Abstract
Abstract: :
Purpose: Apoptosis has been observed in human and canine keratoconjunctivitis sicca. The purpose of this study was to evaluate the effect of experimental dry eye on ocular surface apoptosis. Methods: Aqueous tear production and clearance were inhibited by subcutaneous scopolamine injection and exposure to an air draft for 12 days in 4-6 week old 129SvEv/CD-1 mixed white mice. Eyes and ocular adnexa were excised, cryosectioned, and evaluated for apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay and immunohistochemical assay for caspase-3, an effector in the apoptosis cascade. Apoptotic cells in different regions of the ocular tissue were quantitated with epifluorescence microscopy. Results: The number of cells undergoing apoptosis in the dry eye mice was significantly increased compared to control mice in the following ocular regions: central corneal epithelium (p<0.0014, n=4), peripheral corneal epithelium (p<0.0001, n=4), bulbar conjunctival epithelium (p<0.0021, n=4), tarsal conjunctival epithelium (p<0.0046, n=4), tarsal conjunctival stroma (p<0.0274, n=4) and lid margin (p<0.0219, n=4). There were no significant differences observed between treated and control groups in the central corneal stroma, peripheral corneal stroma, bulbar conjunctival stroma, meibomian glands, skin, retina/choroid, or episcleral regions. Immunohistochemical assay for caspase-3 revealed increased immunoreactivity in regions of increased apoptosis, as demonstrated by TUNEL-positive cells. Conclusion: Ocular surface apoptosis occurs in an experimental mouse model for dry eye with induction primarily in the exposure zone. Apoptosis may play a key role in the pathogenesis of keratoconjunctivitis sicca and may be an important therapeutic target.
Keywords: 370 cornea: basic science • 323 apoptosis/cell death