• Fisher, Mark
• Miller, Kyle
• Klitzman, Bruce
• Leong, Kam W.
• Selim, M. Angelica
• Medina, Manuel A.
• Lorden, Elizabeth R.
• Quiles, Carlos
• Ehanire, Tosan
• Bergeron, Andrew
• Bond, Jennifer
• Ibrahim, Mohamed M.
• Levinson, Howard

Abstract

<jats:title>Abstract</jats:title><jats:p>Hypertrophic scar (<jats:styled-content style="fixed-case">HS</jats:styled-content>c) contraction following burn injury causes contractures. Contractures are painful and disfiguring. Current therapies are marginally effective. To study pathogenesis and develop new therapies, a murine model is needed. We have created a validated immune‐competent murine <jats:styled-content style="fixed-case">HS</jats:styled-content>c model. A third‐degree burn was created on dorsum of <jats:styled-content style="fixed-case">C</jats:styled-content>57<jats:styled-content style="fixed-case">BL</jats:styled-content>/6 mice. Three days postburn, tissue was excised and grafted with ear skin. Graft contraction was analyzed and tissue harvested on different time points. Outcomes were compared with human condition to validate the model. To confirm graft survival, green fluorescent protein (<jats:styled-content style="fixed-case">GFP</jats:styled-content>) mice were used, and histologic analysis was performed to differentiate between ear and back skin. Role of panniculus carnosus in contraction was analyzed. Cellularity was assessed with 4′,6‐diamidino‐2‐phenylindole. Collagen maturation was assessed with Picro‐sirius red. Mast cells were stained with <jats:styled-content style="fixed-case">T</jats:styled-content>oluidine blue. Macrophages were detected with <jats:styled-content style="fixed-case">F</jats:styled-content>4/80 immune. Vascularity was assessed with <jats:styled-content style="fixed-case">CD</jats:styled-content>31 immune. <jats:styled-content style="fixed-case">RNA</jats:styled-content> for contractile proteins was detected by quantitative real‐time polymerase chain reaction (q<jats:styled-content style="fixed-case">RT</jats:styled-content>‐<jats:styled-content style="fixed-case">PCR</jats:styled-content>). Elastic moduli of 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 <jats:styled-content style="fixed-case">GFP</jats:styled-content> mouse skin onto wild‐type mice, 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 that panniculus carnosus doesn't contribute to contraction. Microscopic analyses showed that grafts show increase in cellularity. Granulation tissue formed after day 3. Collagen analysis revealed increases in collagen maturation over time. <jats:styled-content style="fixed-case">CD</jats:styled-content>31 stain revealed increased vascularity. Macrophages and mast cells were increased. q<jats:styled-content style="fixed-case">RT</jats:styled-content>‐<jats:styled-content style="fixed-case">PCR</jats:styled-content> showed up‐regulation of transforming growth factor beta, alpha smooth muscle actin, and rho‐associated protein kinase 2 in <jats:styled-content style="fixed-case">HS</jats:styled-content>c. Tensile testing revealed that human skin and scar tissues are tougher than mouse skin and scar tissues.</jats:p>

Topics

• density
• impedance spectroscopy