氟对体外培养大鼠成釉细胞活性和细胞凋亡的影响

目的 观察氟对体外培养的大鼠成釉细胞活性的影响,为探讨氟斑牙的形成机制提供依据。方法 取对数生长期的大鼠成釉细胞,在培养液中加入浓度为0、0.4、0.8、1.6、3.2、6.4 mmol/L的 NaF溶液,培养24、48、72 h后,采用CCK-8检测各组细胞的活性。荧光显微镜下观察成釉细胞核形态的变化,流式细胞术分析氟对细胞凋亡的影响。采用SPSS13.0软件包对数据进行统计学分析。结果 ①NaF浓度为0.4、0.8 mmol/L时,对成釉细胞有促增殖作用;NaF浓度为1.6、3.2、6.4 mmol/L时,对成釉细胞的活性有抑制作用,随着NaF浓度的增加,对细胞的抑制作用也逐渐增强,并且这种双向调节作用呈时间依赖性。②NaF浓度为0.4、0.8 mmol/L时,鲜见核破碎;NaF浓度为1.6、3.2 mmol/L时,存在核破碎,并且随着浓度的提高,核破碎的数量随之增加,即1.6 mmol/L浓度的NaF可引起成釉细胞凋亡,随着浓度的增加,细胞凋亡的数量随之增加。结论 ①氟对体外培养成釉细胞的增殖具有双向调节作用,即低浓度促进,高浓度抑制。②浓度超过1.6 mmol/L时,NaF诱导成釉细胞凋亡。     

过量氟诱导成釉细胞钙超载及细胞凋亡的实验研究

目的 研究过量氟对体外培养大鼠成釉细胞内钙超载及细胞凋亡的影响。方法 取大鼠成釉细胞系HAT-7细胞,分别加入不同浓度（0、0.4、0.8、1.6、3.2、6.4 mmol·L^-1）的氟化钠培养液,培养48 h后,采用Cell Counting Kit 8（CCK-8）试剂盒检测各组细胞的活性,流式细胞术分析氟对细胞凋亡的影响,激光扫描共聚焦显微镜、Western blot试验和实时荧光定量聚合酶链反应技术检测过量氟诱导大鼠成釉细胞内Ca²⁺浓度和钙网蛋白表达的变化。结果 氟化钠浓度高于1.6 mmol·L^-1时,可抑制成釉细胞的活性,成釉细胞内Ca²⁺浓度升高,钙网蛋白表达上调,细胞早期凋亡数量增加,并且随着浓度的增加,细胞凋亡的数量也随之增加。结论 过量氟可引起成釉细胞内钙超载,诱导成釉细胞凋亡。     

氟对体外培养大鼠成釉细胞 HAT-7细胞活性和对细胞内 Ca2+浓度的影响

目的:观察氟对体外培养的大鼠成釉细胞HAT-7细胞活性及细胞内Ca2+浓度的影响。方法:取对数生长期的HAT-7细胞,分别加入不同浓度的Na F培养液,培养24、48、72 h后,用CCK-8检测细胞的活性;流式细胞术分析氟对细胞凋亡的影响;激光共聚焦显微镜检测细胞内钙离子的浓度。结果:Na F浓度为0.4、0.8 mmol/L时,促进成釉细胞增殖;当Na F浓度大于1.6 mmol/L时,促进成釉细胞凋亡,Na F浓度为1.6 mmol/L时,细胞早期凋亡数量增加,激光共聚焦显微镜检测证实,1.6mmol/L Na F可以诱导大鼠成釉细胞内Ca2+浓度升高,Na F对HAT-7细胞的上述作用与浓度和作用时间呈正相关。结论:低浓度氟促进HAT-7细胞增殖,高浓度则抑制其增殖。Na F浓度超过1.6 mmol/L时,可诱导成釉细胞凋亡,并诱导成釉细胞内Ca2+浓度增加。     

