Organization of extracellular matrix in epiphyseal growth plate

Abstract

Three cations of varying size and charge density, egg-white lysozyme, protamine and ruthenium red, were used to stain the extracellular matrix of epiphyseal cartilage growth plate. With these stains, it was possible to distinguish three types of proteoglycans or materials associated with them, which may well have as their major differences the type of cross linking to the tissue. One type was stained by ruthenium red and protamine but not by lysozyme, was extractable with 3 M guanidinium chloride and was relatively uniformly dispersed throughout the matrix of the growth plate. The other two types were stained by all three cations, were not extractable with 3 M guanidinium chloride and were intimately associated with fibrils. One of these was found on the collagen fibrils, was relatively scanty in the resting zone near the articular surface, relatively restricted to the extralacunar area in the columnar zones and appeared to diminish in amount in the hypertrophic zone. This material often had a 640-A periodic array on the surface of collagen fibrils. The third type also was stained by all three cations and was not extractable with 3 M guanidinium chloride. It was distinguished from the other class of lysozyme-reactive matrix components by the larger volume of distribution occupied by the stained material. It also had a different distribution in that it was widely dispersed in the resting zone, was restricted to the lacuna in the columnar zone and was absent in the hypertrophic zone. Thus, cartilage matrix as well as the chondrocytes undergo differentiation in the epiphyseal growth plate.