Changes of Circulating MicroRNAs in Response to Treatment With Teriparatide or Denosumab in Postmenopausal Osteoporosis

Week-by-week changes in serum levels of bone-related circulating microRNAs and bone turnover markers

MicroRNAs are involved in post-transcriptional regulation of gene expression. Due to their regulatory role, microRNAs are differently expressed during specific conditions in healthy and diseased individuals, so microRNAs circulating in the blood could be used as diagnostic and prognostic biomarkers for various diseases and conditions. We want to investigate the variability of circulating microRNAs and bone turnover markers in weekly time intervals in older women. In a single-site longitudinal study, a panel of 19 bone-related miRNAs was measured using the osteomiR RT-qPCR assay in serum samples of 35 postmenopausal women divided into 3 groups: healthy controls (n = 12), low BMD (n = 14), and vertebral fractures (n = 9). Blood samples for measurement of CTX, PINP, OC, and bone ALP were collected once per week for 8 weeks at 9:00 AM after overnight fasting. Serum samples from all participants were analyzed for 19 microRNA bone biomarkers and 4 bone turnover markers over 8 weeks. We analyzed the data using a mixed model analysis of variance and found no significant changes between week-by-week time points in any of the groups. To estimate intraindividual variability between weekly time points, we have calculated the median coefficient of variation (CV). This was between 28.4% and 80.2% for microRNA, with an assay CV of 21.3%. It was between 8.5% and 15.6% for bone turnover markers, with an assay CV of 3.5% to 6.5%. The intraindividual variability was similar between groups. Circulating microRNAs measured in serum had a higher weekly intraindividual variability than bone turnover markers due in part to a higher assay CV.

Investigating the Differential Circulating microRNA Expression in Adolescent Females with Severe Idiopathic Scoliosis: A Proof-of-Concept Observational Clinical Study

Adolescent Idiopathic Scoliosis (AIS) is the most common form of three-dimensional spinal disorder in adolescents between the ages of 10 and 18 years of age, most commonly diagnosed in young women when severe disease occurs. Patients with AIS are characterized by abnormal skeletal growth and reduced bone mineral density. The etiology of AIS is thought to be multifactorial, involving both environmental and genetic factors, but to date, it is still unknown. Therefore, it is crucial to further investigate the molecular pathogenesis of AIS and to identify biomarkers useful for predicting curve progression. In this perspective, the relative abundance of a panel of microRNAs (miRNAs) was analyzed in the plasma of 20 AIS patients and 10 healthy controls (HC). The data revealed a significant group of circulating miRNAs dysregulated in AIS patients compared to HC. Further bioinformatic analyses evidenced a more restricted expression of some miRNAs exclusively in severe AIS females. These include some members of the miR-30 family, which are considered promising regulators for treating bone diseases. We demonstrated circulating extracellular vesicles (EVs) from severe AIS females contained miR-30 family members and decreased the osteogenic differentiation of mesenchymal stem cells. Proteomic analysis of EVs highlighted the expression of proteins associated with orthopedic disease. This study provides preliminary evidence of a miRNAs signature potentially associated with severe female AIS and suggests the corresponding vesicular component may affect cellular mechanisms crucial in AIS, opening the scenario for in-depth studies on prognostic differences related to gender and grade.

Aberrant expression of miR-33a-3p/IGF2 in postmenopausal osteoporosis patients and its role and mechanism in osteoporosis

BACKGROUND

Postmenopausal osteoporosis (PMOP), the most frequent bone-related disease, is characterized by bone loss and fragile fractures, which is related to low bone density (BMD). This study aimed to illustrate the expression and mechanism of miR-33a-3p in osteoporosis.

METHODS

TargetScan and luciferase reporter assay were applied for verifying the relevance between miR-33a-3p and IGF2. Levels of miR-33a-3p, IGF2, Runx2, ALP and Osterix were checked using RT-qPCR and western blotting. hBMSCs proliferation, apoptosis and ALP activity were analyzed by MTT, flow cytometry (FCM) analysis and ALP detection kit, respectively. Moreover, the calcification of cells was assessed using Alizarin Red S staining. The average BMD was evaluated by dual-energy X-ray absorptiometry (DEXA) assay.

RESULTS

IGF2 was a target of miR-33a-3p. The level of miR-33a-3p was substantially higher and IGF2 expression was memorably lower in the serum of osteoporosis patients than that in healthy volunteers. Our results also pointed out that miR-33a-3p was reduced and IGF2 expression was enhanced during osteogenic differentiation. We concluded that miR-33a-3p negatively regulated the level of IGF2 in hBMSCs. Besides, miR-33a-3p mimic inhibited the osteogenic differentiation of hBMSCs via inhibiting the level of Runx2, ALP and Osterix and decreasing ALP activity. IGF2 plasmid dramatically reversed the influence of miR-33a-3p mimic on IGF2 expression, hBMSCs proliferation and apoptosis, and osteogenic differentiation of hBMSCs.

CONCLUSION

miR-33a-3p affected osteogenic differentiation of hBMSCs by targeting IGF2, indicating a potential use of miR-33a-3p as plasma biomarker and therapeutic target for postmenopausal osteoporosis.

Epigenetic regulation of bone remodeling and its role in the pathogenesis of primary osteoporosis

Discovery of molecular mechanisms of primary osteoporosis development is fundamental to understand the pathogenesis of musculoskeletal diseases in general and for identifying key links in the genetic and epigenetic regulation of bone remodelling genes. The number of identified molecular genetic markers for osteoporosis is increasing but there is a need to describe their functional interactions. These interactions have been determined to be associated with the control of expression of a number of transcription factors and the differentiation of mesenchymal stem cells through the pathway of osteoblastogenesis or adipogenesis, and monocytic precursors through the pathway of osteoclastogenesis. The results of epigenetic studies have significantly increased the understanding of the role of post-translational modifications of histones, DNA methylation and RNA interference in the osteoporosis pathogenesis and in bone remodelling. However, the knowledge should be systematised and generalised according to the results of research on the role of epigenetic modifiers in the development of osteoporosis, and the influence of each epigenetic mechanism on the individual links of bone remodelling during ontogenesis of humans in general, including the elderly, should be described. Understanding which mechanisms and systems are involved in the development of this nosology is of interest for the development of targeted therapies, as the possibility of using microRNAs to regulate genes is now being considered. Systematisation of these data is important to investigate the differences in epigenetic marker arrays by race and ethnicity. The review article analyses references to relevant reviews and original articles, classifies information on current advances in the study of epigenetic mechanisms in osteoporosis and reviews the results of studies of epigenetic mechanisms on individual links of bone remodelling.

