Mg-Cross-Linked Alginate Hydrogel Induces BMSC/Macrophage Crosstalk to Enhance Bone Tissue Regeneration via Dual Promotion of the Ligand-Receptor Pairing of the OSM/miR-370-3p-gp130 Signaling Pathway

Macrophages play a pivotal role in the crosstalk between the immune and skeletal systems, while Mg-based biomaterials demonstrate immunomodulatory capabilities in this procedure. However, the mechanism of how Mg2+ promotes osteogenesis through the interplay of bone marrow-derived mesenchymal stem cells (BMSCs) and macrophages remains undescribed. Here, we demonstrated that a Mg-cross-linked alginate hydrogel exerted a dual enhancement of BMSCs osteogenic differentiation through the ligand-receptor pairing of the OSM/miR-370-3p-gp130 axis. On the one hand, Mg2+, released from the Mg-cross-linked hydrogel, stimulates bone marrow-derived macrophages to produce and secrete more OSM. On the other hand, Mg2+ lowers the miR-370-3p level in BMSCs and in turn, reverses its suppression on gp130. Then, the OSM binds to the gp130 heterodimer receptor and activates intracellular osteogenic programs in BMSCs. Taken together, this study reveals a novel cross-talk pattern between the skeletal and immune systems under Mg2+ stimulation. This study not only brings new insights into the immunomodulatory properties of Mg-based biomaterials for orthopedic applications but also enriches the miRNA regulatory network and provides a promising target to facilitate bone regeneration in large bone defects.

Sex dimorphic response to osteocyte miR21 deletion in murine calvaria bone as determined by RNAseq analysis

Low levels of microRNA (miR) 21 may explain the higher osteocyte apoptosis with Cx43-deficient and aged female mice. However, miR21 exerts a sex-divergent role in osteocytes, regulating bone mass and architecture through non-cell autonomous effects on osteoblasts and osteoclasts, via sex-specific regulation of osteocyte cytokine production. miR21 deficiency improves bone strength in females, and, to a higher extent, in male miR21-deficient mice. To understand the molecular basis for the effects of miR21 deletion, mRNA was isolated from miR21fl/fl (controls) or miR21-deficient (by deletion in cells expressing Cre recombinase under the control of the 8 kb fragment of the DMP1 promoter: miR21ΔOt mice). miR21 was 50% lower in miR21ΔOt whole calvaria bone compared to control mice of the corresponding sex. RNAseq was performed in 4 samples/sex and genotype. There were 152 genes with <.05 P-value and >1 absolute log2 fold change in the male data analysis, and expression of most genes was higher in the miR21fl/fl group. Two of the genes, Actn3 and Myh4, had a false discovery rate < 0.1. Gene enrichment analysis of significant genes on both KEGG pathways and gene ontology (GO) gene sets shows that the significant genes were enriched in muscle contraction. Some muscle-related genes like Actn3 were included in multiple significant pathways. For females, only 65 genes had P-value <.05 and >1 absolute log2 fold change. Yet, no significant KEGG or GO pathways, including ≥5 significant genes, were seen, and no overlap of significant genes was found between male and female samples. Therefore, deletion of miR21 has a stronger effect on male transcriptome in calvaria, compared to females. Further, no enrichment of any pathway was detected in female samples. Thus, either there are no differences between 2 groups in female or the effect size is small, and a larger sample size is needed to uncover miR21-dependent differences.

Transforming growth factor-beta superfamily regulates mesenchymal stem cell osteogenic differentiation: A microRNA linking

The ability to differentiate into cells of different lineages, such as bone cells, is the principal value of adult mesenchymal stem cells (MSCs), which can be used with the final aim of regenerating damaged tissue. Due to its potential use and importance in regenerative medicine and tissue engineering, several questions have been raised regarding the molecular mechanisms of MSC differentiation. As one of the crucial mediators in organism development, the transforming growth factor-beta (TGF-β) superfamily directs MSCs' commitment to selecting differentiation pathways. This review aims to give an overview of the current knowledge on the mechanisms of the TGF-β superfamily in MSCs bone differentiation, with additional insight into the mutual regulation of microRNAs and TGF-β in osteogenesis.

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.

The role of non-coding RNAs in diabetes-induced osteoporosis

Diabetes mellitus (DM) and osteoporosis are two major health care problems worldwide. Emerging evidence suggests that DM poses a risk for osteoporosis and can contribute to the development of diabetes-induced osteoporosis (DOP). Interestingly, some epidemiological studies suggest that DOP may be at least partially distinct from those skeletal abnormalities associated with old age or postmenopausal osteoporosis. The increasing number of DM patients who also have DOP calls for a discussion of the pathogenesis of DOP and the investigation of drugs to treat DOP. Recently, non-coding RNAs (ncRNAs) have received more attention due to their significant role in cellular functions and bone formation. It is worth noting that ncRNAs have also been demonstrated to participate in the progression of DOP. Meanwhile, nano-delivery systems are considered a promising strategy to treat DOP because of their cellular targeting, sustained release, and controlled release characteristics. Additionally, the utilization of novel technologies such as the CRISPR system has expanded the scope of available options for treating DOP. Hence, this paper explores the functions and regulatory mechanisms of ncRNAs in DOP and highlights the advantages of employing nanoparticle-based drug delivery techniques to treat DOP. Finally, this paper also explores the potential of ncRNAs as diagnostic DOP biomarkers.

Cytocompatibility and Osteoinductive Properties of Collagen-Fibronectin Hydrogel Impregnated with siRNA Targeting Glycogen Synthase Kinase 3β: In Vitro Study

In this study, we developed an osteoplastic material based on collagen-fibronectin hydrogel impregnated with siRNA molecules targeting glycogen synthase kinase 3β (GSK3β), which inhibits the osteogenic differentiation of mesenchymal stem cells. The hydrogel impregnated with polyplexes containing siRNA GSK3β and polyethylenimine has been shown to have no cytotoxic effect: there was no statistically significant change in the cell's viability after 7 days of incubation in its presence compared to the control group. On days 2 and 7, an increase in the level of expression of markers of osteogenic differentiation was observed, which confirms the osteoinductive qualities of the material. It has been demonstrated that the hydrogel maintains cell adhesion. Our results obtained in vitro indicate cytocompatibility and osteoinductive properties of collagen-fibronectin hydrogel impregnated with siRNA GSK3β molecules.

Ubiquitin-specific proteases: Vital regulatory molecules in bone and bone-related diseases

Stabilization of bone structure and function involves multiple cell-to-cell and molecular interactions, in which the regulatory functions of post-translational modifications such as ubiquitination and deubiquitination shouldn't be underestimated. As the largest family of deubiquitinating enzymes, the ubiquitin-specific proteases (USPs) participate in the development of bone homeostasis and bone-related diseases through multiple classical osteogenic and osteolytic signaling pathways, such as BMP/TGF-β pathway, NF-κB/p65 pathway, EGFR-MAPK pathway and Wnt/β-catenin pathway. Meanwhile, USPs may also broadly regulate regulate hormone expression level, cell proliferation and differentiation, and may further influence bone homeostasis from gene fusion and nuclear translocation of transcription factors. The number of patients with bone-related diseases is currently enormous, making exploration of their pathogenesis and targeted therapy a hot topic. Pathological increases in the levels of inflammatory mediators such as IL-1β and TNF-α lead to inflammatory bone diseases such as osteoarthritis, rheumatoid arthritis and periodontitis. While impaired body metabolism greatly increases the probability of osteoporosis. Abnormal physiological activity of bone-associated cells results in a variety of bone tumors. The regulatory role of USPs in bone-related disease has received particular attention from academics in recent studies. In this review, we focuse on the roles and mechanisms of USPs in bone homeostasis and bone-related diseases, with the expectation of informing targeted therapies in the clinic.

