柚皮苷对破骨细胞凋亡的影响

[目的]探讨不同浓度柚皮苷单体对破骨细胞的凋亡的影响及相关机制。[方法]采用100 ng/ml浓度RANKL诱导小鼠单核细胞RAW264.7细胞株获取破骨细胞,之后采用含有不同浓度柚皮苷培养基对破骨细胞进行干预3 d。行TRAP染色,扫描电镜观察骨薄片上骨吸收,流式细胞仪检测破骨细胞凋亡,荧光定量PCR检测破骨细胞凋亡基因BCL-2、BAX、 Caspase-3及MMP-9表达的影响。[结果]与空白对照组比较,各浓度组柚皮苷均可以有效的减少RANKL诱导破骨细胞的数量(P0.05),减少薄骨片的吸收面积(P0.05),且呈剂量依赖。流式细胞仪检测显示各浓度柚皮苷组可增加破骨细胞的凋亡率(P0.05)。与空白对照相比,各柚皮苷组BCL-2和MMP-9的mRNA相对表达量降低(P0.05),而BAX和Caspase-3的mRNA相对表达量升高(P0.05),呈剂量依赖。[结论]柚皮苷可降低破骨细胞数量和骨吸收能力,这可能与下调BCL-2和MMP-9,上调BAX的caspase-3,增加破骨细胞凋亡有关。     

CTGF对破骨前体细胞RAW264.7增殖及碳酸酐酶Ⅱ分化的影响

目的研究结缔组织生长因子(CTGF)对体外培养的破骨细胞前体细胞RAW264.7增殖及对核因子Kappa B配体受体(RANKL)诱导体外培养的破骨细胞前体细胞RAW264.7分化为成熟多核破骨细胞的影响。方法使用200 ng/mLCTGF干预培养的破骨细胞前体细胞RAW264.7,采用3H-TdR掺入法检测RAW264.7细胞增殖率;使用200 ng/mL CTGF与RANKL单独或共同处理RAW264.7细胞,抗酒石酸酸性磷酸酶(TRAP)染色观察TRAP阳性多核细胞,Western blot检测碳酐酶Ⅱ蛋白的表达。结果 CTGF可显著促进RAW264.7细胞增殖;200 ng/mLCTGF与RANKL共同处理RAW264.7细胞可促进RAW264.7细胞分化为成熟多核破骨细胞;200 ng/mL CTGF与RANKL共同处理RAW264.7细胞可促进RAW264.7细胞碳酐酶Ⅱ蛋白的表达。结论 CTGF促进体外培养的破骨细胞前体细胞RAW264.7增殖,促进RANKL诱导的破骨细胞前体细胞RAW264.7分化为成熟多核破骨细胞。     

诱导小鼠破骨前体细胞成熟分化的实验条件探讨

目的探讨小鼠单核细胞RAW264.7能否在RANKL诱导下向破骨细胞成熟分化。方法 RANKL作用RAW264.7细胞7天～9天,光镜、透射电镜、扫描电镜(scanning electron microscope,SEM)分别观察其细胞形态学变化,用抗酒石酸酸性磷酸酶(tartrate-resistant acid phosphatase,TRAP)染色法观察TRAP阳性的多核细胞,RT-PCR检测破骨细胞表型和功能基因表达变化情况,扫描电镜观察破骨细胞在骨片上形成骨吸收陷窝。结果光镜、透射电镜下可见细胞胞体增大,为椭圆形或不规则形,胞核5～10个,扫描电镜下可见细胞表面大量的伪足样突起;此外,RANKL能诱导RAW264.7细胞分化为TRAP染色阳性的多核破骨细胞,细胞多为超过5个核的多核巨细胞;RAW264.7细胞成熟分化后具有骨吸收功能,并且能上调Cathepsin-K、TRAP、RANK等典型破骨细胞表型和功能基因mRNA的表达。结论 RAW264.7细胞是一种较好的破骨前体细胞模型,单用50ng/ml的RANKL体外连续诱导7天以上,能明显促进它向成熟的破骨细胞分化。     