Micro-RNA: A Future Approach to Personalized Diagnosis of Bone Diseases

Osteoporosis is a highly prevalent bone disease worldwide and the most studied bone-associated pathological condition. Although its diagnosis makes use of advanced and clinically relevant imaging and biochemical tools, the information suffers from several limitations and has little or no prognostic value. In this context, circulating micro-RNAs represent a potentially attractive alternative or a useful addition to the diagnostic arsenal and offer a greater prognostic potential than the conventional approaches. These short non-coding RNA molecules act as inhibitors of gene expression by targeting messenger RNAs with different degrees of complementarity, establishing a complex multilevel network, the basis for the fine modulation of gene expression that finally regulates every single activity of a cell. Micro-RNAs may passively and/or actively be released in the circulation by source cells, and being measurable in biological fluids, their concentrations may be associated to specific pathophysiological conditions. Mounting, despite debatable, evidence supports the use of micro-RNAs as markers of bone cell metabolic activity and bone diseases. Indeed, several micro-RNAs have been associated with bone mineral density, fractures and osteoporosis. However, concerns such as absence of comparability between studies and, the lack of standardization and harmonization of the methods, limit their application. In this review, we describe the pathophysiological bases of the association between micro-RNAs and the deregulation of bone cells activity and the processes that led to the identification of potential micro-RNA-based markers associated with metabolic bone diseases.

Circulating miRNAs Respond to Denosumab Treatment after Two Years in Postmenopausal Women with Osteoporosis

CONTEXT

MicroRNAs (miRNAs) are short, single-stranded, non-coding RNAs which regulate gene expression. They originate from various tissues including bone and regulate different biological mechanisms including bone metabolism.

OBJECTIVE

The aim of this project was to investigate circulating miRNAs as promising biomarkers for treatment monitoring in women with postmenopausal osteoporosis on denosumab (DMAB) therapy.

DESIGN, SETTING AND PATIENTS

In this prospective, observational, single-centre study twenty-one postmenopausal women treated with DMAB were included for a longitudinal follow-up of two years.

INTERVENTIONS AND MAIN OUTCOME MEASURES

Next-generation sequencing (NGS) was performed to screen for serological miRNAs at defined time points (baseline, month 6 and month 24). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was used to confirm NGS findings in the entire cohort. Bone turnover markers (BTM) P1NP and CTX, and bone mineral density (BMD) by Dual X-Ray absorptiometry (DXA) were assessed and correlated to miRNAs.

RESULTS

BMD at the hip (5,5%, p = 0.0006) and lumbar spine significantly increased (11,4%, p-value = 0.017) and CTX (64,1%, p < 0.0001) and P1NP (69,3%, p < 0.0001) significantly decreased during treatment. NGS analysis revealed significant changes in miRNAs after 2-years of DMAB treatment, but not after 6-months. Seven miRNAs were confirmed by RT-qPCR to be significantly changed during a 2-year course of DMAB treatment compared to baseline. Four of these were found to be mainly transcribed in blood cells including monocytes. Correlation analysis identified a significant correlation between change in miRNA and change in BTMs as well as BMD. Based on effect size and correlation strength, miR-454-3p, miR-26b-5p and miR-584-5p were defined as top biomarker candidates with the strongest association to the sustained effect of denosumab on bone in osteoporotic patients.

CONCLUSIONS

Two years of DMAB-treatment resulted in the upregulation of 7 miRNAs, four of which are mainly transcribed in monocytes indicating a potential impact of DMAB on circulating osteoclast precursor cells. These changes were associated to BMD gain and BTM suppression and could therefore be useful for monitoring DMAB-treatment response.

Interactome of PTH-Regulated miRNAs and Their Predicted Target Genes for Investigating the Epigenetic Effects of PTH (1-34) in Bone Metabolism

Osteoporosis is a metabolic bone disease that mostly affects the elderly. A lot of drugs are available, mostly with an antiresorptive effect but just a few with an osteoanabolic effect, meaning they promote bone building. PTH (1-34) or teriparatide is an osteoanabolic drug, but its efficacy varies between individuals. We performed a literature review and extracted a dataset of 62 microRNAs (miRNAs) from 10 different studies; predicted miRNA target interactions (MTIs) were obtained with the help of four software tools: DIANA, miRWalk, miRDB and TargetScan. With the construction of an interactome of PTH-regulated miRNAs and their predicted target genes, we elucidated miR-146a-5p, miR-551b-5p, miR-205-3p, miR-33a-3p, miR-338-5p as miRNAs with the most interactions and miR-410-3p as the miRNA targeting bone-related pathways with the highest significance. These miRNAs could help in further understanding the mechanism of action of PTH on bone metabolism and osteoporosis. They also have the potential for novel network-based biomarkers for osteoporosis treatment efficacy and safety and as new therapeutic targets.

The effect of pharmacological cessation and restoration of menstrual cycle on bone metabolism in premenopausal women with endometriosis

INTRODUCTION

GnRH-analogs induce bone loss. We aimed to investigate the effects of goserelin-induced menstrual cessation (MC) and subsequent menstrual restoration (MR) on bone metabolism (BM).

METHODS

In this prospective cohort study, premenopausal women (PMW) with histologically verified endometriosis (n = 21) received goserelin monthly for 6 months (6 m) resulting in MC and were followed up for another 6 m after MR (12 m). Age- and BMI-matched healthy PMW (n = 20) served as controls for bone mineral density (BMD) measurements. The primary endpoint was changes in lumbar spine (LS)-BMD at 6 m and 12 m; Secondary endpoints were changes in femoral neck (FN)-BMD, bone turnover markers (P1NP and CΤx), sclerostin, and expression of bone-related circulating microRNAs (miRNAs) at 6 m and 12 m.

RESULTS

Goserelin-induced MC reduced LS- and FN-BMD at 6 m (both p < 0.001). From 6 m to 12 m, LS-BMD increased (p < 0.001) but remained below baseline values (p = 0.012), whereas FN-BMD remained stable (p = 1.000). CTx and P1NP levels increased at 6 m (both p < 0.001) and decreased at 12 m (p < 0.001 and p = 0.013, respectively), while CTx (p = 1.000) alone and not P1NP (p = 0.020) returned to baseline. Sclerostin levels did not change. Relative expression of miRNAs targeting RUNX 2 and beta-catenin was significantly downregulated at 6 m compared to baseline (p < 0.001), while the expression of miRNAs targeting osteoblast and osteoclast function at both directions demonstrated a robust increase (up to 400fold) at 12 m (p < 0.001).

CONCLUSIONS

Six months of goserelin-induced MC lead to significant bone loss associated with increased bone turnover and changes in the expression of bone-related miRNAs, changes that are only partially reversed at 6 m after MR.

Menopausal Transition: Prospective Study of Estrogen Status, Circulating MicroRNAs, and Biomarkers of Bone Metabolism

OBJECTIVE

Osteoporosis is associated with an impaired balance between bone resorption and formation, which in turn leads to bone loss and fractures. Many recent studies have underlined the regulatory role of microRNAs (miRNAs) in bone remodeling processes and their potential as biomarkers of osteoporosis. The purpose of this study was to prospectively examine the association of circulating miRNAs and bone biomarkers with estrogen status in women before and after oophorectomy, as well as in oophorectomized women on estrogen therapy.

