MicroRNA miR-15b-5p linked to severe pneumonia severity and epithelial cell injury

Researchers report that the microRNA miR-15b-5p, measured in serum, shows potential as both a diagnostic and prognostic marker in severe pneumonia. The study, published open access in BMC Immunology on 29 October 2026 by Bo Wang, Ying Chen, Pan Long and Zhenxiang Liu, compared 140 pneumonia patients—71 with mild pneumonia and 69 with severe pneumonia—against 65 healthy controls, and combined the clinical measurements with laboratory experiments on human bronchial epithelial cells.

Serum and cellular levels of miR-15b-5p were quantified by PCR, and the authors assessed diagnostic performance using ROC analysis. According to the results, elevated miR-15b-5p expression helped distinguish severe pneumonia from mild pneumonia, and mild pneumonia from healthy controls. The microRNA also correlated significantly with inflammatory markers associated with severe pneumonia, including white blood cell count, neutrophils, lymphocytes, C-reactive protein and procalcitonin, as well as with severity scores such as APACHE II and SOFA and with pulmonary function measures, specifically respiratory rate and the PaO₂/FiO₂ ratio.

Survival analyses using Kaplan-Meier curves and Cox regression indicated that higher miR-15b-5p levels predicted worse prognosis, and the molecule emerged as an independent prognostic factor for severe pneumonia in this cohort.

To probe a possible mechanism, the team established in vitro injury models using LPS-induced human bronchial epithelial cells (16HBE). LPS exposure increased miR-15b-5p expression in these cells and reduced cell viability, measured with CCK-8 assays, while exacerbating inflammation and oxidative stress, both assessed with commercial kits. Knocking down miR-15b-5p reversed these effects, suggesting that the microRNA contributes to epithelial cell injury in this experimental system rather than merely marking it.

The experiments also pointed to a candidate molecular target. WNT3A was downregulated in LPS-treated cells, and this downregulation was rescued when miR-15b-5p was inhibited. Dual-luciferase assays confirmed a direct interaction between miR-15b-5p and WNT3A, supporting a pathway in which miR-15b-5p may promote bronchial epithelial cell injury partly through suppressing WNT3A. The authors conclude that miR-15b-5p might promote severe pneumonia progression by aggravating bronchial epithelial cell injury, potentially via WNT3A downregulation. Because this evidence comes from cell culture models, it describes a plausible mechanism but does not by itself establish causation in patients, and no therapeutic application follows directly from the data.

Subject of Research: The diagnostic and prognostic role of miR-15b-5p in severe pneumonia and its effects on bronchial epithelial cell injury

Article Title: The role of miR-15b-5p in severe pneumonia and its effect on bronchial epithelial cell injury

Article References: Wang, B., Chen, Y., Long, P., & Liu, Z. (2026). The role of miR-15b-5p in severe pneumonia and its effect on bronchial epithelial cell injury. BMC Immunology. https://doi.org/10.1186/s12865-026-00923-8

Image Credits: AI Generated

DOI: 10.1186/s12865-026-00923-8

Keywords: miR-15b-5p, severe pneumonia, microRNA biomarker, bronchial epithelial cells, 16HBE, WNT3A, LPS-induced injury, oxidative stress, inflammation, APACHE II, SOFA score, ROC analysis