A novel long noncoding RNA PGC1β-OT1 regulates adipocyte and osteoblast differentiation through antagonizing miR-148a-3p

Unraveling the molecular and immunological landscape: Exploring signaling pathways in osteoporosis

Osteoporosis, characterized by compromised bone density and microarchitecture, represents a significant global health challenge, particularly in aging populations. This comprehensive review delves into the intricate signaling pathways implicated in the pathogenesis of osteoporosis, providing valuable insights into the pivotal role of signal transduction in maintaining bone homeostasis. The exploration encompasses cellular signaling pathways such as Wnt, Notch, JAK/STAT, NF-κB, and TGF-β, all of which play crucial roles in bone remodeling. The dysregulation of these pathways is a contributing factor to osteoporosis, necessitating a profound understanding of their complexities to unveil the molecular mechanisms underlying bone loss. The review highlights the pathological significance of disrupted signaling in osteoporosis, emphasizing how these deviations impact the functionality of osteoblasts and osteoclasts, ultimately resulting in heightened bone resorption and compromised bone formation. A nuanced analysis of the intricate crosstalk between these pathways is provided to underscore their relevance in the pathophysiology of osteoporosis. Furthermore, the study addresses some of the most crucial long non-coding RNAs (lncRNAs) associated with osteoporosis, adding an additional layer of academic depth to the exploration of immune system involvement in various types of osteoporosis. Finally, we propose that SKP1 can serve as a potential biomarker in osteoporosis.

Effect of LncRNA LOC106505926 on myogenesis and Lipogenesis of porcine primary cells

BACKGROUND

Skeletal muscle development and fat deposition have important effects on meat quality. The study of regulating skeletal muscle development and fat deposition is of great significance in improving the quality of carcass and meat. In the present study, whole transcriptome sequencing (including RNA-Seq and miRNA-Seq) was performed on the longissimus dorsi muscle (LDM) of Jinfen White pigs at 1, 90, and 180 days of age.

RESULTS

The results showed that a total of 245 differentially expressed miRNAs were screened in any two comparisons, which may be involved in the regulation of myogenesis. Among them, compared with 1-day-old group, miR-22-5p was significantly up-regulated in 90-day-old group and 180-day-old group. Functional studies demonstrated that miR-22-5p inhibited the proliferation and differentiation of porcine skeletal muscle satellite cells (PSCs). Pearson correlation coefficient analysis showed that long non-coding RNA (lncRNA) LOC106505926 and CXXC5 gene had strong negative correlations with miR-22-5p. The LOC106505926 and CXXC5 were proven to promote the proliferation and differentiation of PSCs, as opposed to miR-22-5p. In terms of mechanism, LOC106505926 functions as a molecular sponge of miR-22-5p to modulate the expression of CXXC5, thereby inhibits the differentiation of PSCs. In addition, LOC106505926 regulates the differentiation of porcine preadipocytes through direct binding with FASN.

CONCLUSIONS

Collectively, our results highlight the multifaceted regulatory role of LOC106505926 in controlling skeletal muscle and adipose tissue development in pigs and provide new targets for improving the quality of livestock products by regulating skeletal muscle development and fat deposition.

Epigenetic Regulation of Autophagy in Bone Metabolism

The skeletal system is crucial for supporting bodily functions, protecting vital organs, facilitating hematopoiesis, and storing essential minerals. Skeletal homeostasis, which includes aspects such as bone density, structural integrity, and regenerative processes, is essential for normal skeletal function. Autophagy, an intricate intracellular mechanism for degrading and recycling cellular components, plays a multifaceted role in bone metabolism. It involves sequestering cellular waste, damaged proteins, and organelles within autophagosomes, which are then degraded and recycled. Autophagy's impact on bone health varies depending on factors such as regulation, cell type, environmental cues, and physiological context. Despite being traditionally considered a cytoplasmic process, autophagy is subject to transcriptional and epigenetic regulation within the nucleus. However, the precise influence of epigenetic regulation, including DNA methylation, histone modifications, and non-coding RNA expression, on cellular fate remains incompletely understood. The interplay between autophagy and epigenetic modifications adds complexity to bone cell regulation. This article provides an in-depth exploration of the intricate interplay between these two regulatory paradigms, with a focus on the epigenetic control of autophagy in bone metabolism. Such an understanding enhances our knowledge of bone metabolism-related disorders and offers insights for the development of targeted therapeutic strategies.

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.

Unveiling Mesenchymal Stem Cells' Regenerative Potential in Clinical Applications: Insights in miRNA and lncRNA Implications

It is now widely recognized that mesenchymal stem cells (MSCs) possess the capacity to differentiate into a wide array of cell types. Numerous studies have identified the role of lncRNA in the regulation of MSC differentiation. It is important to elucidate the role and interplay of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) in the regulation of signalling pathways that govern MSC function. Furthermore, miRNAs and lncRNAs are important clinical for innovative strategies aimed at addressing a wide spectrum of existing and emerging disease. Hence it is important to consider their impact on MSC function and differentiation. Examining the data available in public databases, we have collected the literature containing the latest discoveries pertaining to human stem cells and their potential in both fundamental research and clinical applications. Furthermore, we have compiled completed clinical studies that revolve around the application of MSCs, shedding light on the opportunities presented by harnessing the regulatory potential of miRNAs and lncRNAs. This exploration of the therapeutic possibilities offered by miRNAs and lncRNAs within MSCs unveils exciting prospects for the development of precision therapies and personalized treatment approaches. Ultimately, these advancements promise to augment the efficacy of regenerative strategies and produce positive outcomes for patients. As research in this field continues to evolve, it is imperative to explore and exploit the vast potential of miRNAs and lncRNAs as therapeutic agents. The findings provide a solid basis for ongoing investigations, fuelling the quest to fully unlock the regenerative potential of MSCs.

LncRNA DGCR5-encoded polypeptide RIP aggravates SONFH by repressing nuclear localization of β-catenin in BMSCs

The differentiation fate of bone marrow mesenchymal stem cells (BMSCs) affects the progression of steroid-induced osteonecrosis of the femoral head (SONFH). We find that lncRNA DGCR5 encodes a 102-amino acid polypeptide, RIP (Rac1 inactivated peptide), which promotes the adipogenic differentiation of BMSCs and aggravates the progression of SONFH. RIP, instead of lncRNA DGCR5, binds to the N-terminal motif of RAC1, and inactivates the RAC1/PAK1 cascade, resulting in decreased Ser675 phosphorylation of β-catenin. Ultimately, the nuclear localization of β-catenin decreases, and the differentiation balance of BMSCs tilts toward the adipogenesis lineage. In the femoral head of rats, overexpression of RIP causes trabecular bone disorder and adipocyte accumulation, which can be rescued by overexpressing RAC1. This finding expands the regulatory role of lncRNAs in BMSCs and suggests RIP as a potential therapeutic target.

