MicroRNA-503-5p inhibits stretch-induced osteogenic differentiation and bone formation

Human dental pulp stem cell-derived exosomes decorated titanium scaffolds for promoting bone regeneration

Exosomes, nanoscale extracellular vesicles crucial for intercellular communication, hold great promise as a therapeutic avenue in cell-free tissue regeneration. In this study, we identified and utilized exosomes to adorn anodized titanium scaffolds, inducing osteogenic differentiation in human dental pulp stem cells (hDPSCs). The osteogenesis of hDPSCs was stimulated by exosomes derived from hDPSCs that underwent various periods of osteogenic differentiation. After purification, these exosomes were loaded onto anodized titanium scaffolds. Notably, the scaffolds loaded with exosomes deriving from osteogenic differentiated hDPSCs demonstrated superior bone tissue regeneration compared to those loaded with exosomes deriving from hDPSCs within 10-week. RNA-sequencing analysis shed light on the underlying mechanism, revealing that the osteogenic exosomes carried specific cargo, which is due to upregulated miRNAs (Hsa-miR-29c-5p, Hsa-miR-378a-5p, Hsa-miR-10b-5p and Hsa-miR-9-3p) associated with osteogenesis. And down-regulated anti-osteogenic miRNA (Hsa-miR-31-3p, Hsa-miR-221-3p, Hsa-miR-183-5p and Hsa-miR-503-5p). In conclusion, the identification and utilization of exosomes derived from osteogenic differentiated stem cells offer a novel and promising strategy for achieving cell-free bone regeneration.

Unveiling Mesenchymal Stem Cells' Regenerative Potential in Clinical Applications: Insights in miRNA and lncRNA Implications

It is now widely recognized that mesenchymal stem cells (MSCs) possess the capacity to differentiate into a wide array of cell types. Numerous studies have identified the role of lncRNA in the regulation of MSC differentiation. It is important to elucidate the role and interplay of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) in the regulation of signalling pathways that govern MSC function. Furthermore, miRNAs and lncRNAs are important clinical for innovative strategies aimed at addressing a wide spectrum of existing and emerging disease. Hence it is important to consider their impact on MSC function and differentiation. Examining the data available in public databases, we have collected the literature containing the latest discoveries pertaining to human stem cells and their potential in both fundamental research and clinical applications. Furthermore, we have compiled completed clinical studies that revolve around the application of MSCs, shedding light on the opportunities presented by harnessing the regulatory potential of miRNAs and lncRNAs. This exploration of the therapeutic possibilities offered by miRNAs and lncRNAs within MSCs unveils exciting prospects for the development of precision therapies and personalized treatment approaches. Ultimately, these advancements promise to augment the efficacy of regenerative strategies and produce positive outcomes for patients. As research in this field continues to evolve, it is imperative to explore and exploit the vast potential of miRNAs and lncRNAs as therapeutic agents. The findings provide a solid basis for ongoing investigations, fuelling the quest to fully unlock the regenerative potential of MSCs.

miR-503 targets MafK to inhibit subcutaneous preadipocyte adipogenesis causing a decrease of backfat thickness in Guanzhong Black pigs

Reducing backfat thickness (BFT), determined by subcutaneous fat deposition, is vital in Chinese developed pig breeds. The level of miR-503 in the backfat of Guanzhong Black pigs was found to be lower than that in Large White pigs, implying that miR-503 may be related to BFT. However, the effect and mechanism of miR-503 on adipogenic differentiation in subcutaneous preadipocytes remain unknown. Compared with Large White pigs, the BFT and body fat content of Guanzhong Black pigs were greater, but the level of miR-503 was lower in subcutaneous adipose tissue (SAT) at 180 days of age. Furthermore, miR-503 promoted preadipocyte proliferation by increasing the proportion of S-phase and EdU-positive cells. However, miR-503 inhibited preadipocyte differentiation by downregulating adipogenic gene expression. Mechanistically, miR-503 directly targeted musculoaponeurotic fibrosarcoma oncogene homolog K (MafK) in both proliferating and differentiating preadipocytes to repress adipogenesis. Our findings provide a novel miRNA biomarker for reducing pig BFT levels to improve carcass quality.

Role of noncoding RNAs in orthodontic tooth movement: new insights into periodontium remodeling

Orthodontic tooth movement (OTM) is biologically based on the spatiotemporal remodeling process in periodontium, the mechanisms of which remain obscure. Noncoding RNAs (ncRNAs), especially microRNAs and long noncoding RNAs, play a pivotal role in maintaining periodontal homeostasis at the transcriptional, post-transcriptional, and epigenetic levels. Under force stimuli, mechanosensitive ncRNAs with altered expression levels transduce mechanical load to modulate intracellular genes. These ncRNAs regulate the biomechanical responses of periodontium in the catabolic, anabolic, and coupling phases throughout OTM. To achieve this, down or upregulated ncRNAs actively participate in cell proliferation, differentiation, autophagy, inflammatory, immune, and neurovascular responses. This review highlights the regulatory mechanism of fine-tuning ncRNAs in periodontium remodeling during OTM, laying the foundation for safe, precise, and personalized orthodontic treatment.

Role of mechano-sensitive non-coding RNAs in bone remodeling of orthodontic tooth movement: recent advances

Orthodontic tooth movement relies on bone remodeling and periodontal tissue regeneration in response to the complicated mechanical cues on the compressive and tensive side. In general, mechanical stimulus regulates the expression of mechano-sensitive coding and non-coding genes, which in turn affects how cells are involved in bone remodeling. Growing numbers of non-coding RNAs, particularly mechano-sensitive non-coding RNA, have been verified to be essential for the regulation of osteogenesis and osteoclastogenesis and have revealed how they interact with signaling molecules to do so. This review summarizes recent findings of non-coding RNAs, including microRNAs and long non-coding RNAs, as crucial regulators of gene expression responding to mechanical stimulation, and outlines their roles in bone deposition and resorption. We focused on multiple mechano-sensitive miRNAs such as miR-21, - 29, -34, -103, -494-3p, -1246, -138-5p, -503-5p, and -3198 that play a critical role in osteogenesis function and bone resorption. The emerging roles of force-dependent regulation of lncRNAs in bone remodeling are also discussed extensively. We summarized mechano-sensitive lncRNA XIST, H19, and MALAT1 along with other lncRNAs involved in osteogenesis and osteoclastogenesis. Ultimately, we look forward to the prospects of the novel application of non-coding RNAs as potential therapeutics for tooth movement and periodontal tissue regeneration.

