外源性单磷酸鸟苷环二聚体对变形链球菌基因表达的影响*☆

背景：前期研究证实变形链球菌内部存在单磷酸鸟苷环二聚体信号通路,该通路介导变形链球菌的生物膜形成及在体外牙釉质表面的黏附。 目的：以基因芯片技术分析单磷酸鸟苷环二聚体对变形链球菌生物学特性的影响。 方法：以外源性单磷酸鸟苷环二聚体干预变形链球菌UA159,提取其总RNA,并以标准菌株的总RNA作为对照,与变形链球菌全基因组芯片杂交,筛选差异基因。 结果与结论：外源性单磷酸鸟苷环二聚体干预后,变形链球菌中glgA、glgB、msmF、gftA、lacG、lepB、rgpAc、bacC 、apt69个基因表达上调,Hrc、ProC、HprT、Pdp、Glk、cdsA共6个基因表达下调。所获得的差异基因主要与细胞趋向性和生物膜形成、信号转导、糖代谢、等途径相关。说明单磷酸鸟苷环二聚体影响变形链球菌的致龋性。 关键词：基因芯片;单磷酸鸟苷环二聚体(c-di-GMP);信号通路;变形链球菌;生物膜;致龋性 doi:10.3969/j.issn.1673-8225.2012.08.027     

变形链球菌gcp基因失活菌株生物膜形成能力及在唾液包被羟基磷灰石表面的黏附率

背景：前期实验发现外源性单磷酸鸟苷环二聚体能够抑制变形链球菌生物膜的形成及其体外黏附能力。变形链球菌内部存在的单磷酸鸟苷环二聚体是否具有同样作用。 目的：成功构建了变形链球菌内部单磷酸鸟苷环二聚体相关基因gcp的失活菌株,观察gcp基因失活后变形链球菌生物学特性的改变。 方法：将gcp失活菌和野生菌菌悬液在96孔酶标板中厌氧培养48 h,用结晶紫染色,乙醇/丙酮混合液显色,测量A575 nm值,以定量反映生物膜形成量;荧光标记gcp失活菌和野生菌,与唾液包被的羟基磷灰石粉末共同孵育后,测定羟基磷灰石沉淀的荧光值,比较黏附率的差异。 结果与结论：gcp失活菌生物膜形成量低于野生菌,gcp失活菌在唾液包被羟基磷灰石表面的黏附率低于野生菌(P < 0.05)。提示gcp基因的失活可抑制变形链球菌生物膜形成能力及在生物体表面的黏附。     

白细胞介素10与沙门菌接合性质粒介导细菌生物膜的形成

背景：既往研究发现接合性质粒pRST98可促进其宿主菌生物膜的形成,携带pRST98的菌株感染细胞和实验动物后,可促进白细胞介素10的分泌和表达。 目的：体外研究不同质量浓度白细胞介素10与接合性质粒pRST98对鼠伤寒沙门菌生物膜形成的相互影响。 方法：体外建立鼠伤寒沙门菌标准株χ3306、突变株χ3337及接合株χ3337/pRST98 3组生物膜模型,3组分别加入0(空白对照),1,10,100 µg/L白细胞介素10,通过结晶紫染色半定量法、共聚焦激光扫描显微镜分析和扫描电镜观察,比较不同质量浓度白细胞介素10对携带和不携带接合性质粒pRST98的鼠伤寒沙门菌生物膜形成的影响。 结果与结论：①3组组内比较：与空白对照组比较,1,10 µg/L白细胞介素10均能促进鼠伤寒沙门菌的聚集,提高生物膜形成能力,且10 µg/L质量浓度效果更明显;100 µg/L白细胞介素10抑制鼠伤寒沙门菌生物膜的形成。②3组组间比较：在同一白细胞介素10质量浓度下,接合株χ3337/pRST98组A570高于标准株χ3306组、突变株χ3337组。结果说明1,10 µg/L白细胞介素10可促进生物膜的形成,且在携带接合性质粒pRST98的情况下促进作用更明显。 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;组织工程全文链接：     

