miRNAs Related to Skeletal Diseases

Highly Multiplexed, Efficient, and Automated Single-Cell MicroRNA Sequencing with Digital Microfluidics

Single-cell microRNA (miRNA) sequencing has allowed for comprehensively studying the abundance and complex networks of miRNAs, which provides insights beyond single-cell heterogeneity into the dynamic regulation of cellular events. Current benchtop-based technologies for single-cell miRNA sequencing are low throughput, limited reaction efficiency, tedious manual operations, and high reagent costs. Here, a highly multiplexed, efficient, integrated, and automated sample preparation platform is introduced for single-cell miRNA sequencing based on digital microfluidics (DMF), named Hiper-seq. The platform integrates major steps and automates the iterative operations of miRNA sequencing library construction by digital control of addressable droplets on the DMF chip. Based on the design of hydrophilic micro-structures and the capability of handling droplets of DMF, multiple single cells can be selectively isolated and subject to sample processing in a highly parallel way, thus increasing the throughput and efficiency for single-cell miRNA measurement. The nanoliter reaction volume of this platform enables a much higher miRNA detection ability and lower reagent cost compared to benchtop methods. It is further applied Hiper-seq to explore miRNAs involved in the ossification of mouse skeletal stem cells after bone fracture and discovered unreported miRNAs that regulate bone repairing.

Surgical suction filter-derived bone graft displays osteogenic miRNA and mRNA patterns

PURPOSE

Recently, a surgical suction filter device was introduced which aims at generating a suction filter-derived bone grafting substitute (SF-BGS). The osteogenic capacity of this grafting material, however, is unclear. MicroRNAs (miRNAs) and osteogenic mRNAs may influence these processes. The aim of this study was therefore to investigate the quality of the SF-BGS by determining the expression of miRNAs and osteogenic mRNAs.

METHODS

Samples were collected during non-union surgery. Upon exposure of the intramedullary canal, the surgical vacuum system was fitted with the suction filter device containing collagen complex and synthetic β-TCP: (Ca3(PO4)2, granule size 5-8 mm, total volume 10 mL (Cerasorb Foam®, Curasan AG, Kleinostheim, Germany). As a control, venous blood was used as in current clinical practice. Samples were snap-frozen and mechanically disrupted. MiRNAs and mRNAs were isolated, transcribed, and pooled for qPCR analysis. Lastly, mRNA targets were determined through in silico target analyses.

RESULTS

The study population consisted of seven patients with a posttraumatic long bone non-union (4♀; mean age 54 ± 16 years). From the array data, distinct differences in miRNA expression were found between the SF-BGS and control samples. Osteogenic marker genes were overall upregulated in the SF-BGS. Qiagen IPA software identified 1168 mRNA targets for 43 of the overall deregulated miRNAs.

CONCLUSION

This study revealed distinctly deregulated and exclusively expressed osteogenic miRNAs in SF-BGS, as well as overall enhanced osteogenic marker gene expression, as compared to the venous blood control group. These expression profiles were not seen in control samples, indicating that the derived material displays an osteogenic profile. It may therefore be a promising tool to generate a BGS or graft extender when needed.

Specific microRNAs are associated with fracture healing phases, patient age and multi-trauma

Background

Methods

Results

Conclusion

The Translational Potential of this Article

A Comparative Study of Mesoporous Silica and Mesoporous Bioactive Glass Nanoparticles as Non-Viral MicroRNA Vectors for Osteogenesis

Micro-ribonucleic acid (miRNA)-based therapies show advantages for bone regeneration but need efficient intracellular delivery methods. Inorganic nanoparticles such as mesoporous bioactive glass nanoparticles (MBGN) and mesoporous silica nanoparticles (MSN) have received growing interest in the intracellular delivery of nucleic acids. This study explores the capacity of MBGN and MSN for delivering miRNA to bone marrow mesenchymal stem cells (BMSC) for bone regenerative purposes, with a focus on comparing the two in terms of cell viability, transfection efficiency, and osteogenic actions. Spherical MBGN and MSN with a particle size of ~200 nm and small-sized mesopores were prepared using the sol-gel method, and then the surface was modified with polyethyleneimine for miRNA loading and delivery. The results showed miRNA can be loaded into both nanoparticles within 2 h and was released sustainedly for up to 3 days. Confocal laser scanning microscopy and flow cytometry analysis indicated a high transfection efficiency (>64%) of both nanoparticles without statistical difference. Compared with MSN, MBGN showed stronger activation of alkaline phosphatase and activation of osteocalcin genes. This translated to a greater osteogenic effect of MBGN on BMSC, with Alizarin red staining showing greater mineralization compared with the MSN group. These findings show the potential for MBGN to be used in bone tissue engineering.

