Expression profiling of microRNAs in human bone tissue from postmenopausal women

Converse modulation of Wnt/β-catenin signaling during expansion and differentiation phases of Infrapatellar fat pad-derived MSCs for improved engineering of hyaline cartilage

Mesenchymal stem cells (MSCs) are potential candidates in cell-based therapy for cartilage repair and regeneration. However, during chondrogenic differentiation, MSCs undergo undesirable hypertrophic maturation. This poses a risk of ossification in the neo-tissue formed that eventually impedes the clinical use of MSCs for cartilage repair. TGF-β is a potent growth factor used for chondrogenic differentiation of MSCs, however, its role in hypertrophy remains ambiguous. In the present work, we decipher that TGF-β activates Wnt/β-catenin signaling through SMAD3 and increases the propensity of Infrapatellar fat pad derived MSCs (IFP-MSCs) towards hypertrophy. Notably, inhibiting TGF-β induced Wnt/β-catenin signaling suppresses hypertrophic progression and enhances chondrogenic ability of IFP-MSCs in plasma hydrogels. Additionally, we demonstrate that activating Wnt signaling during expansion phase, promotes proliferation and reduces senescence, while improving stemness of IFP-MSCs. Thus, conversely modulating Wnt signaling in vitro during expansion and differentiation phases generates hyaline-like cartilage with minimal hypertrophy. Importantly, pre-treatment of IFP-MSCs encapsulated in plasma hydrogel with Wnt modulators followed by subcutaneous implantation in nude mice resulted in formation of a cartilage tissue with negligible calcification. Overall, this study provides technological advancement on targeting Wnt/β-catenin pathway in a 3D scaffold, while maintaining the standard chondro-induction protocol to overcome the challenges associated with the clinical use of MSCs to engineer hyaline cartilage.

Wnt antagonism without TGFβ induces rapid MSC chondrogenesis via increasing AJ interactions and restricting lineage commitment

Human mesenchymal stem cells (MSCs) remain one of the best cell sources for cartilage, a tissue without regenerative capacity. However, MSC chondrogenesis is commonly induced through TGFβ, a pleomorphic growth factor without specificity for this lineage. Using tissue- and induced pluripotent stem cell-derived MSCs, we demonstrate an efficient and precise approach to induce chondrogenesis through Wnt/β-catenin antagonism alone without TGFβ. Compared to TGFβ, Wnt/β-catenin antagonism more rapidly induced MSC chondrogenesis without eliciting off-target lineage specification toward smooth muscle or hypertrophy; this was mediated through increasing N-cadherin levels and β-catenin interactions-key components of the adherens junctions (AJ)-and increasing cytoskeleton-mediated condensation. Validation with transcriptomic analysis of human chondrocytes compared to MSCs and osteoblasts showed significant downregulation of Wnt/β-catenin and TGFβ signaling along with upregulation of α-catenin as an upstream regulator. Our findings underscore the importance of understanding developmental pathways and structural modifications in achieving efficient MSC chondrogenesis for translational application.

Three functional polymorphisms in CCDC170 were associated with osteoporosis phenotype

MicroRNAs (miRNAs) play essential roles in regulating bone formation and homeostasis. Genomic variations within miRNA target sites may therefore be important sources of genetic differences in osteoporosis risk. The function of CCDC170 in bone biology is still unclear. To verify the function of CCDC170, we knocked down CCDC170 in cells and mice and searched for miRNA recognition sites within CCDC170 using the TargetScan, miRNASNP, and miRBase databases. In this study, our results demonstrated that CCDC170 plays an important role in the positive regulation of bone formation. MiR-153-3p, miR-374b-3p, miR-4274, miR-572 and miR-2964a-5p inhibited CCDC170 expression in an allele-specific manner by binding GWAS lead SNPs rs6932603, rs3757322 and rs3734806. These findings may improve our understanding of the association between CCDC170, miRNAs, GWAS lead SNPs, and osteoporosis pathogenesis and may provide a potential therapeutic target for osteoporosis therapy.

Summary: CCDC170 may provide a potential therapeutic target for osteoporosis therapy.

