Session Title: Neurodevelopment and Neurodegeneration
Presentation Date: Friday, March 14 – Saturday, March 15, 2009
EFFECTS OF AGEING ON ADULT HIPPOCAMPAL NEUROGENESIS
N. Morgenstern, G. Lombardi, A. Schinder
Neuronal Plasticity Lab, Fundacion Instituto Leloir, Buenos Aires, Argentina
Aims: Age is the major risk factor for neurodegenerative disorders. In addition, the healthy brain displays a marked age-dependent decrease in cognitive abilities that is paralleled by diminished neuronal plasticity including activity-dependent synaptic modification and adult hippocampal neurogenesis. Although the decrease in the rate of neurogenesis has been extensively documented in the ageing hippocampus, the specific characteristics of dentate granule cells born in such a continuously changing environment have received little attention. The objective of this work was to compare the level of complexity and excitatory afferents that newborn neurons reached in the ageing brain.
Methods: We have used retroviral expression of GFP to label the progeny of neural progenitor cells of the adult mouse dentate gyrus. Morphological properties of labeled neurons born at different ages were analyzed by confocal microscopy. Dendritic spine density was measured from reconstructed three-dimensional images to estimate glutamatergic afferent connectivity.
Results: Fully mature neurons born at the age of 2 months displayed ∼2.3 spines/µm and maintained their overall morphology and spine density in 1-year-old mice. Surprisingly, granule cells born in 10-month-old mice, at which time the rate of neurogenesis has decreased by ∼40-fold, reached a similar spine density to that of neurons born in young adulthood.
Conclusions: In spite of the sharp decline in cell proliferation, differentiation and overall neuronal number, the ageing hippocampus presents a suitable environment for new surviving neurons to reach a high level of complexity, comparable to that of all other dentate granule cells.