Effect of gamma-ray irradiated poly(L-lactide) on the differentiation of mouse osteoblast-like MC3T3-E1 cells

The purpose of this study was to clarify the effects of gamma-ray irradiated poly(L-lactide) (PLLA) on the proliferation and differentiation of mouse osteoblast-like MC3T3-E1 cells. The PLLA was y-irradiated at the dose of 10, 25 or 50 kGy, and the molecular weight of irradiated PLLA decreased with increasing irradiation dose. The proliferation and differentiation of MC3T3-E1 cells cultured on irradiated PLLA for 2 weeks were evaluated using micromass culture. The y-irradiation of PLLA did not affect the proliferation, but stimulated the differentiation of MC3T3-E1 cells cultured on irradiated PLLA. These results suggested that lower change in the molecular weight of PLLA was responsible for stimulation of the differentiation of MC3T3-E1 cells cultured on irradiated PLLA. Furthermore, the proliferation and calcification of MC3T3-E1 cells cultured in the medium containing low molecular weight PLLA for 2 weeks were evaluated. The low molecular weight PLLA also stimulated the calcification of MC3T3-E1 cells with no effect on the proliferation. The y-irradiation was suitable for PLLA on the differentiation of mouse osteoblasts.     

Effect of heat treatment of poly(L-lactide) on the response of osteoblast-like MC3T3-E1 cells

Poly(L-lactide) (PLLA) products are molded by heat extrusion. These treatments may change chemical properties and biological response of the PLLA to cells. In this study, the effect of heat treatment of PLLA on osteoblast proliferation and differentiation was examined in vitro. Osteoblast-like MC3T3-E1 cells were cultured for 2 weeks on the PLLA subjected to various heating temperature and time combinations. The protein, DNA, and hydroxyproline (HYP) contents and alkaline phosphatase (ALP) activity of cells cultured on the untreated (non-heated) PLLA with a weight average molecular weight (Mw) of 1,000,000 (high Mw PLLA) were not significantly different from those of cells cultured on glass. The activation of osteoblast differentiation by the high Mw PLLA was weak. In contrast, increases in ALP activity and HYP content were found for cells cultured on the PLLA heated at a high temperature of 200 or 250 degrees C. Heat treatment of high Mw PLLA increased differentiation of MC3T3-E1 cells cultured upon it. Significant degradation of PLLA (decrease in molecular weight and increase in molecular weight distribution) were observed following heat treatment. The Mw of PLLA decreased from 1,000,000 to below 20,000, and 14.4 microg of L-lactic acid was released from 10 mg of PLLA by heating at 250 degrees C. Therefore, the effect of low Mw chemicals, which were expected to be the degradation products of high Mw PLLA after heat treatment, on MC3T3-E1 cell activities was examined. Increases in the protein, DNA and HYP amounts and ALP activity for cells cultured with L-lactide or L-lactic acid were observed at 100 microg/ml, but not at 10 microg/ml. When the cells were cultured on the low Mw PLLA (Mw 20,000), their biological parameters also increased. Twelve micrograms of L-lactic acid released from 10 mg of the low Mw PLLA during 2 weeks incubation. The concentration of L-lactic acid in the incubation solution of low Mw PLLA or heat-treated PLLA was too small to cause cell activation. These results suggested that increases in osteoblast differentiation on the heat-treated PLLA was not to due to soluble degradation chemicals, such as L-lactic acid, rather than the remaining low Mw PLLA.     

Poly(L-lactide) crystallization topography directs MC3T3-E1 cells response

Biomaterial surface topography significantly influences cellular form and function. Using poly(L-lactic acid) films with normal spherulites, banded spherulites, and amorphous surfaces as model substrates, we conducted a systematic assessment of the role for polymer crystallization induced surface morphologies on cell growth and contact guidance. Microscopy and image analysis showed that the MC3T3-E1 cells spread out in a random fashion on the amorphous substrate. At 24 h post-seeding, MC3T3-E1 cells on both types of spherulite surfaces were elongated and aligned along the spherulite radius direction. For the banded spherulite surface with radial stripes and coupling annular grooves, the cell orientation and cell nuclear localization were related to the grooves structure. With increasing time, this orientation preference was weaker. These results demonstrate that the patterning of polymer crystallization structure provide important signals for guiding cells to exhibit characteristic orientation and morphology especially in the early stages of regeneration.     

