INSERM, Unité U 955, Equipe 03, Créteil, France.
J Cardiovasc Pharmacol Ther. 2013 Jul;18(4):367-75. doi: 10.1177/1074248412475158. Epub 2013 Feb 13.
The use of in vitro experimental models of hypoxia-reoxygenation (H/R) that mimic in vivo ischemia-reperfusion represents a powerful tool to investigate cardioprotective strategies against myocardial infarction. Most in vitro studies are performed using neonatal cardiac cells or immortalized embryonic cardiac cell lines which may limit the extrapolation of the results. We developed an H/R model using adult cardiomyocytes freshly isolated from mice and compared its characteristics to the in vivo ischemia-reperfusion conditions. First, cell death was assessed at different values of pH medium during hypoxia (6.2 vs 7.4) to simulate extracellular pH during in vivo ischemia. Cardiomyocyte mortality was aggravated with hypoxia under acidic pH. We next evaluated the relationship between the duration of hypoxia and cell death. Hypoxia time-dependently reduced myocyte viability (-24%, -36%, -53%, and -74% with 1, 1.5, 2, and 3 hours of hypoxia followed by 17 hours of reoxygenation, respectively). We then focused on the duration of reoxygenation as cardioprotective strategies have been reported to have different effects with short and long durations of reperfusion. We observed that cardiomyocyte mortality was increased when the duration of reoxygenation was increased from 2 h to 17 hours. Finally, we used our characterized model to investigate the cardioprotective effect of regular treadmill exercise. Myocyte viability was significantly greater in exercised when compared to sedentary mice (44% and 26%, respectively). Similarly, mice submitted to in vivo ischemia-reperfusion elicited infarct sizes reaching 27%, 43%, and 55% with 20, 30, and 45 minutes of coronary artery occlusion. In addition, infarct size was significantly reduced by exercise. In conclusion, this H/R model of cardiomyocytes freshly isolated from adult mice shows similar characteristics to the in vivo ischemia-reperfusion conditions. The comparison of in vivo and in vitro settings represents a powerful approach to investigate cardioprotective strategies and to distinguish between direct and indirect cardiomyocyte-dependent mechanisms.
体外缺氧-复氧（H/R）实验模型模拟体内缺血-再灌注，是研究心肌梗死保护策略的有力工具。大多数体外研究使用新生心脏细胞或永生化胚胎心脏细胞系进行，这可能限制了结果的外推。我们使用从成年小鼠中分离的新鲜心肌细胞建立了 H/R 模型，并将其特征与体内缺血-再灌注条件进行了比较。首先，在模拟体内缺血时细胞外 pH 值的不同缺氧（6.2 与 7.4）条件下评估细胞死亡，发现缺氧下细胞死亡率在酸性 pH 值时加重。接下来，我们评估了缺氧时间与细胞死亡的关系。缺氧时间依赖性地降低了心肌细胞活力（分别用 1、1.5、2 和 3 小时缺氧，随后再复氧 17 小时，导致细胞活力降低 24%、36%、53%和 74%）。然后，我们关注复氧时间，因为据报道，心脏保护策略在短时间和长时间再灌注时具有不同的效果。结果发现，随着复氧时间从 2 小时延长至 17 小时，心肌细胞死亡率增加。最后，我们使用我们的模型研究了常规跑步机运动的心脏保护作用。与久坐不动的小鼠相比，运动小鼠的心肌细胞活力显著更高（分别为 44%和 26%）。同样，体内缺血-再灌注引起的心肌梗死面积在 20、30 和 45 分钟冠状动脉闭塞时分别达到 27%、43%和 55%。此外，运动显著减小了梗死面积。总之，从成年小鼠中分离的新鲜心肌细胞的这种 H/R 模型具有与体内缺血-再灌注相似的特征。体内和体外设置的比较代表了一种强大的方法来研究心脏保护策略，并区分直接和间接依赖心肌细胞的机制。
