Matrix Management
http://www.100md.com
《动脉硬化血栓血管生物学》
From AstraZeneca (C.W., W.M., E.H.-C.), R&D, Molecular Pharmacology, M?lndal; and Wallenberg Laboratory (E.H.-C.), Gothenburg University, Sahlgrenska Academy, Sweden.
Correspondence to Dr Eva Hurt-Camejo, Molecular Pharmacology, RA CV & GI, AstraZeneca, R&D, M?lndal, Sweden, S-431 83. E-mail eva.hurt-camejo@astrazeneca.com
Geometric remodeling is an important component of vascular pathologies, including restenosis and atherosclerosis. Although our understanding of the precise events involved in vascular remodeling is far from complete, it is generally accepted that local breakdown of extracellular matrix (ECM), smooth muscle cell migration, and matrix reorganization are important components.1 In this respect, particular attention has been directed toward the role of matrix metalloproteinases (MMPs), enzymes capable of remodeling the ECM. However, being able to understand the specific contribution of individual members of a proteinase family that share overlapping substrates is a significant challenge.
See page 54
MMPs are Zn-containing neutral endopeptidases. At least 23 different MMPs have been identified that, as a family, have the capacity to degrade all components of the ECM, in addition to some nonmatrix substrates.2 Within the family, several subgroups exist, based on substrate specificities or domain structures. The activity of MMPs is controlled at several distinct levels, including transcription, activation of zymogens, and interaction with specific inhibitors, the TIMPs (tissue inhibitors of MMPs). The two gelatinases MMP-2 and MMP-9 have received particular attention in analysis of vascular remodeling due to their expression by smooth muscle cells and leukocytes and ability to breakdown components of the basement membrane and collagens. At least in vitro, both enzymes have a very similar substrate profile. However, their expression in the vascular wall is differently controlled, in that a basal expression of MMP-2 can be detected within the media, whereas MMP-9 expression is only apparent after injury or inflammatory stimulation. Likewise, activation of these two MMPs can be mediated differently, and they may interact selectively with different TIMPs (MMP-2 with TIMP-2 and MMP-9 with TIMP-1).
A variety of approaches has been used to study the roles of MMPs in models of vascular remodeling, including the use of chemical inhibitors,3,4 adenoviral delivery of TIMPs,5 and more recently, through analysis of the response in knockout (KO) mice lacking specific MMPs.6–8The first two approaches are attractive because they can be carefully controlled since genetically identical mice can be used. However, most inhibitors are active against several MMPs such that the role of a particular MMP is difficult to ascertain. KO models are therefore attractive as they offer the potential to understand the specific role of individual MMPs and may reveal which would be an appropriate therapeutic target. In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology, Johnson and Galis9 have taken this approach in an attempt to address the relative role of MMP-2 and MMP-9 in a murine model of intimal hyperplasia. While both MMPs appeared to contribute to smooth muscle cell migration and neointima growth, the authors present preliminary evidence that MMP-9 may in addition have a role in collagen assembly and compaction.
Following their previous study using 129/SvEv mice,6 the authors studied the extent of intimal hyperplasia in MMP-2 and MMP-9 KO mice on a C57/BL6 background after carotid artery ligation. An absence of either MMP significantly reduced the formation of intimal hyperplasia 28 days after ligation, corresponding to fewer numbers of intimal smooth muscle cells and reduced intima thickness compared with wild-type, suggesting a significant decrease in smooth muscle cell migration. In vitro analysis of the migratory capacity of smooth muscle cells indicated that both MMP-2 and MMP-9 are important for migration through a gelatin matrix, and that neither can completely compensate for the other. However, a significant difference was observed when smooth muscle cells were assayed for their effects on collagen assembly and collagen gel compaction. Thus, whereas absence of MMP-2 had no effect, MMP-9 deficiency impaired both collagen assembly and compaction. Although the authors did not prove that wild-type cells release active MMP-9 in their assays (an important test based on the tight control of MMP-9 expression in smooth muscle cells), they were able to rescue the phenotype of MMP-9–deficient cells by adding MMP-9 to the assay. The authors also found that MMP-9 may serve as a bridge between cells and the ECM, in that MMP-9–deficient smooth muscle cells had a reduced capacity to bind to gelatin, and they conclude that this may contribute to traction during cell migration. However, this is not supported by the results with MMP-2–deficient cells, whose migration is apparently impaired to a greater extent than MMP-9–deficient cells. Of particular interest, the authors found that an interaction between MMP-9 and the hyaluronan receptor, CD44, was necessary for the role of MMP-9 in collagen assembly and compaction. A role for CD44 in the contraction of collagen gels containing hyaluronan has previously been reported,10 but the specific role of MMP-9 was not explored.
