Inhibition of transforming growth factor-β type I receptor signaling by RNA interference suppresses the proliferation, collagen synthesis, and inflammation factors in human embryonic lung fibroblasts

Transforming growth factor-beta 1 (TGF-beta 1) is an important mediator of pulmonary fibrosis. The purpose of this study was to determine whether small interference RNA (siRNA) directed to the transforming growth factor-beta type I receptor (T beta RI) could be used to suppress the action of TGF-beta 1 in human embryonic lung fibroblasts (HELF). Here we constructed 4 specific recombinant lentivirus vectors, targeting the T beta RI gene to transfect the HELF. We observed their effects on T beta RI expression using real-time PCR and Western blot. The HELF were stimulated with TGF-beta 1 after transfection with lentivirus vectors. The expression of p-Smad3 was measured using Western blot. The proliferation activity of the HELF was determined with an MTT assay, the cell cycle was analyzed using flow cytometry, the collagen expression was observed with Sirius Red staining, the expression of alpha-smooth muscle actin (alpha-SMA) was measured using RT-PCR, and the supernatant tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), collagen I and collagen III levels were measured with ELISA testing. We found that T beta RI siRNA abrogated the receptor transcription and protein expression in growing HELF. The lentivirus-mediated siRNA targeting the T beta RI gene could inhibit the activation of HELF and the expression of p-Smad3 stimulated by TGF-beta 1, and effectively suppressed its effects on cell proliferation, the cell cycle, collagen synthesis, alpha-SMA, collagen I, collagen III, TNF-alpha and IL-6 expression in HELF. T beta RI-specific siRNAs were efficacious in knocking down TGF-beta 1 action in vitro. Application of siRNA in HELF to downregulate T beta RI expression may provide a novel therapy for preventing pulmonary inflammation and fibrosis.