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B1 integrin regulates epithelial proliferation and cell shape during alveolar repair

ABSTRACT: Integrins are extracellular matrix receptors comprised of an a and b subunit that connect and mediate signaling between cells and the surrounding matrix. In organogenesis of epithelial tissues, the b1 integrin subunit regulates essential epithelial cell functions, but the role of b1 integrin in epithelial repair is poorly understood. To define the role of b1 integrin during alveolar repair, we challenged b1 integrin deficient mice with intratracheal lipopolysaccharide, resulting in increased mortality with emphysematous lungs 21 days following injury. The alveolar barrier was repopulated with an overabundance of type 2 alveolar epithelial cells, with reduced numbers of elongated alveolar type 1 cells, suggesting b1 integrin is required for type 2 to type 1 epithelial transition. Consistent with this finding, b1 deficient type 2 epithelial cells proliferated at increased rates throughout repair, lacked actin-rich cellular protrusions necessary for lateral cellular extension, and exhibited transcriptomic dysregulation of adherens junction and actin polymerization pathways. Finally, we show that b1 integrin balances actin polymerization versus stabilization through GTPase activation. Taken together, these data support a novel role for b1 integrin in re-establishing the alveolar niche after injury through modulation of type 2 epithelial cell proliferation and cytoskeletal-dependent cell shape change.

ORGANISM(S): Mus musculus

PROVIDER: GSE205882 | GEO | 2023/06/10

REPOSITORIES: GEO

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Project description:BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease consisting of emphysema, small airway obstruction, and/or chronic bronchitis that results in significant loss of lung function over time. METHODS: In order to gain insights into the molecular pathways underlying progression of emphysema and explore computational strategies for identifying COPD therapeutics, we profiled gene expression in lung tissue samples obtained from regions within the same lung with varying amounts of emphysematous destruction from smokers with COPD (8 regions x 8 lungs = 64 samples). Regional emphysema severity was quantified in each tissue sample using the mean linear intercept (Lm) between alveolar walls from micro-CT scans. RESULTS: We identified 127 genes whose expression levels were significantly associated with regional emphysema severity while controlling for gene expression differences between individuals. Genes increasing in expression with increasing emphysematous destruction included those involved in inflammation, such as the B-cell receptor signaling pathway, while genes decreasing in expression were enriched in tissue repair processes, including the transforming growth factor beta (TGF beta) pathway, actin organization, and integrin signaling. We found concordant differential expression of these emphysema severity-associated genes in four cross-sectional studies of COPD. Using the Connectivity Map, we identified GHK as a compound that can reverse the gene-expression signature associated with emphysematous destruction and induce expression patterns consistent with TGF beta pathway activation. Treatment of human fibroblasts with GHK recapitulated TGF beta-induced gene-expression patterns, led to the organization of the actin cytoskeleton, and elevated the expression of integrin beta1. Furthermore, addition of GHK or TGF beta restored collagen I contraction and remodeling by fibroblasts derived from COPD lungs compared to fibroblasts from former smokers without COPD. CONCLUSIONS: These results demonstrate that gene-expression changes associated with regional emphysema severity within an individualÂ¿s lung can provide insights into emphysema pathogenesis and identify novel therapeutic opportunities for this deadly disease. They also suggest the need for additional studies to examine the mechanisms by which TGF beta and GHK each reverse the gene-expression signature of emphysematous destruction and the effects of this reversal on disease progression. Paired samples were obtained from 8 regions at regular intervals between the apex and base of each explanted lung from six patients with severe COPD and two donors. The degree of emphysematous destruction was quantified in one sample from each region by mean linear intercept (Lm), while gene expression was profiled in the adjacent sample from the same region using the Affymetrix Human Exon 1.0 ST GeneChip. Human fibroblast cell lines (HLF-1) were treated with GHK or TGF-Beta1 for 48 hours and profiled using the Affymetrix Human Gene 1.0 ST GeneChip.

Project description:BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease consisting of emphysema, small airway obstruction, and/or chronic bronchitis that results in significant loss of lung function over time. METHODS: In order to gain insights into the molecular pathways underlying progression of emphysema and explore computational strategies for identifying COPD therapeutics, we profiled gene expression in lung tissue samples obtained from regions within the same lung with varying amounts of emphysematous destruction from smokers with COPD (8 regions x 8 lungs = 64 samples). Regional emphysema severity was quantified in each tissue sample using the mean linear intercept (Lm) between alveolar walls from micro-CT scans. RESULTS: We identified 127 genes whose expression levels were significantly associated with regional emphysema severity while controlling for gene expression differences between individuals. Genes increasing in expression with increasing emphysematous destruction included those involved in inflammation, such as the B-cell receptor signaling pathway, while genes decreasing in expression were enriched in tissue repair processes, including the transforming growth factor beta (TGF beta) pathway, actin organization, and integrin signaling. We found concordant differential expression of these emphysema severity-associated genes in four cross-sectional studies of COPD. Using the Connectivity Map, we identified GHK as a compound that can reverse the gene-expression signature associated with emphysematous destruction and induce expression patterns consistent with TGF beta pathway activation. Treatment of human fibroblasts with GHK recapitulated TGF beta-induced gene-expression patterns, led to the organization of the actin cytoskeleton, and elevated the expression of integrin beta1. Furthermore, addition of GHK or TGF beta restored collagen I contraction and remodeling by fibroblasts derived from COPD lungs compared to fibroblasts from former smokers without COPD. CONCLUSIONS: These results demonstrate that gene-expression changes associated with regional emphysema severity within an individual¿s lung can provide insights into emphysema pathogenesis and identify novel therapeutic opportunities for this deadly disease. They also suggest the need for additional studies to examine the mechanisms by which TGF beta and GHK each reverse the gene-expression signature of emphysematous destruction and the effects of this reversal on disease progression.

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B1 integrin regulates epithelial proliferation and cell shape during alveolar repair

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