Osteoclast induction in periodontal tissue during experimental movement of incisors in osteoprotegerin‐deficient mice

Osteoprotegerin (OPG) is a novel secreted member of the tumor necrosis factor (TNF) receptor superfamily that negatively regulates osteoclastogenesis. The receptor activator of the NFKB ligand (RANKL) is one of the key regulatory molecules in osteoclast formation and binds to OPG. In this study, it was suggested that OPG and RANKL are involved in alveolar bone remodeling during orthodontic tooth movement. We examined RANKL localization and osteoclast induction in periodontal tissues during experimental movement of incisors in OPG‐deficient mice. To produce orthodontic force, an elastic band was inserted between the upper right and left incisors for 2 or 5 days, and the dissected maxillae were examined for cytochemical and immunocytochemical localization of tartrate‐resistant acid phosphatase (TRAP), vacuolar‐type H⁺‐ATPase, and RANKL. Compared to wild‐type OPG (+/+) littermates, TRAP‐positive multinucleated cells were markedly induced in the periodontal ligament (PDL) on the compressed side and in the adjacent alveolar bone of OPG‐deficient mice. These multinucleated cells exhibited intense vacuolar‐type H⁺‐ATPase along the ruffled border membranes. Because of accelerated osteoclastic resorption in OPG‐deficient mice, alveolar bone was severely destroyed and partially perforated at 2 and 5 days after force application. In both wild‐type and OPG‐deficient mice, RANKL expression became stronger at 2 and 5 days after force application than before force application. There was no apparent difference in intensity of RANKL expression between OPG (+/+) littermates and OPG‐deficient mice. In both wild‐type and OPG‐deficient mice, expression of RANKL protein was detected in osteoblasts, fibroblasts, and osteoclasts mostly located in resorption lacunae. These results suggest that during orthodontic tooth movement, RANKL and OPG in the periodontal tissues are important determinants regulating balanced alveolar bone resorption. Anat Rec 266:218–225, 2002. © 2002 Wiley‐Liss, Inc.     

Influence of lipopolysaccharide and interleukin‐6 on RANKL and OPG expression and release in human periodontal ligament cells

Recent research into periodontal disease pathology focuses on the role of receptor activator of nuclear factor‐κB ligand (RANKL) and osteoprotegerin (OPG) in periodontal bone destruction processes. RANKL regulates the differentiation of osteoclast by binding to its specific receptor RANK, while OPG inhibits the differentiation of osteoclasts by binding RANKL and therefore preventing RANKL to bind RANK. The aim of the present study was to investigate the influence of Porphyromonas gingivalis lipopolysaccharide (LPS) and interleukin‐6 (IL‐6) on RANKL and OPG expression and release in periodontal ligament (PDL) cells. Human PDL cells were stimulated for 48 h with purified P. gingivalis LPS and IL‐6. OPG and sRANKL release were assessed by using enzyme‐linked immunosorbent assay technique. OPG and RANKL expression was quantitatively measured by using the real‐time PCR technique. Whereas P. gingivalis LPS induced sRANKL release, expression was only slightly increased, IL‐6 did not show an effect on RANKL expression or release. In conclusion the data demonstrate that stimulation of PDL cells with P. gingivalis LPS leads to an increased release of sRANKL, rather than increased RANKL expression. Through this action, P. gingivalis LPS may exert its biological effect on osteoclast formation and bone resorption.     

Growing the Mandible: Role of the Periosteum and its Cells

Mandibular periosteum moves in the direction of new apposition. This displacement, usually termed “migration,” is thought to involve the fibrous layer of periosteum, with the deeper osteogenic layer remaining at its original location except for its blood vessels. To assess whether periosteal displacement includes cells as well as matrix and whether the osteogenic layer has a role, a longitudinal study was undertaken. Young pigs (n = 10) were injected with a replication marker and killed 3 hr, 2 weeks, or 4 weeks later. Sections of the mandibular ramus were scored for labeled cell density. Some sections were double‐labeled with lectin to identify blood vessels. Statistical differences were seen between but not within age groups. Three hours after labeling, the fibroblastic layer had sparse, evenly distributed replicating cells, whereas the osteogenic layer had numerous replicating cells, especially at the caudal border. At 2 and 4 weeks later, a decrease in labeled osteogenic layer cells was accompanied by an increase in labeled osteocytes. Zones of labeled osteocytes in these late‐sacrifice groups were used to approximate the position of the ramal borders at the time of injection. Beyond these zones, in active growing sites, labeled cells were found not only in the fibrous layer but also in the osteogenic layer and in bone. Therefore, periosteal displacement does involve cells and is not restricted to the fibrous layer. Anat Rec 290:1366‐1376, 2007. © 2007 Wiley‐Liss, Inc.     

