Gene expression pattern of chondrocytes after in vivo inoculation in scaffolds. Chondrocytes from healthy donors (n = 3, white bars) and from osteoarthritis (OA) patients (n = 4, black bars) were expanded in primary culture, seeded onto scaffolds and incubated for four days in vitro, followed by implantation for eight weeks subcutaneously in SCID mice. Scaffolds were harvested and RNA was extracted from the cells to investigate the gene expression patterns by qRT-PCR for type I and II collagen (CI and CII, respectively), aggrecan (AGG), IL-1β and activin-like kinase (ALK)-1 as indicated. The mRNA levels were normalized to GAPDH and amplified by a factor of 106. Cells from healthy donors expressed slightly more collagen, but no significant differences in gene expressions or differences in the type I to type II collagen ratio were observed between the ACT versus OA cells. ND, not detectable.