Freeze-fracture Images of Matrix Vesicles of Epiphyseal Cartilage and Non-calcified Tracheal Cartilage

Abstract

In the present investigation matrix vesicles of epiphyseal cartilage from rat tibia and of tracheal cartilage from newborn rats were observed after freeze-frecturing, and the results obtained from calcifying regions were compared with those obtained from non-calcified regions. Matrix vesicles in the hyper-trophic zone may be divided into three types according to the density and distribution of particles in the P-face of vesicular membrane. The membrane of matrix vesicles type I is extremely rich in particles. A fracture image of matrix vesicles type II reveals fewer loosely distributed particles on the P-face compared to those of type I. Matrix vesicles type III have few particles or may be devoid of them. However matrix vesicles seen in the reserve zone and tracheal cartilage, where no calcification can be observed, have few or no particles whereas the P-faces of chondrocytes in these regions have many particles. The possible function of the membrane-associated particles of matrix vesicles and the origin of the matrix vesicle were discussed.