Evolution of ischemia and neovascularization in a murine model of full thickness human wound healing

Abstract

Translation of wound healing research is limited by the lack of an appropriate animal model, due to the anatomic and wound healing differences in animals and humans. Here, we characterize healing of grafted, full‐thickness human skin in an in vivo model of wound healing. Full‐thickness human skin, obtained from reconstructive operations, was grafted onto the dorsal flank of NOD.Cg‐KitW41J Tyr + Prkdcscid Il2rgtm1Wjl/ThomJ mice. The xenografts were harvested 1 to 12 weeks after grafting, and histologic analyses were completed for viability, neovascularization, and hypoxia. Visual inspection of the xenograft shows drying and sloughing of the epidermis starting at week four. By week 12, the xenograft appears healed but has lost 63.05 ± 0.24% of the initial graft size. There is histologic evidence of epidermolysis as early as 2 weeks, which progresses until week 4, when new epidermis appears from the wound edges. Epidermal regeneration is complete by week 12, although the epidermis appears hypertrophied. An initial increase of infiltrating immune mouse cells into the xenograft normalizes to baseline 6 months after grafting. Neovascularization, as evidenced by positive staining for the proteins human CD31 and alpha smooth muscle actin, is present as early as 2 weeks after grafting at the interface between the xenograft and the mouse tissue. CD31 and alpha smooth muscle actin staining increased throughout the xenograft over the 12 weeks, leading to greater viability of the tissue. Likewise, there is increased Hypoxia Inducible Factor 1‐alpha expression at the interface of viable and nonviable tissue, which suggest a hypoxia‐driven process causing early graft loss. These findings illustrate human skin wound healing in an ischemic environment, providing a timeline for use of full thickness human skin after grafting in a murine model to study mechanisms underlying human skin wound healing.

Robbing Peter to Pay Paul: Chlorhexidine gluconate demonstrates short‐term efficacy and long‐term cytotoxicity

“…To test the cytotoxicity of CHG on human skin wounds in vivo, we used an established xenografted mouse model of human skin wound healing. 37,38 All procedures on mice were approved by the University of Wisconsin Institutional Animal Care and Use Committee and the Research Animal Resource and Compliance office. Briefly, four male athymic nude mice (6-7 weeks old, Jackson Laboratory, Bar Harbour, ME) were grafted on bilateral flanks with partial thickness human skin procured from elective surgery.…”

PDGF-BB-derived supramolecular hydrogel for promoting skin wound healing

“…Unlike the PBS group, the collagen fibers were much clearer and more organized. Since blood vessels transport oxygen and nutrients to the wound tissue and play a key role in wound healing [ 33 ], the expression level of the vascular endothelial-specific marker CD31 was examined [ 34 ]. Immunohistochemistry staining (Additional file 1 : Fig.…”

Accelerated complete human skin architecture restoration after wounding by nanogenerator-driven electrostimulation

“…To test the efficacy of NG-driven ES on human skin wounds, we used an established xenograft mouse model of human skin wound healing [ 15 ]. The de-identified human skin tissues were obtained through an Institutional Review Board exempt protocol in accordance with laws and regulations of the University of Wisconsin-Madison School of Medicine and Public Health.…”

“…To move this exciting discovery to humans, it is essential to evaluate the impact of ES on the re-epithelialization process of human skin. The use of human skin transplanted onto immunocompromised mice is an effective method used for examining human skin wound healing in vivo [ 13 – 15 ]. Immunohistochemically, the xenografts can maintain morphological, immunological and functional characteristics of human skin even after wounding [ 13 , 16 ].…”