Exosomal miR-100-5p inhibits osteogenesis of hBMSCs and angiogenesis of HUVECs by suppressing the BMPR2/Smad1/5/9 signalling pathway

Targeting BMP2 for therapeutic strategies against hepatocellular carcinoma

OBJECTIVES

This study aimed to investigate the role of BMP2 in hepatocellular carcinoma (HCC) growth and metastasis using a dual approach combining single-cell RNA sequencing (scRNA-seq) and bulk RNA-seq.

METHODS

scRNA-seq data from the GEO database and bulk RNA-seq data from the TCGA database were analyzed. Differentially expressed marker genes of endothelial cells were identified and analyzed using enrichment analysis, PPI analysis, correlation analysis, and GSEA. In vitro, experiments were conducted using the Huh-7 HCC cell line, and in vivo, models of HCC growth and metastasis were established by knocking down BMP2.

RESULTS

The scRNA-seq analysis identified BMP2 as a key marker gene in endothelial cells of HCC samples. Elevated BMP2 expression correlated with poor prognosis in HCC. In vitro experiments showed that silencing BMP2 inhibited the proliferation, migration, and invasion of liver cancer cells. In vivo studies confirmed increased BMP2 expression in HCC tissues, promoting angiogenesis and HCC growth.

CONCLUSION

This study highlights the role of BMP2 in tumor angiogenesis and HCC progression. Targeting BMP2 could be a promising therapeutic strategy against HCC.

Investigating Novel Therapeutic Approaches for Idiopathic Short Stature: Targeting siRNA and Growth Hormone Delivery to the Growth Plate Using Exosome Nanoparticles

Idiopathic short stature (ISS) is a common childhood condition with largely unknown underlying causes. Recent research highlights the role of circulating exosomes in the pathogenesis of various disorders, but their connection to ISS remains unexplored. In the experiments, human chondrocytes are cocultured with plasma exosomes from ISS patients, leading to impaired chondrocyte growth and bone formation. Elevated levels of a specific long non-coding RNA (lncRNA), ISSRL, are identified as a distinguishing factor in ISS, boasting high specificity and sensitivity. Silencing ISSRL in ISS plasma exosomes reverses the inhibition of chondrocyte proliferation and bone formation. Conversely, overexpression of ISSRL in chondrocytes impedes their growth and bone formation, revealing its mechanism of action through the miR-877-3p/GZMB axis. Subsequently, exosomes (CT-Exo-siISSRL-oeGH) with precise cartilage-targeting abilities are engineered, loaded with customized siRNA for ISSRL and growth hormone. This innovative approach offers a therapeutic strategy to address ISS by rectifying abnormal non-coding RNA expression in growth plate cartilage and delivering growth hormone with precision to promote bone growth. This research provides valuable insights into ISS diagnosis and treatment, highlighting the potential of engineered exosomes.

Mesenchymal Stem Cell-Derived Extracellular Vesicles in Bone-Related Diseases: Intercellular Communication Messengers and Therapeutic Engineering Protagonists

Extracellular vesicles (EVs) can deliver various bioactive molecules among cells, making them promising diagnostic and therapeutic alternatives in diseases. Mesenchymal stem cell-derived EVs (MSC-EVs) have shown therapeutic potential similar to MSCs but with drawbacks such as lower yield, reduced biological activities, off-target effects, and shorter half-lives. Improving strategies utilizing biotechniques to pretreat MSCs and enhance the properties of released EVs, as well as modifying MSC-EVs to enhance targeting abilities and achieve controlled release, shows potential for overcoming application limitations and enhancing therapeutic effects in treating bone-related diseases. This review focuses on recent advances in functionalizing MSC-EVs to treat bone-related diseases. Firstly, we underscore the significance of MSC-EVs in facilitating crosstalk between cells within the skeletal environment. Secondly, we highlight strategies of functional-modified EVs for treating bone-related diseases. We explore the pretreatment of stem cells using various biotechniques to enhance the properties of resulting EVs, as well as diverse approaches to modify MSC-EVs for targeted delivery and controlled release. Finally, we address the challenges and opportunities for further research on MSC-EVs in bone-related diseases.

