A porcine large animal model of radiofrequency ablation-induced left bundle branch block

Background

Electrocardiographic (ECG) features of left bundle branch (LBB) block (LBBB) can be observed in up to 20%-30% of patients suffering from heart failure with reduced ejection fraction. However, predicting which LBBB patients will benefit from cardiac resynchronization therapy (CRT) or conduction system pacing remains challenging. This study aimed to establish a translational model of LBBB to enhance our understanding of its pathophysiology and improve therapeutic approaches.

Methods

Fourteen male pigs underwent radiofrequency catheter ablation of the proximal LBB under fluoroscopy and ECG guidance. Comprehensive clinical assessments (12-lead ECG, bloodsampling, echocardiography, electroanatomical mapping) were conducted before LBBB induction, after 7, and 21 days. Three pigs received CRT pacemakers 7 days after LBB ablation to assess resynchronization feasibility.

Results

Following proximal LBB ablation, ECGs displayed characteristic LBBB features, including QRS widening, slurring in left lateral leads, and QRS axis changes. QRS duration increased from 64.2 ± 4.2 ms to 86.6 ± 12.1 ms, and R wave peak time in V6 extended from 21.3 ± 3.6 ms to 45.7 ± 12.6 ms. Echocardiography confirmed cardiac electromechanical dyssynchrony, with septal flash appearance, prolonged septal-to-posterior-wall motion delay, and extended ventricular electromechanical delays. Electroanatomical mapping revealed a left ventricular breakthrough site shift and significantly prolonged left ventricular activation times. RF-induced LBBB persisted for 3 weeks. CRT reduced QRS duration to 75.9 ± 8.6 ms, demonstrating successful resynchronization.

Conclusion

This porcine model accurately replicates the electrical and electromechanical characteristics of LBBB observed in patients. It provides a practical, cost-effective, and reproducible platform to investigate molecular and translational aspects of cardiac electromechanical dyssynchrony in a controlled and clinically relevant setting.

Regnase-1 overexpression as a therapeutic approach of Marfan syndrome

Rupture or dissection of thoracic aortic aneurysms is still the leading cause of death for patients diagnosed with Marfan syndrome. Inflammation and matrix digestion regulated by matrix metalloproteases (MMPs) play a major role in the pathological remodeling of the aortic media. Regnase-1 is an endoribonuclease shown to cleave the mRNA of proinflammatory cytokines, such as interleukin-6. Considering the major anti-inflammatory effects of regnase-1, here, we aimed to determine whether adeno-associated virus (AAV)-mediated vascular overexpression of the protein could provide protection from the development and progression of aortic aneurysms in Marfan syndrome. The overexpression of regnase-1 resulted in a marked decrease in inflammatory parameters and elastin degradation in aortic smooth muscle cells in vitro. Intravenous injection of a vascular-targeted AAV vector resulted in the efficient transduction of the aortic wall and overexpression of regnase-1 in a murine model of Marfan syndrome, associated with lower circulating levels of proinflammatory cytokines and decreased MMP expression and activity. Regnase-1 overexpression strongly improved elastin architecture in the media and reduced aortic diameter at distinct locations. Therefore, AAV-mediated regnase-1 overexpression may represent a novel gene therapy approach for inhibiting aortic aneurysms in Marfan syndrome.

Cavoatrial hypernephroma resection on cardiopulmonary bypass: Mild/normo-versus moderate hypothermia

INTRODUCION

Renal cell carcinoma (RCC) is one of the most prevalent malignant tumors. It extends up into the systemic veins and right atrium. Surgical extraction of such extensions is usually carried out using cardiopulmonary bypass (CPB) with moderate hypothermic (MH) being frequently applied in order to obtain a clear surgical field. However, due to obvious disadvantages of hypothermia, approaches with mild/normothermia (NT) during CPB have also been established. The current study aims to compare the outcomes of patients undergoing RCC tumor and extensions resection using MH versus NT.

MATERIAL AND METHODS

This is a retrospective, non-randomized study. All patients who underwent RCC tumor and extensions resection for stage III or IV (Staehler) RCC in a single center between 2006 and 2020 were included. During surgery, MH or NT were applied. CPB was realized using aortic and bicaval cannulation. We compared the procedural times, transfusion requirements and postoperative outcomes, respectively between the MH and NT groups.

RESULTS

A total of 24 consecutive patients (n(NT) = 12, n(MH) = 12) were included in the study (median age NT 68.5 and MH 66.5). The study only showed a significant difference in heart-lung machine times (median CPB time NT 45.5 min and MH 110.0 min, p = 0.004). All other results, loss of drainage, administration of blood products, as well as the postoperative course and mortality were comparable in both groups.

CONCLUSION

The results showed a high perioperative and long-term mortality. The perioperative course was similar after surgery with NT or MH. Therefore, NT which minimizes potential complications of MH should be preferred.

