Lipofuscin-like autofluorescence within microglia and its impact on studying microglial engulfment
Jacob M Stillman1,2, Francisco M Lopes1, Jing-Ping Lin3
1Department of Neurobiology, Brudnick Neuropsychiatric Research Institute, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA.
Abstract:
Engulfment of cellular material and proteins is a key function for microglia, a resident macrophage of the central nervous system (CNS). Among the techniques used to measure microglial engulfment, confocal light microscopy has been used the most extensively. Here, we show that autofluorescence (AF), likely due to lipofuscin and typically associated with aging, can also be detected within microglial lysosomes in the young mouse brain by light microscopy. This lipofuscin-AF signal accumulates first within microglia and increases with age, but it is not exacerbated by amyloid beta-related neurodegeneration. We further show that this lipofuscin-AF signal within microglia can confound the interpretation of antibody-labeled synaptic material within microglia in young adult mice. Finally, we implement a robust strategy to quench AF in mouse, marmoset, and human brain tissue.
Insights
Microglia engulf cellular material, but autofluorescence (AF) from lipofuscin in young mice can mimic synaptic material. A new method quenches AF in brain tissue for accurate microglia research.
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Microglia, the central nervous system's (CNS) resident macrophages, are crucial for engulfing cellular debris and proteins.
- Confocal light microscopy is a primary technique for studying microglial engulfment.
- Autofluorescence (AF), often linked to aging lipofuscin, is present in microglia.
Approach:
- Investigated autofluorescence (AF) in microglia using light microscopy in young and aging mouse brains.
- Examined the impact of amyloid beta-related neurodegeneration on microglial AF.
- Developed and implemented a strategy to quench AF in various brain tissues.
Key Points:
- Lipofuscin-associated AF is detectable in microglia lysosomes even in young mice.
- Microglial AF increases with age but is not significantly affected by amyloid beta pathology.
- AF can lead to misinterpretation of antibody-labeled synaptic material within microglia.
Conclusions:
- A novel AF quenching method was successfully applied to mouse, marmoset, and human brain tissue.
- This strategy enhances the accuracy of quantifying microglial engulfment, particularly synaptic material.
- Accurate assessment of microglial function is vital for understanding CNS health and disease.