METHODS

In this prospective study, we included 11 women before oophorectomy and hysterectomy and at 201 ± 24 days after the surgery. Another 11 women were evaluated 508 ± 127 days after oophorectomy and hysterectomy and after an additional 203 ± 71 days of estradiol treatment. Serum miRNAs were profiled by sequencing. Estrogen status and biomarkers of bone metabolism were quantified. Bone mineral density was assessed in the lumbar spine.

RESULTS

Our analysis revealed 17 miRNAs associated with estrogen levels. Of those miRNAs that were upregulated with estrogen deficiency and downregulated after estrogen therapy, miR-422a correlated with serum beta-carboxy-terminal type I collagen crosslinks (β-CTX) and procollagen 1 N-terminal propeptide (P1NP); and miR-1278 correlated with serum β-CTX, P1NP, osteocalcin, sclerostin, and Dickkopf-1(Dkk1). In contrast, we found an inverse association of miR-24-1-5p with estrogen status and a negative correlation with serum β-CTX, P1NP, osteoprotegerin, and sclerostin levels.

CONCLUSION

The reported miRNAs associated with estrogen status and bone metabolism could be potential biomarkers of bone pathophysiology and would facilitate studies on the prevention of postmenopausal osteoporosis. Our findings require validation in an extended cohort.

Longitudinal Changes of Circulating miRNAs During Bisphosphonate and Teriparatide Treatment in an Animal Model of Postmenopausal Osteoporosis

MicroRNAs regulate bone homeostasis, and circulating microRNAs have been proposed as novel bone biomarkers. The effect of anti-osteoporotic treatment on circulating microRNAs has not been described in detail. Therefore, we performed a comprehensive analysis of microRNA serum levels in ovariectomized (OVX) and sham-operated (SHAM) rats over 12 weeks of antiresorptive or osteoanabolic treatment. Forty-two Sprague Dawley rats underwent SHAM surgery (n = 10) or ovariectomy (n = 32). After 8 weeks, OVX rats were randomized to antiresorptive treatment with zoledronate (n = 11), osteoanabolic treatment with teriparatide (n = 11), or vehicle treatment (n = 10). Serum samples were collected at weeks 8, 12, 16, and 20 after surgery. A total of 91 microRNAs were analyzed by RT-qPCR in serum samples collected at week 20. Based on the results, 29 microRNAs were selected for longitudinal analysis at all four study time points. Changes in bone mineral density and microstructure were followed up by in vivo micro-CT and ex vivo nano-CT. Ovariectomy resulted in the loss of trabecular bone, which was reversed by osteoanabolic and antiresorptive treatment. Differential expression analysis identified 11 circulating miRNAs that were significantly regulated after treatment. For example, miR-107 and miR-31-5p increased in vehicle-treated OVX animals, whereas they decreased during teriparatide treatment. Additional miRNAs were identified that showed significant correlations to bone microstructure or bone miRNA expression, including miR-203a-3p, which exhibited a significant negative correlation to vertebral and tibial trabecular bone volume fraction (%). Longitudinal analysis confirmed eight microRNAs with significant changes in serum over time that were prevented by teriparatide and zoledronate treatment (miR-34a-5p, miR-31-5p, miR-30d-3p, miR-378a-5p) or teriparatide treatment only (miR-375-3p, miR-183-5p, miR-203a-3p, miR-203b-3p). Gene target network analysis identified WNT and Notch signaling as the main signaling pathways controlled by these miRNAs. Thus, ovariectomy results in time-dependent deregulation of circulating miRNAs compared with SHAM animals. Anti-osteoporotic treatments can rescue this effect, showing that bone-related miRNAs might act as novel biomarkers for treatment monitoring. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Circulating microRNAs Related to Bone Metabolism in HIV-Associated Bone Loss

The pathophysiology of human immunodeficiency virus (HIV)-associated bone loss is complex and to date largely unknown. In this study, we investigated serum expression of microRNAS (miRNAs) linked to bone metabolism in HIV-associated bone loss. This was a case-control study. Thirty male individuals with HIV infection (HIV+) and osteoporosis/osteopenia (HIV+/OP+) (cases) and 30 age-matched male HIV+ individuals with normal bone mass (HIV+/OP-) (controls) were included in the analysis. Thirty male individuals matched for age without HIV infection (HIV-), were also included as second controls. The selected panel of miRNAs was as follows: hsa-miRNA-21-5p; hsa-miRNA-23a-3p; hsa-miRNA-24-2-5p; hsa-miRNA-26a-5p; hsa-miRNA-29a-3p; hsa-miRNA-124-3p; hsa-miRNA-33a-5p; and hsa-miRNA-133a-3p. Within the cohort of HIV+ individuals, relative serum expression of miRNA-21-5p and miRNA-23a-3p was significantly lower (p < 0.001) while the expression of miRNA-24-2-5p was significantly higher (p = 0.030) in HIV+/OP+ compared to HIV+/OP-. Expression of miRNA-21-5p demonstrated a sensitivity of 84.6% and a specificity of 66.7 in distinguishing HIV+/OP+ individuals. Expression of circulating miRNAs related to bone metabolism; miRNA-23a-3p, miRNA-24-2-5p, and miRNA-21-5p is significantly altered in HIV+OP+ individuals, in line with data on other causes of osteoporosis, suggesting a common pattern of circulating miRNAs independent of the underlying cause.

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.

miR-133a silencing rescues glucocorticoid-induced bone loss by regulating the MAPK/ERK signaling pathway

BACKGROUND

Dysfunction of mesenchymal stem cells (MSCs) is recognized as critical to the pathogenesis of glucocorticoid-induced osteoporosis (GIO), suggesting the potential of MSC-targeting interventions for this disorder. As the miR-133a has been shown to play an important role in bone metabolism, we hypothesized that miR-133a may also be involved in GIO.

METHODS

In the in vitro study, we examined the effect of miR-133a antagomir on DEX-treated MSCs, including proliferation, apoptosis, osteoblast, and adipocyte differentiation, then, we explored the mechanism of these effects of miR-133a silencing through measuring the phosphorylation of ERK1/2 and its regulator FGFR1 via western blot and qRT-PCR. In the in vivo study, we developed a GIO rat model by injecting methylprednisolone and modulated the miR-133a expression in the femur by intramedullary injection of the miR-133a antagomir, and then micro-CT analyses and histological staining of the femurs were used to investigate the effect of miR-133a silencing on bone loss of the GIO rats.

RESULTS

qRT-PCR analysis indicated that glucocorticoid induced high miR-133a expression in MSCs and animal models. The in vitro study showed that miR-133a antagomir significantly promoted cell proliferation, viability, and osteoblast differentiation and inhibited adipocyte differentiation in DEX-treated MSCs. Furthermore, the expression of p-ERK1/2 and FGFR1 in DEX-treated MSCs was also upregulated by miR-133a antagomir. Then we investigated the effect of miR-133a silencing on the bone architecture of GIO models, micro-CT analysis showed that miR-133a antagomir attenuated the loss of bone mass and improved the trabecular and cortical parameters induced by methylprednisolone. Histological study showed that miR-133a silencing simultaneously increased bone formation and decreased marrow fat accumulation in GIO rats.

