The role of osteoblasts in energy homeostasis

The role of SphK/S1P/S1PR signaling pathway in bone metabolism

There are a large number of people worldwide who suffer from osteoporosis, which imposes a huge economic burden, so it is necessary to explore the underlying mechanisms to achieve better supportive and curative care outcomes. Sphingosine kinase (SphK) is an enzyme that plays a crucial role in the synthesis of sphingosine-1-phosphate (S1P). S1P with paracrine and autocrine activities that act through its cell surface S1P receptors (S1PRs) and intracellular signals. In osteoporosis, S1P is indispensable for both normal and disease conditions. S1P has complicated roles in regulating osteoblast and osteoclast, respectively, and there have been exciting developments in understanding how SphK/S1P/S1PR signaling regulates these processes in response to osteoporosis therapy. Here, we review the proliferation, differentiation, apoptosis, and functions of S1P, specifically detailing the roles of S1P and S1PRs in osteoblasts and osteoclasts. Finally, we focus on the S1P-based therapeutic approaches in bone metabolism, which may provide valuable insights into potential therapeutic strategies for osteoporosis.

Medications and medical expenditures for diabetic patients with osteoporosis in Beijing, China: A retrospective study

AIMS

This study aimed to clarify the changes in treatment regimens and medical expenditures in diabetic patients with osteoporosis.

METHODS

We recruited 2,853,036 diabetic patients from the Beijing medical insurance database between 2016 and 2018. Among them, 406,221 patients also had osteoporosis. Clinical characteristics, treatment regimens, and medical costs were investigated in diabetic patients with and without osteoporosis.

RESULTS

Diabetes and osteoporosis were most prevalent in participants aged 45---84 years. Compared with diabetic patients without osteoporosis, those with osteoporosis were prone to developing comorbidities and diabetic complications. They often required multiple glucose-lowering drugs and had a higher rate of insulin use. Similarly, osteoporosis leads to an increased number of medications for non-hypoglycemia as well as higher healthcare costs. These medications and costs increased with the number of complications and comorbidities. Interestingly, from 2016 to 2018, although diabetic patients with osteoporosis took more drugs, medical costs were lower year by year.

CONCLUSIONS

Osteoporosis might contribute to a worse condition in diabetic patients, and this population often requires more medications with higher medical costs.

Plasma undercarboxylated osteocalcin dynamics with glycemic stress reflects insulin sensitivity and beta-cell function in humans with and without T2DM

This study aimed to better understand the relationship between bone-related biomarkers and nutrient stress in the context of metabolic health. We investigated plasma osteocalcin (OC) during an oral glucose challenge and experimental hyperinsulinemia in Type 2 diabetes (T2DM) and lean healthy controls (LHC). Older individuals with obesity and T2DM (n = 9) and young LHCs (n = 9) underwent a 75g oral glucose tolerance test (OGTT) and a 40 mU/m2/min hyperinsulinemic-euglycemic clamp. Plasma undercarboxylated OC (ucOC) and total OC were measured at baseline, 60mins, and 120mins of the OGTT and clamp via ELISA. In addition, plasma alkaline phosphatase (ALP), leptin, adiponectin, Vitamin D and insulin were measured and indices of insulin sensitivity and β-cell function were derived. The T2DM group had lower (p<0.05) ucOC and ucOC:total OC ratio than LHC during both the OGTT and clamp. Further, baseline ucOC was positively correlated to indices of β-cell function and negatively correlated to indices of insulin resistance when both groups were combined (all p<0.05). Suppression of OC observed in T2DM may be related to glucose intolerance and insulin resistance. Similarly, our data suggest that the observed phenotypic differences between groups are likely a product of long-term glucose dysregulation rather than acute flux in glucose or insulin.

Consequences of Aging on Bone

With the aging of the global population, the incidence of musculoskeletal diseases has been increasing, seriously affecting people's health. As people age, the microenvironment within skeleton favors bone resorption and inhibits bone formation, accompanied by bone marrow fat accumulation and multiple cellular senescence. Specifically, skeletal stem/stromal cells (SSCs) during aging tend to undergo adipogenesis rather than osteogenesis. Meanwhile, osteoblasts, as well as osteocytes, showed increased apoptosis, decreased quantity, and multiple functional limitations including impaired mechanical sensing, intercellular modulation, and exosome secretion. Also, the bone resorption function of macrophage-lineage cells (including osteoclasts and preosteoclasts) was significantly enhanced, as well as impaired vascularization and innervation. In this study, we systematically reviewed the effect of aging on bone and the within microenvironment (including skeletal cells as well as their intracellular structure variations, vascular structures, innervation, marrow fat distribution, and lymphatic system) caused by aging, and mechanisms of osteoimmune regulation of the bone environment in the aging state, and the causal relationship with multiple musculoskeletal diseases in addition with their potential therapeutic strategy.

Microplastics - Back to Reality: Impact of Pristine and Aged Microplastics in Soil on Earthworm Eisenia fetida under Environmentally Relevant Conditions

Recently, studies have highlighted the potential danger for soil organisms posed by film-derived microplastics (MPs). However, the majority of those does not accurately reflect the field conditions and the degree of MP contamination that can be found in actual settings. To fill the gap between laboratory and field scenarios, the polyethylene (PE) plastic film was made into PE-MPs and aged. Toxicity and molecular mechanisms of pristine PE-MPs (PMPs) and aged PE-MPs (AMPs) with the concentration at 500 mg/kg of dry weight were determined after 14 days of exposure by measuring the oxidative stress, osmoregulation pressure, gut microbiota, and metabolic responses in earthworms under environmentally relevant conditions. Our research showed that, when compared to PMPs (13.13 ± 1.99 items/g), AMPs accumulated more (16.19 ± 8.47 items/g), caused more severe tissue lesions, and caused a higher increase of cell membrane osmotic pressure in earthworms' intestines. Furthermore, the proportion of probiotic bacteria Lactobacillus johnsonii in the gut bacterial communities was 24.26%, 23.26%, and 12.96%, while the proportion of pathogenic bacteria of the phylum Verrucomicrobia was 2.28%, 4.79%, and 10.39% in the control and PMP- and AMP-exposed earthworms, indicating that the decrease in number of probiotic bacteria and the increase in number of pathogenic bacteria were more pronounced in the gut of AMP- rather than PMP-exposed earthworms. Metabolomic analysis showed that AMP exposure reduced earthworm energy metabolites. Consequently, the constant need for energy may result in protein catabolism, which raises levels of some amino acids, disturbs normal cell homeostasis, causes changes of cell membrane osmolarity, and destroys the cell structure. Our studies showed that aged MPs, with the same characteristics as those found in the environment, have greater toxicity than pristine MPs. The results of this study broaden our understanding of the toxicological effects of MPs on soil organisms under environmentally relevant conditions.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

Effect of pilose antler polypeptide on the mechanism of bone homeostasis in osteoporosis

Osteoporosis stands out as a prevalent metabolic disorder, bearing significant repercussions on human well-being and overall quality of life. It remains an urgent concern within the global public health framework due to its widespread occurrence. Osteoporosis arises from an abnormal metabolism in osteoblasts and osteoclasts, resulting in a disruption of the delicate equilibrium between bone formation and bone resorption. Within this context, deer antler peptides emerge as natural active compounds, wielding a pivotal role in governing the differentiation, proliferation, and mineralization of osteoblasts, as well as influencing the activity of osteoclasts. This article aims to consolidate our comprehension of the mechanisms underpinning the dynamic balance between bone formation and resorption, meticulously orchestrated by osteoblasts and osteoclasts in osteoporosis. Furthermore, it offers a comprehensive overview of how deer antler peptides, through their modulation of relevant signaling pathways, contribute to the enhancement of bone homeostasis. These insights deepen our understanding of the pathological processes through which deer antler peptides ameliorate bone homeostasis, while also presenting novel strategies for osteoporosis management.

stVAE deconvolves cell-type composition in large-scale cellular resolution spatial transcriptomics

MOTIVATION

Recent rapid developments in spatial transcriptomic techniques at cellular resolution have gained increasing attention. However, the unique characteristics of large-scale cellular resolution spatial transcriptomic datasets, such as the limited number of transcripts captured per spot and the vast number of spots, pose significant challenges to current cell-type deconvolution methods.

RESULTS

In this study, we introduce stVAE, a method based on the variational autoencoder framework to deconvolve the cell-type composition of cellular resolution spatial transcriptomic datasets. To assess the performance of stVAE, we apply it to five datasets across three different biological tissues. In the Stereo-seq and Slide-seqV2 datasets of the mouse brain, stVAE accurately reconstructs the laminar structure of the pyramidal cell layers in the cortex, which are mainly organized by the subtypes of telencephalon projecting excitatory neurons. In the Stereo-seq dataset of the E12.5 mouse embryo, stVAE resolves the complex spatial patterns of osteoblast subtypes, which are supported by their marker genes. In Stereo-seq and Pixel-seq datasets of the mouse olfactory bulb, stVAE accurately delineates the spatial distributions of known cell types. In summary, stVAE can accurately identify spatial patterns of cell types and their relative proportions across spots for cellular resolution spatial transcriptomic data. It is instrumental in understanding the heterogeneity of cell populations and their interactions within tissues.

