Iron accumulation regulates osteoblast apoptosis through lncRNA XIST/miR-758-3p/caspase 3 axis leading to osteoporosis

LncRNA CRNDE ameliorates bone fracture by regulating cell viability and apoptosis of osteoblasts

BACKGROUND

Delayed healing is a common postoperative complication among fractured patients, imposing an additional financial burden. This research examined the clinical relationship between CRNDE and delayed fracture healing (DFH) and the potential regulatory mechanisms underlying fracture improvement.

METHODS

qRT-PCR was utilized to assess the expression of CRNDE and miR-29a-3p in serum and cellular samples, and to evaluate the expression of genes associated with osteogenic differentiation. The diagnostic and predictive significance of serum CRNDE was analyzed using ROC analysis and logistic regression. Additionally, an hFOB 1.19 osteogenic differentiation model was established. The CCK-8 assay and flow cytometry techniques were used to investigate the effects of silencing CRNDE, as well as the concurrent inhibition of both CRNDE and miR-29a-3p, on the proliferation and apoptosis of hFOB 1.19 cells.

RESULTS

CRNDE was down-regulated, while miR-29a-3p was up-regulated in DFH patients. The serum CRNDE could effectively identify DFH patients and predict the DFH occurrence. In the hFOB 1.19 osteogenic differentiation model, silencing CRNDE led to a significant decrease in the expression of osteogenic differentiation markers, a reduction in the proliferation activity of hFOB 1.19 cells, and an increase in apoptosis. There was a negative regulatory interaction between CRNDE and miR-29a-3p. Concurrently inhibiting the expression of both CRNDE and miR-29a-3p could effectively restore the functional activity of hFOB 1.19 cells.

CONCLUSION

Serum CRNDE holds potential as a biomarker for the diagnosis and prediction of DFH. The sponging effect of CRNDE on miR-29a-3p could ameliorate fracture healing.

Three signalling pathways for iron overload in osteoporosis: a narrative review

Osteoporosis is a metabolic bone disease characterized by a decrease in the amount of bone tissue per unit volume and changes in bone microstructure, often resulting in bone fragility and increased susceptibility to fracture. Iron plays an important role in the normal physiological activities of human body, and its abnormal metabolism is one of the risk factors of osteoporosis. Iron overload, as an abnormality of iron metabolism, has been reported to be associated with osteoporosis in recent years. However, the mechanism of iron overload involved in the process of osteoporosis is not fully understood. In this review, we summarize what we have learned about iron overload-associated bone loss from clinical studies and animal models. Starting from the three signaling pathways of Wnt/β-catenin, BMP/SMADs, PI3K/AKT/mTOR, the mechanism of iron overload affecting the process of osteoporosis was explored, we got the conclusion that iron overload accelerates the process of osteoporosis by inhibiting normal wnt signaling, suppressing the BMP-2/SMADs pathway, down-regulating the PI3K/AKT/mTOR pathway to inhibit bone formation, and destroying the bone strength and load-bearing capacity, which providing a new direction for clinical treatment.

Programmed Cell Death in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, progressive, systemic autoimmune disease characterised by synovial inflammation, synovial pannus formation and subsequent destruction of articular cartilage and bone. Programmed cell death (PCD), encompassing apoptosis, autophagy, pyroptosis, necroptosis, and ferroptosis, plays a pivotal role in the pathogenesis of RA. An imbalance in PCD causes a variety of immune cells to release large amounts of inflammatory factors and mediators that exacerbate not only chronic synovial inflammation, but also bone and joint damage. The purpose of this article is to review the relevant studies between PCD and RA, with the aim of providing further insights and considerations for a deeper understanding of the pathogenesis of RA and to guide clinical management.

Exploring the Mechanisms of Sanguinarine in the Treatment of Osteoporosis by Integrating Network Pharmacology Analysis and Deep Learning Technology

BACKGROUND

Sanguinarine (SAN) has been reported to have antioxidant, antiinflammatory, and antimicrobial activities with potential for the treatment of osteoporosis (OP).

OBJECTIVE

This work purposed to unravel the molecular mechanisms of SAN in the treatment of OP.

