An Essential Role for gp130 in Neointima Formation Following Arterial Injury

SummaryPlatelet degranulation at the site of vascular injury prevents bleeding and may affect the chronic vascular wound healing response. Transforming Growth Factor (TGF)-β1 is a major component of platelet α-granules known to accumulating in thrombi. It was our aim to determine the role of TGFβ1 released from activated platelets for neointima formation following arterial injury and thrombosis. Mice with platelet-specific deletion of TGFβ1 (Plt.TGFβ-KO) underwent carotid artery injury. Immunoassays confirmed the absence of active TGFβ1 in platelet releasates and plasma of Plt.TGFβ-KO mice. Whole blood analyses revealed similar haematological parameters, and tail cut assays excluded major bleeding defects. Platelet aggregation and the acute thrombotic response to injury in vivo did not differ between Plt.TGFβ-KO and Plt.TGFβ-WT mice. Morphometric analysis revealed that absence of TGFβ1 in platelets resulted in a significant reduction of neointima formation with lower neointima area, intima-to-media ratio, and lumen stenosis. On the other hand, the media area was enlarged in mice lacking TGFβ1 in platelets and contained increased amounts of proteases involved in latent TGFβ activation, including MMP2, MMP9 and thrombin. Significantly increased numbers of proliferating cells and cells expressing the mesenchymal markers platelet-derived growth factor receptor-β or fibroblast-specific protein-1, and the macrophage antigen F4/80, were observed in the media of Plt.TGFβ-KO mice, whereas the medial smooth muscle-actin-immuno-positive area and collagen content did not differ between genotypes. Our findings support an essential role for platelet-derived TGFβ1 for the vascular remodelling response to arterial injury, apparently independent from the role of platelets in thrombosis or haemostasis.Supplementary Material to this article is available online at www.thrombosis-online.com.

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C5a Receptor Targeting in Neointima Formation After Arterial Injury in Atherosclerosis-Prone Mice

Circulation ◽

10.1161/circulationaha.110.954370 ◽

2010 ◽

Vol 122 (10) ◽

pp. 1026-1036 ◽

Cited By ~ 42

Author(s):

Erdenechimeg Shagdarsuren ◽

Kiril Bidzhekov ◽

Sebastian F. Mause ◽

Sakine Simsekyilmaz ◽

Thomas Polakowski ◽

...

Keyword(s):

Arterial Injury ◽

Neointima Formation ◽

C5a Receptor ◽

Receptor Targeting

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Abstract 1172: Neointima Formation is Dependent on p38α Mitogen-Activated Protein Kinase

Circulation ◽

10.1161/circ.116.suppl_16.ii_237 ◽

2007 ◽

Vol 116 (suppl_16) ◽

Author(s):

Brandon M Proctor ◽

Anthony J Muslin

Keyword(s):