The significance of these in vitro observations remain to be thoroughly addressed in vivo. Staining with specific antibodies and picrosirius red suggested that MMP-9 deficiency results in a decreased accumulation and organization of collagen during hyperplasia, but qualitative information on the collagen network is difficult to gauge in the absence of ultrastructure analyses (for example by electron microscopy). It is interesting that, despite having a larger neointima, the lumen of the MMP-2–deficient mice appeared larger than in the MMP-9–deficient mice 28 days after ligation. This was not apparently due to outward remodeling of the artery, because EEL measurements were not significantly different. Previously, the authors observed an accumulation of collagen in the adventia of MMP-9–deficient mice after carotid artery ligation. This may contribute to the extra constriction seen in the MMP-9 KO compared with the MMP-2 KO, while the decrease in collagen compaction observed for MMP-9 KO smooth muscle cells in vitro may contribute to the reduced constriction of the lumen compared with wild-type. However, it will also be important to investigate other components of the ECM. In this respect, analysis of the organization of hyaluronan and proteoglycans would be interesting because these high molecular weight hydrophilic complexes can trap water and cause tissue swelling, a factor that could contribute to intima hyperplasia in experimental animal models.
The observations of Johnson and Galis9 begin to address the individual contribution of different MMPs to vascular remodeling and imply that there can be subtle differences in the roles of enzymes with overlapping substrate preferences. However, the chosen model, although technically demanding, produces a relatively straightforward and predictable outcome. A more significant challenge is to understand the contributions of different MMPs to a more complex vascular pathology, such as atherosclerosis where remodeling is complicated by the presence of monocyte/macrophages with the capacity to produce a range of different MMPs, lipid accumulation, and a local inflammatory response. The same authors have previously reported that monocyte/macrophage infiltration after carotid artery ligation in atherosclerotic-prone apoE KO mice can dramatically influence the remodeling process.11 Inhibition of MMP activity has been suggested as an approach to both stabilize vulnerable plaques by reducing matrix breakdown and to limit stenosis by reducing plaque growth. Recent data has addressed the influence of MMPs on plaque stability and, intriguingly, shows opposite effects of MMP-9 and MMP-12.12 Furthermore, investigations using KO or transgenic expression of MMPs or TIMPs have revealed that the contribution of matrix remodeling to lesion growth is complex.13–15 The availability of highly selective inhibitors would be a valuable tool for investigating the relative contribution of individual MMPs in lesion growth, along with the kind of work using KOs and transgenics described by Johnson and Galis.9 However, we can still expect that the task of unraveling the role of individual MMPs will be complex.
References
Galis ZS, Khatri JJ. Matrix metalloproteinases in vascular remodeling and atherogenesis: the good, the bad, and the ugly. Circ Res. 2002; 90: 251–262.
Nagase H, Woessner JF Jr. Matrix metalloproteinases. J Biol Chem. 1999; 274: 21491–21494.
Bendeck MP, Conte M, Zhang M, Nili N, Strauss BH, Farwell SM. Doxycycline modulates smooth muscle cell growth, migration, and matrix remodeling after arterial injury. Am J Pathol. 2002; 160: 1089–1095.
Prescott MF, Sawyer WK, Von Linden-Reed J, Jeune M, Chou M, Caplan SL, Jeng AY. Effect of matrix metalloproteinase inhibition on progression of atherosclerosis and aneurysm in LDL receptor-deficient mice overexpressing MMP-3, MMP-12, and MMP-13 and on restenosis in rats after balloon injury. Ann NY Acad Sci. 1999; 878: 179–190.
Dollery CM, Humphries SE, McClelland A, Latchman DS, McEwan JR. Expression of tissue inhibitor of matrix metalloproteinases 1 by use of an adenoviral vector inhibits smooth muscle cell migration and reduces neointimal hyperplasia in the rat model of vascular balloon injury. Circulation. 1999; 99: 3199–3205.
Galis ZS, Johnson C, Godin D, Magid R, Shipley JM, Senior RM, Ivan E. Targeted disruption of the matrix metalloproteinase-9 gene impairs smooth muscle cell migration and geometrical arterial remodeling. Circ Res. 2002; 91: 852–859.
