In vivo visualization of 111In labeled CD133+ peripheral blood stem cells after intracoronary administration in...

Stem cell homing to injured tissue is necessary for local tissue repair. But homing of stem cells in chronic ischemic heart disease (CIHD) is poorly understood. This study investigated homing of peripheral blood stem cells (PBSC) expressing the CD133 antigen. After intracoronary injection. The cells were (111)In labeled for in vivo visualization.

PBSC were mobilized with granulocyte-colony stimulating factor and collected by apheresis on d-1. On d0, CD133+ cells were enriched up to a median purity of 89% (range: 79-97%) with an immunomagnetic separation device (CliniMACS, Miltenyi). A fraction of the cells was radiolabeled with [(111)In]oxine in 0.1 M TRIS at pH 7.4 for 45-60 min. Cell viability after labeling was assessed using trypan-blue. The cells were injected at a radioactive concentration of 0.9 MBq/10(6) cells into the target open coronary vessel through a balloon catheter. During balloon inflation [(99m)Tc]sestamibi was injected intravenously to identify the myocardium and the target vascular territory. Eight patients (mean age: 53 years; range: 50-72 years) with stable CIHD and reduced left ventricular function (NYHA class I-II) after acute myocardial infarction (>12 months) were studied. After a first cohort of 3 patients received an injectate of 5-10 x 10(6) cells, our final protocol was applied in 5 patients in whom an average of 34.4 x 10(6) (range: 18.6-49.4) CD133+ cells was injected. Whole body and single photon emission computed tomography (SPECT) scans were acquired at different time points after injection (energy windows set at 140, 171 and 245 keV). Residual activity in the heart was assessed by drawing a region of interest around the heart on the anterior whole body views.

Mean labeling efficiency of [111In]oxine labeling was 51.2% and cell viability after labeling averaged 88%. In the 5 patients receiving the higher amount of labeled cells, a clear (111)In-signal was observed in the heart region up to 3 days after administration. Fused [(99m)Tc]sestamibi/(111)In SPECT images demonstrated that the regional distribution of the transplanted cells within the target zone, as delineated by the flow tracer, remained unchanged over time. A biodistribution study in 2 patients showed a residual activity in the heart, liver and spleen of 6.9-8%, 23.1-26.8%, 3.1-3.7%, respectively, after 1-2 h and 2.3-3.2% 23.8-28.3%, 3.5-3.8%, respectively, after 12 h (decay corrected and expressed as a percentage of total body initial activity). No adverse events were observed during the procedure and up to 3 months follow-up.

Radiolabeling with [(111)In]oxine is a suitable method for follow-up of cell distribution during the first days after transplantation. A significant amount of CD133+ PBSC home to the heart after intracoronary injection in patients with CIHD. The results of this study are useful for the design of trials that evaluate the tissue repair potential of CD133+ PBSC in the setting of CIHD.