A potential therapeutic drug for osteoporosis: prospect for osteogenic LncRNAs

Long non-coding RNAs (LncRNAs) play essential roles in multiple physiological processes including bone formation. Investigators have revealed that LncRNAs regulated bone formation through various signaling pathways and micro RNAs (miRNAs). However, several problems exist in current research studies on osteogenic LncRNAs, including sophisticated techniques, high cost for in vivo experiment, as well as low homology of LncRNAs between animal model and human, which hindered translational medicine research. Moreover, compared with gene editing, LncRNAs would only lead to inhibition of target genes rather than completely knocking them out. As the studies on osteogenic LncRNA gradually proceed, some of these problems have turned osteogenic LncRNA research studies into slump. This review described some new techniques and innovative ideas to address these problems. Although investigations on osteogenic LncRNAs still have obtacles to overcome, LncRNA will work as a promising therapeutic drug for osteoporosis in the near future.

miR-196b-5p Regulates Osteoblast and Osteoclast Differentiation and Bone Homeostasis by Targeting SEMA3A

miR-196b-5p plays a role in various malignancies. We have recently reported its function in regulating adipogenesis. However, it remains to be clarified whether and how miR-196b-5p affects bone cells and bone homeostasis. In this study, in vitro functional experiments showed an inhibitory effect of miR-196b-5p on osteoblast differentiation. Mechanistic explorations revealed that miR-196b-5p directly targeted semaphorin 3a (Sema3a) and inhibited Wnt/β-catenin signaling. SEMA3A attenuated the impaired osteogenesis induced by miR-196b-5p. Osteoblast-specific miR-196b transgenic mice showed significant reduction of bone mass. Trabecular osteoblasts were reduced and bone formation was suppressed, whereas osteoclasts, marrow adipocytes, and serum levels of bone resorption markers were increased in the transgenic mice. The osteoblastic progenitor cells from the transgenic mice had decreased SEMA3A levels and exhibited retarded osteogenic differentiation, whereas those marrow osteoclastic progenitors exhibited enhanced osteoclastogenic differentiation. miR-196b-5p and SEMA3A oppositely regulated the expression of receptor activator of nuclear factor-κB ligand and osteoprotegerin. The calvarial osteoblastic cells expressing the transgene promoted osteoclastogenesis, whereas the osteoblasts overexpressing Sema3a inhibited it. Finally, in vivo transfection of miR-196b-5p inhibitor to the marrow reduced ovariectomy-induced bone loss in mice. Our study has identified that miR-196b-5p plays a key role in osteoblast and osteoclast differentiation and regulates bone homeostasis. Inhibition of miR-196b-5p may be beneficial for amelioration of osteoporosis. © 2023 American Society for Bone and Mineral Research (ASBMR).

A Novel LncRNA MSTRG.310246.1 Promotes Differentiation and Thermogenesis in Goat Brown Adipocytes

Brown adipose tissue (BAT) plays a critical role in maintaining the body temperature in newborn lamb due to its unique non-shivering thermogenesis. Previous studies have found that BAT thermogenesis is regulated by several long non-coding RNAs (lncRNAs). Here, we identified a novel lncRNA, MSTRG.310246.1, which was enriched in BAT. MSTRG.310246.1 was localized in both the nuclear and cytoplasmic compartments. In addition, MSTRG.310246.1 expression was upregulated during brown adipocyte differentiation. Overexpression of MSTRG.310246.1 increased the differentiation and thermogenesis of goat brown adipocytes. On the contrary, the knockdown of MSTRG.310246.1 inhibited the differentiation and thermogenesis of goat brown adipocytes. However, MSTRG.310246.1 had no effect on goat white adipocyte differentiation and thermogenesis. Our results show that MSTRG.310246.1 is a BAT-enriched LncRNA that improves the differentiation and thermogenesis of goat brown adipocytes.

lncRNA MEG3 Promotes PDK4/GSK-3β/β-Catenin Axis in MEFs by Targeting miR-532-5p

Studies reported the positive and negative osteogenic effects of MEG3 in mesenchymal stem cells (MSCs). This study aims at clarifying the osteogenic potential of MEG3 and the underlying mechanism. Bone morphogenetic protein 9- (BMP9-) transfected MSCs were recruited as an osteogenic model in vitro, and ectopic bone formation were used in vivo to explore the effect of MEG3 on osteogenesis. We found that overexpression of MEG3 facilitated BMP9-induced osteogenic markers, ALP activities, and matrix mineralization. However, knockdown of MEG3 attenuated BMP9-induced osteogenic markers. MEG3 increased the phosphorylation of GSK-3β and the protein level of β-catenin. Pyruvate dehydrogenase kinase 4 (PDK4) can also combine with GSK-3β and increase the latter phosphorylation. Moreover, MEG3 increased the mRNA level of PDK4. The ceRNA analysis showed that MEG3 may regulate the expression of PDK4 via microRNA 532-5p (miR-532-5p). The MEG3-enhanced GSK-3β/β-catenin axis can be attenuated by miR-532-5p, and miR-532-5p inhibitor partly rescued endogenous PDK4 and MEG3-mediated expression of PDK4. MEG3 may potentiate PDK4 and GSK-3β/β-catenin by inhibiting miR-532-5p.

MiR-148a deletion protects from bone loss in physiological and estrogen-deficient mice by targeting NRP1

Bone metabolic homeostasis is largely dependent on the dynamic balance between osteoblasts and osteoclasts. MicroRNAs (miRNAs) play critical roles in regulating bone metabolism. In this study, we explored the role of a new miRNA (miR-148a) in osteoporosis. We compared the bone phenotype between miR-148a knockout (KO) mice and the wild-type (WT) littermates. We found miR-148a KO mice exhibited an increased bone mass phenotype and decreased osteoclastogenesis compared to the WT group. In vitro, miR-148a overexpression promoted osteoclastogenesis and bone resorption function. Mechanistically, NRP1 was identified as a novel direct target of miR-148a, and NRP1 silencing reversed the effect of miR-148a knockout. In OVX and calvarial osteolysis models, miR-148a KO protects mice against excessive bone resorption, while miR-148a agomiR/AAV-shNRP1 accelerates pathologic bone loss. Finally, the miR-148a level was found to be positively correlated with β-CTX in postmenopausal osteoporosis (PMOP) serum specimens. In summary, our findings revealed that miR-148a genetic deletion ameliorates bone loss under physiological and pathological conditions by targeting NRP1. In osteoclast-related bone metabolic diseases such as PMOP, miR-148a may be an attractive therapeutic target in the future.

Identification of MYEOV-Associated Gene Network as a Potential Therapeutic Target in Pancreatic Cancer

The molecular mechanism that promotes pancreatic cancer remains unclear, so it is important to find the molecular network of important genes related to pancreatic cancer. To find the key molecule of pancreatic cancer, differential gene expression analyses were analyzed by the Deseq2 package, edgeR package, and limma-voom package, respectively. Pancreatic cancer survival-related genes were analyzed by COX survival analysis. Finally, we integrated the results to obtain the significantly differentially expressed gene, MYEOV (myeloma overexpressed gene), most strongly related to survival in pancreatic cancer. Experimental verification by qRT-PCR confirmed that transcription levels of MYEOV mRNA markedly increased in pancreatic cancer cells relative to normal human pancreatic ductal epithelial cells (HPDE). Through the comprehensive analysis of multiple databases, we constructed a molecular network centered on MYEOV and found specific links between molecules in this network and tumor-associated immune cells. It was noted that MYEOV could serve as a ceRNA by producing molecular sponging effects on hsa-miR-103a-3p and hsa-miR-107, thus affecting the role of GPRC5A, SERPINB5, EGFR, KRAS, EIF4G2, and PDCD4 on pancreatic cancer progression. Besides, we also identified that infiltrated immune cells are potential mediators for the molecules in the MYEOV-related network to promote pancreatic cancer progression. It is the first report to focus on the possibility that MYEOV may act as a competing endogenous RNA (ceRNA) to form an interactive network with some pancreatic cancer-related genes such as KRAS and serve as a key therapeutic target of pancreatic cancer treatment.

