Histological study and localization of type I, II and X collagens on experimental expansion of midpalatal suture in the rat

Abstract

The purpose of this study was to clarify the types of collagen compositions in the matrix of the midpalatal cartilage, and to demonstrate the changes following mechanical expansion by using immunohistochemistry. The obtained results were as follows:
1. The cartilage tissue was degenerated with the matrix spontaneously splitting.
2. Mechanical stress accelerated the ossification of the matrix compared with normal subjects.
3. Immunostaining showed collagen type I in the central portion, predominanted type II in almost all layers and weak type X in the hypertrophic cell layer of the sutured cartilage in control subjects.
4. Mechanical factors affected the synthesis of collagens in the matrix, i. e., an increased immunoreaction area of type X collagen, which was synchronized with suture expansion.
These results indicate that midpalatal suture cartilage may be considered as articular or fibrous cartilage since collagen type I was recognized in the central portion of the matrix, which is not normally present in the epiphyseal growth plate. Mechanical stress altered the composition of the extracellular matrix of the cartilage, i. e., it increased collagen type X in the hypertrophic cell layer. From these results, it may be concluded that mechanical stress increased the ossification of the suture cartilage, due to the changes in collagen composition and the acceleration of hypertrophic cell proliferation.