Acute cellular rejection elicits distinct microRNA signatures in airway epithelium of lung transplant patients.

Acute cellular rejection (ACR) is a common complication in lung transplantation and associated with increased risk of chronic allograft dysfunction. MicroRNAs are critical controllers of cellular transcription whose expression can be altered in disease states. The purpose of this pilot study was to evaluate whether microRNA profiling of epithelial cells obtained from airway brushings can distinguish lung transplant patients with ACR from those without rejection. We studied 21 subjects (10 with ACR, 11 without ACR) and assessed the expression of over 700 microRNAs in their airway epithelium. We identified 117 differentially expressed microRNAs that robustly segregated the two groups, and were uniformly downregulated in patients with ACR. Leveraging experimentally verified microRNA targets, we systematically mapped pathways and processes regulated by ACR-induced microRNAs and noted enrichment of programs involved in development, proliferation, migration, and repair. Collectively, our study suggests that ACR is associated with a distinct epithelial microRNA signature that can provide insight into the pathogenesis of acute rejection and potentially serve as a sensitive, minimally invasive biomarker tool for diagnostic and prognostic stratification of lung transplant patients.