Analysing and improving preoperative medication management in cardiac surgery

AIMS

The objective of this study was to analyse the preoperative medication management within the cardiac surgery patient population and measure the effectiveness of an interprofessional intervention in routine care.

METHODS

A jointly developed preoperative medication management was implemented in routine care on multiple levels (inclusion in admission letter to primary care, hotline for inquiries, pocket cards for physicians and correspondence with referring centres). The effectiveness was evaluated by analysing preoperative management before and after implementation. The primary endpoint was the number of drugs managed correctly according to the guidelines after implementation. Secondary endpoints consisted amongst others of bleeding on the intensive care unit, re-thoracotomy, postoperative infarction and cerebrovascular complications. Additionally, possible associations between the correct management and different variables were investigated by multivariate analysis.

RESULTS

After the implementation, the number of drugs managed correctly according to guidelines increased from 54.0 to 73.5% (P < .001). The effect was more prominent for direct oral anticoagulants and prophylactic aspirin where the guideline adherence increased from 29.2 to 74.5% and from 78.6 to 95.1%, respectively. No difference was seen for sodium-glucose transporter-2 inhibitors, metformin, vitamin-K antagonists and dual-antiplatelet therapy. Secondary endpoints showed no safety signals with regard to bleeding or thrombotic events. In multivariate analysis, the intervention was effective (odds ratio 2.17, 95% confidence interval [1.32-3.62]) after adjusting for possible confounders.

CONCLUSION

An interprofessional programme was effective to improve preoperative medication management in cardiac surgery patients. Sodium-glucose transporter-2 inhibitors, metformin and direct oral anticoagulants appear to be especially at risk for incorrect management before cardiac surgery with possible adverse events.

Target induction of heme oxygenase-1 attenuates anti-HLA I antibody induced transplant vasculopathy in an allogeneic aortic transplantation model in mice

Introduction

After solid organ transplantation every second patient develops transplant vasculopathy (TV), which still remains the major obstacle for long-term graft survival. The main risk factor for developing TV are de novo synthesized donor-specific antibodies binding molecules of the MHC complex (HLA complex in humans, respectively) on the surface of endothelial cells (EC). EC become activated, vascular smooth muscle cells proliferate, and monocytes are recruited, contributing the development of the neointima a hallmark of TV. We have demonstrated that the anti-HLA I antibody (w6/32) significantly increases transmigration of monocytes across an endothelial monolayer in vitro. These interactions were dependent on modulating the anti-inflammatory enzyme heme oxygenase (HO)-1.

Purpose

The aim of the project is to investigate which adhesion molecule might mediate the antibody-induced transmigration of monocytes sensitive to HO-1 modulation and whether this modulation has beneficial effects in an allogenic aortic transplantation model in mice.

Methods

Before w6/32 stimulation, HO-1 was modulated by pretreating Human Coronary Artery Endothelial Cells (HCAEC) either with CoPPIX as a HO-1 activator or with statins to test for a therapeutic approach. Expression of a variety of established adhesion receptors in HCAEC was screened after HO-1 modulation and w6/32 stimulation. Antibody-induced transmigration and adhesion of THP-1 were quantified in the presence of CD62E-blocking antibodies. Thoracic aorta was transplanted into the abdominal aorta between fully MHC mismatched mice and applying the corresponding anti-MHC I antibody (SF1-1.1) induced TV. Mice were treated with CoPPIX, statins or CORM to evaluate the effects of HO-1 modulation or its metabolite CO on TV development. Statistical evaluation was performed with t-test or ANOVA.

Results

HO-1 modulation in HCAEC diminished w6/32-induced THP-1 transmigration. CD62E-expression in HCAECs was enhanced after w6/32 stimulation on mRNA and protein level, but preincubation with CoPPIX or statins reduced these effects. Incubation of HCAEC with a CD62E-blocking antibody after w6/32 stimulation significantly diminished the rate of transmigration normalized to isotype-stimulated HCAEC (isotype 100%, w6/32 + IgG 226% vs. w6/32 + CD62E-block 138%, p&lt;0.05.). Treatment of mice with CoPPIX resulted in a significant reduction of the SF1-1.1-induced number of transmigrated monocytes (SF1-1.1: 10 vs. CoPPIX: 5.4; p&lt;0.05). Application of statins (SF1-1.1: 10 vs. statin 6.6; p&lt;0.05) or CORM (CORM: 6.1 vs. iCORM: 11.3, p&lt;0.05) significantly reduces monocyte number as well. In all treatment groups, the SF1-1.1-induced neointima formation was ameliorated.