MicroRNA Modulation during Orthodontic Tooth Movement: A Promising Strategy for Novel Diagnostic and Personalized Therapeutic Interventions

The Orthodontic Tooth Movement (OTM) is allowed through a mediated cell/tissue mechanism performed by applying a force or a pair of forces on the dental elements, and the tooth movement is a fundamental requirement during any orthodontic treatment. In this regard, it has been widely shown that each orthodontic treatment has a minimum duration required concerning numerous factors (age, patient compliance, type of technique used, etc.). In this regard, the aim of the following revision of the literature is to give readers a global vision of principal microRNAs (miRNAs) that are most frequently associated with OTM and their possible roles. Previously published studies of the last 15 years have been considered in the PubMed search using "OTM" and "miRNA" keywords for the present review article. In vitro and in vivo studies and clinical trials were mainly explored. Correlation between OTM and modulation of several miRNAs acting through post-transcriptional regulation on target genes was observed in the majority of previous studied. The expression analysis of miRNAs in biological samples, such as gingival crevicular fluid (GCF), can be considered a useful tool for novel diagnostic and/or prognostic approaches and for new personalized orthodontic treatments able to achieve a better clinical response rate. Although only a few studies have been published, the data obtained until now encourage further investigation of the role of miRNA modulation during orthodontic treatment. The aim of this study is to update the insights into the role and impact of principal micro-RNAs (miRNAs) that are most frequently associated during OTM.

Mechanoimmunology: Are inflammatory epigenetic states of macrophages tuned by biophysical factors?

Many inflammatory diseases that are responsible for a majority of deaths are still uncurable, in part as the underpinning pathomechanisms and how to combat them is still poorly understood. Tissue-resident macrophages play pivotal roles in the maintenance of tissue homeostasis, but if they gradually convert to proinflammatory phenotypes, or if blood-born proinflammatory macrophages persist long-term after activation, they contribute to chronic inflammation and fibrosis. While biochemical factors and how they regulate the inflammatory transcriptional response of macrophages have been at the forefront of research to identify targets for therapeutic interventions, evidence is increasing that physical factors also tune the macrophage phenotype. Recently, several mechanisms have emerged as to how physical factors impact the mechanobiology of macrophages, from the nuclear translocation of transcription factors to epigenetic modifications, perhaps even DNA methylation. Insight into the mechanobiology of macrophages and associated epigenetic modifications will deliver novel therapeutic options going forward, particularly in the context of increased inflammation with advancing age and age-related diseases. We review here how biophysical factors can co-regulate pro-inflammatory gene expression and epigenetic modifications and identify knowledge gaps that require urgent attention if this therapeutic potential is to be realized.

MiR-20a: a mechanosensitive microRNA that regulates fluid shear stress-mediated osteogenic differentiation via the BMP2 signaling pathway by targeting BAMBI and SMAD6

Background

MicroRNAs (miRNAs) are crucial regulators of diverse biological and pathological processes. This study aimed to investigate the role of microRNA 20a (miR-20a) in fluid shear stress (FSS)-mediated osteogenic differentiation.

Methods

In the present study, we subjected osteoblast MC3T3-E1 cells or mouse bone marrow stromal cells (BMSCs) to single bout short duration FSS (12 dyn/cm² for 1 hour) using a parallel plate flow system. The expression of miR-20a was quantified by miRNA array profiling and real-time quantitative polymerase chain reaction (qRT-PCR) during FSS-mediated osteogenic differentiation. The expression of osteogenic differentiation markers such as Runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), and SP7 transcription factor (SP7) was detected. Bioinformatics analysis and a luciferase assay were performed to confirm the potential targets of miR-20a.

Results

Osteoblast-expressed miR-20a is sensitive to the mechanical environments of FSS, which are differentially up-regulated during steady FSS-mediated osteogenic differentiation. MiR-20a enhances FSS-induced osteoblast differentiation by activating the bone morphogenetic protein 2 (BMP2) signaling pathway. Both BMP and activin membrane-bound inhibitor (BAMBI) and mothers against decapentaplegic family member 6 (SMAD6) are targets of miR-20a that negatively regulate the BMP2 signaling pathway.

Conclusions

MiR-20a is a novel mechanosensitive miRNA that can enhance osteoblast differentiation in FSS mechanical environments, implying that this miRNA might be a target for bone tissue engineering and orthodontic bone remodeling for regenerative medicine applications.

A Quartet Network Analysis Identifying Mechanically Responsive Long Noncoding RNAs in Bone Remodeling

Mechanical force, being so ubiquitous that it is often taken for granted and overlooked, is now gaining the spotlight for reams of evidence corroborating their crucial roles in the living body. The bone, particularly, experiences manifold extraneous force like strain and compression, as well as intrinsic cues like fluid shear stress and physical properties of the microenvironment. Though sparkled in diversified background, long noncoding RNAs (lncRNAs) concerning the mechanotransduction process that bone undergoes are not yet detailed in a systematic way. Our principal goal in this research is to highlight the potential lncRNA-focused mechanical signaling systems which may be adapted by bone-related cells for biophysical environment response. Based on credible lists of force-sensitive mRNAs and miRNAs, we constructed a force-responsive competing endogenous RNA network for lncRNA identification. To elucidate the underlying mechanism, we then illustrated the possible crosstalk between lncRNAs and mRNAs as well as transcriptional factors and mapped lncRNAs to known signaling pathways involved in bone remodeling and mechanotransduction. Last, we developed combinative analysis between predicted and established lncRNAs, constructing a pathway–lncRNA network which suggests interactive relationships and new roles of known factors such as H19. In conclusion, our work provided a systematic quartet network analysis, uncovered candidate force-related lncRNAs, and highlighted both the upstream and downstream processes that are possibly involved. A new mode of bioinformatic analysis integrating sequencing data, literature retrieval, and computational algorithm was also introduced. Hopefully, our work would provide a moment of clarity against the multiplicity and complexity of the lncRNA world confronting mechanical input.

Mechanical Stimulation on Mesenchymal Stem Cells and Surrounding Microenvironments in Bone Regeneration: Regulations and Applications

Treatment of bone defects remains a challenge in the clinic. Artificial bone grafts are the most promising alternative to autologous bone grafting. However, one of the limiting factors of artificial bone grafts is the limited means of regulating stem cell differentiation during bone regeneration. As a weight-bearing organ, bone is in a continuous mechanical environment. External mechanical force, a type of biophysical stimulation, plays an essential role in bone regeneration. It is generally accepted that osteocytes are mechanosensitive cells in bone. However, recent studies have shown that mesenchymal stem cells (MSCs) can also respond to mechanical signals. This article reviews the mechanotransduction mechanisms of MSCs, the regulation of mechanical stimulation on microenvironments surrounding MSCs by modulating the immune response, angiogenesis and osteogenesis, and the application of mechanical stimulation of MSCs in bone regeneration. The review provides a deep and extensive understanding of mechanical stimulation mechanisms, and prospects feasible designs of biomaterials for bone regeneration and the potential clinical applications of mechanical stimulation.

