Vishwa Deep Dixit, an Indian-origin scientist at Yale School of Medicine, has identified how a special class of immune cells changes with age, shedding new light on the causes of chronic inflammation and its role in aging. The findings were published this month in Nature Aging.
Dixit’s research shows that a specialized group of macrophages, called nerve-associated macrophages (NAMs), help regulate fat metabolism and control age-related inflammation. These NAMs decline over time, while another subset of immune cells, which the team has termed age-associated macrophages (AAMs), emerges during aging.
“When we found that these macrophages in fat tissue contained such high levels of neurotransmitters, we began to wonder, what are they doing there, and do they change with age?” Dixit told Yale. He is senior author of the study and Waldemar Von Zedtwitz Professor of Pathology.
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The researchers examined fat tissue from young and old mice, using imaging and genetic sequencing to map the immune cells present. They identified 13 distinct groups of macrophages, including both NAMs and AAMs. The AAMs were found only in aged animals and expressed high levels of inflammatory markers, indicating they may drive inflammaging.
“We found 13 different macrophages, all with different cellular machinery,” Dixit told Yale. “And there was a bonus of discovering cells we didn’t know existed.”
Claire Leveau, a postdoctoral fellow in the Dixit lab and co-author of the study, told Yale that the team had little knowledge about these macrophages at the start. “We did not know anything about these macrophages, so we had a lot of groundwork to do,” she said.
The study also showed that eliminating NAMs in older animals led to further tissue decline. Without these macrophages, fat breakdown was impaired, and chronic inflammation worsened.
“Now that we understand how these macrophages change with age, the next step is figuring out how to preserve the healthy ones and prevent harmful, age-associated types from emerging,” Dixit told Yale. “If we can do that, aging will continue with time, but the decline in tissue function could be reduced.”
The researchers said the discovery of new macrophage subtypes highlights how nerves and immune cells interact across the lifespan. According to Dixit, “This discovery is truly just a stepping stone towards understanding the complex biology of aging and the complex intercommunication between nerves and macrophages.”
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