Transforming growth factor-β1 small interfering RNA inhibits growth of human embryonic lung fibroblast HFL-I cells in vitro and defends against radiation-induced lung injury in vivo

In the present study, a human transforming growth factor-beta 1 (TGF-beta 1) small interfering RNA (siRNA) plasmid vector (TGF-beta 1-siRNA) was constructed to investigate its effects on the proliferation and differentiation of human lung fibroblasts in vitro and its interference effects on radiation-induced lung injury in vivo. Reverse transcription quantitative polymerase chain reaction and enzyme linked immunosorbent assay revealed that the mRNA and protein expression of TGF-beta 1 in the HFL-I cells were inhibited by TGF-beta 1-siRNA and flow cytometry demonstrated a significant increase in apoptosis of the HFL-I cells. Adult, female, specific-pathogen-free C57BL/6 mice were used in the in vivo animal investigations and were randomly divided into the four following groups: control without any treatment, radiation alone, radiation followed by empty vector transfection and radiation followed by TGF-beta 1-siRNA vector transfection. Hematoxylin and eosin and Van-Gieson staining revealed that certain radiation-induced histopathological changes of the lung, including inflammation, edema, the density of surface pulmonary interstitial collagen fibers in the alveolar septum, TGF-beta 1-positive reactions in alveolar epithelial cells and pulmonary interstitial macrophages were less marked in the mice transfected with TGF-beta 1-siRNA compared with the mice without transfection or those transfected with empty vectors. The serum levels of TGF-beta 1 levels in the irradiated mice increased significantly at four weeks and peaked at eight weeks after radiation, compared with the control. Serum levels of TGF-beta 1 in the irradiated mice transfected with TGF-beta 1-siRNA also increased gradually and a significant difference was observed compared with those irradiated without transfection. The mRNA expression levels of TGF-beta 1 in the mice transfected with TGF-beta 1-siRNA were markedly lower compared with those of the other radiation groups. The present study suggested that the TGF-beta 1-siRNA vector reduced the activity of TGF-beta 1 by downregulating the mRNA expression of TGF-beta 1 and thereby effectively suppressing inflammatory reactions and defending against radiation-induced lung injury.