The Role Oral Microbiome in the Development and Progression of Aorta Aneurysm and Carotid Atherosclerosis

Overview

The goal of this observational study is to compare the microbiome (bacterial al community) of the diseased vascular site and the oral cavity with specific attention to chronic inflammatory periodontitis in patients who have aorta aneurysm or carotid stenosis needing surgical treatment. The main question it aims to answer is whether pathogen members of the oral microbial community, that cause periodontal disease, are also present in the diseased vascular site proving its translocation from the oral cavity to the vascular system. We hypothesize that bacteria causing chronic periodontal disease can be found at the diseased vascular site highlighting the importance of maintaining and restoring oral health as preventive measure for vascular diseases. Participants will be asked to take part in a dental screening before vascular surgery, during which few samples will be taken non-invasively for analysis.

Background According to the statement by the World Health Organization, cardiovascular diseases are currently the primary cause of death. Around 202 million people are suffering from lower extremity arterial disease worldwide. The occurrence of moderate to severe carotid artery stenosis is less frequent, with a prevalence of only 4.2% according to recent reports. However, it can be a probable cause of TIA or stroke in 12-25% of acute ischemic strokes. Fortunately, the prevalence of abdominal aortic aneurysms and incidence rates have decreased over the last 20 years, which has been attributed partially to the decline in smoking. Aortic aneurysms are the most common dilations in the human body, which occur primarily in the abdominal aorta section. The disease affects approximately 1-5% of the adult population. Its main risk factors include age over 65, smoking, and male gender. The exact pathomechanism of the disease is still unknown but the importance of degenerative (atherosclerosis, fibromuscular dysplasia, cystic media degeneration), congenital (Marfan syndrome, Ehlers-Danlos syndrome, coarctation aortae), mechanical (traumatic, iatrogenic, post stenotic) and inflammatory (bacterial, autoimmune) factors arise. The pathological role of atherosclerosis mainly emerges in the background of the degenerative processes that develop in the walls of blood vessels. In addition, based on the latest scientific research results, knowledge of the systemic autoimmune processes involved in the etiology of aortic aneurysms and the consequent local inflammatory mechanisms is of particular importance. According to our latest scientific knowledge at a molecular level, histopathological classification, tissue transformation, mapping of the degradation of structural proteins that weaken the aortic wall, spatial aspects, and immunological factors all contribute to the development of aneurysms. Although the importance of immunological processes seems to be crucial, the precise contribution of the immunological factors to the aneurysm formation is largely unknown. A wide variety of abnormal immunological responses associated with inflammation and autoimmunity in the vessel wall are known, such as loss of immune tolerance, activation of pro-inflammatory cytokines, age-related vascular wall remodeling, and immunosenescence. Clinically, large vessel vasculitis and vasculitis associated with other systemic autoimmune diseases may play a role in the development of aneurysms through the shift in these immunological processes. Inflammatory processes may persist for years in addition to the remission of these diseases, promoting the development of aneurysms years after diagnosis of vasculitis. On the other hand, the importance of persistent subclinical local inflammatory processes in the development of aneurysms, which does not show a clinical picture of large vessel vasculitis, also arises. Gut microbiota dysbiosis and microbiome pattern is also an important cause of aneurysm formation. In summary, knowledge of local immunological processes and microbiome patterns involved in the etiology of aortic aneurysms may promote improved diagnosis and treatment. The coincidence of peripheral vascular diseases and poor oral health has been a well-observed phenomenon in recent years. Periodontitis is an oral disease that is highly prevalent worldwide. It is an inflammatory disease affecting about 50% of the global population, its severe form is present in more than 750 million people, therefore it is the 6th most prevalent disease in mankind. In Europe, alone the prevalence of mild to moderate periodontitis is 40-60%, and of severe periodontitis, it is 10-20%. The inflammatory process starts with dental plaque collecting on the tooth surface in patients with inadequate oral hygiene containing hundreds of microbial species. This bacterial biofilm causes a reversible gingival inflammation known as gingivitis, but if untreated and neglected, it may progress to periodontitis in patients where periopathogenic species dominate. This in turn induces an inflammatory host response and burdens the immune system. Periodontitis is the leading cause of adult tooth loss due to the breakdown of teeth-supporting tissues. Furthermore, it may induce inflammatory processes in other parts of the body, such as the nervous system, and the cardiovascular system. Whether the relationship between oral and vascular lesions is causal or not is unclear, but periodontal pockets act as a portal for bacterial entrance into the circulation. Understanding the microbiome of symptomatic and asymptomatic patients may help in the early detection and possible prevention of symptomatic manifestations of carotid artery stenosis. More and more evidence has been published about the potential relationship between periodontal and cardiovascular diseases. According to the published results, a correlation was revealed between the severity of periodontal disease and pathogen load detected from vascular samples of atherosclerotic plaques and aneurismatic walls. Although, a microbiomial pattern, compatible with oral samples was found in only 21% of samples taken from carotid plaques. The role of periodontitis has also been examined in cases with abdominal aortic aneurysms. The progression of aneurysm significantly correlates with periodontal inflammation. Some periopathogens present in periodontal pockets were detected in the aneurysmatic vessel wall. The presence of a significant periopathogen, Porphyromonas gingivalis can be detected in aneurysmatic samples in around 23% of the examined cases, which is a similar ratio detected from samples collected from carotid plaques. Aim of the study The main aim of the study will be to identify the presence of periopathogenic bacteria in the vascular wall of arterial aneurysm and atherosclerotic plaque. We would like to compare the asymptomatic and symptomatic patient cohort going under carotid artery reconstruction and the patient group with abdominal aneurysm based on the presence of periodontitis with the microbiome from oral and anal samples using carotid plaque and aneurysm samples and data. Design of the study This is a prospective study based on samples collected during vascular surgery. The study group consists of 100 patients enrolled (25 with asymptomatic carotid stenosis, 25 with symptomatic carotid stenosis, 50 with AAA) needing carotid endarterectomy or open aneurysm reconstruction in the Department of Vascular and Endovascular Surgery. The indication for the surgery is according to the national clinical guidelines. Patients are informed of the aim of the study and sign an informed consent. The study is approved by the Ethical Committee. Reasons for exclusion are: generalized antibiotics prescribed in the previous 3 months. Methodology and organization of the study All patients are invited for a dental check-up and if needed urgent dental treatment prior to vascular surgery. Stomato-oncological screening and a search for de-epithelized areas are done. Dental status, the number of teeth and edentulousness are noted. A panoramic x-ray is taken for general screening. Detailed periodontal status is documented. The following data are described: basic periodontal examination (BPE) index, bleeding on probing (BOP), probing depth, clinical attachment loss, mobility, furcation involvement and the presence of suppuration. Samples will be taken from the saliva, the bucca, the back of the tonque, the periodontal pockets. Then the patients will undergo vascular surgery during which blood and vascular samples will be taken.