AVAILABILITY AND IMPLEMENTATION

stVAE is available in GitHub (https://github.com/lichen2018/stVAE) and Figshare (https://figshare.com/articles/software/stVAE/23254538).

Single-cell transcriptomic analysis identifies a highly replicating Cd168+ skeletal stem/progenitor cell population in mouse long bones

Skeletal stem/progenitor cells (SSPCs) are tissue-specific stem/progenitor cells localized within skeletons and contribute to bone development, homeostasis, and regeneration. However, the heterogeneity of SSPC populations in mouse long bones and their respective regenerative capacity remain to be further clarified. In this study, we perform integrated analysis using single-cell RNA sequencing (scRNA-seq) datasets of mouse hindlimb buds, postnatal long bones, and fractured long bones. Our analyses reveal the heterogeneity of osteochondrogenic lineage cells and recapitulate the developmental trajectories during mouse long bone growth. In addition, we identify a novel Cd168+ SSPC population with highly replicating capacity and osteochondrogenic potential in embryonic and postnatal long bones. Moreover, the Cd168+ SSPCs can contribute to newly formed skeletal tissues during fracture healing. Furthermore, the results of multicolor immunofluorescence show that Cd168+ SSPCs reside in the superficial zone of articular cartilage as well as in growth plates of postnatal mouse long bones. In summary, we identify a novel Cd168+ SSPC population with regenerative potential in mouse long bones, which adds to the knowledge of the tissue-specific stem cells in skeletons.

The role of sclerostin in lipid and glucose metabolism disorders

Lipid and glucose metabolism are critical for human activities, and their disorders can cause diabetes and obesity, two prevalent metabolic diseases. Studies suggest that the bone involved in lipid and glucose metabolism is emerging as an endocrine organ that regulates systemic metabolism through bone-derived molecules. Sclerostin, a protein mainly produced by osteocytes, has been therapeutically targeted by antibodies for treating osteoporosis owing to its ability to inhibit bone formation. Moreover, recent evidence indicates that sclerostin plays a role in lipid and glucose metabolism disorders. Although the effects of sclerostin on bone have been extensively examined and reviewed, its effects on systemic metabolism have not yet been well summarized. In this paper, we provide a systemic review of the effects of sclerostin on lipid and glucose metabolism based on in vitro and in vivo evidence, summarize the research progress on sclerostin, and prospect its potential manipulation for obesity and diabetes treatment.

Bone marrow adiposity modulation after long duration spaceflight in astronauts

Space travel requires metabolic adaptations from multiple systems. While vital to bone and blood production, human bone marrow adipose (BMA) tissue modulation in space is unknown. Here we show significant downregulation of the lumbar vertebrae BMA in 14 astronauts, 41 days after landing from six months' missions on the International Space Station. Spectral analyses indicated depletion of marrow adipose reserves. We then demonstrate enhanced erythropoiesis temporally related to low BMA. Next, we demonstrated systemic and then, local lumbar vertebrae bone anabolism temporally related to low BMA. These support the hypothesis that BMA is a preferential local energy source supplying the hypermetabolic bone marrow postflight, leading to its downregulation. A late postflight upregulation abolished the lower BMA of female astronauts and BMA modulation amplitude was higher in younger astronauts. The study design in the extreme environment of space can limit these conclusions. BMA modulation in astronauts can help explain observations on Earth.

The Relationship between Renin-Angiotensin-Aldosterone System (RAAS) Activity, Osteoporosis and Estrogen Deficiency in Type 2 Diabetes

Type 2 diabetes (T2D) is associated with a plethora of comorbidities, including osteoporosis, which occurs due to an imbalance between bone resorption and formation. Numerous mechanisms have been explored to understand this association, including the renin-angiotensin-aldosterone system (RAAS). An upregulated RAAS has been positively correlated with T2D and estrogen deficiency in comorbidities such as osteoporosis in humans and experimental studies. Therefore, research has focused on these associations in order to find ways to improve glucose handling, osteoporosis and the downstream effects of estrogen deficiency. Upregulation of RAAS may alter the bone microenvironment by altering the bone marrow inflammatory status by shifting the osteoprotegerin (OPG)/nuclear factor kappa-Β ligand (RANKL) ratio. The angiotensin-converting-enzyme/angiotensin II/Angiotensin II type 1 receptor (ACE/Ang II/AT1R) has been evidenced to promote osteoclastogenesis and decrease osteoblast formation and differentiation. ACE/Ang II/AT1R inhibits the wingless-related integration site (Wnt)/β-catenin pathway, which is integral in bone formation. While a lot of literature exists on the effects of RAAS and osteoporosis on T2D, the work is yet to be consolidated. Therefore, this review looks at RAAS activity in relation to osteoporosis and T2D. This review also highlights the relationship between RAAS activity, osteoporosis and estrogen deficiency in T2D.

Peroxisome proliferator activated receptor-γ in osteoblasts controls bone formation and fat mass by regulating sclerostin expression

The nuclear receptor peroxisome proliferator activated receptor-γ (PPARγ) is a key contributor to metabolic function via its adipogenic and insulin-sensitizing functions, but it has negative effects on skeletal homeostasis. Here, we questioned whether the skeletal and metabolic actions of PPARγ are linked. Ablating Pparg expression in osteoblasts and osteocytes produced a high bone mass phenotype, secondary to increased osteoblast activity, and a reduction in subcutaneous fat mass because of reduced fatty acid synthesis and increased fat oxidation. The skeletal and metabolic phenotypes in Pparg mutants proceed from the regulation of sclerostin production by PPARγ. Mutants exhibited reductions in skeletal Sost expression and serum sclerostin levels while increasing production normalized both phenotypes. Importantly, disrupting the production of sclerostin synergized with the insulin-sensitizing actions of a PPARγ agonist while preventing bone loss. These data suggest that modulating sclerostin action may prevent bone loss associated with anti-diabetic therapies and augment their metabolic actions.

Icariin promotes osteogenic differentiation by upregulating alpha-enolase expression

Osteogenic differentiation is a crucial biological process for maintaining bone remodelling. Aerobic glycolysis is the main source of energy for osteogenic differentiation. Alpha-enolase (Eno1), a glycolytic enzyme, is a therapeutic target for numerous diseases. Icariin, a principal active component of the traditional Chinese medicine Epimedium grandiflorum, can stimulate osteogenic differentiation. Here, we aimed to determine if icariin promotes osteogenic differentiation via Eno1. Icariin (1 μM) significantly promoted osteogenic differentiation of MC3T3-E1 cells. Icariin upregulated Eno1 protein and gene expressions during osteogenic differentiation. Moreover, ENOblock, a specific inhibitor of Eno1, markedly inhibited icariin-induced osteogenic differentiation. Futhermore, western blot assay showed that Eno1 might mediate osteogenic differentiation through the BMP/Smad4 signalling pathway. Collectively, Eno1 could be a promising drug target for icariin to regulate osteogenic differentiation.

RNA-binding Protein QKI Inhibits Osteogenic Differentiation Via Suppressing Wnt Pathway

BACKGROUND

Dysregulation of MSCs differentiation is associated with many pathophysiological processes. Genetically modified MSCs transplantation helps restore bone loss efficiently.

METHODS

BMSCs-specific QKI overexpressing and knockdown mice were built to explore QKI's role in bone formation and fat accumulation. Primary BMSCs with QKI overexpression and knockout were subjected to osteogenic and adipogenic differentiation. ALP staining and oil red O staining were performed to evaluate the differences between the groups. RNA immunoprecipitation was performed to identify the QKI-related pathway. QKI deficient BMSCs were transplanted into mice with glucocorticoid-induced osteoporosis to evaluate its therapeutic potential.

RESULTS

Mice harboring BMSC-specific transgenic QKI exhibited reduced bone mass, while BMSC-specific QKI-deficient mice showed an increase in bone mass. Osteogenic differentiation of QKI deficient BMSCs was promoted and adipogenic differentiation was inhibited, while QKI overexpression in BMSCs displayed the opposite effects. To define the underlying mechanisms, RIP sequencing was performed. Wnt pathway-related genes were the putative direct target mRNAs of QKI, Canonical Wnt pathway activation was involved in QKI's effects on osteogenic differentiation. RNA immunoprecipitation quantitative real-time Polymerase Chain Reaction (PCR) and RNA fluorescence in situ hybridization experiments further validated that QKI repressed the expressions of Wnt5b, Fzd7, Dvl3 and β-catenin via direct binding to their putative mRNA specific sites. Glucocorticoid-induced osteoporotic mice transplanted with QKI deficient BMSCs exhibited less bone loss compared with mice transplanted with control BMSCs.

