Effects of mesenchymal stem cells encapsulated within crosslinked collagen carrier gels on alkali burns in a corneal organ culture model

Abstract

Purpose : Alkali burns of the cornea cause a profound inflammatory response that leads to neovascularization, stromal opacification, and blindness. Although bone marrow-derived human mesenchymal stem cells (MSCs) and their secreted factors (secretome) have been studied for their anti-inflammatory properties, the optimal way of delivery is still unknown due to the challenges and inefficiencies of administering them in eye drops. Here we investigate strategies to deliver hMSCs and their secreted factors to the corneal surface in a rabbit organ culture model after alkaline burn. The delivery methods are comprised of (1) hMSCs within collagen gels crosslinked by copper-free click chemistry, (2) hMSCs within collagen gels crosslinked by a multifunctional PEG-N-hydroxysuccinimide (NHS) linker and (3) hMSCs in culture media.

Methods : An ex vivo organ culture model using rabbit corneas were subject to an alkaline burn of diameter of 0.5 mm using 1M NaOH-soaked filter paper for 1min and wash thoroughly. The corneas were then transferred to an agar mold and the following treatments were applied to the cornea surfaces: hMSCs within collagen gels crosslinked by copper free click chemistry, hMSCs within collagen gels crosslinked linked using four-arm PEG-N-hydroxysuccinimide (NHS), and hMSCs in media. Fluorescein dye was used to track the closure of the epithelial wounds, andcryosections of the treated and untreated corneas were fixed and stained for alpha smooth muscle actin (alpha-SMA) and analyzed by confocal microscopy.

Results : The corneas lost their transparency immediately after alkali burn. Corneas treated with hMSCs healed faster and were more transparent than no treatment controls at one week. Corneas treated with hMSCs encapsulated within collagen gels cross-linked by click chemistry exhibited a higher degree of transparency compared to treatment with cells encapsulated in collagen gels crosslinked by 4-arm PEG-NHS. Treatment with hMSCs within both types of crosslinked gels expressed less alpha-SMA compared to no treatment and hMSCs alone.

Conclusions : hMSCs and their secreted factors have the potential to heal severe alkaline burns of the cornea. Further work is merited to ascertain the mechanisms by which these cross-linked gels foster improved therapeutic effects from hMSCs.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.