胰岛素对高糖条件下体外培养的大鼠牙囊细胞增殖、分化的影响

目的:探讨胰岛素对高糖条件下体外培养的大鼠牙囊细胞(dental follicle cells,DFC.)增殖、分化的影响.方法:取出生7d的SD大鼠上、下颌磨牙牙囊,原代培养牙囊细胞,选取生长状态良好的第4代细胞,在糖生理浓度(5.5mmol/L)和高糖条件下(16.5 mmol/L和49.5 mmol/L)与6μg/mL胰岛素共同孵育,分别于培养1、3、7、9d时采用MTT法和1～7d采用碱性磷酸酶试剂盒检测胰岛素对高糖条件下体外培养的大鼠牙囊细胞增殖、分化的影响.采用SPSS13.0软件包对数据进行统计学分析.结果:所培养的细胞波形丝蛋白阳性,角蛋白阴性.在第1、3天,16.5mmol/L葡萄糖促进第4代大鼠牙囊细胞的增殖,而49.5 mmol/L葡萄糖抑制牙囊细胞的增殖,胰岛素下调16.5 mmol/L葡萄糖下牙囊细胞的增殖,上调49.5 mmol/L葡萄糖下牙囊细胞增殖;在第7、9天,高糖促进牙囊细胞增殖,胰岛素上调高糖下牙囊细胞的增殖.在1～7d内,高糖提高第4代大鼠牙囊细胞碱性磷酸酶活性,胰岛素下调高糖下牙囊细胞的碱性磷酸酶活性(P<0.05).结论:本实验培养的细胞是来源于外胚层间充质的牙囊细胞.实验结果表明,胰岛素能纠正急性高糖对大鼠牙囊细胞增殖和分化的影响.     

低浓度氟化钠对人牙髓细胞的成骨/成牙本质分化的影响

目的 探讨低浓度氟化钠对人牙髓细胞（human dental pulp cells,hDPCs）成骨/成牙本质分化的影响。方法 本研究已通过单位伦理委员会审查批准。原代培养hDPCs，采用MTT法检测不同浓度氟化钠对hDPCs增殖的影响；选取合适浓度的氟化钠加入成骨/成牙本质分化诱导培养液中，对hDPCs进行体外诱导，通过茜素红染色检测hDPCs成骨/成牙本质分化能力的变化，RT-qPCR检测分化相关基因的mRNA表达；同时通过RT-qPCR和Western blot检测h DPCs成骨/成牙本质分化过程中内质网应激相关基因的表达。结果 低浓度氟化钠（0.1 mmol/L）在体外可刺激h DPCs增殖，高浓度氟化钠（5～10 mmol/L）可抑制hDPCs增殖（P<0.05）。选取0.1 mmol/L氟化钠体外混合成骨/成牙本质分化诱导培养后hDPCs的茜素红染色增加，成骨/成牙本质分化相关基因牙本质涎磷蛋白（dentin sialophosphoprotein,DSPP）、骨涎蛋白（bone sialoprotein,BSP）和骨钙蛋白（osteocalcin,OCN）mRNA...     

镁离子影响人上颌窦黏膜干细胞体外成骨分化的研究

目的:研究不同浓度镁离子(Mg²⁺)对人上颌窦黏膜干细胞(human maxillary sinus membrane stem cells, hMSMSCs)生物行为的影响。方法:体外提取hMSMSCs后利用流式细胞术和多向分化实验来鉴定其间充质干细胞特征,随后将细胞分别培养在0.8 mmol/L、1.8 mmol/L、2.8 mmol/L和5.8 mmol/L的Mg²⁺浓度下。通过CCK-8实验和Calcein AM/PI染色检测hMSMSCs的细胞黏附和增殖,采用罗丹明鬼笔环肽-DAPI染色评估细胞的黏附伸展。对成骨诱导培养后的hMSMSCs进行ALP活性、ALP染色和茜素红染色,同时利用qRT-PCR实验检测成骨相关生长因子的表达差异。结果:适宜浓度Mg²⁺能有效改善hMSMSCs的黏附、伸展和增殖。1.8 mmol/L Mg²⁺提高了hMSMSCs的ALP活性,并显著改善细胞外钙结节的形成并上调成骨相关基因的表达,而过高浓度的Mg²⁺相对抑制了hMSMSCs的成骨分化...     

氯化锂对人牙周膜干细胞增殖和成骨分化的影响

目的:探讨Wnt/β-catenin通路激活剂—氯化锂(lithium chloride,LiCl)对体外培养的人牙周膜干细胞(human periodontal ligament stem cells,hPDLSCs)增殖和成骨分化的影响。方法:低密度多克隆法分离培养人PDLSCs,分别与不同浓度的LiCl(5、10、20、40 mmol/L)共同培养。分别检测各组细胞的增殖情况、碱性磷酸酶(alkaline phosphatase,ALP)活性、钙化结节形成量以及Col-1、OCN、Runx-2等成骨相关基因的表达水平。结果:LiCl无促细胞增殖作用,且高浓度LiCl能明显抑制细胞的增殖。浓度为5 mmol/L的LiCl可促进hP-DLSCs成骨性分化,表现为提高细胞的ALP活性、促进钙化结节的形成、上调Col-1、OCN、Runx-2的mRNA表达水平,与对照组相比,差异均具有统计学意义(P<0.05)。而高浓度(≥10 mmol/L)LiCl则对成骨分化具有抑制作用。结论:终浓度为5 mmol/L的LiCl可明显促进hPDLSCs的成骨分化。     

