Abnormal expression of the costimulatory molecule B7-H4 in placental chorionic villous and decidual basalis tissues of patients with preeclampsia and HELLP syndrome.

Background B7-H4, a checkpoint molecule of the B7 family, regulates a broad spectrum such as T-cell activation, cytokine secretion, tumour progression and invasion capacities. Our previous data revealed that soluble B7-H4 (sB7-H4) blood serum levels are elevated in women at high risk for the hypertensive pregnancy disorder preeclampsia (PE) in the first trimester, as well as in patients with confirmed early/ late-onset PE. Aim We here aim to investigate the expression pattern of B7-H4 in placental tissues of PE and HELLP Syndrome versus control group. Methods B7-H4 protein expression and localization were investigated by immunoblotting as well as co-immunohistochemistry in placental chorionic villous and decidual basalis tissues. Results B7-H4 protein was prominently expressed at the cell membrane, in the cytoplasm of the syncytiotrophoblast (STB) and interstitial extravillous trophoblast (EVT). B7-H4 protein levels in placental chorionic villous tissue was significantly higher in women with early-onset/late-onset PE and HELLP, while it was decreased in decidual basalis tissues of early-onset PE and HELLP compared to controls. Conclusion B7-H4 was inversely expressed in placental chorionic villous and decidual basalis tissues of PE and HELLP patients. The increase of B7-H4 in the STB in PE and HELLP may lead to excessive apical expression and release of soluble B7-H4 in the maternal circulation. In contrast, the decrease of B7-H4 in decidual basalis tissues could be related to the decrease in invasion ability of the EVT in PE. Thus, the current results strongly suggest that B7-H4 is involved in the pathogenesis of PE and HELLP.