MFG-E8 promotes osteogenic differentiation of human bone marrow mesenchymal stem cells through GSK3ß/ß-catenin signaling pathway.

Fracture nonunion and bone defects are challenging for orthopedic surgeons. Milk fat globule-epidermal growth factor 8 (MFG-E8), a glycoprotein possibly secreted by macrophages in a fracture hematoma, participates in bone development. However, the role of MFG-E8 in the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is unclear. We investigated the osteogenic effect of MFG-E8 in vitro and in vivo. The CCK-8 assay was used to assess the effect of recombinant human MFG-E8 (rhMFG-E8) on the viability of hBMSCs. Osteogenesis was investigated using RT-PCR, Western blotting, and immunofluorescence. Alkaline phosphatase (ALP) and Alizarin red staining were used to evaluate ALP activity and mineralization, respectively. An enzyme-linked immunosorbent assay was conducted to evaluate the secretory MFG-E8 concentration. Knockdown and overexpression of MFG-E8 in hBMSCs were established via siRNA and lentivirus vector transfection, respectively. Exogenous rhMFG-E8 was used to verify the in vivo therapeutic effect in a tibia bone defect model based on radiographic analysis and histological evaluation. Endogenous and secretory MFG-E8 levels increased significantly during the early osteogenic differentiation of hBMSCs. Knockdown of MFG-E8 inhibited the osteogenic differentiation of hBMSCs. Overexpression of MFG-E8 and rhMFG-E8 protein increased the expression of osteogenesis-related genes and proteins and enhanced calcium deposition. The active ß-catenin to total ß-catenin ratio and the p-GSK3ß protein level were increased by MFG-E8. The MFG-E8-induced enhanced osteogenic differentiation of hBMSCs was partially attenuated by a GSK3ß/ß-catenin signaling inhibitor. Recombinant MFG-E8 accelerated bone healing in a rat tibial-defect model. In conclusion, MFG-E8 promotes the osteogenic differentiation of hBMSCs by regulating the GSK3ß/ß-catenin signaling pathway and so, is a potential therapeutic target.

ALX1-transcribed LncRNA AC132217.4 promotes osteogenesis and bone healing via IGF-AKT signaling in mesenchymal stem cells.

The osteogenic potential of bone marrow mesenchymal stem cells (BMSCs) is critical for bone formation and regeneration. A high non-/delayed-union rate of fracture healing still occurs in specific populations, implying an urgent need to discover novel targets for promoting osteogenesis and bone regeneration. Long non-coding (lnc)RNAs are emerging regulators of multiple physiological processes, including osteogenesis. Based on differential expression analysis of RNA sequencing data, we found that lncRNA AC132217.4, a 3'UTR-overlapping lncRNA of insulin growth factor 2 (IGF2), was highly induced during osteogenic differentiation of BMSCs. Afterward, both gain-of-function and loss-of-function experiments proved that AC132217.4 promotes osteoblast development from BMSCs. As for its molecular mechanism, we found that AC132217.4 binds with IGF2 mRNA to regulate its expression and downstream AKT activation to control osteoblast maturation and function. Furthermore, we identified two splicing factors, splicing component 35 KDa (SC35) and heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1), which regulate the biogenesis of AC132217.4 at the post-transcriptional level. We also identified a transcription factor, ALX1, which regulates AC132217.7 expression at the transcriptional level to promote osteogenesis. Importantly, in-vivo over-expression of AC132217.4 essentially promotes the bone healing process in a murine tibial drill-hole model. Our study demonstrates that lncRNA AC132217.4 is a novel anabolic regulator of BMSC osteogenesis and could be a plausible therapeutic target for improving bone regeneration.

The role of mitochondrial dysfunction in mesenchymal stem cell senescence.

Mesenchymal stem cells (MSCs) hold enormous potential for the treatment of immune-related conditions and degenerative diseases, owing to their self-renewal and multilineage differentiation capabilities. Nevertheless, cellular senescence significantly impacts the quantity and quality of MSCs, limiting their clinical use. Mitochondria play essential roles in energy production by oxidative phosphorylation and metabolism of energy sources via the tricarboxylic acid cycle. Therefore, mitochondrial dysfunction is a primary cause of senescence in MSCs. Herein, we summarize the current knowledge regarding the mechanisms underlying mitochondrial dysfunction-associated cellular senescence. We also discuss potential methods to prevent or even reverse MSC senescence.

