miRNA-133a-5p Inhibits the Expression of Osteoblast Differentiation-Associated Markers by Targeting the 3' UTR of RUNX2

Calcium sulfate-Cu2+ delivery system improves 3D-Printed calcium silicate artificial bone to repair large bone defects

There are still limitations in artificial bone materials used in clinical practice, such as difficulty in repairing large bone defects, the mismatch between the degradation rate and tissue growth, difficulty in vascularization, an inability to address bone defects of various shapes, and risk of infection. To solve these problems, our group designed stereolithography (SLA) 3D-printed calcium silicate artificial bone improved by a calcium sulfate-Cu2+ delivery system. SLA technology endows the scaffold with a three-dimensional tunnel structure to induce cell migration to the center of the bone defect. The calcium sulfate-Cu2+ delivery system was introduced to enhance the osteogenic activity of calcium silicate. Rapid degradation of calcium sulfate (CS) induces early osteogenesis in the three-dimensional tunnel structure. Calcium silicate (CSi) which degrades slowly provides mechanical support and promotes bone formation in bone defect sites for a long time. The gradient degradation of these two components is perfectly matched to the rate of repair in large bone defects. On the other hand, the calcium sulfate delivery system can regularly release Cu2+ in the temporal and spatial dimensions, exerting a long-lasting antimicrobial effect and promoting vascular growth. This powerful 3D-printed calcium silicate artificial bone which has rich osteogenic activity is a promising material for treating large bone defects and has excellent potential for clinical application.

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.

Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs

Osteoporosis is characterized by the alteration of bone homeostasis due to an imbalance between osteoclastic bone resorption and osteoblastic bone formation. Estrogen deficiency causes bone loss and postmenopausal osteoporosis, the pathogenesis of which also involves oxidative stress, inflammatory processes, and the dysregulation of the expression of microRNAs (miRNAs) that control gene expression at post-transcriptional levels. Oxidative stress, due to an increase in reactive oxygen species (ROS), proinflammatory mediators and altered levels of miRNAs enhance osteoclastogenesis and reduce osteoblastogenesis through mechanisms involving the activation of MAPK and transcription factors. The present review summarizes the principal molecular mechanisms involved in the role of ROS and proinflammatory cytokines on osteoporosis. Moreover, it highlights the interplay among altered miRNA levels, oxidative stress, and an inflammatory state. In fact, ROS, by activating the transcriptional factors, can affect miRNA expression, and miRNAs can regulate ROS production and inflammatory processes. Therefore, the present review should help in identifying targets for the development of new therapeutic approaches to osteoporotic treatment and improve the quality of life of patients.

Runx2 and Nell-1 in dental follicle progenitor cells regulate bone remodeling and tooth eruption

Dental follicles are necessary for tooth eruption, surround the enamel organ and dental papilla, and regulate both the formation and resorption of alveolar bone. Dental follicle progenitor cells (DFPCs), which are stem cells found in dental follicles, differentiate into different kinds of cells that are necessary for tooth formation and eruption. Runt‐related transcription factor 2 (Runx2) is a transcription factor that is essential for osteoblasts and osteoclasts differentiation, as well as bone remodeling. Mutation of Runx2 causing cleidocranial dysplasia negatively affects osteogenesis and the osteoclastic ability of dental follicles, resulting in tooth eruption difficulties. Among a variety of cells and molecules, Nel-like molecule type 1 (Nell-1) plays an important role in neural crest-derived tissues and is strongly expressed in dental follicles. Nell-1 was originally identified in pathologically fused and fusing sutures of patients with unilateral coronal synostosis, and it plays indispensable roles in bone remodeling, including roles in osteoblast differentiation, bone formation and regeneration, craniofacial skeleton development, and the differentiation of many kinds of stem cells. Runx2 was proven to directly target the Nell-1 gene and regulate its expression. These studies suggested that Runx2/Nell-1 axis may play an important role in the process of tooth eruption by affecting DFPCs. Studies on short and long regulatory noncoding RNAs have revealed the complexity of RNA-mediated regulation of gene expression at the posttranscriptional level. This ceRNA network participates in the regulation of Runx2 and Nell-1 gene expression in a complex way. However, non-study indicated the potential connection between Runx2 and Nell-1, and further researches are still needed.

