Satu Helske

Aortic valve stenosis: an active atheroinflammatory process.

Purpose of review To summarize the current understanding of the pathobiology of aortic valve stenosis and portray the major advances in this field. Recent findings Stenotic aortic valves are characterized by atherosclerosis-like lesions, consisting of activated inflammatory cells, including T lymphocytes, macrophages, and mast cells, and of lipid deposits, calcific nodules, and bone tissue. Active mediators of calcification and cells with osteoblast-like activity are present in diseased valves. Extracellular matrix remodeling, including collagen synthesis and elastin degradation by matrix metalloproteinases and cathepsins, contributes to leaflet stiffening. In experimental animals, hypercholesterolemia induces calcification and bone formation in aortic valves, which can be inhibited by statin treatment. The potential of statins to retard progression of aortic valve stenosis has also been recognized in clinical studies; however, further prospective trials are needed. Angiotensin II-forming enzymes are upregulated in stenotic valves. Angiotensin II may participate in profibrotic progression of aortic valve stenosis and may serve as a possible therapeutic target. Summary Recent findings regarding the interaction of inflammatory cells, lipids, mediators of calcification, and renin–angiotensin system in stenotic valves support the current opinion of aortic valve stenosis being an actively regulated disease, potentially amenable to targeted molecular therapy. Evidence from prospective clinical studies is eagerly awaited.

Increased Expression of Elastolytic Cathepsins S, K, and V and Their Inhibitor Cystatin C in Stenotic Aortic Valves

Objective—To investigate the possible role of elastolytic cathepsins S, K, and V and their endogenous inhibitor cystatin C in adverse extracellular matrix remodeling of stenotic aortic valves. Methods and Results—Stenotic aortic valves were collected at valve replacement surgery and control valves at cardiac transplantations. The expression of cathepsins S, K, and V and cystatin C was studied by conventional and real-time polymerase chain reaction and by immunohistochemistry. Total cathepsin activity in the aortic valves was quantified by a fluorometric microassay. When compared with control valves, stenotic valves showed increased mRNA expression of cathepsins S, K, and V (P<0.05 for each) and a higher total cathepsin activity (P<0.001). In stenotic valves, cystatin C mRNA was increased (P<0.05), and cystatin C protein was found particularly in areas with infiltrates of inflammatory cells. Both cathepsin S and cystatin C were present in bony areas of the valves, whereas cathepsin V localized to endothelial cells in areas rich of neovascularization. Incubation of thin sections of aortic valves with cathepsins S, K, and V resulted in severe disruption of elastin fibers, and this cathepsin effect could be blocked by adding cystatin C to the incubation system. Conclusions—Stenotic aortic valves show increased expression and activity of elastolytic cathepsins S, K, and V. These cathepsins may accelerate the destruction of aortic valvular extracellular matrix, so promoting the progression of aortic stenosis.

Increased circulating concentrations and augmented myocardial extraction of osteoprotegerin in heart failure due to left ventricular pressure overload.

Osteoprotegerin (OPG) and the receptor activator of nuclear factor‐kB ligand (RANKL), two cytokines regulating bone remodeling, have recently been raised as potential pathogenetic factors in cardiovascular diseases. We have studied circulating and myocardial OPG and RANKL in patients having severe aortic stenosis (AS) with or without heart failure (HF).

Vascular Endothelial Growth Factor–Secreting Mast Cells and Myofibroblasts. A Novel Self-Perpetuating Angiogenic Pathway in Aortic Valve Stenosis

Objective—To examine the proangiogenic potential of myofibroblasts and mast cells, 2 types of cells present in human aortic valves. Methods and Results—Aortic valve stenosis is an active atheroinflammatory disease, characterized by the accumulation of inflammatory cells and the neovascularization of the valves. A total of 85 stenotic valves and 20 control valves were obtained during valve replacement surgery. The results of immunohistochemistry analysis revealed stenotic aortic valves that contained 3 types of neovessels: small microvessels, medium microvessels, and organized arterioles. The distribution density of the neovessels was significantly higher in stenotic valves than in control valves (P<0.001) and correlated positively with valvular calcification gradus (r=0.26, P=0.02) and mast cell density (r=0.38, P<0.001). In the neovascularized areas of stenotic aortic valves, mast cells contained vascular endothelial growth factor and were degranulated, indicating their activation. The stimulation of cultured myofibroblasts derived from aortic valves with a mast cell–preconditioned medium, hypoxic culture conditions, or tobacco smoke all induced vascular endothelial growth factor secretion in the myofibroblasts. Finally, mast cell tryptase was able to degrade the antiangiogenic molecule endostatin in vitro. Conclusion—Mast cells and myofibroblasts may accelerate the progression of aortic valve stenosis by altering the balance between angiogenic and antiangiogenic factors in the valves, thus promoting valvular neovascularization.