Conclusion

w6/32-induced monocyte transmigration is CD62E-dependent. SF1-1.1-induced monocytic infiltrate and intimal hyperplasia in a murine aortic transplantation model is also CD62E dependent and amenable to HO-1 modulation.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This sudy was funded by the German Research Foundation to Jan Larmann

Targeted overexpression of regnase-1 in the aorta prevents aneurysm growth in a murine model of Marfan syndrome

Background/Introduction

Marfan syndrome is a rare genetic disorder caused by mutations in the fibrillin-1 gene. This markedly affects the cardiovascular system, with patients being at a high risk of aortic aneurysm formation. The main players in the disease progression are matrix-metalloproteinases (MMPs) as well as proinflammatory cytokines, in particular interleukin-6 (IL-6). Regnase-1 is a newly identified endoribonuclease that targets the mRNA of proinflammatory markers.

Purpose

We aimed to characterize the role of regnase-1 in Marfan syndrome, particularly the effects of its overexpression on inflammatory parameters and elastin degradation in a well-characterized murine model for the disease.

Methods

Regnase-1 expression in aortic tissue was assessed using immunohistochemistry. Aortic smooth muscle cells (SMC) from mgR/mgR (Marfan) mice were transduced with vascular targeted AAV9SLR encoding either regnase-1 or enhanced green fluorescent protein (EGFP) as control. Interferon γ (IFN-γ) served as a proinflammatory stimulus and was added to cell culture medium after transduction. We measured elastin and gelatin degradation and analyzed several inflammatory parameters using real-time qPCR, Western Blot, macrophage migration assay and enzyme-linked immunosorbent assay (ELISA). For in vivo studies, mgR/mgR mice were systemically injected with NP3-tagged AAV9 expressing either regnase-1 or EGFP. 4 weeks after injection, aortic diameter was measured using echocardiography. Thoracic aorta and blood samples were taken for further analysis.

Results

Immunostaining revealed a marked decrease in regnase-1 levels in the media in aortic tissue of Marfan patients and mgR/mgR mice as compared to controls. AAV-mediated regnase-1 overexpression in vitro decreased elastin degradation and reduced secretion of proinflammatory cytokines, including IL-6, in murine Marfan SMC. It also lowered MMP9 expression and activity as well as NFkB activation. Furthermore, we could prove a marked decline in macrophage migration towards the supernatant of treated SMCs. NP3-tagged AAV9 led to efficient transduction of both aortic endothelial cells and SMC in vivo. Importantly, echocardiographic measurements showed that regnase-1 overexpression significantly reduced aortic diameter at distinct locations. In addition, elastin architecture was markedly improved in the treatment group compared to controls, male mice presented with higher numbers of structural defects. Moreover, our approach led to less expression of MMPs in the media and to lower plasma levels of IL-6 and macrophage chemoattractant protein 1 (MCP-1).

Conclusion

Here we show that AAV-mediated regnase-1 overexpression in the aorta ameliorates pathological remodeling in the aortic wall of Marfan mice and could thus potentially prevent progression of aortic aneurysms in Marfan syndrome. We underline, for the first time, a major role of regnase-1 in aortic aneurysm progression in the context of Marfan syndrome.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Deutsches Zentrum für Herz-Kreislauf-Forschung (Oliver Müller)

Short-term rapamycin treatment increases life span and attenuates aortic aneurysm in a murine model of Marfan-Syndrome

BACKGROUND

Marfan syndrome (MFS) is a genetic disorder leading to medial aortic degeneration and life-limiting dissections. To date, there is no causal prevention or therapy. Rapamycin is a potent and selective inhibitor of the mechanistic target of rapamycin (mTOR) protein kinase, regulating cell growth and metabolism. The mgR/mgR mice represent an accepted MFS model for studying aortic pathologies to understand the underlying molecular pathomechanisms. This study investigated whether rapamycin inhibits the development of thoracic aortic aneurysms and dissections in mgR/mgR mice.

METHODS

Isolated primary aortic smooth muscle cells (mAoSMCs) from mgR/mgR mice were used for in vitro studies. Two mg kg/BW rapamycin was injected intraperitoneally daily for two weeks, beginning at 7-8 weeks of age. Mice were sacrificed 30 days post-treatment. Histopathological and immunofluorescence analyses were performed using adequate tissue specimens and techniques. Animal survival was evaluated accompanied by periodic echocardiographic examinations of the aorta.

RESULTS

The protein level of the phosphorylated ribosomal protein S6 (p-RPS6), a downstream target of mTOR, was significantly increased in the aortic tissue of mgR/mgR mice. In mAoSMCs isolated from these animals, expression of mTOR, p-RPS6, tumour necrosis factor α, matrix metalloproteinase-2 and -9 was significantly suppressed by rapamycin, demonstrating its anti-inflammatory capacity. Short-term rapamycin treatment of Marfan mice was associated with delayed aneurysm formation, medial aortic elastolysis and improved survival.

CONCLUSIONS

Short-term rapamycin-mediated mTOR inhibition significantly reduces aortic aneurysm formation and thus increases survival in mgR/mgR mice. Our results may offer the first causal treatment option to prevent aortic complications in MFS patients.