TET enzymes regulate skeletal development through increasing chromatin accessibility of RUNX2 target genes

The Ten-eleven translocation (TET) family of dioxygenases mediate cytosine demethylation by catalyzing the oxidation of 5-methylcytosine (5mC). TET-mediated DNA demethylation controls the proper differentiation of embryonic stem cells and TET members display functional redundancy during early gastrulation. However, it is unclear if TET proteins have functional significance in mammalian skeletal development. Here, we report that Tet genes deficiency in mesoderm mesenchymal stem cells results in severe defects of bone development. The existence of any single Tet gene allele can support early bone formation, suggesting a functional redundancy of TET proteins. Integrative analyses of RNA-seq, Whole Genome Bisulfite Sequencing (WGBS), 5hmC-Seal and Assay for Transposase-Accessible Chromatin (ATAC-seq) demonstrate that TET-mediated demethylation increases the chromatin accessibility of target genes by RUNX2 and facilities RUNX2-regulated transcription. In addition, TET proteins interact with RUNX2 through their catalytic domain to regulate cytosine methylation around RUNX2 binding region. The catalytic domain is indispensable for TET enzymes to regulate RUNX2 transcription activity on its target genes and to regulate bone development. These results demonstrate that TET enzymes function to regulate RUNX2 activity and maintain skeletal homeostasis.

Here the authors investigate the role of the TET family of DNA demethylases in mammalian skeletal development. They find that loss of TETs leads to hypermethylation that results in decreased chromatin accessibility of RUNX2 target genes, repressing osteoblast differentiation and leading to skeletal defects in mouse such as short limbs.

Non-coding RNA delivery for bone tissue engineering: progress, challenges and potential solutions

More than 20 million individuals worldwide suffer from congenital or acquired bone defects annually. The development of bone scaffold materials that simulate natural bone for bone defect repair remains challenging. Recently, ncRNA-based therapies for bone defects have attracted increasing interest because of the great potential of ncRNAs in disease treatment. Various types of ncRNAs regulate gene expression in osteogenesis-related cells via multiple mechanisms. The delivery of ncRNAs to the site of bone loss through gene vectors or scaffolds is a potential therapeutic option for bone defect repair. Therefore, this study discusses and summarizes the regulatory mechanisms of miRNAs, siRNAs, and piRNAs in osteogenic signaling and reviews the widely used current RNA delivery vectors and scaffolds for bone defect repair. Additionally, current challenges and potential solutions of delivery scaffolds for bone defect repair are proposed, with the aim of providing a theoretical basis for their future clinical applications.

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

Background

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

Methods

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

Results

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

Conclusions

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

Effect of miR-381-3p/FGF7 axis on the osteogenic differentiation of bone marrow mesenchymal stem cells through MEK/ERK signaling pathway

