MicroRNA-138 Inhibits Osteogenic Differentiation and Mineralization of Human Dedifferentiated Chondrocytes by Regulating RhoC and the Actin Cytoskeleton

Integrated transcriptomic analysis of human induced pluripotent stem cell-derived osteogenic differentiation reveals a regulatory role of KLF16

Osteogenic differentiation is essential for bone development, metabolism, and repair; however, the underlying regulatory relationships among genes remain poorly understood. To elucidate the transcriptomic changes and identify novel regulatory genes involved in osteogenic differentiation, we differentiated mesenchymal stem cells (MSCs) derived from 20 human iPSC lines into preosteoblasts (preOBs) and osteoblasts (OBs). We then performed transcriptome profiling of MSCs, preOBs and OBs. The iPSC-derived MSCs and OBs showed similar transcriptome profiles to those of primary human MSCs and OBs, respectively. Differential gene expression analysis revealed global changes in the transcriptomes from MSCs to preOBs, and then to OBs, including the differential expression of 840 genes encoding transcription factors (TFs). TF regulatory network analysis uncovered a network comprising 451 TFs, organized into five interactive modules. Multiscale embedded gene co-expression network analysis (MEGENA) identified gene co-expression modules and key network regulators (KNRs). From these analyses, KLF16 emerged as an important TF in osteogenic differentiation. We demonstrate that overexpression of Klf16 in vitro inhibited osteogenic differentiation and mineralization, while Klf16 +/- mice exhibited increased bone mineral density, trabecular number, and cortical bone area. Our study underscores the complexity of osteogenic differentiation and identifies novel regulatory genes such as KLF16, which plays an inhibitory role in osteogenic differentiation both in vitro and in vivo.

A Multifunctional Scaffold for Bone Infection Treatment by Delivery of microRNA Therapeutics Combined With Antimicrobial Nanoparticles

Treating bone infections and ensuring bone repair is one of the greatest global challenges of modern orthopedics, made complex by antimicrobial resistance (AMR) risks due to long-term antibiotic treatment and debilitating large bone defects following infected tissue removal. An ideal multi-faceted solution would will eradicate bacterial infection without long-term antibiotic use, simultaneously stimulating osteogenesis and angiogenesis. Here, a multifunctional collagen-based scaffold that addresses these needs by leveraging the potential of antibiotic-free antimicrobial nanoparticles (copper-doped bioactive glass, CuBG) to combat infection without contributing to AMR in conjunction with microRNA-based gene therapy (utilizing an inhibitor of microRNA-138) to stimulate both osteogenesis and angiogenesis, is developed. CuBG scaffolds reduce the attachment of gram-positive bacteria by over 80%, showcasing antimicrobial functionality. The antagomiR-138 nanoparticles induce osteogenesis of human mesenchymal stem cells in vitro and heal a large load-bearing defect in a rat femur when delivered on the scaffold. Combining both promising technologies results in a multifunctional antagomiR-138-activated CuBG scaffold inducing hMSC-mediated osteogenesis and stimulating vasculogenesis in an in vivo chick chorioallantoic membrane model. Overall, this multifunctional scaffold catalyzes killing mechanisms in bacteria while inducing bone repair through osteogenic and angiogenic coupling, making this platform a promising multi-functional strategy for treating and repairing complex bone infections.

MicroRNA-138: an emerging regulator of skeletal development, homeostasis, and disease

