Aortic Debanding is a useful experimental model for studying myocardial reverse remodeling in rodents and for a reveling novel insights into the mechanisms of cardiomyocytes regression and iso lic functional recovery. These metal facilitates the evolution of critique reverse modeling in VIVO and the collection of biological samples for in-vitro and molecular studies at different time points during the disease progression. This technique mimics the progression of myocardial remodeling and reversely remodeling and allows exploring the mechanisms of incomplete myocardial recovery.
This protocol provides insights into the mechanisms and the line complete and incomplete myocardial reverse remodeling in chronic pressure overload related pathologies such as eye pretension or aortic stenosis. Connect the orotracheal tube to the ventilator to initiate the mechanical ventilation and adjust the ventilator to a frequency of 160 breaths per minute and a tidal volume of 10 milliliters per kilogram. Before beginning the band procedure, confirm a lack of response to pain reflex in a six to eight week old C57 black six mouse, shave and applied depilatory cream from the neck line to the mid chest level of the mouse and apply ointment to the animal's eyes.
Place a rectal probe and the oximeter for monitoring temperature blood oxygenation and heart rate. Place the mouse in the right lateral decubitus on a heating pad and tape the limbs to the magnetic fixator retraction system to maintain the animal in the correct position during the procedure. Then, disinfect the chest with consecutive 70%alcohol and povidone-iodine solution scrubs then and open the skin muscle and ribs in order to perform the band to the aorta.
At the end of the procedure apply povidone-iodine solution to the skin suture site and administer analgesia twice daily for two to three days, Then inject sterile saline intraperitoneal Lea to prevent dehydration in cases of significant bleeding during the surgery and place the animal in an incubator with monitoring until full recovery. Seven weeks after the banding surgery, gently dissect to the tissues, adhesion and fibrosis around the aorta in half of the banded animals until the constriction becomes visible. Carefully dissect the aorta and separate the suture from the vessel, then use scissors to cut the suture.
Note that's a prolonged occlusion of the ax indigo water during binding or demonic may lead to lung edema, an excessive activation of inflammatory pathways. Close the chest wall with a simple interrupted or continuous six old polypropylene sutures using the minimum number of stitches possible and close the skin with a six O silk polypropylene suture in a continuous suture pattern, then perform the postoperative care as demonstrated. Every two to three weeks after the surgery remove the fur from the neck line to the mid chest level as demonstrated and place the animal on a heating pad in the supine position Place ECG electrodes onto the exposed skin and confirm the presence of a good ECG trace and a heart rate between 300 and 350 beats per minute.
Monitor the temperature and apply echo gel to the chest region. Place the mice in dorsal recumbency slightly turned to the right and start the echocardiograph using the appropriate settings. Next, position an ultrasound probe over the thorax and assess the pressure gradient across the aorta.
Record two dimensional guided images of the aorta showing the presence or absence of the ascending aorta constriction to anatomically visualize the efficacy of the banding and debanding. To assess the hypertrophy, position the probe at a left ventricle short axis at the papillary muscle level and press the mode tracing button to visualize the left ventricle anterior wall, left ventricle diameter and left ventricle posterior wall in diacetyl and systole. Then assess the systolic function and calculate the ejection fraction and fractional shortening according to standard protocols.
To assess the diastolic function, determine the peak of the post wave Doppler of the early and leaf mitral flow velocity using an atypical four chamber view just above the mitral leaflets and record the lateral mitral annular myocardial early diastolic and peak systolic velocities using post tissue doppler imaging and the apical four chamber view. The success of aortic constriction can be verified by an increased left ventricle and systolic pressure. And by Doppler aortic flow velocities greater than 2.5 meters per second.
Compared to Sham operated animals, bending induced left ventricle hypertrophy is demonstrated by an increased in left ventricle mass and an impaired diastolic function as evidenced by higher filling pressures and left ventricular end diastolic pressure. Histologically, seven weeks of aortic banding induces significant cardiomyocytes hypertrophy and fibrosis. In my subjected to debanding, as successful removal of the aortic stenosis can be verified by echo Doppler velocities.
Overall debanding promotes a significant decrease in the afterload and the left ventricle hypertrophy assessed by LV mass. Moreover, a normalization of the diastolic function is also observed. When you play it carefully the avoiding prolonged ethical collusion in order to guarantee that the blood oxygenation remains above 90%This minimum model allows us to study my cardiac remodeling and reverse remodeling at different time points of the disease progression and to even wake the most dysregulated pathways at each time point.
This procedure allows to assess the therapeutic potential of promising drugs as well as to study the impact of several co-morbidities in myocardial reverse remolding and recovery.
