Research on the correlation between mechanical signaling molecules of hypertrophic scar and post injury time in burn patients in scar remodeling stage

Objective To analyze the correlation between integrin β₁, focal adhesion kinase (FAK), extracellular signal-regulated kinase 1/2 (ERK1/2) of hypertrophic scar (HS) and post injury time in burn patients in scar remodeling stage. Methods Thirty-four patients with 34 HS specimens admitted to Department of Burns and Plastic Surgery of Chengdu No.2 Hospital and Institute of Burn Research of the First Affiliated Hospital of Army Medical University (originally the Third Military Medical University) from May 2013 to April 2016 were recruited by convenient sampling method, and normal skin specimens were obtained from donor sites of another 6 patients from the above-mentioned departments who had scar resection and skin grafting for this cross-sectional and observational study. Vancouver Scar Scale (VSS) was used to assess the height, vascularity, pigmentation, and pliability of scars. Diasonograph was used to assess scar thickness. Immunohistochemical method was used to observe the expressions of integrin β₁, FAK, and ERK1/2 in dermis and epidermis of scar and normal skin. Correlations between the post injury time and the scar thickness, the post injury time and the expressions of integrin β₁, FAK, and ERK1/2 in epidermis of scar, the post injury time and the expressions of integrin β₁, FAK, and ERK1/2 in dermis of scar, the expressions of integrin β₁, FAK, and ERK1/2 in dermis and those in epidermis of scar were analyzed by Pearson correlation analysis. Locally estimated scatterplot smoothing curve fitting line was used to demonstrate the non-linear regression relationship between the expressions of integrin β₁, FAK, and ERK1/2 in dermis and those in epidermis of scar, the scar thickness and the post injury time. Results (1) The total VSS score of scars of patients was (8.3±2.3) points, with height scored (2.2±0.7) points, vascularity scored (2.0±0.8) points, pigmentation scored (2.3±0.7) points, and pliability scored (1.9±0.7) points. The thickness of scar was (2.8±1.1) mm. (2) The expressions of integrin β₁, FAK, and ERK1/2 in dermis and epidermis of scar were more than those in normal skin. (3) There was significantly positive correlation between the scar thickness and the post injury time (r=0.39, P<0.05). There was significantly positive correlation between the expression of integrin β₁ in epidermis of scar and the post injury time (r=0.33, P<0.05). There were no significantly correlations between the expressions of FAK and ERK1/2 in epidermis of scar and the post injury time (r=-0.03, -0.04, P>0.05). There was significantly negative correlation between the expression of FAK in dermis of scar and the post injury time (r=-0.34, P<0.05). There were no significantly correlations between the expressions of integrin β₁ and ERK1/2 in dermis of scar and the post injury time (r=0.07, -0.23, P>0.05). There were significantly positive correlation between the expressions of integrin β₁, FAK, and ERK1/2 in dermis and those in epidermis of scar (r=0.70, 0.60, 0.64, P<0.01). (4) The expressions of integrin β₁, FAK, and ERK1/2 in dermis and epidermis of scar were changed from downtrend in 1 to 2 months post injury to uptrend in 2 to 3 months post injury, which reached the peak around 3 to 4 months post injury. Hereafter the expressions of mechanical signaling molecules in epidermis of scar were gradually declined, while the expressions of mechanical signaling molecules in dermis of scar were at a quite high level within half a year post injury. Scar thickness was steadily increased after 1 month post injury. Conclusions In scar remodeling stage of burn patients, the HS thickness increases continuously along with the increasing post injury time in the early stage of scar formation. The vulnerability of integrin β₁, FAK, and ERK1/2 of HS to external mechanical stimuli increases gradually within 4 months post injury.