METHODS

OP-related genes and SAN-related targets were predicted from public databases. Differential expression analysis and VennDiagram were adopted to detect SAN-related targets against OP. Protein-protein interaction (PPI) network was served for core target identification. Molecular docking and DeepPurpose algorithm were further adopted to investigate the binding ability between core targets and SAN. Gene pathway scoring of these targets was calculated utilizing gene set variation analysis (GSVA). Finally, we explored the effect of SAN on the expressions of core targets in preosteoblastic MC3T3-E1 cells.

RESULTS

A total of 21 candidate targets of SAN against OP were acquired. Furthermore, six core targets were identified, among which CASP3, CTNNB1, and ERBB2 were remarkably differentially expressed in OP and healthy individuals. The binding energies of SAN with CASP3, CTNNB1, and ERBB2 were -6, -6.731, and -7.162 kcal/mol, respectively. Moreover, the GSVA scores of the Wnt/calcium signaling pathway were significantly lower in OP cases than in healthy individuals. In addition, the expression of CASP3 was positively associated with Wnt/calcium signaling pathway. CASP3 and ERBB2 were significantly lower expressed in SAN group than in DMSO group, whereas the expression of CTNNB1 was in contrast.

CONCLUSION

CASP3, CTNNB1, and ERBB2 emerge as potential targets of SAN in OP prevention and treatment.

Inhibition of SLC40A1 represses osteoblast formation via inducing iron accumulation and activating the PERK/ATF4/CHOP pathway mediated oxidative stress

OBJECTIVE

This study aimed to investigate the effects of solute carrier family 40 member 1 (SLC40A1) on iron accumulation, oxidative stress and differentiation in osteoblasts and potential mechanisms.

METHODS

Mouse preosteoblastic MC3T3-E1 cells were transfected with the SLC40A1 overexpression vector (oeSLC40A1) and siRNA (siSLC40A1), then cell differentiation was induced via ascorbic acid and β-glycerophosphate. Besides, Ferrostatin-1 (ferroptosis inhibitor) and GSK2606414 (PERK inhibitor) were added with siSLC40A1.

RESULTS

Fe2+, malondialdehyde (MDA), and reactive oxygen species (ROS) were higher but reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio was lower after siSLC40A1 transfection, while reduced Fe2+ and ROS but elevated GSH/GSSG ratio was observed after oeSLC40A1 transfection. Alkaline phosphatase (ALP) staining, Alizarin Red S (ARS) staining, osteopontin (OPN) and bone morphogenetic protein 2 (BMP2) were lower after siSLC40A1 transfection but were greater after oeSLC40A1 transfection. Furthermore, SLC40A1 negatively regulated the PERK/ATF4/CHOP pathway. Further exploration revealed that Fe2+, MDA, ROS, and the PERK/ATF4/CHOP pathway were attenuated, while GSH/GSSG ratio, ALP staining, ARS staining, and OPN expression were increased after ferrostatin-1 treatment in the siSLC40A1-transfected cells. Similar trends were observed with respect to GSK2606414 treatment with siSLC40A1.

CONCLUSION

SLC40A1 inhibition suppresses osteoblast formation by facilitating iron accumulation and activating the PERK/ATF4/CHOP pathway-mediated oxidative stress.

Repair and regeneration: ferroptosis in the process of remodeling and fibrosis in impaired organs

As common clinical-pathological processes, wound healing and tissue remodelling following injury or stimulation are essential topics in medical research. Promoting the effective healing of prolonged wounds, improving tissue repair and regeneration, and preventing fibrosis are important and challenging issues in clinical practice. Ferroptosis, which is characterized by iron overload and lipid peroxidation, is a nontraditional form of regulated cell death. Emerging evidence indicates that dysregulated metabolic pathways and impaired iron homeostasis play important roles in various healing and regeneration processes via ferroptosis. Thus, we review the intrinsic mechanisms of tissue repair and remodeling via ferroptosis in different organs and systems under various conditions, including the inflammatory response in skin wounds, remodeling of joints and cartilage, and fibrosis in multiple organs. Additionally, we summarize the common underlying mechanisms, key molecules, and targeted drugs for ferroptosis in repair and regeneration. Finally, we discuss the potential of therapeutic agents, small molecules, and novel materials emerging for targeting ferroptosis to promote wound healing and tissue repair and attenuate fibrosis.

