Degradation of Fetal Rat Cartilage in Organ Culture: Effect ofStreptomycesHyaluronidase

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Abstract
Degradation of cartilage matrix was studied by characterizing the size and amount of products released from cultures of fetal rat long bones into the medium. Na35SO4 was administered to pregnant rats and the fetal radii and ulnae were explanted 24 hours later and cultured in chemically defined medium. Under these conditions, 35S-activity is released from the cartilagenous ends of the explants into the culture medium gradually over 72 hours. The 35S-labeled molecules in the medium were smaller than proteoglycan monomers and larger than papain-released products when chromatographed on Sepharose 2B. The amount of 35S-activity released into the medium decreased when heat-inactivated rat serum or plasma or heparin was added to the medium. Adding proteases or hyaluronidases or freeze-thawing the tissue enhanced release of 35S-activity. Streptomyces hyaluronidase was chromatographed on CM-cellulose and Ultrogel to remove protease activity. The protease-free enzyme released 35S-labeled molecules, similar in size to proteoglycan monomers, from cartilage which was heated before culturing to inactivate endogenous enzymes. These results indicate that hyaluronidase can degrade matrix by releasing proteoglycan monomers. Other treatments released smaller 35S-labeled molecules. These findings indicate that endogenous enzymes degrade matrix proteoglycans into smaller units.

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