Effect of prophylactic and therapeutic mitomycin C on corneal apoptosis, cellular proliferation, haze, and long-term keratocyte density in rabbits.
OBJECTIVE
To determine the mechanism through which topical mitomycin C prevents and treats corneal haze after photorefractive keratectomy (PRK) and to examine the effects of dosage and duration of exposure.


METHODS
In 224 New Zealand rabbits, -9.0 diopter PRK with mitomycin C or balanced salt solution was performed. Haze level was graded at the slit-lamp. Rabbits were sacrificed at 4 hours, 24 hours, 4 weeks, or 6 months after surgery and immunohistochemistry was performed with TUNEL assay, Ki67, and alpha-SMA.


RESULTS
TUNEL-positive apoptotic cells marginally increased in all mitomycin C groups whereas Ki67-positive mitotic cells decreased significantly following mitomycin C application. A greater decrease in myofibroblasts was noted with prophylactic mitomycin C treatment than therapeutic mitomycin C treatment. There was, however, an anterior stromal acellular zone (approximately 20% of the total stroma) in eyes treated with mitomycin C, which persisted to the maximum follow-up of 6 months.


CONCLUSIONS
Mitomycin C treatment induces apoptosis of keratocytes and myofibroblasts, but the predominate effect in inhibiting or treating haze appears to be at the level of blocked replication of keratocytes or other progenitor cells of myofibroblasts. Treatment with 0.002% mitomycin C for 12 seconds to 1 minute appears to be just as effective as higher concentrations for longer duration in the rabbit model. However, a persistent decrease in keratocyte density in the anterior stroma could be a warning sign for future complications and treatment should be reserved for patients with significant risk of developing haze after PRK.
Netto
Marcelo V
MV
The Cole Eye Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA.
Mohan
Rajiv R
RR
Sinha
Sunilima
S
Sharma
Ajay
A
Gupta
Pankaj C
PC
Wilson
Steven E
SE
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002452:Cell Count; D049109:Cell Proliferation / Q000187:drug effects*; D003315:Cornea / Q000187:drug effects / Q000473:pathology*; D003318:Corneal Opacity / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D004195:Disease Models, Animal; D005260:Female; D005500:Follow-Up Studies; D066298:In Vitro Techniques; D054018:Lasers, Excimer; D016685:Mitomycin / Q000008:administration & dosage*; D009216:Myopia / Q000601:surgery; D019384:Nucleic Acid Synthesis Inhibitors / Q000008:administration & dosage*; D018903:Photorefractive Keratectomy; D011183:Postoperative Complications; D011817:Rabbits; D013997:Time Factors; D016896:Treatment Outcome
D019384:Nucleic Acid Synthesis Inhibitors; D016685:Mitomycin