The role of apoptosis in the early corneal wound healing after excimer laser keratectomy in the rat.
BACKGROUND
The potential role of apoptosis in corneal wound healing after excimer laser keratectomy was investigated in a rat model.


METHODS
Lewis rats underwent laser keratectomy using a 193-nm excimer laser. The central corneas were ablated in three depths: group A, epithelium; group B, superficial stroma; group C, deep stroma. Eyes were collected at 1, 12, 24, and 36 h and 1 week. Cellular markers associated with apoptosis--Fas, Fas ligand (FasL), Bcl-2, and Bax were examined by immunohistochemistry. Keratocyte depletion and endothelial changes were evaluated histologically. In situ end labeling of double-stranded DNA breaks was used to demonstrate apoptosis in corneal sections.


RESULTS
Keratocyte depletion was observed in 6 (50%) of 12 rats (total from groups A, B, and C) at 12 h, 11 (73%) of 15 at 24 h, 3 (20%) of 15 at 36 h, and 2 (15%) of 13 at 1 week after laser surgery. Corneal endothelial edema was observed in the ablation zone. Expression of Fas, FasL, Bcl-2, and Bax in corneal cells showed dynamics similar to that of keratocyte depletion and endothelial changes. There was less expression of apoptotic molecules in newly generated epithelial cells and more in endothelial cells of the stromal ablation groups.


CONCLUSIONS
Excimer laser keratectomy triggered apoptosis of corneal keratocytes and endothelial cells. More endothelial edema was observed in the stromal ablation than in the epithelial ablation group. The expression of apoptotic molecules coincided with the period of keratocyte depletion and regeneration and of endothelial recovery, suggesting that apoptosis is a dynamic part of corneal wound healing and remodeling after excimer laser keratectomy.
Li
Q
Q
Refractive Surgery Research, The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287-9121, USA.
Ashraf
M F
MF
Bekoe
N A
NA
Stark
W J
WJ
Chan
C C
CC
O'Brien
T P
TP
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D015415:Biomarkers / Q000032:analysis; D002452:Cell Count; D003315:Cornea / Q000378:metabolism / Q000473:pathology / Q000601:surgery*; D015715:Corneal Edema / Q000175:diagnosis / Q000209:etiology; D003319:Corneal Stroma / Q000378:metabolism; D004728:Endothelium, Corneal / Q000378:metabolism; D053222:Fas Ligand Protein; D005347:Fibroblasts / Q000378:metabolism; D007124:Immunoenzyme Techniques; D054018:Lasers, Excimer; D008562:Membrane Glycoproteins / Q000378:metabolism; D018903:Photorefractive Keratectomy; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D014945:Wound Healing / Q000502:physiology*; D051028:bcl-2-Associated X Protein; D019014:fas Receptor / Q000378:metabolism
C494828:Bax protein, rat; D015415:Biomarkers; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; D008562:Membrane Glycoproteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D019014:fas Receptor