Two CD34+ stem cells from umbilical cord blood enrichment methods.

The authors describe the relation between clamping time and blood volume collected, and two enrichment systems of CD34+ stem cells from umbilical cord blood, to determine an excellent recovery with high proliferate ability and bone marrow reconstitution. After an obstetrician-based cord blood collection, the purification of stem cells was performed either with a combination of monoclonal antibodies (negative selections) using the Stem Sep method, or with a positive cells selection thanks to their surface CD34 antigens, using the Mini Macs system. An excellent recovery of hematopoietic progenitors, burst-forming unit erythroid, colony-forming unit granulocyte and macrophage, and colony-forming unit granulocyte, erythroid, monocyte, and macrophage, inversely related to the rising of clamping time, was performed with the Mini Macs system (54% of colonies, with a 90% purity), while with Stem Sep method, hematopoietic progenitor recovery was 35% (with an 80% purity). By applying early clamping of the umbilical cord blood a greater number of CD34+ cells was obtained and their clonogenic activity increased with enrichment. This is particularly useful, considering that the number of CD34+ stem cells contained in a unit of placental blood is enough for transplanting to a child, but not for an adult engraftment. Thus, using this method, a larger number of CD34+ stem cells can be obtained, which increases the possibility to reduce graft versus host disease also in adult patients, producing survival rates similar to the ones obtained with transplantation of bone marrow from unrelated donors.