Noncoding microRNAs are powerful epigenetic regulators of cellular processes by their ability to target and suppress expression of numerous protein-coding mRNAs. This multitargeting function is a unique and complex feature of microRNAs. It is now well-described that microRNAs play important roles in regulating the development and homeostasis of many cell/tissue types, including those that make up the skeletal system. In this review, we focus on microRNA-138 (miR-138) and its effects on regulating bone and cartilage cell differentiation and function. In addition to its reported role as a tumor suppressor, miR-138 appears to function as an inhibitor of osteoblast differentiation. This review provides additional information on studies that have attempted to alter miR-138 expression in vivo as a means to dampen ectopic calcification or alter bone mass. However, a review of the published literature on miR-138 in cartilage reveals a number of contradictory and inconclusive findings with respect to regulating chondrogenesis and chondrocyte catabolism. This highlights the need for more research in understanding the role of miR-138 in cartilage biology and disease. Interestingly, a number of studies in other systems have reported miR-138-mediated effects in dampening inflammation and pain responses. Future studies will reveal if a multifunctional role of miR-138 involving suppression of ectopic bone, inflammation, and pain will be beneficial in skeletal conditions such as osteoarthritis and heterotopic ossification.

The osteogenic and angiogenic potential of microRNA-26a delivered via a non-viral delivery peptide for bone repair

Bone-related injuries and diseases are among the most common causes of morbidity worldwide. Current bone-regenerative strategies such as auto- and allografts are invasive by nature, with adverse effects such as pain, infection and donor site morbidity. MicroRNA (miRNA) gene therapy has emerged as a promising area of research, with miRNAs capable of regulating multiple gene pathways simultaneously through the repression of post-transcriptional mRNAs. miR-26a is a key regulator of osteogenesis and has been found to be upregulated following bone injury, where it induces osteodifferentiation of mesenchymal stem cells (MSCs) and facilitates bone formation. This study demonstrates, for the first time, that the amphipathic, cell-penetrating peptide RALA can efficiently deliver miR-26a to MSCs in vitro to regulate osteogenic signalling. Transfection with miR-26a significantly increased expression of osteogenic and angiogenic markers at both gene and protein level. Using a rat calvarial defect model with a critical size defect, RALA/miR-26a NPs were delivered via an injectable, thermo-responsive Cs-g-PNIPAAm hydrogel to assess the impact on both rate and quality of bone healing. Critical defects treated with the RALA/miR-26a nanoparticles (NPs) had significantly increased bone volume and bone mineral density at 8 weeks, with increased blood vessel formation and mechanical properties. This study highlights the utility of RALA to deliver miR-26a for the purpose of bone healing within an injectable biomaterial, warranting further investigation of dose-related efficacy of the therapeutic across a range of in vivo models.

The Effect of miR-140-5p with HDAC4 towards Growth and Differentiation Signaling of Chondrocytes in Thiram-Induced Tibial Dyschondroplasia

There is evidence to suggest that microRNA-140-5p (miR-140), which acts as a suppressor, is often elevated and has a role in various malignancies. Nevertheless, neither the function nor the mechanisms in chondrocytes linked with bone disorders, e.g., tibial dyschondroplasia (TD), have been satisfactorily established. The purpose of this study was to look into the role of microRNA-140-5p (miR-140) and its interaction with HDAC4 in chondrocytes, as well as the implications for tibial dyschondroplasia (TD), with a particular focus on the relationship between low miR-140 expression and poor pathologic characteristics, as well as its physiological effects on chondrocyte growth, differentiation, and chondrodysplasia. In this investigation, we discovered that TD had a reduced expression level of the miR-140. There was a correlation between low miR-140 expression, poor pathologic characteristics, and the short overall survival of chondrocytes. Our findings show an aberrant reduction in miR-140 expression, and HDAC4 overexpression caused disengagement in resting and proliferation zones. This further resulted in uncontrolled cell proliferation, differentiation, and chondrodysplasia. Mechanistically, HDAC4 inhibited the downstream transcription factors MEF2C and Runx2 and interacted with Col-Ⅱ, Col-X, and COMP. However, miR-140 binding to the 3'-UTR of HDAC4 resulted in the growth and differentiation of chondrocytes. Moreover, the expression of HDAC4 through LMK-235 was significantly decreased, and the expression was significantly increased under ITSA-1, referring to a positive feedback circuit of miR-140 and HDAC4 for endochondral bone ossification. Furthermore, as a prospective treatment, the flavonoids of Rhizoma drynariae (TFRD) therapy increased the expression of miR-140. Compared to the TD group, TFRD treatment increased the expression of growth-promoting and chondrocyte differentiation markers, implying that TFRD can promote chondrocyte proliferation and differentiation in the tibial growth plate. Hence, directing this circuit may represent a promising target for chondrocyte-related bone disorders and all associated pathological bone conditions.

