Preclinical Evaluation of the Safety and Efficacy of Cryopreserved Bone Marrow Mesenchymal Stromal Cells for Corneal Repair

PURPOSE: Mesenchymal stromal cells (MSCs) have been shown to enhance tissue repair as a cell-based therapy. In preparation for a phase I clinical study, we evaluated the safety, dosing, and efficacy of bone marrow–derived MSCs after subconjunctival injection in preclinical animal models of mice, rats, and rabbits. METHODS: Human bone marrow–derived MSCs were expanded to passage 4 and cryopreserved. Viability of MSCs after thawing and injection through small-gauge needles was evaluated by vital dye staining. The in vivo safety of human and rabbit MSCs was studied by subconjunctivally injecting MSCs in rabbits with follow-up to 90 days. The potency of MSCs on accelerating wound healing was evaluated in vitro using a scratch assay and in vivo using 2-mm corneal epithelial debridement wounds in mice. Human MSCs were tracked after subconjunctival injection in rat and rabbit eyes. RESULTS: The viability of MSCs after thawing and immediate injection through 27- and 30-gauge needles was 93.1% ± 2.1% and 94.9% ± 1.3%, respectively. Rabbit eyes demonstrated mild self-limiting conjunctival inflammation at the site of injection with human but not rabbit MSCs. In scratch assay, the mean wound healing area was 93.5% ± 12.1% in epithelial cells co-cultured with MSCs compared with 40.8% ± 23.1% in controls. At 24 hours after wounding, all MSC-injected murine eyes had 100% corneal wound closure compared with 79.9% ± 5.5% in controls. Human MSCs were detectable in the subconjunctival area and peripheral cornea at 14 days after injection. CONCLUSIONS: Subconjunctival administration of MSCs is safe and effective in promoting corneal epithelial wound healing in animal models. TRANSLATIONAL RELEVANCE: These results provide preclinical data to support a phase I clinical study.