Ultrastructural changes in the retinopathy, globe enlarged (rge) chick cornea

Area of Science:

• Ophthalmology
• Biomaterials Science
• Developmental Biology

Background:

• The cornea's structure, particularly collagen organization, is crucial for its form and function.
• Abnormal collagen alignment has been observed in the misshapen corneas of chickens with the retinopathy, globe enlarged (rge) mutation.

Purpose of the Study:

• To characterize the developmental changes in corneal ultrastructure in rge mutant chicks.
• To investigate the relationship between collagen organization, globe enlargement, and corneal morphometrics in rge mutant chickens.

Main Methods:

• Wide-angle and small-angle X-ray scattering to analyze collagen lamellae and fibril organization.
• Transmission electron microscopy with cuprolinic blue staining to assess proteoglycan morphology.
• Numerical simulation of tissue mechanics to model collagen remodeling.

Main Results:

• Alterations in dominant collagen lamellae directions were observed in rge chick corneas compared to controls.
• Progressive loss of circumferential collagen alignment in the peripheral cornea and limbus occurred in rge birds older than 1 month.
• Collagen fibril separation and diameter increased more rapidly towards the periphery in rge corneas by 3 months post-hatch, while central diameter remained unchanged. Proteoglycan morphology was unaltered.

Conclusions:

• Progressive collagen remodeling in rge mutant chickens during post-hatch globe enlargement is linked to observed corneal morphometric changes.
• The study highlights the critical role of collagen organization in maintaining corneal integrity and shape.
• Understanding these developmental changes provides insights into the pathogenesis of the rge mutation.