Variation with ageing and degeneration of the serine and cysteine proteinase inhibitors of human articular cartilage.

The proteoglycans, and proteinase inhibitors of normal and degenerate human articular cartilage have been isolated by 4.0M GuHCl extraction, CsCl density gradient ultracentrifugation and Sephadex G-75 gel filtration chromatography. While a small amount of trypsin inhibitory activity eluted in the Sephadex G-75 void volume, the major proteinase inhibitors were included in the column with MWs within the range 1 - 3 X 10(4) daltons. The large molecular weight trypsin inhibitor was identified as alpha 1-trypsin inhibitor, which was present in greater amounts in degenerate tissue. The Sephadex G75 included fractions (LMWCI) showed inhibition against cysteine and serine proteinases and were reduced in degenerate tissue, but slightly elevated in aged "normal" cartilage. We suggest that the resistance of ageing cartilage to enzymatic degradation may be related to the levels of LMWCI within these tissues.