Ferroptosis: Regulatory mechanisms and potential targets for bone metabolism: A review

Bone homeostasis is a homeostasis process constructed by osteoblast bone formation and osteoclast bone resorption. Bone homeostasis imbalance and dysfunction are the basis for the development of various orthopedic diseases such as osteoporosis, osteoarthritis, and steroid-induced avascular necrosis of femoral head. Previous studies have demonstrated that ferroptosis can induce lipid peroxidation through the generation of reactive oxygen species, activate a number of signaling pathways, and participate in the regulation of osteoblast bone formation and osteoclast bone resorption, resulting in bone homeostasis imbalance, which is an important factor in the pathogenesis of many orthopedic diseases, but the mechanism of ferroptosis is still unknown. In recent years, it has been found that, in addition to iron metabolism and intracellular antioxidant system imbalance, organelle dysfunction is also a key factor affecting ferroptosis. This paper takes this as the starting point, reviews the latest literature reports at home and abroad, elaborates the pathogenesis and regulatory pathways of ferroptosis and the relationship between ferroptosis and various organelles, and summarizes the mechanism by which ferroptosis mediates bone homeostasis imbalance, with the aim of providing new directions for the research related to ferroptosis and new ideas for the prevention and treatment of bone and joint diseases.

Knockdown of LncRNA Lcn2-204 alleviates sepsis-induced myocardial injury by regulation of iron overload and ferroptosis

Ferroptosis is an iron-dependent programmed cell death form resulting from lipid peroxidation damage, it plays a key role in organ damage and tumor development from various causes. Sepsis leads to severe host response after infection with high mortality. The long non-coding RNAs (LncRNAs) are involved in different pathophysiological mechanisms of multiple diseases. Here, we used cecal ligation and puncture (CLP) operation to mimic sepsis induced myocardial injury (SIMI) in mouse model, and LncRNAs and mRNAs were profiled by Arraystar mouse LncRNA Array V3.0. Based on the microarray results, 552 LncRNAs and 520 mRNAs were differentially expressed in the sham and CLP groups, among them, LncRNA Lcn2-204 was the highest differentially expressed up-regulated LncRNA. Iron metabolism disorder was involved in SIMI by bioinformatics analysis, meanwhile, myocardial iron content and lipocalin-2 (Lcn2) protein expressions were increased. The CNC network comprised 137 positive interactions and 138 negative interactions. Bioinformatics analysis showed several iron-related terms were enriched and six genes (Scara5, Tfrc, Lcn2, Cp, Clic5, Ank1) were closely associated with iron metabolism. Then, we constructed knockdown LncRNA Lcn2-204 targeting myocardium and found that it ameliorated cardiac injury in mouse sepsis model through modulating iron overload and ferroptosis. In addition, we found that LncRNA Lcn2-204 was involved in the regulation of Lcn2 expression in septic myocardial injury. Based on these findings, we conclude that iron overload and ferroptosis are the key mechanisms leading to myocardial injury in sepsis, knockdown of LncRNA Lcn2-204 plays the cardioprotective effect through inhibition of iron overload, ferroptosis and Lcn2 expression. It may provide a novel therapeutic approach to ameliorate sepsis-induced myocardial injury.

Noncoding RNAs: the crucial role of programmed cell death in osteoporosis

Osteoporosis is the most common skeletal disease characterized by an imbalance between bone resorption and bone remodeling. Osteoporosis can lead to bone loss and bone microstructural deterioration. This increases the risk of bone fragility and fracture, severely reducing patients' mobility and quality of life. However, the specific molecular mechanisms involved in the development of osteoporosis remain unclear. Increasing evidence suggests that multiple noncoding RNAs show differential expression in the osteoporosis state. Meanwhile, noncoding RNAs have been associated with an increased risk of osteoporosis and fracture. Noncoding RNAs are an important class of factors at the level of gene regulation and are mainly involved in cell proliferation, cell differentiation, and cell death. Programmed cell death is a genetically-regulated form of cell death involved in regulating the homeostasis of the internal environment. Noncoding RNA plays an important role in the programmed cell death process. The exploration of the noncoding RNA-programmed cell death axis has become an interesting area of research and has been shown to play a role in many diseases such as osteoporosis. In this review, we summarize the latest findings on the mechanism of noncoding RNA-mediated programmed cell death on bone homeostasis imbalance leading to osteoporosis. And we provide a deeper understanding of the role played by the noncoding RNA-programmed cell death axis at the gene regulatory level of osteoporosis. We hope to provide a unique opportunity to develop novel diagnostic and therapeutic approaches for osteoporosis.

