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Show UNIVERSITY OF UTAH PARENT FUND SCHOLAR 2012-2013 DYNAMICS OF VASCULAR DEVELOPMENT WITH CONOTRUNCAL BANDED HEART IN CHICK EMBRYO Mikaelyn M. Kooyman (Norman Hu) Department of Pediatrics University of Utah School of Medicine University of Utah Altering myocardial growth interferes with hemodynamic parameters such as blood flow or pressure, and subsequently alters vascular development. W e hypothesized that experimentally increasing hemodynamic stress by conotruncal banding during early heart development would result in a remodeling of the arterial wall. The outflow tract of a stage-21 (3Vi-d) chick embryo was constricted with an overhand knot of a 10-0 nylon suture, and the embryo was returned to the incubator. Normal embryo was not operated. Intracardiac flow patterns were recorded using a digital camera attached to the stereophotomicroscope. A bolus of 1.0-nl Fast Green diluted in PBS (0.28 mg/100 ml) was injected through the 2nd bifurcation of the right vitelline vein at stage-21 (n=13) immediately after the ligation, and at stage-24 (4-d, n=10). W e also recorded blood flow in similar normal embryos. W e harvested the embryo at stage-34 (8-d), and fixed the heart in diastole with 0.025 ug/Kg diltiazem in 4 % paraformaldehyde. Transverse sections of the carotid artery were stained with H&E staining, and the dorsal aorta was treated with rhodamin-phalloidin a-smooth muscle antibody staining. En face sections of the aorta were examined under confocal microscopy. Actin alignment and density were quantitated by customized MatLab software. Data are presented as mean±SEM, and analyzed by Fisher Exact test or Student's t test with statistical significance defined as a p value < 5%. 71.4% of the ligated embryos showed blood flowing dominantly through the 3rd or 6th aortic arches rather than the 4th as in normal stage-24 embryos. Both right and left carotid arteries in the banded heart had thinner vascular walls. S o m e vessels in the banded hearts displayed dilation and variation in size between the right and left arteries. Alignment analysis revealed that the fiber orientation in the banded hearts was anisotropic and more widely spaced (Figure 1). The actin filament density in the ligated tissue had almost 5 0 % less volume, and a decrease in thickness (Figure 2). Altered growth in the developing heart caused by altering the hemodynamics results in secondary abnormalities in development due to abnormal vascular architecture. These factors m a y be important in the understanding of heart development with defects such as coarctation of the aorta, vascular rings, aortic stenosis and interrupted aortic arch. Figure 1. The arrangement of the actin filaments is more discordant and less dense in the conotruncal banded heart (B) when compared to those of the normal embryo (A). Normal Heart Conotruncal Banded Heart Figure 2: The alignment (A) and density (B) indices are significantly decreased in the banded hearts when compared to the normal |