Fig 1.
2D modeling of a human placentone as a porous medium and simulation of maternal circulation in the IVS.
A: Modeling of the placentone as a porous medium (porosity ϕ = 0.5, permeability k = 10−8). The placentone contains a central inlet 2 mm in diameter (spiral artery), two identical 2 mm-diameter outlets (decidual veins) and a central cavity above the spiral artery. Eight circles with the same diameter as a terminal villus (50 μm) are symmetrically distributed in the placentone. The wall shear stress applied to the perimeter of 5 circles (A, B, C, D, E) was computed. B: Velocity plots for the 4 inlet velocities (50, 100, 200 and 300 mm.s-1). C: Mean fluid velocities (mm.s-1) in the porous medium as a function of the inlet velocity. D: Mean wall shear stress (WSS) (dyn.cm-2) applied to the contour of each of the 5 circles (A,B,C,D,E) as a function of inlet velocity.
Fig 2.
2D realistic modeling of a human placentone and simulation of maternal circulation in the IVS.
A: (1) Digitization, binarization and vectorization of a vertical cross-section from the chorionic plate (blue line = fetal side) to the basal plate (pink line = maternal side) of a third-trimester normal human placenta. (2) Correction of the placental collapse; the coordinates (xA;yA) of the center of gravity for each solid element were determined, and the ordinate (y) of each center of gravity was then multiplied by 2. (3) Reconstruction of a placentone with 4 vertical corrected sections assembled by axial symmetry. B: Velocity plots for the 4 inlet velocities (50, 100, 200 and 300 mm.s-1). C: Mean wall shear stress (WSS) (dyn.cm-2) in the IVS as a function of the inlet velocity. D: For an abscissa (x = 1), WSS (dyn.cm-2) as a function of y (heigh in the IVS).
Fig 3.
3D modeling and numerical simulation of the maternal circulation around a terminal villosity.
A: 3D reconstruction of a terminal villosity from a scanning electron microscopic image of a third-trimester terminal villosity. B: 3D geometry built in COMSOL Multiphysics and used in the simulation; the terminal villosity is positioned inside a cylinder with a 200 μm diameter and 500 μm height. C: 3D plot of the wall shear stress exerted on the surface of the terminal villosity (inlet velocity = 1mm.s-1). D: 3D mean wall shear stress exerted on the surface of the terminal villosity as a function of input velocity in the cylinder.
Fig 4.
Experimental device for applying increasing levels of wall shear stress to the human syncytiotrophoblast in primary culture.
A: Human syncytiotrophoblasts were obtained by spontaneous fusion of villous cytotrophoblasts (VT) after 48 hours of culture. VT and STBs were fixed and immunostained for desmoplakin (DPK, 5 μg.mL-1, green), and nuclei were counterstained with 4’,6-diamidino-2-phenylindole (DAPI, blue). B: STBs were exposed to steady unidirectional laminar shear stress with the culture medium containing human erythrocytes infected by Plasmodium falciparum (hematocrit: 1%, parasitemia: 2%) for one hour. Channel slides (sticky-slides Luer I 0.4, Luer I 0.6, Luer I 0.8, Ibidi® GmbH Martinsreid, Germany) with increasing heights (h = 400/600/800 μm), arranged in series and connected to a pump system (Ibidi® GmbH Martinsreid, Germany) generating flow rates of 0.45 mL.min-1 and 3.8 mL.min-1, were used to apply a increasing levels of wall shear stress (0.15, 0.30, 0.60, 1.2, 2.4 and 5 dyn.cm-2). C: Infections with the human malaria parasite Plasmodium falciparum during pregnancy lead to cytoadhesion of parasitized erythrocytes in the intervillous space. Cytoadherence is conferred by the specific interaction of the parasite-encoded adhesin VAR2CSA with chondroitin-4-sulfate A (CSA) present on human syncytiotrophoblast proteoglycans.
Fig 5.
Cytoadhesion experiments with infected erythrocytes (IEs) under flow conditions with increasing levels of wall shear stress.
A: Giemsa staining of IEs adherent to the STB after 1 hour under flow conditions (0.15 dyn.cm-2). Black arrow: IEs, red arrow: STB nucleus. B: IEs adherent to the STB, after 1 hour under flow conditions (0.15 dyn.cm-2). The plasma membrane of the adherent IE is immunolabeled with a monoclonal anti-human Band 3 (Clone BIII-136 B 9277 Sigma 0.1μg.ml-1) antibody. STB nuclei are labeled with DAPI. C: Scanning electron micrograph of the STB after 1 hour under flow conditions (0.15 dyn.cm-2) without erythrocytes. D: Scanning electron micrograph of the STB after 1 hour under flow conditions (0.15 dyn.cm-2) with IEs expressing VAR2CSA (VAR2CSA+). E: cytoadhesion quantification of IEs after 1 hour under flow conditions with increasing levels of wall shear stress (mean±SEM). * significant difference (p<0.05) compared with 0.15 dyn.cm-2. ** significant difference (p<0.05) compared with 0.60 dyn.cm-2. *** significant difference (p<0.05) compared with 1.2 dyn.cm-2. F: Comparison of cytoadhesion after 1 hour under flow conditions (0.15 dyn.cm-2) between IEs expressing VAR2CSA (IE VAR2CSA+), IEs VAR2CSA+ pre-incubated with soluble chondroitin-4-sulfate A (CSA 10 μg.mL-1) and IEs VAR2CSA-. * significant difference (p<0.05) compared with IEs VAR2CSA+.
Fig 6.
A: Placenta (green line), uterus (blue line), fetus (pink line). The intraplacental progression of the contrast-enhanced maternal blood in the IVS was measured (yellow arrows) every Δt in a perpendicular direction between the basal plate and the chorionic plate. B-G: Progression of the gadolinium is measured every 4.8s, from the first MRI picture with gadolinium in the placenta (Fig 6D) in order to avoid calculating the velocity of the maternal blood in the central cavity (CC) of the placentone. The mean flow velocity of maternal blood measured in the IVS is 0.94±0.14 mm.s-1.