Safety of Subconjunctival Injection of Allogeneic Mesenchymal Stem Cells in Horses

Clinical trials should be performed to assess subconjunctival injection of allogeneic mesenchymal stem cells (MSCs) in the treatment of equine eye disorders. Authors’ addresses: Large Animal Clinical Sciences, (Joswig, Hardy, Easterwood, and Watts); and Veterinary Integrative Biosciences (Cummings), Texas A&M University, College Station TX 77843; e-mail: AWatts@cvm.tamu.edu

1. Introduction

Subconjunctival injection of allogeneic mesenchymal stem cells (MSCs) has the potential to become a new therapeutic in equine ophthalmology. Our objective was to evaluate the safety of allogeneic MSC subconjunctival injection. We hypothesized there would be no difference in adverse events after subconjunctival MSC injection versus control.

2. Methods

Upper-lid subconjunctival injection of 3 million MSCs in 0.5 mL was performed in a randomly assigned eye (n = 14 horses). The opposite eye was injected with cell-free medium (0.5 mL). Serial evaluations of both eyes were performed by investigators blinded to treatment assignment. The injections were repeated to the same eye 3 weeks later. Flow cytometry was used to determine major histocompatibility complex (MHC) II expression of MSCs.

3. Results

There were no adverse events or complications in either the MSC or control injected eyes. Redness and chemosis were significantly different (higher scores in the MSC treated eyes) on days 1, 22, and 28, but not at other time points. Blepharospasm, blepharoedema, and miosis were absent throughout the study. Eyes that had epiphora on day 0 continued to have epiphora throughout the trial and there were no significant differences in epiphora between groups. The MSCs were negative for MHC II. 

4. Discussion

In preclinical models, subconjunctival injection of MSCs speeds healing after chemical keratitis. This may be due to the regulation of inflammation and healing. In the horse, subconjunctival administration of two injections of 3 million allogeneic MSCs appears to be safe.

Acknowledgments

Funded by the Link Endowment for Equine Research at Texas A&M University.

Conflict of Interest

The Authors declare no conflicts of interest.