Summary

Taking our first breaths marks the beginning of a new life, yet this may be the very act that limits our ability to grow and heal as adults. Studies in mice have pinned down a newborn’s exhalation of carbon dioxide, immediately after birth, as the starting gun that switches off their cells’ intrinsic ability to regenerate. “We were very surprised and excited by the CO2 effect,” says Zhigang He at Harvard Medical School, who led the research.

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