Osteomyelitis and non-coding RNAS: A new dimension in disease understanding

Osteomyelitis, a debilitating bone infection, presents considerable clinical challenges due to its intricate etiology and limited treatment options. Despite strides in surgical and chemotherapeutic interventions, the treatment landscape for osteomyelitis remains unsatisfactory. Recent attention has focused on the role of non-coding RNAs (ncRNAs) in the pathogenesis and progression of osteomyelitis. This review consolidates current knowledge on the involvement of distinct classes of ncRNAs, including microRNAs, long ncRNAs, and circular RNAs, in the context of osteomyelitis. Emerging evidence from various studies underscores the potential of ncRNAs in orchestrating gene expression and influencing the differentiation of osteoblasts and osteoclasts, pivotal processes in bone formation. The review initiates by elucidating the regulatory functions of ncRNAs in fundamental cellular processes such as inflammation, immune response, and bone remodeling, pivotal in osteomyelitis pathology. It delves into the intricate network of interactions between ncRNAs and their target genes, illuminating how dysregulation contributes to the establishment and persistence of osteomyelitic infections. Understanding their regulatory roles may pave the way for targeted diagnostic tools and innovative therapeutic interventions, promising a paradigm shift in the clinical approach to this challenging condition. Additionally, we delve into the promising therapeutic applications of these molecules, envisioning novel diagnostic and treatment approaches to enhance the management of this challenging bone infection.

Iron accumulation induced by hepcidin1 knockout accelerates the progression of aging osteoporosis

OBJECTIVE

Iron accumulation is associated with osteoporosis. This study aims to explore the effect of chronic iron accumulation induced by hepcidin1 deficiency on aging osteoporosis.

METHODS

Iron accumulation in hepcidin1 knockout aging mice was assessed by atomic absorption spectroscopy and Perl's staining. Bone microarchitecture was observed using Micro-CT. Hepcidin, ferritin, oxidative stress, and markers of bone turnover in serum were detected by enzyme-linked immunosorbent assay. Bone formation and resorption markers were measured by real-time quantitative PCR. Cell aging was induced by D-galactose treatment. CCK-8, flow cytometry, EdU assays, and Alizarin red staining were performed to reveal the role of hepcidin1 knockout in cell model. Iron Colorimetric Assay Kit and western blot were applied to detect iron and ferritin levels in cells, respectively.

RESULTS

In hepcidin1-knockout mice, the ferritin and iron contents in liver and tibia were significantly increased. Iron accumulation induced by hepcidin1 knockout caused a phenotype of low bone mass and deteriorated bone microarchitecture. Osteogenic marker was decreased and osteoclast marker was increased in mice, accompanied by increased oxidative stress level. The mRNA expression levels of osteoclast differentiation markers (RANKL, Mmp9, OPG, Trap, and CTSK) were up-regulated, while bone formation markers (OCN, ALP, Runx2, SP7, and Col-1) were down-regulated in model group, compared to wild type mice. In vitro, hepcidin1 knockdown inhibited proliferation and osteogenic differentiation, while promoted apoptosis, with increased levels of iron and ferritin.

CONCLUSION

Iron accumulation induced by hepcidin1 deficiency aggravates the progression of aging osteoporosis via inhibiting osteogenesis and promoting osteoclast genesis.

