Time-course expression of major components of the chondrocyte-associated extracellular matrix (ECM). The gene-expression profile of mesenchymal stem cells (MSCs; n = 2) was analysed by real-time PCR during their differentiation towards chondrocytes in micropellets. (a) and (b) Change in the expression levels of various proteoglycans (PGs), collagens and proteins of the ECM. Genes were arbitrarily distributed. COMP, cartilage oligomeric matrix protein; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; PCR, polymerase chain reaction.