CONCLUSIONS

QKI suppressed BMSCs osteogenic differentiation by downregulating the expressions of Wnt5b, Fzd7, Dvl3 and β-catenin. Loss of QKI in BMSCs transplantation may provide a new strategy for the treatment of orthopedic diseases such as osteoporosis.

ER Stress, the Unfolded Protein Response and Osteoclastogenesis: A Review

Endoplasmic reticulum (ER) stress and its adaptive mechanism, the unfolded protein response (UPR), are triggered by the accumulation of unfolded and misfolded proteins. During osteoclastogenesis, a large number of active proteins are synthesized. When an imbalance in the protein folding process occurs, it causes osteoclasts to trigger the UPR. This close association has led to the role of the UPR in osteoclastogenesis being increasingly explored. In recent years, several studies have reported the role of ER stress and UPR in osteoclastogenesis and bone resorption. Here, we reviewed the relevant literature and discussed the UPR signaling cascade response, osteoclastogenesis-related signaling pathways, and the role of UPR in osteoclastogenesis and bone resorption in detail. It was found that the UPR signal (PERK, CHOP, and IRE1-XBP1) promoted the expression of the receptor activator of the nuclear factor-kappa B ligand (RANKL) in osteoblasts and indirectly enhanced osteoclastogenesis. IRE1 promoted osteoclastogenesis via promoting NF-κB, MAPK signaling, or the release of pro-inflammatory factors (IL-6, IL-1β, and TNFα). CREBH promoted osteoclast differentiation by promoting NFATc1 expression. The PERK signaling pathway also promoted osteoclastogenesis through NF-κB and MAPK signaling pathways, autophagy, and RANKL secretion from osteoblasts. However, salubrinal (an inhibitor of eIF2α dephosphorylation that upregulated p-eIF2α expression) directly inhibited osteoclastogenesis by suppressing NFATc1 expression and indirectly promoted osteoclastogenesis by promoting RANKL secretion from osteoblasts. Therefore, the specific effects and mechanisms of p-PERK and its downstream signaling on osteoclastogenesis still need further experiments to confirm. In addition, the exact role of ATF6 and BiP in osteoclastogenesis also required further exploration. In conclusion, our detailed and systematic review provides some references for the next step to fully elucidate the relationship between UPR and osteoclastogenesis, intending to provide new insights for the treatment of diseases caused by osteoclast over-differentiation, such as osteoporosis.

Influence of Cholesterol on the Regulation of Osteoblast Function

Bone is a dynamic tissue composed of cells, an extracellular matrix, and mineralized portion. Osteoblasts are responsible for proper bone formation and remodeling, and function. These processes are endergonic and require cellular energy in the form of adenosine triphosphate (ATP), which is derived from various sources such as glucose, fatty acids, and amino acids. However, other lipids such as cholesterol have also been found to play a critical role in bone homeostasis and can also contribute to the overall bioenergetic capacity of osteoblasts. In addition, several epidemiological studies have found a link between elevated cholesterol, cardiovascular disease, an enhanced risk of osteoporosis, and increased bone metastasis in cancer patients. This review focuses on how cholesterol, its derivatives, and cholesterol-lowering medications (statins) regulate osteoblast function and bone formation. It also highlights the molecular mechanisms underlying the cholesterol-osteoblast crosstalk.

Identification of Differentially Expressed Genes and Molecular Pathways Involved in Osteoclastogenesis Using RNA-seq

Osteoporosis is a disease that is characterised by reduced bone mineral density (BMD) and can be exacerbated by the excessive bone resorption of osteoclasts (OCs). Bioinformatic methods, including functional enrichment and network analysis, can provide information about the underlying molecular mechanisms that participate in the progression of osteoporosis. In this study, we harvested human OC-like cells differentiated in culture and their precursor peripheral blood mononuclear cells (PBMCs) and characterised the transcriptome of the two cell types using RNA-sequencing in order to identify differentially expressed genes. Differential gene expression analysis was performed in RStudio using the edgeR package. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to identify enriched GO terms and signalling pathways, with inter-connected regions characterised using protein-protein interaction analysis. In this study, we identified 3201 differentially expressed genes using a 5% false discovery rate; 1834 genes were upregulated, whereas 1367 genes were downregulated. We confirmed a significant upregulation of several well-established OC genes including CTSK, DCSTAMP, ACP5, MMP9, ITGB3, and ATP6V0D2. The GO analysis suggested that upregulated genes are involved in cell division, cell migration, and cell adhesion, while the KEGG pathway analysis highlighted oxidative phosphorylation, glycolysis and gluconeogenesis, lysosome, and focal adhesion pathways. This study provides new information about changes in gene expression and highlights key biological pathways involved in osteoclastogenesis.

Arl13b promotes the proliferation, migration, osteogenesis, and mechanosensation of osteoblasts

Primary cilia are microtubule-based organelles presenting on the surface of most postmitotic mammalian cells. As being signaling hubs and sensory organelles, primary cilia can respond to mechanical and chemical stimuli from the extracellular environment. Arl13b (ADP-ribosylation factor-like 13B), an atypical Arf/Arl family GTPase, was identified in genetic screening as a protein essential for maintaining the integrity of cilia and neural tubes. Previous studies on Arl13b have mostly focused on its role in the development of neural tubes, polycystic kidneys, and tumors, but no role in bone patterns was described. This study reported the essential roles of Arl13b in bone formation and osteogenic differentiation. Arl13b was highly expressed in bone tissues and osteoblasts, positively correlated with osteogenic activity during bone development. Furthermore, Arl13b was essential for primary cilium maintenance and Hedgehog signaling activation in osteoblasts. Arl13b knockdown in osteoblasts decreased the length of primary cilia and the upregulated levels of Gli1, Smo, and Ptch1 upon Smo agonist treatment. Additionally, Arl13b knockdown inhibited cell proliferation and migration. Moreover, Arl13b mediated osteogenesis and cell mechanosensation. Cyclic tension strain upregulated the Arl13b expression. Arl13b knockdown suppressed osteogenesis and mitigated cyclic tension strain-induced osteogenesis. These results suggest that Arl13b have important roles in bone formation and mechanosensation.

Integrative Analysis of ceRNA Networks in human periodontal ligament stem cells under hypoxia

OBJECTIVE

This study aims to investigate the regulatory effect of hypoxia on human periodontal ligament stem cells (PDLSCs) through RNA sequencing (RNA SEQ). Human PDLSCs were cultured in normoxia (20% O₂ ) or hypoxia (2% O₂ ).

MATERIAL AND METHODS

Total RNA was extracted and sequenced. The expression profiles of circRNAs, lncRNAs, and miRNAs were determined, and the lncRNA/circRNA-miRNA-mRNA networks were analyzed.

RESULTS

In total, 15 miRNAs, 449 lncRNAs, and 53 circRNAs were differentially expressed. Among them, 21 circRNAs, 262 lncRNAs, 5 miRNAs, and 5 mRNAs were selected to construct competing endogenous RNA (ceRNA) networks. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were carried out to explore potential related pathways and regulatory functions. Several ceRNA axes (lncRNA-FTX/circRNA-FAT1-hsa-miR-4781-3p-SMAD5 and circRNA LPAR1-hsa-miR-342-3p-ADAR) may provide a theoretical basis on the study of osteogenic differentiation of PDLSCs under hypoxia.

CONCLUSION

This study revealed that the expression profiles of circRNAs, lncRNAs, and miRNAs had changed significantly in PDLSCs cultured in 2% O₂ ; specific circRNAs/lncRNAs may play a competitive role in the differentiation of PDLSCs.

Bone mineral density and normal-weight obesity syndrome: beyond body weight and body mass index

INTRODUCTION

This study aimed to evaluate, for the first time, the bone profile of adult women and men with and without normal-weight obesity (NWO) syndrome and its association with bone health-related nutrient intake, anthropometry, and body composition.

MATERIALS AND METHODS

This was a cross-sectional study of adults aged between 20 and 59 years with normal body weight, separated according to body fat (BF) percentage into NWO and non-NWO syndrome groups. BF > 30% and > 19% were considered high for women and men, respectively. Socioeconomic, physical activity, food consumption, anthropometric, and body composition data were evaluated. Student's t-test or Mann-Whitney test and Pearson's χ² or Fisher's exact tests were applied for comparisons. Multiple linear regression models were developed, with bone parameters as the dependent variables and anthropometric, body composition, and food consumption data as the main independent variables.

RESULTS

The sample consisted of 224 adults (69.2% women) with a median (interquartile range) age of 23 (21-25) years, 71% of whom had NWO syndrome. Compared with women, a higher percentage of men had a lower-than-expected spinal bone mineral density (BMD) Z-score for age (10%; p = 0.0214). Bone parameters were similar between groups. Spinal BMD was negatively associated with male sex and positively associated with body weight. The femoral BMD was negatively associated with BF percentage and positively associated with body mass index.