Mechanism of Liuwei Dihuang Pills in treating osteoporosis based on network pharmacology

Osteoporosis is a prevalent age-related disease that poses a significant public health concern as the population continues to age. While current treatments have shown some therapeutic benefits, their long-term clinical efficacy is limited by a lack of stable curative effects and significant adverse effects. Traditional Chinese Medicine has gained attention due to its positive curative effects and fewer side effects. Liuwei Dihuang Pill has been found to enhance bone mineral density in patients with osteoporosis and rats, but the underlying mechanism is not yet clear. To shed more light on this problem, this study aims to explore the pharmacological mechanism of Liuwei Dihuang Pill in treating osteoporosis using network pharmacology and molecular docking. The findings indicate that Liuwei Dihuang Pills treat osteoporosis through various targets and channels. Specifically, it mainly involves TNF, IL17, and HIF-1 signaling pathways and helps regulate biological processes such as angiogenesis, apoptosis, hypoxia, and gene expression. Furthermore, molecular docking demonstrates excellent binding properties between the drug components and key targets. Therefore, this study offers a theoretical foundation for understanding the pharmacological mechanism and clinical application of Liuwei Dihuang Pills in treating osteoporosis more comprehensively.

Functional micro-RNA drugs acting as a fate manipulator in the regulation of osteoblastic death

Bone loss is prevalent in clinical pathological phenomena such as osteoporosis, which is characterized by decreased osteoblast function and number, increased osteoclast activity, and imbalanced bone homeostasis. However, current treatment strategies for bone diseases are limited. Regulated cell death (RCD) is a programmed cell death pattern activated by the expression of specific genes in response to environmental changes. Various studies have shown that RCD is closely associated with bone diseases, and manipulating the death fate of osteoblasts could contribute to effective bone treatment. Recently, microRNA-targeting therapy drugs have emerged as a potential solution because of their precise targeting, powerful curative effect, and limited side effects. Nevertheless, their clinical application is limited by their inherent instability, easy enzymatic degradation, and poor membrane penetrability. To address this challenge, a self-assembling tetrahedral DNA nanostructure (TDN)-based microRNA (Tmi) delivery system has been proposed. TDN features excellent biocompatibility, cell membrane penetrability, serum stability, and modification versatility, making it an ideal nucleic acid carrier for miRNA protection and intracellular transport. Once inside cells, Tmi can dissociate and release miRNAs to manipulate key molecules in the RCD signaling pathway, thereby regulating bone homeostasis and curing diseases caused by abnormal RCD activation. In this paper, we discuss the impact of the miRNA network on the initiation and termination of four critical RCD programs in bone tissues: apoptosis, autophagy, pyroptosis, and ferroptosis. Furthermore, we present the Tmi delivery system as a miRNA drug vector. This provides insight into the clinical translation of miRNA nucleic acid drugs and the application of miRNA drugs in bone diseases.

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.

Inhibition of ferroptosis through regulating neuronal calcium homeostasis: An emerging therapeutic target for Alzheimer's disease

Alzheimer's disease (AD), a chronic and progressive neurodegenerative disease, generates a serious threat to the health of the elderly. The AD brain is microscopically characterized by amyloid plaques and neurofibrillary tangles. There are still no effective therapeutic drugs to restrain the progression of AD though much attention has been paid to exploit AD treatments. Ferroptosis, a type of programmed cell death, has been reported to promote the pathological occurrence and development of AD, and inhibition of neuronal ferroptosis can effectively improve the cognitive impairment of AD. Studies have shown that calcium (Ca²⁺) dyshomeostasis is closely related to the pathology of AD, and can drive the occurrence of ferroptosis through several pathways, such as interacting with iron, and regulating the crosstalk between endoplasmic reticulum (ER) and mitochondria. This paper mainly reviews the roles of ferroptosis and Ca²⁺ in the pathology of AD, and highlights that restraining ferroptosis through maintaining the homeostasis of Ca²⁺ may be an innovative target for the treatment of AD.

Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs

Osteoporosis is characterized by the alteration of bone homeostasis due to an imbalance between osteoclastic bone resorption and osteoblastic bone formation. Estrogen deficiency causes bone loss and postmenopausal osteoporosis, the pathogenesis of which also involves oxidative stress, inflammatory processes, and the dysregulation of the expression of microRNAs (miRNAs) that control gene expression at post-transcriptional levels. Oxidative stress, due to an increase in reactive oxygen species (ROS), proinflammatory mediators and altered levels of miRNAs enhance osteoclastogenesis and reduce osteoblastogenesis through mechanisms involving the activation of MAPK and transcription factors. The present review summarizes the principal molecular mechanisms involved in the role of ROS and proinflammatory cytokines on osteoporosis. Moreover, it highlights the interplay among altered miRNA levels, oxidative stress, and an inflammatory state. In fact, ROS, by activating the transcriptional factors, can affect miRNA expression, and miRNAs can regulate ROS production and inflammatory processes. Therefore, the present review should help in identifying targets for the development of new therapeutic approaches to osteoporotic treatment and improve the quality of life of patients.

