Exploring interspecies differences in ex vivo models of Pseudomonas aeruginosa keratitis: a comparative study of human, pig and sheep corneas

Introduction. Interspecies differences in human, pig and sheep corneal thickness may affect the Pseudomonas aeruginosa colonization. Currently, there is no research investigating the impact of these differences, along with variable storage and culture conditions on infection in ex vivo cornea models. These factors could significantly influence utilizing ex vivo models for drug testing research.

Aim. In this study, we aim to compare the relevance of sheep and pig cornea infection models to human.

Methodology. The corneas were stored in McCarey-Kaufman medium or Eagle’s Minimum Essential Medium or Dulbecco’s Modified Eagle’s Medium/Mixture F-12 Ham medium (incubator) and then infected after varying storage durations. The effect of added foetal bovine serum (FBS) to media and continuous shaking mimicking rinsing with tears on infection was also investigated. The infection outcome was evaluated by comparing c.f.u. between conditions.

Results. The study found that storage conditions, culture media, FBS and continuous rinsing of corneas with media had no significant effect on infection progression in ex vivo keratitis models across selected species.

Conclusions. Pig and sheep models yield results comparable to human corneas. These findings support the interchangeability of ex vivo human, pig and sheep keratitis models for P. aeruginosa infection studies, emphasizing their relevance and reliability in research contexts. This interchangeability is particularly useful for research groups where one particular animal model may not be available. The media in this ex vivo keratitis model can be free of animal components by the removal of FBS, which reduces the reliance on animal-derived products, aligning with ethical considerations and promoting more sustainable and humane scientific practices. This study advances the understanding of ex vivo keratitis models, demonstrating their robustness and potential for broader application in ophthalmic research and drug testing.