Inductive plethysmography in rats: towards a new standard for longitudinal non-invasive cardiac output monitoring in preclinical studies

Jacketed telemetry in rats: a novel non-invasive method for cardiorespiratory phenotyping during treadmill exercise

The development of alternative methods for monitoring cardiorespiratory function without restraint or surgical implantation is attracting growing interest for both ethical and scientific reasons. For this purpose, a new non-invasive jacketed telemetry tool consisting in a radio device maintained in a jacket worn by the animal was previously developed to improve cardiorespiratory monitoring. It allows simultaneous monitoring of cardiac activity by surface electrocardiagram, respiratory function by respiratory inductive plethysmography, and locomotor activity by accelerometry. However, this tool has only been validated under conditions of low/intermediate activity levels or in anesthetized animals. This study aimed to evaluate the feasibility of using this system in the challenging conditions of an exertion protocol. Male Wistar rats (n = 10, 8-9 weeks old) were subjected to an incremental treadmill exercise protocol including speed levels from 5 to 40 cm s-1 separated by 30-s breaks. Heart rate (HR) and minute ventilation (assessed by minute volume; MV) were continuously monitored. At the end of each running level and during the 30-s breaks, HR and MV showed a significant increase compared to resting values. They returned to the baseline within 60 min of post-exercise recovery. Overall, our results demonstrated (i) the ability of the animal to run while wearing the device and (ii) the ability of the device to reliably monitor cardiorespiratory adaptation to treadmill exercise despite significant mechanical disturbances. In conclusion, this study highlights the possibility of non-invasively monitoring cardiorespiratory functional variables that were previously unattainable under conditions of high activity in freely moving animals.

Leonurine pretreatment protects the heart from myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion (I/R), an important complication of reperfusion therapy for myocardial infarction, is characterized by hyperactive oxidative stress and inflammatory response. Leonurine (4-guanidino-n-butyl syringate, SCM-198), an alkaloid extracted from Herbaleonuri, was previously found to be highly cardioprotective both in vitro and in vivo. Our current study aimed to investigate the effect of SCM-198 preconditioning on myocardial I/R injury in vitro and in vivo, respectively, as well as to decipher the mechanism involved. Rats were pretreated with SCM-198 before subjected to 45 min of myocardial ischemia, which was followed by 24 h of reperfusion. Primary neonatal rat cardiac ventricular myocytes (NRCMs) were exposed to hypoxia (95% N2 + 5% CO2) for 12 h, and then to 12 h reoxygenation so as to mimic I/R. The enzymatic measurements demonstrated that SCM-198 reduced the release of infarction-related enzymes, and the hemodynamic and echocardiography measurements showed that SCM-198 restored cardiac functions, which suggested that SCM-198 could significantly reduce infarct size, maintaining cardiomyocyte morphology, and that SCM-198 pretreatment could significantly reduce cardiomyocytes apoptosis. Moreover, we demonstrated that SCM-198 could exert a cardioprotective effect by reducing reactive oxygen species (ROS) level and Akt phosphorylation while reducing the phosphorylation of p38 and JNK. In addition, the upregulation of p-Akt, Bcl-2/Bax induced by SCM-198 treatment were blocked by PI3K inhibitor LY294002, and the total protein level of Akt was not affected by SCM-198 pretreatment. Our experimental results indicated that SCM-198 could have a cardioprotective effect on I/R injury, which confirmed the utility of SCM-198 preconditioning as a strategy to prevent I/R injury.

Inductive Plethysmography for aortic Pulse Wave Velocity

Aortic stiffening is a process that is linked to cardiovascular risk factor increase. Then, aortic stiffness evaluation is considered as a good index of the evolution of pathophysiological situations, including myocardial infarction, heart failure, atherosclerosis or stroke. Today, pulse wave velocity (PWV) measurement is considered as the gold standard for evaluation of arterial stiffness. However, most of the current measurement techniques of PWV consider the time for the blood pressure pulse to propagate through a combined length of arteries and give access to arterial PWV. Therefore, none of the available techniques focuses only on the aorta. In the present context of smart clothes development, Inductive Plethsymography (IP) can be an interesting alternative for aortic PWV measure, since it has recently been shown that combination of thoracic and abdominal IP recordings can give cardiac information. We therefore investigate the potential of IP for aortic PWV measurement. In this preliminary study, a comparative analysis of PWV estimated from IP and PWV evaluated from the arm has been carried out on 11 healthy volunteers. Results show a significant linear correlation between both measures (r = 0.86, p<0.001), promising for future investigations on pathological populations.