Morphometric, immunohistochemical and ultrastructural examination of age-related structural alterations in optic nerve

Year 2024, Volume: 7 Issue: 4, 416 - 425, 30.07.2024

Serpil Çilingiroğlu Anlı , Engin Çalgüner , Deniz Erdoğan , Dural Kadıoğlu Çiğdem Elmas , Rabet Gozil , Meltem Bahçelioğlu

https://doi.org/10.32322/jhsm.1486594

Abstract

Aims: As individuals age, there is a known decline in visual function attributed to a reduction in the optic nerve fibers and myelin sheath degeneration. Studies present conflicting findings on whether aging affects axonal integrity in the human optic nerve. This study aims to investigate degenerative changes in the aging rat optic nerve.
Methods: The investigation involved 36 Wistar albino rats. The rats were divided into six groups: the newborn, prepubertal, pubertal, junior, adult, and elderly groups. This study investigated optic nerve axon counts, axon diameters, levels of glial fibrillary acidic protein immunoreactivity (GFAP-IR) and nerve growth factor immunoreactivity (NGF-IR), as well as findings from light microscopy (LM) and electron microscopy (EM) in these groups.
Results: This study observed age-related alterations in rat optic nerves, including increased diameter, irregular axon count fluctuations (both increases and decreases), elevated astrocyte count, and a simultaneous decline in oligodendrocyte count. Additionally, it was observed that NGF-IR was predominantly at the membrane level in newborns and moderately in the cytoplasm, whereas in older ages, it was evident at both cellular and axonal levels furthermore, it was observed that GFAP-IR increased with age. However, in LM and EM examinations, axonal loss and rarefaction, accumulation of osmiophilic substances, splitting of the myelin sheath, vacuolization, axonal retraction were observed.
Conclusion: In this study, it was found that one of the causes of age-related vision loss is the advanced degenerative changes in the optic nerve and it was concluded that the remaining small-diameter myelinated nerve fibers may partially compensate for the sense of vision. Our study reveals that age-related degenerative changes in the central nervous system resemble those in multiple sclerosis (MS), suggesting a potential contribution to MS pathogenesis.

Keywords

Optic nerve, age-related changes, nerve growth factor, glial fibrillary acidic protein, electron microscopy, multiple sclerosis

Ethical Statement

The study obtained ethical approval from the Ethics Committee of Gazi University on November 9, 2004, with reference number 15517 and code number GÜTF-04.030.

Supporting Institution

Gazi Üniversitesi'nin Bilimsel Araştırma Projesi'nden destek alındı.

Thanks

We would like to express our sincere gratitude to Prof. Dr. Bulent BAKAR, Department of Neurosurgery, Kirikkale University Faculty of Medicine for his invaluable guidance, insightful suggestions, and unwavering support throughout the course of this research. With gratitude, we express our appreciation to Dr. Bahar Kartal for her invaluable contributions to the immunohistochemical evaluations presented in the manuscript.

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