MicroRNA-137 dysregulation predisposes to osteoporotic fracture by impeding ALP activity and expression via suppression of leucine-rich repeat-containing G-protein-coupled receptor 4 expression

MiR-137-mediated negative relationship between LGR4 and RANKL modulated osteogenic differentiation of human adipose-derived mesenchymal stem cells

MicroRNA-137 (miR-137) has recently emerged as an osteogenic regulator in several cell lines. This study aimed to identify the function of miR-137 on the crosstalk between leucine rich repeat containing G protein-coupled receptor 4 (LGR4) and receptor activator of nuclear factor-κB ligand (RANKL), thus unveiling the critical role of LGR4-RANKL interplay in the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hASCs). By examining the osteogenic capacity and possible downstream genes expression with miR-137 overexpression/knockdown, we found that miR-137 downregulated LGR4 while upregulating RANKL. According to the results of dual-luciferase reporter assay, LGR4 was validated as a direct target of miR-137. Surprisingly, a negative relationship between LGR4 and RANKL was confirmed by the knockdown of these two genes. Furthermore, RANKL inhibitor could alleviate or reverse the inhibitory effects on osteogenesis generated by LGR4 knockdown. Collectively, this study indicated that miR-137-induced a negative crosstalk between LGR4 and RANKL that could contribute to the osteogenic regulation of hASCs and provide more systematic and in-depth understanding of epigenetic modulation by miR-137.

Tetracycline-grafted mPEG-PLGA micelles for bone-targeting and osteoporotic improvement

Aim: We aimed to create a nano drug delivery system with tetracycline (TC)-grafted methoxy poly-(ethylene-glycol)‒poly-(D, L-lactic-co-glycolic acid) (mPEG‒PLGA) micelles (TC‒mPEG‒PLGA) with TC and mPEG‒PLGA for potential bone targeting. Prospectively, TC‒mPEG‒PLGA aims to deliver bioactive compounds, such as astragaloside IV (AS), for osteoporotic therapy.

Methods: Preparation and evaluation of TC‒mPEG‒PLGA were accomplished via nano-properties, cytotoxicity, uptake by MC3T3-E1 cells, ability of hydroxyapatite targeting and potential bone targeting in vivo, as well as pharmacodynamics in a rat model.

Results: The measured particle size of AS-loaded TC‒mPEG‒PLGA micelles was an average of 52.16 ± 2.44 nm, which exhibited a sustained release effect compared to that by free AS. The TC‒mPEG‒PLGA demonstrated low cytotoxicity and was easily taken by MC3T3-E1 cells. Through assaying of bone targeting in vitro and in vivo, we observed that TC‒mPEG‒PLGA could effectively increase AS accumulation in bone. A pharmacodynamics study in mice suggested potentially increased bone mineral density by AS-loaded TC‒mPEG‒PLGA in ovariectomized rats compared to that by free AS.

Conclusion: The nano drug delivery system (TC‒mPEG‒PLGA) could target bone in vitro and in vivo, wherein it may be used as a novel delivery method for the enhancement of therapeutic effects of drugs with osteoporotic activity.

Emerging Roles for LGR4 in Organ Development, Energy Metabolism and Carcinogenesis

The leucine-rich repeats containing G protein-coupled receptor 4 (LGR4) belonging to G protein-coupled receptors (GPCRs) family, had various regulatory roles at multiple cellular types and numerous targeting sites, and aberrant LGR4 signaling played crucial roles in diseases and carcinogenesis. On the basis of these facts, LGR4 may become an appealing therapeutic target for the treatment of diseases and tumors. However, a comprehensive investigation of its functions and applications was still lacking. Hence, this paper provided an overview of the molecular characteristics and signaling mechanisms of LGR4, its involvement in multiple organ development and participation in the modulation of immunology related diseases, metabolic diseases, and oxidative stress damage along with cancer progression. Given that GPCRs accounted for almost a third of current clinical drug targets, the in-depth understanding of the sophisticated connections of LGR4 and its ligands would not only enrich their regulatory networks, but also shed new light on designing novel molecular targeted drugs and small molecule blockers for revolutionizing the treatment of various diseases and tumors.