[Research Progress in the Regulatory Role of circRNA-miRNA Network in Bone Remodeling]

The dynamic balance between bone formation and bone resorption is a critical process of bone remodeling. The imbalance of bone formation and bone resorption is closely associated with the occurrence and development of various bone-related diseases. Under both physiological and pathological conditions, non-coding RNAs (ncRNAs) play a crucial regulatory role in protein expression through either inhibiting mRNAs translation or promoting mRNAs degradation. Circular RNAs (circRNAs) are a type of non-linear ncRNAs that can resist the degradation of RNA exonucleases. There is accumulating evidence suggesting that circRNAs and microRNAs (miRNAs) serve as critical regulators of bone remodeling through their direct or indirect regulation of the expression of osteogenesis-related genes. Additionally, recent studies have revealed the involvement of the circRNAs-miRNAs regulatory network in the process by which mesenchymal stem cells (MSCs) differentiate towards the osteoblasts (OB) lineage and the process by which bone marrow-derived macrophages (BMDM) differentiate towards osteoclasts (OC). The circRNA-miRNA network plays an important regulatory role in the osteoblastic-osteoclastic balance of bone remodeling. Therefore, a thorough understanding of the circRNA-miRNA regulatory mechanisms will contribute to a better understanding of the regulatory mechanisms of the balance between osteoblastic and osteoclastic activities in the process of bone remodeling and the diagnosis and treatment of related diseases. Herein, we reviewed the functions of circRNA and microRNA. We also reviewed their roles in and the mechanisms of the circRNA-miRNA regulatory network in the process of bone remodeling. This review provides references and ideas for further research on the regulation of bone remodeling and the prevention and treatment of bone-related diseases.

Long noncoding RNA KCNMA1-AS1 promotes osteogenic differentiation of human bone marrow mesenchymal stem cells by activating the SMAD9 signaling pathway

The human bone marrow mesenchymal stem cells (hBMSCs) undergo intense osteogenic differentiation, a crucial bone formation mechanism. Evidence from prior studies suggested an association between long noncoding RNAs (lncRNAs) and the osteogenic differentiation of hBMSCs. However, precise roles and molecular mechanisms are still largely unknown. In this work, we report for the first time that lncRNA KCNMA1 antisense RNA 1 (KCNMA1-AS1) plays a vital role in regulating hBMSCs' osteogenic differentiation. Here, it was observed that the KCNMA1-AS1 expression levels were significantly upregulated during osteogenic differentiation. In addition, KCNMA1-AS1 overexpression enhanced in vitro osteogenic differentiation of hBMSCs and in vivo bone formation, whereas knockdown of KCNMA1-AS1 resulted in the opposite result. Additionally, the interaction between KCNMA1-AS1 and mothers against decapentaplegic homolog 9 (SMAD9) was confirmed by an RNA pull-down experiment, mass spectrometry, and RIP assay. This interaction regulated the activation of the SMAD9 signaling pathway. Moreover, rescue assays demonstrated that the inhibitor of the SMAD9 signaling pathway reversed the stimulative effects on osteogenic differentiation of hBMSCs by KCNMA1-AS1 overexpression. Altogether, our results stipulate that KCNMA1-AS1 promotes osteogenic differentiation of hBMSCs via activating the SMAD9 signaling pathway and can serve as a biomarker and therapeutic target in treating bone defects.

