A gene expression signature of emphysema-related lung destruction and its reversal by the tripeptide GHK

Abstract

BackgroundChronic 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.MethodsIn 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 × 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.ResultsWe 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 (TGFβ) 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 TGFβ pathway activation. Treatment of human fibroblasts with GHK recapitulated TGFβ-induced gene-expression patterns, led to the organization of the actin cytoskeleton, and elevated the expression of integrin β1. Furthermore, addition of GHK or TGFβ restored collagen I contraction and remodeling by fibroblasts derived from COPD lungs compared to fibroblasts from former smokers without COPD.ConclusionsThese 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 TGFβ and GHK each reverse the gene-expression signature of emphysematous destruction and the effects of this reversal on disease progression.

Small Airways Disease in Chronic Obstructive Pulmonary Disease: A 50 Years History

“…That these gene expression changes may have functional consequences in that fibroblasts from ex-smokers with severe COPD showed the deficient formation of focal adhesions and reduced ability to contract collagen-I gels compared to fibroblasts from former smokers without COPD 48 . Moreover, these findings have been replicated by other groups 9,49 . Fibrillar collagens, such as collagen I form, nanoscale ropes that are essential for providing tensile strength within the tissue, also act as a scaffold for elastic fibres as well as fibronectin, decorin, and associated proteins in the ECM.…”

Personalized Management of Chronic Obstructive Pulmonary Disease via Transcriptomic Profiling of the Airway and Lung

“…GHK treatment of a disease-relevant in vitro model was found to induce TGF-b pathway gene expression and reverse emphysema-associated gene expression patterns. Furthermore, treatment with either GHK or TGF-b restored collagen I contraction and remodeling in cultured fibroblasts from patients with COPD (16). This example highlights the usefulness of coupling pathway-based and compoundbased approaches to develop relevant therapeutics capable of impacting diseaserelated phenotypes.…”

“…Using multiple samples obtained from a lung, each taken from a region with different emphysema severity, a 127-gene expression signature of regional (16). Similar approaches leveraging the clinical heterogeneity of COPD might lead to even more insights about the molecular mechanisms underlying these different disease-associated phenotypes and potential novel therapeutics targeted to these different subtypes of the disease.…”

“…Using curated pathway lists from publicly available sources (37), gene expression profiles associated with regional emphysema severity were enriched in genes in the TGF-b pathway (16). In parallel analysis of the Connectivity Map, the gene expression signature of the tripeptide compound GHK was found to be the inverse of the emphysema gene expression signature, suggesting that it might serve as a potential therapy for this disease (16). GHK treatment of a disease-relevant in vitro model was found to induce TGF-b pathway gene expression and reverse emphysema-associated gene expression patterns.…”

“…Emphysema, or destruction of the alveolar septal walls without fibrosis (15) leading to overinflation and impairment in gas exchange, occurs in varying amounts among patients with airflow obstruction due to COPD. Furthermore, the degree of emphysema varies regionally within the lungs of smokers with COPD, representing the complex relationship between cigarette smoking and resultant lung disease related to emphysema (16). Additionally, there is cellular heterogeneity within lung tissue samples from smokers with COPD, with a larger extent of inflammation by neutrophils, macrophages, B lymphocytes, and CD4 cells in lung tissue from patients with more severely impaired FEV 1 .…”