After establishing an asthma model with ovalbumin, it was demonstrated that miRNA-21-5p expression was upregulated in alveolar M-sEVs, transferred to rat trachea epithelial cells to target Smad7, and affected the pro-fibrotic TGFβ1/Smad signaling pathway, promoting EMT and airway remodeling and exacerbating asthma progression (Li et al., 2021c). Here, SMAD7 is linked to asthma.