Transient Disruption of Autocrine TGF-β Signaling Leads to Enhanced Survival and Proliferation Potential in Single Primitive Human Hemopoietic Progenitor Cells

Abstract

Hemopoietic stem cells (HSCs) are maintained at relative quiescence by the balance between the positive and negative regulatory factors that stimulate or inhibit their proliferation. Blocking the action of negative regulatory factors may provide a new approach for inducing HSCs into proliferation. A variety of studies have suggested that TGF-β negatively regulates cell cycle progression of HSCs. In this study, a dominant negatively acting mutant of TGF-β type II receptor (TβRIIDN) was transiently expressed in HSCs by using adenoviral vector-mediated gene delivery, such that the effects of disrupting the autocrine TGF-β signaling in HSCs can be directly examined at a single cell level. Adenoviral vectors allowing the expression of TβRIIDN and green fluorescence protein in the same CD34+CD38−Lin− cells were constructed. Overexpression of TβRIIDN specifically disrupted TGF-β-mediated signaling. Autocrine TGF-β signaling in CD34+CD38−Lin− cells was studied in single cell assays under serum-free conditions. Transient blockage of autocrine TGF-β signaling in CD34+CD38−Lin− cells enhanced their survival. Furthermore, the overall proliferation potential and proliferation kinetics in these cells were significantly enhanced compared with the CD34+CD38−Lin− cells expressing green fluorescence protein alone. Therefore, we have successfully blocked the autocrine TGF-β-negative regulatory loop of primitive hemopoietic progenitor cells.

Enhanced Immune Reconstitution by Sex Steroid Ablation following Allogeneic Hemopoietic Stem Cell Transplantation

“…As a corollary, disruption of TGF-␤ signaling in HSCs (via the transient expression of a mutant type II receptor) enhances survival and proliferation of these cells (69). These findings are entirely consistent with the possibility that the increased number of HSCs seen 28 days after allogeneic HSCT and castration may in fact be due to a decrease in the production of TGF-␤ by BM stromal cells, as indicated from the RT-PCR analysis.…”

The role of Smad signaling in hematopoiesis

“…This suggests that endogenous TGF-b signaling, in this experimental setting, only executes significant antiproliferative effects when positive acting signals are kept at low levels. The same phenomenon was seen when primitive human progenitors overexpressing a dominant-negative mutant of the TGF-b type II receptor were grown under similar conditions with varying cytokine stimulation (Fan et al, 2002). Together, these observations demonstrate the context dependency of TGF-b signaling in HSCs and how activation of several signaling pathways can result in interference.…”

The satellite cell as a companion in skeletal muscle plasticity:currency, conveyance, clue, connector and colander

“…For example, growth factor production by muscle precursors affects consequent properties of differentiation by those precursors, as does the presence of the fiber in close proximity (e.g. Allen and Boxhorn, 1987; Allen and Boxhorn, 1989;Fan et al, 2002;Florini and Magri, 1989;Gal-Levi et al, 1998;Goel and Dey, 2002;Hameed et al, 2003;Husmann et al, 1996;Li et al, 2005a;Liou et al, 2002;Liu et al, 1998;Rabinovsky et al, 2003;Sheehan et al, 2000;Shefer and Yablonka-Reuveni, 2005;Yablonka-Reuveni and Anderson, 2006). It is also important to recall that growth factors such as VEGF have roles in muscle function, distinct from those in angiogenesis.…”