Cell-intrinsic differences between human airway epithelial cells from children and adults

Abstract

The airway epithelium is a key protective barrier whose integrity is preserved by the selfrenewal and differentiation of basal progenitor cells. Epithelial cells are central to the pathogenesis of multiple lung diseases. In chronic diseases, increasing age is a principle risk factor. In acute diseases, such as COVID-19, children suffer less severe symptoms than adults and have a lower rate of mortality. Few studies have explored differences between airway epithelial cells in children and adults to explain this age dependent variation in diseases. Here, we perform bulk RNA sequencing studies in laser-capture microdissected whole epithelium, FACS-sorted basal cells and cultured basal cells, as well as in vitro cell proliferation experiments, to address the intrinsic molecular differences between paediatric and adult airway basal cells. We find that, while the cellular composition of the paediatric and adult tracheobronchial epithelium is broadly similar, in cell culture, paediatric airway epithelial cells displayed higher colony forming ability, better in vitro growth and outcompeted adult cells in competitive proliferation assays. In RNA sequencing experiments, we observed potentially important differences in airway epithelial gene expression between samples from children and adults. However, genes known to be associated with SARS-CoV-2 infection were not differentially expressed between children and adults. Our results chart cell-intrinsic differences in transcriptional profile and regenerative capacity between proximal airway epithelial cells of children and adults.

Pediatric nasal epithelial cells are less permissive to SARS-CoV-2 replication compared to adult cells

“…Increased ISG expression, and the subsequent anti-viral response may contribute to the reduced viral replication observed in pediatric cells. These findings are consistent with those of Maughan et al, who analysed transcriptional profile of airway (tracheobronchial) epithelium and observed upregulated type I and II IFNs associated genes expression levels in children (25). Similarly, in the nasal fluid of children and adults presenting to the Emergency Department with SARS-CoV-2 there were significantly higher levels of IFN-a2 in the fluid derived from children.…”

“…SARS-CoV-2 is a poor inducer of the type I and III interferon response (23), and the significance of interferons in controlling SARS-CoV-2 infection is best demonstrated by the fact that the presence of neutralising anti-type I IFNs antibodies increases the risk of severe COVID-19 (24). Recent RNA sequencing of the whole epithelium from pediatric and adult proximal airways suggest that there is a higher expression of genes associated with interferon alpha and gamma responses in children compared to adults (25). However, whether this results in reduced replication of SARS-CoV-2 in the nasal epithelium of children remains to be determined.…”

Type 2 and interferon inflammation regulate SARS-CoV-2 entry factor expression in the airway epithelium

“…Although our results are based on a single adult donor, they correspond strongly to and validate the results of several recently published, large scRNA-seq surveys 36,37 . We also note that a recent report shows that airway epithelial expression of ACE2 and TMPRSS2 is similar between adults and children 38 . Importantly, we were able to show that ACE2 protein is expressed at the apical surface of the tracheal airway epithelium, particularly colocalizing with ciliated cells, a pattern we also observed among in vitro nasal mucociliary airway epithelial cultures.…”

COVID-19 in Immunosuppressed Children

“…Another means of resistance to SARS-CoV-2 in young patients is their lower threshold of IFN antiviral response and their higher basal expression of IFN-I/III-associated genes in the respiratory epithelium ( 72 , 73 ) with respect to adults. These first traits account for a lower viral replication.…”