic method. Part of the cells were cultured in osteoblasts and observed by alizarin red staining at 2 and 3 weeks. Forty New Zealand white rabbits were used to prepare SONFH models by using hormone and endotoxin. Thirty two rabbits who were successful modeling were screened out by MRI and randomly divided into 4 groups (groups A, B, C and D, n=8); another 6 normal rabbits were taken as normal control (group E). The rabbits in group A did not receive any treatment; and in groups B, C, and D were injected with normal saline, allogeneic BMSCs, and APA microencapsulated transgenic BMSCs respectively after core decompression. At 6 and 12 weeks after operation, specimens of femoral head were taken for HE staining to observe bone ingrowth; the expressions of osteocalcin (OCN), peroxisome proliferative activated receptor γ 2 (PPARγ-2), and vascular endothelial growth factor (VEGF) proteins were observed by immunohistochemistry staining. At 12 weeks after operation, the bone microstructure was observed by transmission electron microscope, and the maximum compressive strength and average elastic modulus of cancellous bone and subchondral bone were measured by biomechanics.

Results

After 2 and 3 weeks of induction culture, alizarin red staining showed the formation of calcium nodules, and the number of calcium nodules increased at 3 weeks when compared with 2 weeks. The rabbits in each group survived until the experiment was completed. Compared with groups A, B, and C, the trabeculae of group D were more orderly, the empty bone lacunae were less, there were abundant functional organelles, and obvious osteogenesis was observed, and the necrotic area was completely repaired at 12 weeks. Immunohistochemical staining showed that, at 6 and 12 weeks after operation, the expressions of OCN and VEGF in groups A, B, and C were significantly lower than those in groups D and E, while those in groups B and C were significantly higher than those in group A, and in group E than in group D ( P<0.05). The expression of PPARγ-2 was significantly higher in groups A, B, and C than in groups D and E, and in group A than in groups B and C, and in group D than in group E ( P<0.05). At 12 weeks after operation, biomechanical test showed that the average elastic modulus and maximum compressive strength of cancellous bone and subchondral bone in groups D and E were significantly higher than those in groups A, B, and C ( P<0.05); there was no significant difference between groups A, B, and C and between groups D and E ( P>0.05).

Conclusion

In vivo transplantation of microencapsulated transgenic BMSCs can repair early SONFH in rabbits.

Repair of non-traumatic femoral head necrosis by marrow core decompression with bone grafting and porous tantalum rod implantation

Objective

To compare the clinical effects of marrow core decompression with bone grafting and marrow core decompression with porous tantalum rod implantation in treating avascular necrosis of non-traumatic femoral head.

Methods

This prospective study selected 60 patients (74 hips) with avascular necrosis of femoral head admitted to Daping Hospital from January 2018 to March 2019. According to treatment methods, the 60 patients were randomly divided into two groups, i.e. 30 patients in one group were treated by marrow core decompression with bone grafting, and the other 30 patients in the other group were treated with marrow core decompression and porous tantalum rod implantation.

Results

All implantation treatments were successful. No significant difference was found in surgical duration, hemorrhage volume and duration of hospitalization stay between the two groups during follow-up. All Harris scores were significantly improved (P<0.05) following treatment compared to those before treatment. The Harris score of patients treated with porous tantalum rod implantation was higher than that of patients treated with bone grafting (P<0.05) after 12 months following treatment and such a difference was significant.

Conclusion

The combination of marrow core decompression and porous tantalum rod implantation can better improve the functions of hip joints with early femoral head necrosis than marrow core decompression with bone grafting, and can also prevent articular cartilage from collapsing gradually.

Curcumin prevents osteocyte apoptosis by inhibiting M1-type macrophage polarization in mice model of glucocorticoid-associated osteonecrosis of the femoral head

Inflammation is a contributing factor in osteocyte apoptosis, which is strongly associated with the development of glucocorticoid-associated osteonecrosis of the femoral head (GA-ONFH). Curcumin is a naturally derived drug that regulates immunity and inhibits inflammation. This study aimed to examine the capacity of curcumin to prevent osteocyte apoptosis and GA-ONFH, while elucidating possible mechanisms of action. C57/BL6 female mice were divided into control, GA-ONFH, and curcumin-treated GA-ONFH groups. We determined the effect of curcumin on the polarization of RAW264.7 and the apoptosis of MLO-Y4 cells. We found that curcumin reduced the infiltration of M1-type macrophages in the femoral heads and alleviated systemic inflammation in GA-ONFH models. Additionally, curcumin decreased the apoptosis of osteocytes in the femoral heads and the ratio of GA-ONFH in mice. Further, in vitro curcumin intervention inhibited M1-type polarization via the Janus kinase1/2-signal transducer and activator of transcription protein1 (JAK1/2-STAT1) pathway. Taken together, this study demonstrates that curcumin is effective in preventing osteocyte apoptosis and the development of GA-ONFH in a mouse model. Curcumin prevents inflammatory-mediated apoptosis of osteocytes in part through inhibition of M1 polarization through the JAK1/2-STAT1 pathway. These findings provide novel insights as well as a potential preventive agent for GA-ONFH. This article is protected by copyright. All rights reserved.