A novel implant surface modification mode of Fe3O4-containing TiO2 nanorods with sinusoidal electromagnetic field for osteoblastogenesis and angiogenesis

Implants made of Ti and its alloys are widely utilized in orthopaedic surgeries. However, insufficient osseointegration of the implants often causes complications such as aseptic loosening. Our previous research discovered that disordered titanium dioxide nanorods (TNrs) had satisfactory antibacterial properties and biocompatibility, but TNrs harmed angiogenic differentiation, which might retarded the osseointegration process of the implants. Magnetic nanomaterials have a certain potential in promoting osseointegration, electromagnetic fields within a specific frequency and intensity range can facilitate angiogenic and osteogenic differentiation. Therefore, this study used Fe₃O₄ to endow magnetism to TNrs and explored the regulation effects of Ti, TNrs, and Fe₃O₄-TNrs under 1 ​mT 15 ​Hz sinusoidal electromagnetic field (SEMF) on osteoblastogenesis, osseointegration, angiogenesis, and its mechanism. We discovered that after the addition of SEMF treatment to VR-EPCs cultured on Fe₃O₄-TNrs, the calcineurin/NFAT signaling pathway was activated, which then reversed the inhibitory effect of Fe₃O₄-TNrs on angiogenesis. Besides, Fe₃O₄-TNrs with SEMF enhanced osteogenic differentiation and osseointegration. Therefore, the implant modification mode of Fe₃O₄-TNrs with the addition of SEMF could more comprehensively promote osseointegration and provided a new idea for the modification of implants.

Trimethylamine-N-oxide sensitizes chondrocytes to mechanical loading through the upregulation of Piezo1

BACKGROUND

Mechanical strain plays a crucial role in chondrocyte apoptosis and osteoarthritis (OA) disease progression through Piezo1. Trimethylamine-N-oxide (TMAO) is a diet-derived metabolite that correlates positively with multiple chronic diseases. Herein, we explored the potential role of TMAO in sensitizing chondrocytes to Piezo1-mediated mechanotransduction.

METHODS

The cytotoxicity of TMAO on chondrocytes was assayed. Piezo1 expression was measured after TMAO intervention. Pathological mechanical loading or Yoda1 (a specific Piezo1 channel activator) was administered in chondrocytes. The calcium levels and cytoskeleton in chondrocytes were observed by fluorescence microscopy. Flow cytometry, western blotting, and mitochondrial membrane potential assays were utilized to evaluate apoptosis. A rat OA model was constructed by anterior cruciate ligament transection. Hematoxylin-eosin staining, Safranin-O/Fast Green staining, immunochemistry, and TUNEL were applied to estimate OA severity.

RESULTS

TMAO intervention alone did not affect chondrocyte viability up to 600 μM. TMAO significantly increased Piezo1 expression and up-regulated intracellular calcium levels, further leading to cytoskeletal damage. Mechanical strain or Yoda1 treatment significantly induced chondrocyte apoptosis. Notably, TMAO intervention further aggravated chondrocyte apoptosis and cartilage destruction under pathological mechanical loading.

CONCLUSION

TMAO significantly up-regulated Piezo1 expression and sensitized chondrocytes to mechanical loading, which may be closely related to the pathogenesis of OA.

