Aspirin reverses the inhibitory effect of soluble fms-like tyrosine kinase-1 on trophoblast invasiveness and ciliogenesis through Sonic hedgehog signaling in preeclampsia

Soluble Flt-1 (sFlt-1) is upregulated in preeclamptic patients and is a predictive biomarker for preeclampsia risk and progression. Aspirin is an effective agent used to prevent preeclampsia and has been shown to suppress sFlt-1 production in trophoblasts; however, the underlying mechanism is not fully understood. Here, we demonstrated that sFlt-1 production was upregulated under hypoxia in two trophoblastic cells (HTR-8/SVneo and JAR). The effects of sFlt-1 and underlying pathways on trophoblast biology and cilia formation were investigated in sFlt-1-pretreated, FLT-1-knockdown HTR-8/SVneo cells under hypoxic conditions and in a preeclampsia mouse model. In the present study, sFlt-1 was shown to inhibit trophoblast invasion and migration under hypoxia, and this inhibitory effect occurred through downregulating ZEB1/2, MMP 2/9, and the Sonic hedgehog (SHH) signaling pathway. Ciliary number and length of trophoblasts were inhibited by sFlt-1 treatment and were enhanced after FLT-1 knockdown. Aspirin was found to reverse the sFlt-1-mediated inhibitory effect on trophoblast invasion/migration, ciliogenesis, and SHH signaling in HTR-8/SVneo cells. Moreover, plasma and placental sFlt-1 protein levels were upregulated in the preeclampsia mouse model, whereas primary cilia formation and SHH-related expression were impaired in the mouse placenta. Aspirin-fed mice presented with reduced sFlt-1 expression, and their placental ciliogenesis and SHH expression were improved in the preeclamptic mouse model. In conclusion, sFlt-1 impairs trophoblast motility and ciliogenesis through SHH signaling under hypoxia. Aspirin exerts its suppressive effect on sFlt-1 upregulation and sFlt-1-mediated cell function and signaling in vitro and in vivo.