Ernestina Schipani, M.D., Ph.D., Professor of Orthopaedic Surgery, Professor of Internal Medicine, Professor of Cell and Developmental Biology, University of Michigan Medical School

The cells that compose the muscular heart wall are called cardiac myofibers. These cells are tubular in nature and are connected together end to end. This is an image of a cross-section of the cardiac muscle of a newborn mouse heart. Here, the individual muscle cells are labeled in green, the nucleus is blue and the cell membranes are outlined in red. Coordinated contractions of these cells pump blood throughout the body. For years, scientists thought that cardiac myofibers never regenerate. However, newer studies show that up to the age of 20, we regenerate about 1% of our cardiac muscle cells every year. Recently, investigators have succeeded in generating contracting cardiac myofibers in a culture dish, starting from cells called embryonic stem cells. Soon, it will be possible to use such cells to repair injured or diseased hearts. 

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