Complement Activation in Maternal and Placental Pathology of Preeclampsia

BACKGROUND: Preeclampsia is a multifactorial, pregnancy-related disorder characterized by new-onset hypertension and proteinuria, with distinct early- and late-onset forms. Although complement dysregulation has been implicated in the pathogenesis of preeclampsia, its causal role remains unclear. In mice, Crry (complement receptor 1-related protein Y) functions as a critical complement regulator at the fetal-maternal interface. Because complete Crry deficiency is embryonically lethal, direct in vivo investigation of complement activation in pregnancy has been challenging. METHODS: We generated a placenta-specific, doxycycline-inducible short hairpin RNA mouse model in which Crry expression can be downregulated in a dose-dependent manner. This system employs Cyp19-driven Cre recombinase and a tetracycline-inducible gene expression system regulatory cassette, enabling precise temporal and spatial control of Crry suppression and restricting complement activation specifically to the placenta. RESULTS: We found that early gestation placental complement activation impairs maternal cardiac and hepatic adaptation, reduces placental efficiency, and causes fetal growth restriction-features consistent with early-onset preeclampsia. Delayed complement activation produces a phenotype resembling late-onset preeclampsia, characterized by maternal hypertension without placental pathology. In the early-onset-like phenotype, fetal growth restriction is accompanied by placental glycogen storage deficiency and impaired endocrine function. Maternal glucose metabolism remains intact; however, compensatory changes in lipid metabolism occur, although these adaptations are insufficient to prevent fetal growth restriction. CONCLUSIONS: This model demonstrates that the timing of placental complement activation determines whether pregnancy develops early- or late-onset-like features. These findings provide mechanistic insight into how complement dysregulation contributes to the spectrum of preeclampsia pathology and establish a powerful experimental platform for studying disease mechanisms and evaluating therapeutic strategies.