The long noncoding RNA lnc-ob1 facilitates bone formation by upregulating Osterix in osteoblasts

Analysis of PANoptosis-related ceRNA network reveals lncRNA MIR17HG involved in osteogenic differentiation inhibition impaired by tumor necrosis factor-α

BACKGROUND

Inflammatory cytokines such as Interleukin 1β(IL1β), IL6,Tumor Necrosis Factor-α (TNF-α) can inhibit osteoblast differentiation and induce osteoblast apoptosis. PANoptosis, a newly identified type of programmed cell death (PCD), may be influenced by long noncoding RNA (lncRNAs) which play important roles in regulating inflammation. However, the potential role of lncRNAs in inflammation and PANoptosis during osteogenic differentiation remains unclear. This study aimed to investigate the regulatory functions of lncRNAs in inflammation and apoptosis during osteogenic differentiation.

METHODS AND RESULTS

High-throughput sequencing was used to identify differentially expressed genes involved in osteoblast differentiation under inflammatory conditions. Two lncRNAs associated with inflammation and PANoptosis during osteogenic differentiation were identified from sequencing data and Gene Expression Omnibus (GEO) databases. Their functionalities were analyzed using diverse bioinformatics methodologies, resulting in the construction of the lncRNA-miRNA-mRNA network. Among these, lncRNA (MIR17HG) showed a high correlation with PANoptosis. Bibliometric methods were employed to collect literature data on PANoptosis, and its components were inferred. PCR and Western Blotting experiments confirmed that lncRNA MIR17HG is related to PANoptosis in osteoblasts during inflammation.

CONCLUSIONS

Our data suggest that TNF-α-induced inhibition of osteogenic differentiation and PANoptosis in MC3T3-E1 osteoblasts is associated with MIR17HG. These findings highlight the critical role of MIR17HG in the interplay between inflammation, PANoptosis, and osteogenic differentiation, suggesting potential therapeutic targets for conditions involving impaired bone formation and inflammatory responses.

METTL3 Modulates Ctsk+ Lineage Supporting Cranial Osteogenesis via Hedgehog

N6-methyladenosine (m6A) modification, a eukaryotic messenger RNA modification catalyzed by methyltransferase-like 3 (METTL3), plays a pivotal role in stem cell fate determination. Calvarial bone development and maintenance are orchestrated by the cranial sutures. Cathepsin K (CTSK)-positive calvarial stem cells (CSCs) contribute to mice calvarial ossification. However, the role of m6A modification in regulating Ctsk+ lineage cells during calvarial development remains elusive. Here, we showed that METTL3 was colocalized with cranial nonosteoclastic Ctsk+ lineage cells, which were also associated with GLI1 expression. During neonatal development, depletion of Mettl3 in the Ctsk+ lineage cells delayed suture formation and decreased mineralization. During adulthood maintenance, loss of Mettl3 in the Ctsk+ lineage cells impaired calvarial bone formation, which was featured by the increased bone porosity, enhanced bone marrow cavity, and decreased number of osteocytes with the less-developed cellular outline. The analysis of methylated RNA immunoprecipitation sequencing and RNA sequencing data indicated that loss of METTL3 reduced Hedgehog (Hh) signaling pathway. Restoration of Hh signaling pathway by crossing Sufufl/+ alleles or by local administration of SAG21 partially rescued the abnormity. Our data indicate that METTL3 modulates Ctsk+ lineage cells supporting calvarial bone formation by regulating the Hh signaling pathway, providing new insights for clinical treatment of skull vault osseous diseases.

Role of epigenetic regulatory mechanisms in age-related bone homeostasis imbalance

Alterations to the human organism that are brought about by aging are comprehensive and detrimental. Of these, an imbalance in bone homeostasis is a major outward manifestation of aging. In older adults, the decreased osteogenic activity of bone marrow mesenchymal stem cells and the inhibition of bone marrow mesenchymal stem cell differentiation lead to decreased bone mass, increased risk of fracture, and impaired bone injury healing. In the past decades, numerous studies have reported the epigenetic alterations that occur during aging, such as decreased core histones, altered DNA methylation patterns, and abnormalities in noncoding RNAs, which ultimately lead to genomic abnormalities and affect the expression of downstream signaling osteoporosis treatment and promoter of fracture healing in older adults. The current review summarizes the impact of epigenetic regulation mechanisms on age-related bone homeostasis imbalance.

Tenascin-C promotes endochondral ossification and fracture healing through Hedgehog and Hippo signaling

Fractures are frequent and severe musculoskeletal injuries. This study aimed to investigate the function of tenascin-C (TNC) in regulating chondrogenic during fracture healing and elucidate the underlying molecular mechanisms. A well-established femur fracture model in male C57BL/6J mice was used to transect the middle diaphysis of the femur. To identify the essential role of TNC, shTNC lentiviruses or TNC protein were administered in the animal model. Micro-CT analysis, histologic analysis, immunostaining assays, and gene expression analysis were employed to investigate the effect of TNC during fracture healing. An in vitro mesenchymal stem cell culture system was developed to investigate the role and molecular mechanism of TNC in regulating chondrogenesis. TNC expression was induced at the inflammatory phase and peaked at the cartilaginous callus phase during fracture healing. Knockdown of TNC expression in callus results in decreased callus formation and impaired fracture healing. Conversely, administration of exogenous TNC promoted chondrogenic differentiation, cartilage template formation and ultimately improved fracture healing. Both the Hedgehog and Hippo signaling pathways were found to be involved in the pro-chondrogenic function of TNC. Our observations demonstrate that TNC is a crucial factor responsible for endochondral ossification in fracture healing and provide a potential therapeutic strategy for promoting fracture healing.

Validating core therapeutic targets for osteoporosis treatment based on integrating network pharmacology and informatics

OBJECTIVE

Our goal was to find metabolism-related lncRNAs that were associated with osteoporosis (OP) and construct a model for predicting OP progression using these lncRNAs.

METHODS

The GEO database was employed to obtain gene expression profiles. The WGCNA technique and differential expression analysis were used to identify hypoxia-related lncRNAs. A Lasso regression model was applied to select 25 hypoxia-related genes, from which a classification model was created. Its robust classification performance was confirmed with an area under the ROC curve close to 1, as verified on the validation set. Concurrently, we constructed a ceRNA network based on these genes to unveil potential regulatory processes. Biologically active compounds of STZYD were identified using the Traditional Chinese Medicine System Pharmacology Database and Analysis Platform (TCMSP) database. BATMAN was used to identify its targets, and we obtained OP-related genes from Malacards and DisGeNET, followed by identifying intersection genes with metabolism-related genes. A pharmacological network was then constructed based on the intersecting genes. The pharmacological network was further integrated with the ceRNA network, resulting in the creation of a comprehensive network that encompasses herb-active components, pathways, lncRNAs, miRNAs, and targets. Expression levels of hypoxia-related lncRNAs in mononuclear cells isolated from peripheral blood of OP and normal patients were subsequently validated using quantitative real-time PCR (qRT-PCR). Protein levels of RUNX2 were determined through a western blot assay.

