Tetraspanin‐ESCRT sorting drives miR‐29b packaging into extracellular vesicles to reverse fibrosis in intrauterine adhesions

Abstract Intrauterine adhesions (IUA), characterized by pathological endometrial fibrosis, represent a significant clinical challenge impairing female reproductive health and fertility. MicroRNA‐29b (MiR‐29b) serves as a negative regulatory factor within the fibrosis‐related transforming growth factor‐β (TGF‐β)/Smad signaling pathway. In this study, we employed extracellular vesicles (EVs) as vehicles for the delivery of miR‐29b to enhance its therapeutic efficacy in the treatment of IUA. Using HEK‐293T cells overexpressing miR‐29b (29b‐OE) as a source of EVs, EVs overloaded with miR‐29b (EV29b) were enriched with miR‐29b via the endosomal sorting complex required for transport‐dependent pathway associated with tetraspanin‐mediated endocytosis. Notably, treatment with EV29b significantly promoted endometrial regeneration. Mechanistically, EV29b was found to target the 3′ untranslated region (3′UTR) of TGFB2, thereby inhibiting the TGF‐β/Smad signaling pathway and promoting repair of endometrial damage in both cultured endometrial stromal cells (EndoSCs) and a rat model of IUA. Collectively, our findings indicate that miR‐29b, when effectively sorted and loaded into EVs, can substantially mitigate endometrial fibrosis by suppressing the TGF‐β/Smad signaling pathway, thereby presenting a novel therapeutic strategy for the treatment of IUA.