Hypertrophic scar contraction (HSc) is caused by granulation tissue contraction propagated by myofibroblast and fibroblast migration and contractility. Identifying the stimulants that promote migration and contractility are key to mitigating HSc. AngiotensinII (AngII) promotes migration and contractility of heart, liver, and lung fibroblasts; thus, we investigated the mechanisms of AngII in HSc. Human scar and unwounded dermis were immunostained for AngII receptors AT1-receptor and AT2-receptor, and analyzed for AT1-receptor expression using western blot. In-vitro assays of fibroblast contraction and migration under AngII stimulation were conducted with AT1-receptor, AT2-receptor, p38, JNK, MEK, and ALK5 antagonism. Excisional wounds were created on AT1-receptor KO and WT mice treated with AngII ± Losartan, and ALK5 and JNK inhibitors SB-431542 and SP-600125 respectively. Granulation tissue contraction was quantified and wounds analyzed by immunohistochemistry. AT1-receptor expression was increased in scar, but not unwounded tissue. AngII induced fibroblast contraction and migration through AT1-receptor. Cell migration was inhibited by ALK5 and JNK, but not p38 or MEK blockade. In-vivo experiments determined that absence of AT1-receptor and chemical AT1-receptor antagonism diminished granulation tissue contraction while AngII stimulated wound contraction. AngII granulation tissue contraction was diminished by ALK5 inhibition, but not JNK. AngII, promotes granulation tissue contraction through AT1-receptor and downstream canonical TGFβ signaling pathway; ALK5. Further understanding the pathogenesis of HSc as an integrated signaling mechanism could improve our approach to establishing effective therapeutic interventions.

Hypertrophic scar (HSc) 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 HSc model. A third-degree burn was created on dorsum of C57BL/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 (GFP) 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 Toluidine blue. Macrophages were detected with F4/80 immune. Vascularity was assessed with CD31 immune. RNA for contractile proteins was detected by quantitative real-time polymerase chain reaction (qRT-PCR). 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 GFP 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. CD31 stain revealed increased vascularity. Macrophages and mast cells were increased. qRT-PCR showed up-regulation of transforming growth factor beta, alpha smooth muscle actin, and rho-associated protein kinase 2 in HSc. Tensile testing revealed that human skin and scar tissues are tougher than mouse skin and scar tissues.

Background: The free split latissimus dorsi flap for lower-extremity reconstruction has some advantages over the traditional latissimus dorsi flap. The flap is harvested with the patient in the supine position and is associated with minimal morbidity as the function of the remaining latissimus dorsi muscle is preserved through the posterior division of the thoracodorsal nerve. Methods: A consecutive single-surgeon 5-year series of free split latissimus dorsi muscle flaps for lower-extremity reconstruction (n = 42) was evaluated. Donor site morbidity was evaluated through assessment of the strength of the remaining latissimus dorsi at least 1 month after surgery. Shoulder function was evaluated postoperatively using the Disabilities of the Arm, Shoulder and Hand (DASH) score, American Shoulder and Elbow Surgeons (ASES) score, and Shoulder Pain and Disability Index (SPADI). Results: The mean age of the 42 patients was 40.7 years. The mean length and width of the flaps were 17.9 cm and 8.6 cm. The majority (71%) of the wounds were due to acute trauma. Of the 42 flap procedures performed, 95% (40) were successful. Assessment of remaining latissimus dorsi strength at least 1 month postoperatively, during 3 activities, showed a Medical Research Council (MRC) grade of 5 in all patients. The mean and median scores were 6.4 and 0 according to the DASH, 6.0/6.4 and 0/0 on the SPADI pain/disability scales, and 90.7 and 100 on the ASES. Conclusions: The free split latissimus dorsi flap is a large reliable muscle flap with negligible donor site morbidity that is particularly advantageous for lower-extremity resurfacing following trauma. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background Pathologic cutaneous scarring affects over 40 million people worldwide and costs billions of dollars annually. Understanding mechanisms of fibroblast activation and granulation tissue contraction is the first step toward preventing pathologic scarring. The authors hypothesize that nucleic acids increase fibroblast activation and cause granulation tissue contraction and sequestration of nucleic acids by application of a nucleic acid scavenger dendrimer, polyamidoamine third-generation dendrimer, will decrease pathologic scarring. Methods In vitro experiments were performed to assess the effect of nucleic acids on pathologic scar–associated fibroblast activity. The effect of nucleic acids on cytokine production (polymerase chain reaction) and migration on mouse fibroblasts was evaluated. Immunofluorescence microscopy was used to determine the effect of nucleic acids on the differentiation of human primary fibroblasts into myofibroblasts. Using a murine model, the effect of polyamidoamine third-generation dendrimer on granulation tissue contraction was evaluated by gross and histologic parameters. Results Mouse fibroblasts stimulated with nucleic acids had increased cytokine production (i.e., transforming growth factor-β, monocyte chemotactic protein 1, interleukin-10, tumor necrosis factor-α, and interferon-γ), migration, and differentiation into myofibroblasts. Polyamidoamine third-generation dendrimer blocked cytokine production, migration, and differentiation into myofibroblasts. Using a murine model of granulation tissue contraction, polyamidoamine third-generation dendrimer decreased wound contraction and angiogenesis. Collagen deposition in polyamidoamine third-generation dendrimer–treated tissues was aligned more randomly and whorl-like compared with control tissue. Conclusions The data demonstrate that nucleic acid–stimulated fibroblast activation and granulation tissue contraction is blocked by polyamidoamine third-generation dendrimer. Sequestration of pathogen-associated molecular patterns may be an approach for preventing pathologic scarring.