CONCLUSION

The negative association of BMD with BF percentage may suggest a higher risk of bone alterations in individuals with NWO syndrome and should be monitored over time.

Age- and sex-specific differences in the association of serum osteocalcin and cardiometabolic risk factors in type 2 diabetes

BACKGROUND

Serum osteocalcin levels are closely related to metabolic syndrome and cardiovascular disease. This study aimed to investigate the relationship between serum osteocalcin levels and cardiometabolic risk factors in patients with type 2 diabetes (T2D) according to age and sex.

METHODS

This cross-sectional study included 1500 patients with T2D (991 men and 509 women) aged ≥ 18 years old. The age- and sex-specific disparities in glycemic and lipid control, as well as cardiometabolic risk factors were evaluated.

RESULTS

The levels of serum osteocalcin were significantly higher in women aged > 50 years compared with women aged ≤ 50 years (15.6 ± 6.5 ng/mL vs. 11.3 ± 4.5 ng/mL, p < 0.0001). However, this was lower in men aged > 50 years than men aged ≤ 50 years (12.2 ± 4.2 ng/mL vs. 12.9 ± 4.3 ng/mL, p = 0.0081). We performed correlation analyses of serum osteocalcin and cardiometabolic parameters. Serum osteocalcin concentrations were negative associated with FBG and HbA1c levels in women and men ≤ 50 years old, but not in men aged > 50 years old. Serum osteocalcin were negatively correlated with TG and positively correlated with HDL-C and LDL-C only in men aged ≤ 50 years. In binary logistic regression analysis, serum osteocalcin levels were associated with multiple cardiovascular risk factors, as follows: overweight/obese (odds ratio [OR], 0.944; 95% confidence interval [CI], 0.9-0.991, p = 0.02) in men aged > 50 years; high HbA1C and high FBG in women and men aged ≤ 50 years, but not in men aged > 50 years; after adjustment for confounding factors, high TG (OR, 0.905; 95% CI 0.865-0.947, p < 0.0001), metabolic syndrome (OR, 0.914; 95% CI 0.874-0.956, p < 0.0001), and low high-density lipoprotein cholesterol (OR, 0.933; 95% CI, 0.893-0.975, p = 0.002) were seen in men aged ≤ 50 years only.

CONCLUSIONS

Serum osteocalcin level has significant relationships with cardiometabolic risk factors and several age- and sex-related differences in patients with T2D. Decreased serum osteocalcin levels are associated with a worse cardiometabolic risk profile.

The Metabolic Features of Osteoblasts: Implications for Multiple Myeloma (MM) Bone Disease

The study of osteoblast (OB) metabolism has recently received increased attention due to the considerable amount of energy used during the bone remodeling process. In addition to glucose, the main nutrient for the osteoblast lineages, recent data highlight the importance of amino acid and fatty acid metabolism in providing the fuel necessary for the proper functioning of OBs. Among the amino acids, it has been reported that OBs are largely dependent on glutamine (Gln) for their differentiation and activity. In this review, we describe the main metabolic pathways governing OBs' fate and functions, both in physiological and pathological malignant conditions. In particular, we focus on multiple myeloma (MM) bone disease, which is characterized by a severe imbalance in OB differentiation due to the presence of malignant plasma cells into the bone microenvironment. Here, we describe the most important metabolic alterations involved in the inhibition of OB formation and activity in MM patients.

Static magnetic field: A potential tool of controlling stem cells fates for stem cell therapy in osteoporosis

Osteoporosis is a kind of bone diseases characterized by dynamic imbalance of bone formation and bone absorption, which is prone to fracture, and seriously endangers human health. At present, there is a lack of highly effective drugs for it, and the existing measures all have some side effects. In recent years, mesenchymal stem cell therapy has brought a certain hope for osteoporosis, while shortcomings such as homing difficulty and unstable therapeutic effects limit its application widely. Therefore, it is extremely urgent to find effective and reliable means/drugs for adjuvant stem cell therapy or develop new research techniques. It has been reported that static magnetic fields(SMFs) has a certain alleviating and therapeutic effect on varieties of bone diseases, also promotes the proliferation and osteogenic differentiation of mesenchymal stem cells derived from different tissues to a certain extent. Basing on the above background, this article focuses on the key words "static/constant magnetic field, mesenchymal stem cell, osteoporosis", combined literature and relevant contents were studied to look forward that SMFs has unique advantages in the treatment of osteoporosis with mesenchymal stem cells, which can be used as an application tool to promote the progress of stem cell therapy in clinical application.

A Novel Prenylflavonoid Icariside I Ameliorates Estrogen Deficiency-Induced Osteoporosis via Simultaneous Regulation of Osteoblast and Osteoclast Differentiation

Regulation of osteoblast-mediated bone formation and osteoclast-mediated bone resorption is crucial for bone health. Currently, most clinical drugs for osteoporosis treatment such as bisphosphonates are commonly used to inhibit bone resorption but unable to promote bone formation. In this study, we discovered for the first time that icariside I (GH01), a novel prenylflavonoid isolated from Epimedium, can effectively ameliorate estrogen deficiency-induced osteoporosis with enhancement of trabecular and cortical bone in an ovariectomy (OVX) mouse model. Mechanistically, our in vitro results showed that GH01 repressed osteoclast differentiation and resorption through inhibition of RANKL-induced TRAF6-MAPK-p38-NFATc1 cascade. Simultaneously, we also found that GH01 dose-dependently promoted osteoblast differentiation and formation by inhibiting adipogenesis and accelerating energy metabolism of osteoblasts. In addition, both in vitro and in vivo studies also suggested that GH01 is not only a non-toxic natural small molecule but also beneficial for restoration of liver injury in OVX mice. These results demonstrated that GH01 has great potential for osteoporosis treatment by simultaneous regulation of osteoblast and osteoclast differentiation.

Hypoxia Pathway in Osteoporosis: Laboratory Data for Clinical Prospects

The hypoxia pathway not only regulates the organism to adapt to the special environment, such as short-term hypoxia in the plateau under normal physiological conditions, but also plays an important role in the occurrence and development of various diseases such as cancer, cardiovascular diseases, osteoporosis. Bone, as a special organ of the body, is in a relatively low oxygen environment, in which the expression of hypoxia-inducible factor (HIF)-related molecules maintains the necessary conditions for bone development. Osteoporosis disease with iron overload endangers individuals, families and society, and bone homeostasis disorder is linked to some extent with hypoxia pathway abnormality, so it is urgent to clarify the hypoxia pathway in osteoporosis to guide clinical medication efficiently. Based on this background, using the keywords "hypoxia/HIF, osteoporosis, osteoblasts, osteoclasts, osteocytes, iron/iron metabolism", a matching search was carried out through the Pubmed and Web Of Science databases, then the papers related to this review were screened, summarized and sorted. This review summarizes the relationship and regulation between the hypoxia pathway and osteoporosis (also including osteoblasts, osteoclasts, osteocytes) by arranging the references on the latest research progress, introduces briefly the application of hyperbaric oxygen therapy in osteoporosis symptoms (mechanical stimulation induces skeletal response to hypoxic signal activation), hypoxic-related drugs used in iron accumulation/osteoporosis model study, and also puts forward the prospects of future research.

Update on the Role of Glucocorticoid Signaling in Osteoblasts and Bone Marrow Adipocytes During Aging

PURPOSE OF REVIEW

Bone marrow adipose tissue (BMAT) in the skeleton likely plays a variety of physiological and pathophysiological roles that are not yet fully understood. In elucidating the complex relationship between bone and BMAT, glucocorticoids (GCs) are positioned to play a key role, as they have been implicated in the differentiation of bone marrow mesenchymal stem cells (BMSCs) between osteogenic and adipogenic lineages. The purpose of this review is to illuminate aspects of both endogenous and exogenous GC signaling, including the influence of GC receptors, in mechanisms of bone aging including relationships to BMAT.

RECENT FINDINGS

Harmful effects of GCs on bone mass involve several cellular pathways and events that can include BMSC differentiation bias toward adipogenesis and the influence of mature BMAT on bone remodeling through crosstalk. Interestingly, BMAT involvement remains poorly explored in GC-induced osteoporosis and warrants further investigation. This review provides an update on the current understanding of the role of glucocorticoids in the biology of osteoblasts and bone marrow adipocytes (BMAds).

MicroRNA-181a-5p Curbs Osteogenic Differentiation and Bone Formation Partially Through Impairing Runx1-Dependent Inhibition of AIF-1 Transcription

BACKGRUOUND

Evidence has revealed the involvement of microRNAs (miRNAs) in modulating osteogenic differentiation, implying the promise of miRNA-based therapies for treating osteoporosis. This study investigated whether miR-181a-5p influences osteogenic differentiation and bone formation and aimed to establish the mechanisms in depth.

