Association of clonal hematopoiesis with chronic obstructive pulmonary disease

Abstract

Chronic obstructive pulmonary disease (COPD) is associated with age and smoking, but other determinants of the disease are incompletely understood. Clonal hematopoiesis of indeterminate potential (CHIP) is a common, age-related state in which somatic mutations in clonal blood populations induce aberrant inflammatory responses. Patients with CHIP have an elevated risk for cardiovascular disease, but the association of CHIP with COPD remains unclear. We analyzed whole-genome sequencing and whole-exome sequencing data to detect CHIP in 48 835 patients, of whom 8444 had moderate to very severe COPD, from four separate cohorts with COPD phenotyping and smoking history. We measured emphysema in murine models in which Tet2 was deleted in hematopoietic cells. In the COPDGene cohort, individuals with CHIP had risks of moderate-to-severe, severe, or very severe COPD that were 1.6 (adjusted 95% confidence interval [CI], 1.1-2.2) and 2.2 (adjusted 95% CI, 1.5-3.2) times greater than those for noncarriers. These findings were consistently observed in three additional cohorts and meta-analyses of all patients. CHIP was also associated with decreased FEV1% predicted in the COPDGene cohort (mean between-group differences, -5.7%; adjusted 95% CI, -8.8% to -2.6%), a finding replicated in additional cohorts. Smoke exposure was associated with a small but significant increased risk of having CHIP (odds ratio, 1.03 per 10 pack-years; 95% CI, 1.01-1.05 per 10 pack-years) in the meta-analysis of all patients. Inactivation of Tet2 in mouse hematopoietic cells exacerbated the development of emphysema and inflammation in models of cigarette smoke exposure. Somatic mutations in blood cells are associated with the development and severity of COPD, independent of age and cumulative smoke exposure.

Graphical abstract

Figure 1.

Distribution of clonal hematopoietic mutations in studied cohorts. Clonal hematopoietic mutations were identified from sequencing of whole genomes (COPDGene, additional TOPMed cohorts) or exomes (ICGN-EOCOPD, UK Biobank) found in samples of peripheral blood. Shown are the 10 most frequently mutated genes in COPDGene. N represents the number of CHIP carriers identified in each cohort. In patients with multiple mutations, the mutated gene with the largest variant allele frequency is shown.

Figure 2.

Association between CHIP status and COPD. Forest plots showing logistic regression results for association between CHIP status and (A) GOLD 2-4 and (B) GOLD 3-4 COPD among all patients. (C) Forest plot showing logistic regression results for association between CHIP status and severity (GOLD 3-4) among patients with GOLD 2-4 COPD. The arrowhead indicates that the limit of the CI is beyond the range annotated on the OR axis at the bottom. Note that the CIs listed for all cohorts are unadjusted. RE, random effects; WGS, whole-genome sequencing.

Figure 3.

Association between CHIP status and FEV₁%p. Forest plots showing linear regression results of association between CHIP status and FEV₁%p (A) across all patients and (B) restricted to those with GOLD 2-4 COPD. Note that the CIs listed for all cohorts are unadjusted. MD, mean difference (%).

Figure 4.

Effect of hematopoietic Tet2 KO on emphysema development. (A) Schematic of experimental approach for mice treated with CS and poly(I:C). (B) Representative images of airspace destruction (Gill’s stain imaged at ×10 magnification) in Tet2 WT and Tet2 KO mice (left) and quantification of emphysema in Tet2 WT (n = 10) and Tet2 KO (n = 10) mice exposed to CS and poly(I:C). Error bars indicate standard error of the mean. (C) UMAP visualization of single-cell RNA sequencing data shows clustering of 25 cell types that were identified in the lungs of Tet2 WT and Tet2 KO mice. (D) Assessment of signature scores in the single-cell transcriptional data of mice exposed to CS and poly(I:C) across all cells for IFN and tumor growth factor β (TGFB) gene sets obtained from Hallmark (H), Reactome (R), Biocarta (B), KEGG (K), or Wikipathways (W). A positive value (blue) represents higher scores in Tet2 WT (WT), and a negative value (orange) reflects higher scores in Tet2 KO mice. The P values were calculated using a Wilcoxon test and adjusted (adj) using a Bonferroni correction. (E-F) For each cluster of cells, the mean of cell signature scores for (E) IFN-α and (F) IFN-γ was determined and plotted for Tet2 WT (y-axis) and Tet2 KO (x-axis) animals. Clusters above the line of identity are enriched for the signature in Tet2 WT mice; clusters that fall below are enriched for the signature in Tet2 KO mice. Clusters in red have significantly higher scores in Tet2 KO mice with the size of each cluster representing the significance of difference between the Tet2 KO and Tet2 WT groups. AM, alveolar macrophage; AT1, alveolar type 1; AT2, alveolar type 2; CEC, circulating endothelial cell; DC, dendritic cell; DN, double negative; EC, endothelial cell; IM, interstitial macrophage; LEC, lymphatic endothelial cell; Mig DC, migratory dendritic cell; NK, natural killer [cell]; P, Pvalue; pDC, plasmacytoid dendritic cell; SMC, smooth muscle cell; Treg, regulatory T cell. pIpC, poly(I:C).