Proliferation and differentiation of osteoblast-like MC3T3-E1 cells on biomimetically and electrolytically deposited calcium phosphate coatings

Biomimetic and electrolytic deposition are versatile methods to prepare calcium phosphate coatings. In this article, we compared the effects of biomimetically deposited octacalcium phosphate and carbonate apatite coatings as well as electrolytically deposited carbonate apatite coating on the proliferation and differentiation of mouse osteoblast-like MC3T3-E1 cells. It was found that MC3T3-E1 cells cultured on the biomimetically deposited carbonate apatite coating demonstrated the greatest proliferation rate and the highest differentiation potential. Cells on the biomimetically deposited octacalcium phosphate coating had lower proliferation rate before day 7, but higher after that, than those on the electrolytically deposited carbonate apatite coating. There was no difference on the expression of early differentiation markers, that is, alkaline phosphatase activity and collagen content, between biomimetically deposited octacalcium phosphate and electrolytically deposited carbonate apatite coatings. However, higher expression of late differentiation markers, that is, osteocalcin and bone sialoprotein mRNA, was found on the biomimetically deposited octacalcium phosphate coating on day 14. These results suggest that the difference in in vitro osteoblast cell performance of calcium phosphate coatings might relate to their physicochemical properties. Biomimetic carbonate apatite coating is the most favorable surface for the proliferation and differentiation of MC3T3-E1 cells.     

Effect of gypsum on proliferation and differentiation of MC3T3-E1 mouse osteoblastic cells

Recently, calcium sulfate dihydrate has been demonstrated as safe biodegradable osteoconductive bone void filler. However, its exact mechanism of action on bone cells is yet unknown. In this study, the influence of gypsum on gene expression and proliferation of MC3T3-E1 mouse pre-osteoblastic cells was investigated. Cells were cultured on gypsum disc, slice, polymethylmethacrylate (PMMA), or plastic culture plate for 15 days. Cell viability, alkaline phosphatase (ALP) activity and expression profile of 15 genes involved in bone metabolism were measured in cultures. Cell proliferation on gypsum was increased by almost 2-fold, while an inhibitory effect of PMMA on proliferation rate of osteoblasts was noted. Cells cultured on gypsum disc surface exhibited an increased ALP activity and markedly different gene expression profile. Quantitative real-time PCR data indicated the expression of genes that might provide a basis for an osteoinductive potential. MC3T3-E1 cells expressed genes typical of bone fracture healing like type II collagen and fibronectin 1. These effects might be related to the calcium content of gypsum and mediated likely via SMAD3. Our results suggest that gypsum can support new bone formation by its calcium content and modulatory effect on gene expression profile of bone cells.     

小鼠p38MAPK重组腺病毒载体的构建及其在成骨细胞系中的表达

目的:利用AdEasyTM system构建携带小鼠p38MAPK基因的重组腺病毒,感染成骨细胞系MC3T3-E1,检测外源p38MAPK在细胞中的表达。方法:用PCR的方法扩增p38MAPK基因,将其克隆到pMD18-T载体中,进行测序。经BglⅡ和HindⅢ双酶切后接入pShuttle-CMV穿梭载体,构建重组腺病毒的穿梭质粒pShuttle-CMV-p38MAPK。将经PmeI线性化的pShuttle-CMV穿梭载体与pAdEasyTMDNA电穿孔共转化BJ5183重组细菌,获取重组腺病毒质粒Ad-p38MAPK,再将经PacI线性化的Ad-p38MAPK重组病毒骨架质粒转染AD293包装细胞,包装并扩增病毒。用Ad-p38MAPK感染小鼠MC3T3-E1成骨样细胞,以Western blot法检测p38MAPK在小鼠成骨细胞中的表达。结果:构建并包装表达p38MAPK蛋白的重组腺病毒,该重组腺病毒在体外能有效感染小鼠成骨细胞系MC3T3-E1并高表达p38MAPK蛋白。结论:成功地构建了携带小鼠p38MAPK基因的重组腺病毒,为研究p38MAPK在成骨细胞中的作用奠定了实验基础。     

