Chondrocyte and matrix
Springer Online Journal Archives 1860-2000
Summary Histological, histochemical, and ultrastructural investigations have been carried out on ageing costal and tracheal cartilage of rats. The following age groups of animals have been studied: 1, 7, 14, 20, 30, 45, 75 days, 6 months, and 2 years. Ageing induces cellular changes which are represented by a reduction in the number of chondrocytes, a progressive increase in glycogen deposition, and processes of degeneration, the most frequent of which is the accumulation of lipidic material within large cytoplasmic vacuoles. Changes in the intercellular matrix become evident after 20 days in costal cartilage and after 30 days in tracheal cartilage. Chondroitin sulphate decreases while keratan sulphate, whose presence is limited to the territorial matrix, increases. Glycoproteins increase slightly in young animals and then remain constant; they decrease in the subperichondrial areas in old animals. Ultrastructurally, the matrix of cartilage of young animals contains thin collagen fibrils, most of which have no periodic banding. Roundish electron dense granules are associated with these fibrils. Irregular filaments associated with small electron-dense circular bodies are present around chondrocytes as well as within cytoplasmic vacuoles. With increasing age, and coincident with the reduction of chondroitin sulphate, the thickness of collagen fibrils increases, their period becomes evident, and the associated matrix granules decrease in number and size. Areas containing these fibrils undergo calcification, which frequently starts within roundish bodies of cellular origin. Collagen fibrils with a period of 640 Å but a highly variable thickness are often present in cartilage of adult and old rats. These fibrils seem to be due to an abnormal synthetic activity of chondrocytes.
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