Inhibition of p38 MAPK activity promotes ex vivo expansion of human cord blood hematopoietic stem cells

Abstract

Ex vivo expansion of hematopoietic stem cells (HSCs) depends on HSC self-renewing proliferation and functional maintenance, which can be negatively affected by HSC differentiation, apoptosis, and senescence. Therefore, inhibition of HSC senescence may promote HSC expansion. To test this hypothesis, we examined the effect of inhibition of p38 mitogen-activated protein kinase (p38) on the expansion of human umbilical cord blood (hUCB) CD133+ cells because activation of p38 has been implicated in the induction of HSC senescence under various physiological and pathological conditions. Our results showed that ex vivo expansion of hUCB CD133+ cells activated p38, which was abrogated by the p38 specific inhibitor SB203580 (SB). Inhibition of p38 activity with SB promoted the expansion of CD133+ cells and CD133+CD38− cells. In addition, hUCB CD133+ cells expanded in the presence of SB for 7 days showed about threefold increase in the clonogenic function of HSCs and engraftment in non-obese diabetic/severe combined immunodeficient mice after transplantation compared to the input cells. In contrast, the cells expanded without SB exhibited a significant reduction in these HSC functions. The enhancement of ex vivo expansion of hUCB HSCs is primarily attributable to SB-mediated inhibition of HSC senescence. In addition, inhibition of HSC apoptosis and upregulation of CXCR4 may also contribute to the enhancement. However, p38 inhibition had no significant effect on HSC differentiation and proliferation. These findings suggest that inhibition of p38 activation may represent a novel strategy to promote ex vivo expansion of hUCB HSCs.

Cytokine-regulated GADD45G induces differentiation and lineage selection in hematopoietic stem cells

“…As recently reported, the inactivation of p38 activity by small molecule inhibitors maintained stemness ex vivo in human and murine HSCs (Baudet et al, 2012;Zou et al, 2012). Furthermore, an increase in reactive oxygen species results in the activation of p38 and finally in HSC …”

p38α Activates Purine Metabolism to Initiate Hematopoietic Stem/Progenitor Cell Cycling in Response to Stress

“…Accordingly, p38MAPK inhibition by SB203580 or by a dominant-negative form of Map3k5 (which phosphorylates and activates p38MAPK) reportedly rescued these HSC defects (Ito et al, 2006). In support of this idea, others reported that small hairpin RNA (shRNA) targeting Mapk14 or treatment with SB203580 promoted expansion of human cord blood HSCs in vivo and ex vivo (Baudet et al, 2012;Zou et al, 2012). Interestingly, p38MAPK is thought to function as both a positive and negative regulator of the cell cycle (Arthur and Ley, 2013;Ashwell, 2006;Grossi et al, 2014).…”

“…Treatment with the antioxidant N-acetyl-L-cysteine (NAC) or a p38MAPK inhibitor rescues HSPC number and function in serial BMT or Atm À/À cells in mice (Ito et al, 2004;Ito et al, 2006). Also, Mapk14 knockdown or p38MAPK inhibition promotes proper cell-cycle progression following BMT or in exvivo-expanded HSPCs (Baudet et al, 2012;Zou et al, 2012). Thus, p38MAPK inhibition is thought to suppress aberrant HSPC proliferation and protect HSPCs from exhaustion or replicative senescence in stress settings or in the context of damage associated with aging (Geiger et al, 2013;Rossi et al, 2008).…”

The Impact of Mesenchymal Stem Cells on Differentiation of Hematopoietic Stem Cells

“…42 Differentiation of HSCs during their expansion increases the process of cell aging and death, 43 but direct contact between the stem cells and microenvironment of the cell represents their essential role in hematopoiesis versus differentiation. 44 Mesenchymal stem cells produce a variety of cytokines and factors affecting hematopoiesis. 45,46 IL-6, Flt3-L (FL), SCF, G-CSF, M-CSF, GM-CSF, TPO, CXCL-12 (SDF1) and IL-11 are among these factors.…”