Roles of MicroRNAs in Osteogenesis or Adipogenesis Differentiation of Bone Marrow Stromal Progenitor Cells

Bone marrow stromal cells (BMSCs) are multipotent cells which can differentiate into chondrocytes, osteoblasts, and fat cells. Under pathological stress, reduced bone formation in favour of fat formation in the bone marrow has been observed through a switch in the differentiation of BMSCs. The bone/fat switch causes bone growth defects and disordered bone metabolism in bone marrow, for which the mechanisms remain unclear, and treatments are lacking. Studies suggest that small non-coding RNAs (microRNAs) could participate in regulating BMSC differentiation by disrupting the post-transcription of target genes, leading to bone/fat formation changes. This review presents an emerging concept of microRNA regulation in the bone/fat formation switch in bone marrow, the evidence for which is assembled mainly from in vivo and in vitro human or animal models. Characterization of changes to microRNAs reveals novel networks that mediate signalling and factors in regulating bone/fat switch and homeostasis. Recent advances in our understanding of microRNAs in their control in BMSC differentiation have provided valuable insights into underlying mechanisms and may have significant potential in development of new therapeutics.

Compression loading of osteoclasts attenuated microRNA-146a-5p expression, which promotes angiogenesis by targeting adiponectin

Osteoclastogenesis in alveolar bone induced by compression stress triggers orthodontic tooth movement. Compression stress also stimulates angiogenesis, which is essential for osteoclastogenesis. However, the effects of osteoclastogenesis induced by compression on angiogenesis are poorly understood. In vivo, we found the markers of angiogenesis increased during orthodontic bone remodeling. In vitro, osteoclast-derived exosomes increased proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs), as well as expression of vascular endothelial growth factor and CD31. The promotive effects of exosomes derived from compressed osteoclasts were greater than those derived from osteoclasts without compression. Next, we analyzed changes in the microRNA transcriptome after compression stress and focused on microRNA146a-5p (miR-146a), which was significantly decreased by compression. Transfection of an inhibitor of miR-146a stimulated angiogenesis of HUVECs while miR-146a mimics repressed angiogenesis. Adiponectin (ADP) was confirmed to be a target of miR-146a by dual luciferase reporter assay. In HUVECs treated with exosomes, we detected increased ADP which promoted angiogenesis. Knockdown of ADP in HUVECs reduced the promotive effects of exosomes. Our results demonstrate that the decreased miR-146a observed in osteoclasts after compression promotes angiogenesis by targeting ADP, suggesting a novel method to interfere with bone remodeling induced by compression stress.

Mechanical loading and the control of stem cell behavior

OBJECTIVE

Mechanical stimulation regulates many cell responses. The present study describes the effects of different in vitro mechanical stimulation approaches on stem cell behavior.

DESIGN

The narrative review approach was performed. The articles published in English language that addressed the effects of mechanical force on stem cells were searched on Pubmed and Scopus database. The effects of extrinsic mechanical force on stem cell response was reviewed and discussed.

RESULTS

Cells sense mechanical stimuli by the function of mechanoreceptors and further transduce force stimulation into intracellular signaling. Cell responses to mechanical stimuli depend on several factors including type, magnitude, and duration. Further, similar mechanical stimuli exhibit distinct cell responses based on numerous factors including cell type and differentiation stage. Various mechanical applications modulate stemness maintenance and cell differentiation toward specific lineages.

CONCLUSIONS

Mechanical force application modulates stemness maintenance and differentiation. Modification of force regimens could be utilized to precisely control appropriate stem cell behavior toward specific applications.

MicroRNA-125a-5p modulates macrophage polarization by targeting E26 transformation-specific variant 6 gene during orthodontic tooth movement

OBJECTIVE

The aim of this study was to investigate the role of microRNA-125a-5p (miR-125a-5p) in macrophages during orthodontic tooth movement (OTM).

DESIGN

Periodontal ligament tissues were collected from patients underwent OTM. Periodontal ligament cells were isolated from periodontal ligament tissues. Periodontal ligament stem cells were isolated from normal human impacted third molars. The miR-125-5p levels were measured by real-time quantitative polymerase chain reaction. The impact of miR-125-5p on macrophage polarization was tested by alizarin red staining assay. The effects of miR-125-5p and E26 transformation-specific variant 6 gene (ETV6) on M1/M2 macrophages phenotype markers were determined by real-time quantitative polymerase chain reaction, western blot, and flow cytometry analyses. The interaction between miR-125-5p and ETV6 was verified using luciferase reporter and RNA immunoprecipitation assays.

RESULTS

Periodontal miR-125a-5p was upregulated under the force. Macrophage polarization facilitated osteogenesis by cocultured system. Moreover, miR-125a-5p was upregulated in macrophages polarized with M2 conditions. MiR-125a-5p downregulation promoted the expression of M1 phenotype markers, while suppressed the expression of M2 markers. Mechanistically, ETV6 was confirmed to be a target of miR-125a-5p. ETV6 overexpression increased the expression of M1 polarized markers, while decreased the expression of M2 polarized markers. Furthermore, ETV6 knockdown reversed the effects of miR-125a-5p inhibitor on both M1 macrophages and M2 macrophages.

CONCLUSIONS

Overall, miR-125a-5p facilitates bone healing by targeting ETV6 to promote macrophage M2 polarization.

Differentially expressed microRNAs as diagnostic biomarkers for infected tibial non-union

BACKGROUND

Infected tibial non-union is a challenging clinical complication of fracture treatment. Improper treatment of infected tibial non-union may result in high treatment costs and a long treatment period, and lead to medical disputes and decreased patient satisfaction. An increasing number of studies have indicated the significant role of microRNAs (miRNAs) in the development and progression of different bone diseases. Therefore, the identification of a specific miRNA expression profile associated with infected tibial non-union is a key step toward establishing a novel strategy for the diagnosis and treatment of infected tibial non-union.

