Abstract
Purpose :
Infectious keratitis is one of the leading causes of blindness worldwide, frequently associated with the use of contact lenses. It is primarily due to the invasion of the corneal tissue caused by a great variety of microorganisms, mainly bacteria. Exosomes are nanovesicles of 30 to 150 nm in diameter involved in both physiological and pathological intercellular communication processes. Regarding eye diseases, the knowledge of their role is still very limited. Based on this, the hypothesis that arises is that microorganisms in contact with exosomes produced by human corneal epithelium cells (HCE), an experimental model, would produce changes in the expression of bacterial virulence factors.
Methods :
Exosomes were isolated and purified from HCE and then added to Gram-positive (Staphylococcus epidermidis) and Gram-negative (Pseudomonas aeruginosa) bacterial cultures. Afterwards, the variation in the expression levels of genes encoding virulence factors were analysed by means of RT-qPCR over time compared to bacteria without any contact with exosomes.
Results :
The expression levels of 7 virulence factors were studied at different times, from 30 minutes to 16 hours. When Staphylococcus epidermidis data was analysed, two clear tendencies were observed: while one group increased their expression up to 4-8 hours and then they remained stable, the other group, after a slight increase in the first 30 minutes, decreased over time. In the case of Pseudomonas aeruginosa, the genes analysed present a common trend, decreasing strongly in the first hours and recovering their expression levels over time.
Conclusions :
Staphylococcus epidermidis, considered a commensal microorganism but also one of the main agents responsible for bacterial keratitis, increases the expression of genes encoding toxins and biofilm, while those related to quorum sensing are reduced over time. In the case of the pathogen Pseudomonas aeruginosa, the virulence factors related to biofilm establishment also modify their levels. Taking into consideration these results, it is deduced that bacteria have the ability to respond and change the expression of virulence factors in the presence of exosomes, with no need for direct tissue contact.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.