Coronary Artery Vessel Healing Pattern, Short and Long Term, After Implantation of the Everolimus-Eluting Bioresorbable Vascular Scaffold

BACKGROUND

Although the Absorb bioresorbable vascular scaffold is increasingly used in daily clinical practice for the treatment of coronary artery disease, the exact vascular healing pattern and the resorption process in humans is unknown because histological data are derived only from animal studies.

METHODS AND RESULTS

We have obtained 4 autopsies (5 scaffolds) since August 2013. Duration of bioresorbable vascular scaffold implantation ranged from 3 to 501 days. All autopsies and histological assessments were performed by dedicated cardiovascular pathologists. At 1 week after bioresorbable vascular scaffold implantation, struts were covered with a fine layer of fibrin and platelets. At 113 days, the scaffold struts were fully covered with smooth muscle cells. Hyaline eosinophilic and proteoglycan material infiltrating the scaffold struts was observed at 501 days after implantation. At all time points, we observed the presence of multinuclear foreign body giant cells adjacent to the scaffold struts.

CONCLUSIONS

Resorption and healing processes after bioresorbable vascular scaffold implantation in human patients mirror those observed in porcine models. The presence of multinucleated foreign body giant cells at both short- and long-term follow-up needs further investigation and may be related to a low-grade absorptive inflammatory response to the polymer.

The hypertrabeculated (noncompacted) left ventricle is different from the ventricle of embryos and ectothermic vertebrates

Ventricular hypertrabeculation (noncompaction) is a poorly characterized condition associated with heart failure. The condition is widely assumed to be the retention of the trabeculated ventricular design of the embryo and ectothermic (cold-blooded) vertebrates. This assumption appears simplistic and counterfactual. Here, we measured a set of anatomical parameters in hypertrabeculation in man and in the ventricles of embryos and animals. We compared humans with left ventricular hypertrabeculation (N=21) with humans with structurally normal left ventricles (N=54). We measured ejection fraction and ventricular trabeculation using cardiovascular MRI. Ventricular trabeculation was further measured in series of embryonic human and 9 animal species, and in hearts of 15 adult animal species using MRI, CT, or histology. In human, hypertrabeculated left ventricles were significantly different from structurally normal left ventricles by all structural measures and ejection fraction. They were far less trabeculated than human embryonic hearts (15-40% trabeculated volume versus 55-80%). Early in development all vertebrate embryos acquired a ventricle with approximately 80% trabeculations, but only ectotherms retained the 80% trabeculation throughout development. Endothermic (warm-blooded) animals including human slowly matured in fetal and postnatal stages towards ventricles with little trabeculations, generally less than 30%. Further, the trabeculations of all embryos and adult ectotherms were very thin, less than 50 μm wide, whereas the trabeculations in adult endotherms and in the setting of hypertrabeculation were wider by orders of magnitude. It is concluded in contrast to a prevailing assumption, the hypertrabeculated left ventricle is not like the ventricle of the embryo or of adult ectotherms. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.

Granulocytes in coronary thrombus evolution after myocardial infarction--time-dependent changes in expression of matrix metalloproteinases

BACKGROUND

Remodeling of extracellular matrix is a key process during wound healing, which is strictly regulated by matrix metalloproteinases (MMPs) and their tissue inhibitors [tissue inhibitors of metalloproteinases (TIMPs)]. In this study, we evaluated intrathrombotic MMPs and TIMPs and their cellular origin during thrombus evolution after disruption of coronary atherosclerotic plaque.

MATERIALS AND METHODS

Thrombectomy materials (N=120) obtained from patients with acute myocardial infarction were histologically classified in three groups based on thrombus age: fresh (<1day), lytic (1-5days), or organized (>5days) thrombi; materials showing a heterogeneous composition were classified according to oldest part. Presence and cellular origin of MMPs (MMP-1, MMP-2, MMP-8, MMP-9, and MMP-14) and TIMPs (TIMP-1, TIMP-2, and TIMP-3) was evaluated with immunostains (double) and with polymerase chain reaction.

