Understanding the Effects of Pseudomonas Aeruginosa Biofilm Conditioned Media on Wound Healing Responses

Background: Majority of biofilm manifestations are associated with chronic wounds, and their presence lead to complications in these wounds which results in a longer timespan for the wound to heal. Pseudomonas aeruginosa is a common biofilm-forming bacterium found in chronic wounds, and extensive research has been carried out to study its influence on wound healing. However, the effects of the secreted factors by Pseudomonas aeruginosa biofilms on wound healing still remains unclear.

Purpose: In our study, we explored the effects of these exudates using biofilm conditioned media (BCM) on human fibroblasts and keratinocytes.

Methods: Using live-cell imaging, we observed dose-dependent decrease in migration rates upon incubation of BCM. Cell spreading was reduced, indicative of reduced migratory capacity. This was further confirmed by delayed cell polarisation, increased expression and dysregulated localization of focal adhesions and adherens junctions via immunocytochemistry and hanging drop assay.

Results: Through live-cell imaging and MTT assay, we showed that BCM decreased cell viability even upon transient exposure, demonstrating that it was cytotoxic and the factors involved initiated irreversible cell death. We also found that the expression and localization of gap junctions were unaffected by BCM using immunoblot analysis and immunocytochemistry.

Conclusions: In conclusion, high concentrations of BCM hampered directed migration, reduced cell viability and disrupted cell-cell and cell-substrate contacts, causing delayed wound healing when an infection occurs. Although debridement is common for biofilm-infected wounds, biofilm exudates would have already penetrated the skin. Taken together, this study deepens our understanding on the limited efficacy of wound debridement and underlines the potential of targeting these secreted factors to increase the effectiveness of treatment.