高糖及TNF-α对RAW264.7细胞向破骨细胞分化的影响

【摘要】 目的 观察高糖及TNF-α的培养条件对RAW264.7细胞向破骨细胞诱导分化的影响。方法 在正常、高糖(30 mmol/L)及TNF-α(10 μmol/L)条件下培养RAW264.7细胞后,加入浓度为100 ng/mL的细胞核转录因子κB受体激活物的配体(receptor activator of NF-κB ligand, RANKL)为诱导剂,诱导RAW264.7向破骨细胞分化;诱导9天后,抗酒石酸酸性磷酸酶(TRAP)染色,比较各组TRAP+细胞数,RT-PCR及Western Blot检测各组破骨细胞标志基因CTR和MMP-9的表达。结果 不同的培养条件下RANKL均能诱导RAW264.7分化为成熟的破骨细胞,其中TNF-α环境中RAW264.7形成的TRAP+阳性细胞数、CTR和MMP-9的表达最高,而在高糖环境下最低。结论 TNF-α可以促进RAW264.7向破骨细胞分化,而高糖对这个过程可能是抑制作用,这一现象符合Ⅰ型和Ⅱ糖尿病患者骨质破坏的表现;高糖及TNF-α的培养条件下RANKL对RAW264.7的作用可模拟糖尿病足病变微环境中OC的诱导分化的过程。     

RANKL诱导小鼠单核细胞RAW264.7分化成成熟破骨细胞

目的观察小鼠的单核／巨噬细胞RAW264．7的一般生物学特征及在RANKL诱导下形成成熟破骨细胞的特征。方法RANKI，诱导RAW264．7细胞6d后，用抗酒石酸酸性磷酸酶(TRAP)染色法观察TRAP阳性多核细胞，吖啶橙染色激光共聚焦显微镜(LCSM)观察多核细胞形态；诱导RAW264．7细胞9d后，RT、PCR检测RAW264．7细胞的破骨细胞表型和功能基因表达及其RANKL诱导后变化；诱导RAW264．7细胞12d后，钙磷覆盖的破骨细胞活性分析板观察破骨细胞的骨吸收功能。结果RAW264．7细胞TRAP染色阴性，单核或2个核，能表达破骨细胞表型和功能基因，无骨吸收功能。RANKL可诱导RAW264．7细胞形成TRAP阳性成熟的多核破骨细胞，上调CathepsinK、CAⅡ、integrinβ3等基因mRNA的表达。结论RAW264．7具有破骨细胞特征性基因表达谱，是一种较好的破骨前体细胞模型。RANKL可诱导RAW264．7细胞形成成熟破骨细胞。     

槲皮苷抑制RANKL诱导的破骨细胞形成及骨吸收

[目的]探讨槲皮苷对核因子κB受体激动剂配体(receptor activator of nuclear factor kappa B ligand,RANKL)诱导的破骨细胞形成及骨吸收功能的影响。[方法]通过CCK-8法观察不同浓度槲皮苷(0~800μmol/L)干预不同时间(48 h、96 h)对RAW 264.7细胞的生存影响,确定合适的体外用药浓度;利用体外RANKL诱导RAW 264.7细胞形成破骨细胞体系,通过抗酒石酸酸性磷酸酶(tartrate resistant acid phosphatase,TRAP)染色计数评价槲皮苷(200、400μmol/L)对破骨细胞形成和生存的影响;通过骨片吸收实验对骨凹陷和骨吸收面积统计分析评价槲皮苷(200、400μmol/L)3 d内对成熟破骨细胞骨吸收功能的影响;釆用实时定量(Real-Time)PCR技术,检测槲皮苷(200、400μmol/L)对RANKL诱导的破骨细胞特异性基因NFATc1、TRAP和c-fos表达水平的影响。[结果]细胞生存实验发现槲皮苷干预96 h后,槲皮苷(0~800μmol/L)对RAW 264.7细胞4 d内生存未发现显著影响;通过TRAP染色发现200、400μmol/L槲皮苷能显著抑制体外RANKL诱导的破骨细胞形成;通过骨片吸收实验发现200、400μmol/L槲皮苷3d内能显著降低骨吸收面积,提示其抑制成熟破骨细胞骨吸收功能;同时,槲皮苷能呈剂量依赖性抑制RANKL诱导活化T细胞核因子(nuclear factor of activated T cells,NFAT)c1、TRAP和c-fos基因表达。[结论]槲皮苷通过抑制NFATc1,TRAP和c-fos的表达,来抑制体外RANKL诱导的破骨细胞形成和骨吸收功能,是一种潜在治疗骨质疏松药物。     

