Does cord blood contain enough progenitor cells for transplantation?

We analyzed 125 blood samples obtained from umbilical cord immediately after delivery of full-term neonates. Between 0.1 and 10.4% (mean 1.13%, SD 1.34) of the density-separated glycophorin A (GPA)-negative mononuclear cells (MNC) expressed CD34 as analyzed by flow cytometry. These hematopoietic progenitor cells did not coexpress CD19, and the majority were negative for CD45RA. The number of MNC determined per ml cord blood ranged from 1 x 10(5) to 200 x 10(5) (mean 20.2 x 10(5), SD 24.7). Regression analysis revealed that a mean of 56% (n = 26, R = 0.8) and 120% (n = 35, R = 0.94) of the analyzed CD34+ MNC gave rise to day 14 colonies in the clonogenic assay when cultured without or with stem cell factor (SCF). The number and the exact phenotype of progenitor cells required for successful transplantation are not known. If the transplantation of 5 x 10(5) CD34% cells/kg body weight is required for engraftment and one-third of the progenitor cells are lost to cell processing, and if 180 ml blood can be collected from a single umbilical cord (and placenta), our data suggest that 90% of the collections do not contain enough precursors to transplant a 25 kg recipient. To meet these conditions, an average of 1439 ml cord blood would be necessary for transplantation.