PDGF-D contributes to neointimal hyperplasia in rat model of vessel injury

In this study, we determined the role of PDGF-D, a new member of the PDGF family, in a rat model of balloon injured artery made with a 2F catheter in Sprague-Dawley male rats. PDGF-D expression was studied in the injured and control segments of abdominal aorta. The function of PDGF-D was evaluated in rat vascular smooth muscle cells stably transfected with PDGF-D gene. We found that in normal abdominal aorta, PDGF-D was highly expressed in adventia, moderate in endothelia, and unidentified in media. Stable transfection of PDGF-D gene into vascular smooth muscle cells increased the cell migration by 2.2-fold, and the proliferation by 2.3-fold, respectively, and MMP-2 production and activity as well. These results support the fact that PDGF-D is involved in the formation of neointimal hyperplasia induced by balloon catheter injury and may serve as a target in preventing vascular restenosis after coronary angioplasty.     

siRNAs target sites selection of ezrin and the influence of RNA interference on ezrin expression and biological characters of osteosarcoma cells

Tissue kallikrein 1 cleaves kininogen substrate to produce vasoactive kinin peptides that have been implicated in inhibiting neointimal hyperplasia in rat carotid arteries after balloon injury. However, its effects on the proliferation, cell cycle and its mechanisms, for example, cyclin-dependent kinase inhibitors, p27(Kip1) and p2l(Cip1) in vascular biology are poorly understood. The objective of this study was to explore the effects of human tissue kallikrein 1 (hTK1) mediated by recombinant adenovirus (Ad-hTK1) on proliferation and cell cycle of vascular smooth muscle cells (VSMCs) derived from spontaneously hypertensive rats induced by platelet-derived growth factor-BB (PDGF-BB) in vitro. The results showed that, within a given multiplicity of infection (MOI) and time, the hTK1 gene delivery inhibited PDGF-BB-stimulating VSMCs growth in a concentration-dependent (20-100 MOI) and time-dependent (2-5 days) manner by cell counting, with a peak inhibition rate at 36.3% at 72 h (P < 0.01). In addition, hTK1 gene delivery significantly suppressed PDGF-BB-induced proliferation of VSMCs by methyl thiazolyl tetrazoliuin assay, and decreased the percentage of cells in the S phase and in DNA synthesis by flow cytometry, with a peak inhibition rate at 30.2 and 36.4%, respectively (P < 0.01). Western blot assay showed that the protein levels of p27(Kip1) and p2l(Cip1) in cells infected with Ad-hTK1 were much more abundant than those in cells only induced by PDGF-BB, with up-modulating rates at 51.8 and 58.7%, respectively (P < 0.001). We also observed that the effects of hTK1 gene delivery in inhibiting VSMCs proliferation, arresting cell cycling in G(0)/G(1) phase and up-regulating the expression of p27(Kip1) and p2l(Cip1) could be blocked by icatibant (Hoe 140), a specific bradykinin B(2) receptor antagonist. Taken together, these results demonstrated that hTK1 overexpressed by recombinant adenovirus potently inhibits VSMCs proliferation that is required for neointimal hyperplasia and restenosis, and may activate p27(Kip1) and p2l(Cip1) signaling pathways via bradykinin B(2) receptor.     

Salvia miltiorrhiza inhibits intimal hyperplasia and monocyte chemotactic protein-1 expression after balloon injury in cholesterol-fed rabbits