Post-Transcriptional Regulatory Crosstalk between MicroRNAs and Canonical TGF-β/BMP Signalling Cascades on Osteoblast Lineage: A Comprehensive Review

MicroRNAs (miRNAs) are a family of small, single-stranded, and non-protein coding RNAs about 19 to 22 nucleotides in length, that have been reported to have important roles in the control of bone development. MiRNAs have a strong influence on osteoblast differentiation through stages of lineage commitment and maturation, as well as via controlling the activities of osteogenic signal transduction pathways. Generally, miRNAs may modulate cell stemness, proliferation, differentiation, and apoptosis by binding the 3'-untranslated regions (3'-UTRs) of the target genes, which then can subsequently undergo messenger RNA (mRNA) degradation or protein translational repression. MiRNAs manage the gene expression in osteogenic differentiation by regulating multiple signalling cascades and essential transcription factors, including the transforming growth factor-beta (TGF-β)/bone morphogenic protein (BMP), Wingless/Int-1(Wnt)/β-catenin, Notch, and Hedgehog signalling pathways; the Runt-related transcription factor 2 (RUNX2); and osterix (Osx). This shows that miRNAs are essential in regulating diverse osteoblast cell functions. TGF-βs and BMPs transduce signals and exert diverse functions in osteoblastogenesis, skeletal development and bone formation, bone homeostasis, and diseases. Herein, we highlighted the current state of in vitro and in vivo research describing miRNA regulation on the canonical TGF-β/BMP signalling, their effects on osteoblast linage, and understand their mechanism of action for the development of possible therapeutics. In this review, particular attention and comprehensive database searches are focused on related works published between the years 2000 to 2022, using the resources from PubMed, Google Scholar, Scopus, and Web of Science.

MicroRNA-loaded biomaterials for osteogenesis

The large incidence of bone defects in clinical practice increases not only the demand for advanced bone transplantation techniques but also the development of bone substitute materials. A variety of emerging bone tissue engineering materials with osteogenic induction ability are promising strategies for the design of bone substitutes. MicroRNAs (miRNAs) are a class of non-coding RNAs that regulate intracellular protein expression by targeting the non-coding region of mRNA3′-UTR to play an important role in osteogenic differentiation. Several miRNA preparations have been used to promote the osteogenic differentiation of stem cells. Therefore, multiple functional bone tissue engineering materials using miRNA as an osteogenic factor have been developed and confirmed to have critical efficacy in promoting bone repair. In this review, osteogenic intracellular signaling pathways mediated by miRNAs are introduced in detail to provide a clear understanding for future clinical treatment. We summarized the biomaterials loaded with exogenous cells engineered by miRNAs and biomaterials directly carrying miRNAs acting on endogenous stem cells and discussed their advantages and disadvantages, providing a feasible method for promoting bone regeneration. Finally, we summarized the current research deficiencies and future research directions of the miRNA-functionalized scaffold. This review provides a summary of a variety of advanced miRNA delivery system design strategies that enhance bone regeneration.

Chitosan-based scaffolds as drug delivery systems in bone tissue engineering

The bone tissue engineering approach for treating large bone defects becomes necessary when the tissue damage surpasses the threshold of the inherent regenerative ability of the human body. A myriad of natural biodegradable polymers and scaffold fabrication techniques have emerged in the last decade. Chitosan (CS) is especially attractive as a bone scaffold material to support cell attachment and proliferation and mineralization of the bone matrix. The primary amino groups in CS are responsible for properties such as controlled drug release, mucoadhesion, in situ gelation, and transfection. CS-based smart drug delivery scaffolds that respond to environmental stimuli have been reported to have a localized sustained delivery of drugs in the large bone defect area. This review outlines the recent advances in the fabrication of CS-based scaffolds as a pharmaceutical carrier to deliver drugs such as antibiotics, growth factors, nucleic acids, and phenolic compounds for bone tissue regeneration.

NEDD4 E3 Ligases: Functions and Mechanisms in Bone and Tooth

Protein ubiquitination is a precisely controlled enzymatic cascade reaction belonging to the post-translational modification of proteins. In this process, E3 ligases catalyze the binding of ubiquitin (Ub) to protein substrates and define specificity. The neuronally expressed developmentally down-regulated 4 (NEDD4) subfamily, belonging to the homology to E6APC terminus (HECT) class of E3 ligases, has recently emerged as an essential determinant of multiple cellular processes in different tissues, including bone and tooth. Here, we place special emphasis on the regulatory role of the NEDD4 subfamily in the molecular and cell biology of osteogenesis. We elucidate in detail the specific roles, downstream substrates, and upstream regulatory mechanisms of the NEDD4 subfamily. Further, we provide an overview of the involvement of E3 ligases and deubiquitinases in the development, repair, and regeneration of another mineralized tissue—tooth.

SHED‐derived exosomes improve the repair capacity and osteogenesis potential of hPDLCs

OBJECTIVE

Exosomes secreted by stem cells are recognized as a critical component in tissue regeneration during stem cell-based therapy. Considering the limited sources and bone regeneration efficiency of human periodontal ligament cells (hPDLCs), we explored whether exosomes secreted by stem cells from human exfoliated deciduous teeth (SHED-exo) could improve the pluripotency and regenerative potential of hPDLCs.

METHODS AND MATERIALS

In hPDLCs, cell proliferation, migration, cell cycle, apoptosis, and osteogenic differentiation were detected after cells were exposed to SHED-exo (SHED-exo group), blank (control group), or control supernatant without exo (Csup group), via CCK-8, scratch analysis, flow cytometric, real-time PCR, and so on. Exosomes sequencing was performed to compare and analyze miRNAs contented in SHED-exo and hPDLC-exo.

RESULTS

As compared to control or Csup, SHED-exo significantly increased migration, apoptosis, and proliferation, promoted cell cycle transition from G1 to S phase in hPDLCs, and enhanced Runx2 expression and mineralization. In addition, it may be explained by the significant differences in miRNA contented in SHED-exo and hPDLC-exo.

CONCLUSION

Exosomes from SHED can improve cell proliferation, migration, cell cycle, apoptosis, and osteogenic differentiation of hPDLCs, which highlights the therapeutic value of this bioactive component in the regeneration of periodontal tissues using hPDLCs in clinical practice.