IL-6对RAW264. 7细胞成熟分化的体外实验研究

目的探讨研究白介素-6(Interleukin-6,IL-6)对核因子NF-κB受体活化因子配体(Receptor activator of nuclear kappa B ligand,RANKL)及对破骨前体细胞的成熟分化和溶骨效应。方法破骨前体细胞RAW264.7细胞经50ng/mL RANKL诱导1 d后将其分为:1、空白对照组(RANKL+PBS)2、低浓度IL-6组(RANKL+50ng/mL IL-6)3、中浓度IL-6组(RANKL+100ng/mL IL-6)4、高浓度IL-6组(RANKL+150ng/mL IL-6)。连续培养9 d后,进行HE染色检测成熟破骨细胞生成量;通过抗酒石酸酸性磷酸酶(Tartrate resistant acid phosphatase, TRAP)染色法观察TRAP阳性多核细胞的情况;运用扫描电镜检测破骨细胞在骨片上的骨吸收陷窝形成情况。结果 HE染色中,成熟破骨细胞生成量中、高浓度IL-6组明显少于低浓度IL-6组(P0.05),低浓度IL-6组和空白对照组间无明显差别(P0.05)。②通过TRAP染色后,经染色阳性区域面积与视野面积的百分比计算,中、高浓度IL-6组与明显少于低浓度和空白对照组(P0.05)。③扫描电镜观察发现骨吸收陷窝面积与视野面积的百分比随着IL-6浓度的增高,相比空白对照组有显著减少,且高浓度IL-6组中陷窝形成最少(P0.05)。结论 IL-6能直接作用于经RANKL诱导的RAW264.7细胞,能明显抑制破骨细胞激活分化,并降低破骨细胞所致的骨吸收效应。当IL-6浓度超过50ng/mL时,其抑制破骨细胞的骨吸收效应更加明显。     

不同浓度金属磨损颗粒对破骨细胞体外分化的影响

[目的]观察不同浓度金属磨损颗粒对RAW 264.7在体外分化成破骨细胞的影响,明确浓度与破骨细胞分化数量的关系.[方法]真空球磨法制备人工关节磨损颗粒:RANKL诱导RAW 264.7体外分化成破骨细胞,通过TRAP染色,电镜扫描检测骨片吸收陷窝来鉴定破骨细胞;不同浓度人工关节磨损颗粒混悬液作用RAW 264.7,并用RANKL诱导后第7 d,TRAP染色后,光镜下计数破骨细胞数量.[结果]不同浓度磨损颗粒作用于RAW 264.7 7 d后,显微镜下计数破骨细胞数量,结果显示随着磨损颗粒混悬液浓度增加,RANKL诱导生成的破骨细胞增多,低、中、高浓度3组破骨细胞数均显著高于空白对照组(P<0.05),中、高浓度组破骨细胞数均显著高于低浓组(P<0.05),高浓度组破骨细胞数亦显著高于中浓组(P<0.05).[结论](1)RAW 264.7是一种较好的破骨前体细胞模型,RAW 264.7诱导形成破骨细胞的方法简便易行,所获得破骨细胞均一性好;(2)人工关节金属磨损颗粒为RAW264.7细胞向具有骨质吸收功能的破骨细胞转化发挥正向作用,而且与混悬液的浓度有量效关系.     