Antioxidants that prevent low density lipoproteins (LDL) from oxidation may inhibit atherosclerosis and post-angioplasty restenosis. Salvia miltiorrhiza (SM) has been shown to inhibit LDL oxidation and reduce atherosclerosis in cholesterol-fed rabbits. The effects of SM on neointimal hyperplasia and monocyte chemotactic protein-1 (MCP-1) expression after balloon injury were studied. Male New Zealand white rabbits were fed a 2% cholesterol diet together with daily SM (4.8 gm/kg body wt.) treatment (SM; n=10) or without SM as a control (C; n=9) for 6 weeks. Probucol-treated (0.6 gm/kg body wt.) rabbits (P; n=9) were used as a positive control group. A balloon injury of the abdominal aorta was performed at the end of the third week. Aortas were harvested at the end of 6 weeks. The plasma cholesterol levels were lowered in SM group. The neointimal hyperplasia in abdominal aortas was significantly inhibited in SM group [neointima/media area ratio: 0.63+/-0.05 (SM) versus 0.78+/-0.05 (C); P < 0.05] and in P group [0.45+/-0.02 (P) versus 0.78+/-0.05 (C); P < 0.05] when compared with C group. SM treatment significantly reduced MCP-1 mRNA and protein expression in balloon-injured abdominal aorta. These inhibitory effects on intimal response after balloon injury might be attributed to antioxidant capacity and cholesterol lowering effect of SM. SM treatment may offer some protection against post-angioplasty restenosis.     

Aging exacerbates negative remodeling and impairs endothelial regeneration after balloon injury

Many older patients, because of their high prevalence of coronary artery disease, are candidates for percutaneous coronary interventions (PCI), but the effects of vascular aging on restenosis after PCI are not yet well understood. Balloon injury to the right carotid artery was performed in adult and old rats. Vascular smooth muscle cell (VSMC) proliferation, apoptotic cell death, together with Akt induction, telomerase activity, p27kip1, and endothelial nitric oxide synthase (eNOS) expression was assessed in isolated arteries. Neointima hyperplasia and vascular remodeling along with endothelial cell regeneration were also measured after balloon injury. Arteries isolated from old rats exhibited a significant reduction of VSMC proliferation and an increase in apoptotic death after balloon injury when compared with adult rats. In the vascular wall of adult rats, balloon dilation induced Akt phosphorylation, and this was barely present in old rats. In arteries from old rats, Akt-modulated cell cycle check points like telomerase activity and p27kip1 expression were decreased and increased, respectively, compared with adults. After balloon injury, old rats showed a significant reduction of neointima formation and an increased vascular negative remodeling compared with adults. These results were coupled by a marked delay in endothelial regeneration in aged rats, partially mediated by a decreased eNOS expression and phosphorylation. Interestingly, chronic administration of L-arginine prevented negative remodeling and improved reendothelialization after balloon injury in aged animals. A decreased neointimal proliferation, an impaired endothelial regeneration, and an increase in vascular remodeling after balloon injury were observed in aged animals. The molecular mechanisms underlying these responses seem to be a reduced Akt and eNOS activity.     

Focal adhesion kinase (FAK)-dependent regulation of S-phase kinase-associated protein-2 (Skp-2) stability. A novel mechanism regulating smooth muscle cell proliferation

Smooth muscle cell (SMC) proliferation is suppressed in intact blood vessels but stimulated in atherosclerosis, restenosis after angioplasty, and vein graft disease. The cyclin-dependent kinase inhibitors, including p27(Kip1), play important roles in maintaining SMC quiescence. Levels of p27(Kip1) are dependent on attachment to and the composition of the extracellular matrix (ECM). Here we sought to elucidate mechanisms underlying the ECM-dependent regulation of p27(Kip1) and hence, SMC proliferation. Serum stimulation decreased p27(Kip1) levels in isolated SMC but not in rat aorta. The effect was post-translational and mediated by proteasomal degradation. We studied the S-phase-associated kinase protein-2 (Skp-2), an F-box protein involved in ubiquitination and proteasome-mediated degradation. Skp-2 protein is strongly induced by serum from undetectable levels in isolated SMCs but remains undetectable in aorta; Skp-2 mRNA is also lower in aorta. Overexpression of wild-type Skp-2 in SMCs decreased p27(Kip1) levels, whereas dominant negative F-box deleted mutant (DeltaF-Skp-2) Skp-2 increased p27(Kip1) levels. Furthermore, hyperphosphorylation of retinoblastoma protein and SMC proliferation were also reciprocally affected by wild-type and dominant negative Skp-2. Skp-2 expression was absolutely dependent on cell attachment to the ECM and was inhibited by laminin and type-1 fibrillar collagen but increased by fibronectin. Expression of Skp-2 protein, but not mRNA, was associated with focal adhesion kinase (FAK) activity and inhibited by overexpression of FAK-related non-kinase and a dominant negative FAK(Y397F) mutant. Furthermore, the inhibition of Skp-2 expression by dominant negative FAK was reversed by the proteasome inhibitor MG-132. Taken together, these data demonstrate that the vascular ECM controls SMC proliferation via FAK-dependent regulation of Skp-2 protein stability.     

