Figure 4. RA inhibits chondrogenesis.

(A) ChMM cultures were treated with various concentrations of RA or RA inhibitors (disulfiram, citral), cultured, stained with Alcian blue, and quantified. Intensity of staining in controls is 100%. Note the reduction of chondrogenesis after RA treatment and induction after treatment with RA antagonists. Results are presented as mean ± SD. *P < 0.05; **P < 0.005. (B) Bead implantations in chicken limb buds at Hamburger Hamilton (HH) 27 with subsequent Col2a1 section in situ hybridization after 20 hours of incubation. Top: Control without bead. Middle: DMSO-soaked control bead with unchanged Col2a1 expression. Bottom: Limb after implantation of RA-soaked beads. Note the suppression of Col2a1 expression. Asterisks indicate beads.