不同浓度葛根素对体外培养成骨细胞的影响

背景：有研究报道中药葛根素具有减少骨吸收、促进骨形成的作用。目的：进一步验证中药葛根素对体外培养成骨细胞增殖的影响。方法：取新生大鼠的颅盖骨进行成骨细胞培养,取第3代细胞分别加入浓度为0,20,40,80 和100 µmol/L的葛根素+含体积分数10%胎牛血清DMEM培养基培养48 h。应用MTT法、碱性磷酸酶试剂盒及茜素红染色方法观察葛根素对体外培养成骨细胞的增殖、碱性磷酸酶活性及矿化结节形成的影响。结果与结论：与空白对照组比较,中药葛根素40,80 µmol/L 浓度组具有刺激成骨细胞增殖的作用;成骨细胞碱性磷酸酶活性检测显示葛根素在40 µmol/L 和 80 µmol/L浓度呈现明显的促进分化作用;在不同浓度葛根素中培养 14 d 可以清晰的观察到矿化组织形成,40 µmol/L 和 80 µmol/L葛根素培养的细胞矿化结节形成数量显著多于对照组。结果证实葛根素对体外培养的成骨细胞有明显的促进增殖作用。 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;组织工程全文链接：     

血糖对树鼩感染表皮葡萄球菌清除能力及植入性材料细菌黏附性的影响

背景：高浓度葡萄糖培养条件下,细菌在生物材料表面有较强的生物膜形成能力。 目的：观察血糖升高对表皮葡萄球菌在动物体内清除能力及植入性生物材料上细菌生物膜形成的影响。 方法：注射链脲佐菌素建立高血糖树鼩模型(血糖≥11.1 mmol/L),采用生物膜形成阳性与阴性表皮葡萄球菌感染高血糖与正常对照树鼩,并同时在动物股静脉内植入PVC导管。 结果与结论：感染生物膜形成阳性的表皮葡萄球菌株后,血糖≥11.1 mmol/L树鼩血液、心脏、肝脏、肾脏、胰腺的细菌感染率及菌落计数较正常对照组高(P < 0.05);扫描电镜观察血糖≥11.1 mmol/L组植入生物材料上有明显的生物膜形成。感染生物膜形成阴性表皮葡萄球菌株后无论血糖高低,均未观察到生物膜形成。表明血糖升高不仅使植入生物材料树鼩的细菌清除能力下降,同时可诱导细菌在植入生物材料表面形成明显的生物膜。     

辛伐他汀对高糖高脂诱导人骨髓间充质干细胞凋亡的影响

背景：研究表明,他汀类药物能够促进骨髓间充质干细胞的增殖与黏附能力,抑制高糖高脂培养下骨髓间充质干细胞的凋亡。 目的：观察辛伐他汀对高糖高脂诱导条件下人骨髓间充质干细胞凋亡的影响。 方法：将0.001,0.01,0.1,1.0 μmol/L辛伐他汀分别与高糖高脂诱导条件下人骨髓间充质干细胞培养48 h,以正常培养骨髓间充质干细胞及高糖高脂诱导条件下培养的骨髓间充质干细胞为对照。倒置显微镜下观察细胞形态,MTT法比较不同浓度辛伐他汀对高糖高脂环境下骨髓间充质干细胞存活率的影响,应用流式细胞术检测细胞凋亡,加入PI3K/Akt信号转导通路抑制剂LY294002后辛伐他汀对骨髓间充质干细胞凋亡的影响。 结果与结论：与高糖高脂诱导组比较,辛伐他汀0.01,0.1,1.0 µmol/L组骨髓间充质干细胞存活率均升高(P < 0.01),其中辛伐他汀浓度在0.1 μmol/L时骨髓间充质干细胞存活率升高最显著(P < 0.01);同时流式细胞仪检测结果显示,辛伐他汀0.01,0.1,1.0 µmol/L组细胞凋亡率下降(P< 0.01),其中0.1 µmol/L组凋亡率下降最显著(P < 0.01)。0.1 µmol/L辛伐他汀对骨髓间充质干细胞的影响可被LY294002阻断。说明辛伐他汀能抑制高糖高脂诱导条件下骨髓间充质干细胞的凋亡,其机制可能与PI3K/Akt信号途径有关。     

