Muscle cells take heart

Skeletal muscle harbors cells that can form heart cells. The population, identified by Steve Winitsky, Neal Epstein, and colleagues (National Heart, Lung, and Blood Institute, Bethesda, MD), should benefit both clinical and basic research.

While isolating cells from mouse skeletal muscle, the authors noticed that a few floating cells in their culture were beating. These cells (which they named Spoc cells) eventually adhered and developed into normal looking and functioning cardiac myocytes. Spocs are the first heart precursors shown to beat and develop in vitro without long-term culture. They may finally provide a convenient set of cultured beating cardiac cells from the various transgenic mice used by cardiac researchers.

Spocs also know their place in vivo. The group injected the freshly isolated cells into the bloodstream of...