Targeted Deletion of CCR2 Impairs Deep Vein Thombosis Resolution in a Mouse Model

Abstract

CCR2 is required for monocyte recruitment in many inflammatory processes, as well as conferring Th1 lymphokine responses. Deep vein thrombosis (DVT) resolution represents a specific inflammatory response whereby the thrombus must be dissolved for restoration of blood flow. Using a stasis model of DVT in the mouse, we investigated the role of CCR2 on DVT resolution. Genetic deletion of CCR2 (CCR2−/−) was associated with larger thrombi at early and later time points, increased thrombus collagen, fewer thrombus monocytes (F4/80), and significantly impaired neovascularization. IL-2 and IFN-γ were significantly reduced in early CCR2−/− thrombi, whereas MCP-1 was significantly increased, and Th2 lymphokines were unaffected. Supplementation of CCR2−/− mice with IFN-γ normalized early thrombus resolution without increasing monocyte influx. Neither Ab depletion of IFN-γ nor genetic deletion of IFN-γ impaired early DVT resolution. Early fibrinolysis was not impaired in CCR2−/− mice, but a significant reduction in both matrix metalloproteinase (MMP)-2 and MMP-9 activity was observed. However, only MMP-9 activity was restored with administration of IFN-γ. We conclude that an early CCR2-dependent Th1 lymphokine response predominates in normal DVT resolution, mediates this in part by MMP-9 activation, but is not solely dependent on IFN-γ.

Induction of Heme Oxygenase-1 is a Beneficial Response in a Murine Model of Venous Thrombosis

“…42 In addition to neutrophils, monocytes are also critically involved in promoting clot resolution because mice lacking CCR2 (the receptor for MCP-1 that is the dominant chemoattractant for monocytes) have markedly impaired resolution of stasis-induced thrombosis. 43 Thus, on the basis of these studies, manipulating the inflammatory milieu may exert dual and contrasting effects on clot resolution.…”

“…42, 43 We thus examined expression of MMP-9 as a possible basis for impaired clot resolution in HO-1 Ϫ/Ϫ mice. However, in our studies, the impairment in clot resolution in HO-1 Ϫ/Ϫ mice was associated with a striking induction of MMP-9.…”

Absence of IFN-γ accelerates thrombus resolution through enhanced MMP-9 and VEGF expression in mice

“…MMP-2 and MMP-9 have crucial roles in collagenolysis during thrombus resolution (18). Thus, we examined the intrathrombotic gene expression and the enzymatic activity of MMP-2 and MMP-9.…”

“…The potential contribution of intrathrombotic leukocytes to the resolution of venous thrombi (12)(13)(14)(15)(16)(17)(18) prompted us to investigate the effects of IFN-γ deficiency on intrathrombotic leukocyte recruitment. Myeloperoxidase (MPO)-positive neutrophils infiltrated thrombi in WT and Ifng -/-mice to similar extents, reaching a maximal level at 1 day after the IVC ligation and decreasing gradually thereafter ( Figure 3, A and C).…”

“…Indeed, TNF-α and IL-1β can potently activate endothelial cells, increase the expression of adhesion molecules by endothelial cells, and promote thrombosis (11)(12)(13)(14)(15). Moreover, TNF-α and IL-1β can induce the expression of chemokines, which can activate leukocytes to accelerate thrombus resolution and intrathrombotic neovascularization (16)(17)(18).…”