Modulation of MicroRNA Expression During In Vitro Chondrogenesis

Since their discovery in 1993, microRNAs (miRNAs) are now recognized as important epigenetic regulators of many mammalian cellular processes including proliferation, apoptosis, metabolism, and differentiation. These small non-coding RNAs function by interacting with specific regions in the 3'-untranslated region of mRNAs, thereby resulting in mRNA degradation or suppression of translation. Since miRNAs have the ability to target many mRNAs within a given cell type, a number of cellular pathways and networks may be regulated as a result. To study the function of miRNAs, a number of methods can be used to modulate their activity in cells such as synthetic mimics or antagomirs for short-term assays or viral-based approaches for longer-term experiments such as cell differentiation assays. In this chapter, we provide our methodology to constitutively overexpress a desired miRNA during in vitro chondrogenesis of human cartilage progenitor cells (CPCs). Specifically, we describe how we obtain CPCs from human articular cartilage specimens, how we generate and titrate lentivirus engineered to overexpress a precursor miRNA, how we transduce CPCs with lentivirus and differentiate them toward the chondrocyte lineage, and how we extract RNA and measure expression levels of the miRNA of interest during in vitro chondrogenesis. We also provide some data from our laboratory demonstrating that we can achieve and maintain miRNA overexpression for up to 14 days in cartilage pellet cultures. We predict that these lentiviral-based approaches will also be useful to study how miRNA modulation of progenitor cells affects cell differentiation and extracellular matrix production within three-dimensional biomaterial scaffolds.

miR-652 Inhibits the Proliferation, Migration, and Invasion of Osteosarcoma Cells by Targeting HOXA9 and Regulating the PI3K/Akt Signaling Pathway

Objective

The aim of this study was to investigate the abnormal expression of miR-652 in osteosarcoma and its related mechanism.

Materials and Methods

Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the expression of miR-652 and HOXA9 in osteosarcoma tissues and normal tissues. A bioinformatics method was used to predict target genes of miR-652, and then luciferase reporter genes and western blot tests were used to verify expression of target genes. The miR-652 overexpression models were established by transfecting miR-652 mimics into osteosarcoma U-2OS cells, and HOXA9 overexpression models were simultaneously established by transfecting pcDNA3.1-HOXA9 into osteosarcoma U-2OS cells. Cell proliferation ability was detected by the CCK-8 assay, cell migration ability was detected by the scratch test, and cell invasion ability was detected by the Transwell invasion assay. Western blot tests were used to verify the expression of HOXA9, p-PI3K, p-AKT, MMP2 and MMP9.

Results

miR-652 and HOXA9 showed low expression and overexpression, respectively, in osteosarcoma tissues. Proliferation, invasion, and migration abilities of osteosarcoma cells and the level of protein expression of p-PI3K, p-Akt, MMP2, and MMP9 were significantly decreased with enhanced miR-652 expression (P < 0.01), while overexpression of HOXA9 reversed this situation. The results of dual-luciferase reporter gene showed that expression and activity of HOXA9 were downregulated accordingly, and the level of HOXA9 protein was decreased with enhancing miR-652 expression (P < 0.01).

Conclusion

miR-652 may negatively regulate HOXA9 expression and inhibit the proliferation, migration, and invasion abilities of osteosarcoma cells through the PI3K/Akt signaling pathway.

MiR-9-5p promotes M1 cell polarization in osteoarthritis progression by regulating NF-κB and AMPK signaling pathways by targeting SIRT1

OBJECTIVE

To investigate the roles and regulatory mechanisms of miR-9-5p in the development of osteoarthritis (OA).

METHODS

Synovial tissues from mouse OA model and control groups were collected and miR-9-5p expression levels and macrophage markers were measured with qPCR. The function of miR-9-5p in macrophage polarization was analyzed by flow cytometry and qPCR. Various databases were employed to screen the target genes one of which was validated with dual-luciferase analysis. Following the validation, rescue research was applied, and the signaling pathways were analyzed with Western blotting. Finally, the role of miR-9-5p in the progression of OA was validated in the mouse model.

RESULTS

MiR-9-5p was highly expressed in the synovial tissues of the OA model and was positively associated with M1 markers. Function analysis demonstrated that miR-9-5p could promote the progression of OA by promoting M1 polarization and inhibiting M2 polarization in vivo and in vitro. The mechanism analysis demonstrated that miR-9-5p could regulate macrophage polarization via NF-κB and AMPK signaling pathways by inhibiting SIRT1 expression.

