Differentiation of human marrow stromal precursor cells: bone morphogenetic protein-2 increases OSF2/CBFA1, enhances osteoblast commitment, and inhibits late adipocyte maturation.

Because regulation of the differentiation to osteoblasts and adipocytes from a common progenitor in bone marrow stroma is poorly understood, we assessed effects of bone morphogenetic protein-2 (BMP-2) on a conditionally immortalized human marrow stromal cell line, hMS(2-6), which is capable of differentiation to either lineage. BMP-2 did not affect hMS(2-6) cell proliferation but enhanced osteoblast differentiation as assessed by a 1.8-fold increase in expression of OSF2/CBFA1 (a gene involved in commitment to the osteoblast pathway), by increased mRNA expression and protein secretion for alkaline phosphatase (ALP), type I procollagen and osteocalcin (OC) (except for OC protein), and by increased mineralized nodule formation. Transient transfection with Osf2/Cbfa1 antisense oligonucleotide substantially reduced BMP-2-stimulated expression of ALP mRNA and protein. The effects of BMP-2 on adipocyte differentiation varied: expression of peroxisome proliferator-activated receptor gamma2 (a gene involved in commitment to the adipocyte pathway) was unchanged, mRNA expression of the early differentiation marker, lipoprotein lipase, was increased, and mRNA and protein levels of the late differentiation marker, leptin, and the formation of cytoplasmic lipid droplets were decreased. Thus, by enhancing osteoblast commitment and by inhibiting late adipocyte maturation, BMP-2 acts to shunt uncommitted marrow stromal precursor cells from the adipocyte to the osteoblast differentiation pathway.     

THSD4基因在小鼠间充质干细胞及MC3T3-E1细胞成骨分化中的作用

目的 探讨THSD4基因对小鼠间充质干细胞和MC3T3-E1细胞成骨分化的影响。方法 提取绝经后骨质疏松症患者的骨髓间充质干细胞进行基因测序分析,与骨关节炎患者的骨髓间充质干细胞进行比较,分析基因表达差异。通过提取不同分化阶段的小鼠骨髓间充质干细胞（M-BMSC）及MC3T3-E1细胞的mRNA来检测THSD4 基因以及成骨分化的标志性基因（ALP、Runx2、Osx）的表达水平。通过构建慢病毒表达载体来实现对M-BMSC及MC3T3-E1细胞中THSD4的敲减及过表达,并观察其对M-BMSC及MC3T3-E1细胞成骨分化能力的影响。结果 THSD4基因在绝经后骨质疏松症患者骨髓间充质干细胞中明显下调,且通过KEGG以及GO富集分析发现THSD4基因可能与PI3K-AKT信号通路及Wnt信号通路相关。随着成骨诱导分化时间的延长,THSD4 mRNA和成骨分化标志性基因（ALP、Runx2、Osx）mRNA在MC3T3-E1以及M-BMSC中表达量均逐渐增加。过表达THSD4可以增强MC3T3-E1细胞和M-BMSC的成骨分化能力,而敲减THSD4则减弱了MC3T3-E1细胞和M-BMSC的成骨分化能力。结论 THSD4基因在绝经后骨质疏松症患者骨髓间充质干细胞中明显下调,且THSD4基因可以增强MC3T3-E1细胞以及M-BMSC的成骨分化能力。     

Activation of mitogen-activated protein kinase cascades is involved in regulation of bone morphogenetic protein-2-induced osteoblast differentiation in pluripotent C2C12 cells

Bone morphogenetic protein (BMP)-2, a member of the transforming growth factor-beta (TGF-beta) superfamily, is able to induce osteoblastic differentiation of C2C12 cells. Both Smad and mitogen-activated protein kinase (MAPK) pathways are essential components of the TGF-beta superfamily signaling machinery. Although Smads have been demonstrated to participate in the BMP-2-induced osteoblastic differentiation of C2C12 cells, the role of MAPK has not been addressed. This report shows that BMP-2 activates ERK and p38, but not JNK, in C2C12 cells. Pretreatment of cells with the p38 inhibitor, SB203580, dramatically reduced BMP-2-induced expression of the osteoblast markers alkaline phosphatase (ALP) and osteocalcin (OC). Nevertheless, overexpression of MKK3, a protein kinase that phosphorylates and activates p38, failed to induce ALP or OC expression in the absence of BMP-2, indicating that p38 activation is necessary but not sufficient for the acquisition of the osteoblast phenotype by these cells. Although ALP induction was increased slightly in the presence of PD-98059, a selective inhibitor of the ERK cascade, this compound significantly inhibited both steady-state and BMP-2-induced OC RNA levels. Our results indicate that p38 and ERK cascades play a crucial role in the osteoblast differentiation of C2C12 cells mediated by BMP-2.     