Emerging functions and clinical applications of exosomal microRNAs in diseases

Exosomes are an important group of extracellular vesicles that transfer several kinds of biomolecules and facilitate cell-cell communication. The content of exosomes, particularly the amounts of microRNA (miRNAs) inside these vesicles, demonstrates a disease-specific pattern reflecting pathogenic processes and may be employed as a diagnostic and prognostic marker. miRNAs may enter recipient cells through exosomes and generate a RISC complex that can cause degradation of the target mRNAs or block translation of their corresponding proteins. Therefore, exosome-derived miRNAs constitute an important mechanism of gene regulation in recipient cells. The miRNA content of exosomes can be used as an important tool in the detection of diverse disorders, particularly cancers. This research field has an important situation in cancer diagnosis. In addition, exosomal microRNAs offer a great deal of promise in the treatment of human disorders. However, there are still certain challenges to be resolved. The most important challenges are as follow: the detection of exosomal miRNAs should be standardized, exosomal miRNAs-associated studies should be conducted in large number of clinical samples, and experiment settings and detection criteria should be consistent across different labs. The goal of this article is to present an overview of the effects of exosome-derived microRNAs on a variety of diseases, including gastrointestinal, pulmonary, neurological, and cardiovascular diseases, with a particular emphasis on malignancies.

microRNAs delivered by small extracellular vesicles in MSCs as an emerging tool for bone regeneration

Bone regeneration is a dynamic process that involves angiogenesis and the balance of osteogenesis and osteoclastogenesis. In bone tissue engineering, the transplantation of mesenchymal stem cells (MSCs) is a promising approach to restore bone homeostasis. MSCs, particularly their small extracellular vesicles (sEVs), exert therapeutic effects due to their paracrine capability. Increasing evidence indicates that microRNAs (miRNAs) delivered by sEVs from MSCs (MSCs-sEVs) can alter gene expression in recipient cells and enhance bone regeneration. As an ideal delivery vehicle of miRNAs, MSCs-sEVs combine the high bioavailability and stability of sEVs with osteogenic ability of miRNAs, which can effectively overcome the challenge of low delivery efficiency in miRNA therapy. In this review, we focus on the recent advancements in the use of miRNAs delivered by MSCs-sEVs for bone regeneration and disorders. Additionally, we summarize the changes in miRNA expression in osteogenic-related MSCs-sEVs under different microenvironments.

miR-486-5p Attenuates Steroid-Induced Adipogenesis and Osteonecrosis of the Femoral Head Via TBX2/P21 Axis

Enhanced adipogenic differentiation of mesenchymal stem cells (MSCs) is considered as a major risk factor for steroid-induced osteonecrosis of the femoral head (SOFNH). The role of microRNAs during this process has sparked interest. miR-486-5p expression was down-regulated significantly in femoral head bone tissues of both SONFH patients and rat models. The purpose of this study was to reveal the role of miR-486-5p on MSCs adipogenesis and SONFH progression. The present study showed that miR-486-5p could significantly inhibit adipogenesis of 3T3-L1 cells by suppressing mitotic clonal expansion (MCE). And upregulated expression of P21, which was caused by miR-486-5p mediated TBX2 decrease, was responsible for inhibited MCE. Further, miR-486-5p was demonstrated to effectively inhibit steroid-induced fat formation in the femoral head and prevented SONFH progression in a rat model. Considering the potent effects of miR-486-5p on attenuating adipogenesis, it seems to be a promising target for the treatment of SONFH.

Osteonecrosis Related to Steroid and Alcohol Use-An Update on Pathogenesis

Osteonecrosis (ON) is usually a progressive disease that negatively affects the quality of life and leads to significant disability. Most patients are aged 30-50 years and require multiple surgical interventions throughout their lifetime. In non-traumatic ON, alcohol abuse and corticosteroids are involved in up to 80% of cases. This narrative review aims to summarize data on their impact on healthy bone and the development of pathophysiological processes leading to ON development. We conducted EMBASE and MEDLINE database reviews to identify relevant research. We found that for both agents, the risk was time and dose-dependent. ON in alcohol and steroid use shared many pathogenetic mechanisms leading to the development of necrosis, including increased adipogenesis, the induction of chronic inflammation, vascular alterations, and impaired bone-cell differentiation. Because both alcohol and steroid use are modifiable factors, both general physicians and orthopedic surgeons should encourage patients to limit ethanol intake and avoid corticosteroid overuse. In the presence of ON, because both alcohol- and steroid-induced disease tend to be multifocal, addiction treatment and limiting steroid use are justified.

