Abstract
Purpose: :
The objective of this study was to develop an in vivo mouse model that consistently produces moderate to severe corneal haze in the anterior stroma of the mouse cornea after excimer laser treatment for studying myofibroblast biology and corneal wound healing.
Methods: :
Regular– or irregular–phototherapeutic keratectomy (PTK) was performed on the black C57BL/6 mice with the Summit Apex excimer laser (Alcon, Ft. Worth, TX). Different numbers of laser pulses (30–110; ablation depth 5–25 µm) were fired on the central cornea, with or without scraping the epithelium prior to excimer laser ablation. Irregularity was generated by positioning a fine mesh screen in the path of laser after firing 50% of the pulses. Eyes were collected 1, 2, 3 and 4 weeks after the procedure. Haze formation was examined with slit lamp biomicroscopy. Antibodies specific for alpha–smooth muscle actin (SMA), a myofibroblast marker, were used to monitor myofibroblasts generation associated with haze. The numbers of SMA–positive cells/400X microscopic field were determined in the anterior corneal stroma by cell counting. Statistical analysis was performed using analysis of variance (AVOVA) with the Bonferonni–Dunn adjustment for repeated measures.
Results: :
Regular–PTK with no epithelial scrape+50 laser pulses (Group 1), irregular–PTK with no epithelial scrape+50 laser pulses (Group 2), regular–PTK with epithelial scrape+45 laser pulses (Group 3) and irregular–PTK with epithelial scrape+45 laser pulses (Group 4) produced haze in the anterior stroma of the mouse cornea. Eyes collected 4 weeks after regular– or irregular–PTK showed 14 ± 2.3 (Group 1), 18 ± 2.3 (Group 2), 22 ± 6.6 (Group 3) or 34 ± 7.9 (Group 4) SMA–positive cells in the anterior cornea. The difference in the SMA–positive cells detected among the four groups was statistically significant (p < 0.01 or <0.001). Less than 4 SMA–positive cells were detected in eyes collected after 1, 2 or 3 weeks of regular or irregular PTK.
Conclusions: :
The optimized PTK excimer laser conditions developed in this study produces haze selectively in anterior stroma of the mouse cornea. Irregular–PTK performed after scraping the epithelium and firing 45 laser pulses was found to be the most effective method to generate myofibroblasts. This in vivo mouse haze model is useful for studying corneal biology, particularly corneal haze formation associated with myofibroblast generation.
Keywords: wound healing • cornea: stroma and keratocytes • cornea: basic science