METHODS

Clinical serum samples were obtained from osteoporosis patients, and MC3T3-E1 cells were treated with osteogenic induction medium (OIM) to induce osteogenic differentiation. miR-181a-5p-, Runt-related transcription factor 1 (Runx1)-, and/or allograft inflammatory factor-1 (AIF-1)-associated oligonucleotides or vectors were transfected into MC3T3-E1 cells to explore their function in relation to the number of calcified nodules, alkaline phosphatase (ALP) staining and activity, expression levels of osteogenesis-related proteins, and apoptosis. Luciferase activity, RNA immunoprecipitation, and chromatin immunoprecipitation assays were employed to validate the binding relationship between miR-181a-5p and Runx1, and the transcriptional regulatory relationship between Runx1 and AIF-1. Ovariectomy (OVX)-induced mice were injected with a miR-181a-5p antagonist for in vivo verification.

RESULTS

miR-181a-5p was highly expressed in the serum of osteoporosis patients. OIM treatment decreased miR-181a-5p and AIF-1 expression, but promoted Runx1 expression in MC3T-E1 cells. Meanwhile, upregulated miR-181a-5p suppressed OIM-induced increases in calcified nodules, ALP content, and osteogenesis-related protein expression. Mechanically, miR-181a-5p targeted Runx1, which acted as a transcription factor to negatively modulate AIF-1 expression. Downregulated Runx1 suppressed the miR-181a-5p inhibitor-mediated promotion of osteogenic differentiation, and downregulated AIF-1 reversed the miR-181a-5p mimic-induced inhibition of osteogenic differentiation. Tail vein injection of a miR-181a-5p antagonist induced bone formation in OVX-induced osteoporotic mice.

CONCLUSION

In conclusion, miR-181a-5p affects osteogenic differentiation and bone formation partially via the modulation of the Runx1/AIF-1 axis.

CX3CL1 deficiency ameliorates inflammation, apoptosis and accelerates osteogenic differentiation, mineralization in LPS-treated MC3T3-E1 cells via its receptor CX3CR1

BACKGROUND

Osteoporosis is a devastating skeletal disease responsible for bone fragility and fracture. CX3C chemokine ligand 1 (CX3CL1) is an inflammatory chemokine which has been identified to possess increased expression in the serum of postmenopausal osteoporotic patients. This paper was to illuminate the impacts of CX3CL1 on inflammation, apoptosis and osteogenic differentiation, mineralization in LPS-treated osteoblasts and investigate the regulatory mechanism.

METHODS

The viability of MC3T3-E1 cells exposed to elevating doses of LPS was detected by CCK-8 assay. CX3CL1 and C-X3-C motif chemokine receptor 1 (CX3CR1) expression were detected by RT-qPCR and western blot. CX3CR1 expression was examined again following CX3CL1 depletion. The binding of CX3CL1 with CX3CR1 was testified through Co-IP assay. In MC3T3-E1 cells co-transduced with CX3CL1 interference and CX3CR1 overexpression plasmids following LPS exposure, cell activity and inflammation were separately estimated via CCK-8 assay and RT-qPCR. Apoptosis was measured by TUNEL assay and western blot. Osteoblast differentiation was evaluated by ALP activity assay, RT-qPCR and western blot. Osteoblast mineralization was assessed by ARS staining, RT-qPCR and western blot. Results The experimental data presented that LPS attenuated the viability and enhanced CX3CL1 and CX3CR1 expression in MC3T3-E1 cells in a dose-dependent manner. CX3CR1 interacted with CX3CL1 and was positively modulated by CX3CL1. The suppressive role of CX3CL1 absence in LPS-evoked viability decrease, inflammation and apoptosis in MC3T3-E1 cells was reversed by CX3CR1 elevation. Besides, CX3CR1 reversed the promoted osteoblast differentiation and mineralization imposed by CX3CL1 interference.

CONCLUSIONS

CX3CL1 knockdown eased inflammation, apoptosis and promoted osteogenic differentiation, mineralization in MC3T3-E1 cells upon LPS exposure through down-regulating CX3CR1.

Endocrine Functions of Sclerostin

Sclerostin, the product of the SOST gene has primarily been studied for its profound impact on bone mass. By interacting with LRP5 and LRP6, the glycoprotein suppresses the propagation of Wnt signals to β-catenin and thereby suppresses new bone formation. In this review, we discuss emerging data which suggest that sclerostin also acts outside the skeleton to influence metabolism. In humans, serum sclerostin levels are associated with body mass index and indices of metabolic function. Likewise, genetic mouse models of Sost gene deficiency indicate sclerostin influences adipocyte development and insulin signaling. These data raise the possibility that sclerostin neutralization may be effective at treating two epidemic conditions: osteoporosis and obesity.

MOTS-c Functionally Prevents Metabolic Disorders

Mitochondrial-derived peptides are a family of peptides encoded by short open reading frames in the mitochondrial genome, which have regulatory effects on mitochondrial functions, gene expression, and metabolic homeostasis of the body. As a new member of the mitochondrial-derived peptide family, mitochondrial open reading frame of the 12S rRNA-c (MOTS-c) is regarding a peptide hormone that could reduce insulin resistance, prevent obesity, improve muscle function, promote bone metabolism, enhance immune regulation, and postpone aging. MOTS-c plays these physiological functions mainly through activating the AICAR-AMPK signaling pathways by disrupting the folate-methionine cycle in cells. Recent studies have shown that the above hormonal effect can be achieved through MOTS-c regulating the expression of genes such as GLUT4, STAT3, and IL-10. However, there is a lack of articles summarizing the genes and pathways involved in the physiological activity of MOTS-c. This article aims to summarize and interpret the interesting and updated findings of MOTS-c-associated genes and pathways involved in pathological metabolic processes. Finally, it is expected to develop novel diagnostic markers and treatment approaches with MOTS-c to prevent and treat metabolic disorders in the future.

Clinical application of the fracture risk assessment tool in the general population and its correlation with bone turnover markers

Objective: To compare the risk of osteoporotic fractures between the urban and urban-rural fringe populations in southern China and to explore the effect of bone turnover markers on fracture risk. Methods: Epidemiological investigations were conducted in the urban and urban-rural fringe areas of southern China in June 2018. Residents aged 40 years and over who signed informed consent forms were included. Physical examination and questionnaire collection were completed. Bone turnover markers (BTMs) including osteocalcin (OC) and beta cross-linked C-telopeptide of type 1 collagen (β-CTX) were tested. Bone mineral density (BMD) of the femoral neck and lumbar vertebrae 1-4 were measured using dual energy X-ray absorptiometry. Fracture risk assessment tool (FRAX) values were calculated to show the probability of major osteoporotic fracture (PMOF) and probability of hip fracture (PHF) over the next 10 years. Results: A total of 1,051 participants were included in this study, including 553 in the urban areas and 498 in the urban-rural fringe areas. The average PMOF and PHF were 3.4 (2.3-5.4) % and .6 (.3-1.5) %, respectively. Compared with that in the urban populations, the femoral neck BMD in the urban-rural fringe populations was lower and FRAX values were generally higher, especially for women. FRAX values in various populations were mainly negatively correlated with lumbar and femoral neck BMD and were positively correlated with β-CTX; meanwhile, only PHF was negatively correlated with OC. After adjusting for sex, elevated β-CTX levels significantly increased the risk of high PMOF in various populations and increased the risk of high PHF in the urban-rural fringe populations. In particular, the risks of increased PMOF and PHF could increase by as much as 33 times and 19.5 times, respectively, in the urban-rural fringe areas. Conclusion: The urban-rural fringe populations in Southern China may be at risk of osteoporotic fracture. In addition to being related to BMD, the FRAX value also correlates with some BTMs. Combining FRAX with BMD, and BTMs may better predict the fracture risk.

RANKL Is Independently Associated with Increased Risks of Non-Alcoholic Fatty Liver Disease in Chinese Women with PCOS: A Cross-Sectional Study

Women with polycystic ovarian syndrome (PCOS) are more likely to have non-alcoholic fatty liver disease (NAFLD) than non-PCOS women; however, the exact mechanism underlying this trend is unknown. The receptor activator of NF-κB ligand (RANKL) is strongly involved in bone metabolism and has multiple functions. Recent studies suggest that RANKL is implicated in hepatic insulin resistance (IR), which is the highest risk factor for NAFLD. This study aimed to assess the role of RANKL in NAFLD in Chinese women with PCOS. A cross-sectional observational study was conducted on women newly diagnosed with PCOS, which included 146 patients with NAFLD and 142 patients without NAFLD. Sex hormones, glucose, insulin, and lipids were measured, and anthropometric data were collected. The concentration of serum total RANKL was measured using commercial ELISA kits. PCOS patients with NAFLD had a significantly higher mean age, body mass index (BMI), waist circumference (WC), and worsened metabolic profile than non-NAFLD subjects. The concentrations of high-sensitivity C-reactive protein, total cholesterol, and low-density lipoprotein cholesterol increased with the RANKL tertile (p for trend = 0.023, 0.026, and 0.035, respectively). A significantly positive association was found between RANKL (per SD change) and the risks of NAFLD (OR = 1.545, 95% CI = 1.086−2.199) after adjusting for confounders, including demographic factors, metabolic markers, and sex hormones. Subgroup multivariate logistic analyses stratified by age, BMI, and WC showed the same tendency. In addition, the positive association between RANKL and NAFLD seemed more prominent in lean patients with a BMI < 24 kg/m2 (OR = 1.70, 95% CI = 1.06−2.75) when compared to overweight/obesity subjects. Therefore, this study suggests that RANKL is positively associated with the increased risk of NAFLD in Chinese women with PCOS, independent of metabolic and reproductive factors.

