Fig 1.
Simultaneous WSS and CS on EC are characterized by the SPA.
Blood flow in the axial direction induces wall shear stress (WSS) and the changes in pressure during the cardiac cycle induce circumferential strain and circumferential stress (CS) on the EC lining the wall of the blood vessel. Due to impedance of the distal circulation, local inertial effects associated with flow in larger vessels and arterial geometry, there is a time lag between WSS and CS characterized by the stress phase angle—SPA = φ(CS-WSS)
Table 1.
Atherosclerosis Related Gene List (43 genes) for PCR Array.
Fig 2.
Endothelial cells seeded on the inner surface of silicone substrates.
(A) Control conditions. ECs formed a confluent monolayer that has a cobblestone appearance. (B) After 7-h-exposure to WSS (10±10 dynes/cm2) and CS (4 ± 4%) at SPA = 0° and (C) SPA = -180°. ECs remained confluent but showed subtle morphological changes. Flow is from left to right; strain is perpendicular to flow.
Fig 3.
Hemodynamic influences on gene expression.
Asynchronous hemodynamic conditions significantly increased the expression of the adhesion molecules CDH5 and VCAM-1 (B). Asynchronous hemodynamic conditions significantly increased EPCR and SCD1 mRNA levels (C). Asynchronous hemodynamic conditions significantly increased the mRNA levels of transcription regulators OLR-1, ADFP, and SCARB1 (D) **p < 0.05, * p<0.1 indicate significant differences for SPA 0° with respect to control or SPA -180° with respect to control. An overbar indicates pairwise significant difference between SPA 0° and SPA -180°. (n = 11)
Fig 4.
Hemodynamic influences on gene expression.
Asynchronous hemodynamic conditions significantly increased the levels of mRNA of the apoptosis factor BCL2. Synchronous hemodynamics significantly reduced BAX and FAS mRNA levels (A). Asynchronous hemodynamics significantly increased the mRNA levels of PPARG, CCL5 and NFκB relative to synchronous conditions (B). Synchronous hemodynamics significantly decreased the mRNA levels of SOD1 compared to controls and SPA = −180° (C). Asynchronous hemodynamics significantly increased the mRNA levels of BMP4, GPC1, TGFb1 and VEGF compared to SPA 0°. Synchronous hemodynamic conditions decreased the gene expression of ANGTP2 and PRDX2 compared to control (D). (n = 11).
Fig 5.
SPA modulates localization of NFKB p105/p50, NFKB p65 and CDH5.
BAEC were exposed to asynchronous or synchornous condition for 7h. Stainings for NFKB p105/p50 (B) and p65 (D) were localized in the citoplasm and the nucleos for EC exposed to SPA = -180. NFKB localization where entirely citoplasmatic for EC exposed to SPA = 0 (A, C). The distribution for CDH5 were continous around the entire periphery of the cells after 7 when cells where exposed to SPA = 0 (E). Exposure of EC to SPA = -180 for 7 hours resulted in an intermitted pattern of CDH5 (F). images showed here are representative resutl from 3 individual experiments.
Fig 6.
SPA modulates the protein expression levels of NFkB p105/p50 and NFkB p65 but does not affect CDH5.
BAEC monolayer were exposed to WSS and CS with either SPA = 0 or SPA = -180 during 7 hours. Cell lysates from different samples (n = 6 each condition) were separated in gradient SDS-PAGE, and the proteins were transferred to nitrocellulose membranes. Nitrocellulose membranes were split into two parts for immunoblotting with NFKB p105/p50 or NFkB p65 using βactin as the endogenous control. Representative blots are shown in Fig 6. Samples were analysed by densitometry and normalized by the βactin control; then the relative protein expressions at SPA = -180 and SPA = 0 were compared. The bar graphs in (A) represent the quantification of 6 individual experiments (mean ± SEM). SPA = -180 increases the expression of NFκB p50 by 1.9 fold compared to SPA = 0 (p = 0.001) and the expression of NFκB p105 by 1.98 fold (p = 0.058). The bar in (B) suggest that SPA = -180 increase the expression of the transcriptional factor NFKB p65 (n = 8) by 1.98 fold (p = 0.002) (ANOVA, all p<0.05). SPA did not affect the CDH5 protein expression levels (n = 3 for each condition) (ANOVA p>0.05) as shown in panel B.
Table 2.
Endothelial genes up-regulated by the athero-prone condition SPA = -180° relative to the athero-protective condition SPA = 0°.