Abstract
Purpose :
Mucins are large glycoproteins extending off the apical surface of corneal epithelial cells and are known to be important for tear film stability and corneal wound healing. To date, murine models have been generated with null mutations in both secreted (Muc5ac-, Muc5b-) and membrane-associated (Muc1-, Muc16-) mucins but no spontaneous ocular phenotype has been identified. However, the highest expressed membrane-associated corneal mucin in the mouse, mucin 4 (Muc4), has not been investigated and we sought to determine its role in ocular health and wound healing.
Methods :
Complete ophthalmic examinations were performed on 6 month-old mice (WT and Muc4 KO mice) using slit lamp biomicroscopy, indirect fundoscopy, phenol red thread test, vital staining of the ocular surface and clinical scoring using a modified SPOTS system. To determine the effect of Muc4 in corneal wound healing, phototherapeutic keratectomy was performed in the right eye (6 month-old, WT and Muc4 KO, n = 8 per genotype, evenly divided between sexes). After wounding, fluorescein stained images of the cornea were taken with cobalt blue photography and the wound size was quantified using ImageJ at 0, 24, 36, and 48 hours post-wounding. An unpaired t-test was performed to determine differences at healing time points between genotypes.
Results :
There were no statistically significant differences identified between Muc4 KO and WT mice on clinical examination, diagnostic testing and clinical scoring. In the corneal wounding study, all mice in both groups were healed by 48 hours post-wounding. In unpaired t-tests, the Muc4 KO group healed significantly slower than the WT group at 24h and 36h post-wounding. At the 24-hour post-wounding, the mean percent of corneal wound healed for the Muc4 KO and WT mouse groups was 43.9% and 63.5%, respectively (P = 0.0480). At the 36-hour post-wounding, the mean percent of corneal wound healed for the Muc4 KO and WT mouse groups was 81.3% and 88.3%, respectively (P = 0.0402).
Conclusions :
Our results suggest that while the loss of Muc4 does not result in an abnormal spontaneous ocular phenotype, it likely plays an important role in corneal epithelial wound healing. These results support further investigation into the role of membrane-associated Muc4 in epithelial cell migration in corneal wound healing.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.