Presence of adipose tissue in aortic valves from aortic regurgitation patients: pathophysiological role and clinical implications

Introduction

Adipose tissue is a common constituent of the heart and it is located, without great clinical relevance, frequently in the pericardium. The presence of adipose tissue in the aortic valve is rare, with unknown significance on valve structural properties and function. Aortic regurgitation (AR) is the third most prevalent valve disease, although it is uncommon to find it in isolation. Myxoid degeneration may be the cause or result of AR, although the pathophysiology remains poorly understood.

Purpose

To describe and characterize the presence of adipose tissue in the aortic valves from a cohort of AR patients.

Methods

116 patients undergoing aortic valve replacement due to severe AR were enrolled. We classified them in two groups according to the histological results showing presence or absence of adipose tissue in the aortic valves.

In the valve tissue molecular analysis were performed by RT-PCR, Western Blot and ELISA to analyze markers of adipocytes (leptin, adiponectin, resistin), inflammation (Rantes, interleukin-6, interleukin-1β), extracellular matrix remodeling (metalloproteinases-1, -2 and -9), proteoglycans (aggrecan, hyaluronan, lumican, syndecan-1, decorin) and fibrosis (collagens, fibronectin).

Results

Adipose tissue was found in 63% of the aortic valves analyzed. Baseline characteristics (age, hypertension, dyslipidemia, diabetes, smoking, left ventricular telediastolic diameter, left ventricular systolic function, ascending aorta) were similar in patients presenting valve adipose tissue as compared with patients without valve adipose tissue. Valves containing adipocytes exhibited a higher leptin content (p<0.001), fibronectin (p<0.01), decorin (p<0,0001), hyaluronan (p=0.03), aggrecan (p=0.04) and metalloproteinase 1 (p=0.03). Interestingly, the presence of adipocytes in the valve was positively correlated with valve thickness measured by echocardiogram (Pearson chi2 statistical significance = 26.3345 p<0.001).

Conclusion

To our knowledge, this is the first study that describes the presence of adipose cells in aortic valves from a cohort of AR patients. Aortic valves containing adipocytes were thicker and exhibited significant higher levels of proteoglycans, suggesting that adipocytes could contribute to the myxomatous degeneration process. Our results propose that the valve adipose tissue could play a role in the pathophysiology of AR.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): Gobierno de Navarra

New insights into the pathophysiology of mitral valve disease: molecular characterisation and comparison of the different aetiologic subtypes

Introduction

Mitral valve disease (MVD) is a frequent cause of heart failure and death. Data regarding its molecular basis are scarce, although current evidences show that primary MVD is an active process with the involvement of several molecular pathways. However, there are no studies that compare such mechanisms among the different subtypes of primary MVD. ST-2/interleukin (IL)-33 pathway is a potential pathophysiological mediator of cardiovascular diseases, although its role in heart valve diseases has not been explored.

Purpose

We aimed to analyse the molecular and cellular mechanisms involved in the main subtypes of primary chronic MVD: myxomatous degeneration, calcific or senile degeneration and rheumatic MVD.

Methods

200 patients undergoing mitral valve replacement due to chronic primary MVD were enrolled. We classified them in the three main aetiologic subtypes according to echocardiographic features and surgeon's description: myxomatous degeneration (89 patients), senile or calcific degeneration (54 patients) and rheumatic disease (57 patients). In all patients the resected valve tissue and blood samples were collected. RT-PCR, Western Blot and ELISA were performed to analyse markers of inflammation (C-reactive protein, Rantes, IL-6, IL-1β/IL-1F2, tumor necrosis factor (TNF)-α), calcification (osteopontin, bone morphogenic protein (BMP)-2 and -4 and periostin), valvular endothelial cells (CD-31, E-cadherin), extracellular matrix remodeling (matrix metalloproteinase (MMP)-1, -2 and -9, tissue inhibitor of MMP-1 and -2), proteoglycans (aggrecan, hyaluronan, lumican, biglycan, syndecan-1, decorin) fibrosis (collagen-1, fibronectin, galectin-3, Transforming growth factor (TGF)-β) and ST-2/IL-33 system.

Results

Each aetiologic subtype showed a distinct marker profile. As compared with the other subtypes, myxomatous valves presented significantly higher levels of inflammatory markers (Rantes, IL-6), fibronectin, proteoglycans (hyaluronan, lumican and biglycan), ST-2 and IL-33. Senile degenerative valves presented significantly higher levels of calcification markers (osteopontin, BMP-2 and -4). Rheumatic valves were characterized by high levels of TNF-α and TGF-β compared to other subtypes and a significant increase in the expression and activity of matrix degradation enzymes (MMP-1 and -2).

Conclusions

Our study provides for the first time the molecular characterisation of the main aetiologic subtypes of chronic MVD. Proteoglycans accumulation, fibrosis and inflammation are the main features of myxomatous changes, whereas calcification define senile degeneration. Rheumatic valves exhibit elevated TNF-α and TGF-β and a dramatic increase in matrix turnover. Moreover, myxomatous valves overexpress the ST-2/IL-33 system, suggesting that this pathway could play a role in the development of myxomatous changes. Unravelling the underlying molecular mechanisms of each aetiology is essential to identify new therapeutic targets.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Fondo de Investigaciones Sanitarias