Although microRNAs (miRNAs) exert an important role in the osteogenesis of mesenchymal stem cells (MSCs), the effect of miR-381-3p on the osteogenic differentiation in MBD‑MSCs is still unclear. The BMMSCs from patients with MBD (MBD‑MSC) or normal participants (Normal‑MSC) were isolated and induced to differentiation with dexamethasone. BMMSCs were transfected with miR-381-3p mimic, miR-381-3p inhibitor, and FGF7 siRNA to regulate the expression of miR-381-3p or FGF7. The direct binding between miR-381-3p and FGF7 was predicted and confirmed by bioinformatics prediction and luciferase reporter assay. The effect of miR-381-3p on the osteogenic differentiation of BMMSCs was assessed by RT‑qPCR, alizarin Red S staining and western blot assays. Isolated BMMSCs showed the regular morphology, and were positive for CD44, CD90 and CD105 but negative for CD34 and CD45 markers. The calcium deposition and the relative mRNA expression levels of ALP, OC and OPN after induction were markedly enhanced. MiR-381-3p was upregulated in BMMSCs. Also, inhibition of miR-381-3p notably promoted osteogenic differentiation, vice versa. Besides, miR-381-3p could directly target FGF7 and negatively modulate the expression of FGF7. Moreover, inhibition of FGF7 attenuated the increase of the calcium deposition, and the relative mRNA expression of ALP, OC and OPN caused by the downregulation of miR-381-3p. In addition, the miR-381-3p inhibitor-induced the enhancement of the relative protein expressions of FGFR2, p-MEK and p-ERK1/2 were significantly reduced by the co-transfection of si-FGF7. Furthermore, the application of LY3214996, the inhibitor of ERK also verified these outcomes. MiR-381-3p directly targeting FGF7 modulated the osteogenic differentiation via MEK/ERK signaling pathway in BMMSCs.

MicroRNA-133 suppresses cell viability and migration of rheumatoid arthritis fibroblast-like synoviocytes by down-regulation of MET, EGFR, and FSCN1 expression

Aberrant proliferation and migration of fibroblast-like synoviocytes (FLS) are major characteristics of rheumatoid arthritis (RA). MicroRNA-133 (miR-133) is a tumor-suppressive miRNA that targets various genes responsive for cell proliferation and migration. The aim of this study was to examine the effect of miR-133 on RA FLS. A high throughput miRNA microarray was performed in synovium from mice with collagen-induced arthritis (CIA). Expression levels of miR-133 and the putative targets were determined in synovium and FLS from patients with RA and mice with CIA. Overexpression of miR-133 in RA FLS was performed by lentiviral vector-mediated transfer of precursor miRNA (pre-miR). The expression of miR-133a/b was decreased in the joint tissue and FLS of CIA mice, as determined by miRNA array and qRT-PCR. Down-regulation of miR-133a/b expression could also be observed in synovium and FLS from patients with RA. Overexpression of miR-133 reduced cell viability and migration of RA FLS, with decreased levels of FSCN1, EGFR, and MET. Our findings demonstrated the inhibitory effects of miR-133 on FLS viability and migration, and might contribute to the pharmacologic development of miR-133 therapeutics in patients with RA.

Upregulated miR-9-5p inhibits osteogenic differentiation of bone marrow mesenchymal stem cells under high glucose treatment

INTRODUCTION

Diabetic osteoporosis (DOP) is a chronic diabetic complication, which is attributed to high glucose (HG)-induced dysfunction of bone marrow mesenchymal stem cells (BMSCs). Studies have revealed that microRNAs (miRNAs) play critical roles in osteogenic differentiation of BMSCs in DOP. Here, the role of miR-9-5p in DOP progression was explored.

MATERIALS AND METHODS

The rat model of DOP was established by intraperitoneal injection of streptozotocin (STZ). BMSCs were treated with high glucose (HG) to establish in vitro models. Gene expression in BMSCs and bone tissues of rats was tested by RT-qPCR. The degree of osteogenic differentiation of BMSCs was examined by Alizarin Red staining and ALP activity analysis. The protein levels of collagen-I (COL1), osteocalcin (OCN), osteopontin (OPN), runt-related transcription factor-2 (RUNX2), and DEAD-Box Helicase 17 (DDX17) in BMSCs were evaluated by western blotting. The interaction between miR-9-5p and DDX17 was identified by luciferase reporter assay. H&E staining was used to test morphological structure of femurs of rats with STZ treatment.

RESULTS

MiR-9-5p was overexpressed in HG-treated BMSCs, while DDX17 was downregulated. Functionally, miR-9-5p knockdown promoted BMSCs osteogenic differentiation under HG condition. Mechanically, miR-9-5p targeted DDX17. DDX17 knockdown reversed the effect of miR-9-5p silencing on osteogenic differentiation of HG-treated BMSCs. In in vivo studies, miR-9-5p downregulation ameliorated the DOP condition of rats and miR-9-5p expression was negatively correlated with DDX17 expression in bone tissues of rats with STZ treatment.

