Estrogen regulates stemness and senescence of bone marrow stromal cells to prevent osteoporosis via ERβ-SATB2 pathway

Liuwei Dihuang pills attenuate ovariectomy-induced bone loss by alleviating bone marrow mesenchymal stem cell (BMSC) senescence via the Yes-associated protein (YAP)-autophagy axis

CONTEXT

Liuwei Dihuang pill (LWDH) has been used to treat postmenopausal osteoporosis (PMOP).

OBJECTIVE

To explore the effects and mechanisms of action of LWDH in PMOP.

MATERIALS AND METHODS

Forty-eight female Sprague-Dawley rats were divided into four groups: sham-operated (SHAM), ovariectomized (OVX), LWDH high dose (LWDH-H, 1.6 g/kg/d) and LWDH low dose (LWDH-L, 0.8 g/kg/d); the doses were administered after ovariectomy via gavage for eight weeks. After eight weeks, the bone microarchitecture was evaluated. The effect of LWDH on the differentiation of bone marrow mesenchymal stem cells (BMSCs) was assessed via osteogenesis- and lipogenesis-induced BMSC differentiation. The senescence-related biological indices were also detected using senescence staining, cell cycle analysis, quantitative real-time polymerase chain reaction and western blotting. Finally, the expression levels of autophagy-related proteins and Yes-associated protein (YAP) were evaluated.

RESULTS

LWDH-L and LWDH-H significantly modified OVX-induced bone loss. LWDH promoted osteogenesis and inhibited adipogenesis in OVX-BMSCs. Additionally, LWDH decreased the positive ratio of senescence OVX-BMSCs and improved cell viability, cell cycle, and the mRNA and protein levels of p53 and p21. LWDH upregulated the expression of autophagy-related proteins, LC3, Beclin1 and YAP, in OVX-BMSCs and downregulated the expression of p62.

DISCUSSION AND CONCLUSIONS

LWDH improves osteoporosis by delaying the BMSC senescence through the YAP-autophagy axis.

Jaw osteoporosis: Challenges to oral health and emerging perspectives of treatment

Osteoporosis is a prevalent bone metabolic disease that poses a significant challenge to global human health. Jaw osteoporosis, characterized by microstructural damage of the jaw resulting from various factors, is one of the common manifestations of this condition. Recent studies have demonstrated that jaw osteoporosis has multifaceted effects on oral health and can negatively impact conditions such as periodontitis, oral implantation, orthodontic treatment, and wound healing. However, there are still some limitations in the conventional treatment of osteoporosis. For instance, while bisphosphonates can enhance bone quality, they may also lead to osteonecrosis of the jaw, which poses a potential safety hazard in oral diagnosis and treatment. In recent years, considerable attention has been focused on improving the pathological condition of jaw osteoporosis. Treatment strategies such as gut microbial regulation, extracellular vesicles, molecular targeted therapy, herbal medicine, mechanical stimulation are expected to enhance efficacy and minimize adverse reactions. Therefore, understanding these effects and exploring novel treatments for jaw osteoporosis may provide new insights for oral health maintenance and disease treatment. This article reviews the impact of jaw osteoporosis on oral health and describes the limitations associated with current methods. It also discusses emerging perspectives on treatment, offering a comprehensive overview of the challenges and future directions in managing jaw osteoporosis.

Epigenetic regulations of cellular senescence in osteoporosis

Osteoporosis (OP) is a prevalent age-related disease that is characterized by a decrease in bone mineral density (BMD) and systemic bone microarchitectural disorders. With age, senescent cells accumulate and exhibit the senescence-associated secretory phenotype (SASP) in bone tissue, leading to the imbalance of bone homeostasis, osteopenia, changes in trabecular bone structure, and increased bone fragility. Cellular senescence in the bone microenvironment involves osteoblasts, osteoclasts, and bone marrow mesenchymal stem cells (BMSCs), whose effects on bone homeostasis are regulated by epigenetics. Therefore, the epigenetic regulatory mechanisms of cellular senescence have received considerable attention as potential targets for preventing and treating osteoporosis. In this paper, we systematically review the mechanisms of aging-associated epigenetic regulation in osteoporosis, emphasizing the impact of epigenetics on cellular senescence, and summarize three current methods of targeting cellular senescence, which is helpful better to understand the pathogenic mechanisms of cellular senescence in osteoporosis and provides strategies for the development of epigenetic drugs for the treatment of osteoporosis.

Unraveling Key m6A Modification Regulators Signatures in Postmenopausal Osteoporosis through Bioinformatics and Experimental Verification

OBJECTIVE

Bone marrow mesenchymal stem cells (BMSCs) show significant potential for osteogenic differentiation. However, the underlying mechanisms of osteogenic capability in osteoporosis-derived BMSCs (OP-BMSCs) remain unclear. This study aims to explore the impact of YTHDF3 (YTH N6-methyladenosine RNA binding protein 3) on the osteogenic traits of OP-BMSCs and identify potential therapeutic targets to boost their bone formation ability.

METHODS

We examined microarray datasets (GSE35956 and GSE35958) from the Gene Expression Omnibus (GEO) to identify potential m6A regulators in osteoporosis (OP). Employing differential, protein interaction, and machine learning analyses, we pinpointed critical hub genes linked to OP. We further probed the relationship between these genes and OP using single-cell analysis, immune infiltration assessment, and Mendelian randomization. Our in vivo and in vitro experiments validated the expression and functionality of the key hub gene.

RESULTS

Differential analysis revealed seven key hub genes related to OP, with YTHDF3 as a central player, supported by protein interaction analysis and machine learning methodologies. Subsequent single-cell, immune infiltration, and Mendelian randomization studies consistently validated YTHDF3's significant link to osteoporosis. YTHDF3 levels are significantly reduced in femoral head tissue from postmenopausal osteoporosis (PMOP) patients and femoral bone tissue from PMOP mice. Additionally, silencing YTHDF3 in OP-BMSCs substantially impedes their proliferation and differentiation.

CONCLUSION

YTHDF3 may be implicated in the pathogenesis of OP by regulating the proliferation and osteogenic differentiation of OP-BMSCs.

Bone-Differentiation-Associated Circ-Spen Regulates Death of Mouse Bone Marrow Mesenchymal Stem Cells by Inhibiting Apoptosis and Promoting Autophagy

The role of estrogen receptor β (ERβ) in bone health is closely associated with its function in vivo, and ERβ-/- mice have been widely utilized to explore the related influences. In this study, ERβ-/- female mice were established to investigate the differential expression of circular RNAs (circRNAs) by RNA-Sequencing (RNA-Seq). Among these circRNAs, mmu_circ_0011379 (named Circ-Spen) exhibited high expression in ERβ-/- female mice. However, the precise mechanism by which Circ-Spen regulates bone health remained unclear. This study identified Circ-Spen as a positive regulator of mouse bone marrow mesenchymal stem cell (mBMSC) viability. The expression of Circ-Spen was markedly increased in ERβ-/- mice femurs tested by RT-qPCR. Moreover, Circ-Spen exhibited an enhanced expression during the bone formation process of mBMSCs. Qualitative experiments also demonstrated that Circ-Spen possessed a circular structure and was localized within the nucleus of mBMSCs. Functionally, it inhibited apoptosis via caspase-3, BCL-2, and BAX, while also promoting autophagy through BECN1 and P62 in mBMSCs tested by MTT assays, transmission electron microscopy (TEM), and Western blotting. These findings reveal the potential of targeting Circ-Spen as a promising therapeutic strategy for rejuvenating senescent mBMSCs and enhancing the efficiency of mBMSC transplantation, which lays the foundation for advancements in the field of bone therapy.

