Biomaterial-enhanced delivery of stem cell-derived exosomes for skin inflammatory diseases: Mechanisms and therapeutic advances.

Inflammatory skin diseases such as psoriasis, atopic dermatitis, vitiligo, and lupus erythematosus present persistent therapeutic challenges due to their chronic nature, immune dysregulation, and suboptimal treatment outcomes. Stem cell-derived exosomes have emerged as a promising cell-free therapeutic approach, capable of modulating immune responses, promoting tissue regeneration, and restoring skin homeostasis. This review provides a comprehensive overview of exosomes derived from various stem cell sources-including adipose tissue, bone marrow, umbilical cord, dental pulp, and induced pluripotent stem cells-and their roles in regulating immune cell function and facilitating skin repair. Particular emphasis is placed on biomaterial-assisted delivery strategies, such as hydrogels, nanoparticles, and engineered scaffolds, which enhance the stability, targeting, and retention of exosomes at inflammatory sites. Key immunomodulatory mechanisms, including Treg/Th17 balance, macrophage polarization, and dendritic cell regulation, are also discussed. Finally, we highlight emerging preclinical and clinical evidence supporting the integration of exosome therapy with bioactive materials as a next-generation strategy for treating inflammatory skin disorders with improved precision and durability.