Multifaceted role of plasminogen activator inhibitor-1 in regulating early remodeling of vein bypass grafts

PAI-1 Regulates the Cytoskeleton and Intrinsic Stiffness of Vascular Smooth Muscle Cells

BACKGROUND

Plasma concentration of PAI-1 (plasminogen activator inhibitor-1) correlates with arterial stiffness. Vascular smooth muscle cells (SMCs) express PAI-1, and the intrinsic stiffness of SMCs is a major determinant of total arterial stiffness. We hypothesized that PAI-1 promotes SMC stiffness by regulating the cytoskeleton and that pharmacological inhibition of PAI-1 decreases SMC and aortic stiffness.

METHODS

PAI-039, a specific inhibitor of PAI-1, and small interfering RNA were used to inhibit PAI-1 expression in cultured human SMCs. Effects of PAI-1 inhibition on SMC stiffness, F-actin (filamentous actin) content, and cytoskeleton-modulating enzymes were assessed. WT (wild-type) and PAI-1-deficient murine SMCs were used to determine PAI-039 specificity. RNA sequencing was performed to determine the effects of PAI-039 on SMC gene expression. In vivo effects of PAI-039 were assessed by aortic pulse wave velocity.

RESULTS

PAI-039 significantly reduced intrinsic stiffness of human SMCs, which was accompanied by a significant decrease in cytoplasmic F-actin content. PAI-1 gene knockdown also decreased cytoplasmic F-actin. PAI-1 inhibition significantly increased the activity of cofilin, an F-actin depolymerase, in WT murine SMCs, but not in PAI-1-deficient SMCs. RNA-sequencing analysis suggested that PAI-039 upregulates AMPK (AMP-activated protein kinase) signaling in SMCs, which was confirmed by Western blotting. Inhibition of AMPK prevented activation of cofilin by PAI-039. In mice, PAI-039 significantly decreased aortic stiffness and tunica media F-actin content without altering the elastin or collagen content.

CONCLUSIONS

PAI-039 decreases intrinsic SMC stiffness and cytoplasmic stress fiber content. These effects are mediated by AMPK-dependent activation of cofilin. PAI-039 also decreases aortic stiffness in vivo. These findings suggest that PAI-1 is an important regulator of the SMC cytoskeleton and that pharmacological inhibition of PAI-1 has the potential to prevent and treat cardiovascular diseases involving arterial stiffening.

First trimester placental mesenchymal stem cells improve cardiac function of rat after myocardial infarction via enhanced neovascularization

Acute myocardial infarction (AMI) is the most critical heart disease. Mesenchymal stem cells (MSCs) have been widely used as a therapy for AMI for several years. The human placenta has emerged as a valuable source of transplantable cells of mesenchymal origin that can be used for multiple cytotherapeutic purposes. However, the different abilities of first trimester placental chorion mesenchymal stem cells (FCMSCs) and third trimester placental chorion mesenchymal stem cells (TCMSCs) have not yet been explored. In this study, we aimed to compare the effectiveness of FCMSCs and TCMSCs on the treatment of AMI. FCMSCs and TCMSCs were isolated and characterized, and then they were subjected to in vitro endothelial cell (EC) differentiation induction and tube formation to evaluate angiogenic ability. Moreover, the in vivo effects of FCMSCs and TCMSCs on cardiac improvement were also evaluated in a rat MI model. Both FCSMCs and TCMSCs expressed a series of MSCs surface markers. After differentiation induction, FCMSCs-derived EC (FCMSCs-EC) exhibited morphology that was more similar to that of ECs and had higher CD31 and vWF levels than TCMSCs-EC. Furthermore, tube formation could be achieved by FCMSCs-EC that was significantly better than that of TCMSCs-EC. Especially, FCMSCs-EC expressed higher levels of pro-angiogenesis genes, PDGFD, VEGFA, and TNC, and lower levels of anti-angiogenesis genes, SPRY1 and ANGPTL1. In addition, cardiac improvement, indicated by left ventricular end-diastolic diameter (LVEDd), left ventricular end-systolic diameter (LVEDs), left ventricular ejection fraction (LVEF) and left ventricular shortening fraction (LVSF), could be observed following treatment with FCMSCs, and it was superior to that of TCMSCs and Bone marrow MSCs (BMSCs). FCMSCs exhibited a superior ability to generate EC differentiation, as evidenced by in vitro morphology, angiogenic potential and in vivo cardiac function improvement; further, increased levels of expression of pro-angiogenesis genes may be the mechanism by which this effect occurred.

SENP3 regulates high glucose-induced endothelial dysfunction via ROS dependent signaling

BACKGROUND

The current study aimed to explore the role of SENP3 in endothelial cell dysfunction in a high-glucose setting.

METHODS

The gene and protein expressions of SENP3 in high-glucose cultured HAECs were examined using quantitative PCR and western blotting. The effects of SENP3 on HAEC viability, apoptosis, migration, and endothelial-monocyte adhesion were evaluated in vitro by knockdown. Moreover, a mouse streptozotocin-induced type I diabetes model was established for SENP3 expression assessment. In addition, the effects of SENP3 on ROS-related signaling pathways were investigated in high-glucose cultured HAECs.

