Limbal stem cell deficiency (LSCD) in rats and mice following whole body exposure to sulfur mustard (SM) vapor.

Ocular injuries following sulfur mustard (SM) exposure are characterized by an acute phase expressed by corneal erosions and inflammation of the anterior segment that after a clinically silent period may be followed by irreversible corneal injuries. The latter includes epithelial defects, chronic inflammation and neovascularization (NV), and were defined in rabbits and in humans as Limbal Stem Cell Deficiency (LSCD), that derived from a delayed loss of corneal epithelial stem cells (ESC), due to secondary processes most likely in the epithelial stem cell (SC) niche. The present study expands our research on SM-induced ocular injury to rodents (rats and mice) following whole body vapor exposure, aiming to define whether the delayed development of LSCD is a general characteristic of SM ocular toxicity. Freely moving rats and mice were exposed to SM vapor (155 µg/l, 10 min). Clinical examination was carried out in rats and included a slit-lamp bio-microscopy, up to 6 months. Eyes were taken for histology at different time points following exposure and evaluation included hematoxylin and eosin (H&E) staining for general morphology, PAS for identification of goblet cells and p63 immunohistochemistry for progenitor epithelial cells. Whole body exposure to SM vapor in rats and mice resulted in acute ocular injury characterized by corneal erosions and ocular inflammation. Following a brief recovery period, 80-90% of the exposed eyes developed corneal NV associated with abnormal corneal epithelium, stromal inflammation and endothelial damage. The late injury was accompanied by migration of conjunctival goblet cells to the cornea and a loss of limbal epithelial progenitor cells, indicating LSCD. The long-term ocular injury shown hereby in rats and mice was consistent with the lesions described in rabbits and in human casualties and demonstrated the general phenomenon of limbal epithelial stem cells deficiency in SM ocular toxicity. The delayed manifestation of this pathology points towards a therapeutic window for the development of medical countermeasures in small animals following exposure in a real life scenario.