RESULTS

CBFB, GLO1, NFKB2 and PIK3CA were identified as central therapeutic targets, and ADD3-AS1, DTX2P1-UPK3BP1-PMS2P11, TTTY1B, ZNNT1 and LINC00623 were identified as core lncRNAs.

CONCLUSIONS

Our work uncovers a possible therapeutic mechanism for STZYD, providing a potential therapeutic target for OP. In addition, a prediction model of metabolism-related lncRNAs of OP progression was constructed to provide a reference for the diagnosis of OP patients.

Long noncoding RNA Malat1 protects against osteoporosis and bone metastasis

MALAT1, one of the few highly conserved nuclear long noncoding RNAs (lncRNAs), is abundantly expressed in normal tissues. Previously, targeted inactivation and genetic rescue experiments identified MALAT1 as a suppressor of breast cancer lung metastasis. On the other hand, Malat1-knockout mice are viable and develop normally. On a quest to discover the fundamental roles of MALAT1 in physiological and pathological processes, we find that this lncRNA is downregulated during osteoclastogenesis in humans and mice. Remarkably, Malat1 deficiency in mice promotes osteoporosis and bone metastasis of melanoma and mammary tumor cells, which can be rescued by genetic add-back of Malat1. Mechanistically, Malat1 binds to Tead3 protein, a macrophage-osteoclast-specific Tead family member, blocking Tead3 from binding and activating Nfatc1, a master regulator of osteoclastogenesis, which results in the inhibition of Nfatc1-mediated gene transcription and osteoclast differentiation. Notably, single-cell transcriptome analysis of clinical bone samples reveals that reduced MALAT1 expression in pre-osteoclasts and osteoclasts is associated with osteoporosis and metastatic bone lesions. Altogether, these findings identify Malat1 as a lncRNA that protects against osteoporosis and bone metastasis.

A DNA tetrahedron-based ferroptosis-suppressing nanoparticle: superior delivery of curcumin and alleviation of diabetic osteoporosis

Diabetic osteoporosis (DOP) is a significant complication that poses continuous threat to the bone health of patients with diabetes; however, currently, there are no effective treatment strategies. In patients with diabetes, the increased levels of ferroptosis affect the osteogenic commitment and differentiation of bone mesenchymal stem cells (BMSCs), leading to significant skeletal changes. To address this issue, we aimed to target ferroptosis and propose a novel therapeutic approach for the treatment of DOP. We synthesized ferroptosis-suppressing nanoparticles, which could deliver curcumin, a natural compound, to the bone marrow using tetrahedral framework nucleic acid (tFNA). This delivery system demonstrated excellent curcumin bioavailability and stability, as well as synergistic properties with tFNA. Both in vitro and in vivo experiments revealed that nanoparticles could enhance mitochondrial function by activating the nuclear factor E2-related factor 2 (NRF2)/glutathione peroxidase 4 (GPX4) pathway, inhibiting ferroptosis, promoting the osteogenic differentiation of BMSCs in the diabetic microenvironment, reducing trabecular loss, and increasing bone formation. These findings suggest that curcumin-containing DNA tetrahedron-based ferroptosis-suppressing nanoparticles have a promising potential for the treatment of DOP and other ferroptosis-related diseases.

Dancr-BRG1 regulates Nfatc1 transcription and Pgc1β-dependent metabolic shifts in osteoclastogenesis

Long non-coding RNA (lncRNA) serves as a vital regulator of bone metabolism, but its role in pathologically overactive osteoclast differentiation remains elusive. Here, we identify lncRNA Dancr (Differentiation Antagonizing Non-protein Coding RNA) as a critical suppressor of osteoclastogenesis and bone resorption, which is down-regulated in response to estrogen deficiency. Global or osteoclast-specific Dancr Knockout mice display significant trabecular bone deterioration and enhanced osteoclast activity, but minimal alteration of bone formation. Moreover, the bone-targeted delivery of Dancr by Adeno-associated viral remarkably attenuates ovariectomy-induced osteopenia in mice. Mechanistically, Dancr establishes a direct interaction with Brahma-related gene 1 to prevent its binding and preserve H3K27me3 enrichment at the nuclear factor of activated T cells 1 and proliferator-activated receptor gamma coactivator 1-beta promoters, thereby maintaining appropriate expression of osteoclastic genes and metabolic programs during osteoclastogenesis. These results demonstrate that Dancr is a key molecule maintaining proper osteoclast differentiation and bone homeostasis under physiological conditions, and Dancr overexpression constitutes a potential strategy for treating osteoporosis.

Role of non-coding RNAs in osteoporosis

Osteoporosis, a prevalent bone disorder influenced by genetic and environmental elements, significantly increases the likelihood of fractures and bone weakness, greatly affecting the lives of those afflicted. Yet, the exact epigenetic processes behind the onset of osteoporosis are still unclear. Growing research indicates that epigenetic changes could act as vital mediators that connect genetic tendencies and environmental influences, thereby increasing the risk of osteoporosis and bone fractures. Within these epigenetic factors, certain types of RNA, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), have been recognized as key regulatory elements. These RNA types wield significant influence on gene expression through epigenetic regulation, directing various biological functions essential to bone metabolism. This extensive review compiles current research uncovering the complex ways in which miRNAs, lncRNAs, and circRNAs are involved in the development of osteoporosis, especially in osteoblasts and osteoclasts. Gaining a more profound understanding of the roles these three RNA classes play in osteoporosis could reveal new diagnostic methods and treatment approaches for this incapacitating condition. In conclusion, this review delves into the complex domain of epigenetic regulation via non-coding RNA in osteoporosis. It sheds light on the complex interactions and mechanisms involving miRNAs, lncRNAs, and circRNAs within osteoblasts and osteoclasts, offering an in-depth understanding of the less explored aspects of osteoporosis pathogenesis. These insights not only reveal the complexity of the disease but also offer significant potential for developing new diagnostic methods and targeted treatments. Therefore, this review marks a crucial step in deciphering the elusive complexities of osteoporosis, leading towards improved patient care and enhanced quality of life.

