Synaptic and mitochondrial morphometry provides structural correlates of successful brain aging.

Area of Science:

• Neuroscience
• Gerontology
• Primate Brain Research

Background:

• Understanding age-related changes in the brain is crucial for identifying factors contributing to successful aging.
• Synaptic and mitochondrial morphology are key indicators of neuronal health and function.

Purpose of the Study:

• To investigate age-related morphometric changes in synapses and mitochondria within the frontal cortex (FC) and temporal cortex (TC) of Macaca fascicularis.
• To determine if observed changes correlate with successful brain aging.

Main Methods:

• Morphometric analysis was employed to measure synaptic size (S), numeric density (Nv), and surface density (Sv).
• Mitochondrial volume, numeric density, and volume density were also quantified.
• Comparisons were made between adult and old monkeys in the FC and TC.

Main Results:

• Synaptic surface density (Sv) remained unchanged with age.
• Synaptic numeric density (Nv) significantly decreased in the TC but not the FC.
• Average synaptic size (S) significantly increased in both FC and TC.
• No significant age-related differences were observed in mitochondrial ultrastructure.

Conclusions:

• The age-related increase in synaptic size and relative constancy of mitochondrial ultrastructure suggest these parameters may serve as structural correlates of successful brain aging.
• Synaptic structural plasticity, rather than loss, might be a feature of aging brains that maintain function.