RESULTS

Significantly increased levels of SENP3 mRNA and protein were found in high-glucose cultured HAECs in a time-dependent manner. SENP3 knockdown reversed high glucose-induced HAEC viability, apoptosis, and migration reduction. SENP3 knockdown attenuated the high glucose-induced intercellular adhesion of THP-1 monocytic cells and HAECs via downregulation of ICAM-1 and VCAM-1 expression. Increased levels of SENP3, ICAM-1, and VCAM-1 expression were observed in the aorta tissue of mice with type I diabetes. Downregulation of SENP3 expression was observed in HAECs cultured with high glucose levels using the free radical scavenger N-acetyl-L-cysteine or NOX4 siRNA.

CONCLUSIONS

SENP3 was involved in high glucose-induced endothelial dysfunction, and ROS-dependent signaling served as the mechanism.

Drug Targeting of Plasminogen Activator Inhibitor-1 Inhibits Metabolic Dysfunction and Atherosclerosis in a Murine Model of Metabolic Syndrome

OBJECTIVE

Enhanced expression of PAI-1 (plasminogen activator inhibitor-1) has been implicated in atherosclerosis formation in humans with obesity and metabolic syndrome. However, little is known about the effects of pharmacological targeting of PAI-1 on atherogenesis. This study examined the effects of pharmacological PAI-1 inhibition on atherosclerosis formation in a murine model of obesity and metabolic syndrome. Approach and Results: LDL receptor-deficient (ldlr-/-) mice were fed a Western diet high in cholesterol, fat, and sucrose to induce obesity, metabolic dysfunction, and atherosclerosis. Western diet triggered significant upregulation of PAI-1 expression compared with normal diet controls. Addition of a pharmacological PAI-1 inhibitor (either PAI-039 or MDI-2268) to Western diet significantly inhibited obesity and atherosclerosis formation for up to 24 weeks without attenuating food consumption. Pharmacological PAI-1 inhibition significantly decreased macrophage accumulation and cell senescence in atherosclerotic plaques. Recombinant PAI-1 stimulated smooth muscle cell senescence, whereas a PAI-1 mutant defective in LRP1 (LDL receptor-related protein 1) binding did not. The prosenescent effect of PAI-1 was blocked by PAI-039 and R2629, a specific anti-LRP1 antibody. PAI-039 significantly decreased visceral adipose tissue inflammation, hyperglycemia, and hepatic triglyceride content without altering plasma lipid profiles.

CONCLUSIONS

Pharmacological targeting of PAI-1 inhibits atherosclerosis in mice with obesity and metabolic syndrome, while inhibiting macrophage accumulation and cell senescence in atherosclerotic plaques, as well as obesity-associated metabolic dysfunction. PAI-1 induces senescence of smooth muscle cells in an LRP1-dependent manner. These results help to define the role of PAI-1 in atherosclerosis formation and suggest a new plasma-lipid-independent strategy for inhibiting atherogenesis.

S100B regulates inflammatory response during osteoarthritis via fibroblast growth factor receptor 1 signaling

The present study aimed to investigate the role of S100B in the inflammation process during osteoarthritis (OA). OA cartilage samples were collected for S100B expression analysis. S100B expression levels were significantly increased in patients with OA compared with the Controls (1.28±0.66 vs. 0.42±0.31; P=0.01) and were determined to be correlated with TNF-α (r=0.42; P=0.04) and IL-1β (r=0.73; P=0.001) expression levels. Orthopedic casting tape was used to immobilize the right knee at 180° extension of adult female New Zealand white rabbits for 4 weeks to establish an OA model. Cartilage specimens from the medial femoral condyle of these rabbits were used for histological confirmation and immunohistochemical analyses, whereas synovial fluid was used in ELISA assays for tumor necrosis factor (TNF)-α and interleukin (IL)-1β expression levels. Human synovial fibroblasts from the knee synovial tissues of normal patients with traumatic injury were transfected with S100B overexpression and knockdown plasmids and subjected to lipopolysaccharide (LPS) stimulation; subsequently, TNF-α and IL-1β expression levels in conditioned medium were determined by ELISA; S100B overexpression and knockdown significantly increased and decreased the TNF-α and IL-1β expression levels, respectively. Increased TNF-α (573.3±15.4 vs. 102.6±8.7 pg) and IL-1β (378.6±7.2 vs. 170.1±5.8 pg) expression levels were detected in OA model rabbits compared with the Control rabbits. Additionally, S100B, fibroblast growth factor (FGF)-1 and FGF receptor (FGFR)-1 mRNA and protein expression levels were increased in OA model rabbits compared with the Control group. FGFR1 knockdown significantly decreased TNF-α and IL-1β expression levels in LPS-stimulated S100B-overexpressing human synovial fibroblasts. S100B is involved in FGFR1 signaling-mediated inflammatory response during OA, which may be considered as a potential therapeutic target.

