p53-miR-34a feedback in lung fibroblasts regulates antifibrotic effects of CSP7, nintedanib, and pirfenidone.

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by progressive and irreversible loss of lung function. CSP7 exerts antifibrotic effects on fibrotic lung (myo)fibroblasts, which are the primary effector cells in progressive pulmonary fibrosis (PF) via restoring p53-microRNA-34a-feedback induction. However, p53-microRNA-34a's role in the antifibrotic effects of nintedanib and pirfenidone has not been explored. We compared the effects of oral-gavage-fed standard-of-care antifibrotic drugs, nintedanib or pirfenidone, with CSP7 administered by intraperitoneal injection or via airway by dry powder inhalation against bleomycin-induced PF using wild type, p53 flox (p53^fl/fl), microRNA-34a flox (microRNA-34a^fl/fl), and tamoxifen inducible conditional knockout mice lacking p53 (p53^cKO) or microRNA-34a (miR-34a^cKO) expression in lung fibroblasts. Compared with wild type or p53^fl/fl or microRNA-34a^fl/fl mice, p53^cKO and miR-34a^cKO mice exhibited more severe post-bleomycin body weight and lung function loss, lower survival, and more extracellular matrix deposition. Although daily treatment of wild-type mice with CSP7 or with nintedanib or pirfenidone between days 14 and 21 post-bleomycin improved survival, body weight and lung function, combination of CSP7 with nintedanib or pirfenidone was more effective than either drug. Interestingly, p53^cKO- and miR-34a^cKO-PF mice resisted these treatments, supporting the importance of restoration of p53-miR-34a-feedback induction in lung (myo)fibroblasts for the antifibrotic effects.NEW & NOTEWORTHY Pulmonary fibrosis is a progressive and fatal fibroproliferative disease. The current drugs (nintedanib/pirfenidone) only slow clinical progression. Myofibroblasts are the primary effector cells of PF. We found that CSP7, nintedanib and pirfenidone exert antifibrotic effects through restoring p53-microRNA-34a feedback induction in lung (myo)fibroblasts. We further found that daily treatment of mice with CSP7/nintedanib/pirfenidone between days 14 and 21 post-bleomycin lung fibrosis improve survival, body weight and lung function, and combination therapy had added benefit.