Distribution of elastic system fibers in hyaline and fibrous cartilages of the rat.

Rat hyaline and fibrous cartilages whose glycosaminoglycans had been removed by hyaluronidase digestion were studied by comparing the ultrastructural features with the observation of sections stained by selective methods for elastic system fibers under the light microscope. Except for the fibrous layer in the perichondrium of tracheal hyaline cartilage, where elastic fibers were found, no elastic fibers could be detected in the cartilages studied. However, cartilaginous tissues contained oxytalan and elaunin fibers. A distinct pattern of distribution of the above-mentioned elastic-related fibers could be observed in both kinds of cartilages. Hyaline cartilages possess oxytalan fibers in the extracellular matrix that surrounds the chondrocytes, whereas elastic fibers were localized in the fibrous layer of the perichondrium that encloses the cartilage. Elaunin fibers could be detected in the transition (chondrogenic) layer adjacent to the perichondrium. The methods used disclosed the presence of oxytalan and elaunin fibers running along the periphery of the collagen bundles in fibrocartilage.