Rutin-Zn(II) complex promotes bone formation - A concise assessment in human dental pulp stem cells and zebrafish

We have assessed the molecular role of Rutin and rutin-Zn(II) complex on osteoblast differentiation and mineralization in human dental pulp cells and zebrafish model. The biocompatibility of the rutin-Zn(II) complex was determined using MTT and chick embryotoxicity assays. Alizarin red staining and ALP measurements were performed to study the osteogenic role of Rutin and rutin-Zn(II) complex at the cellular level in hDPSCs. At molecular level, following rutin and rutin-Zn(II) exposure, the mRNA expression profile of osteoblast markers such Runx2, type 1 col, OC, and ON were investigated. In addition to this, the expression of negative regulators of osteoblast development such Smad7, Smurf1, and HDAC7 waere studied by Real time RT-PCR analysis. The osteogenic role of prepared complex under in vivo was studied by an in-house zebrafish scale model followed by osteoblast differentiation markers expression profiling and Ca:P level measurement by ICP-MS. Rutin and the rutin-Zn(II) complex were found to be non-toxic till 10 μM and increased the expression of osteoblast differentiation marker genes. It also enhanced calcium deposition in both in vitro and in vivo models. Osteogenic property of rutin-Zn(II) in hDPSCs was found be mediated by Smad7, Smurf1, and HDAC7 and enhancing Runx2 expression. Our study warrants the possible use of rutin-Zn(II) as naïve agent or in combination with other bone scaffolding systems/materials for bone tissue engineering applications.

A computational approach on studying the regulation of TGF-β1-stimulated Runx2 expression by MicroRNAs in human breast cancer cells

BACKGROUND

Transforming growth factor-beta1 (TGF-β1) acts as a most effective growth inhibitor for normal epithelial cells. Loss of this anti-proliferative factor in breast tissues favors invasion and development of osteolytic metastases, aided by a master transcription factor, runt-related transcription factor 2 (Runx2). Several reports identified Runx2 regulation with the help of non-coding RNAs such as microRNAs (miRNAs) under physiological and pathological conditions.

METHODS

Using bioinformatics tools such as miRDB, STarMir, Venny, TarBase, a unique list of miRNAs that putatively target the 3' UTR Runx2 was identified. Further, the expression patterns of those miRNAs at the precursor and mature levels were studied by RT-qPCR analyses. Following this, computational analyses using software like TransmiR and bc-GenExMiner v4.6 were done to speculate the miRNA's other target genes that indirectly regulate Runx2 activity in breast cancer.

RESULTS

There were 13 miRNAs that putatively target Runx2 identified using bioinformatics tools. Among these miRNAs, miR-5703 expression was significantly downregulated at both precursor and mature levels upon TGF-β1-treatment in human breast cancer cells. Computational analyses speculated an indirect targeting of Runx2 by miR-5703 by influencing multiple Runx2 regulatory signaling pathways including Jak/Stat, MAPK, Wnt/β-Catenin, Notch, BMP, and PKA pathways. Furthermore, a correlation of the expression profiles of the speculated genes and Runx2 with miR-5703 was depicted in triple-negative breast cancer patients.

CONCLUSION

Identification of miR-5703 and its network for Runx2 regulation directly or indirectly in breast cancer cells could significantly advance our understanding of breast cancer-mediated bone metastasis. In addition, it would potentially pave the way for miRNAs to be used as biomarkers and therapeutic agents in cancer research.

MicroRNA-432-5p regulates sprouting and intussusceptive angiogenesis in osteosarcoma microenvironment by targeting PDGFB

Osteosarcoma (OS) is a type of bone tumor conferred with high metastatic potential. Attainable growth of tumors necessitates functional vasculature mediated by sprouting angiogenesis (SA) and intussusceptive angiogenesis (IA). However, the regulation of IA and SA is still unclear in OS. To understand the mechanisms adopted by OS to induce angiogenesis, initially, we assessed the expression profile of a set of miRNAs' in both OS cells (SaOS2 and MG63) and normal bone cells. Amongst them, miR-432-5p was found to be highly downregulated in OS. The functional role of miR-432-5p in OS was further analyzed using miR-432-5p mimic/inhibitor. Platelet-derived growth factor-B (PDGFB) was found to be a putative target of miR-432-5p and it was further confirmed that the PDGFB 3'UTR is directly targeted by miR-432-5p using the luciferase reporter gene system. PDGFB was found to be secreted by OS to regulate angiogenesis by targeting the cells in its microenvironment. The conditioned medium obtained from miR-432-5p mimic transfected MG63 and SaOS2 cells decreased cell viability, proliferation, migration, and aorta ring formation in endothelial cells. The miRNA mimic/inhibitor transfected MG63 and SaOS2 cells were placed on SA (day 6) and IA (day 9) phase of CAM development to analyze SA and IA mechanisms. It was found that miR-432-5p mimic transfection in OS promotes the transition of SA to IA which was documented by the angiogenic parameters and SA and IA-associated gene expression. Interestingly, this outcome was also supported by the zebrafish tumor xenograft model. Corroborating these results, it is clear that miR-432-5p expression in OS cells regulates SA and IA by targeting PDGFB genes. We conclude that targeting miR-432-5p/PDGFB signaling can be a potential therapeutic strategy to treat OS along with other existing strategies.

Long non-coding RNA exploration for mesenchymal stem cell characterisation

BACKGROUND

The development of RNA sequencing (RNAseq) and the corresponding emergence of public datasets have created new avenues of transcriptional marker search. The long non-coding RNAs (lncRNAs) constitute an emerging class of transcripts with a potential for high tissue specificity and function. Therefore, we tested the biomarker potential of lncRNAs on Mesenchymal Stem Cells (MSCs), a complex type of adult multipotent stem cells of diverse tissue origins, that is frequently used in clinics but which is lacking extensive characterization.

RESULTS

We developed a dedicated bioinformatics pipeline for the purpose of building a cell-specific catalogue of unannotated lncRNAs. The pipeline performs ab initio transcript identification, pseudoalignment and uses new methodologies such as a specific k-mer approach for naive quantification of expression in numerous RNAseq data. We next applied it on MSCs, and our pipeline was able to highlight novel lncRNAs with high cell specificity. Furthermore, with original and efficient approaches for functional prediction, we demonstrated that each candidate represents one specific state of MSCs biology.

CONCLUSIONS

We showed that our approach can be employed to harness lncRNAs as cell markers. More specifically, our results suggest different candidates as potential actors in MSCs biology and propose promising directions for future experimental investigations.

Expression and function of Smad7 in autoimmune and inflammatory diseases

Transforming growth factor-β (TGF-β) plays a critical role in the pathological processes of various diseases. However, the signaling mechanism of TGF-β in the pathological response remains largely unclear. In this review, we discuss advances in research of Smad7, a member of the I-Smads family and a negative regulator of TGF-β signaling, and mainly review the expression and its function in diseases. Smad7 inhibits the activation of the NF-κB and TGF-β signaling pathways and plays a pivotal role in the prevention and treatment of various diseases. Specifically, Smad7 can not only attenuate growth inhibition, fibrosis, apoptosis, inflammation, and inflammatory T cell differentiation, but also promotes epithelial cells migration or disease development. In this review, we aim to summarize the various biological functions of Smad7 in autoimmune diseases, inflammatory diseases, cancers, and kidney diseases, focusing on the molecular mechanisms of the transcriptional and posttranscriptional regulation of Smad7.

