Trabecular Bone Loss Research Articles

Extracellular vesicles from bone marrow mesenchymal stem cells alleviate osteoporosis in mice through USP7-mediated YAP1 protein stability and the Wnt/β-catenin pathway

Mesenchymal stem cells (MSCs) and their derived extracellular vesicles (EVs) have emerged as promising tools for promoting bone regeneration. This study investigates the functions of EVs derived from bone marrow-derived MSCs (BMSCs) in osteoporosis (OP) and the molecular mechanism. EVs were isolated from primary BMSCs in mice. A mouse model with OP was induced by ovariectomy. Treatment with EVs restored bone mass and strength, attenuated trabecular bone loss and cartilage damage, and increased osteogenesis while suppressing osteoclastogenesis in ovariectomized mice. In vitro, the EVs treatment improved the osteogenic differentiation of MC-3T3 while inhibiting osteoclastic differentiation of RAW264.7 cells. Microarray analysis revealed a significant upregulation of ubiquitin specific peptidase 7 (USP7) expression in mouse bone tissues following EV treatment. USP7 was found to interact with Yes1 associated transcriptional regulator (YAP1) and stabilize YAP1 protein through deubiquitination modification. YAP1-related genes were enriched in the Wnt/β-catenin signaling, and overexpression of YAP1 promoted the nuclear translocation of β-catenin. Functional experiments underscored the critical role of maintaining USP7, YAP1, and β-catenin levels in the pro-osteogenic and anti-osteoclastogenic properties of the BMSC-EVs. In conclusion, this study demonstrates that USP7, delivered by BMSC-derived EVs, stabilizes YAP1 protein, thereby ameliorating bone formation in OP through the Wnt/β-catenin activation.

Abstract P180: Hypertension-linked Immune Activation Regulates Osteoclastogenesis

Osteoporosis is an age-related disease affecting 18% of adults. Hypertension is associated with increased risk for fragility fracture and accelerated bone loss in adults. We hypothesized that experimental hypertension would induce osteoporosis and examined the mechanisms involved. We used two preclinical models in 12-week-old male C57Bl/6J mice: angiotensin (ang) II infusion (490 ng/kg/min) and deoxycorticosterone acetate (DOCA)-salt. After 6 weeks of ang II or 3 weeks of DOCA-salt, the left femur and sixth lumbar vertebral body were studied. Mechanical testing showed that ang II reduced femoral ultimate strength (170.7±4.794 vs 157.3±3.670 MPa, p=0.0325; 154.1±7.403 vs. 119.9±4.375 MPa, p=0.0026) and peak moment (39.09±1.660 vs. 32.77±0.9380 Newton millimeters (Nmm), p=0.0018; 29.15±1.291 vs 19.58±1.308 Nmm, p=0.0004) with cortical and trabecular bone loss compared to controls. μCT showed that hypertension reduced vertebral body bone volume fraction (30.1±1.41 vs 25.1±0.992 %, p=0.0068; 25.9±2.03 vs 18.5±1.29 %, p=0.0119) and trabecular thickness (62±1.6 vs 57±1.4 μm, p=0.0105; 60±2.1 vs 51 ±1.6 μm, p=0.0069). Flow cytometry of bone marrow from ang II-treated mice revealed that CD4+ T cells and γδ T cells produce increased IL-17A which is known to induce osteoclastogenesis. Colony stimulating factor-1 (CSF1) is also known to stimulate osteoclast formation. Using in situ hybridization, we observed increased CSF1 mRNA in endothelial cells (ECs) of transcortical arterioles of hypertensive mice. Subsequent studies of cultured bone marrow derived ECs showed that CSF1 mRNA expression increased with 0% and 10% compared to 5% stretch. 5% stretch treated with endothelial nitric oxide synthase inhibitor, L-NAME, increased expression comparable to 0% and 10%, indicating that nitric oxide inhibits CSF1 production. Thus, T-cell activation and nitric oxide-dependent EC dysfunction in hypertension may skew the bone marrow to favor osteoclastogenesis, leading to bone loss. Understanding this mechanism will elucidate novel pharmacological targets to mitigate hypertension-induced bone loss.

Computed Tomography Provides Improved Quantification of Trabecular Lumbar Spine Bone Loss Compared to Dual-Energy X-Ray Absorptiometry in Ovariectomized Sheep.

