A Differential Expression Proteomic Study on Hypoxic Preconditioning DPC-Derived Exosomes

Objectives: Our previous study revealed that dental pulp cells derived exosomes (DPC-Exos) stimulate human umbilical vein endothelial cells angiogenesis. This study aimed to examine the proteomic of hypoxic preconditioning dental pulp cell-derived exosomes (hypoxic DPC-Exos) and the role of proteins associated with angiogenesis, thus study the angiogenesis mechanism by DPCs and the underlying mechanism of the angiogenic effect of DPC-Exos.
Methods: Isolating the exosomes derived from dental pulp cells (Control and hypoxic) by ultracentrifugation. Exosomes were subjected to iTRAQ-based comparative proteomics analysis. Data analysis and bioinformatics analyses were applied to identify proteins that are significant differentially expressed.
Results: 7114 peptides and 1792 proteins were identified from the hypoxic DPC-Exos samples with the 1% FDR. When referring to cellular component, the proteins were most enriched in the categories cell, and molecular functions analysis revealed that these proteins were most responsible for catalytic activity and binding acitivity. The result of biological process analysis indicated that these proteins were most responsible for cellular process and single-organism process. Proteins with average ratio of more than 1.2 folds and Q-value less than 0.05 were determined to be differentially expressed. Compared with control group, 39 proteins were up-regulated and 40 proteins were down-regulated in hypoxic DPC-Exos. The majority of biological processs that differentially expressed proteins involved are endothelial cell proliferation, regulation of focal adhesion assembly, blood vessel morphogenesis, angiogenesis and regulation of fibroblast growth factor receptor signaling pathway. The result of protein-protein interaction (PPI) networks revealed that MMP-2， SDC4 and DCN proteins located in the center with higher degrees in the network.
Conclusions: Through proteomics analysis, we characterized the differential expressed proteins of hypoxic DPC-Exos. These results provide a compressive reference to understand and further study the underlying mechanism of the angiogenic effect of DPC-Exos and supplement the existing angiogenesis mechanism by DPCs.