METHODS

We utilised a microarray analysis to compare the specific expression of bone tissue miRNA in patients with infected tibial non-union and closed tibial fractures. Quantitative real-time reverse transcription-polymerase chain reaction was performed to validate the microarray results. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic efficacy of the identified regulated miRNA(s) isolated from bone tissue as potential biomarker(s).

RESULTS

Microarray analysis showed 20 differentially expressed miRNAs. Differential expression of miR-649, miR-29b-3p, miR-498, miR-365a-5p, miR-328-5p, and miR-345-3p was further confirmed in a validation cohort. ROC curve analyses showed an AUC (Areas Under the ROC Curve) of 0.808 (95% confidence interval [CI]: 0.675-0.940), 0.778 (95% CI: 0.634-0.921), 0.769 (95% CI: 0.619-0.919), 0.798 (95% CI: 0.662-0.933), 0.818 (95% CI: 0.690-0.945), 0.839 (95% CI: 0.715-0.963) for miR-649, miR-29b-3p, miR-498, miR-365a-5p, miR-328-5p, and miR-345-3p, respectively. The combined use of three miRNAs (miR-649, miR-328-5p, and miR-345-3p) yielded an overall diagnostic accuracy of AUC = 0.953, indicating a robust diagnostic value.

CONCLUSION

Our findings highlight the role of miR-649, miR-328-5p, and miR-345-3p as novel candidate biomarkers for infected tibial non-union diagnosis, suggesting that these differentially expressed miRNAs could be utilised as novel diagnostic and therapeutic tools to identify infected tibial non-union.

MicroRNA-21 facilitates osteoblast activity

MicroRNAs are emerging as critical post-transcriptional modulators in bone remodeling, regulating the functions of osteoblasts and osteoclasts. Intercellular crosstalk between osteoblasts and osteoclasts is mediated by miR-21 that controls the bone homeostasis response, providing potential targets for the maintenance of osteoblast function. The aim of this study was to investigate the effects of miR-21 on osteoblast function, and to explore the underlying mechanism. Increased alkaline phosphatase (ALP) activity and accelerated matrix mineralization was observed in mouse pre-osteoblast MC3T3-E1 cells compared with the non-induction (control) group. MiR-21 positively regulates osteogenic differentiation and mineralization by facilitating the expression of key osteogenic factors (ALP, Runx2, Osteopontin (OPN), Osterix (OSX) and Mef2c) in MC3T3-E1 cells. Furthermore, a deficiency of miR-21 suppresses the expression of those factors at both the mRNA and protein levels, indicating that miR-21 is a positive regulator of osteoblastic differentiation. H-E staining, Azan staining, Masson's Trichrome staining and Toluidine blue staining were performed in jaw and femur tissues of miR-21 knockout (miR-21KO) and wild-type (WT) mice. Immunohistochemical staining revealed substantially lower levels of ALP, Runx2 and OSX expression in jaw and femur tissues of miR-21KO mice. A similar trend was observed in femur tissues using quantitative real-time (RT) PCR. A total of 17 osteogenesis-related mRNAs were found to be differentially expressed in miR-21KO femur tissues using Mouse Gene Expression Microarray analysis. GeneSpring and Ingenuity Pathway Analysis revealed several potential target genes that are involved in bone remodeling, such as IL-1β and HIF-1α. Several important pathways were determined to be facilitators of miR-21, which provides a reliable reference for future studies to elucidate the biological mechanisms of osteoblast function. Taken together, these results lead us to hypothesize a potential role for miR-21 in regulating osteoblast function, thus representing a potential biomarker of osteogenesis.

miRNA-187-5p Regulates Osteoblastic Differentiation of Bone Marrow Mesenchymal Stem Cells in Mice by Targeting ICAM1

Osteoporosis (OP) is a common bone metabolic disease, the process of which is fundamentally irreversible. Therefore, the investigation into osteoblastic differentiation of bone marrow mesenchymal stem cells (BMSCs) will provide more clues for OP treatment. In the present study, we found that microRNA-187-5p (miR-187-5p) played a key role on osteoblastic differentiation, which was significantly upregulated during osteogenic differentiation of BMSCs in mice. Moreover, overexpression of miR-187-5p suppressed osteoblastic differentiation of BMSCs through increasing alkaline phosphatase (ALP), matrix mineralization, and levels of Osterix (OSX), and osteopontin (OPN) as well as runt-related transcription factor 2 (Runx2) in vitro. The results in vivo indicated that the upregulation of miR-187-5p enhanced the efficacy of new bone formation in the heterotopic bone formation assay. Luciferase reporter assay and western blot analysis revealed that miR-187-5p was involved in osteogenesis by targeting intracellular adhesion molecule 1 (ICAM-1). Furthermore, ICAM-1 silence inhibited osteoblastic differentiation of BMSCs. Taken together, our results suggested for the first time that miR-187-5p may promote osteogenesis by targeting ICAM-1, and provided a possible therapeutic target for bone metabolic diseases.

Mechanosensitivity of Cells and Its Role in the Regulation of Physiological Functions and the Implementation of Physiotherapeutic Effects (Review)

Regulatory signals in the body are not limited to chemical and electrical ones. There is another type of important signals for cells: those are mechanical signals (coming from the environment or arising from within the body), which have been less known in the literature. The review summarizes new information on the mechanosensitivity of various cells of connective tissue and nervous system. Participation of mechanical stimuli in the regulation of growth, development, differentiation, and functioning of tissues is described. The data focus on bone remodeling, wound healing, neurite growth, and the formation of neural networks. Mechanotransduction, cellular organelles, and mechanosensitive molecules involved in these processes are discussed as well as the role of the extracellular matrix. The importance of mechanical characteristics of cells in the pathogenesis of diseases is highlighted. Finally, the possible role of mechanosensitivity in mediating the physiotherapeutic effects is addressed.

