Fig. 5. Immunoblot analysis of culture medium from cocultures and monocultures. Medium aliquots were subjected to SDS-PAGE on 4.5-15% gradient gels under reducing conditions. Proteins were transferred to nitrocellulose and analyzed with specific antibodies recognizing pro- and active forms of: (A) MMP-1, (B) MMP-3, (C) MMP-9 and (D) TIMP-2. Lane 1: monocyte monoculture, lane 2: chondrocyte monoculture, lane 3: coculture of chondrocytes with monocytes. Stars indicate the active enzyme forms.