Stem cells promoting expansion

Wrzesinski C et al. Hematopoietic stem cells promote the expansion and function of adoptively transferred antitumor CD8 T cells. J Clin Invest 2007 117 492-501. 

SCEPF stem cell expansion promoting factor... 

Doucet, C, Ernou, I., Zhang, Y. Z., et al. (2005), Platelet lysates promote mesenchymal stem cell expansion A safety substitute for animal serum in cell-based therapy applications. J. Cell. Physiol, 205(2), 228-236. 

Most stem cells can divide via either asymmetric or symmetric modes (22). Because each asymmetric division generates one daughter with a stem-cell fate (self-renewal) and one daughter that differentiates, it was postulated that asymmetric division could be a barrier to stem cell expansion. Therefore, conversion of asymmetric division to symmetric division would promote self-renewal and long-term culture of stem cells. Indeed, this idea was confirmed by using one small molecule, the purine nucleoside xanthosine (Xs) (23). This small molecule promotes guanine ribonucleotide biosynthesis that reversibly converts cells from asymmetric division kinetics to symmetric division kinetics. It was found that Xs derived from stem cell lines exhibit Xs-dependent symmetric kinetics, and this derived stable line shows enhanced self-renewal. This study underscores the importance of balance between the two modes of division, both to stem cell expansion and to the regenerative capacity of adult stem cells. 

Small Molecules to Promote Stem Cell Expansion... 

Table 4.1 Selected small molecules to promote stem cell expansion/proliferation. 

Expansion of Rho kinase Promotes embryonic inhibitor survival of stem cells dissociated... 

Qiu, H. Y, Y. Fujimori, S. R. Kai et al. 2003. Establishment of mouse embryonic fibroblast ceU lines that promote ex vivo expansion of human cord blood CD34(-l-) hematopoietic progenitors./ffemfltoffier Stem Cell Res 12(1) 39-46. 

In general, then, we may view the auxins and GA s as promoters of cell elongation and ABA and ethylene as inhibitors. The cytokinins act as promoters of leaf cell expansion and inhibitors of stem elongation. This is somewhat oversimplified in light of the aforementioned exceptions, and the evidence that effects of applied hormones are often modified by or mediated by other hormones. 

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