Reconstructed Human Skin Models to Study Superficial and Deep Skin Wound Healing In Vitro

Wound healing is an essential and complex biological mechanism to repair barrier breaches in the human body, but it results in scar formation. The extent of scar formation is associated with the depth of injury. Stromal cells play a vital role in wound healing and scar formation, but the role of the subcutaneous tissue in human skin wound healing remains largely unknown. In order to dissect the role of dermal fibroblasts, adipose stromal cells, and adipocytes in superficial and deep skin wound healing, we created a human tissue-engineered skin model and assessed healing outcomes in vitro. Three different reconstructed skin models were created, with dermal fibroblasts, adipose stromal cells, or adipocytes in the wound bed underneath a standardised biopsy punch wound. The superficial skin wound model with only dermal fibroblasts in the wound bed was completely healed within 14 days. The engineered 'deep' wounds with adipocytes in the wound bed showed delayed wound closure with reduced Ki67 proliferating keratinocytes and reduced basement membrane collagen IV deposition. This was accompanied by increased wound contraction and α-SMA protein expression underneath the newly formed epidermis, indicative of early scar formation. The 'deep' wound model with adipose stromal cells but without adipocytes showed improved re-epithelialisation but still healed with increased α-SMA protein expression. Furthermore, decreased leptin was observed in the supernatant of the 'deep' wound model. The superficial and deep wound models presented here can be used to test future therapies to improve wound closure which will lead to improved scar formation.