IGFBP7 regulates the osteogenic differentiation of bone marrow-derived mesenchymal stem cells via Wnt/ß-catenin signaling pathway.

Insulin-like growth factor-binding protein 7 (IGFBP7), a low-affinity IGF binder, may play an important role in bone metabolism. However, its function in osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (BMSCs) remains unclear. Therefore, we investigated its effects on osteogenic differentiation. Overexpression of IGFBP7 enhanced the expression of osteo-specific genes and proteins, and IGFBP7 knockdown decreased osteogenesis-specific markers. More mineral deposits and higher alkaline phosphatase activity were observed after the up-regulation of IGFBP7. Moreover, ß-catenin levels were up-regulated by the overexpression of IGFBP7 or the addition of extracellular IGFBP7 protein and were reduced by the depletion of IGFBP7. The increase in osteogenic differentiation due to the overexpression of IGFBP7 was partially decreased by specific Wnt/ß-catenin signaling inhibitors. Using a rat tibial osteotomy model, a sheet of IGFBP7-overexpressing BMSCs improved bone healing, as demonstrated by imaging, biomechanical, and histologic analyses. Taken together, these findings indicate that IGFBP7 regulates the osteogenic differentiation of BMSCs partly via the Wnt/ß-catenin signaling pathway.-Zhang, W., Chen, E., Chen, M., Ye, C., Qi, Y., Ding, Q., Li, H., Xue, D., Gao, X., Pan, Z. IGFBP7 regulates the osteogenic differentiation of bone marrow-derived mesenchymal stem cells via Wnt/ß-catenin signaling pathway.

Concentration-dependent, dual roles of IL-10 in the osteogenesis of human BMSCs via P38/MAPK and NF-κB signaling pathways.

Microenvironmental conditions can influence the differentiation and functional roles of mesenchymal stem cells (MSCs). Recent studies have suggested that an inflammatory microenvironment can significantly affect the osteogenic differentiation of MSCs. Here, we show, for the first time, that IL-10 has concentration-dependent, dual roles in the osteogenesis of human bone marrow mesenchymal stem cells (hBMSCs). Low physiologic concentrations of IL-10 (0.01-1.0 ng/ml) activate the p38/MAPK signaling pathway to promote the osteogenesis of hBMSCs, but higher pathologic doses of IL-10 (10-100 ng/ml) inhibit p38/MAPK signaling by activating NF-κB, inhibiting osteogenesis. These results demonstrate that p38/MAPK and NF-κB signaling mediates the double-edged sword effect of IL-10 on hBMSCs. The osteogenic impairment was reversed at higher doses of IL-10 when cells were supplemented with the NF-κB inhibitor BAY11-7082. These data provide important insights into the regulatory effects of IL-10 on the biologic behavior of hBMSCs.-Chen, E., Liu, G., Zhou, X., Zhang, W., Wang, C., Hu, D., Xue, D., Pan, Z. Concentration-dependent, dual roles of IL-10 in the osteogenesis of human BMSCs via P38/MAPK and NF-κB signaling pathways.

Open reduction and internal fixation with bone grafts for comminuted mason type II radial head fractures.

