Dietary inulin supplementation in early gestation regulates uterine fluid exosomes and angiogenesis to improve embryo implantation in sows

Embryo implantation in early gestation is crucial for reproductive success, while dietary fiber plays a key role in regulating sow fertility. However, the underlying mechanisms remain unclear. This study explores the influence of dietary inulin on embryonic implantation using a sow model. Sows were fed a diet supplemented with 11 g/kg of inulin during early gestation and were slaughtered on gestation day 19 (G19). Uterine fluid exosomes (UFEs) and endometrial tissues were collected for high-throughput sequencing and for analysis of the expression of angiogenesis-related genes and proteins, respectively. Furthermore, UFEs obtained from slaughtered sows were injected into G19 sows to investigate the effects on reproduction and angiogenesis. The results showed that inulin significantly increased the number of blood vessels in the endometrium and expression of the angiogenesis-related proteins MMP2 and ANGPT1 in G19 sows (P < 0.05). Bioinformatics analysis revealed that inulin significantly downregulated miRNAs associated with angiogenesis inhibition in UFEs, while upregulating miRNAs related to trophoblast physiological activities and regulation of the uterine fluid microenvironment (P < 0.05). Furthermore, intravenous injection of G19 sows with UFEs from sows fed a diet containing inulin had significantly promoted vascular formation in the endometrium and embryos, and increased the number of live embryos on gestation day 28 (G28) (P < 0.05). Additionally, the mRNA expression levels of MMP2, ANGPT1, and VEGF in the placentas of sows were significantly elevated on G28 and at farrowing in the UFEs injection group (P < 0.05). Dietary supplementation with inulin during early gestation in sows promoted embryo implantation by regulating angiogenesis at the maternal–fetal interface through the modulation of miRNA expression in UFEs. These findings provide a theoretical reference for the application of dietary fiber in sow nutrition.