miR-150 Targets Cxcr4 to Regulate MNC Mobilization Figure 4. Lentivirus-mediated knockdown of miR-150 augments CXCR4 expression and mobilization of MNCs. (A) Structures of Lenti- miR-150 inhibitor and Lenti-Sc which contains mCherry reporter gene (red signal), (B) Titeration and transduction efficiency of lentivirus-mediated miR-150 inhibition in MNCs was evaluated by mCherry signal under microsope. (C) Lentivirus-mediated knockdown of miR-150 elevated CXCR4 protein expression in MNCs. (D) Number of BM-MNCs mobilized to PB was markedly increased in peripheral circulation of BN transplantation of mice which received MNCs lacking miR-150. doi:10.1371/journal.pone.0023114.g004 enhanced mobilization and migration of BM MNCs. In our microarray-based miR profiling data indicated that miR-29c, miR-150, and miR-494 expression in BM-MNCs was significantly decreased by 4 fold at 5 days after AMI and the major objective of this study was to determine Cxcr4 as a putative target gene of miR- 150. The interaction of SDF-1a/CXCR4 plays a crucial role in stem cell mobilization. SDF-1a expression is upregulated by ischemia resulting in the recruitment and homing of hematopoietic stem/progenitor cells expressing CXCR4 receptor to ischemic sites [20]. Indeed, intramuscular injection of the chemoattractant chemokine SDF-1a has recently been shown to increase the number of incorporated EPCs and to improve neovascularization in vivo [21]. CXCR4 is a G protein-coupled 7-transmembrane receptor and plays crucial role in embryonic development as well as in maintaining the stem cell niche. Our data showed the numbers of PB-MNCs as well as CXCR4 positive MNCs were PLoS ONE | www.plosone.org 7 October 2011 | Volume 6 | Issue 10 | e23114