BACKGROUND: The use of bone graft for the radial head fractures has been previously described and occasionally used by other authors.This is the first paper, to my knowledge, dealing with the relevant issue about the importance that the use of an autologous bone graft can have on the radial head fractures. METHODS: From July 2010 to July 2014, 20 consecutive patients who underwent open reduction and internal fixation for a closed Mason type II radial head fracture were retrospectively reviewed. Patients with Mason type I, III, simple type II, and comminuted type II fractures treated without bone grafting were excluded. A clinical examination and radiographic evaluation were performed. The overall functional result was evaluated using the Mayo Elbow Performance Score (MEPS). The Broberg and Morrey classification was used to evaluate traumatic arthritis. RESULTS: The average follow-up duration was 31 months (range, 24-50 months). Bone union of the radial head fracture was achieved in all patients at an average of 13.5 weeks (range, 12-17 weeks). Postoperative radiographs showed no cases of postsurgical ligamentous instability, necrosis of the radial head, or internal fixation failure. The mean range of motion of the affected elbow was 128° ± 8.4° in flexion, 14.5° ± 11.1° in extension, 68.7° ± 14.1° in pronation, and 65.2° ± 18.2° in supination. The mean MEPS was 92 ± 7.9 points (range, 80-100); the outcome was excellent (90-100 points) in 13 patients and good (75-89 points) in 7 patients. The MEPS tended to be higher in patients with an isolated fracture (p = 0.016). Based on the Broberg and Morrey classification for radiographic assessment of post-traumatic arthritis, 15 elbows had no evidence of degenerative changes (grade 0), and 5 elbows had grade 1 changes. CONCLUSION: Although radial head fractures may not be amenable to internal fixation, our findings suggest that open reduction and internal fixation with an autogenous bone graft from the lateral epicondyle of the humerus provides satisfactory elbow function in patients with comminuted Mason type II radial head fractures.

Icariin Promotes Tendon-Bone Healing during Repair of Rotator Cuff Tears: A Biomechanical and Histological Study.

To investigate whether the systematic administration of icariin (ICA) promotes tendon-bone healing after rotator cuff reconstruction in vivo, a total of 64 male Sprague Dawley rats were used in a rotator cuff injury model and underwent rotator cuff reconstruction (bone tunnel suture fixation). Rats from the ICA group (n = 32) were gavage-fed daily with ICA at 0.125 mg/g, while rats in the control group (n = 32) received saline only. Micro-computed tomography, biomechanical tests, serum ELISA (calcium; Ca, alkaline phosphatase; AP, osteocalcin; OCN) and histological examinations (Safranin O and Fast Green staining, type I, II and III collagen (Col1, Col2, and Col3), CD31, and vascular endothelial growth factor (VEGF)) were analyzed two and four weeks after surgery. In the ICA group, the serum levels of AP and OCN were higher than in the control group. More Col1-, Col2-, CD31-, and VEGF-positive cells, together with a greater degree of osteogenesis, were detected in the ICA group compared with the control group. During mechanical testing, the ICA group showed a significantly higher ultimate failure load than the control group at both two and four weeks. Our results indicate that the systematic administration of ICA could promote angiogenesis and tendon-bone healing after rotator cuff reconstruction, with superior mechanical strength compared with the controls. Treatment for rotator cuff injury using systematically-administered ICA could be a promising strategy.

Secreted klotho protein attenuates osteogenic differentiation of human bone marrow mesenchymal stem cells in vitro via inactivation of the FGFR1/ERK signaling pathway.

Increasing evidence indicates that the osteogenic differentiation of mesenchymal stem cells (MSCs) is related to bone formation, heterotopic ossification, and even vascular calcification. Therefore, it is essential to understand the microenvironment that regulates these processes. The Klotho gene plays an important role in tissue mineralization, and its secreted protein functions as a hormone. We investigated the effects of secreted Klotho protein on the osteogenesis of human bone marrow MSC (hBMSCs). To this end, the cells received osteogenic medium with or without Klotho protein. The results showed that osteoblast-specific gene expression and mineral deposition were decreased when MSCs were incubated with Klotho. Klotho reduced the expression of fibroblast growth factor receptor 1 (FGFR1) and phosphorylated extracellular signal-regulated kinase 1/2. However, both MEK and FGFR1 inhibitors delayed bone mineral formation more than Klotho. These data suggest that secreted Klotho protein attenuates the osteogenic differentiation of hBMSCs in vitro through FGFR1/ERK signaling.

Reversing the imbalance in bone homeostasis via sustained release of SIRT-1 agonist to promote bone healing under osteoporotic condition.