Regulation Mechanisms and Maintenance Strategies of Stemness in Mesenchymal Stem Cells

Stemness pertains to the intrinsic ability of mesenchymal stem cells (MSCs) to undergo self-renewal and differentiate into multiple lineages, while simultaneously impeding their differentiation and preserving crucial differentiating genes in a state of quiescence and equilibrium. Owing to their favorable attributes, including uncomplicated isolation protocols, ethical compliance, and ease of procurement, MSCs have become a focal point of inquiry in the domains of regenerative medicine and tissue engineering. As age increases or ex vivo cultivation is prolonged, the functionality of MSCs decreases and their stemness gradually diminishes, thereby limiting their potential therapeutic applications. Despite the existence of several uncertainties surrounding the comprehension of MSC stemness, considerable advancements have been achieved in the clarification of the potential mechanisms that lead to stemness loss, as well as the associated strategies for stemness maintenance. This comprehensive review provides a systematic overview of the factors influencing the preservation of MSC stemness, the molecular mechanisms governing it, the strategies for its maintenance, and the therapeutic potential associated with stemness. Finally, we underscore the obstacles and prospective avenues in present investigations, providing innovative perspectives and opportunities for the preservation and therapeutic utilization of MSC stemness.

Study on the mechanism of naringin in promoting bone differentiation: In vitro and in vivo study

Objective

Osteoporosis is a common clinical bone disease that occurs most frequently in middle-aged and elderly people. Various traditional herbal medicine formulations have shown significant benefits in models of osteoporosis. In this study, we aim to investigate the osteogenic efficacy of naringin (NRG) in the osteoporotic state.

Design

We treated Bone marrow stromal cells (BMSCs) with various concentrations of NRG for 3 and 7 days. BMSC proliferation was measured by the MTT assay. The effect of NRG on the osteogenic differentiation of BMSCs was detected by ALP and alizarin red staining. The effect of NRG on the BMP2/Runx2/Osterix signaling pathway was analyzed by using real-time PCR. The effect of NRG on the oestrogen receptor was measured by Enzyme-linked immunosorbent assay. In vivo animal experiments were performed by micro-computed tomography and ALP immunohistochemistry to determine the ectopic osteogenic effect of NRG sustained-release nanoparticles in a mouse model of osteoporosis.

Results

NRG promoted the proliferation and osteogenic differentiation of BMSCs. Moreover, it also activated the BMP2/Runx2/Osterix signaling pathway. When NRG sustained-release nanoparticles were added in vivo in animal experiments, we found that NRG sustained-release nanoparticles had better ectopic osteogenic effects in a mouse model of osteoporosis.

Conclusions

NRG induced osteoblastic differentiation of BMSCs by activating the BMP2/Runx2/Osterix signaling pathway and promoted the regulation of oestrogen receptor pathway protein expression, and NRG sustained-release nanoparticles exerted a more significant in vivo ectopic osteogenic effect in an osteoporosis mouse model. Therefore, naringin is expected to be developed as a novel treatment for inducing osteogenesis, because of its ubiquitous, cost-efficient, and biologically active characteristics. However, further research is needed on how to improve the pharmacokinetic properties of naringin and its specific mechanism.

Progress of epigenetic modification of SATB2 gene in the pathogenesis of non-syndromic cleft lip and palate

Non-syndromic Cleft Lip and Palate (NSCLP) is one of the most common congenital craniofacial malformations. However, there is no enough knowledge about its mechanism, even through many relevant studies verify that cleft lip and palate is caused by interactions between environmental and genetic factors. SATB2 gene is one of the most common candidate genes of NSCLP, and the development of epigenetics provides a new direction on pathogenesis of cleft lip and palate. This review summarizes SATB2 gene in the pathogenesis of non-syndromic cleft lip and palate, expecting to provide strategies to prevent and treat cleft and palate in the future.

Sex-Specific Genetic Determinants of Asthma-COPD Phenotype and COPD in Middle-Aged and Older Canadian Adults: An Analysis of CLSA Data

The etiology of sex differences in the risk of asthma-COPD phenotype and COPD is still not completely understood. Genetic and environmental risk factors are commonly believed to play an important role. This study aims to identify sex-specific genetic markers associated with asthma-COPD phenotype and COPD using the Canadian Longitudinal Study on Aging (CLSA) Baseline Comprehensive and Genomic data. There were a total of 1,415 COPD cases. Out of them, 504 asthma-COPD phenotype cases were identified. 20,524 participants without a diagnosis of asthma and COPD served as controls. We performed genome-wide SNP-by-sex interaction analysis. SNPs with an interaction p-value < 10^-5 were included in a sex-stratified multivariable logistic regression for asthma-COPD phenotype and COPD outcomes. 18 and 28 SNPs had a significant interaction term p-value < 10^-5 with sex in the regression analyses of asthma-COPD phenotype and COPD outcomes, respectively. Sex-stratified multivariable analysis of asthma-COPD phenotype showed that 7 SNPs in/near SMYD3, FHIT, ZNF608, RIMBP2, ZNF133, BPIFB1, and S100B loci were significant in males. Sex-stratified multivariable analysis of COPD showed that 8 SNPs in/near MAGI1, COX18, OSTC, ELOVL5, C7orf72 FGF14, and NKAIN4 were significant in males, and 4 SNPs in/near genes CAMTA1, SATB2, PDE10A, and LINC00908 were significant in females. An SNP in the ZPBP gene was associated with COPD in both males and females. Identification of sex-specific loci associated with asthma-COPD phenotype and COPD may offer valuable evidence toward a better understanding of the sex-specific differences in the pathophysiology of the diseases.

ER-β accelerates the process of primary osteoporosis by promoting VEGFA-mediated apoptosis of osteoblasts

Primary osteoporosis (POP) is a widespread and severe disorder of bone metabolism characterized by reduced bone mass and destruction of bone structure, frequently inducing fracture risk and imposing a heavy economic burden on public life. The development of POP partially revolves around the estrogen receptor β (ER-β), one of the major mediator receptors of estrogen that influences apoptosis in a range of cells. We performed KEGG and GO analysis by mining the transcriptomic dataset of POP samples showing significant enrichment of differentially expressed genes (DEGs) in multiple apoptosis-related pathways. The results of the Spearman correlation analysis and Protein-Protein Interaction (PPI) Networks screening of hub genes indicated that vascular endothelial growth factor A (VEGFA) may be a key target of ER-β in controlling osteoblast apoptosis. Further, we carried out high-throughput sequencing of ESR2-silenced MC3T3-E1 cells and noticed a substantial suppression in VEGFA expression and all apoptosis-related pathways. In addition, we determined the cell cycle and apoptosis by constructing a VEGFA-silenced cell model utilizing flow cytometry (FCM), and the results showed that ER-β could regulate the osteoblast cycle and thus promote osteoblast apoptosis by promoting VEGFA expression. And Western blot results showed that apoptosis was most likely realized through the regulation of downstream apoptosis markers c-JUN (c-Jun N-terminal kinase, JNK) and GADD45G (Growth Arrest and DNA Damage-Inducible Protein 45 gamma). The effects of ESR2 and VEGFA on the proliferation of osteoblasts were lastly assessed using the cell counting kit- 8 (CCK-8) assay. In conclusion, this study identifies that the roles of ER-β in the regulation of osteoblast apoptosis are closely related to VEGFA and provides a new target for POP treatment.

Causal association between body mass index and temporomandibular disorders: a bidirectional two-sample Mendelian randomization analysis

BACKGROUND

Observational studies have shown that body mass index (BMI) is highly correlated with the occurrence of temporomandibular disorders (TMDs). However, these studies failed to present a causal relationship. Thus, we aimed to performed a Mendelian randomization (MR) study to investigate causality between BMI and TMDs.

METHODS

We performed a two-sample bidirectional MR analysis using large-scale genome-wide association studies (GWAS). Data were obtained from a large-scale BMI dataset (N = 322,154), TMDs dataset (N = 134,280). The causal effects were estimated with inverse-variance weighted (IVW) method, MR Egger, weighted median. Sensitivity analyses were implemented with Cochran's Q test, MR-Egger intercept test, MR-PRESSO, leave-one-out analysis and the funnel plot.