RECK基因在兔颈动脉壁损伤后再狭窄过程中的表达

目的:通过建立动物损伤模型,分析RECK基因在兔子颈动脉球囊损伤术后的表达与动脉内膜变化和官腔狭窄的相关性。方法:兔子手术损伤侧的动脉血管设置为实验组,未进行手术操作的一侧动脉作为对照组。建立动脉模型的四个时间点7、14、21、28 d,在麻醉状态下处死模型动物。取得所需长度的损伤动脉血管及对照组动脉血管。将取得的标本进行HE病理染色,通过计算机图像计算软件观察标本动脉内膜随时间的变化;同时通过western-blot方法测定RECK蛋白表达水平、real-time PCR测量RECK基因表达量。结果:血管手术损伤后,血管内膜面积在随着术后日期的增长呈逐渐增厚变化,血管内膜与中层比值逐渐增大,同对照实验组比较,有统计学意义(P0.05)。实验组及对照组的中膜无显著增生。结论:RECK基因在组织中表达变化影响MMPs基因表达。实验论证了在动脉损伤后RECK基因参与了血管再狭窄,为血管再狭窄研究寻得新的研究方向。     

Porous balloon delivery of S-dC28 does not prevent restenosis in the porcine coronary artery model of balloon injury

Phosphorothioate (PS) oligodeoxynucleotides (ODN) inhibit vascular smooth muscle cell proliferation through antisense and G-quartet aptameric mechanisms. PS-ODN such as the cytidine homopolymers, have been demonstrated to have non-G-quartet, nonsequence-specific inhibitory effects in a rat carotid balloon injury model of neointimal proliferation. We sought to test the efficacy of S-dC28, a cytidine homopolymer lacking G-quartets, on neointimal proliferation in the porcine coronary artery model of balloon injury. A total of 23 animals (11 controls, 12 treated) were subjected to balloon injury in a coronary artery, followed by infusion of control solution or S-dC28 via porous balloon, the Scimed Dispatch Coronary Infusion Catheter. After a mean interval of 49 days, the animals were killed, and the target coronary segments were examined histologically. S-dC28 did not significantly inhibit neointimal formation. Fluorescein isothiocyanate (FITC)-labeled S-dC28 was present in the intima and media immediately after administration but was present mainly within the adventitia 3 hours after administration. S-dC28, when delivered by a Scimed Dispatch Coronary Infusion Catheter (Maple Grove, MN), did not significantly affect neointimal proliferation after balloon injury in a porcine coronary artery model.     

Heightened efficacy of nitric oxide-based therapies in type II diabetes mellitus and metabolic syndrome

