Abstract: Objective To explore the effect of M2 macrophage-derived exosomal lncRNA NR_028113.1 on macrophage polarization and its possible mechanism. Methods Bone marrow-derived macrophages (BMDMs) from BALB/c mice were isolated and cultured in vitro. After IL-4 treatment to induce M2 macrophage polarization, exosomes (M2-exo) were extracted from the supernatant of M2 macrophages and identified. The expression of lncRNA in M2-exo was detected by qRT-PCR. BMDMs were co-cultured with M2-exo (100 μg/mL) or PBS for 48 h, and the changes in cellular expression levels of Arg1, YM-1, FIZZ1, iNOS and TNF-α were detected using qRT-PCR and Western blotting. The percentage of CD206+ cells was analyzed using flow cytometry, and the phosphorylation levels of JAK2/STAT3 proteins were detected using Western blotting. A lncRNA smart silencer was designed to specifically inhibit the expression of lncRNA NR_028113.1 in the M2 macrophages, from which exosomes were extracted and co-cultured with BMDMs for 48 h. The mRNA expression levels of Arg1, YM-1, FIZZ1, iNOS and TNF-α, CD206+ cell percentage and the phosphorylation levels of JAK2/STAT3 proteins were detected using qRT-PCR, flow cytometry and Western blotting. Results LncRNA NR_028113.1 was highly expressed in the exosomes of M2 macrophages (P<0.05). Co-culture with M2-exo significantly increased mRNA expressions of M2 macrophage marker genes Arg1, YM- 1 and FIZZ1 (P<0.05), lowered the expressions of iNOS and TNF-α (P<0.05), and increased CD206+ cell percentage and JAK2/STAT3 protein phosphorylation level in BMDMs (P<0.05). After inhibiting the expression of lncRNA NR_028113.1 in M2 macrophages, the extracted M2-exo caused significant down- regulation of the mRNA expressions of Arg1, YM-1 and FIZZ1 and up- regulation of iNOS and TNF-α mRNA (P<0.05), resulting also in significantly reduced CD206 + cell percentage and lowered phosphorylation levels of JAK2/STAT3 proteins in co-cultured BMDM (P<0.05). Conclusions M2 macrophage-derived exosomal lncRNA NR_028113.1 can significantly promote M2 polarization of macrophages possibly by activating the JAK2/STAT3 signaling pathway.

Key words: exosomes; long non-coding RNA; macrophage polarization; JAK2; STAT3