Vascularized human skin assembloids model compartmental skin organization and immune responsiveness in vitro

Allergic skin diseases, including atopic and contact dermatitis, are prevalent inflammatory disorders imposing clinical and socioeconomic burdens. Their pathogenesis involves impaired barrier function, genetic susceptibility and immune dysregulation, yet mechanistic insights remain limited by the lack of physiologically relevant human in vitro models. Conventional human skin organoids capture aspects of epidermal stratification but generally lack vascular components, limiting tissue maintenance and physiological relevance. To overcome these limitations, vascularized skin assembloids (VSAs) are generated by combining human induced pluripotent stem cell-derived skin organoids with blood vessel organoids under air-liquid interface conditions. This modular assembly supports the formation of key skin-like structural features, including a multilayered epidermis, organized dermal matrix and interconnected vascular-like networks associated with improved barrier maturation and dermal-vascular organization, while providing an accessible platform for epidermal allergen exposure and inflammatory analysis in a vascularized skin-like tissue context. Incorporation of immune cells establishes an immune-integrated and immune-responsive microenvironment that enables modelling of allergen-induced inflammation. Upon exposure to house dust mite extract, VSAs exhibit inflammatory remodelling with atopic dermatitis-relevant features, characterized by barrier disruption, keratinocyte stress responses, immune-cell infiltration and induction of type 2 mediators (IL-4, IL-13, TSLP, CCL17, CCL26). Treatment with clinically used atopic dermatitis therapeutics upadacitinib (JAK1 inhibitor) and dupilumab (IL-4Rα antagonist) improves barrier-associated features and suppresses STAT6-associated inflammatory signalling, showing responses consistent with their known mechanisms of action. Collectively, these findings support VSAs as a human-relevant, vascularized and immune-integrated skin assembloid model for mechanistic studies and preclinical evaluation of pharmacological responses in inflammatory skin diseases.