Type II diabetes mellitus (DM) and metabolic syndrome are associated with accelerated restenosis following vascular interventions due to neointimal hyperplasia. The efficacy of nitric oxide (NO)-based therapies is unknown in these environments. Therefore, the aim of this study is to examine the efficacy of NO in preventing neointimal hyperplasia in animal models of type II DM and metabolic syndrome and examine possible mechanisms for differences in outcomes. Aortic vascular smooth muscle cells (VSMC) were harvested from rodent models of type II DM (Zucker diabetic fatty), metabolic syndrome (obese Zucker), and their genetic control (lean Zucker). Interestingly, NO inhibited proliferation and induced G0/G1 cell cycle arrest to the greatest extent in VSMC from rodent models of metabolic syndrome and type II DM compared with controls. This heightened efficacy was associated with increased expression of cyclin-dependent kinase inhibitor p21, but not p27. Using the rat carotid artery injury model to assess the efficacy of NO in vivo, we found that the NO donor PROLI/NO inhibited neointimal hyperplasia to the greatest extent in type II DM rodents, followed by metabolic syndrome, then controls. Increased neointimal hyperplasia correlated with increased reactive oxygen species (ROS) production, as demonstrated by dihydroethidium staining, and NO inhibited this increase most in metabolic syndrome and DM. In conclusion, NO was surprisingly a more effective inhibitor of neointimal hyperplasia following arterial injury in type II DM and metabolic syndrome vs. control. This heightened efficacy may be secondary to greater inhibition of VSMC proliferation through cell cycle arrest and regulation of ROS expression, in addition to other possible unidentified mechanisms that deserve further exploration.     

Intramuscular gene transfer of CGRP inhibits neointimal hyperplasia after balloon injury in the rat abdominal aorta

CGRP is a well-known neuropeptide that has various protective effects on cardiovascular system. Our previous studies have shown that CGRP inhibits vascular smooth muscle cell (VSMC) proliferation in vitro. The present study aimed to explore the role of the CGRP in neointimal formation after balloon injury in the rat aortic wall and the underlying mechanism. Gene transfer of CGRP was performed with the use of intramuscular electroporation in a balloon-injured rat aorta model. Apoptosis in VSMCs was determined by electrophoresis assessment of DNA fragmentation and terminal deoxynucleotide transferase-mediated dUTP nick-end labeling assay. Overexpression of the CGRP gene significantly inhibited the neointimal formation after balloon injury compared with the mock transfer, as assessed by the intima-to-media ratio 14 days after balloon injury (29.2 +/- 3.7% vs. 52.7 +/- 5.4%; n = 9-12, P < 0.05). In addition, CGRP gene expression increased the number of apoptotic cells in the neointima in vivo 14 days after balloon injury. Similarly, the addition of bioactive CGRP and the nitric oxide donor induced similar apoptosis in cultured VSMCs. The antagonist of the CGRP(1) receptor and inhibitors of cAMP-PKA and nitric oxide blocked CGRP-mediated apoptosis. Furthermore, CGRP gene transfer increased inducible nitric oxide synthase and p53 but decreased PCNA and Bcl-2 protein levels in balloon-injured rat aorta. Our data demonstrated that CGRP potently inhibited neointimal thickening in the rat aorta, at least in part through its distinct effects on apoptosis and proliferation of VSMCs both in vivo and in vitro. Therefore, delivery of the CGRP gene may have therapeutic implications in limiting vascular restenosis.     

Bone marrow-derived mesenchymal stem cells inhibit vascular smooth muscle cell proliferation and neointimal hyperplasia after arterial injury in rats

We investigated whether mesenchymal stem cell (MSC)-based treatment could inhibit neointimal hyperplasia in a rat model of carotid arterial injury and explored potential mechanisms underlying the positive effects of MSC therapy on vascular remodeling/repair. Sprague-Dawley rats underwent balloon injury to their right carotid arteries. After 2 days, we administered cultured MSCs from bone marrow of GFP-transgenic rats (0.8 × 10⁶ cells, n = 10) or vehicle (controls, n = 10) to adventitial sites of the injured arteries. As an additional control, some rats received a higher dose of MSCs by systemic infusion (3 × 10⁶ cells, tail vein; n = 4). Local vascular MSC administration significantly prevented neointimal hyperplasia (intima/media ratio) and reduced the percentage of Ki67 + proliferating cells in arterial walls by 14 days after treatment, despite little evidence of long-term MSC engraftment. Notably, systemic MSC infusion did not alter neointimal formation. By immunohistochemistry, compared with neointimal cells of controls, cells in MSC-treated arteries expressed reduced levels of embryonic myosin heavy chain and RM-4, an inflammatory cell marker. In the presence of platelet-derived growth factor (PDGF-BB), conditioned medium from MSCs increased p27 protein levels and significantly attenuated VSMC proliferation in culture. Furthermore, MSC-conditioned medium suppressed the expression of inflammatory cytokines and RM-4 in PDGF-BB-treated VSMCs. Thus, perivascular administration of MSCs may improve restenosis after vascular injury through paracrine effects that modulate VSMC inflammatory phenotype.     

