Pilot candidate gene analysis of patients ≥ 60 years old with aortic stenosis involving a tricuspid aortic valve

Dantrolene inhibits lysophosphatidylcholine-induced valve interstitial cell calcific nodule formation via blockade of the ryanodine receptor

Calcific aortic valve disease (CAVD), a fibrocalcific thickening of the aortic valve leaflets causing obstruction of the left ventricular outflow tract, affects nearly 10 million people worldwide. For those who reach end-stage CAVD, the only treatment is highly invasive valve replacement. The development of pharmaceutical treatments that can slow or reverse the progression in those affected by CAVD would greatly advance the treatment of this disease. The principal cell type responsible for the fibrocalcific thickening of the valve leaflets in CAVD is valvular interstitial cells (VICs). The cellular processes mediating this calcification are complex, but calcium second messenger signaling, regulated in part by the ryanodine receptor (RyR), has been shown to play a role in a number of other fibrocalcific diseases. We sought to determine if the blockade of calcium signaling in VICs could ameliorate calcification in an in vitro model. We previously found that VICs express RyR isotype 3 and that its modulation could prevent VIC calcific nodule formation in vitro. We sought to expand upon these results by further investigating the effects of calcium signaling blockade on VIC gene expression and behavior using dantrolene, an FDA-approved pan-RyR inhibitor. We found that dantrolene also prevented calcific nodule formation in VICs due to cholesterol-derived lysophosphatidylcholine (LPC). This protective effect corresponded with decreases in intracellular calcium flux, apoptosis, and ACTA2 expression but not reactive oxygen species formation caused by LPC. Interestingly, dantrolene increased the expression of the regulator genes RUNX2 and SOX9, indicating complex gene regulation changes. Further investigation via RNA sequencing revealed that dantrolene induced several cytoprotective genes that are likely also responsible for its attenuation of LPC-induced calcification. These results suggest that RyR3 is a viable therapeutic target for the treatment of CAVD. Further studies of the effects of RyR3 inhibition on CAVD are warranted.

Tendon and Ligament Genetics: How Do They Contribute to Disease and Injury? A Narrative Review

A significant proportion of patients requiring musculoskeletal management present with tendon and ligament pathology. Our understanding of the intrinsic and extrinsic mechanisms that lead to such disabilities is increasing. However, the complexity underpinning these interactive multifactorial elements is still not fully characterised. Evidence highlighting the genetic components, either reducing or increasing susceptibility to injury, is increasing. This review examines the present understanding of the role genetic variations contribute to tendon and ligament injury risk. It examines the different elements of tendon and ligament structure and considers our knowledge of genetic influence on form, function, ability to withstand load, and undertake repair or regeneration. The role of epigenetic factors in modifying gene expression in these structures is also explored. It considers the challenges to interpreting present knowledge, the requirements, and likely pathways for future research, and whether such information has reached the point of clinical utility.

A Twenty-Year Analysis of Demographics, Surgical Management, and Outcomes of Aortic Stenosis in New Jersey

We investigated the incidence and characteristics of 14,996 patients with aortic stenosis (AS) who were hospitalized in New Jersey between the years 1995 to 2015. The average age was 72, the majority were Caucasian males and common co-morbidities were hypertension, coronary artery disease and hypercholesterolemia. Hospital admission for AS declined between 1995 to 2007, to 10/100,000 patients, and increased to 15/100,000 patients in 2015 (p for trend <0.001). During the study period, the percentage of patients who received aortic valve replacement (AVR) increased (p <0.001). All-cause and cardiovascular mortality were higher among patients who did not undergo AVR at 1-year (HR 1.98 CI 1.75 to 2.23, p <0.001 and HR 1.82 CI 1.57 to 2.11, p <0.001, respectively) and 3-years (HR 2.16 CI 1.96 to 2.38, p <0.001 and HR 2.16 CI 1.90 to 2.45, p <0.001, respectively). The probability for readmission for AS was higher in patients who did not receive AVR compared to patients who had AVR at 1 year (HR 92.95 CI 57.85 to 149.35, p <0.001) and 3 years (HR 70.36 CI 47.18 to 104.95, p <0.001). These data imply that earlier diagnosis of AS and AVR when indicated will improve outcomes.

