破骨细胞与骨质疏松症的关系研究进展

破骨细胞是一种巨大的多核细胞,它的形成和活性异常可导致骨质疏松、类风湿关节炎、关节置换后假体无菌性松动等许多疾病;骨质疏松症是一种多因素导致的全身代谢性骨骼疾病,其治疗靶点主要集中在抑制破骨细胞的活性及促进成骨细 胞的形成方面,随着破骨细胞对骨作用的信号通路等骨生物学研究的深人,一些新的治疗靶点被陆续发现;目前,0PG/, RANKL /RANK信号通路、肿瘤坏死因子信号通路、一氧化氮和雌激素、过氧化物酶体增殖物激活受体γ、小眼畸形相关转录因子等信号通路认为与破骨细胞关系密切,本文就破骨细胞与骨质疏松症关系作一综述,为骨质疏松症的防治提供相关依据。     

破骨细胞功能与形成相关调节因子研究进展

破骨细胞数量和骨吸收活性的改变是引起骨溶解疾病的重要机制,如何调节破骨细胞的形成和功能,抑制骨吸收活性是治疗骨质疏松、骨髓瘤等骨溶解疾病的关键.研究发现破骨细胞分化、形成及作用的发挥受多种细胞因子调节,如破骨细胞标志性基因之间的相互作用可调节破骨细胞分化,某些转录因子可调节破骨细胞形成,其他相关因子可对破骨细胞产生影响等.该文就相关因子对破骨细胞调节的研究进展作一简要综述.     

破骨细胞骨吸收机制研究进展

以绝经后骨量迅速下降为主要特征的绝经后骨质疏松症是生殖健康领域中的重要问题。破骨细胞 (osteoclast)作为骨吸收的主要细胞 ,对于骨量的变化具重要作用。因此 ,研究破骨细胞的生物学特性及骨吸收的机理对于预防和治疗骨质疏松症等代谢性骨病具有十分重要的意义。本综述着重论述破骨细胞的生物学特性及骨吸收的分子生物学机制和机理 ,抑制破骨细胞骨吸收的相关因素 ,以期进一步推动破骨细胞骨吸收功能的研究 ,加强骨质疏松等骨代谢疾病的治疗。一、破骨细胞的生物学特性破骨细胞来源于希腊文“Osteon”(骨 )和“klio”(破坏 )两词的组合…     

雌激素对破骨细胞功能调控的研究进展

雌激素对骨骼的保护性作用主要在于它能抑制破骨细胞性骨吸收。雌激素水平变化时,破骨细 胞的形态、信号传导通路以及破骨细胞功能都会受到影响。     

原发性骨质疏松症的骨骼免疫机制研究进展

原发性骨质疏松症是以骨质减少,骨的微观结构退化为特征的,致使骨的脆性增加以及易于发生骨折的骨骼疾病。其发病机制与多种因素相关,除了传统的内分泌机制之外,一种新的骨骼免疫机制已逐渐被深入研究:通过免疫细胞T淋巴细胞和B淋巴细胞、树突状细胞等,分泌多种细胞因子,并与多种细胞因子相互作用,通过信号通路的正负反馈调控,精细调节成骨细胞和破骨细胞的分化与增殖平衡,从而影响原发性骨质疏松症的发生。与破骨形成相关的T细胞,Th17细胞通过双重机制调控骨质吸收,Th1和Th2细胞亚群分别分泌IFN-γ和IL-4,通过抑制破骨细胞前体细胞发育成成熟的破骨细胞,从而抑制骨质吸收。Treg细胞通过表达CTLA-4,促进破骨细胞前体细胞的凋亡,抑制骨质吸收。B淋巴细胞通过调控RANKL和OPG的比例参与骨质代谢。树突状细胞既可以与CD4+T细胞结合,启动经典的RANKL/RANK破骨细胞形成的信号通路,参与骨质疏松的形成;也可以作为破骨细胞前体细胞的方式,在M-CSF等炎性因子的刺激下,直接分化为破骨细胞。现就这种免疫细胞与细胞因子精细调节骨质生成与骨质吸收平衡作用机制的最新研究进展进行阐述。     

