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Apoptosis of ocular surface cells in experimentally induced dry eye
Steven Yeh1, Xiu Jun Song, William Farley
1Department of Ophthalmology, Ocular Surface Center, Cullen Eye Institute, Baylor College of Medicine, 6565 Fannin, Houston, TX 77030, USA.
Purpose:
To evaluate to effect of experimental dry eye on ocular surface apoptosis.
Methods:
Aqueous tear production and clearance were inhibited by systemic administration of scopolamine and exposure to an air draft for 12 days in 4- to 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, immunohistochemical assay for caspase-3 and poly(ADP-ribose) phosphate (PARP), and examination of nuclear morphologic changes by Hoechst DNA nuclear staining and transmission electron microscopy.
Results:
The number of TUNEL-positive cells in the mice with induced dry eye was significantly increased compared with control mice in the following ocular regions: central corneal (P < 0.0014), peripheral corneal (P < 0.0001), bulbar conjunctival (P < 0.0021), and tarsal conjunctival (P < 0.0046) epithelia; tarsal conjunctival stroma (P < 0.0274); and lid margin (P < 0.0219, n = 4 in all cases). There were no significant differences observed between treated and control groups in the central corneal, peripheral corneal, or bulbar conjunctival stroma; meibomian glands; skin; retina-choroid; or episcleral regions. Immunohistochemistry for caspase-3 and poly(ADP-ribose) polymerase p85 fragment revealed increased immunoreactivity in regions of increased TUNEL positivity, particularly in the corneal and conjunctival epithelial cells. Ultrastructural morphologic changes consistent with apoptosis were observed in the conjunctival epithelial cells.
Conclusions:
Experimentally induced dry eye in mice causes apoptosis of cells in ocular surface tissues including the central and peripheral corneal epithelium, bulbar and tarsal conjunctival epithelia, tarsal conjunctival stroma, and lid margin. Apoptosis may play a key role in the pathogenesis of keratoconjunctivitis sicca and may be a therapeutic target for this condition.
Insights
Experimental dry eye in mice induces significant ocular surface cell apoptosis, particularly in corneal and conjunctival tissues. This finding suggests apoptosis plays a key role in dry eye disease pathogenesis and may offer a therapeutic target.
Area of Science:
- Ophthalmology
- Cell Biology
- Pathology
Background:
- Dry eye disease (keratoconjunctivitis sicca) is a prevalent condition with complex etiologies.
- Ocular surface cell death, specifically apoptosis, is increasingly recognized as a significant factor in dry eye pathogenesis.
Purpose of the Study:
- To investigate the effect of experimentally induced dry eye on ocular surface apoptosis in a mouse model.
- To identify specific ocular surface tissues affected by apoptosis in dry eye.
Main Methods:
- Dry eye was induced in mice by inhibiting tear production and increasing tear clearance.
- Apoptosis was assessed using TUNEL assays, immunohistochemistry for caspase-3 and PARP, and nuclear morphology staining.
- Ocular tissues, including cornea, conjunctiva, and eyelids, were examined.
Main Results:
- A significant increase in TUNEL-positive cells (apoptosis) was observed in the central and peripheral corneal epithelium, bulbar and tarsal conjunctival epithelia, tarsal conjunctival stroma, and lid margin of mice with induced dry eye.
- Immunohistochemistry confirmed increased caspase-3 and PARP activity in these affected regions.
- Ultrastructural analysis revealed apoptotic changes in conjunctival epithelial cells.
Conclusions:
- Experimentally induced dry eye leads to apoptosis in key ocular surface tissues.
- Apoptosis is implicated as a critical mechanism in the pathogenesis of dry eye disease (keratoconjunctivitis sicca).
- Targeting apoptotic pathways presents a potential therapeutic strategy for managing dry eye.