Peripheral CD34+ cells and the risk of in-stent restenosis in patients with coronary heart disease.

In-stent restenosis represents the major limitation of percutaneous coronary revascularization. The underlying neointimal hyperplasia mainly consists of smooth muscle cells (SMCs), which can be derived from bone marrow cells. We hypothesized that changes in the peripheral progenitor cell counts after coronary stenting may predict the development of restenosis. We prospectively studied men with atherosclerotic coronary artery disease who had undergone successful elective stenting of solitary target lesions (n = 17). Peripheral blood samples were drawn at baseline (before stenting) and 1 day after stenting. The CD34+ cell count was determined by flow cytometry. Follow-up quantitative coronary angiography was performed after 8.1 +/- 2.6 months. Except for longer primary lesions in patients with angiographic restenosis, no significant differences in patient and lesion characteristics were seen. The rate of restenosis (75% vs 11%, p = 0.015) and the extent of diameter stenosis at follow-up (56.9 +/- 26.9% vs 26.5 +/- 16.5%, p = 0.012) were higher in patients with a postprocedural increase in CD34+ cells than in those with a decrease in CD34+ cells. Postprocedural CD34+ cell counts were increased in patients with restenosis but decreased in those without restenosis (p = 0.002). A robust correlation was seen between the change in CD34+ cells and late lumen loss (r = 0.65, p <0.005). In a multivariate regression model, the change in CD34+ cells, lesion length, and preprocedural minimal lumen diameter independently predicted for late lumen loss. In conclusion, an increase in circulating CD34+ cells after coronary stenting constitutes an independent risk factor predicting in-stent restenosis and may be suggestive of their involvement in neointimal hyperplasia.

Crucial role of the CCL2/CCR2 axis in neointimal hyperplasia after arterial injury in hyperlipidemic mice involves early monocyte recruitment and CCL2 presentation on platelets.

Monocyte chemoattractant protein-1 (also known as CC chemokine ligand 2 [CCL2]) and its receptor CC chemokine receptor 2 (CCR2) play a central role in the inflammatory response and neointimal formation after vascular injury. In the context of hyperlipidemia, this appears to involve neointimal monocyte infiltration. Hence, we investigated the function of the CCL2/CCR2 axis in early monocyte recruitment to injured arteries. Wire-induced injury of the carotid artery in apoE-/- mice caused a rapid increase of JE/CCL2 protein in the vessel wall peaking at 24 hours after injury, whereas serum JE/CCL2 was increased solely at 6 hours and blood cell-associated levels were unaltered, as demonstrated by enzyme-linked immunosorbent assay. Immunohistochemistry revealed intense staining for JE/CCL2 in smooth muscle cells (SMCs) and in association with platelets adherent to the denuded vessel wall 24 hours after injury. In vitro, exogenous or SMC-derived JE/CCL2 binds to the platelet surface and triggers monocyte arrest on adherent platelets but not on SMCs in flow assays. Accordingly, monocyte arrest in ex vivo perfused apoE-/- carotid arteries isolated 24 hours after injury was profoundly inhibited by pretreatment with a JE/CCL2 antibody. In CCR2-/-/apoE-/- mice, neointimal plaque area was reduced by 47% compared with CCR2+/+/apoE-/- mice. Moreover, CCR2 deletion markedly decreased neointimal macrophage content while expanding SMC content. Vascular JE/CCL2 expressed by SMCs and immobilized by adherent platelets after endothelial denudation is crucial for mediating early monocyte recruitment to injured arteries in hyperlipidemic mice. This mechanism may explain reduced neointimal macrophage infiltration and lesion formation in CCR2-deficient apoE-/- mice.

Stabilization of atherosclerotic plaques by blockade of macrophage migration inhibitory factor after vascular injury in apolipoprotein E-deficient mice.

BACKGROUND: Macrophage migration inhibitory factor (MIF), a cytokine that controls cell-mediated inflammatory responses, is upregulated in atherogenesis; however, its functional contribution to lesion development has not been evaluated. METHODS AND RESULTS: We studied the role of MIF on neointima lesion formation after wire-induced injury of carotid arteries in apolipoprotein E-deficient (apoE(-/-)) mice. Immunohistochemistry revealed that MIF expression was detectable in endothelial cells before injury and upregulated in smooth muscle cells (SMCs) 24 hours after endothelial denudation. Three weeks after injury, MIF was predominantly found in endothelial cells and macrophage-derived foam cells. Neutralizing MIF with a monoclonal antibody resulted in a marked reduction of neointimal macrophages and inhibited transformation of macrophages into foam cells. Conversely, the content of SMCs and of collagen in the neointima were increased, amounting to a slight but not significant reduction in neointima and media size after 3 weeks of MIF monoclonal antibody treatment. Notably, serum levels of the cytokines IL-2, IL-4, IL-6, IL-10, and tumor necrosis factor were increased in MIF monoclonal antibody-treated mice. In vitro flow assays revealed that MIF pretreatment of aortic endothelium enhanced monocyte recruitment and that the monocyte arrest induced by oxidized LDL is mediated by endothelial MIF, as shown by monoclonal antibody inhibition. CONCLUSIONS: Inhibition of MIF resulted in a shift in the cellular composition of neointimal plaques toward a stabilized phenotype with reduced macrophage/foam cell content and increased SMC content. This might be attributable to a reduction of monocyte recruitment mediated by endothelial MIF.

Crucial role of stromal cell-derived factor-1alpha in neointima formation after vascular injury in apolipoprotein E-deficient mice.

BACKGROUND: Recent evidence indicates that stromal cell-derived factor-1alpha (SDF-1alpha) is expressed in human atherosclerotic plaques, whereas high plasma levels are clinically associated with stable coronary artery disease. Herein, we investigate the involvement of SDF-1alpha in neointimal formation after vascular injury. METHODS AND RESULTS: SDF-1alpha was detected by immunohistochemistry in carotid arteries of apolipoprotein E-deficient (apoE-/-) mice at various stages of neointima formation after wire-induced injury. Double immunofluorescence revealed that SDF-1alpha staining was mostly confined to smooth muscle cells (SMCs). Furthermore, SDF-1alpha plasma levels peaked 1 day after vascular injury. Treatment of apoE-/- mice after carotid injury with a neutralizing SDF-1alpha monoclonal antibody for 3 weeks reduced neointimal lesion area by 44% (n=5, P<0.05) compared with isotype control. In SDF-1alpha antibody-treated apoE-/- mice, neointimal SMC content was decreased (21.7+/-2% versus 39.4+/-4%, n=5, P=0.005), whereas the relative content of neointimal macrophages remained unchanged. As shown by flow cytometry, carotid injury resulted in a marked expansion of circulating Sca-1+lineage- progenitor cells (PBPCs) in the peripheral blood of apoE-/- mice after 1 day, which was mediated by SDF-1alpha. Systemic injection of isolated PBPCs after vascular injury demonstrated their recruitment to neointimal lesions, where they can adopt an SMC-like phenotype. CONCLUSIONS: SDF-1alpha plays an instrumental role in neointimal formation after vascular injury in apoE-/- mice by regulating neointimal SMC content. This contribution appears to be attributable to SDF-1alpha-dependent recruitment of circulating SMC progenitor cells.