Proteomics of Ascending Aortic Aneurysm with Bicuspid or Tricuspid Aortic Valve

Metabolomic profiling of ascending thoracic aortic aneurysms and dissections - Implications for pathophysiology and biomarker discovery

Objective

Our basic understanding of ascending thoracic aortic aneurysm (ATAA) pathogenesis is still very limited, hampering early diagnosis, risk prediction, and development of treatment options. “Omics”-technologies, ideal to reveal tissue alterations from the normal physiological state due to disease have hardly been applied in the field. Using a metabolomic approach, with this study the authors seek to define tissue differences between controls and various forms of ATAAs.

Methods

Using a targeted FIA-MS/MS metabolomics approach, we analysed and compared the metabolic profiles of ascending thoracic aortic wall tissue of age-matched controls (n = 8), bicuspid aortic valve-associated aneurysms (BAV-A; n = 9), tricuspid aortic valve-associated aneurysms (TAV-A; n = 14), and tricuspid aortic valve-associated aortic dissections (TAV-Diss; n = 6).

Results

With sphingomyelin (SM) (OH) C22:2, SM C18:1, SM C22:1, and SM C24:1 only 4 out of 92 detectable metabolites differed significantly between controls and BAV-A samples. Between controls and TAV-Diss samples only phosphatidylcholine (PC) ae C32:1 differed. Importantly, our analyses revealed a general increase in the amount of total sphingomyelin levels in BAV-A and TAV-Diss samples compared to controls.

Conclusions

Significantly increased levels of sphingomyelins in BAV-A and TAV-Diss samples compared to controls may argue for a repression of sphingomyelinase activity and the sphingomyelinase-ceramide pathway, which may result in an inhibition of tissue regeneration; a potential basis for disease initiation and progression.

Focus on the unique mechanisms involved in thoracic aortic aneurysm formation in bicuspid aortic valve versus tricuspid aortic valve patients: clinical implications of a pilot study

OBJECTIVES

The involvement of different factors in the onset of thoracic aortic aneurysm (TAA) in patients with a bicuspid aortic valve (BAV) vs those with a tricuspid aortic valve (TAV) is well recognized. However, the molecular, genetic and cellular mechanisms driving TAA remain unclear. The aim of this study was to identify the different mechanisms involved in TAA development in patients with BAV vs TAV.

METHODS

Aorta specimens and DNA samples were collected from 24 BAV (18 men and 6 women; mean age: 54.2 ± 14.39 years) and 110 TAV (79 men and 31 women, mean age: 66 ± 9.8 years) patients. A control group of 128 subjects (61 men and 67 woman, mean age: 61.1 ± 5.8 years) was also enrolled. Histopathological and immunohistochemical analyses were performed, as well as genotyping of 10 polymorphisms.

RESULTS

In BAV-associated ascending aortas, significant severe plurifocal apoptosis of smooth muscle cells and matrix metalloproteinase-9 (MMP-9) amounts were detected. In contrast, TAV-associated ascending aortas were characterized by a significant severity of elastic fragmentation, cystic medial necrosis, medial fibrosis and inflammation. In addition, in BAV cases, the -1562TMMP-9 and -735TMMP-2 alleles represent independent risk factors for TAA. The effects of these genotypes combined with hypertension and smoking in BAV cases result in an increase in both the apoptosis (P = 0.0001) and levels of MMP-9 (P = 0.001). In TAV cases, the D angiotensin-converting enzyme and +896A Toll-like receptor-4 alleles seem to be the predictive factors for TAA risk. They, combined with hypertension and age, significantly increase both the microscopic lesions and inflammation.

CONCLUSIONS

Our data seem to suggest that TAA in BAV and TAV patients arises from different molecular, cellular and genetic mechanisms. They might help to identify the potential molecular and genetic biomarkers that are useful to detect BAV subjects at high TAA risk, to monitor and treat them differently from those with TAV, with approaches such as the complete removal of the ascending aorta, including the aortic root with or without dilatation.

Proteomic profiling of medial degeneration in human ascending aorta

OBJECTIVE

The objective of this study was the construction of a reference map for aortic medial degeneration by a proteomic approach.

DESIGN AND METHODS

A proteomic profiling of the media of human ascending aorta was performed by two-dimensional electrophoresis and MALDI-TOF mass spectrometry.

RESULTS

A reliable protocol for two-dimensional electrophoresis analysis of human aortic media proteins was developed allowing the selection and identification of 52 spots. Protein identifications revealed that the predominant vascular smooth muscle cell proteins isolated from grade 1 aortic medial degeneration (MD) included proteins involved in muscle contraction, protein folding, cytoskeletal structure and metabolic processes, and those with antioxidant or transport functions. The most populated functional classes were those related to muscle contraction and cytoskeletal proteins, including actin, calmodulin, calponin, myosin light chain, tropomyosin, vimentin, profilin and transgelin.

CONCLUSIONS

The obtained aortic MD proteomic profile provides a relevant background for future studies aimed to find further specific molecular changes potentially related to the aortic MD process.

Quantitative proteome analysis in cardiovascular physiology and pathology. I. Data processing

Methodological evaluation of the proteomic analysis of cardiovascular-tissue material has been performed with a special emphasis on establishing examinations that allow reliable quantitative analysis of silver-stained readouts. Reliability, reproducibility, robustness and linearity were addressed and clarified. In addition, several types of normalization procedures were evaluated and new approaches are proposed. It has been found that the silver-stained readout offers a convenient approach for quantitation if a linear range for gel loading is defined. In addition, a broad range of a 10-fold input (loading 20-200 microg per gel) fulfills the linearity criteria, although at the lowest input (20 microg) a portion of protein species will remain undetected. The method is reliable and reproducible within a range of 65-200 microg input. The normalization procedure using the sum of all spot intensities from a silver-stained 2D pattern has been shown to be less reliable than other approaches, namely, normalization through median or through involvement of interquartile range. A special refinement of the normalization through virtual segmentation of pattern, and calculation of normalization factor for each stratum provides highly satisfactory results. The presented results not only provide evidence for the usefulness of silver-stained gels for quantitative evaluation, but they are directly applicable to the research endeavor of monitoring alterations in cardiovascular pathophysiology.