Sunflower seed extract enhances the differentiation of osteoblastic MC3T3-E1 cells

Osteoporosis is recognised as one of the major hormonal deficiency diseases, especially in menopausal women and the elderly. The present study investigated whether treatment with sunflower (Helianthus annuus L.) seed extract (SSE) may affect the function of MC3T3-E1 osteogenic cells. In order to determine the growth and differentiation of osteoblast, MTT (3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide) assay, alkaline phosphatase (ALP) activity, collagen synthesis and osteocalcin secretion were performed. Also, the production of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and nitric oxide (NO) in osteoblastic MC3T3-E1 cells was measured. SSE significantly (p<0.05) increased cell growth, ALP activity, collagen content and osteocalcin secretion compared with control. The effect of SSE (50 µg/ml) in increasing cell growth, ALP activity and collagen content was prevented by the presence of 10^?6 M cycloheximide and 10^?6 M ICI182780, suggesting that SSE's effect results from a newly synthesised protein component and might be partly involved in oestrogen action. Treatment with SSE (10 and 50 µg/ml) decreased the 5 µg/ml lipopolysaccharide-induced production of TNF-α, IL-6 and NO in osteoblasts. Our data indicate that the enhancement of osteoblast function by sunflower seed may result in the prevention for osteoporosis and inflammatory bone diseases.     

Anabolic effect of genistein in osteoblastic MC3T3-E1 cells

Genistein is a natural isoflavone found in Leguminosae. The effect of genistein on osteoblastic MC3T3-E1 cells was investigated. Cells were cultured for 48 h in the presence of genistein (10(-7)-10(-5) M). Genistein (10(-6) and 10(-5) M) caused a significant elevation of protein content, alkaline phosphatase activity, and deoxyriboncleic acid (DNA) content in the cells. The effect of genistein (10-5 M) in increasing protein content, alkaline phosphatase activity and DNA content in the cells was completely prevented by the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis, suggesting that the isoflavone's effect results from a newly synthesized protein component. The effect of genistein (10(-5) M) in elevating cellular protein content and alkaline phosphatase activity was completely inhibited by the presence of trifluo-perazine (10(-5) M), staurosporine (10(-7) M) or vanadate (10(-6) M), various protein kinase inhibitors. Moreover, genistein (10(-5) M)-increased protein content and alkaline phosphatase activity in the cells was clearly abolished by the presence of anti-estrogen tamoxifen (10(-6) M). The effect of 17beta-estradiol (10(-9) M) in elevating protein and alkaline phosphatase activity in the cells was not enhanced by the presence of genistein (10(-5) M). Genistein's effect might be partly involved in estrogen action. The present study demonstrates that genistein has an anabolic effect on osteoblastic MC3T3-E1 cells.     

A voltage-dependent calcium current in mouse MC3T3-E1 osteogenic cells

MC3T3-E1 osteogenic cells in a growing state were voltage-clamped by the whole-cell patch-clamp method. The MC3T3-E1 cells exhibited a transient, fast-inactivating Ca inward current upon depolarizing pulses from a holding potential of -80 mV. This current had a threshold of activation of about -50 mV and was insensitive to the dihydropyridine, nifedipine. These results show that MC3T3-E1 cells have a voltage-dependent Ca channel corresponding to the "T-type."     

Stimulation of DNA synthesis in osteoblast-like MC3T3-E1 cells by Bordetella bronchiseptica dermonecrotic toxin.