Early detection of osteoporosis using advanced imaging is imperative to the successful treatment and prevention of high morbidity fractures in aging patients. In this preclinical study, we aimed to compare dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) to quantify bone mineral density (BMD) changes in the sheep lumbar spine. We also aimed to determine the relationship of BMD to microarchitecture in the same animals as an estimate of imaging modality precision. Osteoporosis was induced in 10 ewes via laparoscopic ovariectomy and administration of high-dose corticosteroids. We performed DXA and QCT imaging to measure areal BMD (aBMD) and trabecular volumetric BMD (Tb.vBMD)/cortical vBMD (Ct.vBMD), respectively, at baseline (before ovariectomy) and at 3, 6, 9, and 12 months after ovariectomy. Iliac crest bone biopsies were collected at each time point for micro-computed tomography (microCT) analysis; bone volume fraction (BV/TV), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp) were reported. aBMD and Tb.vBMD both decreased significantly by 3 and 6 months (p < 0.05) compared with baseline, whereas no changes to Ct.vBMD were observed. Combined (Tb. and Ct.) vBMD was significantly correlated with aBMD at all time points (all p < 0.05). Additionally, greater significant correlations were found between BV/TV and Tb.vBMD at all five time points (R 2 = 0.54, 0.57, 0.66, 0.46, and 0.56, respectively) than with aBMD values (R 2 = 0.23, 0.55, 0.41, 0.20, and 0.19, respectively). The higher correlation of microCT values with QCT than with DXA indicates that QCT provides additional detailed information regarding bone mineral density changes in preclinical settings. Because trabecular bone is susceptible to rapid density loss and structural changes during osteoporosis, QCT can capture these subtle changes more precisely than DXA in a large animal preclinical model. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Lactobacillus Reuteri 6475 Prevents Bone Loss in a Clinically Relevant Oral Model of Glucocorticoid-Induced Osteoporosis in Male CD-1 Mice.

Glucocorticoids (GCs) are commonly used anti-inflammatory medications with significant side effects, including glucocorticoid-induced osteoporosis (GIO). We have previously demonstrated that chronic subcutaneous GC treatment in mice leads to gut barrier dysfunction and trabecular bone loss. We further showed that treating with probiotics or barrier enhancers improves gut barrier function and prevents GIO. The overall goal of this study was to test if probiotics could prevent GC-induced gut barrier dysfunction and bone loss in a clinically relevant oral-GC model of GIO. Eight-week-old male CD-1 mice were treated with vehicle or corticosterone in the drinking water for 4 weeks and administered probiotics Lactobacillus reuteri ATCC 6475 (LR 6475) or VSL#3 thrice weekly via oral gavage. As expected, GC treatment led to significant gut barrier dysfunction (assessed by measuring serum endotoxin levels) and bone loss after 4 weeks. Serum endotoxin levels significantly and negatively correlated with bone volume. Importantly, LR 6475 treatment effectively prevented both GC-induced increase in serum endotoxin and trabecular bone loss. VSL#3 had intermediate results, not differing from either control or GC-treated animals. GC-induced reductions in femur length, cortical thickness, and cortical area were not affected by probiotic treatment. Taken together, these results are the first to demonstrate that LR 6475 effectively prevents the detrimental effects of GC treatment on gut barrier, which correlates with enhanced trabecular bone health in an oral mouse model of GIO. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Genetic activation of glycolysis in osteoblasts preserves bone mass in type I diabetes

Type I diabetes (T1D) impairs bone accrual in patients, but the mechanism is unclear. Here in a murine monogenic model for T1D, we demonstrate that diabetes suppresses bone formation resulting in a rapid loss of both cortical and trabecular bone. Single-cell RNA sequencing uncovers metabolic dysregulation in bone marrow osteogenic cells of diabetic mice. Invivo stable isotope tracing reveals impaired glycolysis in diabetic bone that is highly responsive to insulin stimulation. Remarkably, deletion of the insulin receptor reduces cortical but not trabecular bone. Increasing glucose uptake by overexpressing Glut1 in osteoblasts exacerbates bone defects in T1D mice. Conversely, activation of glycolysis by Pfkfb3 overexpression preserves both trabecular and cortical bone mass in the face of diabetes. The study identifies defective glucose metabolism in osteoblasts as a pathogenic mechanism for osteopenia in T1D, and furthermore implicates boosting osteoblast glycolysis as a potential bone anabolic therapy.