Immunolocalization of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in Meckel's cartilage compared with developing endochondral bones in mice

We examined the immunolocalization of receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) in areas of resorption caused by osteoclasts/chondroclasts on embryonic days 14-16 (E14-16) in Meckel's cartilage, and compared the results with those in endochondral bones in mice. Intense RANKL and OPG immunoreactivity was detected in the chondrocytes in Meckel's cartilage. On E15, when the incisor teeth were closest to the middle portion of Meckel's cartilage, tartrate-resistant acid phosphatase (TRAP)-positive cells appeared on the lateral side of the cartilage. Furthermore, the dental follicle showed moderate immunoreactivity for RANKL and OPG, whereas osteoblasts derived from perichondral cells were immunonegative for RANKL and OPG in that area. On E16, cartilage resorption by TRAP-positive cells had progressed at the differential position, and intensely immunoreactive products of RANKL were overlapped on and found to exist next to TRAP-positive cells in the resorption area. In developing metatarsal tissue, OPG immunoreactivity was intense in periosteal osteoblasts, whereas RANKL was only faintly seen in some of the periosteal cells. In epiphyseal chondrocytes of the developing femur, RANKL immunoreactivity was moderate, and OPG scarcely detected. These results indicate a peculiarity of RANKL and OPG immunolocalization in resorption of Meckel's cartilage. Growth of the incisor teeth may be involved in the time- and position-specific resorption of Meckel's cartilage through local regulation of the RANKL/OPG system in dental follicular cells and periosteal osteoblasts, whereas RANKL and OPG in chondrocytes seem to contribute to resorption through regulation of the chondroclast function.     

In situ hybridisation study of type I, II, X collagens and aggrecan mRNAs in the developing condylar cartilage of fetal mouse mandible

The aim of this study was to investigate the developmental characteristics of the mandibular condyle in sequential phases at the gene level using in situ hybridisation. At d 14.5 of gestation, although no expression of type II collagen mRNA was observed, aggrecan mRNA was detected with type I collagen mRNA in the posterior region of the mesenchymal cell aggregation continuous with the ossifying mandibular bone anlage prior to chondrogenesis. At d 15.0 of gestation, the first cartilaginous tissue appeared at the posterior edge of the ossifying mandibular bone anlage. The primarily formed chondrocytes in the cartilage matrix had already shown the appearance of hypertrophy and expressed types I, II and X collagens and aggrecan mRNAs simultaneously. At d 16.0 of gestation, the condylar cartilage increased in size due to accumulation of hypertrophic chondrocytes characterised by the expression of type X collagen mRNA, whereas the expression of type I collagen mRNA had been reduced in the hypertrophic chondrocytes and was confined to the periosteal osteogenic cells surrounding the cartilaginous tissue. At d 18.0 of gestation before birth, cartilage-characteristic gene expression had been reduced in the chondrocytes of the lower half of the hypertrophic cell layer. The present findings demonstrate that the initial chondrogenesis for the mandibular condyle starts continuous with the posterior edge of the mandibular periosteum and that chondroprogenitor cells for the condylar cartilage rapidly differentiate into hypertrophic chondrocytes. Further, it is indicated that sequential rapid changes and reductions of each mRNA might be closely related to the construction of the temporal mandibular ramus in the fetal stage.     

