miR-29a-3p participates in the pathogenesis of spontaneous abortion by inhibiting trophoblast function targeting COL4A2/COL5A1.

Spontaneous abortion (SA), affecting approximately 15 % of pregnancies, involves multifactorial mechanisms including chromosomal abnormalities, immune dysregulation, and placental insufficiency. Trophoblast invasion into the endometrium is essential for placental development, and microRNAs (miRNAs) have emerged as important regulators in pregnancy complications. In this study, high-throughput miRNA sequencing identified 4 high-expressed miRNAs in villous tissues from patients with spontaneous abortion compared to those from normal pregnancies (log2FC > 1.5, p < 0.05), significantly upregulated miR-29a-3p was confirmed by qRT-PCR (log2FC > 2). To assess its function, agomiR-29a-3p was injected via tail vein in pregnant mice. Histological analyses revealed placental structural abnormalities and reduced vascularization. miR-29a-3p overexpression significantly increased embryo resorption and decreased litter size and weight. In vitro, miR-29a-3p was modulated in extravillous trophoblast (EVT) cells (HTR-8/SVneo cells). Western blot, Transwell, EdU, and CCK-8 assays demonstrated that miR-29a-3p inhibited migration, invasion, and proliferation of HTR-8/SVneo cells. qRT-PCR analysis showed that miR-29a-3p had no significant effect on decidualization markers in endometrial stromal cells, while Transwell and CCK-8 assays revealed no impact on their migration or proliferation, suggesting a limited role of miR-29a-3p in stromal cell decidualization and function. Bioinformatic prediction, dual-luciferase assays, and expression studies identified COL4A2 and COL5A1 as direct miR-29a-3p targets. Functional rescue experiments confirmed that miR-29a-3p regulates behaviors of HTR-8/SVneo cells via COL4A2 and COL5A1. In conclusion, excessive miR-29a-3p contributes to spontaneous abortion by impairing EVT function through COL4A2/COL5A1 targeting, suggesting its potential as a biomarker for early diagnosis of miscarriage.