Expression of matrix metalloproteinases during ascorbate-induced differentiation of osteoblastic MC3T3-E1 cells.

The mouse calvarial osteoblast MC3T3-E1 cells released 92 kDa and 68 kDa of gelatinase activities into the conditioned media (CMs) from undifferentiated cells. When differentiation was induced by cultivating cells with ascorbate-2-phosphate (AscP), 68-kDa activity increased significantly in parallel with production of 60-kDa activity. These enzymes required Ca2+ and Zn2+ ions for their proteolytic activities. The 68-kDa activity was immunologically identified as latent matrix metalloproteinase 2 (MMP-2). The 92-kDa activity was deduced to be latent MMP-9 based on its molecular mass. The 60-kDa activity band was found to possess both gelatin and beta-casein hydrolyzing activities, indicating that this activity band might comprise the active form of MMP-2 and latent MMP-13. MC3T3-E1 cells were found to express MMP-2, MMP-13, and membrane type (MT)1-MMP genes by Northern blotting. MMP-2 was expressed constitutively. MMP-13 was up-regulated during the growth with AscP. MT1-MMP expression also was modulated by AscP; at the early stage of differentiation, its messenger RNA (mRNA) level increased and then decreased gradually to the control level. These changes in the profiles of MMPs observed here could be attributed to the maturation of collagenous extracellular matrix (ECM) induced by AscP.     

Ghrelin stimulates proliferation and differentiation and inhibits apoptosis in osteoblastic MC3T3-E1 cells

Ghrelin is a 28-amino-acid peptide identified in the stomach as an endogenous ligand of the growth hormone secretagogue receptor (GHS-R) that strongly stimulates the release of growth hormone at the hypothalamus and pituitary level. Although GHS-Rs are expressed in a variety of peripheral tissues, little is known about its effect on bone independent of GH/IGF-1 axis. This study was undertaken to investigate whether ghrelin exerts a direct effect on osteoblasts. We identified mRNA and protein expression of GHS-R in primary osteoblasts as well as a number of osteoblastic cell lines, including MC3T3-E1, ROS 17/2.8, UMR-106, MG63, and SaOS2 cells. Treatment of ghrelin (10(-11) to 10(-7) M) to MC3T3-E1 cells showed dose-dependent stimulation of proliferation, which was abrogated by treatment with [d-Lys]-GHRP-6 (10(-3) M), a selective antagonist of the ghrelin receptor. Ghrelin activated ERK1/2 MAPK and pretreatment with MAPK kinase inhibitors, PD98059 attenuated the ghrelin-induced cell proliferation. Ghrelin also inhibited TNFalpha-induced apoptosis and suppressed caspase-3 activation that occurs in response to TNFalpha as well as during in vitro differentiation process. Moreover, ghrelin treatment enhanced in vitro osteoblast differentiation as evidenced by matrix mineralization, alkaline phosphatase activity, and osteoblast-specific gene expression. These results suggest that ghrelin promotes proliferation and differentiation and inhibits apoptosis of osteoblasts.     

Lysophosphatidic acid induces chemotaxis in MC3T3-E1 osteoblastic cells

Lysophosphatidic acid (LPA) is a bioactive lipid that has pleiotropic effects on a variety of cell types and enhances the migration of endothelial and cancer cells, but it is not known if this lipid can alter osteoblast motility. We performed transwell migration assays using MC3T3-E1 osteoblastic cells and found LPA to be a potent chemotactic agent. Quantitative time-lapse video analysis of osteoblast migration after wounds were introduced into cell monolayers indicated that LPA stimulated both migration velocity and the average migration distance per cell. LPA also elicited substantial changes in cell shape and actin cytoskeletal structure; lipid-treated cells contained fewer stress fibers and displayed long membrane processes that were enriched in F-actin. Quantitative RT-PCR analysis showed that MC3T3-E1 cells express all four known LPA-specific G-protein-coupled receptors (LPA1-LPA4) with a relative mRNA abundance of LPA1>LPA4>LPA2>LPA3. LPA-induced changes in osteoblast motility and morphology were antagonized by both pertussis toxin and Ki16425, a subtype-specific blocker of LPA1 and LPA3 receptor function. Cell migration in many cell types is linked to changes in intracellular Ca2+. Ki16425 also inhibited LPA-induced Ca2+ signaling in a dose-dependent manner, suggesting a link between LPA-induced Ca2+ transients and osteoblast chemotaxis. Our data show that LPA stimulates MC3T3-E1 osteoblast motility via a mechanism that is linked primarily to the G-protein-coupled receptor LPA1.     

