Osteoblast-derived WNT16 represses osteoclastogenesis and prevents cortical bone fragility fractures

Calorie restriction in mice impairs cortical but not trabecular peak bone mass by suppressing bone remodeling

Calorie restriction (CR) can lead to weight loss and decreased substrate availability for bone cells. Ultimately, this can lead to impaired peak bone acquisition in children and adolescence and bone loss in adults. But the mechanisms that drive diet-induced bone loss in humans are not well characterized. To explore those in greater detail, we examined the impact of 30% CR for 4 and 8 wk in both male and female 8-wk-old C57BL/6 J mice. Body composition, areal bone mineral density (aBMD), skeletal microarchitecture by micro-CT, histomorphometric parameters, and in vitro trajectories of osteoblast and adipocyte differentiation were examined. After 8 wk, CR mice lost weight and exhibited lower femoral and whole-body aBMD vs ad libitum (AL) mice. By micro-CT, CR mice had lower cortical bone area fraction vs AL mice, but males had preserved trabecular bone parameters and females showed increased bone volume fraction compared to AL mice. Histomorphometric analysis revealed that CR mice had a profound suppression in trabecular as well as endocortical and periosteal bone formation in addition to reduced bone resorption compared to AL mice. Bone marrow adipose tissue was significantly increased in CR mice. In vitro, the pace of adipogenesis in bone marrow stem cells was greatly accelerated with higher markers of adipocyte differentiation and more oil red O staining, whereas osteogenic differentiation was reduced. qRT-PCR and western blotting suggested that the expression of Wnt16 and the canonical β-catenin pathway was compromised during CR. In sum, CR causes impaired peak cortical bone mass due to a profound suppression in bone remodeling. The increase in marrow adipocytes in vitro and in vivo is related to both progenitor recruitment and adipogenesis in the face of nutrient insufficiency. Long-term CR may lead to lower bone mass principally in the cortical envelope, possibly due to impaired Wnt signaling.

An Exploration of the Role of Osteoclast Lineage Cells in Bone Tissue Engineering

Bone defects because of age, trauma, and surgery, which are exacerbated by medication side effects and common diseases such as osteoporosis, diabetes, and rheumatoid arthritis, are a problem of epidemic scale. The present clinical standard for treating these defects includes autografts and allografts. Although both treatments can promote robust regenerative outcomes, they fail to strike a desirable balance of availability, side effect profile, consistent regenerative efficacy, and affordability. This difficulty has contributed to the rise of bone tissue engineering (BTE) as a potential avenue through which enhanced bone regeneration could be delivered. BTE is founded upon a paradigm of using biomaterials, bioactive factors, osteoblast lineage cells (ObLCs), and vascularization to cue deficient bone tissue into a state of regeneration. Despite promising preclinical results, BTE has had modest success in being translated into the clinical setting. One barrier has been the simplicity of its paradigm relative to the complexity of biological bone. Therefore, this paradigm must be critically examined and expanded to better account for this complexity. One potential avenue for this is a more detailed consideration of osteoclast lineage cells (OcLCs). Although these cells ostensibly oppose ObLCs and bone regeneration through their resorptive functions, a myriad of investigations have shed light on their potential to influence bone equilibrium in more complex ways through their interactions with both ObLCs and bone matrix. Most BTE research has not systematically evaluated their influence. Yet contrary to expectations associated with the paradigm, a selection of BTE investigations has demonstrated that this influence can enhance bone regeneration in certain contexts. In addition, much work has elucidated the role of many controllable scaffold parameters in both inhibiting and stimulating the activity of OcLCs in parallel to bone regeneration. Therefore, this review aims to detail and explore the implications of OcLCs in BTE and how they can be leveraged to improve upon the existing BTE paradigm.

Loss of cped1 does not affect bone and lean tissue in zebrafish

Human genetic studies have nominated Cadherin-like and PC-esterase Domain-containing 1 (CPED1) as a candidate target gene mediating bone mineral density (BMD) and fracture risk heritability. Recent efforts to define the role of CPED1 in bone in mouse and human models have revealed complex alternative splicing and inconsistent results arising from gene targeting, making its function in bone difficult to interpret. To better understand the role of CPED1 in adult bone mass and morphology, we conducted a comprehensive genetic and phenotypic analysis of cped1 in zebrafish, an emerging model for bone and mineral research. We analyzed two different cped1 mutant lines and performed deep phenotyping to characterize more than 200 measures of adult vertebral, craniofacial, and lean tissue morphology. We also examined alternative splicing of zebrafish cped1 and gene expression in various cell/tissue types. Our studies fail to support an essential role of cped1 in adult zebrafish bone. Specifically, homozygous mutants for both cped1 mutant alleles, which are expected to result in loss-of-function and impact all cped1 isoforms, exhibited no significant differences in the measures examined when compared to their respective wildtype controls, suggesting that cped1 does not significantly contribute to these traits. We identified sequence differences in critical residues of the catalytic triad between the zebrafish and mouse orthologs of CPED1, suggesting that differences in key residues, as well as distinct alternative splicing, could underlie different functions of CPED1 orthologs in the two species. Our studies fail to support a requirement of cped1 in zebrafish bone and lean tissue, adding to evidence that variants at 7q31.31 can act independently of CPED1 to influence BMD and fracture risk.

The role of Clec11a in bone construction and remodeling

Bone is a dynamically active tissue whose health status is closely related to its construction and remodeling, and imbalances in bone homeostasis lead to a wide range of bone diseases. The sulfated glycoprotein C-type lectin structural domain family 11 member A (Clec11a) is a key factor in bone mass regulation that significantly promotes the osteogenic differentiation of bone marrow mesenchymal stem cells and osteoblasts and stimulates chondrocyte proliferation, thereby promoting longitudinal bone growth. More importantly, Clec11a has high therapeutic potential for treating various bone diseases and can enhance the therapeutic effects of the parathyroid hormone against osteoporosis. Clec11a is also involved in the stress/adaptive response of bone to exercise via mechanical stimulation of the cation channel Pieoz1. Clec11a plays an important role in promoting bone health and preventing bone disease and may represent a new target and novel drug for bone disease treatment. Therefore, this review aims to explore the role and possible mechanisms of Clec11a in the skeletal system, evaluate its value as a potential therapeutic target against bone diseases, and provide new ideas and strategies for basic research on Clec11a and preventing and treating bone disease.

Osteomodulin deficiency in mice causes a specific reduction of transversal cortical bone size

Skeletal growth, modeling, and remodeling are regulated by various molecules, one of them being the recently identified osteoanabolic factor WNT1. We have previously reported that WNT1 transcriptionally activates the expression of Omd, encoding Osteomodulin (OMD), in a murine mesenchymal cell line, which potentially explained the skeletal fragility of mice with mutational WNT1 inactivation, since OMD has been shown to regulate type I collagen fibril formation in vitro. In this study we confirmed the strong induction of Omd expression in a genome-wide expression analysis of transfected cells, and we obtained further evidence for Omd being a direct target gene of WNT1. To assess the in vivo relevance of this regulation, we crossed Omd-deficient mice with a mouse line harboring an inducible, osteoblast-specific Wnt1 transgene. After induction of Wnt1 expression for 1 or 3 weeks, the osteoanabolic potency of WNT1 was not impaired despite the Omd deficiency. Since current knowledge regarding the in vivo physiological function of OMD is limited, we next focused on skeletal phenotyping of wild-type and Omd-deficient littermates, in the absence of a Wnt1 transgene. Here we did not observe an impact of Omd deficiency on trabecular bone parameters by histomorphometry and μCT either. Importantly, however, male and female Omd-deficient mice at the ages of 12 and 24 weeks displayed a slender bone phenotype with significantly smaller long bones in the transversal dimension, while the longitudinal bone growth remained unaffected. Although mechanical testing revealed no significant changes explained by impaired bone material properties, atomic force microscopy of the femoral bone surface of Omd-deficient mice revealed moderate changes at the nanostructural level, indicating altered regulation of collagen fibril formation and aggregation. Taken together, our data demonstrate that, although OMD is dispensable for the osteoanabolic effect of WNT1, its deficiency in mice specifically modulates transversal cortical bone morphology.

A maternal brain hormone that builds bone

In lactating mothers, the high calcium (Ca2+) demand for milk production triggers significant bone loss1. Although oestrogen normally counteracts excessive bone resorption by promoting bone formation, this sex steroid drops precipitously during this postpartum period. Here we report that brain-derived cellular communication network factor 3 (CCN3) secreted from KISS1 neurons of the arcuate nucleus (ARCKISS1) fills this void and functions as a potent osteoanabolic factor to build bone in lactating females. We began by showing that our previously reported female-specific, dense bone phenotype2 originates from a humoral factor that promotes bone mass and acts on skeletal stem cells to increase their frequency and osteochondrogenic potential. This circulatory factor was then identified as CCN3, a brain-derived hormone from ARCKISS1 neurons that is able to stimulate mouse and human skeletal stem cell activity, increase bone remodelling and accelerate fracture repair in young and old mice of both sexes. The role of CCN3 in normal female physiology was revealed after detecting a burst of CCN3 expression in ARCKISS1 neurons coincident with lactation. After reducing CCN3 in ARCKISS1 neurons, lactating mothers lost bone and failed to sustain their progeny when challenged with a low-calcium diet. Our findings establish CCN3 as a potentially new therapeutic osteoanabolic hormone for both sexes and define a new maternal brain hormone for ensuring species survival in mammals.

