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Nerve-epithelial interactions in sulfur mustard ocular injuries

TitleNerve-epithelial interactions in sulfur mustard ocular injuries
Publication TypeConference Proceedings
Year of Conference2004
AuthorsKadar T., Dachir S., Cohen M., Gutman H., Cohen L., Amir A.
Conference NameProceedings of the U.S. Army Medical Defense Bioscience Review
Volume215
Pagination1-10
Conference LocationAberdeen Proving Ground, MD
Abstract

Ocular injuries induced by sulfur mustard (HD) exposure are characterized by acute and delayed pathology leading to irreversible visual deficits. Corneal nerves were shown to play an important role in the maintenance of corneal metabolism and healthy ocular surface. The present study focused on the role of corneal nerves in the pathogenesis and healing processes of the acute HD ocular injuries and their contribution to the development of delayed injuries. For this purpose, rabbit eyes were exposed to HD vapor using our previously described animal model for ocular injuries. The effect of HD on the structure of nerves was studied in whole mount corneas, stained by cholinesterase (ChE) histochemistry, using both light microscopy observations and morphometric analysis of neural density. Typical signs of HD toxicity were observed within 3-4 hrs after exposure and thereafter, severe ocular injuries were developed, associated with inflammation and corneal erosions. The later healed spontaneously within 5 days, however, the newly regenerating epithelium formed a thin layer that detached frequently from the underlying stroma. Corneal nerves displayed a typical Wallerian degeneration beginning few hours after exposure and lasted for weeks. Only partial regeneration was noted even months following the initial exposure. Thus, weeks after HD exposure two simultaneous opposing processes were taking place at the cornea: healing of the epithelium, concomitant with the degeneration of corneal nerves. We propose that the damaged nerves fail to release neurotrophic factors such as SP and CGRP that are essential for normal cornea maintenance and for successful epithelial healing. This contributes to the development of abnormal epithelium, expressed clinically by recurrent erosions, irregularities of corneal surface and bulla. It is suggested that supplement of trophic factors may help the formation of normal corneal epithelium and may prevent the delayed corneal injuries following HD exposure.

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