RESULTS AND CONCLUSION

MMPs and TIMPs were present in all the thrombectomy samples. A distinct temporal change in extent and cellular origin of MMPs and TIMPs during thrombus evolution was observed. In the early (fresh and lytic) stages of thrombus, high numbers of neutrophilic granulocytes occupy the thrombus mass and produce large amounts of MMPs and TIMPs. However, with progression of thrombus evolution (organizing stage) and diminishment of neutrophil granulocytes, there is disappearance of MMP-8 and MMP-9, steep decline of MMP-1 and TIMP-2, and progressive decrease of TIMP-3. In contrast, intrathrombotic MMP-2 and MMP-14 are present at a constant high level during the entire process of thrombus evolution. These temporal changes indicate a complex time-dependent function of MMPs, which are largely granulocyte derived, in the healing process of thrombus after plaque disruption.

Distal embolization of hydrophilic-coating material from coronary guidewires after percutaneous coronary interventions

BACKGROUND

Coronary guidewires are indispensable during percutaneous coronary interventions. Nowadays, most guidewires have hydrophilic coatings to improve their trackability, allowing easy lesion passage and facilitating balloon and stent positioning. Recent reports, however, have raised concerns about detachment and subsequent embolization of these hydrophilic coatings.

METHODS AND RESULTS

We have retrospectively reviewed the histological samples of the myocardium, obtained during autopsies in the period 2009 to 2013, from all patients who had a history of percutaneous coronary interventions (n=40). Foreign material was observed in the distal myocardium in 4 patients (10%). Furthermore, we have reviewed 205 thrombus specimens which were obtained during thrombus aspiration in the setting of primary percutaneous coronary interventions in the period 2005 to 2009. In 45% of the cases, foreign material was observed within the thrombus. Finally, we have examined the histopathologic appearance of hydrophilic-guidewire coating material ex vivo by embedding the coating in placenta specimen and cut and stain it in exactly the same manner as the myocardium and thrombus specimen. The histopathologic appearance of the hydrophilic coating ex vivo was identical to the foreign material found in vivo.

CONCLUSIONS

Distal embolization of hydrophilic-coating material was observed in 10% of the patients who had a history of percutaneous coronary interventions. Hydrophilic-coating material was found in 45% of coronary thrombus specimen obtained during thrombus aspiration. These findings suggest that detachment and distal embolization of hydrophilic-coating material from coronary guidewires occur more often than the sparse literature on this topic suggests.

Treatment of Basal Cell Carcinoma Using a One-Stop-Shop With Reflectance Confocal Microscopy: Study Design and Protocol of a Randomized Controlled Multicenter Trial

Background

Basal cell carcinoma (BCC) is the most common cancer diagnosed in white populations worldwide. The rising incidence of BCC is becoming a major worldwide public health problem. Therefore, there is a need for more efficient management.

Objective

The aim of this research is to assess the efficacy and safety of a one-stop-shop (OSS) concept, using real-time in vivo reflectance confocal microscopy (RCM) (Vivascope 1500; Lucid Technologies, Henrietta, NY, USA) as a diagnostic tool, prior to surgical management of new primary BCCs.

Methods

This is a prospective non-inferiority multi-center RCT designed to compare the “OSS concept using RCM” to current standards of care in diagnosing and treating clinically suspected BCC. Patients ≥ 18 years attending our outpatient clinic at the Department of Dermatology, Academic Medical Center, University of Amsterdam, and the Department of Dermatology, the Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital (Amsterdam, The Netherlands) with a clinically suspected new primary BCC lesion will be considered for enrollment using predefined inclusion and exclusion criteria, and will be randomly allocated to the experimental or control group. The main outcome parameter is the assessment of incomplete surgical excision margins on the final pathology report of confirmed BCC lesions (either by punch biopsy or RCM imaging). Other outcome measures include diagnostic accuracy (sensitivity and specificity) of RCM for diagnosing BCC and dividing between subtypes, and throughput time. Patient satisfaction data will be collected postoperatively after 3 months during routine follow-up.

Results

This research is investigator-initiated and received ethics approval. Patient recruitment started in February 2015, and we expect all study-related activities to be completed by fall 2015.

