Fig. 3. Protein expression and degradation of aggrecan and collagen II in mono- and cocultures. (A) [¹⁴C]-serine-labeled proteoglycans extracted from cells (lanes 2-4) and culture media (lanes 5-7) were digested with ABC-chondroitinase and ß-endo-galactosidase before being subjected to 3.5-12% gradient SDS-PAGE under nonreducing conditions. Lane 1: 30 µg purified bovine aggrecan stained with Sypro Red protein stain (standard); lanes 2, 5: monocyte monoculture; lanes 3, 6: chondrocyte monoculture; lanes 4, 7: coculture of chondrocytes with monocytes. Stars indicate degradation products. (B) [³⁵S]-methionine/cysteine and [¹⁴C]-proline-labelled collagens were extracted from cells plus culture media and subjected to 3.5-12% gradient SDS-PAGE under reducing conditions. Lane 1: chondrocyte monoculture; lane 2: coculture of chondrocytes with monocytes; lane 3: 15 µg purified bovine collagen II stained with Sypro Red protein stain (standard).