Emerging nano-scale delivery systems for the treatment of osteoporosis

Osteoporosis is a pathological condition characterized by an accelerated bone resorption rate, resulting in decreased bone density and increased susceptibility to fractures, particularly among the elderly population. While conventional treatments for osteoporosis have shown efficacy, they are associated with certain limitations, including limited drug bioavailability, non-specific administration, and the occurrence of adverse effects. In recent years, nanoparticle-based drug delivery systems have emerged as a promising approach for managing osteoporosis. Nanoparticles possess unique physicochemical properties, such as a small size, large surface area-to-volume ratio, and tunable surface characteristics, which enable them to overcome the limitations of conventional therapies. These nanoparticles offer several advantages, including enhanced drug stability, controlled release kinetics, targeted bone tissue delivery, and improved drug bioavailability. This comprehensive review aims to provide insights into the recent advancements in nanoparticle-based therapy for osteoporosis. It elucidates the various types of nanoparticles employed in this context, including silica, polymeric, solid lipid, and metallic nanoparticles, along with their specific processing techniques and inherent properties that render them suitable as potential drug carriers for osteoporosis treatment. Furthermore, this review discusses the challenges and future suggestions associated with the development and translation of nanoparticle drug delivery systems for clinical use. These challenges encompass issues such as scalability, safety assessment, and regulatory considerations. However, despite these challenges, the utilization of nanoparticle-based drug delivery systems holds immense promise in revolutionizing the field of osteoporosis management by enabling more effective and targeted therapies, ultimately leading to improved patient outcomes.

New insights into the role of long non-coding RNAs in osteoporosis

Osteoporosis is a common disease in elderly individuals, and osteoporosis can easily lead to bone and hip fractures that seriously endanger the health of elderly individuals. At present, the treatment of osteoporosis is mainly anti-osteoporosis drugs, but there are side effects associated with anti-osteoporosis drugs. Therefore, it is very important to develop early diagnostic indicators and new therapeutic drugs for the prevention and treatment of osteoporosis. Long noncoding RNAs (lncRNAs), noncoding RNAs longer than 200 nucleotides, can be used as diagnostic markers for osteoporosis, and lncRNAs play an important role in the progression of osteoporosis. Many studies have shown that lncRNAs can be the target of osteoporosis. Therefore, herein, the role of lncRNAs in osteoporosis is summarized, aiming to provide some information for the prevention and treatment of osteoporosis.

"Intercellular Mass Transport" Mimic Enables ASO Entry Completely into the Cell Nucleus for Enhanced Ischemia Therapy

Currently, the development of a new therapeutic technology is focused on antisense oligonucleotides (ASOs), where ASOs are used to complementarily pair with DNA, messenger RNA, or long noncoding RNA (lncRNA) to regulate the cell behavior by inhibiting the target gene expression. However, the targeted regulation toward nuclear genes still faces great challenges in ASO delivery for clinical applications, i.e., two essential criteria (high nuclear entry and delivery vehicle safety/simplification) generally compromise each other and are not simultaneously satisfactory. Herein, for the first time, inspired by "intercellular-mass-transport", we report an important discovery that the cell membrane of endothelial cells (ECs) serving as the biointerface enables ASOs to rapidly and completely enter the EC nucleus. Thereby, we innovatively fabricate a nanosystem only by sequential self-assembly of natural/off-the-shelf biomaterials to well overcome the above-mentioned contradiction. The efficacy is strikingly superior to that of the previous delivery vehicles. Furthermore, our technology is applied to successfully silence lncRNA MEG3 in the EC nucleus, significantly augmenting EC morphogenesis. More importantly, this nanosystem is applicable for in vivo intramuscular injection to enhance the therapeutic outcome in a critical limb ischemia mouse model. This work brings a new hope for the technological innovation of ASO nuclear delivery and opens a new avenue to explore natural/off-the-shelf materials for cargo delivery into subcellular compartments.

Bone marrow mesenchymal stem cell-derived exosomal microRNA-382 promotes osteogenesis in osteoblast via regulation of SLIT2

BACKGROUND

Osteoporosis (OP) is a systemic skeletal disorder with increased bone fragility. Human bone marrow mesenchymal stem cells (hBMSCs) have multi-lineage differentiation ability, which may play important roles in osteoporosis. In this study, we aim to investigate the role of hBMSC-derived miR-382 in osteogenic differentiation.

METHODS

The miRNA and mRNA expressions in peripheral blood monocytes between persons with high or low bone mineral density (BMD) were compared. Then we collected the hBMSC-secreted sEV and examined the dominant components. The over-expression of the miR-382 in MG63 cell and its progression of osteogenic differentiation were investigated by qRT-PCR, western blot and alizarin red staining. The interaction between miR-382 and SLIT2 was confirmed by dual-luciferase assay. The role of SLIT2 was also confirmed through up-regulation in MG63 cell, and the osteogenic differentiation-associated gene and protein were tested.

RESULTS

According to bioinformatic analysis, a series of differential expressed genes between persons with high or low BMD were compared. After internalization of hBMSC-sEV in MG63 cells, we observed that the ability of osteogenic differentiation was significantly enhanced. Similarly, after up-regulation of miR-382 in MG63 cells, osteogenic differentiation was also promoted. According to the dual-luciferase assay, the targeting function of miR-382 in SLIT2 was demonstrated. Moreover, the benefits of hBMSC-sEV in osteogenesis were abrogated through up-regulation of SLIT2.

CONCLUSION

Our study provided evidence that miR-382-contained hBMSC-sEV held great promise in osteogenic differentiation in MG63 cells after internalization by targeting SLIT2, which can be served as molecular targets to develop effective therapy.

Dual-Targeted Nanodiscs Revealing the Cross-Talk between Osteogenic Differentiation of Mesenchymal Stem Cells and Macrophages

Ongoing research has highlighted the significance of the cross-play of macrophages and mesenchymal stem cells (MSCs). Lysine-specific demethylase 6B (KDM6B) has been shown to control osteogenic differentiation of MSCs by depleting trimethylated histone 3 lysine 27 (H3K27me3). However, to date, the role of KDM6B in bone marrow-derived macrophages (BMDMs) remains controversial. Here, a chromatin immunoprecipitation assay (ChIP) proved that KDM6B derived from osteogenic-induced BMSCs could bind to the promoter region of BMDMs' brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein-1 (BMAL1) gene in a coculture system and activate BMAL1. Transcriptome sequencing and experiments in vitro showed that the overexpression of BMAL1 in BMDM could inhibit the TLR2/NF-κB signaling pathway, reduce pyroptosis, and decrease the M1/M2 ratio, thereby promoting osteogenic differentiation of BMSCs. Furthermore, bone and macrophage dual-targeted GSK-J4 (KDM6B inhibitor)-loaded nanodiscs were synthesized via binding SDSSD-apoA-1 peptide analogs (APA) peptide, which indirectly proved the critical role of KDM6B in osteogenesis in vivo. Overall, we demonstrated that KDM6B serves as a positive circulation trigger during osteogenic differentiation by decreasing the ratio of M1/M2 both in vitro and in vivo. Collectively, these results provide insight into basic research in the field of osteoporosis and bone repair.