Conclusions

This RCT is the first to examine an OSS concept using RCM for diagnosing and treating clinically suspected BCC lesions. Results of this research are expected to have applications in evidence-based practice for the increasing number of patients suffering from BCC and possibly lead to a more efficient disease management strategy.

Trial Registration

ClinicalTrials.gov: NCT02285790; https://clinicaltrial.gov/ct2/show/NCT02285790 (Archived by WebCite at http://www.webcitation.org/6b2LfDKWu).

Laser-assisted vascular welding: optimization of acute and post-hydration welding strength

BACKGROUND

Liquid solder laser-assisted vascular welding using biocompatible polymeric scaffolds (ssLAVW) is a novel technique for vascular anastomoses. Although ssLAVW has pronounced advantages over conventional suturing, drawbacks include low welding strength and extensive thermal damage.

AIM

To determine optimal ssLAVW parameters for maximum welding strength and minimal thermal damage.

METHODS

Substudy 1 compared breaking strength (BS) of aortic strips welded with electrospun poly(ε-caprolactone) (PCL) or poly(lactic-co-glycolic acid) (PLGA) scaffold, 670-nm laser, 50-s single-spot continuous lasing (SSCL), and semi-solid solder (48% bovine serum albumin (BSA)/0.5% methylene blue (MB)/3% hydroxypropylmethylcellulose (HPMC)). Substudy 2 compared the semi-solid solder to 48% BSA/0.5% MB/0.38% genipin and 48% BSA/0.5% MB/3% HPMC/0.38% genipin solder. Substudy 3 compared SSCL to single-spot pulsed lasing (SSPL).

RESULTS

PCL-ssLAVW yielded an acute BS of 248.0 ± 54.0 N/cm² and remained stable up to 7d of hydration. PLGA-ssLAVW obtained higher acute BS (408.6 ± 78.8 N/cm²) but revealed structural defects and a BS of 109.4 ± 42.6 N/cm² after 14 d of hydration. The addition of HPMC and genipin improved the 14-d BS of PLGA-sLAVW (223.9 ± 19.1 N/cm²). Thermal damage was reduced with SSPL compared with SSCL.

CONCLUSIONS

PCL-ssLAVW yielded lower but more stable welds than PLGA-ssLAVW. The addition of HPMC and genipin to the solder increased the post-hydration BS of PLGA-ssLAVW. SSPL regimen reduced thermal damage. PLGA-ssLAVW using 48% BSA/0.5% MB/3% HPMC/0.38% genipin solder and SSPL constitutes the most optimal welding modality.

RELEVANCE FOR PATIENTS

Surgical patients requiring vascular anastomoses may benefit from the advantages that ssLAVW potentially offers over conventional sutures (gold standard). These include no needle trauma and remnant suture materials in the patient, reduction of foreign body reaction, immediate liquid-tight sealing, and the possibility of a faster and easier procedure for minimally invasive and endoscopic anastomotic techniques.

Consensus statement on surgical pathology of the aorta from the Society for Cardiovascular Pathology and the Association for European Cardiovascular Pathology: I. Inflammatory diseases

Inflammatory diseases of the aorta include routine atherosclerosis, aortitis, periaortitis, and atherosclerosis with excessive inflammatory responses, such as inflammatory atherosclerotic aneurysms. The nomenclature and histologic features of these disorders are reviewed and discussed. In addition, diagnostic criteria are provided to distinguish between these disorders in surgical pathology specimens. An initial classification scheme is provided for aortitis and periaortitis based on the pattern of the inflammatory infiltrate: granulomatous/giant cell pattern, lymphoplasmacytic pattern, mixed inflammatory pattern, and the suppurative pattern. These inflammatory patterns are discussed in relation to specific systemic diseases including giant cell arteritis, Takayasu arteritis, granulomatosis with polyangiitis (Wegener's), rheumatoid arthritis, sarcoidosis, ankylosing spondylitis, Cogan syndrome, Behçet's disease, relapsing polychondritis, syphilitic aortitis, and bacterial and fungal infections.

