Pericytes reduce inflammation and collagen deposition in acute wounds

Background: Pericytes have been shown to have mesenchymal stromal cell like properties and play a role in tissue regeneration. The goal of this study was to determine whether the addition of a pericyte sheet to a full-thickness dermal wound would enhance the healing of an acute wound. Methods: Human muscle-derived pericytes and human dermal fibroblasts were formed into cell sheets, then applied to full-thickness excisional wounds on the dorsum of nu/nu mice. Histology was performed to evaluate epidermal and dermal reformation, inflammation and fibrosis. In addition, real-time reverse transcriptase-polymerase chain reaction (RT-PCR) was used to determine cytokine response. Results: Pericytes were detected in the wounds until day 16 but not fibroblasts. Decrease in wound size was noted in pericyte sheet-treated wounds. Enhanced neo-vascularization and healthy granulation tissue formation were noted in the pericyte-treated wounds. Expression of type I collagen messenger RNA (mRNA) was significantly higher in the fibroblast-treated group, whereas Type III collagen mRNA showed significant increase in the pericyte group at days 3, 6 and 9 compared with the fibroblast and no-cell groups. Trichrome staining revealed thick unorganized collagen fibrils in the fibroblast-treated wounds, whereas pericytetreated wounds contained thinner and more alligned collagen fibrils. Tumor necrosis factor (TNF)-alpha mRNA levels were increased in the fibroblast-treated wounds compared with pericyte-treated wounds. Discussion: The addition of pericytes may confer beneficial effects to wound healing resulting in reduced recruitment of inflammatory cells and collagen I deposition, potential to enhance wound closure and better collagen alignment promoting stronger tissue.