A novel ceRNA regulatory network involving the long noncoding NEAT1, miRNA-466f-3p and its mRNA target in osteoblast autophagy and osteoporosis

Osteoporosis (OP) is a systemic metabolic disorder characterized by a reduction in bone tissue volume. LncRNAs have been reported to act as regulators of several human diseases. Specifically, lncRNA nuclear paraspeckle assembly transcript 1 (NEAT1) is involved in proliferation, differentiation and apoptosis in osteoclasts and bone marrow mesenchymal stem cells and regulates the occurrence and development of OP. However, the relationship between NEAT1 and osteoblast autophagy and its mechanism are still unclear. Western blotting of LC3 and P62 was used to evaluate the effect of fluid shear stress (FSS) on autophagy in MC3T3-E1 osteoblasts. Total transcriptome sequencing and bioinformatics analyses were performed on osteoblasts loaded with and without FSS. qPCR was performed to examine the expression of NEAT1 in OP bone tissues and osteoblasts. The RNA-FISH was performed to study the localization of lncRNA NEAT1 and miR-466f-3p in MC3T3-E1 osteoblasts. In vitro, western blotting, transmission electron microscopy (TEM), immunofluorescence (IF) staining and qPCR were performed to verify the biological functions of NEAT1, miR-466f-3p and HK2. Subsequently, we conducted bioinformatics analysis and dual luciferase reporter assays to identify the relationships among NEAT1, miR-466f-3p and HK2. Additionally, rescue assays were conducted on osteoblasts to clarify the regulatory network of the NEAT1/miR-466f-3p/HK2 signalling pathway. In vivo, the OVX mouse model was used to investigate the effects of si-NEAT1 on autophagy in OP mice. The distal femur and serum were collected for further micro-CT analysis, blood biochemistry, and haematoxylin-eosin and Alizarin red staining (ARS). Immunohistochemistry (IHC) was performed to assess the protein expression of LC3 and HK2. NEAT1 expression was upregulated in OP tissues and osteoblast lines exposed to FSS. Knockdown of NEAT1 inhibited autophagy in vitro and in vivo. Further studies demonstrated that NEAT1 positively regulated HK2 expression via its competing endogenous RNA effects on miR-466f-3p. Moreover, we found the NEAT1/miR-466f-3p/HK2 axis regulated autophagy in osteoblasts. Knocking down NEAT1 inhibited autophagy in osteoblasts via the miR-466f-3p/HK2 signalling pathway, which may provide new ideas for novel molecular therapeutic targets of postmenopausal OP. KEY MESSAGES: • Fluid shear stress (FSS) can promote autophagy of osteoblast and performed transcriptome sequencing. • NEAT1 is overexpressed in osteoporosis and could regulate osteoblast cells autophagy. • Knockdown of lncRNA NEAT1 inhibited osteoblast cells autophagy by sponging miRNA-466f-3p and targeting HK2 in osteoporosis.

Peptide modified geniposidic acid targets bone and effectively promotes osteogenesis

Background

Geniposidic acid (GPA), one of the active components of Eucommia ulmoides, promote bone formation and treat osteoporosis by activating farnesoid X receptor (FXR). However, GPA has low oral availability and lack of bone targeting in the treatment of bone related diseases. With the development of modern technology, small molecules, amino acids, or aptamers are used for biological modification of drugs and target cells in bone tissue, which has become the trend of bone targeted research.

Methods

In this study, SDSSD (an osteoblast-targeting peptide) were modified in GPA using Fmoc solid-phase synthesis technique to form a new SDSSD-GPA conjugate (SGPA). The bone targeting of SGPA was evaluated using in vivo imaging and cell co-culture. In vitro, the effect of SGPA on cytotoxicity, osteoblastic activity, and mineralization ability were studied in mouse primary osteoblasts (OBs). In vivo, the therapeutic effect of SGPA on osteoporosis using an ovariectomized (OVX) mouse model. The bone mass, histomorphometry, serum biochemical parameters, and the molecular mechanism were evaluated.

Results

SGPA was enriched in OBs and tends to accumulate in bone tissue. In vitro, SGPA significantly enhanced the osteogenic activity and mineralization of OBs compared with GPA. In vivo, SGPA enhanced serum BALP and P1NP levels, increased the trabecular bone mass of the mice, and SGPA administration have a higher bone mineralization deposition rate than the GPA-treated mice. Moreover, SGPA significantly activated FXR and Runt-related transcription factor 2 (RUNX2).

Conclusions

Collectively, SGPA is enriched into OBs, and promotes bone formation by activating FXR-RUNX2 signalling, effectively treating osteoporosis at relatively low doses.

The translational potential of this article

This study demonstrates a more efficient and safe application of GPA in treating osteoporosis, provide a new concept for the bone targeted application of natural compounds.

Activation of farnesoid X receptor signaling by geniposidic acid promotes osteogenesis

BACKGROUND

New targets and strategies are urgently needed for the identification and development of anabolic drugs for osteoporosis. Farnesoid X receptor (FXR) is a promising novel therapeutic target for bone metabolism diseases. Although used clinically, FXR agonists have obvious side effects; therefore, the development of new FXR agonists for the treatment of osteoporosis would be welcomed. Geniposidic acid (GPA) is a bioactive compound extracted from Eucommiae cortex, which is used for treating arthritis, osteoporotic fractures, and hypertension. However, the therapeutic effects of GPA against osteoporosis remain underexplored.

PURPOSE

This study aims to reveal the potential osteogenic effects of FXR and to explore the effect of GPA on bone formation, osteoporosis treatment, and FXR signaling.

STUDY DESIGN & METHODS

The role of FXR in promoting bone formation was evaluated in Fxr knockout (Fxr^-/-) mice and cell models. GPA activation of FXR was evaluated by molecular docking and luciferase reporter gene assays. Thirty female C57BL/6J mice were randomly assigned into a sham operation group (Sham) and four ovariectomized (OVX) groups (n=6 each) and were treated with vehicle or different doses of GPA (25, 50, and 100 mg/kg/day). The therapeutic effect of GPA on osteoporosis was systematically analyzed by performing bone histomorphometry and measuring serum biochemical parameters, and the molecular mechanism was also evaluated. Furthermore, the action of GPA in Fxr^-/- mice was evaluated to investigate its dependency on FXR in promoting bone formation and treating osteoporosis.