Osteoprotegerin (OPG) Production by Cells in the Osteoblast Lineage is Regulated by Pulsed Electromagnetic Fields in Cultures Grown on Calcium Phosphate Substrates

Pulsed electromagnetic fields (PEMF) used clinically to stimulate bone formation enhance the osteogenic effects of BMP-2 on human mesenchymal stem cells (MSCs) if the MSCs are grown in osteogenic medium and are cultured on calcium phosphate (CaP) surfaces rather than tissue culture polystyrene plastic (TCPS). This study tested if PEMF’s effects on cells in the osteoblast lineage are substrate dependent and if factors produced by osteoblasts that regulate osteoclastic bone resorption, might also be regulated by PEMF. Human MSCs treated with BMP-2 and human osteoblast-like cells (normal human osteoblasts [NHOst cells], MG63 cells, SaOS-2 cells) were cultured on CaP or TCPS and their response to PEMF (4.5 ms bursts of 20 pulses repeating at 15 Hz for 8 h/day) determined as a function of decoy receptor osteoprotegerin (OPG) and RANK ligand (RANKL) production, both of which are associated with regulation of osteoclast differentiation. The results showed that when osteoblast-like cells were cultured on CaP, PEMF decreased cell number and increased production of paracrine factors associated with reduced bone resorption like OPG. RANKL was unaffected, indicating that the OPG/RANKL ratio was increased, further supporting a surface-dependent osteogenic effect of PEMF. Moreover, effects of estrogen were surface dependent and enhanced by PEMF, demonstrating that PEMF can modulate osteogenic responses to anabolic regulators of osteoblast function. These effects of PEMF would not be evident in models examining cells in traditional culture on plastic.     

Porphyromonas gingivalis induces RANKL in bone marrow stromal cells: involvement of the p38 MAPK

Periodontitis is a bacterially-induced oral inflammatory disease that is characterised by tissue degradation and bone loss. Porphyromonas gingivalis is a gram negative bacterial species highly associated with the pathogenesis of chronic periodontitis. Receptor activator of nuclear factor-kB ligand (RANKL) induces bone resorption whilst osteoprotegerin (OPG) is a decoy receptor that blocks this process. Cyclooxygenase-2 (COX-2) is an enzyme responsible for the production of prostaglandin (PGE)_2, which is a major inflammatory mediator of bone resorption. Mitogen-activated protein kinases (MAPK) are intracellular signalling molecules involved in various cell processes, including inflammation. This study aimed to investigate the effect of P. gingivalis on MAPKs and their involvement in the regulation of RANKL, OPG and COX-2 expression in bone marrow stromal cells. P. gingivalis challenge resulted in the phosphorylation of primarily the p38 MAPK. RANKL and COX-2 mRNA expressions were up-regulated, whereas OPG was down-regulated by P. gingivalis. The p38 synthetic inhibitor SB203580 abolished the P. gingivalis-induced RANKL and COX-2 expression, but did not affect OPG. Collectively, these results suggest that the p38 MAPK pathway is involved in the induction of RANKL and COX-2 by P. gingivalis, providing further insights into the pathogenic mechanisms of periodontitis.     

Osteoclast induction in periodontal tissue during experimental movement of incisors in osteoprotegerin-deficient mice

Osteoprotegerin (OPG) is a novel secreted member of the tumor necrosis factor (TNF) receptor superfamily that negatively regulates osteoclastogenesis. The receptor activator of the NFKB ligand (RANKL) is one of the key regulatory molecules in osteoclast formation and binds to OPG. In this study, it was suggested that OPG and RANKL are involved in alveolar bone remodeling during orthodontic tooth movement. We examined RANKL localization and osteoclast induction in periodontal tissues during experimental movement of incisors in OPG-deficient mice. To produce orthodontic force, an elastic band was inserted between the upper right and left incisors for 2 or 5 days, and the dissected maxillae were examined for cytochemical and immunocytochemical localization of tartrate-resistant acid phosphatase (TRAP), vacuolar-type H(+)-ATPase, and RANKL. Compared to wild-type OPG (+/+) littermates, TRAP-positive multinucleated cells were markedly induced in the periodontal ligament (PDL) on the compressed side and in the adjacent alveolar bone of OPG-deficient mice. These multinucleated cells exhibited intense vacuolar-type H(+)-ATPase along the ruffled border membranes. Because of accelerated osteoclastic resorption in OPG-deficient mice, alveolar bone was severely destroyed and partially perforated at 2 and 5 days after force application. In both wild-type and OPG-deficient mice, RANKL expression became stronger at 2 and 5 days after force application than before force application. There was no apparent difference in intensity of RANKL expression between OPG (+/+) littermates and OPG-deficient mice. In both wild-type and OPG-deficient mice, expression of RANKL protein was detected in osteoblasts, fibroblasts, and osteoclasts mostly located in resorption lacunae. These results suggest that during orthodontic tooth movement, RANKL and OPG in the periodontal tissues are important determinants regulating balanced alveolar bone resorption.     

