Search for biomarkers of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a vascular pathology characterized by an increase of aorta diameter to at least 1.5 times the diameter of reference and a loss of parallelism of the aortic wall at the infrarenal region. AAA primarily affects elderly males with a prevalence of 5%. Its rupture is responsible for 1-4% of the total mortality in males older than 65 years. In case of rupture the mortality is up to 70-95%. Thus, AAA comes up as one of the leading causes of death in industrialized countries with aging populations. Age, male gender, tobacco consumption, genetic susceptibility and the presence of another atherosclerotic localization are known clinical risk factors for the development of AAA. Rupture can be prevented by vascular surgery which decreases mortality in AAA patients. Nevertheless, most AAA patients are asymptomatic and the majority not diagnosed prior to rupture. In this PhD work we have used differential proteomic techniques in order to analyze and compare human blood samples (plasma) and cells (smooth muscle cells and monocyte-differentiated macrophages) from patients presenting an AAA to unaffected patients. These analyses were performed with the aim of the following objectives: a) To identify and evaluate potential biological markers for AAA screening, that will ensure early diagnosis and subsequent early treatment of this fatal disease. b) To provide a better understanding of the physiopathological mechanisms involved in the evolution of AAA through the interpretation of the results in differential proteomic analysis. Regarding cell proteomic analysis, the use of saturation DIGE, together with SameSpots software, allowed the identification of 2 different protein profile in both cell types independently on the disease status of the patient. These two different proteome are the result of a technical bias during the application of DNase I treatment on the samples for the elimination of nucleic acids. We showed that DNase I treatment produced changes in proteome profiles of these cell types. The proteins mainly affected by this treatment were those involved in cell motion, actin cytoskeleton reorganization, and apoptosis. Due to the presence of this technical bias, comparison between AAA and non-AAA cell samples did not get any concluding result. Plasma proteome analysis was performed in collaboration with the laboratory of Pr. Goodlett, in Seattle (USA). Two different mass spectrometry based approaches were applied to compare plasma samples of AAA to plasma samples of non-AAA patients. The first approach combined the use of PAcIFIC MS analysis with spectral count while the second approach combined the use of data independent MS analysis with TMT isobaric labeling. After validation by Western blot analysis, four proteins were found to be differentially expressed between plasma samples of both groups of patients: adiponectin, extracellular superoxide dismutase, kallistatin and carboxypeptidase B2. These proteins are involved in aneurismal pathology and may be potential biological markers for AAA diagnosis. Large cohort studies are needed to validate their application for the screening of AAA in the population at risk. That will allow early detection of the disease and decrease of mortality on elderly population in developed countries.