破骨细胞的骨吸收机制

破骨细胞是一种巨大的多核细胞,起源于单核巨噬细胞/单核系造血前体细胞,在骨吸收过程中发挥重要作用。破骨细胞的形成和活性异常可导致骨质疏松、类风湿关节炎、关节置换后假体无菌性松动等许多疾病,因此破骨细胞是治疗这些疾病的靶点之一。目前对破骨细胞的分化形成研究较多,但对破骨细胞如何识别、降解骨组织方面的研究较少。骨盐被认为是破骨细胞识别的重要成分,但是近年来的研究发现骨基质不是破骨细胞激活的必需成分,玻连蛋白包被的培养皿也能使破骨细胞出现骨吸收的特有形态,玻连蛋白对破骨细胞的激活有重要的作用。此外,最近的研究证明骨基质降解产物的吞入和分泌对破骨细胞的分化和功能的保持有重要意义。这些分子机制的研究可能为骨骼疾病提供新的治疗靶点。     

骨质疏松症骨折愈合的扫描电镜观察

为了解骨质疏松症骨折愈合过程,通过对30例骨质疏松症患者股骨粗隆间骨折愈合过程进行扫描电镜观察,结果发现骨质疏松症骨折后两周左右时:骨折骨小梁表面及周围有大量大小不等的卵圆形细胞增殖,骨吸收陷窝内有胶原纤维形成,但比较稀疏、紊乱。在骨折塑形改造期,破骨细胞性骨吸收活动显得异常活跃,而成骨细胞性骨形成显得异常微弱,骨形成滞留于骨吸收向骨形成转换期,称为Cement line现象,致使骨质疏松症骨折愈合塑形改建期,松质骨小梁变细、穿孔、离断,骨强度明显进一步下降。认为骨质疏松症骨折的治疗,不但要使骨折良好复位,坚强固定,而且在骨折塑形改造期,更应该促进成骨细胞的活性,使骨形成加快,抑制破骨细胞的活性,使骨吸收减少。扫描电镜是研究骨质疏松症骨折骨组织形态学、成骨细胞和破骨细胞的形态学变化、骨动力、骨细胞功能和骨细胞活动的一种高精度灵活性强的有效工具。     

Wnt信号通路在骨稳态中的作用

人体内的骨稳态是由骨形成和骨吸收活动组成的动态平衡过程.骨稳态的失衡和功能障碍是包括骨质疏松症和骨硬化症在内的多种骨骼疾病的基础.以往研究证实Wnt、BMP、PTH/PTHrP、Notch和Hedgehog等信号通路参与调控成骨细胞/破骨细胞功能及骨稳态的平衡,其中Wnt信号通路的作用尤为关键和重要.本综述以此为切入点...     

糖代谢对骨骼细胞的影响

骨骼细胞之间的相互平衡是维持骨骼健康的重要因素之一,骨骼细胞之间失衡容易造成骨质疏松等骨骼疾病。很多研究表明,糖代谢异常会打破骨形成和骨吸收的平衡,从而引起骨量减少和骨质疏松性骨折等疾病。笔者对成骨细胞、破骨细胞以及骨细胞相关的糖代谢的最新研究进展进行总结,系统剖析糖代谢对成骨细胞、破骨细胞以及骨细胞分化和功能的关键调控作用,为骨质疏松等骨疾病的治疗提供理论指导。     

分子信号通路在骨质疏松症发生机制中的研究进展

目的骨质疏松症正成为影响老年人健康的老年疾病之一,主要原因是骨吸收大于骨形成,成骨细胞数量减少和活性下降。目前研究重点主要通过调节骨合成代谢的信号传导通路,抑制破骨细胞骨吸收,降低骨转换以达到减少骨量丢失。本文总结了骨代谢相关调控通路,包括MAPK信号转导途径、Notch信号通路、Wnt/-catenin信号途径、BMPs信号通路、PPAR-r信号通路、TGF-信号通路和Hedgehog信号转导途径。多个信号通路相互交叉,共同参与通路中相关因子的调节,通过激活或抑制一些关键环节的细胞因子,在骨代谢过程中发挥了主要作用。     

