Xiaoyao powder improves endometrial receptivity via VEGFR-2-mediated angiogenesis through the activation of the JNK and P38 signaling pathways

Xiaoyao powder (XYP) is a traditional Chinese medicine formula which has wide scope of indications related to liver stagnation, reconcile qi and blood in TCM syndrome. Infertility can induce similar symptoms and signs to the clinical features of liver stagnation syndrome, the treatment of infertility by soothing the liver is obvious. XYP can increase the clinical pregnancy rate, follicle development, oocyte quality and improve endometrial receptivity. However, its underlying pharmacological mechanism of improving endometrial receptivity is unclear. The aim of the study was to investigate the effect of XYP on pregnancy rates and endometrial angiogenesis, to determine the potent mechanism in association with the pro-angiogenic behavior which closely related to improving endometrial receptivity. We established an animal model exhibiting decreasing endometrial receptivity by controlled ovarian hyperstimulation and a human endometrial microvascular endothelial cell (HEMEC) model. Endometrial morphology was observed by hematoxylin-eosin staining and Scanning electron microscopy. Western blot and qRT-PCR analysis were used to detect expression of PCNA, Cyclin D1, MMP9 and MAPK signaling pathway. Scratch-wound assay and tube formation assay were used to observe HEMEC migration and tubulogenesis. The results demonstrated that XYP pretreatment could improve endometrial receptivity, which leads to high pregnancy rates. In the endometrium, XYP facilitated angiogenesis by promoting tube formation. XYP could enhance HEMEC proliferation and migration induced by VEGF, which were observed by the microscope and Scratch-wound assays. XYP promoted HEMEC proliferation and migration via the p38 and JNK MAPK signaling pathways. XYP promotes HEMEC proliferation and migration via the P38 and the JNK MAPK signaling pathways, which contribute to the endometrial angiogenesis mediated by VEGFR-2 that is favorable for endometrial receptivity. We firstly elucidated the molecular mechanisms by which XYP improved endometrial receptivity by promoting angiogenesis. Graphical abstract: Proposed model for the mechanism by which XYP improves endometrial receptivity through the promotion of HEMEC angiogenesis. XYP, which could increase the expression of VEGF in HEMECs, induced the interaction of VEGF with VEGFR-2 and then promoted HEMEC proliferation and migration via activation of the P38 and JNK MAPK signaling pathway, thus led to angiogenesis. [Display omitted]