Fibrotic Aortic Valve Stenosis in Hypercholesterolemic/Hypertensive Mice

Diagnostic Value of Aortic Valve Calcification Levels in the Assessment of Low-Gradient Aortic Stenosis

BACKGROUND

In patients with low-gradient aortic stenosis (AS) and low transvalvular flow, dobutamine stress echocardiography (DSE) is recommended to determine AS severity, whereas the degree of aortic valve calcification (AVC) supposedly correlates with AS severity according to current European and American guidelines.

OBJECTIVES

The purpose of this study was to assess the relationship between AVC and AS severity as determined using echocardiography and DSE in patients with aortic valve area <1 cm2 and peak aortic valve velocity <4.0 m/s.

METHODS

All patients underwent DSE to determine AS severity and multislice computed tomography to quantify AVC. Receiver-operating characteristics curve analysis was used to assess the diagnostic value of AVC for AS severity grading as determined using echocardiography and DSE in men and women.

RESULTS

A total of 214 patients were included. Median age was 78 years (25th-75th percentile: 71-84 years) and 25% were women. Left ventricular ejection fraction was reduced (<50%) in 197 (92.1%) patients. Severe AS was diagnosed in 106 patients (49.5%). Moderate AS was diagnosed in 108 patients (50.5%; in 77 based on resting transthoracic echocardiography, in 31 confirmed using DSE). AVC score was high (≥2,000 for men or ≥1,200 for women) in 47 (44.3%) patients with severe AS and in 47 (43.5%) patients with moderate AS. AVC sensitivity was 44.3%, specificity was 56.5%, and positive and negative predictive values for severe AS were 50.0% and 50.8%, respectively. Area under the receiver-operating characteristics curve was 0.508 for men and 0.524 for women.

CONCLUSIONS

Multi-slice computed tomography-derived AVC scores showed poor discrimination between grades of AS severity using DSE and cannot replace DSE in the diagnostic work-up of low-gradient severe AS.

Type 2 Diabetes, Circulating Metabolites, and Calcific Aortic Valve Stenosis: A Mendelian Randomization Study

Epidemiological studies have shown an association between type 2 diabetes (T2D) and calcific aortic valve stenosis (CAVS), but the potential causal relationship and underlying mechanisms remain unclear. Therefore, we conducted a two-sample and two-step Mendelian randomization (MR) analysis to evaluate the association of T2D with CAVS and the mediating effects of circulating metabolites and blood pressure using genome-wide association study (GWAS) summary statistics. The inverse variance weighted (IVW) method was used for the primary MR analysis, and comprehensive sensitivity analyses were performed to validate the robustness of the results. Our results showed that genetically predicted T2D was associated with increased CAVS risk (OR 1.153, 95% CI 1.096-1.214, p < 0.001), and this association persisted even after adjusting for adiposity traits in multivariable MR analysis. Furthermore, the two-step MR analysis identified 69 of 251 candidate mediators that partially mediated the effect of T2D on CAVS, including total branched-chain amino acids (proportion mediated: 23.29%), valine (17.78%), tyrosine (9.68%), systolic blood pressure (8.72%), the triglyceride group (6.07-11.99%), the fatty acid group (4.78-12.82%), and the cholesterol group (3.64-11.56%). This MR study elucidated the causal impact of T2D on CAVS risk independently of adiposity and identified potential mediators in this association pathways. Our findings shed light on the pathogenesis of CAVS and suggest additional targets for the prevention and intervention of CAVS attributed to T2D.

Toll-like Receptor 4 Differentially Modulates Cardiac Function in Response to Chronic Exposure to High-Fat Diet and Pressure Overload

BACKGROUND/AIM

The impact of myocardial stressors such as high-fat diet (HFD) and pressure overload has been extensively studied. Toll-like receptor 4 (TLR4) deficiency has been suggested to have a protective role in response to these stressors, although some conflicting data exist. Furthermore, there is limited information about the role of TLR4 on cardiac remodeling in response to long-term exposure to stressors. This study aims to investigate the effects of TLR4 deficiency on cardiac histology and physiology in response to chronic stressors.

