Neuronal Control of Bone Remodeling

The brain-bone axis: unraveling the complex interplay between the central nervous system and skeletal metabolism

The brain-bone axis has emerged as a captivating field of research, unveiling the intricate bidirectional communication between the central nervous system (CNS) and skeletal metabolism. This comprehensive review delves into the current state of knowledge surrounding the brain-bone axis, exploring the complex mechanisms, key players, and potential clinical implications of this fascinating area of study. The review discusses the neural regulation of bone metabolism, highlighting the roles of the sympathetic nervous system, hypothalamic neuropeptides, and neurotransmitters in modulating bone remodeling. In addition, it examines the influence of bone-derived factors, such as osteocalcin and fibroblast growth factor 23, on brain function and behavior. The therapeutic potential of targeting the brain-bone axis in the context of skeletal and neurological disorders is also explored. By unraveling the complex interplay between the CNS and skeletal metabolism, this review aims to provide a comprehensive resource for researchers, clinicians, and students interested in the brain-bone axis and its implications for human health and disease.

Systematic review on effects of experimental orthodontic tooth displacement on brain activation assessed by fMRI

BACKGROUND

Orthodontic treatment is often accompanied by discomfort and pain in patients, which are believed to be a result of orthodontic tooth displacement caused by the mechanical forces exerted by the orthodontic appliances on the periodontal tissues. These lead to change blood oxygen level dependent response in related brain regions.

OBJECTIVE

This systematic review aims to assess the impact of experimental orthodontic tooth displacement on alterations in central nervous system activation assessed by tasked based and resting state fMRI.

MATERIALS AND METHODS

A literature search was conducted using online databases, following PRISMA guidelines and the PICO framework. Selected studies utilized magnetic resonance imaging to examine the brain activity changes in healthy participants after the insertion of orthodontic appliances.

RESULTS

The initial database screening resulted in 791 studies. Of these, 234 were duplicates and 547 were deemed irrelevant considering the inclusion and exclusion criteria. Of the ten remaining potential relevant studies, two were excluded during full-text screening. Eight prospective articles were eligible for further analysis. The included studies provided evidence of the intricate interplay between orthodontic treatment, pain perception, and brain function. All of the participants in the included studies employed orthodontic separators in short-term experiments to induce tooth displacement during the early stage of orthodontic treatment. Alterations in brain activation were observed in brain regions, functional connectivity and brain networks, predominantly affecting regions implicated in nociception (thalamus, insula), emotion (insula, frontal areas), and cognition (frontal areas, cerebellum, default mode network).

CONCLUSIONS

The results suggest that orthodontic treatment influences beyond the pain matrix and affects other brain regions including the limbic system. Furthermore, understanding the orthodontically induced brain activation can aid in development of targeted pain management strategies that do not adversely affect orthodontic tooth movement. Due to the moderate to serious risk of bias and the heterogeneity among the included studies, further clinical trials on this subject are recommended.

Peripheral nerve-derived Sema3A promotes osteogenic differentiation of mesenchymal stem cells through the Wnt/β-catenin/Nrp1 positive feedback loop

Sensory nerves play a crucial role in maintaining bone homeostasis by releasing Semaphorin 3A (Sema3A). However, the specific mechanism of Sema3A in regulation of bone marrow mesenchymal stem cells (BMMSCs) during bone remodelling remains unclear. The tibial denervation model was used and the denervated tibia exhibited significantly lower mass as compared to sham operated bones. In vitro, BMMSCs cocultured with dorsal root ganglion cells (DRGs) or stimulated by Sema3A could promote osteogenic differentiation through the Wnt/β-catenin/Nrp1 positive feedback loop, and the enhancement of osteogenic activity could be inhibited by SM345431 (Sema3A-specific inhibitor). In addition, Sema3A-stimulated BMMSCs or intravenous injection of Sema3A could promote new bone formation in vivo. To sum up, the coregulation of bone remodelling is due to the ageing of BMMSCs and increased osteoclast activity. Furthermore, the sensory neurotransmitter Sema3A promotes osteogenic differentiation of BMMSCs via Wnt/β-catenin/Nrp1 positive feedback loop, thus promoting osteogenesis in vivo and in vitro.