MicroRNA-1-3p enhances osteoblast differentiation of MC3T3-E1 cells by interacting with hypoxia-inducible factor 1 α inhibitor (HIF1AN)

Studies have proved that miRNAs participate in the regulation of osteoblast differentiation (OD), and abnormal expression of miRNAs is related with various states of OD. In this study, we investigated the role of miRNA-1-3p in OD using MC3T3-E1 cells. BMP2 is used to induce OD of MC3T3-E1 cells. MiRNA-1-3p mimics or miRNA-1-3p inhibitor was transfected to MC3T3-E1 cells with BMP2. The expression levels of miRNA-1-3p were determined by qRT-PCR. The expression of Runx2, OSX, OPN, and OCN was detected by Western blotting. ALP assay was performed to measure alkaline phosphatase activity. Calcium nodules were evaluated by alizarin red staining. Over-expression of hypoxia-inducible factor 1-alpha inhibitor (HIF1AN) was performed and miRNA-1-3p rescue experiments were carried out. Over-expression of miRNA-1-3p promoted osteogenic differentiations and calcifications, as demonstrated by increased ALP, calcification and osteogenic markers. Knock-down of miRNA-1-3p generated the opposite results. HIF1AN was identified to be directly targeted by miRNA-1-3p. Over-expression of HIF1AN suppressed OD and calcifications, and miRNA-1-3p reversed the effect. Our results demonstrated that miRNA-1-3p could enhance OD of MC3T3-E1 cells through interacting with HIF1AN, which might be employed as therapeutic applications for bone formation and regeneration.

miR‑10a‑5p inhibits osteogenic differentiation of bone marrow‑derived mesenchymal stem cells

The use of human bone marrow mesenchymal stem cells (hBMSCs) as a tissue engineering application for individuals affected by osteoporosis and other types of bone loss diseases has been well studied in recent years. The osteogenic differentiation of hBMSCs can be regulated by a number of cues. MicroRNAs (miRNAs/miRs) serve as the key regulators of various biological processes; however, to the best of our knowledge, no information exists with regards to the specific modulatory effects of miR-10a-5p on osteogenic differentiation of hBMSCs. The aim of the present study was to investigate the relationship between hBMSCs and miR-10a-5p and, ultimately, to determine how miR-10a-5p affects the osteogenic differentiation process of hBMSCs in vitro and in vivo. The hBMSCs used in the present study were transfected with mirVana™ miRNA inhibitors and mimics, and transfection efficiency was assessed by fluorescence microscopy and reverse transcription-quantitative PCR (RT-qPCR). Viability of hBMSCs following transfection was analyzed using a Cell Counting Kit-8 assay. The mRNA expression levels of specific osteoblast markers, including alkaline phosphatase (ALP) and runt-related transcription factor 2 (RUNX2) were measured using RT-qPCR and western blot analysis. New bone formation was evaluated by Goldner's trichrome staining and micro-CT analysis in vivo. No significant difference in cell viability was observed among the different groups 24 h post-transfection. Overexpression of miR-10a-5p inhibited the expression of osteoblast makers in hBMSCs, whereas inhibition of miR-10a-5p upregulated the expression of ALP and RUNX2 in vitro. Furthermore, miR-10a-5p acted as a suppressor during the process of new bone formation in vivo. In conclusion, the findings of the present study suggested that miR-10a-5p served as a negative regulatory factor during osteoblast differentiation of hBMSCs and may be utilized in a treatment approach for bone repair in osteogenic-related diseases.

Effect of miR-181a-3p on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells by targeting BMP10

Objective: To explore the regulation relationship between miR-181a-3p and BMP10, and their mechanism of osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (MSCs).Methods: After osteogenic induction of MSCs, the ALP activity was detected by ELISA. The expression of miRNA-181a-3p and BMP10 was detected by RT-qPCR, and the protein levels of BMP10 and osteogenic differentiation marker proteins ALK and RUNX2 were detected by Western blot. The TargetScan online website was used to predict the putative target of miR-181a-3p, and dual luciferase reporter assay was performed to validate the targeting relationship between miR-181a-3p and BMP10.Results: In osteogenic differentiation of MSCs, ALP activity, the level of ALK and RUNX2 was evidently increased (p < .05), and the expression of miR-181a-3p was significantly downregulated (p < .05). Moreover, overexpression of miR-181a-3p obviously decreased the expression of BMP10 (p < .05), miR-181a-3p knockdown increased the expression of BMP10 prominently (p < .05). The transfection of miR-181a-3p mimics resulted in significantly downregulation of ALP activity and RUNX2 protein expression in MSCs (p < .05). In addition, overexpression of BMP10 could reverse the inhibitory effect of miR-181a-3p on osteogenic differentiation (p < .05).Conclusions: In conclusion, we found that miR-181a-3p inhibited osteogenic differentiation of MCSs by targeting BMP10.

Targeted silencing of miRNA-132-3p expression rescues disuse osteopenia by promoting mesenchymal stem cell osteogenic differentiation and osteogenesis in mice

Background

Skeletal unloading can induce severe disuse osteopenia that often occurs in spaceflight astronauts or in patients subjected to prolonged bed-rest or immobility. Previously, we revealed a mechano-sensitive factor, miRNA-132-3p, that is closely related to the osteoblast function. The aim of this study was to investigate whether miRNA-132-3p could be an effective target for treating disuse osteopenia.

Methods

The 2D-clinostat device and the hindlimb-unloaded (HU) model were used to copy the mechanical unloading condition at the cellular and animal levels, respectively. Mimics or inhibitors of miRNA-132-3p were used to interfere with the expression of miRNA-132-3p in bone marrow-derived mesenchymal stem cells (BMSCs) in vitro for analyzing the effects on osteogenic differentiation. The special in vivo antagonists of miRNA-132-3p was delivered to the bone formation regions of HU mice for treating disuse osteopenia by a bone-targeted (AspSerSer)₆-cationic liposome system. The bone mass, microstructure, and strength of the hindlimb bone tissue were analyzed for evaluating the therapeutic effect in vivo.

Results

miRNA-132-3p expression was declined under normal conditions and increased under gravitational mechanical unloading conditions during osteogenic differentiation of BMSCs in vitro. The upregulation of miRNA-132-3p expression resulted in the inhibition of osteogenic differentiation, whereas the downregulation of miRNA-132-3p expression enhanced osteogenic differentiation. The inhibition of miRNA-132-3p expression was able to attenuate the negative effects of mechanical unloading on BMSC osteogenic differentiation. Most importantly, the targeted silencing of miRNA-132-3p expression in the bone tissues could effectively preserve bone mass, microstructure, and strength by promoting osteogenic differentiation and osteogenesis in HU mice.

Conclusion

The overexpression of miRNA-132-3p induced by mechanical unloading is disadvantageous for BMSC osteogenic differentiation and osteogenesis. Targeted silencing of miRNA-132-3p expression presents a potential therapeutic target for the prevention and treatment of disuse osteoporosis.

