As we age, our organs lose function—cardiac muscles slacken, brain cells die, the diaphragm weakens and other organs shrink. One shrinking organ, in both humans and mice, is the thymus, “the place where the immune system’s T-cells mature,” says The Economist:
T-cells have various jobs, such as destroying body cells infected with viruses. As an animal grows older, its thymus shrinks and the organ’s internal structure changes. As a result, the supply of new T-cells diminishes. That is why elderly people are more subject than the young to infection.
In a new study, researchers got a specially bred mouse to reverse the course of aging in its thymus. The mouse was engineered so that its thymus would express a specific gene upon exposure to a specific chemical. From there, the induced activity of the gene caused the mouse's thymus to reverse its age-related degradation.
[W]hen the researchers studied the enlarged thymuses microscopically, and compared them with those from untreated control animals of the same ages, they found that the organs’ internal structures had reverted to their youthful nature. Most important of all, they found, the density of relevant T-cells in the experimental animals’ lymph was twice that of the controls.
The research is far, far away from being useful as a medical intervention. But, this sort of gene-targeted medicine, using the body's own systems to repair itself, is a promising pathway. The approach of targeted gene expression, says Reuters, is also a change from the major focus on stem cells that has driven the nascent field of regenerative medicine recently.