579: Physiologic and pathologic concentrations of Interleukin-6 maintain amnion membrane integrity by regulating cellular transitions

Abstract

During pregnancy, amnion epithelial cells (AECs) undergo cyclic cellular transitions (epithelial-to-mesenchymal [EMT] and mesenchymal-to-epithelial [MET]) and often remain in a metastate (in between) to maintain cellular homeostasis protecting fetal membrane integrity. At term, inflammation forces a terminal state of EMTcausing fetal membrane weakening. IL-6, a proinflammatory cytokine, is constitutively expressed throughout pregnancy but elevated at term and preterm, specifically in pPROM. We hypothesize that physiologic or pathophysiologic doses IL-6 regulate AEC transitions that will determine membrane functional status to either maintain pregnancy or to promote parturition. Primary AECs (n=5) cultures were treated with IL-6 for 48 hours at physiologic (mid gestation: 330 pg/mL and term labor: 3330 pg/mL) and pathologic concentrations (pPROM: 16,000 pg/mL). We determined; of EMT/ MET by cell shape index (microscopy), immunocytochemistry/western blots for cytokeratin (CK) -18 and E-cadherin (epithelial markers) and Vimentin and N-cadherin, (mesenchymal markers). IL-6 induced dose dependent AEC transitions as follows: Mid gestation IL-6 - metastate with mesenchymal morphology but increased epithelial markers (vimentin/CK-18 ratio) Term labor IL-6 - EMT phenotype (mesenchymal morphology and increased vimentin/CK-18 ratio) Pathologic IL-6 – MET (epithelial morphology, decreased vimentin/CK-18 and N-cadherin/E-cadherin ratio) Data suggest that IL-6 plays a role maintaining cellular homeostasis by regulating amnion membrane cellular transitions. Mid gestation IL-6 maintains AEC in a metastate, while at term labor IL-6 promotes EMT, an inflammatory state that can cause fetal membrane weakening and rupture. Durring pPROM, IL-6 induced MET is likely an attempt to maintain pregnacy by restoring membrane integrity.View Large Image Figure ViewerDownload Hi-res image Download (PPT)