Preclinical Rodent Models for Human Bone Disease, Including a Focus on Cortical Bone

Preclinical models (typically ovariectomized rats and genetically altered mice) have underpinned much of what we know about skeletal biology. They have been pivotal for developing therapies for osteoporosis and monogenic skeletal conditions, including osteogenesis imperfecta, achondroplasia, hypophosphatasia, and craniodysplasias. Further therapeutic advances, particularly to improve cortical strength, require improved understanding and more rigorous use and reporting. We describe here how trabecular and cortical bone structure develop, are maintained, and degenerate with aging in mice, rats, and humans, and how cortical bone structure is changed in some preclinical models of endocrine conditions (eg, postmenopausal osteoporosis, chronic kidney disease, hyperparathyroidism, diabetes). We provide examples of preclinical models used to identify and test current therapies for osteoporosis, and discuss common concerns raised when comparing rodent preclinical models to the human skeleton. We focus especially on cortical bone, because it differs between small and larger mammals in its organizational structure. We discuss mechanisms common to mouse and human controlling cortical bone strength and structure, including recent examples revealing genetic contributors to cortical porosity and osteocyte network configurations during growth, maturity, and aging. We conclude with guidelines for clear reporting on mouse models with a goal for better consistency in the use and interpretation of these models.

Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and disease

Wnts are secreted, lipid-modified proteins that bind to different receptors on the cell surface to activate canonical or non-canonical Wnt signaling pathways, which control various biological processes throughout embryonic development and adult life. Aberrant Wnt signaling pathway underlies a wide range of human disease pathogeneses. In this review, we provide an update of Wnt/β-catenin signaling components and mechanisms in bone formation, homeostasis, and diseases. The Wnt proteins, receptors, activators, inhibitors, and the crosstalk of Wnt signaling pathways with other signaling pathways are summarized and discussed. We mainly review Wnt signaling functions in bone formation, homeostasis, and related diseases, and summarize mouse models carrying genetic modifications of Wnt signaling components. Moreover, the therapeutic strategies for treating bone diseases by targeting Wnt signaling, including the extracellular molecules, cytosol components, and nuclear components of Wnt signaling are reviewed. In summary, this paper reviews our current understanding of the mechanisms by which Wnt signaling regulates bone formation, homeostasis, and the efforts targeting Wnt signaling for treating bone diseases. Finally, the paper evaluates the important questions in Wnt signaling to be further explored based on the progress of new biological analytical technologies.

GREM2 inactivation increases trabecular bone mass in mice

Osteoporosis is a common skeletal disease affecting millions of individuals world-wide, with an increased risk of fracture, and a decreased quality of life. Despite its well-known consequences, the etiology of osteoporosis and optimal treatment methods are not fully understood. Human genetic studies have identified genetic variants within the FMN2/GREM2 locus to be associated with trabecular volumetric bone mineral density (vBMD) and vertebral and forearm fractures, but not with cortical bone parameters. GREM2 is a bone morphogenetic protein (BMP) antagonist. In this study, we employed Grem2-deficient mice to investigate whether GREM2 serves as the plausible causal gene for the fracture signal at the FMN2/GREM2 locus. We observed that Grem2 is moderately expressed in bone tissue and particularly in osteoblasts. Complete Grem2 gene deletion impacted mouse survival and body growth. Partial Grem2 inactivation in Grem2+/- female mice led to increased trabecular BMD of femur and increased trabecular bone mass in tibia due to increased trabecular thickness, with an unchanged cortical thickness, as compared with wildtype littermates. Furthermore, Grem2 inactivation stimulated osteoblast differentiation, as evidenced by higher alkaline phosphatase (Alp), osteocalcin (Bglap), and osterix (Sp7) mRNA expression after BMP-2 stimulation in calvarial osteoblasts and osteoblasts from the long bones of Grem2-/- mice compared to wildtype littermates. These findings suggest that GREM2 is a possible target for novel osteoporotic treatments, to increase trabecular bone mass and prevent osteoporotic fractures.

Wnt16 Increases Bone-to-Implant Contact in an Osteopenic Rat Model by Increasing Proliferation and Regulating the Differentiation of Bone Marrow Stromal Cells

Osseointegration is a complex biological cascade that regulates bone regeneration after implant placement. Implants possessing complex multiscale surface topographies augment this regenerative process through the regulation of bone marrow stromal cells (MSCs) that are in contact with the implant surface. One pathway regulating osteoblastic differentiation is Wnt signaling, and upregulation of non-canonical Wnts increases differentiation of MSCs on these titanium substrates. Wnt16 is a non-canonical Wnt shown to regulate bone morphology in mouse models. This study evaluated the role of Wnt16 during surface-mediated osteoblastic differentiation of MSCs in vitro and osseointegration in vivo. MSCs were cultured on Ti substrates with different surface properties and non-canonical Wnt expression was determined. Subsequently, MSCs were cultured on Ti substrates +/-Wnt16 (100 ng/mL) and anti-Wnt16 antibodies (2 μg/mL). Wnt16 expression was increased in cells grown on microrough surfaces that were processed to be hydrophilic and have nanoscale roughness. However, treatment MSCs on these surfaces with exogenous rhWnt16b increased total DNA content and osteoprotegerin production, but reduced osteoblastic differentiation and production of local factors necessary for osteogenesis. Addition of anti-Wnt16 antibodies blocked the inhibitor effects of Wnt16. The response to Wnt16 was likely independent of other osteogenic pathways like Wnt11-Wnt5a signaling and semaphorin 3a signaling. We used an established rat model of cortical and trabecular femoral bone impairment following botox injections (2 injections of 8 units/leg each, starting and maintenance doses) to assess Wnt16 effects on whole bone morphology and implant osseointegration. Wnt16 injections did not alter whole bone morphology significantly (BV/TV, cortical thickness, restoration of trabecular bone) but were effective at increasing cortical bone-to-implant contact during impaired osseointegration in the botox model. The mechanical quality of the increased bone was not sufficient to rescue the deleterious effects of botox. Clinically, these results are important to understand the interaction of cortical and trabecular bone during implant integration. They suggest a role for Wnt16 in modulating bone remodeling by reducing osteoclastic activity. Targeted strategies to temporally regulate Wnt16 after implant placement could be used to improve osseointegration by increasing the net pool of osteoprogenitor cells.

Bone health index in the assessment of bone health: The Generation R Study

Bone Health Index (BHI) has been proposed as a useful instrument for assessing bone health in children. However, its relationship with fracture risk remains unknown. We aimed to investigate whether BHI is associated with bone mineral density (BMD) and prevalent fracture odds in children from the Generation R Study. We also implemented genome-wide association study (GWAS) and polygenic score (PGS) approaches to improve our understanding of BHI and its potential. In total, 4150 children (49.4 % boys; aged 9.8 years) with genotyped data and bone assessments were included in this study. BMD was measured across the total body (less head following ISCD guidelines) using a GE-Lunar iDXA densitometer; and BHI was determined from the hand DXA scans using BoneXpert®. Fractures were self-reported collected with home questionnaires. The association of BHI with BMD and fractures was evaluated using linear models corrected for age, sex, ethnicity, height, and weight. We observed a positive correlation between BHI and BMD (ρ = 0.32, p-value<0.0001). Further, every SD decrease in BHI was associated with an 11 % increased risk of prevalent fractures (OR:1.11, 95 % CI 1.00-1.24, p-value = 0.05). Our BHI GWAS identified variants (lead SNP rs1404264-A, p-value = 2.61 × 10-14) mapping to the ING3/CPED1/WNT16 locus. Children in the extreme tails of the BMD PGS presented a difference in BHI values of -0.10 standard deviations (95% CI -0.14 to -0.07; p-value<0.0001). On top of the demonstrated epidemiological association of BHI with both BMD and fracture risk, our results reveal a partially shared biological background between BHI and BMD. These findings highlight the potential value of using BHI to screen children at risk of fracture.

Toll-like receptor-2 induced inflammation causes local bone formation and activates canonical Wnt signaling

It is well established that inflammatory processes in the vicinity of bone often induce osteoclast formation and bone resorption. Effects of inflammatory processes on bone formation are less studied. Therefore, we investigated the effect of locally induced inflammation on bone formation. Toll-like receptor (TLR) 2 agonists LPS from Porphyromonas gingivalis and PAM2 were injected once subcutaneously above mouse calvarial bones. After five days, both agonists induced bone formation mainly at endocranial surfaces. The injection resulted in progressively increased calvarial thickness during 21 days. Excessive new bone formation was mainly observed separated from bone resorption cavities. Anti-RANKL did not affect the increase of bone formation. Inflammation caused increased bone formation rate due to increased mineralizing surfaces as assessed by dynamic histomorphometry. In areas close to new bone formation, an abundance of proliferating cells was observed as well as cells robustly stained for Runx2 and alkaline phosphatase. PAM2 increased the mRNA expression of Lrp5, Lrp6 and Wnt7b, and decreased the expression of Sost and Dkk1. In situ hybridization demonstrated decreased Sost mRNA expression in osteocytes present in old bone. An abundance of cells expressed Wnt7b in Runx2-positive osteoblasts and ß-catenin in areas with new bone formation. These data demonstrate that inflammation, not only induces osteoclastogenesis, but also locally activates canonical WNT signaling and stimulates new bone formation independent on bone resorption.

