Steroid-induced osteonecrosis of the femoral head (SONFH) is a common debilitating orthopedic disease. The bone marrow mesenchymal stem cells (BMSCs) are a type of mesenchymal stem cells which play crucial roles in bone repair. The adipogenic/osteogenic differentiation disorder of BMSCs has been widely perceived contributing to SONFH. However, the regulatory mechanism of BMSCs differentiation disorder still remains unclear. Circular RNA (circRNA), a kind of stable ncRNA, plays important roles in regulating gene expression via various ways. To date, there are no studies to uncover the circRNA expression profile and screen out the key circRNAs playing crucial roles in adipogenic/osteogenic differentiation disorder of SONFH-BMSCs. In present study, we detected the circRNA expression profiles in SONFH-BMSCs for the first time. A total of 820 circRNAs were differentially expressed in SONFH-BMSCs, including 460 up- and 360 down-regulated circRNAs. Bioinformatics analysis indicates circRNA CDR1as, one up-regulated circRNA, may play crucial role in adipogenic/osteogenic differentiation disorder of SONFH-BMSCs via CDR1as-miR-7-5p-WNT5B axis. Knocking-down CDR1as resulted in increasing of osteogenic differentiation and decreasing of adipogenic differentiation of BMSCs, while over-expressing CDR1as resulted in decreasing of osteogenic differentiation and increasing of adipogenic differentiation of BMSCs. The miR-7-5p binding sites of CDR1as and WNT5B were verified by luciferase reporter gene assay. Our study may provide new insights into the molecular mechanisms of osteogenic/adipogenic differentiation disorder of SONFH-BMSCs and new biomarkers for the diagnosis and treatment of SONFH.

Spinal tuberculosis is the most common extrapulmonary tuberculosis, characterized by intervertebral disc destruction, which seriously affects people’s quality of life. Recent studies have suggested that the TGF-β1/SMADs signaling pathway plays an important regulatory role in the process of intervertebral disc destruction caused by spinal tuberculosis. However, the abnormal TGF-β1/SMADs signaling pathway in spinal tuberculosis is not fully understood. Herein, we found for the first time that HCG18 was significantly upregulated in spinal tuberculosis nucleus pulposus clinical samples and confirmed that HCG18 negatively regulates the proliferation and migration ability of nucleus pulposus cells (NPCs). In vitro experiments further suggest that overexpression of HCG18 can significantly promote TGF-β1/SMADs pathway activity and inhibit proliferation, migration, and apoptosis of NPCs, an effect which can be reversed by overexpressing hsa-miR-146a-5p. On the contrary, knocking down HCG18 yields the opposite result. In vivo experiments suggest that knocking down HCG18 can significantly alleviate the destruction of the nucleus pulposus in rats with spinal tuberculosis by inhibiting the activity of the TGF-β1/SMADs pathway. In summary, our research suggests that HCG18 can promote the progression of spinal tuberculosis by alleviating the inhibitory effect of hsa-miR-146a-5p on the TGF-β1/SMADs pathway. This study provides new insights into the occurrence and development of spinal tuberculosis, as well as new strategies for the prevention and treatment of spinal tuberculosis.

Background. Osteoarthritis (OA) is the most common degenerative disease in orthopedics. However, the cause and underlying molecular mechanisms are not clear. This study aims to identify the hub genes and pathways involved in the occurrence of osteoarthritis. Methods. The raw data of GSE89408 were downloaded from the Gene Expression Omnibus (GEO) database, and the differentially expressed genes (DEGs) were identified by R software. The DAVID database was used for pathway and gene ontology analysis, and p2 were set as the cut-off point. Moreover, protein-protein interaction (PPI) network construction was applied for exploring the hub genes in osteoarthritis. The expression levels of the top ten hub genes in knee osteoarthritis synovial membranes and controls were detected by quantitative real-time PCR system. Results. A total of 229 DEGs were identified in osteoarthritis synovial membranes compared with normal synovial membranes, including 145 upregulated and 84 downregulated differentially expressed genes. The KEGG pathway analysis results showed that up-DEGs were enriched in proteoglycans in cytokine-cytokine receptor interaction, chemokine signaling pathway, rheumatoid arthritis, and TNF signaling pathway, whereas down-DEGs were enriched in the PPAR signaling pathway and AMPK signaling pathway. The qRT-PCR results showed that the expression levels of ADIPOQ, IL6, and CXCR1 in the synovium of osteoarthritis were significantly increased (p <0.05).

Disorders of bone homeostasis are the key factors leading to metabolic bone disease, such as senile osteoporosis, which is characterized by age-related bone loss. Bone marrow stromal cells (BMSCs) possess high osteogenic capacity which has been regarded as a practical approach to preventing bone loss. Previous studies have shown that the osteogenic differentiation ability of BMSCs is significantly decreased in senile osteoporosis. Recently, circular RNAs (circRNAs) have been regarded as critical regulators in controlling the osteogenic differentiation of BMSCs by sponging microRNAs (miRNAs). Our study aimed to discover new and critical osteogenesis-related circRNAs that can promote bone formation in senile osteoporosis. We detected the dysregulated circRNAs of BMSCs upon osteogenic differentiation induction and identified the critical osteogenic circRNA (circ-3626). The relationship between circ-3626 and osteoporosis was further verified in clinical bone samples and aged mice by qPCR. Moreover, circ-3626 AAV was constructed to examine the osteogenic effect of circ-3626 on bone formation via using Micro-CT, double calcein labeling, and the three-point bending tests. Bioinformatics analysis, Luciferase report gene assays, FISH, RNA pull-down, qPCR, Western Blots, and alizarin red staining assay explore the effects and mechanisms of circ-3626 on osteogenic differentiation of BMSCs. Circ-3626 was identified as a pivotal osteogenesis-related circRNA via RNA sequencing. The results of alizarin red staining, Western blots, and qPCR assays suggest that overexpressing circ-3626 dramatically accelerates the osteogenic capability of BMSCs. Furthermore, the bone repair capability of aging mice could be significantly improved by circ-3626 AAV treatment. Micro RNA miR-338-3p was identified as the downstream target of circ-3626. Overexpression of circ-3626 increases the expression of Runx2 by sponging miR-338-3p, thereby promoting the osteogenic differentiation of BMSCs by upregulating the expression of osteogenic genes. In addition, Western blots, and qPCR assays suggest circ-3626 AAV treatment promote the expression of Runx2 and osteogenic marker genes. Thus, we demonstrate that circ-3626 plays a pivotal role in promoting bone formation through the miR-338-3p/Runx2 axis and may provide new strategies for preventing and treating the bone loss of senile osteoporosis.