A Hydrogel Construct and Fibrin-based Glue Approach to Deliver Therapeutics in a Murine Myocardial Infarction Model.

The overall goal of this procedure is to transfer a therapeutic hydrogel patch to the surface of the heart in an effort to minimize the damage that follows a myocardial infarction. This is accomplished by first exposing the heart surface by thoracotomy. In the second step, a small suture knot is placed at the left coronary artery to induce a myocardial infarction.

Next, the therapeutic hydrogel patch is attached to the surface of the heart with a fibrin glue, and then the chest cavity is closed. Ultimately, histological analysis and small animal echocardiography are used to evaluate the changes in heart structure and function that occur in the presence and absence of these interventional techniques. This method can help answer key questions in the stem cell engineering field, such as determining what cell number and delivery methods are necessary for improving heart function.

Post myocardial infarction, Though this method is used to provide insight into therapies for myocardial infarctions. It can also be used for other tissue engineering and revascularization systems, such as the hind limb ischemia model. Begin by placing a healthy anesthetized mouse on the intubation stand and directing a light source towards the animal's chest cavity.

Next, use forceps to retract the laryngeal surface and expose the vocal cords. Then carefully guide a 20 gauge angio cath between the vocal cords and smoothly. Insert it into the trachea.

Connect the catheter to a small animal ventilator and to mechanically move the chest cavity one time to confirm proper positioning of the catheter. Then place the animal in the supine position on a heating pad to prevent hypothermia. Use a depilatory cream to remove the hair from the surgical site, followed by three alternating sterilizing scrubs with Betadine and 75%ethanol.Place.

Vet ointment on the animal's eyes to prevent dryness during the procedure, and then drape the surgical site. Now, begin the surgical procedure by making a skin incision approximately one centimeter to the left and running the entire length of the sternum. Locate the delineating line that represents the pectoralis major and use forceps to lift the muscle slightly to separate it from the underlying external oblique muscle.

Retracting the muscle medially. Free the external oblique muscle from the underlying rib cage in the same manner, but with a lateral retraction. To provide an unobscured view of the second, third, and fourth ribs.

Gently lift the fourth rib and use a cauterizer to open the chest cavity between the third and fourth ribs. Then place retractors to further open the cavity, exposing the heart using forceps, rupture the pericardium, then ligate the left coronary artery with an eight oh monofilament nylon suture approximately four millimeters from the apex of the heart directly below the bottom tip of the left atrium. If the suture is properly placed, a blanching of the ventricular myocardium and an increase in the size of the left atrium will be observed.

To place the patch, use a flat ended spatula to gently position the hydrogel on the surface of the heart at the site of the infarction. Using the spatula lightly hold the patch in place while an assistant quickly mixes the glue for about a minute. When the glue reaches the desired viscosity, quickly transfer approximately 10 microliters to the patch surface.

Then use three to four individual interrupted six oh mono filament nylon sutures to close the rib layer. Before closing the intercostal layer, insert a PE 10 cannula into the incision. Then close the pectoral muscles with three to four individual interrupted sutures.

Seal the skin layer with a continuous suture and attach a one milliliter syringe to the end of the cannula. Finally, evacuate the chest cavity, administer post-surgery analgesia within six to eight hours of closure, monitoring the animal until it is fully recovered and mode echocardiography measurements taken as early as two days post infarction, exhibit cessation of the left wall movement indicative of the muscle reconstruction. Qualitative calculations made from the data demonstrate a decrease in the ejection fraction and stroke volume in the infarcted hearts.

Histological analysis of healthy and infarcted hearts demonstrates the dilation of the left ventricle and thinning of the left ventricular wall observed in the infarcted myocardium. Both signs of tissue remodeling and scar tissue deposition application of the patch is therefore a useful therapeutic approach for treating the infarction as the fibrin glue does not harm the myocardium. Indeed, no tissue remodeling or ventricular thinning is observed at the site and the cardiomyocytes remain intact despite the addition of both the cardiac patch and the accompanying glue.

Additionally, viability testing confirms that the administration of the glue to the external surface of the cell encapsulating hydrogel patch does not affect cell survival within the patch. Once mastered, this technique can be performed in 30 to 40 minutes if performed properly While attempting this procedure, it's important to time the delivery of the fibrin glue to ensure proper adhesion of the patch to the hard surface.