Abstract
BackgroundIn human and non-human primates, migratory trophoblasts penetrate the uterine epithelium, invade uterine matrix, and enter the uterine vasculature. Invasive trophoblasts show increased expression of β1 integrin. Since trophoblast migration within the uterine vasculature involves trophoblast attachment to endothelial cells lining the vessel walls, this raises the possibility that cell-cell contact and/or factors released by endothelial cells could regulate trophoblast integrin expression. To test this, we used an in vitro system consisting of early gestation macaque trophoblasts co-cultured on top of uterine microvascular endothelial cells.ResultsWhen cultured alone, trophoblasts expressed low levels of β1 integrin as determined by quantitative immunofluorescence microscopy. When trophoblasts were cultured on top of endothelial cells for 24 h, the expression of trophoblast β1 integrin was significantly increased as determined by image analysis. β1 Integrin expression was not increased when trophoblasts were cultured with endothelial cell-conditioned medium, suggesting that upregulation requires direct contact between trophoblasts and endothelial cells. To identify endothelial cell surface molecules responsible for induction of trophoblast integrin expression, trophoblasts were cultured in dishes coated with recombinant platelet endothelial cell adhesion molecule-1 (PECAM-1), intercellular adhesion molecule-1 (ICAM-1), or αVβ3 integrin. Trophoblast β1 integrin expression (assessed by immunofluorescence microscopy and Western blotting) was increased when PECAM-1 or αVβ3 integrin, but not ICAM-1, was used as substrate.ConclusionsDirect contact between trophoblasts and endothelial cells increases the expression of trophoblast β1 integrin.
Highlights
In human and non-human primates, migratory trophoblasts penetrate the uterine epithelium, invade uterine matrix, and enter the uterine vasculature
Trophoblast β1 integrin is upregulated by contact with endothelial cells When early gestation (40–60 days) macaque trophoblasts were cultured for 24 h on fibronectin-coated slides under serum-free conditions, the cells attached to the substrate and remained rounded
When the cocultures were stained for β1 integrin (Fig. 1B), the trophoblast cells showed a diffuse, punctate fluorescence that was much brighter than trophoblasts cultured in the absence of endothelial cells
Summary
In human and non-human primates, migratory trophoblasts penetrate the uterine epithelium, invade uterine matrix, and enter the uterine vasculature. As part of the implantation process and development of the placenta in human and non-human primates, migratory trophoblasts penetrate the uterine epithelium, invade the uterine matrix, and enter the uterine vasculature [1,2,3,4,5,6,7]. These invasive trophoblasts show increased expression of β1 and α1 integrins and down-regulation of β4 integrin when compared to non-invasive villous trophoblast cells (page number not for citation purposes). Trophoblast integrin expression is increased when trophoblast cells are cultured on fibronectin or in the presence of TGFβ [18,19] and we recently showed that β1 integrin expression by macaque trophoblasts was increased when the cells were exposed to physiological levels of shear stress [11]
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