Action of prostaglandins on clonal osteoblastic MC3T3-E1 cells

Prostaglandins (PG's) are well known as an important local regulator of bone metabolism. In this study, we examined to characterize the effects of PGs on osteoblasts, using a clonal osteoblastic MC3T3-E1 cells. Among PG metabolites, PGE₂ is a main prostanoid released in bone tissues. MC3T3-E1 cells also produced predominantly PGE₂. PG E₂ at low doses (1–100 ng/ml) and PGE₁ increased activity of alkaline phosphatase (ALP), an marker enzyme of early differentiation of osteoblasts, with positive correlation of elevating intracellular cAMP content. The stimulatory effects are amplified by the addition of isobutylmethyl xanthine (IBMX) and mimicked those of forskolin, a direct activator of adenylate cyclase. those results suggest that PGE₂ at low doses and PGE₁ act predominantly on adenylate cyclase to stimulate the early differntiation of the cells. On the other hand, PGE₂ at high doses (500–2000 ng/ml) and PGF_2α stimulated DNA synthesis of the cells in a dose-related manner. In the same range of concentrations, PGE₂ and PGF_2α augmented the accumulation of inositol triphosphates. Further, the effect of these PGs on the DNA synthesis is negated by addition of H-7, a potent inhibitor of protein kinase C. These date suggest that PGE₂ at high doses and PGF_2α stimulate the proliferation of the cells via enhance of phosphatidyl inositol (PI) turnover system and following activation of protein kinase C. Since PGE₂ reveals diverse effects on the cells dependent on its concentration, it is difficult to clarify the mechanism of PGE₂ action. Thus, we chose PGF_2α to elucidate the stimulatory effect of PGs on the prolferation of the cells. At least 12h time-lag was present between PG F_2α-signal transduction and an increase in DNA synthesis, and α-amanitin and cyclohexamide counteracted the effects, suggesting that some proteins involved in DNA synthesis are produced by the addition of PGF_2α in the duration. Further, neutralizing anti IGF-I antibody blocked the stimulation of DNA synthesis by PGF_2α. However, PGF_2α didn't affect the endogenous production of IGF-I of the cells. On the other hand, PGF_2α greatly elevated level of IGF-I binding sites on the cells, and the increase appeared bout 3h earlier than did the stimulation of DNA synthesis, indicating increase in responsiveness of the cells to IGF-I. These results suggest that the proliferation of the cells is stimulated by synergistic action of PGF_2α and IGF-I produced endogenously.     

Enamel matrix derivative inhibits TNF-alpha-induced apoptosis in osteoblastic MC3T3-E1 cells.

OBJECTIVE: The purpose of this study was to examine the effect of enamel matrix derivative (EMD) on TNF-alpha-induced apoptosis in osteoblastic MC3T3-E1 cells. STUDY DESIGN: MC3T3-E1 cells were cultured at an initial density of 5000/cm 2 in Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) and allowed to adhere for 24 hours. Medium was then changed into DMEM with 0.5% FBS. After 16 hours, cells were treated with EMD (100 microg/mL) alone, tumor necrosis factor alpha (TNF-alpha) (20 ng/mL) alone, transforming growth factor beta 1 (TGF-beta1) (10 ng/mL) alone, TNF-alpha plus TGF-beta1, or TNF-alpha plus EMD. Cells cultured with DMEM and 0.5% FBS served as control. Following 24-hour incubation, apoptosis was assessed by terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay, and quantified by cell death enzyme-linked immunosorbent assay (ELISA). RESULTS: Both TUNEL assay and cell death ELISA show that TNF-alpha induces apoptosis in MC3T3-E1 cells. TNF-alpha increases cell death by approximately 2-fold, which is attenuated by both EMD and TGF-beta1. CONCLUSION: Like TGF-beta1, EMD protects osteoblasts from inflammation-induced apoptosis.     