Oncostatin M: Dual Regulator of the Skeletal and Hematopoietic Systems

PURPOSE OF THE REVIEW

The bone and hematopoietic tissues coemerge during development and are functionally intertwined throughout mammalian life. Oncostatin M (OSM) is an inflammatory cytokine of the interleukin-6 family produced by osteoblasts, bone marrow macrophages, and neutrophils. OSM acts via two heterodimeric receptors comprising GP130 with either an OSM receptor (OSMR) or a leukemia inhibitory factor receptor (LIFR). OSMR is expressed on osteoblasts, mesenchymal, and endothelial cells and mice deficient for the Osm or Osmr genes have both bone and blood phenotypes illustrating the importance of OSM and OSMR in regulating these two intertwined tissues.

RECENT FINDINGS

OSM regulates bone mass through signaling via OSMR, adaptor protein SHC1, and transducer STAT3 to both stimulate osteoclast formation and promote osteoblast commitment; the effect on bone formation is also supported by action through LIFR. OSM produced by macrophages is an important inducer of neurogenic heterotopic ossifications in peri-articular muscles following spinal cord injury. OSM produced by neutrophils in the bone marrow induces hematopoietic stem and progenitor cell proliferation in an indirect manner via OSMR expressed by bone marrow stromal and endothelial cells that form hematopoietic stem cell niches. OSM acts as a brake to therapeutic hematopoietic stem cell mobilization in response to G-CSF and CXCR4 antagonist plerixafor. Excessive OSM production by macrophages in the bone marrow is a key contributor to poor hematopoietic stem cell mobilization (mobilopathy) in people with diabetes. OSM and OSMR may also play important roles in the progression of several cancers. It is increasingly clear that OSM plays unique roles in regulating the maintenance and regeneration of bone, hematopoietic stem and progenitor cells, inflammation, and skeletal muscles. Dysregulated OSM production can lead to bone pathologies, defective muscle repair and formation of heterotopic ossifications in injured muscles, suboptimal mobilization of hematopoietic stem cells, exacerbated inflammatory responses, and anti-tumoral immunity. Ongoing research will establish whether neutralizing antibodies or cytokine traps may be useful to correct pathologies associated with excessive OSM production.

Independent mesenchymal progenitor pools respectively produce and maintain osteogenic and chondrogenic cells in zebrafish

Skeletal tissues including cartilage and bones are characteristic features of vertebrates that are crucial for supporting body morphology and locomotion. Studies mainly in mice have shown that osteoblasts and chondroblasts are supplied from several progenitors like the sclerotome cells in the embryonic stage, osteo-chondroprogenitors in growing long bones, and skeletal stem cells of bone marrow in the postnatal period. However, the exact origins of progenitor cells, their lineage relationships, and their potential to differentiate into osteoblasts and chondroblasts from embryos to adult tissues are not well understood. In this study, we conducted clonal cell tracking in zebrafish and showed that sox9a+ cells are already committed to either chondrogenic or osteogenic fates during embryonic stages and that respective progenies are independently maintained as mesenchymal progenitor pools. Once committed, they never change their lineage identities throughout animal life, even through regeneration. In addition, we further revealed that only osteogenic mesenchymal cells replenish the osteoblast progenitor cells (OPCs), a population of reserved tissue stem cells found to be involved in the de novo production of osteoblasts during regeneration and homeostasis in zebrafish. Thus, our clonal cell tracking study in zebrafish firstly revealed that the mesenchymal progenitor cells that are fated to develop into either chondroblasts or osteoblasts serve as respective tissue stem cells to maintain skeletal tissue homeostasis. Such mesenchymal progenitors dedicated to producing either chondroblasts or osteoblasts would be important targets for skeletal tissue regeneration.

Wnt16 Promotes Vascular Smooth Muscle Contractile Phenotype and Function via Taz (Wwtr1) Activation in Male LDLR-/- Mice

Wnt16 is expressed in bone and arteries, and maintains bone mass in mice and humans, but its role in cardiovascular physiology is unknown. We show that Wnt16 protein accumulates in murine and human vascular smooth muscle (VSM). WNT16 genotypes that convey risk for bone frailty also convey risk for cardiovascular events in the Dallas Heart Study. Murine Wnt16 deficiency, which causes postnatal bone loss, also reduced systolic blood pressure. Electron microscopy demonstrated abnormal VSM mitochondrial morphology in Wnt16-null mice, with reductions in mitochondrial respiration. Following angiotensin-II (AngII) infusion, thoracic ascending aorta (TAA) dilatation was greater in Wnt16-/- vs Wnt16+/+ mice (LDLR-/- background). Acta2 (vascular smooth muscle alpha actin) deficiency has been shown to impair contractile phenotype and worsen TAA aneurysm with concomitant reductions in blood pressure. Wnt16 deficiency reduced expression of Acta2, SM22 (transgelin), and other contractile genes, and reduced VSM contraction induced by TGFβ. Acta2 and SM22 proteins were reduced in Wnt16-/- VSM as was Ankrd1, a prototypic contractile target of Yap1 and Taz activation via TEA domain (TEAD)-directed transcription. Wnt16-/- VSM exhibited reduced nuclear Taz and Yap1 protein accumulation. SiRNA targeting Wnt16 or Taz, but not Yap1, phenocopied Wnt16 deficiency, and Taz siRNA inhibited contractile gene upregulation by Wnt16. Wnt16 incubation stimulated mitochondrial respiration and contraction (reversed by verteporfin, a Yap/Taz inhibitor). SiRNA targeting Taz inhibitors Ccm2 and Lats1/2 mimicked Wnt16 treatment. Wnt16 stimulated Taz binding to Acta2 chromatin and H3K4me3 methylation. TEAD cognates in the Acta2 promoter conveyed transcriptional responses to Wnt16 and Taz. Wnt16 regulates cardiovascular physiology and VSM contractile phenotype, mediated via Taz signaling.

Unraveling the prevalence of various signalling pathways in non-small-cell lung cancer: a review

Cancer has become a huge public health issue all around the world. The focus of research is on innovative cancer therapy techniques that include the disease's unique targets. Among the cancer-related deaths that occur, lung cancer is considered to be one of the major, accounting for about 1.6 million fatalities globally in 2012, or nearly 20% of all cancer deaths. Non-small-cell lung cancer, a type of lung cancer comprises upto 84% of lung cancer cases, demonstrating the need for a more effective treatment. A novel category of cancer management, known as targeted cancer medicines, has risen to prominence in recent years. Targeted cancer treatments, like traditional chemotherapy, employ pharmacological drugs to slow cancer development, enhance cell death, and prevent it from spreading. Targeted treatments, as the name implies, work by interfering with particular proteins implicated in cancer. Numerous research conducted in the last several decades have led to the conclusion that signalling pathways are involved in the growth of lung cancer. All malignant tumours are produced, spread, invade, and behave in various abnormal ways due to abnormal pathways. Numerous significant signalling pathways, including the RTK/RAS/MAP-Kinase pathway (hence often referred to as RTK-RAS for simplicity), PI3K/Akt signalling, and others, have been discovered as commonly genetically changed. The current developments in research on various signalling pathways, as well as the underlying mechanisms of the molecules implicated in these pathways, are innovatively summarised in this review. To give a good sense of the study that has been done so far, many routes are placed together. Thus, this review includes the detailed description regarding each pathways, the mutations formed, and the present treatment strategy to overcome the resistance.

Wnt pathway in bone: knowledge structure and hot spots from 1993 to 2022

Background: The role of the Wnt pathway in bone and its targets in skeletal disease has garnered interest, but the field lacks a systematic analysis of research. This paper presents a bibliometric study of publications related to the Wnt signaling pathway in bone to describe the current state of study and predict future outlooks. Methods: All relevant articles and reviews from 1993 to 2022 were collected from the Web of Science Core Collection (WoSCC). Bibliometric analysis and visualization were performed using CiteSpace 6.1 R3, VOSviewer 1.6.15, and the Online Analysis Platform of Literature Metrology (http://bibliometric.com/). Results: A total of 7,184 papers were retrieved, authored by 28,443 researchers from 89 countries/regions and published in 261 academic journals. The annual publication numbers peaked in 2021. China and United States are the leading countries, with the University of California and Harvard University as the most active institutions. Wang, Yang is the most prolific author. Bone has the most published research, while Proceedings of the National Academy of Sciences of the United States is the most cited journal on average. The main keywords include expression, Wnt, osteoporosis, bone, and osteogenic differentiation. Current and developing research hotspots focus on bone mass, sclerostin antibody, multiple myeloma, and cartilage development. Conclusion: This paper provides new insights for researchers to delve into the mechanisms of Wnt and bone related diseases and translate into clinical studies. It reveals the development and future research trends in Wnt and skeletal-related studies.

Sfrp4 is required to maintain Ctsk-lineage periosteal stem cell niche function

We have previously reported that the cortical bone thinning seen in mice lacking the Wnt signaling antagonist Sfrp4 is due in part to impaired periosteal apposition. The periosteum contains cells which function as a reservoir of stem cells and contribute to cortical bone expansion, homeostasis, and repair. However, the local or paracrine factors that govern stem cells within the periosteal niche remain elusive. Cathepsin K (Ctsk), together with additional stem cell surface markers, marks a subset of periosteal stem cells (PSCs) which possess self-renewal ability and inducible multipotency. Sfrp4 is expressed in periosteal Ctsk-lineage cells, and Sfrp4 global deletion decreases the pool of PSCs, impairs their clonal multipotency for differentiation into osteoblasts and chondrocytes and formation of bone organoids. Bulk RNA sequencing analysis of Ctsk-lineage PSCs demonstrated that Sfrp4 deletion down-regulates signaling pathways associated with skeletal development, positive regulation of bone mineralization, and wound healing. Supporting these findings, Sfrp4 deletion hampers the periosteal response to bone injury and impairs Ctsk-lineage periosteal cell recruitment. Ctsk-lineage PSCs express the PTH receptor and PTH treatment increases the % of PSCs, a response not seen in the absence of Sfrp4. Importantly, in the absence of Sfrp4, PTH-dependent increase in cortical thickness and periosteal bone formation is markedly impaired. Thus, this study provides insights into the regulation of a specific population of periosteal cells by a secreted local factor, and shows a central role for Sfrp4 in the regulation of Ctsk-lineage periosteal stem cell differentiation and function.