BMP-2 controls alkaline phosphatase expression and osteoblast mineralization by a Wnt autocrine loop.

Wnt/beta-catenin signaling has recently been suggested to be involved in bone biology. The precise role of this cascade in osteoblast differentiation was examined. We show that a Wnt autocrine loop mediates the induction of alkaline phosphatase and mineralization by BMP-2 in pre-osteoblastic cells. INTRODUCTION: Loss of function of LRP5 leads to osteoporosis (OPPG syndrome), and a specific point mutation in this same receptor results in high bone mass (HBM). Because LRP5 acts as a coreceptor for Wnt proteins, these findings suggest a crucial role for Wnt signaling in bone biology. MATERIALS AND METHODS: We have investigated the involvement of the Wnt/LRP5 cascade in osteoblast function by using the pluripotent mesenchymal cell lines C3H10T1/2, C2C12, and ST2 and the osteoblast cell line MC3T3-E1. Transfection experiments were carried out with a number of elements of the Wnt/LRP5 pathway. Measuring osteoblast and adipocyte differentiation markers addressed the effect of this cascade on osteoblast differentiation. RESULTS: In mesenchymal cells, only Wnt's capable of stabilizing beta-catenin induced the expression of alkaline phosphatase (ALP). Wnt3a-mediated ALP induction was inhibited by overexpression of either Xddl, dickkopf 1 (dkk1), or LRP5deltaC, indicating that canonical beta-catenin signaling is responsible for this activity. The use of Noggin, a bone morphogenic protein (BMP) inhibitor, or cyclopamine, a Hedgehog inhibitor, revealed that the induction of ALP by Wnt is independent of these morphogenetic proteins and does not require de novo protein synthesis. In contrast, blocking Wnt/LRP5 signaling or protein synthesis inhibited the ability of both BMP-2 and Shh to induce ALP in mesenchymal cells. Moreover, BMP-2 enhanced Wntl and Wnt3a expression in our cells. In MC3T3-E1 cells, where endogenous ALP levels are maximal, antagonizing the Wnt/LRP5 pathway led to a decrease of ALP activity. In addition, overexpression of dkkl reduced extracellular matrix mineralization in a BMP-2-dependent assay. CONCLUSIONS: Our data strongly suggest that the capacity of BMP-2 and Shh to induce ALP relies on Wnt expression and the Wnt/LRP5 signaling cascade. Moreover the effects of BMP-2 on extracellular matrix mineralization by osteoblasts are mediated, at least in part, by the induction of a Wnt autocrine/paracrine loop. These results may help to explain the phenotype of OPPG patients and HBM.     

黄芩素通过BMP-2/Smad通路促进MC3T3-E1成骨作用的实验研究

目的 探讨黄芩素（BAI）对小鼠胚胎成骨细胞前体细胞（MC3T3-E1）成骨分化的作用及其分子机制。方法 将MC3T3-E1分为对照组（正常培养）和BAI组（以Baicalein处理）,在成骨分化条件培养下采用CCK-8检测BAI对MC3T3-E1细胞增殖的影响;分别以碱性磷酸酶染色（ALP）、茜素红染色（ARS）检测MC3T3-E1细胞成骨分化水平与矿化能力,实时荧光定量PCR检测成骨标志基因ALP、COL1A1、RUNX2、OSX的mRNA表达水平,通过免疫印迹法（Western-blot）检测MC3T3-E1细胞中BMP-2、Smad1、p-Smad1蛋白表达水平,通过免疫荧光技术（IF）检测RUNX2、COL1A1表达水平。结果 与对照组比较,BAI干预1 d后发现,BAI组COL1A1（P<0.001）、RUNX2（P <0.05）、OSX（P <0.05） mRNA表达水平在成骨分化中表达上升;干预3 d后发现,与对照组比较,BAI组ALP（P <0.05）、RUNX2（P <0.001）mRNA表达上升;干预7 d后发现,与对照组比较,BAI组COL1A1（P <0.05）mRNA表达水平较对照组上升,BMP-2、p-Smad1/Smad1蛋白表达水平上升（P <0.05）。免疫荧光中成骨标志蛋白RUNX2、COL1A1表达增多（P <0.05）。结论 BAI可通过激活BMP-2/Smad通路促进MC3T3-E1成骨分化。     

