Retiring retired cells

I’m looking at a picture of two mice. The one on the right looks healthy. The one on the left has graying fur, a hunched back, and an eye that’s been whitened by cataracts. “People ask: What the hell did you do to the mouse on the left?” says Nathaniel David. “We didn’t do anything.” Time did that. The left mouse is justold. The one on the right was born at the same time and is genetically identical. It looks spry because scientists have been subjecting it to an unusual treatment: For several months, they cleared retired cells from its body.

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