Reactive oxygen species and oxidative stress in osteoclastogenesis,skeletal aging and bone diseases

Osteoclasts are cells derived from bone marrow macrophages and are important in regulating bone resorption during bone homeostasis. Understanding what drives osteoclast differentiation and activity is important when studying diseases characterized by heightened bone resorption relative to formation, such as osteoporosis. In the last decade, studies have indicated that reactive oxygen species (ROS), including superoxide and hydrogen peroxide, are crucial components that regulate the differentiation process of osteoclasts. However, there are still many unanswered questions that remain. This review will examine the mechanisms by which ROS can be produced in osteoclasts as well as how it may affect osteoclast differentiation and activity through its actions on osteoclastogenesis signaling pathways. In addition, the contribution of ROS to the aging-associated disease of osteoporosis will be addressed and how targeting ROS may lead to the development of novel therapeutic treatment options.     

Direct stimulation of osteoclastic bone resorption by bone morphogenetic protein (BMP)-2 and expression of BMP receptors in mature osteoclasts

Bone morphogenetic proteins (BMPs) play an important role in various kinds of pattern formation and organogenesis during vertebrate development. In the skeleton, BMPs induce the differentiation of cells of chondrocytic and osteoblastic cell lineage and enhance their function. However, the action of BMPs on osteoclastic bone resorption, a process essential for pathophysiological bone development and regeneration, is still controversial. In this study, we examine the direct effect of BMPs on osteoclastic bone-resorbing activity in a culture of highly purified rabbit mature osteoclasts. BMP-2 caused a dose- and time-dependent increase in bone resorption pits excavated by the isolated osteoclasts. BMP-4 also stimulated osteoclastic bone resorption. The increase in osteoclastic bone resorption induced by BMP-2 was abolished by the simultaneous addition of follistatin, a BMP/activin binding protein that negates their biological activity. Just as it increased bone resorption, BMP-2 also elevated the messenger RNA expressions of cathepsin K and carbonic anhydrase II, which are key enzymes for the degradation of organic and inorganic bone matrices, respectively. Type IA and II BMP receptors (BMPRs), and their downstream signal transduction molecules, Smad1 and Smad5, were expressed in isolated osteoclasts as well as in osteoblastic cells, whereas type IB BMPR was undetectable. BMPs directly stimulate mature osteoclast function probably mediated by BMPR-IA and BMPR-II and their downstream molecules expressed in osteoclasts. The results presented here expand our understanding of the multifunctional roles of BMPs in bone development.     

Macrophage colony stimulating factor increases bone resorption in dispersed osteoclast cultures by increasing osteoclast size.

Several reports indicate that macrophage colony stimulating factor (MCSF) is one of the major factors required for osteoclast proliferation and differentiation. Paradoxically, it has also been reported that MCSF inhibits osteoclastic activity. We therefore decided to investigate in detail the effects of MCSF on resorption and osteoclast formation to try and clarify this issue. Osteoclast-containing cultures were obtained from rabbit long bones and cultured on plastic culture dishes or devitalized bovine bone slices. MCSF (4-400 ng/ml) stimulated osteoclastic bone resorption in a time-dependent manner and at all doses examined. After 48 h of culture in the presence of MCSF, we observed a 2-fold increase in the total area of bone resorbed, as well as a significant increase in the area of bone resorbed per osteoclast and the number of resorption pits per osteoclast. This effect was paralleled by an increase in the number of larger osteoclasts (as determined by the number of nuclei per cell) and an increase in the size and depth of the resorption pits. Since the total number of osteoclasts remained the same, the MCSF-induced increase in resorptive activity appeared to be related to an increase in the average size of the osteoclasts. When resorption was expressed as the amount of bone resorbed per osteoclast nucleus, larger osteoclasts resorbed more per nucleus, suggesting that large osteoclasts, as a population, are more effective resorbers than small osteoclasts. Interestingly, when osteoclasts were plated at one-fifth the standard density, the amount of bone resorbed per osteoclast decreased considerably, indicating that resorptive activity is also affected by cell density of osteoclasts and/or of other cells present. However, at this lower density MCSF still increased osteoclast size and resorption by the same fold increase over control, suggesting that the effect of MCSF was independent of factors related to cell density.     