CONCLUSION

MiR-9-5p knockdown promotes HG-induced osteogenic differentiation BMSCs in vitro and mitigates the DOP condition of rats in vivo by targeting DDX17.

miRNAs Related to Different Processes of Fracture Healing: An Integrative Overview

Fracture healing is a complex, dynamic process that is directed by cellular communication and requires multiple cell types, such as osteoblasts, osteoclasts, and immune cells. Physiological fracture healing can be divided into several phases that consist of different processes, such as angiogenesis, osteogenesis, and bone resorption/remodelling. This is needed to guarantee proper bone regeneration after fracture. Communication and molecular regulation between different cell types and within cells is therefore key in successfully orchestrating these processes to ensure adequate bone healing. Among others, microRNAs (miRNAs) play an important role in cellular communication. microRNAs are small, non-coding RNA molecules of ~22 nucleotides long that can greatly influence gene expression by post-transcriptional regulation. Over the course of the past decade, more insights have been gained in the field of miRNAs and their role in cellular signalling in both inter- and intracellular pathways. The interplay between miRNAs and their mRNA targets, and the effect thereof on different processes and aspects within fracture healing, have shown to be interesting research topics with possible future diagnostic and therapeutic potential. Considering bone regeneration, research moreover focusses on specific microRNAs and their involvement in individual pathways. However, it is required to combine these data to gain more understanding on the effects of miRNAs in the dynamic process of fracture healing, and to enhance their translational application in research, as well as in the clinic. Therefore, this review aims to provide an integrative overview on miRNAs in fracture healing, related to several key aspects in the fracture healing cascade. A special focus will be put on hypoxia, angiogenesis, bone resorption, osteoclastogenesis, mineralization, osteogenesis, osteoblastogenesis, osteocytogenesis, and chondrogenesis.

Down-regulation of miR-340-5p promoted osteogenic differentiation through regulation of runt-related transcription factor-2 (RUNX2) in MC3T3-E1 cells

Diabetic osteoporosis (DOP) is a chronic complication of diabetes in the skeletal system. High level of miR-340-5p may be harmful to the bone formation. In this study, the DOP model of rats was successfully established via streptozotocin (STZ) and ovariectomy (OVX) treatment. It was manifested by reduced body weight, insulin level, alkaline phosphatase (ALP) activity, and osteocalcin (OCN) and collagen-I expressions, as well as increased concentration of fasting blood glucose. Moreover, we found that miR-340-5p expression was increased while runt-related transcription factor-2 (RUNX2) was decreased in femurs. Furthermore, the effects of miR-340-5p on osteogenic differentiation (OD) in high glucose (HG)-treated MC3T3-E1 cells were explored. Exposure to OD and HG contributed to elevated miR-340-5p level. Inhibition of miR-340-5p enhanced ALP level, calcium deposition, and OCN, collagen-I and RUNX2 levels. On the contrary, miR-340-5p overexpression reversed these promotional effects. Luciferase assay indicated that RUNX2 may be a target gene of miR-340-5p. Moreover, RUNX2 deficiency decreased miR-340-5p inhibition-induced ALP activity, calcium accumulation and OCN, collagen-I, RUNX2 levels. In short, the above findings revealed that inhibition of miR-340-5p facilitated osteogenic differentiation through regulating RUNX2 in MC3TC-E1 cells, which provided targeted therapeutic strategies for the treatment of DOP.

