Fig. (3) mRNA quantification of proliferative and chondrogenic markers expressed by fresh and frozen cells in superficial and deep origin articular cartilage biopsies. Fresh or frozen human knee superficial and deep articular cartilage chondrocytes were stimulated by culturing with Dulbecco's Modified Eagle's Medium (DMEM) with 10% fetal bovine serum (FBS). qRT-PCR was performed to determine the expression of CCND1 [A], SOX9 [B] and Col II [C] mRNA. The data were normalized against the lowest value obtained for each marker assessed which was assigned the value of 1, and were measured as relative expression levels (R.E.L). *p<0.05.