Background: It is well known that exosomes (EXO) play an important role in cell-cell communication and cellular functions. We hypothesized that specific myoangiogenic miRs (e.g. miR-30a) can be concentrated in Exo released from stem cells overexpressing miR30a to promote angiogenesis.
Methods and Results: (1) miR-130a-modified mesenchymal stem cells (MSCmiR-130a) were constructed using lentivirus carrying miR-130a precursor. Control MSCs were transfected with lentivirus carrying miR-scramble (MSCScr). EXO were isolated from conditioned medium of MSCmiR-130a (ExomiR-130a) and MSCScr (ExoScr). The expression of miR-130a in MSCmiR-130a and ExomiR-130a was 8.5-fold and 3.6-fold higher than their counterparts, respectively. (2) Real-time images recorded by IncuCyte Imaging System showed that EXO were quickly internalized by human umbilical vein endothelial cells (HUVECs). (3) Co-incubation of ExomiR-130a with HUVECs for 16 h strongly promoted tube-like structure formation and spheroid-based sprouting compared with those of ExoScr. In addition, the neovasculature visualized by immunofluorescence staining of CD31 showed that mobilized endothelial cells in Matrigel plug containing ExomiR-130a were significantly more than those containing ExoScr. (4) The expression of miR-130a in HUVECs treated with ExomiR-130a was 4.2 fold higher than that in HUVECs treated with ExoScr. Based on the TargetScan database, both anti-angiogenic homeobox genes, GAX and HOXA5 are the potential target of miR-130a. Real-time PCR and western blot results showed that the expressions of GAX and HOXA5 were down-regulated in HUVECs treated with ExomiR-130a compared with that treated with ExoScr. (5) Finally, HUVECs were directly transfected with miR-130a (HUVECmiR-130a) and the cumulative tube length was significantly increased in HUVECmiR-130a compared to that in HUVECs transduced with scrambled-miR (HUVECScr). The expressions of GAX and HOXA5 were significantly reduced in HUVECmiR-130a.
Conclusion: EXO derived from MSCmiR-130a were rich in miR-130a which promoted angiogenesis extensively by acting on antiangiogenic homeobox genes GAX and HOXA5. Therefore, EXO can be cleverly exploited as carriers for desired genes in therapeutic purpose.