骨保护素体外抑制小鼠单核巨噬细胞 成熟分化的实验研究

目的研究骨保护素（Osteoprotegerin, 0PG)抑制核因子NF-KB受体活化因子配体（Receptor activator of nuclear kappa B ligand,RANKL)诱导小鼠单核细胞RAW264. 7成熟分化而导致的溶骨效 应。方法50 ng/mL RANKL诱导RAW264. 7细胞1 d后,加人100 ng/mL 0PG(实验组,即0PG + RANKL组）或不加人0PG(对照组,即RANKL组）分别培养7 d和9 d,经细胞形态学观察其变化,抗 酒石酸酸性碟酸酶（Tartrate resistant acid phosphatase, TRAP)染色法观察TRAP阳性多核细胞,扫描 电镜下观察在骨片上的破骨细胞所致的骨吸收陷窝形成情况。结果对照组培养7 d时,在倒置相 差显微镜、透射电镜、光镜下可见细胞形状为椭圆形或不规则形,胞体明显较KAW264.7细胞增大, 胞核多为6 ~ 10个,扫描电镜下还可见大量伪足形成,而实验组培养7 d后,细胞形状多为圆形,且扫 描电镜下未见明显伪足形成;对照组9 d时可见大量TRAP染色阳性的多核巨细胞（含3个或3个以 上的细胞核）,而实验组中TRAP染色阳性的多核破骨细胞偶见多核巨细胞,培养9 d时很难找到多 核巨细胞;仅用RANKL诱导RAW264.7细胞分化7 d时,对照组中破骨细胞表面可见大量伪足伸出, 并形成明显的骨吸收陷窝,实验组中破骨细胞见少许伪足突出,不能看到明显的骨陷窝形成。结论 单用50 ng/mL RANKL体外连续诱导RAWM4.7细胞7 d时,可以促进成熟的破骨细胞显著分化。 100 ng/mL 0PG培养9 d能有效地抑制破骨细胞的分化,减少破骨细胞的骨吸收效应。     

复合振动抑制RAW264.7细胞分化成熟

目的研究复合振动对核因子-κB受体活化因子配体(RANKL)诱导的RAW264.7细胞分化的影响,探讨复合振动对破骨细胞分化的影响及机制。方法 RAW264.7细胞RANKL诱导培养3或4d并施加复合振动干预,通过抗酒石酸酸性磷酸酶(TRAP)染色观察TRAP阳性多核细胞形成的变化,real-time RT-PCR分析破骨细胞特异性基因组织蛋白酶K(cathepsin K),金属蛋白酶-9(MMP-9)和TRAP表达的变化。结果复合振动能抑制RANKL诱导破骨细胞形成,下调破骨细胞特异基因cathepsin K,MMP-9和TRAP的表达。结论 RANKL促进RAW264.7细胞向破骨细胞分化,并增加特异基因的表达,但RANKL的促进作用受复合振动抑制。这进一步的阐释复合振动抗骨质疏松的作用机制。     

BSP and RANKL induce osteoclastogenesis and bone resorption synergistically.

RANKL and BSP are upregulated in several bone resorptive disorders. However, the mechanisms by which these two factors might induce osteoclastogenesis and bone resorption synergistically under pathological conditions remain largely unknown. INTRODUCTION: RANKL and bone sialoprotein II (BSP) have been shown to be upregulated in the serum of individuals with abnormally high osteoclastogenic and bone resorptive activities. Here we provide experimental evidence that RANKL and BSP induce osteoclastogenesis and bone resorption synergistically but mediate opposite effects in osteoclast survival and apoptosis. MATERIALS AND METHODS: RAW264.7 cells and mouse bone marrow-derived monocytes/macrophages were treated with human recombinant BSP in the presence and absence of RANKL. TRACP stainings, bone resorption assays, Western blotting, immunoprecipitation analyses, and semiquantitative RT-PCR were used to evaluate the effects of BSP in osteoclast differentiation and bone resorption. Survival, DNA condensation, and caspase activity assays were used to determine the putative effects of BSP in osteoclast survival and apoptosis. RESULTS AND CONCLUSIONS: RANKL induced osteoclast differentiation and bone resorption at a higher extent in the presence than in the absence of BSP in RAW264.7 cells and bone marrow-derived monocytes/macrophages. c-Src-dependent c-Cbl phosphorylation was 8-fold higher in RAW264.7 cells treated with BSP and RANKL than in those treated with RANKL alone. Furthermore, BSP and RANKL activated the master regulator of osteoclastogenesis nuclear factor of activated T cells (NFAT)-2 and increased the mRNA expression of other differentiation markers such as cathepsin K or TRACP. Inhibition of c-Src activity or chelating intracellular calcium inhibited the synergistic effects in bone resorption and the phosphorylation of the c-Src substrate c-Cbl. Inhibition of calcineurin or intracellular calcium elevation inhibited the synergistic effects in osteoclastogenesis and decreased NFAT-2 nuclear levels. On the other hand, BSP and RANKL mediated opposite effects in osteoclast survival and apoptosis. Thus, BSP increased survival and decreased apoptosis markers in differentiated RANKL-treated RAW267.5 cells and RANKL/macrophage-colony stimulating factor (M-CSF)-treated bone marrow-derived monocytes/macrophages. In addition, RAW267.5 cells treated with BSP and RANKL exhibited decreased activation of the proapoptotic Jun N-terminal kinase pathway and increased activation of anti-apoptotic AKT pathway than cells treated with RANKL or BSP alone. Taken together, our findings suggest that BSP contributes to RANKL-mediated bone resorption by inducing osteoclastogenesis and osteoclast survival and decreasing osteoclast apoptosis.     