Effect of anti-ApoA-I antibody-coating of stents on neointima formation in a rabbit balloon-injury model

Background and Aims

Since high-density lipoprotein (HDL) has pro-endothelial and anti-thrombotic effects, a HDL recruiting stent may prevent restenosis. In the present study we address the functional characteristics of an apolipoprotein A-I (ApoA-I) antibody coating in vitro. Subsequently, we tested its biological performance applied on stents in vivo in rabbits.

Materials and Methods

The impact of anti ApoA-I- versus apoB-antibody coated stainless steel discs were evaluated in vitro for endothelial cell adhesion, thrombin generation and platelet adhesion. In vivo, response to injury in the iliac artery of New Zealand white rabbits was used as read out comparing apoA-I-coated versus bare metal stents.

Results

ApoA-I antibody coated metal discs showed increased endothelial cell adhesion and proliferation and decreased thrombin generation and platelet adhesion, compared to control discs. In vivo, no difference was observed between ApoA-I and BMS stents in lumen stenosis (23.3±13.8% versus 23.3±11.3%, p=0.77) or intima surface area (0.81±0.62 mm² vs 0.84±0.55 mm², p=0.85). Immunohistochemistry also revealed no differences in cell proliferation, fibrin deposition, inflammation and endothelialization.

Conclusion

ApoA-I antibody coating has potent pro-endothelial and anti-thrombotic effects in vitro, but failed to enhance stent performance in a balloon injury rabbit model in vivo.

Irreversible electroporation: just another form of thermal therapy?

BACKGROUND

Irreversible electroporation (IRE) is (virtually) always called non-thermal despite many reports showing that significant Joule heating occurs. Our first aim is to validate with mathematical simulations that IRE as currently practiced has a non-negligible thermal response. Our second aim is to present a method that allows simple temperature estimation to aid IRE treatment planning.

METHODS

We derived an approximate analytical solution of the bio-heat equation for multiple 2-needle IRE pulses in an electrically conducting medium, with and without a blood vessel, and incorporated published observations that an electric pulse increases the medium's electric conductance.

RESULTS

IRE simulation in prostate-resembling tissue shows thermal lesions with 67-92°C temperatures, which match the positions of the coagulative necrotic lesions seen in an experimental study. Simulation of IRE around a blood vessel when blood flow removes the heated blood between pulses confirms clinical observations that the perivascular tissue is thermally injured without affecting vascular patency.

CONCLUSIONS

The demonstration that significant Joule heating surrounds current multiple-pulsed IRE practice may contribute to future in-depth discussions on this thermal issue. This is an important subject because it has long been under-exposed in literature. Its awareness pleads for preventing IRE from calling "non-thermal" in future publications, in order to provide IRE-users with the most accurate information possible. The prospect of thermal treatment planning as outlined in this paper likely aids to the important further successful dissemination of IRE in interventional medicine. Prostate 75:332-335, 2015. © 2014 The Authors. The Prostate Published by Wiley Periodicals, Inc.

Atrial fibrosis and conduction slowing in the left atrial appendage of patients undergoing thoracoscopic surgical pulmonary vein isolation for atrial fibrillation

BACKGROUND

Atrial fibrosis is an important component of the arrhythmogenic substrate in patients with atrial fibrillation (AF). We studied the effect of interstitial fibrosis on conduction velocity (CV) in the left atrial appendage of patients with AF.

METHODS AND RESULTS

Thirty-five left atrial appendages were obtained during AF surgery. Preparations were superfused and stimulated at 100 beats per minute. Activation was recorded with optical mapping. Longitudinal CV (CVL), transverse CV (CVT), and activation times (> 2 mm distance) were measured. Interstitial collagen was quantified and graded qualitatively. The presence of fibroblasts and myofibroblasts was assessed immunohistochemically. Mean CVL was 0.55 ± 0.22 m/s, mean CVT was 0.25 ± 0.15 m/s, and the mean activation time was 9.31 ± 5.45 ms. The amount of fibrosis was unrelated to CV or patient characteristics. CVL was higher in left atrial appendages with thick compared with thin interstitial collagen strands (0.77 ± 0.22 versus 0.48 ± 0.19 m/s; P = 0.012), which were more frequently present in persistent patients with AF. CVT was not significantly different (P = 0.47), but activation time was 14.93 ± 4.12 versus 7.95 ± 4.12 ms in patients with thick versus thin interstitial collagen strands, respectively (P = 0.004). Fibroblasts were abundantly present and were associated with the presence of thick interstitial collagen strands (P = 0.008). Myofibroblasts were not detected in the left atrial appendage.

