Analysis of the expression of adhesion molecules on CD34+ progenitors from bone marrow, umbilical cord blood and G-CSF mobilized peripheral blood

Umbilical cord blood (UCB) and leukapheresis products (LP) are increasingly used as an alternative source of CD34+ hematopoietic progenitor cells (HPC) in transplantation settings. We have investigated 35 samples of LP, 12 of UCB and 9 of bone marrow (BM) to assess possible differences in the expression of adhesion molecules (CAMs) and differentiation antigens. Such expression was also evaluated in terms of mean fluorescence intensity ratio (MFIr) obtained dividing the MFI of the positive sample by that of the isotype matched control. The highest percentage of hematopoietic progenitors cells (HPC) was found in LP (P = .002). Conversely, CD34 MFIr was higher for UCB HPC (P = .012). Progenitors from UCB and BM showed a large percentage of CD49d (P = .002) with an higher MFIr (P < .001). L-selectin MFIr was higher on HPC from BM (P = .003). CD11a and CD18 were more frequently expressed on UCB HPC (P < .001 for both). CD11c was more expressed on LP HPC (P < .001). MFIr for both CD11a and CD11c was higher on BM HPC (P = .002 and .009, respectively). We also compared BM, UCB and LP to an homogeneous group of 10 G-CSF mobilized normal donors (ND) to avoid possible differences in CD34+ cells phenotype due to different mobilization procedures: all comparisons maintained the same statistical significance. Remarkably, LP and ND showed a similar pattern of CAMs expression. CD38, HLA-DR, were positive on > 90% of CD34+ cells from the 3 sources. CD13 and CD33 showed a lower expression on BM HPC. An higher percentage of CD34+/Thyl+/ HLA-DR(=) cells was observed in UCB while CD34+/CD38+/HLA-DR- and CD34+/CD38-/HLA-DR- cells predominated in BM. In conclusion, LP is the richest source of CD34+ progenitors while UCB precursors showed more numerous CD34+/Thyl+ cells and a 'dim' expression of C-kit: both characteristics belong to more clonogenic precursors. UCB progenitors expressed a CD49d and L-selectin MFIr which were similar to that of BM and LP stem cells, respectively. Both LP and UCB have a pattern of adhesion and differentiation molecules consistent with the presence of long term proliferating HPC, this explains, at least in part, why they may represent a valid alternative to BM as a source of CD34+ progenitors for transplantation.