Hum. Reprod. Advance Access published online on January 24, 2009
Human Reproduction, doi:10.1093/humrep/den479
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Molecular mechanisms of ovarian hyperstimulation syndrome: paracrine reduction of endothelial claudin 5 by hCG in vitro is associated with increased endothelial permeability
1 Department of Obstetrics and Gynecology, University of Ulm, Prittwitzstrasse 43, 89075 Ulm, Germany 2 Division of Reproductive and Developmental Sciences, University of Edinburgh, Edinburgh, UK 3 Medical Research Council Human Reproductive Sciences Unit, Edinburgh, UK 4 IVF-Zentrum Ulm, Ulm, Germany
5 Correspondence address. Tel: +49-73150058557; Fax: +49-73150058502; E-mail: webmaster{at}tine-wulff.de
BACKGROUND: Ovarian hyperstimulation syndrome (OHSS) is a potentially life-threatening complication of ovarian stimulation associated with severe vascular hyperpermeability. Primary co-cultures of human luteinized granulosa cells (LGCs) and human umbilical vein endothelial cells (HUVECs) were used as a model of steroidgenic/endothelial cell interaction in OHSS.
METHODS: hCG and the vascular endothelial growth factor (VEGF) inhibitor, Flt-1Fc, were added to co-cultures of LGCs and HUVECs separated by a micropore membrane. Endothelial permeability to labeled bovine serum albumin was measured and the expression of the endothelial cell-specific adhesion protein claudin 5 was investigated using immunocytochemistry and western blotting.
RESULTS: The addition of hCG increased HUVEC permeability in the presence of LGCs (P < 0.05). hCG increased VEGF concentrations in both chambers of the co-culture system (P < 0.05). The increased permeability in the presence of LGCs and hCG was inhibited when VEGF was blocked by Flt-1Fc (P < 0.05). Endothelial membrane claudin 5 protein was reduced in the presence of hCG and LGCs, as measured by immunocytochemistry (P < 0.05) and western blotting (P < 0.05) and this reduction was inhibited by Flt-1Fc. hCG had no direct effects on endothelial cell claudin 5.
CONCLUSIONS: For OHSS, this novel paradigm suggests that hCG can increase endothelial permeability by up-regulating VEGF in LGCs which causes reduction in endothelial claudin 5 expression.
Key words: permeability/tight junctions/ovarian hyperstimulation syndrome/human umbilical vein endothelial cells/luteinized granulosa cells
The first two authors contributed equally to this work. Submitted on May 16, 2008; resubmitted on October 24, 2008; accepted on October 30, 2008.