The activity in ex vivo expansion of cord blood myeloid progenitor cells before and after cryopreservation

A total of 50 human umbilical cord blood (UCB) samples were studied. The he matopoietic stem/progenitor (CD34+) populations were isolated from UCB mono nuclear cells (MNC) by means of immunomagnetic separation. Double immunoflu orescent staining of UCB CD34+ cells revealed that there was a high proport ion (82.33 +/- 4.47%) of CD34+ cells co-expressing CD13, while the percenta ge of CD34+ CD33+ cells was much lower (22.17 +/- 3.35%). In contrast, for co-expressing lymphoid differentiation antigens, the proportion of CD34+CD3 8+ cells (38.34 +/- 6.09%) was relatively higher than that of CD34+CD10+ ce lls (11.52 +/- 1.24%) or CD34+CD2+ cells (9.84 +/- 2.30%). For stimulating the ex vivo expansion of UCB progenitor cells, no single hematopoietic grow th factor (HGF) was efficacious when used alone, while combination of 4 HGF s, such as GM-CSF, G-CSF, IL-3, and SCF could induce a 55-fold increase in the myeloid progenitor cells, day-14 CFU-GM, in a short term of 7 days' liq uid culture. Cryopreservation of UCB as WING preparations at -196 degreesC could satisfactorily retain the number a nd activity of CD34+ cells. After thawing, a high recovery rate of about 80% CD34+ cells was obtained. When s uspended in liquid cultures containing a combination of 4 HGFs, as shown ab ove, the frozen cord blood progenitor cells could be well expanded, reachin g a > 50-fold increase in day-14 CFU-GM, which was very similar to that of the fresh UCB samples. In addition, a similar result was also seen in CFU-G EMM, indicating that after cryopreservation the recovered UCB progenitor ce lls retain an intact clonogeneic ability capable of efficiently responding to hematopoietic growth factors for ex vivo expansion. Copyright (C) 2001 S . Karger AG, Basel.