The imbalance of bone homeostasis is the root cause of osteoporosis. However current therapeutic approaches mainly focus on either anabolic or catabolic pathways, which often fail to turn the imbalanced bone metabolism around. Herein we reported that a SIRT-1 agonist mediated molecular therapeutic strategy to reverse the imbalance in bone homeostasis by simultaneously regulating osteogenesis and osteoclastogenesis via locally sustained release of SRT2104 from mineral coated acellular matrix microparticles. Immobilization of SRT2104 on mineral coating (MAM/SRT) harnessing their electrostatic interactions resulted in sustained release of SIRT-1 agonist for over 30 days. MAM/SRT not only enhanced osteogenic differentiation and mineralization, but also attenuated the formation and function of excessive osteoclasts via integrating multiple vital upstream signals (ß-catenin, FoxOs, Runx2, NFATc1, etc.) in vitro. Osteoporosis animal model also validated that it accelerated osteoporotic bone healing and improved osseointegration of the surrounding bone. Overall, our work proposes a promising strategy to treat osteoporotic bone defects by reversing the imbalance in bone homeostasis using designated small molecule drug delivery systems.

Finite element analysis of sacral-alar-iliac screw fixation for sacroiliac joint dislocation.

The percutaneous sacroiliac (SI) screw is a common fixation option for posterior ring disruption in pelvic fractures. However, SI screw placement is difficult and can injure adjacent neurovascular structures. The sacral-alar-iliac screw (SAI) is a safe, reliable free-hand sacral pelvic fixation technique. To investigate the biomechanical stability of SAI for SI joint dislocation, finite element analysis was performed in unstable Tile-Type B and C pelvic ring injuries. The displacement in S1 (fixation of a unilateral S1 segment with one SI screw), TS1 (fixation of the S1 segment with a transsacra 1 screw), TS2 (fixation of the S2 segment with a transsacra 2 screw), S1AI, and S2AI exceeded the normal SI joint mobility. Sufficient stability after SI joint dislocation was obtained with (TS1 + TS2), (TS2 + S1), (S1AI + S2AI + rod), (S1AI + S2AI), and (S1 + S2AI + S1 pedicle) fixation. The TS1 + TS2 group had the smallest displacement and lowest peak screw stress, followed by (S1 + S2AI + S1 pedicle) placement. Our findings suggest that SAI screws are a valuable option for SI joint dislocation.

Parkin Inhibits RANKL-Induced Osteoclastogenesis and Ovariectomy-Induced Bone Loss.

Osteoporosis and osteoporotic fractures comprise a substantial health and socioeconomic burden. The leading cause of osteoporosis is an imbalance in bone formation and bone resorption caused by hyperactive osteoclasts. Therefore, a new strategy to suppress osteoclastogenesis is needed. Parkin is likely closely associated with bone metabolism, although its role in osteoclastogenesis is unclear. In this study, the Parkin protein inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation, osteoclast-specific gene expression, F-actin ring formation, and bone resorption pit formation in vitro. Moreover, depletion of Parkin enhanced RANKL-induced osteoclast formation, osteoclast-specific gene expression, F-actin ring formation, and bone resorption pit formation. Reactive oxygen species (ROS) activity was suppressed, while autophagy was upregulated with the presence of the Parkin protein. ROS activity was upregulated and autophagy was decreased due to Parkin knockdown. In addition, intravenous administration of Parkin rescued ovariectomy-induced bone loss and reduced osteoclastogenesis in vivo. Collectively, Parkin has therapeutic potential for diseases associated with overactive osteoclasts.

Arthroscopy-Assisted Reduction Percutaneous Internal Fixation Versus Open Reduction Internal Fixation for Tibial Plateau Fracture: A Systematic Review and Meta-analysis.

