Increased vascular injury reduces the degree of intimal hyperplasia following angioplasty in rabbits

Corrugated nanofiber tissue-engineered vascular graft to prevent kinking for arteriovenous shunts in an ovine model

Objective

Prosthetic grafts are often needed in open vascular procedures. However, the smaller diameter prosthetic grafts (<6 mm) have low patency and often result in complications from infection. Tissue-engineered vascular grafts (TEVGs) are a promising replacement for small diameter prosthetic grafts. TEVGs start as a biodegradable scaffold to promote autologous cell proliferation and functional neotissue regeneration. Owing to the limitations of graft materials; however, most TEVGs are rigid and easily kinked when implanted in limited spaces, which precludes clinical application. We have developed a novel corrugated nanofiber graft to prevent kinking.

Methods

TEVGs with corrugated walls (5-mm internal diameter by 10 cm length) were created by electrospinning a blend of poly-ε-caprolactone and poly(L-lactide-co-caprolactone). The biodegradable grafts were then implanted between the carotid artery and the external jugular vein in a U-shape using an ovine model. TEVGs were implanted on both the left and right side of a sheep (n = 4, grafts = 8). The grafts were explanted 1 month after implantation and inspected with mechanical and histologic analyses. Graft patency was confirmed by measuring graft diameter and blood flow velocity using ultrasound, which was performed on day 4 and every following week after implantation.

Results

All sheep survived postoperatively except for one sheep that died of acute heart failure 2 weeks after implantation. The graft patency rate was 87.5% (seven grafts out of eight) with one graft becoming occluded in the early phase after implantation. There was no significant kinking of the grafts. Overall, endothelial cells were observed in the grafts 1 month after the surgeries without graft rupture, calcification, or aneurysmal change.

Conclusions

Our novel corrugated nanofiber vascular graft displayed neotissue formation without kinking in large animal model.

This basic science research article reported tissue-engineered vascular grafts for arteriovenous shunt procedures. Nanofibrous grafts were electrospun with polyglycolic acid and poly-ε-caprolactone with a corrugated wall design to prevent graft kinking. The tissue-engineered vascular grafts were then implanted in U-shape between the carotid artery and the external jugular vein of an ovine model. This graft had 87.5% patency rate and did not display significant kinking. Overall, re-endothelialization was observed in the grafts one month after the surgeries without graft rupture, calcification or aneurysmal change. This graft is a promising alternative to small diameter prosthetic grafts.

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.

Oxidative stress induces early-onset apoptosis of vascular smooth muscle cells and neointima formation in response to injury

The rapid onset of VSMC apoptosis after arterial injury is driven by the accumulation of reactive oxygen species in the vascular wall and the activation of redox-sensible MAPK pathways. This process leads to vascular inflammation and neointimal hyperplasia.

The present study dissects the mechanisms underlying the rapid onset of apoptosis that precedes post injury vascular remodelling. Using the rat balloon injury model, we demonstrated that a significant number of arterial vascular smooth muscle cells (VSMC) undergo apoptosis at 90 min after the procedure. This apoptotic wave caused significant loss in media cellularity (>90%) over the next 3 h and was accompanied by a marked accumulation of oxidative stress by-products in the vascular wall. Early apoptotic VSMC were rich in p38 mitogen-activated protein kinase (MAPK) and the transcription factor c-Jun and secreted IL-6 and GRO/KC into the milieu as determined using multiplex bead assays. Neointima thickness increased steadily starting on day 3 as a result of pronounced repopulation of the media. A second apoptotic wave that was detected at 14 days after injury affected mostly the neointima and was insufficient to control hyperplasia. Suppression of reactive oxygen species (ROS) production using either the NAD(P)H oxidase inhibitor VAS2870 or pegylated superoxide dismutase (PEG-SOD) significantly decreased the number of apoptotic cells during the first apoptotic wave and showed a trend towards reduction in the neointima-to-media thickness ratio at 30 days post injury. These results indicate that oxidative stress in response to injury induces early-onset apoptosis of VSMC through the activation of redox-sensible MAPK pro-apoptotic pathways. This remodelling process leads to the local accumulation of inflammatory cytokines and repopulation of the media, which ultimately contribute to neointima formation.

Reversion-inducing-cysteine-rich protein with Kazal motif is involved in intimal hyperplasia in carotid arteries: a new insight in the prevention of restenosis after vascular angioplasty

BACKGROUND

Overexpression of matrix metalloproteinase (MMP) has been implicated in the incidence of restenosis after vascular angioplasty. Reversion-inducing cysteine-rich protein with kazal motifs (RECK) is a membrane-anchored glycoprotein that negatively regulates the activity of MMPs, such as MMP-9 and MMP-2, which play a key role in the angiogenesis during tumor growth. This study was designed to investigate the potential association between RECK and restenosis after vascular angioplasty.

METHODS

Balloon-injured rabbit carotid arterial models were established. Arterial morphology was assessed by hematoxylin-eosin staining. The area of intimal hyperplasia was measured using image microscopy and image analyzer. The messenger RNA (mRNA) expression levels of RECK, MMP-9, and MMP-2 were detected using reverse transcription-polymerase chain reaction (RT-PCR) at 7, 14, and 21 days. Vascular smooth muscle cells (VSMCs) were transfected with RECK small interfering RNA (siRNA). VSMC proliferation rate was detected by MTT assay at 24, 48 and 72 hr. The protein expression of RECK, MMP-9, and MMP-2 was determined by Western blot.

