Supplementary Material for: Dehydroabietic Acid Induces Regeneration of Collagen Fibers in Ultraviolet B-Irradiated Human Dermal Fibroblasts and Skin Equivalents

<b><i>Background/Aims:</i></b> Dehydroabietic acid (DAA) is a natural phytochemical found in red pine trees and herbal plants. While DAA and its derivatives are known for improving diabetes and hyperlipidemia, the antiaging effect and its underlying mechanisms of DAA on skin have not been fully examined. Here, we assessed the antiaging effects of DAA on human dermal fibroblasts and skin equivalents. <b><i>Methods:</i></b> We investigated the effect of DAA on the secretion of type I procollagen and matrix metalloproteinase-1 (MMP-1) in ultraviolet B (UVB)-irradiated neonatal normal human dermal fibroblasts (NHDFn). Using nonlinear optical imaging techniques, we visualized quantitative and qualitative changes of collagen fibers by DAA treatment in human skin equivalent models. <b><i>Results:</i></b> DAA induces increases in type I procollagen secretion when treated on UVB-irradiated NHDFn. DAA also downregulates secretion of MMP-1 through the inhibition of the JNK signaling pathway. In human skin equivalent models, we successfully visualized the spatial distribution of collagen fibers in the dermis and found that quantity, diameter, and arrangement of collagen fibers in the dermis were significantly improved by DAA treatment. <b><i>Conclusion:</i></b> Our results suggest that DAA could be a useful agent for improving skin photoaging through the protection and regeneration of collagen fibers in skin.