Down-Regulation of Osteoblastic Cell Differentiation by Epidermal Growth Factor Receptor

The role of epidermal growth factor receptors (EGF-R) in osteogenic cell differentiation was investigated using preosteoblastic MC3T3-E1 (MC3T3) cells and osteoblast-like ROS 17/2.8 (ROS) cells. When cultured in the presence of β-glycerophosphate (GP) and ascorbic acid (AA), MC3T3 cells underwent spontaneous differentiation into osteoblasts which was confirmed as they expressed osteoblast markers such as alkaline phosphatase (ALP), bone sialoprotein (BSP) and osteocalcin (OC). Interestingly, the number of EGF-binding sites decreased during their differentiation into osteoblasts, and the osteogenic protein-1 (OP-1) treatment, which accelerated their differentiation, lowered the number of EGF-binding sites even further. On the other hand, ROS cells with high expression levels of osteoblast markers and no EGF-R, after being transfected with human EGF-R cDNA (EROS cells), expressed numerous EGF-binding sites as well as EGF-R mRNA and protein; in the process, they ceased to express osteoblast markers, indicating their dedifferentiation into osteoprogenitor cells. Both MC3T3 and EROS cells showed increased cell growth in response to EGF, whereas ROS cells did not. These results imply that the EGF/EGF-R system in osteogenic cells has a crucial function in osteoblast phenotype suppression and osteogenic cell proliferation.     

持续性甲状旁腺素抑制成骨细胞分化 的实验研究

目的探讨持续性给与甲状旁腺素(PTH)对成骨细胞分化过程的抑制作用。方法培养MC3T3-E1成骨前体细胞,持续性给与PTH处理,碱性磷酸酶(ALP)染色方法,检测细胞内ALP的分泌;免疫荧光方法检测细胞内Osterix(Osx)蛋白的表达;real-time RT-PCT法和Westernblot方法检测细胞内成骨因子基因和蛋白的表达。结果 MC3T3-E1成骨前体细胞具有自发向成骨细胞方向分化的特征,与对照组相比,经PTH持续性处理的细胞ALP染色强度明显降低,Osx免疫荧光强度较弱,细胞内成骨因子基因和蛋白的表达亦显著低于对照组。结论持续性给与PTH具有抑制成骨细胞分化的作用。     

转染核结合因子a1/成骨细胞特异性转录因子2基因在兔皮肤成纤维细胞成骨表达中的作用

目的探讨外源性小鼠核结合因子a1(Cbfa1)／成骨细胞特异性转录因子2(Osf2)基因在兔皮肤成纤维细胞中的瞬时表达对该细胞成骨表型表达的作用。方法在阳离子脂质体介导下,将含外源性小鼠Cbfa1／Osf2基因的真核表达载体pSG5一Cbfa1／Osf2导入新西兰兔皮肤成纤维细胞。用RT—PCR方法检测Cbfa1、骨钙素、碱性磷酸酶及Ⅰ型胶原前肽基因表达,以Western—Blot方法检测Cbfa1蛋白表达,以对硝基苯二磷酸底物法及放射免疫方法分别检测碱性磷酸酶活性及骨钙素分泌情况,并通过茜素红染色及扫描电子显微镜检测转染细胞形成骨性结节的能力。结果转染pSG5-Cbfa1／Osf2真核表达质粒的兔皮肤成纤维细胞内可见Cbfa1 mRNA及Cbfa1蛋白瞬时表达,骨钙素mRNA、碱性磷酸酶mRNA及Ⅰ型胶原前肽mRNA大量表达,碱性磷酸酶活性增强,骨钙素大量分泌,细胞表面形成骨性结节。结论转染．pSG5-Cbfa1／Osf2真核表达质粒的兔皮肤成纤维细胞能表达成骨相关基因及蛋白质,并在其表面形成骨性结节。     

Fidgetin-like 1 gene inhibited by basic fibroblast growth factor regulates the proliferation and differentiation of osteoblasts.

