Probing the mitotic history and developmental stage of hematopoietic cells using single telomere length analysis (STELA).

In most human somatic cells, telomeres shorten as a function of DNA replication. Telomere length is therefore an indirect measure of the replicative history of cells. We measured the telomere lengths at XpYp chromosomes in purified human hematopoietic populations enriched for stem cells (Lin(-)CD34(+)CD38(-)Rho(-)) and successively more mature cells.

Improved purification of hematopoietic stem cells based on their elevated aldehyde dehydrogenase activity.

Background And Objectives: Primitive human hematopoietic cells contain higher levels of aldehyde dehydrogenase (ALDH) activity than their terminally differentiating progeny but the particular stages when ALDH levels change have not been well defined. The objective of this study was to compare ALDH levels among the earliest stages of hematopoietic cell differentiation and to determine whether these could be exploited to obtain improved purity of human cord blood cells with long-term lympho-myeloid repopulating activity in vivo.

Design And Methods: ALDEFLUOR-stained human cord blood cells displaying different levels of ALDH activity were first analyzed for co-expression of various surface markers.