低频振动刺激骨髓基质干细胞修复骨缺损核因子受体激活剂/核因子受体激活剂配体/骨保护素通路变化的体内实验*

背景：关于低频振动对体内骨髓基质干细胞成骨分化的实验缺乏报道。 目的：通过体内实验研究不同频率振动刺激骨髓基质干细胞修复骨缺损过程中核因子受体激活剂/核因子受体激活剂配体/骨保护素调节通路的变化,并初步探讨其机制。 方法：取新西兰兔骨髓基质干细胞和脱钙骨基质制备复合物,80只新西兰兔制作骨缺损模型,骨缺损区植入复合物后随机数字表法均分组对照组、12.5,25,50,100 Hz振动组,振动组于第7天开始接受不同频率振动干预5周,振动结束后分别对骨保护素mRNA、核激活因子受体配体mRNA进行检测。 结果与结论：与对照组比较,各振动组骨髓基质干细胞骨保护素、核激活因子受体配体基因表达明显上调(P < 0.05),以25,50 Hz显著(P < 0.01);但100 Hz振动时表达则下调(P < 0.05)。说明给予一定频率振动刺激骨髓基质干细胞修复骨缺损,可能与其促进骨保护素基因表达上调有关,理想的振动频率为25,50 Hz。     

Bone morphogenetic proteins 5 and 6 stimulate osteoclast generation

Bone regeneration is required for fracture-healing, and different procedures have been used to promote osteogenesis. Recently, BMP-2 has been shown to induce bone formation in vivo and has been tested in clinical trials. A recent in vitro study evaluated the osteogenic activity of 14 BMPs on osteoblastic progenitor cells with an osteogenic hierarchical model in which BMP-2 and BMP-6 may play an important role in inducing osteoblast differentiation. Although the relative osteoinductive activity of each BMP is important, bone regeneration is a process consisting of bone formation and bone resorption. Therefore, it remains unclear which effects BMP-5 and -6 have on the generation of osteoclasts and by which mechanism osteoclastogenesis is stimulated. To compare osteoclastic potency of each BMP, primary murine bone marrow cells were treated with human recombinant BMP-2, BMP-5, or BMP-6 and 1,25-(OH)2 vitamin D3 and stained for the TRAP enzyme. Osteogenic activity of BMP-5 was determined by measuring induction of ALP-activity and proliferation after incubation with primary murine osteoblasts. For elucidating the molecular mechanism, primary bone marrow cells with various concentrations of OPG were added to the TRAP assay and mRNA levels of RANKL and OPG were measured after stimulation with BMP-5. The presented data show that BMP-5 and BMP-6, unlike BMP-2, enhanced the formation of murine TRAP+/MNCs in a biphasic curve. BMP-5 and -6 were less potent in stimulating osteoclastogenesis compared to BMP-2. Concerning the effects of BMP-5 on osteoblasts, there was a dose-dependent increase of ALP activity and proliferation up to a maximum dose of 300 ng/mL. At the mRNA level, BMP-5 increased the RANKL/OPG ratio. In conclusion, this study demonstrates that in contrast to BMP-2, BMP-5 and -6 influences the generation of osteoclasts in a biphasic mode. Both proteins might be very important regulators of bone homeostasis, and therefore, potent candidates for future treatment strategies of bone regeneration.     

Oral biofilm challenge regulates the RANKL-OPG system in periodontal ligament and dental pulp cells

Inflammatory bone destruction triggered by oral bacteria is a hallmark of chronic and apical periodontitis. Receptor activator of NF-κB ligand (RANKL) activates bone resorption, whereas osteoprotegerin (OPG) blocks its action. These are members of the tumor necrosis factor ligand and receptor families, respectively. Although individual oral pathogens are known to regulate RANKL and OPG expression in cells of relevance to the respective diseases, such as periodontal ligament (PDL) and dental pulp (DP) cells, the effect of polymicrobial oral biofilms is not known. This study aimed to investigate the effect of the Zürich in vitro supragingival biofilm model on RANKL and OPG gene expression, in human PDL and DP cell cultures, by quantitative real-time polymerase chain reaction. RANKL expression was more pronouncedly up-regulated in DP than PDL cells (4-fold greater), whereas OPG was up-regulated to a similar extent. The RANKL/OPG ratio was increased only in DP cells, indicating an enhanced capacity for inducing bone resorption. The expression of pro-inflammatory cytokine interleukin-1β was also increased in DP, but not PDL cells. Collectively, the high responsiveness of DP, but not PDL cells to the supragingival biofilm challenge could constitute a putative pathogenic mechanism for apical periodontitis, which may not crucial for chronic periodontitis.     