CONCLUSIONS

Our findings suggested that miR-133a is strongly associated with GIO and similar disorders induced by glucocorticoids in MSCs. Silencing miR-133a resulted in positive effects on GC-treated MSCs and on bone loss in GIO animal models. Moreover, the FGFR1-MAPK/ERK signaling may be involved in the protective effect of miR-133a silencing.

Exosomal hsa_circ_0006859 is a potential biomarker for postmenopausal osteoporosis and enhances adipogenic versus osteogenic differentiation in human bone marrow mesenchymal stem cells by sponging miR-431-5p

BACKGROUND

As one of the most common chronic diseases in the world, osteoporosis occurs especially in postmenopausal women. Circular RNAs (circRNAs) are emerging as major drivers in human disease. The aim of the present study was to analyse circRNA expression profiles in osteoporosis and to explore the clinical significance and the regulatory molecular mechanism of hsa_circ_0006859 during osteoporosis.

METHODS

Exosomes were isolated from clinically collected serum samples. A circRNA microarray was performed to screen differentially expressed circRNAs. Quantitative real-time PCR (qRT-PCR) and western blot were performed to analyse target gene mRNA expression and protein expression. Alizarin red staining (ARS) was performed to evaluate the mineralization ability of human bone marrow mesenchymal stem cells (hBMSCs). Oil Red O staining was performed to evaluate the lipid droplet formation ability of hBMSCs. Bioinformatics analysis and the luciferase reporter assay were performed to investigate the interaction between two genes.

RESULTS

Hsa_circ_0006859 was identified as one of the most upregulated circRNAs in the microarray analysis. Hsa_circ_0006859 in exosomes was upregulated in osteoporosis patients compared to healthy controls. Hsa_circ_0006859 differentiated osteopenia or osteoporosis patients from healthy controls with high sensitivity and specificity. Hsa_circ_0006859 suppressed osteoblastic differentiation and promoted adipogenic differentiation of hBMSCs. Hsa_circ_0006859 directly bound to miR-431-5p, and ROCK1 was identified as a novel target gene of miR-431-5p. Hsa_circ_0006859 is a competing endogenous RNA (ceRNA) of miR-431-5p that promotes ROCK1 expression. Hsa_circ_0006859 suppressed osteogenesis and promoted adipogenesis by sponging miR-431-5p to upregulate ROCK1.

CONCLUSIONS

Exosomal hsa_circ_0006859 is a potential biomarker for postmenopausal osteoporosis and controls the balance between osteogenesis and adipogenesis in hBMSCs by sponging miR-431-5p.

Epigenetic therapies of osteoporosis

The study of epigenetics reaches its 50th anniversary, however, its clinical application is gradually coming into the clinical setting. Osteoporosis is one of the major and widely diffused bone diseases. Pathogenic mechanisms at the epigenetic level may interfere with bone remodeling occurring during osteoporosis. Preclinical models were used to understand whether such events may interfere with the disease. Besides, observational clinical trials investigated epigenetic-related biomarkers. This effort leads to some epigenetic-related therapies in clinical trials for the treatment of osteoporosis. Bisphosphonates (BPs), target therapy blocking RANK/RANKL pathway, and anti-sclerostin antibody (SOST) are the main therapeutic approaches. However, future large trials will reveal whether epigenetic therapies of osteoporosis will remain a work in progress or data will become more robust in the real-world management of these frailty patients.

Identification of key non-coding RNAs and transcription factors regulators and their potential drugs for steroid-induced femoral head necrosis

Steroid-induced necrosis of femoral head (SINFH) is a femoral head necrotic disease caused by prolonged use of hormones. The detailed pathogenesis has not been fully demonstrated. In this study, we employed the bioinformatics approach to probe the roles of SINFH inhibitors. Core dysfunction modules related to SINFH was obtained. Meanwhile, GO and KEGG analysis of genes in dysfunction modules are carried out. Furthermore, the pivot prediction analysis of dysfunction modules related to ncRNA and transcription factor (TF) has been performed. The functions of the enriched modules were focused on multiple perspectives, including circulation, gland development, bone development and reconstruction, calcium production, and fatty acid metabolism regulation. The ncRNAs and TFs analysis showed that miR-322-5p, miR-124-3p, miR-125a-3p, and Ctnnb1 were important members of SINFH dysfunction. Drug targets suggested that Zinc and adenosine monophosphate may have an impact on SINFH dysfunction. SINFH was closely related to bone development and reconstruction.

Expression of Circulating MicroRNAs Linked to Bone Metabolism in Chronic Kidney Disease-Mineral and Bone Disorder

The pathophysiology of chronic kidney disease-mineral and bone disorder (CKD-MBD) is complex and multifactorial. Recent studies have identified a link between microRNAs (miRNAs) and bone loss. In this study, we investigated the expression of miRNAs in CKD-MBD. In this case-control study, we included thirty patients with CKD-MBD (cases) and 30 age- and gender-matched healthy individuals (controls). Bone mineral density (BMD) and trabecular bone score (TBS) evaluation was performed with dual X-ray absorptiometry. The selected panel of miRNAs included: hsa-miRNA-21-5p; hsa-miRNA-23a-3p; hsa-miRNA-24-2-5p; hsa-miRNA-26a-5p; hsa-miRNA-29a-3; hsa-miRNA-124-3p; hsa-miRNA-2861. The majority of cases had low BMD values. The relative expression of miRNA-21-5p was 15 times lower [fold regulation (FR): -14.7 ± 8.1, p = 0.034), miRNA-124-3p, 6 times lower (FR: -5.9 ± 4, p = 0.005), and miRNA-23a-3p, 4 times lower (FR: -3.8 ± 2.0, p = 0.036) in cases compared to controls. MiRNA-23a-3p was significantly and inversely correlated with TBS, adjusted for calcium metabolism and BMD values (beta = -0.221, p = 0.003, 95% CI -0.360, -0,081) in cases. In a receiver operating characteristic (ROC) analysis, expression of miRNA-124-3p demonstrated 78% sensitivity and 83% specificity in identifying CKD patents with osteoporosis. Serum expression of miRNAs related to osteoblasts (miRNA-23a-3p) and osteoclasts (miRNA-21-5p, miRNA-124-3p) is significantly altered in patients with CKD-MBD.

The Osteoporosis/Microbiota Linkage: The Role of miRNA

Hundreds of trillions of bacteria are present in the human body in a mutually beneficial symbiotic relationship with the host. A stable dynamic equilibrium exists in healthy individuals between the microbiota, host organism, and environment. Imbalances of the intestinal microbiota contribute to the determinism of various diseases. Recent research suggests that the microbiota is also involved in the regulation of the bone metabolism, and its alteration may induce osteoporosis. Due to modern molecular biotechnology, various mechanisms regulating the relationship between bone and microbiota are emerging. Understanding the role of microbiota imbalances in the development of osteoporosis is essential for the development of potential osteoporosis prevention and treatment strategies through microbiota targeting. A relevant complementary mechanism could be also constituted by the permanent relationships occurring between microbiota and microRNAs (miRNAs). miRNAs are a set of small non-coding RNAs able to regulate gene expression. In this review, we recapitulate the physiological and pathological meanings of the microbiota on osteoporosis onset by governing miRNA production. An improved comprehension of the relations between microbiota and miRNAs could furnish novel markers for the identification and monitoring of osteoporosis, and this appears to be an encouraging method for antagomir-guided tactics as therapeutic agents.