METHODS

TLR4-deficient (TLR4-/-) and wild-type (WT) mice were subjected to either HFD or a normal diet (ND) for 28 weeks. Another group underwent abdominal aortic constriction (AAC) or a sham procedure and was monitored for 12 weeks. Inflammatory markers, histology, and echocardiography were used to assess the effects of these interventions.

RESULTS

TLR4-/- mice exhibited reduced cardiac hypertrophy and fibrosis after long-term HFD exposure compared to ND without affecting cardiac function. On the other hand, TLR4 deficiency worsened cardiac function in response to AAC, leading to decreased ejection fraction (EF%) and increased end-systolic volume (ESV).

CONCLUSIONS

TLR4 deficiency provided protection against HFD-induced myocardial inflammation but impaired hemodynamic cardiac function under pressure overload conditions. These findings highlight the crucial role of TLR4 and its downstream signaling pathway in maintaining cardiac output during physiologic cardiac hypertrophy in response to pressure overload.

Challenges of aortic valve tissue culture - maintenance of viability and extracellular matrix in the pulsatile dynamic microphysiological system

BACKGROUND

Calcific aortic valve disease (CAVD) causes an increasing health burden in the 21st century due to aging population. The complex pathophysiology remains to be understood to develop novel prevention and treatment strategies. Microphysiological systems (MPSs), also known as organ-on-chip or lab-on-a-chip systems, proved promising in bridging in vitro and in vivo approaches by applying integer AV tissue and modelling biomechanical microenvironment. This study introduces a novel MPS comprising different micropumps in conjunction with a tissue-incubation-chamber (TIC) for long-term porcine and human AV incubation (pAV, hAV).

RESULTS

Tissue cultures in two different MPS setups were compared and validated by a bimodal viability analysis and extracellular matrix transformation assessment. The MPS-TIC conjunction proved applicable for incubation periods of 14-26 days. An increased metabolic rate was detected for pulsatile dynamic MPS culture compared to static condition indicated by increased LDH intensity. ECM changes such as an increase of collagen fibre content in line with tissue contraction and mass reduction, also observed in early CAVD, were detected in MPS-TIC culture, as well as an increase of collagen fibre content. Glycosaminoglycans remained stable, no significant alterations of α-SMA or CD31 epitopes and no accumulation of calciumhydroxyapatite were observed after 14 days of incubation.

CONCLUSIONS

The presented ex vivo MPS allows long-term AV tissue incubation and will be adopted for future investigation of CAVD pathophysiology, also implementing human tissues. The bimodal viability assessment and ECM analyses approve reliability of ex vivo CAVD investigation and comparability of parallel tissue segments with different treatment strategies regarding the AV (patho)physiology.

Activation of the Hedgehog signaling pathway leads to fibrosis in aortic valves

BACKGROUND

Fibrosis is a pathological wound healing process characterized by excessive extracellular matrix deposition, which interferes with normal organ function and contributes to ~ 45% of human mortality. Fibrosis develops in response to chronic injury in nearly all organs, but the a cascade of events leading to fibrosis remains unclear. While hedgehog (Hh) signaling activation has been associated with fibrosis in the lung, kidney, and skin, it is unknown whether hedgehog signaling activation is the cause or the consequence of fibrosis. We hypothesize that activation of hedgehog signaling is sufficient to drive fibrosis in mouse models.

RESULTS

In this study, we provide direct evidence to show that activation of Hh signaling via expression of activated smoothened, SmoM2, is sufficient to induce fibrosis in the vasculature and aortic valves. We showed that activated SmoM2 -induced fibrosis is associated with abnormal function of aortic valves and heart. The relevance of this mouse model to human health is reflected in our findings that elevated GLI expression is detected in 6 out of 11 aortic valves from patients with fibrotic aortic valves.

CONCLUSIONS

Our data show that activating hedgehog signaling is sufficient to drive fibrosis in mice, and this mouse model is relevant to human aortic valve stenosis.