cAMP regulates 11β-hydroxysteroid dehydrogenase-2 and Sp1 expression in MLO-Y4/MC3T3-E1 cells

11β-hydroxysteroid dehydrogenase-2 (11β-HSD2) is one of the key enzymes in glucocorticoid metabolism, which can inactivate local corticosterone and regulate the level of active glucocorticoid in tissues. The expression of 11β-HSD2 and its regulatory pathway serve an important role in the apoptosis of steroid induced osteonecrosis of the femoral head (SANFH). The present study aimed to identify the regulatory effects of cAMP on the expression of Sp1 transcription factor (Sp1) and 11β-HSD2 in osteocytes at the cellular level. Murine long bone osteocyte Y4 (MLO-Y4) clone cells and mouse embryo osteoblast-like (MC3T3-E1) cells were cultured in vitro with adenylate cyclase activator or inhibitor (forskolin and SQ22536, respectively) to investigate the effects of alterations to intracellular cAMP levels. mRNA and protein expression levels of Sp1 and 11β-HSD2 were detected by reverse transcription-quantitative PCR and western blotting, respectively. Compared with the negative control group, the mRNA and protein expression levels of Sp1 were significantly increased in the activation group, whereas Sp1 expression levels were significantly decreased in the inhibition group. Similarly, compared with the negative control group, the mRNA and protein expression levels of 11β-HSD2 were significantly increased in the activator group, but significantly decreased in the inhibitor group. The aforementioned results indicated that intracellular cAMP levels significantly regulated the expression of Sp1 and 11β-HSD2 in mouse osteocytes and osteoblasts. Therefore, the present study suggested a potential therapeutic strategy for the prevention of osteonecrosis of the femoral head.

Mechanism of Methylprednisolone-Induced Primary Cilia Formation Disorder and Autophagy in Osteoblasts

Objective

To study the role of primary cilia formation disorder and osteoblasts autophagy in the pathogenesis of steroid‐induced avascular necrosis of the femoral head (SANFH).

Methods

Osteoblasts were isolated from rabbit bones and treated with 1 μM Methylprednisolone for 0, 12, 24, 48, and 72 h. The Beclin1, MAP1LC3, Atg‐5, Atg‐12, IFT20 and OFD1 mRNAs and proteins were detected by PCR and Western blotting, and their correlation was statistically analyzed. The lengths of osteoblast cilia were measured under a laser confocal microscope, and the autophagy flux was tracked by transfecting the osteoblasts with GFP‐RFP‐LC3 lentivirus.

Results

Methylprednisolone significantly upregulated Beclin1, MAP1LC3, Atg‐5, Atg‐12 and OFD1 mRNAs and proteins in a time‐dependent manner, and decreased that of IFT20 (P < 0.05). In addition, the autophagy flux in the osteoblasts also increased and the ciliary length decreased in a time‐dependent manner after Methylprednisolone treatment. The length of the cilia were 5.46 ± 0.11 um at 0 h, 4.08 ± 0.09 um at 12 h, 3.07 ± 0.07 um at 24 h, 2.31 ± 0.10 um at 48 h, and finally 1.15 ± 0.04 um at 72 h. Methylprednisolone treatment also affects primary cilium numbers in cultures, for 0 to 72 h. The autophagy regulatory genes, Beclin1, MAP1LC3, Atg‐5 and Atg‐12, were found to be negatively correlated with IFT20, with an average correlation coefficient of −0.81. A negative correlation was also found between OFD1 and IFT20, with an average correlation coefficient of −0.53.

Conclusion

Methylprednisolone inhibits primary cilia formation and promotes autophagy, which could be the pathological basis of SANFH. The exact regulatory mechanism needs to be further studied in vivo.