RESULTS

In the forward MR analysis, a genetic prediction of low BMI was causally associated with a higher risk of TMDs (IVW OR: 0.575, 95% CI: 0.415-0.798, p: 0.001). Similar results were obtained using other complementary methods (MR Egger OR: 0.270, 95% CI: 0.104-0.698, p: 0.009; weighted median OR: 0.496, 95% CI: 0.298-0.826, p: 0.007). In the reverse MR results, TMDs was shown to have no significant effect on BMI (all p > 0.05). No pleiotropy and heterogeneity were detected in the bidirectional analysis (p > 0.05).

CONCLUSION

A lower BMI might be causally associated with increased risk of TMDs, supporting the importance of weight control for the prevention of TMDs. Clinicians should pay more attention to the low-BMI patients among those seeking medical advice due to temporomandibular joint discomfort.

Exosomes derived from mesenchymal stromal cells promote bone regeneration by delivering miR-182-5p-inhibitor

Exosomes, small extracellular vesicles that function as a key regulator of cell-to-cell communication, are emerging as a promising candidate for bone regeneration. Here, we aimed to investigate the effect of exosomes from pre-differentiated human alveolar bone-derived bone marrow mesenchymal stromal cells (AB-BMSCs) carrying specific microRNAs on bone regeneration. Exosomes secreted from AB-BMSCs pre-differentiated for 0 and 7 days were cocultured with BMSCs in vitro to investigate their effect on the differentiation of the BMSCs. MiRNAs from AB-BMSCs at different stages of osteogenic differentiation were analyzed. BMSCs seeded on poly-L-lactic acid(PLLA) scaffolds were treated with miRNA antagonist-decorated exosomes to verify their effect on new bone regeneration. Exosomes pre-differentiated for 7 days effectively promoted the differentiation of BMSCs. Bioinformatic analysis revealed that miRNAs within the exosomes were differentially expressed, including the upregulation of osteogenic miRNAs (miR-3182, miR-1468) and downregulation of anti-osteogenic miRNAs (miR-182-5p, miR-335-3p, miR-382-5p), causing activation of the PI3K/Akt signaling pathway. The treatment of BMSC-seeded scaffolds with anti-miR-182-5p decorated exosomes demonstrated enhanced osteogenic differentiation and efficient formation of new bone. In conclusion, Osteogenic exosomes secreted from pre-differentiated AB-BMSCs were identified and the gene modification of exosomes provides great potential as a bone regeneration strategy. DATA AVAILABILITY STATEMENT: Data generated or analyzed in this paper partly are available in the GEO public data repository(http://www.ncbi.nlm.nih.gov/geo).

17β-estradiol plays the anti-osteoporosis role via a novel ESR1-Keap1-Nrf2 axis-mediated stress response activation and Tmem119 upregulation

Increased oxidative stress and decreased osteoblastic bone formation contribute to estrogen deficiency-induced osteoporosis. However, the role and mechanism of estrogen-deficiency in regulating oxidative stress and osteoblastic activity remain unclear. Here, we showed that estrogen-deficient bone marrow stromal/stem cells (BMSCs) exhibited impaired capacity to combat stress, characterized by increased oxidative stress, shortened cell survival and reduced osteogenic differentiation and bone formation, which were due to a decrease of nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 re-activation induced by the pyrazinyl dithiolethione oltipraz significantly rescued the cell phenotype of estrogen-deficient BMSCs in vitro and ex vivo. Mechanistically, we found that 17β-estradiol/ESR1 (Estrogen Receptor 1) facilitated Nrf2 accumulation, and activated its target genes by competing with Nrf2 for binding to Kelch-like ECH-associated protein 1 (Keap1) via ESR1 containing a highly conserved DLL motif. Of note, oltipraz, an Nrf2 activator, rescued ovariectomy-induced osteoporosis partly by inhibiting oxidative stress and promoting osteoblastic bone formation via Nrf2-induced antioxidant signaling activation and Tmem119 (transmembrane protein 119) upregulation. Conversely, Nrf2 knockout largely blocked the bone anabolic effect of 17β-estradiol in vivo and ex vivo. This study provides insight into the mechanisms whereby estrogen prevents osteoporosis through promoting osteoblastic bone formation via Nrf2-mediated activation of antioxidant signaling and upregulation of Tmem119, and thus provides evidence for Nrf2 as a potential target for clinical prevention and treatment of menopause-related osteoporosis.

Compromised osteogenic effect of exosomes internalized by senescent bone marrow stem cells via endocytoses involving clathrin, macropinocytosis and caveolae

Stem cell senescence leads to progressive functional declines and disrupts the physiological homeostasis of bone environment. Stem cell-derived exosomes are emerging as promising therapeutical approaches to treat diverse aging-related osseous diseases. Herein, a previously reported osteoinductive exosome (OI-exo) was applied as a therapeutic agent for bone repair in aging individuals and its internalization mechanisms in senescent bone marrow stem cells (BMSCs) were explored. The results demonstrated that OI-exos derived from young BMSCs could partially rescue the proliferation, osteogenic differentiation and alleviate aging phenotypes in vitro. OI-exo-delivered hierarchical mesoporous bioactive glass (MBG) scaffold effectively promote in vivo bone formation in aging rat cranial defect model. However, the osteogenic effects of OI-exo both in vitro and in vivo were compromised in senescent individuals and for aging BMSCs compared to younger ones. This study revealed that non-senescent BMSCs internalized exosomes exclusively via clathrin-mediated endocytosis, while senescent BMSCs additionally evoked macropinocytosis and caveolae-mediated endocytosis to mediate the internalization of exosomes. The alteration of endocytic manner of senescent BMSCs and the involvement of macropinocytosis might be responsible for the compromised effects of therapeutical exosomes. The phenomena discovered in this study could also be extended to other scenarios where drugs or treatments exerted compromised effects in aging individuals. The influence of endocytic manner, avoidance of macropinocytosis-related negative effects should be taken into considerations in future therapeutic design for aging populations.

Eldecalcitol prevented OVX-induced osteoporosis through inhibiting BMSCs senescence by regulating the SIRT1-Nrf2 signal

Background: Aging and oxidative stress are considered to be the proximal culprits of postmenopausal osteoporosis. Eldecalcitol (ED-71), a new active vitamin D derivative, has shown a good therapeutic effect on different types of osteoporosis, but the mechanism is unclear. This study focused on exploring whether ED-71 could prevent bone loss in postmenopausal osteoporosis by regulating the cell senescence of bone mesenchymal stem cells (BMSCs), and explaining its specific mechanism of action. Materials and methods: An ovariectomized (OVX) rat model was established and 30 ng/kg ED-71 was administered orally once a day. The weight of rats was recorded regularly. Micro-computed tomography (CT) and histochemical staining were used to evaluate bone mass, histological parameters, and aging-related factors. Rat bone mesenchymal stem cells were extracted and cultivated in vitro. Aging cells were marked with senescence-associated β-gal (SA-β-gal) dyeing. The mRNA and protein levels of aging-related factors and SIRT1-Nrf2 signal were detected by RT-PCR, Western blot, and immunofluorescence staining. The reactive oxygen species (ROS) levels were detected by DCFH-DA staining. Results: Compared with the Sham group, the bone volume of the ovariectomized group rats decreased while their weight increased significantly. ED-71 prevented bone loss and inhibited weight gain in ovariectomized rats. More importantly, although the expression of aging-related factors in the bone tissue increased in the ovariectomized group, the addition of ED-71 reversed changes in these factors. After extracting and in vitro culturing bone mesenchymal stem cells, the proportion of aging bone mesenchymal stem cells was higher in the ovariectomized group than in the Sham group, accompanied by a significant decrease in the osteogenic capacity. ED-71 significantly improved the bone mesenchymal stem cells senescence caused by ovariectomized. In addition, ED-71 increased the expression of SIRT1 and Nrf2 in ovariectomized rat bone mesenchymal stem cells. Inhibition of SIRT1 or Nrf2 decreased the inhibitory effect of ED-71 on bone mesenchymal stem cells senescence. ED-71 also showed a suppression effect on the reactive oxygen species level in bone mesenchymal stem cells. Conclusion: Our results demonstrated that ED-71 could inhibit the cell senescence of bone mesenchymal stem cells in ovariectomized rats by regulating the SIRT1-Nrf2 signal, thereby preventing bone loss caused by osteoporosis.

