Comparison of Normal Human Skin and Hypertrophic Scar Tissue Samples of Different Ages, Locations, and Stages of Maturity.

Background: Scars disrupt the normal structure and function of the skin. The primary goal of plastic surgery is to prevent and reduce scarring. Therefore, we aimed to establish a comparison scheme between normal skin (NS) tissues of different ages and locations; hypertrophic scars (HTS) of different ages, locations, and maturities; and NS and HTS tissues to provide evidence on scar severity for improving treatment evaluation.

Methods: Various methods including histology, immunohistochemistry, and immunofluorescence were employed to compare the general appearance, macrophage infiltration, fibroblast activity, degree of angiogenesis, and collagen fiber type and arrangement in human-sourced NS and HTS tissues of different ages, locations, and maturities in seven patients (three with NS and four with HTS) from the Department of Burn and Plastic Surgery of the Shandong Provincial Hospital from January 2019 to December 2020.

Results: The thicknesses of the epidermis and dermis of NS tissues varied with age and location. The epidermis of the upper arms, face, and upper eyelids of NS tissues sequentially thickened, whereas the dermis was sequentially thinner. Several glandular structures were identified in the upper eyelids but rarely in the face and upper arms. Histological changes in HTS tissue of different ages, locations, and maturity occur as scar formation time is prolonged, accompanied by increased CD86 levels and fibrosis. As the scar matured, connexin and VEGFR2 expression decreased, indicating reduced inflammation, fibroblast activity, and angiogenesis. The comparison between NS and HTS tissue also revealed significant differences; the positive expression of VEGFR2 and total collagen in HTS tissue was higher than that in NS tissue.

Conclusions: We discovered significant differences among NS, HTS, and NS and HTS tissues of different ages, locations, and maturities. Further, this study may provide a basis for clarifying the treatment effect of different methods for HTS compared with those for NS, efficiently individualizing patients' treatment plans and ultimately shortening the scar treatment process.