Cardiovascular diseases are accompanied by changes in the extracellular matrix (ECM) including the re-expression of fibronectin and tenascin-C splicing variants. Using human recombinant small immunoprotein (SIP) format antibodies, a molecular targeting of these proteins is of therapeutic interest. Tissue samples of the right atrial auricle from patients with coronary artery disease and valvular heart disease were analysed by PCR based ECM gene expression profiling. Moreover, the re-expression of fibronectin and tenascin-C splicing variants was investigated by immunofluoerescence labelling. We demonstrated changes in ECM gene expression depending on histological damage or underlying cardiac disease. An increased expression of fibronectin and tenascin-C mRNA in association to histological damage and in valvular heart disease compared to coronary artery disease could be shown. There was a distinct re-expression of ED-A containing fibronectin and A1 domain containing tenascin-C detectable with human recombinant SIP format antibodies in diseased myocardium. ED-A containing fibronectin showed a clear vessel positivity. For A1 domain containing tenascin-C, there was a particular positivity in areas of interstitial and perivascular fibrosis. Right atrial myocardial tissue is a valuable model to investigate cardiac ECM remodelling. Human recombinant SIP format antibodies usable for an antibody-mediated targeted delivery of drugs might offer completely new therapeutic options in cardiac diseases.

Aortic valve stenosis (AVS) and coronary artery disease (CAD) are accompanied by changes in the cardiac extra cellular matrix (cECM) including the re-expression of oncofetal fibronectin (Fn) and tenascin-C (Tn-C) variants. Human antibodies against these variants are usable for targeted therapy. Aim of the study was the comparative analysis of cECM remodelling in tissue samples from right atrial auricle (RAA) and left ventricular septum (LVS). RAA and LVS specimens from 30 patients (17 × AVS; 13 × AVS+CAD) were analysed with respect to histological changes and ECM remodelling using PCR based ECM gene expression profiling. Re-expression of ED-A(+) Fn and A1(+) Tn-C was investigated on the mRNA and on the protein level. For immunofluorescence, human recombinant small immunoprotein (SIP) format antibodies were used. There was a positive correlation of the grade of histological changes in RAA and corresponding LVS samples (r = 0.695). ECM gene expression levels were higher in LVS compared to RAA. For 24 genes, a corresponding relevant (>2.5-fold) up- or down-regulation in RAA and LVS occurred. Using SIP antibodies, a positive correlation of protein deposition levels in RAA and corresponding LVS (r = 0.818) could be shown for ED-A(+) Fn. Cardiac tissue remodelling is likely a process involving the entire heart reflected by intra-individually comparable histology and cECM changes in RAA and LVS samples. ED-A(+) Fn might be an excellent target for an antibody-mediated delivery of diagnostic or therapeutic agents. The RAA is a valuable and representative tool to evaluate cardiac remodelling and to plan individualized therapy.

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Introduction Echocardiographic detection of residual peri-device leakage (PDL) after percutaneous left atrial appendage closure (LAAC) remains crucial. Significance of PDL and cardiac tissue remodeling after LAAC are still poorly understood but might have diagnostic implications. This study aims to characterize and verify if a novel echocardiographic classification system to asses the success of LAAC in combination with quantifiable biomarkers of cardiovascular tissue remodeling can help in the prediction of PDL. Methods Patients eligible for LAAC were included. Serum levels of the cardiac remodeling marker Galectin-3 were determined before device implantation (baseline), 45 days (45d) and 6 months (6M) after LAAC using ELISAs. Transesophageal echocardiography (TEE) was carried out to assess success of the LAAC procedure. All echo images were retrospectively evaluated by two independent investigators. Based on the amount of echodensity and luceny inside the devices after LAAC, three types can be distinguished that grade the degree of closure of the LAA. Type A has complete homogenous echodensity in 0, 45, 90 and 135°, indicating completely thrombosed device. Type B shows inhomogeneous echo-lucencies (<50% of device). Type C describes a partially thrombosed device with echo-lucencies >50%. Novel classification according to Hamadanchi, Jena, Germany (Fig. 1). Results We included 44 patients (characteristics listed in Table 1). Complete LAAC (without any residual flow) was achieved in 64% (28 patients) after 45 days and in 80% (35 patients) after 6 months. Mean PDL diameter was 3.5±1.5mm. Type A showed the lowest rate of PDL after 45d (Type A: 22% vs. Type B: 33% vs. Type C: 88%; p=0.007) and after 6M (Type A: 12% vs. Type B: 28% vs. Type C: 100%; p=0.002). Galectin-3 levels did not show a relevant difference regarding the type of AF at baseline (paroxysmal AF: 11.7±5.4 ng/ml vs. permanent AF: 12.1±6.3 ng/ml; p=0.45). We observed a significant increase and distribution of serum levels of Galectin-3 [ng/ml] after 45 days among the three types (Baseline: 13.1±5.8; 45d: 16.3±7.2 (Type A) vs. 19.2±8.6 (Type B) vs. 25.8±9.4 (Type C); p=0.031) followed after 6 months by a drop of Galectin-3 for type A and B toward and below baseline levels (6M: 8.9±3.1 (Type A) vs. 12.4±5.5 (Type B)) whereas type C persisted in showing elevated Galectin-3 levels compared to all other types (6M: 17.5±4.5 (Type C); p<0.001), Fig. 2. Correlation analysis shows a significant negative correlation trend between Galectin-3 and mean PDL diameter (−0.51; p=0.016) after 45 days and a relevant positive correlation after 6 months (0.58; p=0.017). Conclusion After LAAC, Galectin-3 levels are elevated, as a marker of myocardial fibrosis in the LAA. Depending on the degree of closure of the LAA, Galectin-3 decreases to the baseline level or stays elevated in case of relevant PDL and could therefore be considered as a new biomarker for closure success. Funding Acknowledgement Type of funding source: None