Estrogens: Two nuclear receptors, multiple possibilities

Much is known about estrogen action in experimental animal models and in human physiology. This article reviews the mechanisms of estrogen activity in animals and humans and the role of its two receptors α and β in terms of structure and mechanisms of action in various tissues in health and in relationship with human pathologies (e.g., osteoporosis). Recently, the spectrum of clinical pictures of estrogen resistance caused by estrogen receptors gene variants has been widened by our description of a woman with β-receptor defect, which could be added to the already known descriptions of α-receptor defect in women and men and β-receptor defect in men. The essential role of the β-receptor in the development of the gonad stands out. We summarize the clinical pictures due to estrogen resistance in men and women and focus on long-term follow-up of two women, one with α- and the other with β-receptor resistance. Some open questions remain on the complex interactions between the two receptors on bone metabolism and hypothalamus-pituitary-gonadal axis, which need further deepening and research.

Estrogen Signaling Dictates Musculoskeletal Stem Cell Behavior: Sex Differences in Tissue Repair

Sexual dimorphisms in humans and other species exist in visually evident features such as body size and less apparent characteristics, including disease prevalence. Current research is adding to a growing understanding of sex differences in stem cell function and response to external stimuli, including sex hormones such as estrogens. These differences are proving significant and directly impact both the understanding of stem cell processes in tissue repair and the clinical implementation of stem cell therapies. Adult stem cells of the musculoskeletal system, including those used for development and repair of muscle, bone, cartilage, fibrocartilage, ligaments, and tendons, are no exception. Both in vitro and in vivo studies have found differences in stem cell number, proliferative and differentiation capabilities, and response to estrogen treatment between males and females of many species. Maintaining the stemness and reducing senescence of adult stem cells is an important topic with implications in regenerative therapy and aging. As such, this review discusses the effect of estrogens on musculoskeletal system stem cell response in multiple species and highlights the research gaps that still need to be addressed. The following evidence from investigations of sex-related phenotypes in adult progenitor and stem cells are pieces to the big puzzle of sex-related effects on aging and disease and critical information for both fundamental tissue repair and regeneration studies and safe and effective clinical use of stem cells. Impact Statement This review summarizes current knowledge of sex differences in and the effects of estrogen treatment on musculoskeletal stem cells in the context of tissue engineering. Specifically, it highlights the impact of sex on musculoskeletal stem cell function and ability to regenerate tissue. Furthermore, it discusses the varying effects of estrogen on stem cell properties, including proliferation and differentiation, important to tissue engineering. This review aims to highlight the potential impact of estrogens and the importance of performing sex comparative studies in the field of tissue engineering.

Progranulin, a moderator of estrogen/estrogen receptor α binding, regulates bone homeostasis through PERK/p-eIF2 signaling pathway

Under normal conditions, the human body employs the synergistic action of osteoblasts and osteoclasts to maintain a dynamic balance between bone formation and resorption. Bone homeostasis plays a very important role in the process of bone formation. Various bone diseases can occur if bone homeostasis is disrupted. In this study, the serum estrogen levels were significantly increased in the granulin (GRN)-deficient mice and PGRN regulates the binding of estrogen and estrogen receptor α (ERα) and then affects estrogen's ability to regulate bone formation and resorption. In addition, this study also explored the role that PGRN plays in regulating bone homeostasis by affecting the binding of estrogen and estrogen receptors through the protein kinase R-like endoplasmic reticulum kinase/phosphorylation of the eukaryotic initiation factor 2 signaling pathway. In summary, we confirmed the important role of PGRN in regulating the estrogen (E2)/ERα signal in maintaining bone homeostasis. Our findings may provide a new strategy for the treatment of osteoporosis and maintaining bone homeostasis. KEY MESSAGES: PGRN is a molecular regulator of the binding of E2 and ERα signal in maintaining bone homeostasis. PGRN plays in regulating bone homeostasis through the PERK/p-eIF2α signaling pathway. The best therapeutic effect of PGRN in osteoporosis is associated with different concentration of E2.

Cellular senescence and the skeleton: pathophysiology and therapeutic implications

Cellular senescence is a fundamental aging mechanism that is currently the focus of considerable interest as a pathway that could be targeted to ameliorate aging across multiple tissues, including the skeleton. There is now substantial evidence that senescent cells accumulate in the bone microenvironment with aging and that targeting these cells prevents age-related bone loss, at least in mice. Cellular senescence also plays important roles in mediating the skeletal fragility associated with diabetes mellitus, radiation, and chemotherapy. As such, there are ongoing efforts to develop "senolytic" drugs that kill senescent cells by targeting key survival mechanisms in these cells without affecting normal cells. Because senescent cells accumulate across tissues with aging, senolytics offer the attractive possibility of treating multiple age-related comorbidities simultaneously.

Melatonin Improves the Resistance of Oxidative Stress-Induced Cellular Senescence in Osteoporotic Bone Marrow Mesenchymal Stem Cells

Accumulation of senescent bone marrow-derived mesenchymal stem cells (BMMSCs) has led to an age-related bone loss. However, the role of stem cell senescence in estrogen deficiency-induced osteoporosis remains elusive. Though melatonin plays a vital role in bone metabolism regulation, the underlying mechanisms of melatonin-mediated antiosteoporosis are partially elucidated. Therefore, this study purposed to explore (1) whether estrogen deficiency causes cellular senescence of BMMSCs, and if so, (2) the potential of melatonin in preventing bone loss via senescence signaling inhibition. BMMSCs derived from ovariectomized (OVX) rats (OVX BMMSCs) showed an impaired osteogenic capacity, albeit having comparable levels of senescence biomarkers than the sham cells. When exposed to low levels of hydrogen peroxide (H₂O₂), OVX BMMSCs rapidly exhibited senescence-associated phenotypes such as the increased activity of senescence-associated β-galactosidase (SA-β-gal) and upregulation of cell cycle inhibitors. Notably, the in vitro treatment with melatonin hindered H₂O₂-induced senescence in OVX BMMSCs and restored their osteogenic capacity. Treatment with either SIRT1 inhibitor (sirtinol) or melatonin receptor antagonists (luzindole and 4-P-PDOT) eliminated melatonin protective effects, thus indicating its potential in preventing stem cell senescence via SIRT1 activation through the melatonin membrane receptors. Following in vivo intravenous administration with melatonin, it successfully protected the bone microstructure and preserved the antisenescence property of BMMSCs in OVX rats. Collectively, our findings demonstrated that melatonin protected against estrogen deficiency-related bone loss by improving the resistance of BMMSCs to cellular senescence. Therefore, melatonin-mediated antisenescence effect on stem cells provides vital information to facilitate the development of a novel and effective strategy for treating postmenopausal OP.

