Quantification of collagens I, II, III and proteoglycans in cell lysates. Protein synthesis of collagens I (A), II (B) and III (C) in cell lysates after 28 days of culture in fibrin gels and GAGs (D) in cell lysates on day 7. BMSC (white bars), mixed cultures (BMSC and chondrocytes in a ratio of 1:1, grey bars) or chondrocytes (black bars) were embedded in fibrin gel and kept in monoculture (F, bars with pattern) or in co- and triculture with OAB explants (FB, blank bars) in chondrogenic medium. (A, B) Collagens I and II were quantified with ELISA, or (C) by densitometrically evaluated dot-blot analysis containing a recombinant collagen III standard curve. (D) Proteoglycan/GAG concentration in cell lysates was quantified by a DMMB assay including a chondroitin sulfate standard curve. Results are mean with standard deviation (SD). N =5; *P <0.05, **P <0.01, ***P <0.001. BMSC, bone marrow-derived mesenchymal stem cells; DMMB, dimethylmethylene blue; F, fibrin gel-embedded monocultures (without subchondral bone explants); FB, fibrin gel-embedded co- and tricultures together with subchondral bone explants; GAG, glycosaminoglycan; OAB, osteoarthritic subchondral bone.