Matrix metalloproteases are involved in granuloma-induced cartilage degradation

The aim of this study was to test the role of matrix metalloproteases (MMP) in the in-vivo degradation of an implanted cartilage, using the modified mouse air-pouch model. Rat femoral-head cartilages were wrapped in cotton and implanted in 6-day-old mouse air-pouches. The mice were killed and the pouches opened 4, 7, 14 and 21 days after implantation. At each time the cartilages were removed and their contents of sulfated proteoglycan and collagen were determined. The collagenolytic activity of the pouch granulation tissue was measured, using a synthetic substrate. The implanted cartilage was found to be degraded, as previously described by Bottomley et al. (1988). The disappearance of proteoglycan and collagen began at days 4 and 7 respectively and increased progressively until day 21. An EDTA-inhibited collagenolytic activity was detected in the granulation tissue, and this increased from day 4 to day 21. These results demonstrate a progressive increase in the collagenolytic activity of the mouse air-pouch granulation tissue with a parallel loss of the matrix-macromolecules content of the implanted cartilage. The characterization of the metalloproteases involved is in progress.