TRAF6 mediates high glucose-induced endothelial dysfunction

To investigate the role of tumor necrosis factor-associated factor 6 (TRAF6) in high glucose-induced endothelial cell dysfunction. Human aortic endothelial cells (HAECs) were cultured in high glucose medium, and TRAF6 expression was assayed by quantitative real-time Polymerase Chain Reaction (PCR) and western blotting. The effect of TRAF6 on in vitro endothelial cell viability, apoptosis, migration, and endothelial-monocyte adhesion was investigated by gene knockdown. The expression of TRAF6 and related adhesion molecules was assayed in a mouse streptozotocin-induced type I diabetes model. The signaling pathways associated with TRAF6 effects on endothelial cells were investigated in high glucose HAEC cultures. Culture of HAECs in high glucose medium significantly increased TRAF6 mRNA and protein expression in a time dependent manner. High glucose markedly reduced HAEC viability, apoptosis, and migration, and these effects was significantly reversed by TRAF6 knockdown. High glucose significantly increased intercellular adhesion of THP-1 monocytic cells and HAECs via upregulation of ICAM-1 and VCAM-1 expression, and TRAF6 knockdown attenuated the effect on THP-1 cell adhesion. TRAF6, ICAM-1, and VCAM-1 expression were increased in aorta tissue of mice with streptozotocin-induced diabetes. The free radical scavenger N-acetyl-L-cysteine attenuated TRAF6 expression in HAECs cultured in high glucose medium, and TRAF6 knockdown inhibited high glucose-induced IκB-α degradation and JNK phosphorylation. TRAF6 mediated high glucose-induced endothelial dysfunction via NF-κB- and AP-1-dependent signaling. Targeting TRAF6 may delay progression of vascular diseases during diabetes mellitus and atherosclerosis.

Murine models of vascular endothelial injury: Techniques and pathophysiology

Vascular endothelial injury (VEI) triggers pathological processes in various cardiovascular diseases, such as coronary heart disease and hypertension. To further elucidate the in vivo pathological mechanisms of VEI, many animal models have been established. For the easiness of genetic manipulation and feeding, murine models become most commonly applied for investigating VEI. Subsequently, countless valuable information concerning pathogenesis has been obtained and therapeutic strategies for VEI have been developed. This review will highlight some typical murine VEI models from the perspectives of pharmacological intervention, surgery and genetic manipulation. The techniques, pathophysiology, advantages, disadvantages and the experimental purpose of each model will also be discussed.

Long noncoding RNA RP4 functions as a competing endogenous RNA through miR-7-5p sponge activity in colorectal cancer

AIM

To investigate the role of long noncoding RNA (lncRNA) RP4 in colorectal cancer.

METHODS

Lentivirus-mediated lncRNA RP4 overexpression and knockdown were performed in the colorectal cancer cell line SW480. Cell proliferation, tumor growth, and early apoptosis were evaluated by a cell counting kit-8 assay, an in vivo xenograft tumor model, and annexin V/propidium iodide staining, respectively. Analysis of the lncRNA RP4 mechanism involved assessment of the association of its expression with miR-7-5p and the SH3GLB1 gene. Western blot analysis was also performed to assess the effect of lncRNA RP4 on the autophagy-mediated cell death pathway and phosphatidylinositol-3-kinase (PI3K)/Akt signaling.

RESULTS

Cell proliferation, tumor growth, and early apoptosis in SW480 cells were negatively regulated by lncRNA RP4. Functional experiments indicated that lncRNA RP4 directly upregulated SH3GLB1 expression by acting as a competing endogenous RNA (ceRNA) for miR-7-5p. This interaction led to activation of the autophagy-mediated cell death pathway and de-repression of PI3K and Akt phosphorylation in colorectal cancer cells in vivo.

CONCLUSION

Our results demonstrated that lncRNA RP4 is a ceRNA that plays an important role in the pathogenesis of colorectal cancer, and could be a potential therapeutic target for colorectal cancer treatment.

Inflammation in Vein Graft Disease

Bypass surgery is one of the most frequently used strategies to revascularize tissues downstream occlusive atherosclerotic lesions. For venous bypass surgery the great saphenous vein is the most commonly used vessel. Unfortunately, graft efficacy is low due to the development of vascular inflammation, intimal hyperplasia and accelerated atherosclerosis. Moreover, failure of grafts leads to significant adverse outcomes and even mortality. The last couple of decades not much has changed in the treatment of vein graft disease (VGD). However, insight is the cellular and molecular mechanisms of VGD has increased. In this review, we discuss the latest insights on VGD and the role of inflammation in this. We discuss vein graft pathophysiology including hemodynamic changes, the role of vessel wall constitutions and vascular remodeling. We show that profound systemic and local inflammatory responses, including inflammation of the perivascular fat, involve both the innate and adaptive immune system.

Plasminogen activator inhibitor-1 regulates the vascular expression of vitronectin

Essentials Vitronectin (VN) is produced by smooth muscle cells (SMCs) and promotes neointima formation. We studied the regulation of vascular VN expression by plasminogen activator inhibitor-1 (PAI-1). PAI-1 stimulates VN gene expression in SMCs by binding LDL receptor-related protein 1. Stimulation of VN gene expression may be a mechanism by which PAI-1 controls vascular remodeling.

SUMMARY

Background Increased expression of vitronectin (VN) by smooth muscle cells (SMCs) promotes neointima formation after vascular injury, and may contribute to chronic vascular diseases, such as atherosclerosis. However, the molecular regulation of vascular VN expression is poorly defined. Given the overlapping expression profiles and functions of VN and plasminogen activator inhibitor (PAI)-1, we hypothesized that PAI-1 regulates vascular VN expression. Objectives To determine whether PAI-1 regulates VN expression in SMCs and in vivo. Methods The effects of genetic alterations in PAI-1 expression, pharmacologic PAI-1 inhibition and recombinant PAI-1 on SMC VN expression were studied, and vascular VN expression in wild-type (WT) and PAI-1-deficient mice was assessed. Results VN expression was significantly lower in PAI-1-deficient SMCs and significantly increased in PAI-1-overexpressing SMCs. PAI-1 small interfering RNA and pharmacologic PAI-1 inhibition significantly decreased SMC VN expression. Recombinant PAI-1 stimulated VN expression by binding LDL receptor-related protein-1 (LRP1), but another LRP1 ligand, α2 -macroglobulin, did not. As compared with WT controls, carotid artery VN expression was significantly lower in PAI-1-deficient mice and significantly higher in PAI-1-transgenic mice. In a vein graft (VG) model of intimal hyperplasia, VN expression was significantly attenuated in PAI-1-deficient VGs as compared with WT controls. The plasma VN concentration was significantly decreased in PAI-1-deficient mice versus WT controls at 4 weeks, but not at 5 days or 8 weeks, after surgery. Conclusions PAI-1 stimulates SMC VN expression by binding LRP1, and controls vascular VN expression in vivo. Autocrine regulation of vascular VN expression by PAI-1 may play important roles in vascular homeostasis and pathologic vascular remodeling.

