The potential therapeutic efficacy of intravenous versus subconjunctival mesenchymal stem cells on experimentally ultraviolet-induced corneal injury in adult male albino rats

Background: The X-rays and the visible light are the main source of ultraviolet radiation (UVR). About 90% of ultraviolet B (UVB) is absorbed by the cornea which may promote corneal inflammation, oedema and damage of its epithelial layer. Bone marrow mesenchymal stem cells (BM-MSCs) have been demonstrated to ameliorate the injured corneal tissue and accelerate its wound healing. This study aimed to compare the healing effect of intravenous (IV) versus subconjunctival (SC) BM-MSCs on the rats' corneas subjected to UVB-irradiation.Materials and methods: Ten rats were used as donors for BM-MSCs and the other 40 were allocated into four equal groups: group I (control group), group II (ultraviolet-irradiated group), group III (ultraviolet-irradiated + IV BM-MSCs-treated group) and group IV (ultraviolet-irradiated +SC BM-MSCs-treated group). Rats of all groups were euthanized after 3 weeks and the corneal specimens were processed for histopathological, immunohistochemical and electron microscopy assessment.Results: Ultraviolet-irradiated group showed remarkable thinning of epithelial thickness, wide partial epithelial separation, and desquamation. Neovascularisation of the disorganised stroma and disrupted Descemet's membrane were observed. The superficial and basal epithelial cells appeared irregular and separated by wide intercellular spaces and inflammatory cells. Immunohistochemical examination showed a significant decrease in proliferating cell nuclear antigen immunoreaction. In contrast, minimal changes were observed in rats treated with BM-MSCs with more improvement associated with the subconjunctival administration compared to IV route.Conclusions: Local SC injection of BM-MSCs has an amazing regenerative efficacy on the corneal injury compared to the systemic IV route. (Folia Morphol 2022; 81, 4: 900-916)