Effect of interleukin 1 beta on osteoblastic clone MC3T3-E1 cells

Summary The effect of recombinant interleukin 1 Beta (IL-1(β)) was investigated on osteoblastic cell line MC3T3-E1 cloned from mouse calvaria. IL-1(β) stimulated cell proliferation which increased cell number and caused dose-related stimulation of DNA synthesis, with a maximal effect at a concentration of 12.5 U/ml; suppressed alkaline phosphatase activity and collagen synthesis maximally at 0.5 and 62.5 U/ml, respectively; and increased the amount of free [³H] hydroxyproline in the cultures, but the amount was quite low. Prostaglandin E₂ synthesis was also stimulated dose dependently by the presence of IL-1(β), with a maximal increase at 2.5 U/ml, at which concentration the prostaglandin E₂ level in the medium was 1.61±0.10 ng/ml. The increased prostaglandin E₂ synthesis did not affect either the IL-1(β)-mediated change in DNA or collagen synthesis or alkaline phosphatase activity. These results extend the possibility that IL-1(β) is to act as a regulator of bone formation.     

Osteopontin is a negative regulator of proliferation and differentiation in MC3T3-E1 pre-osteoblastic cells

Osteopontin (OPN) is an important mediator of bone remodeling. However, the role of OPN in the process of bone formation is not fully understood. In previous studies, we have shown that MC3T3-E1 pre-osteoblastic cells at higher passage number exhibited weakened osteogenic capacity and elevated OPN mRNA expression. In this work, we investigated the role of OPN on proliferation and differentiation of low-passage MC3T3-E1 cells by studying stable cell lines overexpressing either OPN mRNA or its antisense RNA. Overexpression was verified by both Northern and Western blot analyses. Overexpression of OPN markedly inhibited proliferation as determined by daily cell counts, while overexpression of antisense RNA stimulated cellular proliferation. We also examined the effect of OPN level on BMP-2-induced alkaline phosphatase activity. Overexpression of OPN inhibited BMP-2 responsiveness while overexpression of antisense RNA enhanced the effect of BMP-2 on alkaline phosphatase activity. Increased OPN expression also caused decreases in expression of osteocalcin and bone sialoproteins while a reduction of OPN level caused the opposite. Furthermore, endogenous OPN expression in response to BMP-2 exhibited a biphasic pattern, that is, it was initially inhibited and then enhanced by the treatment of BMP-2, indicating that OPN might function as a negative feedback regulator for osteoblastic differentiation. Finally, overexpression of OPN inhibited mineral deposition. In contrast, overexpression of antisense RNA enhanced mineral deposition. These results indicate that OPN is a negative regulator of proliferation and differentiation in MC3T3-E1 cells.     

The effects of low dose X-irradiation on osteoblastic MC3T3-E1 cells in vitro

Background

Recently anti-CCP testing has become popular in the diagnosis of rheumatoid arthritis (RA). However, the inadequate reporting of the relevant diagnostic studies may overestimate and bias the results, directing scientists into making false decisions. The aim of the present study was to evaluate the reporting quality of studies used anti-CCP2 for the diagnosis of RA and to explore the impact of reporting quality on pooled estimates of diagnostic measures.

Methods

PubMed was searched for clinical studies investigated the diagnostic accuracy of anti-CCP. The studies were evaluated for their reporting quality according to STARD statement. The overall reporting quality and the differences between high and low quality studies were explored. The effect of reporting quality on pooled estimates of diagnostic accuracy was also examined.

