Researchers from the Albert Einstein College of Medicine have discovered that aging in mice is regulated by cells in the hypothalamus, the structure found in vertebrates' brains that control metabolism and growth.
In their Nature paper, the team showed that hypothalamic stem cells are least partly responsible for how fast the aging process occurs. The number of these cells begins to diminish when the rats are 10 months old, which is considerably earlier than when the first visible signs of aging appear. By 24 months, when the mice were very old, most of these cells were gone.
"Our research shows that the number of hypothalamic neural stem cells naturally declines over the life of the animal, and this decline accelerates aging," senior author Professor Dongsheng Cai said in a statement. "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."
The hypothalamic stem cells release microRNA molecules into the cerebrospinal fluid of animals. Unlike standard RNA molecules that are crucial to the synthesis of proteins, the microRNA’s function appears to be the regulation of gene expression.
The scientists took a group of middle-aged mice and disrupted the hypothalamic stem cells in their brains. The disrupted mice began aging faster than regular mice. "This disruption greatly accelerated aging compared with control mice, and those animals with disrupted stem cells died earlier than normal," added Dr Cai.
The team also wondered if the hypothalamic stem cells could be used in reverse to slow down the aging process. The researchers injected microRNA extracted from the hypothalamic stem cells into the cerebrospinal fluid of the control mice and the middle-aged mice whose hypothalamus had been disrupted. Aging in both groups was seen to slow down, which was measured by assessing coordination, muscle endurance, social behavior, and cognitive ability.
Researchers are now looking into exactly how the microRNA molecules help to fight the aging process and if this can be translated to humans. Apart from an apparent youth elixir, these molecules could be pivotal to fight age-related degenerative diseases.