MicroRNA-loaded biomaterials for osteogenesis

The large incidence of bone defects in clinical practice increases not only the demand for advanced bone transplantation techniques but also the development of bone substitute materials. A variety of emerging bone tissue engineering materials with osteogenic induction ability are promising strategies for the design of bone substitutes. MicroRNAs (miRNAs) are a class of non-coding RNAs that regulate intracellular protein expression by targeting the non-coding region of mRNA3′-UTR to play an important role in osteogenic differentiation. Several miRNA preparations have been used to promote the osteogenic differentiation of stem cells. Therefore, multiple functional bone tissue engineering materials using miRNA as an osteogenic factor have been developed and confirmed to have critical efficacy in promoting bone repair. In this review, osteogenic intracellular signaling pathways mediated by miRNAs are introduced in detail to provide a clear understanding for future clinical treatment. We summarized the biomaterials loaded with exogenous cells engineered by miRNAs and biomaterials directly carrying miRNAs acting on endogenous stem cells and discussed their advantages and disadvantages, providing a feasible method for promoting bone regeneration. Finally, we summarized the current research deficiencies and future research directions of the miRNA-functionalized scaffold. This review provides a summary of a variety of advanced miRNA delivery system design strategies that enhance bone regeneration.

Enhancement of Osteoblast Function through Extracellular Vesicles Derived from Adipose-Derived Stem Cells

Adipose-derived stem cells (ADSCs) are a type of mesenchymal stem cell that is investigated in bone tissue engineering (BTE). Osteoblasts are the main cells responsible for bone formation in vivo and directing ADSCs to form osteoblasts through osteogenesis is a research topic in BTE. In addition to the osteogenesis of ADSCs into osteoblasts, the crosstalk of ADSCs with osteoblasts through the secretion of extracellular vesicles (EVs) may also contribute to bone formation in ADSC-based BTE. We investigated the effect of ADSC-secreted EVs (ADSC-EVs) on osteoblast function. ADSC-EVs (size ≤ 1000 nm) were isolated from the culture supernatant of ADSCs through ultracentrifugation. The ADSC-EVs were observed to be spherical under a transmission electron microscope. The ADSC-EVs were positive for CD9, CD81, and Alix, but β-actin was not detected. ADSC-EV treatment did not change survival but did increase osteoblast proliferation and activity. The 48 most abundant known microRNAs (miRNAs) identified within the ADSC-EVs were selected and then subjected to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. The GO analysis revealed that these miRNAs are highly relevant to skeletal system morphogenesis and bone development. The KEGG analysis indicated that these miRNAs may regulate osteoblast function through autophagy or the mitogen-activated protein kinase or Ras-related protein 1 signaling pathway. These results suggest that ADSC-EVs enhance osteoblast function and can contribute to bone regeneration in ADSC-based BTE.

Oncostatin M receptor regulates osteoblast differentiation via extracellular signal-regulated kinase/autophagy signaling

Background

Oncostatin M receptor (OSMR), as one of the receptors for oncostatin M (OSM), has previously been shown to mediate the stimulatory role of OSM in osteoclastogenesis and bone resorption. However, it remains to be clarified whether and how OSMR affects the differentiation of osteoblasts.

Methods

The expression level of OSMR during osteoblast and adipocyte differentiation was examined. The role of OSMR in the differentiation was investigated using in vitro gain-of-function and loss-of-function experiments. The mechanisms by which OSMR regulates bone cell differentiation were explored. Finally, in vivo function of OSMR in cell fate determination and bone homeostasis was studied after transplantation of OSMR-silenced bone marrow stromal cells (BMSCs) to the marrow of ovariectomized mice.

Results

OSMR was regulated during osteogenic and adipogenic differentiation of marrow stromal progenitor cells and increased in the metaphysis of ovariectomized mice. OSMR suppressed osteogenic differentiation and stimulated adipogenic differentiation of progenitor cells. Mechanistic investigations showed that OSMR inhibited extracellular signal-regulated kinase (ERK) and autophagy signaling. The downregulation of autophagy, which was mediated by ERK inhibition, suppressed osteogenic differentiation of progenitor cells. Additionally, inactivation of ERK/autophagy signaling attenuated the stimulation of osteogenic differentiation induced by Osmr siRNA. Furthermore, transplantation of BMSCs in which OSMR was silenced to the marrow of mice promoted osteoblast differentiation, attenuated fat accumulation and osteoclast differentiation, and thereby relieved the osteopenic phenotype in the ovariectomized mice.

Conclusions

Our study has for the first time established the direct role of OSMR in regulating osteogenic differentiation of marrow stromal progenitor cells through ERK-mediated autophagy signaling. OSMR thus contributes to bone homeostasis through dual regulation of osteoblasts and osteoclasts. It also suggests that OSMR may be a potential target for the treatment of metabolic disorders such as osteoporosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02958-1.

Long noncoding RNAs in mesenchymal stromal/stem cells osteogenic differentiation: Implications in osteoarthritis pathogenesis

This letter focuses on a recently published article that provided an exceptional description of the effect of epigenetic modifications on gene expression patterns related to skeletal system remodeling. Specifically, it discusses a novel modality of epigenetic regulation, the long noncoding RNAs (lncRNAs), and provides evidence of their involvement in mesenchymal stromal/stem cells osteo-/adipo-genic differentiation balance. Despite focus on lncRNAs, there is an emerging cross talk between lncRNAs and miRNAs interaction as a novel mechanism in the regulation of the function of the musculoskeletal system, by controlling bone homeostasis and bone regeneration, as well as the osteogenic differentiation of stem cells. Thus, we touched on some examples to demonstrate this interaction. In addition, we believe there is still much to discover from the effects of lncRNAs on progenitor and non-progenitor cell differentiation. We incorporated data from other published articles to review lncRNAs in normal progenitor cell osteogenic differentiation, determined lncRNAs involved in osteoarthritis pathogenesis in progenitor cells, and provided a review of lncRNAs in non-progenitor cells that are differentially regulated in osteoarthritis. In conclusion, we really enjoyed reading this article and with this information we hope to further our understanding of lncRNAs and mesenchymal stromal/stem cells regulation.