Regulation of Osteoblast to Osteocyte Differentiation by Cyclin-Dependent Kinase-1.

Osteocytes have recently been identified as a new regulator of bone remodeling, but the detailed mechanism of their differentiation from osteoblasts remains unclear. The purpose of this study is to identify cell cycle regulators involved in the differentiation of osteoblasts into osteocytes and determine their physiological significance. The study uses IDG-SW3 cells as a model for the differentiation from osteoblasts to osteocytes. Among the major cyclin-dependent kinases (Cdks), Cdk1 is most abundantly expressed in IDG-SW3 cells, and its expression is down-regulated during differentiation into osteocytes. Inhibition of CDK1 activity reduces IDG-SW3 cell proliferation and differentiation into osteocytes. Osteocyte and Osteoblast-specific Cdk1 knockout in mice (Dmp1-Cdk1KO ) results in trabecular bone loss. Pthlh expression increases during differentiation, but inhibiting CDK1 activity reduces Pthlh expression. Parathyroid hormone-related protein concentration is reduced in the bone marrow of Dmp1-Cdk1KO mice. Four weeks of Parathyroid hormone administration partially recovers the trabecular bone loss in Dmp1-Cdk1KO mice. These results demonstrate that Cdk1 plays an essential role in the differentiation from osteoblast to osteocyte and the acquisition and maintenance of bone mass. The findings contribute to a better understanding of the mechanisms of bone mass regulation and can help develop efficient therapeutic strategies for osteoporosis treatment.

Premature aging of skeletal stem/progenitor cells rather than osteoblasts causes bone loss with decreased mechanosensation

A distinct population of skeletal stem/progenitor cells (SSPCs) has been identified that is indispensable for the maintenance and remodeling of the adult skeleton. However, the cell types that are responsible for age-related bone loss and the characteristic changes in these cells during aging remain to be determined. Here, we established models of premature aging by conditional depletion of Zmpste24 (Z24) in mice and found that Prx1-dependent Z24 deletion, but not Osx-dependent Z24 deletion, caused significant bone loss. However, Acan-associated Z24 depletion caused only trabecular bone loss. Single-cell RNA sequencing (scRNA-seq) revealed that two populations of SSPCs, one that differentiates into trabecular bone cells and another that differentiates into cortical bone cells, were significantly decreased in Prx1-Cre; Z24f/f mice. Both premature SSPC populations exhibited apoptotic signaling pathway activation and decreased mechanosensation. Physical exercise reversed the effects of Z24 depletion on cellular apoptosis, extracellular matrix expression and bone mass. This study identified two populations of SSPCs that are responsible for premature aging-related bone loss. The impairment of mechanosensation in Z24-deficient SSPCs provides new insight into how physical exercise can be used to prevent bone aging.

Application of biomaterials in treating early osteonecrosis of the femoral head: Research progress and future perspectives.

Osteonecrosis of the femoral head (ONFH), a progressive pathological process of femoral head ischemia and osteocyte necrosis, is a refractory orthopedic disease caused by multiple etiologies and there is no complete cure at present. With the extension of ONFH duration, osteocyte apoptosis and trabecular bone loss can decrease the load-bearing capacity of the femoral head, which leads to the collapse of the articular cartilage and subchondral bone. Therefore, an urgent clinical need exists to develop effective treatment strategies of early-stage ONFH for maintaining the hip joint function and preventing femoral head collapse. In recent years, extensive attention has been paid to the application of diverse biomaterials in treating early ONFH for sustaining the normal morphology and function of the autologous femoral head, and slowing disease progression. Herein, we review the research progress of bone grafts, metallic materials, bioceramics, bioglasses and polymer materials for early ONFH treatment, and discuss the biological mechanisms of bone repair and regeneration in the femoral-head necrotic area. We propose suggestions for future research directions, from a special perspective of improving the local microenvironment in femoral head by facilitating vessel-associated osteoclasts (VAOs) generation and coupling of bone-specific angiogenesis and osteogenesis, as well as inhibiting bone-associated osteoclasts (BAOs) and BAO-mediated bone resorption. This review can provide ideas for the research, development, and clinical application of biomaterials for treating early ONFH. STATEMENT OF SIGNIFICANCE: We believe that at least three aspects of this manuscript make it interesting to readers of the Acta Biomaterialia. First, we briefly summarize the incidence, pathogenesis, risk factors, classification criteria and treatment of early osteonecrosis of the femoral head (ONFH). Second, we review the research progress in biomaterials for early ONFH treatment and the biological mechanisms of bone repair and regeneration in femoral-head necrotic area. Third, we propose future research progress on improving the local microenvironment in femoral head by facilitating vessel-associated osteoclasts generation and coupling of bone-specific angiogenesis and osteogenesis, as well as inhibiting bone-associated osteoclasts and bone resorption. We hope this review can provide ideas for the research, development, and clinical application of biomaterials for treating early ONFH.