Dexamethasone promotes mesenchymal stem cell apoptosis and inhibits osteogenesis by disrupting mitochondrial dynamics

Long‐term or heavy use of glucocorticoids can cause severe necrosis of the femoral head, but the underlying mechanisms are still unclear. Recent studies have found that mitochondrial dynamics play an important role in femoral head necrosis. Here, we investigated the effect of dexamethasone on the mitochondrial function of mesenchymal stem cells. We observed that high concentrations of dexamethasone (10⁻⁶ mol·L⁻¹) decreased cell activity, promoted apoptosis, elevated levels of reactive oxygen species and disrupted mitochondrial dynamics. Furthermore, dexamethasone (10⁻⁶ mol·L⁻¹) inhibited osteogenesis of stem cells and promoted adipogenesis. These findings may facilitate greater understanding of the adverse effects of dexamethasone on the femoral head.

Extracellular vesicles from endothelial progenitor cells prevent steroid-induced osteoporosis by suppressing the ferroptotic pathway in mouse osteoblasts based on bioinformatics evidence

Abnormal antioxidative capabilities were observed in the pathogenesis of steroid-induced osteoporosis (SIOP). Ferroptosis is a recently discovered type of cell death that is characterized by the overproduction of ROS in response to GPX4 and system X^c− downregulation, which is mediated by an Fe²⁺ fenton reaction. However, investigations focusing on the relationship between ferroptosis and steroid-induced bone disease remain limited. In the present study, high-dose dexamethasone was used to establish a mouse SIOP model, and extracellular vesicles extracted from bone marrow-derived endothelial progenitor cells (EPC-EVs) alleviated the pathological changes in SIOP via microtomography (micro-CT), with elevations in bone volume (BV), bone surface (BS), trabecular thickness (Tb.Th), and trabecular connectivity density (Conn-D) and decreases in trabecular separation (Tb.sp) and the structure model index (SMI). Histopathological analysis, such as haematoxylin and eosin (HE) and Masson staining, showed that EPC-EVs treatment increased the volume and density of the trabecular bone and bone marrow. RNA sequencing (RNA-seq) and bioinformatics analysis revealed subcellular biological alterations upon steroid and EPC-EVs treatment. Compared with the control, high-dose dexamethasone downregulated GPX4 and system X^C−, and the Kyoto Encyclopedia of Genes and Genomes (KEGG)-based gene set enrichment analysis suggested that the ferroptotic pathway was activated. In contrast, combination treatment with EPC-EVs partly reversed the KEGG-mapped changes in the ferroptotic pathway at both the gene and mRNA expression levels. In addition, alterations in ferroptotic marker expression, such as SLC3A2, SLC7A11, and GPX4, were further confirmed by RNA-seq. EPC-EVs were able to reverse dexamethasone treatment-induced alterations in cysteine and several oxidative injury markers, such as malondialdehyde (MDA), glutathione (GSH), and glutathione disulphide (GSSG) (as detected by ELISA). In conclusion, EPC-EVs prevented mouse glucocorticoid-induced osteoporosis by suppressing the ferroptotic pathway in osteoblasts, which may provide a basis for novel therapies for SIOP in humans.

Glucocorticoid Enhanced the Expression of Ski in Osteonecrosis of Femoral Head: The Effect on Adipogenesis of Rabbit BMSCs

Glucocorticoid (GC)-induced osteonecrosis has been considered as the most serious side effect in long-term or over-dose steroid therapy. The decreased bone mass and increased marrow fat tissue demonstrated that GC can destroy the normal differentiation of bone marrow mesenchymal stem cells (BMSCs), which accelerates adipogenesis but not osteogenesis. However, the underlying mechanisms are still unclear. Ski, an evolutionary conserved protein, is a multifunctional transcriptional regulator that involved in regulating signaling pathways associated with adipogenesis differentiation, but the concrete function remains unclear. In this work, we first established a methylprednisolone (MPS)-induced osteonecrosis of femoral head (ONFH) rabbit model, in which the expression of Ski, PPAR-γ, and FABP4 was up-regulated compared with control group, and then we induced the isolated BMSCs from rabbit with dexamethasone (Dex) in vitro and the results showed that the Ski expression was up-regulated by Dex in a dose- and time-dependent manner. Therefore, we demonstrated that the expression of Ski was up-regulated in glucocorticoid-related osteonecrosis disease in vivo and in vitro. Moreover, the adipogenesis differentiation capacity of BMSCs was enhanced after induced by Dex, which was identified by Oil Red O staining, and the up-regulated PPAR-γ and FABP4 expression. To further study the function of Ski in BMSC after induced by Dex, Ski specific small interfering RNA (Ski-siRNA) was used. Results showed that knockdown of Ski obviously decreased adipogenesis differentiation evident by Oil Red O staining, and the expression of PPAR-γ and FABP4 was down-regulated simultaneously. Collectively, our findings suggest that Ski increased significantly during glucocorticoid-induced adipogenic differentiation of BMSCs, and the expression level was consistent with adipogenic-related proteins including PPAR-γ and FABP4. Based on the above data, we believe that Ski might become a new molecule in the treatment of GC-induced ONFH and our study could provide a basis for further study on the detailed function of Ski in ONFH.