Methyl-CpG-binding protein 2 promotes osteogenic differentiation of bone marrow mesenchymal stem cells through regulating forkhead box F1/Wnt/β-Catenin axis

Postmenopausal osteoporosis is characterized by inadequate bone formation of osteoblasts and excessive bone resorption of osteoclasts. Bone marrow mesenchymal stem cells (BMSCs), with the potential of osteogenic differentiation, have been widely used in the bone tissues engineering for the treatment of bone diseases, including postmenopausal osteoporosis. Methyl-CpG-binding protein 2 (MECP2) has been reported to be implicated in bone formation during the development of Rett syndrome. However, the influence of MeCP2 on osteogenic differentiation of BMSCs during osteoporosis remains unclear. Firstly, mice model with estrogen deficiency-induced osteoporosis was established through ovariectomy (OVX). MeCP2 was found to be down-regulated in bone tissues and BMSCs of OVX-induced osteoporosis mice. Secondly, over-expression of MeCP2 enhanced the calcium deposition of BMSCs isolated from the OVX-induced osteoporosis mice. Moreover, expression of osteogenic biomarkers including alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), collagen type I alpha 1 (COL1A1), and osteocalcin (OCN) was increased in BMSCs by overexpression of MeCP2. Thirdly, over-expression of MeCP2 reduced protein expression of forkhead box F1 (FOXF1) and adenomatous polyposis coli (APC), while enhanced Wnt5a and β-catenin expression in BMSCs. Over-expression of FOXF1 attenuated MeCP2 over-expression-induced decrease of FOXF1 and APC, as well as increase of Wnt5a and β-catenin. Finally, the increased calcium deposition, protein expression of ALP, RUNX2COL1A1 and OCN induced by concomitant overexpression of MeCP2 were also restored by FOXF1 over-expression. In conclusion, MeCP2 promoted osteogenic differentiation of BMSCs through regulating FOXF1/Wnt/β-Catenin axis to attenuate osteoporosis. MeCP2 over-expression reduced FOXF1 to promote the activation of Wnt5a/β-Catenin and promote osteogenic differentiation of BMSCs during the prevention of postmenopausal osteoporosis.

Estrogen prevents cellular senescence and bone loss through Usp10-dependent p53 degradation in osteocytes and osteoblasts: the role of estrogen in bone cell senescence

Estrogens play multiple roles in maintaining skeletal homeostasis by regulating many physiological processes in bone cells. Recently, cellular senescence in bone cells, especially in osteocytes, has been demonstrated to be a pivotal factor in bone loss. However, whether and how estrogen mediates cellular senescence in bone cells remains unknown. Here, we show that estrogen is negatively correlated with p53-related cellular senescence, primarily through the regulation of p53 protein levels, both in vivo and in vitro. Further study confirmed that estrogen attenuated the nuclear import of p53 and accelerated p53 degradation in osteocyte-like MLO-Y4 cells and osteoblastic MC3T3-E1 cells. A screen of p53-related ubiquitinating/deubiquitinating enzymes indicated that estrogen induced the degradation of p53 through the regulation of Usp10, a deubiquitinase that is directly linked to p53. Usp10 inhibition attenuated H₂O₂-induced senescence in MLO-Y4 cells, as indicated by p53/p21 quantification, a senescence-associated β-galactosidase (SA-β-gal) assay, and p53 localization visualization with a confocal microscope. Usp10 overexpression abolished the estrogen-mediated regulation of p53 and the downstream transcriptional gene p21. The injection of ovariectomized (OVX) mice with Spautin-1, a Usp10 inhibitor, inhibited the expression of p53 and the transcription of downstream senescence markers, as well as promoted bone mass recovery. Taken together, our study unveils the regulatory function of estrogen in the prevention of cellular senescence through the regulation of Usp10, thereby accelerating the degradation of senescent factor p53 and inhibiting its nuclear import.

Individuals with SATB2-associated syndrome with and without autism have a recognizable metabolic profile and distinctive cellular energy metabolism alterations

SATB2-associated syndrome (SAS) is a multisystemic disorder characterized by developmental delay often with concurrent autistic tendencies. This study aimed to characterize cellular metabolic pathways and energy metabolism from cells derived from individuals with SAS. The cellular production of NADH (nicotinamide adenine dinucleotide, reduced form) as determined by the Phenotype Mammalian MicroArrays was measured in lymphoblastoid cell lines derived from 11 subjects with a molecularly confirmed diagnosis of SAS and compared to a control population of 50 age-matched typically developing individuals. All patients were evaluated clinically by a multidisciplinary team. Eleven individuals (five in a screening cohort and six in the validation cohort, mean age 6.1 years) were recruited to the study. All individuals had developmental delay and the diagnosis of autism was previously established in five of them. Key metabolic findings included reduced NADH production in the presence of phosphorylated carbohydrates (with corresponding increased production in the presence of alternative carbon-based energy sources), increased response to certain hormones (β-estradiol in particular), and significantly reduced levels of NADH in wells containing tryptophan. The individual analysis revealed no particular differences among the SAS subjects based on molecular findings or phenotypic features. In conclusion, individuals with SAS have a common and recognizable metabolic profile. A lower capacity to utilize glucose as an energy substrate could be contributing to the neurodevelopment phenotype of SAS. The identified abnormalities offer previously unexplored insight into the potential pathophysiology of common SAS phenotypic features.

Estrogen promotes lncRNA H19 expression to regulate osteogenic differentiation of BMSCs and reduce osteoporosis via miR-532-3p/SIRT1 axis

Osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) plays an essential role in bone formation. Its imbalance can lead to osteoporosis. Estrogen and long noncoding RNAs (lncRNAs) have been confirmed to participate in osteogenesis. However, the underlying mechanism remains unclear. The purpose of our study was to explore the function of lncRNA H19 in estrogen-induced osteogenic differentiation of BMSCs. The present research demonstrated that the expression levels of lncRNA H19 and SIRT1 were markedly downregulated in postmenopausal osteoporosis (PMOP), while miR-532-3p expression was obviously increased. Moreover, estrogen induced the osteogenic differentiation of BMSCs by upregulating lncRNA H19. Furthermore, our integrated experiments showed that lncRNA H19 caused a decrease in the expression of miR-532-3p, which was verified to target SIRT1 directly. Additionally, estrogen alleviated osteoporosis in OVX rats through lncRNA H19-mediated miR-532-3p/SIRT1 axis. Our findings imply that lncRNA H19 mediates estrogen-regulated osteogenic differentiation in BMSCs via miR-532-3p/SIRT1 signalling and may become a novel target for alleviating PMOP.

Sodium hydrosulfide alleviates dexamethasone-induced cell senescence and dysfunction through targeting the miR-22/sirt1 pathway in osteoblastic MC3T3-E1 cells

Glucocorticoid-induced osteoporosis is characterized by osteoblastic cell and microarchitecture dysfunction, as well as a loss of bone mass. Cell senescence contributes to the pathological process of osteoporosis and sodium hydrosulfide (NaHS) regulates the potent protective effects through delaying cell senescence. The aim of the present study was to investigate whether senescence could contribute to dexamethasone (Dex)-induced osteoblast impairment and to examine the effect of NaHS on Dex-induced cell senescence and damage. It was found that the levels of the senescence-associated markers, p53 and p21, were markedly increased in osteoblasts exposed to Dex. A p53 inhibitor reversed Dex-induced osteoblast injury, a process that was mitigated by NaHS administration through alleviating osteoblastic cell senescence. MicroRNA (miR)-22 blocked the impact of NaHS on Dex-induced osteoblast damage and senescence through targeting the regulation of Sirtuin 1 (sirt1) expression, as shown by the decreased cell viability and alkaline phosphatase activity, as well as an increased expression of p53 and p21. It was revealed that the sirt1 gene was the target of miR-22 in osteoblastic MC3T3-E1 cells through combining the results of dual luciferase reporter assays and reverse transcription-quantitative PCR, as well as western blot analyses. Silencing of sirt1 abolished the protective effect of NaHS against Dex-associated osteoblast senescence and injury. Taken together, the present study showed that NaHS prevents Dex-induced cell senescence and damage through targeting the miR-22/sirt1 pathway in osteoblastic MC3T3-E1 cells.

