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Evidence of apoptotic cell death in keratoconus
Roger M Kaldawy1, Janet Wagner, Steven Ching
1Department of Ophthalmology, Trygve Gundersen Eye Center, Boston University School of Medicine, 720 Harrison Ave., 10th Floor, Boston, MA, USA. roger.kaldawy@BMC.org
Purpose:
To determine the potential role of apoptosis in the noninflammatory degeneration characteristic of keratoconus.
Methods:
Four normal corneas and 16 keratoconus corneas were obtained as archival specimens. Tissues were examined histopathologically for TUNEL immunoreactivity to detect the presence of DNA fragmentation. Tissues were also subjected to single-stranded DNA (ssDNA) analysis, a more apoptosis-specific stain.
Results:
Normal corneas exhibited fewer than five TUNEL-positive epithelial cells per section, these being very lightly stained. All 16 keratoconus corneas demonstrated extensive, intense TUNEL staining in at least one layer. Fifteen of 16 exhibited staining in the epithelial layer, 11 of 16 in the stromal layer, and 13 of 16 in the endothelial layer, whereas 10 of 16 keratoconus cases demonstrated TUNEL immunoreactivity in all three layers. The ssDNA stain was also positive and evident in all three layers of the cornea, although to a lesser degree than the TUNEL assay.
Conclusions:
The noninflammatory nature of keratoconus, coupled with the TUNEL in situ results, suggests apoptosis as a mode of cell death in this degenerative disease.
Insights
Apoptosis, or programmed cell death, plays a significant role in the noninflammatory degeneration observed in keratoconus (KC) corneas. TUNEL and ssDNA staining confirmed widespread cell death in KC tissues.
Area of Science:
- Ophthalmology
- Cell Biology
- Pathology
Background:
- Keratoconus (KC) is a progressive, noninflammatory corneal ectasia.
- The underlying cellular mechanisms of KC degeneration remain incompletely understood.
Purpose of the Study:
- To investigate the potential involvement of apoptosis in the characteristic noninflammatory degeneration of keratoconus.
- To identify specific cell death pathways contributing to corneal tissue remodeling in KC.
Main Methods:
- Histopathological examination of archival corneal tissues from normal (n=4) and keratoconus (n=16) donors.
- Detection of DNA fragmentation using Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.
- Apoptosis-specific staining with single-stranded DNA (ssDNA) analysis.
Main Results:
- Normal corneas showed minimal TUNEL-positive cells with light staining.
- All keratoconus corneas exhibited extensive and intense TUNEL staining across epithelial, stromal, and endothelial layers.
- ssDNA staining confirmed apoptosis in all three corneal layers of keratoconus specimens, though to a lesser extent than TUNEL.
Conclusions:
- The findings strongly suggest apoptosis as a key mode of cell death in the noninflammatory degeneration of keratoconus.
- Apoptotic cell death contributes to the pathological changes observed in keratoconus.
- Further research into apoptosis modulation may offer therapeutic avenues for keratoconus.