Role of IL-17 in LPS-induced acute lung injury: an in vivo study

To assess the clinical significance of IL-17 in patients with sepsis-induced acute respiratory distress syndrome (ARDS) and to investigate the effects of IL-17 blocking in a mouse model of acute lung injury (ALI). Significantly increased IL-17 level was found in patients with sepsis-related ARDS compared to healthy controls, whereas significantly increased plasma IL-17 level was also observed in non-survivors compared to that in survivors. According to the data from the mouse ALI model, we found significantly increased IL-17 level in lung tissue lysates, mouse bronchoalveolar lavage fluid (mBALF) and plasma at 6, 12 and 24 h after ALI. Histological analyses revealed that reduced sign of pathological changes and lung injury score in the lungs at 48 h after IL-17 blocking antibody administration. Reduced level of proinflammatory tumor necrosis factor α and increased level of anti-inflammatory factor interleukin-10 were found in both mBALF and plasma. Moreover, IL-17 blocking antibody administration attenuated the expression of RORγt and activity of PI3K-Akt pathway. Increased IL-17 was presented in patients with sepsis-induced ARDS and IL-17 may serve as a biomarker to indicate the severity of ARDS. Moreover, IL-17 antibody administration could relieve the ALI symptom by affecting RORγt level and PI3K pathway.

Oxidized low density lipoprotein facilitates tumor necrosis factor‑α mediated chondrocyte death via autophagy pathway

We aimed to investigate the role of oxidized low density lipoprotein (ox-LDL) in tumor necrosis factor-α (TNF-α) mediated chondrocyte death and explore the mechanisms. Ten osteoarthritis (OA) and normal control cartilage tissue and synovial fluid (SF) samples were collected, and the expression of lectin-like ox-LDL receptor-1 (LOX-1) and ox-LDL level was examined by real time quantitative PCR and enzyme-linked immunosorbent assay (ELISA). An in vitro chondrocyte model was established by the introduction of TNF-α and ox-LDL, cell death was analyzed by trypan blue assay and the mechanisms were explored based on the apoptosis related pathway and autophagy pathway. Significantly increased ox-LDL level (70.30±17.83 vs. 37.22±19.97, P<0.05) in SF sample and LOX-1 expression level (0.51±0.10 vs. 0.32±0.04, P<0.05) in cartilage tissue was found in OA patients compared to those corresponding samples from control subjects. Ox-LDL could facilitate TNF-α mediated chondrocyte death and this effect could be blocked by LOX-1 antibody neutralization. Autophagy inhibition by 3-MA and Atg-5 siRNA could reverse the cell death effect mediated by TNF-α and ox-LDL co-treatment on chondrocytes. Oxidized low density lipoprotein facilitates tumor necrosis factor-α mediated chondrocyte death via its interaction with LOX-1, and autophagy is involved in the mechanisms.

Upregulation of MiR-29b contributes to mesenchymal stem cell dysfunction in patients with severe pre-eclampsia

The aim of this study was to investigate the role of miR-29b in the regulation of decidua-derived mesenchymal stem cells (dMSCs) to influence the pathogenesis of pre-eclampsia (PE). dMSCs were isolated from decidua tissue and characterized. The expression of miRNAs was evaluated by quantitative PCR. Overexpression and inhibition of miR-29b were achieved in dMSCs, and the effect of miR-29b overexpression on the migration and angiogenic potential of human umbilical vein endothelial cells (HUVEC) was assessed. Furthermore, we performed bioinformatic analyses, luciferase reporter gene assays, and gene expression analyses to identify the potential targets of miR-29b and to verify the effect of target genes on dMSC function. Upregulation of miR-29b was confirmed in severe PE patients. Overexpression of miR-29b attenuated cell proliferation of dMSCs. Overexpression of miR-29b in dMSCs decreased the migratory and tubule formation ability of HUVECs. Histone deacetylase 4 (HDAC4) was identified as a target gene of miR-29b. Decreased migration and tubule formation in HUVECs was observed upon incubation with conditioned medium from dMSCs treated with the HDAC inhibitor trichostatin A. Our results demonstrated that upregulation of miR-29b in dMSCs has an important paracrine effect and might be involved in the development of PE.

Recombinant soluble apyrase APT102 inhibits thrombosis and intimal hyperplasia in vein grafts without adversely affecting hemostasis or re-endothelialization

Essentials New strategies are needed to inhibit thrombosis and intimal hyperplasia (IH) in vein grafts (VG). We studied effects of apyrase (APT102) on VGs and smooth muscle and endothelial cells (SMC/EC). APT102 inhibited thrombosis, SMC migration, and IH without impairing hemostasis or EC recovery. Apyrase APT102 is a single-drug approach to inhibit multiple processes that cause VG failure.