BACKGROUND: Arthroscopy-assisted reduction percutaneous internal fixation (ARIF) has emerged recently as an alternative treatment method in treating lower-energy tibial plateau fractures. To date, the comparison of clinical efficacy between ARIF and open reduction internal fixation (ORIF) is limited, with divergent conclusions. PURPOSE: To review studies on the clinical efficacy of ARIF and ORIF in the treatment of tibial plateau fracture. STUDY DESIGN: Systematic review; Level of evidence, 3. METHODS: A search was conducted using the PubMed, Web of Science, Cochrane Library, and EMBASE databases between inception and August 20, 2020, for retrospective and prospective studies evaluating ARIF versus ORIF in the treatment of tibial plateau fracture. We identified 6 clinical studies that met the inclusion criteria, with 231 patients treated with ARIF and 386 patients treated with ORIF. The risk of bias and the quality of evidence of the included studies were assessed. The 2 treatment types were compared in terms of clinical results and complications by using odds ratios (ORs), mean differences (MDs), or standardized mean differences (SMDs), with 95% confidence intervals (CIs). Heterogeneity among studies was quantified using the I 2 statistic. RESULTS: The quality of the studies was high. Compared with ORIF, treatment with ARIF led to better clinical function (SMD = 0.31; 95% CI, 0.14 to 0.48; I 2 = 15%; P = .0005), shorter hospital stay (MD = -2.37; 95% CI, -2.92 to -1.81; I 2 = 0%; P < .001), and more intra-articular lesions found intraoperatively (OR = 3.76; 95% CI, 1.49 to 9.49; I 2 = 66%; P = .005). There were no complications or significant differences between the techniques in the radiological evaluation of reduction. CONCLUSION: Compared with ORIF, the ARIF technique for tibial plateau fractures led to faster postoperative recovery and better clinical function and the ability to find and treat more intra-articular lesions during the operation. However, the radiological evaluation of reduction and complications were not significantly different between the 2 groups.

Low-dose IL-34 has no effect on osteoclastogenesis but promotes osteogenesis of hBMSCs partly via activation of the PI3K/AKT and ERK signaling pathways.

BACKGROUND: Inflammatory microenvironment is significant to the differentiation and function of mesenchymal stem cells (MSCs). It evidentially influences the osteoblastogenesis of MSCs. IL-34, a newly discovered cytokine, playing a key role in metabolism. However, the research on its functional role in the osteogenesis of MSCs was rarely reported. Here, we described the regulatory effects of low-dose IL-34 on both osteoblastogenesis and osteoclastogenesis. METHODS: We performed the osteogenic effects of hBMSCs by exogenous and overexpressed IL-34 in vitro, so were the osteoclastogenesis effects of mBMMs by extracellular IL-34. CCK-8 was used to assess the effect of IL-34 on the viability of hBMSCs and mBMMs. ALP, ARS, and TRAP staining was used to evaluate ALP activity, mineral deposition, and osteoclastogenesis, respectively. qRT-PCR and Western blotting analysis were performed to detect the expression of target genes and proteins. ELISA was used to evaluate the concentrations of IL-34. In vivo, a rat tibial osteotomy model and an OVX model were established. Radiographic analysis and histological evaluation were performed to confirm the therapeutic effects of IL-34 in fracture healing and osteoporosis. Statistical differences were evaluated by two-tailed Student's t test, one-way ANOVA with Bonferroni's post hoc test, and two-way ANOVA with Bonferroni multiple comparisons post hoc test in the comparison of 2 groups, more than 2 groups, and different time points of treated groups, respectively. RESULTS: Promoted osteoblastogenesis of hBMSCs was observed after treated by exogenous or overexpressed IL-34 in vitro, confirmed by increased mineral deposits and ALP activity. Furthermore, exogenous or overexpressed IL-34 enhanced the expression of p-AKT and p-ERK. The specific AKT and ERK signaling pathway inhibitors suppressed the enhancement of osteoblastogenesis induced by IL-34. In a rat tibial osteotomy model, imaging and histological analyses testified the local injection of exogenous IL-34 improved bone healing. However, the additional IL-34 has no influence on both osteoclastogenesis of mBMMs in vitro and osteoporosis of OVX model of rat in vivo. CONCLUSIONS: Collectively, our study demonstrate that low-dose IL-34 regulates osteogenesis of hBMSCs partly via the PIK/AKT and ERK signaling pathway and enhances fracture healing, with neither promoting nor preventing osteoclastogenesis in vitro and osteoporosis in vivo.

Current and future uses of skeletal stem cells for bone regeneration.

The postnatal skeleton undergoes growth, modeling, and remodeling. The human skeleton is a composite of diverse tissue types, including bone, cartilage, fat, fibroblasts, nerves, blood vessels, and hematopoietic cells. Fracture nonunion and bone defects are among the most challenging clinical problems in orthopedic trauma. The incidence of nonunion or bone defects following fractures is increasing. Stem and progenitor cells mediate homeostasis and regeneration in postnatal tissue, including bone tissue. As multipotent stem cells, skeletal stem cells (SSCs) have a strong effect on the growth, differentiation, and repair of bone regeneration. In recent years, a number of important studies have characterized the hierarchy, differential potential, and bone formation of SSCs. Here, we describe studies on and applications of SSCs and/or mesenchymal stem cells for bone regeneration.

