Scientists have identified a potential biological tipping point that may determine whether Alzheimer's disease-related brain changes lead to dementia. This key factor involves how the brain's immune cells, called microglia, respond to amyloid-beta plaques and tau tangles. The findings suggest new targets for treatments aimed at extending cognitive resilience.
Researchers from VIB, KU Leuven, the UK Dementia Research Institute (UK-DRI), and Muna Therapeutics studied donated brain tissue. They analyzed samples from older adults with and without cognitive decline, including cognitively healthy centenarians. The team uncovered distinct cellular programs and immune cell states. These states were linked to both disease progression and resistance.
Alzheimer's disease affects over 55 million people globally. It is characterized by the buildup of amyloid-beta plaques and tau tangles in the brain. However, these biological markers do not always correlate with a person's mental state. Some individuals accumulate significant amounts of plaques and tangles but remain cognitively healthy. This observation has shifted scientific focus to how brain cells react to these abnormal proteins.
Microglia are crucial in this process. These immune cells monitor and protect the brain. Their behavior can change significantly as Alzheimer's disease progresses. Understanding these changes could explain why some people remain resilient. It could also identify new ways to prevent cognitive decline.
The study combined spatial transcriptomics and single-cell sequencing. These methods examine tissue at the individual cell level. Researchers identified six distinct tissue domains representing different stages of Alzheimer's progression. A critical transition separated regions dominated by amyloid-beta plaques from those associated with tau pathology and neurodegeneration. This shift coincided with a major change in microglial behavior.
During earlier disease stages, microglia entered an inflammatory state linked to amyloid plaques. Later, they transitioned into an antigen-presenting state, appearing concurrently with tau pathology. This change may mark a biological turning point that determines whether Alzheimer's pathology progresses to brain cell damage and dementia. The findings suggest that future Alzheimer's treatments could focus on preserving beneficial early microglial activity or influencing the transition between microglial states.
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