Quantification of cytokines, bFGF and GAGs in cell-free bone supernatants. Concentration of (A) IL-1ß, (B) IL-6 and (C) IL-8, (D) bFGF and soluble (E) GAGs was determined in cell-free OAB explants (white bars) and NB explants (bars with pattern) kept in chondrogenic medium for 7 or 28 days. Results are mean with standard deviation (SD). N =4; *P <0.05; **P <0.01; ***P <0.001. bFGF, basic fibroblast growth factor; GAG, glycosaminoglycan; IL, interleukin; NB, normal subchondral bone; OAB, osteoarthritic subchondral bone.