The effects of Staphylococcus aureus biofilm conditioned media on 3T3 fibroblasts

Staphylococcus aureus (SA) is the most common bacterial species in chronic wounds. However, there is a lack of understanding of how SA secretions affect the cell biology during the healing process. We studied the effects of biofilm-secretions from SA strain SA29213 on 3T3 fibroblasts. SA29213 is a chronic wound isolate and widely used as a reference strain. We used a series of concentrations of biofilm-conditioned media (BCM) and found 100% BCM is lethal within 10 h. Cells survived in ≤75% BCM but the rate of closure in scratch wound assays was reduced. Treatment with 75% and 50% BCM caused fibroblasts to change shape and develop dendrite like processes. Prolonged treatment with 75% and 50% BCM reduced cell proliferation and increased the 4n deoxyribonucleic acid cell population with cell cycle arrest. There was also an elevation in the senescence marker beta galactosidase and the number of multinucleated cells. Shorter treatments with 75% and 50% SA BCM caused an increase in cell-cell adhesion and a redistribution of β-catenin from the cell membrane to the cytoplasm along with a change in the appearance and decrease in size of ZO-1, vinculin and paxillin structures. Fibroblasts in the edge of chronic wounds exposed to the secretions of SA may suffer similar effects such as induction of senescence, reduced proliferation and migration, which may contribute to the delayed healing of these chronic infected wounds.