A heart attack (myocardial infarction) is caused by the blockage of one or more coronary arteries and causes the heart to be starved of essential nutrients and oxygen, resulting in damage to the heart muscle and consequently weakening its ability to pump blood around the body. Current treatments for heart attacks depend on the severity of the patient’s symptoms and how soon the patient can gain access to treatment. Percutaneous coronary intervention (PCI) may be performed which is a procedure to widen narrowed coronary arteries; however, a coronary angiography must be performed first to assess the patient’s suitability for PCI. In addition to PCI, thrombolytic medicines (e.g. alteplase and streptokinase) may be used to break down blood clots. Despite these interventions, damage caused to the heart from the initial heart attack increases the likelihood of a secondary heart attack and consequent heart failure.
Over recent years engineered heart tissue (EHT) patches have been developed as a novel therapy for patients who have suffered a heart attack. The proposition and design of the EHT is a thumb-sized patch of heart tissue (3cm x 2cm) that contains up to 50 million human induced pluripotent stem cell–derived cardiomyocytes (hPSC-CMs). The cells are grown over a small scaffold that aligns and organises them so they may become functional heart tissue. The heart patch would be sewn onto the patient’s heart where it would develop into a healthy working muscle and help restore efficient pumping of the ventricle.
The engineered heart tissue (EHT) patches have been shown to be effective in small animal models of myocardial infarction (specifically rats and guinea pigs) and indicate improvements in vascularization, scar size, cellular retention and heart function without developing any arrhythmias within four weeks of implantation. More recently, to establish the efficacy and feasibility of this technique in a larger animal, the use of EHT patches has been tested in a rabbit myocardial infarction model. The rabbit heart has more similarities to the human heart than other commonly used laboratory animals. The cardiac action potential in a rabbit has a morphology and ionic composition similar to humans compared to rats and mice which lack certain ion channels (eg hERG). In addition, the process for intracellular calcium removal within the heart cells in rabbits is more akin to the human situation. This makes the rabbit a more relevant species and so allows a better representation, relevance, and application to the human situation. The findings from the study in the rabbit model concluded that EHT implantation was safe and feasible, did not cause any significant development of abnormal heart rhythms but improved ventricular function and reduced scar size. These results in laboratory animals will be used to design the clinical trials required to test the safety and efficacy of this potential new treatment in humans.
Use of animals in research is important when developing novel technologies that may be of benefit to human health. All new drugs and various medical technologies in use today have undergone standard regulatory preclinical procedures using animals before being allowed to proceed into human clinical trials. The welfare of the animals in our care is of the utmost importance to Vivonics and central to good quality science.