Estrogens as regulator of hematopoietic stem cell, immune cells and bone biology

Hematopoietic stem cells provide continuous supply of all the immune cells, through proliferation and differentiation decisions. These decisions are controlled by local bone marrow environment as well as by long-range signals for example endocrine system. Sex dependent differential immunological responses have been described under homeostasis and disease conditions. Females show higher longevity than male counterpart that seems to depend on major female sex hormone, estrogen. There are four estrogens - Estrone (E1), estradiol (E2), Estriol (E3) and Estetrol (E4) that spatially and temporarily present during different female reproductive phases. In this review, we discussed recent updates describing the effects of estrogen on HSC, immune cells and in bone biology. Estradiol (E2) being a major/abundant estrogen is extensively investigated, while effects of other estrogens E1, E3 and E4 are started to unravel recently. Furthermore, clinical effect of estrogen as hormone therapy is discussed in HSC and immune cells perspectives. The data presented in this review is compiled by searches of PubMed, database of American Cancer Society (ACS). We have included article from September 1994 to March 2020 as covering all article in chronological order is not fissile so we included relevant article with substantial information in this specific area of research by using the search term (alone or in combination) estrogen, hematopoietic stem cell, immune cells, gender difference, estrone, estriol, estetrol, therapeutic application, pregnancy, effect on bone.

The Role of Chronic Inflammatory Bone and Joint Disorders in the Pathogenesis and Progression of Alzheimer's Disease

Late-onset Alzheimer's Disease (LOAD) is a devastating neurodegenerative disorder that causes significant cognitive debilitation in tens of millions of patients worldwide. Throughout disease progression, abnormal secretase activity results in the aberrant cleavage and subsequent aggregation of neurotoxic Aβ plaques in the cerebral extracellular space and hyperphosphorylation and destabilization of structural tau proteins surrounding neuronal microtubules. Both pathologies ultimately incite the propagation of a disease-associated subset of microglia-the principle immune cells of the brain-characterized by preferentially pro-inflammatory cytokine secretion and inhibited AD substrate uptake capacity, which further contribute to neuronal degeneration. For decades, chronic neuroinflammation has been identified as one of the cardinal pathophysiological driving features of AD; however, despite a number of works postulating the underlying mechanisms of inflammation-mediated neurodegeneration, its pathogenesis and relation to the inception of cognitive impairment remain obscure. Moreover, the limited clinical success of treatments targeting specific pathological features in the central nervous system (CNS) illustrates the need to investigate alternative, more holistic approaches for ameliorating AD outcomes. Accumulating evidence suggests significant interplay between peripheral immune activity and blood-brain barrier permeability, microglial activation and proliferation, and AD-related cognitive decline. In this work, we review a narrow but significant subset of chronic peripheral inflammatory conditions, describe how these pathologies are associated with the preponderance of neuroinflammation, and posit that we may exploit peripheral immune processes to design interventional, preventative therapies for LOAD. We then provide a comprehensive overview of notable treatment paradigms that have demonstrated considerable merit toward treating these disorders.

SATB2: A versatile transcriptional regulator of craniofacial and skeleton development, neurogenesis and tumorigenesis, and its applications in regenerative medicine

SATB2 (special AT-rich sequence-binding protein 2) is a member of the special AT-rich binding protein family. As a transcription regulator, SATB2 mainly integrates higher-order chromatin organization. SATB2 expression appears to be tissue- and stage-specific, and is governed by several cellular signaling molecules and mediators. Expressed in branchial arches and osteoblast-lineage cells, SATB2 plays a significant role in craniofacial pattern and skeleton development. In addition to regulating osteogenic differentiation, SATB2 also displays versatile functions in neural development and cancer progression. As an osteoinductive factor, SATB2 holds great promise in improving bone regeneration toward bone defect repair. In this review, we have summarized our current understanding of the physiological and pathological functions of SATB2 in craniofacial and skeleton development, neurogenesis, tumorigenesis and regenerative medicine.

Exosomal circLPAR1 Promoted Osteogenic Differentiation of Homotypic Dental Pulp Stem Cells by Competitively Binding to hsa-miR-31

Human dental pulp stem cells (DPSCs) hold great promise in bone regeneration. However, the exact mechanism of osteogenic differentiation of DPSCs remains unknown, especially the role of exosomes played in. The DPSCs were cultured and received osteogenic induction; then, exosomes from osteogenic-induced DPSCs (OI-DPSC-Ex) at different time intervals were isolated and sequenced for circular RNA (circRNA) expression profiles. Gradually, increased circular lysophosphatidic acid receptor 1 (circLPAR1) expression was found in the OI-DPSC-Ex coincidentally with the degree of osteogenic differentiation. Meanwhile, results from osteogenic differentiation examinations showed that the OI-DPSC-Ex had osteogenic effect on the recipient homotypic DPSCs. To investigate the mechanism of exosomal circLPAR1 on osteogenic differentiation, we verified that circLPAR1 could competently bind to hsa-miR-31, by eliminating the inhibitory effect of hsa-miR-31 on osteogenesis, therefore promoting osteogenic differentiation of the recipient homotypic DPSCs. Our study showed that exosomal circRNA played an important role in osteogenic differentiation of DPSCs and provided a novel way of utilization of exosomes for the treatment of bone deficiencies.

Effect of Icosapent Ethyl on Gynoid Fat and Bone Mineral Health in the Metabolic Syndrome: A Preliminary Report

PURPOSE

The metabolic syndrome (MetS) is a systemic disorder associated with reduced atheroprotective gynoid fat and bone mineral content (BMC). The goal of this pilot study was to assess whether administration of icosapent ethyl (IPE), a purified formulation of eicosapentaenoic acid, would maintain gynoid fat and BMC over a 9-month treatment period.

METHODS

Patients with MetS aged ≥40 years were randomly assigned to receive 4 g daily of IPE (2 g BID with food) or placebo (paraffin oil 2 g BID with food) for 9 months. Data were collected at baseline and 9 months later. The data included anthropometric measures, biochemical analysis, and whole body fat mass, including gynoid fat. Bone mineral density and BMC were measured by using dual-energy X-ray absorptiometry. A two-tailed P value ≤ 0.05 was considered statistically significant.

FINDINGS

The study sample consisted of 13 patients with MetS (mean age, 61.6 years; age range, 44-77 years; 77% female and 23% male). Compared with the IPE group, the placebo group experienced statistically significant mean reductions in percent gynoid fat (pre/post, 46.8%-43.5%; P = 0.02), BMC (pre/post, 2461 g-2423 g; P = 0.02), and bone mineral density (pre/post, 1.24 g/cm² to 1.22 g/cm²; P = 0.05) over the 9-month study period.

IMPLICATIONS

The results of this pilot study raise the possibility that IPE supplementation may preserve gynoid fat distribution and bone mineral health in patients with MetS. Larger, randomized longitudinal studies are necessary to determine the potential long-term metabolic benefits of IPE treatment.

Estrogen effects on orthodontic tooth movement and orthodontically-induced root resorption

Estrogen is an essential regulator of the bone tissue. The remodeling of the alveolar bone and periodontal ligament is the basis of orthodontic tooth movement (OTM). There is a negative coregulation between physiological estrogen levels and the rate of OTM. As a possible inhibitory factor of OTM, estrogen suppresses bone resorption by inhibiting osteoclastic differentiation and restraining osteoclast lifespan though multiple pathways and cytokines, leading to the suppression of the initiation step of bone remodeling. On the other hand, estrogen stimulates osteoblastic differentiation and function. Estrogen receptor-α (ERα) involves in the osteogenic responses to mechanical stimulation, and the ERα expression is regulated positively by the levels of circulatory estrogen. Orthodontically induced root resorption (OIRR) is a common side-effect of orthodontic treatment. Estrogen may have some inhibitory effects on OIRR, but more studies are needed to get an effective conclusion.