Thermoneutral housing does not rescue olanzapine-induced trabecular bone loss in C57BL/6J female mice

Antipsychotic drugs are prescribed to a wide range of individuals to treat mental health conditions including schizophrenia. However, antipsychotic drugs cause bone loss and increase fracture risk. We previously found that the atypical antipsychotic (AA) drug risperidone causes bone loss through multiple pharmacological mechanisms, including activation of the sympathetic nervous system in mice treated with clinically relevant doses. However, bone loss was dependent upon housing temperature, which modulates sympathetic activity. Another AA drug, olanzapine, has substantial metabolic side effects, including weight gain and insulin resistance, but it is unknown whether bone and metabolic outcomes of olanzapine are also dependent upon housing temperature in mice. We therefore treated eight week-old female mice with vehicle or olanzapine for four weeks, housed at either room temperature (23 °C) or thermoneutrality (28–30 °C), which has previously been shown to be positive for bone. Olanzapine caused significant trabecular bone loss (−13% BV/TV), likely through increased RANKL-dependent osteoclast resorption, which was not suppressed by thermoneutral housing. Additionally, olanzapine inhibited cortical bone expansion at thermoneutrality, but did not alter cortical bone expansion at room temperature. Olanzapine also increased markers of thermogenesis within brown and inguinal adipose depots independent of housing temperature. Overall, olanzapine causes trabecular bone loss and inhibits the positive effect of thermoneutral housing on bone. Understanding how housing temperature modulates the impact of AA drugs on bone is important for future pre-clinical studies, as well as for the prescription of AA drugs, particularly to older adults and adolescents who are most vulnerable to the effects on bone.

Abaloparatide prevents immobilization-induced cortical but not trabecular bone loss after spinal cord injury.

Spinal cord injury (SCI) causes severe and resistant sublesional disuse bone loss. Abaloparatide, a modified parathyroid hormone related peptide, is an FDA approved drug for treatment of severe osteoporosis with potent anabolic activity. The effects of abaloparatide on SCI-induced bone loss remain undefined. Thus, female mice underwent sham or severe contusion thoracic SCI causing hindlimb paralysis. Mice then received subcutaneous injection of vehicle or 20 μg/kg/day abaloparatide for 35 days. Micro-computed tomography (micro-CT) analysis of the distal and midshaft femoral regions of the SCI-vehicle mice revealed reduced trabecular fractional bone volume (56%), thickness (75%), and cortical thickness (80%) compared to sham-vehicle controls. Treatment with abaloparatide did not prevent SCI-induced changes in trabecular or cortical bone. However, histomorphometry evaluation of the SCI-abaloparatide mice demonstrated that abaloparatide treatment increased osteoblast (241%) and osteoclast (247%) numbers and the mineral apposition rate (131%) compared to SCI-vehicle animals. In another independent experiment, treatment with 80 μg/kg/day abaloparatide significantly attenuated SCI-induced loss in cortical bone thickness (93%) when compared to SCI-vehicle mice (79%) but did not prevent SCI-induced trabecular bone loss or elevation in cortical porosity. Biochemical analysis of the bone marrow supernatants of the femurs showed that SCI-abaloparatide animals had 2.3-fold increase in procollagen type I N-terminal propeptide, a bone formation marker than SCI-vehicle animals. SCI groups had 70% higher levels of cross-linked C-telopeptide of type I collagen, a bone resorption marker, than sham-vehicle mice. These findings suggest that abaloparatide protects the cortical bone against the deleterious effects of SCI by promoting bone formation.

Inhibition of histone lysine demethylase 6A promotes chondrocytic activity and attenuates osteoarthritis development through repressing H3K27me3 enhancement of Wnt10a.