MicroRNA-103a regulates the calcification of vascular smooth muscle cells by targeting runt-related transcription factor 2 in high phosphorus conditions

Vascular calcification, such as atherosclerosis, is a serious complication of chronic kidney disease that is characterized by tunica media calcification, and has gained increasing attention from researchers. The commonly observed association between vascular calcification and osteoporosis suggests a link between bone and vascular disorders. As microRNAs (miRNAs) have a wide range of gene regulation functions, such as cell proliferation, apoptosis, stress and transdifferentiation, the current study aimed to determine whether miRNAs play a vital role in the calcification and osteoblastic differentiation of rat thoracic aorta vascular smooth muscle cells (VSMCs). Gene expression analysis was performed on seven miRNAs (miR-29a, -30b, -103a, -125b, -133a, -143 and -211) that maybe potentially involved in the differentiation of smooth muscle cells into osteoblastic cells. The results showed that the levels of miR-29a, -30b, -103a, -125b and -143 were markedly reduced in the VSMC calcification model, particularly miR-103a, whereas runt-related transcription factor 2 (RUNX2) expression was increased. Furthermore, it was found that the expression of RUNX2 was significantly decreased following the upregulation of miR-103a, and that the expression of RUNX2 was significantly increased by downregulating miR-103a in VSMCs. Therefore, it was concluded that miR-103a plays a notable role in the transdifferentiation of the VSMCs in high phosphorus-induced calcification by targeting the regulation of RUNX2, and may therefore constitute a new target for the diagnosis and treatment of vascular calcification.

LncRNA LINC00963 promotes osteogenic differentiation of hBMSCs and alleviates osteoporosis progression by targeting miRNA-760/ETS1 axis

Although long non-coding RNA LINC00963 has been reported to play a crucial regulatory role in osteoporosis (OP), its specific mechanism has not been well studied. Cell viability of human bone marrow mesenchymal stem cells (hBMSCs) transfected with short hairpin RNA targeting LINC00963 (sh-LINC00963) and negative control (sh-NC) was analysed by cell counting kit-8 (CCK-8) assay. Alkaline phosphatase (ALP) activity in hBMSCs transfected with sh-LINC00963 and sh-NC after induction by osteogenic medium (OM) on day 7 was detected. The protein expression levels of osteocalcin (OCN) and osteopontin (OPN) in hBMSCs transfected with sh-LINC00963 and sh-NC during OM induction on day 3 were detected by western blot. The relationship among LINC00963, miR-760, and E26 transformation specific-1 (ETS1) was determined by bioinformatics analysis, luciferase reporter assay, and RNA-binding protein immunoprecipitation (RIP) assay. A rat model with OP was established to confirm the role of LINC00963 in vivo. The expression level of LINC00963 was much lower in hBMSCs isolated from the discarded femoral head tissues of OP patients compared with that in health patients. Meanwhile, the expression level of LINC00963 was significantly increased and the expression level of miR-760 was decreased in hBMSCs during osteogenic induction. LINC00963 could bind to the 3'-untranslated region (3'-UTR) of miR-760 and negatively regulate the expression of miR-760, then promote the osteogenic differentiation in hBMSCs. ETS1 was identified as a target of miR-760. Moreover, overexpression of LINC00963 obviously reduced bone mineral density (BMD) of the left femur in OP rats and alleviated OP progression in vivo. Our results demonstrated that LINC00963 positively regulated the expression of ETS1 by directly targeting miR-760, and then promoted osteogenic differentiation of hBMSCs in vitro, and also attenuated OP progression in vivo, suggesting that LINC00963 might be a potential therapeutic target for OP.

MicroRNA-133a Regulates the Viability and Differentiation Fate of Bone Marrow Mesenchymal Stem Cells via MAPK/ERK Signaling Pathway by Targeting FGFR1