RESULTS

We found that FXR was highly expressed in bone tissues and enriched in osteoblasts. Notably, deletion of FXR significantly reduced the bone formation rate and bone mass of the Fxr^-/- mice compared with wild-type mice. Furthermore, using a high throughput drug screening strategy based on fluorescent reporter genes, we found that GPA functions as a natural agonist of FXR. We confirmed the activities of GPA on FXR activation and osteogenesis in both osteoblast differentiation models and OVX-induced osteoporosis models. We revealed that GPA strongly promotes bone formation by activating FXR/RUNX2 signaling. Moreover, the osteoporotic therapeutic effect of GPA was abolished in Fxr^-/- mice.

CONCLUSION

This study demonstrated that FXR is a promising target for treating osteoporosis and that GPA promotes bone formation in OVX-induced osteoporosis by activating FXR signaling. These findings provide novel insight into the mechanism by which GPA promotes bone formation and more evidence for its application in the treatment of osteoporosis.

Long noncoding RNA Gm31629 promotes bone regeneration by maintaining bone marrow mesenchymal stem cells activity

Background

Long noncoding RNA Gm31629 can regulate hypothalamic neural stem cells (htNSCs) senescence and the aging process. However, the effect of Gm31629 on the senescence of bone marrow mesenchymal stem cells (BMSCs) and bone regeneration is unclear. In the present study, we investigated the effects of Gm31629 on the senescence of BMSCs and bone regeneration.

Methods

Gm31629 knockout (Gm31629-KO) and wild-type (WT) mice were used to establish a bone regeneration model. The Brdu labelling, CCK8 assay, wound healing assay, β-gal staining and osteogenic differentiation assay were used to assess the effects of Gm31629 on the functions of BMSCs. Micro-computed tomography (CT), histochemical and immunohistochemical staining were used to evaluate the ability of bone regeneration. The mimic of Gm31629, theaflavin 3-gallate, was used to investigate its role on the senescence of BMSCs and bone regeneration.

Results

The expression of Gm31629 reduced in BMSCs of middle-aged mice was compared with that of young mice. The deletion of Gm31629 was sufficient to drive the senescence of BMSCs, resulting in impaired bone regeneration in mice. Mechanistically, Gm31629 could interact with Y-box protein 1(YB-1) and delay its degradation, decreasing the transcription of p16^INK4A of BMSCs. We also found that theaflavin 3-gallate could alleviate the senescence of BMSCs and promote bone regeneration in middle-aged mice.

Conclusion

These results indicated that Gm31629 played an important role on BMSCs senescence and bone regeneration and provided a therapeutic target to promote bone regeneration.

Histone Modifications and Non-Coding RNAs: Mutual Epigenetic Regulation and Role in Pathogenesis

In the last few years, more and more scientists have suggested and confirmed that epigenetic regulators are tightly connected and form a comprehensive network of regulatory pathways and feedback loops. This is particularly interesting for a better understanding of processes that occur in the development and progression of various diseases. Appearing on the preclinical stages of diseases, epigenetic aberrations may be prominent biomarkers. Being dynamic and reversible, epigenetic modifications could become targets for a novel option for therapy. Therefore, in this review, we are focusing on histone modifications and ncRNAs, their mutual regulation, role in cellular processes and potential clinical application.

Sp7 Action in the Skeleton: Its Mode of Action, Functions, and Relevance to Skeletal Diseases

Osteoblast differentiation is a tightly regulated process in which key transcription factors (TFs) and their target genes constitute gene regulatory networks (GRNs) under the control of osteogenic signaling pathways. Among these TFs, Sp7 works as an osteoblast determinant critical for osteoblast differentiation. Following the identification of Sp7 and a large number of its functional studies, recent genome-scale analyses have made a major contribution to the identification of a "non-canonical" mode of Sp7 action as well as "canonical" ones. The analyses have not only confirmed known Sp7 targets but have also uncovered its additional targets and upstream factors. In addition, biochemical analyses have demonstrated that Sp7 actions are regulated by chemical modifications and protein-protein interaction with other transcriptional regulators. Sp7 is also involved in chondrocyte differentiation and osteocyte biology as well as postnatal bone metabolism. The critical role of SP7 in the skeleton is supported by its relevance to human skeletal diseases. This review aims to overview the Sp7 actions in skeletal development and maintenance, particularly focusing on recent advances in our understanding of how Sp7 functions in the skeleton under physiological and pathological conditions.

Emerging role of m6A modification in osteogenesis of stem cells

The differentiation of stem cells into osteoblasts is a key link in the treatment of bone defects and other orthopedic diseases. N6-methyladenosine (m6A) modification, an important post-transcriptional modification, is a methylation that occurs at the N6 site of RNA adenylate. The modification plays a regulatory role in the growth and development of biological individuals, the directional differentiation of stem cells and the occurrence of diseases. It is involved in various processes of the fate decision of stem cells. And it regulates the development and constant renewal of bone and keeps bone homeostasis by controlling and maintaining the balance between osteogenesis and adipogenesis. Meanwhile, it also affects the progress of orthopedic-associated diseases such as degenerative osteoporosis and bone tumor. In this review, we mainly summarize the new findings of three key molecules including Writers, Erasers and Readers which regulate m6A modification, and the emerging role of m6A modification in determining the fate and directed differentiation potential of stem cells, especially highlight the regulatory mechanism of osteogenic differentiation, the balance between osteogenesis and adipogenesis and the occurrence and development of bone-related diseases. It may provide some important ideas about finding new strategies to recover from bone defect and degenerative bone disease.

Generation of functional oligopeptides that promote osteogenesis based on unsupervised deep learning of protein IDRs

Deep learning (DL) is currently revolutionizing peptide drug development due to both computational advances and the substantial recent expansion of digitized biological data. However, progress in oligopeptide drug development has been limited, likely due to the lack of suitable datasets and difficulty in identifying informative features to use as inputs for DL models. Here, we utilized an unsupervised deep learning model to learn a semantic pattern based on the intrinsically disordered regions of ~171 known osteogenic proteins. Subsequently, oligopeptides were generated from this semantic pattern based on Monte Carlo simulation, followed by in vivo functional characterization. A five amino acid oligopeptide (AIB5P) had strong bone-formation-promoting effects, as determined in multiple mouse models (e.g., osteoporosis, fracture, and osseointegration of implants). Mechanistically, we showed that AIB5P promotes osteogenesis by binding to the integrin α5 subunit and thereby activating FAK signaling. In summary, we successfully established an oligopeptide discovery strategy based on a DL model and demonstrated its utility from cytological screening to animal experimental verification.