Rspo2 exacerbates rheumatoid arthritis by targeting aggressive phenotype of fibroblast-like synoviocytes and disrupting chondrocyte homeostasis via Wnt/β-catenin pathway

BACKGROUND

The aggressive phenotype of fibroblast-like synoviocytes (FLS) has been identified as a contributing factor to the exacerbation of rheumatoid arthritis (RA) through the promotion of synovitis and cartilage damage. Regrettably, there is currently no effective therapeutic intervention available to address this issue. Recent research has shed light on the crucial regulatory role of R-spondin-2 (Rspo2) in cellular proliferation, cartilage degradation, and tumorigenesis. However, the specific impact of Rspo2 on RA remains poorly understood. We aim to investigate the function and mechanism of Rspo2 in regulating the aggressive phenotype of FLS and maintaining chondrocyte homeostasis in the context of RA.

METHODS

The expression of Rspo2 in knee joint synovium and cartilage were detected in RA mice with antigen-induced arthritis (AIA) and RA patients. Recombinant mouse Rspo2 (rmRspo2), Rspo2 neutralizing antibody (Rspo2-NAb), and recombinant mouse DKK1 (rmDKK1, a potent inhibitor of Wnt signaling pathway) were used to explore the role and mechanism of Rspo2 in the progression of RA, specifically in relation to the aggressive phenotype of FLS and chondrocyte homeostasis, both in vivo and in vitro.

RESULTS

We indicated that Rspo2 expression was upregulated both in synovium and articular cartilage as RA progressed in RA mice and RA patients. Increased Rspo2 upregulated the expression of leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), as the ligand for Rspo2, and β-catenin in FLS and chondrocytes. Subsequent investigations revealed that intra-articular administration of rmRspo2 caused striking progressive synovitis and articular cartilage destruction to exacerbate RA progress in mice. Conversely, neutralization of Rspo2 or inhibition of the Wnt/β-catenin pathway effectively alleviated experimental RA development. Moreover, Rspo2 facilitated FLS aggressive phenotype and disrupted chondrocyte homeostasis primarily through activating Wnt/β-catenin pathway, which were effectively alleviated by Rspo2-NAb or rmDKK1.

CONCLUSIONS

Our data confirmed a critical role of Rspo2 in enhancing the aggressive phenotype of FLS and disrupting chondrocyte homeostasis through the Wnt/β-catenin pathway in the context of RA. Furthermore, the results indicated that intra-articular administration of Rspo2 neutralizing antibody or recombinant DKK1 might represent a promising therapeutic strategy for the treatment of RA.

An atlas of genetic determinants of forearm fracture

Osteoporotic fracture is among the most common and costly of diseases. While reasonably heritable, its genetic determinants have remained elusive. Forearm fractures are the most common clinically recognized osteoporotic fractures with a relatively high heritability. To establish an atlas of the genetic determinants of forearm fractures, we performed genome-wide association analyses including 100,026 forearm fracture cases. We identified 43 loci, including 26 new fracture loci. Although most fracture loci associated with bone mineral density, we also identified loci that primarily regulate bone quality parameters. Functional studies of one such locus, at TAC4, revealed that Tac4-/- mice have reduced mechanical bone strength. The strongest forearm fracture signal, at WNT16, displayed remarkable bone-site-specificity with no association with hip fractures. Tall stature and low body mass index were identified as new causal risk factors for fractures. The insights from this atlas may improve fracture prediction and enable therapeutic development to prevent fractures.

Anemoside B4 attenuates RANKL-induced osteoclastogenesis by upregulating Nrf2 and dampens ovariectomy-induced bone loss

Increased numbers and functional overactivity of osteoclasts are the pathological basis for bone loss diseases such as osteoporosis, which are characterized by cortical bone thinning, decreased trabecular bone quantity, and reduced bone mineral density. Effective inhibition of osteoclast formation and bone resorption are important means of treating such skeletal diseases. Anemoside B4 (AB4), the main active component of Pulsatilla chinensis, possesses a wide range of anti-inflammatory and immunoregulatory effects. However, its effect and mechanism in osteoclast differentiation remain unclear. In this study, we found through tartrate-resistant acidic phosphatase (TRAcP) staining and immunofluorescence staining that AB4 inhibited the differentiation, fusion, and bone-resorption functions of osteoclasts induced by receptor activator of nuclear factor κB ligand (RANKL) in vitro. Additionally, real time PCR (RT-qPCR) and western blot analysis showed AB4 downregulated the expression of osteoclast marker genes, including Nfatc1, Fos, and Ctsk, while upregulating Nrf2 expression. AB4 (5 mg/kg) alleviated bone loss in ovariectomized mice by inhibiting osteoclast formation. Furthermore, the knockout of Nrf2 weakened the inhibitory effects of AB4 on osteoclast formation and related gene expression. In summary, the results suggest AB4 can inhibit osteoclast differentiation and function by activating Nrf2 and indicate AB4 may be a candidate drug for osteoporosis.

Genetic Variants in WNT16 and PKD2L1 Locus Affect Heel Ultrasound Bone Stiffness: Analyses from the General Population and Patients Evaluated for Osteoporosis

Osteoporosis, a complex chronic disease with increasing prevalence, is characterised by reduced bone mineral density (BMD) and increased fracture risk. The high heritability of BMD suggests substantial impact of the individual genetic disposition on bone phenotypes and the development of osteoporosis. In the past years, genome-wide association studies (GWAS) identified hundreds of genetic variants associated with BMD or osteoporosis. Here, we analysed 1103 single nucleotide polymorphisms (SNPs), previously identified as associated with estimated BMD (eBMD) in the UK Biobank. We assessed whether these SNPs are related to heel stiffness index obtained by quantitative ultrasound in 5665 adult participants of the Study of Health in Pomerania (SHIP). We confirmed 45 significant associations after correction for multiple testing. Next, we analysed six selected SNPs in 631 patients evaluated for osteoporosis [rs2707518 (CPED1/WNT16), rs3779381 (WNT16), rs115242848 (LOC101927709/EN1), rs10239787 (JAZF1), rs603424 (PKD2L1) and rs6968704 (JAZF1)]. Differences in minor allele frequencies (MAF) of rs2707518 and rs3779381 between SHIP participants (higher MAF) and patients evaluated for osteoporosis (lower MAF) indicated a protective effect of the minor allele on bone integrity. In contrast, differences in MAF of rs603424 indicated a harmful effect. Co-localisation analyses indicated that the rs603424 effect may be mediated via stearoyl-CoA desaturase (SCD) expression, an enzyme highly expressed in adipose tissue with a crucial role in lipogenesis. Taken together, our results support the role of the WNT16 pathway in the regulation of bone properties and indicate a novel causal role of SCD expression in adipose tissue on bone integrity.

Transcriptomics reveals the molecular regulation of Chinese medicine formula on improving bone quality in broiler

Skeletal disorder is of concern to the poultry industry as it affects animal welfare and production performance. Traditional Chinese medicine could improve bone quality and reduce the incidence of bone disease, but the molecular regulation of Chinese medicine formula (CMF) on improving bone quality in broilers is still unclear. This study was performed to research the effects of CMF on skeletal performance of Cobb broilers and reveal the molecular regulation. A total of 120 one-day-old Cobb broilers were randomly allocated into 4 equal groups of 30 chickens, with 5 replicates and 6 chickens in each replicate. The control (CON) group was fed a diet without CMF, while the CMF1, CMF2, and CMF3 groups were supplemented with different CMF at 6,000 mg/kg diet, respectively. The broilers were raised to 60 d of age, then bone tissues were collected for biomechanical properties, micro-CT detection and transcriptomic sequencing analysis. The results showed that CMF3 improved the biomechanical properties of broiler tibia, via increasing the elastic modulus (P < 0.05), yield strength (P > 0.05), maximum stress (P < 0.05) and fracture stress (P < 0.05) of the tibia. Micro-CT analysis indicated that CMF3 increased the bone mineral density (BMD), bone volume/total volume (BV/TV), bone surface density (BS/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and decreased the trabecular separation (Tb.Sp) of femur cancellous bone (P < 0.05). RNA-seq analysis revealed 2,177 differentially expressed genes (DEGs) (|log2FoldChange| ≥ 1, FDR < 0.05) between the CMF3 group and CON group. Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) analysis showed 13 pathways mostly associated with bone growth and development and bone metabolism, and we identified 39 bone-related DEGs. This study suggests that CMF3 could improve bone strength and bone microstructure of broilers, and showed a positive effect on bone performance. Our research could provide a theoretical reference for the development of pollution-free feed additives to improve the skeletal performance of broilers, which could help promote healthy farming of chickens.

