Wound Repair and Regeneration (Impact Factor: 2.77). 10/2014; DOI: 10.1111/wrr.12238
ABSTRACT Hypertrophic scar contraction (HSc) following burn injury causes contractures. Contractures are painful and disfiguring. Current HSc therapies are marginally effective. To study pathogenesis and develop new therapies, a murine model is needed. We have created a validated immune-competent murine HSc model. A third-degree burn was created on the dorsum of C57BL/6 mice. Three days post-burn, tissue was excised and grafted with ear skin. Graft contraction was analyzed by computer planimetry and tissue harvested on different time points. Outcomes were compared to human condition to validate the model. To confirm graft survival, green fluorescent protein mice (GFP) were used and histologic analysis was performed to differentiate between ear and back skin. Role of panniculus carnosus (PC) in contraction was analyzed. Cellularity was assessed with DAPI. Collagen maturation was assessed with Picro-sirius red. Mast cells were stained with Toluidine blue. Macrophages were detected with F4/80 immune. Vascularity was assessed with CD31 immune. RNA for contractile proteins was detected by qRT-PCR. Elastic moduli of human and murine skin and scar tissue were analyzed using a microstrain analyzer. Grafts contracted to ∼45% of their original size by day 14 and maintained their size. Grafting of GFP mouse skin onto wild type mice and vice-versa and analysis of dermal thickness and hair follicle density, confirmed graft survival. Interestingly, hair follicles disappeared after grafting and regenerated in ear skin configuration by day 30. Radiological analysis revealed the PC does not contribute to contraction. Microscopic analyses demonstrated that grafts show increase in cellularity. Granulation tissue formed after day 3. Collagen analysis revealed increases in collagen maturation over time. CD31 stain revealed increased vascularity. Macrophages and mast cells were increased. qRT-PCR demonstrated upregulation of TGF-β, ASMA, NMMII, and ROCK2 in HSc. Tensile testing revealed that human skin and scar tissues are tougher than mouse skin and scar tissues.
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