Effects of the fibroblast activation protein inhibitor, PT100, in a murine model of pulmonary fibrosis

Bleomycin (BLM) induced lung injury is detectable in C57BL/6 mice using magnetic resonance imaging (MRI). We investigated the effects of the fibroblast activation protein (FAP) inhibitor, PT100, in this model. BLM (0.5 mg/kg/day) was administered on days −7, −6, −5, −2, −1, 0 in the nostrils of male mice. PT100 (40 µg/mouse) or vehicle (0.9%NaCl) was dosed per os twice daily from day 1–14. MRI was performed before BLM and at days 0, 7 and 14. After the last MRI acquisition, animals were euthanised and the lungs harvested for histological and quantitative real-time polymerase chain reaction (qRT-PCR) analyses. As evidenced longitudinally by MRI, the BLM-elicited lesions in the lungs of vehicle-treated mice progressed over time. In contrast, responses elicited by BLM did not progress in animals receiving PT100. Histology demonstrated significant less fibrosis in PT100- than in vehicle-treated, BLM-challenged mice. Significant correlation (R=0.91, P