Cholesterol Crystal Dissolution Rate of Serum Predicts Outcomes in Patients With Aortic Stenosis Undergoing Transcatheter Aortic Valve Replacement

BACKGROUND

Aortic stenosis has pathophysiological similarities with atherosclerosis, including the deposition of cholesterol-containing lipoproteins. The resulting cholesterol crystals activate the NLRP3 (NOD-like receptor protein 3) inflammasome, leading to inflammation and cardiovascular diseases. We aimed to investigate the cholesterol crystal dissolution rate (CCDR) of serum in patients with aortic stenosis and to assess the prognostic value of this biomarker.

METHODS AND RESULTS

The study included 348 patients with aortic stenosis undergoing transcatheter aortic valve replacement. The CCDR was measured using flow cytometry to enumerate cholesterol crystals that were added to a serum solution, at baseline and after 2 hours of incubation. Based on the median CCDR, the cohort was stratified into high and low cholesterol crystal dissolvers. The incidence of the primary end point, a composite of 1-year all-cause mortality and major vascular complication, was significantly lower in the high CCDR group (7.3 per 100 person-years) compared with the low CCDR group (17.0 per 100 person-years, P=0.01). This was mainly driven by a lower 1-year mortality rate in patients with a high CCDR (7.3 versus 15.1 per 100 person-years, P=0.04). Unplanned endovascular interventions were significantly less frequent in high cholesterol crystal dissolvers (12.8 versus 22.6 per 100 person-years, P=0.04). Although low-density lipoprotein cholesterol levels were comparable in both groups (101.8±37.3 mg/dL versus 97.9±37.6 mg/dL, P=0.35), only patients with a low CCDR showed a benefit from statin treatment. In multivariate analysis, low CCDR (hazard ratio, 2.21 [95% CI, 0.99-4.92], P=0.04) was significantly associated with 1-year mortality.

CONCLUSIONS

The CCDR is a novel biomarker associated with outcome in patients with aortic stenosis undergoing transcatheter aortic valve replacement. It may provide new insights into patients' anti-inflammatory capacity and additional prognostic information beyond classic risk assessment.

Telemetric long-term assessment of autonomic function in experimental heart failure

Despite medical advances in the treatment of heart failure (HF), mortality remains high. It has been shown that alterations of the autonomic-nervous-system (ANS) are associated with HF progression and increased mortality. Preclinical models are required to evaluate the effectiveness of novel treatments modulating the autonomic imbalance. However, there are neither standard models nor diagnostic methods established to measure sympathetic and parasympathetic outflow continuously. Digital technologies might be a reliable tool for continuous assessment of autonomic function within experimental HF models. Telemetry devices and pacemakers were implanted in beagle dogs (n = 6). HF was induced by ventricular pacing. Cardiac hemodynamics, plasma catecholamines and parameter describing the ANS ((heart rate variability (HRV), deceleration capacity (DC), and baroreflex sensitivity (BRS)) were continuously measured at baseline, during HF conditions and during recovery phase. The pacing regime led to the expected depression in cardiac hemodynamics. Telemetric assessment of the ANS function showed a significant decrease in Total power, DC, and Heart rate recovery, whereas BRS was not significantly affected. In contrast, plasma catecholamines, revealing sympathetic activity, showed only a significant increase in the recovery phase. A precise diagnostic of the ANS in the context of HF is becoming increasingly important in experimental models. Up to now, these models have shown many limitations. Here we present the continuous assessment of the autonomic function in the progression of HF. We could demonstrate the advantage of highly resolved ANS measurement by HR and BP derived parameters due to early detection of an autonomic imbalance in the progression of HF.