miR-375 is cold exposure sensitive and drives thermogenesis in visceral adipose tissue derived stem cells

Activation of brown adipose tissue may increase energy expenditure by non-shivering thermogenesis. Cold exposure is one of the options to activate brown adipocytes. To link changes in energy metabolism with microRNA expression (miRNAs), we analyzed 158 miRNAs in serum of 169 healthy individuals before and after cold exposure. Validating the results of a miRNA array, a significant down-regulation of miR-375 after cold exposure (P < 0.0001) was detected. These changes went along with a significant negative correlation between miR-375 and visceral adipose tissue (VAT) mass (P < 0.0001), implicating a specific function of miR-375 in this depot. Significantly higher expression levels of miR-375 were found in VAT in comparison to subcutaneous fat (SAT). Using in silico prediction, we identified putative miR-375 target genes involved in the thermogenesis pathway. Cold-stimulation of subcutaneous and visceral pre-adipocytes (PACs) led to significantly higher expression levels of FABP4, FGF21, PPARGC1A and PRDM16 in VC-PACs. Analyzing miR-375 knock down and cold stimulated VC-PACs revealed a significant up-regulation of thermogenesis associated genes PPARGC1A, ELOVL3 and PRDM16. In summary, our findings identified miR-375 as a potential adipogenic and thermogenesis-associated miRNA exclusively acting in visceral adipose tissue.

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.

Interactions Among lncRNA/circRNA, miRNA, and mRNA in Musculoskeletal Degenerative Diseases

Musculoskeletal degenerative diseases (MSDDs) are pathological conditions that affect muscle, bone, cartilage, joint and connective tissue, leading to physical and functional impairments in patients, mainly consist of osteoarthritis (OA), intervertebral disc degeneration (IDD), rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) are novel regulators of gene expression that play an important role in biological regulation, involving in chondrocyte proliferation and apoptosis, extracellular matrix degradation and peripheral blood mononuclear cell inflammation. Research on MSDD pathogenesis, especially on RA and AS, is still in its infancy and major knowledge gaps remain to be filled. The effects of lncRNA/circRNA-miRNA-mRNA axis on MSDD progression help us to fully understand their contribution to the dynamic cellular processes, provide the potential OA, IDD, RA and AS therapeutic strategies. Further studies are needed to explore the mutual regulatory mechanisms between lncRNA/circRNA regulation and effective therapeutic interventions in the pathology of MSDD.

Efficient transfection and long-term stability of rno-miRNA-26a-5p for osteogenic differentiation by large pore sized mesoporous silica nanoparticles

MicroRNA (miRNA) based therapy for bone repair has shown promising results for regulating stem cell proliferation and differentiation, an efficient and stable vector for delivery of microRNA delivery is needed. The present study explored the stability and functionality of lyophilized mesoporous silica nanoparticles with core-cone structure and coated with polyethylenimine (MSN-CC-PEI) as a system for delivering Rattus norvegicus (rno)-miRNA-26a-5p into rat marrow mesenchymal cells (rBMSCs) to promote their osteogenic differentiation. We assessed the cellular uptake and transfection efficiency of nanoparticles loaded with labelled miRNA using confocal laser scanning microscopy and flow cytometry, and the cell viability using the MTT assay. The expression levels of osteogenic genes after one and two weeks were analysed by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Extracellular matrix deposition and mineralization at 3 weeks were evaluated using Picro Sirius red and Alizarin red staining. We also assessed the performance of the delivery system after long term storage, by freeze drying rno-miRNA-26a-5p@MSN-CC-PEI with 5% trehalose and keeping them at -30 °C for 3 and 6 months. Osteogenic differentiation, matrix deposition, and mineralization were all significantly increased by rno-miRNA-26a-5p. In addition, this enhancement was not significantly altered by lyophilization and storage. Overall, these findings support the concept of MSN-CC-PEI as a delivery system for gene therapy. The complex of rno-miRNA-26a-5p@MSN-CC-PEI could efficiently transfect rBMSCs and enhance their osteogenic differentiation. In addition, the lyophilized complexes remain functional after 6 months of storage.

The future of basic science in orthopaedics and traumatology: Cassandra or Prometheus?