miRNAs as potential game-changers in bone diseases: Future medicinal and clinical uses

MicroRNAs (miRNAs), short, highly conserved non-coding RNA, influence gene expression by sequential mechanisms such as mRNA breakdown or translational repression. Many biological processes depend on these regulating substances, thus changes in their expression have an impact on the maintenance of cellular homeostasis and result in the emergence of a variety of diseases. Relevant studies have shown in recent years that miRNAs are involved in many stages of bone development and growth. Additionally, abnormal production of miRNA in bone tissues has been closely associated with the development of numerous bone disorders, such as osteonecrosis, bone cancer, and bone metastases. Many pathological processes, including bone loss, metastasis, the proliferation of osteosarcoma cells, and differentiation of osteoblasts and osteoclasts, are under the control of miRNAs. By bringing together the most up-to-date information on the clinical relevance of miRNAs in such diseases, this study hopes to further the study of the biological features of miRNAs in bone disorders and explore their potential as a therapeutic target.

Bone tissue engineering for treating osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a devastating and complicated disease with an unclear etiology. Femoral head-preserving surgeries have been devoted to delaying and hindering the collapse of the femoral head since their introduction in the last century. However, the isolated femoral head-preserving surgeries cannot prevent the natural progression of ONFH, and the combination of autogenous or allogeneic bone grafting often leads to many undesired complications. To tackle this dilemma, bone tissue engineering has been widely developed to compensate for the deficiencies of these surgeries. During the last decades, great progress has been made in ingenious bone tissue engineering for ONFH treatment. Herein, we comprehensively summarize the state-of-the-art progress made in bone tissue engineering for ONFH treatment. The definition, classification, etiology, diagnosis, and current treatments of ONFH are first described. Then, the recent progress in the development of various bone-repairing biomaterials, including bioceramics, natural polymers, synthetic polymers, and metals, for treating ONFH is presented. Thereafter, regenerative therapies for ONFH treatment are also discussed. Finally, we give some personal insights on the current challenges of these therapeutic strategies in the clinic and the future development of bone tissue engineering for ONFH treatment.

Mechanical force induces macrophage-derived exosomal UCHL3 promoting bone marrow mesenchymal stem cell osteogenesis by targeting SMAD1

BACKGROUND

Orthodontic tooth movement (OTM), a process of alveolar bone remodelling, is induced by mechanical force and regulated by local inflammation. Bone marrow-derived mesenchymal stem cells (BMSCs) play a fundamental role in osteogenesis during OTM. Macrophages are mechanosensitive cells that can regulate local inflammatory microenvironment and promote BMSCs osteogenesis by secreting diverse mediators. However, whether and how mechanical force regulates osteogenesis during OTM via macrophage-derived exosomes remains elusive.

RESULTS

Mechanical stimulation (MS) promoted bone marrow-derived macrophage (BMDM)-mediated BMSCs osteogenesis. Importantly, when exosomes from mechanically stimulated BMDMs (MS-BMDM-EXOs) were blocked, the pro-osteogenic effect was suppressed. Additionally, compared with exosomes derived from BMDMs (BMDM-EXOs), MS-BMDM-EXOs exhibited a stronger ability to enhance BMSCs osteogenesis. At in vivo, mechanical force-induced alveolar bone formation was impaired during OTM when exosomes were blocked, and MS-BMDM-EXOs were more effective in promoting alveolar bone formation than BMDM-EXOs. Further proteomic analysis revealed that ubiquitin carboxyl-terminal hydrolase isozyme L3 (UCHL3) was enriched in MS-BMDM-EXOs compared with BMDM-EXOs. We went on to show that BMSCs osteogenesis and mechanical force-induced bone formation were impaired when UCHL3 was inhibited. Furthermore, mothers against decapentaplegic homologue 1 (SMAD1) was identified as the target protein of UCHL3. At the mechanistic level, we showed that SMAD1 interacted with UCHL3 in BMSCs and was downregulated when UCHL3 was suppressed. Consistently, overexpression of SMAD1 rescued the adverse effect of inhibiting UCHL3 on BMSCs osteogenesis.

