State Key Laboratory of Oral Diseases, Department of Preventive Dentistry, West China Hospital of Stomatology, Sichuan University, Chengdu, China; West China Hospital, Sichuan University, Chengdu, China; Department of Advanced Oral Sciences and Therapeutics, University of Maryland School of Dentistry, Baltimore, Maryland.
West China School of Public Health, Sichuan University, Chengdu, China.
J Endod. 2019 Mar;45(3):295-301.e2. doi: 10.1016/j.joen.2018.11.011.
Enterococcus faecalis is considered a predominant pathogen for persistent periapical infections and in addition is reportedly resistant to calcium hydroxide medication. The WalRK 2-component system of E. faecalis is essential for environmental adaptation, survival, and virulence. The goal of this study was to investigate the potential roles of walR in the regulation of biofilm aggregation, alkaline stress, and susceptibility to calcium hydroxide (CH) medication.
Antisense walR RNA (aswalR) overexpression strains were constructed. Exopolysaccharide (EPS) production and bacterial viability of E. faecalis biofilms were evaluated by confocal laser scanning microscopy. Quantitative real-time polymerase chain reaction was used to investigate the expressions of virulent factor genes. The proportion of viable bacteria and EPS production in dentin were assessed after CH medication.
We showed that walR interference by aswalR RNA leads to a reduction in the dextran-dependent aggregation in E. faecalis biofilm. The overexpression of aswalR reduced the transcripts of the virulence genes and alkaline stress tolerance ability. Furthermore, the down-regulation of walR sensitized E. faecalis in infected canals to CH medication associated with inhibiting EPS synthesis.
The data suggest a role for the walR regulator in the susceptibility to CH associated with dispelling the EPS matrix, which could be explored as a potential supplementary therapy for the management of root canal infection.
粪肠球菌被认为是持续性根尖周感染的主要病原体，此外，据报道其对氢氧化钙药物有耐药性。粪肠球菌的 WalRK 双组分系统对于环境适应、生存和毒力至关重要。本研究的目的是研究 walR 在调节生物膜聚集、碱性应激和对氢氧化钙 (CH) 药物敏感性中的潜在作用。
构建了反义 walR RNA (aswalR) 过表达菌株。通过共聚焦激光扫描显微镜评估粪肠球菌生物膜的胞外多糖 (EPS) 产生和细菌活力。采用实时定量聚合酶链反应检测毒力因子基因的表达。在 CH 药物治疗后，评估牙本质中活细菌的比例和 EPS 产生。
我们表明，通过 aswalR RNA 干扰 walR 会导致粪肠球菌生物膜中依赖右旋糖酐的聚集减少。aswalR 的过表达降低了毒力基因的转录本和碱性应激耐受能力。此外，walR 的下调使感染根管中的粪肠球菌对 CH 药物敏感，同时抑制 EPS 合成。
数据表明 walR 调节剂在 CH 易感性中起作用，与驱散 EPS 基质有关，这可能作为根管感染管理的潜在辅助治疗方法进行探索。
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