Autophagy of umbilical cord mesenchymal stem cells conduces to pro-angiogenic function of conditioned medium

Abstract BackgroundAngiogenesis is a key prerequisite for wound healing. The conditioned medium following culture of umbilical cord mesenchymal stem cells (UCMSCs) has a potential to promote angiogenesis, but the efficacy is very low. Autophagy is an important process in protein recycling and a contributor for cell exocrine, which maybe stimulate the release of cytokines from UCMSCs to the medium and enhance the pro-angiogenic efficacy of the conditioned medium.MethodsAutophagy in UCMSCs was induced by 100 nM, 1 µM and 10 µM rapamycin for 6-hour and then detected by LC-3 immunofluorescence staining. After induction, the cells were washed with PBS for 3 times and cultured in fresh medium without rapamycin for additional 24-hour. And then, the conditioned medium was collected for the following experiments. The angiogenic effects of different groups of conditioned medium were verified by in vitro and in vivo tube formation assays in the matrigel-coated plates and matrigel plaques injected in mouse inguinal areas. Finally, the expressions of angiogenic factors including VEGF, FGF-1, FGF-2, TGF-α, MMP-3, MMP-9, PDGF-α, PDGF-β, HIF-1α and Ang II in the autophagic and control UCMSCs were measured by q-PCR assay.ResultsRapamycin induced autophagy of UCMSCs in a dose dependent manner, but the conditioned medium in 100 nM rapamycin-induced group was with the best pro-angiogenic efficacy. Thus, this group of medium was viewed as the optimal conditioned medium. The in vivo tube formation assay showed that angiogenesis in matrigel plaques injected daily with the optimal conditioned medium was more obvious than that injected with the control conditioned medium. Further, the expressions of VEGF, FGF-2, PDGF-α, MMP-9 and HIF-1α were markedly increased in UCMSCs following treatment with 100 nM rapamycin.ConclusionAppropriate autophagy improves the pro-angiogenic efficacy of the conditioned medium, which might be utilized to optimize the applications of UCMSCs-derived conditioned medium in wound healing and tissue repair.Trial registrationNot applicable.