Oxygen-controllable gelatin-based hydrogel platforms for engineering hypoxic atopic dermatitis microenvironments

Atopic dermatitis (AD) is a common chronic skin disease characterized by severe itching. The complex physiology and diverse pathogenesis of AD make clinical outcomes difficult to predict. Therefore, it is essential to develop preclinical models that closely mimic the features of AD. Recently, various AD models have been developed to investigate skin physiology and disease pathology. However, current models still have limitations in replicating the 3D microenvironment of human skin in 2D, face ethical issues, and exhibit inherent structural differences in animal models. To overcome these limitations, we developed gelatin-based AD models to recapitulate AD characteristics. First, to investigate the features of AD microenvironments, we performed single-cell RNA sequencing analysis using publicly available data from patients with AD. We confirmed the presence of collagen type VI alpha 5 chain-positive fibroblasts in AD tissues, cell interaction with dorsal root ganglions that induce itching, and overexpression of hypoxia-related factors in AD tissues. Based on these findings, we first fabricated in situ crosslinked hydrogels via thiol-ene reaction and disulfide bond formation. Next, AD models were developed by encapsulating human dermal fibroblasts (HDFs) within the hydrogels and inducing immune responses and hypoxic environments through interleukin-4 (IL-4) treatment and oxygen concentration control. The AD models exhibited high cytocompatibility and maintained a hypoxic (pO₂ < 5%) condition under controlled oxygen concentration. After IL-4 treatment and oxygen concentration control, the models showed upregulated hypoxia- and immune-related genes, as well as overexpression of itch-related factors. Furthermore, therapeutic drug responses were evaluated using the models. In conclusion, our gelatin-based AD models have potential as preclinical platforms for drug screening and fundamental research of AD pathophysiology.