Expression of E-cadherin and its repressor Snail in placental tissue of normal, preeclamptic and HELLP pregnancies

Incomplete invasion of extravillous trophoblasts (EVT) is thought to be associated with complications of pregnancy. Snail, a zinc-finger transcription factor represses the transcription of the cell adhesion molecule E-cadherin. The aim of this study was to investigate the expression of E-cadherin and Snail in placental tissue with preeclampsia or HELLP. Placental tissues were obtained from five patients with HELLP syndrome, seven patients with preeclampsia and seven patients after a normal term birth and analysed for Snail and E-cadherin immunoreactivity with specific monoclonal antibodies. Immunohistochemical staining of the placental tissue was analysed using an immunoreactivity score for the evaluation of staining intensity. In preeclamptic EVT, Snail immunoreactivity showed a significant 1.7-fold increase, accompanied by a significant 1.9-fold reduction of E-cadherin immunoreactivity. A 1.7-fold increase of Snail and in parallel a 1.3-fold reduction of E-cadherin was observed in EVT of HELLP placentas although without statistical significance. Loss of E-cadherin can be observed during epithelial-mesenchymal transition (EMT), a key process in normal development and trophoblast differentiation. Snail represses the transcription of E-cadherin triggering a complete EMT. Results obtained in this study showed changes of Snail and E-cadherin immunoreactivity in preeclamptic placentas that could be accompanied with an altered EMT in trophoblasts.