CD34 circulating cells display signs of immune activation in patients with acute coronary syndrome.

Bone marrow-derived endothelial progenitor cells (EPC) are released into the peripheral blood in situations of vascular repair/angiogenesis. Regulation of vascular repair and angiogenesis by EPC depends not only on the number of circulating EPC but also on their functionality. As endothelial cells can act as antigen-presenting cells in coronary artery disease (CAD), we postulated that EPC can be immune activated here as well. CD34-EPC were isolated from peripheral blood of patients with ST-elevation myocardial infarction (STEMI, n = 12), non-STEMI/unstable angina (UA, n = 15), and stable CAD (SA, n = 18). Expression of HLA-DR, adhesion and costimulatory molecules by isolated CD34-EPC were compared with levels in healthy controls (n = 18). There were no significant differences in VCAM-1 and CD80 expression by peripheral circulating CD34-EPC between the four groups, yet expression of CD86 was highest in UA (p < 0.05). ICAM-1 expression was lowest in SA (p < 0.01). CD34-EPC constitutively expressed HLA-DR across all groups. Of note, patients pretreated with HMG-CoA reductase inhibitors exhibited lower expression of VCAM-1 by CD34-EPC throughout all patient groups; furthermore, statins significantly limited ex vivo-induced upregulation of ICAM-1 by TNF-alpha. To the best of our knowledge, this is the first study to examine the expression of immune markers in peripheral circulating CD34-EPC ex vivo. We demonstrate that CD34-EPC display different patterns of adhesion and costimulatory molecules in various states of CAD. Expression levels were affected by pretreatment with statins. Hence, immune activity of peripheral circulating CD34 cells might play a pathophysiologic role in evolution of CAD.