CONCLUSIONS

MiR-9-5p could promote M1 polarization and OA progression by regulating NF-κB and AMPK signaling pathways by inhibiting SIRT1 expression.

Expression profiling of mitochondria-associated microRNAs during osteogenic differentiation of human MSCs

Small non-coding microRNAs (miRNAs) have the ability to target and bind to many mRNAs within the cytosol resulting in reduced protein expression and modulation of a number of cellular pathways and networks. In addition to the cytosol, miRNAs have been identified in other cellular compartments and organelles, including the mitochondria. While a few mitochondria-associated miRNAs (mitomiRs) are predicted to be derived from the mitochondrial genome, the majority appear to be transcribed from nuclear DNA and somehow transported into the mitochondria. These findings raise interesting questions about why miRNAs are located in the mitochondria and if they play a role in regulating processes within these organelles. Previously published work from our laboratory showed that miR-181a/b can regulate osteogenesis, in part, by enhancing mitochondrial metabolism. In other published studies, miR-181 paralogs and many other miRNAs have been identified in mitochondrial extracts derived from common cell lines and specific primary cells and tissues. Taken together, we were motivated to identify mitomiR expression profiles during in vitro osteogenesis. Specifically, we obtained RNA from purified mitochondrial extracts of human bone marrow-derived mesenchymal stem/stromal cells (MSCs) and from whole cell extracts of MSCs at day 0 or following osteogenic induction for 3, 7 and 14 days. Utilizing Affymetrix GeneChip™ miRNA 4.0 arrays, mitomiR expression signatures were determined at each time point. Based on the Affymetrix detection above background algorithm, the total number of miRNAs detected in MSC mitochondria extracts was 527 (non-induced MSCs), 627 (day 3 induced), 372 (day 7 induced) and 498 (day 14 induced). In addition, we identified significantly differentially-expressed mitomiRs at day 7 and day 14 of osteogenic induction when compared to day 0 (fold change ≥1.5; adjusted p value <0.05). In general, the most pronounced and highly significant changes in mitomiR expression during osteogenesis were observed at the day 7 time point. Interestingly, most miRNAs found to be differentially-expressed in mitochondria extracts did not show significantly altered expression in whole cell extracts at the same time points during osteoblast differentiation. This array study provides novel information on miRNAs associated with the mitochondria in MSCs during differentiation toward the osteoblast phenotype. These findings will guide future research to identify new miRNA candidates that may function in regulating mitochondrial function and/or bone formation, homeostasis or repair.

Changes in cytoarchitecture and mobility in B16F1 melanoma cells induced by 5-Br-2'-dU coincide with Rock2, miRNAs 138-5p and 455-3p reciprocal expressions

ROCK2 is a protein involved in the restructuring of the cytoskeleton in cell adhesion and contractibility processes. miR-138-5p and miR-455-3p regulate Rock2 expression, cell proliferation, migration, and invasion in different experimental cell models. However, their participation in the cytoarchitecture and mobility of B16F1 melanoma cells exposed to 5-Br-2'-dU is partially known. This work aimed to analyze ROCK2 and miRs 138-5p and 455-3p expression associated with morphological and mobility changes of B16F1 mouse melanoma cells exposed to the thymidine analog 5-Bromo-2'-deoxyuridine (5-Br-2'-dU). We observed an increase (2.2X n = 3, p < 0.05) in the cell area, coinciding with an increase in cell diameter (1.27X n = 3, p < 0.05), as well as greater cell granularity, capacity for circularization, adhesion, which was associated with more significant polymerization of F-actin, collapsed in the intermediate filaments of vimentin (VIM), and coinciding with a decrease in migration (87%). Changes coincided with a decrease in Rock2 mRNA expression (2.88X n = 3, p < 0.05), increased vimentin and a reciprocal decrease in miR-138-5p (1.8X), and an increase in miR-455-3p (2.39X). The Rock2 kinase inhibitor Y27632 partially rescued these changes. These results suggest ROCK2 and VIM regulate the morphological and mobility changes of B16 melanoma cells after exposure to 5-Br-2'-dU, and its expression may be reciprocally regulated, at least in part, by miR-138-5p and miR-455-3p.

