Objective To observe changes of matrix metalloproteinase-20 (MMP-20) and kallikrein 4 (KLK4) expressions in ameloblasts of rats fed with water containing fluoride of different concentrations so as to explore the pathogenesis of dental fluorosis. Methods Three male and three female SD rats were matched and divided into three groups. Rats in each group were fed with water containing fluoride of 0 mg/L, 50 mg/L and 100 mg/L, respectively, till parturition. Then the offspring rats were killed, and the mandible was taken out to make sections for detecting MMP-20 and KLK4 expressions in rat ameloblasts by immunohistochemical method. Simultaneously, the molar germs were removed to measure the expressions of MMP-20 mRNA and KLK4 mRNA by real-time quantitative PCR. Results The protein and mRNA expression of MMP-20 was decreased with an increased fluoride concentration in drinking water. The same tendency was demonstrated in the mRNA and protein expression of KLK4; however, high-dose and low-dose groups did not differ significantly. Conclusion Secretion of MMP-20 and KLK4 by rat ameloblasts may be reduced by the presence of fluoride, which might cause delay of enamel matrix degradation and abnormal enamel mineralization, finally leading to dental fluorosis.%目的 观察用含不同浓度氟饮水喂养的SD大鼠所产的子鼠成釉细胞中基质金属蛋白酶-20(MMP-20)、激肽释放酶(KLK4)的表达变化,探讨氟牙症的发病机制.方法 给母体SD大鼠分别饮用氟质量浓度为0、50、100mg/L的饮水,待母鼠自然分娩后,取其子鼠下颌骨制作切片并提取牙胚组织,分别用免疫组化和实时定量PCR方法检测不同染氟组大鼠成釉细胞中MMP-20及KLK4的蛋白及基因表达,应用Image-Pro Plus 6.0和GraphPad Prism 5软件对免疫组化和PCR数据结果进行分析.结果 ①随着饮水氟质量浓度的增加,成釉细胞中MMP-20蛋白及其mRNA的表达量逐渐减少;②KLK4蛋白和KLK4 mRNA的表达量在两实验组呈现了类似的变化,但高氟组与低氟组间的差别不明显.结论 氟可使成釉细胞减少对MMP-20及KLK4的分泌.这可能是釉基质蛋白降解延迟、釉质矿化异常,最终导致氟牙症产生的机制之一.
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