Reelin Signaling in Vascular Endothelial Cell Biology
Authors: Scott Ellen , Dougherty Timothy J , Gorski Grzegorz , Hatcher Cathy J 
Published: June 2021

IntroductionEstablishment of the coronary circulation is a critical step in heart development. Formation of functional coronary vessels is required for the heart to undergo successful compaction of the ventricular myocardium. Oxygen and nutrients are delivered to the contractile myocardium through the coronary vasculature. Molecular signaling pathways that control formation of the coronary vessels are being identified. Immunofluorescent studies from our lab indicate that the Reelin extracellular matrix glycoprotein is expressed within the vascular endothelial cells of developing and mature coronary vessels of the mouse heart. The Reelin signaling pathway is known to contribute to brain and lymphatic system development by influencing neuronal and endothelial cell behaviors such as adhesion and migration. However, its role in coronary vascular development is as yet unidentified.Study ObjectiveThe goal of this study was to elucidate the potential roles of Reelin in formation of the coronary vasculature by identifying how it regulates vascular endothelial cell behaviors. We hypothesized that Reelin signaling regulates establishment of coronary vessel integrity during cardiogenesis by influencing vascular endothelial cell adhesion as well as cell membrane permeability and resistance.MethodsWe utilized the primary human dermal microvascular endothelial cell line (HDMEC) as an in vitro system to examine contributions of Reelin to vascular endothelial cell behavior. A small interfering RNA‐mediated approach was used to silence the endogenous RELN gene in HDMECs and reduce Reelin protein expression. Transfected HDMECs were subjected to cell‐based assays to assess changes in vascular endothelial cell behavior in response to RELN silencing. We assessed vascular endothelial cell adhesion on extracellular matrices that are required during coronary vessel development. Vessel integrity was examined by assaying endothelial cell membrane permeability and resistance in RELN‐silenced cells. Also, we examined the effect of Reelin expression on cell viability.ResultsRELN‐silenced HDMECs exhibited a >90% reduction in Reelin expression in comparison to non‐targeting, negative control HDMECs. This significant Reelin reduction altered vascular endothelial cell adhesion to certain extracellular matrices. These RELN‐silenced HDMECs exhibited a significant decrease in baseline cell membrane permeability and concomitant changes in cell membrane resistance. Furthermore, we observed changes in cell morphology in RELN‐silenced cells versus control cells. Preliminary data suggests that loss of RELN expression affects vascular endothelial cell morphology and expression of components within the Reelin signaling pathway.ConclusionsBased on this evidence, we conclude that Reelin influences adhesion, morphology, membrane permeability and membrane resistance of vascular endothelial cells in order to regulate vessel wall integrity. These findings may provide key evidence as to how Reelin expression in nascent vascular endothelial cells impacts formation of the coronary vessels during mammalian cardiovascular development.Support or Funding InformationAHA 17AIREA3360773 and PCOM Center for Chronic Disorders of AgingThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.