Sickle Cell Disease Mediates Middle Cerebral Artery Shear Stress Profiles That Affect Endothelial Cell Responses

Sickle cell anemia is a blood disorder that causes red blood cells to become sickle and stick to the interior surface of blood vessels. Many sickle cell anemia patients experience an accelerated elastic lamina degradation which predisposes children with sickle cell to strokes at an early age. There is believed to be a correlation between the shear stress that sickle cell anemia patients experience in their blood vessels and the strokes that children experience between the ages of 2 and 5. My project studied the effect of shear stress profiles on cathepsin levels to understand the biochemical pathway that predisposes children to strokes. We hypothesized that the atheroprone sickle shear stress profile would activate cathepsin expression in the cells. To test this, we cultured human aortic endothelial cells (HAEC). When cells reached confluency, they were placed into a bioreactor to simulate various shear stress profiles. Upon analysis, the atheroprotective shear stress profile for sickle and non-sickle patients had a significantly higher average angular velocity than the atheroprone angular velocity profile for sickle and non-sickle patients. After cells were exposed to shear stress, they were lysed and the protein was quantified. Then, a cathepsin zymography was performed to determine which cathepsins were active in each shear stress profile. For all cells, phosphorylated eNOS was higher in the atheroprotective shear stress in comparison to static and pro-remodeling. Additionally, cells exposed to ICA vasoprotective stress showed signs of increased cathepsin expression while cells exposed to MCA pro-remodeling stress showed signs of increased cathepsin expression.