MPC30-DEA70载AMO-miR-222对大鼠颈总动脉球囊损伤后血管狭窄的影响

目的:阳离子磷酸胆碱聚合物(MPC30-DEA70)为非病毒类转基因载体,可与AMO-mi R-222络合,通过导管球囊系统将MPC30-DEA70/AMO-mi R-222基因复合物导入大鼠颈内动脉球囊损伤处,观察对血管平滑肌细胞增生及血管狭窄程度的影响。方法:90只雄性SD大鼠随机分为未损伤组、多聚赖氨酸(PLL组)、MPC30-DEA70/AMO-mi R-222组、PLL/AMO-mi R-222组、PLL/MPC30-DEA70组、AMO-mi R-222组、单纯损伤组、PLL载P/A=3:1组和P/A=5:1组,每组各10只。构建大鼠颈总动脉球囊损伤模型,予血管损伤段行PLL、MPC30-DEA70/AMO-mi R-222、PLL/AMO-mi R-222、PLL/MPC30-DEA70、AMO-mi R-222、PLL载P/A=3:1和P/A=5:1复合物的转运。4周后通过光学显微镜观察HE染色血管段组织形态学改变。Western blot法检测各组血管段p57Kip2、p27Kip1蛋白的表达情况。RT-PCR法检测各组血管段mi R222扩增情况。结果:光学显微镜下,多聚赖氨酸(PLL组)、裸MPC30-DEA70/AMO-mi R-222组、PLL/AMO-mi R-222组、PLL/MPC30-DEA70组、AMO-mi R-222组、MPC30-DEA70组可见内膜显著增生,新生内膜/中膜比值无组间差异,较PLL载P/A=3:1组和P/A=5:1组有组间差异,后两组比较无组间差异,未损伤组未见新生内膜增殖。Western blot法检测显示PLL载P/A=3:1组和P/A=5:1组P57kip2、P27kip1蛋白表达含量较未损伤组降低(P0.05),较余六组增高(P0.05),组间比较无显著差异(P0.05)。RT-PCR法检测显示,mi R-222表达在未损伤组很低,PLL载P/A=3:1组和P/A=5:1组增高,余六组过表达(组间比较无显著差异)。结论:MPC30-DEA70可与AMO-mi R-222络合,有效抑制球囊损伤后血管mi R222表达,从而抑制新生内膜增生及血管狭窄。     

Exosomes from mesenchymal stem cells expressing miR‐125b inhibit neointimal hyperplasia via myosin IE

Intercellular communication between mesenchymal stem cells (MSCs) and their target cells in the perivascular environment is modulated by exosomes derived from MSCs. However, the potential role of exosome‐mediated microRNA transfer in neointimal hyperplasia remains to be investigated. To evaluate the effects of MSC‐derived exosomes (MSC‐Exo) on neointimal hyperplasia, their effects upon vascular smooth muscle cell (VSMC) growth in vitro and neointimal hyperplasia in vivo were assessed in a model of balloon‐induced vascular injury. Our results showed that MSC‐Exo were internalised by VSMCs and inhibited proliferation and migration in vitro. Further analysis revealed that miR‐125b was enriched in MSC‐Exo, and repressed the expression of myosin 1E (Myo1e) by targeting its 3? untranslated region. Additionally, MSC‐Exo and exosomally transferred miR‐125b repressed Myo1e expression and suppressed VSMC proliferation and migration and neointimal hyperplasia in vivo. In summary, our findings revealed that MSC‐Exo can transfer miR‐125b to VSMCs and inhibit VSMC proliferation and migration in vitro and neointimal hyperplasia in vivo by repressing Myo1e, indicating that miR‐125b may be a therapeutic target in the treatment of vascular diseases.     