Emodin Regulates Bone Remodeling by Inhibiting Osteoclastogenesis and Stimulating Osteoblast Formation

Bone remodeling, a physiological process in which new bone is formed by osteoblasts and the preexisting bone matrix is resorbed by osteoclasts, is vital for the maintenance of healthy bone tissue in adult humans. Imbalances in this process can cause various pathological conditions, including osteoporosis. Emodin, a naturally occurring anthraquinone derivative found in Asian herbal medicines, has numerous beneficial pharmacologic effects, including anticancer and antidiabetic activities. However, the effect of emodin on the regulation of osteoblast and osteoclast activity has not yet been investigated. We show here that emodin is a potential target for osteoporosis therapeutics, as treatment with this agent enhances osteoblast differentiation and bone growth and suppresses osteoclast differentiation and bone resorption. In this study, emodin suppressed receptor activator of nuclear factor‐κB (NF‐κB) ligand (RANKL)‐induced osteoclast differentiation of bone marrow macrophages (BMMs) and the bone‐resorbing activity of mature osteoclasts by inhibiting RANKL‐induced NF‐κB, c‐Fos, and NFATc1 expression. Emodin also increased ALP, Alizarin Red‐mineralization activity, and the expression of osteoblastogenic gene markers, such as Runx2, osteocalcin (OCN), and ALP in mouse calvarial primary osteoblasts, as well as activated the p38‐Runx2 pathway, which enhanced osteoblast differentiation. Moreover, mice treated with emodin showed marked attenuation of lipopolysaccharide (LPS)‐induced bone erosion and increased bone‐forming activity in a mouse calvarial bone formation model based on micro‐computed tomography and histologic analysis of femurs. Our findings reveal a novel function for emodin in bone remodeling, and highlight its potential for use as a therapeutic agent in the treatment of osteoporosis that promotes bone anabolic activity and inhibits osteoclast differentiation. © 2014 American Society for Bone and Mineral Research.     

Identification of biphenylcarboxylic acid derivatives as a novel class of bone resorption inhibitors.

A novel class of biphenylcarboxylic acid derivatives are described that inhibit osteoclastic bone resorption in vitro by promoting osteoclast apoptosis and that prevent ovariectomy-induced bone loss in vivo. The compounds act by a novel mechanism that seems to be distinct from existing antiresorptive drugs. INTRODUCTION: Many common bone diseases such as osteoporosis, Paget's disease, and cancer-associated bone disease are characterized by excessive bone loss caused by increased osteoclastic activity. Successful treatment of these diseases is based on osteoclast inhibition. The osteoclast inhibitory drugs that are currently available fall into relatively few mechanistic classes, indicating the need to identify novel antiresorptives. Here we describe a series of biphenylcarboxylic acid derivatives that have potent inhibitory effects on osteoclastic bone resorption in vitro and on ovariectomy-induced bone loss in vivo. MATERIALS AND METHODS: Compounds were tested for inhibitory effects on bone resorption in vitro using mouse osteoblast-bone marrow co-cultures, isolated rabbit osteoclasts, and mouse osteoclasts generated from bone marrow. Some experiments were also performed on human osteoclasts generated from peripheral blood mononuclear cells. We also investigated the effects of specific compounds on ovariectomy-induced bone loss in vivo in mice. RESULTS: One of the most potent compounds identified was the butanediol ester of biphenyl carboxylic acid (ABD056), which inhibited osteoclast formation in mouse osteoblast-bone marrow co-cultures by 50% (IC50) at a concentration of 26 microM and in macrophage-colony stimulating factor (M-CSF)- and RANKL-stimulated mouse bone marrow cultures with an IC50 of 8 microM. Mechanistic studies showed that ABD056 caused osteoclast apoptosis and inhibited TNFalpha-induced NF-kappaB activation. No inhibitory effects on osteoblast growth or differentiation were observed at concentrations of up to 100 microM. When administered to mice at doses of 5 and 10 mg/kg/day, ABD056 prevented ovariectomy-induced bone loss. CONCLUSIONS: Butanediol biphenylcarboxylic acid derivatives represent a new class of antiresorptive drug that might be of therapeutic value in the prevention and treatment of diseases characterized by osteoclast activation such as osteoporosis, cancer-associated bone disease, and Paget's disease of bone.     