Orthopaedic and trauma research is a gateway to better health and mobility, reflecting the ever-increasing and complex burden of musculoskeletal diseases and injuries in Germany, Europe and worldwide. Basic science in orthopaedics and traumatology addresses the complete organism down to the molecule among an entire life of musculoskeletal mobility. Reflecting the complex and intertwined underlying mechanisms, cooperative research in this field has discovered important mechanisms on the molecular, cellular and organ levels, which subsequently led to innovative diagnostic and therapeutic strategies that reduced individual suffering as well as the burden on the society. However, research efforts are considerably threatened by economical pressures on clinicians and scientists, growing obstacles for urgently needed translational animal research, and insufficient funding. Although sophisticated science is feasible and realized in ever more individual research groups, a main goal of the multidisciplinary members of the Basic Science Section of the German Society for Orthopaedics and Trauma Surgery is to generate overarching structures and networks to answer to the growing clinical needs. The future of basic science in orthopaedics and traumatology can only be managed by an even more intensified exchange between basic scientists and clinicians while fuelling enthusiasm of talented junior scientists and clinicians. Prioritized future projects will master a broad range of opportunities from artificial intelligence, gene- and nano-technologies to large-scale, multi-centre clinical studies. Like Prometheus in the ancient Greek myth, transferring the elucidating knowledge from basic science to the real (clinical) world will reduce the individual suffering from orthopaedic diseases and trauma as well as their socio-economic impact.

Skeletal Aging and Osteoporosis: Mechanisms and Therapeutics

Bone is a dynamic organ maintained by tightly regulated mechanisms. With old age, bone homeostasis, which is maintained by an intricate balance between bone formation and bone resorption, undergoes deregulation. Oxidative stress-induced DNA damage, cellular apoptosis, and cellular senescence are all responsible for this tissue dysfunction and the imbalance in the bone homeostasis. These cellular mechanisms have become a target for therapeutics to treat age-related osteoporosis. Genetic mouse models have shown the importance of senescent cell clearance in alleviating age-related osteoporosis. Furthermore, we and others have shown that targeting cellular senescence pharmacologically was an effective tool to alleviate age- and radiation-induced osteoporosis. Senescent cells also have an altered secretome known as the senescence associated secretory phenotype (SASP), which may have autocrine, paracrine, or endocrine function. The current review discusses the current and potential pathways which lead to a senescence profile in an aged skeleton and how bone homeostasis is affected during age-related osteoporosis. The review has also discussed existing therapeutics for the treatment of osteoporosis and rationalizes for novel therapeutic options based on cellular senescence and the SASP as an underlying pathogenesis of an aging bone.

Designing biomaterials for the delivery of RNA therapeutics to stimulate bone healing

Ribonucleic acids (small interfering RNA, microRNA, and messenger RNA) have been emerging as a promising new class of therapeutics for bone regeneration. So far, however, research has mostly focused on stability and complexation of these oligonucleotides for systemic delivery. By comparison, delivery of RNA nanocomplexes from biomaterial carriers can facilitate a spatiotemporally controlled local delivery of osteogenic oligonucleotides. This review provides an overview of the state-of-the-art in the design of biomaterials which allow for temporal and spatial control over RNA delivery. We correlate this concept of spatiotemporally controlled RNA delivery to the most relevant events that govern bone regeneration to evaluate to which extent tuning of release kinetics is required. In addition, inspired by the physiological principles of bone regeneration, potential new RNA targets are presented. Finally, considerations for clinical translation and upscaled production are summarized to stimulate the design of clinically relevant RNA-releasing biomaterials.

microRNAs Mediated Regulation of the Ribosomal Proteins and its Consequences on the Global Translation of Proteins

Ribosomal proteins (RPs) are mostly derived from the energy-consuming enzyme families such as ATP-dependent RNA helicases, AAA-ATPases, GTPases and kinases, and are important structural components of the ribosome, which is a supramolecular ribonucleoprotein complex, composed of Ribosomal RNA (rRNA) and RPs, coordinates the translation and synthesis of proteins with the help of transfer RNA (tRNA) and other factors. Not all RPs are indispensable; in other words, the ribosome could be functional and could continue the translation of proteins instead of lacking in some of the RPs. However, the lack of many RPs could result in severe defects in the biogenesis of ribosomes, which could directly influence the overall translation processes and global expression of the proteins leading to the emergence of different diseases including cancer. While microRNAs (miRNAs) are small non-coding RNAs and one of the potent regulators of the post-transcriptional gene expression, miRNAs regulate gene expression by targeting the 3' untranslated region and/or coding region of the messenger RNAs (mRNAs), and by interacting with the 5' untranslated region, and eventually finetune the expression of approximately one-third of all mammalian genes. Herein, we highlighted the significance of miRNAs mediated regulation of RPs coding mRNAs in the global protein translation.