Quercetin protects against iron overload-induced osteoporosis through activating the Nrf2/HO-1 pathway

AIMS

Eucommia is the tree bark of Eucommia japonica, family Eucommiaceae. In traditional Chinese medicine, Eucommia is often used to treat osteoporosis. Quercetin (QUE), a major flavonoid extract of Eucommia japonica, has been reported to have anti-osteoporosis effects. However, there are no studies reporting the mechanism of QUE in the treatment of iron overload-induced osteoporosis. This study set out to investigate the therapeutic effects of QUE against iron overload-induced bone loss and its potential molecular mechanisms.

MATERIALS AND METHODS

In vitro, MC3T3-E1 cells were used to study the effects of QUE on osteogenic differentiation, anti-apoptosis and anti-oxidative stress damage in an iron overload environment (FAC 200 μM). In vivo, we constructed an iron overload mouse model by injecting iron dextrose intraperitoneally and assessed the osteoprotective effects of QUE by Micro-CT and histological analysis.

KEY FINDINGS

In vitro, we found that QUE increased the ALP activity of MC3T3-E1 cells in iron overload environment, promoted the formation of bone mineralized nodules and upregulated the expression of Runx2 and Osterix. In addition, QUE was able to reduce FAC-induced apoptosis and ROS production, down-regulated the expression of Caspase3 and Bax, and up-regulated the expression of Bcl-2. In further studies, we found that QUE activated the Nrf2/HO-1 signaling pathway and attenuated FAC-induced oxidative stress damage. The results of the in vivo study showed that QUE was able to reduce iron deposition induced by iron dextrose and attenuate bone loss.

SIGNIFICANCE

Our results suggested that QUE protects against iron overload-induced osteoporosis by activating the Nrf2/HO-1 signaling pathway.

Iron overload-induced ferroptosis of osteoblasts inhibits osteogenesis and promotes osteoporosis: An in vitro and in vivo study

Growing evidence indicates that iron overload is an independent risk factor for osteoporosis. However, the mechanisms are not fully understood. The purpose of our study was to determine whether iron overload could lead to ferroptosis in osteoblasts and to explore whether ferroptosis of osteoblasts is involved in iron overload-induced osteoporosis in vitro and in vivo. Ferric ammonium citrate was used to mimic iron overload conditions, while deferoxamine and ferrostatin-1 were used to inhibit ferroptosis of MC3T3-E1 cells in vitro. The ferroptosis, osteogenic differentiation and mineralization of MC3T3-E1 cells were assessed in vitro. A mouse iron overload model was established using iron dextran. Immunohistochemical analysis was performed to determine ferroptosis of osteoblasts in vivo. Enzyme-linked immunosorbent assays and calcein-alizarin red S labelling were used to assess new bone formation. Dual x-ray absorptiometry, micro-computed tomography and histopathological analysis were conducted to evaluate osteoporosis. The results showed that iron overload reduced cell viability, superoxide dismutase and glutathione levels, increased reactive oxygen species generation, lipid peroxidation, malondialdehyde levels and ferroptosis-related protein expression, and induced ultrastructural changes in mitochondria. Iron overload could also inhibit osteogenic differentiation and mineralization in vitro. Inhibiting ferroptosis reversed the changes described above. Iron overload inhibited osteogenesis, promoted the ferroptosis of osteoblasts and induced osteoporosis in vivo, which could also be improved by deferoxamine and ferrostatin-1. These results demonstrate that ferroptosis of osteoblasts plays a crucial role in iron overload-induced osteoporosis. Maintaining iron homeostasis and targeting ferroptosis of osteoblasts might be potential measures of treating or preventing iron overload-induced osteoporosis.

