Will we regrow limbs some day?

Animals like newts and zebra fish can regenerate limbs, fins, even part of the heart. A human can renew his liver to some extent, and regrow a fingertip while very young, but not much more. But humans have very little regenerative capacity, probably because of an evolutionary trade-off: suppressing cell growth reduced the risk of cancer, enabling humans to live longer.

Two studies reported in The New York Times suggest that we may be able to have this ability after all.

By inactivating two genes that work to suppress tumors, researchers at Stanford University got mouse muscle cells to revert to a younger state, start dividing and help repair tissue. 

“We have shown we can recapitulate in mammalian cells behavior of lower vertebrate cells that is required for regeneration,” Dr. Jason H. Pomerantz said. “We would propose using it in amputations of a limb or part of a limb or in cardiac muscle.” Interfering with tumor suppressor genes is a dangerous game, but Dr. Pomerantz said the genes could be inhibited for just a short period by applying the right dose of drug. When the drug has dissipated, the antitumor function of the gene would be restored.

In the second study, at the University of California at San Francisco, researchers have developed a way of reprogramming the ordinary tissue cells of a mouse heart into heart muscle cells, the type that is irretrievably lost in a heart attack. To make clinical use of the discovery, they would need to duplicate the process with human cells, and then develop three drugs that could substitute for the three proteins used in the conversion process. The drugs could be loaded into a stent, a small tube used in coronary bypass operations. With the stent inserted into a heart artery, the drugs would convert some of the heart’s tissue cells into heart muscle cells.