Effects of the chorion on the developmental toxicity of organophosphate esters in zebrafish embryos

Many toxicological studies have utilized zebrafish embryos to investigate the developmental toxicity of organophosphate esters (OPEs). However, in respect of the presence or absence of the chorion, a consistent experimental methodology has yet to be developed. In this study, we used a fixed exposure scheme to compare the developmental toxicities of six major OPEs in chorionated and dechorionated zebrafish embryos. Removal of the chorion increased sensitivity to OPEs: we found higher incidence of mortality and malformation in dechorionated embryos. In a behavioral assay, the locomotive activity of zebrafish larvae was consistently inhibited by OPEs except tris (1-chloropropyl) phosphate regardless of chorion presence. However, at the molecular level, the expression of ZHE1 and mmp9 was affected by the presence of the chorion in zebrafish embryos exposed to tributyl phosphate and triphenyl phosphate (TPHP), respectively. Furthermore, in zebrafish embryos exposed to TPHP, the increased expression of miR-137 and miR-141 was abolished by the presence of the chorion. Our results demonstrate for the first time that the presence of the chorion influences phenotypic morbidity, organismal behavior, and gene expression in zebrafish embryos exposed to chemicals; thus, we suggest that dechorionation is desirable for exploring the toxicity mechanisms that underlie effects of chemical exposure.

Circulating microRNA let‑7e is decreased in knee osteoarthritis, accompanied by elevated apoptosis and reduced autophagy

Knee osteoarthritis (KOA) is a major cause of leg disability in the elderly population. Recently, the expression levels of circulating microRNA (miRNA) let-7e have been reported to be significantly reduced in KOA. The aims of the present study were to assess the feasibility of let-7e as a serum marker for detecting KOA and to explore the underlying mechanisms of its involvement. Based on previous studies and bioinformatics analysis, let-7e may regulate apoptosis and autophagy of articular chondrocytes. A total of 10 patients with KOA and 10 patients with trauma without KOA were recruited to examine the levels of let-7e in peripheral blood. Subsequently, KOA rat models were established, and the levels of let-7e in the cartilage and serum were examined, the expression of apoptotic proteins and autophagy-related proteins in the cartilage were investigated, and apoptotic and autophagic activities of primary cultured chondrocytes were also detected. In patients with KOA, let-7e levels in the peripheral serum were significantly decreased compared with the control group, and this result was confirmed in the peripheral serum and cartilage of KOA rats. In addition, the expression levels of proteins involved in the apoptotic pathway were increased in the cartilage of KOA rats, and apoptotic activity was increased. The expression of autophagy-related proteins beclin 1 and microtubule associated protein 1 light chain 3 β (LC3B) II/LC3BI in the articular cartilage of KOA rats was lower compared with the controls, and autophagy was decreased. Si-Miao-San (SMS) treatment restored the expression of let-7e and reversed the changes in apoptosis and autophagy. Therefore, the present study provided additional evidence that circulating let-7e may be a potential serum biomarker for the diagnosis and treatment of KOA. Elevated apoptosis levels and decreased autophagy levels of cartilage tissue are involved in KOA, and treatment with SMS may reverse these effects.

Hyperbaric oxygen inhibits the HMGB1/RAGE signaling pathway by upregulating Mir-107 expression in human osteoarthritic chondrocytes

OBJECTIVE

MicroRNA (miRNA)107 expression is downregulated but high mobility group box 1 (HMGB-1), Toll-like receptors (TLRs), and receptor for advanced glycation end products (RAGE) are upregulated in osteoarthritic (OA) cartilage. We investigated mir-107/HMGB-1 signaling in OA after hyperbaric oxygen (HBO) treatment.

DESIGN

MiR-107 mimic was transfected and the HMGB-1 was analyzed in OA chondrocytes. MiRNA targets were identified using bioinformatics and a luciferase reporter assay. After HBO treatment, the mRNA or protein levels of HMGB-1, RAGE, TLR2, TLR4, and inducible nitric oxide (NO) synthase (iNOS) and phosphorylation of mitogen-activated protein kinase (MAPK) were evaluated. The secreted HMGB-1 and matrix metalloproteases (MMPs) levels were quantified. Finally, we detected the HMGB-1 and iNOS expression in rabbit cartilage defects.

RESULTS

Overexpression of miR-107 suppressed HMGB-1 expression in OA chondrocytes. The 3'UTR of HMGB-1 mRNA contained a 'seed-matched-sequence' for miR-107. MiR-107 was induced by HBO and a marked suppression of HMGB-1 was observed simultaneously in OA chondrocytes. Knockdown of miR-107 upregulated HMGB-1 expression in hyperoxic cells. HBO downregulated the mRNA and protein expression of HMGB-1, RAGE, TLR2, TLR4, and iNOS, and the secretion of HMGB-1. HBO decreased the nuclear translocation of nuclear factor (NF)-κB, downregulated the phosphorylation of MAPK, and significantly decreased the secretion of MMPs. Morphological and immunohistochemical observation demonstrated that HBO markedly enhanced cartilage repair and the area stained positive for HMGB-1 and iNOS tended to be lower in the HBO group.

