A cellular model for drug interactions on hematopoiesis: The use of human umbilical cord blood progenitors as a model for the study of drug-related myelosuppression of normal hematopoiesis

A cellular model of hematopoiesis which would be more convenient than bone marrow (BM) progenitors and directly relevant to human pathology is needed in order to investigate xenobiotic toxicity. Human umbilical cord blood (HCB), previously shown to be able to repopulate BM, provides a powerful in vitro model of normal human hematopoiesis. In order to validate the use of normal HCB progenitors as targets for dose-related myelosuppression, we used clonogenic assays and expansion in a liquid culture of progenitor-enriched cell suspensions from HCB. A series of 8 reference molecules, doxorubicin, cytosine-arabinoside, 5-fluorouracil, 3-azido-3-deoxythymidine, acetylsalicyclic acid, sodium valproate and two cephalosporin antibiotics, were tested. In vitro 50% inhibition concentrations (IC₅₀) were compared to those observed or reported with BM progenitors, and to the values of plasma concentrations from treated patients. HCB progenitors as in vitro targets for cytotoxic molecules were easy to access and handle, and their use was sensitive, specific and reproducible. They gave results similar to BM progenitors and allowed a qualitative approach to cellular metabolism and toxicity using morphological, flow cytometric and chromatographic methods.Abbreviations ARA-CC cytosine arabinoside - AS acetylsalicylic acid - AZTT 3-azido-3-deoxythymidine - BFUU burst-forming units - BM bone marrow - CFU colony-forming units - DOXX doxorubicin - FU 5-fluorouracil - glyAA glyAcophorin A - HCB human umbilical cord blood - IU international units - PCMEM human placenta-conditioned medium - VA sodium valproate     

Transforming growth factor-beta 1 enhances the suppression of human hematopoiesis by tumor necrosis factor-alpha or recombinant interferon-alpha

The effects of transforming growth factor-beta 1 (TGF-beta 1) on human hematopoiesis were evaluated in combination with two other regulatory cytokines, namely, recombinant human tumor necrosis factor-alpha (TNF-alpha) and recombinant human interferon-alpha (rIFN-alpha). Combinations of TNF-alpha and TGF-beta 1 resulted in a synergistic suppression of colony formation by erythroid progenitor cells (BFU-E) and an additive suppression of granulocyte-macrophage (CFU-GM) and multipotential (CFU-GEMM) progenitor cells. In addition, TGF-beta 1 synergized with rIFN-alpha to suppress CFU-GM formation, while the combined suppressive effects of both cytokines on CFU-GEMM and BFU-E were additive. When TGF-beta 1 was tested with TNF-alpha or IFN-alpha on granulocyte/macrophage colony-stimulating factor (GM-CSF)-stimulated bone marrow cells in a 5-day proliferation assay, the antiproliferative effects of TGF-beta 1 and TNF-alpha were additive, while those with TGF-beta 1 and rIFN-alpha were synergistic. A similar pattern was seen in the suppression of the myeloblastic cell line KG-1 where TGF-beta 1 in combination with TNF-alpha resulted in an additive suppression while inhibition by TGF-beta 1 and IFN-alpha was synergistic. These results demonstrate for the first time the cooperative effects between TGF-beta and TNF-alpha and IFN-alpha in the suppression of hematopoietic cell growth, raising the possibility that TGF-beta might be used in concert with TNF-alpha or IFN-alpha in the treatment of various myeloproliferative disorders.     

Lineage specification in the fly nervous system and evolutionary implications

Over the last decades, it has become clear that glia are multifunctional and plastic cells endowed with key regulatory roles. They control the response to developmental and/or pathological signals, thereby affecting neural proliferation, remodeling, survival, and regeneration. It is, therefore, important to understand the biology of these cells and the molecular mechanisms controlling their development/activity. The fly community has made major breakthroughs by characterizing the bases of gliogenesis and function. Here we describe the regulation and the role of the fly glial determinant. Then, we discuss the impact of the determinant in cell plasticity and differentiation. Finally, we address the conservation of this pathway across evolution.     

The BTB-ZF transcription factors

The BTB-ZF (broad-complex, tramtrack and bric-à-brac - zinc finger) proteins are encoded by at least 49 genes in mouse and man and commonly serve as sequence-specific silencers of gene expression. This review will focus on the known physiological functions of mammalian BTB-ZF proteins, which include essential roles in the development of the immune system. We discuss their function in terminally differentiated lymphocytes and the progenitors that give rise to them, their action in hematopoietic malignancy and roles beyond the immune system.     

Single-Cell Proteomics Reveal that Quantitative Changes in Co-expressed Lineage-Specific Transcription Factors Determine Cell Fate

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Primitive and definitive blood share a common origin in Xenopus: a comparison of lineage techniques used to construct fate maps

Primitive blood constitutes the ventralmost mesoderm in amphibians, and its cleavage-stage origin reveals important clues about the orientation of the dorsal/ventral axis in the embryo. In recent years, investigators employing various lineage-labeling strategies have reported disparate results for the origin of primitive blood in Xenopus [W. D. Tracey, Jr., M. E. Pepling, G. H. Thomsen, and J. P. Gergen (1998). Development 125, 1371-1380; M. C. Lane W. C. Smith (1999). Development 126, 423-434; K. R. Mills, D. Kruep, and M. S. Saha (1999). Dev. Biol. 209, 352-368; A. Ciau-Uitz, M. Walmsley, and R. Patient (2000). Cell 102, 787-796]. These discrepancies must be resolved in order to elucidate early embryonic patterning mechanisms in vivo. We directly compared two of the techniques used to determine the origin of the ventral blood islands and primitive blood, injection of either beta-galactosidase mRNA or conjugated dextrans, by coinjecting both tracers simultaneously into individual blastomeres in cleavage-stage embryos. We find that dextrans label progeny efficiently, while beta-galactosidase activity is not present in many of the progeny of an injected blastomere, suggesting that mRNA fails to diffuse throughout a blastomere. This result demonstrates that beta-galactosidase mRNA fails to meet the criterion for a true lineage label, namely efficient detection of the progeny of a blastomere, and raises questions about interpretations based on mapping the ventral blood islands using Lac Z mRNA as a tracer. We examined the origins of the ventral blood islands and primitive blood from the vegetal region of the marginal zone in regularly cleaving embryos by coinjecting both reporters into C-tier blastomeres. Our results demonstrate that both the ventral blood islands and primitive blood routinely arise from all C-tier blastomeres. Our data, in combination with published mapping results for the dorsal aorta, demonstrate that primitive and definitive blood do not have separate origins at the 32-cell stage in Xenopus. In addition, these results support a proposal to align the dorsal/ventral axis of the mesendoderm with the animal/vegetal axis in pregastrula Xenopus.