Synergistic regulation of human megakaryocyte development.

Abstract

Little information exists concerning differing levels of regulation occurring during human megakaryocyte development. We hypothesize that megakaryocytic proliferation and maturation is controlled by two, synergistic regulatory factors. One, megakaryocyte colony-stimulating activity, is an obligate requirement for colony formation and drives the development of relatively immature cells. Megakaryocyte colony-stimulating activity is a functional component of the human recombinant proteins, interleukin 3 or GM-CSF. Human recombinant growth factors, interleukin 1, interleukin 6, or crythropoietin, do not effect megakaryocyte development either alone or in combination with interleukin 3. Full maturation requires a second synergistic activity which increases megakaryocyte number, size, and cytoplasmic and antigenic content. In culture, this synergistic regulator augments maturation by increasing the number of colonies, colony cellularity, and size. In suspension cultures, this cofactor increases megakaryocyte cytoplasmic and antigenic content, and shifts the morphological distribution from immature to mature megakaryocytes. Finally, this activity also increases the number of antigen positive megakaryocytes, either by stimulating proliferation or conversion of antigen-negative to antigen-positive cells. Comparative studies of megakaryocytic regulation suggests that this in vitro regulator mimicks some of the known effects of thrombopoietin in vivo.

Regulation of megakaryocyte phenotype in human erythroleukemia cells.

“…Cell cultivation and induction ofdifferentiation HEL were cultivated in RPMI-1640 medium containing a 10% fetal calf serum (FCS; Hyclone Laboratories, Logan, UT), 1 mM pyruvate, and 2 mM glutamate as described previously (3,8). For studies on the induction of differentiation, HEL cells were grown to a density of 1.5 X 106 cells/ml, washed twice in phosphate-buffered saline (PBS), and cultivated at 1 X 105 cells/ml in the presence or absence (control) of tumor-promoting phorbol diesters.…”

“…Similarly, an increase in macrophage phenotype occurs after high-dose (10-6 M) 4-flphorbol myristate acetate (PMA) treatment (5). Inducible changes in megakaryocyte/platelet-associated antigens have also been reported (3,(6)(7)(8)(9). However, little information exists on the capacity of HEL cells to undergo full megakaryocyte development.…”

“…The entire process is promoted at several points by soluble regulatory cytokines, each with distinct and, in some cases, overlapping targets (8, 10, 1 1). Among these, the committed megakaryocyte progenitor cell and the immature megakaryocyte are the most sensitive to developmental signals, responding with predominantly proliferative or maturational development, respectively (8,10,12). Ultimately, an understanding of the, intracellular events mediating megakaryocyte lineage determination and development requires biological, biochemical, and molecular analysis of purified populations of each of these megakaryocyte subpopulations.…”

The sequence of the hemoregulatory peptide is present in Giα proteins

“…For example, the Gi protein has recently been localized in human neutrophils [15]. Based on indirect studies, there is also evidence that hemopoietic progenitor cell proliferation as well as interleukin-3 and CSF-1 action are mediated through the same mechanism [16,17]. On this background it is remarkable that the synthetic analog oligopeptides with structural homology to G-proteins are able to inhibit myelopoietic colony formation.…”

IL‐13 upregulates GPIIb expression in megakaryocytic cell lines via STAT6

“…HEL cells can undergo further differentiation along various hematopoietic pathways depending on the stimulus (Tabilio et al, 1984;Long et al, 1988Long et al, , 1990. In recent years, HEL cells have been increasingly used as model system to study molecular aspects of the induction of megakaryocyte differentiation (Hong et al, 1996).…”