Osteogenic peptides in periodontal ligament stem cell-containing three-dimensional bioscaffolds promote bone healing

Bone tissue engineering shows great potential in bone regeneration; however, the lack of bone growth factors with high biocompatibility and efficiency is a major concern. Oligopeptides have drawn great attention due to their high biological efficacy, low toxicity, and low molecular weight. The oligopeptide SDSSD promotes the osteogenesis of human periodontal ligament stem cells (hPDLSCs) in vitro. The SDSSD-modified three-dimensional (3D) bioscaffolds promote osteogenesis and bone formation in the subcutaneous pockets of BALB/c nude mice and facilitate bone healing in vivo. Mechanistically, SDSSD promoted bone formation by binding to G protein-coupled receptors and regulating the AKT signaling pathway. 3D-printing bioscaffolds with SDSSD may be potential bone tissue engineering materials for treating bone defects.

Epigenetic regulation by long noncoding RNAs in osteo-/adipogenic differentiation of mesenchymal stromal cells and degenerative bone diseases

Bone is a complex tissue that undergoes constant remodeling to maintain homeostasis, which requires coordinated multilineage differentiation and proper proliferation of mesenchymal stromal cells (MSCs). Mounting evidence indicates that a disturbance of bone homeostasis can trigger degenerative bone diseases, including osteoporosis and osteoarthritis. In addition to conventional genetic modifications, epigenetic modifications (i.e., DNA methylation, histone modifications, and the expression of noncoding RNAs) are considered to be contributing factors that affect bone homeostasis. Long noncoding RNAs (lncRNAs) were previously regarded as ‘transcriptional noise’ with no biological functions. However, substantial evidence suggests that lncRNAs have roles in the epigenetic regulation of biological processes in MSCs and related diseases. In this review, we summarized the interactions between lncRNAs and epigenetic modifiers associated with osteo-/adipogenic differentiation of MSCs and the pathogenesis of degenerative bone diseases and highlighted promising lncRNA-based diagnostic and therapeutic targets for bone diseases.

Inflammatory osteoclasts-derived exosomes promote bone formation by selectively transferring lncRNA LIOCE into osteoblasts to interact with and stabilize Osterix

Bone loss is a hallmark of inflammatory bone diseases caused by aberrantly activated osteoclasts (OCLs). Studies have shown that OCLs exhibit various phenotypes and functions due to variations in the source(s) of precursor cells, cytokine expressions, and microenvironment-dependent factors. During these conditions, inflammatory osteoclasts (iOCLs) lose their immune-suppressive effect relative to OCLs under physiological conditions. This induces TNF α-producing CD4⁺ T cells in an antigen-dependent manner and finally leads to cascade amplification of iOCLs. OCL-derived exosomes have been reported to regulate OCL formation and inhibit the osteoblast activity. However, the specific function and mechanism of iOCL-derived exosomes on osteoblast have not been studied yet. In the present study, we compare the osteoblast promoting activities of iOCL-derived exosomes and OCL-derived exosomes. We found that iOCLs exosomes specifically target osteoblasts through ephrinA2/EphA2. Mechanistically, the lncRNA LIOCE is enriched in iOCL exosomes and promotes the osteoblast activity after being incorporated into osteoblasts. Furthermore, our results revealed that exosomal lncRNA LIOCE stabilizes osteogenic transcription factor Osterix by interacting and reducing the ubiquitination level of Osterix. This study demonstrated that the bone loss is alleviated in the inflammatory osteolysis mice model after injection of iOCL exosomes encapsulating lncRNA LIOCE. The role of exosomes encapsulating lncRNA LIOCE in promoting bone formation was well established in the rat bone repair model. Our results indicate that iOCL-derived exosomal lncRNA LIOCE promotes bone formation by upregulating Osx expression, and thus, the exosomes encapsulating lncRNA LIOCE may be an effective strategy to increase bone formation in osteoporosis and other bone metabolic disorders.

DANCR Mediates the Rescuing Effects of Sesamin on Postmenopausal Osteoporosis Treatment via Orchestrating Osteogenesis and Osteoclastogenesis

As one of the leading causes of bone fracture in postmenopausal women and in older men, osteoporosis worldwide is attracting more attention in recent decades. Osteoporosis is a common disease mainly resulting from an imbalance of bone formation and bone resorption. Pharmaceutically active compounds that both activate osteogenesis, while repressing osteoclastogenesis hold the potential of being therapeutic medications for osteoporosis treatment. In the present study, sesamin, a bioactive ingredient derived from the seed of Sesamum Indicum, was screened out from a bioactive compound library and shown to exhibit dual-regulating functions on these two processes. Sesamin was demonstrated to promote osteogenesis by upregulating Wnt/β-catenin, while repressing osteoclastogenesis via downregulating NF-κB signaling . Furthermore, DANCR was found to be the key regulator in sesamin-mediated bone formation and resorption . In an ovariectomy (OVX)-induced osteoporotic mouse model, sesamin could rescue OVX-induced bone loss and impairment. The increased serum level of DANCR caused by OVX was also downregulated upon sesamin treatment. In conclusion, our results demonstrate that sesamin plays a dual-functional role in both osteogenesis activation and osteoclastogenesis de-activation in a DANCR-dependent manner, suggesting that it may be a possible medication candidate for osteoporotic patients with elevated DNACR expression levels.

The Roles of Long Non-coding RNA in Osteoporosis

The Human Genome Project (HGP) announced in 2001 that it had sequenced the entire human genome, yielding nearly complete human DNA. About 98.5 percent of the human genome has been found to be non-coding sequences. Long non-coding RNA (lncRNA) is a non-coding RNA with a length between 200 and 100,000 nucleotide units. Because of shallow research on lncRNA, it was believed that it had no biological functions, but exists as a by-product of the transcription process. With the development of high-throughput sequencing technology, studies have shown that lncRNA plays important roles in many processes by participating in epigenetics, transcription, translation and protein modification. Current researches have shown that lncRNA also has an important part in the pathogenesis of osteoporosis. Osteoporosis is a common disorder of bone metabolism, also a major medical and socioeconomic challenge worldwide. It is characterized by a systemic reduction in bone mass and microstructure changes, which increases the risk of brittle fractures. It is more common in postmenopausal women and elderly men. However, the roles of lncRNA and relevant mechanisms in osteoporosis remain unclear. Based on this background, we hereby review the roles of lncRNA in osteoporosis, and how it influences the functions of osteoblasts and osteoclasts, providing reference to clinical diagnosis, treatment and prognosis of osteoporosis.