CONCLUSIONS

HBO inhibits HMGB-1/RAGE signaling related pathways by upregulating miR-107 expression in human OA chondrocytes.

miRNA-26a-5p Accelerates Healing via Downregulation of PTEN in Fracture Patients with Traumatic Brain Injury

Patients who sustain a traumatic brain injury (TBI) are known to have a significantly quicker fracture healing time than patients with isolated fractures, but the underlying mechanism has yet to be identified. In this study, we found that the upregulation of miRNA-26a-5p induced by TBI correlated with a decrease in phosphatase and tensin homolog (PTEN) in callus formation. In vitro, overexpressing miRNA-26a-5p inhibited PTEN expression and accelerated osteoblast differentiation, whereas silencing of miRNA-26a-5p inhibited osteoblast activity. Reduction of PTEN facilitated osteoblast differentiation via the PI3K/AKT signaling pathway. Through luciferase assays, we found evidence that PTEN is a miRNA-26a-5p target gene that negatively regulates the differentiation of osteoblasts. Moreover, the present study confirmed that preinjection of agomiR-26a-5p leads to increased bone formation. Collectively, these results indicate that miRNA-26a-5p overexpression may be a key factor governing the improved fracture healing observed in TBI patients after the downregulation of PTEN and PI3K/AKT signaling. Upregulation of miRNA-26a-5p may therefore be a promising therapeutic strategy for promoting fracture healing.

Stem cells in Osteoporosis: From Biology to New Therapeutic Approaches

Osteoporosis is a systemic disease that affects the skeleton, causing reduction of bone density and mass, resulting in destruction of bone microstructure and increased risk of bone fractures. Since osteoporosis is a disease affecting the elderly and the aging of the world's population is constantly increasing, it is expected that the incidence of osteoporosis and its financial burden on the insurance systems will increase continuously and there is a need for more understanding this condition in order to prevent and/or treat it. At present, available drug therapy for osteoporosis primarily targets the inhibition of bone resorption and agents that promote bone mineralization, designed to slow disease progression. Safe and predictable pharmaceutical means to increase bone formation have been elusive. Stem cell therapy of osteoporosis, as a therapeutic strategy, offers the promise of an increase in osteoblast differentiation and thus reversing the shift towards bone resorption in osteoporosis. This review is focused on the current views regarding the implication of the stem cells in the cellular and physiologic mechanisms of osteoporosis and discusses data obtained from stem cell-based therapies of osteoporosis in experimental animal models and the possibility of their future application in clinical trials.

The Therapeutic Potential of MicroRNAs as Orthobiologics for Skeletal Fractures

The repair of a fractured bone is critical to the well-being of humans. Failure of the repair process to proceed normally can lead to complicated fractures, exemplified by either a delay in union or a complete nonunion. Both of these conditions lead to pain, the possibility of additional surgery, and impairment of life quality. Additionally, work productivity decreases, income is reduced, and treatment costs increase, resulting in financial hardship. Thus, developing effective treatments for these difficult fractures or even accelerating the normal physiological repair process is warranted. Accumulating evidence shows that microRNAs (miRNAs), small noncoding RNAs, can serve as key regulatory molecules of fracture repair. In this review, a brief description of the fracture repair process and miRNA biogenesis is presented, as well as a summary of our current knowledge of the involvement of miRNAs in physiological fracture repair, osteoporotic fractures, and bone defect healing. Further, miRNA polymorphisms associated with fractures, miRNA presence in exosomes, and miRNAs as potential therapeutic orthobiologics are also discussed. This is a timely review as several miRNA-based therapeutics have recently entered clinical trials for nonskeletal applications and thus it is incumbent upon bone researchers to explore whether miRNAs can become the next class of orthobiologics for the treatment of skeletal fractures.

Micrornas at the Interface between Osteogenesis and Angiogenesis as Targets for Bone Regeneration

Bone formation and regeneration is a multistep complex process crucially determined by the formation of blood vessels in the growth plate region. This is preceded by the expression of growth factors, notably the vascular endothelial growth factor (VEGF), secreted by osteogenic cells, as well as the corresponding response of endothelial cells, although the exact mechanisms remain to be clarified. Thereby, coordinated coupling between osteogenesis and angiogenesis is initiated and sustained. The precise interplay of these two fundamental processes is crucial during times of rapid bone growth or fracture repair in adults. Deviations in this balance might lead to pathologic conditions such as osteoarthritis and ectopic bone formation. Besides VEGF, the recently discovered important regulatory and modifying functions of microRNAs also support this key mechanism. These comprise two principal categories of microRNAs that were identified with specific functions in bone formation (osteomiRs) and/or angiogenesis (angiomiRs). However, as hypoxia is a major driving force behind bone angiogenesis, a third group involved in this process is represented by hypoxia-inducible microRNAs (hypoxamiRs). This review was focused on the identification of microRNAs that were found to have an active role in osteogenesis as well as angiogenesis to date that were termed "CouplingmiRs (CPLGmiRs)". Outlined representatives therefore represent microRNAs that already have been associated with an active role in osteogenic-angiogenic coupling or are presumed to have its potential. Elucidation of the molecular mechanisms governing bone angiogenesis are of great relevance for improving therapeutic options in bone regeneration, tissue-engineering, and the treatment of bone-related diseases.

