Comparison of expression of napsin A and surfactant protein D in bleomycin-induced pulmonary fibrosis mouse model

Introduction :We have shown elevation of serum napsin A in patients with idiopathic pulmonary fibrosis (IPF), and suggest that napsin A may be a candidate biomarker for IPF. However, napsin A has not been confirmed as a marker for bleomycin-induced pulmonary fibrosis model. Objective : To confirm expression of napsin A in bleomycin-induced pulmonary fibrosis mouse model compared with that of surfactant protein D (SP-D). Methods : Pulmonary fibrosis was induced in C57BL/6J mice by intratracheal injection of 3.0 mg/kg of bleomycin. Five mice underwent bronchoalveolar lavage (BAL) and were sacrificed on 5 individual days, including before the injection (Day 0) and at 2, 7, 14, and 21 days after. The levels of napsin A and SP-D in BAL fluids and serum were measured by ELISA (Mouse Napsin-A kit, CUSABIO, China; Rat/Mouse SP-D kit YAMASA EIA, Yamasa, Japan). Lung tissues were used for immunohistochemistry (IHC) analysis. Result : Napsin A levels in BAL fluids were 119.01 ± 23.63 pg/ml for Day 0, 561.86 ± 178.53 pg/ml for Day 7, and 571.70 ± 279.18 pg/ml for Day 21. Napsin A levels in BAL fluids in bleomycin-induced model were significantly increased after Day 7 and were still detected on Day 21 (p<0.001). However serum napsin A levels showed no significant elevation. SP-D was significantly elevated in BALF fluids and serum (p<0.001). IHC analysis of bleomycin-induced model revealed elevated napsin A and SP-D in lung epithelial cells. Conclusion s: The present study demonstrated napsin A as a marker for bleomycin-induced pulmonary-fibrosis model in BAL fluids and lung tissues.