Priming with angiopoietin-1 augments the vasculogenic potential of the peripheral blood stem cells mobilized with granulocyte colony-stimulating factor through a novel Tie2/Ets-1 pathway

BACKGROUND

The low engraftment rate of stem/progenitor cells infused via the intracoronary route to the ischemic myocardium is one of the most important factors limiting the efficacy of cell therapy. We investigated the concept of priming peripheral blood stem cells enriched by granulocyte colony-stimulating factor mobilization and apheresis ((mob)PBSCs) with angiopoietin-1 (Ang1), to enhance the engraftment into the ischemic tissue and neovasculogenic potential.

METHODS AND RESULTS

The expression of Tie2, the Ang1 receptor, was significantly higher in (mob)PBSCs than naïve peripheral blood mononuclear cells (19.2+/-3.0% versus 1.2+/-0.8% versus 1.2+/-0.2%; P<0.001 for (mob)PBSCs from acute myocardial infarction (AMI) patients with granulocyte colony-stimulating factor treatment for 3 days versus peripheral blood mononuclear cells from AMI patients versus peripheral blood mononuclear cells from stable angina patients). After 4 hours of cartilage oligomeric matrix protein (COMP)-Ang1 stimulation, (mob)PBSCs committed to the endothelial lineage with the induction of CD31 and VE-cadherin expression, mediated by Tie2/Ets-1 pathway. Priming of (mob)PBSCs with COMP-Ang1 induced the expression of alpha4beta1 and alpha5beta1 integrins, which are also Ets-1 downstream molecules, leading to enhanced adhesion to endothelial cells or fibronectin. In a rabbit ear ischemia/reperfusion model, priming of (mob)PBSCs with COMP-Ang1 improved first-pass engraftment to the distal vascular bed after intraarterial delivery. In a murine ischemic hind-limb model, intravascular delivery of primed (mob)PBSCs enhanced both engraftment and neovascularization.

CONCLUSIONS

The short-term priming with COMP-Ang1 may be a feasible and promising option to activate (mob)PBSCs by enhancing differentiation and adhesiveness and to improve the efficacy of cell therapy for ischemic diseases.

Sulfasalazine induces haem oxygenase-1 via ROS-dependent Nrf2 signalling, leading to control of neointimal hyperplasia

AIMS

Inflammation, and the subsequent proliferative activity of vascular smooth muscle cells (VSMCs), is one of the major pathophysiological mechanisms associated with neointimal hyperplasia following vascular injury. Although sulfasalazine (SSZ) has been used as an anti-inflammatory and immune-modulatory agent in various inflammatory diseases, its primary targets and therapeutic effects on vascular disease have not yet been determined. We investigated whether SSZ could suppress VSMC growth and prevent neointimal hyperplasia.

METHODS AND RESULTS

SSZ was found to have pro-apoptotic and anti-proliferative activity in cultured VSMCs. Unexpectedly, these effects were not mediated by nuclear factor kappa B (NF-kappaB) inhibition, which has been suggested to be the anti-inflammatory mechanism associated with the effects of SSZ. Instead, cell-cycle arrest of the VSMCs was observed, which was mediated by induction of haem oxygenase-1 (HO-1) followed by an increased expression of p21(waf1/Cip1). The underlying mechanism for SSZ-induced HO-1 expression was by reactive oxygen species (ROS)-dependent nuclear translocation and activation of nuclear factor erythroid-2-related factor 2 (Nrf2). In a rat carotid artery balloon injury model, administration of SSZ significantly suppressed neointimal growth. In a series of reverse experiments, inhibition of HO-1 by shRNA, ROS by N-acetylcysteine (NAC) or Nrf2 by dominant-negative Nrf2 abrogated the beneficial effects of SSZ.

CONCLUSION

Our data demonstrate that SSZ inhibits VSMC proliferation in vitro and in vivo through a novel signalling pathway and may be a promising therapeutic option for the treatment of proliferative vascular disease.