Roles for miRNAs in osteogenic differentiation of bone marrow mesenchymal stem cells

Bone marrow mesenchymal stem cells (BMSCs), which were first discovered in bone marrow, are capable of differentiating into osteoblasts, chondrocytes, fat cells, and even myoblasts, and are considered multipotent cells. As a result of their potential for multipotential differentiation, self-renewal, immune regulation, and other effects, BMSCs have become an important source of seed cells for gene therapy, tissue engineering, cell replacement therapy, and regenerative medicine. MicroRNA (miRNA) is a highly conserved type of endogenous non-protein-encoding RNA of about 19-25 nucleotides in length, whose transcription process is independent of other genes. Generally, miRNA plays roles in regulating cell proliferation, differentiation, apoptosis, and development by binding to the 3' untranslated region of target mRNAs, whereby they can degrade or induce translational silencing. Although miRNAs play a regulatory role in various metabolic processes, they are not translated into proteins. Several studies have shown that miRNAs play an important role in the osteogenic differentiation of BMSCs. Herein, we describe in-depth studies of roles for miRNAs during the osteogenic differentiation of BMSCs, as they provide new theoretical and experimental rationales for bone tissue engineering and clinical treatment.

Oleanolic acid inhibits RANKL-induced osteoclastogenesis via ER alpha/miR-503/RANK signaling pathway in RAW264.7 cells

Oleanolic acid (OA) has recently become a research hotspot in the treatment of many human diseases, especially osteoporosis and arthritis. However, the mechanisms are not elucidated completely. We aimed to elucidate the target and the mechanism via which OA inhibited osteoclast differentiation. We used TRAP staining and toluidine blue dye to test OA effect on osteoclastogenesis and bone resorption respectively. We detected the expression level of osteoclast differentiation related genes, estrogen receptor alpha (ERα) and miR-503. We blocked ERα with its specific blocker, methylpiperidino pyrazole (MPP). We antagonized the function of miR-503 with antagomir-503-5p. RT-PCR and ELISA kits were used to investigate the effects of OA on miR-503 formation and maturation-relevant enzymes Dicer and Drosha at gene and protein levels. The data suggested that OA inhibited osteoclastogenesis and bone resorption. OA upregulated ERα and miR-503 expression levels, inhibited RANK expression. MPP significantly attenuated the OA effect including inhibiting osteoclastogenesis, inhibiting bone resorption and up-regulating miR-503 expression. It showed that ERα was the target of OA and OA up-regulated miR-503 expression through ERα. Antagomir-503-5p inhibited the function of miR-503 and attenuated the inhibition of OA on osteoclastogenesis, suggesting that OA inhibited osteoclast by up-regulating miR-503 expression. In addition, OA up-regulated miR-503 by up-regulating Dicer expression. In conclusion, OA inhibits RANKL-induced osteoclastogenesis via ERα/miR-503/RANK signaling pathway in RAW264.7 cells.

Role of microRNAs in osteogenesis of stem cells

Osteogenic differentiation is a controlled developmental process in which external and internal factors including cytokines, growth factors, transcription factors (TFs), signaling pathways and microRNAs (miRNAs) play important roles. Various stimulatory and inhibitory TFs contribute to osteogenic differentiation and are responsible for bone development. In addition, cross-talk between several complex signaling pathways regulates the osteogenic differentiation of some stem cells. Although much is known about regulatory genes and signaling pathways in osteogenesis, the role of miRNAs in osteogenic differentiation still needs to be explored. miRNAs are small, approximately 22 nucleotides, single-stranded nonprotein coding RNAs which are abundant in many mammalian cell types. They paly significant regulated roles in various biological processes and serve as promising biomarkers for disease states. Recently, emerging evidence have shown that miRNAs are the key regulators of osteogenesis of stem cells. They may endogenously regulate osteogenic differentiation of stem cells through direct targeting of positive or negative directors of osteogenesis and depending on the target result in the promotion or inhibition of osteogenic differentiation. This review aims to provide a general overview of miRNAs participating in osteogenic differentiation of stem cells and explain their regulatory effect based on the genes targeted with these miRNAs.

Compression and tension variably alter Osteoprotegerin expression via miR-3198 in periodontal ligament cells

Background

Osteoclasts play a critical role in bone resorption due to orthodontic tooth movement (OTM). In OTM, a force is exerted on the tooth, creating compression of the periodontal ligament (PDL) on one side of the tooth, and tension on the other side. In response to these mechanical stresses, the balance of receptor activator of nuclear-factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) shifts to stimulate osteoclastogenesis. However, the mechanism of OPG expression in PDL cells under different mechanical stresses remains unclear. We hypothesized that compression and tension induce different microRNA (miRNA) expression profiles, which account for the difference in OPG expression in PDL cells.

To study miRNA expression profiles resulting from OTM, compression force (2 g/cm²) or tension force (15% elongation) was applied to immortalized human PDL (HPL) cells for 24 h, and miRNA extracted. The miRNA expression in each sample was analyzed using a human miRNA microarray, and the changes of miRNA expression were confirmed by real-time RT-PCR. In addition, miR-3198 mimic and inhibitor were transfected into HPL cells, and OPG expression and production assessed.

Results

We found that certain miRNAs were expressed differentially under compression and tension. For instance, we observed that miR-572, − 663, − 575, − 3679-5p, UL70-3p, and − 3198 were upregulated only by compression. Real-time RT-PCR confirmed that compression induced miR-3198 expression, but tension reduced it, in HPL cells. Consistent with previous reports, OPG expression was reduced by compression and induced by tension, though RANKL was induced by both compression and tension. OPG expression was upregulated by miR-3198 inhibitor, and was reduced by miR-3198 mimic, in HPL cells. We observed that miR-3198 inhibitor rescued the compression-mediated downregulation of OPG. On the other hand, miR-3198 mimic reduced OPG expression under tension. However, RANKL expression was not affected by miR-3198 inhibitor or mimic.

Conclusions

We conclude that miR-3198 is upregulated by compression and is downregulated by tension, suggesting that miR-3198 downregulates OPG expression in response to mechanical stress.

