RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

RANK/RANKL/OPG系统的作用及临床意义

作为骨重建过程的关键因子--NF-κB受体激活因子(receptor activator of NF-κB,RANK)/NF-κB配体激活因子(receptor activator of NF-κB ligand,RANKL)/护骨素(osteo-protegerin,OPG)系统是骨代谢研究的里程碑[1].     

Effects of polyethylene and TiAIV wear particles on expression of RANK,RANKL and OPG mRNA

Background?Wear debris has been associated with periprosthetic osteolysis and loosening of total joint arthroplasties. RANKL (receptor activator of NF-κB ligand), RANK (receptor activator of NF-κB) and OPG (osteoprotegerin) are three key molecules which regulate differentiation, survival, fusion, and activation of osteoclasts.Material and methods?We evaluated the effect of TiAlV and polyethylene particles on expression of RANK, RANKL and OPG mRNA. We used a human monocytic leukemic cell line (THP-1) in this in vitro study. THP-1 monocytes were differentiated into macrophage-like cells and exposed to polyethylene particles and prosthesis-derived TiAlV particles. The supernantant was used for measurement of TNFα protein and total RNA was extracted from the cells. Expression of the genes coding for OPG, RANKL and RANK was analysed at the mRNA level using a semiquantitative RT-PCR method.Results?Both polyethylene and TiAlV particles induced a significant release of TNFα after 6?h of exposure and a significant upregulation of RANK mRNA. OPG mRNA expression was transiently upregulated after exposure to polyethylene and TiAlV particles. These effects were dependent on particle dose. RANKL mRNA was not detectable in our THP-1 model. In contrast, LPS exhibited a different pattern of RANK/RANKL/OPG mRNA expression.Interpretation?Our findings provide evidence that both polyethylene and TiAlV particles induce upregulation of RANK expression in cells of the monocytic lineage, which may be important for periprosthetic osteoclastogenesis.     

共轭亚油酸c9,t11-CLA及t10,c12-CLA对大鼠骨髓细胞骨代谢相关基因表达的影响

目的 观察c9,t11-CLA及t10,c12-CLA干预后,大鼠骨髓细胞过氧化物酶体增殖物激活受体2(PPARγ2)及核因子(NF)-κB活化受体配体(RANKL)、碱性磷酸酶(ALP)、骨保护素(OPG)、NF-κB活化受体(RANK)、抗酒石酸酸性磷酸酶(TRAP) mRNA表达的变化,探讨其对骨代谢的影响.方法 体外培养大鼠骨髓细胞,分别加入c9,t11-CLA及t10,c12-CLA干预24h,逆转录-聚合酶链反应(RT-PCR)检测PPARγ2、RANKL、ALP、OPG、RANK、TRAP mRNA表达水平,比较其对骨髓细胞上述基因表达的影响.结果 (1)c9,t11-CLA呈剂量依赖性下调RANK、TRAP mRNA表达,组间比较差异有统计学意义(P＜0.05,P＜0.01),而其对RANKL、ALP、OPG及PPARγ2 mRNA 表达的影响不明显.(2) t10,c12-CLA呈剂量依赖性上调RANKL、OPG mRNA的表达,同时下调 RANK、TRAP及PPARγ2 mRNA的表达,组间比较差异有统计学意义(P＜0.05,P＜0.01),但对ALP mRNA的表达无明显影响.结论 c9,t11-CLA可能通过抑制破骨细胞标记物基因表达阻断骨髓细胞向破骨细胞分化,而t10,c12-CLA在抑制破骨细胞标记物基因表达的同时也可促进成骨细胞标记物基因表达,两者均有利于骨形成.     