Transcriptome landscape comparison of periodontium in developmental and renewal stages

OBJECTIVES

Periodontium regeneration remains a significant challenge in clinics and research, and it is essential to understand the stage-specific biological process in situ. However, differing findings have been reported, and the mechanism has yet to be elucidated. The periodontium of adult mice molars is considered to be stable remodeling tissue. At the same time, the continuously growing incisors and the developing dental follicle (DF) of postnatal mice highly represent fast remodeling tissue. In this study, we attempted to explore different clues of temporal and spatial comparisons to provide improved references for periodontal regeneration.

METHODS

Periodontal tissues from the developing periodontium (DeP) of postnatal mice, and continuously growing periodontium (CgP) and stable remodeling periodontium (ReP) of adult mice were isolated and compared using RNA sequencing. Based on the Dep and CgP separately compared with the ReP, differentially expressed genes and signaling pathways were analyzed using GO, KEGG databases, and Ingenuity Pathway Analysis (IPA). The results and validation were obtained by immunofluorescence staining and RT-PCR assays. Data were expressed as means ± standard deviation (SD) and analyzed by GraphPad Prism 8 software package, and one-way ANOVA was used to test multiple groups.

RESULTS

Principal component analysis showed that the three groups of periodontal tissue were successfully isolated and had distinct expression profiles. A total of 792 and 612 DEGs were identified in the DeP and CgP groups compared with the ReP. Upregulated DEGs in the DeP were closely related to developmental processes, while the CgP showed significantly enhanced cellular energy metabolism. The DeP and CgP showed a common downregulation of the immune response, with activation, migration, and recruitment of immune cells. IPA and further validation jointly suggested that the MyD88/p38 MAPK pathway played an essential regulatory role in periodontium remodeling.

CONCLUSION

Tissue development, energy metabolism, and immune response were critical regulatory processes during periodontal remodeling. Developmental and adult stages of periodontal remodeling showed different expression patterns. These results contribute to a deeper understanding of periodontal development and remodeling and may provide references for periodontal regeneration.

Integration of metabolomics and transcriptomics provides insights into enhanced osteogenesis in Ano5Cys360Tyr knock-in mouse model

INTRODUCTION

Gnathodiaphyseal dysplasia (GDD; OMIM#166260) is a rare autosomal dominant disorder characterized by diaphyseal sclerosis of tubular bones and cemento-osseous lesions in mandibles. GDD is caused by point mutations in the ANO5 gene. However, the mechanisms underlying GDD have not been disclosed. We previously generated the first knock-in mouse model for GDD expressing a human mutation (p.Cys360Tyr) in ANO5 and homozygous Ano5 knock-in (Ano5^KI/KI ) mice exhibited representative traits of human GDD especially including enhanced osteogenesis.

METHODS

Metabolomics and transcriptomics analyses were conducted for wildtype (Ano5^+/+ ) and Ano5^KI/KI mature mouse calvarial osteoblasts (mCOBs) grown in osteogenic cultures for 14 days to identify differential intracellular metabolites and genes involved in GDD. Subsequently, related differential genes were validated by qRT-PCR. Cell proliferation was confirmed by CCK8 assay and calcium content in mineral nodules was detected using SEM-EDS.

RESULTS

Metabolomics identified 42 differential metabolites that are primarily involved in amino acid and pyrimidine metabolism, and endocrine and other factor-regulated calcium reabsorption. Concomitantly, transcriptomic analysis revealed 407 differentially expressed genes in Ano5^KI/KI osteoblasts compared with wildtype. Gene ontology and pathway analysis indicated that Ano5^Cys360Tyr mutation considerably promoted cell cycle progression and perturbed calcium signaling pathway, which were confirmed by validated experiments. qRT-PCR and CCK-8 assays manifested that proliferation of Ano5^KI/KI mCOBs was enhanced and the expression of cell cycle regulating genes (Mki67, Ccnb1, and Ccna2) was increased. In addition, SEM-EDS demonstrated that Ano5^KI/KI mCOBs developed higher calcium contents in mineral nodules than Ano5^+/+ mCOBs, while some calcium-related genes (Cacna1, Slc8a1, and Cyp27b1) were significantly up-regulated. Furthermore, osteocalcin which has been proved to be an osteoblast-derived metabolic hormone was upregulated in Ano5^KI/KI osteoblast cultures.

DISCUSSION

Our data demonstrated that the Ano5^Cys360Tyr mutation could affect the metabolism of osteoblasts, leading to unwonted calcium homeostasis and cellular proliferation that can contribute to the underlying pathogenesis of GDD disorders.

Recent advances in the crosstalk between adipose, muscle and bone tissues in fish

Control of tissue metabolism and growth involves interactions between organs, tissues, and cell types, mediated by cytokines or direct communication through cellular exchanges. Indeed, over the past decades, many peptides produced by adipose tissue, skeletal muscle and bone named adipokines, myokines and osteokines respectively, have been identified in mammals playing key roles in organ/tissue development and function. Some of them are released into the circulation acting as classical hormones, but they can also act locally showing autocrine/paracrine effects. In recent years, some of these cytokines have been identified in fish models of biomedical or agronomic interest. In this review, we will present their state of the art focusing on local actions and inter-tissue effects. Adipokines reported in fish adipocytes include adiponectin and leptin among others. We will focus on their structure characteristics, gene expression, receptors, and effects, in the adipose tissue itself, mainly regulating cell differentiation and metabolism, but in muscle and bone as target tissues too. Moreover, lipid metabolites, named lipokines, can also act as signaling molecules regulating metabolic homeostasis. Regarding myokines, the best documented in fish are myostatin and the insulin-like growth factors. This review summarizes their characteristics at a molecular level, and describes both, autocrine effects and interactions with adipose tissue and bone. Nonetheless, our understanding of the functions and mechanisms of action of many of these cytokines is still largely incomplete in fish, especially concerning osteokines (i.e., osteocalcin), whose potential cross talking roles remain to be elucidated. Furthermore, by using selective breeding or genetic tools, the formation of a specific tissue can be altered, highlighting the consequences on other tissues, and allowing the identification of communication signals. The specific effects of identified cytokines validated through in vitro models or in vivo trials will be described. Moreover, future scientific fronts (i.e., exosomes) and tools (i.e., co-cultures, organoids) for a better understanding of inter-organ crosstalk in fish will also be presented. As a final consideration, further identification of molecules involved in inter-tissue communication will open new avenues of knowledge in the control of fish homeostasis, as well as possible strategies to be applied in aquaculture or biomedicine.

Skeletal interoception in bone homeostasis and pain

Accumulating evidence indicates that interoception maintains proper physiological status and orchestrates metabolic homeostasis by regulating feeding behaviors, glucose balance, and lipid metabolism. Continuous skeletal remodeling consumes a tremendous amount of energy to provide skeletal scaffolding, support muscle movement, store vital minerals, and maintain a niche for hematopoiesis, which are processes that also contribute to overall metabolic balance. Although skeletal innervation has been described for centuries, recent work has shown that skeletal metabolism is tightly regulated by the nervous system and that skeletal interoception regulates bone homeostasis. Here, we provide a general discussion of interoception and its effects on the skeleton and whole-body metabolism. We also discuss skeletal interoception-mediated regulation in the context of pathological conditions and skeletal pain as well as future challenges to our understanding of these process and how they can be leveraged for more effective therapy.