Using tissue clearing and light sheet fluorescence microscopy for the three-dimensional analysis of sensory and sympathetic nerve endings that innervate bone and dental tissue of mice

Bone and dental tissues are richly innervated by sensory and sympathetic neurons. However, the characterization of the morphology, molecular phenotype, and distribution of nerves that innervate hard tissue has so far mostly been limited to thin histological sections. This approach does not adequately capture dispersed neuronal projections due to the loss of important structural information during three-dimensional (3D) reconstruction. In this study, we modified the immunolabeling-enabled imaging of solvent-cleared organs (iDISCO/iDISCO+) clearing protocol to image high-resolution neuronal structures in whole femurs and mandibles collected from perfused C57Bl/6 mice. Axons and their nerve terminal endings were immunolabeled with antibodies directed against protein gene product 9.5 (pan-neuronal marker), calcitonin gene-related peptide (peptidergic nociceptor marker), or tyrosine hydroxylase (sympathetic neuron marker). Volume imaging was performed using light sheet fluorescence microscopy. We report high-quality immunolabeling of the axons and nerve terminal endings for both sensory and sympathetic neurons that innervate the mouse femur and mandible. Importantly, we are able to follow their projections through full 3D volumes, highlight how extensive their distribution is, and show regional differences in innervation patterns for different parts of each bone (and surrounding tissues). Mapping the distribution of sensory and sympathetic axons, and their nerve terminal endings, in different bony compartments may be important in further elucidating their roles in health and disease.

Interoceptive regulation of skeletal tissue homeostasis and repair

Recent studies have determined that the nervous system can sense and respond to signals from skeletal tissue, a process known as skeletal interoception, which is crucial for maintaining bone homeostasis. The hypothalamus, located in the central nervous system (CNS), plays a key role in processing interoceptive signals and regulating bone homeostasis through the autonomic nervous system, neuropeptide release, and neuroendocrine mechanisms. These mechanisms control the differentiation of mesenchymal stem cells into osteoblasts (OBs), the activation of osteoclasts (OCs), and the functional activities of bone cells. Sensory nerves extensively innervate skeletal tissues, facilitating the transmission of interoceptive signals to the CNS. This review provides a comprehensive overview of current research on the generation and coordination of skeletal interoceptive signals by the CNS to maintain bone homeostasis and their potential role in pathological conditions. The findings expand our understanding of intersystem communication in bone biology and may have implications for developing novel therapeutic strategies for bone diseases.

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

Serum sclerostin and sympathetic skin response: relationship with myeloma bone disease

Background

Myeloma bone disease (MBD) is a common complication that significantly contributes to morbidity and mortality in multiple myeloma (MM). Serum sclerostin level and sympathetic activity can affect MBD. The purpose of this study is evaluation of serum sclerostin level and sympathetic activity (using sympathetic skin response “SSR”) in MM patients, and studying the relationship between both of them as well as their relationship with MBD. 35 smoldering myeloma patients (group I) and 35 newly diagnosed MM (group II) and 35 controls (group III) were included in the study. All the participants were subjected to complete history taking, and clinical examination. Assessment of serum sclerostin level, SSR, MM stages [by the international staging system (ISS)], MBD grading (according to the Durie–Salmon staging system) were done for all patients within 7 days from the diagnosis.

Results

Undetectable and decreased SSR amplitude are significantly more detected in group I and II (compared with group III). Autonomic manifestations, and loss of SSR is significantly more detected in group II than group I. Autonomic manifestations were absent in group III. SSR amplitude of median and tibial nerves is significantly decreased in group II than group I and III. MBD was detected in all patients of group II. Serum sclerostin and LDH were significantly increased in group II than group I. Group I and II had significantly higher levels of sclerostin when compared with group III. Group II had significantly higher levels of sclerostin and lower levels of ALP in comparison with group I. Serum sclerostin level was correlated positively with LDH and negatively with ALP and SSR amplitude. MBD was significantly affected by ISS stage III, LDH level, SSR affection and serum sclerostin level ≥ 0.40 ng/ml. SSR response affection was the most significant risk factor for advanced MBD followed by increased sclerostin level.

Conclusions

Serum sclerostin level was significantly increased and sympathetic activity was significantly decreased in MBD. Loss of the SSR response was the most significant risk factor for advanced MBD followed by increased sclerostin level.

Recommendations

Potentially validating the use of bone-turnover markers in larger studies, in addition to electrophysiological examination of SSR to stratify patients who are at high-risk for progressive MBD, as the use of newer agents with anabolic effects such as anti-sclerostin antibodies have shown potential in repair of MBD. These newer agents could potentially change the treatment landscape in patients with MBD.