米诺环素对体外培养的成年大鼠牙槽骨成骨细胞生物活性的影响

目的:研究不同浓度的米诺环素对体外培养的成年大鼠牙槽骨成骨细胞(mature rat alveolarosteoblast,MRAOBs)增殖、蛋白合成及碱性磷酸酶活性(alkaline phosphatase,ALP)的影响。方法:将不同浓度的米诺环素(1、5、10、20、40、100、200mg/L)加入体外培养的第4代MRAOBs中,孵育2d和4d后,倒置显微镜下观察其对细胞形态的影响,并于2d后检测其对细胞的增殖活性及蛋白合成的影响,4d后检测其对细胞的碱性磷酸酶活性的影响。结果:在1-200mg/L的浓度范围内,米诺环素对细胞形态无影响,可显著促进MRAOB的增殖和蛋白合成(P<0.01),1-100mg/L浓度范围内随着浓度的增加,促进细胞增殖和蛋白合成的作用显著增强,至100mg/L时达最大促进效应。1-200mg/L的米诺环素能显著抑制MRAOBs的ALP活性,随浓度的增加抑制作用逐渐增强。结论:一定浓度的米诺环素有促进成骨细胞的增殖、蛋白合成和抑制成骨细胞分化的作用。     

氟对大鼠切牙成釉细胞内质网伴侣分子表达的影响

目的：研究不同浓度氟化物对大鼠切牙成釉细胞的影响,探讨内质网应激在氟斑牙形成中的作用。方法：30只Wistar大鼠随机分为3组,建立氟斑牙动物模型。观察大鼠切牙成釉细胞的形态学和GRP78、XBP-1、CRT和caspase-12表达的改变,采用MetaMorph显微图像分析软件和SPSS 13.0软件包对数据进行统计学分析。结果：随着饮水氟离子浓度的升高,切牙逐渐出现氟斑牙症状。免疫组化结果显示,CRT(F=11.72,P<0.05)、GRP78(F=27.42,P<0.05)、XBP-1(F=139.7,P<0.05)、caspase-12(F=43.91,P<0.05)表达随氟离子浓度的升高而升高,且各组间均具有显著性差异。结论：成釉细胞在一定浓度的氟化物作用下,其CRT、GRP78、XBP-1和caspase-12 均过表达,表明成釉细胞处于内质网应激状态,且caspase-12是导致细胞凋亡的重要途径。     

辛伐他汀对大鼠颅骨成骨细胞生物学特性的影响

目的：研究辛伐他汀对原代培养大鼠颅骨成骨细胞增殖、分化及矿化功能的影响。方法：组织块法分离培养大鼠颅骨成骨细胞,分别在含不同浓度辛伐他汀（1.0μmol/L、0.5μmol/L、0.25μmol/L、0.125μmol/L）培养液环境下培养成骨细胞,采用MTT法测定细胞增殖情况;检测细胞碱性磷酸酶（ALP）活性以及培养液中骨钙素（OC）含量;Von Kossa染色观察成骨细胞矿化结节,用Image-Pro Plus（IPP6.0）软件及其相关系统完成图像采集及分析计算成骨细胞矿化面积的百分比,通过矿化结节面积百分比计算检测细胞的矿化能力。采用SPSS13.0对数据进行单因素方差分析。结果：辛伐他汀抑制成骨细胞的增殖,呈剂量依赖性。各浓度组的ALP活性均增加,以0.250μmol/L浓度组的作用效应最为显著;骨钙素水平增加,与对照组比较均有统计学意义;辛伐他汀能使成骨细胞矿化面积百分比显著增加,差异有统计学意义（P〈0.05）。结论：辛伐他汀抑制体外培养大鼠颅骨成骨细胞的增殖,但却促进成骨细胞的分化及矿化,发挥促进骨形成的作用。     