Lipid Lowering in Aortic Stenosis Still Some Light at the End of the Tunnel

Aortic valve stenosis (AS) is the end stage of an active fibrocalcific process with local inflammation, lipid deposition, fibrosis, and calcification as its key features.1 Adverse remodeling of a stenotic valve includes collagen deposition and elastin degradation, resulting from myofibroblast proliferation and activation, recruitment of inflammatory cells, and expression of proinflammatory cytokines.2 Activation of local calcific mediators results in massive calcification and even bone formation in the affected leaflets.1 In addition, oxidative stress is increased and neovascularization occurs in the normally avascular valve tissue.3,4 Lipid accumulation and oxidation may further contribute a proinflammatory impetus toward calcification and ossification.5 Moreover, valvular myofibroblasts undergo phenotypic transdifferentiation into osteoblastic cells, which spontaneously form calcific nodules, a process accelerated by inflammatory cytokines and oxidized cholesterol.2,5 Furthermore, in experimental animal models, hypercholesterolemia increases aortic valve cholesterol content and results in osteoblastic differentiation and bone formation; these adverse changes can be prevented by atorvastatin.5 Indeed, several experimental and retrospective clinical studies have suggested that statins may retard AS development.1,5 Article see p 2693 Inspired by these observations and epidemiological studies revealing an association between AS and hypercholesterolemia,1 several prospective trials of statins in patients with AS have been conducted. The prospective but not randomized Rosuvastatin Affecting Aortic Valve Endothelium (RAAVE) trial (n=121) showed a smaller decline in valve area in AS patients receiving rosuvastatin. However, only patients with elevated serum low-density lipoprotein received the investigated drug.6 In contrast, 2 prospective randomized lipid-lowering trials both failed to show a decrease in hemodynamic progression of AS or a delay in aortic valve replacements: the Scottish Aortic Stenosis and Lipid Lowering Trial, Impact on Regression (SALTIRE) compared atorvastatin to placebo in 155 patients,7 and the Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) trial compared simvastatin-ezetimibe therapy to placebo …

Norepinephrine, adrenocorticotropin, cortisol and beta‐endorphin in women suffering from fear of labor: responses to the cold pressor test during and after pregnancy

Background.  Women suffering from fear of labor have reduced pain tolerance during a cold pressor test (CPT) during and after pregnancy.

High-density lipoproteins (HDL) are present in stenotic aortic valves and may interfere with the mechanisms of valvular calcification

OBJECTIVE To determine whether differences exist in valvular high density lipoprotein (HDL) content between non-stenotic and stenotic aortic valves, and whether HDL could retard valvular calcification locally. METHODS Stenotic aortic valves were obtained from valve replacement surgery and non-stenotic control valves from cardiac transplantations or at autopsy. The valvular localization and concentration of apolipoproteinA-I (apoA-I) were analyzed by immunohistochemistry and ELISA. The effects of HDL on the secretion of calcifying mediators and proinflammatory cytokines by cultured aortic valve myofibroblasts were assessed by ELISA and real-time PCR. RESULTS The concentration of apoA-I was higher in control than in stenotic valves (p < 0.05). ApoA-I surrounded the calcific deposits in stenotic valves, co-localizing with apoB, apoE, and osteoprotegerin (OPG). Incubation of cultured valve myofibroblasts with HDL increased their secretion of OPG (p < 0.001). Furthermore, incubation of myofibroblasts with HDL led to decreased mRNA expression of tumor necrosis factor alpha (TNF-α) (p < 0.05). CONCLUSIONS The amount of valvular HDL is reduced in aortic valve stenosis. HDL both induces the secretion of OPG and reduces the expression of TNF-α in vitro. Since OPG is known to inhibit and TNF-α to promote aortic valve calcification, HDL may have an anti-calcifying effect in human aortic valves.

