Donor BMSC‐derived small extracellular vesicles relieve acute rejection post‐renal allograft through transmitting Loc108349490 to dendritic cells

Bone marrow‐derived mesenchymal stem cell (BMSC)‐derived small extracellular vesicles (sEVs) are potent candidates for the suppression of acute rejection post‐renal allograft and have been reported to halt dendritic cells (DCs) maturation. However, whether BMSC‐derived sEVs mitigate acute rejection post‐renal allograft by targeting DCs is still unclear. In this study, donor BMSC‐derived sEVs (sEVs) relieved the inflammatory response and suppressed mature DCs (mDCs) location in kidney grafts, and increased regulatory T (Treg) cell population in the spleens of the rats that underwent kidney allograft. In lipopolysaccharide (LPS)‐stimulated immature DCs (imDCs), sEVs suppressed the maturation and migration of DCs and inactivated toll‐like receptor 4 (TLR4) signaling. Compared with LPS‐treated imDCs, imDCs treated with LPS+sEVs promoted CD4⁺T cells differentiated toward Treg cells. Subsequently, we found that Loc108349490, a long non‐coding RNA (lncRNA) abundant in sEVs, mediated the inhibitory effect of sEVs on DC maturation and migration by promoting TLR4 ubiquitination. In rats that underwent an allograft, Loc108349490 deficiency weakened the therapeutic effect of sEVs on acute rejection. The present study firstly found that sEVs alleviated acute rejection post‐renal allograft by transferring lncRNA to DCs and screened out the functional lncRNA loaded in sEVs was Loc108349490.