The cytolethal distending toxin induces receptor activator of NF-kappaB ligand expression in human gingival fibroblasts and periodontal ligament cells

Actinobacillus actinomycetemcomitans is associated with localized aggressive periodontitis, a disease characterized by rapid loss of the alveolar bone surrounding the teeth. Receptor activator of NF-kappaB Ligand (RANKL) and osteoprotegerin (OPG) are two molecules that regulate osteoclast formation and bone resorption. RANKL induces osteoclast differentiation and activation, whereas OPG blocks this process by acting as a decoy receptor for RANKL. The purpose of this study was to investigate the effect of A. actinomycetemcomitans on the expression of RANKL and OPG in human gingival fibroblasts and periodontal ligament cells. RANKL mRNA expression was induced in both cell types challenged by A. actinomycetemcomitans extract, whereas OPG mRNA expression remained unaffected. Cell surface RANKL protein was also induced by A. actinomycetemcomitans, whereas there was no change in OPG protein secretion. A cytolethal distending toxin (Cdt) gene-knockout strain of A. actinomycetemcomitans did not induce RANKL expression, in contrast to its wild-type strain. Purified Cdt from Haemophilus ducreyi alone, or in combination with extract from the A. actinomycetemcomitans cdt mutant strain, induced RANKL expression. Pretreatment of A. actinomycetemcomitans wild-type extract with Cdt antiserum abolished RANKL expression. In conclusion, A. actinomycetemcomitans induces RANKL expression in periodontal connective tissue cells. Cdt is crucial for this induction and may therefore be involved in the pathological bone resorption during the process of localized aggressive periodontitis.     

低强度高频率振动对成骨细胞生物学特性的影响

目的　研究低强度高频率振动（low-magnitude high-frequency vibration, LMHFV）对成骨细胞生物学特性的影响。 方法　建立LMHFV加载MC3T3-E1细胞模型,观察不同频率LMHFV对MC3T3-E1细胞OPG/RANKL浓度比的影响,获得OPG/RANKL浓度比最高的频率（F）为后续研究频率;以0 Hz为对照,观察LMHFV对MC3T3-E1细胞碱性磷酸酶 (ALP)、骨钙素(OCN) mRNA和蛋白活性,及钙化结节形成的影响;LMHFV加载形成的条件培养液（CMF）孵育RAW264.7细胞,观察CMF对破骨细胞抗酒石酸酸性磷酸酶（TRAP）染色、多核破骨细胞形成、TRAP mRNA及蛋白活性的影响;观察LMHFV对MC3T3-E1细胞环氧化酶2(COX-2)蛋白水平的表达及COX-2抑制剂NS-398对LMHFV影响MC3T3-E1细胞分化的作用。 结果　30 Hz LMHFV获得OPG/RANKL浓度比最高,促进ALP、OCN mRNA及蛋白活性增加,增加钙化结节形成。30 Hz LMHFV形成的CM抑制RAW264.7细胞向多核破骨细胞分化,抑制TRAP mRNA及活性;LMHFV可诱导COX-2蛋白水平增加,NS-398能抑制LMHFV促进成骨细胞分化。 结论　30 Hz的LMHFV对MC3T3-E1细胞OPG/RANKL浓度比及成骨分化具有积极的影响,通过调控成骨细胞OPG/RANKL浓度比间接抑制骨吸收,COX-2通路参与了LMHFV对成骨细胞生物学特性的调节作用。     

Loss of RUNX3 expression promotes cancer‐associated bone destruction by regulating CCL5, CCL19 and CXCL11 in non‐small cell lung cancer

