CUL1 promotes trophoblast cell invasion at the maternal–fetal interface

Q Zhang,H-Y Lin,X Lu,H Zhang,Y Tan,H Wang,E Duan,Q Chen,C Zhu,Z Zhou

doi:10.1038/cddis.2013.1

Abstract

Human trophoblast progenitor cells differentiate via two distinct pathways, to become the highly invasive extravillous cytotrophoblast (CTB) cells (EVT) or fuse to form syncytiotrophoblast. Inadequate trophoblast differentiation results in poor placenta perfusion, or even complications such as pre-eclampsia (PE). Cullin1 (CUL1), a scaffold protein in cullin-based ubiquitin ligases, plays an important role in early embryonic development. However, the role of CUL1 in trophoblast differentiation during placenta development has not been examined. Here we show that CUL1 was expressed in CTB cells and EVT in the first trimester human placentas by immunohistochemistry. CUL1 siRNA significantly inhibited outgrowth of extravillous explants in vitro, as well as invasion and migration of HTR8/SVneo cells of EVT origin. This inhibition was accompanied by decreased gelatinolytic activities of matrix metalloproteinase (MMP)-9 and increased expression of tissue inhibitors of MMPs (TIMP-1 and -2). Consistently, exogenous CUL1 promoted invasion and migration of HTR8/SVneo cells. Notably, CUL1 was gradually decreased during trophoblast syncytialization and CUL1 siRNA significantly enhanced forskolin-induced fusion of choriocarcinoma BeWo cells. CUL1 protein levels in human pre-eclamptic placental villi were significantly lower as compared to their matched control placentas. Taken together, our results suggest that CUL1 promotes human trophoblast cell invasion and dysregulation of CUL1 expression may be associated with PE.

Highlights

Trophoblast invasion is temporally and spatially regulated in an autocrine or paracrine manner by trophoblastic and uterine factors at the maternal–fetal interface
CUL1 is highly expressed in human placental trophoblast cells exhibiting high invasive and proliferative capacities during the first trimester
CUL1 was expressed in CTB cells (Figure 1Ab) and moderate staining was observed in invasive extravillous cytotrophoblast cells (EVT) cells in the maternal decidua as defined by cytokeratin 7 (CK7) staining (Figure 1Ac and Ad)

Summary

Introduction

Trophoblast invasion is temporally and spatially regulated in an autocrine or paracrine manner by trophoblastic and uterine factors at the maternal–fetal interface. We show that CUL1 protein is highly expressed in CTBs and EVT, but not in STB of the placental villi from the first trimester, suggesting that CUL1 may regulate trophoblast invasion and migration. This is further confirmed by using human placental extravillous explant culture, in vitro cell invasion and migration assays combined with RNA interference (RNAi), overexpression and gelatinolytic zymography. The above evidence supports a role of CUL1 in promoting invasion, but not syncytialization of human trophoblast cells They suggest that dysregulation of CUL1 expression may be associated with PE

Methods

Results

Conclusion