氟对大鼠氟斑牙形成和成釉细胞DNA损伤的研究

目的：研究在氟中毒引起氟斑牙时,氟对大鼠切牙成釉细胞DNA损伤的影响。方法：给雄性SD大鼠饮用含10、50、100mg/LNaF的高氟水120d,制备氟斑牙模型,用单细胞凝胶电泳检测DNA的损伤。结果：雄性SD大鼠饮用高氟水后,血清氟含量较对照组显著增高,P〈0.05。饮水氟含量与血清氟含量的相关系数为0.9153（P〈0.05）,具有较好的剂量-效应关系,大鼠切牙呈现典型的氟斑牙改变。在50mg/LNaF的剂量条件下,大鼠切牙成釉细胞彗星长与对照组比较,P〈0.05。在100mg/LNaF的剂量条件下,彗星长、Olive尾距、尾分布距与对照组比较,P〈0.05,而尾长值虽比对照组增加,但P〉0.05。低剂量染氟组（10mg/LNaF）大鼠切牙成釉细胞DNA损伤情况与对照组比较,没有显著性差异（P〉0.05）。结论：在氟中毒引起氟斑牙的过程中,大鼠切牙成釉细胞发生明显的DNA损伤。     

High-fluoride promoted phagocytosis-induced apoptosis in a matured ameloblast-like cell line

Endocytosis and phagocytosis are important physiologic activities occurring during ameloblast differentiation. We have previously found that excess fluoride inhibited ameloblasts endocytotic functions. Here, we hypothesized that increasing amounts of fluoride may affect ameloblast phagocytotic function during their differentiation. Using cell culture, we first induced maturation of the mouse ameloblast-like LS8 cells by treatment with exogenous retinoic acid (RA) and dexamethasone (DEX). We measured their phagocytotic activity by fluorescent microscopy using a live cell visualization station. We found that ameloblast-like LS8 cells matured with RA/DEX treatment and the increasing amounts of fluoride demonstrated the up-regulated expression of the phagocytotic marker proteins, LAMP1 and CD68. A connection between phagocytosis and apoptosis was confirmed by the increased number of phagocytotic vacuole-like structures and the heterochromatin margination phenomenon observed in the RA/DEX with NaF treatment group. The increase in albumin uptake by ameloblasts was confirmed using whole organ culture of incisor tooth germs. Here, in fluoride treated tooth germs, mature canonical ameloblasts showed greater amounts of albumin uptake, which was accompanied by decreased expression of the anti-apoptosis marker, Bcl-2 along with up-regulated expression of CD68. From these observations, we inferred that high doses of fluoride may cause apoptosis by increasing the phagocytosis of protein particles in mature-stage ameloblasts and loss of Bcl-2 signals might be involved in this process.     

氟对大鼠成釉细胞GRP-78和caspase-12表达的影响

目的研究GRP-78和caspase-12在氟致大鼠成釉细胞内质网应激和细胞凋亡中的作用,探讨氟所介导的内质网应激是否导致细胞凋亡。方法应用CCK8和流式细胞术观察不同浓度的氟对成釉细胞活性及凋亡数量的影响,以实时定量PCR和Western印迹法检测氟对内质网伴侣分子GRP-78和caspase-12基因和蛋白表达的影响,应用SPSS13.0软件包对数据进行统计学分析。结果随着氟浓度的不断增加,大鼠成釉细胞活性呈逐渐下降趋势,流式细胞术同样显示发生凋亡的细胞数量逐渐上升;实时定量RT-PCR和Western印迹结果显示,GRP-78和caspase-12的表达量随着氟浓度增加而增加。结论过量氟介导了大鼠成釉细胞内质网应激,并且通过内质网应激,引起细胞凋亡。     

Ameloblasts require active RhoA to generate normal dental enamel

RhoA plays a fundamental role in regulation of the actin cytoskeleton, intercellular attachment, and cell proliferation. During amelogenesis, ameloblasts (which produce the enamel proteins) undergo dramatic cytoskeletal changes and the RhoA protein level is up‐regulated. Transgenic mice were generated that express a dominant‐negative RhoA transgene in ameloblasts using amelogenin gene‐regulatory sequences. Transgenic and wild‐type (WT) molar tooth germs were incubated with sodium fluoride (NaF) or sodium chloride (NaCl) in organ culture. Filamentous actin (F‐actin) stained with phalloidin was elevated significantly in WT ameloblasts treated with NaF compared with WT ameloblasts treated with NaCl or with transgenic ameloblasts treated with NaF, thereby confirming a block in the RhoA/Rho‐associated protein kinase (ROCK) pathway in the transgenic mice. Little difference in quantitative fluorescence (an estimation of fluorosis) was observed between WT and transgenic incisors from mice provided with drinking water containing NaF. We subsequently found reduced transgene expression in incisors compared with molars. Transgenic molar teeth had reduced amelogenin, E‐cadherin, and Ki67 compared with WT molar teeth. Hypoplastic enamel in transgenic mice correlates with reduced expression of the enamel protein, amelogenin, and E‐cadherin and cell proliferation are regulated by RhoA in other tissues. Together these findings reveal deficits in molar ameloblast function when RhoA activity is inhibited.     