The role of microRNAs in the osteogenic and chondrogenic differentiation of mesenchymal stem cells and bone pathologies

Mesenchymal stem cells (MSCs) have been identified in many adult tissues. MSCs can regenerate through cell division or differentiate into adipocytes, osteoblasts and chondrocytes. As a result, MSCs have become an important source of cells in tissue engineering and regenerative medicine for bone tissue and cartilage. Several epigenetic factors are believed to play a role in MSCs differentiation. Among these, microRNA (miRNA) regulation is involved in the fine modulation of gene expression during osteogenic/chondrogenic differentiation. It has been reported that miRNAs are involved in bone homeostasis by modulating osteoblast gene expression. In addition, countless evidence has demonstrated that miRNAs dysregulation is involved in the development of osteoporosis and bone fractures. The deregulation of miRNAs expression has also been associated with several malignancies including bone cancer. In this context, bone-associated circulating miRNAs may be useful biomarkers for determining the predisposition, onset and development of osteoporosis, as well as in clinical applications to improve the diagnosis, follow-up and treatment of cancer and metastases. Overall, this review will provide an overview of how miRNAs activities participate in osteogenic/chondrogenic differentiation, while addressing the role of miRNA regulatory effects on target genes. Finally, the role of miRNAs in pathologies and therapies will be presented.

MicroRNAs Modulate Signaling Pathways in Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) have been identified in many adult tissues and they have been closely studied in recent years, especially in view of their potential use for treating diseases and damaged tissues and organs. MSCs are capable of self-replication and differentiation into osteoblasts and are considered an important source of cells in tissue engineering for bone regeneration. Several epigenetic factors are believed to play a role in the osteogenic differentiation of MSCs, including microRNAs (miRNAs). MiRNAs are small, single-stranded, non-coding RNAs of approximately 22 nucleotides that are able to regulate cell proliferation, differentiation and apoptosis by binding the 3' untranslated region (3'-UTR) of target mRNAs, which can be subsequently degraded or translationally silenced. MiRNAs control gene expression in osteogenic differentiation by regulating two crucial signaling cascades in osteogenesis: the transforming growth factor-beta (TGF-β)/bone morphogenic protein (BMP) and the Wingless/Int-1(Wnt)/β-catenin signaling pathways. This review provides an overview of the miRNAs involved in osteogenic differentiation and how these miRNAs could regulate the expression of target genes.

MicroRNAs regulating TGFβ and BMP signaling in the osteoblast lineage

This review showcases miRNAs contributing to the regulation of bone forming osteoblasts through their effects on the TGFβ and BMP pathways, with a focus on ligands, receptors and SMAD-mediated signaling. The goal of this work is to provide a basis for broadly understanding the contribution of miRNAs to the modulation of TGFβ and BMP signaling in the osteoblast lineage, which may provide a rationale for potential therapeutic strategies. Therefore, the search strategy for this review was restricted to validated miRNA-target interactions within the canonical TGFβ and BMP signaling pathways; miRNA-target interactions based only bioinformatics are not presented. Specifically, this review discusses miRNAs targeting each of the TGFβ isoforms, as well as BMP2 and BMP7. Further, miRNAs targeting the signaling receptors TGFβR1 and TGFβR2, and those targeting the type 1 BMP receptors and BMPR2 are described. Lastly, miRNAs targeting the receptor SMADs, the common SMAD4 and the inhibitory SMAD7 are considered. Of these miRNAs, the miR-140 family plays a prominent role in inhibiting TGFβ signaling, targeting both ligand and receptor. Similarly, the miR-106 isoforms target both BMP2 and SMAD5 to inhibit osteoblastic differentiation. Many of the miRNAs targeting TGFβ and BMP signaling components are induced during fracture, mechanical unloading or estrogen deprivation. Localized delivery of miRNA-based therapeutics that modulate the BMP signaling pathway could promote bone formation.

Bleomycin: A novel osteogenesis inhibitor of dental follicle cells via a TGF-β1/SMAD7/RUNX2 pathway

BACKGROUND AND PURPOSE

Tooth eruption is a complicated process regulated by the dental follicles (DF). Our recent study discovered that tooth eruption was inhibited upon injection of bleomycin into DF. However, the mechanisms were unknown.

EXPERIMENTAL APPROACH

Human dental follicle cells (hDFCs) were treated by bleomycin or exogenous TGF-β1 or transfected by plasmids loading SMAD7 or shRNA targeting SMAD7, followed by osteogenesis induction assay and signalling analysis. Human fresh DF tissues and Wistar rats were used to further confirm bleomycin function.

KEY RESULTS

Bleomycin decreased expression of RUNX2 and osteogenic genes in hDFCs, reducing osteogenic capacity. TGF-β1 expression was up-regulated in bleomycin-treated hDFCs. The effects of exogenous TGF-β1 were similar to those of bleomycin in hDFCs. Additionally, compared to SMAD2/3, SMAD7 expression increased more in bleomycin- or TGF-β1-treated hDFCs. Overexpression of SMAD7 likewise significantly decreased RUNX2 expression and osteogenic capacity of hDFCs. Knockdown of SMAD7 markedly attenuated the inhibitory effects of bleomycin and TGF-β1 on osteogenic capacity and RUNX2 expression of hDFCs. Most importantly, changes in TGF-β1, SMAD7, and RUNX2 expressions were similar in the DF of rats and humans treated with bleomycin.

CONCLUSION AND IMPLICATIONS

SMAD7 was a negative regulator of osteogenic differentiation in DFCs through suppressing RUNX2 expression. Bleomycin or TGF-β1 inhibited osteogenic differentiation of DFCs via a TGF-β1/SMAD7/RUNX2 pathway. Our findings might be beneficial for enhancing the osteogenic activity of DFCs or inhibiting the eruption of undesirable teeth.

Current perspectives on inhibitory SMAD7 in health and disease

Transforming growth factor β (TGF-β) family members play an extensive role in cellular communication that orchestrates both early development and adult tissue homeostasis. Aberrant TGF-β family signaling is associated with a pathological outcome in numerous diseases, and in-depth understanding of molecular and cellular processes could result in therapeutic benefit for patients. Canonical TGF-β signaling is mediated by receptor-regulated SMADs (R-SMADs), a single co-mediator SMAD (Co-SMAD), and inhibitory SMADs (I-SMADs). SMAD7, one of the I-SMADs, is an essential negative regulator of the pleiotropic TGF-β and bone morphogenetic protein (BMP) signaling pathways. In a negative feedback loop, SMAD7 inhibits TGF-β signaling by providing competition for TGF-β type-1 receptor (TβRI), blocking phosphorylation and activation of SMAD2. Moreover, SMAD7 recruits E3 ubiquitin SMURF ligases to the type I receptor to promote ubiquitin-mediated proteasomal degradation. In addition to its role in TGF-β and BMP signaling, SMAD7 is regulated by and implicated in a variety of other signaling pathways and functions as a mediator of crosstalk. This review is focused on SMAD7, its function in TGF-β and BMP signaling, and its role as a downstream integrator and crosstalk mediator. This crucial signaling molecule is tightly regulated by various mechanisms. We provide an overview of the ways by which SMAD7 is regulated, including noncoding RNAs (ncRNAs) and post-translational modifications (PTMs). Finally, we discuss its role in diseases, such as cancer, fibrosis, and inflammatory bowel disease (IBD).

