182 M. Edvinsson et al. recent studies have demonstrated the presence of inﬂammatory cells in the aneurysm, indicating that inﬂammation may have a role in the pathogenesis of thoracic aortic aneurysms (3). Moreover, because gene expression studies have demonstrated up- regulated genes involved in inﬂammatory pro- cesses, inﬂammation may have a role also in aortic dissection (4). The respiratory pathogen Chlamydophila pneumo- niae (C. pneumoniae) has been suggested to be involved in the pathogenesis of atherosclerosis as an initiator and stimulator of the chronic inﬂamma- tion in the atherosclerotic plaque (5). This obligate intracellular bacterium has a unique biphasic life cycle that sometimes may be interrupted so that the bacterium passes into a persistent state unsusceptible to antibiotics (6). This ability of C. pneumoniae to cause chronic disease makes it difﬁcult to isolate from patient materials; in fact, only a few studies have succeeded in culturing C. pneumoniae from atherosclerotic tissue (7,8). On the other hand, many studies have demonstrated the presence of C. pneumoniae DNA within the atherosclerotic plaque (9); however, the presence of bacterial DNA does not indicate whether the bacterium is replicating and metabolically active or not. Viable and metabolically active C. pneumoniae may instead be proven by demonstration of bacterial mRNA in the tissue, which has been done in biopsies from the thoracic aorta in patients undergoing cor- onary artery by-pass surgery (CABG) (10). Dissem- ination of C. pneumoniae from the respiratory tract is believed to be mediated by alveolar macrophages, and in patients suffering from cardiovascular diseases C. pneumoniae has often been detected in peripheral blood mononuclear cells (PBMC) at a higher detection rate than in healthy blood donors (11). We have previously demonstrated the presence of C. pneumoniae DNA in 12% of thoracic aortic aneu- rysm biopsies and in none of six aortic dissection biopsies (12). In a more recent study of patients undergoing thoracic surgery because of thoracic aortic aneurysm we have demonstrated the presence of C. pneumoniae DNA in 26% of the thoracic aortic aneurysms (13). Moreover, trace elements were mea- sured in serum and aortic tissue in these patients, and changes indicating on-going infection/inﬂammation were demonstrated compared to healthy controls. In the present study we aimed to further characterize the state of the infection in these patients by investigating the presence of C. pneumoniae mRNA in aortic tissue as well as the presence of C. pneumoniae in PBMC. Furthermore, the presence of C. pneumoniae was also determined in patients undergoing thoracic surgery because of Type A aortic dissection. Material and methods Patients and patient samples In the present study 25 patients undergoing thoracic surgery because of ascending thoracic aortic aneu- rysm and 21 patients undergoing surgery because of Type A aortic dissection were included. The aneu- rysm patient group consisted of 17 men and 8 women with a mean age of 61 years (range 30–81 years). The aortic dissection patient group had a mean age of 61 years (range 45–78 years) and consisted of 15 men and 6 women. Clinical data on patients are presented in Table I. None of the patients had a hereditary connective tissue disorder. Thoracic aortic wall biop- sies were obtained from aneurysmatic or dissecting tissue during surgery and aseptically divided. One part of the biopsy was placed in RNAlater (Qiagen, Solna, Sweden) overnight and then frozen at 70 C, and another was ﬁxed in 10% formalin solution. The remaining parts of the biopsy were immediately frozen at 70 C until further processing. Blood samples were collected for antibody and for preparation of PBMC. Sera were frozen at 20 C until further Table I. Clinical data on thoracic aortic aneurysm (n = 25) and aortic dissection patients (n = 21). Arterial hypertension Hyperlipidemia Diabetes mellitus Smoker/former smoker Angina pectoris Previous myocardial infarction Undergoing CABG in same operation Undergoing aortic valve replacement in same operation Normal coronary arteries veriﬁed by coronary angiography Bicuspid aortic valve Family history of cardiovascular disease Aneurysm 44% (11/25) 28% (7/25) 4% (1/25)a 52% (13/25) 20% (5/25) 4% (1/25) 16% (4/25) 60% (15/25) 74% (17/23)b 32% (8/25) 20% (5/25) Dissection 71% (15/21) 14% (3/21) 0% (0/21) 43% (9/21) 14% (3/21) 5% (1/21) 14% (3/21) 10% (2/21) nd nd 5% (1/21) aThe one patient with diabetes mellitus had Type 1 diabetes mellitus. bAngiography was not performed on two patients. CABG = coronary artery by-pass surgery; nd = not determined.