Human amnion-derived mesenchymal stem cells promote osteogenic differentiation of human bone marrow mesenchymal stem cells via H19/miR-675/APC axis

Bone volume inadequacy is an emerging clinical problem impairing the feasibility and longevity of dental implants. Human bone marrow mesenchymal stem cells (HBMSCs) have been widely used in bone remodeling and regeneration. This study examined the effect of long noncoding RNAs (lncRNAs)-H19 on the human amnion-derived mesenchymal stem cells (HAMSCs)-droved osteogenesis in HBMSCs. HAMSCs and HBMSCs were isolated from abandoned amniotic membrane samples and bone marrow. The coculture system was conducted using transwells, and H19 level was measured by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). The mechanism was further verified. We here discovered that osteogenesis of HBMSCs was induced by HAMSCs, while H19 level in HAMSCs was increased during coculturing. H19 had no significant effect on the proliferative behaviors of HBMSCs, while its overexpression of H19 in HAMSCs led to the upregulated osteogenesis of HBMSCs in vivo and in vitro; whereas its knockdown reversed these effects. Mechanistically, H19 promoted miR-675 expression and contributed to the competitively bounding of miR-675 and Adenomatous polyposis coli (APC), thus significantly activating the Wnt/β-catenin pathway. The results suggested that HAMSCs promote osteogenic differentiation of HBMSCs via H19/miR-675/APC pathway, and supply a potential target for the therapeutic treatment of bone-destructive diseases.

Periostin Mediates Oestrogen-Induced Osteogenic Differentiation of Bone Marrow Stromal Cells in Ovariectomised Rats

Osteoporosis is a metabolic disease that results in the progressive loss of bone mass, which, in postmenopausal women, is related to oestrogen deficiency. Periostin (POSTN) plays a key role in the early stages of bone formation. However, whether POSTN participates in oestradiol regulation of osteogenic differentiation of bone marrow stromal cells (BMSCs) from ovariectomised (OVX) rats remains unclear. In vivo, using microcomputed tomography (micro-CT), immunohistochemistry, and dynamic analysis of femurs, we found that 17β-E2 promotes bone formation and POSTN expression at the endosteal surface. In vitro, 17β-E2 upregulated POSTN expression in OVX-BMSCs. POSTN overexpression activated the Wnt/β-catenin signalling pathway and enhanced osteogenic differentiation of OVX-BMSCs. Furthermore, knockdown of Postn blocks the involvement of 17β-E2 in the osteogenic differentiation of OVX-BMSCs. Collectively, our study indicated the role of POSTN in the osteogenesis and stemness of OVX-BMSCs and proves that 17β-E2 reduces osteoporosis and promotes osteogenesis through the POSTN-Wnt/β-catenin pathway. POSTN could, therefore, be a novel target gene for anti-osteoporosis therapies.

MicroRNA-19b-3p promotes cell proliferation and osteogenic differentiation of BMSCs by interacting with lncRNA H19

BACKGROUND

To investigated the role of miR-19b-3p in regulating bone marrow mesenchymal stem cell (BMSC) proliferation and osteoblast differentiation.

METHODS

The expression of miR-19b-3p and lncRNA H19 were measured in postmenopausal osteoporosis patients and BMP-22 induced BMSCs using qRT-PCR. MiR-19b-3p mimic or inhibitor was transfected into BMP-2 induced BMSCs. Cell proliferation was measured by BrdU method. Protein expression of RUNX2 and COL1A1 were measured by western blot. PcDNA3.1-lncRNA H19 with or without miR-19b-3p mimic was transfected into BMP-2 induced BMSCs.

RESULTS

The expression of miR-19b-3p was significantly up-regulated in postmenopausal osteoporosis patients and BMP-2 induced BMSCs. MiR-19b-3p overexpression dramatically elevated, while miR-19b-3p inhibition decreased cell proliferation of BMSCs. Additionally, protein expression levels of RUNX2 and COL1A1, as well as ALP activity were significantly promoted by miR-19b-3p mimic transfection and inhibited by miR-19b-3p inhibitor transfection. LncRNA H19 was obviously down-regulated in postmenopausal osteoporosis patients. H19 overexpression significantly decreased cell proliferation and differentiation by down-regulating miR-19b-3p. Moreover, the expression of miR-19b-3p was inhibited, while H19 elvated in 17β-estradiol (E2) treated BMSCs in a dose-dependent manner.

CONCLUSION

These data were the first to reveal the critical role of H19/miR-19b-3p in postmenopausal osteoporosis, and provided a new therapeutic target for OP.

Association between high levels of gynoid fat and the increase of bone mineral density in women

Introduction: In women, bone mineral density (BMD) is related to age, estrogenic action, and appendicular skeletal muscle mass (ASMM). The gynoid fat distribution is linked to estrogenic action.Objective: This study aimed to assess whether an increase of gynoid fat is associated with high BMD independent of age and ASMM.Methods: An observational study was performed in women aged between 20 and 79 years. Fat mass, ASMM, and BMD were measured with dual-energy X-ray absorptiometry. The binned scatterplots and multivariate linear regression models were used to study the relationship between hip BMD and age, height, android fat, gynoid fat, and ASMM.Results: Of 673 women invited, 596 accepted to participate. Their mean age was 55.4 ± 12.8 years, weight 63.4 ± 9.4 kg, height 1.61 ± 0.06 m, body mass index 24.54 ± 3.59 kg/m², average hip BMD 0.914 ± 0.122 g/cm², android fat 2.12 ± 0.83 kg, gynoid fat 4.54 ± 1.07 kg, and ASMM 15.15 ± 1.97 kg. The final regression model included age (linear coefficient -0.004; 95% confidence interval [CI]: -0.005 to -0.003; p < 0.001), ASMM (linear coefficient 0.013; 95% CI: 0.009 to 0.018; p < 0.001), and gynoid fat (linear coefficient 0.013; 95% CI: 0.005 to 0.022; p < 0.002).Conclusion: Gynoid fat is associated with BMD in the hip independently of age and ASMM.

LncRNA MALAT1 shuttled by bone marrow-derived mesenchymal stem cells-secreted exosomes alleviates osteoporosis through mediating microRNA-34c/SATB2 axis

Long non-coding RNAs (lncRNAs) have emerged as promising novel modulators during osteogenesis in mesenchymal stem cells (MSCs). Enhanced SATB2 has been demonstrated to promote osteogenic differentiation of bone marrow-derived mesenchymal stem cells (hBMSCs) in patients with osteonecrosis. Preliminary bioinformatic analysis identified putative binding sites between microRNA-34c (miR-34c) and metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) or miR-34c and SATB2 3’UTR. Thus, the current study aimed to clarify the potential functional relevance of MALAT1-containing exosomes from BMSCs in osteoporosis. The extracted exosomes from primary BMSCs were co-cultured with human osteoblasts (hFOB1.19), followed by evaluation of the hFOB1.19 cell proliferation, alkaline phosphatase (ALP) activity and mineralized nodules. The obtained findings indicated that BMSC-Exos promoted the expression of SATB2 in osteoblasts, and SATB2 silencing reduced the ALP activity of osteoblasts and mineralized nodules. MALAT1 acted as a sponge of miR-34c to promote the expression of SATB2. Additionally, BMSCs-derived exosomal MALAT1 promoted osteoblast activity. Moreover, in vivo experiments indicated that miR-34c reversed the effect of MALAT1, and SATB2 reversed the effect of miR-34c in ovariectomized mice. Taken together, this study demonstrates that BMSCs-derived exosomal MALAT1 enhances osteoblast activity in osteoporotic mice by mediating the miR-34c/SATB2 axis.

