Initial CD34+ cell-enrichment of cord blood determines hematopoietic stem/progenitor cell yield upon Ex vivo expansion

• Published in: Journal of cellular biochemistry 2011-07, Vol.112 (7), p.1822-1831
• Main Authors: Andrade, Pedro Z., da Silva, Cláudia Lobato, dos Santos, Francisco, Almeida-Porada, Graça, Cabral, Joaquim M.S.
• Format: Article
• Language: English
• Subjects: Antigens, CD34 - metabolism; CD34 Enrichment; Cell Culture Techniques; Cell Cycle; Cell Differentiation; Cell Proliferation; Cells, Cultured; Ex-vivo expansion; Fetal Blood - cytology; Flow Cytometry; Hematopoietic Stem Cells - cytology; Hematopoietic Stem Cells - metabolism; Hematopoietic stem/progenitor cells; Humans; Immunomagnetic Separation; Leukocytes, Mononuclear - metabolism; Phenotype; Umbilical cord blood
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.23099

Since umbilical cord blood (UCB), contains a limited hematopoietic stem/progenitor cells (HSC) number, successful expansion protocols are needed to overcome the hurdles associated with inadequate numbers of HSC collected for transplantation. UCB cultures were performed using a human stromal‐based serum‐free culture system to evaluate the effect of different initial CD34+ cell enrichments (Low: 24 ± 1.8%, Medium: 46 ± 2.6%, and High: 91 ± 1.5%) on the culture dynamics and outcome of HSC expansion. By combining PKH tracking dye with CD34+ and CD34+CD90+ expression, we have identified early activation of CD34 expression on CD34− cells in Low and Medium conditions, prior to cell division (35 ± 4.7% and 55 ± 4.1% CD34+ cells at day 1, respectively), affecting proliferation/cell cycle status and ultimately determining CD34+/CD34+CD90+ cell yield (High: 14 ± 1.0/3.5 ± 1.4‐fold; Medium:22 ± 2.0/3.4 ± 1,0‐fold; Low:31 ± 3.0/4.4 ± 1.5‐fold) after a 7‐day expansion. Considering the potential benefits of using expanded UCB HSC in transplantation, here we quantified in single UCB units, the impact of using one/two immunomagnetic sorting cycles (corresponding to Medium and High initial progenitor content), and the average CD34+ cell recovery for each strategy, on overall CD34+ cell expansion. The higher cell recovery upon one sorting cycle lead to higher CD34+ cell numbers after 7 days of expansion (30 ± 2.0 vs. 13 ± 1.0 × 106 cells). In particular, a high (>90%) initial progenitor content was not mandatory to successfully expand HSC, since cell populations with moderate levels of enrichment readily increased CD34 expression ex‐vivo, generating higher stem/progenitor cell yields. Overall, our findings stress the importance of establishing a balance between the cell proliferative potential and cell recovery upon purification, towards the efficient and cost‐effective expansion of HSC for cellular therapy. J. Cell. Biochem. 112: 1822–1831, 2011. © 2011 Wiley‐Liss, Inc.