Fig. 5.

Collagen type I expression during in vivo and in vitro articular cartilage developmental maturation. In freshly isolated tissue, labelling for anti-collagen type I antibodies was observed as a broad and diffuse surface layer, and, localised as a thinner layer at the surface in mature cartilage (A). Labelling in cartilage explants cultured in serum-free (ITS) or growth factor medium (ITS-FGF2-TGFβ1) was more intense and was consolidated at the surface of these cartilages. Bar equals 50 μm. The ratio of collagen type IαI (in nanograms) normalised to 18S rRNA (in nanograms) is shown (B). Transcript levels of collagen type IαI decrease approximately 3-fold (P < 0.05) as cartilage matures, but following in vitro experimental maturation transcript levels increase approximately 6-fold compared to serum-free cultured (ITS) cartilage explants (P < 0.02).