Up-regulated CST5 inhibits bone resorption and activation of osteoclasts in rat models of osteoporosis via suppression of the NF-κB pathway

Here, we aim at exploring the effect of CST5 on bone resorption and activation of osteoclasts in osteoporosis (OP) rats through the NF‐κB pathway. Microarray analysis was used to screen the OP‐related differentially expressed genes. Osteoporosis was induced in rats by intragastric retinoic acid administration. The serum levels of tartrate‐resistant acid phosphatase (TRAP), bone alkaline phosphatase (BALP) and osteocalcin (OC) and the expression of CD61 on the surface of osteoclasts were examined. The number of osteoclasts and the number and area of resorption pits were detected. Besides, the pathological changes and bone mineral density in bone tissues of rats were assessed. Also, the relationship between CST5 and the NF‐κB pathway was identified through determining the expression of CST5, RANKL, RANK, OPG, p65 and IKB. Poorly expressed CST5 was indicated to affect the OP. CST5 elevation and inhibition of the NF‐κB pathway decreased serum levels of TRAP, BALP and OC and expression of CD61 in vivo and in vitro. In OP rats, CST5 overexpression increased trabecular bones and bone mineral density of bone tissues, but decreased trabecular separation, fat within the bone marrow cavities and the number of osteoclasts through inhibiting the NF‐κB pathway. In vivo experiments showed that CST5 elevation inhibited growth in number and area of osteoclastic resorption pits and restrained osteoclastic bone absorption by inhibiting the NF‐κB pathway. In summary, overexpression of CST5 suppresses the activation and bone resorption of osteoclasts by inhibiting the activation of the NF‐κB pathway.

Time since menopause, but not age, is associated with increased risk of osteoporosis

Objectives: This study aimed to determine whether estrogen deficiency is a sole risk factor for osteoporosis or is also associated with age, through indicators such as gender, age, and time since menopause. Methods: A cross-sectional study was conducted evaluating 938 postmenopausal women who underwent bone mineral densitometry. We collected the following data: age, ethnic group, body mass index, smoking, and time since menopause. These data were correlated to the presence of osteoporosis, according to the T-score of the femur and lumbar spine. Results: The prevalence of osteoporosis was 37.8%. Ethnic group (p = 0.47) and smoking habits (p = 0.19) were not associated with osteoporosis. In the group of women with osteoporosis, mean age was significantly higher (p < 0.001), mean body mass index was significantly lower (p < 0.001), and time since menopause was significantly higher (p < 0.001) than in the group of women with no osteoporosis. After multivariate analysis was performed, the only variables that remained independently associated with osteoporosis were body mass index and time since menopause. Higher body mass index was a protective factor (odds ratio = 0.80 [95% confidence interval 0.76; 0.84], p < 0.001). Time since menopause represented a risk factor for osteoporosis (odds ratio = 1.04 [1.02; 1.06], p < 0.001). When divided into categories, the risk increased after 20 years of menopause and gradually every 5 years. Conclusion: Time since menopause and body mass index were the most important factors associated with osteoporosis, confirming that estrogen deficiency, and not age, is the major cause of the disease.

Bone Morphogenetic Protein-6 Attenuates Type 1 Diabetes Mellitus-Associated Bone Loss

Patients with type 1 diabetes mellitus (T1DM) often suffer from osteopenia or osteoporosis. Although most agree that T1DM-induced hyperglycemia is a risk factor for progressive bone loss, the mechanisms for the link between T1DM and bone loss still remain elusive. In this study, we found that bone marrow-derived mesenchymal stem cells (BMSCs) isolated from T1DM donors were less inducible for osteogenesis than those from non-T1DM donors and further identified a mechanism involving bone morphogenetic protein-6 (BMP6) that was produced significantly less in BMSCs derived from T1DM donors than that in control cells. With addition of exogenous BMP6 in culture, osteogenesis of BMSCs from T1DM donors was restored whereas the treatment of BMP6 seemed not to affect non-T1DM control cells. We also demonstrated that bone mineral density (BMD) was reduced in streptozotocin-induced diabetic mice compared with that in control animals, and intraperitoneal injection of BMP6 mitigated bone loss and increased BMD in diabetic mice. Our results suggest that bone formation in T1DM patients is impaired by reduction of endogenous BMP6, and supplementation of BMP6 enhances osteogenesis of BMSCs to restore BMD in a mouse model of T1DM, which provides insight into the development of clinical treatments for T1DM-assocaited bone loss. Stem Cells Translational Medicine 2019;8:522-534.

Tanshinone prevents alveolar bone loss in ovariectomized osteoporosis rats by up-regulating phosphoglycerate dehydrogenase

Osteoporosis is manifested by reduced bone mass. Tanshinone has been shown to affect osteoclast differentiation, but its role in osteoporosis remains less clear. This study aimed to investigate the effects and molecular mechanisms of tanshinone on osteoporosis. Osteoporosis was induced by bilateral ovariectomy (OVX) in adult female rats treated with or without tanshinone. Trabecular bone structure was assessed by micro-computed tomography (micro-CT). Bone marrow stromal cells (BMSCs) were isolated for analysis of stemness and senescence. mRNA levels of age related genes were examined and the role of the gene that was upregulated by tanshinone treatment was suppressed to determine its involvement in tanshinone mediated effects. Finally, the mechanism underlying tanshinone induced gene upregulation was explored. We found that tanshinone treatment restored alveolar bone structure in OVX rats as well as the stemness and senescence status of BMSCs isolated from OVX rats. Tanshinone upregulated Phgdh mRNA levels and inhibition of phosphoglycerate dehydrogenase Phgdh, the protein encoded by the Phgdh gene, abolished the effects of tanshinone on BMSC stemness and senescence. Finally, we found that OVX lead to hypermethylation of the promoter region of Phgdh which was suppressed by tanshinone treatment. Our study shows that tanshinone potently suppress OVX induced osteoporosis and BMSC senescence through upregulation of PHGDH.

Epigenetic Control of Mesenchymal Stem Cell Fate Decision via Histone Methyltransferase Ash1l

Previous research indicates that knocking out absent, small, or homeotic-like (Ash1l) in mice, a histone 3 lysine 4 (H3K4) trimethyltransferase, can result in arthritis with more severe cartilage and bone destruction. Research has documented the essential role of Ash1l in stem cell fate decision such as hematopoietic stem cells and the progenitors of keratinocytes. Following up on those insights, our research seeks to document the function of Ash1l in skeletal formation, specifically whether it controls the fate decision of mesenchymal progenitor cells. Our findings indicate that in osteoporotic bones, Ash1l was significantly decreased, indicating a positive correlation between bone mass and the expression of Ash1l. Silencing of Ash1l that had been markedly upregulated in differentiated C3H10T1/2 (C3) cells hampered osteogenesis and chondrogenesis but promoted adipogenesis. Consistently, overexpression of an Ash1l SET domain-containing fragment 3 rather than Ash1lΔN promoted osteogenic and chondrogenic differentiation of C3 cells and simultaneously inhibited adipogenic differentiation. This indicates that the role of Ash1l in regulating the differentiation of C3 cells is linked to its histone methyltransferase activity. Subcutaneous ex vivo transplantation experiments confirmed the role of Ash1l in the promotion of osteogenesis. Further experiments proved that Ash1l can epigenetically affect the expression of essential osteogenic and chondrogenic transcription factors. It exerts this impact via modifications in the enrichment of H3K4me3 on their promoter regions. Considering the promotional action of Ash1l on bone, it could potentially prompt new therapeutic strategy to promote osteogenesis. Stem Cells 2019;37:115-127.

Sex Hormones in Acquired Immunity and Autoimmune Disease

Women have stronger immune responses to infections and vaccination than men. Paradoxically, the stronger immune response comes at a steep price, which is the high incidence of autoimmune diseases in women. The reasons why women have stronger immunity and higher incidence of autoimmunity are not clear. Besides gender, sex hormones contribute to the development and activity of the immune system, accounting for differences in gender-related immune responses. Both innate and adaptive immune systems bear receptors for sex hormones and respond to hormonal cues. This review focuses on the role of sex hormones particularly estrogen, in the adaptive immune response, in health, and autoimmune disease with an emphasis on systemic lupus erythematosus.