The immunomodulatory effects of topical extracellular vesicles derived from mesenchymal stem cells (MSC) in a corneal scarring model.

Abstract

Purpose : Corneal scarring is a major cause of blindness worldwide and an important indication for corneal transplantation. With the limitations of corneal grafting, there is a need to explore alternative therapies for corneal scarring. We have previously reported on the optimal dosing frequency and safety of topical delivery of MSC-derived extracellular vesicles (EV) in normal rat corneas. In this study, we investigated the potential therapeutic effects of MSC-EV in a rat corneal scarring model.

Methods : Conditioned media of human embryonic stem cells (ESC)-derived MSC was concentrated and fractionated to obtain enriched EV fractions (80-150nm). Irregular phototherapeutic keratectomy (irr-PTK) was used to induce corneal scarring in Sprague Dawley rats. Topical EV or saline were applied to the injured rat corneas for 6 days or until the epithelium was healed, whichever was earlier. Corneal clarity was assessed using slit-lamp imaging and in-vivo confocal microscopy (IVCM). Stromal reflectivity was quantitatively analyzed. Immunohistochemistry of the excised corneas was performed.

Results : Following irr-PTK, corneas that received topical EV treatment were relatively clearer (with a significantly lower mean corneal haze score) throughout the follow-up period compared to the corneas in the control group with saline treatment (p=0.002). Stromal reflectivity imaged using IVCM also showed a significant reduction of haze intensity (p=0.004). Corneal vascularisation, quantified by the area of vascularized quadrant, vessel length and diameter, was also significantly lower in EV-treated corneas. Lower expression of CD31 (vascular endothelial marker), LYVE1 (lymphatic marker), fibronectin and Col3a1 (fibrosis markers) were detected in EV treated corneas. EV-treated corneas also displayed a regenerative immune phenotype characterised by a higher infiltration of regenerative M2 over M1 macrophages.

Conclusions : Our findings demonstrated that ESC-derived MSC EV are potential regenerative therapies for corneal injuries, effected through anti-angiogenesis, anti-fibrosis, and immunomodulation.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.