变形链球菌gcp基因敲除菌株表达谱基因芯片

背景：前期研究中经证实变形链球菌内部存在单磷酸鸟苷环二聚体信号通路,构建了变形链球菌gcp基因敲除菌株。 目的：比较变形链球菌野生菌种和gcp基因突变菌株基因表达的差异情况,筛选与生物膜相关的基因,进入后续研究。 方法：提取两种细菌的总RNA,反转录后分别用cy3和cy5染色。与基因芯片杂交后,扫描结果,进行数据分析,获取差异基因信息,对筛选的基因进行Real-Time PCR验证。 结果与结论：差异基因主要与糖代谢、生物膜形成有关,选择了2个基因进行验证,PCR结果与芯片结果相符合。变形链球菌gcp基因敲除后,突变菌株ahpC基因表达上调,磷酸转移酶系统基因表达下调,说明这2个基因与c-di-GMP信号通路的下游途径相关。     

apelin-13下调caveolae可促进血管平滑肌细胞增殖

背景：结合课题组以往研究成果,提出caveolae可能参与apelin-13促血管平滑肌细胞增殖的假设。 目的：实验观察细胞膜特殊凹陷结构caveolae参与G蛋白偶联受体APJ的内源性配体apelin-13促进大鼠血管平滑肌细胞增殖的作用。 方法：采用组织贴块法培养大鼠胸主动脉血管平滑肌细胞,用MTT方法观察血管平滑肌细胞增殖,Western Blotting方法观察信号蛋白表达,免疫共沉淀技术检测信号分子复合物的形成。 结果与结论：①caveolae结构破坏剂β-环糊精(5 mmol/L,25 h)可明显增强apelin-13诱导的血管平滑肌细胞增殖。②apelin-13(0,1,2,4,8 µmol/L)刺激血管平滑肌细胞,caveolin-1的表达下调,在1 µmol/L时下调明显。③β-环糊精        (5 mmol/L)破坏caveolae后,可使apelin-13下调caveolin-1表达的作用增强。④对照组(体积分数为0.1%胎牛血清孵育)及处理组(apelin-13刺激)caveolin-1与PI3K及ERK1/2均有复合物形成,在apelin-13刺激的情况caveolin-1-PI3K复合物减少、caveolin-1-ERK1/2复合物减少,即apelin-13可能促进caveolin-1与PI3K及ERK1/2解离。结果提示细胞膜特殊凹陷结构caveolae参与apelin-13促血管平滑肌细胞增殖作用。     

5-氮胞苷诱导大鼠骨髓间充质干细胞向心肌样细胞分化及黄芪甲苷的协同作用***☆

背景：大多学者使用5-氮胞苷作为诱导剂诱导骨髓间充质干细胞向心肌细胞定向分化。 目的：观察联合应用黄芪甲苷及5-氮胞苷诱导骨髓间充质干细胞向心肌细胞定向分化中心肌细胞相关受体的表达。 方法：选用生长良好的第3代骨髓间充质干细胞,分为4组。Ⅰ组：仅更换L-DMEM培养液;Ⅱ组：100 mg/L黄芪甲苷+5 µmol/L 5-氮胞苷诱导24 h后,更换L-DMEM培养液。Ⅲ组：10 µmol/L 5-氮胞苷孵育24 h后,更换L-DMEM培养液;Ⅳ组：5 µmol/L 5-氮胞苷孵育24 h后,更换L-DMEM培养液。各组均每3 d换液1次,诱导30 d后对分化细胞进行鉴定。 结果与结论：①Ⅲ组、Ⅳ组及Ⅱ组诱导后细胞心肌细胞特异性蛋白Nkx2.5、cTnT及Desmin的表达均为阳性,与Ⅰ组比较,差异有非常显著性意义(P < 0.01)。Ⅱ组及Ⅲ组诱导后2周,镜下见cTnT、Desmin表达数量高于Ⅳ组(P < 0.01)。Nkx2.5在两组表达亦高于Ⅳ组,其中Ⅱ组与Ⅳ组比较,差异有极显著性意义(P < 0.01),Ⅲ组与Ⅳ组比较,差异有显著性意义(P < 0.05)。Ⅰ组无上述蛋白的阳性表达。②诱导后2周,镜下可见Ⅱ组、Ⅲ组细胞出现心肌细胞样的节律性跳动,证明部分细胞在诱导因素的作用下,已向心肌细胞分化。结果表明用100 mg/L黄芪甲苷+5 µmol/L 5-氮胞苷联合诱导可产生与   10 µmol/L 5-氮胞苷相似的诱导效果,这可能与黄芪甲苷对细胞具有保护作用,促血管内皮细胞增殖作用,增强细胞对5-氮胞苷细胞毒性的耐受,上调心肌特异性蛋白的表达有关。     

