ORIGINAL PAPER Journal of Pathology J Pathol 2010; 221: 87–95 Published online 21 January 2010 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/path.2690 The role of autocrine TGFβ1 in endothelial cell activation induced by phagocytosis of necrotic trophoblasts: a possible role in the pathogenesis of pre-eclampsia Qi Chen, 1,2 * Limei Chen, 2 Bonnia Liu, 1 Chez Vialli, 1 Peter Stone, 1 Lai-Ming Ching 3 and Lawrence Chamley 1,4 1 Department of Obstetrics and Gynaecology, University of Auckland, New Zealand 2 Hospital of Obstetrics and Gynaecology, Fudan University, People’s Republic of China 3 Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, University of Auckland, New Zealand 4 Fertility Plus, Green Lane Hospital, Auckland, New Zealand *Correspondence to: Qi Chen, Department of Obstetrics and Gynaecology, Faculty of Medical and Health Sciences, University of Auckland, 85 Park Road, Grafton, Auckland, New Zealand. e-mail: q.chen@auckland.ac.nz Abstract Pre-eclampsia is a disorder of pregnancy characterized by hypertension and endothelial cell dysfunction. The causes of pre-eclampsia are unclear but it is proposed that a factor released from the placenta triggers the maternal symptoms. One possible triggering factor is dead trophoblasts that are shed from the placenta, then deported to become trapped in the maternal pulmonary capillaries. It is hypothesized that trophoblasts die by apoptosis in normal pregnancy, but by necrosis in pre-eclampsia. Deported trophoblasts may be phagocytosed by the pulmonary endothelial cells and we have previously shown that phagocytosis of necrotic trophoblasts leads to the activation of endothelial cells, accompanied by the release of interleukin-6 from these cells. However, the mechanistic pathway linking phagocytosis of necrotic trophoblasts and endothelial cell activation is unknown. Here we show that, after phagocytosis of necrotic, but not apoptotic, trophoblasts, endothelial cells secrete TGFβ1. Using recombinant endoglin to inhibit the function of TGFβ1 we have shown that the TGFβ1 does not directly activate endothelial cells but rather it induces endothelial IL-6 secretion. The IL-6 then induces endothelial cell activation. Inhibiting either TGFβ1 or IL-6 prevented endothelial cell activation in response to phagocytosing necrotic trophoblasts, but inhibiting IL-6 did not prevent secretion of TGFβ1, confirming the order of signalling. IL-6 also reduced endothelial cell-surface endoglin but increased the amount of soluble endoglin released from placental explants. These interactions between the IL-6 and TGFβ1 pathways in both the endothelium and placenta may help to regulate the maternal response to deported trophoblasts in pregnancy. Copyright  2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. Keywords: pre-eclampsia; TGFβ; IL-6; trophoblast; endothelial Received 6 September 2009; Revised 10 January 2010; Accepted 13 January 2010 No conflicts of interest were declared. Introduction Pre-eclampsia is a disease unique to human pregnancy and is characterized by high blood pressure and pro- teinuria. It affects 5–8% of pregnant women world- wide and is responsible for 18% of maternal deaths in the USA, as well as long-term complications for both mother and child [1]. The clinical symptoms of pre-eclampsia are preceded by an exaggerated inflam- matory response and generalized maternal endothelial cell activation, the causes of which remain uncertain but which are likely to be triggered by a factor or fac- tors from the placenta [2,3]. The increased inflammatory reaction seen in women with pre-eclampsia is characterized by elevated cir- culating levels of inflammatory cytokines, such as interleukin-6 (IL-6) and transforming growth factor beta (TGFβ) [4,5]. The TGFβ family of multifunctional cytokines regulate endothelial cell growth and angio- genesis, affect the nature of immune responses and can affect various functions of trophoblasts. Endoglin is a co-receptor for TGFβ1 and TGFβ3 that is prominently expressed on the cell membranes of endothelial cells, the placental syncytiotrophoblast and some extravil- lous trophoblasts [6]. In addition, a soluble form of endoglin, soluble endoglin (sEndoglin), acts as a recep- tor antagonist blocking TGFβ1 signalling [7]. Levels of sEndoglin are reportedly elevated in the blood of many women with pre-eclampsia [8]. Although elevated lev- els of many soluble factors, such as TGFβ, are elevated in pre-eclamptic women, the origin of these factors remains uncertain; they may be released from the pla- centa or, alternatively, they may be secreted from the endothelium or other maternal cells as a part of the Copyright  2010 Pathological Society of Great Britain and Ireland. J Pathol 2010; 221: 87–95 Published by John Wiley & Sons, Ltd. www.pathsoc.org.uk www.thejournalofpathology.com