Tetrahedral Framework Nucleic Acids Re-establish Immune Tolerance and Restore Thyroid Function in Hashimoto's Thyroiditis via NOTCH1 Signaling Pathway Inhibition.

Hashimoto's thyroiditis (HT) is a chronic autoimmune disorder in which persistent immune dysregulation gradually impairs thyroid structure and endocrine function. Although levothyroxine replacement can correct hypothyroidism, it has little effect on the underlying autoimmune activity that drives the progression of the disease. Tetrahedral framework nucleic acids (tFNAs) are self-assembled DNA nanostructures that have demonstrated immunomodulatory capabilities in several inflammatory conditions. In this study, we investigated whether tFNAs could exert therapeutic effects in experimental models of HT and explored the involved mechanisms. In vivo administration of tFNAs alleviated multiple disease-associated symptoms, including thyroid enlargement, lymphocytic infiltration, elevated autoantibodies levels, hormonal dysfunction, and follicular cell apoptosis. These changes were accompanied by a shift in CD4+ T-cell differentiation, characterized by decreased T helper 1 (Th1), T helper 17 (Th17), and follicular helper T (Tfh) responses and a relative increase in T helper 2 (Th2) cells and regulatory T cells (Tregs). In vitro, tFNAs were efficiently internalized by thyroid follicular cells, where they mitigated the inflammatory environment induced by interferon-gamma (IFN-γ) by reducing cytokine release, preserving mitochondrial membrane potential, and limiting cell death. Further analyses indicated that these effects were closely associated with the suppression of NOTCH1 pathway activation. No obvious systemic toxicity was observed. Collectively, the data suggest that tFNAs may provide a strategy to modulate autoimmune activity in HT beyond hormone replacement therapy alone.