Differentially expressed genes and signalling pathways are involved in mouse osteoblast-like MC3T3-E1 cells exposed to 17-β estradiol

Oestrogen is essential for maintaining bone mass, and it has been demonstrated to induce osteoblast proliferation and bone formation.In this study, complementary DNA（cDNA） microarrays were used to identify and study the expression of novel genes that may be involved in MC3T3-E1 cells’ response to 17-b estradiol. MC3T3-E1 cells were inoculated in minimum essential media alpha（a-MEM）cell culture supplemented with 17-b estradiol at different concentrations and for different time periods. MC3T3-E1 cells treated with1028mol？L2117-b estradiol for 5 days exhibited the highest proliferation and alkaline phosphatase（ALP） activity; thus, this group was chosen for microarray analysis. The harvested RNA was used for microarray hybridisation and subsequent real-time reverse transcription polymerase chain reaction（RT-PCR） to validate the expression levels for selected genes. The microarray results were analysed using both functional and pathway analysis. In this study, microarray analysis detected 5 403 differentially expressed genes,of which 1 996 genes were upregulated and 3 407 genes were downregulated, 1 553 different functional classifications were identified by gene ontology（GO） analysis and 53 different pathways were involved based on pathway analysis. Among the differentially expressed genes, a portion not previously reported to be associated with the osteoblast response to oestrogen was identified. These findings clearly demonstrate that the expression of genes related to osteoblast proliferation, cell differentiation, collagens and transforming growth factor beta（TGF-b）-related cytokines increases, while the expression of genes related to apoptosis and osteoclast differentiation decreases, following the exposure of MC3T3-E1 cells to a-MEM supplemented with 17-b estradiol. Microarray analysis with functional gene classification is critical for a complete understanding of complementary intracellular processes. This microarray analysis provides large-scale gene expression data that require further confirmatory studies.

Effects of salvia miltiorrhiza bung （SMB） onosteoblast－like cell lin （clonal MC3T3－E1 cells）

Objective:To investigate the role of SMB on the growth , differentiation and metabolism of osteoblastlike cells in vitro, we studied the effects of SMB on DNA synthesis and alkaline phosphatase(ALPase) activity of the cloned osteoblast like cells-MC3T3-E1. Methods: The cells were cultured in α-MEM with 0. 3% of fetal bovine serum and treated with SMB at the concentration of 0. 1 - 10. 0 g/L. Results : There was no significant difference in DNA synthesis between the groups in different concentration of SMB and the group of control. But SMB increased ALPase activity in a concentration-dependent fashion in later stage of cells , and up to maximum at the level of 5. 0 g/L , in which concentration , ALPase activity was about 135 % greater than that of control. However ,ALPase activity was inhibited in early stage of cells by the addition of SMB. Conclusion : SMB has the stimulating effect on the activity of osteoblast-like cells in vitro, and may play an important role in accelerating the remodeling of bone in vivo as well.

In Vitro Biocompatibility of MC3T3-E1 Osteoblast-like Cells on Arg-Gly-Asp Acid Peptides Immobilized Graphite-like Carbon Coating on Carbon/Carbon Composites

Carbon/carbon （C/C） composites were deposited with graphite-like carbon （GLC） coating, and then, Arg-Gly- Asp acid （RGD） peptides were successfully immobilized onto the functionalized GLC coating. GLC coating was utilized to prevent carbon particles releasing and create a uniform surface condition for C/C composites. RGD peptides were utilized to improve biocompatibility of GLC coating. Surface chemical characterizations of functionalized GLC coating were detected by contact angle measurement, X-ray photoelectron spectroscopy and Raman spectra. Optical morphology of GLC coatings was observed by confocal laser scanning microscopy. In vitro biological performance was determined using samples seeded with MC3T3-E1 osteoblast-like cells and cultured for 1 week. Surface characterizations and morphological analysis indicated that C/C composites were covered by a dense and uniform GLC coating. Contact angle of GLC coating was reduced to 27.2° when it was functionalized by H202 oxidation at 40 ℃ for 1 h. In vitro cytological test showed that the RGD peptides immobilized GLC coating had a significant improvement in biocompatibility. It was suggested that RGD peptides provided GLC coating with a bioactive surface to improve cell adhesion and proliferation on C/C composites.

