Complement C3-Deficient Mice Fail to Display Age-Related Hippocampal Decline
Qiaoqiao Shi1, Kenneth J Colodner2, Sarah B Matousek1
1Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital.
Summary
Complement protein C3 contributes to age-related synapse and neuron loss in the brain. C3-deficient mice showed protected synapses, improved cognition, and reduced anxiety with aging, suggesting C3 is detrimental to brain health.
Area of Science:
- Neuroscience
- Immunology
- Aging Research
Background:
- The complement system, crucial for innate immunity and synaptic pruning during development, has an understudied role in normal brain aging.
- Complement protein C3 is a central component of this system, but its specific impact on age-related synaptic and neuronal changes remains unclear.
Purpose of the Study:
- To investigate the role of complement C3 in maintaining synaptic health and function throughout the aging process.
- To determine if C3 deficiency impacts age-related behavioral, electrophysiological, synaptic, and neuronal alterations in the brain.
Main Methods:
- Comparison of C3-deficient (C3 KO) male mice with wild-type (WT) littermates at postnatal day 30, 4 months, and 16 months of age.
- Assessment of behavioral changes, electrophysiology, synaptic density, and neuronal counts in specific brain regions.
- Analysis of hippocampal CA3 and CA1 regions for age-dependent changes in synapses and neurons.
Main Results:
- Aged WT mice exhibited region-specific, age-dependent synapse loss and subsequent neuron loss in the hippocampal CA3 region, which were absent in aged C3 KO mice.
- Aged C3 KO mice demonstrated significantly enhanced long-term potentiation (LTP), improved cognitive function, and reduced anxiety compared to aged WT mice.
- Synaptic puncta in the CA3 region were comparable between WT and C3 KO mice at a young age (P30), indicating aging as the critical factor for observed differences.
Conclusions:
- Complement protein C3 plays a significant role in mediating age-related, region-specific synaptic dysfunction and plasticity decline in the aging brain.
- The absence of C3 protects against age-related synapse and neuron loss, preserves synaptic plasticity, and improves cognitive function and anxiety levels in aged mice.
- These findings highlight a novel, detrimental role for complement C3 in brain aging, suggesting C3 or its downstream signaling pathways as potential therapeutic targets.