Histone hypermethylation represses gene transcription, which affects cartilage homeostasis or joint remodeling. Trimethylation of lysine 27 of histone 3 (H3K27me3) changes epigenome signatures, regulating tissue metabolism. This study aimed to investigate whether loss of H3K27me3 demethylase Kdm6a function affected osteoarthritis development. We revealed that chondrocyte-specific Kdm6a knockout mice developed relatively long femurs and tibiae as compared to wild-type mice. Kdm6a deletion mitigated osteoarthritis symptoms, including articular cartilage loss, osteophyte formation, subchondral trabecular bone loss, and irregular walking patterns of destabilized medial meniscus-injured knees. In vitro, loss of Kdm6a function compromised the loss in expression of key chondrocyte markers Sox9, collagen II, and aggrecan and improved glycosaminoglycan production in inflamed chondrocytes. RNA sequencing showed that Kdm6a loss changed transcriptomic profiles, which contributed to histone signaling, NADPH oxidase, Wnt signaling, extracellular matrix, and cartilage development in articular cartilage. Chromatin immunoprecipitation sequencing uncovered that Kdm6a knockout affected H3K27me3 binding epigenome, repressing Wnt10a and Fzd10 transcription. Wnt10a was, among others, functional molecules regulated by Kdm6a. Forced Wnt10a expression attenuated Kdm6a deletion-induced glycosaminoglycan overproduction. Intra-articular administration with Kdm6a inhibitor GSK-J4 attenuated articular cartilage erosion, synovitis, and osteophyte formation, improving gait profiles of injured joints. In conclusion, Kdm6a loss promoted transcriptomic landscapes contributing to extracellular matrix synthesis and compromised epigenetic H3K27me3-mediated promotion of Wnt10a signaling, preserving chondrocytic activity to attenuate osteoarthritic degeneration. We highlighted the chondroprotective effects of Kdm6a inhibitor for mitigating the development of osteoarthritic disorders.

The role and mechanism of tumor necrosis factor-alpha in alcohol-induced bone loss.

It is well known that alcohol can cause bone loss and that bone mineral density has an inverse relationship with bone marrow adipocyte (BMA). However, little is known about the mechanisms that link alcohol and bone loss, and existing studies lack data on BMA in alcohol-induced bone loss. Here, wild-type (WT) and tumor necrosis factor-alpha knockout (TNF-α KO) mice were used to examine the effects of alcohol on bone metabolism. The effects of alcohol on bone metabolism were demonstrated in vivo by feeding WT and TNF-α KO mice with alcohol. The osteogenesis and adipogenesis of primary bone marrow stromal cells (BMSCs) derived from WT and TNF-α KO mice under alcohol intervention were compared in vitro. Tissue staining, cell staining, micro-CT, and quantitative RT-PCR were used to explore the potential mechanism. Alcohol induced trabecular bone loss, increased BMA, and promoted the mRNA expression of Adipoq, Fabp4, visfatin， Pparg, TNF-α, IL-1β, and IL-6 in BMA in WT mice, but not in TNF-α KO mice. In addition, alcohol promoted BMSC adipogenesis and inhibited BMSC osteogenesis, while TNF-α knockout could restrain this situation. Our study demonstrated that alcohol may reduce bone mass by disrupting the balance of osteogenesis and adipogenesis in bone marrow, and TNF-α plays an important role in this process.