Comprehensive analysis of lncRNA expression profiles in postmenopausal osteoporosis

To explore the key lncRNAs affecting postmenopausal osteoporosis (PMOP) progression, the transcriptome sequencing of peripheral blood mononuclear cells from fifteen early postmenopausal women, according to bone mineral density, were divided into groups of osteoporosis, osteopenia and normality, in each of which the expression profiles of lncRNAs was investigated. From the results we observed nine candidates of lncRNAs, which were to be compared with miRBase, and found that MIR22HG as one candidate of lncRNA was most likely to be directly used as miRNA precursor. Based on the KEGG annotation and lncRNA-miRNA-mRNA-KEGG network, we analyzed the potential role of candidate lncRNAs. The results showed that the expression profiles of lncRNAs could help identify the novel ones involved in the progression of PMOP, and that MIR22HG could serve as a miRNA precursor to regulate FoxO signaling pathway in bone metabolism. Our findings can be of great help in predicting and diagnosing early PMOP.

Screening of crosstalk and pyroptosis-related genes linking periodontitis and osteoporosis based on bioinformatics and machine learning

Background and objective

This study aimed to identify crosstalk genes between periodontitis (PD) and osteoporosis (OP) and potential relationships between crosstalk and pyroptosis-related genes.

Methods

PD and OP datasets were downloaded from the GEO database and were performed differential expression analysis to obtain DEGs. Overlapping DEGs got crosstalk genes linking PD and OP. Pyroptosis-related genes were obtained from literature reviews. Pearson coefficients were used to calculate crosstalk and pyroptosis-related gene correlations in the PD and OP datasets. Paired genes were obtained from the intersection of correlated genes in PD and OP. PINA and STRING databases were used to conduct the crosstalk-bridge-pyroptosis genes PPI network. The clusters in which crosstalk and pyroptosis-related genes were mainly concentrated were defined as key clusters. The key clusters' hub genes and the included paired genes were identified as key crosstalk-pyroptosis genes. Using ROC curve analysis and XGBoost screened key genes. PPI subnetwork, gene-biological process and gene-pathway networks were constructed based on key genes. In addition, immune infiltration was analyzed on the PD dataset using the CIBERSORT algorithm.

Results

A total of 69 crosstalk genes were obtained. 13 paired genes and hub genes TNF and EGFR in the key clusters (cluster2, cluster8) were identified as key crosstalk-pyroptosis genes. ROC and XGBoost showed that PRKCB, GSDMD, ARMCX3, and CASP3 were more accurate in predicting disease than other key crosstalk-pyroptosis genes while better classifying properties as a whole. KEGG analysis showed that PRKCB, GSDMD, ARMCX3, and CASP3 were involved in neutrophil extracellular trap formation and MAPK signaling pathway pathways. Immune infiltration results showed that all four key genes positively correlated with plasma cells and negatively correlated with T cells follicular helper, macrophages M2, and DCs.

Conclusion

This study shows a joint mechanism between PD and OP through crosstalk and pyroptosis-related genes. The key genes PRKCB, GSDMD, ARMCX3, and CASP3 are involved in the neutrophil extracellular trap formation and MAPK signaling pathway, affecting both diseases. These findings may point the way to future research.

Three Classes of Antioxidant Defense Systems and the Development of Postmenopausal Osteoporosis

Osteoporosis is a common bone imbalance disease that threatens the health of postmenopausal women. Estrogen deficiency accelerates the aging of women. Oxidative stress damage is regarded as the main pathogenesis of postmenopausal osteoporosis. The accumulation of reactive oxygen species in the bone microenvironment plays a role in osteoblast and osteoclast apoptosis. Improving the oxidative state is essential for the prevention and treatment of postmenopausal osteoporosis. There are three classes of antioxidant defense systems in the body to eliminate free radicals and peroxides including antioxidant substances, antioxidant enzymes, and repair enzymes. In our review, we demonstrated the mechanism of antioxidants and their effect on bone metabolism in detail. We concluded that glutathione/oxidized glutathione (GSH/GSSG) conversion involved the PI3K/Akt-Nrf2/HO-1 signaling pathway and that the antioxidant enzyme-mediated mitochondrial apoptosis pathway of osteoblasts was necessary for the development of postmenopausal osteoporosis. Since the current therapeutic effects of targeting bone cells are not significant, improving the systemic peroxidation state and then regulating bone homeostasis will be a new method for the treatment of postmenopausal osteoporosis.