Mechanical Force Modulates Alveolar Bone Marrow Mesenchymal Cells Characteristics for Bone Remodeling during Orthodontic Tooth Movement through Lactate Production

Orthodontic tooth movement (OTM) relies on mechanical force-induced bone remodeling. As a metabolic intermediate of glycolysis, lactate has recently been discovered to participate in bone remodeling by serving as a signaling molecule. However, whether lactate could respond to mechanical stimulus during OTM, as well as whether lactate has an impact on the alveolar bone remodeling during orthodontics, remain to be further elucidated. In the current study, we observed physiologically elevated production of lactate along with increased osteogenic differentiation, proliferation, and migration of alveolar bone marrow mesenchymal cells (ABMMCs) under mechanical force. Inhibition of lactate, induced by cyclic mechanical stretch by GNE-140, remarkably suppressed the osteogenic differentiation, proliferation, and migration, yet enhanced apoptosis of ABMMCs. Mechanistically, these regulatory effects of lactate were mediated by histone lactylation. Taken together, our results suggest that force-induced lactate is involved in controlling bone remodeling-related cellular activities in ABMMCs and plays a vital role in the alveolar bone remodeling during OTM. Our findings indicate that lactate might be a critical modulator for alveolar bone remodeling during OTM, providing a novel therapeutic target for the purpose of more effectively controlling tooth movement and improving the stability of orthodontic results.

Regulatory of miRNAs in tri-lineage differentiation of C3H10T1/2

MicroRNAs (miRNAs) are non-coding single-stranded RNA molecules encoded by endogenous genes, which play a vital role in cell generation, metabolism, apoptosis and stem cell differentiation. C3H10T1/2, a mesenchymal cell extracted from mouse embryos, is capable of osteogenic differentiation, adipogenic differentiation and chondrogenic differentiation. Extensive studies have shown that not only miRNAs can directly trigger targeted genes to regulate the tri-lineage differentiation of C3H10T1/2, but it also can indirectly regulate the differentiation by triggering different signaling pathways or various downstream molecules. This paper aims to clarify the regulatory roles of different miRNAs on C3H10T1/2 differentiation, and discussing their balance effect among osteogenic differentiation, adipogenic differentiation and chondrogenic differentiation of C3H10T1/2. We also review the biogenesis of miRNAs, Wnt signaling pathways, MAPK signaling pathways and BMP signaling pathways and provide some specific examples of how these signaling pathways act on C3H10T1/2 tri-lineage differentiation. On this basis, we hope that a deeper understanding of the differentiation and regulation mechanism of miRNAs in C3H10T1/2 can provide a promising therapeutic method for the clinical treatment of bone defects, osteoporosis, osteoarthritis and other diseases.

A Scoping Review of the Skeletal Effects of Naringenin

BACKGROUND

Osteoporosis is caused by the deterioration of bone density and microstructure, resulting in increased fracture risk. It transpires due to an imbalanced skeletal remodelling process favouring bone resorption. Various natural compounds can positively influence the skeletal remodelling process, of which naringenin is a candidate. Naringenin is an anti-inflammatory and antioxidant compound found in citrus fruits and grapefruit. This systematic review aims to present an overview of the available evidence on the skeletal protective effects of naringenin.

METHOD

A systematic literature search was conducted using the PubMed and Scopus databases in August 2022. Original research articles using cells, animals, or humans to investigate the bone protective effects of naringenin were included.

RESULTS

Sixteen eligible articles were included in this review. The existing evidence suggested that naringenin enhanced osteoblastogenesis and bone formation through BMP-2/p38MAPK/Runx2/Osx, SDF-1/CXCR4, and PI3K/Akt/c-Fos/c-Jun/AP-1 signalling pathways. Naringenin also inhibited osteoclastogenesis and bone resorption by inhibiting inflammation and the RANKL pathway.

CONCLUSIONS

Naringenin enhances bone formation while suppressing bone resorption, thus achieving its skeletal protective effects. It could be incorporated into the diet through fruit intake or supplements to prevent bone loss.

Hyunganol II Exerts Antiadipogenic Properties via MAPK-Mediated Suppression of PPARγ Expression in Human Bone Marrow-Derived Mesenchymal Stromal Cells

Bone marrow adiposity has been associated with several metabolic syndromes such as diabetes and osteoporosis. Imbalance in adipogenic and osteoblastogenic differentiation of human bone marrow mesenchymal stromal cells (hBM-MSCs) was suggested to be the cause of elevated bone marrow adiposity. There are several drugs, of both natural and synthetic origin, to treat bone loss. In this study, as a part of a recent trend to discover natural products with more biocompatibility and fewer side effects to treat bone loss, the effect of hyunganol II (HNG), a coumarin isolated from Corydalis heterocarpa, on hBM-MSC adipogenesis was investigated. Cells treated with HNG showed decreased lipid accumulation indicating a diminished adipocyte phenotype. Treatment with HNG also suppressed the mRNA and protein expressions of PPARγ, C/EBPα, and SREBP1c, and three adipogenic marker genes. Further analysis of MAPK signaling pathway exhibited that HNG treatment elevated ERK activation and suppressed the JNK-mediated cFos and cJun phosphorylation, which inhibits PPARγ transcriptional activity. Taken together, HNG treatment was shown to inhibit adipogenesis via suppressed PPARγ expression as a result of altered MAPK signaling. Therefore, it was suggested that HNG might prevent bone marrow adiposity by inhibiting hBM-MSC adipogenesis and can be utilized as a drug or nutraceutical with beneficial effects on bone. Thus, further studies should be conducted to analyze its effect in vivo.

The oxytocin signalling gene pathway contributes to the association between loneliness and cardiometabolic health

Increasing evidence has shown adverse effects of loneliness on cardiometabolic health. The neuromodulator and hormone oxytocin has traditionally been linked with social cognition and behaviour. However, recent implications of the oxytocin system in energy metabolism and the overrepresentation of metabolic issues in psychiatric illness suggests that oxytocin may represent a mechanism bridging mental and somatic traits. To clarify the role of the oxytocin signalling system in the link between cardiometabolic risk factors and loneliness, we calculated the contribution of single nucleotide polymorphisms (SNPs) in the oxytocin signalling pathway gene-set (154 genes) to the polygenic architecture of loneliness and body mass index (BMI). We investigated the associations of these oxytocin signalling pathway polygenic scores with body composition measured using body magnetic resonance imaging (MRI), bone mineral density (BMD), haematological markers, and blood pressure in a sample of just under half a million adults from the UK Biobank (BMD subsample n = 274,457; body MRI subsample n = 9796). Our analysis revealed significant associations of the oxytocin signalling pathway polygenic score for BMI with abdominal subcutaneous fat tissue, HDL cholesterol, lipoprotein(a), triglycerides, and BMD. We also found an association between the oxytocin signalling pathway polygenic score for loneliness and apolipoprotein A1, the major protein component of HDL. Altogether, these results provide additional evidence for the oxytocin signalling pathway's role in energy metabolism, lipid homoeostasis, and bone density, and support oxytocin's complex pleiotropic effects.

Tocotrienol as a Protecting Agent against Glucocorticoid-Induced Osteoporosis: A Mini Review of Potential Mechanisms

Glucocorticoid-induced osteogenic dysfunction is the main pathologyical mechanism underlying the development of glucocorticoid-induced osteoporosis. Glucocorticoids promote adipogenic differentiation and osteoblast apoptosis through various pathways. Various ongoing studies are exploring the potential of natural products in preventing glucocorticoid-induced osteoporosis. Preclinical studies have consistently shown the bone protective effects of tocotrienol through its antioxidant and anabolic effects. This review aims to summarise the potential mechanisms of tocotrienol in preventing glucocorticoid-induced osteoporosis based on existing in vivo and in vitro evidence. The current literature showed that tocotrienol prevents oxidative damage on osteoblasts exposed to high levels of glucocorticoids. Tocotrienol reduces lipid peroxidation and increases oxidative stress enzyme activities. The reduction in oxidative stress protects the osteoblasts and preserves the bone microstructure and biomechanical strength of glucocorticoid-treated animals. In other animal models, tocotrienol has been shown to activate the Wnt/β-catenin pathway and lower the RANKL/OPG ratio, which are the targets of glucocorticoids. In conclusion, tocotrienol enhances osteogenic differentiation and bone formation in glucocorticoid-treated osteoblasts while improving structural integrity in glucocorticoid-treated rats. This is achieved by preventing oxidative stress and osteoblast apoptosis. However, these preclinical results should be validated in a randomised controlled trial.

Deletion of Tfam in Prx1-Cre expressing limb mesenchyme results in spontaneous bone fractures

INTRODUCTION

Osteoblasts require substantial amounts of energy to synthesize the bone matrix and coordinate skeleton mineralization. This study analyzed the effects of mitochondrial dysfunction on bone formation, nano-organization of collagen and apatite, and the resultant mechanical function in mouse limbs.

MATERIALS AND METHODS

Limb mesenchyme-specific Tfam knockout (Tfam^f/f;Prx1-Cre: Tfam-cKO) mice were analyzed morphologically and histologically, and gene expressions in the limb bones were assessed by in situ hybridization, qPCR, and RNA sequencing (RNA-seq). Moreover, we analyzed the mitochondrial function of osteoblasts in Tfam-cKO mice using mitochondrial membrane potential assay and transmission electron microscopy (TEM). We investigated the pathogenesis of spontaneous bone fractures using immunohistochemical analysis, TEM, birefringence analyzer, microbeam X-ray diffractometer and nanoindentation.

