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Idiopathic Pulmonary Fibrosis (IPF) is a progressive fibrosing lung disease for which treatment remains suboptimal. Fibrogenic cytokines, including transforming growth factor-β, are central to its pathogenesis. Protein Tyrosine Phosphatase-alpha (PTPα) has emerged as a key regulator of fibrogenic signaling in fibroblasts. We have reported that mice globally deficient in PTPα (Ptpra-/-) were protected from experimental pulmonary fibrosis, in part via alterations in TGF-β signaling. The goal of this study was to determine the lung cell types and mechanisms by which PTPα controls fibrogenic pathways and whether these pathways are relevant to human disease. Immunohistochemical analysis of lungs from IPF patients revealed that PTPα was highly expressed by mesenchymal cells in fibroblastic foci and by airway and alveolar epithelial cells. To determine whether PTPα promotes profibrotic signaling pathways in lung fibroblasts and/or epithelial cells, we generated mice with conditional (floxed) Ptpra alleles (Ptpraf/f). These mice were crossed with Dermo1-Cre or with Sftpc-CreERT2 mice to delete Ptpra in mesenchymal cells and alveolar type (AT) II cells, respectively. Dermo1-Cre/Ptpraf/f mice were protected from bleomycin-induced pulmonary fibrosis, while Sftpc-CreERT2/Ptpraf/f mice developed pulmonary fibrosis equivalent to controls. Both canonical and non-canonical TGF-β signaling and downstream TGF-β-induced fibrogenic responses were attenuated in isolated Ptpra-/- compared to wild type fibroblasts. Further, TGF-β-induced tyrosine phosphorylation of TGF-βRII and of PTPα was attenuated in Ptpra-/- compared to WT fibroblasts. The phenotype of cells genetically deficient in PTPα was recapitulated with the use of a Src inhibitor. These findings suggest that PTPα amplifies pro-fibrotic TGF-β-dependent pathways signaling in lung fibroblasts.

The Acute Respiratory Distress Syndrome (ARDS) is a major healthcare problem, accounting for significant mortality and long-term disability. Approximately 25% of patients with ARDS will develop an over-exuberant fibrotic response, termed fibroproliferative ARDS (FP-ARDS) that portends a poor prognosis and increased mortality. The cellular pathologic processes that drive FP-ARDS remain incompletely understood. We have previously shown that the transmembrane receptor-type tyrosine phosphatase Protein Tyrosine Phosphatase-a (PTPa) promotes pulmonary fibrosis in preclinical murine models through regulation of TGF-b signaling. In this study, we examine the role of PTPa in the pathogenesis of FP-ARDS in a preclinical murine model of acid (HCl)-induced acute lung injury. We demonstrate that while mice genetically deficient in PTPa (Ptpra-/-) are susceptible to early HCl-induced lung injury, they exhibit markedly attenuated fibroproliferative responses. Additionally, early pro-fibrotic gene expression is reduced in lung tissue after acute lung injury in Ptpra-/- mice, and stimulation of naïve lung fibroblasts with the BAL fluid from these mice results in attenuated fibrotic outcomes compared to wild type littermate controls. Transcriptomic analyses demonstrates reduced Extracellular Matrix (ECM) deposition and remodeling in mice genetically deficient in PTPa. Importantly, human lung fibroblasts modified with a CRISPR-targeted deletion of PTPRA exhibit reduced expression of profibrotic genes in response to TGF-β stimulation, demonstrating the importance of PTPa in human lung fibroblasts. Together, these findings demonstrate that PTPa is a key regulator of fibroproliferative processes following acute lung injury and could serve as a therapeutic target for patients at risk for poor long-term outcomes in ARDS.

After radio- and chemo-therapy, human tumors display many dead eukaryotic cells with pyknotic nuclei. But amitotic metakaryotic cells with hollow, bell-shaped nuclei appear unaffected as expected of treatment-resistant cancer stem cells. These same phenomena may be observed in vitro using any of many tumor- or metastasis-derived cell lines, for which their immortality is conferred by the presence of amitotic, metakaryotic cancer stem cells. About 5% of human colonic adenocarcinoma-derived HT-29 cells in exponential growth are immortal metakaryotic stem cells that increase by symmetric amitoses and continuously create mortal mitotic eukaryotic cells by asymmetric amitoses. Two assays for agents/conditions lethal to metakaryotic stem cells have been devised: (1) microscopic recognition of necrotic metakaryotic nuclei; and (2) survival of cells forming large immortal colonies visibly containing metakaryotic stem cells in vitro. X-rays and chemotherapeutic agents (i.e., alkylating agents, antimetabolites, and mitocides) kill eukaryotic cells, but not metakaryotic cells, at doses commonly used in cancer therapy. In contradistinction, multiple classes of common drugs are preferentially cytotoxic to metakaryotic stem cells including NSAIDS, antibiotics, and drugs used to treat diabetes or hypertension. Given lesion penetration and treatments of sufficient duration, regimens using multiple metakaryocidal drugs offer means to treat and prevent cancers.