Upregulation of Parkin Accelerates Osteoblastic Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells and Bone Regeneration by Enhancing Autophagy and ß-Catenin Signaling.

Osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) plays a key role in bone formation. Parkin, an E3 ubiquitin ligase, related to Parkinson's disease and aging. Previous studies have indicated that Parkinson's disease have a higher risk of osteoporotic fracture. To investigate the effects and underlying mechanism of Parkin in the osteogenic differentiation of BMSCs, osteogenic differentiation was analyzed following upregulation or downregulation of Parkin. We found that Parkin was increased during differentiation. Parkin overexpression enhanced osteo-specific markers, and downregulation of Parkin mitigated osteo-specific markers. Moreover, upregulation of Parkin promoted ß-catenin expression and autophagy and vice versa. The upregulation of ß-catenin enhanced autophagy, and the activation of autophagy also increased the expression of ß-catenin in Parkin-downregulated BMSCs. Parkin-overexpressed cell sheets accelerated bone healing in a tibial fracture model. Based on these results, we concluded that Parkin meditates osteoblastic differentiation of BMSCs via ß-catenin and autophagy signaling.

IGFBP7 acts as a negative regulator of RANKL-induced osteoclastogenesis and oestrogen deficiency-induced bone loss.

OBJECTIVES: Insulin-like growth factor-binding protein 7 (IGFBP7) is a low-affinity insulin growth factor (IGF) binder that may play an important role in bone metabolism. We previously reported that IGFBP7 enhanced osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) via the Wnt/ß-catenin signalling pathway. In this study, we tried to reveal its function in osteoclast differentiation and osteoporosis. METHODS: We used both in vitro and in vivo studies to investigate the effects of IGFBP7 on RANKL-induced osteoclastogenesis and osteoporosis, together with the underlying molecular mechanisms of these processes. RESULTS: We show that IGFBP7 inhibited receptor activation of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclastogenesis, F-actin ring formation and bone resorption, which was confirmed by using recombinant IGFBP7 protein, lentivirus and siRNA. The NF-κB signalling pathway was inhibited during this process. Moreover, in a mouse ovariectomy-induced osteoporosis model, IGFBP7 treatment attenuated osteoporotic bone loss by inhibiting osteoclast activity. CONCLUSIONS: Taken together, these findings show that IGFBP7 suppressed osteoclastogenesis in vitro and in vivo and suggest that IGFBP7 is a negative regulator of osteoclastogenesis and plays a protective role in osteoporosis. These novel insights into IGFBP7 may facilitate the development of potential treatment strategies for oestrogen deficiency-induced osteoporosis and other osteoclast-related disorders.

Apelin enhances the osteogenic differentiation of human bone marrow mesenchymal stem cells partly through Wnt/ß-catenin signaling pathway.

BACKGROUND: Management of fracture healing with a large bone defect remains a tricky subject in orthopedic trauma. Enhancing osteogenesis of human bone marrow-derived mesenchymal stem cells (hBMSCs) is one of the useful therapeutic strategies for fracture healing. Previous studies have revealed that Apelin may play an important role in bone metabolism. However, its function in the osteogenesis of hBMSCs remains unclear. Therefore, in this study, we investigated the effects and mechanism of Apelin on osteogenic differentiation. METHODS: We investigated the osteogenesis effects of hBMSCs by both exogenous Apelin protein and overexpression Apelin in vitro. Cell proliferation assay was used to assess the effect of Apelin on the proliferation of hBMSCs. ALP staining and Alizarin Red staining were used to evaluate ALP activity and mineral deposition respectively. qPCR and Western blotting analysis were used to detect the expression of target genes and proteins. In vivo, a rat tibial osteotomy model was established; radiographic analysis and histological evaluation were used to confirm the therapeutic effects of Apelin in fracture healing. Statistical significance was determined by two-tailed Student's t test when 2 groups were compared. When more than 2 groups were compared, one-way ANOVA followed by Bonferroni's post-hoc test was used. And two-way ANOVA, followed by Bonferroni multiple comparisons post-hoc test, was performed when the treatment groups at different time points were compared. RESULTS: The addition of exogenous Apelin protein or overexpression of Apelin promoted osteoblast differentiation of hBMSCs in vitro. Increased mineral deposits were observed after treatment with extracellular Apelin protein or after the upregulation of Apelin. Moreover, ß-catenin levels were upregulated by Apelin. The enhancement of osteogenic differentiation induced by Apelin was attenuated by specific Wnt/ß-catenin signaling pathway inhibitors. In a rat tibial osteotomy model, local injection of exogenous Apelin protein improved bone healing, as demonstrated by imaging and histological analyses. CONCLUSIONS: Taken together, these findings indicate that Apelin regulates osteogenic differentiation of hMSCs partly via the Wnt/ß-catenin signaling pathway and effectively promotes fracture healing.

