-Original-

Photodynamic Therapy Delays Cutaneous Wound Healing in Mice

Yan Sun^1,2, Mamiko Tosa², Hiroya Takada² and Rei Ogawa²

¹Department of Dermatology, The First Hospital of China Medical University, Shenyang, China
²Department of Plastic, Reconstructive and Aesthetic Surgery, Nippon Medical School, Tokyo, Japan

Background: Cutaneous wound healing is a complex, dynamic physiological process. Traditional methods of promoting wound healing are not always effective. Consequently, alternative modalities, such as photodynamic therapy (PDT), are needed. We examined the effectiveness and underlying mechanisms of PDT in a murine model of acute wound healing.
Methods: Two excisional wounds were produced, one on each side of the midline, in C57bL/6J mice. Methyl 5-aminolevulinate hydrochloride (MAL) was applied to the right-side wound. After 1 to 3 hours of incubation, the wound was irradiated with red light. The left-side wound was not treated with MAL or red light. On Day 14, the wounds were excised and subjected to histological and immunohistochemical analysis.
Results: During the first week, no difference was seen between the two sides. However, at week 2, PDT-treated wounds exhibited delayed re-epithelialization. On Day 14, hematoxylin and eosin (HE) staining showed a continuous epithelial lining in untreated wounds. In contrast, PDT-treated wounds partially lacked epithelium in the wound bed. Masson's Trichrome (MTC) staining showed a thicker dermis and more collagen fibers and inflammatory cells in PDT-treated wounds than in untreated wounds. Immunohistochemical analyses showed significantly fewer CD31⁺ blood vessels and greater collagen III density in PDT-treated wounds than in untreated wounds. However, treated and untreated wounds did not differ in collagen I density.
Conclusions: PDT delayed acute wound healing in a murine model of secondary intention wound healing.

J Nippon Med Sch 2020; 87: 110-117

Keywords
photodynamic therapy, wound healing, mice

Correspondence to
Yan Sun, Department of Dermatology, The First Hospital of China Medical University, 155 North Nanjing Street, Shenyang 110001, China
sunyan805@163.com

Received, June 14, 2019
Accepted, October 29, 2019