Short exposure to high levels of fluoride induces stage-dependent structural changes in ameloblasts and enamel mineralization

We tested the hypothesis that the sensitivity of forming dental enamel to fluoride (F^–) is ameloblast developmental stage-dependent and that enamel mineralization disturbances at the surface of fluorotic enamel are caused by damage to late-secretory- and transitional-stage ameloblasts. Four-day-old hamsters received a single intraperitoneal dose of 2.5–20 mg NaF/kg body weight and were examined, 24 h later, by histology and histochemistry. A single dose of ≥ 5 mg of NaF/kg induced the formation of a hyper- followed by a hypomineralized band in the secretory enamel, without changing the ameloblast structure. At 10 mg of NaF/kg, cystic lesions became apparent under isolated populations of distorted late-secretory- and transitional-stage ameloblasts. Staining with von Kossa stain showed that the enamel under these lesions was hypermineralized. At 20 mg of NaF/kg, cystic lesions containing necrotic cells were also found in the early stages of secretory amelogenesis and were also accompanied with hypermineralization of the enamel surface. We concluded that the sensitivity to F^– is ameloblast developmental stage-dependent. Groups of transitional ameloblasts are most sensitive, followed by those at early secretory stages. These data suggest that a F-induced increase in cell death in the transitional-stage ameloblasts accompanies the formation of cystic lesions, which may explain the formation of enamel pits seen clinically in erupted teeth.     

High-fluoride acitivates the FasL signalling pathway and leads to damage of ameloblast ultrastructure

ObjectiveHigh fluoride can induce stress-mediated apoptosis and degradation of ameloblasts. Fas ligand (FasL) has been regarded as a key regulator in intracellular responses for stress-induced apoptosis in reproductive or cancerous cell lineages. The objective of this study is to explore the role of FasL in the regulation of ameloblast ultrastructure damage.DesignPrimary ameloblasts were isolated from the molar tooth germ of 4-day-old SD rats. The ameloblasts were incubated with 3.2 mM NaF or nothing. After incubation for different time arranging from 12 h to 72 h, ELISA was used to detected the secretion levels of FasL in the medium. Then at 48 h post treatment, the ameloblast ultrastructure was detected with Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), and expression of apoptotic proteins and peroxidative enzymes/products were examined. Finally, a specific FasL inhibitor was applied to co-treat the ameloblasts with NaF, and the ameloblast ultrastructure was detected with TEM and SEM.ResultsThe secretion of FasL was notably increased by 3.2 mM NaF treatment, and the increase reached to the peak after incubation for 48 h. High fluoride incubation damaged the ameloblast untrastructure manifesting a series of intracelluar stress responsing cell organelle destruction, and a marked increase in expression of apoptotic genes and oxidative stress. The FasL inhibitor treatment partially mitigated the untrastructure damage caused by high dose NaF.ConlusionHigh-fluoride leads to damage of the ameloblast ultrastructure through paritially acitivating the FasL signalling pathway.     

The amyloid protein APin is highly expressed during enamel mineralization and maturation in rat incisors

This study investigated the expression and localization of APin (which was previously identified and cloned from a rat odontoblast cDNA library), during ameloblast differentiation in rat incisors, by using in situ hybridization and immunohistochemistry. The subcellular localization of APin varied during ameloblast differentiation, but was stage-specific. APin mRNA was not expressed in pre-ameloblasts, was weakly expressed in secretory ameloblasts, and was strongly expressed in maturation-stage ameloblasts as well as in the junctional epithelium attached to the enamel of erupted molars. In the maturation-stage ameloblasts, APin protein was conspicuous in the supranuclear area (Golgi complex) of smooth-ended ameloblasts as well as in both the supranuclear area and the ruffle end of ruffle-ended ameloblasts. During ameloblast-lineage cell culture, APin was expressed at a low level in the early stages of culture, but at a high level in the late stage of culture, which was equivalent to the maturation stage. APin protein was efficiently secreted from transfected cells in culture. Furthermore, its overexpression and inactivation caused an increase and decrease in matrix metalloproteinase-20 (MMP-20) and tuftelin expression, respectively. These findings indicate a functional role for APin in the mineralization and maturation of enamel that is mediated by the expression of MMP-20 and tuftelin.