CONCLUSIONS

This study suggests that mechanical force-induced macrophage-derived exosomal UCHL3 promotes BMSCs osteogenesis by targeting SMAD1, thereby promoting alveolar bone formation during OTM.

Prognostic and therapeutic potential of microRNAs for fracture healing processes and non-union fractures: A systematic review

BACKGROUND

Approximately 10% of all bone fractures result in delayed fracture healing or non-union; thus, the identification of biomarkers and prognostic factors is of great clinical interest. MicroRNAs (miRNAs) are known to be involved in the regulation of the bone healing process and may serve as functional markers for fracture healing.

AIMS AND METHODS

This systematic review aimed to identify common miRNAs involved in fracture healing or non-union fractures using a qualitative approach. A systematic literature search was performed with the keywords 'miRNA and fracture healing' and 'miRNA and non-union fracture'. Any original article investigating miRNAs in fracture healing or non-union fractures was screened. Eventually, 82 studies were included in the qualitative analysis for 'miRNA and fracture healing', while 19 were selected for the 'miRNA and fracture non-union' category.

RESULTS AND CONCLUSIONS

Out of 151 miRNAs, miR-21, miR-140 and miR-214 were the most investigated miRNAs in fracture healing in general. miR-31-5p, miR-221 and miR-451-5p were identified to be regulated specifically in non-union fractures. Large heterogeneity was detected between studies investigating the role of miRNAs in fracture healing or non-union in terms of patient population, sample types and models used. Nonetheless, our approach identified some miRNAs with the potential to serve as biomarkers for non-union fractures, including miR-31-5p, miR-221 and miR-451-5p. We provide a discussion of involved pathways and suggest on alignment of future research in the field.

Tissue engineering in growth plate cartilage regeneration: Mechanisms to therapeutic strategies

The repair of growth plate injuries is a highly complex process that involves precise spatiotemporal regulation of multiple cell types. While significant progress has been made in understanding the pathological mechanisms underlying growth plate injuries, effectively regulating this process to regenerate the injured growth plate cartilage remains a challenge. Tissue engineering technology has emerged as a promising therapeutic approach for achieving tissue regeneration through the use of functional biological materials, seed cells and biological factors, and it is now widely applied to the regeneration of bone and cartilage. However, due to the unique structure and function of growth plate cartilage, distinct strategies are required for effective regeneration. Thus, this review provides an overview of current research on the application of tissue engineering to promote growth plate regeneration. It aims to elucidates the underlying mechanisms by which tissue engineering promotes growth plate regeneration and to provide novel insights and therapeutic strategies for future research on the regeneration of growth plate.

Epigenetics: Novel crucial approach for osteogenesis of mesenchymal stem cells

Bone has a robust regenerative potential, but its capacity to repair critical-sized bone defects is limited. In recent years, stem cells have attracted significant interest for their potential in tissue engineering. Applying mesenchymal stem cells (MSCs) for enhancing bone regeneration is a promising therapeutic strategy. However, maintaining optimal cell efficacy or viability of MSCs is limited by several factors. Epigenetic modification can cause changes in gene expression levels without changing its sequence, mainly including nucleic acids methylation, histone modification, and non-coding RNAs. This modification is believed to be one of the determinants of MSCs fate and differentiation. Understanding the epigenetic modification of MSCs can improve the activity and function of stem cells. This review summarizes recent advances in the epigenetic mechanisms of MSCs differentiation into osteoblast lineages. We expound that epigenetic modification of MSCs can be harnessed to treat bone defects and promote bone regeneration, providing potential therapeutic targets for bone-related diseases.

