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Insights into mustard gas keratopathy- characterizing corneal layer-specific changes in mice exposed to nitrogen
Hamid Alemi1, Shima Dehghani1, Katayoon Forouzanfar1
1Schepens Eye Research Institute of Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
Abstract:
Exposure to mustard agents, such as sulfur mustard (SM) and nitrogen mustard (NM), often results in ocular surface damage. This can lead to the emergence of various corneal disorders that are collectively referred to as mustard gas keratopathy (MGK). In this study, we aimed to develop a mouse model of MGK by using ocular NM exposure, and describe the subsequent structural changes analyzed across the different layers of the cornea. A 3 μL solution of 0.25 mg/mL or 5 mg/mL NM was applied to the center of the cornea via a 2-mm filter paper for 5 min. Mice were evaluated prior to and after exposure on days 1, 3, 7, 14, and 28 for 4 weeks using slit lamp examination with fluorescein staining. Anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM) tracked changes in the epithelium, stroma, and endothelium of the cornea. Histologic evaluation was used to examine corneal cross-sections collected at the completion of follow-up. Following exposure, mice experienced central corneal epithelial erosion and thinning, accompanied by a decreased number of nerve branches in the subbasal plexus and increased activated keratocytes in the stroma in both dosages. The epithelium was recovered by day 3 in the low dose group, followed by exacerbated punctuate erosions alongside persistent corneal edema that arose and continued onward to four weeks post-exposure. The high dose group showed persistent epitheliopathy throughout the study. The endothelial cell density was reduced, more prominent in the high dose group, early after NM exposure, which persisted until the end of follow-up, along with increased polymegethism and pleomorphism. Microstructural changes in the central cornea at 4 weeks post-exposure included dysmorphic basal epithelial cells and reduced epithelial thickness, and in the limbal cornea included decreased cellular layers. We present a mouse model of MGK using NM that successfully replicates ocular injury caused by SM in humans who have been exposed to mustard gas.
Insights
Researchers developed a mouse model for mustard gas keratopathy (MGK) using nitrogen mustard (NM) eye exposure. This model replicates human ocular injuries, showing persistent corneal damage and structural changes.
Area of Science:
- Ophthalmology
- Toxicology
- Corneal disease modeling
Background:
- Mustard agents like sulfur mustard (SM) and nitrogen mustard (NM) cause significant ocular surface damage.
- These injuries can lead to various corneal disorders collectively known as mustard gas keratopathy (MGK).
- Existing models may not fully capture the complex structural changes observed in human MGK.
Purpose of the Study:
- To develop and characterize a novel mouse model of mustard gas keratopathy (MGK) using ocular nitrogen mustard (NM) exposure.
- To analyze the structural changes in different corneal layers following NM exposure.
- To establish a reproducible preclinical model for studying MGK pathogenesis and potential treatments.
Main Methods:
- Ocular exposure of mice to two different concentrations of nitrogen mustard (NM).
- Serial examinations using slit lamp microscopy with fluorescein staining over 4 weeks.
- Anterior segment optical coherence tomography (AS-OCT) and in vivo confocal microscopy (IVCM) to assess corneal layers.
- Histological evaluation of corneal cross-sections.
Main Results:
- NM exposure induced central corneal epithelial erosion, thinning, and subbasal nerve plexus reduction.
- Low-dose NM showed initial epithelial recovery followed by persistent edema; high-dose NM resulted in sustained epitheliopathy.
- Endothelial cell density was significantly reduced post-exposure, with increased polymegethism and pleomorphism persisting for 4 weeks.
- Microstructural changes included dysmorphic basal epithelial cells and reduced epithelial thickness.
Conclusions:
- The developed mouse model effectively replicates ocular injuries seen in humans exposed to mustard gas.
- NM-induced ocular exposure causes persistent, dose-dependent structural damage across corneal layers.
- This model provides a valuable tool for investigating the mechanisms of MGK and evaluating therapeutic interventions.
