Drynaria Naringin alleviated mechanical stress deficiency-caused bone loss deterioration via Rspo1/Lgr4-mediated Wnt/ß-catenin signalling pathway.

Osteoporosis is a metabolic condition distinguished by the degradation of bone microstructure and mechanical characteristics. Traditional Chinese medicine (TCM) has been employed in China for the treatment of various illnesses. Naringin, an ingredient found in Drynariae TCM, is known to have a significant impact on bone metabolism. For this research, we studied the precise potential effect of Drynaria Naringin on protecting against bone loss caused by stress deficiency. In this study, a tail-suspension (TS) test was performed to establish a mouse model with hind leg bone loss. Some mice received subcutaneous injections of Drynaria Naringin for 30 d. Trabecular bone microarchitecture was evaluated using micro-computed tomography analysis and bone histological analysis. Bone formation and resorption markers were quantified in blood samples from mice or in the supernatant of MC3T3-E1 cells by ELISA analysis, Western blotting, and PCR. Immunofluorescence was utilized to visualize the location of ß-catenin. Additionally, siRNA was employed to knockdown-specific genes in the cells. Our findings highlight the efficacy of Drynaria Naringin in protecting against the deterioration of bone loss and promoting bone formation and Rspo1 expression in a mouse model following the TS test. Specifically, in vitro experiments also indicated that Drynaria Naringin may promote osteogenesis through the Wnt/ß-catenin signalling pathway. Moreover, our results suggest that Drynaria Naringin upregulates the expression of Rspo1/Lgr4, leading to the promotion of osteogenesis via the Wnt/ß-catenin signalling pathway. Therefore, Drynaria Naringin holds potential as a therapeutic medication for osteoporosis. Drynaria Naringin alleviates bone loss deterioration caused by mechanical stress deficiency through the Rspo1/Lgr4-mediated Wnt/ß-catenin signalling pathway.

Oxidative Stress Aggravates Apoptosis of Nucleus Pulposus Cells through m6A Modification of MAT2A Pre-mRNA by METTL16.

The process of intervertebral disc degeneration (IVDD) is complex, and its mechanism is considered multifactorial. Apoptosis of oxidative stressed nucleus pulposus cells (NPCs) should be a fundamental element in the pathogenesis of IVDD. In our pilot study, we found that the expression of MAT2A decreased, and METTL16 increased in the degenerative nucleus pulposus tissues. Previous studies have shown that the balance of splicing, maturation, and degradation of MAT2A pre-mRNA is regulated by METTL16 m6A modification. In the current study, we aimed to figure out whether this mechanism was involved in the aberrant apoptosis of NPCs and IVDD. Human NPCs were isolated and cultured under oxidative stress. An IVDD animal model was established. It showed that significantly higher METTL16 expression and lower MAT2A expression were seen in either the NPCs under oxidative stress or the degenerative discs of the animal model. MAT2A was inhibited with siRNA in vitro or cycloleucine in vivo. METTL16 was overexpressed with lentivirus in vitro or in vivo. Downregulation of MAT2A or upregulation of METTL16 aggravated nucleus pulposus cell apoptosis and disc disorganization. The balance of splicing, maturation, and degradation of MAT2A pre-mRNA was significantly inclined to degradation in the NPCs with the overexpression of METTL16. Increased apoptosis of NPCs under oxidative stress could be rescued by reducing the expression of METTL16 using siRNA with more maturation of MAT2A pre-mRNA. Collectively, oxidative stress aggravates apoptosis of NPCs through disrupting the balance of splicing, maturation, and degradation of MAT2A pre-mRNA, which is m6A modified by METTL16.

Evidence of the Role of R-Spondin 1 and Its Receptor Lgr4 in the Transmission of Mechanical Stimuli to Biological Signals for Bone Formation.

