FIG. 3.

(A) Chondrogenic differentiation of MSCs, which involves three main stages influenced mainly by the Sox family transcription factors, followed by the ossification process. Once chondrocytes reach their mature phenotypic state, osteogenic transcription factors Osterix and Runx 2 are expressed and chondrocytes evolve to a hypertrophic state. Different GFs are expressed by cells, depending on their differentiation state. BMP-2 is expressed throughout the process, while TGF-β family is highly expressed during the MSCs condensation step. The mechanism here described occurs in the growth plate of long bones and it is responsible for the endochondralossification for bone turn-over. Adapted from ^236,243 (B). Cartilage layers expressing TGF-β1 and TGF-β3 increased between day 1 and 3 and TGF-β1 maintained approximately those levels until day 14. An increase of insulin growth factor (IGF)-I and FGF-2 was observed between day 3 and 7. IGF-I, FGF-2, and TGF-β3 reached a new peak level at day 7 and showed gradual decrease afterward. At day 28, GF expression returned to basal levels. Color images available online at www.liebertpub.com/teb