The FIGNL1 gene was proven to be a new subfamily member of ATPases associated with diverse cellular activities (AAA proteins). In this in vitro study, the AAA proteins inhibited osteoblast proliferation and stimulated osteoblast differentiation. We showed that FIGNL1 may play some regulatory role in osteoblastogenesis. INTRODUCTION: The fidgetin-like 1 (FIGNL1) gene encodes a new subfamily member of ATPases associated with diverse cellular activities (AAA proteins). Although the FIGNL1 protein localizes to both the nucleus and cytoplasm, the function of FIGNL1 remains unknown. In a previous study, we identified several genes that mediate the anabolic effects of basic fibroblast growth factor (bFGF) on bone by using microarray data. FIGNL1 was one of the genes that downregulated >2-fold in MC3T3-E1 cells after treatment with bFGF. Therefore, this study was aimed to identify and confirm the function of FIGNL1 on osteoblastogenesis. MATERIALS AND METHODS: We examined the effect of the FIGNL1 gene on proliferation, differentiation, and apoptosis in mouse osteoblast cells (MC3T3-E1 and mouse primary calvarial cells) using flow cytometry, RT-PCR, cell proliferation assay, and cell death assay. MC3T3-E1 cells and mouse calvarial cells were transfected with small interfering RNA (siRNA) directed against the FIGNL1 or nontargeting control siRNA and examined by cell proliferation and cell death assays. Also, FIGNL1 was fused to enhance green fluorescent protein (EGFP), and the EGFP-fused protein was transiently expressed in MC3T3-E1 cells. RESULTS: Reduced expression of FIGNL1 by bFGF and TGF-beta1 treatment was verified by RT-PCR analysis. Overexpression of FIGNL1 reduced the proliferation of MC3T3-E1 and calvarial cells, more than the mock transfected control cells did. In contrast, siFIGNL1 transfection significantly increased the proliferation of osteoblasts, whereas overexpression of FIGNL1 did not seem to alter apoptosis in osteoblasts. Meanwhile, overexpression of FIGNL1 enhanced the mRNA expression of alkaline phosphatase (ALP) and osteocalcin (OCN) in osteoblasts. In contrast, siFIGNL1 decreased the expression of ALP and OCN. A pEGFP-FIGNL1 transfected into MCT3-E1 cells had an initially ubiquitous distribution and rapidly translocated to the nucleus 1 h after bFGF treatment. CONCLUSIONS: From these results, we proposed that FIGNL1, a subfamily member of the AAA family of proteins, might play some regulatory role in osteoblast proliferation and differentiation. Further analyses of FIGNL1 will be needed to better delineate the mechanisms contributing to the inhibition of proliferation and stimulation of osteoblast differentiation.     

通过p38MAPK信号通路探讨仙灵骨葆胶囊对MC3T3-E1成骨分化的影响

目的 探讨仙灵骨葆胶囊含药血清对小鼠胚胎成骨细胞前体细胞（MC3T3-E1）增殖分化的影响及与p38MAPK信号通路的关系。方法 用仙灵骨葆胶囊含药血清干预MC3T3-E1,CCK8法筛选最佳干预时间及浓度,试剂盒检测各组细胞ALP活性。将细胞分为A、B、C、D 4组,分别加入10%含药血清、10%空白血清、10%含药血清+SB203580、10%空白血清+SB203580,利用免疫印迹法（Western blot）检测p38丝裂原活化蛋白激酶（p38）、磷酸化p38（p-p38）、成骨相关转录因子2（Runx2）、骨形态发生蛋白2（BMP-2）的蛋白表达量,荧光定量PCR检测p38、Runx2和BMP-2 mRNA的表达水平。结果 与空白血清组相比,不同浓度的仙灵骨葆胶囊含药血清均能促进MC3T3-E1的增殖分化,提高ALP的活性,其中10%含药血清干预36 h的作用最为明显（P＜0.05）;与B组比较,A组p38、p-p38、Runx2、BMP-2蛋白及p38、Runx2、BMP-2 mRNA的表达明显增高（P＜0.05）;加入信号通路阻断剂SB203580后,C组与D组上述指标的表达明显降低（P＜0.05）;与C组相比,D组p38、p-p38、Runx2、BMP-2蛋白及p38、Runx2、BMP-2 mRNA表达更低（P＜0.05）。结论 仙灵骨葆胶囊含药血清能促进MC3T3-E1的分化生长,其作用机制可能与激活p38MAPK信号通路、上调成骨相关因子Runx2、BMP-2的表达有关。     

