BMSC-derived exosomal ANTXR1 inhibits erythroid differentiation by suppressing the TLR4/MyD88/NF-κB signaling pathway

Aplastic anemia (AA) is a bone marrow failure syndrome characterized by impaired hematopoiesis and a dysfunctional marrow microenvironment. Bone marrow-derived mesenchymal stem cell (BMSC)-derived exosomes play a crucial role in intercellular communication; however, the role of exosomal anthrax toxin receptor 1 (ANTXR1) in erythroid differentiation remains unclear. Mouse BMSCs were isolated, characterized, and transfected with either ANTXR1-overexpressing or ANTXR1-silencing lentiviral vectors. Exosomes were collected and identified using transmission electron microscopy, nanoparticle tracking analysis, and exosomal marker detection. K562 cells and human cord blood CD34⁺cells were treated with these exosomes. Erythroid differentiation was evaluated through flow cytometry for CD235a and CD71, benzidine staining, RT-qPCR, and Western blot analysis of GATA1 and ALAS2. Apoptosis and inflammatory signaling were examined using flow cytometry, ELISA, Western blotting, and co-immunoprecipitation. TLR4 inhibitor and agonist treatments were applied to verify pathway involvement. BMSC-derived exosomes successfully carried ANTXR1, and their abundance reflected ANTXR1 expression in donor BMSCs. Exosomes enriched in ANTXR1 inhibited erythroid differentiation, as evidenced by reduced CD235a/CD71 expression, decreased GATA1 and ALAS2 levels, and diminished hemoglobin synthesis. In contrast, ANTXR1-deficient exosomes promoted erythroid differentiation and apoptosis while activating the TLR4/MyD88/NF-κB pathway. Pharmacological inhibition of TLR4 attenuated these effects, whereas TLR4 agonist treatment enhanced them. Co-immunoprecipitation further supported an interaction between ANTXR1 and TLR4. BMSC-derived exosomal ANTXR1 suppresses erythroid differentiation, at least in part, by modulating the TLR4/MyD88/NF-κB signaling pathway. These findings identify exosomal ANTXR1 as a potential regulator of erythropoiesis.