雌二醇通过雌激素受体α/糖原合酶激酶-3β/β联蛋白信号通路调节成骨细胞增殖

目的研究观察雌二醇对小鼠成骨细胞前体细胞增殖影响并研究经典wnt通路在其增殖过程中的作用。方法本研究利用小鼠胚胎成骨细胞前体细胞Mc3T3-E1为细胞模型,不同浓度雌二醇处理Mc3T3-E1细胞,四甲基偶氮唑蓝(MTT)检测细胞增殖率,蛋白印迹法和免疫荧光技术检测经典Wnt信号通路信号分子表达。结果研究表明不同浓度雌二醇处理Mc3T3-E1细胞,MTT显示随着雌二醇浓度增加,Mc3T3-E1细胞增殖率增加,其中以10-7 mol/L浓度处理后细胞获得最佳增殖率。蛋白印迹法结果显示随着雌激素浓度增加,小鼠Mc3T3-E1细胞中p-GSK-3β,β联蛋白(catenin),细胞周期蛋白(Cyclin)D1的表达增加。经雌激素受体(ER)α沉默后,相对于空白对照组小鼠Mc3T3-E1细胞p-GSK-3β,β-catenin及Cyclin D1表达下降,而ERβ沉默后,同对照组相比成骨细胞中各分子表达则无明显变化。结论雌二醇可通过ERα/GSK-3β/β-catenin信号通路调节小鼠成骨细胞增殖。

Eucommia ulmoides Oliv.antagonizes H_2O_2-induced rat osteoblastic MC3T3-E1 apoptosis by inhibiting expressions of caspases 3,6,7,and 9

Eucommia ulmoides Oliv.(EuO),also known as Duzhong,native to China,has been reported to have antioxidative function,but its cellular mechanism is not fully examined yet.We investigated inhibitory effects of EuO leaf ethanol extracts on H2O2-induced apoptosis in rat osteoblastic MC3T3-E1 cells and underlying mechanisms.Locally-grown Duzhong leaves were extracted with ethanol.MC3T3-E1 cells were treated with EuO (6.25,12.5,25,50,and 100 μg/ml) for 24 h,and then H2O2 (800 μmol/L) for an additional 24 h.Cell survival rate,percentage of apoptosis,and expressions of caspases 3,6,7,and 9 were examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay,microscopic analysis,Western blotting,and reverse transcription polymerase chain reaction (RT-PCR).The final EuO leaf ethanol extract powder was detected to contain caffeotannic acid at 58 mg/g and geniposide at 3.45 mg/g by high performance liquid chromatography (HPLC).EuO remarkably restrained cell oxidative damage and increased cell survival rate in a dose-dependent manner: 0 μg/ml,0.21;6.25 μg/ml,0.28;12.5 μg/ml,0.31;25 μg/ml,0.48;50 μg/ml,0.54;and 100 μg/ml,0.66 (P<0.05),with the half-effective concentration being around 25 μg/ml.MTT results were confirmed by microscopic analysis.Western blotting and RT-PCR analyses showed that the expressions of caspases 3,6,7,and 9 were significantly decreased in the EuO-treated cells compared with the control (EuOand H2O2-free) (P<0.05),with the half-effective concentration of EuO ranging from 12.5 to 25 μg/ml.We conclude that the ethanol-extracted EuO leaf extracts promoted the growth of MC3T3-E1 cells,and suppressed the H2O2-induced apoptosis in a rat MC3T3-E1 osteogenic cell model,likely due to the inhibition of caspases’ activities.The results indicate that EuO is a potent antioxidant,which may contribute to its many cellular protective functions,including the promotion of bone growth.

Study of Cell Behaviors on Anodized TiO_2 Nanotube Arrays with Coexisting Multi-Size Diameters

It has been revealed that the different morphologies of anodized TiO_2 nanotubes, especially nanotube diameters, triggered different cell behaviors. However, the influence of TiO_2 nanotubes with coexisting multi-size diameters on cell behaviors is seldom reported. In this work, coexisting four-diameter TiO_2 nanotube samples, namely,one single substrate with the integration of four different nanotube diameters(60, 150, 250, and 350 nm), were prepared by repeated anodization. The boundaries between two different diameter regions show well-organized structure without obvious difference in height. The adhesion behaviors of MC3T3-E1 cells on the coexisting fourdiameter TiO_2 nanotube arrays were investigated. The results exhibit a significant difference of cell density between smaller diameters(60 and 150 nm) and larger diameters(250 and 350 nm) within 24 h incubation with the coexistence of different diameters, which is totally different from that on the single-diameter TiO_2 nanotube arrays. The coexistence of four different diameters does not change greatly the cell morphologies compared with the singlediameter nanotubes. The findings in this work are expected to offer further understanding of the interaction between cells and materials.