Non‐small cell lung cancer (NSCLC) frequently metastasizes to bone, which is associated with significant morbidity and a dismal prognosis. RUNX3 functions as a tumour suppressor in lung cancer and loss of expression occurs more frequently in invasive lung adenocarcinoma than in pre‐invasive lesions. Here, we show that RUNX3 and RUNX3‐regulated chemokines are linked to NSCLC‐mediated bone resorption. Notably, the receptor activator of nuclear factor‐κB ligand (RANKL)/osteoprotegerin (OPG) ratio, an index of osteoclastogenic stimulation, was significantly increased in human osteoblastic cells treated with conditioned media derived from RUNX3‐knockdown NSCLC cells. We aimed to identify RUNX3‐regulated factors that modify the osteoblastic RANKL/OPG ratio and found that RUNX3 knockdown led to CCL5 up‐regulation and down‐regulation of CCL19 and CXCL11 in NSCLC cells. Tumour size was noticeably increased and more severe osteolytic lesions were induced in the calvaria and tibiae of mice that received RUNX3‐knockdown cells. In response to RUNX3 knockdown, serum and tissue levels of CCL5 increased, whereas CCL19 and CXCL11 decreased. Furthermore, CCL5 increased the proliferation, migration, and invasion of lung cancer cells in a dose‐dependent manner; however, CCL19 and CXCL11 did not show any significant effects. The RANKL/OPG ratio in osteoblastic cells was increased by CCL5 but reduced by CCL19 and CXCL11. CCL5 promoted osteoclast differentiation, but CCL19 and CXCL11 reduced osteoclastogenesis in RANKL‐treated bone marrow macrophages. These findings suggest that RUNX3 and related chemokines are useful markers for the prediction and/or treatment of NSCLC‐induced bone destruction. © 2015 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Distribution of BMP6 in the alveolar bone during mouse mandibular molar eruption

Eruption requires synchrony of the tooth with the surrounding tissues, particularly the bone. One important step during eruption is remodelling of the alveolar bone at the base of the tooth and along the roots. Expression of BMP6 was reported to be increased in the basal half of the dental follicle prior to eruption and inhibition of BMP6 affected bone formation at the base of the alveolar crypt. The aim of this study was to further investigate BMP6 protein in relation to tooth eruption and the corresponding bone remodelling using temporospatial correlations of BMP6 localization with morphogenetic events (proliferation, differentiation, apoptosis and bone apposition/resorption), other BMPs (BMP2 and BMP7) and three-dimensional images of tooth–bone development. BMP6 expression pattern was mapped in the mandibular molar teeth and related structures around eruption. Localization of BMP6 dominated in osteoblasts, in regions of bone formation within the alveolar crypt. These findings positively correlated with proliferation at the tooth base region, osteocalcin expression in the osteoblasts/osteocytes and BMP2 and BMP7 presence in the alveolar bone surrounding the tooth. Osteoclast activity and apoptotic elimination in the root region gradually decreased before eruption and totally ceased at eruption stages. Generally, BMP6 positively correlated with BMP2, BMP7 and osteocalcin-positive osteoblasts, and areas of bone remodelling. Moreover, BMP6 was found in the periodontium and cementoblasts. BMP6 expression in the alveolar bone accompanied tooth eruption. Notably, the expression pattern of BMP6 in the bone did not differ around individual molar teeth at the same stage of development. The expression of BMP6 in periodontal ligaments may contribute to interaction between the tooth and bone during the eruption and anchoring process.     

Regulation of RANKL and OPG gene expression in human gingival fibroblasts and periodontal ligament cells by Porphyromonas gingivalis: a putative role of the Arg-gingipains

Porphyromonas gingivalis is highly implicated in the pathogenesis of periodontitis, which is characterized by the destruction of periodontal connective tissues and the supporting alveolar bone. Receptor Activator of NF-kappaB Ligand (RANKL) stimulates bone resorption, whereas osteoprotegerin (OPG) blocks its action, and this bi-molecular system is implicated in periodontitis. The aim of this work was (a) to investigate the regulation of RANKL and OPG gene expression in human periodontal ligament (PDL) cells and gingival fibroblasts (GF), in response to P. gingivalis culture supernatants, by quantitative real-time PCR and (b) to attempt to identify putative virulence factors involved in this process. The results indicated that P. gingivalis induced RANKL and reduced OPG mRNA expression by the studied cells, resulting in an increased RANKL/OPG expression ratio. Heat-inactivation of P. gingivalis resulted in significant reduction of RANKL mRNA expression. A Lys-gingipain mutant strain did not affect, whereas an Arg-gingipain mutant strain further enhanced RANKL mRNA expression, compared to their parental wild-type strain. In conclusion, P. gingivalis up-regulates the RANKL/OPG expression ratio in GF and PDL cells, denoting an enhanced osteoclastogenic potential by the cells. The component mainly responsible for RANKL induction appears to be proteinaceous, and it may be regulated by the Arg-gingipains.     