P38 Mapk ◽

Carotid Arteries ◽

Thymidine Incorporation ◽

Fold Increase ◽

Arterial Injury ◽

Mitogen Activated Protein Kinase ◽

Neointima Formation ◽

Mapk Activity ◽

Mitogen Activated Protein ◽

P38α Mapk

Neointima formation frequently occurs after arterial injury and is responsible for substantial human morbidity. We previously demonstrated that the intracellular linker protein Grb2 is required for neointima formation, and that Grb2 regulates p38α mitogen-activated protein kinase (MAPK) activation in vascular smooth muscle cells (SMCs). In this work, the role of p38α MAPK in neointima formation was examined. In vitro experiments showed that pharmacological inhibition of p38 MAPK activity in cultured SMCs blocked platelet-derived growth factor (PDGF)-stimulated DNA replication and cell proliferation. Specifically, in control SMCs, overnight stimulation with PDGF induced an 11.8-fold increase in thymidine incorporation and a 1.9 fold increase in cell number. However, inhibition of p38 MAPK activity reduced PDGF-induced thymidine incorporation to 2.8-fold (P = 0.0006) and completely blocked PDGF-stimulated cell proliferation (P = 0.0001). Also, p38 MAPK activity was required for PDGF-induced inactivation of the retinoblastoma tumor suppressor protein, Rb, and induction of mini-chromosome maintenance protein-6 (MCM6), a fundamental regulator of DNA replication. Next, compound transgenic mice were generated with doxycycline (Dox)-inducible, SMC-specific expression of a dominant-negative form of p38α MAPK (SMC-DN-p38α ). Dox induced robust expression of DN-p38α mRNA and protein in the aorta and carotid arteries of compound transgenic mice, and inactivation of native, arterial p38 MAPK. SMC-DN-p38α and single transgenic, control mice were subjected to carotid injury by use of an epoxy resin-beaded probe. After 21 days, control mice developed robust neointima formation that frequently resulted in an occlusive lesion with a mean neointima/media ratio of 2.62 (N = 8). In contrast, SMC-DN-p38α mice were resistant to the development of neointima. Specifically, neointima/media ratio was reduced to 0.63 for SMC-DN-p38α mice (N = 12; P = 0.045). In addition, compared to control mice, injured carotid arteries of SMC-DN-p38α mice showed defective p38 MAPK activation in SMCs of the tunica media. Our results demonstrate that vascular SMC p38α MAPK is required for neointima formation after arterial injury.

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Abstract 160: Tuberosis Sclerosis Complex 1 Mediated Neointima Formation and Arterial Thrombosis Following Vascular Injury

Circulation Research ◽

10.1161/res.115.suppl_1.160 ◽

2014 ◽

Vol 115 (suppl_1) ◽

Author(s):

Eo Jin Kim ◽

Yong-Joo Ahn ◽

Maya Hwewon Kim ◽

Hyung-Hwan Kim

Keyword(s):

Smooth Muscle ◽

Carotid Artery ◽

Vascular Injury ◽

Knockout Mice ◽

Arterial Thrombosis ◽

Immunoblot Analysis ◽

Arterial Injury ◽

Conditional Knockout ◽

Neointima Formation

Objectives: Vascular injury and thrombosis are main leading causes of cardiovascular diseases. Tuberous sclerosis complex (TSC) is a genetic disorder caused by heterozygous mutations in either of two genes, TSC1 and TSC2. Although role of TSCs has been implicated in cardiovascular diseases, the tissue- and isoform-specific roles of TSCs in the vascular response to injury are not known. Methods and Results: To determine the role of TSC1 in arterial injury and thrombosis, we generated vascular smooth muscle cell-specific TSC1 conditional knockout mice (TSC1SM22-/-) by crossing vascular smooth muscle cell-specific Cre (SM22Cre) mice with TSC1flox/flox mice and performed carotid artery ligation in haploinsufficient TSC1 conditional knockout mice (TSC1SM22+/-) compared with that of WT or haploinsufficient TSC2 knockout mice (TSC2+/-). Acute carotid artery occlusion was investigated by 5% ferric chloride injury. Arterial thrombosis and neointima formation were measured at 14 days after arterial ligation. Expression of proteins was observed by immunoblot analysis. The neointima formation was significantly increased in TSC1SM22+/- mice (intimal thickness/medial thickness ratio; 1.14 ± 0.14, p<0.001) compared with that of WT mice (0.13 ± 0.03). Two weeks after arterial injury, arterial thrombus area was increased in TSC1SM22+/- mice (thrombus area/luminal area ratio; 72.1 ± 4.4, p<0.001) compared with that of WT mice (0.1 ± 0.0) but there are no significant effect in acute arterial thrombosis induced by ferric chloride. Loss of TSC1 and hyper-activation of mammalian target of rapamycin complex 1 including mTOR and S6 proteins were observed by immunoblot analysis of carotid artery tissue lysates of TSC1SM22+/- mice compared with that of WT. Conclusion: These findings suggest that regulation of TSC1 and mTOR might be useful for therapeutic intervention in vascular injury and thrombosis.

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