Single-Cell Integration of BMD GWAS Results Prioritize Candidate Genes Influencing Age-Related Bone Loss

The regulation of bone mineral density (BMD) is highly influenced by genetics and age. Although genome-wide association studies (GWAS) for BMD have uncovered many genes through their proximity to associated variants (variant nearest-neighbor [VNN] genes), the cell-specific mechanisms of each VNN gene remain unclear. This is primarily due to the inability to prioritize these genes by cell type and age-related expression. Using age-related transcriptomics, we found that the expression of many VNN genes was upregulated in the bone and marrow from aged mice. Candidate genes from GWAS were investigated using single-cell RNA-sequencing (scRNA-seq) datasets to enrich for cell-specific expression signatures. VNN candidate genes are highly enriched in osteo-lineage cells, osteocytes, hypertrophic chondrocytes, and Lepr+ mesenchymal stem cells. These data were used to generate a "blueprint" for Cre-loxp mouse line selection for functional validation of candidate genes and further investigation of their role in BMD maintenance throughout aging. In VNN-gene-enriched cells, Sparc, encoding the extracellular matrix (ECM) protein osteonectin, was robustly expressed. This, along with expression of numerous other ECM genes, indicates that many VNN genes likely have roles in ECM deposition by osteoblasts. Overall, we provide data supporting streamlined translation of GWAS candidate genes to potential novel therapeutic targets for the treatment of osteoporosis. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

CircFam190a: a critical positive regulator of osteoclast differentiation via enhancement of the AKT1/HSP90β complex

The identification of key regulatory factors that control osteoclastogenesis is important. Accumulating evidence indicates that circular RNAs (circRNAs) are discrete functional entities. However, the complexities of circRNA expression as well as the extent of their regulatory functions during osteoclastogenesis have yet to be revealed. Here, based on circular RNA sequencing data, we identified a circular RNA, circFam190a, as a critical regulator of osteoclast differentiation and function. During osteoclastogenesis, circFam190a is significantly upregulated. In vitro, circFam190a enhanced osteoclast formation and function. In vivo, overexpression of circFam190a induced significant bone loss, while knockdown of circFam190a prevented pathological bone loss in an ovariectomized (OVX) mouse osteoporosis model. Mechanistically, our data suggest that circFam90a enhances the binding of AKT1 and HSP90β, promoting AKT1 stability. Altogether, our findings highlight the critical role of circFam190a as a positive regulator of osteoclastogenesis, and targeting circFam190a might be a promising therapeutic strategy for treating pathological bone loss.

Generic Platform for the Multiplexed Targeted Electrochemical Detection of Osteoporosis-Associated Single Nucleotide Polymorphisms Using Recombinase Polymerase Solid-Phase Primer Elongation and Ferrocene-Modified Nucleoside Triphosphates

Osteoporosis is a multifactorial disease influenced by genetic and environmental factors, which contributes to an increased risk of bone fracture, but early diagnosis of this disease cannot be achieved using current techniques. We describe a generic platform for the targeted electrochemical genotyping of SNPs identified by genome-wide association studies to be associated with a genetic predisposition to osteoporosis. The platform exploits isothermal solid-phase primer elongation with ferrocene-labeled nucleoside triphosphates. Thiolated reverse primers designed for each SNP were immobilized on individual gold electrodes of an array. These primers are designed to hybridize to the SNP site at their 3'OH terminal, and primer elongation occurs only where there is 100% complementarity, facilitating the identification and heterozygosity of each SNP under interrogation. The platform was applied to real blood samples, which were thermally lysed and directly used without the need for DNA extraction or purification. The results were validated using Taqman SNP genotyping assays and Sanger sequencing. The assay is complete in just 15 min with a total cost of 0.3€ per electrode. The platform is completely generic and has immense potential for deployment at the point of need in an automated device for targeted SNP genotyping with the only required end-user intervention being sample addition.

Examining craniofacial variation among crispant and mutant zebrafish models of human skeletal diseases

Genetic diseases affecting the skeletal system present with a wide range of symptoms that make diagnosis and treatment difficult. Genome-wide association and sequencing studies have identified genes linked to human skeletal diseases. Gene editing of zebrafish models allows researchers to further examine the link between genotype and phenotype, with the long-term goal of improving diagnosis and treatment. While current automated tools enable rapid and in-depth phenotyping of the axial skeleton, characterizing the effects of mutations on the craniofacial skeleton has been more challenging. The objective of this study was to evaluate a semi-automated screening tool can be used to quantify craniofacial variations in zebrafish models using four genes that have been associated with human skeletal diseases (meox1, plod2, sost, and wnt16) as test cases. We used traditional landmarks to ground truth our dataset and pseudolandmarks to quantify variation across the 3D cranial skeleton between the groups (somatic crispant, germline mutant, and control fish). The proposed pipeline identified variation between the crispant or mutant fish and control fish for four genes. Variation in phenotypes parallel human craniofacial symptoms for two of the four genes tested. This study demonstrates the potential as well as the limitations of our pipeline as a screening tool to examine multi-dimensional phenotypes associated with the zebrafish craniofacial skeleton.

Fgfr1 deficiency in osteocytes leads to increased bone mass by enhancing Wnt/β-catenin signaling

Osteoporosis (OP) is the most common skeletal disease in middle-aged and elderly people. A comprehensive understanding of the pathogenesis of osteoporosis is important. Fibroblast growth factor receptor 1 (FGFR1) is an important molecule for skeletal development and bone remodeling. Osteocytes are the most numerous cells in bone and play critical roles in bone homeostasis, however the effect of FGFR1 on osteocytes is still unclear. To clarify the direct effects of FGFR1 on osteocytes, we conditionally deleted Fgfr1 in osteocytes with Dentin matrix protein 1 (Dmp1)-Cre. We found that mice lacking Fgfr1 in osteocytes (Fgfr1^f/f;Dmp-cre, MUT) showed increased trabecular bone mass at 2 and 6 months of age, which resulted from enhanced bone formation and decreased bone resorption. Furthermore, the cortical bone was thicker in WT mice than that in MUT mice at 2 and 6 months of age. Histological analysis showed that MUT mice had a decreased number of osteocytes but an increased number of osteocyte dendrites. We further found that mice lacking Fgfr1 in osteocytes showed enhanced activation of β-catenin signaling. The expression of sclerostin, an inhibitor of Wnt/β-catenin signaling, was obviously decreased in MUT mice. Furthermore, we found that FGFR1 can inhibit the expression of β-catenin and decrease the activity of β-catenin signaling. In brief, our study showed that FGFR1 in osteocytes can regulate bone mass by regulating Wnt/β-catenin signaling, providing genetic evidence that FGFR1 plays essential roles in osteocytes during bone remodeling and suggesting that FGFR1 is a potential therapeutic target for the prevention of bone loss.

The osteocyte and its osteoclastogenic potential

The skeleton is an organ of dual functionality; on the one hand, it provides protection and structural competence. On the other hand, it participates extensively in coordinating homeostasis globally given that it is a mineral and hormonal reservoir. Bone is the only tissue in the body that goes through strategically consistent bouts of bone resorption to ensure its integrity and organismal survival in a temporally and spatially coordinated process, known as bone remodeling. Bone remodeling is directly enacted by three skeletal cell types, osteoclasts, osteoblasts, and osteocytes; these cells represent the acting force in a basic multicellular unit and ensure bone health maintenance. The osteocyte is an excellent mechanosensory cell and has been positioned as the choreographer of bone remodeling. It is, therefore, not surprising that a holistic grasp of the osteocyte entity in the bone is warranted. This review discusses osteocytogenesis and associated molecular and morphological changes and describes the osteocytic lacunocanalicular network (LCN) and its organization. We highlight new knowledge obtained from transcriptomic analyses of osteocytes and discuss the regulatory role of osteocytes in promoting osteoclastogenesis with an emphasis on the case of osteoclastogenesis in anosteocytic bones. We arrive at the conclusion that osteocytes exhibit several redundant means through which osteoclast formation can be initiated. However, whether osteocytes are true "orchestrators of bone remodeling" cannot be verified from the animal models used to study osteocyte biology in vivo. Results from studying osteocyte biology using current animal models should come with the caveat that these models are not osteocyte-specific, and conclusions from these studies should be interpreted cautiously.

Spatial Lipidomic Profiling of Mouse Joint Tissue Demonstrates the Essential Role of PHOSPHO1 in Growth Plate Homeostasis

Lipids play a crucial role in signaling and metabolism, regulating the development and maintenance of the skeleton. Membrane lipids have been hypothesized to act as intermediates upstream of orphan phosphatase 1 (PHOSPHO1), a major contributor to phosphate generation required for bone mineralization. Here, we spatially resolve the lipid atlas of the healthy mouse knee and demonstrate the effects of PHOSPHO1 ablation on the growth plate lipidome. Lipids spanning 17 subclasses were mapped across the knee joints of healthy juvenile and adult mice using matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS), with annotation supported by shotgun lipidomics. Multivariate analysis identified 96 and 80 lipid ions with differential abundances across joint tissues in juvenile and adult mice, respectively. In both ages, marrow was enriched in phospholipid platelet activating factors (PAFs) and related metabolites, cortical bone had a low lipid content, whereas lysophospholipids were strikingly enriched in the growth plate, an active site of mineralization and PHOSPHO1 activity. Spatially-resolved profiling of PHOSPHO1-knockout (KO) mice across the resting, proliferating, and hypertrophic growth plate zones revealed 272, 306, and 296 significantly upregulated, and 155, 220, and 190 significantly downregulated features, respectively, relative to wild-type (WT) controls. Of note, phosphatidylcholine, lysophosphatidylcholine, sphingomyelin, lysophosphatidylethanolamine, and phosphatidylethanolamine derived lipid ions were upregulated in PHOSPHO1-KO versus WT. Our imaging pipeline has established a spatially-resolved lipid signature of joint tissues and has demonstrated that PHOSPHO1 ablation significantly alters the growth plate lipidome, highlighting an essential role of the PHOSPHO1-mediated membrane phospholipid metabolism in lipid and bone homeostasis. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

The role of wnt signaling in diabetes-induced osteoporosis

Osteoporosis, a chronic complication of diabetes mellitus, is characterized by a reduction in bone mass, destruction of bone microarchitecture, decreased bone strength, and increased bone fragility. Because of its insidious onset, osteoporosis renders patients highly susceptible to pathological fractures, leading to increased disability and mortality rates. However, the specific pathogenesis of osteoporosis induced by chronic hyperglycemia has not yet been fully elucidated. But it is currently known that the disruption of Wnt signaling triggered by chronic hyperglycemia is involved in the pathogenesis of diabetic osteoporosis. There are two main types of Wnt signaling pathways, the canonical Wnt signaling pathway (β-catenin-dependent) and the non-canonical Wnt signaling pathway (non-β-catenin-dependent), both of which play an important role in regulating the balance between bone formation and bone resorption. Therefore, this review systematically describes the effects of abnormal Wnt pathway signaling on bone homeostasis under hyperglycemia, hoping to reveal the relationship between Wnt signaling and diabetic osteoporosis to further improve understanding of this disease.