Differential Effects of Neurectomy and Botox-induced Muscle Paralysis on Bone Phenotype and Titanium Implant Osseointegration

Metabolic bone is highly innervated by both sensory and sympathetic nerves. In addition to skeletal development, neural regulation participates in local bone remodeling, which is important for successful osseointegration of titanium implants. Neurectomy is a model used to investigate the lack of neural function on bone homeostasis, but the relative impacts of direct denervation to bone or denervation-induced muscle paralysis are less well defined. To investigate this difference, we used two nerve intervention models, sciatic and femoral neurectomy (SFN) v. botox-induced muscle paralysis (BTX) and assessed the resulting femoral bone phenotype and Ti implant osseointegration. Male Sprague Dawley rats (19) were randomly divided into three groups: implant control (n = 5), SFN (n = 7), and BTX (n = 7). Ti implants (microrough/hydrophilic [modSLA], Institut Straumann AG) were placed in the distal metaphysis of each femur on day 24 post-SFN or BTX. Bone and muscle were examined on day 28 after implant insertion. Both nerve intervention models impaired osseointegration. MicroCT and histology indicated that both models had reduced trabecular bone formation. Only BTX reduced cortical bone formation and increased cortical bone porosity. BTX resulted in more bone loss characterized by the least trabecular and cortical bone, as well as osseointegration. Osteoblasts isolated from the tibia exhibited a model-specific phenotype when they were grown on Ti substrates in vitro. Neurectomy caused more severe muscle atrophy than botox injection. These results indicate that neural regulation directly modulates bone formation and osseointegration. Muscle paralysis modulated the effects of loss of neural inputs into bone, supporting the hypothesis that mechanical loading of bone is a factor in achieving successful osseointegration. The different effects of botox and neurectomy on bone phenotype indicated that the sensory and sympathetic nerves had a role in the osseointegration process.

Crosstalk between Bone and Nerves within Bone

For the past two decades, the function of intrabony nerves on bone has been a subject of intense research, while the function of bone on intrabony nerves is still hidden in the corner. In the present review, the possible crosstalk between bone and intrabony peripheral nerves will be comprehensively analyzed. Peripheral nerves participate in bone development and repair via a host of signals generated through the secretion of neurotransmitters, neuropeptides, axon guidance factors and neurotrophins, with additional contribution from nerve-resident cells. In return, bone contributes to this microenvironmental rendezvous by housing the nerves within its internal milieu to provide mechanical support and a protective shelf. A large ensemble of chemical, mechanical, and electrical cues works in harmony with bone marrow stromal cells in the regulation of intrabony nerves. The crosstalk between bone and nerves is not limited to the physiological state, but also involved in various bone diseases including osteoporosis, osteoarthritis, heterotopic ossification, psychological stress-related bone abnormalities, and bone related tumors. This crosstalk may be harnessed in the design of tissue engineering scaffolds for repair of bone defects or be targeted for treatment of diseases related to bone and peripheral nerves.

Does Hip Bone Density Differ between Paretic and Non-Paretic Sides in Hemiplegic Stroke Patients? and Its Relationship with Physical Impairment

Background

Bone loss after stroke escalates the risk of fractures, mainly in the hip, leading to further disability in individuals with stroke. We aimed to investigate the skeletal effect of bone mineral density (BMD) based on the duration of onset of stroke, compare the BMD of the paretic and non-paretic sides, and elucidate the relationship between BMD and disability variables.

Methods

The 31 male hemiplegic stroke patients between 20 and 70 years of age with cerebral infarction or hemorrhage were considered in this study. Subacute and chronic cases included 13 and 18 patients with lag time from the onset of 1 to 6 months and beyond 6 months, respectively. BMD in the lumbar, paretic, and non-paretic hip as well as the disability variables were analyzed retrospectively.

Results

The subacute group showed a significant reduction in the femoral neck BMD on the paretic side compared to that on the non-paretic side based on T-scores (P=0.013). Bone loss was significantly correlated with lower limb muscle strength and overall physical impairment (P<0.05). The chronic group demonstrated significant reduction in femur neck and total femur BMD on the paretic side compared to that on the non-paretic side based on T-scores (P=0.002 and P<0.001, respectively). T-scores of BMD in the chronic phase were not significantly associated with the clinical parameters.

Conclusions

Early screening of bilateral hip BMD in the early stages after stroke, monitoring, and timely implementation of prevention strategies are important to minimize subsequent bone loss and prevent possible complications in patients who experience stroke.

