Exosome-shuttled PCBP1 from hypoxic preconditioned urine-derived stem cells accelerates wound healing

We previously found that hypoxia - preconditioned human urine-derived stem cells (USCs) accelerated wound healing. Since exosomes are one of the key mediator of USCs to support skin repair, we wonder whether the healing-promoting effects of hypoxia-treated USCs were associated with exosomes. A full-thickness cutaneous wound model of female C57BL/6J mice was established. Label-free exosome proteomics was performed to investigate the differentially expression protein from exosomes derived from hypoxia-treated USCs (H-USCs-exo). Transcriptomics was carried out to explore the downstream signaling of exosome recipient cells. H-USCs-exo facilitated the wound healing via angiogenesis and re-epithelialization. Also, the pro-angiogenesis results were obtained in vitro, as evidenced by the enhancement of proliferation, migration, and angiogenic abilities of human microvascular endothelial cell line HMEC-1. Subsequently, using Label-free exosome proteomics, a protein named poly (RC) binding protein 1 (PCBP1, an RNA-binding protein) was found to be significantly upregulated (Fold change = 3.34, p < 0.05) in H-USCs-exo. Exosomes delivered PCBP1 into endothelial cells, and exosomal PCBP1 mediated the pro-angiogenic effects of H-USCs-exo on HMEC-1 cells. The healing-delaying function was confirmed in mice treated with exosomes secreted by hypoxia-pretreated USCs with PCBP1 knockdown. In addition, as a tissue repair facilitator, hypoxia inducible factor 1 subunit alpha (HIF-1α) was upregulated in USCs under hypoxia condition. HIF-1α potentiated the transcription of PCBP1 , leading to the high abundance of PCBP1 in H-USCs and H-USCs-exo. Further high-throughput transcriptomics illustrated that PCBP1 upregulated the expression of WNT5A (Fold change = 2.75, p < 0.05) and its downstream factors including vascular endothelial growth factor A and TEK receptor tyrosine kinase (Fold change = 2.85 and 5.75, respectively; p < 0.05). Exosome-shuttled PCBP1 from hypoxic preconditioned USCs accelerated wound healing, which might be associated with WNT5A signaling pathway.