唑来膦酸对小鼠胚胎成骨细胞增殖和分化的影响

目的研究唑来膦酸对小鼠胚胎成骨细胞体外增殖和成骨分化的影响。方法将小鼠胚胎成骨细胞体外传代培养,使用含不同浓度（1.0、0.1μmol/L）唑来膦酸的成骨诱导培养基干预细胞,不含唑来膦酸的培养基作对照,培养1、3、5 d采用CCK-8试剂盒检测唑来膦酸对成骨细胞增殖的影响;培养14 d行碱性磷酸酶（ALP）染色;培养21 d行茜素红染色;培养7 d,实时定量聚合酶链式反应（Real-time PCR）检测转录因子Runx2、成骨标志物Ⅰ型胶原（Collagen TypeⅠ）、ALP、骨钙素（OCN）基因的表达,免疫印迹法（Western Blotting）检测转录因子Runx2蛋白的表达。结果不同浓度的唑来膦酸干预细胞后,CCK-8实验检测吸光度值随天数增加而升高,各组之间差异无统计学意义（P〉0.05）。随着唑来膦酸浓度的升高,ALP染色和茜素红染色逐渐变浅,Runx2、Collagen TypeⅠ、ALP、OCN基因的表达量降低,Runx2蛋白的表达量降低,差异均有统计学意义（P〈0.05）。结论唑来膦酸在选定浓度（1.0、0.1μmol/L）下不影响成骨细胞的增殖,但对其分化功能的抑制作用随着浓度的增加而增强。     

续苓健骨汤含药血清对MC3T3-E1细胞分化及增殖的影响

目的探讨续苓健骨汤含药血清对MC3T3-E1成骨细胞分化及增殖的影响。方法制备续苓健骨汤含药血清,实验分为空白对照组、含药血清低剂量组、中剂量组和高剂量组。采用CCK-8法和流式细胞术检测续苓健骨汤含药血清对MC3T3-E1细胞增殖和细胞周期的影响;碱性磷酸酶(ALP)活性测定MC3T3-E1细胞的成骨分化能力;茜素红染色检测MC3T3-E1细胞的矿化能力;实时荧光定量PCR检测成骨分化基因Runx2、OC、Bmp2、Col1a1mRNA水平。结果与空白对照组比较,中、高剂量续苓健骨汤含药血清能促进MC3T3-E1细胞增殖、S期细胞比率和细胞增殖指数,并且呈现一定的剂量依赖性;同时中高剂量续苓健骨汤含药血清组能明显提高MC3T3-E1细胞ALP活性(P0.01)和钙化能力(P0.01),促进Runx2、OC、Bmp2、Col1a1 mRNA的表达(P0.05)。结论续苓健骨汤含药血清能促进成骨细胞MC3T3-E1的增殖,并通过上调骨形成相关基因Runx2、OC、BMP2、Col1a1的表达水平,提高MC3T3-E1细胞的成骨能力。     

不同剂量的甲状旁腺素对成骨细胞分化的不同作用的实验研究

目的探讨不同剂量的甲状旁腺素(PTH)对成骨细胞分化过程的影响。方法培养MC3T3-E1成骨前体细胞,给与不同浓度的PTH处理细胞,real-time PCR方法,检测细胞内成骨因子基因mRNA的表达;碱性磷酸酶(ALP)染色方法,检测细胞内ALP的分泌;Alizarin Red染色方法,检测细胞内成骨钙化作用。结果 1 nmol/L浓度的PTH和10 nmol/L浓度的PTH都具有明显的促进成骨细胞分化的作用,以10 nmol/L浓度的PTH的作用更强。100 nmol/L较高浓度的PTH没有明显促进成骨细胞分化的作用。结论不同剂量的PTH对成骨细胞的分化作用,具有不同的影响。