Introduction Left atrial cardiac tissue remodeling following left atrial appendage closure (LAAC) is a scientifically neglected phenomenon until now but might have impact on functional outcome of patients suffering from atrial fibrillation (AF). Thus, our study is focused on quantification of key biomarkers reflecting fibrosis development as a major component within cardiovascular tissue remodeling. Methods Patients (CHA2DS2VASC score ≥1, HASBLED score ≥3) with bleeding complications under anticoagulation therapy and therefore eligible for LAAC were included in the present study. Serum levels of biomarkers of cardiac fibrosis and remodeling (Galectin-3, ST2/IL-2, ST2/IL-1, B domain containing Tenascin-C (B+ Tn-C), C domain containing Tenascin- C (C+ Tn-C)) were determined before device implantation (baseline), 45 days (45d) and 6 months (6M) after LAAC using commercially available ELISAs. To quantify functional outcome, all patients performed a 6-minutes walk test (6- MWT). Transesophageal echocardiography (TEE) was carried out to assess success of the LAAC procedure regarding peri-device leakage (PDL). Results We included 33 patients (age: 73.5±6.7 years; 21 men (64%) and 12 women (36%); BMI: 29.1±5.1 kg/m2; CHA2DS2VASC score: 4.2±1.2; left ventricular ejection fraction: 61.1±9.3%; mean occluder size: 25.9±3.9 mm; type of AF: 46% paroxysmal (15 patients), 55% permanent (18 patients)). Complete LAAC (without any residual low) was achieved in 60% (19 patients) after 45 days and in 87% (29 patients) after 6 months. At baseline, Galectin-3 levels did not show a relevant difference regarding the type of AF (paroxysmal AF: 14.7±5.4 ng/ml vs. permanent AF: 13.1±6.3 ng/ml; p=0.45). We observed a significant increase of serum levels of Galectin-3 [ng/ml] after 45 days vs. baseline (baseline: 13.3±5.8 vs. 45d: 18.3±10.6; p=0.005) with a return to baseline levels after 6 months (baseline: 13.3±5.8 vs. 6M: 12.5±5.4; p=0.28). Compared to patients with successful LAAC, patients with PDL had a trend towards higher levels of Galectin-3 after 6 months (11.3±5.5 ng/ml vs. 16.1±4.1 ng/ml, p=0.09). Measurements of other fibrosis markers were statistically not significantly different. The walking distance measured by the 6-MWT increased significantly from 298.5±89.5 meters at baseline to 335.5±95.1 meters (p=0.04) after 45d and remained significantly elevated after 6M (346.7±122.7 meters; p=0.02). Conclusion The implantation of an LAA occluder device is accompanied by significantly increased circulating levels of the fibrosis biomarker Galectin-3 after 45 days in patients with AF. The regression in serum levels after 6 months probably reflects a successful fibrotic remodeling in the left atrial appendage over time and might be used as surrogate parameter for LAAC success. Increased and stable exercise tolerance after 45 days can be observed. Funding Acknowledgement Type of funding source: None