Dysfunction of bone marrow mesenchymal stem cells (BMSCs) is recognized critical in bone deteriorations of osteoporosis. However, the specific mechanisms that determine the fate of BMSCs remain elusive. MicroRNA-133a (miR-133a), a highly conserved microRNA, was investigated under both in vitro and in vivo conditions. In the in vitro study, cell proliferation, cell apoptosis, and osteoblast/adipocyte differentiation of BMSCs as a result of overexpression or knockdown of miR-133a was investigated. In the in vivo study, the ovariectomy (OVX) model was applied on mice, with further treatment of the models with BMSC-specific miR-133a antagomir through femur intramedullary injection. Microcomputed tomography scanning and histological analysis of the proximal and middle femur were performed to evaluate the morphological changes. The results revealed that overexpression of miR-133a suppressed cell proliferation, cell viability, and osteoblast differentiation of BMSCs, but increased adipocyte differentiation. We also found that FGFR1, an important upstream regulator of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signal pathway, was a major target of miR-133a. We also recorded that BMSC-specific knockdown of miR-133a attenuates bone loss in OVX mice. Our study suggested that miR-133a played an important role in maintaining the viability and balance between osteoblast and adipocyte differentiation of BMSCs through the MAPK/ERK signaling pathway by targeting FGFR1.

The effects of biophysical stimulation on osteogenic differentiation and the mechanisms from ncRNAs

Ample proof showed that non-coding RNAs (ncRNAs) play a crucial role in proliferation and differentiation of osteoblasts and bone marrow stromal cells (BMSCs). Varied forms of biophysical stimuli like mechanical strain, fluid shear stress (FSS), microgravity and vibration are verified to regulate ncRNAs expression in osteogenic differentiation and influence the expression of target genes associated with osteogenic differentiation and ultimately regulate bone formation. The consequences of biophysical stimulation on osteogenic differentiation validate the prospect of exercise for the prevention and treatment of osteoporosis. In this review, we tend to summarize the studies on regulation of osteogenic differentiation by ncRNAs beneath biophysical stimulation and facilitate to reveal the regulatory mechanism of biophysical stimulation on ncRNAs, and provide an update for the prevention of bone metabolism diseases by exercise.

MiR-133a delivery to osteoblasts ameliorates mechanical unloading-triggered osteopenia progression in vitro and in vivo

Mechanical unloading-induced bone loss is a clinical challenge, and deep understanding for this disease is necessary for developing novel and effective therapies. MicroRNAs (miRNAs) are small non-coding RNAs, and involved in bone remodeling. In the study, we attempted to explore the potential of miR-133a in regulating osteoblast activation and its anti-osteopenia function both in vitro and in vivo. Our in vitro studies at first showed that miR-133a could significantly promote the expression of osteocalcin (OCN), Collagen I, alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) and osterix (Osx), promoting the activation and mineralization of osteoblasts. Then, hindlimb unloading (HU)-challenged mice were established with or without intravenous injection of agomir-miR-133a using an osteoblast-targeting delivery system. We found that miR-133a in osteoblasts significantly alleviated the bone loss, microstructural, and biomechanical property in mice with mechanical unloading, contributing to osteopenia alleviation. Furthermore, both in vitro and in vivo experiments showed that miR-133a could restrain osteoclastogenesis via tartrate-resistant acid phosphatase (TRAP) staining. In conclusion, our results suggested that miR-133a may be a promising factor in mediating the occurrence and progression of osteopenia caused by mechanical unloading, and thus targeting miR-133a could be considered as an effective therapeutic strategy for the suppression of pathological osteopenia.

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.

The interaction of miR-181a-5p and sirtuin 1 regulated human bone marrow mesenchymal stem cells differentiation and apoptosis

Osteoporosis (OP) characterizes a decrease in bone density and bone mass which leads to brittle fractures and serious damages to individuals. In recent years, various researches have proved that miRNAs act pivotally in the onset of bone-related diseases. In our research, we probed into the impact of miR-181a-5P on viability, differentiation, as well as apoptosis of human bone marrow mesenchymal stem cells (hBMSCs). Our study reported that overexpressing miR-181a-5p considerably reduced the cell growth, whereas the miR-181a-5p inhibition showed opposite results. Furthermore, the hBMSCs apoptosis percentage was visually elevated or minimized after overexpressing or silencing miR-181a-5p, respectively. Our data also indicated that miR-181a-5p overexpression significantly inhibited ALP activity, and level of OPN, Runx2 and OCN at mRNA and protein level, whereas miR-181a-5p inhibition presented opposite results. In addition, based on luciferase reporter assay, sirtuin 1 (Sirt1) was confirmed as the target of miR-181a-5p in hBMSCs. Finally, Sirt1 overexpression significantly inhibited the impact of miR-181a-5p mimic on apoptosis and inhibited differentiation, while silencing Sirt1 eliminated the inhibitory effects of miR-181a-5p on apoptosis and promoted differentiation via PI3K/AKT pathway. In conclusion, this work revealed that miR-181a-5p could regulate hBMSCs apoptosis as well as differentiation via regulating Sirt1/PI3K/AKT signaling pathway.