The function of microRNA-211 expression in post-fracture bone cell apoptosis involving the transforming growth factor-β/ phosphoinositide 3-kinase signaling pathway

Background

The underlying mechanism of micro (mi)RNA-211 in bone cell apoptosis after fracture remains unclear. This study aimed to determine the effect and function of miRNA-211 in bone cell apoptosis in fracture patients.

Methods

Serum samples were collected from patients with fractures and healthy controls. Serum miR-211 expression was detected by quantitative PCR. MC3T3-E1 cells were transfected with a transforming growth factor (TGF)-β inhibitor and phosphoinositide 3-kinase (PI3K) inhibitor. The viability of MC3T3-E1 cells was detected by the MTT assay, and apoptosis was detected by flow cytometry. Caspase-3/9 activity and the protein expression of TGF-β, PI3K, and p-Akt were detected by western blot and immunoprecipitation.

Results

In the fracture group, miRNA-211 expression was significantly up-regulated compared with controls. We used miRNA-211 mimics to up-regulate miRNA-211 expression, and observed inhibited cell viability and induced apoptosis and lactate dehydrogenase (LDH) activity. miRNA-211 up-regulation also suppressed the expression of TGF-β, PI3K, and p-Akt proteins. Conversely, miRNA-211 down-regulation increased cell viability and reduced apoptosis and LDH activity, as well as inducing the expression of TGF-β, PI3K, and p-Akt. Inhibiting TGF-β decreased the effect of anti-miRNA-211 on osteocyte apoptosis.

Conclusion

Our data indicate that miRNA-211 functions via the TGF-β/PI3K/Akt signaling pathway in patients with fractures.

The Role of LGR4 (GPR48) in Normal and Cancer Processes

Leucine-rich repeats containing G protein-coupled receptor 4 (LGR4) is a receptor that belongs to the superfamily of G protein-coupled receptors that can be activated by R-spondins (RSPOs), Norrin, circLGR4, and the ligand of the receptor activator of nuclear factor kappa-B (RANKL) ligands to regulate signaling pathways in normal and pathological processes. LGR4 is widely expressed in different tissues where it has multiple functions such as tissue development and maintenance. LGR4 mainly acts through the Wnt/β-catenin pathway to regulate proliferation, survival, and differentiation. In cancer, LGR4 participates in tumor progression, invasion, and metastasis. Furthermore, recent evidence reveals that LGR4 is essential for the regulation of the cancer stem cell population by controlling self-renewal and regulating stem cell properties. This review summarizes the function of LGR4 and its ligands in normal and malignant processes.

MiR-193a-3p Promotes Fracture Healing via Targeting PTEN Gene

The aim of this study was to investigate the role and potential mechanism of miR-193a-3p in fracture healing. The 70 fragility fracture patients and 45 healthy controls were enrolled in this study. Quantitative real-time PCR (qRT-PCR) was used for the measurement of the expression levels of miR-193a-3p and PTEN. MTT assay and flow cytometry were used to detect cell viability and apoptosis in the mouse osteoblastic cell line MC3T3-E1. Luciferase reporter assay was performed to confirm the correlation of miR-193a-3p with PTEN. The serum expression level of miR-193a-3p showed no significant change in fracture patients 7 days after fixation treatment, but over time, there was a significant decrease in the expression at 14 days and 21 days after treatment (P < 0.01). Overexpression of miR-193a-3p significantly enhanced cell viability and inhibited cell apoptosis in MC3T3-E1 cells (P < 0.001). Serum PTEN level in fracture patients was increased gradually during the fracture healing process (P < 0.01). PTEN was demonstrated to be a target gene of miR-9-5p and reversed the effect of miR-193a-3p on cell viability and apoptosis (P < 0.001). miR-193a-3p promoted fracture healing via regulating PTEN and may serve as a novel potential target for enhancing bone repair of fragility fracture.

miR-137 targets the inhibition of TCF4 to reverse the progression of osteoarthritis through the AMPK/NF-κB signaling pathway

Purpose: To explore the regulatory mechanism of miR-137 and transcription factor 4 (TCF4) in the progression of osteoarthritis (OA).