Dynamic of miRNA-101a-3p and miRNA-200a during Induction of Osteoblast Differentiation in Adipose-derived Mesenchymal Stem Cells

miRNAs are known as the cellular phenomena regulators that exert their effects in post-transcriptional level. Recent studies highlight the role of miRNAs in mesenchymal stem cells differentiation into osteoblasts. The purpose of this study was to recognize the pattern of miRNA-101a-3p and miRNA-200a expression during osteoblastic differentiation of human adipose tissue-derived mesenchymal stem cells. The cells were incubated in osteoblastic differentiation medium for a period of 21 days. Alizarin red S staining was performed to confirm the successful differentiation of adipose-derived mesenchymal stem cells into osteoblast cells. The expression levels of miRNA-101a-3p and miRNA-200a were analyzed by real-time PCR during 0, 7, 14, and 21 days after differentiation induction. Data exhibited the increase of extracellular red color deposition which was evident at the end of the incubation period. The expression of miRNA-101a-3p and miRNA-200a was up regulated during adipose-derived mesenchymal stem cells trans-differentiation into osteoblast-like cells. These miRNAs could be potential novel biomarkers for monitoring successful differentiation of mesenchymal stem cells toward osteoblasts.

The Role of MicroRNAs in Bone Metabolism and Disease

Bone metabolism is an intricate process involving various bone cells, signaling pathways, cytokines, hormones, growth factors, etc., and the slightest deviation can result in various bone disorders including osteoporosis, arthropathy, and avascular necrosis of femoral head. Osteoporosis is one of the most prevalent disorders affecting the skeleton, which is characterized by low bone mass and bone mineral density caused by the disruption in the balanced process of bone formation and bone resorption. The current pharmaceutical treatments such as bisphosphonates, selective estrogen receptor modulator, calcitonin, teriparatide, etc., could decrease the risk of fractures but have side-effects that have limited their long term applications. MicroRNAs (miRNAs) are one of many non-coding RNAs. These are single-stranded with a length of 19–25 nucleotides and can influence various cellular processes and play an important role in various diseases. Therefore, in this article, we review the different functions of different miRNA in bone metabolism and osteoporosis to understand their mechanism of action for the development of possible therapeutics.

Melatonin regulates tumor angiogenesis via miR-424-5p/VEGFA signaling pathway in osteosarcoma

Melatonin is recognized as an anti-angiogenic agent, but its function in the tumor microenvironment especially in osteosarcoma remains uncertain. Among the selected miRNAs, miR-205, miR-424, miR-140, miR-106, and miR-519 were upregulated by melatonin in osteosarcoma cells. The functional role of miR-424-5p in osteosarcoma was further analyzed using miR-424-5p mimic/inhibitor. VEGFA mRNA and protein expression were altered by miR-424-5p mimic/inhibitor transfection with and without melatonin treatment and it was further identified that the VEGFA 3'UTR is directly targeted by miR-424-5p using the luciferase reporter gene system. The conditioned medium from SaOS2 and MG63 cells treated with melatonin and/or transfected with miR-424-5p mimic/inhibitor was exposed to endothelial cells, and cell proliferation and migration was analyzed. MG-63 and SaOS2 cells are also transfected with miR-424-5p inhibitors and positioned on CAM vascular bed to study the angiogenic activity at both morphological and molecular level under melatonin treatment. Our observations demonstrate for the first time that, melatonin upregulated the expression of miR-424-5p in osteosarcoma inhibiting VEGFA. Furthermore, it suppresses tumor angiogenesis, modulating surrounding endothelial cell proliferation and migration as well as the morphology of blood vessels, and angiogenic growth factors. These findings suggest that melatonin could play a pivotal role in tumor suppression via miR-424-5p/VEGFA axis.

Zingerone Promotes Osteoblast Differentiation Via MiR-200c-3p/smad7 Regulatory Axis in Human Bone Mesenchymal Stem Cells

BACKGROUND Osteoblast differentiation is a critical process to maintain the stability of the bone homeostasis. Zingerone, 4-(4-hydroxy-3-methoxyphenyl)-2-butanone (ZG), isolated from ginger, performs a wide range of biological functions in human diseases. The objective of this paper was to clarify the role of ZG in human bone mesenchymal stem cells (hBMSCs) and associated mechanisms of ZG promoting osteoblast differentiation. MATERIAL AND METHODS The cytotoxicity of ZG was detected by MTT assay. The expression levels of miR-200c-3p, smad7, and osteoblast differentiation markers (alkaline phosphatase [ALP], osteocalcin [OC], osterix [OSX] and runt-related transcription factor 2 [RUNX2]) were assessed by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of smad7, ALP, OC, OSX, and RUNX2 were quantified by western blot analysis. The target mRNAs were predicted by bioinformatics tools TargetScan. The interaction between miR-200c-3p and smad7 was verified by luciferase reporter assay and RIP assay. RESULTS ZG was nontoxic to hBMSCs, and it accelerated osteoblast differentiation by inducing the expression of ALP, OC, OSX, and RUNX2. MiR-200c-3p was upregulated, but smad7 was downregulated in hBMSCs treated with ZG at different concentrations at different periods. Besides, miR-200c-3p positively regulated the expression of ALP, OC, OSX, and RUNX2 in ZG-induced hBMSCs. Moreover, miR-200c-3p targeted smad7 and strengthened the expression of ALP, OC, OSX, and RUNX2 in ZG-induced hBMSCs by downregulating smad7. CONCLUSIONS ZG contributed to osteoblast differentiation via miR-200c-3p/smad7 regulatory axis by promoting the expression of ALP, OC, OSX, and RUNX2 in hBMSCs.

Berberine encapsulated PEG-coated liposomes attenuate Wnt1/β-catenin signaling in rheumatoid arthritis via miR-23a activation

Bone erosion is a debilitating pathological process of osteopathic disorder like rheumatoid arthritis (RA). Current treatment strategies render low disease activity but with disease recurrence. To find an alternative, we designed this study with an aim to explore the underlying therapeutic effect of PEGylated liposomal BBR (PEG-BBR) against Wnt1/β-catenin mediated bone erosion in adjuvant-induced arthritic (AA) rat model and fibroblast-like synoviocytes (FLS) with reference to microRNA-23a (miR-23a) activity. Our initial studies using confocal microscopy and Near-Infrared Imaging (NIR) showed successful internalization of PEG-BBR and PEG-miR-23a in vitro and in vivo respectively and was retained till 48 h. The preferential internalization of PEG-BBR into the inflamed joint region significantly reduced the gene and protein level expression of major Wnt1 signaling mediators and reduced bone erosion in rats. Moreover, PEG-BBR treatment in FLS cells attenuated the gene and protein expression levels of FZD4, LRP5, β-catenin, and Dvl-1 through the induction of CYLD. Furthermore, inhibition of these factors resulted in reduced bone loss and increased calcium retainability by altering the RANKL/OPG axis. PEG-BBR treatment markedly inhibited the expression of LRP5 protein on par with the DKK-1 (LRP5/Wnt signaling inhibitor) and suppressed the transcriptional activation of β-catenin inside the cells. We further witnessed that miR-23a altered the expression levels of LRP5 through RNA interference. Overall, our findings endorsed that miR-23a possesses a multifaceted therapeutic efficiency like berberine in RA pathogenesis and can be considered as a potential candidate for therapeutic targeting of Wnt1/β-catenin signaling in RA disease condition.