Effects of Rapamycin on the Expression of Redox Enzymes in Aortic Vascular Smooth Muscle Cells from Marfan Syndrome Mice

Activation of the mechanistic target of rapamycin (mTOR) pathway has been implicated in an increasing number of diseases, including Marfan syndrome (MFS), an inherited connective tissue disorder. mTOR-dependent reactive oxygen species (ROS) formation has also been suggested to play a role in aortic aneurysm formation in MFS patients. This study aimed to characterize the effects of mTOR inhibition by rapamycin on key redox enzymes and NADPH oxidases (NOX) in cultured vascular smooth muscle cells of a murine MFS model. Therefore, the influence of 5 and 20 nmol/L rapamycin solved in 0.1% (vol/vol) DMSO on glutathione peroxidases 1 (Gpx1) and 4 (Gpx4), superoxide dismutase 2 (Sod2), and catalase (Cat) mRNA and protein expression was investigated in isolated murine aortic smooth muscle cells. Rapamycin inhibited the mRNA expression of all redox enzymes by 30-50%, except Gpx1. In the same cells, the mRNA expression of the transcription factor NFE2-related factor-2 and peroxisome proliferator-activated receptor-γ, key factors against oxidative stress, and controlling redox gene expression were also inhibited to a comparable extent under these conditions. In addition, Nox1 but not Nox4 mRNA expression was significantly inhibited by up to 40%. DMSO alone increased nearly 2-fold the redox enzyme protein expression, which was reduced considerably to basal levels by rapamycin. Proteasomal inhibition by bortezomib could not reverse the observed decrease of GPx protein content. The rapamycin-mediated decrease in GPx protein abundance was reflected in a reduced total GPx enzymatic activity. Higher rapamycin concentrations did not further decrease but led to a renewed increase in enzymatic activity despite low GPx protein concentrations. Baseline ROS formation was slightly inhibited at 13% with 5 nmol/L rapamycin and returned to baseline levels with the higher 20 nmol/L rapamycin concentration. In conclusion, this study further characterized the mechanism of action of rapamycin. It provided an insight into how rapamycin interferes with the regulation of redox homeostasis essential for ROS-dependent signaling that does not incur cellular damage.

Translational Medicine: Towards Gene Therapy of Marfan Syndrome

Marfan syndrome (MFS) is one of the most common inherited disorders of connective tissue caused by mutations of the fibrillin-1 gene (FBN1). Vascular abnormalities, such as the enlargement of the aorta with the risk of life-threatening rupture are frequently observed. However, current treatment is limited and therapeutic options focus solely on symptomatic therapy. Gene therapy focuses on genetically modifying cells to produce a therapeutic effect and may be a promising treatment option for MFS. Here, we first provide an overview of the historical background and characterization of MFS. Subsequently, we summarise current gene therapy options and possible translational concepts for this inherited disorder that affects connective tissue.

Renal Safety of Hydroxyethyl starch 130/0.42 After Cardiac Surgery: A Retrospective Cohort Analysis

Introduction

The risk for renal complications from hydroxyethyl starch 130/0.42 (HES) impacts treatment decisions in patients after cardiac surgery.

Objective

The objective of this study was to determine the impact of postoperatively administered HES on renal function and 90-day mortality compared to sole crystalloid administration in patients after elective cardiac surgery.

Methods

Using electronic health records from a university hospital, confounding-adjusted models analyzed the associations between postoperative HES administration and the occurrence of postoperative acute kidney injury. In addition, 90-day mortality was evaluated. The impact of HES dosage and timing on renal function on trajectories of estimated glomerular filtration rates over the postoperative period was investigated using linear mixed-effects models.

Results

Overall 1009 patients (45.0%) experienced acute kidney injury. Less acute kidney injury occurred in patients receiving HES compared with patients receiving only crystalloids for fluid resuscitation (43.7% vs 51.2%, p = 0.008). In multivariate acute kidney injury models, HES had a protective association (odds ratio: 0.89; 95% confidence interval 0.82–0.96). Crystalloids were not as protective as HES (odds ratio: 0.98; 95% confidence interval 0.95–1.00). There was no association between HES and 90-day mortality (odds ratio: 1.05; 95% confidence interval 0.88–1.25). Renal function trajectories were dose dependent and biphasic, HES appeared to slow down the late postoperative decline.

Conclusions

This study showed no association between HES and the postoperative occurrence of acute kidney injury and thus further closes the evidence gap on HES safety in cardiac surgery patients. Although this was a retrospective cohort study, the results indicated that HES might be safely administered to cardiac surgery patients with regard to renal outcomes, especially if it was administered early and dosed appropriately.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40264-021-01116-5.