SUMMARY

Background Occlusion of vein grafts (VGs) after bypass surgery, owing to thrombosis and intimal hyperplasia (IH), is a major clinical problem. Apyrases are enzymes that scavenge extracellular ATP and ADP, and promote adenosine formation at sites of vascular injury, and hence have the potential to inhibit VG pathology. Objectives To examine the effects of recombinant soluble human apyrase, APT102, on platelets, smooth muscle cells (SMCs) and endothelial cells (ECs) in vitro, and on thrombosis and IH in murine VGs. Methods SMC and EC proliferation and migration were studied in vitro. Inferior vena cava segments from donor mice were grafted into carotid arteries of recipient mice. Results APT102 potently inhibited ADP-induced platelet aggregation and VG thrombosis, but it did not impair surgical hemostasis. APT102 did not directly inhibit SMC or EC proliferation, but significantly attenuated the effects of ATP on SMC and EC proliferation. APT102 significantly inhibited SMC migration, but did not inhibit EC migration, which may be mediated, at least in part, by inhibition of SMC, but not EC, migration by adenosine. At 4 weeks after surgery, there was significantly less IH in VGs of APT102-treated mice than in control VGs. APT102 significantly inhibited cell proliferation in VGs, but did not inhibit re-endothelialization. Conclusions Systemic administration of a recombinant human apyrase inhibits thrombosis and IH in VGs without increasing bleeding or compromising re-endothelialization. These results suggest that APT102 has the potential to become a novel, single-drug treatment strategy to prevent multiple pathologic processes that drive early adverse remodeling and occlusion of VGs.

Metformin inhibits endothelial progenitor cell migration by decreasing matrix metalloproteinases, MMP-2 and MMP-9, via the AMPK/mTOR/autophagy pathway

The aim of the present study was to investigate the effect of metformin on endothelial progenitor cell (EPC) migration and to explore the possible mechanisms. EPCs were treated with metformin, and the migration of EPCs was evaluated by wound healing and Matrigel invasion assays. We also examined the expression levels of of MMP-2 and MMP-9 in EPCs with or without metformin treatment via RT-PCR and western blot analysis, and activities of MMP-2 and MMP-9 in EPCs under different conditions was examined by zymography. Moreover, we also assessed the AMPK/mTOR/autophagy pathway to explore the possible mechanisms. Metformin treatment significantly downregulated matrix metalloproteinase-2 (MMP-2) and MMP-9 expression, and subsequently decreased the migration of EPCs. Increased levels of phosphorylated (p)-AMPK and LC3II expression, as well as decreased levels of p-mTOR and p62 contributed to this phenomenon. The AMPK inhibitor compound C reversed the effect exerted by metformin. In conclusion, our results showed that metformin inhibited the migration of EPCs by decreasing MMP-2 and MMP-9. The AMPK/mTOR/autophagy pathway was demonstrated to be involved in the regulatory mechanisms.

Extracellular Vesicles Derived from Adipose Mesenchymal Stem Cells Regulate the Phenotype of Smooth Muscle Cells to Limit Intimal Hyperplasia

PURPOSE

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) play important roles in the reduction of inflammation in multiple disease models. However, their role in vein graft (VG) remodeling is undefined. We aimed to investigate the effect of EVs from adipose MSCs (ADMSC-EVs) on VG intimal hyperplasia and to explore the possible mechanisms.

METHODS

After generation and characterization of control-EVs and ADMSC-EVs in vitro, we investigated their effect on the proliferation and migration of vascular smooth muscle cells (VSMCs) in vitro. Next, we established a mouse model of VG transplantation. Mice underwent surgery and received control-EVs or ADMSC-EVs by intraperitoneal injection every other day for 20 days. VG remodeling was evaluated after 4 weeks. We also assessed the effect of ADMSC-EVs on macrophage migration and inflammatory cytokine expression.

RESULTS

Significant inhibitory effects of ADMSC-EVs on in vitro VSMC proliferation (p < 0.05) and migration (p < 0.05) were observed compared with control-EVs. The extent of intimal hyperplasia was significantly decreased in ADMSC-EV-treated mice compared with control-EV-treated mice (26 ± 8.4 vs. 45 ± 9.0 μm, p < 0.05). A reduced presence of macrophages was observed in ADMSC-EV-treated mice (p < 0.05). Significantly decreased expression of inflammatory cytokines interleukin (IL)-6 and monocyte chemoattractant protein-1 (MCP-1) was also found in the ADMSC-EV-treated group (both p < 0.05). In addition, phosphorylation of Akt, Erk1/2, and p38 in VGs was decreased in the ADMSC-EV-treated group.

CONCLUSIONS

We demonstrated that ADMSC-EVs exert an inhibitory effect on VG neointima formation by regulating VSMC proliferation and migration, macrophage migration, inflammatory cytokine expression, and the related signaling pathways.

Pharmacological Targeting of Plasminogen Activator Inhibitor-1 Decreases Vascular Smooth Muscle Cell Migration and Neointima Formation

OBJECTIVE

Plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor that promotes and inhibits cell migration, plays a complex and important role in adverse vascular remodeling. Little is known about the effects of pharmacological PAI-1 inhibitors, an emerging drug class, on migration of vascular smooth muscle cells (SMCs) and endothelial cells (ECs), crucial mediators of vascular remodeling. We investigated the effects of PAI-039 (tiplaxtinin), a specific PAI-1 inhibitor, on SMC and EC migration in vitro and vascular remodeling in vivo.

