Development of an ischemia/reperfusion injury model in the living myocardial slice

The most effective treatment for acute myocardial infarction is reperfusion; however, reperfusion injury can increase infarct size by 50%. Although many benchtop studies have had success treating or preventing ischemia/reperfusion (I/R) injury these results have failed to translate into the clinic. One proposed reason for this failure is the simplicity of in vitro models. We have developed an in vitro I/R model using the living myocardial slice (LMS) which bridges the gap between the flexibility of cell studies and the in vivo complexity of animal models. LMS from Lewis rats (250-400 g) are initially cultured for 1.5 hours in a hypoxic environment (1% O2). Afterwards, the media is slowly reoxygenated over the course of 1 hour and the LMS are cultured for an additional 19-23 hours. After culture we quantify functional changes in the LMS by measuring contractility at physiological load and by quantifying changes in the Frank-Starling relationship. The active force in the I/R group decreased by 57% compared to the control group (p<0.05). Additionally, the slope of the Frank-Starling curve decreased in the I/R group by 48% compared to the control group (p<0.05). We also applied the I/R model to LMS made from rejected donor hearts and biopsies from failing heart tissue. In human tissue the active force also decreased in the I/R group. The I/R model in the LMS captures a decrease in function in response to hypoxia. This model can be used to further characterise the I/R response in heart tissue and be more effective for testing new treatments in vitro.