Association between genetic polymorphisms and osteonecrosis in steroid treatment populations: a detailed stratified and dose-response meta-analysis

Steroid treatment has become recognized as an important risk factor for avascular osteonecrosis of the femoral head. However, not all patients who receive long-term, high-dose steroids develop osteonecrosis, indicating that there are individual differences in occurrence.We explored the relationship between polymorphisms and steroid-induced osteonecrosis of the femoral head (SONFH) incidence with variables. We used a multilevel mixed-effects logistic regression model, which is an expansion of logistic regression, for each type of steroid, primary disease, drug dose, applied duration, and single-nucleotide polymorphism (SNP). We also conducted a dose-response meta-analysis to analyze the cumulative dosage and SONFH risk in mutation carriers. There were significant correlations between the ABCB1 rs1045642 mutant and SONFH in the prednisone-use and methylprednisolone/prednisone-use populations. The ABCB1 rs2032582 mutant homozygote had a protective effect in the methylprednisolone/prednisolone renal transplant population. For ApoB rs693, mutation increased the incidence of SONFH in prednisone-use and methylprednisolone/prednisolone-use populations and renal transplant patients. For ApoB rs1042031, mutation increased the risk of SONFH in the prednisone-use population. The PAI-1 rs1799768 mutation had a protective effect on the SONFH risk prednisone-use and renal transplant populations. ABCB1 rs1045642 mutations have a protective effect against SONFH, and ApoB rs693 and rs1042031 increase the SONFH risk. Cumulative dosage and treatment duration had little effect on the results. In addition, there was a dose-effect correlation in ABCB1 rs1045642 and rs2032582 mutation carriers.

[Effects of icariin on autophagy and exosome production of bone microvascular endothelial cells]

Objective

To evaluate the effects of icariin on autophagy induced by low-concentration of glucocorticoid and exosome production in bone microvascular endothelial cells (BMECs).

Methods

BMECs were isolated from femoral heads resected in total hip arthroplasty and then intervened with hydrocortisone of low concentration (0, 0.03, 0.06, 0.10 mg/mL), which were set as groups A, B, C, and D, respectively. On the basis of hydrocortisone intervention, 5×10 ^-5 mol/L of icariin was added to each group (set as groups A1, B1, C1 and D1, respectively). Western blot was used to detect the expressions of microtubule-associated protein 1 light chain 3B (LC3B) and dead bone slice 1 (p62) after 24 hours. Exosomes were extracted from BMECs treated with icariin (intervention group) and without icariin (non-intervention group), and the diameter and concentration of exosomes were evaluated by nanoparticle tracking analysis technique. The total protein content of exosomes was detected by BCA method, and the expressions of proteins carried by exosomes including CD9, CD81, transforming growth factor β ₁ (TGF-β ₁), and vascular endothelial growth factor A (VEGFA) were assessed by Western blot. The BMECs were further divided into three groups: BMECs in the experimental group and the control group were co-cultured with exosomes secreted by BMECs treated with or without icariin, respectively; the blank control group was BMECs without exosome intervention. The three groups were treated with hydrocortisone and Western blot was used to detect the expressions of LC3B and p62. The scratching assay was used to detect cell migration ability; angiogenic ability of BMECs was also assessed.