Alginate hydrogel polymers enable efficient delivery of a vascular-targeted AAV vector into aortic tissue

Gene therapeutic approaches to aortic diseases require efficient vectors and delivery systems for transduction of endothelial cells (ECs) and smooth muscle cells (SMCs). Here, we developed a novel strategy to efficiently deliver a previously described vascular-specific adeno-associated viral (AAV) vector to the abdominal aorta by application of alginate hydrogels. To efficiently transduce ECs and SMCs, we used AAV9 vectors with a modified capsid (AAV9SLR) encoding enhanced green fluorescent protein (EGFP), as wild-type AAV vectors do not transduce ECs and SMCs well. AAV9SLR vectors were embedded into a solution containing sodium alginate and polymerized into hydrogels. Gels were surgically implanted around the adventitia of the infrarenal abdominal aorta of adult mice. Three weeks after surgery, an almost complete transduction of both the endothelium and tunica media adjacent to the gel was demonstrated in tissue sections. Hydrogel-mediated delivery resulted in induction of neutralizing antibodies but did not cause inflammatory responses in serum or the aortic wall. To further determine the translational potential, aortic tissue from patients was embedded ex vivo into AAV9SLR-containing hydrogel, and efficient transduction could be confirmed. These findings demonstrate that alginate hydrogel harboring a vascular-targeting AAV9SLR vector allows efficient local transduction of the aortic wall.

AAV-mediated AP-1 decoy oligonucleotide expression inhibits aortic elastolysis in a mouse model of marfan syndrome

AIMS

Marfan syndrome is one of the most common inherited disorders of connective tissue caused by fibrillin-1 mutations, characterized by enhanced transcription factor AP-1 DNA binding activity and subsequently abnormally increased expression and activity of matrix-metalloproteinases (MMPs). We aimed to establish a novel adeno-associated virus (AAV)-based strategy for long-term expression of an AP-1 neutralising RNA hairpin (hp) decoy oligonucleotide (dON) in the aorta to prevent aortic elastolysis in a murine model of Marfan syndrome.

METHODS AND RESULTS

Using fibrillin-1 hypomorphic mice (mgR/mgR), aortic grafts from young (9 weeks old) donor mgR/mgR mice were transduced ex vivo with AAV vectors and implanted as infrarenal aortic interposition grafts in mgR/mgR mice. Grafts were explanted after 30 days. For in vitro studies isolated primary aortic smooth muscle cells from mgR/mgR mice were used. Elastica-van-Giesson staining visualized elastolysis, ROS production was assessed using DHE staining. RNA F.I.S.H. verified AP-1 hp dON generation in the ex vivo transduced aortic tissue. MMP expression and activity were assessed by western blotting and immunoprecipitation combined with zymography.Transduction resulted in stable therapeutic dON expression in endothelial and smooth muscle cells. MMP expression and activity, ROS formation as well as expression of monocyte chemoattractant protein-1 were significantly reduced. Monocyte graft infiltration declined and the integrity of the elastin architecture was maintained. RNAseq analyzis confirmed the beneficial effect of AP-1 neutralisation on the pro-inflammatory environment in smooth muscle cells.

CONCLUSIONS

This novel approach protects from deterioration of aortic stability by sustained delivery of nucleic acids-based therapeutics and further elucidated how to interfere with the mechanism of elastolysis.

TRANSLATIONAL PERSPECTIVE

This study provides a novel single treatment option to achieve long-term expression of a transcription factor AP-1 neutralising decoy oligonucleotide in the aorta of mgR/mgR mice with the potential to prevent life-threatening elastolysis and aortic complications.

Vascular Signaling in Allogenic Solid Organ Transplantation - The Role of Endothelial Cells

Graft rejection remains the major obstacle after vascularized solid organ transplantation. Endothelial cells, which form the interface between the transplanted graft and the host’s immunity, are the first target for host immune cells. During acute cellular rejection endothelial cells are directly attacked by HLA I and II-recognizing NK cells, macrophages, and T cells, and activation of the complement system leads to endothelial cell lysis. The established forms of immunosuppressive therapy provide effective treatment options, but the treatment of chronic rejection of solid organs remains challenging. Chronic rejection is mainly based on production of donor-specific antibodies that induce endothelial cell activation—a condition which phenotypically resembles chronic inflammation. Activated endothelial cells produce chemokines, and expression of adhesion molecules increases. Due to this pro-inflammatory microenvironment, leukocytes are recruited and transmigrate from the bloodstream across the endothelial monolayer into the vessel wall. This mononuclear infiltrate is a hallmark of transplant vasculopathy. Furthermore, expression profiles of different cytokines serve as clinical markers for the patient’s outcome. Besides their effects on immune cells, activated endothelial cells support the migration and proliferation of vascular smooth muscle cells. In turn, muscle cell recruitment leads to neointima formation followed by reduction in organ perfusion and eventually results in tissue injury. Activation of endothelial cells involves antibody ligation to the surface of endothelial cells. Subsequently, intracellular signaling pathways are initiated. These signaling cascades may serve as targets to prevent or treat adverse effects in antibody-activated endothelial cells. Preventive or therapeutic strategies for chronic rejection can be investigated in sophisticated mouse models of transplant vasculopathy, mimicking interactions between immune cells and endothelium.