Toll-like receptor-3 contributes to the development of aortic valve stenosis

Aortic valve stenosis (AS) development is driven by distinct molecular and cellular mechanisms which include inflammatory pathways. Toll-like-receptor-3 (TLR3) is a lysosomal pattern-recognition receptor that binds double-stranded RNA and promotes pro-inflammatory cellular responses. In recent years, TLR3 has emerged as a major regulator of vascular inflammation. The exact role of TLR3 in the development of AS has not been investigated. Isolated human valvular interstitial cells (VICs) were stimulated with the TLR3-agonist polyIC and the resulting pro-inflammatory and pro-osteogenic response measured. Severe AS was induced in wildtype- and TLR3^-/- mice via mechanical injury of the aortic valve with a coronary springwire. TLR3 activation was achieved by polyIC injection every 24 h after wire injury, while TLR3 inhibition was realized using Compound 4a (C4a) every 48 h after surgery. Endothelial mesenchymal transition (EndoMT) of human valvular endothelial cells (VECs) was assessed after polyIC stimulation. Stimulation of human VICs with polyIC promoted a strong inflammatory and pro-osteogenic reaction. Similarly, injection of polyIC marginally increased AS development in mice after wire injury. AS induction was significantly decreased in TLR3^-/- mice, confirming the role of endogenous TLR3 ligands in AS pathology. Pharmacological inhibition of TLR3 with C4a not only prevented the upregulation of inflammatory cytokines and osteogenic markers in VICs, and EndoMT in VECs, but also significantly abolished the development of AS in vivo. Endogenous TLR3 activation significantly contributes to AS development in mice. Pharmacological inhibition of TLR3 with C4a prevented AS formation. Therefore, targeting TLR3 may be a viable treatment option.

Novel assay for quantifying the cholesterol crystal dissolution capacity of serum predicts outcomes in patients with severe aortic stenosis undergoing TAVR

Background

Aortic stenosis (AS) is the most common valvular heart disease (VHD) in developed countries. The pathophysiology of calcific AS has several clinical and pathobiological findings in common with atherosclerosis including chronic inflammation and lipoprotein deposition. Histopathological examination has revealed atherosclerosis-like lesions, that mainly contain cholesterol crystals (CC) in resected calcific aortic valve cusps. Previous studies have demonstrated that CCs can activate the NLRP3 inflammasome, resulting in an IL-1 driven systemic inflammation, that leads to the development of atherosclerotic plaques.

Purpose

In this study, we sought to validate a novel assay for measuring the serum capacity to dissolve cholesterol crystals (CCDC) in patients with AS and to examine whether this biomarker may be associated with clinical outcomes.

Methods

Our study cohort included 348 patients with AS undergoing transcatheter aortic valve replacement. The CCDC was measured using flow cytometry to enumerate CC, that were added to a 50% serum solution, at baseline and after two hours of incubation. The dissolution capacity was indicated as percentage change in CC count at baseline and after incubation. The study cohort was stratified according to the median CCDC into high and low CC dissolvers.

Results

The study population was 47.7% female and had a mean age of 80.9±6.2 years. The primary end point, a composite of one-year all-cause mortality and major vascular complication occurred less frequently in the high CCDC group (7.0%) as compared with the low CCDC group (15.3%, p=0.01). This was mainly driven by lower rates of one-year mortality in patients with a high CCDC (7.0% vs 13.6%, p=0.05), as presented in Figure 1. Furthermore, unplanned endovascular interventions were significantly less frequent in high CC dissolvers in contrast to low CC dissolvers (12.2% vs 20.5%, p=0.04). Although LDL cholesterol (101.8±37.3 mg/dL vs 97.9±37.6 mg/dL, p=0.35) and total cholesterol levels (158.1±43.8 mg/dL vs 154.1±40.2, p=0.41) were comparable in the high and low CCDC group, only patients with a low CCDC showed a benefit from statin treatment (Figure 2). In multivariate analysis, only low CCDC (OR: 2.51 [95% CI: 1.02–6.15], p=0.05) and Albumin (OR: 0.88 [95% CI: 0.79–0.98], p=0.03) were independently associated with one-year all-cause mortality

Conclusion

The CCDC is a novel biomarker associated with clinical outcome in patients with AS undergoing TAVR. It may provide new insights into patient's preventative anti-inflammatory capacity and additional prognostic information to identify vulnerable patients beyond classic risk assessment.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation).