LncRNA LINC01503 aggravates the progression of cervical cancer through sponging miR-342-3p to mediate FXYD3 expression

Cervical cancer (CC), an aggressive malignancy, has a high risk of relapse and death, mainly occurring in females. Accumulating investigations have confirmed the critical role of long noncoding RNAs (lncRNAs) in diverse cancers. LncRNA LINC01503 has been reported as an oncogene in several cancers. Nonetheless, its role and molecular mechanism in CC have not been explored. In the present study, we found that FXYD3 expression was considerably up-regulated in CC tissues and cells. Moreover, FXYD3 deficiency conspicuously hampered cell proliferation and migration while facilitated cell apoptosis in CC cells. Subsequently, molecular mechanism experiments implied that FXYD3 was a downstream target gene of miR-342-3p, and FXYD3 expression was reversely mediated by miR-342-3p. Moreover, we discovered that LINC01503 acted as the endogenous sponge for miR-342-3p. Besides, LINC01503 negatively regulated miR-342-3p expression and positively regulated FXYD3 expression in CC. Rescue assays revealed that LINC01503 depletion-induced repression on CC progression could be partly recovered by miR-342-3p inhibition, and then the co-transfection of sh-FXYD3#1 rescued this effect. Conclusively, LINC01503 aggravated CC progression through sponging miR-342-3p to mediate FXYD3 expression, providing promising therapeutic targets for CC patients.

The role of microRNAs in bone development

Epigenetic regulation is critical for proper bone development. Evidence from a large body of published literature informs us that microRNAs (miRNAs) are important epigenetic factors that control many aspects of bone development, homeostasis, and repair processes. These small non-coding RNAs function at the post-transcriptional level to suppress expression of specific target genes. Many target genes may be affected by one miRNA resulting in alteration in cellular pathways and networks. Therefore, changes in levels or activity of a specific miRNA (e.g. via genetic mutations, disease scenarios, or by over-expression or inhibition strategies in vitro or in vivo) can lead to substantial changes in cell processes including proliferation, metabolism, apoptosis and differentiation. In this review, Section 1 briefly covers general background information on processes that control bone development as well as the biogenesis and function of miRNAs. In Section 2, we discuss the importance of miRNAs in skeletal development based on findings from in vivo mouse models and human clinical reports. Section 3 focuses on describing more recent data from the last three years related to miRNA regulation of osteoblast differentiation in vitro. Some of these studies also involve utilization of an in vivo rodent model to study the effects of miRNA modulation in scenarios of osteoporosis, bone repair or ectopic bone formation. In Section 4, we provide some recent information from studies analyzing the potential of miRNA-mediated crosstalk in bone and how exosomes containing miRNAs from one bone cell may affect the differentiation or function of another bone cell type. We then conclude by summarizing where the field currently stands with respect to miRNA-mediated regulation of osteogenesis and how information gained from developmental processes can be instructive in identifying potential therapeutic miRNA targets for the treatment of certain bone conditions.