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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.

MyomiR-OsteomiR crosstalk induced by different modes and intensities of exercise training and its role in controlling osteogenic differentiation in old male Wistar rats

The crosstalk between skeletal muscles and other tissues such as bones is typically established via the secretion of myokines and myomiRs induced by exercise training (ET). The present study aimed at evaluating the relationship between changes made by different ET modes and intensities in myomiRs, osteomiRs, and other myogenic and osteogenic biomarkers in old male Wistar rats. To this end, a total number of 50 old (23 months of age) male Wistar rats were randomly assigned to four experimental groups, namely, moderate-intensity endurance training (MIET), high-intensity endurance training (HIET), moderate-intensity resistance training (MIRT), high-intensity resistance training (HIRT), and control (CON), each one comprised of 10 subjects. The study findings revealed positive correlations between myomiRs (i.e., miR-1) and myomiR-204a (r = 0.725; p = 0.042), myomiR-1, and runt-related transcription factor 2 (RUNX2) osteogenic marker (r = 0.869; p = 0.025) in the HIET group, myomiR-206 and peroxisome proliferator-activated receptor gamma (PPARγ) (r = 0.908; p = 0.012) in the MIRT group, myomiR-133a and osteomiR-133a (r = 0.971; p = 0.005) in the MIET group, myomiR-133a and osteomiR-204a in the MIRT group (r = 0.971; p = 0.004), and myomiR-133a and RUNX2 gene expression in the HIET group (r = 0.861; p = 0.027). It was concluded that myomiRs involved in myoblast-osteoblast differentiation might not alone regulate the myogenic and osteogenic targets in response to different modes and intensities of ET treatments.

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.

Pharmacologic epigenetic modulators of alkaline phosphatase in chronic kidney disease

In chronic kidney disease (CKD), disturbance of several metabolic regulatory mechanisms cause premature ageing, accelerated cardiovascular disease (CVD), and mortality. Single-target interventions have repeatedly failed to improve the prognosis for CKD patients. Epigenetic interventions have the potential to modulate several pathogenetic processes simultaneously. Alkaline phosphatase (ALP) is a robust predictor of CVD and all-cause mortality and implicated in pathogenic processes associated with CVD in CKD.

LncRNA FER1L4 Promotes Oral Squamous Cell Carcinoma Progression via Targeting miR-133a-5p/Prx1 Axis

Background

Oral squamous cell carcinoma (OSCC) is a common cancer especially young people in the world. The long non-coding RNA Fer-1-like protein 4 (FER1L4) has been reported to be closely associated with the progression of various human cancers. However, the role of FER1L4 in OSCC remains unclear.

Methods

The expression level of FER1L4 in OSCC tissues and cancer cell lines was detected by using quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was evaluated by cell counting kit-8 (CCK-8) assay and EdU staining assay. Cell invasion and migration were evaluated by Transwell assay. Cell apoptosis was detected by flow cytometry. Luciferase reporter assay was performed to determine the targeting relationship between FER1L4, miR-133a-5p and Prx1. The protein expression of Prx1 was detected by Western blot. In addition, a xenograft tumor model in vivo was constructed to confirm the function of FER1L4.

