ABSTRACT
Purpose: To investigate the effects of riboflavin and/or ultraviolet?A (UV?A) irradiation on the cell viability of ex?vivo?cultured rat limbal stem cells (LSCs). Methods: LSCs of male Wistar rats (N = 12 eyes) were cultured, and immunofluorescence staining was performed to evaluate them. After characterization, these cells were assigned to four groups of control (C), a group that was exposed to UV?A radiation (UV), a group that was treated with riboflavin (R), and a group that cotreated with both UV?A and riboflavin (UV+R). To determine the cell viability of LSCs, these cells were subjected to MTT assay on days 1, 3, and 7 after exposure to UV?A and/or riboflavin. The duration of exposure to UV?A and riboflavin was similar to levels used during the conventional corneal collagen cross?linking procedure. Results: Compared with the viable cells in the control group, there was a significant decrease (P < 0.0001) in the number of LSCs in the UV group during all study days. In the R group, the level of viable LSCs was as same as the level of viable LSCs in the C group. Combined treatment with UV?A plus riboflavin significantly decreased the survival of LSCs on days 1 and 3 (P < 0.0001, P < 0.001, respectively) compared with the control group. Interestingly, in the UV+R group, the photosensitizing effect of riboflavin significantly decreased the cytotoxic effect of UV irradiation 7 days after exposure. Conclusion: These results suggest that the administered UV energy in the presence or absence of riboflavin can damage LSCs. Likewise, riboflavin could decrease the toxic effect of UVA on LSCs