Revisiting the Aortic Valve Calcium Score in Evaluating the Severity of Aortic Stenosis in Japanese Patients - A Single-Center Study

Background: In patients with aortic stenosis (AS), measurement of aortic valve calcification (AVC) using computed tomography (CT) is recommended in cases where echocardiographic measurements are inconclusive. However, sex-specific AVC thresholds proposed in the guidelines for predicting severe AS (women: 1,200 arbitrary units [AU]; men: 2,000 AU) are based on studies from Western countries. Methods and Results: We retrospectively included 512 Japanese patients with at least moderate AS who underwent transthoracic echocardiography and CT. AVC was quantified using the Agatston method. AVC was positively correlated with peak aortic jet velocity and mean transvalvular gradient (mPG), and negatively correlated with aortic valve area (AVA) and the AVA index (AVAi). In 257 patients with concordant AS grading (152 severe AS [AVAi ≤0.6 cm2/m2, mPG ≥40 mmHg], 105 moderate AS [AVAi >0.6 cm2/m2, mPG <40 mmHg]), receiver operating characteristic curve analysis of AVC predicting severe AS yielded an area under the curve of 0.91 (95% confidence interval [CI] 0.87-0.95; P<0.001) in women and 0.86 (95% CI 0.75-0.98; P<0.001) in men. The optimal thresholds (women: 1,379 AU; men: 1,802 AU) were close to those proposed in the guidelines. The diagnostic accuracy of the thresholds in the guidelines was similar to that of the optimal thresholds. Conclusions: The sex-specific AVC thresholds proposed in international guidelines can be applied to Japanese AS patients, yielding similar diagnostic accuracy as the optimal cut-off derived from the study patients.

Transcriptome Sequencing Data Reveal LncRNA-miRNA-mRNA Regulatory Network in Calcified Aortic Valve Disease

Background

Calcified aortic valve disease (CAVD) is one of the most common valvular heart diseases in the elderly population. However, no effective medical treatments have been found to interfere with the progression of CAVD, and specific molecular mechanisms of CAVD remain unclear.

Materials and Methods

Transcriptome sequencing data of GSE55492 and GSE148219 were downloaded from the European Nucleotide Archive, and the microarray dataset, GSE12644 was acquired from the Gene Expression Omnibus database. Software, including FastQC, HISAT2, samtools, and featureCounts was applied to generate the read count matrix. The “Limma” package in R was utilized to analyze differentially expressed genes (DEGs). Thereafter, weighted gene co-expression network analysis, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and the protein-protein interaction (PPI) network were used to identify hub genes associated with CAVD, which were further validated by receiver operating characteristic curve (ROC) analysis using GSE12644. The long non-coding RNA (LncRNA)-mediated regulatory network was established based on the differentially expressed LncRNAs and hub genes, which were detected using quantitative real-time PCR (qRT-PCR) in clinical samples and valve interstitial cells. Moreover, CIBERSORT was used to calculate the expression distribution of immune cell infiltration in CAVD.

Results

A total of 126 DEGs were included in the PPI network. PI3K-Akt signaling pathway, ECM-receptor interaction, hematopoietic cell lineage, cell adhesion molecules, and focal adhesion were the most enriched pathways revealed by KEGG. Four LncRNAs, including TRHDE-AS1, LINC00092, LINC01094, and LINC00702 were considered the differentially expressed LncRNA. SPP1, TREM1, GPM6A, CCL19, CR1, NCAM1, CNTN1, TLR8, SDC1, and COL6A6 were the 10 hub genes identified to be associated with CAVD. Moreover, the calcified aortic valve samples had a greater level of Tregs, naïve B cells, and M0 macrophages than the noncalcified ones, whereas CAVD samples had a lower M2 macrophage expression compared to the noncalcified valve tissues.

Conclusion

The current study identified SPP1, TREM1, TLR8, SDC1, GPM6A, and CNTN1 as hub genes that could potentially be associated with CAVD. The LINC00702–miR-181b-5p–SPP1 axis might participate in the development of CAVD. Additionally, M2 macrophages, Tregs, naïve B cells, and M0 macrophages might possibly play a role in the initiation of CAVD.