CONCLUSIONS

In patients with AF, thick interstitial collagen strands are associated with higher CVL and increased activation time. Our observations demonstrate that the severity and structure of local interstitial fibrosis is associated with atrial conduction abnormalities, presenting an arrhythmogenic substrate for atrial re-entry.

Reduction of cardiac cell death after helium postconditioning in rats: transcriptional analysis of cell death and survival pathways

Helium, a noble gas, has been used safely in humans. In animal models of regional myocardial ischemia/reperfusion (I/R) it was shown that helium conditioning reduces infarct size. Currently, it is not known how helium exerts its cytoprotective effects and which cell death/survival pathways are affected. The objective of this study, therefore, was to investigate the cell protective effects of helium postconditioning by PCR array analysis of genes involved in necrosis, apoptosis and autophagy. Male rats were subjected to 25 min of ischemia and 5, 15 or 30 min of reperfusion. Semiquantitative histological analysis revealed that 15 min of helium postconditioning reduced the extent of I/R-induced cell damage. This effect was not observed after 5 and 30 min of helium postconditioning. Analysis of the differential expression of genes showed that 15 min of helium postconditioning mainly caused upregulation of genes involved in autophagy and inhibition of apoptosis versus I/R alone. The results suggest that the cytoprotective effects of helium inhalation may be caused by a switch from pro-cell-death signaling to activation of cell survival mechanisms, which appears to affect a wide range of pathways.

Total burden of intraplaque hemorrhage in coronary arteries relates to the use of coumarin-type anticoagulants but not platelet aggregation inhibitors

Intraplaque hemorrhage (IPH) is a crucial factor in progression and destabilization of an atherosclerotic plaque. Anti-thromboembolic drugs are widely used as prophylactic treatment against arterial and venous thrombotic diseases, but a major complication is bleeding. We investigated the association between exposure to anti-thromboembolic therapy and IPH in postmortem coronary arteries. Coronary arteries with postmortem angiographically confirmed extensive atherosclerosis were obtained at autopsy from patients who had received oral anticoagulants (n = 10), platelet aggregation inhibitors (n = 10), or no anti-thrombotic drugs (n = 10) before death. Coronary arteries were cut at 3-mm interval, and all plaque-containing segments were immunohistochemically screened for IPH and microvessels. These data were related to overall plaque composition and the use of anti-thromboembolic therapies. IPH was found in 483 out of 904 (53 %) coronary segments with advanced atherosclerotic plaques and more frequently in patients on oral anticoagulants (174/284, 61 %) than in patients on anti-platelets (198/376, 53 %) or without therapy (111/244, 46 %) (P = 0.02 and P = 0.001, respectively). Also, intraplaque microvascular leakage was more frequently observed in patients on anticoagulants than in non-treated patients (P = 0.03). Finally, the IPH appeared to be larger in plaques of patients on anticoagulant treatment (P < 0.001). Density of intraplaque microvessels was highest in plaques of patients on platelet inhibitors (P < 0.05), but this was not associated with increased hemorrhagic burden. Prophylactic therapy with oral coumarin-type anticoagulants appears to be associated with a higher hemorrhagic burden in atherosclerotic coronary arteries, which may lead to increase in plaque volume over time, in this selected subgroup of patients.

Mutation in KERA identified by linkage analysis and targeted resequencing in a pedigree with premature atherosclerosis

AIMS

Genetic factors explain a proportion of the inter-individual variation in the risk for atherosclerotic events, but the genetic basis of atherosclerosis and atherothrombosis in families with Mendelian forms of premature atherosclerosis is incompletely understood. We set out to unravel the molecular pathology in a large kindred with an autosomal dominant inherited form of premature atherosclerosis.

