Expression and localisation of FoxO3 and FoxO4 in human placenta and fetal membranes

Forkhead box O (FoxO) proteins regulate inflammation, extracellular matrix (ECM) remodelling and apoptosis. We have previously identified FoxO1 proteins in human gestational tissues, and demonstrated a link between FoxO1 and rupture of fetal membranes. There is, however, no data available on the expression and localisation of FoxO3 and FoxO4 in human intrauterine tissues. Thus the aim of this study was to characterise the localisation and expression of FoxO3 and FoxO4 in (i) human placenta and fetal membranes before term spontaneous labour onset, and (ii) supracervical site (SCS) and distal site (DS) fetal membranes from non-labouring women. Immunohistochemistry, Western blotting and quantitative RT-PCR (qRT-PCR) was used to localise and quantitate FoxO3 and FoxO4 protein and mRNA expressions. Cytoplasmic and nuclear FoxO3 was localised in the syncytiotrophoblast layer, chorionic trophoblasts, amnion epithelium and decidua. Cytoplasmic FoxO4 was localised in the syncytiotrophoblasts and chorionic trophoblasts. No or very little FoxO4 protein and mRNA was present in amnion epithelium. The intensity and extent of staining of FoxO3 and FoxO4 was greater in fetal membranes obtained from the SCS compared to DS. Presence of FoxO3 and FoxO4 are expected to contribute to apoptosis and/or cell cycle regulation associated with fetal membrane rupture.