Genes That Escape X Chromosome Inactivation Modulate Sex Differences in Valve Myofibroblasts

BACKGROUND

Aortic valve stenosis is a sexually dimorphic disease, with women often presenting with sustained fibrosis and men with more extensive calcification. However, the intracellular molecular mechanisms that drive these clinically important sex differences remain underexplored.

METHODS

Hydrogel biomaterials were designed to recapitulate key aspects of the valve tissue microenvironment and to serve as a culture platform for sex-specific valvular interstitial cells (VICs; precursors to profibrotic myofibroblasts). The hydrogel culture system was used to interrogate intracellular pathways involved in sex-dependent VIC-to-myofibroblast activation and deactivation. RNA sequencing was used to define pathways involved in driving sex-dependent activation. Interventions with small molecule inhibitors and siRNA transfections were performed to provide mechanistic insight into sex-specific cellular responses to microenvironmental cues, including matrix stiffness and exogenously delivered biochemical factors.

RESULTS

In both healthy porcine and human aortic valves, female leaflets had higher baseline activation of the myofibroblast marker α-smooth muscle actin compared with male leaflets. When isolated and cultured, female porcine and human VICs had higher levels of basal α-smooth muscle actin stress fibers that further increased in response to the hydrogel matrix stiffness, both of which were higher than in male VICs. A transcriptomic analysis of male and female porcine VICs revealed Rho-associated protein kinase signaling as a potential driver of this sex-dependent myofibroblast activation. Furthermore, we found that genes that escape X-chromosome inactivation such as BMX and STS (encoding for Bmx nonreceptor tyrosine kinase and steroid sulfatase, respectively) partially regulate the elevated female myofibroblast activation through Rho-associated protein kinase signaling. This finding was confirmed by treating male and female VICs with endothelin-1 and plasminogen activator inhibitor-1, factors that are secreted by endothelial cells and known to drive myofibroblast activation through Rho-associated protein kinase signaling.

CONCLUSIONS

Together, in vivo and in vitro results confirm sex dependencies in myofibroblast activation pathways and implicate genes that escape X-chromosome inactivation in regulating sex differences in myofibroblast activation and subsequent aortic valve stenosis progression. Our results underscore the importance of considering sex as a biological variable to understand the molecular mechanisms of aortic valve stenosis and to help guide sex-based precision therapies.

Spontaneous Degenerative Aortic Valve Disease in New Zealand Obese Mice

Background Degenerative aortic valve (AoV) disease and resulting aortic stenosis are major clinical health problems. Murine models of valve disease are rare, resulting in a translational knowledge gap on underlying mechanisms, functional consequences, and potential therapies. Naïve New Zealand obese (NZO) mice were recently found to have a dramatic decline of left ventricular (LV) function at early age. Therefore, we aimed to identify the underlying cause of reduced LV function in NZO mice. Methods and Results Cardiac function and pulmonary hemodynamics of NZO and age-matched C57BL/6J mice were monitored by serial echocardiographic examinations. AoVs in NZO mice demonstrated extensive thickening, asymmetric aortic leaflet formation, and cartilaginous transformation of the valvular stroma. Doppler echocardiography of the aorta revealed increased peak velocity profiles, holodiastolic flow reversal, and dilatation of the ascending aorta, consistent with aortic stenosis and regurgitation. Compensated LV hypertrophy deteriorated to decompensated LV failure and remodeling, as indicated by increased LV mass, interstitial fibrosis, and inflammatory cell infiltration. Elevated LV pressures in NZO mice were associated with lung congestion and cor pulmonale, evident as right ventricular dilatation, decreased right ventricular function, and increased mean right ventricular systolic pressure, indicative for the development of pulmonary hypertension and ultimately right ventricular failure. Conclusions NZO mice demonstrate as a novel murine model to spontaneously develop degenerative AoV disease, aortic stenosis, and the associated end organ damages of both ventricles and the lung. Closely mimicking the clinical scenario of degenerative AoV disease, the model may facilitate a better mechanistic understanding and testing of novel treatment strategies in degenerative AoV disease.