Results

FERIL4 was significantly upregulated in OSCC tissues and cancer cell lines. Moreover, high level of FER1L4 predicted a poor prognosis of OSCC patients. Silencing of FER1L4 not only significantly inhibited cell growth, invasion, migration and induced apoptosis in SCC-9 and HN4 cells in vitro, but also effectively suppressed the tumorigenesis of OSCC cells in vivo. Knockdown of FER1L4 significantly enhanced the expression of miR-133a-5p by sponging it, and then downregulated Prx1 expression.

Conclusion

Our study elucidated a new mechanism of lncRNA FER1L4 that promoting OSCC progression by directly targeting miR-133a-5p/Prx1 axis and provided novel therapeutic targets for OSCC.

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.

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.

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.

Hydrostatic pressure induces osteogenic differentiation of adipose-derived mesenchymal stem cells through increasing lncRNA-PAGBC

Induced osteogenesis of adipose-derived mesenchymal stem cells (AMSCs) has been used to facilitate bone regeneration. Specifically, hydrostatic pressure (HP) has been implicated as a key regulator of AMSC differentiation, whereas the mechanisms that underlie the effects of HP on osteogenesis of AMSCs are not fully understood. Long noncoding RNAs (lncRNAs) are emerging regulators for osteogenic differentiation from AMSCs. In the current study, we found that lncRNA-PAGBC was a specific lncRNA that significantly upregulated during osteogenic differentiation of AMSCs based on published database. HP increased lncRNA-PAGBC, which is a competitive endogenous RNA (ceRNA) that binds to the osteogenesis-inhibitory microRNA, miR-133b, to regulate osteogenic differentiation of AMSCs. Moreover, a key osteogenesis-trigger gene, runt-related transcription factor 2 (RUNX2), was identified as a target gene for miR-133b. Suppression of RUNX2 by miR-133b caused impaired osteogenic differentiation of AMSCs. Furthermore, lncRNA-PAGBC overexpression upregulated, whereas lncRNA-PAGBC silencing decreased the expression of RUNX2 through miR-133b. Together, these data suggest that HP induces osteogenic differentiation of AMSCs through increasing lncRNA-PAGBC.

Cladophora glomerata enriched by biosorption with Mn(II) ions alleviates lipopolysaccharide-induced osteomyelitis-like model in MC3T3-E1, and 4B12 osteoclastogenesis

Chronic osteomyelitis, a bone infectious disease, is characterized by dysregulation of bone homeostasis, which results in excessive bone resorption. Lipopolysaccharide (LPS) which is a gram‐negative endotoxin was shown to inhibit osteoblast differentiation and to induce apoptosis and osteoclasts formation in vitro. While effective therapy against bacteria‐induced bone destruction is quite limited, the investigation of potential drugs that restore down‐regulated osteoblast function remains a major goal in the prevention of bone destruction in infective bone diseases. This investigation aimed to rescue LPS‐induced MC3T3‐E1 pre‐osteoblastic cell line using the methanolic extract of Cladophora glomerata enriched with Mn(II) ions by biosorption. LPS‐induced MC3T3‐E1 cultures supplemented with C. glomerata methanolic extract were tested for expression of the main genes and microRNAs involved in the osteogenesis pathway using RT‐PCR. Moreover, osteoclastogenesis of 4B12 cells was also investigated by tartrate‐resistant acid phosphatase (TRAP) assay. Treatment with algal extract significantly restored LPS‐suppressed bone mineralization and the mRNA expression levels of osteoblast‐specific genes such as runt‐related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteocalcin (OCN), osteopontin (OPN), miR‐27a and miR‐29b. The extract also inhibited osteoblast apoptosis, significantly restored the down‐regulated expression of Bcl‐2, and decreased the loss of MMP and reactive oxygen spices (ROS) production in MC3T3‐E1 cells induced by LPS. Furthermore, pre‐treatment with algal extract strongly decreased the activation of osteoclast in MC3T3‐E1‐4B12 coculture system stimulated by LPS. Our findings suggest that C. glomerata enriched with Mn(II) ions may be a potential raw material for the development of drug for preventing abnormal bone loss induced by LPS in bacteria‐induced bone osteomyelitis.

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.

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.

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.

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.

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