We investigated the effects of Bordetella bronchiseptica dermonecrotic toxin on DNA synthesis in MC3T3-E1 cells. The rate of [methyl-3H]thymidine incorporation increased in the toxin-treated cells more than 24 h after addition of the toxin under the serum-starved conditions. This effect was dependent on the toxin concentration ranging from 0.3 to 3 ng/ml and was eliminated by aphidicolin and hydroxyurea, inhibitors for DNA replication. In the toxin-treated culture, the number of cells did not increase but polynucleated cells appeared and their number increased to ca. 50% of the total number of cells 6 days after the toxin addition. From these results, we concluded that the toxin stimulates DNA replication in MC3T3-E1 cells without cell proliferation.     

Surface modifications by gas plasma control osteogenic differentiation of MC3T3-E1 cells

Numerous studies have shown that the physicochemical properties of biomaterials can control cell activity. Cell adhesion, proliferation, differentiation as well as tissue formation in vivo can be tuned by properties such as the porosity, surface micro- and nanoscale topography and chemical composition of biomaterials. This concept is very appealing for tissue engineering since instructive properties in bioactive materials can be more economical and time efficient than traditional strategies of cell pre-differentiation in vitro prior to implantation. The biomaterial surface, which is easy to modify due to its accessibility, may provide the necessary signals to elicit a certain cellular behavior. Here, we used gas plasma technology at atmospheric pressure to modify the physicochemical properties of polylactic acid and analyzed how this influenced pre-osteoblast proliferation and differentiation. Tetramethylsilane and 3-aminopropyl-trimethoxysilane with helium as a carrier gas or a mixture of nitrogen and hydrogen were discharged to polylactic acid discs to create different surface chemical compositions, hydrophobicity and microscale topographies. Such modifications influenced protein adsorption and pre-osteoblast cell adhesion, proliferation and osteogenic differentiation. Furthermore polylactic acid treated with tetramethylsilane enhanced osteogenic differentiation compared to the other surfaces. This promising surface modification could be further explored for potential development of bone graft substitutes.     

β-蜕皮甾酮促进小鼠前成骨细胞体外增殖及诱导成骨分化

文题释义：β-蜕皮甾酮：又称蜕皮激素、20-羟基蜕皮甾酮,分子式C₂₇H₄₄O₇,为黄棕色至白色粉末,味苦;主要存在于昆虫、蚕、露水草、牛膝、川牛膝等动植物体内,具有调节血糖血脂、促进胶原蛋白合成、抗疲劳、促进细胞生长和刺激真皮细胞分裂等作用,目前广泛应用于化妆品、医疗以及养殖业等领域。骨形态发生蛋白质2：是从脊椎动物骨骼基质中分离提纯的蛋白质,具有内肽酶活性、表皮生长因子模体,同源二聚体之间以二硫键相连,属于转化生长因子β家族,能诱导骨与软骨形成。骨桥蛋白：存在于矿化和活性沉积区,是一种含有Arg-Gly-Asp(RGD)结构的酸性糖蛋白,它与诱导成骨细胞成熟表型表达和矿化骨基质形成的活性蛋白密切相关。在成矿阶段,骨连接素、纤连蛋白与骨桥蛋白的表达高度相关。Ⅰ型胶原是钙盐沉积和细胞附着的支架,可促进细胞附着并刺激细胞分化。背景：β-蜕皮甾酮作为“植物类雌激素”不仅具有刺激蛋白质合成,促进碳水化合物和脂质代谢,缓解高血糖、高脂血症,以及保护内皮细胞免于凋亡并诱导其增殖的多种生物活性,而且有学者报道其在治疗骨质疏松症、骨折和其他骨骼炎症性疾病方面也有着重要的作用。 目的：观察β-蜕皮甾酮对小鼠前成骨细胞(MC3T3-E1细胞)体外增殖的影响,以及在安全剂量下,β-蜕皮甾酮是否对该细胞具有诱导成骨分化的作用。方法：取第4代MC3T3-E1细胞在成骨诱导分化培养基中培养7,10,14,21,28 d后,检测细胞不同时间段成骨分化蛋白(碱性磷酸酶、Ⅰ型胶原蛋白、骨桥蛋白以及钙化结节)的表达量,以鉴定该细胞是否具有成骨分化的能力;然后将MC3T3-E1细胞接种于含不同终浓度β-蜕皮甾酮(0.01,0.1,1,10,100 µmol/L)的诱导培养基中,分别于第1,2,3,4,5,6,7天利用CCK8法检测细胞的增殖活性;最后设置对照组(普通诱导培养基组)和实验组(普通诱导培养基+β-蜕皮甾酮),在相同条件下进行培养,并测定不同时间段各组细胞成骨标志蛋白的表达量。结果与结论：①MC3T3-E1细胞在成骨诱导培养基刺激下,第10天碱性磷酸酶染色以及Ⅰ型胶原蛋白荧光染色表达较高,同时碱性磷酸酶活性检测也验证了这一结果(P < 0.05);诱导培养第14天骨桥蛋白免疫细胞化学染色也有明显表达;茜红素染色显示成骨诱导后的细胞较对照组结节数量明显增加,第28天比第21天的钙结节形成数目更多、直径更大、颜色更深;②CCK 8法测得β-蜕皮甾酮对MC3T3-E1细胞作用5 d后增殖活性达到最佳,促增殖活性最佳剂量为0.01 µ mol/L、0.1 µmol/L,2种浓度之间差异无显著性意义(P > 0.05);③实验组细胞经β-蜕皮甾酮诱导培养第10天较对照组细胞碱性磷酸酶、Ⅰ型胶原蛋白表达更高;第14天实验组细胞内骨桥蛋白、骨钙素表达更高;第28天2组钙结节染色无明显差异;④结果说明,β-蜕皮甾酮能促进MC3T3-E1细胞体外增殖,且在安全剂量下能提高MC3T3-E1细胞向成骨细胞分化的能力。ORCID: 0000-0001-5641-6353(严才平) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