LncRNA Nron Inhibits Bone Resorption in Periodontitis

Periodontitis is the most common chronic oral disease and is characterized by active osteoclast activity and significant alveolar bone resorption. However, the key regulatory factors of periodontal bone loss have yet to be determined, and reasonable intervention methods for periodontitis have not been developed. Currently, long noncoding RNAs (lncRNAs) have shown a remarkable ability to maintain normal cell and tissue homeostasis. Interestingly, we recently found that the lncRNA Nron is negatively correlated with alveolar bone resorption in periodontitis model. To explore the role of Nron in periodontal bone loss, osteoclastic-specific Nron knockout mice and osteoclastic-specific Nron transgenic mice were generated. Nron effectively inhibited osteoclastogenesis and alveolar bone resorption. Mechanistically, Nron was found to effectively promote the nuclear transport of NF-κb repressing factor (NKRF). In addition, NKRF in the nucleus significantly repressed the transcription of Nfatc1, which is a major NF-κb signaling molecule. Importantly, local injection of the Nron overexpression vector significantly inhibited osteoclastogenesis and alveolar bone resorption, which indicated the translational application potential of lncRNAs in the treatment of bone resorption in periodontitis.

A functional motif of long noncoding RNA Nron against osteoporosis

Long noncoding RNAs are widely implicated in diverse disease processes. Nonetheless, their regulatory roles in bone resorption are undefined. Here, we identify lncRNA Nron as a critical suppressor of bone resorption. We demonstrate that osteoclastic Nron knockout mice exhibit an osteopenia phenotype with elevated bone resorption activity. Conversely, osteoclastic Nron transgenic mice exhibit lower bone resorption and higher bone mass. Furthermore, the pharmacological overexpression of Nron inhibits bone resorption, while caused apparent side effects in mice. To minimize the side effects, we further identify a functional motif of Nron. The delivery of Nron functional motif to osteoclasts effectively reverses bone loss without obvious side effects. Mechanistically, the functional motif of Nron interacts with E3 ubiquitin ligase CUL4B to regulate ERα stability. These results indicate that Nron is a key bone resorption suppressor, and the lncRNA functional motif could potentially be utilized to treat diseases with less risk of side effects.

LncRNAs are implicated in the pathogenesis of a number of diseases. Here, the authors show that the lncRNA Nron suppresses bone resorption, and show that delivery of a functional motif of Nron increases bone mass in mouse models of osteoporosis.

Advances in the occurrence and biotherapy of osteoporosis

Osteoporosis (OP) is a bone metabolic disease, is characterized by degeneration of bone structure and decreased bone mass. It happens in more than 1/3 women and 1/5 men of over than 50 years old, which affects the health and lives of people. The main mechanism of OP is mainly that the dynamic balance between the bone formation and resorption is broken, so that bone resorption is more than bone formation. It is prone to result in bone metabolism disorder. There are many precipitating factor such as elder age, low hormone level, genetic factors and bad hobbies. At the same time, the occurrence of the OP and its complications has different degrees of impact on people's quality of life. Based on the current understanding of the OP, we summarized the etiology, current clinical drugs and potential targeting therapy for OP. Although the research have made many progress in explore what is the novel mechanism and how to improve the effect, there are still many problems in the treatment method that limit its application prospects and need to be solved. In this review, we mainly focus on the mechanism of OP and related research on the targeted treatment of OP. Hopefully, our summary will provide a reference to develop some novel strategies for the target therapy of OP.

LncRNA LINC00680 promotes lung adenocarcinoma growth via binding to GATA6 and canceling GATA6-mediated suppression of SOX12 expression

Lung adenocarcinoma (LUAD) is a major subtype of non-small-cell lung cancers (NSCLC). LINC00680 has been characterized as a novel oncogenic lncRNA in LUAD, but its regulatory mechanisms remain largely unclear. This study aimed to explore the subcellular localization of LINC00680 in LUAD and its regulation on the transcriptional process. LUAD cell lines (A549, H1650, and H1299) were used for in vitro and in vivo studies. Results showed LINC00680 depletion resulted in G0/G1 phase arrest of LUAD cells and reduced CDK4 and cyclin D1 expression in H1650 and H1299 cells. LINC00680 overexpression promoted A549 cell proliferation and increased CDK4 and cyclin D1 expression. RNA-fluorescence in situ hybridization (FISH) assay showed that LINC00680 has both cytoplasmic and nuclear distribution in LUAD cells. RNA pulldown and western blotting assays confirmed a physical interaction between LINC00680 and GATA6. In LUAD cells, GATA6 overexpression only slightly suppressed SOX12 transcription. ChIP-qPCR and dual-luciferase assay showed that GATA6 only weakly bound to the SOX12 promoter and decreased its activity. However, when LINC00680 was depleted, these transcriptional suppressive effects were significantly enhanced. These findings suggested that LINC00680 forms a complex with GATA6 and weakens its transcriptional suppressive effect on SOX12 expression. In the nude mice model, LINC00680 overexpression partly abrogated the growth-suppressive effects of GATA6 on A549 derived tumors. In summary, this study revealed a novel LINC00680-GATA6-SOX12 axis in promoting LUAD cell cycle progression and proliferation. Future studies should be conducted for a better understanding of the complex networking of LINC00680 in LUAD.

The Involvement of Long Non-Coding RNAs in Bone

A harmonious balance between osteoblast and osteoclast activity guarantees optimal bone formation and resorption, pathological conditions affecting the bone may arise. In recent years, emerging evidence has shown that epigenetic mechanisms play an important role during osteoblastogenesis and osteoclastogenesis processes, including long non-coding RNAs (lncRNAs). These molecules are a class of ncRNAs with lengths exceeding 200 nucleotides not translated into protein, that have attracted the attention of the scientific community as potential biomarkers to use for the future development of novel diagnostic and therapeutic approaches for several pathologies, including bone diseases. This review aims to provide an overview of the lncRNAs and their possible molecular mechanisms in the osteoblastogenesis and osteoclastogenesis processes. The deregulation of their expression profiles in common diseases associated with an altered bone turnover is also described. In perspective, lncRNAs could be considered potential innovative molecular biomarkers to help with earlier diagnosis of bone metabolism-related disorders and for the development of new therapeutic strategies.

Preosteoblast-enriched lnc-Evf2 facilitates osteogenic differentiation by targeting Notch

Ossification of ligaments (OL) and osteoporosis (OP) are multifactorial disorders without definitive clinical biomarkers. Long non-coding RNAs (lncRNAs) are known to involve in regulating pathogenesis. Here, we have identified a preosteoblast-enriched lnc-Evf2 that was overexpressed in ossified ligamentum flavum (OLF) and down-expressed in OP. lnc-Evf2 is gradually upregulated during osteogenic induction, correlating with the enhanced expression of osteogenic marker genes and matrix mineralization. Moreover, knockdown of lnc-Evf2 significantly inhibits the expression of osteogenic differentiation markers and delays the osteoblastic mineralization process, indicating that this molecule is involved in osteogenesis. Mechanistically, we demonstrated that silencing of lnc-Evf2 decreases the protein level but not the mRNA levels of Notch2, Notch3, and Hes1, all of which correlate with osteogenesis. Taken together, our data demonstrate that lnc-Evf2 promotes osteogenic differentiation and bone formation through the Notch signaling, revealing that lnc-Evf2 may serve as a novel potential clinical target of OL and OP.

