Abstract
Purpose :
Maintaining corneal health and transparency are necessary pre-requisites for exquisite vision; a function ascribed to stem cells (SCs) nestled within the limbus. Perturbations to this site or depletion of its SCs, results in limbal stem cell deficiency (LSCD). Whilst characterizing a murine model of this disease, we discovered a rare and unreported phenomenon on the cornea; goblet cell metaplasia (GCM). Our goal was to unravel the mechanism through which it transpires.
Methods :
C57BL/6 (n=138) and aged matched K14CreER-Confetti (n=30) mice were used. Partial and total LSCD was induced by mechanical debridement. Suture-induced (n=6) and nu/nu athymic (n=3) mice were employed as acute and chronic models of corneal neovascularization. Mice were clinically evaluated and procured tissue assessed after PAS-staining, immunofluorescence for the presence of keratins (K8, K12, K13, K14), mucins (MUC5AC) and blood vessels (CD31), and cell proliferation (BrdU/EdU).
Results :
In mapping the evolution of LSCD, PAS+/MUC5AC+ GCs were not detected in the region spanning the bulbar conjunctiva-limbus suggesting they did not migrate from their forniceal cull-de-sac. Rather, they appeared 7 days post-injury, arising from K8 conjunctival precursors which invaded the cornea as part of conjunctivalization. Fluorescence intensity for K12 in the central cornea decreased concomitant with elevated MUC5AC and CD31 compared to controls (15.14 v 37.94, p<0.0001; 31.12 v 11.03, p<0.0001; 27.38 v 20.23, p<0.0001, respectively). GCs strongly correlated with blood vessels (r=0.95, p=0.004). In Confetti mice, multicolored GC rosettes formed indicating that they have a K14 ancestry. In the absence of limbal damage but amidst an acute or chronic corneal neovascular response, GCs were not detected.
Conclusions :
This first report on GCM on the murine cornea dismisses the theory that these cells emigrate as a component of conjunctivalization. While neovascularization encouraged GCM, it was not the principal driver, rather a breach in the limbal barrier was necessary to initiate metaplasia. Whether GCM manifests in corneas of patients with LSCD is yet to be determined, nonetheless it should be investigated to determine whether this type of cell identity change can be suppressed or corrected pharmacologically to prevent sequela such as the formation of vision-obstructing mucous plaques.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.