Circulating exosomal miR-18a-5p exacerbates Hirschsprung-associated enterocolitis by suppressing STAT3 signaling to drive M1 macrophage polarization

Background/objective This study characterized circulating exosomal miR-18a-5p in Hirschsprung-associated enterocolitis (HAEC) and explored its role in macrophage polarization via the STAT3 pathway. Methods Exosomes were isolated from peripheral blood serum samples of 30 HAEC participants. Bone marrow–derived macrophages (BMDMs) were cultured with unmodified exosomes or exosomes carrying miR-18a-5p mimic/NC mimic, under conditions with or without miR-18a-5p inhibitor administration or STAT3 overexpression. Expression levels of pro-inflammatory factors and STAT3 phosphorylation were assessed via quantitative real-time PCR and Western blotting. Ednrb −/− mice were treated systemically with exosomes carrying various modifications coupled with a miR-18a-5p antagomir. Exosome uptake, colonic tissue damage, inflammatory cytokine secretion, and STAT3 signaling intensity were analyzed utilizing flow cytometry, histology, qPCR, and Western blotting techniques. Results Exosomal miR-18a-5p was significantly elevated in HAEC serum (2.9 ± 0.4, P < 0.001). miR-18a-5p–rich exosomes increased TNF-α, IL-6, and IL-1β mRNA in BMDMs ( P < 0.001), promoting M1 polarization while suppressing STAT3 phosphorylation ( P < 0.001); STAT3 overexpression partially reversed these effects. In Ednrb −/− mice, miR-18a-5p exosomes increased DiD + intestinal macrophages (P < 0.001), worsened intestinal injury (score: 7.3 ± 0.5 vs 3.4 ± 0.2, P < 0.001), and elevated pro-inflammatory cytokines ( P < 0.001). The miR-18a-5p antagomir attenuated these effects and restored STAT3 signaling ( P < 0.001). Exosomal miR-18a-5p correlated positively with injury scores (r = 0.738) and colonic TNF-α, IL-6, and IL-1β (r = 0.718, 0.725, 0.654). ROC analysis yielded an AUC of 0.875 (95% CI : 0.770–0.952), with 76.7% sensitivity and 95.0% specificity. Conclusions Circulating exosomal miR-18a-5p promotes HAEC progression by suppressing STAT3 signaling and driving macrophage M1 polarization, supporting its potential as both a diagnostic biomarker and therapeutic target.