RESULTS

Forelimbs in Tfam-cKO mice were significantly shortened from birth, and spontaneous fractures occurred after birth, resulting in severe limb deformities. Histological and RNA-seq analyses showed that bone hypoplasia with a decrease in matrix mineralization was apparent, and the expression of type I collagen and osteocalcin was decreased in osteoblasts of Tfam-cKO mice, although Runx2 expression was unchanged. Decreased type I collagen deposition and mineralization in the matrix of limb bones in Tfam-cKO mice were associated with marked mitochondrial dysfunction. Tfam-cKO mice bone showed a significantly lower Young's modulus and hardness due to poor apatite orientation which is resulted from decreased osteocalcin expression.

CONCLUSION

Mice with limb mesenchyme-specific Tfam deletions exhibited spontaneous limb bone fractures, resulting in severe limb deformities. Bone fragility was caused by poor apatite orientation owing to impaired osteoblast differentiation and maturation.

Effect of Hydroxyapatite Coating by Er: YAG Pulsed Laser Deposition on the Bone Formation Efficacy by Polycaprolactone Porous Scaffold

Composite scaffolds obtained by the combination of biodegradable porous scaffolds and hydroxyapatite with bone regeneration potential are feasible materials for bone tissue engineering. However, most composite scaffolds have been fabricated by complicated procedures or under thermally harsh conditions. We have previously demonstrated that hydroxyapatite coating onto various substrates under a thermally mild condition was achieved by erbium-doped yttrium aluminum garnet (Er: YAG) pulsed laser deposition (PLD). The purpose of this study was to prepare a polycaprolactone (PCL) porous scaffold coated with the hydroxyapatite by the Er: YAG-PLD method. Hydroxyapatite coating by the Er: YAG-PLD method was confirmed by morphology, crystallographic analysis, and surface chemical characterization studies. When cultured on PCL porous scaffold coated with hydroxyapatite, rat bone marrow-derived mesenchymal stem cells adhered, spread, and proliferated well. The micro-CT and staining analyses after the implantation of scaffold into the critical-sized calvaria bone defect in rats indicate that PCL porous scaffold coated with hydroxyapatite demonstrates accelerated and widespread bone formation. In conclusion, PCL porous scaffold coated with hydroxyapatite obtained by the Er: YAG-PLD method is a promising material in bone tissue engineering.

Investigating calcification-related candidates in a non-symbiotic scleractinian coral, Tubastraea spp

In hermatypic scleractinian corals, photosynthetic fixation of CO2 and the production of CaCO3 are intimately linked due to their symbiotic relationship with dinoflagellates of the Symbiodiniaceae family. This makes it difficult to study ion transport mechanisms involved in the different pathways. In contrast, most ahermatypic scleractinian corals do not share this symbiotic relationship and thus offer an advantage when studying the ion transport mechanisms involved in the calcification process. Despite this advantage, non-symbiotic scleractinian corals have been systematically neglected in calcification studies, resulting in a lack of data especially at the molecular level. Here, we combined a tissue micro-dissection technique and RNA-sequencing to identify calcification-related ion transporters, and other candidates, in the ahermatypic non-symbiotic scleractinian coral Tubastraea spp. Our results show that Tubastraea spp. possesses several calcification-related candidates previously identified in symbiotic scleractinian corals (such as SLC4-γ, AMT-1like, CARP, etc.). Furthermore, we identify and describe a role in scleractinian calcification for several ion transporter candidates (such as SLC13, -16, -23, etc.) identified for the first time in this study. Taken together, our results provide not only insights about the molecular mechanisms underlying non-symbiotic scleractinian calcification, but also valuable tools for the development of biotechnological solutions to better control the extreme invasiveness of corals belonging to this particular genus.

Estrogen Receptor 1 (ESR1) and the Wnt/β-Catenin Pathway Mediate the Effect of the Coumarin Derivative Umbelliferon on Bone Mineralization

Bone physiology is regulated by osteoblast and osteoclast activities, both involved in the bone remodeling process, through deposition and resorption mechanisms, respectively. The imbalance between these two phenomena contributes to the onset of bone diseases. Among these, osteoporosis is the most common metabolic bone disorder. The therapies currently used for its treatment include antiresorptive and anabolic agents associated with side effects. Therefore, alternative therapeutic approaches, including natural molecules such as coumarin and their derivatives, have recently shown positive results. Thus, our proposal was to investigate the effect of the coumarin derivative umbelliferon (UF) using an interesting model of human osteoblasts (hOBs) isolated from osteoporotic patients. UF significantly improved the activity of osteoporotic-patient-derived hOBs via estrogen receptor 1 (ESR1) and the downstream activation of β-catenin pathway. Additionally, hOBs were co-cultured in microgravity with human osteoclasts (hOCs) using a 3D system bioreactor, able to reproduce the bone remodeling unit in bone loss conditions in vitro. Notably, UF exerted its anabolic role by reducing the multinucleated cells. Overall, our study confirms the potential efficacy of UF in bone health, and identified, for the first time, a prospective alternative natural compound useful to prevent/treat bone loss diseases such as osteoporosis.

Effects of diabetes on osteocytes

PURPOSE OF REVIEW

Better understanding of the mechanisms underlying skeletal dysfunction in the context of diabetes is needed to guide the development of therapeutic interventions to reduce the burden of diabetic fractures. Osteocytes, the 'master regulators' of bone remodeling, have emerged as key culprits in the pathogenesis of diabetes-related skeletal fragility.

RECENT FINDINGS

Both type 1 diabetes and type 2 diabetes cause chronic hyperglycemia that, over time, reduces bone quality and bone formation. In addition to acting as mechanosensors, osteocytes are important regulators of osteoblast and osteoclast activities; however, diabetes leads to osteocyte dysfunction. Indeed, diabetes causes the accumulation of advanced glycation end-products and senescent cells that can affect osteocyte viability and functions via increased receptor for advanced glycation endproducts (RAGE) signaling or the production of a pro-inflammatory senescence-associated secretory phenotype. These changes may increase osteocyte-derived sclerostin production and decrease the ability of osteocytes to sense mechanical stimuli thereby contributing to poor bone quality in humans with diabetes.

SUMMARY

Osteocyte dysfunction exists at the nexus of diabetic skeletal disease. Therefore, interventions targeting the RAGE signaling pathway, senescent cells, and those that inhibit sclerostin or mechanically stimulate osteocytes may alleviate the deleterious effects of diabetes on osteocytes and bone quality.

A Review on the Molecular Mechanisms of Action of Natural Products in Preventing Bone Diseases

The drugs used for treating bone diseases (BDs), at present, elicit hazardous side effects that include certain types of cancers and strokes, hence the ongoing quest for the discovery of alternatives with little or no side effects. Natural products (NPs), mainly of plant origin, have shown compelling promise in the treatments of BDs, with little or no side effects. However, the paucity in knowledge of the mechanisms behind their activities on bone remodeling has remained a hindrance to NPs’ adoption. This review discusses the pathological development of some BDs, the NP-targeted components, and the actions exerted on bone remodeling signaling pathways (e.g., Receptor Activator of Nuclear Factor κ B-ligand (RANKL)/monocyte/macrophage colony-stimulating factor (M-CSF)/osteoprotegerin (OPG), mitogen-activated protein kinase (MAPK)s/c-Jun N-terminal kinase (JNK)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), Kelch-like ECH-associated protein 1 (Keap-1)/nuclear factor erythroid 2–related factor 2 (Nrf2)/Heme Oxygenase-1 (HO-1), Bone Morphogenetic Protein 2 (BMP2)-Wnt/β-catenin, PhosphatidylInositol 3-Kinase (PI3K)/protein kinase B (Akt)/Glycogen Synthase Kinase 3 Beta (GSK3β), and other signaling pathways). Although majority of the studies on the osteoprotective properties of NPs against BDs were conducted ex vivo and mostly on animals, the use of NPs for treating human BDs and the prospects for future development remain promising.

Calcium and phosphorus co-doped carbon dots enhance osteogenic differentiation for calvarial defect repairin situ

Calvarial bone defect remains a clinical challenge due to the lack of efficient osteo-inductive agent. Herein, a novel calcium and phosphorus codoped carbon dot (Ca/P-CD) for bone regeneration was synthesized using phosphoethanolamine and calcium gluconate as precursors. The resultant Ca/P-CDs exhibited ultra-small size, stable excitation dependent emission spectra and favorable dispersibility in water. Moreover, Ca/P-CDs with good biocompatibility rapidly entered the cytoplasm through endocytosis and increased the expression of bone differentiation genes. After mixing with temperature-sensitive hydrogel, Ca/P-CDs were injectedin situinto calvarial defect and promoted the repair of bone injury. These Ca/P-CDs provide a new treatment method for the bone repair and should be expended the application in the biomedical fields.