Neurological heterotopic ossification: novel mechanisms, prognostic biomarkers and prophylactic therapies

Neurological heterotopic ossification (NHO) is a debilitating condition where bone forms in soft tissue, such as muscle surrounding the hip and knee, following an injury to the brain or spinal cord. This abnormal formation of bone can result in nerve impingement, pain, contractures and impaired movement. Patients are often diagnosed with NHO after the bone tissue has completely mineralised, leaving invasive surgical resection the only remaining treatment option. Surgical resection of NHO creates potential for added complications, particularly in patients with concomitant injury to the central nervous system (CNS). Although recent work has begun to shed light on the physiological mechanisms involved in NHO, there remains a significant knowledge gap related to the prognostic biomarkers and prophylactic treatments which are necessary to prevent NHO and optimise patient outcomes. This article reviews the current understanding pertaining to NHO epidemiology, pathobiology, biomarkers and treatment options. In particular, we focus on how concomitant CNS injury may drive ectopic bone formation and discuss considerations for treating polytrauma patients with NHO. We conclude that understanding of the pathogenesis of NHO is rapidly advancing, and as such, there is the strong potential for future research to unearth methods capable of identifying patients likely to develop NHO, and targeted treatments to prevent its manifestation.

Autonomic nervous system control of multiple myeloma

The autonomic nervous system (ANS), which consists of antagonistic sympathetic (adrenergic) and parasympathetic (cholinergic) arms, has emerged as an important regulator of neoplastic development, yet little is known about its role in multiple myeloma (MM). Clinical findings that anti-adrenergic β-blocker intake reduces risk of disease-specific death and overall mortality in patients with MM have indicated that adrenergic input may worsen myeloma outcome. However, preclinical studies using β-adrenergic receptor agonists or antagonists produced controversial results as to whether sympathetic pathways promote or inhibit myeloma. Retrospective outcome data demonstrating that high message levels of cholinergic receptor genes predict inferior survival in the Multiple Myeloma Research Foundation CoMMpass trial suggest that parasympathetic input may drive myeloma progression in a subset of patients. Here we review the ill-defined role of the ANS in MM, put myeloma in the context of other cancers, and discuss knowledge gaps that may afford exciting research opportunities going forward.

Co-culture systems of osteoblasts and osteoclasts: Simulating in vitro bone remodeling in regenerative approaches

Bone is an extremely dynamic tissue, undergoing continuous remodeling for its whole lifetime, but its regeneration or augmentation due to bone loss or defects are not always easy to obtain. Bone tissue engineering (BTE) is a promising approach, and its success often relies on a "smart" scaffold, as a support to host and guide bone formation through bone cell precursors. Bone homeostasis is maintained by osteoblasts (OBs) and osteoclasts (OCs) within the basic multicellular unit, in a consecutive cycle of resorption and formation. Therefore, a functional scaffold should allow the best possible OB/OC cooperation for bone remodeling, as happens within the bone extracellular matrix in the body. In the present work OB/OC co-culture models, with and without scaffolds, are reviewed. These experimental systems are intended for different targets, including bone remodeling simulation, drug testing and the assessment of biomaterials and 3D scaffolds for BTE. As a consequence, several parameters, such as cell type, cell ratio, culture medium and inducers, culture times and setpoints, assay methods, etc. vary greatly. This review identifies and systematically reports the in vitro methods explored up to now, which, as they allow cellular communication, more closely resemble bone remodeling and/or the regeneration process in the framework of BTE. STATEMENT OF SIGNIFICANCE: Bone is a dynamic tissue under continuous remodeling, but spontaneous healing may fail in the case of excessive bone loss which often requires valid alternatives to conventional treatments to restore bone integrity, like bone tissue engineering (BTE). Pre-clinical evaluation of scaffolds for BTE requires in vitro testing where co-cultures combining innovative materials with osteoblasts (OBs) and osteoclasts (OCs) closely mimic the in vivo repair process. This review considers the direct and indirect OB/OC co-cultures relevant to BTE, from the early mouse-cell models to the recent bone regenerative systems. The co-culture modeling of bone microenvironment provides reliable information on bone cell cross-talk. Starting from improved knowledge on bone remodeling, bone disease mechanisms may be understood and new BTE solutions are designed.

