Prodrug BMP-7 attenuates pulmonary fibrosis through downregulation of bone marrow derived ApoE+ alveolar macrophage

Background: Bone morphogenetic protein-7 (BMP-7) antagonises transforming growth factor-β (TGF-β). This study investigated the ability of a prodrug BMP-7, designed as micelle nanoparticles for nasal inhalation, to ameliorate pulmonary fibrosis in a bleomycin (BLM)-induced murine model. Materials and Methods: Fluorescently labelled BMP-7 was delivered to murine lungs via nasal inhalation. Thirty-eight C57BL/6J mice were divided into three groups: control, BLM and BLM with prodrug BMP-7. We then administered the prodrug BMP-7 and vehicle nasally every 72 hours for 21 days. Single-cell RNA sequencing was performed on bronchoalveolar lavage fluid (BALF) from 18 mice, divided into four groups: control, prodrug BMP-7 alone, BLM and BLM with prodrug BMP-7, to assess effects on alveolar macrophages (AM). The expression of ApoE+ AM was compared between normal and idiopathic pulmonary fibrosis (IPF) patients. Results: The prodrug BMP-7 group showed reduced BALF inflammatory cells and significant fibrosis reduction compared to the BLM group. Western blot showed decreased levels of collagen I, α-SMA and fibronectin in the prodrug BMP-7 group, along with downregulation of TGF-β/SMAD signalling. ELISA indicated decreased levels of chemokines CXCL10 and CXCL2 in tissue and BALF. Single-cell RNA sequencing revealed a significant increase in bone marrow-derived ApoE+ AM in the BLM group, which was reduced with prodrug BMP-7. Additionally, ApoE+ expression was higher in IPF patients compared to controls. Conclusions: Prodrug BMP-7 shows potential as a therapeutic agent for pulmonary fibrosis by modulating ApoE+ AM.