Abstract
[Background] Pulmonary fibrosis is considered a fatal respiratory disease characterized by scar formation associated with fibrotic lesion secondary to inflammation. There is still no effective drug for the treatment of pulmonary fibrosis that prolongs survival. Therefore, it is important to establish a new pulmonary fibrosis model as well as to discover a new therapeutic option. Currently, a single intratracheal instillation of bleomycin in mouse is used as the most common experimental model for pulmonary fibrosis. However, both incidence of fibrosis and mortality rate of mice largely vary in accordance with variations in dosage, which often limits research outputs. Here, we established a new pulmonary fibrosis model.
[Methods] We performed the left thoracotomy at the 6th and 7th intercostal space and injected 50 µl FeCl3 solution (0.8% in water) into the left upper lobe central part of mouse at 12 weeks of age, under anaesthesia with 1.5% isoflurane. After collecting the bronchoalveolar lavage fluid at designated days, the left lung lobe was dissected out and longitudinally cut into two pieces. Then, one was fixed, sectioned and analyzed by HE and MT stainings and immunofluorescent study, and the other was homogenized to prepare protein samples for western blot (WB).
[Results] At 3 days post-injection (dpi), moderate fibrosis was observed throughout the left lung, and analysis of BALF revealed that infiltration of neutrophils remarkably increased. At 10 dpi, severe fibrosis of the whole left lung was observed, which was supported by analysis of the modified Aschcroft scale and by WB and immunofluorescent study with anti-αSMA antibody. Notably, body weights of operated mice transiently decreased but recovered to the starting levels with or without the FeCl3 injection. Likewise, the FeCl3 treatment did not affect mortality of mice.
[Conclusion] The FeCl3 injection method efficiently and uniformly induces fibrosis at the target site with higher incidence, less mortality and shorter time period for fibrotic formation, compared with an existing bleomycin-induced pulmonary fibrosis mouse model. We will discuss the molecular mechanisms underlying pulmonary fibrosis induced by FeCl3.
(342 words/Abstract)