Patients and Methods: The expressions of miR-137 and TCF4 were detected in OA cartilage tissue, chondrocytes and OA rat cartilage tissue. miR-137 and TCF4 were up-regulated or down-regulated and transfected into chondrocytes and OA rat cartilage tissue. The gene expression, protein level, cell proliferation, apoptosis and inflammatory factors were detected, respectively. LPS and anterior cruciate ligament transection (ACLT) on the right knee were used to induce chondrocyte inflammation and establish rat OA model, respectively.

Results: miR-137 was low expressed in cartilage tissue of OA group, while TCF4 expression and protein level were significantly higher, showing significant negative correlation. In LPS group, chondrocyte activity was significantly inhibited, cell apoptosis ability was significantly enhanced, and the levels of inflammatory factors TNF-α, IL-1β, IL-6 were significantly increased. However, the above results were significantly improved after the up-regulation of miR-137 or down-regulation of TCF4. Double luciferase report revealed that miR-137 and TCF4 had targeted relationship. LPS induced activation of AMPK/NF-κB pathway and higher level of apoptosis. AMPK/NF-κB pathway inhibitor C could inhibit activation of this pathway, and up-regulation of miR-137 or down-regulation of TCF4 could significantly weaken the regulation of LPS on the pathway and apoptosis. Analysis of OA rat model showed that over-expression of miR-137 could inhibit up-regulation of inflammatory factors and activation of AMPK/NF-κB pathway.

Conclusion: miR-137 targets the inhibition of TCF4 to reverse the progression of OA through the AMPK/NF-κB signaling pathway.

Overexpression of miR125b Promotes Osteoporosis Through miR-125b-TRAF6 Pathway in Postmenopausal Ovariectomized Rats

BACKGROUND

Postmenopausal osteoporosis is one of the most common types of osteoporosis that women suffer from. Studies involving molecular mechanisms for designing better therapeutic strategies for postmenopausal osteoporosis are still rare. The present study investigates the role of miR-125b in postmenopausal osteoporosis.

METHODS

Microarray analysis was done to screen the gene database. Tissue samples of postmenopausal women were collected to study the miRNA profiles. MC3T3-E1 cells were used and were submitted for transfection. CCK-8 assay was done to check the viability of cells, whereas toxicity was done by lactate dehydrogenase assay kit. TargetScan was done to target genes of miR-125b followed by confirmation by Luciferase reporter assay. For animal studies a rat model of ovariectomized rats was created. Bone mineral density and biomechanics were measured by densitometer. The mRNA levels were assessed by qRT-PCR and proteins by Western blot assay.

RESULTS

miR-125b was over-expressed in human osteoporosis samples. In vitro studies suggested that miR-125b suppressed the cell viability and promoted release of LDH, it also enhanced the RANKL/OPG ratio and suppressed levels of BMP2 and Runx2. Bioinformatics identified TRAF6 as a potential target of miR-125b, further confirmed by luciferase assay, also miR-125b negatively regulated the levels of TRAF6 gene in osteoporosis bones involving the JAK2/STAT3 cascade. In the rat model, miR-125b decreased the bone mineral density and biomechanical parameters in bones by altering the TRAF6 gene involving the JAK2/STAT3 pathway.

CONCLUSION

The outcomes suggested that miR-125b was responsible for the development of postmenopausal osteoporosis and promoted its progression by the TRAF6 gene via the JAK2/STAT3 pathway.