LncRNA XIST accelerates burn wound healing by promoting M2 macrophage polarization through targeting IL-33 via miR-19b

Burn injuries are a serious threat to quality of life. The aim of this study was to investigate the mechanism of burn wound healing. The lncRNA XIST has been associated with burn wound healing, but the mechanism is not clear. In the present study, in vitro and in vivo models of burn injuries were established by thermal injury treatment of human skin fibroblasts (HSFs) and mice, respectively. Pathological changes in skin tissues were detected by haematoxylin and eosin (HE) staining. Immunofluorescence double staining was performed to detect M2 macrophages. Furthermore, the changes of cell proliferation, apoptosis and migration by CCK-8, flow cytometry, scratch and Transwell assays to evaluate the effect of XIST on burn wound healing. The binding relationships among XIST, miR-19b and IL-33 were analyzed by RNA immunoprecipitation (RIP) and dual luciferase reporter assays. Our results found that there were targeted binding sites between XIST and miR-19b, miR-19b and IL-33. We investigated whether XIST enhanced the polarization of M2 macrophages to promote the healing of burn wounds. After fibroblast burn injury, the expression levels of XIST and IL-33 increased in a time-dependent manner, whereas miR-19b expression decreased in a time-dependent manner. XIST contributed to the proliferation and migration of skin fibroblasts by inhibiting miR-19b and enhanced fibroblast extracellular matrix production by promoting the transformation of macrophages to the M2 phenotype. In short, these findings indicate that XIST can promote burn wound healing and enhance the polarization of M2 macrophages by targeting the IL-33/miR-19b axis, which may serve as a potential theoretical basis for the treatment of burn wound healing.

[Knockdown of long non-coding RNA MIR4697 host gene inhibits adipogenic differentiation in bone marrow mesenchymal stem cells]

OBJECTIVE

To preliminarily investigate the role of long non-coding RNA (lncRNA) MIR4697 host gene (MIR4697HG) in regulating the adipogenic differentiation of bone marrow mesenchymal stem cells (BMSCs).

METHODS

For adipogenic differentiation, BMSCs were induced in adipogenic media for 10 days. The mRNA expression levels of lncRNA MIR4697HG and adipogenic marker genes including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhanced binding protein α (CEBP/α) and adiponectin (ADIPQ) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) at different time points (0, 1, 2, 3, 5, 7, 10 days). The MIR4697HG stable knockdown-BMSC cell line was generated by infection of MIR4697HG shRNA-containing lentiviruses. To avoid off-target effect, two target sequences (shMIR4697HG-1, shMIR4697HG-2) were designed. And then cells were induced to differentiate in adipogenic medium. Oil red O staining, Western blot and qRT-PCR were used to detect the effect of MIR4697HG knockdown on adipogenic differentiation of BMSCs.

RESULTS

The mRNA expression level of MIR4697HG was significantly increased during adipogenic differentiation (P < 0.01), and adipogenic differentiation of BMSCs was evidenced by upregulated mRNA levels of specific adipogenesis-related genes including PPARγ, CEBP/α and ADIPQ. Observed by fluorescence microscopy, more than 90% transfected target cells expressed green fluorescent protein successfully after shMIR4697HG-1 group, shMIR4697HG-2 group and shNC group transfection for 72 h. And the transfection efficiency of MIR4697HG examined by qRT-PCR was above 60%. Then the BMSCs were treated with adipogenic media for 7 days and showed that the mRNA expression levels of adipogenesis-related genes including PPARγ, CEBP/α and ADIPQ were significantly decreased in the MIR4697HG knockdown group (P < 0.01), while the expression levels of PPARγ and CEBP/α proteins were decreased remarkably as well (P < 0.01). Consistently, MIR4697HG knockdown BMSCs formed less lipid droplets compared with the control BMSCs, which further demonstrated that MIR4697HG knockdown inhibited adipogenic differentiation of BMSCs.

CONCLUSION

lncRNA MIR4697HG played a crucial role in regulating the adipogenic differentiation of BMSCs, and MIR4697HG knockdown significantly inhibited the adipogenic differentiation of BMSCs. These data may suggest that lncRNA MIR4697HG could serve as a therapeutic potential target for the aberrant adipogenic differentiation-associated disorders including osteoporosis.

LncRNA GACAT2 binds with protein PKM1/2 to regulate cell mitochondrial function and cementogenesis in an inflammatory environment

Periodontal ligament stem cells (PDLSCs) are a key cell type for restoring/regenerating lost/damaged periodontal tissues, including alveolar bone, periodontal ligament and root cementum, the latter of which is important for regaining tooth function. However, PDLSCs residing in an inflammatory environment generally exhibit compromised functions, as demonstrated by an impaired ability to differentiate into cementoblasts, which are responsible for regrowing the cementum. This study investigated the role of mitochondrial function and downstream long noncoding RNAs (lncRNAs) in regulating inflammation-induced changes in the cementogenesis of PDLSCs. We found that the inflammatory cytokine-induced impairment of the cementogenesis of PDLSCs was closely correlated with their mitochondrial function, and lncRNA microarray analysis and gain/loss-of-function studies identified GACAT2 as a regulator of the cellular events involved in inflammation-mediated mitochondrial function and cementogenesis. Subsequently, a comprehensive identification of RNA-binding proteins by mass spectrometry (ChIRP-MS) and parallel reaction monitoring (PRM) assays revealed that GACAT2 could directly bind to pyruvate kinase M1/2 (PKM1/2), a protein correlated with mitochondrial function. Further functional studies demonstrated that GACAT2 overexpression increased the cellular protein expression of PKM1/2, the PKM2 tetramer and phosphorylated PKM2, which led to enhanced pyruvate kinase (PK) activity and increased translocation of PKM2 into mitochondria. We then found that GACAT2 overexpression could reverse the damage to mitochondrial function and cementoblastic differentiation of PDLSCs induced by inflammation and that this effect could be abolished by PKM1/2 knockdown. Our data indicated that by binding to PKM1/2 proteins, the lncRNA GACAT2 plays a critical role in regulating mitochondrial function and cementogenesis in an inflammatory environment.

Long noncoding RNA Lnc-DIF inhibits bone formation by sequestering miR-489-3p

Osteoporosis has become a high incident bone disease along with the aging of human population. Long noncoding RNAs (LncRNAs) play an important role in osteoporosis incidence. In this study, we screened out an LncRNA negatively correlated with osteoblast differentiation, which was therefore named Lnc-DIF (differentiation inhibiting factor). Functional analysis proved that Lnc-DIF inhibited bone formation. A special structure containing multiple 53 nucleotide repeats was found in the trailing end of Lnc-DIF. Our study suggested that this repeat sequence could sequester multiple miR-489-3p and inhibit bone formation through miR-489-3p/SMAD2 axis. Moreover, siRNA of Lnc-DIF would rescue bone formation in both aging and ovariectomized osteoporosis mice. This study revealed a kind of LncRNA that could function as a sponge and regulate multiple miRNAs. RNA therapy techniques that target these LncRNAs could manipulate its downstream miRNA-target pathway with significantly higher efficiency and specificity. This provided potential therapeutic insight for RNA-based therapy for osteoporosis.

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Identified LncRNA Lnc-DIF that inhibited bone formation

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Lnc-DIF sequestered multiple miR-489-3p by the repeat sequences on its trailing end

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Lnc-DIF repeat sequence inhibited bone formation via miR-489-3p/SMAD2 axis

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Lnc-DIF siRNA showed strong capability on rescuing osteoporosis

Role of lncRNAs into Mesenchymal Stromal Cell Differentiation

Currently, findings support that 75% of the human genome is actively transcribed, but only 2% is translated into a protein, according to databases such as ENCODE (Encyclopedia of DNA Elements) [1]. The development of high-throughput sequencing technologies, computational methods for genome assembly and biological models have led to the realization of the importance of the previously unconsidered non-coding fraction of the genome. Along with this, noncoding RNAs have been shown to be epigenetic, transcriptional and post-transcriptional regulators in a large number of cellular processes [2]. Within the group of non-coding RNAs, lncRNAs represent a fascinating field of study, given the functional versatility in their mode of action on their molecular targets. In recent years, there has been an interest in learning about lncRNAs in MSC differentiation. The aim of this review is to address the signaling mechanisms where lncRNAs are involved, emphasizing their role in either stimulating or inhibiting the transition to differentiated cell. Specifically, the main types of MSC differentiation are discussed: myogenesis, osteogenesis, adipogenesis and chondrogenesis. The description of increasingly new lncRNAs reinforces their role as players in the well-studied field of MSC differentiation, allowing a step towards a better understanding of their biology and their potential application in the clinic.