Signaling axis in osteoclast biology and therapeutic targeting in the RANKL/RANK/OPG system

Bone integrity is maintained through a balance between bone formation and bone resorption, and osteoclasts are primary cells involved in bone resorption. Recent studies have revealed an essential role of macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor kappa-B ligand (RANKL) in the development of osteoclasts, and detailed molecular cascades that induce osteoclast differentiation, activation and apoptosis have been clarified. Osteoclasts are involved in various pathologic conditions, such as osteoporosis, rheumatoid arthritis and tumor-induced bone disease, which are characterized by abnormal bone resorption, and the finding of RANKL has provided us a good therapeutic target for such pathologic conditions.     

Dual effect of strontium ranelate: stimulation of osteoblast differentiation and inhibition of osteoclast formation and resorption in vitro

Strontium ranelate is a newly developed drug that has been shown to significantly reduce the risk of vertebral and non-vertebral fractures, including those of the hip, in postmenopausal women with osteoporosis. In contrast to other available treatments for osteoporosis, strontium ranelate increases bone formation and decreases resorption. In this study, the dual mode of action of strontium ranelate in bone was tested in vitro, on primary murine osteoblasts and osteoclasts derived from calvaria and spleen cells, respectively. We show that strontium ranelate treatment, either continuously or during proliferation or differentiation phases of mouse calvaria cells, stimulates osteoblast formation. Indeed after 22 days of continuous treatment with strontium ranelate, the expression of the osteoblast markers ALP, BSP and OCN was increased, and was combined with an increase in bone nodule numbers. On the other hand, the number of mature osteoclasts strongly decreased after strontium ranelate treatment. Similarly to previous studies, we confirm that osteoclasts resorbing activity was also reduced but we found that strontium ranelate treatment was associated with a disruption of the osteoclast actin-containing sealing zone. Therefore, our in vitro assays performed on primary murine bone cells confirmed the dual action of strontium ranelate in vivo as an anabolic agent on bone remodeling. It stimulates bone formation through its positive action on osteoblast differentiation and function, and decreases osteoclast differentiation as well as function by disrupting actin cytoskeleton organization.     

BMP9 Reduces Bone Loss in Ovariectomized Mice by Dual Regulation of Bone Remodeling

Bone remodeling is dynamic and is tightly regulated through bone resorption dominated by osteoclasts and bone formation dominated by osteoblasts. Imbalances in this process can cause various pathological conditions, such as osteoporosis. Bone morphogenetic protein 9 (BMP9), a biomolecule produced and secreted by the liver, has many pharmacological effects, including anti-liver fibrosis, antitumor, anti-heart failure, and antidiabetic activities. However, the effects of BMP9 on the regulation of osteoblast and osteoclast functions and the underlying molecular mechanism(s) have not yet been investigated. In this study, BMP9 increased the expression of osteoblastogenic gene markers, such as ALP, Cola1, OCN, RUNX2, and OSX, and ALP activity in MC3T3-E1 cells by upregulating LGR6 and activating the Wnt/β-catenin pathway. BMP9 also suppressed receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL)-induced osteoclast differentiation of bone marrow macrophages (BMMs) by inhibiting the Akt-NF-κB-NFATc1 pathway. More importantly, in an ovariectomy (OVX) mouse model, BMP9 attenuated bone loss and improved bone biomechanical properties in vivo by increasing bone-forming activity and suppressing bone resorption activity. Accordingly, our current work highlights the dual regulatory effects that BMP9 exerts on bone remodeling by promoting bone anabolic activity and inhibiting osteoclast differentiation in OVX mice. © 2020 American Society for Bone and Mineral Research.     

