Experimental assessment of a modified retrograde traction tracheal intubation method for increasing the success rate of myocardial infarction model in rats

Background Animal models of myocardial infarction （MI） have been widely used to study the pathologi- cal and physiological changes that occur in MI, and to objectively evaluate the efficacy of new treatments. They are an important tool in this procedure. However, the mortality rate of MI animal models has so far been higher than in real-life situations. The aim of this study was to explore the use of a modified retrograde traction tracheal intubation （MRTI） method for increasing the success rate of MI models in rats. Methods Sixty male Sprague-Dawley rats were used in the experiment. Using the MRTI method of artificial airway generation, we established the MI model by ligation of the left anterior descending branch of the coronary artery. We analyzed the effects of MRTI, the use of lidocaine, operative details, nursing considerations during the operation, and post-operative factors on the success rate of the MI model in rats. Results The success rate of generating an MI model in rats can be significantly increased using the following methods： 1） Setting up the artificial airway through the use of MRTI by using a single-lumen central venous catheter; 2） Selecting a ligation site 2 mm be- low the midpoint of the connection between the left atrial appendage and the pulmonary cone; 3） Adding a drop of lidocaine to the surface of the heart to slow down the heart rate, make the operation easier to perform, and prevent arrhythmias postoperatively; 4） Clearing up airway secretions timely both intra and postoperative- ly; 5） Making sure that rats are in a warm state both intra and postoperatively; 6） Preventing wound infection. Conclusions Use of the MRTI method can quickly establish an artificial airway in rats. Intraoperative use of lidocaine, selecting a precise vascular ligation site, and appropriate care both intra and postoperatively can in- crease the success rate of MI model generation.

GENE TRANSFER INTO PORCINE MYOCARDIUM VIA PERICARDIAL CAVITY BY HOMEMADE EASY PUNCTURE DEVICE

Objective To explore the feasibility and safety of gene transfer into porcine myocardium via the pericardial cavity by a homemade easy device. Methods Replication-deficient recombinant adenoviral vector carrying LacZ report gene (Ad-LacZ) was constructed by the calcium phosphate precipitation method. Twelve healthy Chinese mini-swine were randomly divided into experimental group (n=6) and control group (n=6). Acute myocardial infarction (AMI) model was established by balloon occlusion of the distal part of D1 branch of left anterior descending (LAD) artery, at the same time the intra-pericardial cavity injections were performed through the small incision of the abdominal wall below the xyphoid appendix using a homemade device. Then gene transfer was performed using a central venous catheter. The pericardium was pretreated with injection of a mixture of collagenase (1 200 U) and hyaluronidase (3 000 U) in both groups. Then 2.0×109 plaque formation unit (PFU) Ad-LacZ was injected into the pericardial cavity in experimental group, while 1 mL of normal saline was injected in the control group. The β-galactosidase activity detection and X-gal staining of the ischemic myocardium were performed on the 3rd, 7th, and 28th day after injection. Results The LAD artery was occluded completely and infarction and ischemia were detected by histological assessment. In experimental group, the X-gal staining positive cells and β-galactosidase activity quantification were detectable on the 3rd day after injection, increased markedly on the 7th day, and then declined on the 28th day. The transfer efficiencies indicated by the positive myocardial cells were 16.7%, 45.6%, 22.8% on the 3rd, 7th, 28th day, respectively. In control group, no positive cells and β-galactosidase activity were observed. Conclusion Adenovirus can be transferred into ischemic myocardium and express target gene in the AMI model for four weeks with the homemade easy device via pericardial cavity pretreated by collagenase and hyaluronidase.