Responses of osteoblasts under varied tensile stress types induced by stretching basement materials

Osteoblasts are mechanosensitive cells.Tensile stress with different conditions,including loading time,frequency,magnitude,etc.would cause varied responses in osteoblasts.However,it was not clarified that the effect of the loading types on the osteoblasts.In this study,we focused on the effect of varied tensile stress types on osteoblasts,including isotropic stretch,biaxial stretch,and uniaxial stretch with the negative ratio of transverse strain to axial strain(NR)-1,0,and 0.2 respectively.Cell proliferation was determined to be most efficient when stimulated by 6%strain at a frequency of 1 Hz and a negative value of 0 for 1 h/day.The varied strain resulted in a thickening of the F-actin cytoskeleton and a thinning of the nucleus.Nuclear flattening caused Yes-associated protein(YAP)to be transported to the nucleus.It was suggested that the influence of loading types on the mechanobiology responses must be noticed.The mechanism of cell mechanical sensitivity under varied loading types was explored,which would provide good sugges-tions for designing microstructures to control deformation patterns in bone tissue engineering.

Bio-inspired Cell Membrane Ingredient Cholesterol-conjugated Chitosan as a Potential Material for Bone Tissue Repair

We prepared a cholesterol-conjugated chitosan（CHCS） material and evaluated its potential application as a bone tissue repair material by in vitro cell experiments. Cell proliferation, differentiation and morphology on CHCS membrane surfaces with different graft degrees were assessed in mouse pre-osteoblasts MC3T3-E1 cells. The results indicate that CHCS materials could promote the proliferation of MC3T3-E1 cells at low graft degrees, but the CHCS material with high graft degree inhibits the proliferation of cells in contrast to the pure chitosan membrane. However, the alkaline phosphatase（ALP） activity of MC3T3-E1 ceils on different CHCS membrane surface increased with in- creasing graft degrees of cholesterol. The area of cells stretched onto the surface of CHCS materials was larger than on the surface of CS materials, and more microfilaments and stress fibers in cells were observed on CHCS materials than on the pure chitosan material surface. After 7 d, the expression of related osteogenic marker genes, such as rum-related transcription factor 2（Runx2）, osterix（OSX）, osteocalcin（OCN）, osteopontin（OPN）, ALP and collagen I（COL-I） were all up-regulated in CHCS materials to different degrees compared to pure chitosan material, which in- dicated that the CHCS materials facilitated MC3T3-EI cell differentiation and maturation, Characterizing CHCS materials is useful in designing and developing strategies for bone tissue engineering.

In vitro Biological Effects of Ti2448 Alloy Modified by Micro-arc Oxidation and Alkali Heatment

The purpose of this study was to test the hypothesis that the combination of micro-arc oxidation and alkali heatment （MAH） would improve the cytocompatibility of a newly designed Ti-24Nb-4Zr-8Sn alloy. In this study, commercially pure titanium （cp Ti） and Ti-24Nb-4Zr-8Sn were used. Surface modification of Ti-24Nb- 4Zr-8Sn by a two-step treatment of micro-arc oxidation （MAO） and alkali heatment was reported. Surface characterizations were performed by scanning electron microscopy （SEM）, thin film X-ray diffraction （TF-XRD） and X-ray photoelectron spectroscopy （XPS）. The MAH layer consisted of finer crystals and possessed a higher degree of crystallity and stability than the MAO layer. A biocompatibility study on treated and untreated Ti- 24Nb-4Zr-8Sn in comparison with cp Ti was carried out to investigate the effect of the different surfaces on the bone integration property in vitro. The cellular assays revealed that the MAO and MAH layer favored the initial adhesion of MC3T3-E1 cells and that the growth rate of MC3T3-E1 cells on MAH layer was significantly higher than that on the conventional MAO-treated layer after 3-day and 5-day incubation, demonstrating the greater potential of the hybrid treatment of micro-arc oxidation followed with alkali heatment as a novel surface modification method for implanting materials.