AAV-mediated TIMP-1 overexpression in aortic tissue reduces the severity of allograft vasculopathy in mice

BACKGROUND

Allograft vasculopathy (AV) is the primary limiting factor for long-term graft survival. An increased activity of matrix metalloproteinases (MMPs) contributes to neointima formation in AV and represents a potential therapeutic target. Adeno-associated virus (AAV)-mediated gene therapy comprises a potentially benign vector model for the long-term expression of MMP antagonists.

METHODS

Aortic allografts from DBA/2 mice were incubated with control buffer, AAV-enhanced green fluorescence protein (EGFP), or tissue inhibitor of metalloproteinases 1 (TIMP-1)-loaded AAV (AAV-TIMP-1) and transplanted into the infrarenal aorta of C57BL/6 mice. Cyclosporine A (10 mg/kg body weight) was administered daily. Explantation as well as histomorphometric and immunohistochemical evaluation was performed after 30 days. Matrix metalloproteinase (MMP) activity was visualized by gelatin in situ zymography.

RESULTS

Intima-to-media area ratio and neointima formation were significantly reduced in the AAV-TIMP-1 treatment group compared with those in the control group (by 40%; p < 0.001) and the AAV-EGFP group (by 38.2%; p < 0.001). TIMP-1 overexpression positively affected several pathomechanisms for the development of AV both in vitro and in vivo as compared to that in the control groups: endothelium integrity was preserved as shown by zona occludens 1 and occludin staining; MMP9 expression and activity were significantly reduced (p = 0.01); and smooth muscle cell migration was significantly reduced as smooth muscle actin positive cells predominantly remained in the aortic media in the treatment group (p = 0.001). Moreover, macrophage infiltration was markedly reduced by 49% in the AAV-TIMP-1 group (p < 0.001).

CONCLUSION

Immediate post-harvesting allograft incubation with AAV-TIMP-1 reduces neointima formation and macrophage infiltration, constituting a possible adjunct therapeutic strategy to preserve graft function after transplantation.

The reimplantation valve-sparing aortic root replacement technique for patients with Marfan syndrome: A single-center experience

Valve-sparing aortic root replacement (VSARR) through reimplantation technique is widely regarded as optimal surgical approach for Marfan syndrome (MFS) patients. Perioperative and long-term data from all MFS patients undergoing VSARR using David's technique at our center from 2007-2018 were analyzed. We included 56 patients with a mean age of 32.3 ± 12.3 years. Logistic EuroSCORE was 7.96 ± 5.2. Among others concomitant surgical procedures included aortic arch surgery (8.9%), mitral valve repair (23.2%) and replacement (1.7%). There were no operative deaths, nor in-hospital-mortality. One patient underwent re-exploration for bleeding, dialysis and pacemaker implantation was required in one case each. There was no occurrence of low-output syndrome nor neurological complications. Significant gender differences were not found, except for intraoperative blood transfusion occurring significantly more often in the female gender (p = 0.009). Despite significantly longer procedural times, concomitant surgery did not negatively impact overall outcome. Freedom of reoperation of the aortic root was 100% at 1 year, 97.7% at 8 years. Until last follow-up (61 ± 38 month) all patients survived, with no evidence of endocarditis. We emphasize once more that VSARR using David's procedure is a safe method for MFS patients with excellent long-term results even if concomitant procedures are performed.

Marfan syndrome: A therapeutic challenge for long-term care

Marfan syndrome (MFS) is an autosomal dominant genetic disorder caused by mutations in the fibrillin-1 gene. Acute aortic dissection is the leading cause of death in patients suffering from MFS and consequence of medial degeneration and aneurysm formation. In addition to its structural function in the formation of elastic fibers, fibrillin has a major role in keeping maintaining transforming growth factor β (TGF-β) in an inactive form. Dysfunctional fibrillin increases TGF-β bioavailability and concentration in the extracellular matrix, leading to activation of proinflammatory transcription factors. In turn, these events cause increased expression of matrix metalloproteinases and cytokines that control the migration and infiltration of inflammatory cells into the aorta. Moreover, TGF-β causes accumulation of reactive oxygen species leading to further degradation of elastin fibers. All these processes result in medial elastolysis, which increases the risk of vascular complications. Although MFS is a hereditary disease, symptoms and traits are usually not noticeable at birth. During childhood or adolescence affected individuals present with severe tissue weaknesses, especially in the aorta, heart, eyes, and skeleton. Considering this, even young patients should avoid activities that exert additional stress and pressure on the aorta and the cardiovascular system. Thus, if the diagnosis is made and prophylactic treatment is initiated in a timely fashion, MFS and its preliminary pathophysiologic vascular remodeling can be successfully ameliorated reducing the risk of life-threatening complications. This commentary focuses on new research opportunities and molecular findings on MFS, discusses future challenges and possible long-term therapies.

