Ultrastructural changes of reconstructed mandibular condylar cartilage under continuous mandibular advancement / 中国组织工程研究

ABSTRACT

BACKGROUND:Previous animal experiments have demonstrated that mandibular advancement can cause the remodeling of temporomandibular joint tissue of young SD rats. This is mainly characterized by accelerated growth rate of the condyle tissue and secondary growth of mandible. But the ultrastructural remodeling of condylar chondrocytes remains poorly understood. OBJECTIVE:To observe the histological and ultrastructural variations of reconstructed condylar cartilage of young rats under the effect of continuous mandibular advancement. METHODS:SD rats aged 4 weeks were randomly divided into control and experimental groups. Rats in the experimental group were subjected to mandibular advancement for 24 hours and sacrificed at 3, 7, 14, 21 and 30 days of intervention. Condylar cartilage samples were harvested and their histological and ultrastructural changes were observed under optical microscope and transmission electron microscope. RESULTS AND CONCLUSION:After 14 days of intervention, the thickness of condylar cartilage in the experimental group increased first and then became thin in the period of observation. The cartilage thickness variations in the postmedian condylar were significant (P < 0.01). After 7 days of intervention, the ultrastructure of condylar chondrocytes was reconstructed, including intracelular karyopyknosis, rough endoplasmic reticulum compartment sweling, smaler even absent lipid droplets, less and irregular microfilaments around the nucleus, broadened and increased extracelular matrix and the emergence of large gaps. These results demonstrate that under continuous mandibular advancement, the rat condylar cartilage wil become thick or thin with the endurance time, and chondrocyte matrix synthesis ability wil be significantly enhanced.