The RANKL/RANK/OPG pathway

Understanding of osteoclast formation and activation has advanced considerably since the discovery of the RANKL/RANK/OPG system in the mid 1990s. Osteoblasts and stromal stem cells express receptor activator of NF-jB ligand (RANKL), which binds to its receptor, RANK, on the surface of osteoclasts and their precursors. This regulates the differentiation of precursors into multinucleated osteoclasts and osteoclast activation and survival both normally and in most pathologic conditions associated with increased bone resorption. Osteoprotegerin (OPG) is secreted by osteoblasts and osteogenic stromal stem cells and protects the skeleton from excessive bone resorption by binding to RANKL and preventing it from interacting with RANK. The RANKL/OPG ratio in bone marrow is thus an important determinant of bone mass in normal and disease states. RANKL/RANK signaling also regulates lymph node formation and mammary gland lactational hyperplasia in mice, and OPG protects large arteries of mice from medial calcification. This article reviews the roles of the RANKL/RANK/OPG system in bone and other tissues.     

RANKL,a necessary chance for clinical application to osteoporosis and cancer-related bone diseases

Osteoporosis is a common bone disease characterized by reduced bone and increased risk of fracture. In postmenopausal women, osteoporosis results from bone loss attributable to estrogen deficiency. Osteoclast differentiation and activation is mediated by receptor activator of nuclear factor-κB ligand (RANKL), its receptor receptor activator of nuclear factor-κB (RANK), and a decoy receptor for RANKL, osteoprotegerin (OPG). The OPG/RANKL/RANK system plays a pivotal role in osteoclast biology. Currently, a fully human anti-RANKL monoclonal antibody named denosumab is being clinically used for the treatment of osteoporosis and cancer-related bone disorders. This review describes recent advances in RANKL-related research, a story from bench to bedside. First, the discovery of the key factors, OPG/RANKL/RANK, revealed the molecular mechanism of osteoclastogenesis. Second, we established three animal models: (1) a novel and rapid bone loss model by administration of glutathione-S transferase-RANKL fusion protein to mice; (2) a novel mouse model of hypercalcemia with anorexia by overexpression of soluble RANKL using an adenovirus vector; and (3) a novel mouse model of osteopetrosis by administration of a denosumab-like anti-mouse RANKL neutralizing monoclonal antibody. Lastly, anti-human RANKL monoclonal antibody has been successfully applied to the treatment of osteoporosis and cancer-related bone disorders in many countries. This is a real example of applying basic science to clinical practice.     

Osteoprotegerin (OPG) and Related Proteins (RANK, RANKL and TRAIL) in Thyroid Disease

Background  

Osteoprotegerin (OPG), receptor activator of nuclear factor kappaB (RANK), RANK ligand (RANKL), and TNF related apoptosis inducing ligand (TRAIL) are the key proteins in the development of bone metastases. Osteoprotegerin improves tumor cell survival and inhibits TRAIL induced apoptosis of cancer cell lines. It also binds to RANKL and inhibits its interaction with RANK (cell surface receptor), which influences osteoclast formation and function. The aim of the present study was to characterize the expression of OPG, RANK, RANKL, and TRAIL in benign and malignant thyroid tissue and thyroid cell lines.     

Expression profiles of receptor activator of nuclear factor kappaB ligand, receptor activator of nuclear factor kappaB, and osteoprotegerin messenger RNA in aged and ovariectomized rat bones.

The receptor activator of nuclear factor-kappaB ligand (RANKL; also known as tumor necrosis factor-related activation-induced cytokine [TRANCE], osteoprotegerin ligand [OPGL], and osteoclast differentiation factor [ODF]) is a transmembrane ligand expressed in osteoblasts and bone marrow stromal cells. It binds to RANK, which is expressed in osteoclast progenitor cells, and induces osteoclastogenesis. OPG, a decoy receptor for RANKL, also binds to RANKL, and competitive binding of RANKL with RANK or OPG is thought to regulate bone metabolism. To investigate roles of the RANKL/RANK/OPG system in pathophysiological conditions, the expression of RANKL, RANK, and OPG messenger RNA (mRNA) was analyzed in bones of aged and ovariectomized rats by means of in situ hybridization. In the control 8-week-old male and sham-operated female rat bones, the expression of RANKL mRNA was detected in hypertrophic chondrocytes of the growth plate and some periosteal and endosteal mesenchymal cells. The expression of RANK mRNA was detected in osteoclast-like cells and mononuclear cells in contact with the cortical and trabecular bones. The expression of OPG mRNA was detected in proliferating chondrocytes and osteocytes. In the 2.5-year-old rat bones, the expression of RANKL, RANK, and OPG mRNA tended to decrease except for the endosteal region. In the ovariectomized rat bones, the expression of RANKL, RANK, and OPG mRNA increased, and high expression of OPG mRNA was induced in resting chondrocytes and osteocytes. These results suggest that estrogen deficiency stimulates the RANKL/RANK/OPG system and induces OPG in cells that have been thought to be less important for bone metabolism.     