mTORC1 信号促进前成骨细胞MC3T3-E1 的分化成熟

目的:研究mTORC1 信号对前成骨细胞MC3T3-E1 向成骨细胞分化成熟的调控作用。方法:通过向MC3T3-E1 转染pcDNA3.1-Raptor,对mTORC1 信号相关蛋白Raptor 进行过表达。向MC3T3-E1 转染Raptor siRNA,对mTORC1 信号蛋白Raptor 进行基因沉默。通过Real-time PCR 方法测定Raptor 的基因表达,通过蛋白免疫印迹法测定Raptor 蛋白水平,并通过茜素红染色检测成骨矿化情况,以测定成骨分化程度。通过Real-time PCR 检测成骨分化指标的基因表达。结果:与对照组相比,Raptor 过表达组的Raptor mRNA 和蛋白水平明显增加;茜素红染色结果显示Raptor 过表达组染色更深,说明成骨矿化程度更高;荧光定量PCR 结果显示,Raptor 过表达组的成骨分化标记基因以及成骨转录因子的表达量均高于对照组。与对照组相比,Raptor siRNA 组的Raptor mRNA 和蛋白水平明显降低;茜素红染色结果显示Raptor siRNA 组染色更浅,说明成骨矿化程度更低;荧光定量PCR 结果显示,Raptor siRNA 组的成骨分化标记基因以及成骨转录因子的表达量均低于对照组。结论:mTORC1 信号促进前成骨细胞MC3T3-E1 向成骨细胞分化成熟。     