LncRNAs as a new regulator of chronic musculoskeletal disorder

Objectives

In recent years, long non‐coding RNAs (lncRNAs) have been found to play a role in the occurrence, progression and prognosis of chronic musculoskeletal disorders.

Design and methods

Literature exploring on PubMed was conducted using the combination of keywords 'LncRNA' and each of the following: 'osteoarthritis', 'rheumatoid arthritis', 'osteoporosis', 'osteogenesis', 'osteoclastogenesis', 'gout arthritis', 'Kashin‐Beck disease', 'ankylosing spondylitis', 'cervical spondylotic myelopathy', 'intervertebral disc degeneration', 'human muscle disease' and 'muscle hypertrophy and atrophy'. For each disorder, we focused on the publications in the last five years (5/1/2016‐2021/5/1, except for Kashin‐Beck disease). Finally, we excluded publications that had been reported in reviews of various musculoskeletal disorders during the last three years. Here, we summarized the progress of research on the role of lncRNA in multiple pathological processes during musculoskeletal disorders.

Results

LncRNAs play a crucial role in regulating downstream gene expression and maintaining function and homeostasis of cells, especially in chondrocytes, synovial cells, osteoblasts, osteoclasts and skeletal muscle cells.

Conclusions

Understanding the mechanisms of lncRNAs in musculoskeletal disorders may provide promising strategies for clinical practice.

MiR-148a-3p Regulates the Invasion and Odontoblastic Differentiation of Human Dental Pulp Stem Cells via the Wnt1/β-Catenin Pathway

Background and Objectives

MiR-148a-3p has been reported to regulate the differentiation of marrow stromal cell osteoblast. In this study, whether miR-148a-3p regulated the odontoblastic differentiation of human dental pulp stem cells (hDPSCs) or not was explored.

Methods and Results

The hDPSCs were isolated and identified via flow cytometry. Targets of miR-148a-3p were identified via bioinformatics and dual-luciferase reporter assay. After the cell was cultured in the odontogenic differentiation medium or infected, cell viability, invasion, and odontoblastic differentiation were detected via MTT, transwell, and Alizarin Red S staining, respectively. The miR-148a-3p, Wnt1, β-catenin, DSPP, DMP-1, RUNX2, OCN, and Smad4 expressions were determined by RT-qPCR and Western blot. The hDPSCs odontoblastic differentiation downregulated the miR-148a-3p expression and upregulated Wnt1 expression. Wnt1 was determined as the target for miR-148a-3p. MiR-148a-3p mimic and siWnt1 suppressed the cell viability, invasion, and odontoblastic differentiation of hDPSCs and inhibited the Wnt1, β-catenin, DSPP, DMP-1, RUNX2, OCN, and Smad4 expressions. In contrast, miR-148a-3p inhibitor and overexpressed Wnt1 promoted the cell viability, invasion, and odontoblastic differentiation of hDPSCs, and upregulated the Wnt1, β-catenin, DSPP, DMP-1, RUNX2, OCN, and Smad4 expressions. Also, miR-148a-3p mimic and inhibitor reversed the effects of Wnt1 overexpression and siWnt1.

Conclusions

MiR-148a-3p modulated the invasion and odontoblastic differentiation of hDPSCs through the Wnt1/β-catenin pathway.

Long Non-coding RNA Regulation of Mesenchymal Stem Cell Homeostasis and Differentiation: Advances, Challenges, and Perspectives

Given the self-renewal, multi-differentiation, immunoregulatory, and tissue maintenance properties, mesenchymal stem cells (MSCs) are promising candidates for stem cell-based therapies. Breakthroughs have been made in uncovering MSCs as key contributors to homeostasis and the regenerative repair of tissues and organs derived from three germ layers. MSC differentiation into specialized cell types is sophisticatedly regulated, and accumulating evidence suggests long non-coding RNAs (lncRNAs) as the master regulators of various biological processes including the maintenance of homeostasis and multi-differentiation functions through epigenetic, transcriptional, and post-translational mechanisms. LncRNAs are ubiquitous and generally referred to as non-coding transcripts longer than 200 bp. Most lncRNAs are evolutionary conserved and species-specific; however, the weak conservation of their sequences across species does not affect their diverse biological functions. Although numerous lncRNAs have been annotated and studied, they are nevertheless only the tip of the iceberg; the rest remain to be discovered. In this review, we characterize MSC functions in homeostasis and highlight recent advances on the functions and mechanisms of lncRNAs in regulating MSC homeostasis and differentiation. We also discuss the current challenges and perspectives for understanding the roles of lncRNAs in MSC functions in homeostasis, which could help develop promising targets for MSC-based therapies.

MACF1 alleviates aging-related osteoporosis via HES1

Ageing-related osteoporosis is becoming an emerging threat to human health along with the ageing of human population. The decreased rate of osteogenic differentiation and bone formation is the major cause of ageing-related osteoporosis. Microtubule actin cross-linking factor 1 (MACF1) is an important cytoskeletal factor that promotes osteogenic differentiation and bone formation. However, the relationship between MACF1 expression and ageing-related osteoporosis remains unclear. This study has investigated the expression pattern of MACF1 in bone tissues of ageing-related osteoporosis patients and ageing mice. The study has further elucidated the mechanism of MACF1 promoting bone formation by inhibiting HES1 expression and activity. Moreover, the therapeutic effect of MACF1 on ageing-related osteoporosis and post-menopausal osteoporosis was evaluated through in situ injection of the MACF1 overexpression plasmid. The study supplemented the molecular mechanisms between ageing and bone formation, and provided novel targets and potential therapeutic strategy for ageing-related osteoporosis.

Long noncoding RNA LYPLAL1-AS1 regulates adipogenic differentiation of human mesenchymal stem cells by targeting desmoplakin and inhibiting the Wnt/β-catenin pathway

Long noncoding RNAs are crucial factors for modulating adipogenic differentiation, but only a few have been identified in humans. In the current study, we identified a previously unknown human long noncoding RNA, LYPLAL1-antisense RNA1 (LYPLAL1-AS1), which was dramatically upregulated during the adipogenic differentiation of human adipose-derived mesenchymal stem cells (hAMSCs). Based on 5' and 3' rapid amplification of cDNA ends assays, full-length LYPLAL1-AS1 was 523 nt. Knockdown of LYPLAL1-AS1 decreased the adipogenic differentiation of hAMSCs, whereas overexpression of LYPLAL1-AS1 enhanced this process. Desmoplakin (DSP) was identified as a direct target of LYPLAL1-AS1. Knockdown of DSP enhanced adipogenic differentiation and rescued the LYPLAL1-AS1 depletion-induced defect in adipogenic differentiation of hAMSCs. Further experiments showed that LYPLAL1-AS1 modulated DSP protein stability possibly via proteasome degradation, and the Wnt/β-catenin pathway was inhibited during adipogenic differentiation regulated by the LYPLAL1-AS1/DSP complex. Together, our work provides a new mechanism by which long noncoding RNA regulates adipogenic differentiation of human MSCs and suggests that LYPLAL1-AS1 may serve as a novel therapeutic target for preventing and combating diseases related to abnormal adipogenesis, such as obesity.