Impact of leptin or melatonin on Sema4D overexpression-related bone metabolism

PurposeThe current study aims to investigate the regulatory impact of leptin or melatonin on bone metabolism as well as the underlying mechanism in conjunction with Sema4D (monoclonal antibody to semaphorin 4D).MethodsRats were used to create the osteoporosis model utilizing the OVX (OVariectomize) technique. Rat tibial specimens from each side were collected for three-dimensional reconstruction and Micro-CT scanning examination. The Hematoxylin-osinstaining (HE) staining technique was used to determine the pathological condition of bone tissues. The ELISA (Enzyme-Linked Immunosorbent Assay) assay was used to measure the amount of estradiol present in the serum. In the current study, there were six groups: control, OVX, OVX + NL (no load group), OVX + Sema4D, OVX + Sema4D + leptin, and OVX + Sema4D + MT (melatonin). Rats were given injections of the Sema4D or leptin overexpressing vectors via the tail vein in accordance with the aforementioned classification. By using a high-resolution micro-CT technology, 3D bone structure was discovered. The activity of tartrate-resistant acid phosphatase-5b (TRAP-5b) and bone-derived alkaline phosphatase (BALP) in serum was assessed using an ELISA. The number of osteoclasts in the metaphysis of the upper tibia was determined using TRAP (tartrate-resistant acid phosphatase) staining. Immunohistochemistry was used to find leptin and bone morphogenetic protein-2 (BMP-2) expressions in bone tissue.ResultsThe BV/TV (Bone volume/Tissue volume), Tb.N (Trabecular number), BMD (Bone Mineral Density), and BMC (Bone Mineral Content) levels were significantly higher in the OVX + Sema4D + leptin and OVX + Sema4D + MT groups compared to OVX + NL, while Tb.Sp (Trabecular separation) levels were significantly lower. In contrast to the OVX group, the bone trabeculae in the OVX + Sema4D + leptin and OVX + Sema4D + MT groups had a relatively complete structure and tended to be organized closely. The amount of bone trabeculae grew drastically, whereas the proportion of TRAP-positive osteoclasts declined dramatically. BMP-2 and leptin were also elevated, while BALP and TRAP-5b activity was reduced.ConclusionLeptin or melatonin improved Sema4d's role in trabecular bone microstructure, bone production, and repairment of trabecular bone loss in osteoporosis rats.

STING-dependent interferon signatures restrict osteoclast differentiation and bone loss in mice

Stimulator of interferon genes (STING) is a key mediator of type-I interferon (IFN-I) signaling in response to a variety of stimuli, but the contribution of STING to homeostatic processes is not fully characterized. Previous studies showed that ligand activation of STING limits osteoclast differentiation invitro through the induction of IFNβ and IFN-I interferon-stimulated genes (ISGs). In a disease model (SAVI) driven by the V154M gain-of-function mutation in STING, fewer osteoclasts form from SAVI precursors in response to receptor activator of NF-kappaB ligand (RANKL) in an IFN-I-dependent manner. Due to the described role of STING-mediated regulation of osteoclastogenesis in activation settings, we sought to determine whether basal STING signaling contributes to bone homeostasis, an unexplored area. Using whole-body and myeloid-specific deficiency, we show that STING signaling prevents trabecular bone loss in mice over time and that myeloid-restricted STING activity is sufficient for this effect. STING-deficient osteoclast precursors differentiate with greater efficiency than wild types. RNA sequencing of wild-type and STING-deficient osteoclast precursor cells and differentiating osteoclasts reveals unique clusters of ISGs including a previously undescribed ISG set expressed in RANKL naïve precursors (tonic expression) and down-regulated during differentiation. We identify a 50 gene tonic ISG signature that is STING dependent and shapes osteoclast differentiation. From this list, we identify interferon-stimulated gene 15 (ISG15) as a tonic STING-regulated ISG that limits osteoclast formation. Thus, STING is an important upstream regulator of tonic IFN-I signatures shaping the commitment to osteoclast fates, providing evidence for a nuanced and unique role for this pathway in bone homeostasis.

Kefir peptides attenuate atherosclerotic vascular calcification and osteoporosis in atherogenic diet-fed ApoE -/- knockout mice.

Aims: Vascular calcification (VC) and osteoporosis were previously considered two distinct diseases. However, current understanding indicates that they share common pathogenetic mechanisms. The available medicines for treating VC and osteoporosis are limited. We previously demonstrated that kefir peptides (KPs) alleviated atherosclerosis in high-fat diet (HFD)-induced apolipoprotein E knockout (ApoE -/- ) mice. The present study further addressed the preventive effects of KPs on VC and osteoporosis in ApoE -/- mice fed a high-cholesterol atherogenic diet (AD). Main methods: Seven-week-old ApoE -/- and wild-type C57BL/6 mice were randomly divided into five groups (n = 6). The development of VC and osteoporosis was evaluated after AD feeding for 13weeks in KP-treated ApoE -/- mice and compared to C57BL/6 and ApoE -/- mice fed a standard chow diet (CD). Key findings: The results indicated that KP-treated ApoE -/- mice exhibited lower serum total cholesterol, oxidized low-density lipoprotein (ox-LDL), malondialdehyde (MDA) levels, and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and creatine kinase (CK) activities, which suggested that KPs prevented hyperlipidemia and possible damages to the liver and muscle in ApoE -/- mice. KPs reduced serum tumor necrosis factor-α (TNF-α) and the local expression of TNF-α, IL-1β, and macrophage-specific CD68 markers in aortic tissues, which suggested that KPs inhibited inflammatory responses in AD-fed ApoE -/- mice. KPs reduced the deposition of lipid, collagen, and calcium minerals in the aortic roots of AD-fed ApoE -/- mice, which suggested that KPs inhibited the calcific progression of atherosclerotic plaques. KPs exerted osteoprotective effects in AD-fed ApoE -/- mice, which was evidenced by lower levels of the bone resorption marker CTX-1 and higher levels of the bone formation marker P1NP. KPs improved cortical bone mineral density and bone volume and reduced trabecular bone loss in femurs. Significance: The present data suggested that KPs attenuated VC and osteoporosis by reducing oxidative stress and inflammatory responses in AD-fed ApoE -/- mice. Our findings contribute to the application of KPs as preventive medicines for the treatment of hyperlipidemia-induced vascular and bone degeneration.

