The RA methylome signature is stable over passages. (A) Hierarchical clustering RA, OA, and NL samples at P3, P5, and P7. Each column shows the methylation level at one of the 1,859 DML. Additionally, samples from P5 of Nakano et al. 2012 are shown as reference and are labeled as rep. (B) The distribution of the difference in beta values between passages for RA sample.