Rare corneal clones in mice suggest an age-related decrease of stem cell activity and support the limbal epithelial...

Area of Science:

• Ophthalmology
• Stem Cell Biology
• Developmental Biology

Background:

• The anterior ocular surface, including the cornea and limbus, relies on stem cells for epithelial maintenance.
• Current hypotheses debate whether corneal stem cells reside in the limbus or throughout the basal corneal epithelium.
• Distinguishing between these stem cell locations requires novel lineage tracing methods.

Purpose of the Study:

• To develop and utilize a new lineage tracing method to identify the location of corneal epithelial stem cells.
• To test the hypothesis that limbal epithelial stem cells (LESCs) maintain the corneal epithelium.
• To investigate the impact of aging on corneal stem cell function.

Main Methods:

• Generation and analysis of KRT5(LacZ/-) transgenic mice to visualize stem cell lineages.
• Observation of β-galactosidase (β-gal)-positive radial stripes as indicators of clonal stem cell activity.
• Assessment of stripe distribution and frequency in relation to the limbus.
• Analysis of corneal maintenance in Pax6(+/-), KRT5(LacZ/-) double transgenic mice.

Main Results:

• KRT5(LacZ/-) mice exhibited rare, β-gal-positive radial stripes in the corneal epithelium, serving as lineage markers.
• The distribution of these stripes indicated centripetal extension from the limbus, supporting the LESC hypothesis.
• Stripe frequency decreased significantly between 15 and 30 weeks of age, suggesting age-related decline in stem cell function.
• Pax6(+/-) corneas displayed abnormal patchy patterns instead of stripes, confirming impaired corneal maintenance.

Conclusions:

• The KRT5(LacZ/-) lineage tracing model supports the limbal epithelial stem cell (LESC) hypothesis for corneal homeostasis.
• Corneal stem cell function appears to diminish with advancing age.
• The Pax6 gene plays a critical role in normal corneal epithelial maintenance.