Establishment of a resazurin-based aortic valve tissue viability assay for dynamic culture in a microphysiological system

BACKGROUND/AIM

Tissue pathogenesis of aortic valve (AV) stenosis is research focus in cardiac surgery. Model limitations of conventional 2D culture of human or porcine valvular interstitial/endothelial cells (VIC/VECs) isolated from aortic valve tissues but also limited ability of (small) animal models to reflect human (patho)physiological situation in AV position raise the need to establish an in vitro setup using AV tissues. Resulting aim is to approximate (patho)physiological conditions in a dynamic pulsatile Microphysiological System (MPS) to culture human and porcine AV tissue with preservation of tissue viability but also defined ECM composition.

MATERIALS/METHODS

A tissue incubation chamber (TIC) was designed to implement human or porcine tissues (3×5 mm2) in a dynamic pulsatile culture in conventional cell culture ambience in a MPS. Cell viability assays based on lactate dehydrogenase (LDH)-release or resazurin-conversion were tested for applicability in the system and applied for a culture period of 14 days with interval evaluation of tissue viability on every other day. Resazurin-assay setup was compared in static vs. dynamic culture using varying substance saturation settings (50-300μM), incubation times and tissue masses and was consequently adapted.

RESULTS

Sterile dynamic culture of human and porcine AV tissue segments was established at a pulsatile flow rate range of 0.9-13.4μl/s. Implementation of tissues was realized by stitching the material in a thermoplastic polyurethane (TPU)-ring and insertion in the TIC-MPS-system. Culture volume of 2 ml caused LDH dilution not detectable in standard membrane integrity assay setup. Therefore, detection of resazurin-conversion of viable tissue was investigated. Optimal incubation time for viability conversion was determined at two hours at a saturated concentration of 300μM resazurin. Measurement in static conditions was shown to offer comparable results as dynamic condition but allowing optimal handling and TIC sterilization protocols for long term culture. Preliminary results revealed favourable porcine AV tissue viability over a 14 day period confirmed via resazurin-assay comparing statically cultured tissue counterparts.

CONCLUSIONS

Human and porcine AV tissue can be dynamically cultured in a TIC-MPS with monitoring of tissue viability using an adapted resazurin-assay setup. Preliminary results reveal advantageous viability of porcine AV tissues after dynamic TIC-MPS culture compared to static control.

Effects of Altering Mitochondrial Antioxidant Capacity on Molecular and Phenotypic Drivers of Fibrocalcific Aortic Valve Stenosis

Background: While a small number of studies suggest that oxidative stress has an influential role in fibrocalcific aortic valve disease (FCAVD), the roles of specific antioxidant enzymes in progression of this disease remain poorly understood. Here, we focused on selectively altering mitochondrial-derived oxidative stress—which has been shown to alter progression of a myriad of age-associated diseases—on the progression of molecular and phenotypic drivers of FCAVD.

Methods: We generated low-density lipoprotein receptor-deficient, Apolipoprotein B100-only mice (LA) that were either haploinsufficient for MnSOD (LA-MnSOD^+/−) or genetically overexpressing MnSOD (LA-MnSOD^Tg/0). After 6 months of Western diet feeding, mice underwent echocardiography to assess valvular and cardiac function and tissues were harvested. Quantitative-RT PCR, immunohistochemistry, and histopathology were used to measure changes in molecular pathways related to oxidative stress, calcification, and fibrosis.