MiR-100-5p inhibits osteogenic differentiation of human bone mesenchymal stromal cells by targeting TMEM135

Osteoporosis is a disorder characterized by reduced bone mass, disruption of bone microarchitecture, and a propensity to fracture. The osteogenic differentiation of human bone mesenchymal stromal cells (hBMSCs) exerts a critical effect on preventing bone loss during osteoporosis. Herein, the study recognized miR-100-5p as a deregulated miRNA during osteoporosis (upregulated) and BMSC osteogenic differentiation (downregulated). miR-100-5p was upregulated in osteoporosis patients-isolated BMSCs compared to non-osteoporosis trauma patients-isolated BMSCs. hBMSCs, overexpression inhibited hBMSC proliferation and osteogenic differentiation, whereas miR-100-5p inhibition exerted opposite effects. TMEM135 was downregulated in osteoporosis and upregulated in differentiated osteoblasts, as well as downregulated upon the overexpression of miR-100-5p. MiR-100-5p directly targeted and inhibited TMEM135. In hBMSCs, TMEM135 silencing also inhibited hBMSC osteogenic differentiation. When co-transfected to hBMSCs, antagomir-100-5p promoted, whereas TMEM135 silencing inhibited hBMSC osteogenic differentiation; TMEM135 knockdown dramatically attenuated the effects of miR-100-5p inhibition. Taken together, miR-100-5p forms a regulatory axis with TMEM135 by direct binding. The miR-100-5p/TMEM135 axis modulates hBMSC differentiation into osteoblast. Considering the critical effect of BMSC osteogenesis on osteoporosis, this axis might play a role in osteoporosis, and further in vivo and clinical investigations are required.

Hsa_circ_0001485 promoted osteogenic differentiation by targeting BMPR2 to activate the TGFβ-BMP pathway

Background

Circular RNAs (circRNAs) are a new type of stable noncoding RNA and have been proven to play a crucial role in osteoporosis. This study explored the role and mechanism of hsa_circ_0001485 in osteogenic differentiation.

Methods

Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and Gene Ontology (GO) enrichment analysis were performed according to the previous sequencing data in human bone marrow mesenchymal stem cells (BMSC) before and after the induction of osteogenic differentiation on the differentially expressed circRNAs, to screen out signaling pathways associated with osteogenic differentiation. The hFOB 1.19 cells were used to verify the function and mechanism of specific circRNAs in osteogenic differentiation. Additionally, small interfering fragments and overexpression plasmids were used to determine the role of specific circRNAs during osteogenic differentiation. Furthermore, pull-down experiments and mass spectrometry were performed to determine the proteins that bind to specific circRNAs.

Results

The KEGG and GO enrichment analyses showed that the TGFβ-BMP signaling pathway was related to the osteogenic differentiation process, and four circRNAs were associated with the pathway. The quantitative polymerase chain reaction analysis revealed that hsa_circ_0001485 expression was increased during the osteogenic differentiation process of BMSCs. Knockdown of hsa_circ_0001485 suppressed the activity of the alkaline phosphatase enzyme and the expression of RUNX2, osteopontin, and osteocalcin in the osteogenic hFOB 1.19 cells, whereas overexpression of hsa_circ_0001485 promoted their expression. Additionally, we found that hsa_circ_0001485 and BMPR2 targeted binding to activate the TGFβ-BMP signaling pathway and promoted osteogenic differentiation through mass spectrometry analysis.

Conclusion

This study demonstrates that hsa_circ_0001485 is highly expressed in the osteogenic hFOB 1.19 cells, which activate the TGFβ-BMP pathway through targeted binding of BMPR2, and plays a positive role in regulating osteogenic differentiation.

