Age-related changes in the human optic nerve.
BACKGROUND
Recent morphologic research has demonstrated the presence of nerve fibres of different diameters in the human optic nerve. The purpose of this study was to investigate age-related changes in fibres of the human optic nerve.


METHODS
We studied the left optic nerve of 50 male cadaveric donors, 16 aged 18 to 22 years (mean 20 [standard deviation 1.2] years) and 34 aged 68 to 76 years (mean 72 [standard deviation 1.6] years). The samples were carefully harvested during autopsy from the intracranial portion of the optic nerve. Each nerve was cut into four 4-mm segments. After morphologic, histochemical and immunohistochemical staining, the optic nerve fibres were counted and measured. Each segment was evaluated under light microscopy for microanatomic details, glial cells and glial fibrillary acidic protein (GFAP) staining. The protein content was determined under biochemical analysis. We performed morphometric analysis by examining the optic nerve images quantitatively.


RESULTS
Compared with the younger group, in the older group there was an increase in mean diameter of the optic nerve (p < 0.001), due to an increase in the optic nerve:meningeal membrane ratio. There was also an increase in mean optic nerve area (p < 0.001) and in mean number of astrocytes and the related GFAP-immunoreactive area (p < 0.001). The mean number of nerve fibres of large diameter (greater than 4 pm) was decreased (p < 0.001). There was no difference in mean protein content of the fibres between the two groups.


CONCLUSIONS
The human optic nerve is sensitive to the aging process and may be considered as a model for studies on neuronal aging.
Cavallotti
Carlo
C
Department of Human Anatomy, University La Sapienza, Rome, Italy. cavallotti@uniroma1.it
Pacella
Elena
E
Pescosolido
Nicola
N
Tranquilli-Leali
Francesca Maria
FM
Feher
Janos
J
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000502:physiology; D009457:Neuroglia / Q000166:cytology / Q000378:metabolism; D009900:Optic Nerve / Q000166:cytology* / Q000378:metabolism
D005904:Glial Fibrillary Acidic Protein