OBJECTIVES The goal of this study was to investigate the effect of mobilized stem cells by granulocyte-colony stimulating factor (G-CSF) on neointimal growth, the biologic impact on vascular healing process, and the utility of paclitaxel-eluting stent (PES) in this circumstance.

BACKGROUND Questions have been raised on the safety of stem cell mobilization because of the tendency of neointimal overgrowth in a recent clinical trial, despite improvement of cardiac function.

METHODS Rabbits underwent iliac artery injury with bare-metal stent (BMS) or PES and then received rhG-CSF or placebo for 6 days. Morphometric analysis and scanning electron microscopy for re-endothelialization were performed. The characteristics of mobilized peripheral blood mononuclear cells were determined in vitro, and the fate of these cells was evaluated by re-infusion with tagging in vivo.

RESULTS At day 60 after stenting, neointimal overgrowth was observed at BMS with G-CSF. The tendency of neointimal overgrowth was substantially reduced on PES. Intriguingly, the delayed endothelial recovery on PES was restored to normal after G-CSF treatment. The G-CSF increased not only the endothelial progenitor cells, but also putative smooth muscle progenitor cells. Paclitaxel, at working concentration, preferentially inhibited proliferation of smooth muscle lineage cells rather than endothelial lineage cells.

CONCLUSIONS Our findings demonstrate that G-CSF mobilizes putative vascular progenitor cells in peripheral blood, which induces neointimal overgrowth at stented vasculature. Unique differential action of paclitaxel results in the enhanced endothelial healing with reduced neointimal growth after G-CSF treatment, suggesting that drug-eluting stents might be the optimal modality for revascularization in cytokine-based stem cell therapy.