Reprogramming rejuvenates nerve cells and restores vision in mice

F.or biologists have been practicing a kind of time travel for years. You can take a speck of human skin and, with the right genetic adjustment, turn its internal clock back until it becomes its embryonic self, stripped of its identity and ready to become virtually any part of the human body. Since the method was published in 2006, the transformation of adult cells into stem cells has enabled all sorts of advances. Researchers can grow organs in dishes. They can replicate what happens in the womb without the regulatory headache of fetal tissue acquisition. It has become a daily tool in laboratory benches around the world and has won a Nobel Prize.

But for David Sinclair’s purposes, it wasn’t enough. His interest was to reverse the slings and arrows of old age, using that genetic time machine to create something that was actually therapeutic. When the cells were rewound into an embryo-like state, they did what embryonic cells do: divide like crazy. Outside of the intricate control of the prenatal environment, which gave rise to cancer. The mice used in such experiments died within days. “We wanted to bring the age of a tissue backwards, but find a way to stop it from going too far,” said Sinclair, a professor of genetics at Harvard Medical School.