RECK in Pulmonary Fibrosis

PROJECT SUMMARY/ABSTRACT: Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal lung disease, and there is a large unmet need for effective therapies. IPF is characterized by epithelial injury and subsequent aberrant activation of fibroblasts which lay down excessive extracellular matrix (ECM) proteins (e.g., collagen). ECM turnover/remodeling and activation of TGF-β1 (the master regulator of fibrosis, which is incorporated in ECM in a latent form) are regulated by a delicate balance between matrix metalloproteinases (MMPs) and their inhibitors, through interactions among cells such as epithelial cells, fibroblasts, and macrophages. Our recent data suggest that 1) reversion-inducing cysteine-rich protein with Kazal motifs (RECK), an MMP inhibitor, is significantly downregulated in human IPF lung samples, and this downregulation is correlated with reduced lung function; 2) RECK expression is downregulated in the lungs of mice treated with bleomycin, particularly in monocytes (but also in other types of cells such as epithelial cells and stromal cells); and 3) mice overexpressing RECK under the lysozyme 2 (Lyz2) promoter, which is widely used to target myeloid cells (including monocytes), recover from bleomycin-induced pulmonary fibrosis more quickly than their RECK wild- type controls. The mechanisms underlying how RECK influences progression and resolution of pulmonary fibrosis remain unknown. Based on our data, we hypothesize that RECK expressed in monocytes and other types of cells mediates resolution of fibrosis in a bleomycin-induced pulmonary fibrosis mouse model. We will test this hypothesis with two specific aims. In the first aim, we will determine the effects of myeloid-specific RECK overexpression on 1) temporal regulation of fibrosis, by measuring the amount of collagen accumulated in the lungs and assessing lung function over time; and 2) cytokine secretion, TGF-β1 activation, and fibroblast activation by monocytes/macrophages isolated from RECK wild-type mice and myeloid-specific RECK overexpression mice. In the second aim, we will determine the effects of global (cell-type non-specific) RECK overexpression on temporal regulation of fibrosis. We will compare the magnitude of fibrosis resolution between the myeloid-specific RECK overexpression mice and the global RECK overexpression mice, to determine the cell compartments that mediate fibrosis resolution via RECK. We will also determine the effects of RECK overexpression on lung transcriptome and the interactions between different types of cells, using single-cell RNA sequencing. We anticipate that we will reveal mechanisms whereby RECK expressed in monocytes and other types of cells promotes resolution of fibrosis and demonstrate the therapeutic potential of RECK overexpression for pulmonary fibrosis.