An integrative systems approach identifies novel candidates in Marfan syndrome-related pathophysiology

Marfan syndrome (MFS) is an autosomal dominant genetic disorder caused by mutations in the FBN1 gene. Although many peripheral tissues are affected, aortic complications, such as dilation, dissection and rupture, are the leading causes of MFS‐related mortality. Aberrant TGF‐beta signalling plays a major role in the pathophysiology of MFS. However, the contributing mechanisms are still poorly understood. Here, we aimed at identifying novel aorta‐specific pathways involved in the pathophysiology of MFS. For this purpose, we employed the Fbn1 under‐expressing mgR/mgR mouse model of MFS. We performed RNA‐sequencing of aortic tissues of 9‐week‐old mgR/mgR mice compared with wild‐type (WT) mice. With a false discovery rate <5%, our analysis revealed 248 genes to be differentially regulated including 20 genes previously unrelated with MFS‐related pathology. Among these, we identified Igfbp2, Ccl8, Spp1, Mylk2, Mfap4, Dsp and H19. We confirmed the expression of regulated genes by quantitative real‐time PCR. Pathway classification revealed transcript signatures involved in chemokine signalling, cardiac muscle contraction, dilated and hypertrophic cardiomyopathy. Furthermore, our immunoblot analysis of aortic tissues revealed altered regulation of pSmad2 signalling, Perk1/2, Igfbp2, Mfap4, Ccl8 and Mylk2 protein levels in mgR/mgR vs WT mice. Together, our integrative systems approach identified several novel factors associated with MFS‐aortic‐specific pathophysiology that might offer potential novel therapeutic targets for MFS.

Reduction of Transplant Vasculopathy by Intraoperative Nucleic Acid-based Therapy in a Mouse Aortic Allograft Model

BACKGROUND

 Transplant vasculopathy (TV) is the main limiting factor for long-term graft survival characterized by fibrosis, myofibroblast, and smooth muscle cell (SMC) proliferation. Decoy oligodeoxynucleotide (dODN) against the transcription factor activator protein-1 (AP-1) might interfere with the expression of AV-related genes that govern neointima formation.

METHODS

 Aortic allografts from DBA/2 mice were incubated with control buffer, consensus, or mutated control AP-1 dODN and were transplanted into the infrarenal aorta of C57BL/6 mice. Cyclosporine A (10 mg/kg body weight [BW]) was administered daily. Explantation and histomorphometric and immunohistochemical evaluation was performed after 30 days. Matrix metalloproteinase (MMP) activity was visualized by gelatin in situ zymography.

RESULTS

 Intima-to-media (I/M) ratio and neointima formation were significantly reduced in the consensus AP-1 dODN treatment group by 37% (p < 0.05) and 67% (p < 0.01), respectively. SMC α-actin-2 staining and macrophage marker expression revealed a marked reduction in the neointima. I/M ratio was found to correlate with the number of tissue macrophages (p < 0.05). MMP and fibrosis marker expression were not significantly altered.

CONCLUSION

 Intraoperative AP-1dODN utilization might be a strategy to preserve graft function after transplantation.

AP-1 Oligodeoxynucleotides Reduce Aortic Elastolysis in a Murine Model of Marfan Syndrome

Marfan syndrome is characterized by high expression of matrix metalloproteinases (MMPs) in aortic smooth muscle cells (AoSMCs) associated with medial elastolysis and aortic root aneurysm. We aimed to reduce aortic elastolysis through decrease of MMP expression with decoy oligodeoxynucleotides (dODNs) neutralizing the transcription factor activating factor-1 (AP-1). AP-1 abundance in nuclear extracts as well as MMP-2 and MMP-9 expression were significantly increased in isolated mAoSMC of mgR/mgR Marfan mice compared to wild-type cells. Exposure to AP-1 neutralizing dODNs resulted in a significant reduction of basal and interleukin-1β-stimulated MMP expression and activity in mAoSMCs. Moreover, increased migration and formation of superoxide radical anions was substantially decreased in mAoSMCs by AP-1 dODN treatment. Aortic grafts from donor Marfan mice were treated with AP-1- dODN ex vivo and implanted as infrarenal aortic interposition grafts in mgR/mgR mice. Pretreatment of aortic grafts with AP-1 dODN led to reduced elastolysis, macrophage infiltration, and MMP activity. Permeability of the endothelial monolayer was increased for dODN in mgR/mgR aortae with observed loss of tight junction proteins ZO-1 and occludin, enabling dODN to reach the tunica media. Targeting AP-1 activity offers a new potential strategy to treat the vascular phenotype associated with Marfan syndrome.

Ischemic Colitis after Cardiac Surgery: Can We Foresee the Threat?

Introduction

Ischemic colitis (IC) remains a great threat after cardiac surgery with use of extracorporeal circulation. We aimed to identify predictive risk factors and influence of early catecholamine therapy for this disease.

