Pulmonary fibrosis may occur after occupational exposure to silica and asbestos or without an identifiable cause, as in Idiopathic Pulmonary Fibrosis (IPF). Unfortunately, there is no effective therapy for these disorders. It is thought tha nonresolving lung injury results in excessive production of fibrogenic growth factors, such as TGF-, which drive progressive fibrosis. Exciting preliminary studies from my laboratory have revealed that genetic deficiency of PTP prevents pulmonary fibrosis in a murine model without altering the genesis or resolution of the acute inflammatory response. This specificity suggests that PTP, a transmembrane PTP with a targetable extracellular domain, could be a promising drug target for fibrosis and highlights the importance of determining how PTP promotes lung fibrosis. We have also discovered that PTP enhances TGF- responsiveness in fibrogenic signaling pathways in the lung. Using reciprocal bone marrow chimeras, we determined that PTP-/- lung resident cells and not bone marrow-derived cells, confer the protective phenotype. However, the limitations imposed by the currently available globally gene-deficient mice prevent us from determining which lung resident cells are responsible for this phenotype. This information is critical to delineate the molecular mechanisms by which PTP selectively drives fibrosis in the lung. We hypothesize that PTP promotes pulmonary fibrosis by augmenting profibrotic TGF- signals in lung fibroblasts.
Aim 1 is to generate mice in which PTP is selectively deleted in either fibroblasts or alveolar type (AT)II epithelial cells. We have purchased B6/N ES cell lines with a targeted PTP allele from EUCOMM and used these to generate chimeric mice that will be mated to generate mice with a floxed PTP allele (PTPf/f). To generate a fibroblast-specific deletion of PTP, we will cross PTPf/f mice with Col12-Cre mice. To generate ATII-specific deletion of PTP, we will cross PTPf/f mice with Sftpc-Cre mice. We will determine whether PTP promotes TGF--induced profibrotic signaling in cultured fibroblasts and ATII cells isolated from these mice.
Aim 2 is to determine the importance of PTP in lung fibroblasts or ATII cells in promoting pulmonary fibrosis using cell type-specific gene-targeted mice. We will compare the severity of pulmonary fibrosis in three models: intratracheal instillation of (i) bleomycin, (ii) silica, or (iii) adenovirus expressing active TGF in mice that are genetically deficient in PTP in either fibroblasts (Col12-Cre/PTPf/f) or ATII cells (Sftpc-Cre/PTPf/f). This high impact approach will enable us to determine whether PTP controls TGF- dependent profibrotic signaling in fibroblasts or ATII cells and will also provide a valuable resource for the community. Knowledge gained from these studies will ultimately be used to develop pharmacological or biological approaches to treat individuals (construction workers, first responders) who are inadvertently exposed to fibrogenic agents such as silica-containing dust to prevent progressive pulmonary fibrosis.
Pulmonary fibrosis (scarring of the lung) is a progressive and ultimately fatal disorder for which there is currently no effective therapy. We have discovered that protein tyrosine phosphatase (PTP)?, an enzyme expressed in lung cells, promotes pathways leading to scarring in the lung by enhancing profibrotic responses to the growth factor TGF-?. Mice that are genetically deficient in PTP? are protected from lung fibrosis but the limitations imposed by the currently available globally gene-deficient mice prevent us from determining which lung resident cells are responsible for this phenotype. We propose to generate mice that are deficient in PTP? in either fibroblasts or lung epithelial cells. Knowledge gained from the proposed studies will ultimately be used to develop pharmacological or biological approaches to treat pulmonary fibrosis in humans.