The Roles of LncRNAs in Osteogenesis, Adipogenesis and Osteoporosis

BACKGROUND

Osteoporosis (OP) is the most common bone disease, which is listed by the World Health Organization (WHO) as the third major threat to life and health among the elderly. The etiology of OP is multifactorial, and its potential regulatory mechanism remains unclear. Long non-coding RNAs (LncRNAs) are the non-coding RNAs that are over 200 bases in the chain length. Increasing evidence indicates that LncRNAs are the important regulators of osteogenic and adipogenic differentiation, and the occurrence of OP is greatly related to the dysregulation of the bone marrow mesenchymal stem cells (BMSCs) differentiation lineage. Meanwhile, LncRNAs affect the occurrence and development of OP by regulating OP-related biological processes.

METHODS

In the review, we summarized and analyzed the latest findings of LncRNAs in the pathogenesis, diagnosis and related biological processes of OP. Relevant studies published in the last five years were retrieved and selected from the PubMed database using the keywords of LncRNA and OP.

RESULTS/CONCLUSION

The present study aimed to examine the underlying mechanisms and biological roles of LncRNAs in OP, as well as osteogenic and adipogenic differentiation. Our results contributed to providing new clues for the epigenetic regulation of OP, making LncRNAs the new targets for OP therapy.

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.

miR-142a-5p promoted osteoblast differentiation via targeting nuclear factor IA

miR-142a-5p plays critical roles in multiple biological processes and diseases, such as inflammation and tumorigenesis. However, it remains to be explored if and how miR-142a-5p contributes to osteoblast differentiation. In this study, our results showed that miR-142a-5p was highly expressed in bone tissue of mice and increased during osteogenesis in preosteoblast MC3T3-E1 cells. Supplementing miR-142a-5p activity using miR-142a-5p agomir promoted osteogenic differentiation in stromal cell line ST2 and preosteoblastic line MC3T3-E1. Conversely, miR-142a-5p antagomir, an inhibitor of endogenous miR-142a-5p, could reduce osteoblast differentiation in ST2 and MC3T3-E1 cells. Nuclear factor IA (NFIA), a site-specific transcriptional factor, was demonstrated to be directly targeted by miR-142a-5p. Overexpression of NFIA inhibited miR-142a-5p-mediated osteoblast differentiation in ST2 cells. Furthermore, mechanism explorations revealed that Wnt/β-catenin signaling transcriptionally regulated the expression of miR-142a-5p during osteogenic differentiation. β-catenin binds to the T-cell factor/lymphoid enhancer factor binding motif within the promoter of miR-142 and positively regulates its transcriptional activity. Our findings suggested that miR-142a-5p promoted osteoblast differentiation via targeting NFIA.

MicroRNA-148a-3p alleviates high glucose-induced diabetic retinopathy by targeting TGFB2 and FGF2

AIMS

Diabetic retinopathy (DR), a common complication of type 1 or type 2 diabetes mellitus, has become the leading cause of blindness among adults in working age. The dysregulation of microRNA has been reported to be strongly related to the initiation or progression of DR. However, neither the biological role nor the molecular mechanism of miR-148a-3p has been researched in DR. This study is designed to investigate the function and mechanism of miR-148a-3p in DR.

METHODS

The bioinformatics analysis (Targetscan: https://www.targetscan.org/vert_72/ ) and numerous experiments including real-time quantitative polymerase chain reaction, terminal deoxynucleotidyltransferase dUTP nick end labeling, CCK-8, western blot, vasculogenesis and luciferase reporter assays were used to research the function and mechanism of miR-148a-3p in DR.

RESULTS

We constructed DR cell model by treating human retinal microvascular endothelial cells (HRECs) with different concentration gradients of high glucose (HG). Additionally, HG treatment reduced miR-148a-3p level in HRECs. In function, overexpression of miR-148a-3p caused an increase in cell viability and a decrease in cell apoptosis. Besides, miR-148a-3p overexpression led to a damage on blood-retinal barrier (BRB) and suppressed angiogenesis. In mechanism, miR-148a-3p specifically bound to 3' untranslated region of TGFB2 and FGF2. At least, rescue assays demonstrated that the inhibitive influence of miR-148a-3p mimics on BRB injury was offset by overexpression of TGFB2 and the attenuation of angiogenesis resulting from miR-148a-3p mimics was abrogated by overexpression of FGF2 CONCLUSIONS: In a word, we discovered that miR-148a-3p alleviated HG-induced DR by targeting TGFB2 and FGF2. This novel discovery indicated miR-148a-3p as a potential target for DR diagnosis or treatment.

Long non-coding RNA Gm15441 attenuates hepatic inflammasome activation in response to PPARA agonism and fasting

Exploring the molecular mechanisms that prevent inflammation during caloric restriction may yield promising therapeutic targets. During fasting, activation of the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) promotes the utilization of lipids as an energy source. Herein, we show that ligand activation of PPARα directly upregulates the long non-coding RNA gene Gm15441 through PPARα binding sites within its promoter. Gm15441 expression suppresses its antisense transcript, encoding thioredoxin interacting protein (TXNIP). This, in turn, decreases TXNIP-stimulated NLR family pyrin domain containing 3 (NLRP3) inflammasome activation, caspase-1 (CASP1) cleavage, and proinflammatory interleukin 1β (IL1B) maturation. Gm15441-null mice were developed and shown to be more susceptible to NLRP3 inflammasome activation and to exhibit elevated CASP1 and IL1B cleavage in response to PPARα agonism and fasting. These findings provide evidence for a mechanism by which PPARα attenuates hepatic inflammasome activation in response to metabolic stress through induction of lncRNA Gm15441.

miR-129-5p Inhibits Bone Formation Through TCF4

Osteoporosis is a frequently occurring bone disease in middle-aged and aged men and women. However, current therapies on this disease are still not ideal. MicroRNAs (miRNAs) are a class of endogenous non-protein-coding RNA with a length of 18–25 nucleotides. miRNAs have been identified as important regulators for development, metabolism, carcinogenesis, and bone formation. miR-129-5p has been reported as a regulator of cancer and neuroscience, whereas studies about its function on bone formation is still limited. In this study, we investigated the function and mechanism of miR-129-5p on osteoblast differentiation and bone formation. We have assessed the expression of miRNAs in bone mesenchymal stem cells from aging and menopause osteoporosis C57BL6 mice. The expression of miR-129-5p was altered in all osteoporosis models. Besides, the expression of miR-129-5p was negatively correlated with osteoblastic differentiation markers in the femur tissues of C57BL/6 mice of different ages. We further demonstrated that overexpression of miR-129-5p inhibited osteoblast differentiation in MC3T3-E1 cell line, as well as bone formation of C57BL/6 mice. On the other hand, down-regulation of miR-129-5p enhanced osteoblast differentiation and bone formation. We also found that miR-129-5p inhibited Wnt/β-catenin pathway in osteoblast. The target gene of miR-129-5p has been forecasted and proved as Tcf4. We further found that plasmid containing Tcf4–3′ UTR sequence enhanced osteoblast differentiation, as well as Wnt/β-catenin pathway in MC3T3-E1 cells. To further investigate the rescue effect of miR-129-5p inhibitor, we manufactured bioengineered novel recombinant miR-129-5p inhibitor through Escherichia coli system and then tested its function. The results showed that the novel recombinant miR-129-5p inhibitor promoted osteoblast differentiation and greatly ameliorated menopause osteoporosis in C57BL6 mice. In conclusion, we have discovered miR-129-5p as an inhibitor of bone formation. miR-129-5p inhibited downstream transcription factors of Wnt/β-catenin pathway through targeting Tcf4. Moreover, novel recombinant miR-129-5p inhibitor showed rescue effect on osteoporosis. This study has revealed a new mechanism of osteogenic differentiation and provided novel therapeutic strategies for treatment of skeletal disorders.

