The action of excess retinol on articular cartilage from growing pigs was studied in organ culture. Retinol had little or no effect on explants of articular cartilage alone, but if the explants were cut so as to include some of the marrow tissue in the invasion cavities, or were cultivated near or in contact with capsular tissue, retinol caused extensive degradation of the cartilage matrix, as indicated by loss of metachromatic staining properties. Many chondrocytes were released from their capsules and assumed a fibroblast-like form. Two types of regeneration were seen. In control explants that included part of the invasion zone, cells below the explant laid down a metachromatic matrix; in similar explants cultured in the presence of retinol, a non-metachromatic osteoid-like tissue was formed at this site. There was little recovery when retinol-treated explants were transferred to normal medium, although both osteoid and chondroid tissue were sometimes regenerated.

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