Circulating miRNAs in bone health and disease

microRNAs have evolved as important regulators of multiple biological pathways essential for bone homeostasis, and microRNA research has furthered our understanding of the mechanisms underlying bone health and disease. This knowledge, together with the finding that active or passive release of microRNAs from cells into the extracellular space enables minimal-invasive detection in biofluids (circulating miRNAs), motivated researchers to explore microRNAs as biomarkers in several pathologic conditions, including bone diseases. Thus, exploratory studies in cohorts representing different types of bone diseases have been performed. In this review, we first summarize important molecular basics of microRNA function and release and provide recommendations for best (pre-)analytical practices and documentation standards for circulating microRNA research required for generating high quality data and ensuring reproducibility of results. Secondly, we review how the genesis of bone-derived circulating microRNAs via release from osteoblasts and osteoclasts could contribute to the communication between these cells. Lastly, we summarize evidence from clinical research studies that have investigated the clinical utility of microRNAs as biomarkers in musculoskeletal disorders. While previous reviews have mainly focused on diagnosis of primary osteoporosis, we have also included studies exploring the utility of circulating microRNAs in monitoring anti-osteoporotic treatment and for diagnosis of other types of bone diseases, such as diabetic osteopathy, bone degradation in inflammatory diseases, and monogenetic bone diseases.

MicroRNA levels in bone and blood change during bisphosphonate and teriparatide therapy in an animal model of postmenopausal osteoporosis

MicroRNAs control the activity of a variety of genes that are pivotal to bone metabolism. Therefore, the clinical utility of miRNAs as biomarkers and drug targets for bone diseases certainly merits further investigation. This study describes the use of an animal model of postmenopausal osteoporosis to generate a comprehensive dataset on miRNA regulation in bone tissue and peripheral blood during bone loss and specifically anti-resorptive and osteo-anabolic treatment. Forty-two Sprague-Dawley rats were randomized to SHAM surgery (n=10) or ovariectomy (OVX, n=32). Eight weeks after surgery, OVX animals were further randomized to anti-resorptive treatment with zoledronate (n=11), osteo-anabolic treatment with teriparatide (n=11), or vehicle treatment (n=10). After 12 weeks of treatment, bone and serum samples were used for microRNA analysis using next-generation sequencing (NGS), mRNA levels using RT-qPCR, and bone microarchitecture analysis using nanoCT. Ovariectomy resulted in loss of trabecular bone, which was fully rescued using osteo-anabolic treatment, and partially rescued using anti-resorptive treatment. NGS revealed that both, anti-resorptive and anabolic treatment had a significant impact on miRNA levels in bone tissue and serum: out of 426 detected miRNAs, 46 miRNAs were regulated by teriparatide treatment an d 10 by zoledronate treatment (p-adj.<0.1). Interestingly, teriparatide and zoledronate treatment were able to revert miRNA changes in tissue and serum of untreated OVX animals, such as the up-regulation of miR-203a-3p, a known osteo-inhibitory miRNA. We confirmed previously established mechanisms of miR-203a by analyzing its direct target Dlx5 in femoral head. Our data reveal a significant effect of ovariectomy-induced bone loss, as well as the two major types of anti-osteoporotic treatment on miRNA transcription in femoral head tissue. These changes are associated with altered activity of target genes relevant to bone formation, such as Dlx5. The observed effects of bone loss and treatment response on miRNA levels in bone are also reflected in the peripheral blood, suggesting the possibility of minimally-invasive monitoring of bone-derived miRNAs using liquid biopsies.

Inhibition of miR-22 promotes differentiation of osteoblasts and improves bone formation via the YWHAZ pathway in experimental mice

INTRODUCTION

In senile osteoporosis countering the age-mediated bone loss, promotion of osteoblastogenesis and identification of responsible micro-RNA (miR) would be a successful strategy.

MATERIAL AND METHODS

miR microarray screening was carried out to identify the suppressed miRs after real time polymerase chain reaction (RT-PCR) analysis in mesenchymal stem cells (MSCs) derived from adult bone marrow during the proliferation to the mineralization stage. The primary calvarial pre-osteoblasts (human) were harvested and received transfection of miR-22's antagomir or agomir in vitro. Bioinformatics study suggested YWHAZ as the favorable target gene. Next, YWHAZ knockdown was studied for its effect on differentiation of osteoblasts. For in vivo studies, ovariectomized or sham mice were injected with miR-22's antagomir for a period of 6 weeks. The stromal cells were isolated in the 6^th week for ex vivo experiments.