CircRNAs and LncRNAs in Osteoporosis

Osteoporosis is a systemic bone disease with bone fragility and increased fracture risk. The non-coding RNAs (ncRNAs) have appeared as important regulators of cellular signaling and pertinent human diseases. Studies have demonstrated that circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs) are involved in the progression of osteoporosis through a variety of pathways, and are considered as targets for the prophylaxis and treatment of osteoporosis. Based on an in-depth understanding of their roles and mechanisms in osteoporosis, we summarize the functions and molecular mechanisms of circRNAs and lncRNAs involved in the progression of osteoporosis and provide some new insights for the prognosis, diagnosis and treatment of osteoporosis.

The regulatory roles of long noncoding RNAs in osteoporosis

Osteoporosis is a common metabolic bone disease characterized by low bone mineral density (BMD) and microarchitectural deterioration of bone tissue, which leads to decreased bone strength and increased fracture risk. Osteoporosis mainly results from a disruption of the balance between bone formation mediated by osteoblasts and bone resorption mediated by osteoclasts. At present, the molecular mechanisms underlying osteoporosis are still not fully understood. Long noncoding RNAs (lncRNAs) are RNA molecules that exceed 200 nucleotides (nt) in length and have limited or no protein-coding capacity. Over the past decade, numerous lncRNAs have been demonstrated to participate in multiple biological processes and to play essential roles in the pathogenesis of various diseases. In this review, we summarize recent progress in research on lncRNAs in osteoporosis and mainly focus on their regulatory roles in osteogenesis and osteoclastogenesis. Moreover, we briefly discuss the potential clinical applications of lncRNAs in osteoporosis.

microRNA-148a-3p in extracellular vesicles derived from bone marrow mesenchymal stem cells suppresses SMURF1 to prevent osteonecrosis of femoral head

Extracellular vesicle (EV)-associated microRNAs (miRNAs) have been found as the important biomarkers participating in the development of osteonecrosis of the femoral head (ONFH). Consequently, this study sought to examine the underlying mechanism of bone marrow mesenchymal stem cell (BMSC)-derived EVs containing miR-148a-3p in ONFH. The ONFH rat models were established. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis were applied to detect miR-148a-3p, Smad ubiquitination regulatory factor 1 (SMURF1), SMAD7 and B-cell CLL/lymphoma 2 (BCL2) expression, followed by determination of relationship between miR-148a-3p and SMURF1. BMSCs were isolated from normal rats and ONFH rats, and EVs were extracted from BMSCs of normal rats. BMSCs from ONFH rats were treated with mimic, inhibitor, small interfering RNA or EVs from miR-148a-3p mimic-treated BMSCs from normal rats (BMSC-EV-miR-148a-3p mimic). Cell Counting Kit-8 and alizarin red staining were utilized to detect cell viability and osteogenic differentiation of BMSCs. ONFH rats were injected with BMSC-EV-miR-148a-3p mimic to explore the function of BMSC-EV-delivered miR-148a-3p in vivo. miR-148a-3p was down-regulated in BMSCs and EVs from ONFH rats following decreased BMSCs viability and osteogenic differentiation. SMURF1 was a target gene of miR-148a-3p, and resulted in ubiquitination and degradation of SMAD7 to decreased BCL2 expression. The proliferation and differentiation of BMSCs were promoted by BMSC-EV-miR-148a-3p mimic or SMURF1 silencing. Additionally, BMSC-EV-miR-148a-3p mimic increased cell proliferation and osteogenic response, diminished SMURF1 expression, and elevated SMAD7 and BCL2 expression in ONFH rats. Collectively, miR-148a-3p overexpressed in BMSC-EVs promoted SMAD7 and BCL2 expression by inhibiting SMURF1, thus alleviating ONFH.

Bone-targeted lncRNA OGRU alleviates unloading-induced bone loss via miR-320-3p/Hoxa10 axis

Unloading-induced bone loss is a threat to human health and can eventually result in osteoporotic fractures. Although the underlying molecular mechanism of unloading-induced bone loss has been broadly elucidated, the pathophysiological role of long noncoding RNAs (lncRNAs) in this process is unknown. Here, we identified a novel lncRNA, OGRU, a 1816-nucleotide transcript with significantly decreased levels in bone specimens from hindlimb-unloaded mice and in MC3T3-E1 cells under clinorotation-unloading conditions. OGRU overexpression promoted osteoblast activity and matrix mineralization under normal loading conditions, and attenuated the suppression of MC3T3-E1 cell differentiation induced by clinorotation unloading. Furthermore, this study found that supplementation of pcDNA3.1(+)–OGRU via (DSS)₆–liposome delivery to the bone-formation surfaces of hindlimb-unloaded (HLU) mice partially alleviated unloading-induced bone loss. Mechanistic investigations demonstrated that OGRU functions as a competing endogenous RNA (ceRNA) to facilitate the protein expression of Hoxa10 by competitively binding miR-320-3p and subsequently promote osteoblast differentiation and bone formation. Taken together, the results of our study provide the first clarification of the role of lncRNA OGRU in unloading-induced bone loss through the miR-320-3p/Hoxa10 axis, suggesting an efficient anabolic strategy for osteoporosis treatment.

Sdccag3 Promotes Implant Osseointegration during Experimental Hyperlipidemia

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

Targeted overexpression of the long noncoding RNA ODSM can regulate osteoblast function in vitro and in vivo

Ameliorating bone loss caused by mechanical unloading is a substantial clinical challenge, and the role of noncoding RNAs in this process has attracted increasing attention. In this study, we found that the long noncoding RNA osteoblast differentiation-related lncRNA under simulated microgravity (lncRNA ODSM) could inhibit osteoblast apoptosis and promote osteoblast mineralization in vitro. The increased expression level of the lncRNA ODSM partially reduced apoptosis and promoted differentiation in MC3T3-E1 cells under microgravity unloading conditions, and the effect was partially dependent on miR-139-3p. LncRNA ODSM supplementation in hindlimb-unloaded mice caused a decrease in the number of apoptotic cells in bone tissue and an increase in osteoblast activity. Furthermore, targeted overexpression of the lncRNA ODSM in osteoblasts partially reversed bone loss induced by mechanical unloading at the microstructural and biomechanical levels. These findings are the first to suggest the potential value of the lncRNA ODSM in osteoporosis therapy and the treatment of pathological osteopenia.

