Scientists Reverse Age-Related Thinking Problems in Mice by Tinkering With Immune Cells in Their Brains

Scientists have reversed age-related thinking problems in mice by tinkering with their immune cells, in work they hope could one day help people with Alzheimer's disease and other forms of dementia.

Our cognitive abilities are thought to decline with age because of changes to our brains, such as a decline in grey matter, as well as the potential effects of medications and health problems

The latest study focused on a type of immune cell called group 2 innate lymphoid cells (ILC2s), which help to repair parts of the central nervous system such as the spinal cord.

In the brains of young—two to three-month-old—and older—18 to 22-month-old—mice, the researchers found ILC2s collected in a part of the brain called the choroid plexus, a specialized brain barrier structure. This sits near the hippocampus, which is key for learning and memory.

In older mice, the team of immunologists and neuroscientists discovered five times as many ILC2s when compared with the younger mice, and that in older mice, these cells were less active.

The team then used a special molecule to reawaken the inactive ILC2s in older mice, and put the animals through a series of tests to see if their cognitive skills had improved—which they did.

The scientists also found a collection of ILC2s in the choroid plexus in brain autopsies of humans over than 65-years-old.

Kristen L. Zuloaga of Albany Medical College, co-author of the paper published in the Journal of Experimental Medicine, told Newsweek their study is the first to identify ILC2 cells in the choroid plexus. "We further discovered that these cells accumulate with aging. Strikingly, these aging-associated ILC2s are capable of improving brain physiology and reducing aging-associated cognitive decline," she said.

Zuloaga acknowledged the study was limited because the work was based largely on mouse models, and the team are yet to investigate the immune cells in human patients with neurodegenerative diseases.

However, the team said they were surprised at the findings.

The study's first author, Ivan Ting Hin Fung, of the department of immunology and microbial disease at Albany Medical College, told Newsweek: "Little is known about the roles immune cells play in brain physiology and function and how they influence aging-associated neurodegenerative diseases like Alzheimer's disease."

They hope the study will help with the development of new ways of combating Alzheimer's disease and other forms of dementia that are related to age. Currently, there are no treatments for Alzheimer's disease, which an estimated 5.8 million Americans are living with.

Richard Siow, director of Ageing Research at King's College London in the U.K. who did not work on the study, told Newsweek experts already knew that learning and memory decline with age, along with adaptive immunity—which in turn makes a person more susceptible to infectious diseases.

"However, this study represents the first demonstration that immune cells can also affect cognitive function in mammals," he said. "The activity of immune cells with aging compensates for decline in adaptive immunity, leading to increased chronic inflammation but this study shows that populations of immune cells with enhanced resilience can combat aging processes."

He stressed that the study was limited because it was largely conducted in mice and "human cognitive ability and mechanisms of age-related brain diseases are very different."

"Further human based studies are necessary to validate these findings. Human tissues were collected from deceased elderly people so not representative of those with earlier stages of cognitive decline," he explained.

Siow said further research exploring ICL2 and the molecule the researchers harnessed will give new insights for the mechanisms of brain aging. This should help the development of strategies to delay the onset of cognitive decline, as well as regenerative therapies to treat brain disease associated with ageing.

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