The frequency and proliferative potential of megakaryocytic colony-formingcells (Meg-CFC) in cord blood, cytokine-mobilized peripheral blood and bone marrow, and their correlation with total CFC numbers: implications for the quantitation of Meg-CFC to predict platelet engraftment following cord blood transplantation

CFC numbers have shown to correlate with success of engraftment and speed o f neutrophil recovery following cord blood (CB) transplantation. To investi gate whether the number of Meg-CFC in a CB stem cell preparation might corr elate with time to platelet engraftment, we evaluated the frequency of Meg- CFC among all CFC types in 134 CB, 21 adult bone marrow (BM) and 52 cytokin e-mobilized peripheral blood (PB) stem cell preparations. The correlation o f Meg-CFC with the total number of CFC and mixed cell-CFC was also assessed . The frequency of Meg-CFC was highest in CB and correlated significantly w ith total CFC numbers (mean 20.8%, correlation coefficient (r) 0.84, P=0.00 01) compared with Meg-CFC from mobilized PB (mean 13.1%, v = 0.29, P = 0.07 ) and BM (mean 4%, r = 0.39, P = 0.13), In addition, mixed-cell CFC numbers in CB were highly correlated with the total number of Meg-CFC (r=0.7, P=0. 0001). No such correlations were found with mobilized PB or BM, We conclude that, based on the high degree of correlation between Meg-C-FC and non-Meg -CFC numbers in CB. no additional information concerning time to platelet e ngraftment would be gained by routinely performing Meg-CFC assays in additi on to non-Meg-CFC assays, The fact that CB Meg-CFC and mixed-cell CFC are s trongly correlated suggests that CB Meg-CFC are more primitive than their c ounterparts in BM and PB and may reflect the number of stem cells in CB.