RESULTS

miR-22 was found to be down-regulated in bone marrow derived mesenchymal stem cells. miR-22's antagomir converted the pre-osteoblasts to a more differentiated and mineralized phenotype showing upregulated protein expression of COL1A1, ALP and CBFA1. The miR-22's antagomir suppressed YWHAZ, enhanced stability of CBFA1 and promoted the differentiation of osteoblasts. In vivo, miR-22's antagomir promoted mineralization and osteoblastogenesis, elevated bone strength and reversed the ovariectomy mediated bone loss in sham mice.

CONCLUSIONS

Inhibition of miR-22 may be a potential target for treating osteoporosis clinically. The findings hence suggest that inhibition of miR-22 may be an effective anabolic therapeutic approach in treating osteoporosis clinically.

MicroRNA-664a-5p promotes osteogenic differentiation of human bone marrow-derived mesenchymal stem cells by directly downregulating HMGA2

Osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (BMSCs) has been regarded as a central issue in fracture healing. MicroRNAs (miRNAs, miRs) participate in diverse physiological processes such as osteoblastic differentiation of BMSCs. In this study, we found that miR-664a-5p was upregulated during osteogenic differentiation of human BMSCs, and this upregulation positively correlated with the expression of osteogenic genes Runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), and osteocalcin (OCN). Overexpression of miR-664a-5p promoted the osteogenic differentiation of BMSCs, whereas a knockdown of miR-664a-5p suppressed it. Additionally, high-mobility group A2 (HMGA2) mRNA was identified as a direct target of miR-664a-5p that mediates the function of this miRNA. Overexpression of HMGA2 obviously attenuated miR-664a-5p-induced osteogenic differentiation of BMSCs. Thus, the newly identified miR-664a-5p-HMGA2 pathway expands our understanding of the mechanisms underlying the osteogenic differentiation of human BMSCs, may provide deeper insights into the regulation of this differentiation, and can point to new effective methods for treating osteoporosis.

MicroRNAs are Critical Regulators of Osteoclast Differentiation

PURPOSE OF REVIEW

Our goal is to comprehensively review the most recent reports of microRNA (miRNA) regulation of osteoclastogenesis. We highlight validated miRNA-target interactions and their place in the signaling networks controlling osteoclast differentiation and function.

RECENT FINDINGS

Using unbiased approaches to identify miRNAs of interest and reporter-3'UTR assays to validate interactions, recent studies have elucidated the impact of specific miRNA-mRNA interactions during in vitro osteoclastogenesis. There has been a focus on signaling mediators downstream of the RANK and CSF1R signaling, and genes essential for differentiation and function. For example, several miRNAs directly and indirectly target the master osteoclast transcription factor, Nfatc1 (e.g. miR-124 and miR-214) and Rho-GTPases, Cdc42 and Rac1 (e.g. miR-29 family).

SUMMARY

Validating miRNA expression patterns, targets, and impact in osteoclasts and other skeletal cells is critical for understanding basic bone biology and for fulfilling the therapeutic potential of miRNA-based strategies in the treatment bone diseases.

Circulating miR-103a-3p and miR-660-5p are associated with bone parameters in patients with controlled acromegaly

Background Biochemical control of GH/IGF-I excess in acromegaly (ACRO) is associated with persistent impairment of trabecular microstructure leading to increased risk of vertebral fractures. Circulating miRNAs modulate the activity of osteoblasts and osteoclasts, and may be potential biomarkers of osteoporosis. Aims Identify differentially expressed miRNAs in the serum of patients with controlled ACRO vs controls and correlate miRNA levels with both biochemical and structural bone parameters. Patients and methods Twenty-seven patients with controlled ACRO (11 males, 16 females; mean age, 48 ± 5 years; BMI, 28 ± 4 kg/m2) and 27 age-, gender- and BMI-matched controls were recruited. Areal BMD at lumbar spine and femur, and trabecular bone score were assessed; volumetric BMD was measured by quantitative computed tomography QCT-Pro (Mindways). Twenty miRNAs, chosen by their putative role in bone, were quantified in serum using real-time qPCR. Results In ACRO patients, miR-103a-3p and miR-191-5p were found overexpressed, whereas miR-660-5p was underexpressed (P < 0.001). miR-103a-3p levels were negatively associated with both trabecular vBMD at trochanter and serum osteoprotegerin concentrations (P < 0.05) and positively with vitamin D concentrations (P < 0.01) and total cross-sectional area of the femoral neck (P < 0.05). miR-660-5p levels were correlated with both trabecular vBMD at trochanter and OPG concentrations (P < 0.05), but were negatively associated with vitamin D levels (P < 0.05). A negative correlation between miR-103-a-3p and miR-660-5p was found in both groups (P < 0.001). Conclusions Circulating miR-103a-3p and miR-660-5p are differentially expressed in controlled ACRO patients and associated with bone structural parameters. miRNAs may be one of the mechanisms involved in the pathogenesis of bone disease and could be used as biomarkers in ACRO patients.