Deep Sea Water Prevents Balloon Angioplasty-Induced Hyperplasia through MMP-2: An In Vitro and In Vivo Study

Major facts about the development of restenosis include vascular smooth muscle cells (VSMCs) proliferation and migration. A previous study showed that in vitro treatment with magnesium chloride has the potential to affect the proliferation and migration of VSMCs. Magnesium is the major element in deep sea water (DSW) and is a biologically active mineral. It is unclear whether DSW intake can prevent abnormal proliferation and migration of VSMCs as well as balloon angioplasty-induced neointimal hyperplasia. Thus, we attempted to evaluate the anti-restenotic effects of DSW and its possible molecular mechanisms. Several concentrations of DSW, based on the dietary recommendations (RDA) for magnesium, were applied to a model of balloon angioplasty in SD rats. The results showed that DSW intake markedly increased magnesium content within the vascular wall and reduced the development of neointimal hyperplasia. The immunohistochemical analysis also showed that the expression of proteins associated with cell proliferation and migration were decreased in the balloon angioplasty groups with DSW supplement. Furthermore, in vitro treatment with DSW has a dose-dependent inhibitory effect on serum-stimulated proliferation and migration of VSMCs, whose effects might be mediated by modulation of mitogen-activated protein kinase (MAPK) signaling and of the activity of matrix metalloproteinase-2 (MMP-2). Our study suggested that DSW intake can help prevent neointimal hyperplasia (or restenosis), whose effects may be partially regulated by magnesium and other minerals.     

Nitric Oxide Inhibits Vascular Smooth Muscle Cell Proliferation and Neointimal Hyperplasia by Increasing the Ubiquitination and Degradation of UbcH10

Nitric oxide (NO) limits formation of neointimal hyperplasia in animal models of arterial injury in large part by inhibiting vascular smooth muscle cell (VSMC) proliferation through cell cycle arrest. The ubiquitin-conjugating enzyme UbcH10 is responsible for ubiquitinating cell cycle proteins for proper exit from mitosis. We hypothesize that NO prevents VSMC proliferation, and hence neointimal hyperplasia, by decreasing levels of UbcH10. Western blotting and immunofluorescent staining showed that NO reduced UbcH10 levels in a concentration-dependent manner in VSMC harvested from the abdominal aortas of Sprague-Dawley rats. Treatment with NO or siRNA to UbcH10 decreased both UbcH10 levels and VSMC proliferation (P<0.001), while increasing UbcH10 levels by plasmid transfection or angiotensin II stimulation increased VSMC proliferation to 150% (P=0.008) and 212% (P=0.002) of control, respectively. Immunofluorescent staining of balloon-injured rat carotid arteries showed a ~4-fold increase in UbcH10 levels, which was profoundly decreased following treatment with NO. Western blotting of carotid artery lysates showed no UbcH10 in uninjured vessels, a substantial increase in the injury alone group, and a significant decrease in the injury+NO group (~3-fold reduction versus injury alone). Importantly, in vitro and in vivo, a marked increase in polyubiquitinated UbcH10 was observed in the NO-treated VSMC and carotid arteries, respectively, indicating that NO may be decreasing unmodified UbcH10 levels by increasing its ubiquitination. Central to our hypothesis, we report that NO decreases UbcH10 levels in VSMC in vitro and following arterial injury in vivo in association with increasing polyubiquitinated-UbcH10 levels. These changes in UbcH10 levels correlate with VSMC proliferation and neointimal hyperplasia, making UbcH10 a promising therapeutic target for inhibiting this proliferative disease.     

