FIG. 1.

Bone morphogenetic protein (BMP)-2 increased the expression of hyaline cartilage-specific markers in chondrocytes cultured in collagen sponges and in hypoxia. Human articular chondrocytes (HACs) were cultured in type I collagen sponges for 7 days in hypoxia, in the absence (control), or in the presence of 50 ng/mL BMP-2. (A) The steady-state mRNA levels of type II collagen, aggrecan, type I, and type X collagens were measured using real-time RT-PCR with primers specific to type II collagen (COL2A1 mRNA), aggrecan (ACAN mRNA), type I collagen (COL1A1 mRNA), or type X collagen (COL10A1 mRNA). All results were normalized to RPL13a mRNA, compared with untreated sponge-cultured cells, and are presented as the relative expression of each gene. Box plots represent four independent experiments in triplicate. Statistically significant differences between the untreated cells and BMP-2-treated cells were determined using the Mann–Whitney U test (*p<0.05). (B) Immunostaining was carried out to detect type I and type II collagens (red). The nuclei were counterstained with DAPI (blue). Images shown are representative of the experimental results. Magnification ×40. Scale bar: 40 μm. Color images available online at www.liebertpub.com/tec