Results: While reductions in MnSOD increased oxidative stress, there was not an overt phenotypic effect of MnSOD deficiency on valvular and cardiac function in LA-MnSOD^+/− mice. While markers of canonical bone morphogenetic protein signaling tended to increase in valve tissue from LA-MnSOD^+/− (e.g., p-SMAD1/5/8 and osterix), we did not observe statistically significant increases in osteogenic signaling. We did, however, observe highly significant reductions in expression of osteopontin, which were associated with significant increases in calcium burden in LA-MnSOD^+/− mice. Reciprocally, genetically increasing MnSOD did not preserve valve function in LA-MnSOD^Tg/0, but we did observe slight reductions in p-SMAD1/5/8 levels compared to their non-transgenic littermates. Interestingly, overexpression of MnSOD dramatically increased expression of osteopontin in valve tissue from LA-MnSOD^Tg/0 mice, but was not sufficient to attenuate calcium burden when compared to their LA-MnSOD^0/0 littermates.

Conclusions: Collectively, this study demonstrates that maintenance of mitochondrial antioxidant capacity is important in preventing accelerated disease progression in a mouse model of FCAVD, but that effectively altering mitochondrial antioxidant capacity as a monotherapeutic approach to slow key histopathological and molecular drivers of FCAVD remains biologically and therapeutically challenging.

Optical coherence tomography and multiphoton microscopy offer new options for the quantification of fibrotic aortic valve disease in ApoE-/- mice

Aortic valve sclerosis is characterized as the thickening of the aortic valve without obstruction of the left ventricular outflow. It has a prevalence of 30% in people over 65 years old. Aortic valve sclerosis represents a cardiovascular risk marker because it may progress to moderate or severe aortic valve stenosis. Thus, the early recognition and management of aortic valve sclerosis are of cardinal importance. We examined the aortic valve geometry and structure from healthy C57Bl6 wild type and age-matched hyperlipidemic ApoE-/- mice with aortic valve sclerosis using optical coherence tomography (OCT) and multiphoton microscopy (MPM) and compared results with histological analyses. Early fibrotic thickening, especially in the tip region of the native aortic valve leaflets from the ApoE-/- mice, was detectable in a precise spatial resolution using OCT. Evaluation of the second harmonic generation signal using MPM demonstrated that collagen content decreased in all aortic valve leaflet regions in the ApoE-/- mice. Lipid droplets and cholesterol crystals were detected using coherent anti-Stokes Raman scattering in the tissue from the ApoE-/- mice. Here, we demonstrated that OCT and MPM, which are fast and precise contactless imaging approaches, are suitable for defining early morphological and structural alterations of sclerotic murine aortic valves.

Clinical Relevance of Plasma Endogenous Tissue-Plasminogen Activator and Aortic Valve Sclerosis: Performance as a Diagnostic Biomarker

Background: Aortic valve sclerosis (AVSc), a common precursor to calcific aortic valve disease, may progress into advanced aortic stenosis with hemodynamic instability. However, plasma biomarkers of such a subclinical condition remain lacking. Since impaired fibrinolysis featuring dysregulated tissue plasminogen activator (t-PA) is involved in several cardiovascular diseases, we investigated whether endogenous t-PA was also associated with AVSc.

Methods: Plasma t-PA levels were measured in 295 consecutive patients undergoing standard echocardiography and Doppler flow imaging. Multiple logistic regression analyses were used to assess the association between t-PA and AVSc. Receiver operating characteristic curve analysis was performed for determining the diagnostic value of t-PA for AVSc. The performance of adding t-PA to clinical signatures of AVSc was evaluated. Concentration of t-PA was assessed in human sclerotic and non-sclerotic aortic valves by histology and immunohistochemistry analysis.

Results: Plasma t-PA was higher in patients with AVSc than in non-AVSc counterparts (median, 2063.10 vs. 1403.17 pg/mL, p < 0.01). C-statistics of plasma t-PA for discriminating AVSc was 0.698 (95%CI: 0.639–0.758). The performance of t-PA for identifying AVSc was better among male and non-hypertensive patients [C-statistics (95%CI): 0.712 (0.634–0.790) and 0.805 (0.693–0.916), respectively]. Combination of t-PA and clinical factors improved classification of the patients (category-free NRI: 0.452, p < 0.001; IDI: 0.020, p = 0.012). The concentration of t-PA was three times higher in sclerotic compared to non-sclerotic aortic valves.