破骨细胞微管正端蛋白动态成像观察

目的 采用活细胞成像技术观察破骨细胞微管正端蛋白EB1在细胞内的分布及运动,初步研究微管在破骨细胞功能中的作用。方法 ①用脂质体转染方法（阳离子脂质体Lip2000）转染EB1-GFP基因至Raw264.7细胞系,G418筛选转染成功的Raw264.7细胞,荧光显微镜下观察后GFP蛋白免疫荧光染色确定稳定转染EB1-GFP的Raw264.7细胞系建立;②活细胞工作站下观察转染EB1-GFP的Raw264.7细胞中EB1蛋白的运动; ③用含100ng/mLRANKL和30ng/mL M-CSF的培养基分别诱导稳定转染EB1-GFP的Raw264.7细胞与正常Raw264.7细胞为破骨细胞,进行TRAP染色鉴定,比较两组细胞形态有无差别;④Raw264.7细胞系诱导出破骨细胞后,用细胞免疫荧光染色方法观察破骨细胞EB1蛋白的形态及分布;⑤活细胞工作站下观察稳转EB1-GFP的Raw264.7细胞诱导出的破骨细胞内EB1蛋白的运动状态。结果 ①脂质体转染方法建立了稳定转染EB1-GFP基因的Raw264.7细胞系;②观察到破骨前体细胞Raw264.7的微管正端蛋白（EB1）的运动轨迹;③转染EB1-GFP基因的Raw264.7细胞与正常Raw264.7细胞诱导的破骨细胞TRAP染色无明显差别;④活细胞工作站观察破骨细胞微管正端蛋白EB1的运动状态,结果表明破骨细胞微管活动性较破骨前体细胞Raw264.7活动性低。结论 ①EB1-GFP基因对破骨前体细胞系Raw264.7诱导破骨细胞无明显影响;②微管活动性降低可能与破骨细胞骨吸收活性相关。     

Bergapten prevents lipopolysaccharide mediated osteoclast formation,bone resorption and osteoclast survival

Purpose

This study was designed to investigate the potential effect of bergapten on lipopolysaccharide (LPS)-mediated osteoclast formation, bone resorption and osteoclast survival in vitro.

Methods

After osteoclast precursor RAW264.7 cells were treated with bergapten (5, 20, 40 μmol/L) for 72 hours in the presence of LPS (100 ng/ml), osteoclastogenesis was identified by tartrate-resistant acid phosphatase (TRAP) staining, and the number of TRAP-positive multinucleated cells [TRAP(+)MNCs] per well were counted. To investigate the effect of bergapten on osteoclastic bone resorption, RAW264.7 cells were treated with bergapten for six days in the presence of LPS, and the area of bone resorption was analyzed with Image Pro-Plus. Next, we examined apoptosis of RAW264.7 cells after bergapten incubation for 48 hours by flow cytometer using annexin V/propidium iodide (PI) double labeling. Finally, osteoclast survival was observed by Hoechst 33342 labeling and Western blotting after bergapten treatment for 24 hours.

Results

Data showed that bergapten (5–40 μmol/L) dose-dependently inhibited LPS-induced osteoclast formation and bone resorption. Treatment with bergapten triggered apoptotic death of osteoclast precursor RAW264.7 cells in a dose-dependent manner. Furthermore, bergapten significantly reduced the survival of mature osteoclast, as demonstrated by emergence of apoptotic nuclei and activation of apoptotic protein caspase 3/9.

Conclusions

These findings suggest that bergapten effectively prevents LPS-induced osteoclastogenesis, bone resorption and survival via apoptotic response of osteoclasts and their precursors. The study identifies bergapten as an inhibitor of osteoclast formation and bone resorption and provides evidence that bergapten might be beneficial as an alternative for prevention and treatment of inflammatory bone loss.     

