A silent worker: Our heart beats from birth to death. But millions of people die from cardiovascular diseases. In vitro models are helping to understand disease mechanisms and developing new therapies.
The human heart performs its impressive task of pumping blood through the body 24 hours a day, 365 days a year, from birth to death. During a person’s lifetime, the heart beats about three billion times (Shaffer et al., 2014). But most people don’t think about their hearts until problems arise. According to the World Health Organization, cardiovascular diseases account for 17.7 million deaths globally every year. Hypertension and atherosclerosis are important contributors to heart-related problems (Dharmashankar and Widlansky, 2010; Gimbrone and García-Cardeña, 2016). Many special features of this extraordinary muscle are determined by its cellular and molecular characteristics, so scientists are increasingly researching at the microscopic level.
Cardiovascular research has been advancing in leaps and bounds: Within the coming years, cardiac cells themselves could increasingly turn from being models to providing the remedy. Scientists have been discussing the potential of regenerative therapies with stem cells (Lee and Walsh, 2016). These cells could support tissue regeneration and the generation of vessels. They also improve overall blood supply and the function of the heart.
New tools from molecular biology have provided researchers with insights on how cardiac disease develops. This could lead to novel therapeutic approaches for hypertension, stroke and coronary heart disease, for example. An important aspect is the electrophysiology of this unique muscle – because heart function is steered by the brain, but the muscle beats independently (Gordan et al., 2015).
Cardiac function is orchestrated by many different cell types (Tirziu et al., 2010). Cardiomyocytes, the cardiac muscle cells, are fundamental, and with 2-3 billion cells, they represent one-third of the cells in the heart. Endothelial cells and smooth muscle cells build the vasculature that nurtures the heart, along with the arteries and veins that connect the heart to the body. Connective tissue consists of fibroblasts and other cells. All of these cells contribute to supplying nutrients to our bodies. And all of them are research subjects. Using in vitro methods, scientists are able to analyze cell and tissue functions independently, as well as in various combinations.
Scientific results from cell models could help to deal with a number of widespread pathologic conditions that greatly affect endothelial and therefore heart function. When the vessels that usually feed the cardiomyocytes are obstructed, physicians call this condition “Ischemic heart disease.” Widespread reasons are atherosclerosis and hypertension that can lead ultimately to life-threatening complications like myocardial infarction (Dharmashankar and Widlansky, 2010; Gimbrone and García-Cardeña, 2016). Insights from cellular studies investigating endothelial dysfunction in those conditions could lead to new therapeutic targets in the future.
Angiogenesis, the formation of blood vessels from existing ones, is one possibility for the heart to heal itself (Schaun et al., 2016). To a certain extent, the heart can induce this reaction on its own, and different bioassays allow researchers to study that fascinating process in vitro and in vivo.