Timelapses of vascular development and gene expression of chick embryos

Mechanical forces generated by blood flow, such as shear stress, will have an effect on vascular remodelling and the expression of genes. In order to study this effect, we have been altering shear stress during vascular development and assessing the effects on vascular network morphology. We find that an increase of the shear stress levels decreases the density of branchpoints. We then looked at changes in gene expression and find that under increased shear stress Nrp2 is upregulated, and PDGF‐B and Dll1 are significantly down‐regulated. Since we saw an increase in the expression of a gene expressed specifically in the venous plexus (Nrp2) and a decrease in the expression of a gene expressed specifically in the arterial plexus (Dll1), we next investigated whether shear stress had a differential effect on these two different regions of the vasculature. We used an in‐ovo timelapse microscopy technique to characterize vascular remodeling both in the arterial or venous region and under either normal or elevated shear stress levels. We found a constant rate of sprouting for the arterial region and an approximate 4‐fold decrease in sprouting for the venous region when comparing control to high shear stress embryos. Conversely, high shear stress inhibited reverse intussusception in the arterial plexus. These results show that increased shear stress is inhibitory for sprouting in venous, but not arterial endothelial cells. Grant Funding Source : CRC, NSERC, SURE