Inhibition of p38 Mitogen-Activated Protein Kinase Promotes Ex Vivo Hematopoietic Stem Cell Expansion

Abstract

Hematopoietic stem cell (HSC) self-renewal is tightly regulated by a complex crosstalk between many cellintrinsic regulators and a variety of extrinsic signals from the stem cell niche. In this study, we examined whether the p38 mitogen-activated protein kinase (p38) is one of the intrinsic regulators that can negatively regulate HSC self-renewal in vitro and whether inhibition of p38 activity with a small molecule inhibitor can promote HSC expansion ex vivo. The results from this study showed that sorted mouse bone marrow Lin -Sca1 + c-kit + cells (LSK + cells) exhibited selective activation of p38 after culture in a serum-free medium supplemented with 100 ng/mL stem cell factor, thrombopoietin, and Flt3 ligand. The activation of p38 was associated with a significant reduction in HSCs and induction of apoptosis and cellular senescence in LSK + cells and their progeny. Addition of the specific p38 inhibitor SB203580 (SB, 5 mM) to the culture inhibited the activation of p38 in LSK + cells, which led to increase in HSC self-renewal and ex vivo expansion as shown by the cobblestone area forming cell assay, competitive repopulation, and serial transplantation. The increase in HSC expansion is likely attributable to SB-mediated inhibition of HSC apoptosis and senescence and upregulation of HoxB4 and CXCR4. These findings suggest that p38 plays an important role in the regulation of HSC self-renewal in vitro and inhibition of p38 activation with a small molecule inhibitor may represent a novel approach to promote ex vivo expansion of HSCs.

Renovascular Hypertension Leads to DNA Damage and Apoptosis in Bone Marrow Cells

“…The present study corroborates previous observations that O 2 -and H 2 O 2 in excess amounts limits the self-renewing capacity and life span of BM hematopoietic stem cells, resulting in apoptosis (Ito et al, 2006;Wang et al, 2011). The importance of the present study is that the Annexin V FITC /PI assay allowed us to demonstrate an increased apoptosis rate of BM cells in renovascular hypertensive animals.…”

Posttranslational regulation of self-renewal capacity: insights from proteome and phosphoproteome analyses of stem cell leukemia

“…The proline-directed p38 MAPK kinase plays a major role in the self-renewal potential of stem cells. [39][40][41] High p38 MAPK activation levels restrict cell proliferation, induce differentiation, and limit the life span of HSCs. 39 Accordingly, pharmacologic inhibition of p38 MAPK restores the long-term repopulating potential of HSCs in vivo.…”

“…Importantly, high activated p38 MAPK levels have been shown to impair stem cell self-renewal and induce differentiation of immature cells. [39][40][41] Activation status of other kinases known to have a role in stem cells and cancer, such as Erk1/2, Jnk, Akt1, mTOR, and Jak-STAT pathways, was further assessed. Despite being activated, no major differences between FLA2 and FLB1 cells were observed ( Figure 4C-D).…”

Insulin-Like Growth Factor 1 Receptor and p38 Mitogen-Activated Protein Kinase Signals Inversely Regulate Signal Transducer and Activator of Transcription 3 Activity to Control Human Dental Pulp Stem Cell Quiescence, Propagation, and Differentiation

“…Interestingly, the inhibition of p38 stimulates the expansion of hematopoietic stem cells (HSC) in vitro and increases their repopulation potential in vivo [84]. In contrast, reactive oxygen speciesinduced p38 MAPK signaling impairs HSC self-renewal [85,86], demonstrating a dual activity of p38 MAPK through which it may either promote or inhibit cellular quiescence [59,61].…”