The neural system regulates bone homeostasis via mesenchymal stem cells: a translational approach

Large bone reconstruction is a major clinical issue associated with several challenges, and autograft is the main method for reconstructing large defects of maxillofacial bone. However, postoperative osteoporosis of the bone graft, even with sufficient vascularization, remains a primary problem. Therefore, better understanding of the mechanisms and clinical translation of bone homeostasis is required. Neuronal innervation of the bone is an emerging research topic, especially with regards to the role of peripheral nerves in regulating bone homeostasis. Moreover, sensory and autonomic nerves regulate this process via different types of neurotransmitters, but the specific mechanism is still elusive. In this review article, the current understanding of the interaction between the peripheral nerve and the skeleton system is summarized, with a particular focus on bone marrow mesenchymal stem cells (BMMSCs), except for osteoblasts and osteoclasts. The novel application of nerve-based bone regeneration via BMMSCs may provide a new strategy in tissue engineering and clinical treatment of osteoporosis and bone disorders.

The assessment of stress, depression, and inflammation as a collective risk factor for periodontal diseases: a systematic review

OBJECTIVES

The purpose of this review was to provide a novel perspective utilizing an assessment of biomarkers to evaluate the impact of stress-related disorders on the progression of periodontal disease and evaluate the growing body of evidence of stress as a risk indicator for periodontal disease progression.

METHODS

Cross-sectional, case-control, and biomarker studies associating psychological disorders and periodontal disease were included in the literature search. Computational studies, animal studies, reviews, and studies lacking healthy controls were excluded. Electronic and manual literature searches were conducted by two independent reviewers in several databases as well as a manual search for relevant articles published up to January 2018.

RESULTS

Twenty-six articles fulfilled the inclusion criteria and were included in the qualitative synthesis. Relationships between stress-related disorders and serum and salivary biomarkers such as cortisol, dehydroepiandrosterone (DHEA), chromogranin A (CgA), and pro-inflammatory cytokines were identified.

CONCLUSIONS

The use of salivary pro-inflammatory cytokines alone is not sufficient for the identification of periodontal disease severity/progression with or without the presence of stress-associated diseases. Keeping in mind the limitations of this review, a positive qualitative correlation was observed in the literature among stress-related biomarkers and the severity of periodontal disease. This correlation may serve as an important reporter of patient susceptibility for periodontal breakdown in the future.

CLINICAL RELEVANCE

Stress-related disorders should be included in the list of globally screened diseases because it can change the biochemistry of both the local periodontal microenvironment as well as the global systemic inflammatory burden.

The roles of Orai and Stim in bone health and disease

Orai and Stim proteins are the mediators of calcium release-activated calcium signaling and are important in the regulation of bone homeostasis and disease. This includes separate regulatory systems controlling mesenchymal stem cell differentiation to form osteoblasts, which make bone, and differentiation and regulation of osteoclasts, which resorb bone. These systems will be described separately, and their integration and relation to other systems, including Orai and Stim in teeth, will be briefly discussed at the end of this review.

A bone-targeting drug-delivery system based on Semaphorin 3A gene therapy ameliorates bone loss in osteoporotic ovariectomized mice

Osteoporosis is a serious health problem worldwide. Semaphorins (Sema) have been described as key molecules involved in the cross-talk between bone cells (osteoblasts/osteoclasts). In this study, we investigated whether plasmid containing Sema3a could ameliorate bone loss in an ovariectomized (OVX) mouse model via (AspSerSer)₆, a selectively bone-targeting moiety. Plasmid pcDNA3.1(+)-Sema3a-GFP was fabricated and transfected cells with the plasmid demonstrated statistically higher levels of Sema3A in vitro (p < 0.001). Mice were ovariectomized and injected twice weekly with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP for four weeks. The aim of the study was twofold: firstly to design an effective bone-targeting drug-delivery system (AspSerSer)₆. Secondly, the effects of Sem3A gene therapy on bone loss was investigated. Here, the targeting selectivity of pcDNA3.1(+)-Sema3a-GFP via (AspSerSer)₆ to the trabecular bone surface was firstly verified by histological observation of frozen sections and immunofluorescence staining. Then, bone microstructure analysis by Micro-CT indicated significantly less bone loss in mice treated with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP compared to the control group (p < 0.05). Furthermore,H&E staining and Safranin O staining of the decalcified sections demonstrated statistically significantly higher bone area/total area in the mice that were injected with (AspSerSer)₆-(STR-R8)+pcDNA3.1(+)-Sema3a-GFP (p < 0.001, p < 0.01,respectively). TRAP staining and immunohistochemistry staining of COL I demonstrated lower numbers of osteoclasts and significantly increased numbers of osteoblasts in the bone-targeting moiety delivering pcDNA3.1(+)-Sema3a-GFP group, when compared to the control group (p < 0.01, p < 0.001,respectively). Together, our findings have identified that, (AspSerSer)₆, a bone-targeting drug-delivery system based on semaphorin3A gene therapy, ameliorated bone loss in osteoporotic ovariectomized mice, by suppressing osteoclastic bone resorption and simultaneously increasing osteoblastic bone formation. Gene therapy by local site-specific Sema3A overexpression might be a potential new strategy for treating osteoporosis and bone defects.

