CD34+ stem cells from umbilical cord blood

We describe the relation between umbilicalcord clamping time and two different enrichmentsystem of CD34+ stem cells from umbilicalcord blood with the proliferative ability andbone marrow reconstitution of the stem cellsobtained. After an obstetrician performed thecord blood collection, the purification of stemcells was performed either with a combinationof monoclonal antibodies (negative selections)using the Stem Sep method, or with a positivecells selection based on their surface CD34antigens using the Mini Macs system. Anexcellent recovery of haematopoietic progenitors[Burst Forming Unit Erythroids (BFUE);Colony Forming Unit Granulocytes andMacrophages (CFU-GM); and Colony FormingUnit Granulocytes, Erythroids, Monocytes andMacrophages (CFU-GME)], inversely relatedto the increase in clamping time, was performedwith the Mini Macs system (54% ofcolonies, with 90% purity). With Stem Sepmethod, haematopoietic progenitor’s recoverywas 35% (with 80% purity). By applying earlyclamping of umbilical cord blood we obtained agreater number of CD34+ cells and their clonogenicactivity was increased with enrichment.This is a useful technique considering that thenumber of CD34+ stem cells usually containedfrom a unit of placental blood is enough for thetransplant to a child, but not for an adult. Thus,using these methods, we can get a larger numberof CD34+ stem cells which reduces the riskof Graft versus Host Disease also in adultpatients, producing survival rates similar tothose obtained with transplantation of bonemarrow from unrelated donors.