RESULTS

MMP-2 and MMP-9 in carotid artery of rats were significantly overexpressed in the injured-artery group, compared with unmanipulated control and contralateral uninjured groups (P < 0.05). With the time of the injury extended, MMP-2 and MMP-9 mRNA levels gradually increased. RECK showed a marked peak of mRNA level at 7 days after injury, compared with unmanipulated control and contralateral uninjured groups (P < 0.001). However, the increasing trend gradually decreased at 14 days after the balloon surgery. RECK mRNA was still detectable at 21 days postoperatively, but the expression level of RECK mRNA in injured and contralateral uninjured groups was significantly lower than that in unmanipulated control group (P < 0.001). The expression level of RECK protein in VSMCs in transfected group was significantly lower compared with that in untransfected group, whereas the expression of MMP-2 and MMP-9 proteins in transfected group was significantly higher compared with that in untransfected group. Over the extension of transfection time, the proliferation of VSMCs in transfected group was increased gradually, compared with negative and blank plasmid controls (P < 0.05).

CONCLUSIONS

RECK, as siRNA-mediated RECK silencing regulation of MMP-9 and MMP-2, plays an important role in intimal hyperplasia, which provides a new target for prevention and treatment of restenosis after vascular angioplasty.

Inhibitory effects of mesenchymal stem cells in intimal hyperplasia after balloon angioplasty

OBJECTIVE

Intimal hyperplasia is a major cause of restenosis after arterial bypass and balloon angioplasty. Induction of rapid re-endothelialization has been proposed to reduce intimal hyperplasia. The aim of this study was to evaluate the inhibitory effect of mesenchymal stem cells on intimal hyperplasia.

METHODS

Male New Zealand white rabbits were fed 1% cholesterol diets from 1 week before balloon angioplasty to the day of harvest. After dissection of rabbit carotid arteries, balloon angioplasty was performed with a 2F Fogarty embolectomy catheter. The injured carotid artery was coated with a mixture of 7 × 10(6) human umbilical cord mesenchymal stem cells (HUC-MSCs) and fibrin matrix. The carotid arteries were harvested 2, 4, and 8 weeks thereafter, and immunofluorescent staining and quantitative real-time polymerase chain reaction analysis were performed.

RESULTS

The intima/media ratio was significantly reduced in the group treated with HUC-MSCs compared with the nontreated group (Student t-tests, *P < .05). The area of re-endothelialization was significantly higher (Student t-tests, *P < .05) in the group treated with HUC-MSCs than in the nontreated group. Expression of angiogenic genes such as vascular endothelial growth factor, platelet-derived growth factor, kinase insert domain receptor 1, angiopoietin 1, and angio-associated migratory cell protein was increased (analysis of variance, P < .05) in the group treated with HUC-MSCs relative to the nontreated group.

CONCLUSIONS

Our study showed that HUC-MSCs reduce the formation of intimal hyperplasia through rapid re-endothelialization. This result might be applied to development of stem cell-coated stents as well as to development of a stem cell-containing sheet coat for inhibition of intimal hyperplasia after angioplasty or surgery.

Molecular mechanism of (-)-epigallocatechin-3-gallate on balloon injury-induced neointimal formation and leptin expression

Leptin contributes to the pathogenesis of vascular repair and cardiovascular events. This study evaluated the molecular mechanism of EGCG in balloon injury-induced leptin expression. According to immunohistochemical and confocal analyses, leptin expression was increased and the aortic lumen exhibited narrowing after balloon injury. EGCG treatment attenuated leptin expression and diminished neointimal formation. The in vitro study showed that angiotensin II (Ang II) induced the migration and proliferation of cultured vascular smooth muscle cells (VSMCs), whereas treatment with EGCG, leptin siRNA, and c-Jun siRNA inhibited the migration and proliferation of VSMCs significantly. The EMSA shows that balloon injury increased AP-1-binding activity, and EGCG and c-Jun siRNA inhibited the AP-1-binding activity. Western blot and real-time RT-PCR analyses revealed similar results in intimal tissue samples. In summary, balloon injury induces leptin expression in the carotid artery of rats, and EGCG inhibits leptin expression through the JNK/AP-1 pathway and also attenuates neointimal formation.

Antirestenosis effect of butein in the neointima formation progression

The development of restenosis involves migration and hyperproliferation of vascular smooth muscle cells (VSMCs). Platelet-derived growth factor (PDGF) is one of the major factors. Butein modulates inflammatory pathways and affects the proliferation and invasion of the tumor. We investigated the hypothesis that butein might prevent the restenosis process via a similar pathway. Our results demonstrated that butein inhibited PDGF-induced VSMC proliferation and migration as determined by BrdU proliferation and two-dimensional migration scratch assay. Butein also concentration-dependently repressed PDGF-induced phosphorylation of PDGF-receptor β, mitogen-activated protein kinases, phosphoinositide 3-kinase/Akt, and phopholipase Cγ/c-Src in VSMCs. In addition, in vivo results showed that butein attenuated neointima formation in balloon-injured rat carotid arteries. These results indicate that butein may inhibit PDGF-induced VSMC proliferation and migration, resulting in attenuation of neointima formation after percutaneous transluminal coronary angioplasty. Our study demonstrates for the first time that systemic administration of butein is able to reduce neointima formation after vascular injury.

Role of microRNAs in peripheral artery disease (review)

Peripheral arterial disease (PAD) involves a general vascular problem of diffuse atherosclerosis. The key pathological process is characterized by the aberrant proliferation of vascular smooth muscle cells and the formation of neointimal lesions. The molecular mechanisms involved in the regulation of the occurrence and development of PAD remain unclear. microRNAs (miRNAs) are highly conserved 20-25 nt-long non-coding RNAs that negatively regulate gene expression. Recent evidence has demonstrated that specific miRNAs are involved in the pathological processes of PAD, and these miRNAs are found to be critical modulators of vascular cell functions, including cell differentiation, contraction, migration, proliferation and apoptosis. This review summarizes findings of studies regarding the roles of specific miRNAs in PAD.