Transcriptomic analysis reveals shared deregulated neutrophil responses in COVID-19 and idiopathic pulmonary fibrosis.

Background: Coronavirus disease 2019 (COVID-19) is a respiratory disease linked with deregulated immune responses, leading to hyperinflammation, acute respiratory distress syndrome, and pulmonary fibrosis, often with fatal outcomes. Neutrophils play a central role in COVID-19 pathogenesis, with elevated peripheral blood neutrophil counts correlating with disease severity. Despite extensive research, the molecular processes associated with neutrophil hyperactivation in COVID-19 remain elusive.

Methods: To investigate the molecular signatures underlying neutrophil-driven pathology, we conducted transcriptome analysis in neutrophils isolated from the peripheral blood of COVID-19 patients versus healthy individuals. To evaluate the specificity of identified neutrophil signatures in COVID-19, we extended our transcriptomic analysis to neutrophils from patients with idiopathic pulmonary fibrosis (IPF), a non-infectious fibrotic lung disease. Additionally, immunofluorescence staining was performed on lung biopsy specimens from IPF patients to validate transcriptomic findings at the tissue level.

Results: Our analysis revealed significant transcriptional changes in COVID-19 neutrophils, particularly in pathways involved in immune regulation, inflammation, and antiviral responses. Additionally, pathways associated with autophagy and chromatin remodeling were upregulated, while translation-related processes were suppressed, indicating an increased predisposition for neutrophil extracellular trap (NET) release. This neutrophil transcriptional signature in COVID-19 appears to be associated with the previously reported deregulation of the Activin/Follistatin system in the periphery. Notably, a comparative transcriptomic analysis with neutrophils isolated from IPF patients revealed the induction of substantially overlapping inflammatory processes, suggesting common deregulated responses in COVID-19 and IPF. Consistently, significant NET formation, a hallmark of COVID-19-related inflammation, was observed within lung biopsies from IPF patients.

Conclusion: By delineating both shared and disease-specific molecular pathways, our findings validate the critical role of neutrophils in COVID-19 and IPF pathophysiology, highlighting their involvement in balancing the inflammatory response across diverse lung diseases.