Osteoprotegerin and its Ligand: A New Paradigm for Regulation of Osteoclastogenesis and Bone Resorption

In just 3 years, striking new advances have been made in understanding the molecular mechanisms that govern the crosstalk between osteoblasts/stromal cells and hematopoietic osteoclast precursor cells that leads to osteoclastogenesis. Led first by the discovery of osteoprotegerin (OPG), a naturally occurring protein with potent osteoclastogenesis inhibitory activity, rapid progress was made to the isolation of RANKL, a transmembrane ligand expressed on osteoblasts/stromal cells that binds to RANK, a transmembrane receptor on hematopoietic osteoclast precursor cells. The interaction of RANK and RANKL initiates a signaling and gene expression cascade that results in differentiation and maturation of osteoclast precursor cells to active osteoclasts capable of resorbing bone. OPG acts as a decoy receptor, binding to RANKL and blocking its interaction with RANK, inhibiting osteoclast development. Many of the calciotropic hormones and cytokines, including 1,25(OH)₂D₃, PTH, PGE₂ and IL-11, appear to act through a dual capacity to inhibit production of OPG and stimulate production of RANKL. Estrogen, on the other hand, appears to inhibit production of RANKL and RANKL-stimulated osteoclastogenesis. Recently, the results of the first clinical trial with OPG supported its potential as a therapeutic agent for diseases such as osteoporosis. The new understanding provided by the RANK/RANKL/OPG paradigm for both differentiation of osteoclasts and their activation has had tremendous impact on the field and opened new avenues for development of possible treatments of diseases characterized by excessive bone resorption.     

Development and characterization of a human in vitro resorption assay: demonstration of utility using novel antiresorptive agents.

A human in vitro resorption assay has been developed using osteoclastoma-derived osteoclasts and used to evaluate novel antiresorptive agents including antagonists of the alphavbeta3 integrin, and inhibitors of cathepsin K and the osteoclast ATPase. The potency of novel compounds in the in vitro resorption assay correlates with functional assays for each class of inhibitor: the human alphavbeta3-mediated cell adhesion assay for the vitronectin receptor antagonists (r2 = 0.82), the chick osteoclast vacuolar ATPase enzyme assay for the H+-ATPase inhibitors (r2 = 0.77) and the recombinant human cathepsin K enzyme assay for the cathepsin K inhibitors (r2 = 0.80). Cell suspensions, rich in osteoclasts, are prepared by collagenase digestion of the tumor tissue. These cells can be stored long-term in liquid nitrogen and upon thawing maintain their bone-resorbing phenotype. The cryopreserved cells can be cultured on bovine cortical bone for 24-48 h and resorption can be measured by either confocal microscopy or biochemical assays. The resorptive activity of osteoclasts derived from a number of tumors can be inhibited reproducibly using a number of mechanistically unique antiresorptive compounds. In addition, the measurement of resorption pits by laser confocal microscopy correlates with the release of type I collagen C-telopeptides or N-telopeptides, as measured by enzyme-linked immunosorbent assay. Resorption can be measured reproducibly using a 48-h incubation of osteoclasts on bone slices, or a 24-h incubation with bone particles. This in vitro human osteoclast resorption assay provides a robust system for the evaluation of inhibitors of osteoclastic function that may be developed for the treatment of metabolic bone diseases such as osteoporosis.