Homeostatic and injury-induced microglia behavior in the aging brain
Jasmin K Hefendehl1, Jonas J Neher, Rafael B Sühs
1Department of Cellular Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, D-72076, Tübingen, Germany.
Abstract:
Microglia cells are essential for brain homeostasis and have essential roles in neurodegenerative diseases. Aging is the main risk factor for most neurodegenerative diseases, and age-related changes in microglia may contribute to the susceptibility of the aging brain to dysfunction and neurodegeneration. We have analyzed morphology and dynamic behavior of neocortical microglia in their physiological environment in young adult (3-month-old), adult (11- to 12-month-old), and aged (26- to 27-month-old) C57BL/6J-Iba1-eGFP mice using in vivo 2-photon microscopy. Results show that surveying microglial cells in the neocortex exhibit age-related soma volume increase, shortening of processes, and loss of homogeneous tissue distribution. Furthermore, microglial process speed significantly decreased with age. While only a small population of microglia showed soma movement in adult mice, the microglia population with soma movement was increased in aged mice. However, in response to tissue injury, the dynamic microglial response was age-dependently diminished. These results provide novel insights into microglial behavior and indicate that microglial dysfunction in the aging brain may contribute to age-related cognitive decline and neurodegenerative diseases.
Insights
Aging brains show altered microglia (immune cells in the brain) morphology and reduced dynamic behavior, contributing to neurodegeneration. These changes impair their response to injury, highlighting a key factor in age-related cognitive decline.
Area of Science:
- Neuroscience
- Immunology
- Aging Research
Background:
- Microglia are crucial for brain health and implicated in neurodegenerative diseases.
- Aging is a primary risk factor for neurodegeneration, with age-related microglial changes potentially increasing brain vulnerability.
- Understanding age-dependent microglial alterations is key to addressing neurodegenerative disease susceptibility in aging populations.
Purpose of the Study:
- To investigate age-related changes in the morphology and dynamic behavior of neocortical microglia in vivo.
- To determine how aging affects microglial surveillance, movement, and response to injury.
- To provide insights into the role of microglial dysfunction in the aging brain and neurodegeneration.
Main Methods:
- In vivo 2-photon microscopy was used to analyze neocortical microglia in young adult, adult, and aged C57BL/6J-Iba1-eGFP mice.
- Morphological parameters such as soma volume and process length were assessed.
- Dynamic behaviors including process speed, soma movement, and response to tissue injury were quantified.
Main Results:
- Aged microglia exhibited increased soma volume, shortened processes, and disrupted tissue distribution compared to younger mice.
- Microglial process speed significantly decreased with age, and a larger population of aged microglia displayed soma movement.
- The dynamic response of microglia to tissue injury was diminished in aged mice, indicating impaired surveillance and response capabilities.
Conclusions:
- Microglial morphology and dynamics undergo significant age-related alterations in the neocortex.
- These age-dependent changes in microglial function, including reduced process speed and impaired injury response, may contribute to the increased susceptibility of the aging brain to neurodegeneration.
- Microglial dysfunction is a potential driver of age-related cognitive decline and neurodegenerative diseases.
