Safety and feasibility of subconjunctival injection of mesenchymal stem cells for acute severe ocular burns: A single-arm study

Investigation of healing strategies in a rat corneal opacity model with polychromatic light and stem cells injection

Corneal opacities are a major cause of vision loss worldwide. However, the current therapies are suboptimal to manage the corneal wound healing process. Therefore, there is an obvious need to develop new treatment strategies that are efficient in promoting wound healing in patients with severe corneal disorders. In this study, we investigated and compared the efficacy of adipose-derived mesenchymal stem cells (ADMSCs) and photobiomodulation (PBM) with polychromatic light in the NIR (600-1200 nm) alone and in combination, on corneal opacity, inflammatory response, and tissue architecture in a rat corneal opacity model created by mechanical injury. All animals were divided into four groups randomly following the injury: injury only (no treatment), ADMSCs treatment, PBM treatment and combined (ADMSCs+PBM) treatment (n = 12 eyes per group). At the 10th and 30th day following injury, corneal opacity formation, neovascularization, and corneal thickness were assessed. On the 30th day the harvested corneas were analyzed by transmission electron microscopy (TEM), histological evaluation, immunohistochemical (IHC) staining and real-time polymerase chain reaction (RT-PCR). On day 30, the corneal opacity score, neovascularization grade, and corneal thickness in all treatment groups were significantly lower in comparison with the untreated injured corneas. The TEM imaging and H&E staining together clearly revealed a significant enhancement in corneal regeneration with improved corneal microenvironment and reduced vascularization in the combined administration of PBM and ADMSCs compared to treatment of PBM and ADMSCs alone. In addition, the IHC staining, and RT-PCR analysis supported our hypothesis that combining ADMSCs therapy with PBM alleviated the inflammatory response, and significantly decreased scar formation compared to either ADMSCs or PBM alone during the corneal wound healing.

Applications of mesenchymal stem cells in ocular surface diseases: sources and routes of delivery

INTRODUCTION

Mesenchymal stem cells (MSCs) are novel, promising agents for treating ocular surface disorders. MSCs can be isolated from several tissues and delivered by local or systemic routes. They produce several trophic factors and cytokines, which affect immunomodulatory, transdifferentiating, angiogenic, and pro-survival pathways in their local microenvironment via paracrine secretion. Moreover, they exert their therapeutic effect through a contact-dependent manner.

AREAS COVERED

In this review, we discuss the characteristics, sources, delivery methods, and applications of MSCs in ocular surface disorders. We also explore the potential application of MSCs to inhibit senescence at the ocular surface.

EXPERT OPINION

Therapeutic application of MSCs in ocular surface disorders are currently under investigation. One major research area is corneal epitheliopathies, including chemical or thermal burns, limbal stem cell deficiency, neurotrophic keratopathy, and infectious keratitis. MSCs can promote corneal epithelial repair and prevent visually devastating sequelae of non-healing wounds. However, the optimal dosages and delivery routes have yet to be determined and further clinical trials are needed to address these fundamental questions.

Corneal regeneration: insights in epithelial stem cell heterogeneity and dynamics

The discovery of slow-cycling cells at the corneal periphery three decades ago established the limbus as the putative corneal stem cell niche. Since then, studies have underscored the importance of the limbal stem cells in maintaining the health and function of the ocular surface. Advancements in our understanding of stem cell biology have been successfully translated into stem cell therapies for corneal diseases. Here, we review recent developments in mouse genetics, intravital imaging, and single-cell genomics that have revealed an underappreciated complexity of the limbal stem cells, from their molecular identity, function, and interactions with their niche environment. Continued efforts to elucidate stem cell dynamics of this extraordinary tissue are critical for not only understanding stem cell biology but also for advancing therapeutic innovation and development.

OUP accepted manuscript

The corneal epithelium serves to protect the underlying cornea from the external environment and is essential for corneal transparency and optimal visual function. Regeneration of this epithelium is dependent on a population of stem cells residing in the basal layer of the limbus, the junction between the cornea and the sclera. The limbus provides the limbal epithelial stem cells (LESCs) with an optimal microenvironment, the limbal niche, which strictly regulates their proliferation and differentiation. Disturbances to the LESCs and/or their niche can lead to the pathologic condition known as limbal stem cell deficiency (LSCD) whereby the corneal epithelium is not generated effectively. This has deleterious effects on the corneal and visual function, due to impaired healing and secondary corneal opacification. In this concise review, we summarize the characteristics of LESCs and their niche, and present the current and future perspectives in the management of LSCD with an emphasis on restoring the function of the limbal niche.

The link module of human TSG-6 (Link_TSG6) promotes wound healing, suppresses inflammation and improves glandular function in mouse models of Dry Eye Disease

PURPOSE

To investigate the potential of the Link_TSG6 polypeptide comprising the Link module of human TSG-6 (TNF-stimulated gene/protein-6) as a novel treatment for dry eye disease (DED).

METHODS

We analyzed the therapeutic effects of topical application of Link_TSG6 in two murine models of DED, the NOD.B10.H2^b mouse model and the desiccating stress model. The effects of Link_TSG6 on the ocular surface and DED were compared with those of full-length TSG-6 (FL_TSG6) and of 0.05% cyclosporine (Restasis®). Additionally, the direct effect of Link_TSG6 on wound healing of the corneal epithelium was evaluated in a mouse model of corneal epithelial debridement.

RESULTS

Topical Link_TSG6 administration dose-dependently reduced corneal epithelial defects in DED mice while increasing tear production and conjunctival goblet cell density. At the highest dose, no corneal lesions remained in ∼50% of eyes treated. Also, Link_TSG6 significantly suppressed the levels of inflammatory cytokines at the ocular surface and inhibited the infiltration of T cells in the lacrimal glands and draining lymph nodes. Link_TSG6 was more effective in decreasing corneal epithelial defects than an equimolar concentration of FL_TSG6. Link_TSG6 was significantly more potent than Restasis® at ameliorating clinical signs and reducing inflammation. Link_TSG6 markedly and rapidly facilitated epithelial healing in mice with corneal epithelial debridement wounds.

CONCLUSION

Link_TSG6 holds promise as a novel therapeutic agent for DED through its effects on the promotion of corneal epithelial healing and tear secretion, the preservation of conjunctival goblet cells and the suppression of inflammation.