光动力疗法对牙菌斑生物膜活性及结构的影响

目的 探讨光动力疗法(PDT)对4种主要致龋菌形成的混合菌菌斑生物膜活性及结构的影响.方法以变形链球菌、血链球菌、嗜酸性乳杆菌和黏性放线菌为实验菌株,建立牙菌斑生物膜模型.实验分为3组:PDT组,洗必泰处理组,生理盐水处理组.平板菌落计数观察牙菌斑生物膜活性,并运用激光共聚焦显微镜(CLSM)对处理后的牙菌斑生物膜进行...     

Effects of electrodeposited poly(ethylene glycol) on biofilm adherence to titanium

Protein-resistant coatings have been studied for inhibiting biofilm formation on implant devices. In this study, titanium (Ti) surfaces were biofunctionalized with poly(ethylene glycol) (PEG) by electrodeposition and were evaluated as biofilm substrates under an oral simulated environment. Streptococcus gordonii, an early colonizer of oral biofilms, was inoculated on Ti and PEG-electrodeposited Ti (PEG-Ti) surfaces and was analyzed quantitatively and topographically. Streptococcus mutans supplemented with sucrose, a late colonizer mainly found in dental plaque, was also used to form biofilms on the surfaces of Ti and PEG-Ti for 20 h followed by sonication as a means of detaching the biofilms. The results indicated that the attachment of S. gordonii on PEG-Ti surfaces was inhibited compared with Ti, and the S. mutans biofilm was easier to be detached from the surface of PEG-Ti than that of Ti. Moreover, the presence of PEG electrodeposited on Ti surface inhibited salivary protein adsorption. The degree of detachment of biofilms from PEG-Ti was associated with the inhibition of the salivary protein adsorption, suggesting weak basal attachment of the biofilms to the electrodeposited surfaces. Therefore, controlling protein adsorption at the initial stage of biofilm formation may be an effective strategy to protect metal surfaces from bacterial contamination not only in dental manipulations but also in orthopedic applications.     

Involvement of sortase anchoring of cell wall proteins in biofilm formation by Streptococcus mutans

Streptococcus mutans is one of the best-known biofilm-forming organisms associated with humans. We investigated the role of the sortase gene (srtA) in monospecies biofilm formation and observed that inactivation of srtA caused a decrease in biofilm formation. Genes encoding three putative sortase-dependent proteins were also found to be up-regulated in biofilms versus planktonic cells and mutations in these genes resulted in reduced biofilm biomass.     

