AIM: To investigate the effects of transforming growth factor beta 1 (TGF-beta 1) on the differentiation of colonic lamina propria fibroblasts (CLPF) into myofibroblasts in vitro. METHODS: Primary CLPF cultures were incubated with TGF-beta 1 and analyzed for production of alpha-smooth muscle actin (alpha-SMA), fibronectin (FN) and FN isoforms. Migration assays were performed in a modified 48-well Boyden chamber. Levels of total and phosphorylated focal adhesion kinase (FAK) in CLPF were analyzed after induction of migration. RESULTS: Incubation of CLPF with TGF-beta 1 for 2 d did not change alpha-SMA levels, while TGF-beta 1 treatment for 6 d significantly increased alpha-SMA production. Short term incubation (6 h) with TGF-beta 1 enhanced CLPF migration, while long term treatment (6 d) of CLPF with TGF-beta 1 reduced migration to 15%-37% compared to untreated cells. FN and FN isoform mRNA expression were increased after short term incubation with TGF-beta 1 (2 d) in contrast to long term incubation with TGF-beta 1 for 6 d. After induction of migration, TGF-beta 1-preincubated CLPF showed higher amounts of FN and its isoforms and lower levels of total and phosphorylated FAK than untreated cells. CONCLUSION: Long term incubation of CLPF with TGF-beta 1 induced differentiation into myofibroblasts with enhanced alpha-SMA, reduced migratory potential and FAK phosphorylation, and increased FN production. In contrast, short term contact (6 h) of fibroblasts with TGF-beta 1 induced a dose-dependent increase of cell migration and FAK phosphorylation without induction of alpha-SMA production.