Identification of Serum Exosomal MicroRNA Expression Profiling in Menopausal Females with Osteoporosis by High-throughput Sequencing

Estrogen deficiency, which mainly occurs in postmenopausal women, is a primary reason for osteoporosis in clinical diagnosis. However, the molecular regulation of osteoporosis in menopausal females is still not adequately explained in the literature, with the diagnosis and treatment for osteoporosis being limited. Herein, exosomal microRNAs (miRNAs) were used to evaluate their diagnosis and prediction effects in menopausal females with osteoporosis. In this study, 6 menopausal females without osteoporosis and 12 menopausal females with osteoporosis were enrolled. The serum exosomes were isolated, and the miRNA expression was detected by miRNA high-throughput sequencing. Exosomal miRNA effects were analyzed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. The miRNA-targeted genes were evaluated by Targetscan 7.2 and the protein-protein interactions (PPI) by STRING. Hub genes were analyzed by the CytoHubba app of Cytoscape. The results showed that 191 aberrant miRNAs were found in the group of menopausal females with osteoporosis, including 72 upregulated miRNAs and 121 downregulated miRNAs. Aberrant miRNAs were involved in many signaling pathways, such as the Wnt, MAPK, and Hippo pathways. Based on PPI network analysis, FBXL3, FBXL13, COPS2, UBE2D3, DCUN1D1, DCUN1D4, CUL3, FBXO22, ASB6, and COMMD2 were the 10 most notable genes in the PPI network. In conclusion, aberrant serum exosomal miRNAs were associated with an altered risk of osteoporosis in menopausal females and may act as potential biomarkers for the prediction of risk of osteoporosis in menopausal females.

Sdccag3 Promotes Implant Osseointegration during Experimental Hyperlipidemia

Hyperlipidemia adversely affects bone metabolism, often resulting in compromised osseointegration and implant loss. In addition, genetic networks associated with osseointegration have been proposed. Serologically defined colon cancer antigen 3 (Sdccag3) is a novel endosomal protein that functions in actin cytoskeleton remodeling, protein trafficking and secretion, cytokinesis, and apoptosis, but its roles in the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and in implant osseointegration under hyperlipidemic conditions have not been uncovered. Here, we performed microarray and RNA sequencing analysis to determine the differential expression of the Sdccag3 gene and related noncoding RNAs (ncRNAs) and to assess the long noncoding RNA (lncRNA) MSTRG.97162.4-miR-193a-3p-Sdccag3 coexpression network in bone tissues within the region 0.5 mm around implants in hyperlipidemic rats. In this experiment, we found that Sdccag3 and the previously uncharacterized lncRNA-MSTRG.97162.4 were downregulated during hyperlipidemia, while miR-193a-3p was upregulated. Sdccag3 overexpression increased new trabecular formation, the bone volume/total volume (BV/TV) (1.24-fold), and bone-implant combination ratio (BIC%) (1.26-fold). An RNA pulldown experiment revealed that Sdccag3 protein targeted lncRNA-MSTRG.97162.4 nucleotides 361 to 389. In addition, lncRNA-MSTRG.97162.4 overexpression significantly enhanced Sdccag3 (2.78-fold) expression and increased BV/TV (1.45-fold) and BIC% (1.07-fold) at the bone-implant interface. Taken together, these findings indicate that Sdccag3 overexpression enhances implant osseointegration under hyperlipidemic conditions by binding to lncRNA-MSTRG.97162.4. Furthermore, miR-193a-3p overexpression inhibited lncRNA-MSTRG.97162.4 (0.63-fold) and Sdccag3 (0.88-fold) expression and induced poor implant osseointegration (BV/TV, 0.86-fold; BIC%, 0.82-fold), while miR-193a-3p downregulation produced the opposite results (lncRNA-MSTRG.97162.4, 10.69-fold; Sdccag3, 6.96-fold; BV/TV, 1.20-fold; BIC%, 1.26-fold). Therefore, our findings show that Sdccag3 promotes implant osseointegration, and its related lncRNA-MSTRG.97162.4 and miR-193a-3p play an important role in osseointegration during hyperlipidemia, which might be a promising therapeutic target for improving dental implantation success rates.