Long non-coding RNAs: From disease code to drug role

Enormous studies have corroborated that long non-coding RNAs (lncRNAs) extensively participate in crucial physiological processes such as metabolism and immunity, and are closely related to the occurrence and development of tumors, cardiovascular diseases, nervous system disorders, nephropathy, and other diseases. The application of lncRNAs as biomarkers or intervention targets can provide new insights into the diagnosis and treatment of diseases. This paper has focused on the emerging research into lncRNAs as pharmacological targets and has reviewed the transition of lncRNAs from the role of disease coding to acting as drug candidates, including the current status and progress in preclinical research. Cutting-edge strategies for lncRNA modulation have been summarized, including the sources of lncRNA-related drugs, such as genetic technology and small-molecule compounds, and related delivery methods. The current progress of clinical trials of lncRNA-targeting drugs is also discussed. This information will form a latest updated reference for research and development of lncRNA-based drugs.

Recent Advances of Osterix Transcription Factor in Osteoblast Differentiation and Bone Formation

With increasing life expectations, more and more patients suffer from fractures either induced by intensive sports or other bone-related diseases. The balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption is the basis for maintaining bone health. Osterix (Osx) has long been known to be an essential transcription factor for the osteoblast differentiation and bone mineralization. Emerging evidence suggests that Osx not only plays an important role in intramembranous bone formation, but also affects endochondral ossification by participating in the terminal cartilage differentiation. Given its essentiality in skeletal development and bone formation, Osx has become a new research hotspot in recent years. In this review, we focus on the progress of Osx's function and its regulation in osteoblast differentiation and bone mass. And the potential role of Osx in developing new therapeutic strategies for osteolytic diseases was discussed.

Mechanisms of miR‑128‑3p in inhibiting osteoblast differentiation from bone marrow‑derived mesenchymal stromal cells

The authors' previous study demonstrated that miR-128 may exert an inhibitory effect on the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BM-MSCs), but its downstream mechanisms remain to be elucidated. The aim of the present study was to investigate the microRNA (miRNA/miR) and mRNA profiles of differentiated and undifferentiated BM-MSCs and explore new downstream targets for miR-128. The sequencing datasets of GSE107279 (miRNA) and GSE112318 (mRNA) were downloaded from the Gene Expression Omnibus database. The differentially expressed miRNAs (DEMs) and genes (DEGs) were identified using the DESeq2 method. The target genes of DEMs were predicted by the miRwalk 2.0 database. The hub target genes of miR-128 were screened by constructing the protein-protein interaction (PPI) network and module analysis. The expression levels of miR-128 and crucial target genes were validated by reverse transcription-quantitative (RT-q) PCR before or after transfection of miR-128 mimics to BM-MSCs. The miRNA expression profile analysis identified miR-128 as one of the significantly downregulated DEMs (total 338) in differentiated BM-MSCs compared with the undifferentiated control. A total of 103 predicted target genes of miR-128-3p were overlapped with upregulated DEGs. By calculating the topological properties of each protein in the PPI network, 6 upregulated genes (KIT, NTRK2, YWHAB, GAB1, AXIN1 and RUNX1; fold change was the highest for NTRK2) were considered to be hub genes. Of these, 4 were enriched in module 4 (RUNX1, KIT, GAB1 and AXIN1; RUNX1 was particularly crucial as it can interact with the others), while one was enriched in module 7 (YWHAB). The expression levels of miR-128 and these 6 target genes during the osteogenic differentiation were experimentally confirmed by RT-qPCR. In addition, the expression levels of these 6 genes were significantly reversed after transfection of miR-128-3p mimics into rat BM-MSCs compared with the miR-control group. These findings indicated that miR-128-3p may inhibit the osteoblast differentiation of BM-MSCs by downregulation of these 6 genes, particularly RUNX1, YWHAB and NTRK2.

Critical regulation of a NDIME/MEF2C axis in embryonic stem cell neural differentiation and autism

A microdeletion within human chromosome 5q14.3 has been associated with the occurrence of neurodevelopmental disorders, such as autism and intellectual disability, and MEF2C haploinsufficiency was identified as main cause. Here, we report that a brain-enriched long non-coding RNA, NDIME, is located near the MEF2C locus and is required for normal neural differentiation of mouse embryonic stem cells (mESCs). NDIME interacts with EZH2, the major component of polycomb repressive complex 2 (PRC2), and blocks EZH2-mediated trimethylation of histone H3 lysine 27 (H3K27me3) at the Mef2c promoter, promoting MEF2C transcription. Moreover, the expression levels of both NDIME and MEF2C were strongly downregulated in the hippocampus of a mouse model of autism, and the adeno-associated virus (AAV)-mediated expression of NDIME in the hippocampus of these mice significantly increased MEF2C expression and ameliorated autism-like behaviors. The results of this study reveal an epigenetic mechanism by which NDIME regulates MEF2C transcription and neural differentiation and suggest potential effects and therapeutic approaches of the NDIME/MEF2C axis in autism.

Roles of long non-coding RNAs and emerging RNA-binding proteins in innate antiviral responses

The diseases caused by viruses posed a great challenge to human health, the development of which was driven by the imbalanced host immune response. Host innate immunity is an evolutionary old defense system that is critical for the elimination of the virus. The overactive innate immune response also leads to inflammatory autoimmune diseases, which require precise control of innate antiviral response for maintaining immune homeostasis. Mounting long non-coding RNAs (lncRNAs) transcribed from the mammalian genome are key regulators of innate antiviral response, functions of which greatly depend on their protein interactors, including classical RNA-binding proteins (RBPs) and the unconventional proteins without classical RNA binding domains. In particular, several emerging RBPs, such as m⁶A machinery components, TRIM family members, and even the DNA binding factors recognized traditionally, function in innate antiviral response. In this review, we highlight recent progress in the regulation of type I interferon signaling-based antiviral responses by lncRNAs and emerging RBPs as well as their mechanism of actions. We then posed the future perspective toward the role of lncRNA-RBP interaction networks in innate antiviral response and discussed the promising and challenges of lncRNA-based drug development as well as the technical bottleneck in studying lncRNA-protein interactions. Our review provides a comprehensive understanding of lncRNA and emerging RBPs in the innate antiviral immune response.