Evaluation of the role of RANK and OPG genes in Paget's disease of bone

Paget's disease of bone (PDB) is one of the most common bone disorders in the western world. PDB is characterized by focal areas of increased osteoclastic bone resorption and bone formation, which leads to the formation of poorly structured bone. These abnormalities of bone turnover and structure predispose affected individuals to various complications including bone pain, deformity, pathological fracture, and an increased risk of osteosarcoma. One of the main mechanisms of osteoclast formation and activation involves the receptor activator of nuclear factor -kappaB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) pathway, where binding of RANKL to RANK results in the differentiation of osteoclast precursors. OPG, on the other hand, acts as an inhibitor of osteoclastogenesis by serving as a decoy receptor for RANKL. Recently, mutations in the RANK gene have been shown to cause familial expansile osteolysis, a rare bone disorder showing great similarity to PDB. We performed mutation analysis in the RANK and OPG genes in 28 PDB patients to investigate whether mutations in these genes could be responsible for PDB. Our data suggest that RANK is not directly involved in PDB in our set of patients, as no mutations in the RANK coding region could be identified and allele frequencies of RANK polymorphisms did not differ in PDB patients as compared with the random population. Also, in the OPG gene, we could not detect PDB-causing mutations. However, of the several polymorphisms identified, one (400 + 4 C/T in intron 2), showed a statistically significant increased frequency for the C allele in PDB patients, suggesting that individuals harboring this allele may be more susceptible for developing PDB.     

Novel Aspects on RANK Ligand and Osteoprotegerin in Osteoporosis and Vascular Disease

The clinical coincidence of osteoporosis and vascular disease has long indicated that common mediators may adversely affect bone metabolism and vascular integrity alike. Receptor activator of NF-kappaB ligand (RANKL) is an important cytokine for bone resorption that acts through its osteoclastic receptor, receptor activator of NF-kappaB (RANK), while osteoprotegerin serves as a decoy receptor that binds RANKL and prevents activation of RANK. Skeletal and vascular cells are sources and targets of RANKL and OPG both in vitro and in vivo. Modulation of the RANKL/RANK/OPG system in animals results in a skeletal and vascular phenotype, and administration of OPG may prevent osteoporosis and vascular calcification. Recent studies on OPG serum levels and gene polymorphisms also suggest an important role of this cytokine system in skeletal and vascular diseases. In summary, there is increasing evidence that RANKL and OPG may link the skeletal with the vascular system.     

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.     

Novel Aspects on RANK Ligand and Osteoprotegerin in Osteoporosis and Vascular Disease

The clinical coincidence of osteoporosis and vascular disease has long indicated that common mediators may adversely affect bone metabolism and vascular integrity alike. Receptor activator of NF-B ligand (RANKL) is an important cytokine for bone resorption that acts through its osteoclastic receptor, receptor activator of NF-B (RANK), while osteoprotegerin serves as a decoy receptor that binds RANKL and prevents activation of RANK. Skeletal and vascular cells are sources and targets of RANKL and OPG both in vitro and in vivo. Modulation of the RANKL/RANK/OPG system in animals results in a skeletal and vascular phenotype, and administration of OPG may prevent osteoporosis and vascular calcification. Recent studies on OPG serum levels and gene polymorphisms also suggest an important role of this cytokine system in skeletal and vascular diseases. In summary, there is increasing evidence that RANKL and OPG may link the skeletal with the vascular system.