Plasma-derived exosomes from Graves' orbitopathy: Pathogenic entities causing tissue lesions

Graves' orbitopathy (GO) is an autoimmune disorder characterized by orbital inflammation, fibrosis, and adipogenesis. circulating exosomesomes, critical mediators of intercellular communication, are implicated in autoimmune pathologies through miRNA cargo delivery. However, their direct role in GO pathogenesis and mechanisms driving systemic-to-local disease progression remain unexplored.

Plasma-derived exosomes from patients with Graves' orbitopathy (GO-Exos) and healthy controls (Con-Exos) were isolated and characterized. Functional assays assessed their impact on primary human orbital fibroblasts (OFs). A GO model was established via weekly intravenous administration of GO-Exos. Disease progression was evaluated through thyroid function tests, histopathology, MRI, and single-cell RNA sequencing. Mechanistic studies focused on miR-221-5p and its downstream CACNG4/AMPK pathway.

In vitro, GO-Exos reprogrammed OFs into proinflammatory, profibrotic, and adipogenic phenotypes, while upregulating disease-associated receptors IGF-1R and TSHR, suggesting a feedforward mechanism for sustained autoimmunity. Strikingly, stable-phase GO-Exos retained bioactivity, inducing comparable cytokine elevations in control OFs. In vivo, weekly intravenous administration of GO-Exos in BALB/c mice over 150 days recapitulated human disease hallmarks, including thyroid dysfunction, exophthalmos, orbital adipose hyperplasia, and collagen deposition, validated by histopathology and MRI. Mechanistically, miR-221-5p was identified as a key driver of orbital remodeling via suppression of CACNG4/AMPK. Partial rescue of pathogenic phenotypes by miR-221-5p inhibition confirmed its functional centrality. Single-cell RNA sequencing revealed exosome-mediated cellular reprogramming, including TREM2+ macrophage enrichment and CD8⁺ T cell infiltration.

Our findings establish circulating exosomesomes as novel pathogenic drivers in GO and provide a foundational resource for understanding exosome-mediated immunopathogenesis in autoimmune orbitopathies.