盐酸小檗碱通过PI3K/Akt信号通路促进小鼠前成骨细胞MC3T3-E1的分化

目的:研究盐酸小檗碱对小鼠前成骨细胞系MC3T3-E1分化与矿化的调控作用及其机制。方法:MC3T3-E1细胞给予不同浓度(0、1、5、10和20 mg/L)的盐酸小檗碱刺激3 d,CCK-8法检测细胞活性。不同浓度的盐酸小檗碱分别干预3 d和7 d,检测细胞碱性磷酸酶(ALP)活性。进一步将实验随机分为4组:对照组、盐酸小檗碱组、盐酸小檗碱+LY249002(PI3K/Akt通路抑制剂)组及LY249002组。干预2 d后,采用real-time PCR检测成骨细胞分化相关因子ALP、骨钙素(OCN)、骨桥蛋白(OPN)及Runt相关转录因子2(Runx2)的mRNA表达情况,采用Western blot检测PI3K/Akt信号通路相关蛋白p-Akt的表达水平。将MC3TC-E1细胞用矿化培养基诱导21 d,茜素红染色检测其矿化情况。结果:与对照组相比,不同浓度的盐酸小檗碱对细胞活性的影响没有明显差异;不同浓度的盐酸小檗碱处理MC3T3-E1细胞后ALP活性有不同程度升高。Real-time PCR结果表明,盐酸小檗碱(5 mg/L)促进ALP、OCN、OPN及Runx2的mRNA表达(P 0. 01),而LY294002能抑制这些分化相关因子的表达。Western blot检测结果表明,盐酸小檗碱(5 mg/L)促进p-Akt蛋白的表达(P 0. 01),其作用被LY249002抑制。茜素红染色发现盐酸小檗碱组矿化明显,但LY294002能抑制盐酸小檗碱的促进作用。结论:盐酸小檗碱可以促进小鼠前成骨细胞的分化与矿化,其机制可能与其激活PI3K/Akt信号通路有关。     

骨碎补总黄酮联合纳米骨材料促进MC3T3-E1细胞的增殖分化

文题释义： 骨碎补总黄酮：是由水龙骨科植物槲蕨的干燥根茎中提取的有效成分,骨碎补总黄酮能够促进成骨细胞增殖,抑制破骨细胞成熟分化。 Wnt/β-catenin信号通路：是一类高度保守的信号通路,广泛存在于多细胞真核生物中,是皮肤发育过程中出现最早的分子信号,调控毛囊的生长发育和毛囊干细胞的迁移分化。β-catenin作为细胞内信号传导蛋白,是Wnt信号通路激活的一种重要的上皮细胞表面黏附分子,能够进入细胞核内传递Wnt信号,进一步激活靶基因开始转录,启动细胞增殖周期。 背景：前期研究发现,骨碎补总黄酮可促进纳米骨材料表面MC3T3-E1细胞的成骨分化,其作用机制有待进一步研究。 目的：探究骨碎补总黄酮联合纳米骨材料对MC3T3-E1细胞发挥作用的机制。 方法：将MC3T3-E1细胞与纳米骨材料共培养,选取100 mg/L和250 mg/L骨碎补总黄酮进行药物干预,以10 μg/L转化生长因子β刺激为阳性对照组。分组如下：①正常组;②DKK1组：Wnt通路抑制剂DKK1      (0.1 mg/L)阻断Wnt/β-catenin信号通路;③DKK1+转化生长因子β组;④DKK1+100 mg/L骨碎补总黄酮组;⑤DKK1+250 mg/L骨碎补总黄酮组;⑥DKK1+纳米骨+转化生长因子β组;⑦DKK1+纳米骨+100 mg/L骨碎补总黄酮组;⑧DKK1+纳米骨+250 mg/L骨碎补总黄酮组。在干预24,48 h后收获细胞,免疫荧光双染法观察Wnt/β-catenin通路中Wnt与LRP结合情况,Real-time PCR和Western blot检测β-catenin、LRP5、Gsk-3β、Cyclin D1、RUNX2的表达。 结果与结论：①激光共聚焦扫描显微镜下显示DKK1+转化生长因子β组、DKK1+250 mg/L骨碎补总黄酮组、DKK1+纳米骨+转化生长因子β组、DKK1+纳米骨+250 mg/L骨碎补总黄酮组棕黄色染色较明显,表明Wnt与LRP结合较其他组更好;②Real-time PCR和Western blot结果显示,骨碎补总黄酮可促进β-catenin、LRP5、RUNX2的表达,下调GSK-3β的表达,说明骨碎补总黄酮通过激活经典Wnt/β-catenin 信号通路促进成骨细胞增殖分化,且骨碎补总黄酮诱导的基因活化呈剂量依赖性。 ORCID: 0000-0002-2031-8644(李晋玉) 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     