Effect of Zuoguiwan on osteoporosis in ovariectomized rats through RANKL/OPG pathway mediated by β2AR

ETHNOPHARMACOLOGICAL RELEVANCE

The deficiency of kidney Yin is the main pathogenesis of postmenopausal osteoporosis (PMOP) according to traditional Chinese medicine (TCM). Zuoguiwan (ZGW) is among the classical prescriptions in TCM and has been applied to various diseases that are due to deficiency of kidney Yin, including osteoporosis, fractures, menopausal syndromes. However, the underlying mechanism of ZGW in treating PMOP remains poorly understood.

AIM OF THE STUDY

ZGW, a traditional Chinese prescription, has been used to nourish Yin and reinforce the kidney since ancient times. The investigation aimed to explore the mechanism of ZGW via the receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG) signaling pathway as mediated by the β2-adrenergic receptor (β2AR) in an osteoporosis rat model.

MATERIALS AND METHODS

An osteoporosis model induced by ovariectomy was established in rats. A total of 40 female Sprague-Dawley rats were randomly assigned into bilateral ovariectomy group (OVX), sham operated group (Sham), 17β-estradiol-treated positive group (E2, 25 μg/kg/d), ZGW low-dose group (ZGW-L, 2.3 g/kg/d lyophilized powder) and ZGW high-dose group (ZGW-H, 4.6 g/kg/d lyophilized powder). The serum markers of bone turnover were measured using enzyme-linked immunosorbent assay (ELISA). The morphological structure changes in bones were detected through H&E staining. Local bone mineral density (BMD) and trabecular bone microarchitecture of the right distal femur were measured and evaluated by using micro-CT. Furthermore, the mRNA and protein expressions levels of β2AR, OPG and RANKL were measured by qPCR and Western blot analysis.

RESULTS

Compared with the OVX group, ZGW groups showed significantly reduced levels of serum tartrate-resistant acid phosphatase 5b (TRACP-5b) and β-cross-linked c-telopeptide of type I collagen (β-CTX) (P ＜ 0.01), increased levels of serum bone-specific alkaline phosphatase (BALP) (P ＜ 0.01) and OPG (P ＜ 0.05), prevention of OVX-induced bone loss, and improved microarchitecture of the trabecular bone of distal femur. Moreover, ZGW mediated the osteoporosis syndrome by reducing the empty bone lacunae, promoting the ordered arrangement of trabeculae structure, and increasing the trabeculae structure thickness. Furthermore, in ZGW groups, the protein expression of OPG in the tibia was notably up-regulated (P ＜ 0.01), whereas the mRNA and protein expression of β2AR in the hippocampus (P ＜ 0.01), and the protein expressions levels of β2AR (P ＜ 0.01) and RANKL (P ＜ 0.05) in the tibia were down-regulated compared with OVX group.

CONCLUSIONS

ZGW through its protective effects, stimulates bone formation and suppresses bone resorption. The underlying mechanism of ZGW in improving perimenopausal syndrome and increasing bone mass might be attributed to the regulation of RANKL/OPG, as mediated by β2AR. Therefore, ZGW may be used as an alternative treatment for PMOP.

Biology of Bone Sarcomas and New Therapeutic Developments

Bone sarcomas are tumours belonging to the family of mesenchymal tumours and constitute a highly heterogeneous tumour group. The three main bone sarcomas are osteosarcoma, Ewing sarcoma and chondrosarcoma each subdivided in diverse histological entities. They are clinically characterised by a relatively high morbidity and mortality, especially in children and adolescents. Although these tumours are histologically, molecularly and genetically heterogeneous, they share a common involvement of the local microenvironment in their pathogenesis. This review gives a brief overview of their specificities and summarises the main therapeutic advances in the field of bone sarcoma.