Lipoxin A4 interferes with embryo implantation via suppression of epithelial‐mesenchymal transition

PROBLEM: To test whether lipoxin A4 (LXA4) interferes with embryo implantation via suppression of epithelial-mesenchymal transition (EMT). METHOD OF STUDY: We developed a mouse model of LXA4 blocking embryo implantation and detected the indicators of EMT to confirm that LXA4 inhibits EMT might be a mechanism of interfering with the embryo implantation. We detected integrin-linked kinase (ILK), N-formylpeptide receptor 2 (FPR2), vascular endothelial growth factor, matrix metalloproteinases (MMPs), Akt, GSK3β, NF-ĸB, twist, vimentin, fibronectin, and β-catenin mRNA expression using reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time RT-PCR; localized protein expression using immunohistochemistry and Western blotting assay; MMPs activity assay by gelatin zymography; and the status of implantation in pregnant animals assessed by pontamine blue reaction test. RESULTS: Preimplantation administration of LXA4 resulted in implantation failure. LXA4 has a time- and dose-dependent effect on embryo implantation. Day 0.5 after fertilization is the most effective time to use LXA4 to block embryo implantation. (a) LXA4 reduced endometrial stroma edema; (b) LXA4 inhibited the activity of MMP9 and significantly upregulated the expression of β-catenin, and downregulated the expression of vimentin, fibronectin, twist, NF-κB, Akt, and Gsk-3β in the endometrium and TEV-1 cells; (c) LXA4 upregulated the expression of FPR2, and downregulated the expression of ILK; FPR2-overexpressing had an inhibitory effect on ILK in TEV-1 cells. CONCLUSION: LXA4 inhibits EMT which attenuates ILK action by enhancing FPR2; therefore, this might be a mechanism of interfering with embryo implantation.