DNA methylation profiles between airway epithelium and proxy tissuesin children

Aim: Epidemiological studies of deoxyribonucleic acid (DNA) methylation in airway disease have largely been conducted using blood or buccal samples. However, given tissue specificity of DNA methylation, these surrogate tissues may not allow reliable inferences about methylation in the lung. We sought to compare the pattern of DNA methylation inblood, buccal and nasal epithelial cells to that in airway epithelial cells from children.

Methods: Samples of blood, and buccal, nasal and airway epithelium were obtained from six children undergoing elective anaesthesia for adenotonsillectomy. DNA methylation was assessed at 450 000 5'-C-phosphate-G-3' (CpG) sites using the Illumina HumanMethylation450 array.

Results: Eighteen samples from all sites were suitable for analysis. Hierarchical clusteringdemonstrated that the methylation profile in nasal epithelium was most representative of that in airway epithelium; the profile in buccal cells was moderately similar and that inblood was least similar.

Conclusion: DNA methylation in blood poorly reflects methylation in airway epithelium. Future epidemiological studies of DNA methylation and airway diseases should consider measurement of methylation either in buccal cells or, preferably, in nasal epithelial cells