Effects of surface modification of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) on physicochemical properties and on interactions with MC3T3-E1 cells

As a new member of the polyhydroxyalkanoate (PHA) family, poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has better mechanical and processible properties than poly (3-hydroxybutyrate) (PHB). Still, it is difficult to introduce functional groups to the polyester carbon chain of PHBHHx, which restricts the modification of PHBHHx for a wide range. In this study, a procedure for the modification of the surface of PHBHHx films under strongly alkaline conditions was described. Through this kind of modification, carboxyl and hydroxyl groups were introduced to the surface and the total surface free energy was increased, which was mainly due to the increased polar components. Meanwhile, this process makes the surface rougher, resulting in larger total surface areas. After mineralization in simulated body fluids (SBFs), the apatite nucleation and growth on the surface-hydrolyzed PHBHHx films were significantly faster than on the unmodified PHBHHx films. This phenomenon should have a close relationship with the increased carboxyl and hydroxyl groups. The physicochemical properties also influenced the cell response to PHBHHx films. Compared to unmodified PHBHHx, fibronectin adsorption, and MC3T3-E1 cell attachment and proliferation were significantly greater on surface-hydrolyzed PHBHHx, which may be due to the increased surface free energy and rougher surface. Therefore, surface hydrolysis makes PHBHHx more suitable for osteoblast cell response and for application in bone-tissue engineering.     

The expression profile of PKC isoforms during MC3T3-E1 differentiation

Protein kinase C (PKC) is a family of kinases whose isoforms show subtle differences in physiological and biochemical responses, with their expression being cell- specific. We hypothesize that there may be a specific profile of expression of PKC isoforms in differentiating osteoblastic cells (OBC) with individual isoforms having specific functions. Herein, the MC3T3-E1 cell line was used as a differentiating model, which was induced from the pre-osteoblast stage to mature osteoblast and characterized with several phenotypic markers, including alkaline phosphatase activity, osteocalcin and bone sialoprotein. The expression of PKC isoforms was monitored using Western blot analysis. Upon induction of osteogenesis, the intracellular localization of PKC eta and theta was determined using immunofluorescence. Lastly, the effect of P38 MAP kinase inhibition was determined using SB203580. Results show 1) PKC alpha, delta, lambda were all highly expressed in MC3T3-E1 osteoblastic cells, 2) the expression of PKC theta was significantly down-regulated upon induction of osteoblastic differentiation; 3) PKC eta was non-detectable at certain cell culture days; however, was up-regulated as the cells transit from each differentiation phase. The increased expression of PKC eta correlated with increases in OC, BSP levels and alkaline phosphatase activity. Immunofluorescence procedure confirmed the Western blot results with an increase in PKC eta and a decrease in PKC theta upon osteogenic stimulation. The inhibition of p38 resulted in a marked down-regulation of PKC eta. The data demonstrate that there is a specific profile of expression of PKC isoforms in differentiating osteoblasts; the different expression pattern of individual isoforms may be either a consequence of the differentiation itself or plays a role in the regulatory mechanism of osteoblastic differentiation. This study has provided primary information on the temporal pattern of expression of PKC isoforms in the differentiating osteoblast and further insight into their possible role in osteoblastic cell maturation.     