The evolutionary background and functional consequences of the rs2071307 polymorphism in human tropoelastin

Elastin is a major polymeric protein of the extracellular matrix, providing critical properties of extensibility and elastic recoil. The rs2071307 genomic polymorphism, resulting in the substitution of a serine for a glycine residue in a VPG motif in tropoelastin, has an unusually high minor allele frequency in humans. A consequence of such allelic heterozygosity would be the presence of a heterogeneous elastin polymer in up to 50% of the population, a situation which appears to be unique to Homo sapiens. VPG motifs are extremely common in hydrophobic domains of tropoelastins and are the sites of transient β-turns that are essential for maintaining the conformational flexibility required for its function as an entropic elastomer. Earlier data demonstrated that single amino acid substitutions in tropoelastin can have functional consequences for polymeric elastin, particularly when present in mixed polymers. Here, using NMR and molecular dynamics approaches, we show the rs2071307 polymorphism reduces local propensity for β-turn formation, with a consequent increase in polypeptide hydration and an expansion of the conformational ensemble manifested as an increased hydrodynamic radius, radius of gyration and asphericity. Furthermore, this substitution affects functional properties of polymeric elastin, particularly in heterogeneous polymers mimicking allelic heterozygosity. We discuss whether such effects, together with the unusually high minor allele frequency of the polymorphism, could imply some some evolutionary advantage for the heterozygous state.

Diagnosis and management of valvular aortic stenosis

Valvular aortic stenosis (AS) is a progressive disease that affects 2% of the population aged 65 years or older. The major cause of valvular AS in adults is calcification and fibrosis of a previously normal tricuspid valve or a congenital bicuspid valve, with rheumatic AS being rare in the United States. Once established, the rate of progression of valvular AS is quite variable and impossible to predict for any particular patient. Symptoms of AS are generally insidious at onset, though development of any of the three cardinal symptoms of angina, syncope, or heart failure portends a poor prognosis. Management of symptomatic AS remains primarily surgical, though transcatheter aortic valve replacement (TAVR) is becoming an accepted alternative to surgical aortic valve replacement (SAVR) for patients at high or prohibitive operative risk.

Association between single-nucleotide polymorphisms in six hypertensive candidate genes and hypertension among northern Han Chinese individuals

Hypertension is one of the leading risk factors for mortality. The renin-angiotensin-aldosterone system (RAAS) is a potent and powerful mediator in the homeostasis of hypertension. Here, the association between six candidate genes, renin, adrenoceptor β3, angiotensinogen, aldosterone synthase, angiotensin II receptor type 1 and angiotensin II receptor type 2, that are related to RAAS and essential hypertension (EH) was evaluated and explored in northern Chinese Han individuals. A case-control study including 1090 EH cases and 700 controls was performed. Eight single-nucleotide polymorphisms (SNPs), rs699, rs4762, rs5707, rs5186, rs4994, rs1799998, rs5193 and rs5194, located in the six genes were genotyped with TaqMan real-time PCR method. Statistical analysis software (SPSS 17.0) was used for descriptive statistics and association analyses. Among the six genes related to RAAS, the frequencies of rs4994 (ADRB3) and rs5194 (AGTR2) were found to be significantly different between the EH cases and controls (P < 0.05). Logistic regression analyses adjusted for covariates showed rs4994 to be closely associated with EH under the recessive (P = 0.019, odds ratio (OR) = 0.373, 95% confidence interval (CI) 0.163-0.851) and homozygous (P = 0.028, OR = 0.394, 95% CI 0.172-0.903) models. The association was also significantly close in the male subset (P < 0.05). Significant association was also observed between rs1799998 (CYP11B2) and EH (P < 0.05) in the dominant, additive and allelic models. These data demonstrated that ADRB3 rs4994 and CYP11B2 rs1799998 were significantly closely associated with EH in northern Han Chinese individuals. The CC of rs4994 and CC or C allele of rs1799998 might be protective genetic factors of hypertension.

Racial differences in the prevalence of severe aortic stenosis

BACKGROUND

In an era of expanded treatment options for severe aortic stenosis, it is important to understand risk factors for the condition. It has been suggested that severe aortic stenosis is less common in African Americans, but there are limited data from large studies.

METHODS AND RESULTS

The Synthetic Derivative at Vanderbilt University Medical Center, a database of over 2.1 million de-identified patient records, was used to identify individuals who had undergone echocardiography. The association of race with severe aortic stenosis was examined using multivariable logistic regression analyses adjusting for conventional risk factors. Of the 272 429 eligible patients (mean age 45 years, 44% male) with echocardiography, 14% were African American and 82% were Caucasian. Severe aortic stenosis was identified in 106 (0.29%) African-American patients and 2030 (0.91%) Caucasian patients (crude OR 0.32, 95% CI [0.26, 0.38]). This difference persisted in multivariable-adjusted analyses (OR 0.41 [0.33, 0.50], P<0.0001). African-American individuals were also less likely to have severe aortic stenosis due to degenerative calcific disease (adjusted OR 0.47 [0.36, 0.61]) or congenitally bicuspid valve (crude OR 0.13 [0.02, 0.80], adjusted OR dependent on age). Referral bias against those with severe valvular disease was assessed by comparing the prevalence of severe mitral regurgitation in Caucasians and African Americans and no difference was found.

CONCLUSIONS

These findings suggest that African Americans are at significantly lower risk of developing severe aortic stenosis than Caucasians.