中药复方鹿角胶丸通过PI3-K/AKT信号通路调节破骨细胞凋亡

目的探索中药复方鹿角胶丸促进破骨细胞凋亡机制的实验研究。方法 RAW264.7细胞培养并传代,RANKL+MCSF诱导RAW264.7细胞向破骨细胞分化;MTS检测不同浓度的鹿角胶丸对破骨细胞增殖活性影响;倒置相差显微镜观察鹿角胶丸对破骨细胞形态学的影响;流式细胞仪检测鹿角胶丸及加入PI3K/AKT通路抑制剂LY294002后对破骨细胞凋亡的影响;Western blot检测Bax、Bcl-2、Caspase-3,Cleaved-Caspase-3、p-AKT、T-AKT的蛋白表达情况,以及检测加入LY294002后对凋亡通路蛋白的影响。结果 MTS显示各个浓度的鹿角胶丸(LJJW高、中、低)均能抑制破骨细胞的增殖活性,其中以LJJW(中浓度)作用24 h后具有明显的增殖活性抑制作用。加入鹿角胶丸后,破骨细胞透光度下降,凋亡的细胞皱缩,漂浮于培养基中。流式细胞仪检测结果显示鹿角胶丸促进破骨细胞凋亡,预处理LY294002后,鹿角胶丸的促破骨细胞凋亡作用受到抑制。免疫印迹结果显示,鹿角胶丸促进线粒体Bax表达,抑制Bcl-2的表达,同时促进Caspase-3的裂解。鹿角胶丸促进AKT磷酸化,加入LY294002后AKT的磷酸化受到抑制,预处理LY294002后鹿角胶丸的促AKT磷酸化作用被抑制。结论中药复方鹿角胶丸通过PI3K/AKT通路促进破骨细胞凋亡。     

Effect of osteoprotegerin in combination with interleukin-6 on inhibition of osteoclast differentiation

Objective： To observe the effect of recombinant interleukin-6 （IL-6） and osteoprotegerin （OPG） on inhibiting bone absorption induced by receptor activa- tor for nuclear factor- rB ligand （RANKL） in murine osteo- clast precursor cells （OCPs） model. Methods： RAW 264.7 cells were solely treated with 50 ng/ml RANKL for 1 day, and then they were divided into three groups： RANKL （control group）, RANKL＋IL-6 （IL-6 group） and RANKL＋IL-6＋OPG （combination group）. These cells were harvested and investigated by means of HE stain- ing under light microscope after consecutive 9 days. Furthermore, staining tartrate-resistant acid phosphatase （TRAP）-positive multinucleated cells were detected by in- verted phase contrast microscope. The absorption pits of bone slices were observed under scanning electron microscope. Results： The number of mature osteoclast cells in control group was more than that in IL-6 alone or IL-6 com- bined with OPG group （P〈0.05）. Interestingly, this experi- ment has also demonstrated that there was a large number of TRAP-positive multinucleated osteoclasts （more than 3 nuclei） and several bone absorption formation in the con- trol group, whereas the outcome was completely different in both IL-6 group and IL-6＋OPG group （P〈0.05）. Conclusion： IL-6 can suppress the differentiation of mature osteoclasts as directly adding it into the RAW 264.7 cells induced by 50 ng/ml RANKL, and further the effect of osteolysis is remarkably reduced. When treatment with IL- 6 combined with OPG, a more effective strategy for the treat- ment of osteoporosis is reached.     

RANKL regulates Fas expression and Fas-mediated apoptosis in osteoclasts.

