['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.', '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.', '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.'] Does angptl4 maintain in vivo repopulation capacity of CD34+ human cord blood cells?