Lung Fibrosis in an Hermansky-Pudlak Syndrome Mouse Model

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DESCRIPTION (provided by applicant): Hermansky Pudlak Syndrome (HPS) is a rare, but serious genetic disorder of partial albinism with pleiotropic effects on platelet dense bodies, melanosomes, and lysosome-related organelles. While effects on platelets and melanosomes are generally moderate or clinically manageable, progressive pulmonary fibrosis (HPS interstitial pneumonia, or HPSIP) can be a consequence of this disorder, which is debilitating and results in premature death. The long-term objective of this project is to establish the authenticity of an animal model for HPS lung fibrosis that will be useful for testing possible therapeutic interventions. A double homozygous HPS mouse model (C57BL/6-HPS1ep Ap3b1pe-J) that mimics human HPS lung abnormalities, especially enlarged surfactant bearing lysosome-like organelles of the alveolar type II cells, will be used in these studies. Preliminary studies with this mutant in our laboratory have shown that some, but not all older animals raised in an open colony develop fibrotic lesions in the lung, and that classical markers of fibrosis including Masson's trichrome staining and hydroxyproline levels show deposition of collagen in young as well as older animals of this strain. We have also shown increased levels of TGF-(1 in bronchial alveolar lavage (BAL) samples from these mice and highly activated alveolar macrophages in cultures of these cells from BAL samples. Specific aims in these studies include the use of high-dose continuous infusion of bleomycin to produce progressive lung fibrosis in this strain, assessment of the biological properties of the morphologically activated alveolar macrophages, and a detailed analysis of apoptosis in the lungs of this HPSIP mouse model using ELISA and immunohistochemisty methods. Results from the double mutant animals will be compared with age matched C57BL/6J+/+ and C57BL/6-Lystbg/Lystbg-J beige mutants. The latter strain shares a dysmorphic alveolar type II cell abnormality with the HPS double mutant, but not alveolar macrophage abnormalities, the development of sporadic cases of pulmonary fibrosis, or increasing levels of collagen with aging. The results from these investigations will determine the authenticity of the C57BL/6-HPS1ep Ap3b1pe-J mouse strain as an animal model for HPS lung fibrosis. Project Narrative: Hermansky-Pudlak Syndrome (HPS) is a rare, heterogeneous genetic disorder affecting lysosome-related organelles, including melanosomes, platelet dense bodies, and alveolar type II epithelial cells. The most challenging and life-threatening aspect of this heritable disease is its effect on the lungs, which results in pulmonary fibrosis in most cases of HPS1 individuals. An HPS mouse that is homozygous recessive for two HPS genes affecting separate pathways of vesicle trafficking, C57BL/6- HPS1ep/ HPS1ep; HPS2Apb3pe/ HPS2Apb3pe-J, has been used in this laboratory as a model for the human disorder, and some animals develop lung fibrosis at late ages when raised in an open colony. The proposed studies investigate whether this model can be made more useful by inducing pulmonary fibrosis in young animals that better mimics the progressive, ultimately fatal disorder in affected humans. Studies of the highly activated alveolar macrophages seen in the double mutant HPS mouse model are also planned that will provide a better understanding of their possible role in early inflammation of the lung, as well as studies of apoptosis in the lungs of this HPS model. These investigations will yield insights on a mouse model for HPS that should help in assessing possible therapeutic strategies for overcoming progressive pulmonary fibrosis.