Scientists turned old mice young again by treating them with an enzyme that prevents the breakdown of chromosomes. The mice were "equivalent to 80-year-old humans" near death before the experiment; afterward, "they were the physiological equivalent of young adults." In these furry little Benjamin Buttons, brain disease was reversed and their sense of smell and fertility were restored.

"The experiment focused on telomerase, an enzyme that makes small units of DNA that seal the tips of chromosomes," The Wall Street Journal's Gautam Naik reports. "These DNA units, known as telomeres, act like the plastic caps at the ends of a shoelace, preventing the chromosomes from fraying and the genes inside them from unraveling." Scientists activated the gene, which caused increased levels of telomerase and "surprising signs of rejuvenation" in the mice.

Could telomerase unlock the secret to stopping human aging? Maybe, but there are complications. Tumors grow by turning on the telomerase gene, and some scientists looking for new ways to fight cancer are focusing on figuring out how to deactivate it.

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Elspeth Reeve