Microglia help protect the spinal cord from age-related damage

Researchers at Karolinska Institutet have discovered that the nervous system's own immune cells help protect the spinal cord from age-related damage. The results, which may contribute to new knowledge about how certain neurological diseases arise, are published in the journal Nature Neuroscience. 

Aging affects the entire body, including the spinal cord, which transmits signals between the brain and the rest of the body. The negative consequences of aging are well known, but could there be positive, protective mechanisms activated? 

The researchers at Karolinska Institutet investigated how aging affects myelin, the protective layer which envelops nerve fibers in the brain and spinal cord. By studying mice of different ages, the researchers found that the myelin in a specific region of the spinal cord – the dorsal columns – gradually accumulates damage during aging. 

The researchers focused on the immune cells of the brain and spinal cord, microglia, which help to keep the nervous system functioning properly. 

It is known that microglia can affect the quality of myelin, so we wanted to understand how these cells respond to age-related myelin damage."

Harald Lund, Assistant Professor, Department of Physiology and Pharmacology at Karolinska Institutet

In the aging spinal cord, the researchers discovered that the microglia activated a signaling molecule called TGF-beta. This appears to act as a brake, preventing the cells from becoming overactive and damaging nerve fibres. 

To test the significance of this brake, the researchers switched off TGF-beta production in older mice. Without the signal, the microglia began to attack the myelin, resulting in the mice developing clinical movement problems. 

"Damage has also been found in this particular region of the spinal cord in people with certain neurological diseases. Our results may help us understand why," says Robert Harris, Professor at the Department of Clinical Neuroscience at Karolinska Institutet, who led the research together with Harald Lund. 

The study was conducted in collaboration with researchers in China, the United States, and France. Funding was provided by the Swedish Research Council, Alltid Litt Sterkere, Neurofonden and Karolinska Institutet's research initiative StratNeuro, among others.