Osteoclast apoptosis is an influential determinant of osteoclast bone-resorbing activity. RANKL, a critical factor for osteoclastogenesis, is also important in osteoclast survival. However, the mechanisms by which RANKL prevents osteoclast apoptosis remain largely unknown. INTRODUCTION: Fas, a death receptor, mediates apoptosis in multiple types of cells including osteoclasts. Here we report that RANKL acts as a survival factor in osteoclasts by downregulating Fas-mediated apoptosis and Fas expression in mature osteoclasts. MATERIALS AND METHODS: RAW264.7 and mouse bone marrow macrophage/monocyte progenitors and progenitor-derived osteoclasts, in the presence of various concentrations of RANKL, were used in this study. Western blotting, semiquantitative RT-PCR, flow cytometry, nuclear staining, and a fluorescent caspase-3 activity assay were used to assess the effect of RANKL on Fas expression and Fas-mediated apoptosis. The involvement of NF-kappaB in the regulation of Fas by RANKL was analyzed by luciferase assay and EMSA. RESULTS: Mature osteoclasts generated in the presence of a high concentration of RANKL (3.33 nM) failed to respond to Fas-induced apoptosis. The lack of responsiveness in mature osteoclasts is caused by the low level of Fas expression, as detected by both semiquantitative PCR and Western blotting. Fas protein and mRNA expression are inhibited by RANKL in concentration-dependent manners. The downregulation of Fas expression by RANKL is not because of modulation of the stability of Fas protein or mRNA. The regulation of Fas expression by RANKL is biphasic. During the early stage of osteoclastogenesis (1 day) when Fas is expressed at a very low level, RANKL upregulates Fas promoter activity by 2.4 +/- 0.1-fold in a concentration-dependent manner and increases Fas mRNA and protein. This event correlates with regulation of the binding activity of NF-kappaB to the Fas promoter by RANKL, as detected by EMSA. In osteoclast precursors, the induction of Fas promoter activity by RANKL was dramatically reduced when NF-kappaB binding sites on the Fas promoter were mutated. CONCLUSION: RANKL upregulates Fas expression in osteoclast progenitors through NF-kappaB, making osteoclasts targets of Fas-stimulated apoptosis. In differentiated mature osteoclasts, RANKL reduces the levels of Fas expression and Fas-mediated apoptosis, acting as a survival factor.     

Oscillatory fluid flow-induced shear stress decreases osteoclastogenesis through RANKL and OPG signaling

Physical activity creates deformation in bone that leads to localized pressure gradients that drive interstitial fluid flow. Due to the cyclic nature of the applied load, this flow is oscillatory by nature. Oscillatory fluid flow (OFF) may lead to positive bone remodeling through effects on both osteoblasts and osteoclasts but its effect on osteoclastogenesis is poorly understood. In this study, the effects of OFF on expression of receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG), two important regulators of osteoclast differentiation, were investigated. In addition, its effect on osteoclast formation was quantified. ST-2 murine bone marrow stromal cells were plated on glass slides and cultured with 1,25-dihydroxyvitamin D(3) to express RANKL. Cells were exposed to various durations of OFF resulting in a peak shear stress of 1 Pa. Time course and dose-response studies were performed and real-time RT-PCR was used to quantify levels of RANKL, OPG mRNA. ST-2 cells exposed to OFF were also co-cultured with RAW 264.7 monocytes and osteoclast number quantified. Decrease in RANKL/OPG was maximal immediately after end of flow and there existed a significant increase in OPG and decrease in RANKL with increasing load duration of up to 2 h. OFF resulted in a decrease in osteoclast formation by ST-2 cells co-cultured with RAW 264.7 cells compared to co-culture of control (non-loaded) ST-2 cells with RAW 264.7 cells. These results suggest that indeed OFF is a potent regulator of bone remodeling, and that shift towards positive bone remodeling mediated by loading-induced fluid flow may occur via suppression of the formation of osteoclasts.     

Prostate-specific antigen induces apoptosis of osteoclast precursors: potential role in osteoblastic bone metastases of prostate cancer

BACKGROUND: Prostate cancer is frequently associated with bone metastases with marked osteoblastic changes and low osteoclastic activity but its mechanism is not well understood. We previously reported that prostate-specific antigen (PSA) stimulated the proliferation and the activation of osteoblasts. In this study, we investigated the effect of PSA on osteoclastogenesis. METHODS: Two human prostate cancer cell lines and PSA were directly injected into human adult bone (HAB) implanted into NOD/SCID mice, followed by morphological analysis. RAW 264.7 cells, murine osteoclast precursor, were treated with PSA. RESULTS: PSA-producing LNCaP and PSA caused a significant decrease of osteoclast precursors and osteoclasts in HAB accompanied by osteoblast proliferation and new bone formation, while PSA-nonproducing PC3 showed increasing osteoclasts with osteolysis. PSA induced apoptosis of RAW 264.7 cells in vitro. PSA-induced apoptosis was dependent of enzymatic activity of PSA and was specific to immature tartrate-resistant acid phosphatase-negative mononuclear RAW 264.7 cells. CONCLUSIONS: PSA plays a crucial role for osteoblastic bone metastasis by promoting both osteoblasts proliferation and apoptosis of osteoclast precursors.