Application of exosome-derived noncoding RNAs in bone regeneration: Opportunities and challenges

With advances in the fields of regenerative medicine, cell-free therapy has received increased attention. Exosomes have a variety of endogenous properties that provide stability for molecular transport across biological barriers to cells, as a form of cell-to-cell communication that regulates function and phenotype. In addition, exosomes are an important component of paracrine signaling in stem-cell-based therapy and can be used as a stand-alone therapy or as a drug delivery system. The remarkable potential of exosomes has paved the pathway for cell-free treatment in bone regeneration. Exosomes are enriched in distinct noncoding RNAs (ncRNAs), including microRNAs, long ncRNAs and circular RNAs. Different ncRNAs have multiple functions. Altered expression of ncRNA in exosomes is associated with the regenerative potential and development of various diseases, such as femoral head osteonecrosis, myocardial infarction, and cancer. Although there is increasing evidence that exosome-derived ncRNAs (exo-ncRNAs) have the potential for bone regeneration, the detailed mechanisms are not fully understood. Here, we review the biogenesis of exo-ncRNA and the effects of ncRNAs on angiogenesis and osteoblast- and osteoclast-related pathways in different diseases. However, there are still many unsolved problems and challenges in the clinical application of ncRNA; for instance, production, storage, targeted delivery and therapeutic potency assessment. Advancements in exo-ncRNA methods and design will promote the development of therapeutics, revolutionizing the present landscape.

C/EBPα regulates the fate of bone marrow mesenchymal stem cells and steroid-induced avascular necrosis of the femoral head by targeting the PPARγ signalling pathway

BACKGROUND

The imbalance of osteogenic/adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is closely related to steroid-induced avascular necrosis of the femoral head (SANFH). We aimed to investigate the epigenetic mechanism of intramedullary fat accumulation and continuous osteonecrosis after glucocorticoid (GC) withdrawal in SANFH.

METHODS

An SANFH model was established in SD rats, which received an intermittent high GC dose for the first 4 weeks followed by an additional 4 weeks without GC. We explored the synergistic effects and mechanisms of C/EBPα and PPARγ on the differentiation of BMSCs by lentivirus-mediated gene knockdown and overexpression assays. A chromatin immunoprecipitation assay was performed to identify epigenetic modification sites on PPARγ in vivo and in vitro.

RESULTS

In the SANFH model, intramedullary fat was significantly increased, and the transcription factors C/EBPα and PPARγ were upregulated simultaneously in the femoral head. In vitro, C/EBPα promoted adipogenic differentiation of BMSCs by targeting the PPARγ signalling pathway, while overexpression of C/EBPα significantly impaired osteogenic differentiation. Further studies demonstrated that histone H3K27 acetylation of PPARγ played an important role in the epigenetic mechanism underlying SANFH. C/EBPα upregulates the histone H3K27 acetylation level in the PPARγ promoter region by inhibiting HDAC1. Additionally, inhibiting the histone acetylation level of PPARγ effectively prevented adipogenic differentiation, thus slowing the progression of SANFH.

CONCLUSIONS

Our results demonstrate the molecular mechanism by which C/EBPα regulates PPARγ expression by acetylating histones and revealed the epigenetic phenomenon in SANFH for the first time.

Extracellular matrix derived from Wharton's Jelly-derived mesenchymal stem cells promotes angiogenesis via integrin αVβ3/c-Myc/P300/VEGF

BACKGROUND

Angiogenesis is required in many physiological conditions, including bone regeneration, wound healing, and tissue regeneration. Mesenchymal stem cells-derived extracellular matrix (MSCs-ECM) could guide intricate cellular and tissue processes such as homeostasis, healing and regeneration.

METHODS

The purpose of this study is to explore the effect and mechanism of ECM derived from decellularized Wharton's Jelly-derived mesenchymal stem cells (WJ-MSCs) on endothelial cell viability and angiogenesis. The human umbilical vein endothelial cells (HUVECs) were pretreated with WJ-MSCs ECM for 2d/7d/14d, respectively. After pretreatment, the angiogenesis ability of HUVECs was detected.