Role of Epigenomics in Bone and Cartilage Disease

Phenotypic variation in skeletal traits and diseases is the product of genetic and environmental factors. Epigenetic mechanisms include information-containing factors, other than DNA sequence, that cause stable changes in gene expression and are maintained during cell divisions. They represent a link between environmental influences, genome features, and the resulting phenotype. The main epigenetic factors are DNA methylation, posttranslational changes of histones, and higher-order chromatin structure. Sometimes non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are also included in the broad term of epigenetic factors. There is rapidly expanding experimental evidence for a role of epigenetic factors in the differentiation of bone cells and the pathogenesis of skeletal disorders, such as osteoporosis and osteoarthritis. However, different from genetic factors, epigenetic signatures are cell- and tissue-specific and can change with time. Thus, elucidating their role has particular difficulties, especially in human studies. Nevertheless, epigenomewide association studies are beginning to disclose some disease-specific patterns that help to understand skeletal cell biology and may lead to development of new epigenetic-based biomarkers, as well as new drug targets useful for treating diffuse and localized disorders. Here we provide an overview and update of recent advances on the role of epigenomics in bone and cartilage diseases. © 2019 American Society for Bone and Mineral Research.

Upregulation of miR-107 expression following hyperbaric oxygen treatment suppresses HMGB1/RAGE signaling in degenerated human nucleus pulposus cells

Background

The expression of both high-mobility group box 1 (HMGB1) and receptor for advanced glycation end-products (RAGE) is upregulated in degenerated discs. HMGB1 is known to function as a coupling factor between hypoxia and inflammation in arthritis, and this inflammatory response is modulated by microRNAs (miRNAs), with miR-107 expression downregulated during hypoxia. In this study, we investigated the regulation of the miR-107/HMGB1/RAGE pathway in degenerated nucleus pulposus cells (NPCs) after hyperbaric oxygen (HBO) treatment.

Methods

NPCs were separated from human degenerated intervertebral disc tissues. The control cells were maintained in 5% CO₂/95% air, and the hyperoxic cells were exposed to 100% O₂ at 2.5 atmospheres absolute. MiRNA expression profiling was performed via microarray and confirmed by real-time PCR, and miRNA target genes were identified using bioinformatics and luciferase reporter assays. The cellular protein and mRNA levels of HMGB1, RAGE, and inducible nitric oxide synthase (iNOS) were assessed, and the phosphorylation of MAPK (p38MAPK, ERK, and JNK) was evaluated. Additionally, cytosolic and nuclear fractions of the IκBα and NF-κB p65 proteins were analyzed, and secreted HMGB1 and metalloprotease (MMP) levels in the conditioned media were quantified.

Results

Using microarray analyses, 96 miRNAs were identified as upregulated and 66 downregulated following HBO treatment. Based on these results, miR-107 was selected for further investigation. Bioinformatics analyses indicated that the 3′ untranslated region of the HMGB1 mRNA contained the “seed-matched-sequence” for hsa-miR-107, which was validated via dual-luciferase reporter assays. MiR-107 was markedly induced by HBO, and simultaneous suppression of HMGB1 was observed in NPCs. Knockdown of miR-107 resulted in upregulation of HMGB1 expression in HBO-treated cells, and HBO treatment downregulated the mRNA and protein levels of HMGB1, RAGE, and iNOS and the secretion of HMGB1. In addition, HBO treatment upregulated the protein levels of cytosolic IκBα and decreased the nuclear translocation of NF-κB in NPCs. Moreover, HBO treatment downregulated the phosphorylation of p38MAPK, ERK, and JNK and significantly decreased the secretion of MMP-3, MMP-9, and MMP-13.

Conclusions

HBO inhibits pathways related to HMGB1/RAGE signaling via upregulation of miR-107 expression in degenerated human NPCs.

