Skin processes excellent regeneration properties allowing its rapid healing upon dermal injury. If wounds fail to heal in an orderly and timely manner, chronic ulcers develop. To test the potential of innovate therapies to promote wound repair, relevant wound infection models are needed. Current research is mainly conducted on animal models, which often limits direct transferability to human and poses ethic issues. These limitations can be overcome by using a proprietary ex vivo human skin model, HypoSkin, produced with leftovers from esthetic surgery.
HypoSkin contains all skin layers (epidermis, dermis and hypodermis). A wound consisting in a 2 mm defect of epidermis and superficial dermis is performed. The skin explant is embedded in proprietary gel-like matrix with epidermal surface left in direct contact with air. HypoSkin model showed preserved tissue integrity and cell viability in all skin layers for up to 7 days culture.
The edge of the wound was a clear cut of the epidermis at day 0. From day 2, an epithelial tongue appeared and migrated. A crust was also visible at day 7. Cells in the migrating epithelial tongue were proliferating (Ki-67 positive staining) and expressing K17 (specific marker of keratinocytes migrating over the wound bed), recapitulating some aspects of wound healing.
We have established a wound infection model by incubating a solution of Staphylococcus aureus for 3 days. Next to bacterial counting assays, infection was validated by histological comparison of intact with infected skin and by scanning electron microscopy. Furthermore, increased release of pro-inflammatory cytokines in supernatant indicates skin inflammation as a potential response to Staphylococcus aureus colonization. 
Future validation will consist in treating the infected wounded model with different wound-healing formulations to assess if a decisive decrease in infection can be observed.

Bacterial infection and wound healing in an ex vivo human skin model