Comparative evaluations of hypertrophic scar formation in in vivo models

Hypertrophic scar (HTS) results from a connective tissue reaction to trauma, inflammation, surgery, or burn on skin. In spite of various techniques for wound generation, the degree of scar in animal models after healing is still unpredictable and less reproducible. The objective of the current study was to identify the appropriate method to create the maximal HTS tissue in a reliable manner by comparing three different methods in vivo.

A 27 ICR mice were tested for the in vivo evaluations. Three different methods were applied to develop wounds on the back of each mice for quantitative evaluations on collagen formation: Group 1 (thermal burn), Group 2 (chemical burn), and Group 3 (physical punch). After injury, each lesion was photographed to examine physical variations in the wound areas. Histological analysis was conducted on days 0, 7, and 28 to assess the extent of the injury in the tissue and to quantitatively compare the amount of collagen formation after wound healing.

Compared with Groups 1 and 3, Group 2 demonstrated the largest wound area that gradually decreased with healing time. However, the minimal axial damage (along tissue depth) occurred to Group 2 at day 0 (183.7 ± 28.9, 38.1 ± 9.2, and 296.0 ± 81.7 µm for Groups 1, 2, and 3, respectively). After 28 days, all the groups showed the complete healing and accompanied a significant increase in the number of fibroblast and collagen generation with well-oriented and denser collagen fibers, in comparison with normal skin. Group 2 yielded twice thicker skin (both epidermis and dermis) than the other groups (970.8 ± 108.8 µm for Group 2 vs. 381.5 ± 30.8 µm for Group 1 and 442.9 ± 56.3 µm for Group 3; P < 0.001).

The proposed chemical burn can be the optimal method to create collagenous scar tissue in the mouse model. Further in vivo investigations with rat models will be performed to validate the current technique for laser scar treatment in terms of reliability and immunohistochemical responses. Lasers Surg. Med. 9999:XX-XX, 2017. © 2017 Wiley Periodicals, Inc.