Haematopoietic repopulating activity in human cord blood CD133+ quiescent cells.

We have demonstrated previously that cord blood CD133(+) cells isolated in the G(0) phase of the cell cycle are highly enriched for haematopoietic stem cell (HSC) activity, in contrast to CD133(+)G(1) cells. Here, we have analysed the phenotype and functional properties of this population in more detail. Our data demonstrate that a large proportion of the CD133(+)G(0) cells are CD38 negative (60.4%) and have high aldehyde dehydrogenase activity (75.1%) when compared with their CD133(+)G(1) counterparts (13.5 and 4.1%, respectively). This suggests that stem cell activity resides in the CD133(+)G(0) population. In long-term BM cultures, the CD133(+)G(0) cells generate significantly more progenitors than the CD34(+)G(0) population (P<0.001) throughout the culture period. Furthermore, a comparison of CD133(+)G(0) versus CD133(+)G(1) cells revealed that multilineage reconstitution was obtained only in non-obese diabetic/SCID animals receiving G(0) cells. We conclude that CD133(+) cells in the quiescent phase of the cell cycle have a phenotype consistent with HSCs and are highly enriched for repopulating activity when compared with their G(1) counterparts. This cell population should prove useful for selection and manipulation in ex vivo expansion protocols.