['To investigate the potential role of prostasin, as an invasion suppressor, in the process of trophoblast invasion in preeclampsia.', 'This case-control study included 19 early-onset severe preeclampsia (⩽ 34 weeks), 20 late-onset severe preeclampsia (>34 weeks) and 20 normal term pregnant women. Immunohistochemistry was conducted to identify the cellular localization of prostasin, as well as the matrix metalloproteinase 2 (MMP2) and MMP9 in the placenta tissues. Enzyme-linked immunosorbent assay was performed to analyze the expression of these three proteins in placental homogenates. The effect of prostasin on the invasive and migratory ability of trophoblast cells was detected by transwell assays. We also examined the regulation of the prostasin antibody in the MMP2 and MMP9 secretion by HTR-8/SVneo cells via blocking the prostasin activity.', 'This study demonstrated that the prostasin, MMP2 and MMP9 were all expressed in the placental syncytiotrophoblasts. Increased expression of prostasin was detected in cases with early-onset severe preeclampsia compared with the late-onset and control groups (P < 0.05), whereas the expression patterns of MMP2 and MMP9 in placental homogenates were opposite to that of prostasin (P < 0.05). Recombinant prostasin inhibited the invasion and migration of trophoblast cells, whereas prostasin antibody enhanced the MMP2 and MMP9 secretion in a dose- and time-dependent manner.'] Does increased expression of prostasin contribute to early-onset severe preeclampsia through inhibiting trophoblast invasion?