CCL12 induces trabecular bone loss by stimulating RANKL production in BMSCs during acute lung injury

In the last three years, the capacity of health care systems and the public health policies of governments worldwide were challenged by the spread of SARS-CoV-2. Mortality due to SARS-CoV-2 mainly resulted from the development of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Moreover, millions of people who survived ALI/ARDS in SARS-CoV-2 infection suffer from multiple lung inflammation-induced complications that lead to disability and even death. The lung-bone axis refers to the relationship between lung inflammatory diseases (COPD, asthma, and cystic fibrosis) and bone diseases, including osteopenia/osteoporosis. Compared to chronic lung diseases, the influence of ALI on the skeleton has not been investigated until now. Therefore, we investigated the effect of ALI on bone phenotypes in mice to elucidate the underlying mechanisms. In vivo bone resorption enhancement and trabecular bone loss were observed in LPS-induced ALI mice. Moreover, chemokine (C-C motif) ligand 12 (CCL12) accumulated in the serum and bone marrow. In vivo global ablation of CCL12 or conditional ablation of CCR2 in bone marrow stromal cells (BMSCs) inhibited bone resorption and abrogated trabecular bone loss in ALI mice. Furthermore, we provided evidence that CCL12 promoted bone resorption by stimulating RANKL production in BMSCs, and the CCR2/Jak2/STAT4 axis played an essential role in this process. Our study provides information regarding the pathogenesis of ALI and lays the groundwork for future research to identify new targets to treat lung inflammation-induced bone loss.

Antibodies to sclerostin or G-CSF receptor partially eliminate bone or marrow adipocyte loss, respectively, following vertical sleeve gastrectomy.

Vertical sleeve gastrectomy (VSG), the most utilized bariatric procedure in clinical practice, greatly reduces body weight and improves a variety of metabolic disorders. However, one of its long-term complications is bone loss and increased risk of fracture. Elevated circulating sclerostin (SOST) and granulocyte-colony stimulating factor (G-CSF) concentrations have been considered as potential contributors to VSG-associated bone loss. To test these possibilities, we administrated antibodies to SOST or G-CSF receptor and investigated alterations to bone and marrow niche following VSG. Neutralizing either SOST or G-CSF receptor did not alter beneficial effects of VSG on adiposity and hepatic steatosis, and anti-SOST treatment provided a further improvement to glucose tolerance. SOST antibodies partially reduced trabecular and cortical bone loss following VSG by increasing bone formation, whereas G-CSF receptor antibodies had no effects on bone mass. The expansion in myeloid cellularity and reductions in bone marrow adiposity seen with VSG were partially eliminated by treatment with Anti-G-CSF receptor. Taken together, these experiments demonstrate that antibodies to SOST or G-CSF receptor may act through independent mechanisms to partially block effects of VSG on bone loss or marrow niche cells, respectively.

Protective Effects of the Postbiotic Lactobacillus plantarum MD35 on Bone Loss in an Ovariectomized Mice Model

