Figure 5. FGF18 inhibits ectopic cartilage formation induced by hedgehog activation in interzone progeny.

E14.5 Cre^– and SmoM2^fl/+ Gdf5-Cre hind limbs were uncultured (A–C and G–K) or cultured with vehicle control (D, E, L, and M) or media supplemented with FGF18 (200 ng/ml; F, G, and N–Q) or FGF4 (H and Q) for 48 hours. Hind limbs were sectioned and stained with SafO (A–D, F, H–K, L, N, O, Q, and R) by histochemistry or Col1a1 (E, G, M, and P) by in situ hybridization. (L and R) Arrows indicate ectopic cartilage formed on the tibia of a SmoM2^fl/+ Gdf5-Cre embryonic limb. (N, O, and Q) Arrowheads denote absence of ectopic cartilage on the tibia of SmoM2^fl/+ Gdf5-Cre embryonic limbs cultured in FGF18-supplemented media. Images are representative of n ≥ 3 hind limb cultures of each genotype/treatment. Scale bar: 200 μm (A).