The roles of miRNA, lncRNA and circRNA in the development of osteoporosis

Osteoporosis is a common metabolic bone disease, influenced by genetic and environmental factors, that increases bone fragility and fracture risk and, therefore, has a serious adverse effect on the quality of life of patients. However, epigenetic mechanisms involved in the development of osteoporosis remain unclear. There is accumulating evidence that epigenetic modifications may represent mechanisms underlying the links of genetic and environmental factors with increased risk of osteoporosis and bone fracture. Some RNAs, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), have been shown to be epigenetic regulators with significant involvement in the control of gene expression, affecting multiple biological processes, including bone metabolism. This review summarizes the results of recent studies on the mechanisms of miRNA-, lncRNA-, and circRNA-mediated osteoporosis associated with osteoblasts and osteoclasts. Deeper insights into the roles of these three classes of RNA in osteoporosis could provide unique opportunities for developing novel diagnostic and therapeutic approaches to this disease.

miR-221-3p and miR-222-3p downregulation promoted osteogenic differentiation of bone marrow mesenchyme stem cells through IGF-1/ERK pathway under high glucose condition

OBJECTIVE

This study aims to investigate the roles of miR-221-3p and miR-222-3p in the regulation of osteogenic differentiation of bone marrow mesenchyme stem cells (BMSCs) under high glucose condition.

MATERIALS AND METHODS

The expreesions of miR-221-3p, miR-222-3p and insulin-like growth factor 1 (IGF-1) were detected by qRT-PCR. The protein levels of osteoblast-related proteins (Osterix, Runx-2 and Osteopontin) were detected by western blot. Whether miR-221-3p and miR-222-3p can target IGF-1 was assessed by dual luciferase reporter gene assay.

RESULTS

miR-221-3p and miR-222-3p were up-regulated in the mandibles of diabetic rats and BMSCs cultured in high glucose condition. Silencing miR-221-3p or/ and miR-222-3p increased ALP activity and up-regulated osteoblast-related protein levels, and the simultaneous silence the two miRNAs showed stronger effects on ALP activity and osteoblast-related protein levels. Next, we confirmed that miR-221-3p and miR-222-3p both targeted IGF-1 and cooperatively regulated its expression. Besides, miR-221-3p and miR-222-3p regulated ERK activation through IGF-1. Silencing miR-221-3p and miR-222-3p promoted osteogenic differentiation of BMSCs through IGF-1 under high glucose condition.

CONCLUSION

miR-221-3p and miR-222-3p inhibited osteogenic differentiation of BMSCs via IGF-1/ERK pathway under high glucose condition.

Serum Profile of microRNAs Linked to Bone Metabolism During Sequential Treatment for Postmenopausal Osteoporosis

CONTEXT

Serum expression of microRNAs (miRs) related to bone metabolism is affected by antiosteoporotic treatment.

OBJECTIVE

To investigate the effect of sequential treatments on miR expression in postmenopausal women with osteoporosis.

DESIGN

Observational, open label, nonrandomized clinical trial.

SETTING

A single-center outpatient clinic.

PATIENTS AND INTERVENTIONS

Denosumab (Dmab) was administered for 12 months in 37 women who were treatment-naïve (naïve group) (n = 11) or previously treated with teriparatide (TPTD group) (n = 20) or zoledronate (ZOL group) (n = 6).

MAIN OUTCOME MEASURES

Relative serum expression of miRs linked to bone metabolism at 3 and 6 months of Dmab treatment.

RESULTS

Baseline relative expression of miR-21a-5p, miR-23a-3p, miR-29a-3p, and miR-338-3p was higher in the TPTD group, while the relative expression of miR-21a-5p was lower in the ZOL group compared to the naïve group. Dmab decreased the relative expression of miR-21a-5p at 3 months (fold change [FC] 0.43, P < 0.001) and 6 months (FC 0.34, P < 0.001), and miR-338-3p and miR-2861 at 6 months (FC 0.31, P = 0.041; FC 0.52, P = 0.016, respectively) in the whole cohort. In subgroup analyses, Dmab decreased the relative expression of miR-21a-5p, miR-29a-3p, miR-338-3p, and miR-2861 at 3 months (FC 0.13, P < 0.001; FC 0.68, P = 0.044; FC 0.46, P = 0.012; and FC 0.16, P < 0.001, respectively) and 6 months (FC 0.1, P < 0.001; FC 0.52, P < 0.001; FC 0.04, P = 0.006; and FC 0.2, P < 0.001, respectively) only within the TPTD group.

CONCLUSIONS

TPTD treatment potentially affects the expression of the pro-osteoclastogenic miR-21a-5p and miRs related to the expression of osteoblastic genes RUNX2 (miR23a-3p), COL1 (miR-29a-3p), and HDAC5 (miR-2861), while sequential treatment with Dmab acts in the opposite direction.

Circulating fractures-related microRNAs distinguish primary hyperparathyroidism-related from estrogen withdrawal-related osteoporosis in postmenopausal osteoporotic women: A pilot study

Primary hyperparathyroidism (PHPT) represents a common cause of secondary osteoporosis in postmenopausal women, where the negative effect of estrogen withdrawal and that of hyperparathyroidism on bone mineralization coexist. Circulating microRNAs (miRNAs) expression profile has been correlated to both osteoporosis and fragility fractures. The study aimed to profile a set of miRNAs associated with osteoporotic fractures, namely miR-21-5p, miR-23a-5p, miR-24-2-5p, miR-24-3p, miR-93-5p, miR-100-5p, miR-122-5p, miR-124-3p, miR-125b-5p and miR-148-3p, in the plasma of 20 postmenopausal PHPT women. PHPT miRNAs profiles were compared with those detected in 10 age-matched postmenopausal non-PHPT osteoporotic women (OP). All the 10 miRNAs were detected in the plasma samples of both PHPT and OP women. The miRNA profiles clearly distinguished PHPT from OP samples, and identified within the PHPT group, two clusters differing for the PHPT severity, in term of ionized calcium and bone mineralization. In particular, miR-93-5p was significantly downregulated in PHPT samples, while miR-24-3p negatively correlated with the T-score at lumbar, femur neck and total hip sites. PHPT women who experienced osteoporotic fractures had plasma miR-24-3p levels higher than those detected in unfractured PHPT women. In conclusion, PHPT may modulate circulating fractures-related miRNAs, in particular, miR-93-5p, which may distinguish estrogen-related from PHPT-related osteoporosis.