Cho A, Reidy MA. Matrix metalloproteinase-9 is necessary for the regulation of smooth muscle cell replication and migration after arterial injury. Circ Res. 2002; 91: 845–851.
Kuzuya M, Kanda S, Sasaki T, Tamaya-Mori N, Cheng XW, Itoh T, Itohara S, Iguchi A. Deficiency of gelatinase a suppresses smooth muscle cell invasion and development of experimental intimal hyperplasia. Circulation. 2003; 108: 1375–1381.
Johnson C, Galis ZS. Matrix metalloproteinase-2 and -9 differentially regulate smooth muscle cell migration and cell-mediated collagen organization. Arterioscler Thromb Vasc Biol. 2004; 24: 54–60.
Travis JA, Hughes MG, Wong JM, Wagner WD, Geary RL. Hyaluronan enhances contraction of collagen by smooth muscle cells and adventitial fibroblasts: Role of CD44 and implications for constrictive remodeling.. Circ Res. 2001; 88: 77–83.
Ivan E, Khatri JJ, Johnson C, Magid R, Godin D, Nandi S, Lessner S, Galis ZS. Expansive arterial remodeling is associated with increased neointimal macrophage foam cell content: the murine model of macrophage-rich carotid artery lesions. Circulation. 2002; 105: 2686–2691.
Johnson J, George S, Newby A, Jackson C. Matrix metalloproteinases-9 and -12 have opposite effects on atherosclerotic plaque stability. Atherosclerosis. 2003; 168: 197–201.
Silence J, Lupu F, Collen D, Lijnen HR. Persistence of atherosclerotic plaque but reduced aneurysm formation in mice with stromelysin-1 (MMP-3) gene inactivation. Arterioscler Thromb Vasc Biol. 2001; 21: 1440–1445.
Lemaitre V, O’Byrne TK, Borczuk AC, Okada Y, Tall AR, D’Armiento J. ApoE knockout mice expressing human matrix metalloproteinase-1 in macrophages have less advanced atherosclerosis. J Clin Invest. 2001; 107: 1227–1234.
Silence J, Collen D, Lijnen HR. Reduced atherosclerotic plaque but enhanced aneurysm formation in mice with inactivation of the tissue inhibitor of metalloproteinase-1 (TIMP-1) gene. Circ Res. 2002; 90: 897–903.(Carl Whatling; William Mc)
Correspondence to Dr Eva Hurt-Camejo, Molecular Pharmacology, RA CV & GI, AstraZeneca, R&D, M?lndal, Sweden, S-431 83. E-mail eva.hurt-camejo@astrazeneca.com
Geometric remodeling is an important component of vascular pathologies, including restenosis and atherosclerosis. Although our understanding of the precise events involved in vascular remodeling is far from complete, it is generally accepted that local breakdown of extracellular matrix (ECM), smooth muscle cell migration, and matrix reorganization are important components.1 In this respect, particular attention has been directed toward the role of matrix metalloproteinases (MMPs), enzymes capable of remodeling the ECM. However, being able to understand the specific contribution of individual members of a proteinase family that share overlapping substrates is a significant challenge.
See page 54
MMPs are Zn-containing neutral endopeptidases. At least 23 different MMPs have been identified that, as a family, have the capacity to degrade all components of the ECM, in addition to some nonmatrix substrates.2 Within the family, several subgroups exist, based on substrate specificities or domain structures. The activity of MMPs is controlled at several distinct levels, including transcription, activation of zymogens, and interaction with specific inhibitors, the TIMPs (tissue inhibitors of MMPs). The two gelatinases MMP-2 and MMP-9 have received particular attention in analysis of vascular remodeling due to their expression by smooth muscle cells and leukocytes and ability to breakdown components of the basement membrane and collagens. At least in vitro, both enzymes have a very similar substrate profile. However, their expression in the vascular wall is differently controlled, in that a basal expression of MMP-2 can be detected within the media, whereas MMP-9 expression is only apparent after injury or inflammatory stimulation. Likewise, activation of these two MMPs can be mediated differently, and they may interact selectively with different TIMPs (MMP-2 with TIMP-2 and MMP-9 with TIMP-1).