Osteoarthritis year in review 2019: genetics, genomics and epigenetics

Although osteoarthritis (OA) aetiology is complex, genetic, genomic and epigenetic studies published within the last decade have advanced our understanding of the molecular processes underlying this common musculoskeletal disease. The purpose of this narrative review is to highlight the key research articles within the OA genetics, genomics and epigenetics fields that were published between April 2018 and April 2019. The review focuses on the identification of new OA genetic risk loci, genomics techniques that have been used for the first time in human cartilage and new publicly available databases, and datasets that will aid OA functional studies. Fifty-six new OA susceptibility loci were identified by two large scale genome wide association study meta-analyses, increasing the number of genome-wide significant risk loci to 90. OA risk variants are enriched near genes involved in skeletal development and morphology, and show genetic overlap with height, hip shape, bone area and developmental dysplasia of the hip. Several functional studies of OA loci were published, including a genome-wide analysis of genetic variation on cartilage gene expression. A specialised data portal for exploring cross-species skeletal transcriptomic datasets has been developed, and the first use of cartilage single cell RNAseq analysis reported. This year also saw the systematic identification of all microRNAs, long non-coding RNAs and circular RNAs expressed in human OA cartilage. Putative transcriptional regulatory regions have been mapped in human chondrocytes genome-wide, providing a dataset that will facilitate the prioritisation and characterisation of OA genetic and epigenetic loci.

Non-Coding RNAs in Cartilage Development: An Updated Review

In the development of the skeleton, the long bones are arising from the process of endochondral ossification (EO) in which cartilage is replaced by bone. This complex process is regulated by various factors including genetic, epigenetic, and environmental elements. It is recognized that DNA methylation, higher-order chromatin structure, and post-translational modifications of histones regulate the EO. With emerging understanding, non-coding RNAs (ncRNAs) have been identified as another mode of EO regulation, which is consist of microRNAs (miRNAs or miRs) and long non-coding RNAs (lncRNAs). There is expanding experimental evidence to unlock the role of ncRNAs in the differentiation of cartilage cells, as well as the pathogenesis of several skeletal disorders including osteoarthritis. Cutting-edge technologies such as epigenome-wide association studies have been employed to reveal disease-specific patterns regarding ncRNAs. This opens a new avenue of our understanding of skeletal cell biology, and may also identify potential epigenetic-based biomarkers. In this review, we provide an updated overview of recent advances in the role of ncRNAs especially focus on miRNA and lncRNA in the development of bone from cartilage, as well as their roles in skeletal pathophysiology.

MicroRNA-181a/b-1 over-expression enhances osteogenesis by modulating PTEN/PI3K/AKT signaling and mitochondrial metabolism

MicroRNAs are small non-coding RNAs that play important roles in many cellular processes including proliferation, metabolism and differentiation. They function by binding to specific regions within the 3'UTR of target mRNAs resulting in suppression of protein synthesis and modulation of potentially many cellular pathways. We previously showed that miRNA expression levels differed between cells from distinct regions of developing human embryonic long bones. Specifically, we found that miR-181a-1 was significantly more highly expressed in hypertrophic chondrocytes compared to proliferating differentiated or progenitor chondrocytes, suggesting a potential role in regulating chondrocyte hypertrophy and/or endochondral bone formation. The goal of this study was to determine how miR-181a-1 together with its clustered miRNA, miR-181b-1, regulates osteogenesis. We show that over-expression of the miR-181a/b-1 cluster enhanced osteogenesis and that cellular pathways associated with protein synthesis and mitochondrial metabolism were significantly up-regulated. Metabolic assays revealed that the oxygen consumption rate and ATP-linked respiration were increased by miR-181a/b-1. To further decipher a potential mechanism causing these metabolic changes, we showed that PTEN (phosphatase and tensin homolog) levels were suppressed following miR-181a/b-1 over-expression, and that PI3K/AKT signaling was subsequently increased. Over-expression of PTEN was found to attenuate the enhancing effects of miR-181a/b-1, providing further evidence that miR-181a/b-1 regulates the PTEN/PI3K/AKT axis to enhance osteogenic differentiation and mitochondrial metabolism. These findings have important implications for the design of miR-181a/b targeting strategies to treat bone conditions such as fractures or heterotopic ossification.