Histone methyltransferase SETDB1 promotes osteogenic differentiation in osteoporosis by activating OTX2-mediated BMP-Smad and Wnt/β-catenin pathways

Osteogenic differentiation plays important roles in the pathogenesis of osteoporosis. In this study, we explored the regulatory mechanism of histone methyltransferase SET domain bifurcated 1 (SETDB1) underlying the osteogenic differentiation in osteoporosis. The common osteoporosis-related genes were retrieved from the GeneCards, CTD, and Phenolyzer databases. The enrichment analysis was conducted on the candidate osteoporosis-related genes using the PANTHER software, and the binding site between transcription factors and target genes predicted by hTFtarget. The bioinformatics analyses suggested 6 osteoporosis-related chromatin/chromatin binding protein or regulatory proteins (HDAC4, SIRT1, SETDB1, MECP2, CHD7, and DKC1). Normal and osteoporosis tissues were collected from osteoporosis patients to examine the expression of SETDB1. It was found that SETDB1 was poorly expressed in osteoporotic femoral tissues, indicating that SETDB1 might be involved in the development of osteoporosis. We induced SETDB1 overexpression/knockdown, orthodenticle homeobox 2 (OTX2) overexpression, activation of Wnt/β-catenin or BMP-Smad pathways alone or in combination in osteoblasts or ovariectomized mice. The data indicated that SETDB1 methylation regulated H3K9me3 in the OTX2 promoter region and inhibited the expression of OTX2. Besides, the BMP-Smad and Wnt/β-catenin pathways were inhibited by OTX2, thereby resulting in inhibited osteogenic differentiation. Animal experiments showed that overexpressed SETDB1 could promote the increase of calcium level and differentiation of femoral tissues. In conclusion, upregulation of SETDB1 promotes osteogenic differentiation by inhibiting OTX2 and activating the BMP-Smad and Wnt/β-catenin pathways in osteoporosis.

Structural characterization and anti-osteoporosis effects of polysaccharide purified from Eucommia ulmoides Oliver cortex based on its modulation on bone metabolism

EuOCP3, with a molecular weight of 38.1 kDa, is an acidic polysaccharide purified from Eucommia ulmoides Oliver cortex. Herein, we determined that the main backbone of EuOCP3 was predominantly composed of →4)-α-GalpA-(1 → 4)-α-GalpA-(1→, →4)-α-GalpA-(1 → 5)-α-Araf-(1→, →4)-α-GalpA-(1 → 2)-α-Rhap-(1→, and →4)-α-GalpA-(1 → 5)-α-Araf-(1 → 2)-α-Rhap-(1 → repeating blocks, which were connected by →2,3,5)-α-Araf-(1→. The side chains, substituted at C-2 and C-5 of →2,3,5)-α-Araf-(1→, contained T-β-Araf→ and T-β-Araf → 4)-α-GalpA-(1 → residues. In dexamethasone (Dex)-induced osteoporosis (OP) mice, EuOCP3 treatment restored cortical bone thickness, increased mineralized bone area, enhanced the number of osteoblasts, and decreased the number of osteoclasts on the surface of cortical bone. Combining analysis of gut microflora, serum metabolite profiles, and biological detection results, we demonstrated that EuOCP3 regulated the abundance of specific species within the gut microflora, such as g_Dorea and g_Prevotella, and ameliorated oxidative stress. In turn, enhancement of osteogenic function and restoration of bone metabolism via the extracellular signal-regulated kinase (ERK)/c-Jun N-terminal kinase (JNK)/nuclear factor erythroid-2 related factor 2 (Nrf2) signaling pathway was indicated. The current findings contribute to understanding the potential of EuOCP3 in anti-OP treatment.

Integrated Analysis of Transcriptome Expression Profiles Reveals miRNA-326-NKX3.2-Regulated Porcine Chondrocyte Differentiation

The porcine body length trait is an essential factor affecting meat production and reproductive performance. It is evident that the development/lengthening of individual vertebrae is one of the main reasons for increases in body length; however, the underlying molecular mechanism remains unclear. In this study, RNA-seq analysis was used to profile the transcriptome (lncRNA, mRNA, and miRNA) of the thoracic intervertebral cartilage (TIC) at two time points (1 and 4 months) during vertebral column development in Yorkshire (Y) and Wuzhishan pigs (W). There were four groups: 1- (Y1) and 4-month-old (Y4) Yorkshire pigs and 1- (W1) and 4-month-old (W4) Wuzhishan pigs. In total, 161, 275, 86, and 126 differentially expressed (DE) lncRNAs, 1478, 2643, 404, and 750 DE genes (DEGs), and 74,51, 34, and 23 DE miRNAs (DE miRNAs) were identified in the Y4 vs. Y1, W4 vs. W1, Y4 vs. W4, and Y1 vs. W1 comparisons, respectively. Functional analysis of these DE transcripts (DETs) demonstrated that they had participated in various biological processes, such as cellular component organization or biogenesis, the developmental process, the metabolic process, bone development, and cartilage development. The crucial bone development-related candidate genes NK3 Homeobox 2 (NKX3.2), Wnt ligand secretion mediator (WLS), gremlin 1 (GREM1), fibroblast growth factor receptor 3 (FGFR3), hematopoietically expressed homeobox (HHEX), (collagen type XI alpha 1 chain (COL11A1), and Wnt Family Member 16 (WNT16)) were further identified by functional analysis. Moreover, lncRNA, miRNA, and gene interaction networks were constructed; a total of 55 lncRNAs, 6 miRNAs, and 7 genes formed lncRNA-gene, miRNA-gene, and lncRNA-miRNA-gene pairs, respectively. The aim was to demonstrate that coding and non-coding genes may co-regulate porcine spine development through interaction networks. NKX3.2 was identified as being specifically expressed in cartilage tissues, and it delayed chondrocyte differentiation. miRNA-326 regulated chondrocyte differentiation by targeting NKX3.2. The present study provides the first non-coding RNA and gene expression profiles in the porcine TIC, constructs the lncRNA-miRNA-gene interaction networks, and confirms the function of NKX3.2 in vertebral column development. These findings contribute to the understanding of the potential molecular mechanisms regulating pig vertebral column development. They expand our knowledge about the differences in body length between different pig species and provide a foundation for future studies.

B4GALNT3 regulates glycosylation of sclerostin and bone mass

BACKGROUND

Global sclerostin inhibition reduces fracture risk efficiently but has been associated with cardiovascular side effects. The strongest genetic signal for circulating sclerostin is in the B4GALNT3 gene region, but the causal gene is unknown. B4GALNT3 expresses the enzyme beta-1,4-N-acetylgalactosaminyltransferase 3 that transfers N-acetylgalactosamine onto N-acetylglucosaminebeta-benzyl on protein epitopes (LDN-glycosylation).

METHODS

To determine if B4GALNT3 is the causal gene, B4galnt3^-/- mice were developed and serum levels of total sclerostin and LDN-glycosylated sclerostin were analysed and mechanistic studies were performed in osteoblast-like cells. Mendelian randomization was used to determine causal associations.

FINDINGS

B4galnt3^-/- mice had higher circulating sclerostin levels, establishing B4GALNT3 as a causal gene for circulating sclerostin levels, and lower bone mass. However, serum levels of LDN-glycosylated sclerostin were lower in B4galnt3^-/- mice. B4galnt3 and Sost were co-expressed in osteoblast-lineage cells. Overexpression of B4GALNT3 increased while silencing of B4GALNT3 decreased the levels of LDN-glycosylated sclerostin in osteoblast-like cells. Mendelian randomization demonstrated that higher circulating sclerostin levels, genetically predicted by variants in the B4GALNT3 gene, were causally associated with lower BMD and higher risk of fractures but not with higher risk of myocardial infarction or stroke. Glucocorticoid treatment reduced B4galnt3 expression in bone and increased circulating sclerostin levels and this may contribute to the observed glucocorticoid-induced bone loss.

INTERPRETATION

B4GALNT3 is a key factor for bone physiology via regulation of LDN-glycosylation of sclerostin. We propose that B4GALNT3-mediated LDN-glycosylation of sclerostin may be a bone-specific osteoporosis target, separating the anti-fracture effect of global sclerostin inhibition, from indicated cardiovascular side effects.

FUNDING

Found in acknowledgements.

