| Caries is one of the most common dental diseases that seriously harms human beings' health. Its initiation and development depends on the microenvironment of dental plaque biofilms. Streptococcus mutans (S.mutans) has been implicated as the main etiological agent of dental caries and an important constituent of dental plaque. Adherence is the foundation of the cariogenesis of S. mutans. When S. mutans makes contact with salivary glycoproteins that coat the tooth surface, two stages of adherence follow to mediate development of the plaque biofilms. The first stage is initial adherence and it is sucrose independent, the second is sucrose dependent adherence. The mechanism of S. mutans adherence may be multifactorial and complex, and it remains to be fully elucidated.Evidence showed that there was difference in cariogenetic virulence among different strains of S.mutans. Variations in genes of cariogenetic virulence factors were speculated as the substance foundation of this cariogenesis difference. As a result, genetic diversity of cariogenetic virulence factors of S. mutans has been the target of extensive studies. Studies on the genetic diversities of the adherence virulence factors of S. mutans and their relationships with cariogenecity have also been reported. However, some evidence recently indicated that the different expression of virulence factors might influence this bacteria's virulence to a bigger extent than the genetic diversity. So lately, researchers exert much attention on regulation of gene expression of S. mutans virulence factors. In this study, through observing the changes of S. mutans adherence and adherence-associated genes expression under different conditions, we aimed to see if there is some relationship between the regulation of S. mutans adherence-associated genes expression and adherence.Methods: Firstly, quantativly detect the initial adherence and sucrose dependent adherence of S. mutans under different culturing conditions. Secondly, construct gene chips and detect the genetic expression of S. mutans under different conditions. Lastly, by utilizing TaqMan RT-RCR technique, we checked the expression of adherence-associated genes and further verified the gene chips results. From these datas, we try to probe into the relationship between regulation of S. mutans adherence-associated genes expression and adherence.Results:(1) Initial adherence of S. mutans increased significantly when environmental glucose increased from 0.2ï¼…to 1ï¼…and 5ï¼…. spaP and srtA expression of more-adherent S. mutans strains was upregulated with the increase of glucose. Especially, the spaP expressional difference between 1ï¼…and 0.2ï¼…glucose and spaP, srtA expressional difference between 5ï¼…and 0.2ï¼…glucose were of statistical significance. spaP and srtA expression of less-adherent S. mutans strains was also upregulated with glucose increasing but the difference was not significant. That increased glucose facilats spaP and srtA expression may be one of the mechanisms underlying the increased initial adherence.(2) In acidc environment, initial adherence and spaP expression of S. mutans decreased significantly. While srtA expression increased. The inhibition of spaP expression and promotion of srtA expression may be one of the mechanisms underlying the decreased initial adherence and S. mutans acidresistance.(3) In 0.2ï¼…, 1ï¼…and 5ï¼…glucose environment, spaP expression of more-adherent strains was statistically higher than that of less-adherent strains; In 0.2ï¼…and 1ï¼…glucose environment, srtA expression of more-adherent strains was also statistically higher than that of less-adherent strains; No matter the initial pH of medium was acidic or neutral, spaP and srtA expression of more-adherent S. mutans strains was higher than that of less-adherent strains. There might be some correlation between different expression of spaP and srtA genes and S. mutans initial adherence.(4) When environmental sucose increased from 0.5ï¼…to 1ï¼…and 5%, sucrose dependent adherence of S. mutans increased significantly and wapA, gbpA,B,C,D genes expression changed. When the cultural sucrose increased from 0.5% to 1%, TaqMan RT-PCR and gene chip analysis both showed that gbpC expression was upregulated significantly. This may be one of the reasons why S. mutans adherence increased in environment with more sucrose.(5) wapA, gbpA,B,C,D expression of more-adherent S. mutans strains was higher than that of less-adherent strains. Especially in 0.5% and 5% sucrose environment, wapA, gbpC,D expressional difference was statistically significant. There might be some correlation between expressional level of S. mutans genes associated with sucrose dependent adherence and adherence ability.Based on these findigs, we can see that environmental factors might regulate S. mutans initial adherence and sucrose-dependent adherence through regulating some adherence-associated genes expression; There might be some correlation between different expression of adherence-associated genes and S. mutans adherence; Gene chips can detect the differently expressed genes in S. mutans and provide a technique platform for S. mutans research.
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