Egr-1的诱骗性寡脱氧核苷酸抑制大鼠颈总动脉损伤后MMP-2的表达

目的观察局部转染早期生长反应因子-1(early growth response factor-1,Egr-1)的特异诱骗寡脱氧核苷酸(decoy oligodeoxynucleotides,decoy ODNs)对球囊损伤颈总动脉后基质金属蛋白酶-2(MMP-2)蛋白表达的影响及内膜增生的情况,初步探讨Egr-1,decoy ODNs抑制球囊损伤后内膜增生的机制。方法 96只健康雄性Wistar大鼠,随机分为4组,分别为假手术组、对照组、杂码组和诱骗组,每组24只。除假手术组外均应用2F球囊导管行颈总动脉球囊损伤术,术中采用转染试剂FuGENE6介导的Egr-1decoy ODNs转染至损伤后大鼠血管中,与假手术组、对照组、杂码组相比较。术后3、7、14、21d每组处死6只动物。应用HE染色和免疫组织化学方法观察大鼠颈总动脉球囊损伤后内膜增生情况和MMP-2蛋白的表达及转染Egr-1decoy ODNs后对它们的影响。结果 (1)、内膜损伤后3d内膜增厚不明显,7d内膜开始增厚,14、21d时内膜明显增厚。(2)、在假手术组近腔面中膜可见MMP-2有少量散在阳性表达;在对照组及杂码组动脉损伤后3d,在近腔面中膜,有少量阳性表达,与假手术组相比,阳性表达指数上升。7d时在新生内膜和靠近新生内膜处中膜表达明显,14d后表达逐渐下降。(3)转染decoy ODNs治疗后,在各个时间点内膜增厚程度减轻,MMP-2蛋白表达减少,与对照组比较差异有显著性(P<0.01)。结论血管球囊损伤后,内膜7d开始增生,14d、21d增生更明显,而MMP-2在7d时表达明显,之后逐渐下降,Egr-1decoy ODNs能抑制MMP-2的表达,从而减轻血管损伤后内膜的增生。     

Long period of balloon inflation and the implantation of stents potentiate smooth muscle cell death. Possible role of chronic vascular injury in restenosis

BACKGROUND: It has been suggested that the severity of acute vascular injury immediately after percutaneous transluminal coronary angioplasty (PTCA) or stent implantation correlates with the extent of neointimal hyperplasia and restenosis. However, the influence of prolonged or chronic vessel injury on the pathogenesis of restenosis is unclear. METHODS: Rabbit iliac arteries were balloon dilated for a short (1 min) or prolonged (10 min) period of time, or were chronically dilated and received a Palmaz-Schatz stent (balloon inflation for 1 min). All arteries were overexpanded to a balloon:artery ratio of 1.2:1 as determined by angiography. The arteries were removed 30 min and 4 weeks after the angioplasty procedures. The sites of injury were evaluated by gross histology and transmission electron microscopy (TEM). Cell death of medial smooth muscle cells (SMCs) was specified by TEM images 30 min after the procedures. Computer-assisted quantification of the neointimal cross-sectional areas was performed after 4 weeks using a light microscope connected to a digital image analyser. RESULTS: The results show that prolonged balloon dilatation and stent implantation increased necrotic SMC death compared with balloon dilatation for 1 min. After 30 min, increased staining of SMC nuclei, enlarged intercellular spaces and changes in SMC shape in the media indicated cell death induced by prolonged balloon dilatation or chronic stent injury. Stent implantation markedly augmented vessel damage by persistent compression of the media, compared with a balloon dilatation for 1 or 10 min. Both prolonged balloon dilatation and stent implantation increased neointimal hyperplasia at 4 weeks compared with balloon dilatation for 1 min (0.6 3 0.2 and 1.0 3 0.2 mm(2) versus 0.2 3 0.1 mm(2), P < 0.001 versus dilatation for 1 min). CONCLUSION: Prolonged or chronic vascular expansion due to long balloon-inflation periods or the implantation of stents increases medial SMC death, which subsequently stimulates neointimal growth in this restenosis model. Chronic vascular injury may be an important stimulus for restenosis after angioplasty procedures.     