Extracellular IL-37 promotes osteogenic differentiation of human bone marrow mesenchymal stem cells via activation of the PI3K/AKT signaling pathway.

Interleukin (IL)-37, a pivotal anti-inflammatory cytokine and a fundamental inhibitor of innate immunity, has recently been shown to be abnormally expressed in several autoimmune-related orthopedic diseases, including rheumatoid arthritis, ankylosing spondylitis, and osteoporosis. However, the role of IL-37 during osteogenic differentiation of mesenchymal stem cells (MSCs) remains largely unknown. In this study, extracellular IL-37 significantly increased osteoblast-specific gene expression, the number of mineral deposits, and alkaline phosphatase activity of MSCs. Moreover, a signaling pathway was activated in the presence of IL-37. The enhanced osteogenic differentiation of MSCs due to supplementation of IL-37 was partially rescued by the presence of a PI3K/AKT signaling inhibitor. Using a rat calvarial bone defect model, IL-37 significantly improved bone healing. Collectively, these findings indicate that extracellular IL-37 enhanced osteogenesis of MSCs, at least in part by activation of the PI3K/AKT signaling pathway.

Suprapatellar versus infrapatellar approach for tibia intramedullary nailing: A meta-analysis.

OBJECTIVE: This meta-analysis was performed to determine the efficacy of suprapatellar versus infrapatellar approach for tibia intramedullary nailing (IMN). METHODS: A systematic search was performed in PubMed, Embase, Cochrane library, CNKI and Wanfang. Cochrane collaboration's tool and the Newcastle-Ottawa scale were used to evaluate literature qualities. Meta-analysis was performed using RevMan 5.3 software. RESULTS: Eight studies were eligible, including two randomized controlled trials (RCTs) and six retrospective cohort trials. There were no significant differences between suprapatellar and infrapatellar approaches in operation time, coronal plane alignment, and incidence of postoperative deep infection, nonunion and secondary operation. However, suprapatellar nailing achieved a significant shorter fluoroscopy time, less VAS pain score, better sagittal plane alignment and lower incidence of angular malalignment. Though pooled results indicated no significant difference in terms of final follow-up knee functional score, the RCT subgroup analysis showed that a higher knee functional score existed in suprapatellar group. CONCLUSIONS: For tibia IMN, suprapatellar approach might be superior to infrapatellar approach with shorter fluoroscopy time, less knee pain, better knee function recovery, and more accurate fracture reduction. Meanwhile, no increased risk of postoperative complications was identified. More RCTs are required for further research.

Role of the heat shock protein family in bone metabolism.

Heat shock proteins (HSPs) are a family of proteins produced by cells in response to exposure to stressful conditions. In addition to their role as chaperones, they also play an important role in the cardiovascular, immune, and other systems. Normal bone tissue is maintained by bone metabolism, particularly by the balance between osteoblasts and osteoclasts, which are physiologically regulated by multiple hormones and cytokines. In recent years, studies have reported the vital role of HSPs in bone metabolism. However, the conclusions remain largely controversial, and the exact mechanisms are still unclear, so a review and analyses of previous studies are of importance. This article reviews the current understanding of the roles and effects of HSPs on bone cells (osteoblasts, osteoclasts, and osteocytes), in relation to bone metabolism.