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Age-dependent decline in lung regeneration with loss of clonogenicity and myofibroblastic differentiation of lung fibroblasts

ABSTRACT: While aging leads to a reduction in the capacity for regeneration after pneumonectomy (PNX) in most mammals, this biological phenomenon has not been characterized over the lifetime of mice. We measured the age-specific (3, 9, 24 month) effects of PNX on physiology, morphometry, cell proliferation and apoptosis, global gene expression, and lung fibroblast phenotype and clonogenicity in female C57BL6 mice. The data show that only 3 month old mice were fully capable of restoring lung volumes by day 7 and total alveolar surface area. By 9 months, the rate of regeneration was slower (with incomplete regeneration by 21 days), and by 24 months there was no regrowth 21 days post-PNX. The early decline in regeneration rate was not associated with changes in alveolar epithelial cell type II (AECII) proliferation or apoptosis rate. However, significant apoptosis and lack of cell proliferation was evident after PNX in both total cells and AECII cells in 24 mo mice. Analysis of gene expression at several time points (1, 3 and 7 days) post-PNX in 3 versus 9 month mice was consistent with a myofibroblast signature (increased Tnc, Lox1, Col3A1, Eln and Tnfrsf12a) and more alpha smooth muscle actin (αSMA) positive myofibroblasts were present after PNX in 9 month than 3 month mice.

ORGANISM(S): Mus musculus

PROVIDER: GSE27964 | GEO | 2011/03/16

SECONDARY ACCESSION(S): PRJNA137755

REPOSITORIES: GEO

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Project description:While aging leads to a reduction in the capacity for regeneration after pneumonectomy (PNX) in most mammals, this biological phenomenon has not been characterized over the lifetime of mice. We measured the age-specific (3, 9, 24 month) effects of PNX on physiology, morphometry, cell proliferation and apoptosis, global gene expression, and lung fibroblast phenotype and clonogenicity in female C57BL6 mice. The data show that only 3 month old mice were fully capable of restoring lung volumes by day 7 and total alveolar surface area. By 9 months, the rate of regeneration was slower (with incomplete regeneration by 21 days), and by 24 months there was no regrowth 21 days post-PNX. The early decline in regeneration rate was not associated with changes in alveolar epithelial cell type II (AECII) proliferation or apoptosis rate. However, significant apoptosis and lack of cell proliferation was evident after PNX in both total cells and AECII cells in 24 mo mice. Analysis of gene expression at several time points (1, 3 and 7 days) post-PNX in 3 versus 9 month mice was consistent with a myofibroblast signature (increased Tnc, Lox1, Col3A1, Eln and Tnfrsf12a) and more alpha smooth muscle actin (αSMA) positive myofibroblasts were present after PNX in 9 month than 3 month mice. Microarray analyses of mRNA expression patterns were performed on lung tissue from 9 month versus 3 month mice, before and after PNX. First, gene expression was compared in whole lungs tissues of young (3 month) vs. middle age (9 month) animals obtained at surgery (left, control lung). Second, the global gene expression responses of 3 vs. 9 mo mice were compared after PNX (1, 3 and 7 days) in the right lung. For each animal in the surgical study, the left (excised) lung lobe was used as a control for the corresponding right lung at the end of the study. This design was intended to increase the statistical power for detecting differences in gene expression by comparing pre- and post-PNX lung tissue from the same biological pools (2 animals/pool, 3 pools per group).

Project description:Background: Pneumococcal secondary infection following influenza A virus (IAV) pneumonia is a synergistic complication with high mortality. While varying invasiveness of pneumococcal serotypes is an important pathogenic factor, serotype-specifc immediate-early transcriptional responses of the IAV-perturbed alveolar epithelium have not been adressed. We comprehensively analyzed gene transcription in alveolar type II epithelial cells (AECII) isolated from mice infected with IAV and/or S. pneumoniae (S.pn.) serotypes 4, 7F and 19F. Results: IAV, 14 days post infection, rendered the lung susceptible to invasive secondary S.pn. infection with serotypes 4 and 7F but not 19F. Only secondary 7F infection induced exacerbated cytokine/chemokine responses. IAV/7F infection induced superior protein expression of type I and II interferons, acesserbated expression in IAV/serotype 4 infection. Inference of a scale-free-like ARACNE gene co-expression network revealed interferon-response network modules in AECII and network-mapping unfolded S.pn. serotype-specific transcriptional network responses/usage. Secondary S.pn. infection abrogated the IAV-induced pneumocyte proliferative configuration and preceeding IAV infection rendered the transcriptional response to 7F infection comparable to that towards serotype 4. This related especially to network genes correlating with the expression of two master regulators of interferon responses: Irf7 and Stat1. Epigenetic ATAC-seq analysis of AECII in resolved IAV infection identified enhanced expression of ARACNE network genes Hist1h2bf, Igtp, Mki67, Rasl10b, H2-Q6 and H2-Q7 to be associated with increased chromatin accessability at promoter regions. Conclusions: We show that AECII sustainably retain an IAV-associated transcriptional configuration with epigenetic involvement, that serotype-specifically affects proliferation and accelerates and enhances the AECII transcriptional response, mainly to interferons, in secondary S.pn. infection.

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Age-dependent decline in lung regeneration with loss of clonogenicity and myofibroblastic differentiation of lung fibroblasts

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