APPROACH AND RESULTS

PAI-039 inhibited SMC migration through collagen gels, including those supplemented with vitronectin and other extracellular matrix proteins, but did not inhibit migration of PAI-1-deficient SMCs, suggesting that its antimigratory effects were PAI-1-specific and physiologically relevant. However, PAI-039 did not inhibit EC migration. PAI-039 inhibited phosphorylation and nuclear translocation of signal transducers and activators of transcription-1 in SMCs, but had no discernable effect on signal transducer and activator of transcription-1 signaling in ECs. Expression of low-density lipoprotein receptor-related protein 1, a motogenic PAI-1 receptor that activates Janus kinase/signal transducers and activators of transcription-1 signaling, was markedly lower in ECs than in SMCs. Notably, PAI-039 significantly inhibited intimal hyperplasia and inflammation in murine models of adverse vascular remodeling, but did not adversely affect re-endothelialization after endothelium-denuding mechanical vascular injury.

CONCLUSIONS

PAI-039 inhibits SMC migration and intimal hyperplasia, while having no inhibitory effect on ECs, which seems to be because of differences in PAI-1-dependent low-density lipoprotein receptor-related protein 1/Janus kinase/signal transducer and activator of transcription-1 signaling between SMCs and ECs. These findings suggest that PAI-1 may be an important therapeutic target in obstructive vascular diseases characterized by neointimal hyperplasia.

Vein graft failure: from pathophysiology to clinical outcomes

Occlusive arterial disease is a leading cause of morbidity and mortality worldwide. Aside from balloon angioplasty, bypass graft surgery is the most commonly performed revascularization technique for occlusive arterial disease. Coronary artery bypass graft surgery is performed in patients with left main coronary artery disease and three-vessel coronary disease, whereas peripheral artery bypass graft surgery is used to treat patients with late-stage peripheral artery occlusive disease. The great saphenous veins are commonly used conduits for surgical revascularization; however, they are associated with a high failure rate. Therefore, preservation of vein graft patency is essential for long-term surgical success. With the exception of 'no-touch' techniques and lipid-lowering and antiplatelet (aspirin) therapy, no intervention has hitherto unequivocally proven to be clinically effective in preventing vein graft failure. In this Review, we describe both preclinical and clinical studies evaluating the pathophysiology underlying vein graft failure, and the latest therapeutic options to improve patency for both coronary and peripheral grafts.

The ADP antagonist MRS2179 regulates the phenotype of smooth muscle cells to limit intimal hyperplasia

PURPOSE

ADP plays an important part in platelet aggregation by activating P2Y1 and P2Y12 receptors. The ADP antagonist MRS2179 has been used in thrombosis-related treatments but its effects on vein graft (VG) remodeling is undefined. We examined the effect of MRS2179 on VG intimal hyperplasia and explored the mechanism of action.

METHODS

A mouse model of VG transplantation was established. Mice underwent surgery and received MRS2179 by intraperitoneal injection every other day for 3 weeks. VG remodeling was assessed 4-weeks later. Vascular smooth muscle cells (VSMCs) were isolated and treated with MRS2179. The effect of MRS2179 on the proliferation, migration and inflammatory-cytokine expression of VSMCs was also evaluated.

RESULTS

MRS2179 significantly inhibited VSMC proliferation compared with the control group. Significant inhibitory effects of MRS2179 on VSMC migration was observed in two-dimensional and three-dimensional models. The extent of intimal hyperplasia was significantly less in MRS2179 treated mice than in controls. Reduced migration of macrophage was found in MRS2179 treated mice. Expression of the inflammatory cytokines IL-1β and TNF-α was decreased significantly in the MRS2179 treated group. In addition, decreased phosphorylation was found on Akt, Erk1/2 and p38.

CONCLUSIONS

These data demonstrate that MRS2179 inhibits neointima formation in VGs by regulating the proliferation, and migration of VSMCs, macrophage migration, inflammatory-cytokine secretion and related signaling pathway. Our study provides novel insights regarding purinergic signaling in SMCs in vivo. The P2Y1 receptor may serve as a therapeutic target in neointima formation.

Autophagy inhibits endothelial progenitor cells migration via the regulation of MMP2, MMP9 and uPA under normoxia condition

OBJECTIVE

The aim of this study was to explore the role of autophagy on the regulation of endothelial progenitor cells (EPCs) migration under normoxic condition.

METHODS

After EPCs were isolated and characterized in vitro, we employed Atg5 knocking down and rapamycin to monitor the autophagy, and performed wound healing and transwell assay to assess the cell migration. On the mechanism, the expression of matrix metalloproteinases (MMPs) and urokinase type plasminogen activator (uPA) was evaluated.

RESULTS

Atg5 knocking down and rapamycin could respectively inhibit and enhance autophagy, which could result in significantly increased and decreased cell migration in wound healing and transwell assay under normoxic condition. Moreover, Atg5 knocking down could significantly increase the expression of MMP2, MMP9 and uPA in EPCs while rapamycin could decrease the expression of uPA and MMP9. In addition, the mTOR-P70 S6K pathway was also involved in EPCs migration regulation.

CONCLUSIONS

These results demonstrated that autophagy could regulate the EPCs migration through mTOR-P70 S6K pathway, and MMP2, MMP9 and uPA may also involve in the regulation mechanism.

