Notch-induced hIL-6 production facilitates the maintenance of self-renewal of hCD34+ cord blood cells through the activation of Jak-PI3K-STAT3 pathway.
ABSTRACT Ex vivo expansion of CD34(+) stem cells in contact culture between hCD34(+)CD38(-)Lin(-) cord blood stem cells and human delta-like-expressing AFT024 feeder cells revealed increased amounts of stemness-related proteins such as HoxB4, GATA2, Bmi-1, and p21 and anti-apoptotic proteins such as Bcl-2, Bcl-xL, Mcl-1, and phospho-Bad, when compared with control or noncontact culture. Production of human IL-6 (hIL-6) was markedly elevated in the culture, but was profoundly inhibited by treatment with γ-secretase inhibitor. In addition, Notch-induced activation of STAT3 was directly involved in gene expression of hIL-6 and soluble hIL-6Rα, indicating the close linkage between Notch signaling and hIL-6 production. Furthermore, depletion of soluble hIL-6 (with hIL-6-specific antibodies) and inhibition of IL-6-mediated signals (with a Jak1 inhibitor and wortmannin) severely affected the maintenance of self-renewal of hCD34(+) cord blood cells. It was also observed that the ex vivo expanded CD34(+) cord blood cells were induced to reconstitute human immune cells in nonobese diabetic mice with severe combined immunodeficiency when compared with freshly isolated CD34(+) cord blood cells. Together, these results strongly demonstrate that Notch signaling in the "cell-to-cell contact" between hCD34(+) cord blood and delta-like-expressing AFT024 feeder cells facilitates maintenance of self-renewal of hCD34(+) cord blood cells through direct regulation of hIL-6 production.
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ABSTRACT: Hox genes were first recognized for their role in embryonic development and may also play important lineage-specific functions in a variety of somatic tissues including the hematopoietic system. We have recently shown that certain members of the Hox A and B clusters, such as HOXB3 and HOXB4, are preferentially expressed in subpopulations of human bone marrow that are highly enriched for the most primitive hematopoietic cell types. To assess the role these genes may play in regulating the proliferation and/or differentiation of such cells, we engineered the overexpression of HOXB4 in murine bone marrow cells by retroviral gene transfer and analyzed subsequent effects on the behavior of various hematopoietic stem and progenitor cell populations both in vitro and in vivo. Serial transplantation studies revealed a greatly enhanced ability of HOXB4-transduced bone marrow cells to regenerate the most primitive hematopoietic stem cell compartment resulting in 50-fold higher numbers of transplantable totipotent hematopoietic stem cells in primary and secondary recipients, compared with serially passaged neo-infected control cells. This heightened expansion in vivo of HOXB4-transduced hematopoietic stem cells was not accompanied by identifiable anomalies in the peripheral blood of these mice. Enhanced proliferation in vitro of day-12 CFU-S and clonogenic progenitors was also documented. These results indicate HOXB4 to be an important regulator of very early but not late hematopoietic cell proliferation and suggest a new approach to the controlled amplification of genetically modified hematopoietic stem cell populations.Genes & Development 08/1995; 9(14):1753-65. · 12.44 Impact Factor
Article: Hematopoietic receptor complexes.[show abstract] [hide abstract]
ABSTRACT: Hematopoietic hormones/cytokines and receptors regulate a wide variety of biological activities and are important in medicine. Through recent biochemical, biophysical, and structural studies we are beginning to understand how these molecules work at the molecular level. These extracellular hormones activate their transmembrane receptors by causing them to oligomerize. The receptor oligomers in turn activate intracellular tyrosine kinase molecules which then activate transcription factors (the JAK-STAT pathways). This review centers on the molecular basis for hormone-receptor binding, and how this information is useful in understanding protein-protein interactions and for the design of second generation molecules.Annual Review of Biochemistry 02/1996; 65:609-34. · 27.68 Impact Factor
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ABSTRACT: Ex vivo culture of human hematopoietic cells is a crucial component of many therapeutic applications. Although current culture conditions have been optimized using quantitative in vitro progenitor assays, knowledge of the conditions that permit maintenance of primitive human repopulating cells is lacking. We report that primitive human cells capable of repopulating nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) mice (SCID-repopulating cells; SRC) can be maintained and/or modestly increased after culture of CD34+CD38- cord blood cells in serum-free conditions. Quantitative analysis demonstrated a 4- and 10-fold increase in the number of CD34+CD38- cells and colony-forming cells, respectively, as well as a 2- to 4-fold increase in SRC after 4 d of culture. However, after 9 d of culture, all SRC were lost, despite further increases in total cells, CFC content, and CD34+ cells. These studies indicate that caution must be exercised in extending the duration of ex vivo cultures used for transplantation, and demonstrate the importance of the SRC assay in the development of culture conditions that support primitive cells.Journal of Experimental Medicine 09/1997; 186(4):619-24. · 13.21 Impact Factor