METHODS AND RESULTS

Parametric linkage analysis was performed in a pedigree comprising 4 generations, of which a total of 11 members suffered from premature vascular events. A parametric LOD-score of 3.31 was observed for a 4.4 Mb interval on chromosome 12. Upon sequencing, a non-synonymous variant in KERA (c.920C>G; p.Ser307Cys) was identified. The variant was absent from nearly 28,000 individuals, including 2,571 patients with premature atherosclerosis. KERA, a proteoglycan protein, was expressed in lipid-rich areas of human atherosclerotic lesions, but not in healthy arterial specimens. Moreover, KERA expression in plaques was significantly associated with plaque size in a carotid-collar Apoe-/- mice (r2 = 0.69; p<0.0001).

CONCLUSION

A rare variant in KERA was identified in a large kindred with premature atherosclerosis. The identification of KERA in atherosclerotic plaque specimen in humans and mice lends support to its potential role in atherosclerosis.

T-cell-mediated inflammatory activity in the stellate ganglia of patients with ion-channel disease and severe ventricular arrhythmias

BACKGROUND

Long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) are electric diseases characterized by catecholamine-induced ventricular arrhythmias. Unbalanced autonomic innervation of the heart may trigger arrhythmic events and stellectomy is a treatment option for patients who are resistant to pharmacological drugs. We analyzed left stellectomy specimens of LQTS and CPVT patients for signs of inflammatory activity.

METHODS AND RESULTS

Stellate ganglia were retrieved from 12 consecutive patients (8F; 4 mol/L; mean age, 23.4±17 years) with either LQTS (n=8) or CPVT (n=4) and serious arrhythmias. Control stellate ganglia were obtained from 10 accidently deceased patients (6F; 4 mol/L; mean age, 35±17.6 years). Sections were immunostained with antibodies against T cells (CD3, CD4, CD8, CD20, Granzyme B), CD68 (macrophages), and HLA-DR (human leukocyte antigen-DR) antigens (activation marker). Immunopositive cells were quantified as cells/mm2. Polymerase chain reaction (PCR) and reverse transcription PCR were performed to screen for herpes virus DNA. Stellate ganglia of all 12 LQTS/CPVT patients revealed mild but distinct inflammatory infiltrates composed of T lymphocytes and macrophages, which were diffusely spread, but also clustered in small foci opposed to ganglion cells, interpreted as T-cell-mediated ganglionitis. Morphometric analysis showed that CD3+ and CD8+ T cells/mm2 were significantly higher in the ganglia of LQTS/CPVT cases than in healthy controls (P=0.0018 and P=0.0009, respectively). Molecular analyses were negative for neurotropic viruses.

CONCLUSIONS

T-cell-mediated cytotoxicity toward ganglion cells may boost adrenergic activity as to trigger or enhance electric instability in LQTS/CPVT patients who are already genetically predisposed to arrhythmias.

The persistent embryonic vein in Klippel–Trenaunay syndrome

Klippel–Trenaunay syndrome (KTS) is a congenital malformation syndrome with prominent vascular anomalies. A persistent embryonic vein (PEV) may be located on the affected leg(s) of patients with KTS. Our understanding of PEVs of the legs is limited and their nomenclature is confusing. The objective of this study was to obtain further insight in the prevalence, nomenclature and etiology of PEVs of the legs in KTS and to propose a standardized description of anomalous leg veins in KTS. We investigated 70 KTS patients for the presence of PEVs (lateral marginal vein, LMV) of the legs by duplex ultrasonography. We performed histopathological analysis of a surgically excised PEV (LMV) of a typical KTS patient, and we conducted an extensive literature study. Duplex ultrasonography showed LMVs in 12/70 (17.1%) patients. The terms used to describe PEVs in the leg are quite variable, while indicating only two types: lateral marginal vein (LMV) and persistent sciatic vein (PSV). The histology of the excised LMV showed remarkable similarity with that of varicose veins found in the general population. In conclusion, the prevalence of LMVs in our KTS cohort is 17.1%. Two PEVs can be found in the legs and we propose nomenclature based on anatomical criteria, thereby using only the terms persistent lateral marginal vein and persistent sciatic vein, combined with the patency of the deep venous system. We hypothesize that PEVs are most likely caused by a genetic defect leading to abnormal venous pattern formation, which is further supported by our histopathological findings.