Methods

We prospectively collected and analyzed data of 224 patients, who underwent laparotomy due to IC after initial cardiac surgery with use of extracorporeal circulation during 2002 and 2014. For further comparability 58 patients were identified, who underwent bypass surgery, aortic valve replacement or combination of both. Age ±5 years, sex, BMI ± 5, left ventricular function, peripheral arterial disease, diabetes and urgency status were used for match-pair analysis (1:1) to compare outcome and detect predictive risk factors. Highest catecholamine doses during 1 POD were compared for possible predictive potential.

Results

Patients’ baseline characteristics showed no significant differences. In-hospital mortality of the IC group with a mean age of 71 years (14% female) was significantly higher than the control group with a mean age of 70 (14% female) (67% vs. 16%, p<0.001). Despite significantly longer bypass time in the IC group (133 ± 68 vs. 101 ± 42, p = 0.003), cross-clamp time remained comparable (64 ± 33 vs. 56 ± 25 p = 0.150). The majority of the IC group suffered low-output syndrome (71% vs. 14%, p<0.001) leading to significant higher lactate values within first 24h after operation (55 ± 46 mg/dl vs. 31 ± 30 mg/dl, p = 0.002). Logistic regression revealed elevated lactate values to be significant predictor for colectomy during the postoperative course (HR 1.008, CI 95% 1.003–1.014, p = 0.003). However, Receiver Operating Characteristic Curve calculates a cut-off value for lactate of 22.5 mg/dl (sensitivity 73% and specificity 57%). Furthermore, multivariate analysis showed low-output syndrome (HR 4.301, CI 95% 2.108–8.776, p<0.001) and vasopressin therapy (HR 1.108, CI 95% 1.012–1.213, p = 0.027) significantly influencing necessity of laparotomy.

Conclusion

Patients who undergo laparotomy for IC after initial cardiac surgery have a substantial in-hospital mortality risk. Early postoperative catecholamine levels do not influence the development of an IC except vasopressin. Elevated lactate remains merely a vague predictive risk factor.

Loss of Endothelial Barrier in Marfan Mice (mgR/mgR) Results in Severe Inflammation after Adenoviral Gene Therapy

Objectives

Marfan syndrome is an autosomal dominant inherited disorder of connective tissue. The vascular complications of Marfan syndrome have the biggest impact on life expectancy. The aorta of Marfan patients reveals degradation of elastin layers caused by increased proteolytic activity of matrix metalloproteinases (MMPs). In this study we performed adenoviral gene transfer of human tissue inhibitor of matrix metalloproteinases-1 (hTIMP-1) in aortic grafts of fibrillin-1 deficient Marfan mice (mgR/mgR) in order to reduce elastolysis.

Methods

We performed heterotopic infrarenal transplantation of the thoracic aorta in female mice (n = 7 per group). Before implantation, mgR/mgR and wild-type aortas (WT, C57BL/6) were transduced ex vivo with an adenoviral vector coding for human TIMP-1 (Ad.hTIMP-1) or β-galactosidase (Ad.β-Gal). As control mgR/mgR and wild-type aortas received no gene therapy. Thirty days after surgery, overexpression of the transgene was assessed by immunohistochemistry (IHC) and collagen in situ zymography. Histologic staining was performed to investigate inflammation, the neointimal index (NI), and elastin breaks. Endothelial barrier function of native not virus-exposed aortas was evaluated by perfusion of fluorescent albumin and examinations of virus-exposed tissue were performed by transmission electron microscopy (TEM).

Results

IHC and ISZ revealed sufficient expression of the transgene. Severe cellular inflammation and intima hyperplasia were seen only in adenovirus treated mgR/mgR aortas (Ad.β-Gal, Ad.hTIMP-1 NI: 0.23; 0.43), but not in native and Ad.hTIMP-1 treated WT (NI: 0.01; 0.00). Compared to native mgR/mgR and Ad.hTIMP-1 treated WT aorta, the NI is highly significant greater in Ad.hTIMP-1 transduced mgR/mgR aorta (p = 0.001; p = 0.001). As expected, untreated Marfan grafts showed significant more elastolysis compared to WT (p = 0.001). However, elastolysis in Marfan aortas was not reduced by adenoviral overexpression of hTIMP-1 (compared to untreated Marfan aorta: Ad.hTIMP-1 p = 0.902; control Ad.β-Gal. p = 0.165). The virus-untreated and not transplanted mgR/mgR aorta revealed a significant increase of albumin diffusion through the endothelial barrier (p = 0.037). TEM analysis of adenovirus-exposed mgR/mgR aortas displayed disruption of the basement membrane and basolateral space.

Conclusions

Murine Marfan aortic grafts developed severe inflammation after adenoviral contact. We demonstrated that fibrillin-1 deficiency is associated with relevant dysfunction of the endothelial barrier that enables adenovirus to induce vessel-harming inflammation. Endothelial dysfunction may play a pivotal role in the development of the vascular phenotype of Marfan syndrome.