Ablative fractional CO2 laser treatment promotes wound healing phenotype in skin macrophages

Objectives Ablative fractional laser (AFL) treatment is a well‐established method for reducing signs of skin photoaging. However, the biological mechanisms underlying AFL‐induced healing responses and skin rejuvenation remain largely unknown. It is known that macrophages play an important role in orchestrating healing, normalization, and remodeling processes in skin. Macrophage phenotypes are characterized by inflammatory markers, including arginase‐1 (Arg1), major histocompatibility class II molecules (MHC II), and CD206. This study aims to explore AFL's effect on macrophage phenotype by evaluating changes in inflammatory markers and the potential concurrent accumulation of Arg1 in the skin. Methods Mice (n = 9) received a single AFL treatment on the left side of the back skin (100 mJ/microbeam, 5% density) while the right side of the back remained untreated as control. Treated and untreated skin from each mouse were collected Day 5 posttreatment for flow cytometry and histology analysis. Flow cytometry evaluated the immune infiltration of macrophages and the expression of macrophage inflammatory markers (Arg1, MHC II, and CD206). In addition, Arg1 presence in the skin was evaluated through antibody staining of histology samples and quantification was performed using QuPath image analysis software. Results Following AFL, the number of macrophages increased 11‐fold (p = 0.0053). Phenotype analysis of AFL‐treated skin revealed an increase in the percentage of macrophages positive for Arg1 (p