Metformin regulates differentiation of bone marrow-derived endothelial progenitor cells via multiple mechanisms

OBJECTIVE

The aim of this study was to investigate the effect of metformin on endothelial progenitor cells (EPCs) differentiation and the possible mechanisms.

METHODS

EPCs were treated with metformin and differentiation, migration and tube formation of EPCs were evaluated. Moreover, we also assessed the AMPK-mTOR-p70S6K pathway, AMPK related autophagy pathway and eNOS-NO pathway to explore the mechanisms.

RESULTS

Metformin treatment could significantly increase differentiation of EPCs. On the mechanisms, increased level of AMPKand eNOS phosphorylation, LC3 expression and NO production, and decreased mTOR, p70 S6K as well as TGF-β expression were found in EPCs. The AMPK inhibitor compound C, Atg5 knocking-down and eNOS inhibitor l-NAME could reverse the effect exerted by metformin.

CONCLUSIONS

Our results here showed that metformin could regulate the differentiation of EPCs. Autophagy related pathway and AMPK-eNOS-NO pathway were involved in the mechanisms.

Plasminogen activator inhibitor-1 suppresses profibrotic responses in fibroblasts from fibrotic lungs

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by progressive interstitial scarification. A hallmark morphological lesion is the accumulation of myofibroblasts or fibrotic lung fibroblasts (FL-fibroblasts) in areas called fibroblastic foci. We previously demonstrated that the expression of both urokinase-type plasminogen activator (uPA) and the uPA receptor are elevated in FL-fibroblasts from the lungs of patients with IPF. FL-fibroblasts isolated from human IPF lungs and from mice with bleomycin-induced pulmonary fibrosis showed an increased rate of proliferation compared with normal lung fibroblasts (NL-fibroblasts) derived from histologically "normal" lung. Basal expression of plasminogen activator inhibitor-1 (PAI-1) in human and murine FL-fibroblasts was reduced, whereas collagen-I and α-smooth muscle actin were markedly elevated. Conversely, alveolar type II epithelial cells surrounding the fibrotic foci in situ, as well as those isolated from IPF lungs, showed increased activation of caspase-3 and PAI-1 with a parallel reduction in uPA expression. Transduction of an adenovirus PAI-1 cDNA construct (Ad-PAI-1) suppressed expression of uPA and collagen-I and attenuated proliferation in FL-fibroblasts. On the contrary, inhibition of basal PAI-1 in NL-fibroblasts increased collagen-I and α-smooth muscle actin. Fibroblasts isolated from PAI-1-deficient mice without lung injury also showed increased collagen-I and uPA. These changes were associated with increased Akt/phosphatase and tensin homolog proliferation/survival signals in FL-fibroblasts, which were reversed by transduction with Ad-PAI-1. This study defines a new role of PAI-1 in the control of fibroblast activation and expansion and its role in the pathogenesis of fibrosing lung disease and, in particular, IPF.

Small molecules inhibitors of plasminogen activator inhibitor-1 - an overview

PAI-1, a glycoprotein from the serpin family and the main inhibitor of tPA and uPA, plays an essential role in the regulation of intra and extravascular fibrinolysis by inhibiting the formation of plasmin from plasminogen. PAI-1 is also involved in pathological processes such as thromboembolic diseases, atherosclerosis, fibrosis and cancer. The inhibition of PAI-1 activity by small organic molecules has been observed in vitro and with some in vivo models. Based on these findings, PAI-1 appears as a potential therapeutic target for several pathological conditions. Over the past decades, many efforts have therefore been devoted to developing PAI-1 inhibitors. This article provides an overview of the publishing activity on small organic molecules used as PAI-1 inhibitors. The chemical synthesis of the most potent inhibitors as well as their biological and biochemical evaluations is also presented.

C-reactive protein induces expression of tissue factor and plasminogen activator inhibitor-1 and promotes fibrin accumulation in vein grafts

BACKGROUND

C-reactive protein (CRP) promotes tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) expression in vitro, and an elevated plasma CRP concentration is associated with an increased risk of vein graft (VG) thrombosis after coronary artery bypass surgery. However, little is known about the effects of CRP on VG TF and PAI-1 expression in vivo, or on VG thrombosis.

OBJECTIVES

We studied transgenic (Tg) mice expressing human CRP in a VG model to explore in vivo cause-and-effect relationships between CRP and TF, PAI-1, and VG thrombosis.

METHODS

Vein segments from wild-type (WT) and CRP-Tg donors were transplanted into carotid arteries of WT and CRP-Tg recipients. VGs were analyzed 1-4 weeks later.

RESULTS

Human CRP accumulated in VGs during the first 4 weeks after surgery, but appeared to originate exclusively from systemic sources, rather than local production. Human CRP significantly increased TF gene expression, protein concentration and activity in VGs. Human CRP also increased PAI-1 concentrations in VGs, although only in vascular endothelial cells. Human CRP stimulated macrophage migration, invasion into VGs, and TF expression. Fibrin deposition was significantly greater in VGs of CRP-Tg mice than in WT controls.

CONCLUSIONS

CRP accumulates in VGs early after surgery, originating from systemic sources rather than local synthesis. Human CRP promotes TF and PAI-1 expression in VGs, although with different expression patterns. Human CRP stimulates macrophage invasion and fibrin deposition within VGs. These results suggest that CRP induces pathologic changes in VGs that contribute to early VG occlusion.

