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Daniel Gibson, Gregory Schultz; Initial Evidence that Immune Cell Infiltrates are Candidate Sources of Post-Surface Ablation Stromal Roughening. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5231. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate potential cellular sources of previously observed post-surgical roughening of the stroma in surface ablated corneas.
New Zealand White rabbits were anesthetized and received bi-lateral 6.0mm x 125µm deep excimer phototherapeutic keratectomy wounds. Rabbits were euthanized daily to generate a time line of wound healing up until re-epithelialization. Immediately post-euthanization, the corneas were excised and fixed overnight. The fixed tissues were paraffin embedded, sectioned, and stained with H&E. The histological time course was grossly analyzed by light microscopy, with an emphasis on finding non-epithelial cells entering the wounded stromal surface.
Based on nuclear morphology, there were many neutrophils present in the anterior stroma with the highest concentration being in regions which were not yet re-epithelialized. Several of the neutrophils were observed in proximity with stromal fibroblasts. Several cellular masses were observed entering the wounded stroma ahead of the migrating epithelium with nuclei shaped like neutrophils or another class of granulocyte. The cells were either still round and on the surface or beginning to flatten and enter the stroma. In at least one sample, a neutrophil was present in front of an epithelial front which had entered the stroma.
Neutrophils are in the right place and at the right time to be considered as the source of post-surgical, biologically induced, stromal roughening. Hypothetically, the proteolytic activity of these infiltrating cells and the tissue displaced by them as they migrate into the stroma creates “tunnels” which can subsequently be entered by the migrating epithelium. Additionally, the crudely apparent cell-cell interaction between the neutrophils and fibroblasts may have a role in activation of the fibroblasts. Given that topical steroids have been reported to be reduce haze and that they are potent neutralizers of neutrophil activities, it may be through a combination of reduced stromal roughening and reduced fibroblast interactions. Additional work is needed to validate this proposed mechanism of action, but the observations reported herein strongly suggest that the neutrophils are at least responsible for biologically induced roughening of the stroma following surface ablation surgery.
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