TRAF6 and Urethral stricture: In a rat urethral fibrosis model induced by TGF-β1, miR-146a-enriched exosomes derived from TNF-α-treated HUMSC suppressed urethral stricture by reduction of IL-1β/-6, IL-1 receptor-associated kinase 1 (IRAK1), TNF receptor-associated factor 6 (TRAF6), and NF-κB levels in target cells [55].