Unbalanced cartilage calcification during development contributes to the formation of irregular articular surfaces as revealed by micro-CT images

Abstract

Abstract Introduction The histological features of irregular mandibular condylar surfaces revealed on CT images remain unknown. Aim In order to seek clarification, the aim of the study was to describe the histological features of irregular mandibular condylar surfaces detected on micro-CT images. Materials and methods Due to different modelling requirements, thirty rats were exposed to five experimental occlusal disturbance models at 6- or 8-weeks of age. Another six age-matched rats were used as controls. After 10 or 12 weeks of modelling, the mandibular condyles were sampled for micro-CT scanning and histology, immunohistochemistry and immunofluorescence assessment. The condyles with irregular surface signs were chosen for analysis. Results Based on the micro-CT images, 10 out of the 30 condyles were diagnosed as having irregular articular surfaces which typically appeared as lacunae on histological sections. The lacunae were filled with degraded cartilage, a fibrous mass, or calcified islets. Type II collagen-, type X collagen- and osterix-positive cells were observed at the side walls of the lacunae. Cleaved caspase-3-positive cells, CD90-positive cells and fibronectin-positive areas were observed inside the lacunae. However, in the subchondral bone at the lower margin of the lacunae, TRAP-positive cells were seldom observed. Conclusions Irregular mandibular condylar surfaces revealed by micro-CT images during development appeared to be a result of unbalanced cartilage calcification.