Functional analysis of Slit3 effects on RASF. (a) Doubling times of rheumatoid arthritis synovial fibroblasts (RASF; n = 2) were obtained from proliferation assays. RASF incubated with mSlit3 showed decreased growth compared to untreated control (ns, not significant). (b) Recombinant mouse Slit3 (0.1 μg/ml) decreased migration of RASF in early passages (P3 and P4; n = 4) to about 55% compared with control both in upper and lower chamber (** P < 0.01). (c) In later passages (P5 and P6), Slit3 treatment has lost its inhibitory effect on migration of RASF compared with control (n = 4). (d) Slit3 incubation (0.1 μg/ml) had no effect on migration of normal SF (n = 2) in early passages (P3 and P4) compared with untreated control. (e) Relative comparison of migratory ability revealed high induction in RASF compared with normal SF (* P < 0.05).