Abstract
Purpose: :
Advanced surface ablation (PRK, LASEK) is a widespread used procedure in corneal refractive laser surgery. A major drawback of the method is its limitation on the amount of stromal ablation since deep stromal ablation leads to an increased risk of corneal scarring. Our aim is to better understand the molecular events leading to corneal scarring after PRK.
Methods: :
Adult male C57BL/6 mice were anaesthesized and their corneas were exposed to ethanol 35% for 3 minutes, followed by mechanical abrasio of the corneal epithelium. PRK was performed to a depth of 30 µm using PTK mode in a 500 Hz scanning spot excimer laser (WaveLight Concerto) with a spot size of 0.8 mm. The PTK zone was limited to a diameter of 1.2 mm using an aperture mask placed on the cornea. Animals were sacrificed at various times after treatment, corneas were immediately frozen and subsequently processed for mRNA preparation. Quantitative (LightCycler) rt–PCR was performed for IL–6, IL–1beta, TNFalpha, Casp–1 and Casp–2. Untreated animals and animals with mechanical abrasio served as controls.
Results: :
Expression of IL–1beta and Casp–1, increased gradually over time with highest expression levels 7 days after abrasio. At this time, Casp–1 mRNA levels were more than 50–fold and IL–1beta more than 700–fold induced. Casp–2 was not strongly regulated and TNFalpha expression was reduced by a factor of 3. IL–6 expression was not detectable in untreated corneas but was induced by laser treatment after one day.
Conclusions: :
We observed distinct upregulation of various cytokines following deep stromal laser ablation. In particular, Casp–1 and IL–1beta showed marked increases in this model. Establishment of advanced surface ablation in the mouse model will allow for the use of various transgenic organisms in future studies.
Keywords: refractive surgery: PRK • cornea: basic science • cytokines/chemokines