Epigenetic Regulation of Skeletal Tissue Integrity and Osteoporosis Development

Bone turnover is sophisticatedly balanced by a dynamic coupling of bone formation and resorption at various rates. The orchestration of this continuous remodeling of the skeleton further affects other skeletal tissues through organ crosstalk. Chronic excessive bone resorption compromises bone mass and its porous microstructure as well as proper biomechanics. This accelerates the development of osteoporotic disorders, a leading cause of skeletal degeneration-associated disability and premature death. Bone-forming cells play important roles in maintaining bone deposit and osteoclastic resorption. A poor organelle machinery, such as mitochondrial dysfunction, endoplasmic reticulum stress, and defective autophagy, etc., dysregulates growth factor secretion, mineralization matrix production, or osteoclast-regulatory capacity in osteoblastic cells. A plethora of epigenetic pathways regulate bone formation, skeletal integrity, and the development of osteoporosis. MicroRNAs inhibit protein translation by binding the 3'-untranslated region of mRNAs or promote translation through post-transcriptional pathways. DNA methylation and post-translational modification of histones alter the chromatin structure, hindering histone enrichment in promoter regions. MicroRNA-processing enzymes and DNA as well as histone modification enzymes catalyze these modifying reactions. Gain and loss of these epigenetic modifiers in bone-forming cells affect their epigenetic landscapes, influencing bone homeostasis, microarchitectural integrity, and osteoporotic changes. This article conveys productive insights into biological roles of DNA methylation, microRNA, and histone modification and highlights their interactions during skeletal development and bone loss under physiological and pathological conditions.

Circulating miRNAs: A New Opportunity in Bone Fragility

Osteoporosis, one of the leading causes of bone fractures, is characterized by low bone mass and structural deterioration of bone tissue, which are associated with a consequent increase in bone fragility and predisposition to fracture. Current screening tools are limited in estimating the proper assessment of fracture risk, highlighting the need to discover novel more suitable biomarkers. Genetic and environmental factors are both implicated in this disease. Increasing evidence suggests that epigenetics and, in particular, miRNAs, may represent a link between these factors and an increase of fracture risk. miRNAs are a class of small noncoding RNAs that negatively regulate gene expression. In the last decade, several miRNAs have been associated with the development of osteoporosis and bone fracture risk, opening up new possibilities in precision medicine. Recently, these molecules have been identified in several biological fluids, and the possible existence of a circulating miRNA (c-miRNA) signature years before the fracture occurrence is suggested. The aim of this review is to provide an overview of the c-miRNAs suggested as promising biomarkers for osteoporosis up until now, which could be helpful for early diagnosis and monitoring of treatment response, as well as fracture risk assessment, in osteoporotic patients.

miR‑27a‑3p negatively regulates osteogenic differentiation of MC3T3‑E1 preosteoblasts by targeting osterix

Osteoporosis is a complex multifactorial disorder characterized by microarchitectural deterioration, low bone mass, and increased risk of fractures or broken bones. Balanced bone remodeling is tightly regulated by the differentiation, activity and apoptosis of bone-forming osteoblasts and bone-resorbing osteoclasts. MicroRNAs (miRs) are dysregulated in osteoporosis, but whether they control osteogenic differentiation and skeletal biology, or could serve as therapeutic targets remains to be elucidated. The present study identified miR-27a-3p as a critical suppressor of osteoblastogenesis. Bioinformatics analysis and luciferase reporter assays demonstrated that miR-27a-3p directly targeted and controlled the expression of osterix (Osx), an early response gene essential for bone formation, through its 3′-untranslated region. miR-27a-3p functionally inhibited the differentiation of preosteoblasts by decreasing Osx expression, which synergistically contributed to bone formation. miR-27a-3p level was significantly decreased during osteogenic differentiation and increased in the serum of patients with osteoporosis. Together, miR-27a-3p contributed to diminished osteogenic function during osteogenic differentiation and might thus serve as a therapeutic target and diagnostic biomarker for osteoporosis.

Circulating miR-181c-5p and miR-497-5p Are Potential Biomarkers for Prognosis and Diagnosis of Osteoporosis

CONTEXT

Osteoporosis is a degenerative bone disease in aging men and women. MiRNAs associated with progressive bone loss in osteoporosis had not been clearly demonstrated.

OBJECTIVE

The evaluation of the differentially expressed miRNAs in the bone tissue and serum of osteoporotic women with aging.

METHODS

MiRNAs GeneChip and real-time PCR were used to screen differently expressed miRNAs in bone tissues of 21 osteoporotic women ages 60-69 years and 80-89 years. Identified miRNAs were detected in the serum of the validation cohort, which consisted of 14 healthy premenopausal women and 86 postmenopausal women with osteopenia or osteoporosis. MiR-181c-5p and miR-497-5p expression were validated in aging and OVX mice models, and osteoblasts. Their role in osteogenesis was validated in vitro.

RESULTS

Twenty-four miRNAs showed the highest differential expression in bone tissues of osteoporotic women in initial screening. Among them, four miRNAs were identified both in the bone tissue and serum in the validation cohort. The levels of miR-181c-5p and miR-497-5p were decreased in the serum of postmenopausal women with osteopenia or osteoporosis, but increased in subjects treated with bisphosphonate plus calcitriol. MiR-181c-5p and miR-497-5p were significantly downregulated in the bone tissue of aging and OVX mice models, and upregulated during the osteogenic differentiation of hFOB1.19 and MC3T3-E1 cells. Overexpression of miR-181c-5p and miR-497-5p promoted the differentiation and mineralization of osteoblasts.

CONCLUSIONS

MiR-181c-5p and miR-497-5p are involved in bone metabolism and associated with progressive bone loss of due to osteoporosis, suggesting that circulating miR-181c-5p and miR-497-5p might act as potential biomarkers for monitoring the effects of antiosteoporotic therapies or the diagnostic approach.

The Clinical Potential of Circulating miRNAs as Biomarkers: Present and Future Applications for Diagnosis and Prognosis of Age-Associated Bone Diseases

Osteoporosis, related fracture/fragility, and osteoarthritis are age-related pathologies that, over recent years, have seen increasing incidence and prevalence due to population ageing. The diagnostic approaches to these pathologies suffer from limited sensitivity and specificity, also in monitoring the disease progression or treatment. For this reason, new biomarkers are desirable for improving the management of osteoporosis and osteoarthritis patients. The non-coding RNAs, called miRNAs, are key post-transcriptional factors in bone homeostasis, and promising circulating biomarkers for pathological conditions in which to perform a biopsy can be problematic. In fact, miRNAs can easily be detected in biological fluids (i.e., blood, serum, plasma) using methods with elevated sensitivity and specificity (RT-qPCR, microarray, and NGS). However, the analytical phases required for miRNAs' evaluation still present some practical issues that limit their use in clinical practice. This review reveals miRNAs' potential as circulating biomarkers for evaluating predisposition, diagnosis, and prognosis of osteoporosis (postmenopausal or idiopathic), bone fracture/fragility, and osteoarthritis, with a focus on pre-analytical, analytical, and post-analytical protocols used for their validation and thus on their clinical applicability. These evidences may support the definition of early diagnostic tools based on circulating miRNAs for bone diseases and osteoarthritis as well as for monitoring the effects of specific treatments.