Results

With the increase of hydrocortisone concentration, the protein expression of LC3B-Ⅱ increased gradually, and the protein expression of p62 decreased gradually ( P<0.01). Compared with group with same concentration of hydrocortisone, the protein expression of LC3B-Ⅱ decreased and the protein expression of p62 increased after the administration of icariin ( P<0.01). The concentration of exosomes in the intervention group was significantly higher than that in the non-intervention group ( t=-10.191, P=0.001); and there was no significant difference in exosome diameter and total protein content between the two groups ( P>0.05). CD9 and CD81 proteins were highly expressed in the non-intervention group and the intervention group, and the relative expression ratios of VEGFA/CD9 and TGF-β ₁/CD9 proteins in the intervention group were significantly higher than those in the non-intervention group ( P<0.01). After co-culture of exosomes, the protein expression of p62 increased in blank control group, control group, and experimental group, while the protein expression of LC3B-Ⅱ decreased. There were significant differences among groups ( P<0.05). When treated with hydrocortisone for 12 and 24 hours, the scratch closure rate of the control group and experimental group was significantly higher than that of the blank control group ( P<0.05), and the scratch closure rate of the experimental group was significantly higher than that of the control group ( P<0.05). When treated with hydrocortisone for 4 and 8 hours, the number of lumens, number of sprouting vessels, and length of tubule branches in the experimental group and the control group were significantly greater than those in the blank control group ( P<0.05); the length of tubule branches and the number of lumens in the experimental group were significantly greater than those in the control group ( P<0.05).

Conclusion

Icariin and BMECs-derived exosomes can improve the autophagy of BMECs induced by low concentration of glucocorticoid.

Polydatin promotes the osteogenic differentiation of human bone mesenchymal stem cells by activating the BMP2-Wnt/β-catenin signaling pathway

Steroid-induced osteonecrosis of the femoral head (SONFH) is a refractory disease induced by glucocorticoids. Marrow mesenchymal stem cells (MSCs) differentiate into multiple bone matrix cells and have been used as cell-based therapies to treat ONFH. However, the osteogenesis of MSCs isolated from patients with SONFH is significantly decreased. Polydatin has been widely used in traditional Chinese remedies due to its multiple pharmacological actions. As shown in our previous study, Polydatin protects from oxidative stress and promotes BMSC migration. However, little is known about its role in BMSC (Bone marrow mesenchymal stem cells) osteogenesis; therefore, we further investigated the effect and mechanism of Polydatin in hBMSC osteogenesis. The ability of Polydatin to promote the proliferation and osteogenic differentiation of hBMSCs was determined using the MTT assay, ALP staining and the ALP activity assay. Next, qPCR and western blotting were performed to measure the levels of genes and proteins related to the osteogenesis of hBMSCs. Then, the effect of Polydatin on the nuclear translocation of β-catenin was determined using immunofluorescence staining. Polydatin (30 μM) markedly enhanced the proliferation of hBMSCs and alkaline phosphatase (ALP) activity. Additionally, it also significantly upregulated the expression of osteogenic genes (Runx2, osteopontin, DLX5, osteocalcin, collagen type I and BMP2) and components of the Wnt signaling pathway (β-catenin, Lef1, TCF7, c-jun, c-myc and cyclin D). These osteogenesis-potentiating effects of Polydatin were blocked by Noggin, an inhibitor of the BMP pathway, and DKK1, an inhibitor of the Wnt/β-catenin pathway. However, DKK1 did not affect Polydatin-induced BMP2 expression. Based on our results, Polydatin promotes the proliferation and osteogenic differentiation of hBMSCs through the BMP2-Wnt/β-catenin signaling pathway.

Lipid Transporter Activity-Related Genetic Polymorphisms Are Associated With Steroid-Induced Osteonecrosis of the Femoral Head: An Updated Meta-Analysis Based on the GRADE Guidelines

Aims: The purpose of this study was to assess the relationship between genetic variants and steroid-induced osteonecrosis of the femoral head (SONFH) in steroid use populations. Methods: We searched the public databases up to April 15, 2018. This study analyzed only the single-nucleotide polymorphisms (SNPs) that have appeared in more than three studies and assessed the level of evidence by classifying the outcomes according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. Results: The ABCB1 rs1045642 C>T mutation had a protective effect against SONFH in the allelic model (I ² = 50.2%; OR: 0.74; 95% CI: 0.55-1.00; p = 0.046). The rs2032582 mutation in the ABCB1 gene showed no relationship to SONFH (allelic model: I ² = 63.4%; OR: 0.85; 95% CI: 0.58-1.23; p = 0.382). In ApoB rs693, four models showed that mutations can increase SONFH risk, but the allelic model did not. The ApoB rs1042031 mutation increased SONFH risk in the dominant model (I ² = 50.3%; OR: 2.90; 95% CI: 1.49-5.66; p = 0.002). Conclusion: An allelic model of ABCB1 rs1045642 showed that mutations have a protective effect against SONFH at a very low level of evidence. The mutations in ApoB rs693 and rs1042031 increase the SONFH risk with moderate levels of evidence.