Discussion
ALF, BPD, term-born, pulmonary insult
REGRESSION, ADHESION, PROLIFERATION
In this exploratory proteomic analysis, we have shown that preterm-born school-aged children who had BPD in infancy have significant differences in protein abundances for key structural proteins involving desmosomes and the cytoskeleton, several years after the initial pulmonary insult which occurred in the neonatal period. Linear regression models demonstrated that for DSG1, DSC1 and JUP, those children with a history of BPD and current low lung function had the reduced abundance of these proteins but the BPD group with normal function did not. We have recently demonstrated that ICS/LABA is an effective treatment for preterm-born children with low lung function, increasing FEVThe mechanism of why some preterm-born children continue to experience lung function deficits in later life including in adulthood remains incompletely understood. Desmosomes have historically been thought to provide inert structural support to tissues, providing strong cell-to-cell adhesion; however more recent evidence shows that they have an active role in cell signalling, proliferation, migration, and apoptosisThe BPD group also had increased cytokeratins (KRT6A and KRT6B). Cytokeratins comprise the intracytoplasmic cytoskeleton of epithelial tissues forming important components of intermediate filaments, which connect to desmosomes, aiding resistance to mechanical stressWe focused our main analyses on proteins detected in every sample to capitalise on our large sample size and ensure robust findings. Overall, the protein content of EBC was low, as previously reportedIt is established that preterm born survivors, both with and without BPD, are at risk of lung function deficits in later lifeThis study represents one of the largest proteomic analyses of EBC, and the first time, to our knowledge, that preterm-born children have been studied. By using EBC, we have been able to directly sample ALF, representative of the biochemistry of the airways, in a simple, well-tolerated and non-invasive manner. We have demonstrated that it is technically possible to perform a quantitative proteomic analysis of EBC using TMT on a large sample size and identify meaningful differences between our clinical groups. By restricting our primary analysis to proteins detected in every sample, we report robust findings, strengthened further by the modulation of these proteins of interest after inhaler treatment. Our untargeted approach and exploratory analysis of less frequently detected proteins has also implicated potentially important protease/antiprotease dynamics that future work should explore. Although collected EBC volumes varied marginally between preterm- and term-born children, our methodology was based on identifying differences in relative protein abundances thus our findings are likely to remain robust. Although some children did not complete their treatment in the RCTIn conclusion, in an exploratory proteomics analysis we report significantly decreased desmosome components, DSG1, DSC1 and JUP, in children who had BPD in infancy. Furthermore, additional analyses suggest that there may be a protease/antiprotease imbalance. Taken together with the recent RCT findings