The effects of ex vivo physical cold atmospheric plasma treatment on endothelial cells in human corneal explants and its potential for in vivo application in refractory corneal ulcers

Physical cold atmospheric plasma (CAP) is a partially ionised, excited gas, which can be generated by applying electrical energy to a gas and comprises various biologically active components with versatile biological effects. Due to its wound-healing and antimicrobial properties, CAP gained attention for medical use. In ophthalmology, the treatment of refractory infectious corneal ulcers may represent a potential field of application. The present study aimed to investigate whether superficial CAP treatment affects deeper layers of the cornea, particularly the postmitotic endothelium, which is critical for corneal transparency and tissue integrity. Therefore, we treated the epithelial surface of human corneal explants for 2, 3, or 5 min with CAP. Before and 24 h after treatment, the corneal endothelial cells were evaluated quantitatively and qualitatively to assess endothelial vitality and functionality. Compared to control, particularly after CAP treatment, endothelial cell loss and damage was observed, indicating depth effects of CAP in corneal tissue. In this context, the treatment duration may have an impact, as endothelial cell loss tended to increase with longer exposure times. Based on these results, we used a modified treatment regimen including repetitive short CAP exposures with intermittent moistening of the cornea in an in vivo CAP application to treat patients with treatment-refractive corneal ulcer conditions. The CAP treatment had a positive outcome on corneal healing and was well tolerated.