Pro-osteoporotic miR-320a impairs osteoblast function and induces oxidative stress

MicroRNAs (miRNAs) are important regulators of many cellular processes, including the differentiation and activity of osteoblasts, and therefore, of bone turnover. MiR-320a is overexpressed in osteoporotic bone tissue but its role in osteoblast function is unknown. In the present study, functional assays were performed with the aim to elucidate the mechanism of miR-320a action in osteoblastic cells. MiR-320a was either overexpressed or inhibited in human primary osteoblasts (hOB) and gene expression changes were evaluated through microarray analysis. In addition, the effect of miR-320a on cell proliferation, viability, and oxidative stress in hOB was evaluated. Finally, matrix mineralization and alkaline phosphatase activity were assessed in order to evaluate osteoblast functionality. Microarray results showed miR-320a regulation of a number of key osteoblast genes and of genes involved in oxidative stress. Regulation of osteoblast differentiation and ossification appeared as the best significant biological processes (PANTHER P value = 3.74E-05; and P value = 3.06E-04, respectively). The other enriched pathway was that of the cellular response to cadmium and zinc ions, mostly by the overexpression of metallothioneins. In hOBs, overexpression of miR-320a increased cell proliferation and oxidative stress levels whereas mineralization capacity was reduced. In conclusion, overexpression of miR-320a increased stress oxidation levels and was associated with reduced osteoblast differentiation and functionality, which could trigger an osteoporotic phenotype.

Identification of miR-708-5p in peripheral blood monocytes: Potential marker for postmenopausal osteoporosis in Mexican-Mestizo population

IMPACT STATEMENT

This is the first study in which hsa-miR-708-5p has been identified in peripheral blood monocytes (osteoclast precursors) and associated with postmenopausal osteoporosis through small RNA-Sequencing, in an Admixed Mexican Mestizo population. By conducting in silico and bioinformatic analyzes, we identified target genes and important signaling pathways involved in bone metabolism pointing hsa-miR-708-5p as a candidate marker for osteoporosis in Mexican population. These approaches provide a landscape of the post-transcriptional regulation, which can be useful for the management of postmenopausal osteoporosis along with the potential use of microRNAs as markers for its early detection.

MicroRNA-451 blockade promotes osteoblastic differentiation and skeletal anabolic effects by promoting YWHAZ-mediated RUNX2 protein stabilization

Background: senile osteoporosis researchers are now seeking to promote osteoblastogenesis and resultant bone formation to directly counteract age-related bone loss. Targeting microRNA (miRNA) activity in adult osteoblasts may be a successful therapeutic strategy for age-related bone loss. We investigated the mechanism(s) by which miRNAs negatively regulate osteoblastogenesis and bone formation in vitro and in vivo. Methods: we performed a miRNA microarray screen followed by PCR validation in adult bone marrow-derived mesenchymal stem cells during the proliferation-to-mineralization transition to identify downregulated miRNAs, most notably miR-451. Primary human calvarial pre-osteoblasts were isolated and transfected with miR-451's agomir or antagomir for in vitro assays. Bioinformatics analysis and in vitro experiments verified YWHAZ as a miR-451 target gene. We next investigated the effects of YWHAZ knockdown on osteoblastic differentiation. To examine the effects of miR-451's antagomir in vivo, we injected ovariectomized (OVX) or sham-operated mice with miR-451's antagomir over a period of six weeks. We isolated stromal cells from murine bone marrow on week six for further ex vivo experimentation. Results: miR-451's antagomir stimulated pre-osteoblast differentiation into a more differentiated, mineralized phenotype. This phenotype was associated with upregulated RUNX2, ALP, and COL1A1 protein expression. miR-451's antagomir derepresses YWHAZ expression, thereby enhancing RUNX2 protein stability and promoting osteoblastic differentiation. When injected in vivo, miR-451's antagomir promotes osteoblastogenesis and mineralization, reversed OVX-induced bone loss, and increased bone strength in OVX and sham-operated mice. Conclusions: miR-451 suppresses osteoblastogenesis in vitro and in vivo. miR-451 inhibition may serve as an effective anabolic therapeutic strategy in senile osteoporosis patients.