Expression of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase in the invasive trophoblasts at the human placental bed

Background: Mitogen- activated protein kinases (MAP kinases) participate in signal transduction pathways that control embryogenesis, cell differentiation, cell proliferation and cell death. The roles of extracellular signal-regulated kinase 1/2 (ERK 1/2) and p38 MAP kinase in the differentiation and invasion of human trophoblasts have been studied. However, the in vivo expression and activation of ERK 1/2 and p38 at the placental bed have not been elucidated. Methods: The study group consisted of placental bed biopsy tissues obtained from the pregnancies without preeclampsia (n = 24) and with preeclampsia (n = 8) between 31 and 40 weeks of gestation. We evaluated the expressions and phosphorylations of ERK 1/2 and p38 MAP kinase in the invasive trophoblasts in the placental bed tissues using immunohistochemistry. Results: p38 and phospho-p38 MAP kinase were not detected in invasive trophoblasts in cases or controls. ERK 1/2 and phospho-ERK 1/2 were positive in invasive trophoblasts albeit with variable staining. Phosphorylation of ERK 1/2 was significantly less frequent in invasive trophoblasts in placental bed biopsies from women with preeclampsia compared with normotensive controls. Conclusion: These findings suggest that preeclampsia is associated with decreased activation of ERK 1/2 in invasive trophoblasts in vivo. (C) 2008 Elsevier Ltd. All rights reserved.