MicroRNA-18a-3p as a biomarker for neonatal respiratory distress syndrome and its effects in alveolar epithelial type II cells

Neonatal respiratory distress syndrome (NRDS) is a major cause of significant morbidity and mortality among neonates, particularly in preterm infants. Existing studies have highlighted various microRNAs (miRNAs) implicated in NRDS, yet the precise molecular mechanisms, particularly regarding miR-18a-3p, remain incompletely understood. This research aimed to elucidate the role of miR-18a-3p as a potential biomarker for NRDS and to explore its functional mechanisms in alveolar type II epithelial cells. A total of 35 NRDS patients and 35 healthy controls were enrolled, with samples of amniotic fluid and neonatal blood collected for expression analysis of miR-18a-3p. Utilizing cell culture, transfection, qRT-PCR techniques, CCK-8 assay, and ELISA assay, the function of miR-18a-3p in alveolar epithelial type II cells (an immortalized cell line, IHPEC-II, and AEC2-like cells derived from human pluripotent stem cells) was investigated. The binding relationship between miR-18a-3p and surfactant pulmonary-associated protein C (SFTPC) was predicted and validated using a dual-luciferase reporter assay. Elevated levels of miR-18a-3p levels were observed in the serum of NRDS cases, with an area under the ROC curve (AUC) of 0.86 for distinguishing NRDS from healthy controls. Increased miR-18a-3p levels were also detected in amniotic fluid from these NRDS cases, yielding an ROC AUC of 0.82 for discriminating between NRDS cases and healthy controls. A positive correlation between serum miR-18a-3p levels and those in amniotic fluid was observed. Functional assays demonstrated that inhibition of miR-18a-3p significantly enhanced cell viability and increased SPC secretion in alveolar epithelial type II cells following surfactant stimulation. Dual-luciferase reporter assays confirmed that miR-18a-3p modulated SFTPC expression. MiR-18a-3p was increased in NRDS cases. MiR-18a-3p can inhibit alveolar epithelial type II cell function, suggesting its potential role in fetal lung development.