RESULTS

In this study, we found for the first time that WJ-MSCs ECM could improve the angiogenesis ability of HUVECs with a time-dependent manner in vitro. Mechanically, WJ-MSCs ECM activated the focal adhesion kinase (FAK)/P38 signaling pathway via integrin αVβ3, which further promoted the expression of the cellular (c)-Myc. Further, c-Myc increased histone acetylation levels of the vascular endothelial growth factor (VEGF) promoter by recruiting P300, which ultimately promoting VEGF expression.

CONCLUSIONS

ECM derived from Wharton's Jelly-derived mesenchymal stem cells promotes angiogenesis via integrin αVβ3/c-Myc/P300/VEGF. This study is expected to provide a new approach to promote angiogenesis in bone and tissue regeneration.

The Emerging Role of Non-Coding RNAs in Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Autologous bone marrow-derived mesenchymal stem cells (BMSCs) are more easily available and frequently used for bone regeneration in clinics. Osteogenic differentiation of BMSCs involves complex regulatory networks affecting bone formation phenomena. Non-coding RNAs (ncRNAs) refer to RNAs that do not encode proteins, mainly including microRNAs, long non-coding RNAs, circular RNAs, piwi-interacting RNAs, transfer RNA-derived small RNAs, etc. Recent in vitro and in vivo studies had revealed the regulatory role of ncRNAs in osteogenic differentiation of BMSCs. NcRNAs had both stimulatory and inhibitory effects on osteogenic differentiation of BMSCs. During the physiological condition, osteo-stimulatory ncRNAs are upregulated and osteo-inhibitory ncRNAs are downregulated. The opposite effects might occur during bone degenerative disease conditions. Intracellular ncRNAs and ncRNAs from neighboring cells delivered via exosomes participate in the regulatory process of osteogenic differentiation of BMSCs. In this review, we summarize the recent advances in the regulatory role of ncRNAs on osteogenic differentiation of BMSCs during physiological and pathological conditions. We also discuss the prospects of the application of modulation of ncRNAs function in BMSCs to promote bone tissue regeneration in clinics.

IRF4 suppresses osteogenic differentiation of BM-MSCs by transcriptionally activating miR-636/DOCK9 axis

OBJECTIVES

Osteoblasts are derived from Bone Marrow-derived Mesenchymal Stem Cells (BM-MSCs), which play an indispensable role in bone formation. In this study, the authors aim to investigate the role of IRF4 in the osteogenic differentiation of BM-MSCs and its potential molecular mechanism.

METHODS

The authors used lentivirus infection to overexpress IRF4 in BM-MSCs. The expression of IRF4 and osteogenesis-related genes were detected by qRT-PCR and western blot analysis. The osteogenic differentiation of BM-MSCs was evaluated by Alkaline Phosphatase (ALP) activity, Alizarin red staining, and Alkaline Phosphatase (ALP) staining. Chromatin Immunoprecipitation (ChIP), Dual-Luciferase reporter assay and RNA Immunoprecipitation Assay were applied to confirm the regulatory mechanism between IRF4, miR-636 and DOCK9.

RESULTS

The authors found IRF4 was down-regulated during the osteogenic differentiation of BM-MSCs, and IRF4 overexpression could decrease the osteogenic differentiation of BM-MSCs by specifically promoting the reduction of Alkaline Phosphatase (ALP) activity and down-regulating osteogenic indicators, including OCN, OPN, Runx2 and CollA1. Mechanistically, IRF4 activated microRNA-636 (miR-636) expression via binding to its promoter region, and Dedicator of Cytokinesis 9 (DOCK9) was identified as the target of miR-636 in BM-MSCs. Moreover, the damage in the capacity of osteogenic differentiation of BM-MSCs induced by IRF4 overexpression could be rescued by miR-636 inhibition.

CONCLUSIONS

In summary, this paper proposed that IRF4/miR-636/DOCK9 may be considered as targets for the treatment of osteoporosis (OP).