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 HH20 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-zero 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 param 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.