A microRNA Approach to Discriminate Cortical Low Bone Turnover in Renal Osteodystrophy

A main obstacle to diagnose and manage renal osteodystrophy (ROD) is the identification of intracortical bone turnover type (low, normal, high). The gold standard, tetracycline‐labeled transiliac crest bone biopsy, is impractical to obtain in most patients. The Kidney Disease Improving Global Outcomes Guidelines recommend PTH and bone‐specific alkaline phosphatase (BSAP) for the diagnosis of turnover type. However, PTH and BSAP have insufficient diagnostic accuracy to differentiate low from non‐low turnover and were validated for trabecular turnover. We hypothesized that four circulating microRNAs (miRNAs) that regulate osteoblast (miRNA‐30b, 30c, 125b) and osteoclast development (miRNA‐155) would provide superior discrimination of low from non‐low turnover than biomarkers in clinical use. In 23 patients with CKD 3‐5D, we obtained tetracycline‐labeled transiliac crest bone biopsy and measured circulating levels of intact PTH, BSAP, and miRNA‐30b, 30c, 125b, and 155. Spearman correlations assessed relationships between miRNAs and histomorphometry and PTH and BSAP. Diagnostic test characteristics for discriminating low from non‐low intracortical turnover were determined by receiver operator curve analysis; areas under the curve (AUC) were compared by χ² test. In CKD rat models of low and high turnover ROD, we performed histomorphometry and determined the expression of bone tissue miRNAs. Circulating miRNAs moderately correlated with bone formation rate and adjusted apposition rate at the endo‐ and intracortical envelopes (ρ = 0.43 to 0.51; p < 0.05). Discrimination of low versus non‐low turnover was 0.866, 0.813, 0.813, and 0.723 for miRNA‐30b, 30c, 125b, and 155, respectively, and 0.509 and 0.589 for PTH and BSAP, respectively. For all four miRNAs combined, the AUC was 0.929, which was superior to that of PTH and BSAP alone and together (p < 0.05). In CKD rats, bone tissue levels of the four miRNAs reflected the findings in human serum. These data suggest that a panel of circulating miRNAs provide accurate noninvasive identification of bone turnover in ROD. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Role of miR-199a-5p in osteoblast differentiation by targeting TET2

OBJECTIVE

miR-199a-5p was increased during osteoblast differentiation, which may target and regulate TET2, a gene attracted a lot of attention in the osteoblast differentiation in the past few years. However, the role of miR-199a-5p in osteoblast differentiation by targeting TET2 is not established.

METHODS

The correlation between miR-199a-5p and TET2 was verified through dual luciferase reporter assay, and their expressions in human bone marrow stromal cells (hBMSCs) during the osteoblast differentiation were detected. hBMSCs were transfected with TET2 siRNA, miR-199a-5p mimic or/and TET2 CRISPR activation plasmid., and then prepared for the induction of osteoblast differentiation, followed by alkaline phosphatase (ALP) and alizarin red staining, qRT-PCR and Western blotting. In vivo, ovariectomized (OVX) mice were injected with agomir-miR-199a-5p, antagomiR-199a-5p or/and TET2 siRNA to calculate the BMD and BV/TV ratio of mice, as well as to measure the expressions of osteogenesis-related genes in bone tissues.

RESULTS

A gradual increase of miR-199a-5p was observed in hBMSCs during the induction of osteoblast differentiation, while TET2 expression was decreased. Besides, miR-199a-5p was reduced in the bone tissue of OVX mice, while TET2 was up-regulated. In addition, overexpression of miR-199a-5p and inhibition of TET2 augmented ALP activity in hBMSCs, with the enhanced calcification and the up-regulated expressions of Runx2, OSX and OCN, which also increased the quality of bone in OVX mice accompanying the enhancement BV/TV ratio, BMD and osteogenesis-related genes.

CONCLUSION

MiR-199a-5p may promote the osteoblast differentiation and prevent OVX-induced osteoporosis by targeting TET2.

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.

Serum microRNAs as novel biomarkers for osteoporotic vertebral fractures

CONTEXT

Vertebral fractures are the hallmark of osteoporosis. MicroRNAs (miRNAs) are a prominent class of gene regulators likely to affect bone homeostasis, including bone remodelling and fracture healing by altering gene expression in bone cells.

OBJECTIVE

This study sought to compare the levels of circulating miRNAs in older women with osteoporotic vertebral fractures, and/or low BMD and healthy controls, and to correlate miRNAs expression levels with BTMs.

DESIGN

A single-site, case-control, observational, cross-sectional study at a university hospital.

PARTICIPANTS

Altogether, 126 postmenopausal women belonging to four different groups were included: healthy (n=42), low BMD and no vertebral fractures (n=39), vertebral fractures and low BMD without a treatment (n=26), or receiving a treatment for osteoporosis (n=19).

MAIN OUTCOME MEASURE

Serum samples from all participants were analyzed for 21 microRNA bone biomarkers.

RESULTS

We identified 7 significantly (p<0.05) up-regulated miRNAs (miR-375, miR-532-3p, miR-19b-3p, miR-152-3p, miR-23a-3p, miR-335-5p, miR-21-5p) in patients with vertebral fractures and low BMD compared to low BMD and healthy individuals, regardless of osteoporosis treatment. No significant differences existed between low BMD and healthy controls. We observed 24 significant correlations (P<0.05) between miRNAs and BTMs (CTX, PINP, OC and bone ALP).

CONCLUSIONS

Specific circulating miRNAs reflect the presence of osteoporotic vertebral fractures in postmenopausal women. They are unlikely to reflect low BMD, and more likely changes in bone quality or fracture healing. The effects of osteoporosis treatment on the selected miRNAs appear to be weaker than effects caused by vertebral fractures. The correlation between miRNAs and BTMs suggest that miRNAs may be involved in bone turnover or fracture healing.

miRNA-seq analysis of human vertebrae provides insight into the mechanism underlying GIOP