Conclusion: Elevated circulating t-PA level confers an increased risk for AVSc. Further prospective studies with larger sample size are needed to examine if t-PA could serve as a diagnostic clinical marker for AVSc.

Sex-differences in echocardiographic assessment of aortic valve in young adult LDLr-/-/ApoB100/100/IGF-II+/- mice

BACKGROUND

LDLr^-/-/ApoB^100/100/IGF-II^+/- mice are used as a calcific aortic valve disease (CAVD) model. However, normal aortic valve hemodynamics i.e. remotely from CAVD onset and the sex-related differences are poorly known.

METHODS AND RESULTS

Four groups of mice, intact males (IM, n = 49) and females (IF, n = 50), castrated males (CxM, n = 79) and ovariectomized females (OxF: 73), underwent a Doppler-echocardiography at 12 weeks of age. Gonadectomy was performed at 8 weeks. Aortic valve assessment using effective orifice area (EOA, using the continuity equation) and peak aortic transvalvular velocity (V_Peak) was feasible in 89% of the mice with good to excellent reliability (intraclass correlation coefficients ranging from 0.90 to 0.98, p < 0.001). Mean V_Peak was 104 ± 17 cm/s and mean EOA was 1.18*10^-2 ± 0.22*10^-2 cm². EOA indexed to body surface area was 1.5 ± 0.3 cm²/m². The 95th percentile of Vpeak was 132 cm/s and the 5th percentile of indexed EOA was 1.0 cm²/m². Interestingly, IM had the highest V_Peak (114 ± 14 cm/s) vs each of the other groups (CxM: 106 ± 19 cm/s, OxF: 97 ± 13 cm/s and IF: 96 ± 12 cm/s, ANOVA and corrected p < 0.001). This was mostly explained by a higher stroke volume (ANOVA and corrected p < 0.001) in IM compared to other groups. There were no major sex-differences in ventricular systolic function parameters.

CONCLUSION

In LDLr^-/-/ApoB^100/100/IGF-II CAVD mice model, an aortic EOA <0.8*10^-2 cm² (or indexed EOA <1.0cm²/m²), and a peak aortic valve velocity > 132 cm/s may be proposed as thresholds to define CAVD. Intact male mice appear to have higher velocities.

Discovery of an Experimental Model of Unicuspid Aortic Valve

Background

The epithelial growth factor receptor family of tyrosine kinases modulates embryonic formation of semilunar valves. We hypothesized that mice heterozygous for a dominant loss‐of‐function mutation in epithelial growth factor receptor, which are Egfr^Vel/+ mice, would develop anomalous aortic valves, valve dysfunction, and valvular cardiomyopathy.

Methods and Results

Aortic valves from Egfr^Vel/+ mice and control mice were examined by light microscopy at 2.5 to 4 months of age. Additional Egfr^Vel/+ and control mice underwent echocardiography at 2.5, 4.5, 8, and 12 months of age, followed by histologic examination. In young mice, microscopy revealed anatomic anomalies in 79% of Egfr^Vel/+ aortic valves, which resembled human unicuspid aortic valves. Anomalies were not observed in control mice. At 12 months of age, histologic architecture was grossly distorted in Egfr^Vel/+ aortic valves. Echocardiography detected moderate or severe aortic regurgitation, or aortic stenosis was present in 38% of Egfr^Vel/+ mice at 2.5 months of age (N=24) and in 74% by 8 months of age. Left ventricular enlargement, hypertrophy, and reversion to a fetal myocardial gene expression program occurred in Egfr^Vel/+ mice with aortic valve dysfunction, but not in Egfr^Vel/+ mice with near‐normal aortic valve function. Myocardial fibrosis was minimal or absent in all groups.

Conclusions

A new mouse model uniquely recapitulates salient functional, structural, and histologic features of human unicuspid aortic valve disease, which are phenotypically distinct from other forms of congenital aortic valve disease. The new model may be useful for elucidating mechanisms by which congenitally anomalous aortic valves become critically dysfunctional.