Postmenopausal osteoporosis is caused by estrogen deficiency, which impairs bone homeostasis, resulting in increased osteoclastic resorption without a corresponding increase in osteoblastic activity. Postbiotics have several therapeutic properties, including anti-obesity, anti-diabetic, anti-inflammatory, and anti-osteoporotic effects. However, the beneficial effects of the postbiotic MD35 of Lactobacillus plantarum on bone have not been studied. In this study, we demonstrated that the postbiotic L. plantarum MD35, isolated from young radish water kimchi, influences osteoclast differentiation in mouse bone marrow-derived macrophage (BMM) culture. In addition, it was effective protecting against estrogen deficiency-induced bone loss in ovariectomized (OVX) mice, an animal model of postmenopausal osteoporosis. In BMM cells, postbiotic MD35 inhibited the receptor activator of nuclear factor-kappa B of NF-κB ligand (RANKL)-induced osteoclast differentiation by attenuating the phosphorylation of extracellular signal-related kinase, significantly suppressing the resorption activity and down-regulating the expression of RANKL-mediated osteoclast-related genes. In the animal model, the oral administration of postbiotic MD35 remarkably improved OVX-induced trabecular bone loss and alleviated the destruction of femoral plate growth. Therefore, postbiotic MD35 could be a potential therapeutic candidate for postmenopausal osteoporosis by suppressing osteoclastogenesis through the regulation of osteoclast-related molecular mechanisms.

Genistein mitigates senescence of bone marrow mesenchymal stem cells via ERRα-mediated mitochondrial biogenesis and mitophagy in ovariectomized rats

Senescence of bone marrow mesenchymal stem cells (BMMSCs) induced by chronic oxidative stress is an important factor contributes to the postmenopausal osteoporosis (PMOP). Mitochondrial quality control takes a pivotal role in regulating oxidative stress and cell senescence. Genistein is a major isoflavone in soy products, which is best known for its ability to inhibit bone loss in both postmenopausal women and ovariectomized (OVX) rodents. Here we show that OVX-BMMSCs displayed premature senescence, elevated reactive oxygen species (ROS) level and mitochondria dysfunction, while genistein rescued these phenotypes. Using network pharmacology and molecular docking, we identified estrogen-related receptor α (ERRα) as the potential target of genistein. Knockdown of ERRα greatly abolished the anti-senescence effect of genistein on OVX-BMMSCs. Further, the mitochondrial biogenesis and mitophagy induced by genistein were inhibited by ERRα knockdown in OVX-BMMSCs. In vivo, genistein inhibited trabecular bone loss and p16INK4a expression, upregulated sirtuin 3 (SIRT3) and peroxisome proliferator-activated receptor gamma coactivator one alpha (PGC1α) expression in the trabecular bone area of proximal tibia in OVX rats. Together, this study revealed that genistein ameliorates senescence of OVX-BMMSCs through ERRα-mediated mitochondrial biogenesis and mitophagy, which provided a molecular basis for advancement and development of therapeutic strategies against PMOP.

The Senolytic Drug Fisetin Attenuates Bone Degeneration in the Zmpste24 -/- Progeria Mouse Model.

Aging leads to several geriatric conditions including osteoporosis (OP) and associated frailty syndrome. Treatments for these conditions are limited and none target fundamental drivers of pathology, and thus identifying strategies to delay progressive loss of tissue homeostasis and functional reserve will significantly improve quality of life in elderly individuals. A fundamental property of aging is the accumulation of senescent cells. Senescence is a cell state defined by loss of proliferative capacity, resistance to apoptosis, and the release of a proinflammatory and anti-regenerative senescence-associated secretory phenotype (SASP). The accumulation of senescent cells and SASP factors is thought to significantly contribute to systemic aging. Senolytics-compounds which selectively target and kill senescent cells-have been characterized to target and inhibit anti-apoptotic pathways that are upregulated during senescence, which can elicit apoptosis in senescent cells and relieve SASP production. Senescent cells have been linked to several age-related pathologies including bone density loss and osteoarthritis in mice. Previous studies in murine models of OP have demonstrated that targeting senescent cells pharmacologically with senolytic drugs can reduce symptomology of the disease. Here, we demonstrate the efficacy of senolytic drugs (dasatinib, quercetin, and fisetin) to improve age-associated degeneration in bone using the Zmpste24-/- (Z24-/-) progeria murine system for Hutchinson-Gilford progeria syndrome (HGPS). We found that the combination of dasatinib plus quercetin could not significantly mitigate trabecular bone loss although fisetin administration could reduce bone density loss in the accelerated aging Z24-/- model. Furthermore, the overt bone density loss observed in the Z24-/- model reported herein highlights the Z24 model as a translational model to recapitulate alterations in bone density associated with advanced age. Consistent with the "geroscience hypothesis," these data demonstrate the utility of targeting a fundamental driver of systemic aging (senescent cell accumulation) to alleviate a common condition with age, bone deterioration.