Oana V. Amarie

WNT1-inducible signaling protein–1 mediates pulmonary fibrosis in mice and is upregulated in humans with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by distorted lung architecture and loss of respiratory function. Enhanced (myo)fibroblast activation, ECM deposition, and alveolar epithelial type II (ATII) cell dysfunction contribute to IPF pathogenesis. However, the molecular pathways linking ATII cell dysfunction with the development of fibrosis are poorly understood. Here, we demonstrate, in a mouse model of pulmonary fibrosis, increased proliferation and altered expression of components of the WNT/beta-catenin signaling pathway in ATII cells. Further analysis revealed that expression of WNT1-inducible signaling protein-1 (WISP1), which is encoded by a WNT target gene, was increased in ATII cells in both a mouse model of pulmonary fibrosis and patients with IPF. Treatment of mouse primary ATII cells with recombinant WISP1 led to increased proliferation and epithelial-mesenchymal transition (EMT), while treatment of mouse and human lung fibroblasts with recombinant WISP1 enhanced deposition of ECM components. In the mouse model of pulmonary fibrosis, neutralizing mAbs specific for WISP1 reduced the expression of genes characteristic of fibrosis and reversed the expression of genes associated with EMT. More importantly, these changes in gene expression were associated with marked attenuation of lung fibrosis, including decreased collagen deposition and improved lung function and survival. Our study thus identifies WISP1 as a key regulator of ATII cell hyperplasia and plasticity as well as a potential therapeutic target for attenuation of pulmonary fibrosis.

Temporal and spatial regulation of bone morphogenetic protein signaling in late lung development.

Bone morphogenetic proteins (BMPs) play important roles in early lung development. No study to date has addressed a role for BMP signaling in late lung development. We describe changes in the expression and localization of BMP receptors (Bmpr1a, Bmpr1b, and Bmpr2) and Smad (Smad1, Smad4, Smad5, and Smad8) intracellular signaling proteins during the saccular and alveolarization stages of late lung development. BMP signaling, assessed by Smad1/5 phosphorylation, nuclear translocation, and induction of id1, id2, and id3 gene expression, was evident throughout late lung development. Our data indicate that BMP signaling is active during late lung development, and points to roles for the BMP system in septal and vascular development, and in the homeostasis of the epithelial layer of large conducting airways in the mature lung. Developmental Dynamics 236:2825–2835, 2007.

Wnt-inducible protein (WISP-1) is a key regulator of alveolar epithelial cell hyperplasia in pulmonary fibrosis

Fibrotic lung disease is characterized by distorted lung architecture and severe loss of respiratory function secondary to alveolar epithelial cell (AEC) hyperplasia, enhanced extracellular matrix (ECM) deposition and fibroblast proliferation. Repetitive epithelial injuries with impaired alveolar wound healing and altered AEC gene expression represent a trigger mechanism for development of fibrosis. To reveal gene regulatory networks in lung fibrosis, we compared gene expression profiles of freshly isolated AEC obtained from mice 14 days after saline or bleomycin (BM) instillation using whole genome microarray analysis. Several genes of the Wnt signaling pathway, in particular WISP-1, a member of the CCN family, were highly regulated. WISP-1 protein expression was demonstrated in proliferating AEC in BM-treated lungs by immunofluorescence. When analyzing all six CCN family members, WISP-1 was upregulated the most 14 days after BM challenge, as analyzed by qRT-PCR. To elucidate WISP-1 function, cultured primary mouse AEC were stimulated with WISP-1 and demonstrated a 230% increase in proliferation, analyzed by 3H-thymidine incorporation. This was mediated through enhanced phosphorylation, but not expression of protein kinase B (PKB/Akt), as detected by immunoblot. Finally, increased expression of WISP-1 was detected in lung homogenates and isolated AEC from IPF patients, using qRT-PCR. Immunohistochemical analysis of WISP-1 and Ki67 verified the existence of hyperplastic and proliferative AEC expressing WISP-1 in vivo. Our study thus identifies WISP-1 as a novel regulator of AEC injury and repair, and suggests that WISP-1 is a key mediator in pulmonary fibrosis.