宿主来源的基质金属蛋白酶对根部牙本质胶原的降解作用

Effect of host derived matrix metalloproteinase on the degradation of root dentin collagen

目的观察根部牙本质中的基质金属蛋白酶(MMP)对牙本质胶原的降解作用。方法将脱矿的根部牙本质粉离心、冷冻干燥后分7组,每组6份,每份50·0mg。各标本中分别加入1ml含不同成分的人工唾液,根据成分不同分为2mmol/L4-乙酰氨基苯汞(APMA)组(MMP活化剂);2、100、200mmol/L乙二胺四乙酸(EDTA)组,0·2%、0·02%醋酸氯己定组(MMP抑制剂);以空白人工唾液作对照组。37℃4h后,用羟脯氨酸试剂盒测定各标本的胶原降解量。扫描电镜观察脱矿及脱矿后置于人工唾液中的根部标本表面结构变化。结果APMA组的胶原降解量最多,其次为对照组,两者间差异有统计学意义(P<0·05)。各MMP抑制剂组的胶原降解量均显著少于APMA组和对照组,差异有统计学意义(P<0·01)。扫描电镜结果表明,仅脱矿的根部表面胶原纤维较完整;而脱矿后置于人工唾液中的标本胶原纤维断裂,结构紊乱。结论脱矿过程中的低pH值能使根部牙本质中的MMP活化,在中性时可降解牙本质胶原。提示宿主来源的MMP可能是龋病进展过程中有机质破坏的重要原因之一。

Objective To evaluate the effect of dentin matrix metalloproteinase （MMP） on the degradation of root dentin collagen. Methods Root dentin powder was demineralized with acetic acid （ pH4. 0） at 4 ℃ for 14 d, then dialysed and centrifuged. Precipitation was divided into 7 groups, with 6 samples in each group, and each sample was 50. 0 mg. One milliliter artifical saliva with a different reagent was added in each sample respectively. The reagents were 2 mmoL/L APMA （ MMP activator）, 2 mmoL/L EDTA, 100 mmol/L EDTA, 200 mmol/L EDTA, 0. 2% and 0. 02% chlorhexidine（ MMP inhibitor） ,and the blank artificial salival was taken as control. The amount of degraded collagen of each sample was determined with hydroxyproline assay kit. Scanning electron microscope was employed to observe the morphological and structural changes of root dentin which was demineralized or put into artificial saliva after being demineralized. Results The mean amount of degraded collagen in APMA group was signiaificanfly higher than that in the blank group（P 〈0. 05）. The mean amount of degraded collagen in 2 mmol/L, 100 mmol/L, 200 mmol/L EDTA, 0. 02% and 0. 2% chlorhexidine groups was dramatically lower than that of the APMA group and the blank （P 〈 0. 01 ）. SEM observation indicated that the structural integrity of the collagen network on root surface dentin still existed in root dentin surface after being demineralized alone, while collagenous fibril was destructed and the structrual integrity on root dentin surface disappeared after being demineralized and treated by artificial saliva. Conclusions MMP in root dentin can degrade root dentin collagen after being activated at low pH followed by neutralization. The results suggest that host MMP may play an important role in the process of dentin caries formation.