Aging and Exercise Affect Hippocampal Neurogenesis via Different Mechanisms

Area of Science:

• Neuroscience
• Aging Research
• Exercise Physiology

Background:

• Neurogenesis, the generation of new neurons, is crucial for hippocampal function.
• Aging is known to decrease neurogenesis rates, but the specific contributing factors remain unclear.
• Exercise (Ex) has been shown to increase neurogenesis, yet its impact on age-related declines is not fully understood.

Purpose of the Study:

• To investigate how aging and exercise affect the key determinants of hippocampal neurogenesis.
• To identify which specific factors (NSC number, proliferation, lineage specification, survival) are most impacted by aging and exercise.

Main Methods:

• Characterization of four neurogenesis determinants in mice across various age groups (3-21 months).
• Comparison between sedentary mice and those undergoing one month of exercise training.
• Use of Bromodeoxyuridine (BrdU) labeling to identify and quantify proliferating cells.

Main Results:

• Newborn neuron numbers decreased by over 95% by nine months of age.
• Aging reduced neural stem cell (NSC) proliferation and neuron specification rates; exercise partially delayed NSC decline and increased specification rates but did not improve proliferation.
• Neuron maturation was significantly impaired by aging but robustly enhanced by exercise; survival rates were unaffected by age or exercise.

Conclusions:

• The age-associated decline in hippocampal neurogenesis is primarily driven by reduced NSC proliferation.
• Exercise partially mitigates aging effects by increasing NSC number and neuron specification, but cannot overcome the drastic drop in proliferation.
• While exercise's overall impact on neurogenesis rate during aging is limited, it significantly enhances the maturation of newly generated neurons.