The miRNA-15b/USP7/KDM6B axis engages in the initiation of osteoporosis by modulating osteoblast differentiation and autophagy

Osteoporosis is a metabolic disease that results from oxidative stress or inflammation in renal disorders. microRNAs (miRNAs) are recently implicated to participate in osteoporosis, but the mechanism remains largely unexplored. Herein, we aimed to explore the potential role of miR-15b in osteoblast differentiation and autophagy in osteoporosis. We established osteoporosis models through ovariectomy and determined that miR-15b was highly expressed whereas USP7 and KDM6B were poorly expressed in tissue of osteoporosis mice. Treatment of silenced miR-15b resulted in the elevation of decreased bone mineral density (BMD), the maximum elastic stress and the maximum load of osteoporosis mice. In osteoblasts, miR-15 overexpression decreased proliferation but suppressed the cell differentiation and autophagy, accompanied with decreased expression of USP7. Mechanistically, miR-15 bound and inhibited USP7 expression, while overexpression of USP7 promoted autophagy of osteoblasts. USP7, importantly, strengthened the stability of KDM6B and promoted KDM6B expression. MG132 protease inhibitor increased KDM6B and USP7 expression in osteoblasts. Silencing of KDM6B reversed the promoting effect on autophagy and proliferation induced by overexpression of USP7. Taken altogether, miR-15b inhibits osteoblast differentiation and autophagy to aggravate osteoporosis by targeting USP7 to regulate KDM6B expression.

Identification of Serum Exosomal MicroRNA Expression Profiling in Menopausal Females with Osteoporosis by High-throughput Sequencing

Estrogen deficiency, which mainly occurs in postmenopausal women, is a primary reason for osteoporosis in clinical diagnosis. However, the molecular regulation of osteoporosis in menopausal females is still not adequately explained in the literature, with the diagnosis and treatment for osteoporosis being limited. Herein, exosomal microRNAs (miRNAs) were used to evaluate their diagnosis and prediction effects in menopausal females with osteoporosis. In this study, 6 menopausal females without osteoporosis and 12 menopausal females with osteoporosis were enrolled. The serum exosomes were isolated, and the miRNA expression was detected by miRNA high-throughput sequencing. Exosomal miRNA effects were analyzed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. The miRNA-targeted genes were evaluated by Targetscan 7.2 and the protein-protein interactions (PPI) by STRING. Hub genes were analyzed by the CytoHubba app of Cytoscape. The results showed that 191 aberrant miRNAs were found in the group of menopausal females with osteoporosis, including 72 upregulated miRNAs and 121 downregulated miRNAs. Aberrant miRNAs were involved in many signaling pathways, such as the Wnt, MAPK, and Hippo pathways. Based on PPI network analysis, FBXL3, FBXL13, COPS2, UBE2D3, DCUN1D1, DCUN1D4, CUL3, FBXO22, ASB6, and COMMD2 were the 10 most notable genes in the PPI network. In conclusion, aberrant serum exosomal miRNAs were associated with an altered risk of osteoporosis in menopausal females and may act as potential biomarkers for the prediction of risk of osteoporosis in menopausal females.

Serum miRNA-142 and BMP-2 are markers of recovery following hip replacement surgery for femoral neck fracture

The present study aimed to investigate the changes in miRNA-142 and bone morphogenetic protein-2 (BMP-2) expression before and after hip replacement surgery, and to determine their association with receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG). For this purpose, 142 cases of hip arthroplasty in patients with femoral neck fracture were selected as the research group, and 50 cases of healthy individuals who underwent a physical examination during the same time period were selected the control group. Serum miR-142 and BMP-2 levels were measured by RT-qPCR before and after surgery in the research group and the control group. Serum RANKL and OPG levels were detected before and after surgery by enzyme-linked immunosorbent assay (ELISA). The levels of serum miR-142 and BMP-2 in the research group were significantly lower than those in the control group. At 1 month after surgery, the levels of serum miR-142 and BMP-2 in the research group were significantly higher than those before surgery, and at 6 months after surgery, and they were higher than those in the control group. Pearson's correlation analysis revealed that the serum levels of miR-142 positively correlated with the BMP-2 levels before surgery, at 1 month after surgery, and at 6 months after surgery in the research group. The results of ROC curve analysis revealed that the AUC values of serum miR-142 and BMP-2 were 0.911 and 0.861, respectively. At 1 month after surgery, the levels of serum miR-142 and BMP-2 in group A (patients with a good or excellent recovery) were significantly higher than those in group B (patients with a fair or poor recovery). The levels of serum RANKL and OPG in the research group significantly increased at 1 month after surgery. The serum levels of miR-142 and BMP-2 positively correlated with those of RANKL and OPG before surgery and at 1 month after surgery. On the whole, the findings of the present study indicate that pre-operative serum miR-142 and BMP-2 levels are valuable for evaluating the post-operative recovery of patients with femoral neck fracture undergoing hip replacement surgery. In addition, in the present study, at 1 month after surgery, the levels of both miR-142 and BMP-2 were related to the recovery of the patients, and positively correlated with the RANKL and OPG levels.

