Clinical Evidence That Oct-4+ ssea-4+ Very Small Embryonic Like Stem Cells (VSEL) Are Mobilized into Peripheral Blood in Patients with Acute Myocardial Infarction (AMI): A Novel Prognostic Indicator

Abstract

We demonstrated that murine bone marrow (BM) contains a mobile population of CXCR4+SSEA-1+Sca-1+lin CD45− very small embryonic like (VSEL) stem cells (Leukemia 2006: 20; 857) that are mobilized into peripheral blood (PB) in SDF-1 dependent manner in murine model of acute myocardiac infarct (AMI) (J Moll Cell Cardiol 2008, 44, 865–873). Since a similar population of CXCR4+CD133+CD34+SSEA-4+Oct-4+lin−CD45− cells resides also in human BM (Leukemia 2007: 21;297), we asked whether in humans, similarly as in mice, the AMI-related stress may trigger mobilization of these cells from BM into PB. To address this question, we evaluatedthe mobilization of VSEL in patients with AMI,measured expression of pluripotential stem cell (PSC), cardiac and endothelial markers in peripheral blood mononuclear cells and purified by FACS VSEL,and finally assessed the factors influencing mobilization of VSEL and correlation of cell number with left ventricular ejection fraction (LVEF).Totally, 31pts with AMI and 30 healthy subjects were enrolled. Peripheral blood was sampled on admission, after 24 hours and 5 days VSEL were enumerated by FACS and sorted by Facs-Aria. Presence of PSC markers (Oct-4, SSEA-4) and chemokine receptor CXCR4 in circulating VSEL was confirmed at the protein level immunofluorescent staining and ImageStream system (ISS) analysis. Plasma levels of SDF-1, HGF, VEGF, G-CSF were measured by ELISA. We noticed that in healthy subjects median number of circulating VSEL is very low [0.8 (0–1.3] cells/μL. In AMI VSEL were mobilized early [2.7 (0.2–3.9) cells/μL; p<0.001), and remained elevated after 24 hrs and 5 days [4.7 (0.2–7.4); p<0.001 and 2.6 (0.3–3.6) cells/μL; p<0.03, respectively]. Circulating VSELs were enriched in mRNA of PSC markers (Oct-4: 206±3-fold; Nanog: 282,1±4-fold), cardiac lineage (GATA-4, Nkx2.5/Csx, MEF2C) and endothelial (VE-cadherin) markers. Highest relative expression level was detected after 24h after acute MI. VSEL size - cell diameter was approx. 7–8 μm. The mobilization of VSEL after 12 and 24 hrs was significantly higher in patients younger than 50y [4.9 (0–6.4) vs. 2.7 (0.2–5.1) cells/μL; P<0.05]. In patients with diabetes the number of mobilized VSEL after 12 and 24 hrs was significantly lower than in those without diabetes [1.9 (0–2.3) vs. 4.8 (0.2–6.2) cells/μL; P<0.05]. Mobilization of VSEL was impaired in patients with LVEF <40% in comparison to LVEF >40% [3.3 (0–4.9) vs. 4.7 (0.4–6.4) cells/μL; P<0.05]. Of note VSEL showed significant negative correlations with cardiac necrosis markers (maximum activity of CK-MB and troponin I) after 12 and 24 hrs, but not 5 days (R=−0.41, R=−0.45). Thus, for the first time in humans we provide evidence that AMI induces mobilization of VSEL expressing pluripotent markers as well SDF-1 binding receptor CXCR4. Mobilization of VSEL is impaired in older patients with diabetes and reduced LVEF. Number of mobilized VSEL is inversely correlated with myocardial necrosis markers and positively with SDF-1 levels.