MiR-331-3p serves as a diagnostic biomarker in children with severe pneumonia

Severe pneumonia poses a life-threatening risk to children's physical health. This study aimed to evaluate the diagnostic value of serum miR-331-3p in pediatric severe pneumonia.

A total of 97 healthy children, 101 children with non-severe pneumonia and 101 children with severe pneumonia were enrolled. Serum miR‑331‑3p expression was detected by RT‑qPCR. An LPS‑induced MRC‑5 cell model was established to simulate severe pneumonia in vitro. Cell proliferation, apoptosis, and inflammatory cytokine levels were measured. The direct targeting relationship between miR‑331‑3p and B cell lymphoma 2 antagonist/killer 1(BAK1) was verified by dual‑luciferase reporter assay.

Serum miR‑331‑3p expression gradually decreased from healthy controls to patients with non-severe pneumonia, and reached the lowest level in children with severe pneumonia. miR-331-3p exhibited good diagnostic efficacy for identifying severe pneumonia from healthy children (AUC = 0.899) and discriminating severe from non-severe pneumonia (AUC = 0.830). Lower miR-331-3p levels were correlated with higher inflammatory indicators in pneumonia patients. In vitro, miR‑331‑3p promoted cell proliferation, inhibited apoptosis, and suppressed the production of TNF‑α and IL‑6 by directly targeting and negatively regulating BAK1. Overexpression of BAK1 abolished the protective effects of miR‑331‑3p.

Serum miR‑331‑3p exhibits favorable differential diagnostic potential for identifying severe pediatric pneumonia in this single-center cohort, while multicenter validation with independent cohorts is still needed to confirm its clinical predictive performance.