Remaking the heart

In recent years, stem cells and progenitor cells have been shown to perform remarkable tricks of transformation, from blood to brain, and skin to nerve. But the concept remains of differentiated cells as fixed personalities. Now Giulio Cossu (University of Rome, Italy), Elisabetta Dejana (FIRC Institute of Molecular Oncology, Milan, Italy) and colleagues have found that a differentiated endothelial cell line can transdifferentiate into contractile cardiac muscle—a feat that may have implications for treating heart attacks.

The endothelial cells do nottransdifferentiate spontaneously, but require the assistance of co- cultured cardiomyocytes. A small fraction of the cocultured endothelial cells begin expressing cardiac markers, and become electrically coupled with the cardiomyocytes. Injection of endothelial cells into heart tissue that has been starved of oxygen results in the formation of cardiac muscle by some of the injected cells.

This phenomenon makes Dejana think that it might be possible to repair tissue damaged by heart attacks. “You have a major problem when you have heart failure because cardiomyocytes cannot divide,” she says. Injected endothelial cells, and even the endothelial cells from microvessels around an oxygen-starved region, might replace dead and dying cardiac muscle cells. But in both cases Dejana believes that the transdifferentiation process must be understood so that it can be improved upon. “Now the major challenge,” she says, “is to make it more efficient.” ▪

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