Lymphangiogenesis in aortic valve stenosis—Novel regulatory roles for valvular myofibroblasts and mast cells

OBJECTIVE To investigate mechanisms of lymphangiogenesis in aortic valve stenosis (AS). METHODS Lymphatic vessels were visualized with LYVE-1 staining in 20 control, 5 sclerotic, and 40 stenotic human aortic valves. Vascular endothelial growth factors (VEGFs) VEGF-C and VEGF-D, and their lymphangiogenic receptor VEGFR-3, and the angiogenic VEGFR-2 were analysed by quantitative real-time PCR and immunohistochemistry. Cultured myofibroblasts derived from human stenotic aortic valves, and cultured human mast cells were used to study VEGF-C regulation, and VEGF-C and VEGF-A were quantified from cell culture media by enzyme immunoassays. RESULTS Lymphatic vessels, VEGF-C, VEGF-D, VEGFR-3 and VEGFR-2 all were present in the aortic valves. In AS, the number of lymphatic vessels and the expression of VEGF-D, VEGFR-3, and VEGFR-2 were increased. Moreover, the numbers of lymphatic vessels correlated positively with those of neovessels (r = 0.525, p = 0.001) and mast cells (r = 0.374, p = 0.017). Cultured valvular myofibroblasts produced VEGF-C, and addition of tumour necrosis factor alpha (TNF-α) to the cells augmented its secretion. In contrast, proteases released by activated human mast cells degraded VEGF-C. CONCLUSION These results show that lymphangiogenesis is induced in advancing AS. Furthermore, valvular myofibroblasts and activated mast cells were identified as novel regulators of lymphangiogenesis in aortic valves.

ACE inhibition attenuates uremia-induced aortic valve thickening in a novel mouse model.

BackgroundWe examined whether impaired renal function causes thickening of the aortic valve leaflets in hyperlipidemic apoE-knockout (apoE-/-) mice, and whether the putative effect on the aortic valves could be prevented by inhibiting the angiotensin-converting enzyme (ACE) with enalapril.MethodsThickening of the aortic valve leaflets in apoE-/- mice was induced by producing mild or moderate chronic renal failure resulting from unilateral nephrectomy (1/2 NX, n = 18) or subtotal nephrectomy (5/6 NX, n = 22), respectively. Additionally, the 5/6 NX mice were randomized to no treatment (n = 8) or enalapril treatment (n = 13). The maximal thickness of each leaflet was measured from histological sections of the aortic roots.ResultsLeaflet thickness was significantly greater in the 5/6 NX mice than in the 1/2 NX mice (P = 0.030) or the unoperated mice (P = 0.003). The 5/6 NX mice treated with enalapril had significantly thinner leaflets than did the untreated 5/6 NX mice (P = 0.014).ConclusionModerate uremia causes thickening of the aortic valves in apoE-/- mice, which can be attenuated by ACE inhibition. The nephrectomized apoE-/- mouse constitutes a new model for investigating the mechanisms of uremia-induced aortic valve disease, and also provides an opportunity to study its pharmacologic prevention.

Transcardiac gradients of circulating apelin: extraction by normal hearts vs. release by hearts failing due to pressure overload

Apelin is a newly discovered inotropic peptide tentatively linked up with the pathophysiology of heart failure (HF). To further assess the role of apelin in HF, we measured its transcardiac arteriovenous gradients in patients with left ventricular pressure overload with or without HF and in patients with structurally normal hearts. Blood samples from the aortic root and coronary sinus were drawn from 49 adult patients undergoing preoperative cardiac catheterization for severe aortic valve stenosis (AS). Similar samples were taken from 12 control patients with structurally normal hearts undergoing electrophysiological studies. Plasma apelin was determined by enzyme immunoassay. In the control group, apelin decreased from a median of 0.39 (0.16-1.94) ng/ml in the aortic root to 0.18 (0.13-1.04) ng/ml in the coronary sinus (P = 0.004). In AS patients free of HF (n = 33), apelin concentration remained unaltered across the heart, but in those with HF (n = 15) apelin rose from a median of 0.26 (0.20-0.82) ng/ml in the aorta to 0.45 (0.24-1.17) ng/ml in the coronary sinus (P = 0.002). The transcardiac apelin gradients differed statistically highly significantly across the three groups (P = 0.00005), and each of the two-group differences was also statistically significant (P < 0.05). In conclusion, left ventricular pressure overload changes the transcardiac arteriovenous differences of circulating apelin. Although normal hearts extract apelin from the coronary blood, hearts failing due to left ventricular pressure overload release apelin into the circulation. Loss of cardiac apelin may be involved in the mechanisms of HF development in AS.