A variety of approaches has been used to study the roles of MMPs in models of vascular remodeling, including the use of chemical inhibitors,3,4 adenoviral delivery of TIMPs,5 and more recently, through analysis of the response in knockout (KO) mice lacking specific MMPs.6–8The first two approaches are attractive because they can be carefully controlled since genetically identical mice can be used. However, most inhibitors are active against several MMPs such that the role of a particular MMP is difficult to ascertain. KO models are therefore attractive as they offer the potential to understand the specific role of individual MMPs and may reveal which would be an appropriate therapeutic target. In this issue of Arteriosclerosis, Thrombosis, and Vascular Biology, Johnson and Galis9 have taken this approach in an attempt to address the relative role of MMP-2 and MMP-9 in a murine model of intimal hyperplasia. While both MMPs appeared to contribute to smooth muscle cell migration and neointima growth, the authors present preliminary evidence that MMP-9 may in addition have a role in collagen assembly and compaction.
Following their previous study using 129/SvEv mice,6 the authors studied the extent of intimal hyperplasia in MMP-2 and MMP-9 KO mice on a C57/BL6 background after carotid artery ligation. An absence of either MMP significantly reduced the formation of intimal hyperplasia 28 days after ligation, corresponding to fewer numbers of intimal smooth muscle cells and reduced intima thickness compared with wild-type, suggesting a significant decrease in smooth muscle cell migration. In vitro analysis of the migratory capacity of smooth muscle cells indicated that both MMP-2 and MMP-9 are important for migration through a gelatin matrix, and that neither can completely compensate for the other. However, a significant difference was observed when smooth muscle cells were assayed for their effects on collagen assembly and collagen gel compaction. Thus, whereas absence of MMP-2 had no effect, MMP-9 deficiency impaired both collagen assembly and compaction. Although the authors did not prove that wild-type cells release active MMP-9 in their assays (an important test based on the tight control of MMP-9 expression in smooth muscle cells), they were able to rescue the phenotype of MMP-9–deficient cells by adding MMP-9 to the assay. The authors also found that MMP-9 may serve as a bridge between cells and the ECM, in that MMP-9–deficient smooth muscle cells had a reduced capacity to bind to gelatin, and they conclude that this may contribute to traction during cell migration. However, this is not supported by the results with MMP-2–deficient cells, whose migration is apparently impaired to a greater extent than MMP-9–deficient cells. Of particular interest, the authors found that an interaction between MMP-9 and the hyaluronan receptor, CD44, was necessary for the role of MMP-9 in collagen assembly and compaction. A role for CD44 in the contraction of collagen gels containing hyaluronan has previously been reported,10 but the specific role of MMP-9 was not explored.
The significance of these in vitro observations remain to be thoroughly addressed in vivo. Staining with specific antibodies and picrosirius red suggested that MMP-9 deficiency results in a decreased accumulation and organization of collagen during hyperplasia, but qualitative information on the collagen network is difficult to gauge in the absence of ultrastructure analyses (for example by electron microscopy). It is interesting that, despite having a larger neointima, the lumen of the MMP-2–deficient mice appeared larger than in the MMP-9–deficient mice 28 days after ligation. This was not apparently due to outward remodeling of the artery, because EEL measurements were not significantly different. Previously, the authors observed an accumulation of collagen in the adventia of MMP-9–deficient mice after carotid artery ligation. This may contribute to the extra constriction seen in the MMP-9 KO compared with the MMP-2 KO, while the decrease in collagen compaction observed for MMP-9 KO smooth muscle cells in vitro may contribute to the reduced constriction of the lumen compared with wild-type. However, it will also be important to investigate other components of the ECM. In this respect, analysis of the organization of hyaluronan and proteoglycans would be interesting because these high molecular weight hydrophilic complexes can trap water and cause tissue swelling, a factor that could contribute to intima hyperplasia in experimental animal models.
The observations of Johnson and Galis9 begin to address the individual contribution of different MMPs to vascular remodeling and imply that there can be subtle differences in the roles of enzymes with overlapping substrate preferences. However, the chosen model, although technically demanding, produces a relatively straightforward and predictable outcome. A more significant challenge is to understand the contributions of different MMPs to a more complex vascular pathology, such as atherosclerosis where remodeling is complicated by the presence of monocyte/macrophages with the capacity to produce a range of different MMPs, lipid accumulation, and a local inflammatory response. The same authors have previously reported that monocyte/macrophage infiltration after carotid artery ligation in atherosclerotic-prone apoE KO mice can dramatically influence the remodeling process.11 Inhibition of MMP activity has been suggested as an approach to both stabilize vulnerable plaques by reducing matrix breakdown and to limit stenosis by reducing plaque growth. Recent data has addressed the influence of MMPs on plaque stability and, intriguingly, shows opposite effects of MMP-9 and MMP-12.12 Furthermore, investigations using KO or transgenic expression of MMPs or TIMPs have revealed that the contribution of matrix remodeling to lesion growth is complex.13–15 The availability of highly selective inhibitors would be a valuable tool for investigating the relative contribution of individual MMPs in lesion growth, along with the kind of work using KOs and transgenics described by Johnson and Galis.9 However, we can still expect that the task of unraveling the role of individual MMPs will be complex.