Mmu-miR-92a-2-5p targets TLR2 to relieve Schistosoma japonicum-induced liver fibrosis

According to conservative estimates, >230 million people are infected with schistosomiasis,which becomes one of the most common parasitic diseases. This study focuses on investigating in vivo and in vitro effects of mmu-miR-92a-2-5p in Schistosoma japonicum-induced liver fibrosis by targeting TLR2. Through bioinformatic analysis, the overexpression of TLR2 and the down-regulation of mmu-miR-92a-2-5p were revealed in the progression of S. japonicum-induced liver fibrosis. BALB/C mice were taken advantage to construct normal control and schistosomiasis liver fibrosis (SLF) model. The mice in model groups were transfected recombinant lentivirus (Lenti-mmu-miR-92a-2-5p or Lenti-NC) to alter the expression of mmu-miR-92a-2-5p in vivo. HE and Masson staining were employed to observe the pathological changes and collagenous fibrosis. QRT-PCR showed that mmu-miR-92a-2-5p was decreased while TLR2 was elevated in the infected groups. However, lenti-mmu-miR-92a-2-5p group could inhibit liver fibrosis. Then the effect of mmu-miR-92a-2-5p on S. japonicum-induced liver fibrosis including cell apoptosis rates, proliferation and proteins related to liver fibrosis was examined in NIH-3T3 mouse embryonic fibroblasts. Moreover, the association between mmu-miR-92a-2-5p and TLR2 was detected by dual-luciferase reporter gene assay and the expression of cytokines IL-4, IFN-γ and TNF-α in SLF model was detected by ELISA. Further, the knockout of TLR2 in C57BL/6J mice was used to confirm the association between mmu-miR-92a-2-5p and TLR2. Thus, these findings demonstrated that mmu-miR-92a-2-5p inhibited S. japonicum-induced liver fibrosis by targeting TLR2 in vitro and in vivo.

Overexpression of SENP1 reduces the stemness capacity of osteosarcoma stem cells and increases their sensitivity to HSVtk/GCV

Osteosarcoma stem cells are able to escape treatment with conventional chemotherapeutic drugs, as the majority of them are in a quiescent state. Recent reports have suggested that small ubiquitin-like modifiers (SUMOs) serve important roles in the maintenance of cancer stem cell stemness. Therefore, a potential strategy to increase the effectiveness of chemotherapeutic agents is to interfere with SUMO modification of proteins associated with the maintenance of stemness in osteosarcoma stem cells. The present study revealed a significant decrease in the expression of SUMO1 specific peptidase 1 (SENP1) in osteosarcoma tissues and osteosarcoma cell lines, and SENP1 expression was much lower in osteosarcoma stem cells than in non-cancer stem cells. Further experiments indicated that the low levels of SENP1 were essential for maintenance of stemness in osteosarcoma stem cells. Overexpression of SENP1 resulted in a marked decrease in the maintenance of stemness, but only slightly induced apoptosis of osteosarcoma cells, which is crucial to reduce the side effects of drugs on normal precursor cells. Finally, SENP1 overexpression led to a significant increase in the sensitivity of osteosarcoma stem cells to the herpes simplex virus 1 thymidine kinase gene in combination with ganciclovir in vitro and in vivo. In conclusion, the present study described a novel method to increase the sensitivity of osteosarcoma stem cells to chemotherapeutic drugs. Notably, this approach may significantly reduce the required dose of conventional chemotherapeutic drugs and reduce side effects.

Epigenetics of Skeletal Diseases

PURPOSE OF REVIEW

Epigenetic mechanisms modify gene activity in a stable manner without altering DNA sequence. They participate in the adaptation to the environment, as well as in the pathogenesis of common complex disorders. We provide an overview of the role of epigenetic mechanisms in bone biology and pathology.

RECENT FINDINGS

Extensive evidence supports the involvement of epigenetic mechanisms (DNA methylation, post-translational modifications of histone tails, and non-coding RNAs) in the differentiation of bone cells and mechanotransduction. A variety of epigenetic abnormalities have been described in patients with osteoporosis, osteoarthritis, and skeletal cancers, but their actual pathogenetic roles are still unclear. A few drugs targeting epigenetic marks have been approved for neoplastic disorders, and many more are being actively investigated. Advances in the field of epigenetics underscore the complex interactions between genetic and environmental factors as determinants of osteoporosis and other common disorders. Likewise, they help to explain the mechanisms by which prenatal and post-natal external factors, from nutrition to psychological stress, impact our body and influence the risk of later disease.

ATF-3/miR-590/GOLPH3 signaling pathway regulates proliferation of breast cancer

Background

Breast cancer is one of the leading causes of death in women worldwide. Fast growth is the important character of breast cancer, which makes sure the subsequent metastasize and invasion breast cancer. Golgi related genes GOLPH3 has been reported to regulate many kinds of cancers proliferation. However, its upregulator remains largely unknown. miRNA modulate gene expression by post-transcriptional repression to participate in many signaling pathway of breast cancer cell proliferation. miR-590 has been reported to regulate tumorgenesis and could be regulated by its own target ATF-3. But whether miR-590 can be the modulator of Golgi related genes to regulate the breast cancer proliferation is unclear.