Results

The overall reporting quality was relatively good but there are some essential methodological aspects of the studies that are seldom reported making the assessment of study validity difficult. Comparing the quality of reporting in high versus low quality articles, significant differences were seen in a relatively large number of methodological items. Overall, the STARD score (high/low) has no effect on the pooled sensitivities and specificities. However, the reporting of specific STARD items (e.g. reporting sufficiently the methods used in calculating the measures of diagnostic accuracy and reporting of demographic and clinical characteristics/features of the study population) has an effect on sensitivity and specificity.

Conclusions

The reporting quality of the diagnostic studies needs further improvement since the study quality may bias the estimates of diagnostic accuracy.     

Properties of Suc-GPLGP-MCAase and dipeptidyl-aminopeptidase in mouse calvaria-derived osteoblastic cells (MC3T3-E1)

Summary In this study the properties of Suc-GPLGP-MCAase and pipeptidyl-aminopeptidase (DAP) in clone MC3T3-E1 cells which have osteoblastic ability were examined. The Suc-GPLGP-MCAase was the most active at pH 8.0 and its molecular weight was about 65,000 as judged by gel filtration method. The enzyme activity was increased by some metal ions such as Mn⁺², Ca⁺², and Mg⁺² but inhibited by Zn⁺² and Cu⁺². EDTA increased the enzyme activity to 23-fold. The enzyme activity was slightly inhibited by thiol inhibitors, N-ethylmaleimide, and p-chloromercuribenzoic acid by 16% and 27%, respectively. The DAP has an optimum pH at 7.5, and a molecular weight of about 100,000. The enzyme was completely inhibited by diisopropylfluorophosphate, but not by N-ethylmaleimide, iodoacetic acid, p-chloromercuribenzoic acid, phenylmethylsulfonyl fluoride, EDTA, and several metals. These results show that Suc-GPLGP-MCAase and DAP in MC3T3-E1 cells have different novel properties compared with these enzymes in the peripheral tissues.     

Modulation of thrombospondin gene expression during osteoblast differentiation in MC3T3-E1 cells.

The levels of expression of two related extracellular matrix protein genes, thrombospondins 1 and 2 (TSP1 and TSP2), were analyzed in the mouse osteogenic cell line, MC3T3-E1. To monitor differentiation, we also measured two potential markers of the osteoblastic phenotype, alkaline phosphatase (ALP) activity, and alpha 1(I) collagen mRNA levels. TSP1 mRNA levels increased 10- to 15-fold during the first nine days of osteoblastic conversion, and then dropped to a level still significantly above baseline values. This increase in TSP1 mRNA closely paralleled that observed in ALP activity. In contrast, TSP2 mRNA levels were unchanged throughout the 21-day time course. These findings suggest that TSP1 is a marker for osteoblast differentiation and could play a role in the cellular changes that accompany acquisition of the osteoblastic phenotype in MC3T3-E1 cells.     