Hydroxyapatite accelerates differentiation and suppresses growth of MC3T3-E1 osteoblasts

Hydroxyapatite describes both the natural mineral phase of bone as well as the widely used calcium-phosphate implant substitute. Given that hydroxyapatite is a major component of the in vivo surface with which osteoblasts interact, it is surprising that most studies examining the regulation of osteoblast growth and differentiation utilize plastic surfaces. Here we demonstrate that the phenotype of mouse MC3T3-E1 osteoblasts is significantly altered on hydroxyapatite compared with plastic surfaces. Specifically, alkaline phosphatase activity and messenger RNA levels, markers of early stages of osteoblast differentiation, are increased in osteoblasts cultured on hydroxyapatite. The precocious appearance of alkaline phosphatase activity on the hydroxyapatite surface suggests that osteoblast differentiation is activated earlier compared with plastic surfaces. Osteocalcin expression, a marker of late-stage differentiation, is also increased on hydroxyapatite and further demonstrates enhanced differentiation. Cell counts indicate that fewer osteoblasts are present on hydroxyapatite versus plastic surfaces 24 h after plating. Measurement of osteoblast attachment, apoptosis, and necrosis indicated no differences between surfaces. In contrast, the number of bromodeoxyuridine-incorporating cells was significantly decreased on hydroxyapatite compared with plastic surfaces. Taken together, our findings indicate that hydroxyapatite enhances osteoblast differentiation while also suppressing growth.     

Gel microstructure regulates proliferation and differentiation of MC3T3-E1 cells encapsulated in alginate beads

For cell transplantation into damaged tissues, viable cells must be delivered to the defect site in a suitable carrier. However, the hypoxic and nutrient-limited environment in the carrier can induce massive cell death. The aims of this study were to increase the viability and regulate the behavior of osteoprogenitor cells encapsulated in alginate hydrogels through control of the gel microstructure. Cell survivability in alginate beads was improved through the use of α-MEM as the solvent for alginic acid sodium salt, and by CaCl(2) solutions, which supplied additional nutrients for the cells compared to water or buffer. The mesh size and shear modulus of the hydrogel were hypothesized to regulate proliferation and differentiation of osteoprogenitor cells. MC3T3-E1 cells demonstrated enhanced osteoblast differentiation when encapsulated in high-density alginate with smaller mesh size and more rigid mechanical properties, as confirmed by increased alkaline phosphatase activity and osteocalcin secretion. However, MC3T3-E1 cells encapsulated in low-density alginate beads with a larger mesh size and more compliant mechanical properties exhibited increased proliferation. These results demonstrate that the microstructure of alginate hydrogels can regulate the behavior of osteoprogenitor cells, thus suggesting that the tuning the properties of the gel may be a useful approach for enhancing new bone formation.     

Co-culture with periodontal ligament stem cells enhanced osteoblastic differentiation of MC3T3-E1 cells and osteoclastic differentiation of RAW264.7 cells

Objectives: Periodontal ligament stem cells (PDLSCs) are characterized by having multipotential differentiation and immunoregulatory properties, which are the main mechanisms of PDLSCs-mediated periodontal regeneration. Periodontal or bone regeneration requires coordination of osteoblast and osteoclast, however, very little is known about the interactions between PDLSCs and osteoblast-like cells or osteoclast precursors. In this study, the indirect co-culture approach was introduced to preliminarily elucidate the effects of PDLSCs on differentiation of osteoblast-like cells and osteoclast precursors in vitro. Materials and methods: Human PDLSCs were obtained from premolars extracted and their stemness was identified in terms of their colony-forming ability, proliferative capacity, cell surface epitopes and multi-lineage differentiation potentials. A noncontact co-culture system of PDLSCs and preosteoblastic cell line MC3T3-E1 or osteoclast precursor cell line RAW264.7 was established, and osteoblastic differentiation of MC3T3-E1 and osteoclastic differentiation of RAW264.7 were evaluated. Results: PDLSCs exhibited features of mesenchymal stem cells. Further investigation through indirect co-culture system showed that PDLSCs enhanced ALP activity, expressions of ALP, Runx2, BSP, OPN mRNA and BSP, OPN proteins and mineralization matrix deposition in MC3T3-E1. Meanwhile, they improved maturation of osteoclasts and expressions of TRAP, CSTK, TRAF6 mRNA and TRAP, TRAF6 proteins in RAW264.7. Conclusions: PDLSCs stimulates osteoblastic differentiation of osteoblast precursors and osteoclastic differentiation of osteoclast precursors, at least partially, in a paracrine fasion.