The bone can adjust its mass and architecture to mechanical stimuli via a series of molecular cascades, which have been not yet fully elucidated. Emerging evidence indicated that R-spondins (Rspos), a family of secreted agonists of the Wnt/ß-catenin signaling pathway, had important roles in osteoblastic differentiation and bone formation. However, the role of Rspo proteins in mechanical loading-influenced bone metabolism has never been investigated. In this study, we found that Rspo1 was a mechanosensitive protein for bone formation. Continuous cyclic mechanical stretch (CMS) upregulated the expression of Rspo1 in mouse bone marrow mesenchymal stem cells (BMSCs), while the expression of Rspo1 in BMSCs in vivo was downregulated in the bones of a mechanical unloading mouse model (tail suspension (TS)). On the other hand, Rspo1 could promote osteogenesis of BMSCs under CMS through activating the Wnt/ß-catenin signaling pathway and could rescue the bone loss induced by mechanical unloading in the TS mice. Specifically, our results suggested that Rspo1 and its receptor of leucine-rich repeat containing G-protein-coupled receptor 4 (Lgr4) should be a novel molecular signal in the transmission of mechanical stimuli to biological signal in the bone, and this signal should be in the upstream of Wnt/ß-catenin signaling for bone formation. Rspo1/Lgr4 could be a new potential target for the prevention and treatment of disuse osteoporosis in the future.

The role of R-spondins and their receptors in bone metabolism.

R-spondins are a family of four secreted proteins and act as agonists of the canonical Wnt/ß-catenin signaling pathway. They are broadly expressed in different phases of skeleton tissues. Recently, three closely related leucine-rich repeat containing G-protein-coupled receptors (Lgr4/5/6) have been identified as the new and exact receptors of R-spondins. On the cell surface, R-spondins binding with Lgr4/5/6 and Znrf3/Rnf43 lead to reduced turnover of Wnts-receptors and potentiate Wnt/ß-catenin signaling pathway which is critical for the control of bone development and remodeling. There has been a growing interest in understanding the role and mechanism of R-spondins and their receptors in multiple biological processes, including bone development and metabolism. Recent advances in the R-spondins revealed the potential modulatory effect on osteoblastogenesis and bone formation and provided a new avenue for the investigation of adult bone metabolism. The receptors of Lgr4/5/6 and stabilized ß-catenin are essential to the regulatory effect of Rspos on skeleton. The findings on Rspo/Lgr signaling might have clinical potentials for the treatment of bone loss related diseases.

[Clinical observation of bone graft and impaction on posterior interbody fusion for lumbar instability].

OBJECTIVE: To investigate the clinical effect and indication of bone graft and impaction on posterior interbody fusion for lumbar instability. METHODS: From January 2001 to July 2008, 95 patients with lumbar instability were treated by bone graft and impaction on posterior interbody fusion. Including 41 males and 54 females, the age from 45 to 76 years old with an average of 59 years. There were 68 cases with single level, 22 cases with two-level, 5 cases with three-level in patients, which were 127 intervertebral space altogether. The neural canal and affected side nerve root were decompressed thoroughly during operation. Resected the disc from the affected side and erased the cartilage to plate extensively combined with pedicle screw fixation, and impaction on interbody fusion with the excisional vertebral plate bone was achieved. To assess the improvement of the patients' symptom, sign, and JOA scores pre and post operatively. Meanwhile, the changes of intervertebral height from the lumbar radiographs were measured and the degrees of interbody bone fusion were evaluated according to SUK method. RESULTS: All the 95 patients were followed up from 12 to 90 months with the mean of 44.8 months. All the clinical symptom were improved significantly or disappeared completely. All the 127 intervertebral space achieved good bone fusion. There was no displacement of bone graft and severe complication happened. According to the radiograph, all the intervertebral heights were increased obviously. The mean JOA score improved from 11.3 +/- 3.3 preoperative to 25.1 +/- 2.8 at 8 weeks postoperative; achieved 24.8 +/- 3.2 with followed up at the last time (P < 0.001). CONCLUSION: Bone graft and impaction on posterior interbody fusion was one of the most effective methods for the lumbar instability. It has extensive range of application, and it's suitable for senile lumbar degeneration instability especially.