References
Galis ZS, Khatri JJ. Matrix metalloproteinases in vascular remodeling and atherogenesis: the good, the bad, and the ugly. Circ Res. 2002; 90: 251–262.
Nagase H, Woessner JF Jr. Matrix metalloproteinases. J Biol Chem. 1999; 274: 21491–21494.
Bendeck MP, Conte M, Zhang M, Nili N, Strauss BH, Farwell SM. Doxycycline modulates smooth muscle cell growth, migration, and matrix remodeling after arterial injury. Am J Pathol. 2002; 160: 1089–1095.
Prescott MF, Sawyer WK, Von Linden-Reed J, Jeune M, Chou M, Caplan SL, Jeng AY. Effect of matrix metalloproteinase inhibition on progression of atherosclerosis and aneurysm in LDL receptor-deficient mice overexpressing MMP-3, MMP-12, and MMP-13 and on restenosis in rats after balloon injury. Ann NY Acad Sci. 1999; 878: 179–190.
Dollery CM, Humphries SE, McClelland A, Latchman DS, McEwan JR. Expression of tissue inhibitor of matrix metalloproteinases 1 by use of an adenoviral vector inhibits smooth muscle cell migration and reduces neointimal hyperplasia in the rat model of vascular balloon injury. Circulation. 1999; 99: 3199–3205.
Galis ZS, Johnson C, Godin D, Magid R, Shipley JM, Senior RM, Ivan E. Targeted disruption of the matrix metalloproteinase-9 gene impairs smooth muscle cell migration and geometrical arterial remodeling. Circ Res. 2002; 91: 852–859.
Cho A, Reidy MA. Matrix metalloproteinase-9 is necessary for the regulation of smooth muscle cell replication and migration after arterial injury. Circ Res. 2002; 91: 845–851.
Kuzuya M, Kanda S, Sasaki T, Tamaya-Mori N, Cheng XW, Itoh T, Itohara S, Iguchi A. Deficiency of gelatinase a suppresses smooth muscle cell invasion and development of experimental intimal hyperplasia. Circulation. 2003; 108: 1375–1381.
Johnson C, Galis ZS. Matrix metalloproteinase-2 and -9 differentially regulate smooth muscle cell migration and cell-mediated collagen organization. Arterioscler Thromb Vasc Biol. 2004; 24: 54–60.
Travis JA, Hughes MG, Wong JM, Wagner WD, Geary RL. Hyaluronan enhances contraction of collagen by smooth muscle cells and adventitial fibroblasts: Role of CD44 and implications for constrictive remodeling.. Circ Res. 2001; 88: 77–83.
Ivan E, Khatri JJ, Johnson C, Magid R, Godin D, Nandi S, Lessner S, Galis ZS. Expansive arterial remodeling is associated with increased neointimal macrophage foam cell content: the murine model of macrophage-rich carotid artery lesions. Circulation. 2002; 105: 2686–2691.
Johnson J, George S, Newby A, Jackson C. Matrix metalloproteinases-9 and -12 have opposite effects on atherosclerotic plaque stability. Atherosclerosis. 2003; 168: 197–201.
Silence J, Lupu F, Collen D, Lijnen HR. Persistence of atherosclerotic plaque but reduced aneurysm formation in mice with stromelysin-1 (MMP-3) gene inactivation. Arterioscler Thromb Vasc Biol. 2001; 21: 1440–1445.
Lemaitre V, O’Byrne TK, Borczuk AC, Okada Y, Tall AR, D’Armiento J. ApoE knockout mice expressing human matrix metalloproteinase-1 in macrophages have less advanced atherosclerosis. J Clin Invest. 2001; 107: 1227–1234.
Silence J, Collen D, Lijnen HR. Reduced atherosclerotic plaque but enhanced aneurysm formation in mice with inactivation of the tissue inhibitor of metalloproteinase-1 (TIMP-1) gene. Circ Res. 2002; 90: 897–903.(Carl Whatling; William Mc)