Developmental and Aging-Related Changes of the Optic Nerve in the Albino Rat: Histological, Histomorphometric and Immunohistochemical Study

Document Type : Original Article

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Department of Anatomy and Embryology, Faculty of Medicine, Tanta University

Abstract

Introduction: Optic nerves development begins throughout pregnancy and continues after birth. Aging entails gradual degeneration of the structure and the number of the optic nerve axons.
Aim of the Work: This research was designed to clarify the prenatal and postnatal development of the optic nerve in the albino rat and the age-related changes in its axons.
Material and Methods: Forty-five albino rats were used. The animals were divided into Prenatal group (Group I) and Postnatal group (Group II). In Group I, ten adult males were put with ten females for mating. Pregnant females were sacrificed at different times of gestation and five embryos were extracted for each subgroup; subgroup IA (aged 7 days of gestation), subgroup IB (aged 14 days of gestation) and subgroup IC (aged 21 days of gestation). In Group II, twenty-five albino rats of different ages were divided into five subgroups; Subgroup IIA (aged one month), Subgroup IIB (aged 3 months), Subgroup IIC (aged 9 months), Subgroup IID (aged 18 months) and Subgroup IIE (aged 24 months). The optic nerves of all subgroups were prepared for histological, immunohistochemical examination. Statistical analysis of immune-positive percentage area and the number of optic nerve axons were performed.
Results: Optic nerve was first formed in rat embryos aged 21 days of gestation. It’s formed of the axons of retinal ganglion cells. Aging causes apparent deterioration of the optic nerve structure with a highly significant increase in CD31 immunopositive cells percentage area. Ultra-structurally, the number of optic nerve axons significantly decreased.
Conclusion: This study provides histological description of development of the optic nerve in the albino rat across different prenatal and postnatal ages. The aging is associated with degeneration, neovascularization and reduction of optic nerve axons which could explain why most elderly have vision loss with varying extent.

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