To demonstrate that the inhibition of BMP4 is necessary to cause JIA FLS to dedifferentiate away from a hypertrophic chondrocyte-like phenotype, using ELISA, we measured chondrocyte marker expression in JIA FLS treated with either noggin or chordin, two prominent BMP4 inhibitors that act by binding directly to BMP4 ligand. This evidence concerns the gene NOG and juvenile idiopathic arthritis.