Figure 5.

Activation of BMP4-pSMAD5 signaling by disturbed fluid flow in venous endothelial cells. (A) Time-dependent (24 and 48 h) mRNA-level expression of BMP4 ligand as well as its effectors SMAD1, SMAD5, and SMAD9 upon exposure of HUVEC to disturbed flow (n = 3). BMP4 and SMAD5 showed significant overexpression in venous endothelial cells exposed to disturbed flow compared to parallel uniform flow as early as 24 h of exposure. The expression of BMP4 and SMAD5 was significantly higher after exposure to disturbed flow for 48 h. mRNA fold values were calculated relative to static control. All data were normalized with GAPDH expression and are given as relative to static control. (B) Disturbed flow at 6 dyn/cm² for 24 h induced a significant expression of BMP4 and pSMAD5 in the venous endothelial cells (scale bar 50 µM, magnification 40×). (C) Mean fluorescence intensity was plotted as the average fluorescence intensity ± SD of five fields per flow condition and from three biological replicates. PF indicates parallel uniform shear stress, and DF represents disturbed shear stress without any oscillatory flow. * indicates p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001 vs. respective static or parallel uniform shear-treated groups.