What is a stem cell?

Abstract

The historical roots of the stem cell concept are traced with respect to its usage in embryology and in hematology. The modern consensus definition of stem cells, comprising both pluripotent stem cells in culture and tissue-specific stem cells in vivo, is explained and explored. Methods for identifying stem cells are discussed with respect to cell surface markers, telomerase, label retention and transplantability, and properties of the stem cell niche are explored. The CreER method for identifying stem cells in vivo is explained, as is evidence in favor of a stochastic rather than an obligate asymmetric form of cell division. In conclusion, it is found that stem cells do not possess any unique and specific molecular markers; and stem cell behavior depends on the environment of the cell as well as the stem cell's intrinsic qualities. Furthermore, the stochastic mode of division implies that stem cell behavior is a property of a cell population not of an individual cell. In this sense, stem cells do not exist in isolation but only as a part of multicellular system. This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Tissue Stem Cells and Niches Adult Stem Cells, Tissue Renewal, and Regeneration > Methods and Principles Adult Stem Cells, Tissue Renewal, and Regeneration > Environmental Control of Stem Cells.

A comparative in vitro study of the effect of biospecific integrin recognition processes and substrate nanostructure on stem cell 3D spheroid formation

“…Conversely, spheroids formed on CBtethered dendron substrates appear to have been less active in depositing their own extracellular matrix and therefore unable to compete with the predominant forces of serum proteins adsorbed on TCP surface in conventional tissue culture conditions [15]. The data of this work contribute to define the fundamental characteristics both of the adult stem cell phenotype and of the micro-environment in which it can be preserved [16,17]. They also contribute to study stem cells in vitro through the development of models that can ascertain their contribution to healthy and disease conditions [18].…”

“…The purity of the two types of dendrons was 95% for RGen3K and 90% in the case of the RGen3K(CB) 16 dendrons, respectively. The chromatogram for both types of dendrons showed early broad peaks ascribed to the mobile phase solvents used.…”

“…A small sharp peak was detected for the RGen3K at a delayed elution time of approximately 10 min suggesting the presence of complexes of dendron rolling along the column. In the case of the RGen3K(CB) 16 dendron, a very early peak in proximity to the solvent peaks was observed suggesting the presence of free CB molecules not grafted to the dendron. The presence of free CB in the sample was deemed to be irrelevant in the following grafting of the dendron to the linear polyK.…”

“…Cleaved dendrons were then precipitated in a large excess of ice-cooled diethyl ether and centrifuged (dend Denley BS400) for three times at 3500 rpm for 5 min. The identification of both Rgen3K(CB) 16 and Rgen3K (YIGSR) 16 was carried out using an electrospray/ionisation time of flight, ESI-TOF MS (Bruker microTOF) at 0.4 bar while their purity was assessed by a standard analytical HPLC (Agilent Infinity).…”

Potential application of aminiotic stem cells in veterinary medicine

“…Totipotent cells are those able to differentiate in all cell lines, including extraembryonic tissues, examples of totipotent cells include the zygote and its early cleavage products. The pluripotent cells are those capable of differentiating only in cells belonging to the three germ layers (Morgani et al, 2013) as embryonic stem cells (ESCs) (Slack, 2018) and induced pluripotent stem cells (iPSCs), somatic cells reprogramed do pluripotency (Takahashi and Yamanaka 2006). The iPSCs were initially produced of cells of mice and humans, however, there is currently reprogramming cells several animal species (Takahashi and Yamanaka, 2006;Takahsshi et al, 2007;Zhang et al, 2015;Gonçalves et al, 2017).…”