Regulation of Runx2 by post-translational modifications in osteoblast differentiation

Osteogenesis is the process of new bone formation where transcription factors play an important role in controlling cell proliferation and differentiation. Runt-related transcription factor 2 (Runx2), a key transcription factor, regulates the differentiation of mesenchymal stem cells into osteoblasts, which further mature into osteocytes. Runx2 acts as a modulator such that it can either stimulate or inhibit the osteoblast differentiation. A defect/alteration in the expression/activity of this gene may lead to skeletal dysplasia. Runx2 thus serves as the best therapeutic model gene for studying bone and bone-related diseases. In this review, we briefly outline the regulation of Runx2 and its activity at the post-translational levels by the virtue of phosphorylation, acetylation, and ubiquitination in controlling the bone homeostasis.

Exosomal hsa-miR-21-5p derived from growth hormone-secreting pituitary adenoma promotes abnormal bone formation in acromegaly

Growth hormone-secreting pituitary adenoma (GHPA), a benign endocrine tumor located in the base of the skull, results in acromegaly. In addition to the mass effect of the tumor itself in the sellar region, GHPA can lead to the overgrowth of almost every organ. Previous findings indicated that the processes underlying acromegaly were partly attributable to hyperactivity of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis. However, the mechanisms driving this syndrome remains largely unknown. Additionally, the roles of GHPA-derived exosomes, which contain functional microRNAs and proteins that manipulate target cell proliferation and differentiation in distal extremities, are also unknown. In this study, we demonstrated that GHPA exosomes promote bone formation in vitro and trabecula number in vivo. The mechanism of increased trabecula formation may be attributable to GHPA exosome-induced osteoblast proliferation via increased cell viability and DNA replication. We further discovered that exosomal hsa-miR-21-5p plays a distinct role from the GH/IGF-1 axis in these processes. Accordingly, the results of this study provide a novel mechanism whereby GHPA influences distal extremities and a new perspective for treating GHPA.

Noncoding RNA miR-205-5p mediates osteoporosis pathogenesis and osteoblast differentiation by regulating RUNX2

As a kind of noncoding RNAs, microRNAs (miRNAs) play important roles in disease pathogenesis by regulating gene expression. However, the molecular mechanism of miRNAs in osteoporosis remains largely unknown. In the present study, we aim to explore the genome-wide miRNAs expression profile and the regulatory mechanism of miR-205-5p in osteoporosis. A total of 72 differentially expressed miRNAs were identified in osteoporosis via microarray technology and bioinformatics analysis. We focused on one of the abnormally expressed miRNAs, miR-205-5p, which was previously unknown in osteoporosis. Quantitative real-time polymerase chain reaction (qRT-PCR) results showed that miR-205-5p was upregulated in osteoporosis samples and its expression was gradually decreased during osteogenic differentiation. Besides, miR-205-5p overexpression could inhibit the activity of osteoblast markers, including collagen, type I, α 1 (COL1A1) and alkaline phosphatase (ALP) while miR-205-5p inhibition showed the opposite results. Moreover, bioinformatics analysis identified the potential targets of miR-205-5p, including runt-related transcription factor 2 (RUNX2), SMAD1 and BCL6, etc. The dual-luciferase reporter assay confirmed RUNX2 was directly targeted by miR-205-5p. Furthermore, the rescue experiments showed that RUNX2 overexpression could significantly weaken the effect of miR-205-5p on osteoblast markers, indicating that miR-205-5p may inhibit osteogenic differentiation by targeting RUNX2.

miR-203a-3p.1 is involved in the regulation of osteogenic differentiation by directly targeting Smad9 in MM-MSCs

MicroRNAs (miRNAs) have emerged as important regulators of bone development and regeneration. The aim of the present study was to determine whether miR-203a-3p.1 is involved in osteogenic differentiation of multiple myeloma (MM)-mesenchymal stem cells (MSCs) and the potential underlying mechanism. MSCs were isolated from patients with MM and normal subjects and confirmed by flow cytometry using specific surface markers. The osteogenic differentiation capacity of MM-MSCs was identified by Alizarin Red S calcium deposition staining and reverse transcription-quantitative PCR (RT-qPCR) of typical osteoblast differentiation markers. The role of miR-203a-3p.1 in the osteoblast differentiation of MM-MSCs was determined by gain or loss of function experiments. The target of miR-203a-3p.1 was identified using bioinformatics (including the miRNA target prediction database TargetScan, miRDB, DIANA TOOLS and venny 2.1.0), luciferase reporter assay, RT-qPCR and western blotting. The expression levels of proteins involved in the Wnt3a/β-catenin signaling pathway were detected by western blot analysis. The results revealed that the osteogenic differentiation capacity of MM-MSCs was reduced when compared with normal (N)-MSCs, as demonstrated by a decrease in calcium deposition and mRNA expression of typical osteoblast differentiation markers, including ALP, OPN and OC. In addition, miR-203a-3p.1 was downregulated in N-MSCs following osteoblast induction, whereas no changes were observed in MM-MSCs. The downregulation of miR-203a-3p.1 resulted in increased osteogenic potential, as indicated by the increase in the mRNA expression levels of the typical osteoblast differentiation markers, including alkaline phosphatase (ALP), osteopontin (OPN) and osteocalcin (OC). Bioinformatics and luciferase reporter assay analysis indicated that mothers against decapentaplegic homolog 9 (Smad9) may be a direct target of miR-203a-3p.1 in N-MSCs. The RT-qPCR and western blot assays revealed that overexpression of smad9 significantly enhanced the effect of miR-203a-3p.1 inhibitors on osteoblast markers, which indicated that miR-203a-3p.1 inhibitors may regulate the osteogenic differentiation of MM-MSCs by upregulating Smad9. In addition, the Wnt3a/β-catenin signaling pathway was activated following miR-203a-3p.1 inhibition. These results suggest that miR-203a-3p.1 may serve an important role in the osteogenic differentiation of MM-MSCs by regulating Smad9 expression.

Regulation of Histone Deacetylases by MicroRNAs in Bone

Formation of new bone by osteoblasts is mediated via the activation of signaling pathways, such as TGF-β, BMP, and Wnt. A number of transcription factors participate in the signaling cascades that are tightly regulated by other regulatory factors. Histone deacetylases (HDACs) are one such class of regulatory factors that play an essential role in influencing chromatin architecture and regulate the expression of the genes that play a role in osteoblast differentiation by the mechanism of deacetylation. Four classes of HDACs have been identified namely, class I, class II A, class II B, class III and class IV. MicroRNAs (miRNAs) are small fragments of non-coding RNAs typically 19-25 nucleotides long that target mRNAs to upregulate or downregulate gene expression at a post-transcriptional level. A number of miRNAs that target HDACs in bone have been recently reported. Hence, in this review, we elaborate on the various miRNAs that target the different classes of HDACs and impact of the same on osteogenesis.

