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Tissue factor (TF) is the primary initiator of the coagulation cascade and is thought to play a key role in the generation of arterial thrombosis. Recent studies have suggested that TF mediates inflammatory processes in the arterial wall and may be an important regulator of intimal hyperplasia. We have employed genetically engineered mice (mTF(-/-) /hTF(+)) with markedly diminished TF activity ( approximately 1% normal levels) o examine the role of TF in mediating the response to arterial injury. mTF(-/-)/hTF(+) displayed a marked reduction in intimal hyperplasia (46% decrease in intimal area, 60% decrease in intimal/medial ratio) in response to femoral artery injury when compared to wild type controls. The decreased intimal hyperplasia seen in low TF mice was noted in a model of vascular injury not associated with significant thrombosis, suggesting that it may be mediated by non-procoagulant properties of TF. Smooth muscle cells from mTF(-/-)/hTF(+) mice grew normally in response to serum, but exhibited a marked defect in cell migration in a modified Boyden chamber assay. In contrast, there was no difference in platelet derived growth factor- induced migration, suggesting that the effect of TF on smooth muscle cell migration is agonist dependent. These data suggest that TF may mediate intimal hyperplasia by regulating smooth muscle cell migration.

Background: Transplant arteriopathy is the leading cause of long term morbidity and mortality following heart transplantation. Animal models have demonstrated that monocyte chemoattractant protein (MCP)-1 is induced early after transplant in cardiac and aortic allografts. We have previously reported that deficiency of MCP-1 or its receptor, CC chemokine receptor 2 (CCR2), is associated with a reduction in intimal proliferation in a mouse femoral artery injury model. Using knockout mice, we have now examined the role of MCP-1 and CCR2 in the development of the intimal proliferation of transplant arteriopathy. Methods: C57Bl/6 CCR2 and MCP-1 wild-type and knockout mice were used in the studies and aortic transplants were performed between Balb/c mice and C57Bl/6 mice. Aortas from recipient animals were harvested 8 weeks after transplant. Results: Unlike arterial injury, in an aortic transplant model inhibition of MCP-1/CCR2 signaling did not result in reduced intimal proliferation. Conclusions: Despite a pathology that appears similar, the inflammatory mediators that regulate transplant arteriopathy differ from those regulating intimal proliferation secondary to wire injury. Our results suggest that targeting MCP-1/CCR2 signaling is not sufficient to block transplant arteriopathy across a complete MHC-mismatch barrier. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]