二甲基乙二酰基甘氨酸对小鼠胚胎成骨细胞前体细胞增殖和分化的影响

目的 :探讨低氧模拟剂二甲基乙二酰基甘氨酸(dimethyloxalylglycine,DMOG)对小鼠胚胎成骨细胞前体细胞(MC3T3-E1)的增殖、成骨分化及血管内皮生长因子(vascular endothelial growth factor,VEGF)表达的影响。方法:将MC3T3-E1细胞接种到培养板24h后,实验组培养基中分别加入50μM(50μM组)和200μM(200μM组)的DMOG,对照组加入完全培养液。分别于培养1、3、5d时采用MTT法检测MC3T3-E1细胞增殖情况,5、10d行碱性磷酸酶(alkaline phosphatase,ALP)染色及ALP活性检测成骨细胞分化,21d用茜素红染色检测MC3T3-E1细胞钙结节的形成并进行定量分析,采用ELISA法检测MC3T3-E1培养3d情况时上清液中的VEGF蛋白含量,并用实时荧光定量PCR法检测MC3T3-E1细胞VEGF mRNA的相对表达量。结果:培养1d时对照组、50μM组和200μM组的MC3T3-E1的光密度(optical density,OD)值分别为0.041±0.009、0.074±0.019、0.086±0.044,3d时分别为0.123±0.027、0.148±0.020、0.224±0.061,5d时分别为0.297±0.044、0.325±0.084、0.354±0.038,1d、3d时50μM组和200μM组与同时间点对照组比较均有显著性差异(P0.05),3d时50μM组与200μM组有显著性差异(P0.05)。培养5d和10d时对照组ALP染色颜色较深,50μM组颜色中等,200μM组颜色较浅;5d时对照组ALP活性为1.943±0.072,50μM组为1.632±0.051,200μM组为1.319±0.065;10d时对照组ALP活性为3.734±0.067,50μM组为3.381±0.070,200μM组为2.831±0.086。三组间同时间点比较均有统计学差异(P0.05),同组10d时与5d时比较均有统计学差异(P0.05)。茜素红染色200μM组可见少量红色结节,50μM组可见中等量红色结节,对照组可见大量红色结节;对照组茜素红含量(μg/ml)为56.178±7.940,50μM组为41.922±2.438,200μM组为31.929±1.922,三组间比较均有统计学差异(P0.05)。培养3d时对照组细胞培养上清液中VEGF蛋白含量(ng/孔)为9.063±0.603,50μM组为12.123±0.870,200μM组为15.540±0.581,三组间比较均有统计学差异(P0.05);50μM组VEGF mRNA表达量为对照组的1.792±0.067,200μM组为对照组的3.963±0.092,三组间比较均有统计学差异(P0.05)。结论 :低氧模拟剂DMOG可促进MC3T3-E1细胞增殖和VEGF表达,抑制其成骨分化。     

不同浓度rhBMP-2对MC3T3-E1细胞增殖、ALP活性及成骨分化的影响

目的研究不同浓度rh BMP-2对MC3T3-E1细胞增殖、ALP活性及成骨分化的影响规律。方法 MC3T3-E1细胞接种到培养板24 h后,试验组分别加入1.25、2.5、5、10μg/ml的rh BMP-2进行药物干预,对照组加入全培。试验组应用CCK-8法检测细胞增殖活性,PNPP法检测细胞ALP活性,RT-PCR法检测成骨标志蛋白m RNA的表达情况。结果rh BMP-2浓度为2.5μg/ml时开始促进细胞的增殖(P0.05),rh BMP-2浓度为5μg/ml时促进作用达到峰值(P0.05)。rh BMP-2浓度为2.5μg/ml时ALP活性显著提高(P0.05);rh BMP-2浓度为5μg/ml和10μg/ml时,ALP活性较浓度为2.5μg/ml时继续升高,但差异无统计学意义(P0.05)。ALP、COL1-α以及转录因子RUNX-2的m RNA含量均在加入浓度5μg/ml rh BMP-2后明显升高(P0.05),继续加大rh BMP-2浓度,m RNA含量没有明显增加。结论在研究范围内,rh BMP-2对MC3T3-E1的影响呈浓度依赖性。     

Stimulation by bone sialoprotein of calcification in osteoblast-like MC3T3-E1 cells

Bone sialoprotein (BSP) containing an Arg-Gly-Asp cell-binding sequence was purified from bovine bone 4 M guanidine-HCl extract after HCl demineralization by a series of chromatographic procedures. When this protein was coated on culture dishes in the presence of type I collagen, it increased both DNA content and alkaline phosphatase (ALP) activity in osteoblast-like MC3T3-E1 cells, and stimulated calcification in the cells, whereas fibronectin, another cell-binding protein, showed a marked increase in the DNA content but had little effect on the ALP activity. These findings suggest that BSP is mitogenic for preosteoblasts and differentiating the cells into osteoblasts, thereby stimulating bone calcification