Pathogenic mechanisms of glucocorticoid-induced osteoporosis

Glucocorticoid (GC) is one of the most prescribed medicines to treat various inflammatory and autoimmune diseases. However, high doses and long-term use of GCs lead to multiple adverse effects, particularly glucocorticoid-induced osteoporosis (GIO). Excessive GCs exert detrimental effects on bone cells, including osteoblasts, osteoclasts, and osteocytes, leading to impaired bone formation and resorption. The actions of exogenous GCs are considered to be strongly cell-type and dose dependent. GC excess inhibits the proliferation and differentiation of osteoblasts and enhances the apoptosis of osteoblasts and osteocytes, eventually contributing to reduced bone formation. Effects of GC excess on osteoclasts mainly include enhanced osteoclastogenesis, increased lifespan and number of mature osteoclasts, and diminished osteoclast apoptosis, which result in increased bone resorption. Furthermore, GCs have an impact on the secretion of bone cells, subsequently disturbing the process of osteoblastogenesis and osteoclastogenesis. This review provides timely update and summary of recent discoveries in the field of GIO, with a particular focus on the effects of exogenous GCs on bone cells and the crosstalk among them under GC excess.

Multiple Mechanisms Explain Genetic Effects at the CPED1-WNT16 Bone Mineral Density Locus

PURPOSE OF REVIEW

Chromosome region 7q31.31, also known as the CPED1-WNT16 locus, is robustly associated with BMD and fracture risk. The aim of the review is to highlight experimental studies examining the function of genes at the CPED1-WNT16 locus.

RECENT FINDINGS

Genes that reside at the CPED1-WNT16 locus include WNT16, FAM3C, ING3, CPED1, and TSPAN12. Experimental studies in mice strongly support the notion that Wnt16 is necessary for bone mass and strength. In addition, roles for Fam3c and Ing3 in regulating bone morphology in vivo and/or osteoblast differentiation in vitro have been identified. Finally, a role for wnt16 in dually influencing bone and muscle morphogenesis in zebrafish has recently been discovered, which has brought forth new questions related to whether the influence of WNT16 in muscle may conspire with its influence in bone to alter BMD and fracture risk.

Wnt-associated adult stem cell marker Lgr6 is required for osteogenesis and fracture healing

Despite the remarkable regenerative capacity of skeletal tissues, nonunion of bone and failure of fractures to heal properly presents a significant clinical concern. Stem and progenitor cells are present in bone and become activated following injury; thus, elucidating mechanisms that promote adult stem cell-mediated healing is important. Wnt-associated adult stem marker Lgr6 is implicated in the regeneration of tissues with well-defined stem cell niches in stem cell-reliant organs. Here, we demonstrate that Lgr6 is dynamically expressed in osteoprogenitors in response to fracture injury. We used an Lgr6-null mouse model and found that Lgr6 expression is necessary for maintaining bone volume and efficient postnatal bone regeneration in adult mice. Skeletal progenitors isolated from Lgr6-null mice have reduced colony-forming potential and reduced osteogenic differentiation capacity due to attenuated cWnt signaling. Lgr6-null mice consist of a lower proportion of self-renewing stem cells. In response to fracture injury, Lgr6-null mice have a deficiency in the proliferation of periosteal progenitors and reduced ALP activity. Further, analysis of the bone regeneration phase and remodeling phase of fracture healing in Lgr6-null mice showed impaired endochondral ossification and decreased mineralization. We propose that in contrast to not being required for successful skeletal development, Lgr6-positive cells have a direct role in endochondral bone repair.

Resveratrol promotes bone mass in ovariectomized rats and the SIRT1 rs7896005 SNP is associated with bone mass in women during perimenopause and early postmenopause

OBJECTIVE

This study aimed to examine the effects of SIRT1 agonist resveratrol on bone mass in ovariectomized (OVX) rats and the SIRT1 single-nucleotide polymorphism (SNP) rs7896005 on bone mass in women during menopause and early postmenopause.

METHODS

An animal experiment was conducted on rats that were sham-operated (SHAM), OVX or OVX and different administered doses of resveratrol. Serum markers and femur microstructure and staining were assessed. A cross-sectional study was conducted in women undergoing menopause. SIRT1 protein and SIRT1 SNP rs7896005 were evaluated.

RESULTS

OVX rats administered resveratrol, especially high doses, showed lower bone loss than OVX rats. Serum osteoprotegerin (OPG) and femur SIRT1, β-catenin and bone mineral density (BMD) were significantly increased, whereas receptor activator of NF-κB ligand (RANKL) was significantly decreased. Serum SIRT1 levels were significantly lower in women with low bone mass (p < 0.01). Women with the CA genotype of rs7896005 had lower bone mass than those with the CC genotype. The A allele showed a significant negative effect on bone loss risk (odds ratio = 3.48; p = 0.025).

CONCLUSIONS

Resveratrol stimulated SIRT1 expression and Wnt/β-catenin signaling to promote bone mass in rat femurs. Among women in perimenopause and early postmenopause, SIRT1 protected bone mass, and the A allele of SIRT1 rs7896005 was a risk factor for reduced bone mass.

Factors associated with bone thickness: Comparison of the cranium and humerus

Cortical bone thickness is important for the mechanical function of bone. Ontogeny, aging, sex, body size, hormone levels, diet, behavior, and genetics potentially cause variations in postcranial cortical robusticity. However, the factors associated with cranial cortical robusticity remain poorly understood. Few studies have examined cortical robusticity in both cranial and postcranial bones jointly. In the present study, we used computed tomography (CT) images to measure cortical bone thicknesses in the cranial vault and humeral diaphysis. This study clearly showed that females have a greater cranial vault thickness and greater age-related increase in cranial vault thickness than males. We found an age-related increase in the full thickness of the temporal cranial vault and the width of the humeral diaphysis, as well as an age-related decrease in the cortical thickness of the frontal cranial vault and the cortical thickness of the humeral diaphysis, suggesting that the mechanisms of bone modeling in cranial and long bones are similar. A positive correlation between cortical indices in the cranial vault and humeral diaphysis also suggested that common factors affect cortical robusticity. We also examined the association of polymorphisms in the WNT16 and TNFSF11 genes with bone thickness. However, no significant associations were observed. The present study provides fundamental knowledge about similarities and differences in the mechanisms of bone modeling between cranial and postcranial bones.

Transplantation of gut microbiota from old mice into young healthy mice reduces lean mass but not bone mass

Aging is associated with low bone and lean mass as well as alterations in the gut microbiota (GM). In this study, we determined whether the reduced bone mass and relative lean mass observed in old mice could be transferred to healthy young mice by GM transplantation (GMT). GM from old (21-month-old) and young adult (5-month-old) donors was used to colonize germ-free (GF) mice in three separate studies involving still growing 5- or 11-week-old recipients and 17-week-old recipients with minimal bone growth. The GM of the recipient mice was similar to that of the donors, demonstrating successful GMT. GM from old mice did not have statistically significant effects on bone mass or bone strength, but significantly reduced the lean mass percentage of still growing recipient mice when compared with recipients of GM from young adult mice. The levels of propionate in the cecum of mice receiving old donor GM were significantly lower than those in mice receiving young adult donor GM. Bacteroides ovatus was enriched in the microbiota of recipient mice harboring GM from young adult donors. The presence of B. ovatus was not only significantly associated with high lean mass percentage in mice, but also with lean mass adjusted for fat mass in the large human HUNT cohort. In conclusion, GM from old mice reduces lean mass percentage but not bone mass in young, healthy, still growing recipient mice. Future studies are warranted to determine whether GM from young mice improves the musculoskeletal phenotype of frail elderly recipient mice.

Phosphorylation of S122 in ERα is important for the skeletal response to estrogen treatment in male mice

Estrogen receptor alpha (ERα) signaling has beneficial skeletal effects in males. ERα signaling also affects other tissues, and to find bone-specific treatments, more knowledge regarding tissue-specific ERα signaling is needed. ERα is subjected to posttranslational modifications, including phosphorylation, which can influence ERα function in a tissue-specific manner. To determine the importance of phosphorylation site S122 (corresponding to human ERα site S118) for the skeleton and other tissues, male mice with a S122A mutation were used. Total areal bone mineral density was similar between gonadal intact S122A and WT littermates followed up to 12 months of age, and weights of estrogen-responsive organs normalized for body weight were unchanged between S122A and WT males at both 3 and 12 months of age. Interestingly, 12-month-old S122A males had decreased body weight compared to WT. To investigate if site S122 affects the estrogen response in bone and other tissues, 12-week-old S122A and WT males were orchidectomized (orx) and treated with estradiol (E2) or placebo pellets for four weeks. E2 increased cortical thickness in tibia in both orx WT (+ 60%, p < 0.001) and S122A (+ 45%, p < 0.001) males. However, the E2 effect on cortical thickness was significantly decreased in orx S122A compared to WT mice (- 24%, p < 0.05). In contrast, E2 affected trabecular bone and organ weights similarly in orx S122A and WT males. Thus, ERα phosphorylation site S122 is required for a normal E2 response specifically in cortical bone in male mice, a finding that may have implications for development of future treatments against male osteoporosis.

