p38 Mitogen Activated Protein Kinase Controls Two Successive-Steps During the Early Mesodermal Commitment of Embryonic Stem Cells

Abstract

Embryonic stem (ES) cells differentiate in vitro into all cell lineages. We previously found that the p38 mitogen activated kinase (p38MAPK) pathway controls the commitment of ES cells toward either cardiomyogenesis (p38 on) or neurogenesis (p38 off ). In this study, we show that p38a knock-out ES cells do not differentiate into cardiac, endothelial, smooth muscle, and skeletal muscle lineages. Reexpression of p38MAPK in these cells partially rescues their mesodermal differentiation defects and corrects the high level of spontaneous neurogenesis of knock-out cells. Wild-type ES cells were treated with a p38MAPK-specific inhibitor during the differentiation process. These experiments allowed us to identify 2 early independent successive p38MAPK functions in the formation of mesodermal lineages. Further, the first one correlates with the regulation of the expression of Brachyury, an essential mesodermal-specific transcription factor, by p38MAPK. In conclusion, by genetic and biochemical approaches, we demonstrate that p38MAPK activity is essential for the commitment of ES cell into cardiac, endothelial, smooth muscle, and skeletal muscle mesodermal lineages. IntroductionE mbryonic stem (ES) cells are pluripotent and retain the potential for unlimited proliferation. Transplantation of ES cells or their derivatives has been proposed as a future therapy for various human diseases. However, molecular mechanisms governing ES cell self-renewal and their commitment into a specific lineage are poorly understood, and their comprehension is necessary to improve the efficiency of differentiation into specific lineages.Self-renewal of mouse ES cells is dependent on intracellular pathways initiated by the leukemia inhibitory factor (LIF), by either serum or bone morphogenetic protein 2 or 4, and by a complex interplay between specific epigenetic processes, miRNAs, and transcription factors involved in the development of the embryo, such as Oct4, Nanog, Sox2, or FoxD3 (for review, see [1]). Removing LIF and adding appropriate differentiation reagents result in the commitment of ES cells into a variety of mature differentiated cell types, including cardiac cells, skeletal muscle cells, neurons, or adipocytes (for review, see [2,3]). ES cell differentiation can be achieved by a wide variety of experimental protocols that lack or include fetal bovine serum (FBS) and the use of specific inducers such as the potent morphogen retinoic acid (RA). The 10 À7 mol=L RA treatment between the second and fifth day is necessary for ES cell differentiation into neurons and adipocytes [4][5][6]. In contrast, ES cell differentiation in the absence of RA yields efficient differentiation to cardiomyocytes with few neurons [4,7]. It is very likely that different differentiation protocols and inducers will selectively activate distinct signaling pathways that turn on cell lineagespecific genetic programs to bring about the observed enrichment in differentiated cell populations. Yet, the precise molecular process of these signaling pathways controlli...

Differential Effects of Retinoids and Inhibitors of ERK and p38 Signaling on Adipogenic and Myogenic Differentiation of P19 Stem Cells

“…Inhibition of p38 was reported to be antimyogenic. Indeed, pharmacological inactivation of p38 inhibited cardiomyogenesis in DMSO-induced P19 cultures [24], and p38 knockout in ES cells reduced the spontaneous generation of SKM and CM [17]. It is worth noting that in those cases compared to our study, myogenesis was triggered in the absence of exogenous atRA or retinoid.…”

“…Like atRA, mitogen-activated protein kinases (MAPK) play an essential role in cell proliferation and differentiation [16][17][18][19][20]. These kinases are components of signaling cascades that relay extracellular stimuli to transcription factors in the nucleus.…”

“…MAPK ERK and p38 have been implicated in mesodermal differentiation, but information is not complete or clear. P38 has an antiadipogenic action [21], while its activity appears to be required in myogenesis [17,[22][23][24][25][26]. However, three recent studies have shown that the use of small concentrations of the p38 inhibitor SB203580 ( £ 10 mM) rather promotes than inhibits cardiomyogenesis [27][28][29].…”

“…This aspect of retinoid status could explain some inconsistencies observed between in vitro and in vivo situations. For instance, while some studies have implicated p38 as an important player in cardiomyogenesis in cell cultures, various strategies of p38 knockout resulted in normal development of the heart [17,20]. In the same line of thought, it is worth of note that retinoid agonists had different effects on differentiation into visceral endoderm in cell cultures depending upon which RAR and RXR had been knockout [59].…”

Fullerene mediates proliferation and cardiomyogenic differentiation of adipose-derived stem cells via modulation of MAPK pathway and cardiac protein expression

“…The control of p38 MAPK activity represented an early switch, committing stem cells into either neurogenesis (p38 off) or cardiomyogenesis (p38 on). [41][42][43] Therefore, fullerene-C 60 modulates the cardiomyogenic differentiation of BADSCs by adjusting the expression of p38 MAPK pathway ( Figure 6). In order to further investigate the effects of fullerene-C 60 on cardiac differentiation efficiency of BADSCs, the expression of cardiomyocyte-specific proteins (cTnT, α-sarcomeric actinin, and Cx-43) was determined …”