Left Atrial Ligation in the Avian Embryo as a Model for Altered Hemodynamic Loading During Early Vascular Development

Our lab focuses on the effect of blood flow and pressure loading on the avian embryonic aortic arches and ventricles. We aim to contribute to the complex biomechanical mechanisms that link vascular morphology to mechanical loading in the LAL model. We also maintain a strong clinical and surgical bioengineering research program.

In a recent collaborative study conducted by Professor Yopp's group at Imperial College, image-based finite element modeling and single-cell RNA sequencing were used to illustrate the increasing dilation on myocardial strains in ventricles after left ultra ligation in stage two and five. Such knowledge may be translated to fatal cardiovascular interventions in humans. A smaller left ventricular cavity and compression in the entire trabecular recesses were absorbed with LAL intervention.

Furthermore, LAL altered the normal ventricular structure and reorientated the appearance of trabecular. In addition, the LAL model caused right ventricular cavity enlargement, changes in trabecular structure, and increased myocardial volume load. The LAL affects hemodynamic loading in the chick embryo leading to hypoplastic left heart syndrome.

The elasticity of the normally developing myocardium undergoes changes, particularly in the HLHS phenotype. These findings can guide the development of potential treatments for clinical trials and guide predictive competition models. Start by gently cleaning the eggshells of fertilized white leghorn chicken eggs with lint-free ethanol soaked wipes.

Incubate the eggs blunt end up until the desired stage, usually HH 20 to 21. Before starting the procedure, prepare the required number of knots by tying a loose overhand knot into a 1.5 centimeter long 10/0 suture. Ensure that the knot is not tight and is large enough to fit over the atria.

Crack open the eggshell gently with the reverse end of the tweezers, supporting the egg firmly to prevent unwanted cracks. Open a window from the blunt end of the egg and remove both the outer and inner membranes. Use micro scissors to remove only the necessary vitelline membrane Once the embryo is free of the vitelline membrane, place the closed tip tweezer under the dorsal segment of the embryo and gently flip it to expose the left side.

Remove all membranes immediately around the atrial bud by removing the coarse membranes first, and then using finer tweezers for fine membrane removal. Position the pre-prepared knot close to the embryo. Correctly orient the open knot over the left atrial bud to execute the knot tightening.

Using micro scissors, cut the excess suture ends as close as possible to the bud and remove the excess suture pieces with tweezers. Finally, using closed tweezers, return the embryo to its original position. After completing the microsurgery, cover the egg with a double layer of paraform and return it to the incubator.

The left atrial ligation or LAL models showed that a more compact myocardial structure was achieved with significant morphological changes compared to normal development. Extracellular matrix deposition was observed around the cardiac interstitium resembling myocardial fibrosis. Morphometric porosity measurements revealed a smaller left ventricular cavity and trabecular compaction in the LAL models.

At HH 25 of the LAL model, an enlarged right ventricular cavity, altered trabecular architecture, and myocardial volume were observed. Optical coherence tomography imaging of LAL models showed a significant reduction in left ventricular size and diameter compared to the control. LAL groups also exhibited an increase in wall thickness compared to control groups at HH 25.