Placenta-derived exosomal miR-24-1-5p is associated with macrophage inflammation and placental endotoxin tolerance in lipopolysaccharide-induced placental inflammation

Intra-amniotic infection (IAI) is a severe obstetric complication associated with significant maternal and neonatal risks. As a central immune organ at the maternal–fetal interface, the placenta plays critical but not yet fully understood roles in immunoregulation during IAI. Emerging evidence suggests that placenta-derived exosomes (Pd-Exos) and their contained microRNAs (miRNAs) participate in immune modulation during pregnancy. This study aimed to investigate placental immunoregulatory responses in IAI and elucidate the underlying molecular mechanisms. An IAI model was established by co-culturing term placental explants from elective cesarean sections with lipopolysaccharide (LPS). RT-qPCR and ELISA were used to assess temporal changes in inflammatory factor expression. Pd-Exos were isolated from the culture supernatant of placental explants and subjected to miRNA sequencing to identify key immunoregulatory miRNAs, followed by functional validation of selected candidates. In the early phase of LPS stimulation, placental explants showed pronounced pro-inflammatory responses with elevated TNF-α and IL-1β. As stimulation prolonged, pro-inflammatory responses declined while anti-inflammatory responses increased, reflected by reduced TNF-α/IL-10 and IL-1β/IL-1Ra ratios. Prolonged LPS exposure led to increased expression of miR-24-1-5p in Pd-Exos. Following internalization by recipient cells (THP-1 cells), miR-24-1-5p was associated with reduced expression of Tumor Necrosis Factor Alpha–Induced Protein 8 (TNFAIP8), as well as decreased TNF-α and IL-1β levels and increased macrophage apoptosis. Prolonged LPS exposure in human placental tissues induced endotoxin tolerance. Placenta-derived exosomal miR-24-1-5p was associated with TNFAIP8 suppression, enhanced macrophage apoptosis, and reduced TNF-α and IL-1β expression, which may contribute to placental endotoxin tolerance.