Distinct transcription factor networks control neutrophil-driven inflammation

Neutrophils display distinct gene expression patters depending on their developmental stage, activation state and tissue microenvironment. To determine the transcription factor networks that shape these responses in a mouse model, we integrated transcriptional and chromatin analyses of neutrophils during acute inflammation. We showed active chromatin remodeling at two transition stages: bone marrow-to-blood and blood-to-tissue. Analysis of differentially accessible regions revealed distinct sets of putative transcription factors associated with control of neutrophil inflammatory responses. Using ex vivo and in vivo approaches, we confirmed that RUNX1 and KLF6 modulate neutrophil maturation, whereas RELB, IRF5 and JUNB drive neutrophil effector responses and RFX2 and RELB promote survival. Interfering with neutrophil activation by targeting one of these factors, JUNB, reduced pathological inflammation in a mouse model of myocardial infarction. Therefore, our study represents a blueprint for transcriptional control of neutrophil responses in acute inflammation and opens possibilities for stage-specific therapeutic modulation of neutrophil function in disease.

Dissolving cholesterol crystals reduces aortic valve stenosis development in mice

Background

Aortic valve stenosis (AS) is the most common valve disease worldwide and is associated with a very high morbidity and mortality. Until today, aortic valve replacement is the only therapeutic option available. Analysis of explanted human aortic valves has shown that atherosclerosis-like lesions, that contain cholesterol crystals (CC), are present in stenotic aortic valve cusps. It has been demonstrated that CCs can activate the NLRP3 inflammasome and hereby trigger a complex, IL-1b driven, inflammatory response. 2-hydroxypropyl-β-cyclodextrin (CD) is a cyclic oligosaccharide that can increase the solubility of CCs, which results in a reduction of CC-load and therefore could inhibit the pro-inflammatory immune response.

Methods

Severe AS was induced in 10 weeks old C57BL/6-J (WT) and Apolipoprotein-E-deficient (ApoE) mice. Acoronary springwire was used to induce an endothelial injury under echocardiographic guidance. AS development was confirmed via ultrasound examinations. ApoE mice were fed a cholesterol-rich western diet and concomitantly received daily injections of 2g/kg/d CD via subcutaneous injection. CCs were visualized with laser reflection confocal microscopy. Serum cholesterol analysis were performed via mass GC-MS-SIM.

Results

In order to evaluate whether hyperlipidemia aggravates AS development, WT and ApoE mice were fed a cholesterol-rich diet and subjected to our model of wire-induced AS. Trans-aortic valve peak velocity levels of ApoE mice were significantly increased six weeks after injury compared to WT mice. Histological analysis of these mice showed large CC-deposits in the aortic valves of ApoE mice. Next, CC solubility was increased in a group of ApoE mice, control mice only received PBS injections. Interestingly, mice treated with CD displayed a significantly reduced peak blood velocity over the aortic valve compared to PBS mice. Left ventricular ejection fraction remained unchanged. Serum cholesterol analysis was performed to analyze the effect of CD on cholesterol metabolism. 27-hydroxycholesterol, an endogenous oxysterol of cholesterol metabolism, which reduces the potential for the conversion of free cholesterol into crystals was significantly increased in CD treated mice. The levels of cholesterol precursors were unchanged, indicating that CD doesn't influence de-novo synthesis of cholesterol. Intestinal absorption of cholesterol was also not affected by CD, as assessed by quantification of phytosterols in the serum of CD and PBS treated mice.

Conclusion

These results underline the importance of hyperlipidemia in the pathogenesis of AS. Particularly CCs seem to act as an important inflammatory trigger in the development of AS. Increasing the solubility of cholesterol through CD reduces AS development in mice and could, as it is already considered safe in human, act as a possible therapeutic option.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): DFG, German Research Foundation

[Spondylitis brucellosa]

The authors report on three cases of spondylitis brucellosa, and their course over a period of more than two years. The clinical and radiological characteristics of spondylitis brucellosa are described, as well as possible ways of distinguishing it diagnostically from tubercular and other non-tubercular types of spondylitis. In the main, confirmation of diagnosis will be provided by immunologic investigations, and these should be routine in any differential diagnostic identification of spondylitis.