Photoprotection of a novel resveratrol analogue: insights from 2D, 3D, and endothelialized bioprinted human skin models.

Excessive exposure to ultraviolet (UV) radiation induces oxidative stress, DNA damage, and extracellular matrix (ECM) disorganization, contributing to skin aging and disease. To enhance photoprotection strategies, antioxidant molecules have been explored as complementary agents to conventional UV filters. Here, we investigated the photoprotective potential of N',N‴,N‴''-((1E,1'E,1″E)-(((1,3,5-triazine-2,4,6-triyl)tris(oxy))tris(benzene-4,1-diyl))tris(methanylylidene))tris(2-hydroxybenzohydrazide) (Trz-HBH3), a novel resveratrol analogue obtained through molecular triplication. The compound was evaluated for UV absorption, photostability, phototoxicity in 3T3 fibroblasts, and protective effects against UVB-induced damage in HaCaT keratinocytes. To improve physiological relevance, three-dimensional (3D) human skin models were developed using fibroblasts and keratinocytes, with or without human umbilical vein endothelial cells (HUVEC), and assembled manually or by extrusion-based bioprinting. Models were characterized by Calcein-AM staining and (immuno)histochemical analysis. To assess oxidative stress responses, tissues were exposed to UVA radiation from two sources (UVA lamp and sun simulator), and intracellular reactive oxygen species (ROS) levels were quantified. While Trz-HBH3 showed no cytotoxic or phototoxic effects, it exhibited broad UV absorption (in the UVB, UVA II and part of UVA I), high photostability (remaining absorbance values of 93.8% ± 2.8% in the UVA region and 86.0% ± 8.0% in the UVB region), and protective effects against UVB-induced damage, maintaining cell viability close to 100%. Notably, Trz-HBH3 effectively reduced UVA-induced ROS by 63.5% and 69.5%, in both reconstructed and endothelialized bioprinted human skin models, respectively. These findings support the antioxidant and photoprotective properties of Trz-HBH3 and reinforce the applicability of bioprinted skin as an advanced in vitro platform to investigate UV-induced skin responses.