Effects of different intensities of strength and endurance training on some osteometabolic miRNAs, Runx2 and PPARγ in bone marrow of old male wistar rats

Bone tissue is known as a living dynamic and complex organ in response to physical activity and mechanical loading such as exercise training; thus, the purpose of this study was to determine the effect of different intensities of strength and endurance training on expression of some osteometabolic miRNAs and runt-related transcription factor 2 (Runx2) and peroxisome proliferator-activated receptor γ (PPARγ) in bone marrow of old male Wistar rats. To this end, a total number of 50 male Wistar rats (aged 23 months, 438.27 g) were obtained from Pasteur Institute of Iran. The rats were randomized into five groups (10 rats/per group) including moderate endurance training (MET), high-intensity endurance training (HET), moderate-intensity resistance training (MRT), high-intensity resistance training (HRT), and control (CON). The four training groups completed 8 weeks of a training program, 5 days a week, according to the study protocol. To evaluate miR-133a, miR-103a, miR-204, and other adipogenic and osteogenic genes such as RUNX2 and PPARγ via real-time PCR, total RNA including mRNA and miRNA was isolated from the bone marrow. The statistical analysis was then performed using two-way analysis of variance (ANOVA). No significant differences in miR-133a (p = 0.197), miR-103a (p = 0.302), miR-204 (p = 0.539), RUNX2 (p = 0.960), and PPARγ (P = 0.872) were observed between the intervention groups and the control one. Furthermore, there were no significant differences in bone force (p = 0.641), fracture energy (p = 0.982), stress (p = 0.753), module (p = 0.147), and elongation (p = 0.292) variables between the intervention groups and the control group. Investigating molecular and cellular changes in the bone after such exercises in longer time could provide clearer results about the beneficial or harmful effects of these types of exercises in healthy and passive elderly people.

Core regulatory RNA molecules identified in articular cartilage stem/progenitor cells during osteoarthritis progression

Aim: To assess cartilage-derived stem/progenitor cells (CSPCs) in osteoarthritis (OA) by employing mRNA-miRNA-circRNA-lncRNA network biology approach. Methods: Differentially expressed (DE) RNAs in CSPCs from 2-/4-/8-month-old STR/Ort and CBA mice were identified to construct networks via RNA sequencing. Results: Compared with age-matched CBA mice, 4-/8-month-old STR/Ort mice had cartilage lesions and their CSPCs exhibited lower proliferative and differentiation capacity (decreased CD44 and CD90), and identified 7082 DE RNAs in STR/Ort mice were associated with strain differences or OA progression. OA-related core RNAs were identified via the networks constructed with the predominant DE RNAs, which were involved in the signaling pathways (NF-κB/MAPK/Hippo/Wnt/TGF-β/cytoskeleton organization). The core RNAs (miR-322-5p/miR-493-5p/miR-378c/CPNE1/Cdh2/PRDM16/CTGF/NCAM1) were validated in CSPCs from OA patients. Conclusion: RNA-based networks identifying core RNAs and signaling pathways contribute to CSPC-dependent OA mechanisms.

Role of Epigenomics in Bone and Cartilage Disease

Phenotypic variation in skeletal traits and diseases is the product of genetic and environmental factors. Epigenetic mechanisms include information-containing factors, other than DNA sequence, that cause stable changes in gene expression and are maintained during cell divisions. They represent a link between environmental influences, genome features, and the resulting phenotype. The main epigenetic factors are DNA methylation, posttranslational changes of histones, and higher-order chromatin structure. Sometimes non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are also included in the broad term of epigenetic factors. There is rapidly expanding experimental evidence for a role of epigenetic factors in the differentiation of bone cells and the pathogenesis of skeletal disorders, such as osteoporosis and osteoarthritis. However, different from genetic factors, epigenetic signatures are cell- and tissue-specific and can change with time. Thus, elucidating their role has particular difficulties, especially in human studies. Nevertheless, epigenomewide association studies are beginning to disclose some disease-specific patterns that help to understand skeletal cell biology and may lead to development of new epigenetic-based biomarkers, as well as new drug targets useful for treating diffuse and localized disorders. Here we provide an overview and update of recent advances on the role of epigenomics in bone and cartilage diseases. © 2019 American Society for Bone and Mineral Research.

MicroRNA-96 is responsible for sevoflurane-induced cognitive dysfunction in neonatal rats via inhibiting IGF1R

Sevoflurane is an experimental potent yet volatile anesthesia agent characterized by a low blood/gas partition coefficient. However, exposure to sevoflurane in neonatal mice has been speculated to result in learning deficits and abnormal social behavior. The aim of the present study was to investigate the relationship between sevoflurane and miR-96, in an attempt to identify the means by which it mediates IGF1R to influence the cognitive dysfunction (CD) in neonatal rats. Relationship between differentially expressed miRNAs and sevoflurane concentration was identified. The potential underlying regulatory mechanisms involved with sevoflurane were investigated through the administration of varying concentrations of the agent (1%, 2% and 4%), combined with miR-96 mimic or an inhibitor. A target prediction program was utilized, while the luciferase activity was determined in order to verify whether miR-96 targets IGF1R. The mRNA and protein levels of IGF1R, Bcl-2, Bax, and caspase-3 were measured followed by the determination of hippocampal neuron apoptosis. Learning and memory performance was assessed using the Morris water maze (MWM) test and step-down test. The obtained results highlighted a positive correlation between miR-96 and the concentration of sevoflurane, while miR-96 was confirmed to negatively target IGF1R. Our analyses indicated that 4% sevoflurane had a significantly stronger effect on reducing the levels of IGF1R and Bcl-2, while elevating the levels of miR-96, Bax and caspase-3 more so than that of 1% or 2% sevoflurane, which resulted in increased hippocampal neuron apoptosis but diminished the learning and memory performance of the rats. The addition of miR-96 mimic was demonstrated to exacerbate the influence of sevoflurane on hippocampal neurons as well as the cognitive function of the rats. The key findings of our study highlighted the role of miR-96 in the potential mechanism of sevoflurane anesthesia-induced CD in neonatal rats through the downregulation of IGF1R.

Bone remodeling induced by mechanical forces is regulated by miRNAs

The relationship between mechanical force and alveolar bone remodeling is an important issue in orthodontics because tooth movement is dependent on the response of bone tissue to the mechanical force induced by the appliances used. Mechanical cyclical stretch (MCS), fluid shear stress (FSS), compression, and microgravity play different roles in the cell differentiation and proliferation involved in bone remodeling. However, the underlying mechanisms are unclear, particularly the molecular pathways regulated by non-coding RNAs (ncRNAs) that play essential roles in bone remodeling. Amongst the various ncRNAs, miRNAs act as post-transcriptional regulators that inhibit the expression of their target genes. miRNAs are considered key regulators of many biologic processes including bone remodeling. Here, we review the role of miRNAs in mechanical force-induced bone metabolism.