变异链球菌生物膜结构观察

目的　建立变异链球菌生物膜模型 ,用激光共聚焦扫描显微镜 (CLSM)观察变异链球菌生物膜结构。方法　在盖玻片上分别形成 6、12、18、2 4、4 8、72h变异链球菌生物膜 ,将得到的各时段生物膜荧光染色后 ,用CLSM观察生物膜的断层扫描图像、生物膜厚度、每层红光绿光的面积 ,计算生物膜中细菌密度和活菌百分比 ,用软件处理扫描数据 ,得到生物膜的三维重建图像。结果　变异链球菌生物膜具有空间立体结构 ,形态多样 ,其中细菌密集 ,由死细菌和活细菌组成 ,还有丰富的基质和管道系统。 2 4h生物膜平均厚度最大 ,生物膜内层、中间层的细菌密度相对较大 ,而外层较低 ,72h内各时间段生物膜中活菌百分比由内往外逐渐增加。结论　变异链球菌生物膜有一定的厚度 ,具有三维立体空间结构 ,结构形态具有多样、不均质、开放的特点。     

Downregulation of GbpB, a component of the VicRK regulon, affects biofilm formation and cell surface characteristics of Streptococcus mutans

The virulence of the dental caries pathogen Streptococcus mutans relies in part on the sucrose-dependent synthesis of and interaction with glucan, a major component of the extracellular matrix of tooth biofilms. However, the mechanisms by which secreted and/or cell-associated glucan-binding proteins (Gbps) produced by S. mutans participate in biofilm growth remain to be elucidated. In this study, we further investigate GbpB, an essential immunodominant protein with similarity to murein hydrolases. A conditional knockdown mutant that expressed gbpB antisense RNA under the control of a tetracycline-inducible promoter was constructed in strain UA159 (UACA2) and used to investigate the effects of GbpB depletion on biofilm formation and cell surface-associated characteristics. Additionally, regulation of gbpB by the two-component system VicRK was investigated, and phenotypic analysis of a vicK mutant (UAvicK) was performed. GbpB was directly regulated by VicR, and several phenotypic changes were comparable between UACA2 and UAvicK, although differences between these strains existed. It was established that GbpB depletion impaired initial phases of sucrose-dependent biofilm formation, while exogenous native GbpB partially restored the biofilm phenotype. Several cellular traits were significantly affected by GbpB depletion, including altered cell shape, decreased autolysis, increased cell hydrophobicity, and sensitivity to antibiotics and osmotic and oxidative stresses. These data provide the first experimental evidence for GbpB participation in sucrose-dependent biofilm formation and in cell surface properties.     

Detachment of Streptococcus mutans biofilm cells by an endogenous enzymatic activity.

Previous studies have shown that Streptococcus mutans NG8 possesses an endogenous surface protein-releasing enzyme (SPRE) activity that liberates its own surface proteins (S. F. Lee, Infect. Immun. 60:4032-4039, 1992). The present study was initiated to investigate the possible role of the release of surface proteins by SPRE in the detachment of biofilm cells in vitro. Initially, the characteristics of surface protein release by the strain (S. mutans BM71) used in this study were shown to be the same as those previously described for S. mutans NG8. BM71 displayed characteristics identical to those of NG8 in terms of pH optima and inhibitor sensitivity for protein release. Monolayer biofilms of S. mutans BM71 were formed on hydroxylapatite rods in a modified chemostat. Detachment of the biofilm cells was measured by viable cell counts of bacteria liberated after incubation of the biofilms in buffers. Results showed that biofilm cells were detached in a pH- dependent manner with a maximum rate of pH 5 (P = 0.016) to 6 (P = 0.002), a range similar to that for optimal surface protein release. The detachment of the biofilm cells was found to be inhibited by ZnCl2 (P = 0.002 to 0.023), which also inhibited surface protein release. Detachment was not inhibited significantly by CaCl2 (P = 0.525 to 0.784), precluding an ionic effect on inhibition by ZnCl2. The extent of detachment could be increased (P = 0.046) by the addition of an SPRE preparation from S. mutans but not heat-inactivated SPRE (P = 0.665) or SPRE in the presence of ZnCl2 (P = 0.199). Detachment was also studied by using biofilms of resting (viable but not dividing) cells. Results similar to those for biofilms formed from growing cells were obtained, indicating that cells detached from biofilms were not daughter cells. The results presented above show that monolayer biofilm cells of S. mutans under conditions of minimal shear force have the ability to detach from a surface and suggest that this detachment was mediated by an endogenous SPRE activity.