Advances in bone biology and new treatments for bone loss

Recent advances in bone biology have led to a more detailed understanding of bone remodeling which is a process that leads to resorption of old bone and replacement by formation of new bone. The most important discoveries in this process of bone remodeling were those of the RANK Ligand/RANK/OPG system which is now recognized the dominant pathway regulating bone resorption. RANK Ligand (RANKL) is a cytokine belonging to the tumor necrosis factor family and is expressed by osteoblasts; it binds to membrane bound receptor RANK on osteoclasts and promotes differentiation of marrow cells through various stages to multinucleated osteoclasts which resorb bone. Several hormones such as parathyroid hormone, calcitriol and prostaglandins stimulate RANK Ligand expression by osteoblasts. Osteoblasts also secrete osteoprotegerin (OPG) which is a soluble receptor that is a potent antagonist of osteoclast formation by binding and inactivating RANKL and OPG is therefore an important regulator of bone resorption. OPG is stimulated by estrogen. OPG has been genetically engineered and in human subjects is a potent inhibitor of bone resorption. Another method for preventing bone resorption is to develope antibodies against RANKL and this has been shown to be a successful strategy. A single subcutaneous injection of this antibody (Denosumab) every 6 months proved to be a potent inhibitor of bone resorption and clinical fracture trials using this agent are now underway. These are novel developments that have risen from basic research in bone biology and other discoveries in the bone remodeling process can be expected to lead to further treatment options for various bone diseases.     

骨形态发生蛋白7诱导骨膜细胞碱性磷酸酶的表达

背景：关于骨形态发生蛋白7作为刺激因子诱导细胞成骨的报道目前较少见。 目的：观察骨膜细胞经骨形态发生蛋白7诱导后碱性磷酸酶的表达。 方法：取材于成人胫骨骨膜,常规细胞培养法行骨膜细胞体外培养,分为实验组和对照组,分别加入骨形态发生蛋白7加成骨细胞培养辅助剂和单纯成骨细胞培养辅助剂,相差显微镜观察骨膜细胞形态特征及超微结构。每组分别在第7,14,21天设3个时间点,每个时间点设3个样本,采用碱性磷酸酶试剂盒法检测成骨细胞特异性标志物碱性磷酸酶表达情况。 结果与结论：骨膜细胞经分组培养后,第7天时,实验组和对照组骨膜细胞均有明显增殖,碱性磷酸酶的可被检测出,但量不多,细胞外形为梭形,实验组比对照组检测的碱性磷酸酶数量稍多;第14天时,实验组及对照组骨膜细胞均显著增殖,细胞外形由梭形变为宽梭形,实验组比对照组检测的碱性磷酸酶数量明显增多。第21天时,实验组及对照组骨膜细胞均增殖,其中实验组细胞增殖明显,细胞外形为宽梭形,实验组比对照组检测的碱性磷酸酶数量显著增多。经过统计学分析由骨形态发生蛋白7诱导的骨膜细胞的成骨标志物碱性磷酸酶阳性率明显高于对照组(P < 0.01)。提示骨膜细胞具有良好的成骨和再生能力, 骨形态发生蛋白7能诱导骨膜细胞加强碱性磷酸酶的表达,能诱导骨膜细胞向成骨细胞转化。     

Increased RANKL expression is related to tumour migration and metastasis of renal cell carcinomas