High-throughput sequencing (HTS) was recently applied to detect microRNA (miRNA) regulation in age-related osteoporosis. However, miRNA regulation has not been reported in glucocorticoid-induced osteoporosis (GIOP) patients and the mechanism of GIOP remains elusive. To comprehensively analyze the role of miRNA regulation in GIOP based on human vertebrae and to explore the molecular mechanism, a high-throughput sequencing strategy was employed to identify miRNAs involved in GIOP. Twenty-six patients undergoing spinal surgery were included in this study. Six vertebral samples were selected for miRNA sequencing (miRNA-seq) analysis and 26 vertebral samples were verified by qRT-PCR. Bioinformatics was utilized for target prediction, to investigate the regulation of miRNA-mRNA networks, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Six significantly up-regulated miRNAs (including one novel miRNA) and three significantly down-regulated miRNAs were verified via miRNA-seq and verified in the vertebrae of GIOP patients. Up-regulated miRNAs included hsa-miR-214-5p, hsa-miR-10b-5p, hsa-miR-21-5p, hsa-miR-451a, hsa-miR-186-5p, and hsa-miR-novel-chr3_49,413 while down-regulated miRNAs included hsa-let-7f-5p, hsa-let-7a-5p, and hsa-miR-27a-3p. Bioinformatics analysis revealed 5983 and 23,463 predicted targets in the up-regulated and down-regulated miRNAs respectively, using the miRanda, miRBase and TargetScan databases. The target genes of these significantly altered miRNAs were enriched to 1939 GO terms and 84 KEGG pathways. GO terms revealed that up-regulated targets were most enriched in actin filament-based processes (BP), anchoring junction (CC), and cytoskeletal protein binding (MF). Conversely, the down-regulated targets were mostly enriched in multicellular organismal development (BP), intracellular membrane-bounded organelles (CC), and protein binding (MF). Top-10 pathway analysis revealed that the differentially expressed miRNAs in GIOP were closely related to bone metabolism-related pathways such as FoxO, PI3K-Akt, MAPK and Notch signaling pathway. These results suggest that significantly altered miRNAs may play an important role in GIOP by targeting mRNA and regulating biological processes and bone metabolism-related pathways such as MAPK, FoxO, PI3K-Akt and Notch signaling, which provides novel insight into the mechanism of GIOP and lays a good foundation for the prevention and treatment of GIOP.

New Insights Into Monogenic Causes of Osteoporosis

Osteoporosis, characterized by deteriorated bone microarchitecture and low bone mineral density, is a chronic skeletal disease with high worldwide prevalence. Osteoporosis related to aging is the most common form and causes significant morbidity and mortality. Rare, monogenic forms of osteoporosis have their onset usually in childhood or young adulthood and have specific phenotypic features and clinical course depending on the underlying cause. The most common form is osteogenesis imperfecta linked to mutations in COL1A1 and COL1A2, the two genes encoding type I collagen. However, in the past years, remarkable advancements in bone research have expanded our understanding of the intricacies behind bone metabolism and identified novel molecular mechanisms contributing to skeletal health and disease. Especially high-throughput sequencing techniques have made family-based studies an efficient way to identify single genes causative of rare monogenic forms of osteoporosis and these have yielded several novel genes that encode proteins partaking in type I collagen modification or regulating bone cell function directly. New forms of monogenic osteoporosis, such as autosomal dominant osteoporosis caused by WNT1 mutations or X-linked osteoporosis due to PLS3 mutations, have revealed previously unidentified bone-regulating proteins and clarified specific roles of bone cells, expanded our understanding of possible inheritance mechanisms and paces of disease progression, and highlighted the potential of monogenic bone diseases to extend beyond the skeletal tissue. The novel gene discoveries have introduced new challenges to the classification and diagnosis of monogenic osteoporosis, but also provided promising new molecular targets for development of pharmacotherapies. In this article we give an overview of the recent discoveries in the area of monogenic forms of osteoporosis, describing the key cellular mechanisms leading to skeletal fragility, the major recent research findings and the essential challenges and avenues in future diagnostics and treatments.

MicroRNA and Human Bone Health

The small non‐coding microRNAs (miRNAs) are post‐transcription regulators that modulate diverse cellular process in bone cells. Because optimal miRNA targeting is essential for their function, single‐nucleotide polymorphisms (SNPs) within or proximal to the loci of miRNA (miR‐SNPs) or mRNA (PolymiRTS) could potentially disrupt the miRNA‐mRNA interaction, leading to changes in bone metabolism and osteoporosis. Recent human studies of skeletal traits using miRNA profiling, genomewide association studies, and functional studies started to decipher the complex miRNA regulatory network. These studies have indicated that miRNAs may be a promising bone marker. This review focuses on human miRNA studies on bone traits and discusses how genetic variants affect bone metabolic pathways. Major ex vivo investigations using human samples supported with animal and in vitro models have shed light on the mechanistic role of miRNAs. Furthermore, studying the miRNAs’ signatures in secondary osteoporosis and osteoporotic medications such as teriparatide (TPTD) and denosumab (DMab) have provided valuable insight into clinical management of the disease. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research

Downregulation of miR-24-3p promotes osteogenic differentiation of human periodontal ligament stem cells by targeting SMAD family member 5

Osteogenic differentiation is a complicated process that depends on various regulatory factors and signal pathways. In our research, the osteogenic differentiation capacity was analyzed by alizarin red staining, alkaline phosphatase activity, and protein levels of osteogenic differentiation markers including runt-related transcription factor 2, bone morphogenetic protein 2, and osteocalcin (OCN). We observed a notable decrease of miR-24-3p level in osteogenic-differentiated human periodontal ligament stem cells (hPDLSCs) by microarray analysis. In our gain- and loss-of-function experiments, we discovered that miR-24-3p has a suppression effect on hPDLSCs osteogenic differentiation. Moreover, SMAD family member 5 (Smad5), the critical osteogenic differentiation transcription factors, was predicted to be targets of miR-24-3p. In addition, luciferase reporter assay further proved that miR-24-3p directly targeted the 3'-untranslated region of Smad5. Similarly, we found that the overexpression of miR-24-3p significantly decreased the Smad5 messenger RNA level in hPDLSCs, which was detected by real-time quantitative polymerase chain reaction. Then hPDLSCs were transfected with miR-24-3p mimics to inhibit Smad5 expression; meanwhile, Smad5 RNA interference could significantly reverse the osteogenic differentiation inhibition effect of miR-24-3p. In brief, a series of data showed that miR-24-3p is a regulator of Smad5, playing an important role in osteogenic differentiation.

Circulating microRNAs as potential diagnostic biomarkers for osteoporosis

Osteoporosis is the most common age-related bone disease worldwide and is usually clinically asymptomatic until the first fracture happens. MicroRNAs are critical molecular regulators in bone remodelling processes and are stabilised in the blood. The aim of this project was to identify circulatory microRNAs associated with osteoporosis using advanced PCR arrays initially and the identified differentially-expressed microRNAs were validated in clinical samples using RT-qPCR. A total of 161 participants were recruited and 139 participants were included in this study with local ethical approvals prior to recruitment. RNAs were extracted, purified, quantified and analysed from all serum and plasma samples. Differentially-expressed miRNAs were identified using miRNA PCR arrays initially and validated in 139 serum and 134 plasma clinical samples using RT-qPCR. Following validation of identified miRNAs in individual clinical samples using RT-qPCR, circulating miRNAs, hsa-miR-122-5p and hsa-miR-4516 were statistically significantly differentially-expressed between non-osteoporotic controls, osteopaenia and osteoporosis patients. Further analysis showed that the levels of these microRNAs were associated with fragility fracture and correlated with the low bone mineral density in osteoporosis patients. The results show that circulating hsa-miR-122-5p and hsa-miR-4516 could be potential diagnostic biomarkers for osteoporosis in the future.