Recent studies have shown efficient gene transfer to primitive progenitors in human cord blood (CB) when the cells are incubated in retrovirus-containing supernatants on fibronectin-coated dishes. We have now used this approach to achieve efficient gene transfer to human CB cells with the capacity to regenerate lymphoid and myeloid progeny in nonobese diabetic (NOD)/severe combined immunodefici...

HSCs either self-renew or differentiate to give rise to multipotent cells whose progeny provide blood cell precursors. However, surprisingly little is known about the factors that regulate this choice of self-renewal versus differentiation. One candidate is the Notch signaling pathway, with ex vivo studies suggesting that Notch regulates HSC differentiation, although a functional role for Notch...

Transforming growth factor-beta (TGF-beta) and macrophage inflammatory protein-l alpha (MIP-1 alpha) are both well-described inhibitors of committed and multipotential hematopoietic progenitors. The effect of these cytokines; on true stem cell activity in ex vivo culture systems as assayed by murine long-term repopulating activity (LTRA) has not been examined. We studied the stem cell effects o...

Maintenance, repair, and renewal of the epidermis are thought to depend on a pool of dedicated epidermal stem cells (EpiSCs). Like for many somatic tissues, isolation of a nearly pure population of stem cells is a primary goal in cutaneous biology. We used a quantitative transplantation assay, using injection of keratinocytes into subcutis combined with limiting dilution analysis, to assess the...

Foamy virus (FV) vectors have shown great promise for hematopoietic stem cell (HSC) gene therapy. Their ability to efficiently deliver transgenes to multi-lineage long-term repopulating cells in large animal models suggests they will be effective for several human hematopoietic diseases. Here, we review FV vector studies in large animal models, including the use of FV vectors with the mutant O...

Human hematopoietic stem cells are defined by their ability to repopulate multiple hematopoietic lineages in the bone marrow of transplanted recipients and therefore are functionally distinct from hematopoietic progenitors detected in vitro. Although factors capable of regulating progenitors are well established, in vivo regulators of hematopoietic repopulating function are unknown. By using a ...

Peripheral blood stem cells and progenitor cells, collected during recovery from exposure to cytotoxic agents or after cytokine administration, are being increasingly used in clinical bone marrow transplantation. To determine factors important for mobilization of both primitive stem cells and progenitor cells to the blood, we studied the blood and splenic and marrow compartments of intact and s...

The stem cell leukemia (SCL) gene is essential for the development of hematopoietic stem cells in the embryo. Here, we used a conditional gene targeting approach to examine the function of SCL in adult hematopoietic stem cells (HSCs). Flow cytometry of bone marrow from SCL-deleted mice demonstrated a 4-fold increase in number of Lin(neg) c-kit(+) Sca-1(+) cells. Despite this increase in the num...

Signal transducer and activator of transcription-5 (STAT5) plays an important role in repopulating activity of hematopoietic stem cells (HSCs). However, the relationship of STAT5 activation with early acting cytokine receptors is not well established. We have directly compared bone marrow (BM) from mice mutant for STAT5a and STAT5b (STAT5ab(-/-)) with that from mice lacking c-Mpl (c-Mpl(-/-)), ...

Many experimental and clinical protocols are being developed that involve ex vivo culture of human hematopoietic cells on stroma or in the presence of cytokines. However, the effect of these manipulations on primitive hematopoietic cells is not known. Our severe combined immune-deficient mouse (SCID)-repopulating cell (SRC) assay detects primitive human hematopoietic cells based on their abilit...