Knockdown of FOXM1 inhibits activation of keloid fibroblasts and extracellular matrix production via inhibition of TGF-β1/Smad pathway

Keloid is characterized by overactive fibroblasts. Forkhead box M1 (FOXM1) is transcription factor that plays important roles in the progression of fibrosis. However, the role of FOXM1 in keloid has not been elucidated. In the present study, we examined the expression levels of FOXM1 in clinical keloid tissue specimens and primary keloid fibroblasts (KFs). The results showed that FOXM1 levels were significantly increased in both keloid tissues and KFs. To further investigate the biological functions of FOXM1, FOXM1 was knocked down in KFs by transfection with small interfering RNA targeting FOXM1 (si-FOXM1). Knockdown of FOXM1 inhibited transforming growth factor-β1 (TGF-β1)-induced cell proliferation and migration of KFs. Besides, the increased expressions of collagen (coll I), connective tissue growth factor (CTGF), and α-smooth muscle actin (α-SMA) in TGF-β1-induced KFs were suppressed by si-FOXM1 transfection. Furthermore, TGF-β1-induced increase in p-Smad2 and p-Smad3 expressions was attenuated by FOXM1 knockdown. These data indicated that knockdown of FOXM1 inhibited TGF-β1-induced KFs activation and extracellular matrix (ECM) accumulation, which was attributed to the inhibition of TGF-β1/Smad pathway.