Validation of Messenger Ribonucleic Acid Markers Differentiating Among Human Acute Respiratory Distress Syndrome Subgroups in an Ovine Model of Acute Respiratory Distress Syndrome Phenotypes.

Background: The discovery of biological subphenotypes in acute respiratory distress syndrome (ARDS) might offer a new approach to ARDS in general and possibly targeted treatment, but little is known about the underlying biology yet. To validate our recently described ovine ARDS phenotypes model, we compared a subset of messenger ribonucleic acid (mRNA) markers in leukocytes as reported before to display differential expression between human ARDS subphenotypes to the expression in lung tissue in our ovine ARDS phenotypes model (phenotype 1 (Ph1): hypoinflammatory; phenotype 2 (Ph2): hyperinflammatory).
Methods: We studied 23 anesthetized sheep on mechanical ventilation with observation times between 6 and 24 h. They were randomly allocated to the two phenotypes ( n = 14 to Ph1 and n = 9 to Ph2). At study end, lung tissue was harvested and preserved in RNAlater. After tissue homogenization in TRIzol, total RNA was extracted and custom capture and reporter probes designed by NanoString Technologies were used to measure the expression of 14 genes of interest and the 6 housekeeping genes on a nCounter SPRINT profiler.
Results: Among the 14 mRNA markers, in all animals over all time points, 13 markers showed the same trend in ovine Ph2/Ph1 as previously reported in the MARS cohort: matrix metalloproteinase 8, olfactomedin 4, resistin, G protein-coupled receptor 84, lipocalin 2, ankyrin repeat domain 22, CD177 molecule, and transcobalamin 1 expression was higher in Ph2 and membrane metalloendopeptidase, adhesion G protein-coupled receptor E3, transforming growth factor beta induced, histidine ammonia-lyase, and sulfatase 2 expression was higher in Ph1. These expression patterns could be found when different sources of mRNA - such as blood leukocytes and lung tissue - were compared.
Conclusion: In human and ovine ARDS subgroups, similar activated pathways might be involved (e.g., oxidative phosphorylation, NF-κB pathway) that result in specific phenotypes.
Competing Interests: KW has received research funding from the Julia und Gottfried Bangerter-Rhyner Stiftung, the Prince Charles Hospital Foundation and the Wesley Medical Research Foundation. In addition, she received a Ph.D. scholarship from the University of Queensland. Samantha Livingstone received a Ph.D. scholarship of the Prince Charles Foundation. GL has received research funds, through his affiliated institution from Fisher & Paykel. JS has received an Advance Queensland Industry Research Fellowship and JF received grant funding from Fisher & Paykel, the Prince Charles Hospital Foundation and the Wesley Medical Research Foundation. KW, KH, JM, SL, MP, MB, EW, GL, JF, and JS are members of the Critical Care Research Group.
(Copyright © 2022 Wildi, Hyslop, Millar, Livingstone, Passmore, Bouquet, Wilson, LiBassi, Fraser and Suen.)