Abstract 223: Brain-derived Neurotrophic Factor Promotes Regenerative Functions of Human Endothelial Progenitor Cells - Roles of miRNAs

Abstract

Our previous study has demonstrated that brain-derived neurotrophic factor (BDNF) enhances anti-oxidant capacity of endothelial progenitor cells (EPCs). Since BDNF is produced in cerebrovascular endothelial cells, and functions as a vasoprotective molecule, we hypothesized that BDNF might enhance regenerative capacity of EPCs. Early EPCs (circulating angiogenic cells) were derived from healthy male subjects (48±1.5 years old, n=10). EPCs were treated with BDNF 100 ng/ml for 7 hours, and miRNA transcriptome was examined using Affymetrix miRNA array (version 3.0). BDNF significantly changed 31 miRNAs (n=4, P<0.05, fold-change cut off=1.5). Notably, miR-181c level was increased by 1.9 fold (P<0.05) after BDNF treatment. Since miR-181c is known to down-regulate TNF-α expression, BDNF may protect EPCs by promoting anti-inflammatory phenotype. We also found that BDNF decreased miR-433 level by 1.6 fold (P<0.05). We further evaluated miR-433 function in human early EPCs. Knock-down of miR-433 in EPCs using siRNA significantly increased expression of guanylate binding protein 2 (GBP2) (n=6, P<0.05), an established direct target for miR-433. In contrast, treatment with miR-433 mimic significantly reduced GBP2 protein expression in EPCs (n=4, P<0.05). Since GBP2 has been shown to play an important role in the growth and colony formation of hematopoietic progenitors, BDNF/miR-433/GBP2 signaling may enhance angiogenic capacity of EPCs. In addition, neither miR-433-siRNA nor miR433 mimic significantly changed protein expressions of other targets such as growth factor receptor-binding protein2, cAMP response element-binding protein-1, cyclin-dependent kinase 6, and γ glutamyl cysteine synthetase (n=4-6, P>0.05). In summary, changes in miRNA transcriptome induced by treatment with BDNF may promote anti-inflammatory and angiogenic phenotype of EPCs. These effects of BDNF may have important implications for therapeutic enhancement of regenerative capacity of EPCs.