Isolation of early hematopoietic cells, including megakaryocyte progenitors, in the ALDH-bright cell population of cryopreserved, banked UC blood

Background ALDH-bright (ALDH(br)) cell populations sorted from freshly collected umbilical cord blood (UCB) on the basis of their high aldehyde dehydrogenase (ALDH) activity are highly enriched for HPC. HPC with low ALDH activity (ALDH(dim)) are primarily short-term progenitors, whereas progenitors that initiate long-term cultures or establish long-term grafts in xenograft models are ALDH(br). We examined the multilineage hematopoietic and platelet progenitor activities of ALDH(br) cells recovered from cryopreserved UCB units typically employed in the practice of clinical transplantation. Methods Frozen UCB units were thawed, washed, immunomagnetically depleted of cells expressing glycophorin A and CD14, reacted for flow cytometric detection of ALDH, and sorted to yield ALDH(br) and ALDH dim populations. We measured surface Ag expression and viability of cells in the ALDH(br) and ALDH dim populations by flow cytometry and hematopoietic (CFC-H) and megakaryocytic (CFC-Mk) colonyforming cells in each population. Results ALDH(br) populations isolated from thawed UCB cells were highly enriched for CD34(+) and CD133(+) cells. Flow-sorted ALDHbr populations were enriched 1116-fold in CFC-H, 10-fold in multilineage GEMM colonies and 2015-fold in CFC-Mk compared with the ALDH(dim) population. All progenitors giving rise to large Mk colonies were derived from ALDH(br) populations. Discussion ALDH(br) populations recovered from thawed, banked UCB with the method we describe have HPC activity and may be useful in the clinic to facilitate reconstitution of erythroid, myeloid and megakaryocytic blood elements.