Methods to expand hematopoietic stem cells (HSCs) ex vivo encompass an attractive approach that would substantially
broaden the clinical applicability of HSCs derived from cord blood (CB). Recently, members of the angiopoietin‐like (Angptl) family of growth factors were shown to expand both murine and human HSCs.
Specifically, Angptl5 has been implicated in the expansion of human NOD/SCID‐repopulating cells (SRCs) ex vivo. Here, we sought to evaluate the potential of additional Angptls
to expand human SRCs from CB. Additionally, the purpose of this study was to evaluate the reproducibility of Angptl‐mediated expansion of SRCs across independent experiments. Methods
Human CD34+ cells from CB were cultured in vitro for eleven or 8 d in the presence or absence of Angptls. The reconstitution
capacity of expanded cells was subsequently measured in vivo by transplantation into NOD/SCID or NSG mice and compared with that of uncultured cells. Results
We report here that Angptl4 functions to maintain SRC activity of CD34+ CB‐derived cells ex vivo as assayed in NOD/SCID
and NSG mice. However, all Angptls tested, including Angptl1, Angptl4, and Angptl5, were associated with variation between experiments.
Our findings indicate that Angptl4 and Angptl5 can lead to increased engraftment capacity of SRCs, but more frequently, these factors are associated with maintenance of SRC
activity during ex vivo culture. Thus, Angptl‐mediated expansion of SRCs ex vivo is associated with more interexperimental variation than previously thought. We conclude that Angptls would be useful in instances
where there is a need to maintain HSCs ex vivo, such as during transduction for gene therapy applications.
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Document Type: Research Article
Publication date: September 1, 2012