Age-Related Changes in Murine Corneal Nerves

Area of Science:

• Ophthalmology
• Neuroscience
• Gerontology

Background:

• The corneal subbasal nerve plexus (SNP) is crucial for corneal innervation and sensation.
• Age-related changes in peripheral nerves are well-documented, but specific data on the corneal SNP in aging mice is limited.

Purpose of the Study:

• To investigate age-related morphological alterations in the corneal subbasal nerve plexus (SNP) of two distinct inbred mouse strains.
• To compare the efficacy of semi-automated and fully automated image analysis techniques for quantifying nerve fiber density (NFD).

Main Methods:

• In vivo confocal laser scanning microscopy (CLSM) was used to image the corneal SNP in C57BL/6J and BALB/c mice across different age groups.
• Nerve fiber density (NFD) was quantified using the semi-automated NeuronJ software and a novel automated computerized technique.
• Ex vivo immunohistochemical analysis with PGP9.5 staining was performed for validation.

Main Results:

• A significant age-related reduction in subbasal NFD was observed in both mouse strains.
• C57BL/6J mice exhibited a lower baseline NFD and a more pronounced decline (up to 66%) with age compared to BALB/c mice (17% reduction).
• The automated quantification method yielded comparable results to manual analysis, demonstrating a 45% reduction in NFD with aging and proving to be objective and time-saving.

Conclusions:

• Corneal subbasal nerve fibers decrease with age in mice, with strain-specific differences likely due to genetic factors.
• The developed automated method is a reliable, objective, and efficient tool for analyzing corneal nerve fiber density in aging mouse models.
• These findings contribute to understanding age-related neurodegeneration in the cornea and have implications for studying ocular surface diseases.