Methods

We performed the bioinformatics analysis of survival rate and expression differences of patients using the data of The Cancer Genome Atlas (TCGA).Both of MTS and BrdU assays were used for cell proliferation analysis. Cell cycle was detected by flow cytometry .qRT-PCR was used for detecting the cell cycle related gene expression. Student’s t-test or One way anova was used for statistics.

Results

We found the upregulation of GOLPH3 in breast cancer samples compared with normal breast tissues, which also was related to the poor prognosis. Overexpression of GOLPH3 significantly promoted proliferation both of MDA-MB-231 cells (ER negative) and MCF-7 cells (ER positive). We further found that miRNA-590-3p could directly target the 3′-UTR of GOLPH3 mRNA to repress its expression. Overexpression of miR-590-3p inhibited the proliferation of MDA-MB-231 and MCF-7 cells. The rescue experiments indicated that overexpression of GOLPH3 significantly resorted the proliferation inhibited by miR-590-3p. We also found that ATF-3 repressed miR-590-3p expression to modulate miR-590/GOLPH3 pathway to regulate breast cancer cells proliferation.

Conclusions

This study not only suggests that the ATF-3/miR-590/GOLPH3 signaling pathway is critically involved in the proliferation of breast cancer cells, but provides a novel therapeutic target and new insight base on epigenetic regulation for future breast cancer diagnosis and clinical treatment.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4031-4) contains supplementary material, which is available to authorized users.

Evaluation of circulating miRNAs during late pregnancy in the mare

MicroRNAs (miRNAs) are small, non-coding RNAs which are produced throughout the body. Individual tissues tend to have a specific expression profile and excrete many of these miRNAs into circulation. These circulating miRNAs may be diagnostically valuable biomarkers for assessing the presence of disease while minimizing invasive testing. In women, numerous circulating miRNAs have been identified which change significantly during pregnancy-related complications (e.g. chorioamnionitis, eclampsia, recurrent pregnancy loss); however, no prior work has been done in this area in the horse. To identify pregnancy-specific miRNAs, we collected serial whole blood samples in pregnant mares at 8, 9, 10 m of gestation and post-partum, as well as from non-pregnant (diestrous) mares. In total, we evaluated a panel of 178 miRNAs using qPCR, eventually identifying five miRNAs of interest. One miRNA (miR-374b) was differentially regulated through late gestation and four miRNAs (miR-454, miR-133b, miR-486-5p and miR-204b) were differentially regulated between the pregnant and non-pregnant samples. We were able to identify putative targets for the differentially regulated miRNAs using two separate target prediction programs, miRDB and Ingenuity Pathway Analysis. The targets for the miRNAs differentially regulated during pregnancy were predicted to be involved in signaling pathways such as the STAT3 pathway and PI3/AKT signaling pathway, as well as more endocrine-based pathways, including the GnRH, prolactin and insulin signaling pathways. In summary, this study provides novel information about the changes occurring in circulating miRNAs during normal pregnancy, as well as attempting to predict the biological effects induced by these miRNAs.

miRNA-338-3p/CDK4 signaling pathway suppressed hepatic stellate cell activation and proliferation

BACKGROUND

Activated hepatic stellate cell (HSC) is the main fibrogenic cell type in the injured liver. miRNA plays an important role in activation and proliferation of HSC.

METHODS

Our previous study examined the expression profiles of microRNAs in quiescent and activated HSC. Real-time PCR and western blot were used to detect the expression of Collagen type I (Col 1) and Alpha-Smooth Muscle Actin (α-SMA). CCK-8 and Edu assay was used to measure the proliferation rate of HSC. Luciferase reporter gene assay was used to tested the binding between miR-338-3p and Cyclin-dependent kinase 4 (CDK4).

RESULTS

We found overexpression of miR-338-3p could inhibit Col 1 and α-SMA, two major HSC activation markers, whereas miR-338-3p inhibitor could promote them. Besides, miR-338-3p overexpression could suppress the growth rate of HSC. Further, we found that CDK4, a pleiotropic signaling protein, was a direct target gene of miR-338-3p. Moreover, we found that overexpression of CDK4 could block the effects of miR-338-3p.

CONCLUSIONS

We found miR-338-3p is an anti-fibrotic miRNA which inhibits cell activation and proliferation. Our findings suggest that miR-338-3p/CDK4 signaling pathway participates in the regulation of HSC activation and growth and may act as a novel target for further anti-fibrotic therapy.