异常咬合对小鼠髁突软骨细胞内质网应激性凋亡的影响研究

目的探讨异常咬合对小鼠髁突软骨细胞内质网应激性凋亡的影响。方法选取6周龄雌性C57BL/6J小鼠54只,随机分为4组,分别饲养1、3、7、11周,其中饲养1、3、7周的小鼠(各12只)再随机分为对照组和单侧前牙反(unilateral anterior crossbite,UAC)组,饲养11周的小鼠(18只)再随机分为对照组、UAC组和去冠组(UAC刺激7周后去除UAC刺激继续饲养至11周),每组小鼠均为6只。各组小鼠处死取材后对髁突软骨进行HE染色、糖相关蛋白78(glucose-regulated protein 78,GRP78)和含半胱氨酸的天冬氨酸蛋白水解酶12(cysteinyl aspartate specific proteinase 12,Caspase12)免疫组织化学染色以及TUNEL染色。结果(1)HE染色结果显示:各饲养期对照组小鼠髁突软骨细胞层次鲜明,软骨内细胞排列整齐;UAC组小鼠髁突软骨内软骨细胞数目减少,排列紊乱,随着时间延长这些变化逐渐加重。与同饲养期对照组相比,UAC组小鼠髁突软骨细胞密度、软骨厚度均显著减小(均P<0.05);去冠组小鼠髁突软骨细胞分层情况明显改善,软骨细胞密度、软骨厚度较UAC组有显著增加(均P<0.05),而与同饲养期对照组相比,差异无统计学意义(均P>0.05)。(2)免疫组织化学染色、TUNEL染色结果显示:各饲养期对照组小鼠髁突软骨中GRP78阳性细胞在软骨浅层和深层均有分布,Caspase12阳性细胞主要分布在软骨深层,但数量均很少;UAC组小鼠髁突软骨中出现大量GRP78和Caspase12阳性细胞。UAC组小鼠髁突软骨GRP78、Caspase12和TUNEL阳性细胞率均高于同饲养期对照组(均P<0.05);去冠组小鼠髁突软骨GRP78、Caspase12和TUNEL阳性细胞率均显著低于UAC组(均P<0.05),而与同饲养期对照组相比,差异无统计学意义(均P>0.05)。结论异常咬合促进髁突软骨细胞内质网应激性凋亡,从而加重髁突软骨的退行性变。

Effect of abnormal occlusion on endoplasmic reticulum stress-induced apoptosis of chondrocytes in the mandibular condylar cartilage of mice

Objective　To investigate the effects of abnormal occlusion on endoplasmic reticulum（ER）stress-induced apoptosis of chondrocytes in the mandibular condylar cartilage of mice. Methods　Fifty-four 6-week-old female C57BL/6J mice were randomly divided into 1-，3-，7- and 11-week groups. Each of the 1-，3-，and 7-week groups was then randomly divided into control and UAC subgroup，and the 11-week group was divided into control，UAC and removal subgroups（in the 11-week subgroup the UAC was removed after 7 weeks of stimulation with UAC and the animals were sampled at the end of the 11th week）. There were 6 mice in each group. The TMJ blocks were randomly selected for HE staining，TUNEL staining，and immunohistochemical staining of GRP78 and Caspase12. Results　（1）HE staining showed that chondrocytes in the condylar cartilage were stratified and arranged neatly in the control group. But in the UAC group，the number of the chondrocytes was reduced and the cellular arrangement was disordered in the cartilage. These changes were gradually aggravated with time. There was significant reduction in the cellular number and cartilage thickness in UAC group compared with the control groups （P < 0.05）. The stratification and arrangement of the chondrocytes were significantly improved in the removal group. The cellular number and cartilage thickness were observably increased in removal group compared with that in the UAC group（P < 0.05），whereas there was no significant difference in comparison with the control group（P > 0.05）.（2）IHC staining and TUNEL staining showed that GRP78 positive cells were distributed in the superficial and deep zones of the condylar cartilage，and the Caspase12 positive cells were predominantly located in the deep zone in control group，but in small number. In contrast，there were increased number of GRP78 and Caspase12 positive cells in the condylar cartilage in UAC group. IHC and TUNEL demonstrated that the percentage of GRP78，Caspase12 and TUNEL positive cells in UAC group was higher than that in control group（P < 0.05）. The percentage of GRP78，Caspase12 and TUNEL positive cells was significantly lower in removal group than in UAC group（P < 0.05），whereas there were no significant differences in comparison with that in the control group（P > 0.05）. Conclusion　Abnormal occlusion promotes ER stress-induced chondrocyte apoptosis and enhances degeneration of the mandibular condylar cartilage.