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Expression of K12 keratin in alkali-burned rabbit corneas
1Department of Ophthalmology, University of Cincinnati, OH 45267-0527.
Abstract:
The healing of alkali-injured corneas is characterized by the persistence of polymorphonuclear leukocytes (PMN) in tissues and recurrent corneal epithelial defects. It has been suggested that the proteolytic enzymes secreted by PMN may account in part for the recurrent epithelial defects in the alkali-burned corneas. Cytoplasmic keratins, which form intracellular intermediate filaments, participate in the formation of hemidesmosomes and play a key role in the focal adhesion of epithelial cells to the basement membranes. The K3/K12 keratin pair is a major constituent of differentiated and stratified corneal epithelium. We have recently cloned the cDNA encoding the rabbit K12 keratin. In the present study we examined the expression of K12 keratin during the healing of alkali-burned rabbit corneas by slot-blot and in situ hybridization. Our results indicate that in normal cornea K12 keratin is equally expressed in all cell layers of stratified corneal epithelium and suprabasal layers of limbal epithelium, but not in bulbar conjunctival and other epithelia, i.e., lens, iris, and retinal pigment epithelium. The basal cells of the detached regenerating epithelium of the injured cornea express a very low level of K12 keratin. These observations are consistent with the notion that defective expression of K3/K12 keratins may play a role in the abnormal attachment of the regenerating epithelium to the basement membrane.
Insights
Alkali-injured corneas show persistent inflammation and recurrent epithelial defects. Defective K3/K12 keratin expression in regenerating corneal epithelium may impair its attachment to the basement membrane, contributing to healing issues.
Area of Science:
- Ophthalmology
- Cell Biology
- Tissue Repair
Background:
- Alkali corneal injuries often lead to persistent inflammation and recurrent epithelial defects.
- Proteolytic enzymes from polymorphonuclear leukocytes (PMN) may contribute to these defects.
- Cytoplasmic keratins, particularly the K3/K12 pair, are crucial for corneal epithelial cell adhesion to basement membranes.
Purpose of the Study:
- To investigate the expression of K12 keratin during the healing process of alkali-burned rabbit corneas.
- To determine if altered K12 keratin expression correlates with impaired epithelial healing and attachment.
Main Methods:
- Utilized slot-blot hybridization to analyze K12 keratin expression levels.
- Employed in situ hybridization to localize K12 keratin expression within corneal tissues.
- Examined both normal and alkali-injured rabbit corneas.
Main Results:
- K12 keratin is normally expressed in all layers of the stratified corneal epithelium and limbal epithelium.
- Expression is absent in conjunctival, lens, iris, and retinal pigment epithelia.
- Regenerating corneal epithelium in injured corneas shows significantly reduced K12 keratin expression, especially in basal cells.
Conclusions:
- Defective expression of K3/K12 keratins is observed during alkali-induced corneal healing.
- This altered keratin expression may be linked to the abnormal attachment of regenerating epithelium to the basement membrane.
- Findings suggest a role for K3/K12 keratins in maintaining corneal epithelial integrity and facilitating proper wound healing.