Stem Cells In The Hypothalamus Influence Aging

Hypothalamic neural stem cells taken from newborn mice delay aging in adult mice

Many researchers believe that aging is regulated in a distinct manner, and is somehow signalled throughout the body as we age - with a rate varying species to species. While this is still hotly debated and there is some evidence on both sides of the argument, the brain has emerged as a possible regulator of systemic (whole body) aging. One of the organs now being studied is the hypothalamus. 

A role for stem cells in the hypothalamus

Researchers noticed that numbers of neural stem cells in the hypothalamus decline sharply in mice at around 10 months of age - a few months prior to the onset of clear aging symptoms. At 2 years of age most mice no longer have any of these cells left. To study this phenomenon further, and whether it was somehow influencing the rate of decline, the research team targeted these cells in healthy mice with viruses to selectively destroy them. The result was a somewhat quickened aging process; accelerating memory problems, muscle weakening and coordination decline. These mice also died sooner. 

"Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal, and this decline accelerates aging. But we also found that the effects of this loss are not irreversible. By replenishing these stem cells or the molecules they produce, it's possible to slow and even reverse various aspects of aging throughout the body"

Exosomes can be used to carry multiple different types of substances throughout the body. Credit: IBM Research Exosomes samples.

Exosomes can be used to carry multiple different types of substances throughout the body. Credit: IBM Research Exosomes samples.

To test this connection further the scientists injected new neural stem cells from newborn mice into the hypothalamus of both healthy mice and those which had undergone destruction of their own hypothalamus stem cells. The injection corrected the decline caused by removing these cells, but more strikingly also extended lifespan by 10% in the ordinary mice. It also boosted cognitive and muscle function. 

What might the mechanism be? 

On closer examination these stem cells appeared to be releasing molecules called microRNAs, which regulate gene expression. These are encapsulated within little spheres called exosomes, and delivered into the cerebrospinal fluid. In this manner they are able to influence a large span of the body, in addition to important endocrine signals mediated through hormones. When these specific microRNA exosomes were extracted and injected into other mice on their own, they also proved able to slow aging and improve similar health parameters. 

While this will take further study to unravel whether other factors may be at play, and whether additional regions of the brain may be modulating the aging process alongside the hypothalamus. It offers some intriguing findings for now however. 

Read more at Nature