Identification of functional lncRNAs based on competing endogenous RNA network in osteoblast differentiation

Adult human mesenchymal stem cells have the potential to differentiate into osteoblast, which plays crucial roles in bone regeneration and repair. Some transcriptional factors (TFs), such as BMP-2 and RUNX2, have been demonstrated to control the differentiation processes. It is important to discover more key regulators in osteoblast differentiation. Recently, some studies found long noncoding RNAs (lncRNAs) participating in osteoblast differentiation, such as MALAT1, DANCR, and ANCR. In this study, we performed a network-based computational analysis to investigate the lncRNA-messenger RNA (mRNA) crosstalks via integrating microRNA (miRNA)-RNA interactions, gene coexpression, and protein-protein interactions. First, multiple topology analyses were performed to osteoblast-differentiation-related lncRNA-mRNA network (ODLMN). Several lncRNAs with central topology structures were identified as key regulators. Results showed that these lncRNAs participated in osteoblast differentiation via phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase, and Ras signals. Previous studies have demonstrated that lncRNAs exert functions by involving in close modules. Second, after performing module searching in ODLMN, two functional modules were identified, which played crucial roles through involving in PI3K/protein kinase B, cyclic adenosine 3',5'-monophosphate, and hypoxia-inducible factor 1 pathways. Third, a subset of core lncRNA-TF crosstalks that might form feedback loops to control the biological processes in osteoblast differentiation was identified. These core lncRNA-TF feedback loops showed more TF binding affinity than other lncRNAs. All these results can help us to uncover the molecular mechanism and provide new targets for bone regeneration and repair.

Regulation of Runx2 by MicroRNAs in osteoblast differentiation

Bone is one of the most dynamic organs in the body that continuously undergoes remodeling through bone formation and resorption. A cascade of molecules and pathways results in the osteoblast differentiation that is attributed to osteogenesis, or bone formation. The process of osteogenesis is achieved through participation of the Wnt pathway, FGFs, BMPs/TGF-β, and transcription factors such as Runx2 and Osx. The activity and function of the master transcription factor, Runx2, is of utmost significance as it can induce the function of osteoblast differentiation markers. A number of microRNAs [miRNAs] have been recently identified in the regulation of Runx2 expression/activity, thus affecting the process of osteogenesis. miRNAs that target Runx2 corepressors favor osteogenesis, while miRNAs that target Runx2 coactivators inhibit osteogenesis. In this review, we focus on the regulation of Runx2 by miRNAs in osteoblast differentiation and their potential for treating bone and bone-related diseases.

TGF-β1-stimulation of matrix metalloproteinase-13 expression by down-regulation of miR-203a-5p in rat osteoblasts

Transforming growth factor-beta1 (TGF-β1) is a pleiotropic and ubiquitous cytokine involved in bone development and bone remodeling. Matrix metalloproteinase-13 (MMP13) plays a role in the degradation of the extracellular matrix (ECM), and the regulation of this gene is critical in bone remodeling. We previously reported that TGF-β1 stimulates MMP13 expression in rat osteoblasts. Recently, studies have examined the regulation of bone metabolism by microRNAs (miRNAs) to determine their therapeutic potential in osteogenesis. Here, we assessed the effect of TGF-β1 on down-regulation of miRNAs that target MMP13 and stimulation of MMP13 expression in osteoblasts. We used in silico analysis and identified 11 specific miRNAs which directly target rat MMP13. Among these miRNAs, miR-203a-5p expression was significantly decreased by TGF-β1-treatment in rat osteoblasts. Transient transfection of a miR-203a-5p mimic into rat osteoblasts reduced MMP13 expression. A luciferase reporter assay confirmed a direct targeting of miR-miR-203a-5p with the 3' untranslated regions of the MMP13 gene. Hence, we suggest that TGF-β1 stimulated down-regulation of miR-203a-5p, resulting in the stimulation of MMP13 expression in rat osteoblasts. Thus, identification of the role of miR-203a-5p via TGF-β1 and MMP13 in bone remodeling indicated its potential as a biomarker or therapeutic agent for treating bone and bone-related diseases.

Osteogenic potential of zingerone, a phenolic compound in mouse mesenchymal stem cells

Zingerone, 4-(4-hydroxy-3-methoxyphenyl)-2-butanone (Zg), a phenolic compound isolated from ginger is reported to have anti-inflammatory and antidiabetic properties. However, its role in the promotion of osteogenesis is not known. In this study, we investigated the therapeutic effect of Zg on osteogenesis at the cellular and molecular levels. Zg treatment was nontoxic to mouse mesenchymal stem cells (mMSCs). At the cellular level, it enhanced osteoblast differentiation as evidenced by more calcium deposits. At the molecular level, Zg stimulated the expression of Runx2 (a bone transcription factor) and other marker genes of osteoblast differentiation in mMSCs. Recent studies indicated that microRNAs (miRNAs) regulate bone metabolism, and we identified that Zg treatment in mMSCs upregulated mir-590, a positive regulator of Runx2 by targeting Smad7, an antagonist of TGF-β1 signaling. Thus, the osteogenic potential of Zg would be beneficial for treating bone and bone-related diseases.

Hypoxia-responsive miRNA-21-5p inhibits Runx2 suppression by targeting SMAD7 in MC3T3-E1 cells

Sustained hypoxia inhibits osteogenesis and osteoblast differentiation by downregulating the expression of runt‐related transcription factor 2 (Runx2). MicroRNAs (miRNAs) have been shown to regulate osteogenesis and osteoblast differentiation. In the present study, we profiled miRNAs, with microRNA array and quantitative real‐time polymerase chain reaction (RT‐PCR) methods, in mouse osteoblast (MC3T3‐E1) cells under hypoxia. Then, we investigated regulation by miRNA‐21‐5p on the expression of Runx2 and other osteoblast differentiation‐associated markers via gain‐of‐function and loss‐of‐function strategies. We found that expression of miRNA‐21‐5p, miRNA‐210‐5p, and other eight miRNAs was upregulated significantly in hypoxia‐treated MC3T3‐E1 cells. miRNA‐21‐5p overexpression downregulated the expression of the mRNA and protein of suppressor of mothers against decapentaplegic (SMAD7) markedly, the 3′‐untranslated region (3′‐UTR) of which was highly homologous with the miRNA‐21‐5p sequence. miRNA‐21‐5p overexpression upregulated the protein expression of Runx2 in hypoxia‐treated MC3T3‐E1 cells, although mRNA expression of Runx2 and other osteoblast differentiation‐associated molecules (eg, osteocalcin, procollagen type 1 amino‐terminal propeptide, P1NP) were not regulated by it; such upregulation was SMAD7‐dependent. In conclusion, hypoxia‐responsive miRNA‐21‐5p promoted Runx2 expression (at least in part) by targeting the 3′‐UTR and downregulating SMAD7 expression. Our study suggests a protective role of miRNA‐21‐5p in promoting osteoblast differentiation under hypoxia.

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.

MicroRNA-92a-1-5p influences osteogenic differentiation of MC3T3-E1 cells by regulating β-catenin

Osteoblastic differentiation is a complex process that is critical for proper bone formation. An increasing number of studies have suggested that microRNAs (miRNAs) are pivotal regulators in various physiological and pathological processes, including osteogenesis. Here, we discuss the influence of miRNA-92a-1-5p on osteogenic differentiation. We found that miR-92a-1-5p was obviously downregulated during osteogenic differentiation of MC3T3-E1 cells. Gain-of-function and loss-of-function experiments revealed that miR-92a-1-5p was a negative regulator of osteogenic differentiation. Experimental validation demonstrated that β-catenin, which acts as a positive regulator of osteogenic differentiation, was negatively regulated by miR-92a1-5p. The findings of this study provide new insights into the possibility of miR-92a1-5p being a potential therapeutic target in the management of bone regeneration-related diseases.