Receptor activator of NF‐κB ligand (RANKL) and its receptor, receptor activator of NF‐κB (RANK), play a key role in osteoclastogenesis, and osteoprotegerin (OPG) acts as a decoy receptor for RANKL. We investigated the role of the RANKL–RANK–OPG system in renal cell carcinomas (RCCs), which frequently metastasize to bones. Real‐time quantitative PCR revealed that RANKL mRNA expression was higher in clear cell RCCs than in papillary and chromophobe RCCs. Similarly, RANKL protein expression level in clear cell RCCs was higher than that in papillary and chromophobe RCCs, showing positive correlations with the primary tumour stage and distant metastasis. There was no significant association between the expression level of RANK, OPG and histological subtypes of RCC. RANKL and RANK expression was observed in metastatic RCCs in the bone and other organs, suggesting that they play a role in metastasis to the bone and other organs. Recombinant RANKL protein stimulated migration of a clear cell RCC cell line, Caki‐1, in vitro, and this enhanced migration was inhibited by the administration of recombinant OPG protein. Furthermore, multivariate Cox analysis revealed that elevated RANKL and RANK expression with low‐OPG expression was a significant and independent predictor of recurrence, bone metastasis and a poor prognosis. These data suggest that the RANKL–RANK–OPG system is involved not only in the bone metastasis of RCCs but also in metastasis to other organs through the stimulation of cancer cell migration. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

脂肪间充质干细胞成骨分化条件培养基联合骨形态发生蛋白2治疗去卵巢大鼠骨质疏松症

文题释义： 骨质疏松症：是由多种原因引起的老年性骨病。通常由于骨量下降、骨的细微结构发生改变,导致骨脆性增加,易发生骨折,好发于胸、腰椎椎体、桡骨远端及股骨上端等。骨质疏松可发生在任何年龄和任何性别,但通常多发生于绝经后妇女和老年男性。 RANKL/OPG：骨重建需要骨形成和骨吸收之间的精确平衡,RANKL/OPG在骨重建中起着至关重要的作用。RANKL是一种细胞因子,可诱导祖细胞分化为成熟的破骨细胞。OPG通过与RANKL结合而成为诱骗受体。因此,RANKL/OPG的比例是维持骨形成和骨吸收之间平衡的关键。 背景：脂肪间充质干细胞分泌各种骨重塑需要的细胞因子和生长因子,被认为是骨再生的优良候选细胞。骨形态发生蛋白2与脂肪间充质干细胞对骨再生有协同作用,并能显著增强脂肪间充质干细胞的成骨分化作用。 目的：探讨脂肪间充质干细胞成骨分化条件培养基与骨形态发生蛋白2联合应用对大鼠绝经后骨质疏松症的影响。 方法：8-10月龄雌性SD大鼠75只,随机取60只采用卵巢切除方法建立绝经后骨质疏松症大鼠模型,余15只进行假手术,未切除卵巢。将60只造模成功大鼠随机分为4组：骨质疏松症组、条件培养基组、骨形态发生蛋白2组、联合治疗组,通过尾静脉分别注射DMEM培养基、脂肪间充质干细胞成骨分化条件培养基、骨形态发生蛋白2、脂肪间充质干细胞成骨分化条件培养基联合骨形态发生蛋白2。治疗12周,取各组大鼠股骨和血清,组织学观察骨小梁数量和结构以及骨小梁间距,ELISA检测血清P1NP、ALP、TRAP、OPG、RANKL水平,Western blot、Realtime PCR检测RANKL、OPG蛋白和mRNA水平,细胞因子芯片分析脂肪间充质干细胞成骨分化条件培养基中细胞因子水平。 结果与结论：①与假手术组相比,骨质疏松症组大鼠的骨小梁间距扩大,骨小梁数量明显减少,骨小梁失去正常结构并且不连续。与骨质疏松症组、条件培养基组、骨形态发生蛋白2组比较,联合治疗组大鼠骨小梁间距扩大较少,骨小梁结构更完整、更连续;②与骨质疏松症组、条件培养基组、骨形态发生蛋白2组比较,联合治疗组大鼠血清P1NP和ALP水平显著升高(P < 0.05),血清TRAP水平显著降低(P < 0.05);③与骨质疏松症组、条件培养基组、骨形态发生蛋白2组比较,联合治疗组RANKL/OPG比值显著降低(P < 0.01),从而促进更多的骨形成;④脂肪间充质干细胞成骨分化条件培养基含有多种与骨形成密不可分的细胞因子,包括骨形态发生蛋白4和7、白血病抑制因子、脑源性神经营养因子、骨保护素、胰岛素样生长因子1等;⑤结果表明,脂肪间充质干细胞成骨分化条件培养基与骨形态发生蛋白2联合应用可减轻卵巢切除大鼠骨质疏松,可能成为治疗绝经后骨质疏松症的新方案。 ORCID: 0000-0003-0552-4818(杨九杰) 中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程