1. Kathryn Repp – Wake Forest University
John LaDisa, PhD
Department of BiomedicalEngineering
UNDERSTANDING MECHANICAL STIMULI ASSOCIATED WITH TWO DIFFERENT CARDIOVASCULAR DISEASES
Wall shear stress (WSS) resulting from the frictional force of blood flow on endothelial cells can alter vascular
structure and homeostasis. Sites of atherosclerosis are known to correlate with low time-averaged WSS and
non-uniform WSS gradients. The success of coronary intervention to atherosclerosis using drug eluting stents
(DES) is limited by restenosis in ~10% of patients, but mechanisms are not fully understood. This study aims to
quantify the response of endothelial cells to WSS experienced after stenting for eventual use in understanding
whether the elution agents from DES impact the known relationship between cellular proliferation and WSS.
Using a syringe pump and Hele-Shaw flow chamber to impose WSS variability, rat endothelial cells were
subjected to a range of WSS from stenting (1.7-17 dyne/cm2). TNF-α in the media (0.3 ng/mL) simulated the
inflammation present with atherosclerosis. The number of cells positively stained for Ki67 served as a
surrogate for restenosis and decreased as WSS increased (y=11.02e-0.519x; R2 = 0.99; n=3). Prior attempts by
various laboratory researchers with this setup failed to show differences in WSS along the length of the
chamber. The current favorable findings are attributed to changes in the protocol influenced by extensive
literature research. This important advancement sets the stage to now quantify the influence of elution agents
from DES on the inverse relationship between restenosis and WSS.
Coarctation of the aorta (CoA) is one of the most common congenital cardiovascular diseases. It consis ts of a
constriction in the proximal descending thoracic aorta, which causes elevated blood pressure (BP) above, and
a BP gradient across, the coarctation. Even after corrective surgery, complications such as hypertension still
exist, leading to a reduced life expectancy. It is likely that CoA patients undergo changes in gene expression
due to the mechanical stimuli (i.e. elevated BP) introduced by the coarctation. In order to better understand
the mechanisms of coarctation pathology in humans, this study used a rabbit model of untreated and
corrected CoA. Comparing microarray data from this rabbit model and RNAseq data of 6 human patients with
CoA, we were able to quantify differentially expressed genes from the region of elevated BP as compared to
regions experiencing normal BP. We observed that the Natriuretic Peptide Receptor 3 (NPR3) gene was
downregulated in the proximal (elevated BP) region of rabbits and humans with CoA. To confirm these
findings, a PCR assay was first run with human control aortic samples to determine the level of NPR3
expression relative to GAPDH for eventual comparison with similar data from the CoA patients. This
experiment revealed 2.5 ng is a sufficient input cDNA when validating the level of NPR3 expression. NPR3
expression in CoA patients can now be more carefully studied using a paired aorta PCR assay. Future studies
will then be performed to understand the functional relevance of the decreased NPR3 expression in CoA
patients.