For their study, the researchers made use of healthy mice. When the animals reached 10 months in age, their hypothalamic neural stem cells began to decrease in number. This occurred despite the fact that the typical signs of aging usually don't manifest until several months later.
To determine whether or not the loss of stem cells had a direct effect on aging, the researchers knocked them out in a group of mice. Not only did this selective disruption hasten aging among these mice, but a few of them even passed away far earlier than normal mice. On the other hand, mice whose brains had been injected with hypothalamic stem cells slowed down or overturned the numerous signs of aging. This applied to both normal mice and mice that had their hypothalamic stem cells depleted.
The anti-aging effects of hypothalamic stem cells was attributed to molecules known as microRNAS or miRNAs. In lieu of affecting protein synthesis, miRNAs are instead involved in gene expression. These molecules can be found in exosomes, which are minute particles present in all eukaryotic fluids, such as blood, urine, and, in the case of the study, cerebrospinal fluid.
Following the discovery of miRNAs, the researchers extracted and isolated the exosomes before introducing them into the cerebrospinal fluid of two different mice groups. This treatment slowed down the aging of animals from the two groups, which consisted of normal mice and mice without destroyed hypothalamic stem cells. On top of living longer, these mice exhibited improved memory retention, muscle endurance, and coordination. All of which had been severely reduced in the mice without exosomes. (Related: Healthy high-fat diet protects the brain from aging.)
Moving forward, the research team is now working towards identifying the RNAs which have the most potent anti-aging effects, as well as figuring out where in the body these RNAs travel to. "[During] the next few years, we still want to understand the whole picture as completely as we can. Then we can more seriously get to the therapeutic stage," said Dr. Dongsheng Cai, a senior author on the study, published in Nature.
Does this mean that the aging process could be stopped in its tracks with a simple injection of exosomes? Yes and no, according to Dr. Shinichiro Imai, a professor of development biology at Washington University. In 2017, Imai, who had no involvement in the study, explained to StatNews.com that there were new methods that made it possible to grow brain stem cells from a skin lesion fragment. However, actually administering them to a patient was a whole other story. The blood-brain barrier, a highly selective filtering mechanism that blocks out certain substances from entering the brain, would make delivering exosomes an incredibly difficult process.
Despite this seemingly insurmountable hurdle (at the time, boring into the brain seemed to be the most feasible option), Imai has nonetheless praised the researchers for their efforts, calling their work a “a really important study in the field of aging research.” Imai added that "It’s getting clearer that a very tiny part of our brain — the hypothalamus — is playing a very important role in controlling age and longevity in mammals."
Go to Brain.news for more studies and breakthroughs involving the brain and aging.
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