Long Noncoding RNA FAM83H-AS1 Modulates SpA-Inhibited Osteogenic Differentiation in Human Bone Mesenchymal Stem Cells

Osteomyelitis, an infection of the bone and bone marrow, imposes a heavy burden on public health care systems owing to its progressive bone destruction and sequestration. Human bone mesenchymal stem cells (hBMSCs) play a key role in the process of bone formation, and mounting evidence has confirmed that long noncoding RNAs (lncRNAs) are involved in hBMSC osteogenic differentiation. Nevertheless, the exact function and molecular mechanism of lncRNAs in osteogenic differentiation during osteomyelitis development remain to be explored. In this study, hBMSCs were treated with staphylococcal protein A (SpA) during osteogenic differentiation induction to mimic osteomyelitis in vitro The results of lncRNA microarray analysis revealed that FAM83H-AS1 presented the lowest expression among the significantly downregulated lncRNAs. Functionally, ectopic expression of FAM83H-AS1 contributed to osteogenic differentiation of SpA-induced hBMSCs. Additionally, our findings revealed that FAM83H-AS1 negatively regulated microRNA 541-3p (miR-541-3p), and WNT3A was validated as a target gene of miR-541-3p. Mechanically, FAM83H-AS1 elevated WNT3A expression by competitively binding with miR-541-3p. Lastly, it was demonstrated that FAM83H-AS1/miR-541-3p/WNT3A ameliorated SpA-mediated inhibition of the osteogenic differentiation of hBMSCs, which provided a novel therapeutic strategy for patients with osteomyelitis.

Downregulation of lncRNA DANCR promotes osteogenic differentiation of periodontal ligament stem cells

BACKGROUND

Long non-coding RNAs (lncRNAs) have been widely known to have an appreciable effect in physiology and pathology. In tooth regeneration, periodontal ligament stem cells (PDLSCs) are regarded as a key effector, whereas, how lncRNA acts in the osteogenic differentiation of PDLSCs have not been completely understood. This study aims to find out the relationship between lncRNA DANCR and the proliferation and osteogenic differentiation of PDLSCs.

METHODS

Microarray was used to observe the different expression of lncRNAs in differentiated and undifferentiated PDLSCs. And then osteogenic-related lncRNA, DANCR was screened out. Its effects on proliferation and osteogenic differentiation was explored by constructing an overexpression and inhibition model. qRT-PCR was used to detect the mRNA expression of osteogenesis related genes. MTT assay was performed to assess the effects of DANCR on cell growth curve. To quantify the effects of DANCR on osteogenic differentiation of PDLSCs, ALP staining and alizarin red was performed in basic culture medium and osteogenic medium. Data were statistically processed.

RESULTS

Compared with the undifferentiated PDLSCs, the alizarin red staining level was higher in differentiated PDLSCs. And the expressions of osteogenic differentiation marker genes Runt-related transcription factor 2 (Runx2), osteocalcin (OCN) and bone morphogenetic protein (BMP-2) were significantly increased in the differentiated PDLSCs. Furthermore, we noticed that comparing with control groups, the expression of lncRNA DANCR decreases markedly in osteogenically induced PDLSCs. DANCR promoted proliferation of PDLSCs, as evidenced by cell viability. Further investigation has proven that the downregulation of DANCR shows in the calcium sediment forming, alkaline phosphatase (ALP) activation and some osteogenic-related gene markers' upregulation including Runx2, OCN and BMP-2, which finally results in the osteogenic differentiation of PDLSCs following the transfection and induction. Conversely, DANCR upregulation was shown to repress the osteogenic differentiation potential of PDLSCs.

CONCLUSIONS

The osteogenic differentiation of PDLSCs has proven to related to the down regulation of lncRNA DANCR. And this paper throws light on the effects of DANCR in the process of PDLSCs' osteogenic differentiation.

LncRNA DANCR sponges miR-216a to inhibit odontoblast differentiation through upregulating c-Cbl

Enhanced odontoblast differentiation of human dental pulp cells (hDPCs) is considered a keystone in dentin-pulp complex formation. We have revealed lncRNA DANCR was implicated in this differentiation program, however, its mechanism in odontoblast differentiation of hDPCs remains further explored. In this study, by employing loss-of-function approach, we identified downregulation of DANCR drived odontoblast differentiaion of hDPCs. Bioinformatics analysis was utilized to show that DANCR contained binding site for miR-216a and an inverse correlation between DANCR and miR-216a was obtained. Dual luciferase reporter assay and RNA-binding protein immunoprecipitation (RIP) were applied to further confirm that DANCR conferred its functions by directly binding to miR-216a. Notably, miR-216a was able to bind to the 3'-UTR of c-Cbl and repressed its expression. In addition, the protein level of c-CBL was significantly downregulated during hDPCs differentiation, while c-Cbl overexpression inhibited odontoblast differentiation of hDPCs. Moreover, downregulation of miR-216a efficiently reversed the suppression of c-Cbl level and odontoblast differentiation induced by knockdown of DANCR. Taken together, these analyses indicated that DANCR positively regulated the expression of c-Cbl, through sponging miR-216a, and inhibited odontoblast differentiation of hDPCs. Our results will extend the field of clinical application for cell-based therapy in regenerative medicine.

IL-10 induces MC3T3-E1 cells differentiation towards osteoblastic fate in murine model

Interleukin‐10 (IL‐10) displays well‐documented anti‐inflammatory effects, but its effects on osteoblast differentiation have not been investigated. In this study, we found IL‐10 negatively regulates microRNA‐7025‐5p (miR‐7025‐5p), the down‐regulation of which enhances osteoblast differentiation. Furthermore, through luciferase reporter assays, we found evidence that insulin‐like growth factor 1 receptor (IGF1R) is a miR‐7025‐5p target gene that positively regulates osteoblast differentiation. In vivo studies indicated that the pre‐injection of IL‐10 leads to increased bone formation, while agomiR‐7025‐5p injection delays fracture healing. Taken together, these results indicate that IL‐10 induces osteoblast differentiation via regulation of the miR‐7025‐5p/IGF1R axis. IL‐10 therefore represents a promising therapeutic strategy to promote fracture healing.

Long noncoding RNAs: a missing link in osteoporosis

Osteoporosis is a systemic disease that results in loss of bone density and increased fracture risk, particularly in the vertebrae and the hip. This condition and associated morbidity and mortality increase with population ageing. Long noncoding (lnc) RNAs are transcripts longer than 200 nucleotides that are not translated into proteins, but play important regulatory roles in transcriptional and post-transcriptional regulation. Their contribution to disease onset and development is increasingly recognized. Herein, we present an integrative revision on the studies that implicate lncRNAs in osteoporosis and that support their potential use as therapeutic tools. Firstly, current evidence on lncRNAs involvement in cellular and molecular mechanisms linked to osteoporosis and its major complication, fragility fractures, is reviewed. We analyze evidence of their roles in osteogenesis, osteoclastogenesis, and bone fracture healing events from human and animal model studies. Secondly, the potential of lncRNAs alterations at genetic and transcriptomic level are discussed as osteoporosis risk factors and as new circulating biomarkers for diagnosis. Finally, we conclude debating the possibilities, persisting difficulties, and future prospects of using lncRNAs in the treatment of osteoporosis.