西洛他唑对大鼠颈总动脉球囊损伤后内膜增生及氧化应激的影响

目的:探讨西洛他唑对大鼠颈总动脉球囊损伤后内膜增生的抑制作用和血管壁氧化应激的影响。方法:SD大鼠24只,随机分组:假手术组、损伤组及西洛他唑治疗组。采用球囊损伤大鼠左侧颈总动脉,于术后2周处死大鼠,取损伤血管标本,进行HE染色、免疫组化染色及原位DHE染色,检测内膜增生、平滑肌细胞增殖及血管壁局部ROS水平。结果:球囊损伤2周后,血管壁内膜显著增生,西洛他唑治疗后内膜增生显著抑制,两组相比P<0.05。PCNA免疫组化染色:假手术组未见PCNA阳性细胞,损伤组PCNA阳性细胞面积百分比明显高于西洛他唑组,主要分布于新生内膜和内弹力膜区域(P<0.05)。原位DHE染色:球囊损伤后局部ROS水平显著升高,较假手术组差异显著P<0.05,西洛他唑干预后局部ROS水平显著降低(P<0.05)。结论:新型抗血小板制剂西洛他唑可显著抑制大鼠颈总动脉球囊损伤后内膜增生及局部氧化应激,抑制局部氧化应激可能是西洛他唑抑制内膜增生的机制之一。     

Cytoplasmic p27Kip1 counteracts the pro-apoptotic function of the open conformation of PTEN by retention and destabilization of PTEN outside of the nucleus

The tumor suppressor activity of p27Kip1 takes place in the cell nucleus by inhibitory binding to cyclin/CDK complexes. p27Kip1 can also be localized in the cytoplasm, where it has been proposed to have oncogenic properties. Here, we describe a novel role for cytoplasmic p27Kip1 which could account for its activity as an oncoprotein by negative regulation of the PTEN tumor suppressor. p27Kip1 physically interacted with the open conformation of PTEN, which is competent to enter the nucleus. In mammalian cells, cytoplasmic p27Kip1 retained to nuclear-targeted PTEN in the cytoplasm. This retention was exerted by the C-terminal p27Kip1 region, and was independent of cyclin/CDK-binding. The nuclear accumulation of PTEN triggered by pro-apoptotic TNFα treatment was abolished by cytoplasmic p27Kip1. Furthermore, conformationally-open PTEN displayed diminished protein stability and pro-apoptotic activity in the presence of cytoplasmic p27Kip1. Our results support a conformationally-dependent model of cytoplasmic retention and negative regulation of the activity of nuclear PTEN by oncogenic cytoplasmic p27Kip1, and suggest the existence of reciprocal mechanisms to regulate the levels of both p27Kip1 and PTEN.     

Perivascular gene transfer of dominant-negative N19RhoA attenuates neointimal formation via inhibition of TGF-β1-Smad2 signaling in rats after carotid artery balloon injury

Phenotypic differentiation of adventitial fibroblasts to myofibroblasts is an essential feature of vascular remodeling. Here, we carried out perivascular gene transfer of dominant-negative N19RhoA to investigate whether antagonism of RhoA signaling attenuates neointimal formation following rat carotid artery balloon injury and alters TGF-β1-Smad2-induced differentiation of adventitial fibroblasts to myofibroblasts. Perivascular delivery of an adenovirus coexpressing dominant-negative N19RhoA and humanized Renilla green fluorescent protein (hrGFP) (Ad-N19RhoA-hrGFP), as demonstrated by hrGFP staining, suppressed neointimal formation at 7 and 14 days post-injury. Ad-N19RhoA-hrGFP administration inhibited neointimal α-smooth muscle-actin and Calponin expression, as markers of myofibroblast differentiation and perivascular collagen deposition, at 14 days after balloon injury. Ad-N19RhoA-hrGFP administration also inhibited adventitial Smad2 phosphorylation, but did not alter local TGF-β1 and total-Smad2 expression after injury. Our results provide evidence that perivascular gene transfer of dominant-negative N19RhoA blocks TGF-β1-Smad2-induced differentiation of adventitial fibroblasts to myofibroblasts, which contributes to intimal hyperplasia after balloon injury.