Microneedle‐Mediated Delivery of Immunomodulators Restores Immune Privilege in Hair Follicles and Reverses Immune‐Mediated Alopecia

Abstract Disorders in the regulatory arm of the adaptive immune system result in autoimmune‐mediated diseases. While systemic immunosuppression is the prevailing approach to manage them, it fails to achieve long‐lasting remission due to concomitant suppression of the regulatory arm and carries the risk of heightened susceptibility to infections and malignancies. Alopecia areata is a condition characterized by localized hair loss due to autoimmunity. The accessibility of the skin allows local rather than systemic intervention to avoid broad immunosuppression. It is hypothesized that the expansion of endogenous regulatory T cells (T_regs) at the site of antigen encounter can restore the immune balance and generate a long‐lasting tolerogenic response. A hydrogel microneedle (MN) patch is therefore utilized for delivery of CCL22, a T_reg‐chemoattractant, and IL‐2, a T_reg survival factor to amplify them. In an immune‐mediated murine model of alopecia, local bolstering of T_reg numbers is shown, leading to sustained hair regrowth and attenuation of inflammatory pathways. In a humanized skin transplant mouse model, expansion of T_regs within human skin is confirmed without engendering peripheral immunosuppression. The patch offers high‐loading capacity and shelf‐life stability for prospective clinical translation. By harmonizing immune responses locally, the aim is to reshape the landscape of autoimmune skin disease management.