MicroRNA-590-5p antagonizes the inhibitory effect of high glucose on osteoblast differentiation by suppressing Smad7 in MC3T3-E1 cells

Objective

MicroRNA-590-5p (miR-590-5p) has been reported to stimulate osteoblast differentiation; however, its effect in diabetic osteoporosis remains unknown. This study investigated the effect of miR-590-5p on high glucose (HG)-suppressed osteoblast differentiation.

Methods

The effect of HG on MC3T3-E1 cell survival was assessed using the MTT assay. The expression levels and activities of osteoblastic proteins were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR), alkaline phosphatase (ALP) assay, and immunoblotting assay. Tumor growth factor-β (TGF-β) signaling in MC3T3-E1 cells was assessed using luciferase assay, qRT-PCR, and immunoblotting. Mineralized nodule formation in MC3T3-E1 cells was examined by using the mineralization assay.

Results

When MC3T3-E1 cells were exposed to HG conditions, there was significant downregulation of miR-590-5p and osteoblastic proteins (e.g., collagen I, Runx2, and ALP); in contrast, Smad7 was upregulated. Furthermore, miR-590-5p targeted Smad7 and inhibited its expression. Additionally, overexpression of miR-590-5p significantly promoted osteoblast growth and differentiation by upregulating TGF-β signaling in HG-treated MC3T3-E1 cells.

Conclusions

Collectively, the results showed that miR-590-5p was involved in osteogenesis; moreover, miR-590-5p may represent a potential target for the treatment of diabetic osteoporosis.

Coxsackievirus B infection induces the extracellular release of miR-590-5p, a proviral microRNA

Coxsackievirus B is a significant human pathogen and is a leading cause of myocarditis. We and others have observed that certain enteroviruses including coxsackievirus B cause infected cells to shed extracellular vesicles containing infectious virus. Recent reports have shown that vesicle-bound virus can infect more efficiently than free virus. Though microRNAs are differentially regulated in cells following infection, few have been associated with the vesicles shed from infected cells. Here we report exclusive trafficking of specific microRNAs into viral vesicles compared to vesicles from non-infected cells. We found that the most highly-expressed unique microRNA in viral vesicles was miR-590-5p, which facilitates prolonged viral replication by blocking apoptotic factors. Cells over-expressing this miR were significantly more susceptible to infection. This may be a mechanism by which coxsackievirus B boosts subsequent rounds of infection by co-packaging virus and a select set of pro-viral microRNAs in extracellular vesicles.

Parathyroid hormone-stimulation of Runx2 during osteoblast differentiation via the regulation of lnc-SUPT3H-1:16 (RUNX2-AS1:32) and miR-6797-5p

Parathyroid hormone (PTH) acts as a regulator of calcium homeostasis and bone remodeling. Runx2, an essential transcription factor in bone, is required for osteoblast differentiation. Noncoding RNAs such as long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) play crucial roles in regulating gene expression in osteoblasts. In this study, we investigated the effects of PTH on osteoblast differentiation via Runx2, lncRNA, and miRNA expression in human bone marrow stromal cells (hBMSCs) and human osteoblastic cells (MG63). PTH-treatment of hBMSCs for 24 h, 7 days, and 14 days stimulated Runx2 mRNA expression. Using bioinformatics tools, we identified 17 lncRNAs originating from human Runx2 gene. Among these, lnc-SUPT3H-1:16 (RUNX2-AS1:32) expression was highly up-regulated by the 7 d PTH-treatment in hBMSCs. We also identified miR-6797-5p as the putative target of lnc-SUPT3H-1:16 and Runx2 using bioinformatics tools. PTH-treatment increased the expression of miR-6797-5p in hBMSCs, and overexpression of miR-6797-5p decreased osteoblast differentiation in MG63 cells, suggesting a role for lnc-SUPT3H-1:16 as sponge molecule. A luciferase gene reporter assay identified direct targeting of miR-6797-5p with lnc-SUPT3H-1:16 and 3'UTR Runx2 in MG63 cells. Thus, PTH stimulated the expression of lnc-SUPT3H-1:16, miR-6797-5p and Runx2, and due to the sponging mechanism of lnc- SUPT3H-1:16 towards miR-6797-5p, Runx2 was protected, resulting in the promotion of osteoblast differentiation.

Berberine modulates ASK1 signaling mediated through TLR4/TRAF2 via upregulation of miR-23a

The current study was designed to explore the underlying therapeutic effect of berberine (BBR), an alkaloid compound against LPS (1 μg/ml)/TNFα (10 ng/ml) mediated apoptosis signal-regulating kinase 1 (ASK1) signaling in RAW 264.7 macrophages and adjuvant-induced arthritic synovial macrophages (AA-SM) with relation to miR-23a levels. LPS and TNFα stimulation abrogated the expression of miR-23a resulting in TLR4/TRAF2 mediated ASK1 activation and downstream phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK). BBR (25-75 μM) treatment ameliorated the gene expression levels of TLR4, TRAF2, TNFα, IL-6, and IL-23 through the upregulation of miR-23a. Subsequently, BBR suppressed the levels of TLR4/TRAF2 mediated phosphorylation of ASK1/p38 and attenuated the expression of various pro-inflammatory cytokines (TNFα, IL-6 & IL-23) in RAW 264.7 macrophages and AA-SM cells. BBR was able to counteract these factors through activation of miR-23a levels in LPS/TNFα stimulated RAW 264.7 macrophages and AA-SM cells. NQDI1 (30 μM) treatment inhibited ASK1 activation resulting in basal levels of miR-23a, owing to the conclusion that ASK1 activation downregulates miR-23a levels inside the cells. Overall, our current findings predict that BBR is a potential candidate for therapeutic targeting of TLR4/TRAF2 mediated ASK1 activation in inflammatory and in RA pathogenesis possibly through post-transcriptional gene silencing via upregulation of miR-23a.

Syringic acid, a phenolic acid, promotes osteoblast differentiation by stimulation of Runx2 expression and targeting of Smad7 by miR-21 in mouse mesenchymal stem cells

Syringic acid (SA), a phenolic acid, has been used in Chinese and Indian medicine for treating diabetes but its role in osteogenesis has not yet been investigated. In the present study, at the molecular and cellular levels, we evaluated the effects of SA on osteoblast differentiation. At the cellular level, there was increased alkaline phosphatase (ALP) activity and calcium deposition by SA treatment in mouse mesenchymal stem cells (mMSCs). At the molecular level, SA treatment of these cells stimulated expression of Runx2, a bone transcription factor, and of osteoblast differentiation marker genes such as ALP, type I collagen, and osteocalcin. It is known that Smad7 is an antagonist of TGF-β/Smad signaling and is a negative regulator of Runx2. microRNAs (miRNAs) play a key role in the regulation of osteogenesis genes at the post-transcriptional level and studies have reported that Smad7 is one of the target genes of miR-21. We found that there was down regulation of Smad7 and up regulation of miR-21 in SA-treated mMSCs. We further identified that the 3'-untranslated region (UTR) of Smad7 was directly targeted by miR-21 in these cells. Thus, our results suggested that SA promotes osteoblast differentiation via increased expression of Runx2 by miR-21-mediated down regulation of Smad7. Hence, SA may have potential in orthopedic applications.