MicroRNA Alterations for Diagnosis, Prognosis, and Treatment of Osteoporosis: A Comprehensive Review and Computational Functional Survey

Osteoporosis (OP) is a systemic bone disease with a series of clinical symptoms. The use of screening biomarkers in OP management is therefore of clinical significance, especially in the era of precision medicine and intelligent healthcare. MicroRNAs (miRNAs) are small, non-coding RNAs with the potential to regulate gene expression at the post-transcriptional level. Accumulating evidence indicates that miRNAs may serve as biomarkers for OP prediction and prevention. However, few studies have emphasized the role of miRNAs in systems-level pathogenesis during OP development. In this article, literature-reported OP miRNAs were manually collected and analyzed based on a systems biology paradigm. Functional enrichment studies were performed to decode the underlying mechanisms of miRNAs in OP etiology and therapeutics in three-dimensional space, i.e., integrated miRNA–gene–pathway analysis. In particular, interactions between miRNAs and three well-known OP pathways, i.e., estrogen–endocrine, WNT/β-catenin signaling, and RANKL/RANK/OPG, were systematically investigated, and the effects of non-genetic factors on personalized OP prevention and therapy were discussed. This article is a comprehensive review of OP miRNAs, and bridges the gap between an understanding of OP pathogenesis and clinical translation.

Silencing MicroRNA-137-3p, which Targets RUNX2 and CXCL12 Prevents Steroid-induced Osteonecrosis of the Femoral Head by Facilitating Osteogenesis and Angiogenesis

The main pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH) includes decreased osteogenic capacity of bone marrow-derived mesenchymal stem cells (BMSCs) and damaged blood supply to the femoral head. MicroRNAs (miRNAs) have been shown to play prominent roles in SONFH development. However, there is no report that a specific miRNA targeting two genes in two different pathogenic pathways has been applied to this disease. The present study investigated the effects of transplantation of miR-137-3p-silenced BMSCs on the prevention and early treatment of SONFH. First, western blotting and dual luciferase assays were employed to verify that miR-137-3p directly targets Runx2 and CXCL12. Then, silencing of miR-137-3p was found to facilitate osteogenic differentiation of BMSCs, which was confirmed by alkaline phosphatase (ALP) staining, alizarin red staining and qRT-PCR. Silencing of miR-137-3p also promoted angiogenesis by human umbilical vein endothelial cells (HUVECs) in the presence or absence of glucocorticoids. Thereafter, overexpression of Runx2 and CXCL12 without the 3′ untranslated region (3′UTR) partially rescued the effects of miR-137-3p on osteogenesis and angiogenesis, respectively. This finding further supported the hypothesis that miR-137-3p exerts its functions partly by regulating the genes, Runx2 and CXCL12. We also demonstrated that SONFH was partially prevented by transplantation of miR-137-3p-silenced BMSCs into a rat model. Micro-CT and histology showed that the transplantation of miR-137-3p-silenced BMSCs significantly improved bone regeneration. Additionally, the results of enzyme-linked immunosorbent assays (ELISA) and flow cytometry suggested that stromal cell-derived factor-1α (SDF-1α) and endothelial progenitor cells (EPCs) participated in the process of vascular repair. Taken together, these findings show that silencing of miR-137-3p directly targets the genes, Runx2 and CXCL12, which can play critical roles in SONFH repair by facilitating osteogenic differentiation and mobilizing EPCs.