RESUMO
Objective:To evaluate the effects of exosomes derived from cardiac fibroblasts treated with hypothermic hypoxia-reoxygenation on ventricular electrical conduction during hypothermic cardiac ischemia-reperfusion (I/R) in rats.Methods:SPF neonatal Sprague-Dawley rats of either sex, aged 1-2 days, were used, and primary cardiac fibroblasts were extracted by differential adhesion method. The cells were passaged for 2-4 generations. When the cell density reached 60%-70%, the cells were transferred and exposed to 95% N 2 + 5% CO 2 for 1 h at 4 ℃, and then exposed to 95% air + 5% CO 2 for 24-48 h at 37 ℃, and then exosomes were extracted. Twenty-four SPF healthy adult male Sprague-Dawley rats, aged 2-3 months, weighing 280-360 g, were divided into 3 groups ( n=8 each) according to the random number table method: control group (group C), hypothermic cardiac IR group (I/R group) and exosome + hypothermic cardiac IR group (Exo-IR group). At 48 h before equilibrium perfusion, 1.5 ml (200 μg) of exosomes secreted by cardiac fibroblasts treated with hypothermic hypoxia-reoxygenation was injected into the tail vein in Exo-IR group, and PBS 1.5 ml was injected into the tail vein in C group and IR group each. Group C received 110 min equilibration perfusion. After 20 min of equilibration, the perfusion was suspended for 60 min (global ischemia) followed by 30 min of reperfusion in IR and Exo-IR groups. Microelectrode arrays were applied at 20 min of equilibrium perfusion and 15 and 30 min of reperfusion to obtain myocardial conduction velocity (CV), absolute conduction inhomogeneity (P 5-95) and inhomogeneity index (P 5-95/P 50) on the left ventricular surface of isolated rat hearts. Results:Compared with group C, the CV was significantly decreased at 15 and 30 min of reperfusion, and P 5-95 and P 5-95/P 50 were increased in IR and Exo-IR groups ( P<0.05). Compared with IR group, CV was significantly increased at 15 and 30 min of reperfusion, and P 5-95 and P 5-95/P 50 were decreased in Exo-IR group ( P<0.05). Conclusions:Exosomes derived from cardiac fibroblasts treated with hypothermic hypoxia-reoxygenation can improve ventricular electrical conduction during hypothermic cardiac I/R in rats.