Long noncoding RNA XIST modulates microRNA-135/CREB1 axis to influence osteogenic differentiation of osteoblast-like cells in mice with tibial fracture healing

Fracture healing is a complex event with the involvement of many cell systems, cytokines, as well as mRNAs. Herein, we report the interactions among long noncoding RNA X-inactive specific transcript (XIST)/microRNA-135 (miR-135)/cAMP response element-binding protein 1 (CREB1) axis during fracture healing. We observed increased expression of XIST in patients with long-term unhealed fracture by microarray analysis. Subsequently, a mouse model with tibial fracture and a cell model using osteoblast-like MC3T3-E1 cells were generated. The XIST overexpression during fracture healing decreased proliferation and differentiation of MC3T3-E1 cells, while silencing of XIST facilitated MC3T3-E1 cell growth. Furthermore, miR-135 targeted CREB1 and negatively regulated its expression. XIST acted as a sponge for miR-135, thereby upregulating CREB1 and promoting the activity of the TNF-α/RANKL pathway. Transfection of miR-135 inhibitor or CREB1 overexpression blocked the stimulating effects of XIST knockdown on MC3T3-E1 cell growth. Besides, specific inhibitors of the TNF-α/RANKL pathway reversed the repressive role of XIST in cell osteogenic differentiation. All in all, these findings suggest that XIST knockdown induces the differentiation of osteoblast-like cells via regulation of the miR-135/CREB1/TNF-α/RANKL axis. XIST, as a consequence, represents an attractive therapeutic strategy to accelerate fracture healing.

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.

Effects of miRNAs, lncRNAs and circRNAs on osteoporosis as regulatory factors of bone homeostasis (Review)

Osteoporosis is a common metabolic bone disorder typically characterized by decreased bone mass and an increased risk of fracture. At present, the detailed molecular mechanism underlying the development of osteoporosis remains to be elucidated. Accumulating evidence shows that non-coding (nc)RNAs, such as microRNAs (miRNAs), long ncRNAs (lncRNAs) and circular RNAs (circRNAs), play significant roles in osteoporosis through the post-transcriptional regulation of gene expression as regulatory factors. Previous studies have demonstrated that ncRNAs participate in maintaining bone homeostasis by regulating physiological and developmental processes in osteoblasts, osteoclasts and bone marrow stromal cells. In the present review, the latest research investigating the involvement of miRNAs, lncRNAs and circRNAs in regulating the differentiation, proliferation, apoptosis and autophagy of cells that maintain the bone microenvironment in osteoporosis is summarized. Deeper insight into the aspects of osteoporosis pathogenesis involving the deregulation of ncRNAs could facilitate the development of therapeutic approaches for osteoporosis.

Long non-coding RNA XIST promotes osteoporosis by inhibiting the differentiation of bone marrow mesenchymal stem cell by sponging miR-29b-3p that suppresses nicotinamide N-methyltransferase

Bone formation is important in the development of osteoporosis (OP). X–inactive specific transcript (XIST), a lncRNA, is involved in this process; however, mode of its action is not known. We compared the serum levels of XIST and miR-29b-3p among the patients with and without OP. In rat bone marrow mesenchymal stem cells (BMSCs), during osteogenic differentiation, XIST expression was detected first, followed by overexpression or suppression of miR-29b-3p and NNMT. Expression of osteogenic genes, ALP (electrochemical alkaline phosphatase) and RUNX2 (Runt-related transcription factor 2) were detected by RT-qPCR and western blots, and the calcium nodules in BMSCs were detected by staining. The relationships of XIST, miR-29b-3p, and NNMT were characterized by dual-luciferase reporter assay. Serum XIST was significantly upregulated in patients of OP. XIST downregulated the ALP and Runx2 levels and inhibited calcium nodules, whereas low expression of XIST reversed these events. MiR-29b-3p was inhibited by XIST sponge and lowered the levels of ALP, Runx2, and calcium nodules. NNMT was negatively regulated by miR-29b-3p, promoting the osteogenic differentiation of BMSCs. In conclusion, XIST is highly expressed in OP, and regulates NNMT by sponging miR-29b-3p to suppress the osteogenic differentiation of BMSCs.