Quaking, an RNA-binding protein, is a critical regulator of vascular smooth muscle cell phenotype

RATIONALE

RNA-binding proteins are critical post-transcriptional regulators of RNA and can influence pre-mRNA splicing, RNA localization, and stability. The RNA-binding protein Quaking (QKI) is essential for embryonic blood vessel development. However, the role of QKI in the adult vasculature, and in particular in vascular smooth muscle cells (VSMCs), is currently unknown.

OBJECTIVE

We sought to determine the role of QKI in regulating adult VSMC function and plasticity.

METHODS AND RESULTS

We identified that QKI is highly expressed by neointimal VSMCs of human coronary restenotic lesions, but not in healthy vessels. In a mouse model of vascular injury, we observed reduced neointima hyperplasia in Quaking viable mice, which have decreased QKI expression. Concordantly, abrogation of QKI attenuated fibroproliferative properties of VSMCs, while potently inducing contractile apparatus protein expression, rendering noncontractile VSMCs with the capacity to contract. We identified that QKI localizes to the spliceosome, where it interacts with the myocardin pre-mRNA and regulates the splicing of alternative exon 2a. This post-transcriptional event impacts the Myocd_v3/Myocd_v1 mRNA balance and can be modulated by mutating the quaking response element in exon 2a of myocardin. Furthermore, we identified that arterial damage triggers myocardin alternative splicing and is tightly coupled with changes in the expression levels of distinct QKI isoforms.

CONCLUSIONS

We propose that QKI is a central regulator of VSMC phenotypic plasticity and that intervention in QKI activity can ameliorate pathogenic, fibroproliferative responses to vascular injury.

Anti-human vascular endothelial growth factor (VEGF) antibody selection for immunohistochemical staining of proliferating blood vessels

Nine commercially available vascular endothelial growth factor (VEGF) antibodies were investigated for their ability to immunostain vascular malformations (VMs) with or without immature capillary proliferation. First, all antibodies were optimized for their performance in IHC, with placenta and colon adenocarcinoma as positive control tissues. Five antibodies were regarded as unfit for VEGF immunostaining based on poor immunostaining criteria. Subsequently, Western blot analysis using VEGF rabbit polyclonal antibody (Thermo RB-9031) revealed a clear 45-kDa band in tissue extracts from VMs with immature capillary proliferation and a high Ki67-labeling index, whereas tissue extracts from mature VMs without microvascular proliferation and no Ki67-labeling index demonstrated only a very weak 45-kDa band. In contrast, two VEGF antibodies, including the popular Santa Cruz A-20, revealed bands at 45 kDa of similar intensity in tissue extracts from both types of VMs. Staining characteristics of the 45-kDa band were reflected in the results obtained in IHC.

Abstract 532: The RNA-binding Protein Quaking Critically Regulates Vascular Smooth Muscle Cell Phenotype

In response to vascular injury, smooth muscle cells (VSMC) adopt a proliferative, synthetic hypocontractile phenotype. This phenotype switch is deemed instrumental in vascular remodeling in both health and disease. Here, we detail a decisive role for the RNA-binding protein Quaking (QKI) in regulating VSMC plasticity. We identified that the RNA-binding protein Quaking (QKI) is highly expressed by neointimal VSMCs of human coronary restenotic lesions, but not in healthy vessels. In a mouse model of vascular injury, we observed reduced neointima hyperplasia in Qk v mice, which have decreased QKI expression. Concordantly, abrogation of QKI attenuated fibroproliferative properties of VSMCs, while potently inducing contractile apparatus protein expression, rendering non-contractile VSMCs with the capacity to contract. We identified that QKI localizes to the spliceosome in proliferative VSMCs, where it interacts with and impacts myocardin (pre)-mRNA metabolism by mediating myocardin exon 2a exclusion. As such, in vitro and in vivo experiments indicate that the modulation of QKI expression directly influences the myocardin_v3 / myocardin_v1 mRNA balance, which could play a role in shifting the Myocardin-induced transcriptional coactivation profile following arterial damage. We propose that QKI is a central regulator of VSMC phenotypic plasticity and that intervention in QKI activity can ameliorate pathogenic, fibroproliferative responses to vascular injury.