Targeting Sclerostin and Dkk1 at Optimized Proportions of Low-Dose Antibody Achieves Similar Skeletal Benefits to Higher-Dose Sclerostin Targeting in the Mature Adult and Aged Skeleton

Age-associated low bone mass disease is a growing problem in the US. Development of osteoanabolic therapies for treating skeletal fragility has lagged behind anti-catabolic therapies, but several bone-building molecules are clinically available. We reported previously that antibody-based neutralization of the Lrp5/Lrp6 inhibitor Dkk1 has minimal effects on bone gain, but can potentiate the already potent osteoanabolic effects of sclerostin inhibition (another Lrp5/Lrp6 inhibitor highly expressed by osteocytes). In this communication, we test whether an optimized ratio of sclerostin and Dkk1 antibodies (Scl-mAb and Dkk1-mAb, respectively), administered at low doses, can maintain the same bone-building effects as higher dose Scl-mAb, in adult (6 months of age) and aged (20 months of age) wild-type mice. A 3:1 dose of Scl-mAb:Dkk1-mAb at 12.5 mg/kg was equally efficacious as 25 mg/kg of Scl-mAb in both age groups, using radiographic (DXA, µCT), biomechanical, (3-point bending tests), and histological (fluorochrome-based bone formation parameters) outcome measures. For some bone properties, including trabecular thickness and bone mineral density in the spine, and endocortical bone formation rates in the femur, the 3:1 treatment was associated with significantly improved skeletal properties compared to twice the dose of Scl-mAb. Cortical porosity in aged mice was also reduced by both Scl-mAb and low-dose 3:1 treatment. Overall, both treatments were efficacious in the mature adult (6 mo.) and aged (20 mo.) skeletons, suggesting Wnt targeting is a viable strategy for improving skeletal fragility in the very old. Further, the data suggest that low dose of combination therapy can be at least equally efficacious as higher doses of Scl-mAb monotherapy.

Induced inactivation of Wnt16 in young adult mice has no impact on osteoarthritis development

Osteoarthritis (OA) is a common disorder and a major cause of disability in the elderly population. WNT16 has been suggested to play important roles in joint formation, bone homeostasis and OA development, but the mechanism of action is not clear. Transgenic mice lacking Wnt16 expression (Wnt16-/-) have a more severe experimental OA than control mice. In addition, Wnt16-/- mice have a reduced cortical thickness and develop spontaneous fractures. Herein, we have used Cre-Wnt16flox/flox mice in which Wnt16 can be conditionally ablated at any age through tamoxifen-inducible Cre-mediated recombination. Wnt16 deletion was induced in 7-week-old mice to study if the Cre-Wnt16flox/flox mice have a more severe OA phenotype after destabilizing the medial meniscus (DMM surgery) than littermate controls with normal Wnt16 expression (Wnt16flox/flox). WNT16 deletion was confirmed in articular cartilage and cortical bone in Cre-Wnt16flox/flox mice, shown by immunohistochemistry and reduced cortical bone area compared to Wnt16flox/flox mice. After DMM surgery, there was no difference in OA severity in the articular cartilage in the knee joint between the Cre-Wnt16flox/flox and Wnt16flox/flox mice in neither female nor male mice. In addition, there was no difference in osteophyte size in the DMM-operated tibia between the genotypes. In conclusion, inactivation of Wnt16 in adult mice do not result in a more severe OA phenotype after DMM surgery. Thus, presence of WNT16 in adult mice does not have an impact on experimental OA development. Taken together, our results from Cre-Wnt16flox/flox mice and previous results from Wnt16-/- mice suggest that WNT16 is crucial during synovial joint establishment leading to limited joint degradation also later in life, after onset of OA. This may be important when developing new therapeutics for OA treatment.

wnt16 regulates spine and muscle morphogenesis through parallel signals from notochord and dermomyotome

Bone and muscle are coupled through developmental, mechanical, paracrine, and autocrine signals. Genetic variants at the CPED1-WNT16 locus are dually associated with bone- and muscle-related traits. While Wnt16 is necessary for bone mass and strength, this fails to explain pleiotropy at this locus. Here, we show wnt16 is required for spine and muscle morphogenesis in zebrafish. In embryos, wnt16 is expressed in dermomyotome and developing notochord, and contributes to larval myotome morphology and notochord elongation. Later, wnt16 is expressed at the ventral midline of the notochord sheath, and contributes to spine mineralization and osteoblast recruitment. Morphological changes in wnt16 mutant larvae are mirrored in adults, indicating that wnt16 impacts bone and muscle morphology throughout the lifespan. Finally, we show that wnt16 is a gene of major effect on lean mass at the CPED1-WNT16 locus. Our findings indicate that Wnt16 is secreted in structures adjacent to developing bone (notochord) and muscle (dermomyotome) where it affects the morphogenesis of each tissue, thereby rendering wnt16 expression into dual effects on bone and muscle morphology. This work expands our understanding of wnt16 in musculoskeletal development and supports the potential for variants to act through WNT16 to influence bone and muscle via parallel morphogenetic processes.

In humans, genetic variants (DNA sequences that vary amongst individuals) have been identified that appear to influence two tissues, bone and skeletal muscle. However, how single genes and genetic variants exert dual influence on both tissues is not well understood. In this study, we found that the wnt16 gene is necessary for specifying the size and shape of both muscle and bone during development in zebrafish. We also disentangled how wnt16 affects both tissues: distinct cellular populations adjacent to muscle and bone secrete Wnt16, where it acts as a signal guiding the size and shape of each tissue. This is important because in humans, genetic variants near the WNT16 gene have effects on both bone- and muscle-related traits. This study expands our understanding of the role of WNT16 in bone and muscle development, and helps to explain how genetic variants near WNT16 affect traits for both tissues. Moreover, WNT16 is actively being explored as a target for osteoporosis therapies, thus our study could have implications with regard to the potential of targeting WNT16 to treat bone and muscle simultaneously.

Autophagy Plays Multiple Roles in the Soft-Tissue Healing and Osseointegration in Dental Implant Surgery-A Narrative Review

Dental endo-osseous implants have become a widely used treatment for replacing missing teeth. Dental implants are placed into a surgically created osteotomy in alveolar bone, the healing of the soft tissue lesion and the osseointegration of the implant being key elements to long-term success. Autophagy is considered the major intracellular degradation system, playing important roles in various cellular processes involved in dental implant integration. The aim of this review is an exploration of autophagy roles in the main cell types involved in the healing and remodeling of soft tissue lesions and implant osseointegration, post-implant surgery. We have focused on the autophagy pathway in macrophages, endothelial cells; osteoclasts, osteoblasts; fibroblasts, myofibroblasts and keratinocytes. In macrophages, autophagy modulates innate and adaptive immune responses playing a key role in osteo-immunity. Autophagy induction in endothelial cells promotes apoptosis resistance, cell survival, and protection against oxidative stress damage. The autophagic machinery is also involved in transporting stromal vesicles containing mineralization-related factors to the extracellular matrix and regulating osteoblasts' functions. Alveolar bone remodeling is achieved by immune cells differentiation into osteoclasts; autophagy plays an important and active role in this process. Autophagy downregulation in fibroblasts induces apoptosis, leading to better wound healing by improving excessive deposition of extracellular matrix and inhibiting fibrosis progression. Autophagy seems to be a dual actor on the scene of dental implant surgery, imposing further research in order to completely reveal its positive features which may be essential for clinical efficacy.

Zebrafish models for glucocorticoid-induced osteoporosis

Glucocorticoid-induced osteoporosis (GIOP) is the most common form of secondary osteoporosis due to excessive or long-term glucocorticoid administration, disturbing the homeostasis between bone formation and bone resorption. The bone biology of zebrafish shares a high degree of similarities with mammals. In terms of molecular level, genes and signaling pathways related to skeletogenesis are also highly correlated between zebrafish and humans. Therefore, zebrafish have been utilized to develop multiple GIOP models. Taking advantage of the transparency of zebrafish larvae, their skeletal development and bone mineralization can be readily visualized through in vivo staining without invasive experimental handlings. Moreover, the feasibility of using scales or fin rays to study bone remodeling makes adult zebrafish an ideal model for GIOP research. Here, we reviewed current zebrafish models for GIOP research, focused on the tools and methods established for examining bone homeostasis. As an in vivo, convenient, and robust model, zebrafish have an advantage in performing high-throughput drug screening and could be used to investigate the action mechanisms of therapeutic drugs.

A probiotic mix partially protects against castration-induced bone loss in male mice

Studies in postmenopausal women and ovariectomized mice show that the probiotic mix Lacticaseibacillus paracasei DSM13434, Lactiplantibacillus plantarum DSM 15312 and DSM 15313 (L. Mix) can protect from bone loss caused by sex steroid deficiency. Whether probiotic bacteria can protect bone also in sex steroid-deficient males is less studied. We used the orchiectomized mouse as a model for age-dependent bone loss caused by decreasing sex hormone levels in males. We treated 10-week-old male mice with either vehicle (veh) or L. Mix for 6 weeks, starting 2 weeks before orchiectomy (orx) or sham surgery. Importantly, mice treated with L. Mix had a general increase in total body bone mineral density (BMD) and lean mass (P ≤ 0.05) compared with veh-treated mice. Detailed computer tomography analysis of dissected bones showed increased trabecular BMD of the distal metaphyseal region of the femur in L. Mix compared to veh-treated orx mice (+8.0%, P ≤ 0.05). In the vertebra, L. Mix treatment increased trabecular bone volume fraction BV/TV (+11.5%, P ≤ 0.05) compared to veh in orx mice. Also, L. Mix increased the levels of short-chain fatty acids (SCFAs) such as propionate and acetate and important intermediates in SCFA synthesis such as succinate and lactate in the cecal content of male mice. In conclusion, L. Mix treatment resulted in a general increase in BMD in adult male mice and prevented trabecular bone loss in femur and vertebra of orx mice. These bone protective effects of L. Mix were associated with increased levels of SCFAs in the cecal content of male mice.