MiR-1297 suppresses pancreatic cancer cell proliferation and metastasis by targeting MTDH

Dysregulation of miR-1297 has been detected in various human cancers, and miR-1297 can function as either an oncogene or tumor suppressor. However, the role of miR-1297 in pancreatic adenocarcinoma has not been previously reported. Here, we investigated miR-1297 expression in pancreatic cancer and the role it plays in the development and metastasis of pancreatic adenocarcinoma. In the present study, MiR-1297 and metadherin (MTDH) expression in pancreatic cancer tissue was detected using quantitative real-time PCR (qRT-PCR) and western blot methods. The CCK-8 assay and EdU incorporation assay were used to analyze the impact of miR-1297 and MTDH on cell proliferation. Flow cytometric and Hoechst 33342 staining methods were used to explore how miR-1297 and MTDH affect cell apoptosis. The Transwell assay and scratch wound healing assay were used to analyze cell migration and invasion capabilities. The dual-luciferase assay was used to confirm that miR-1297 targets MTDH. Here, we found that miR-1297 expression was decreased in pancreatic adenocarcinoma tissues, while MTDH expression was increased in those tissues. Furthermore, western blot and dual-luciferase assay results confirmed that MTDH was a direct target of miR-1297. Additionally, overexpression of miR-1297 or knockdown of MTDH suppressed BxPC-3 and PANC-1 cell proliferation, and upregulation of miR-1297 or suppression of MTDH promoted BxPC-3 and PANC-1 cell apoptosis. Finally, BxPC-3 and PANC-1 cell migration and invasion abilities were suppressed by either overexpression of miR-1297 or downregulation of MTHD. In conclusion, our results suggest that miR-1297 inhibits the growth and metastasis of pancreatic adenocarcinoma by downregulating MTDH expression, and the miR-1297/MTDH pathway is a potential target for treating pancreatic adenocarcinoma.

MicroRNA profiles of BMSCs induced into osteoblasts with osteoinductive medium

MicroRNA (miRNA) plays an important role in cell differentiation and functions as a regulator. Therefore, miRNA is important in the process of bone marrow mesenchymal stem cells (BMSCs) being induced into osteoblasts. In this study, mouse BMSCs were induced with osteoinductive medium, the indices related to osteoblastic differentiation were assayed, including alkaline phosphatase, the deposit of calcium and protein levels of osteocalcin. Using miRNA microarray and reverse transcription-quantitative polymerase chain reaction analyses, differentially expressed miRNAs in the cells, which were induced with osteoinductive medium, were selected and identified. The target genes of the differentially expressed miRNAs were then predicted using bioinformatics analysis. The results revealed that osteoinductive medium promoted osteoblastic differentiation of BMSCs, and let-7c-5p, miR-181c-3p, miR-3092-3p and miR-5132-3p were identified as differentially expressed miRNAs in the cells treated with osteoinductive medium for 14 and 21 days. Certain target genes and signal pathways related to osteoblastic differentiation of the four miRNAs were predicted. These findings indicated the four differently expressed miRNAs may be potential regulators of osteoblastic differentiation, providing a basis for further study on the regulation of miRNAs in the osteogenic differentiation of BMSCs.

Tension force-induced bone formation in orthodontic tooth movement via modulation of the GSK-3β/β-catenin signaling pathway

Orthodontic force-induced osteogenic differentiation and bone formation at tension sites play a critical role in orthodontic tooth movement. However, the molecular mechanism underlying this phenomenon is poorly understood. In the current study, we investigated the involvement of the GSK-3β/β-catenin signaling pathway, which is critical for bone formation during tooth movement. We established a rat tooth movement model to test the hypothesis that orthodontic force may stimulate bone formation at the tension site of the moved tooth and promote the rate of tooth movement via regulation of the GSK-3β/β-catenin signaling pathway. Our results showed that continued mechanical loading increased the distance between the first and second molar in rats. In addition, the loading force increased bone formation at the tension site, and also increased phospho-Ser9-GSK-3β expression and β-catenin signaling pathway activity. Downregulation of GSK-3β activity further increased bone parameters, including bone mineral density, bone volume to tissue volume and trabecular thickness, as well as ALP- and osterix-positive cells at tension sites during tooth movement. However, ICG-001, the β-catenin selective inhibitor, reversed the positive effects of GSK-3β inhibition. In addition, pharmaceutical inhibition of GSK-3β or local treatment with β-catenin inhibitor did not influence the rate of tooth movement. Based on these results, we concluded that GSK-3β/β-catenin signaling contributes to the bone remodeling induced by orthodontic forces, and can be used as a potential therapeutic target in clinical dentistry.

MicroRNA-495 Inhibits New Bone Regeneration via Targeting High Mobility Group AT-Hook 2 (HMGA2)

Background

MicroRNAs play critical roles in post-translational gene expression. In this study, we explored the role of miR-495 in new bone regeneration.

Material/Methods

Murine calvarial osteoblasts were isolated and cultured. Microarray was performed to identify differential miRNAs in medicarpin-induced osteoblasts differentiation. Luciferase reporter assay was performed to identify the target gene of miRNA. Murine osteoblast cells were transfected with miC, miR-495, or anti-miR-495. CCK-8 and flow cytometry were performed to detect osteoblasts proliferation and apoptosis. Western blot was used to analyze apoptosis-related proteins. qRT-PCR analysis was performed to detect gene expression. ALP activity and mineralized nodule formation test were used to evaluate bone formation. Dill-hole injury model was constructed and micro CT was utilized to measuring bone healing.

Results

Microarray analysis identified miR-495 as our miRNA of interest and luciferase reporter assay identified HMGA2 as its target gene. Over-expression of miR-495 significantly inhibited ALP activity and mineralized nodule formation as well as the expression of RUNX-2, BMP-2, and Osterix. Also, miR-495 over-expression inhibited osteoblasts proliferation and promoted apoptosis obviously. In this in vivo study, the downregulation of miR-495 promoted murine femur healing.

Conclusions

MiR-495 inhibits new bone regeneration via targeting high mobility group AT-Hook 2 (HMGA2). We propose that targeting miR-495 may be a promising therapeutic approach for bone regeneration.

Mechanosensitive miRNAs and Bone Formation

Mechanical stimuli are required for the maintenance of skeletal integrity and bone mass. An increasing amount of evidence indicates that multiple regulators (e.g., hormone, cytoskeleton proteins and signaling pathways) are involved in the mechanical stimuli modulating the activities of osteogenic cells and the process of bone formation. Significantly, recent studies have showed that several microRNAs (miRNAs) were sensitive to various mechanical stimuli and played a crucial role in osteogenic differentiation and bone formation. However, the functional roles and further mechanisms of mechanosensitive miRNAs in bone formation are not yet completely understood. This review highlights the roles of mechanosensitive miRNAs in osteogenic differentiation and bone formation and underlines their potential therapeutic application for bone loss induced by the altering of mechanical stimuli.