tRNA derived fragment tsRNA-14783 promotes M2 polarization of macrophages in keloid

Keloid is a common pathological scar, which involves the regulation of immune microenvironment. tRNA derived fragments (tsRNAs/tRFs) are a novel type of functional small non-coding RNAs. To this day, the role and effect of tRFs in keloid remain unclear. Herein, our purpose was to confirm that tRFs participate in the occurrence and development of keloid by regulating M2 macrophages. The infiltration of M2 macrophages in keloid tissue was detected by immunofluorescence. The tRFs expression profiles in M1 and M2 macrophages were evaluated by small RNA sequencing. We validated the expression of key differentially expressed tRFs and the effect of a key tRF on M2 polarization of macrophages was measured by RT-qPCR, Western blot and immunofluorescence. M2 macrophages infiltration was increased and M1 macrophages was decreased in keloid tissue, compared with normal skin tissue. Meanwhile, 2896 tRFs were differentially expressed between M2 macrophages and M1 macrophages, with the expression of 1661 tRFs were increased and 1235 were decreased in M2 macrophages. Functional annotation exposed that target genes of the tRFs significantly enriched in the function of transcription, DNA-templated; protein binding and cytoplasm. Pathway analysis showed that the differentially expressed tRFs were mainly involved in macrophage polarization-related signaling pathways, including MAPK signaling pathways, Wnt signaling pathways and PI3K-AKt signaling pathways. The results of RT-qPCR detection for tsRNA-14777, tsRNA-14778 and tsRNA-14783 were in accordance with the small RNA sequencing date. Finally, overexpression of tsRNA-14783 promoted macrophage M2 polarization, as evidence by the increase of M2 macrophage marker TGF-β, IL-10 and CD206, and the decrease of M1 macrophage marker IL-1 and NOS2. Our results proved that tsRNA-14783 might be participated in keloid formation via regulation of M2 macrophages polarization. tsRNA-14783 may be potential therapeutic target for keloid.