Altered phenotypic gene expression of 10T1/2 mesenchymal cells in nonuniformly stretched PEGDA hydrogels

Disease-related phenotype modulation of many cell types has been shown to be closely related to mechanical loading conditions; for example, vascular smooth muscle cell (SMC) phenotype shift from a mature, contractile state to a proliferative, synthetic state contributes to the formation of neointimal tissue during atherosclerosis and restenosis development and is related to SMC mechanical loading in vivo. The majority of past in vitro cell-stretching experiments have employed simplistic (uniform, uniaxial or biaxial) stretching environments to elucidate mechanobiological pathways involved in phenotypic shifts. However, the in vivo mechanics of the vascular wall consists of highly nonuniform stretch. Here we subjected 10T1/2 murine mesenchymal cells (an SMC precursor) to two- and three-dimensional nonuniform stretch environments. After 24 h of stretch, cells on an elastomeric membrane demonstrated varied proliferation [assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation] depending on location upon the membrane, with maximal proliferation occurring in a region of high, uniaxial stretch. Cells subjected to a nonuniform stretching regimen within three-dimensional polyethylene glycol diacrylate (PEGDA) hydrogel constructs demonstrated marked changes in mRNA expression of several phenotype-related proteins, indicating a sort of "hybrid" phenotype with contractile and synthetic markers being both upregulated and downregulated. Furthermore, expression levels of mRNAs were significantly different between various locations within the stretched gel. With the proliferation results, these data exhibit the capability of nonuniform stretching devices to induce heterogeneous cell responses, potentially indicative of spatial distributions of disease-related behaviors in vivo.

Role of hemodynamic forces in the ex vivo arterialization of human saphenous veins

BACKGROUND

Human saphenous vein grafts are one of the salvage bypass conduits when endovascular procedures are not feasible or fail. Understanding the remodeling process that venous grafts undergo during exposure to arterial conditions is crucial to improve their patency, which is often compromised by intimal hyperplasia. The precise role of hemodynamic forces such as shear stress and arterial pressure in this remodeling is not fully characterized. The aim of this study was to determine the involvement of arterial shear stress and pressure on vein wall remodeling and to unravel the underlying molecular mechanisms.

METHODS

An ex vivo vein support system was modified for chronic (up to 1 week), pulsatile perfusion of human saphenous veins under controlled conditions that permitted the separate control of arterial shear stress and different arterial pressure (7 mm Hg or 70 mm Hg).

RESULTS

Veins perfused for 7 days under high pressure (70 mm Hg) underwent significant development of a neointima compared with veins exposed to low pressure (7 mm Hg). These structural changes were associated with altered expression of several molecular markers. Exposure to an arterial shear stress under low pressure increased the expression of matrix metalloproteinase (MMP)-2 and MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1 at the transcript, protein, and activity levels. This increase was enhanced by high pressure, which also increased TIMP-2 protein expression despite decreased levels of the cognate transcript. In contrast, the expression of plasminogen activator inhibitor-1 increased with shear stress but was not modified by pressure. Levels of the venous marker Eph-B4 were decreased under arterial shear stress, and levels of the arterial marker Ephrin-B2 were downregulated under high-pressure conditions.

CONCLUSIONS

This model is a valuable tool to identify the role of hemodynamic forces and to decipher the molecular mechanisms leading to failure of human saphenous vein grafts. Under ex vivo conditions, arterial perfusion is sufficient to activate the remodeling of human veins, a change that is associated with the loss of specific vein markers. Elevation of pressure generates intimal hyperplasia, even though veins do not acquire arterial markers.

CLINICAL RELEVANCE

The pathological remodeling of the venous wall, which leads to stenosis and ultimately graft failure, is the main limiting factor of human saphenous vein graft bypass. This remodeling is due to the hemodynamic adaptation of the vein to the arterial environment and cannot be prevented by conventional therapy. To develop a more targeted therapy, a better understanding of the molecular mechanisms involved in intimal hyperplasia is essential, which requires the development of ex vivo models of chronic perfusion of human veins.

Promoter variants of VTN are associated with vascular disease

BACKGROUND

Vitronectin is involved in the whole process of atherosclerosis. Our aim is to determine the association of VTN functional promoter variants with different types of vascular disease, and conclude the roles of vitronectin involved in vascular disease.

METHODS

Gel shift assays and luciferase reporter assays were used to determine the impact of variants on promoter activity. The correlation of plasma vitronectin levels with the variant was assessed in normal controls. The association of the variant with vascular disease was determined in 3 case-control studies.

RESULTS

A strong linkage disequilibrium was found between rs2227721 and rs2227720 in VTN promoter in Chinese (r(2)=1.0). Both variants resulted in a decreased transcription activity, and rs2227721 decreased the binding efficiency of transcription factor YY1 to the region. The rs2227721 was correlated with plasma vitronectin levels in normal controls (r=-0.207, P=0.028). The rs2227721 was associated with susceptibility of vascular disease; the odds ratios among subjects carrying rs2227721-T allele were 1.298 (95% Confidence Interval-CI, 1.033-1.631) for non-MI CAD (P<0.05), 1.346 (95% CI, 1.068-1.695) for chronic MI (P<0.05), 1.486 (95% CI, 1.145-1.928) for acute MI (P<0.001), and 1.619 (95% CI, 1.108-2.366) for deep venous thrombosis (P<0.05).

CONCLUSION

VTN promoter haplotype would be a novel genetic marker for vascular disease.