Postnatal and Adult Aortic Heart Valves Have Distinctive Transcriptional Profiles Associated With Valve Tissue Growth and Maintenance Respectively

Heart valves are organized connective tissues of high mechanical demand. They open and close over 100,000 times a day to preserve unidirectional blood flow by maintaining structure-function relationships throughout life. In affected individuals, structural failure compromises function and often leads to regurgitant blood flow and progressive heart failure. This is most common in degenerative valve disease due to age-related wear and tear, or congenital malformations. At present, the only effective treatment of valve disease is surgical repair or replacement and this is often impermanent and requires anti-coagulation therapy throughout life. Therefore, there is a critical need to discover new alternatives. A promising therapeutic area is tissue regeneration and in non-valvular tissues this requires a tightly regulated genetic “growth program” involving cell proliferation. To explore this in heart valves, we performed RNA-seq analysis to compare transcriptional profiles of aortic valve tissue isolated from mice during stages of growth (postnatal day (PND) 2) and adult maintenance (4 months). Data analysis reveals distinct mRNA profiles at each time point and pathway ontology identifies associated changes in biological functions. The PND2 aortic valve is characterized by extensive cell proliferation and expression of mRNAs related to the extracellular matrix (ECM). At 4 months, proliferation is not significant and a differential set of ECM-related genes are expressed. Interestingly there is enrichment of the defense response biological process at this later time point. Together, these data highlight the unique transcriptome of the postnatal valve during stages of growth and maturation, as well as biological functions associated with adult homeostatic valves. These studies create a platform for future work exploring the molecular programs altered in the onset of heart valve disease after birth and provide insights for the development of mechanistic-based therapies.

Effects of teriparatide on morphology of aortic calcification in aged hyperlipidemic mice

Calcific aortic vasculopathy correlates with bone loss in osteoporosis in an age-independent manner. Prior work suggests that teriparatide, the bone anabolic treatment for postmenopausal osteoporosis, may inhibit the onset of aortic calcification. Whether teriparatide affects the progression of preexisting aortic calcification, widespread among this patient population, is unknown. Female apolipoprotein E-deficient mice were aged for over 1 yr to induce aortic calcification, treated for 4.5 wk with daily injections of control vehicle (PBS), 40 µg/kg teriparatide (PTH40), or 400 µg/kg teriparatide (PTH400), and assayed for aortic calcification by microcomputed tomography (microCT) before and after treatment. In a followup cohort, aged female apolipoprotein E-deficient mice were treated with PBS or PTH400 and assayed for aortic calcification by serial microCT and micropositron emission tomography. In both cohorts, aortic calcification detected by microCT progressed similarly in all groups. Mean aortic ¹⁸F-NaF incorporation, detected by serial micropositron emission tomography, increased in the PBS-treated group (+14 ± 5%). In contrast, ¹⁸F-NaF incorporation decreased in the PTH400-treated group (-33 ± 20%, P = 0.03). Quantitative histochemical analysis by Alizarin red staining revealed a lower mineral surface area index in the PTH400-treated group compared with the PBS-treated group ( P = 0.04). Furthermore, Masson trichrome staining showed a significant increase in collagen deposition in the left ventricular myocardium of mice that received PTH400 [2.1 ± 0.6% vs. control mice (0.5 ± 0.1%), P = 0.02]. In summary, although teriparatide may not affect the calcium mineral content of aortic calcification, it reduces ¹⁸F-NaF uptake in calcified lesions, suggesting the possibility that it may reduce mineral surface area with potential impact on plaque stability. NEW & NOTEWORTHY Parathyroid hormone regulates bone mineralization and may also affect vascular calcification, which is an important issue, given that its active fragment, teriparatide, is widely used for the treatment of osteoporosis. To determine whether teriparatide alters vascular calcification, we imaged aortic calcification in mice treated with teriparatide and control mice. Although teriparatide did not affect the calcium content of cardiovascular deposits, it reduced their fluoride tracer uptake.