Aspects on properties, use and ethical considerations of embryonic stem cells - A short review

miR-34a inhibits differentiation of human adipose tissue-derived stem cells by regulating cell cycle and senescence induction

MicroRNAs (miRNAs) are critical in the maintenance, differentiation, and lineage commitment of stem cells. Stem cells have the unique property to differentiate into tissue-specific cell types (lineage commitment) during cell division (self-renewal). In this study, we investigated whether miR-34a, a cell cycle-regulating microRNA, could control the stem cell properties of adipose tissue-derived stem cells (ADSCs). First, we found that the expression level of miR-34a was increased as the cell passage number was increased. This finding, however, was inversely correlated with our finding that the overexpression of miR-34a induced the decrease of cell proliferation. In addition, miR-34a overexpression decreased the expression of various cell cycle regulators such as CDKs (-2, -4, -6) and cyclins (-E, -D), but not p21 and p53. The cell cycle analysis showed accumulation of dividing cells at S phase by miR-34a, which was reversible by co-treatment with anti-miR-34a. The potential of adipogenesis and osteogenesis of ADSCs was also decreased by miR-34a overexpression, which was recovered by co-treatment with anti-miR-34a. The surface expression of stem cell markers including CD44 was also down-regulated by miR-34a overexpression as similar to that elicited by cell cycle inhibitors. miR-34a also caused a significant decrease in mRNA expression of stem cell transcription factors as well as STAT-3 expression and phosphorylation. Cytokine profiling revealed that miR-34a significantly modulated IL-6 and -8 production, which was strongly related to cellular senescence. These data suggest the importance of miR-34a for the fate of ADSCs toward senescence rather than differentiation.

Identity tests: determination of cell line cross-contamination

Cell line cross-contamination is a phenomenon that arises as a result of the continuous cell line culture. It has been estimated that around 20% of the cell lines are misidentified, therefore it is necessary to carry out quality control tests for the detection of this issue. Since cell line cross-contamination discovery, different methods have been applied, such as isoenzyme analysis for inter-species cross-contamination; HLA typing, and DNA fingerprinting using short tandem repeat and a variable number of tandem repeat for intra-species cross-contamination. The cell banks in this sense represent the organizations responsible for guaranteeing the authenticity of cell lines for future research and clinical uses.

Stem cells: From embryology to cellular therapy? An appraisal of the present state of art

ABTRACT: A series of publications has dealt in the last years with topics as the isolation, properties and applications of animal stem cells (Weissman 2000. Cell 100: 157-168; Weissman 2002. N. Engl. J. Med. 346: 1567-1579; Lovell-Badge 2001. Nature 414: 88-91; Marshak et al. 2001. Stem Cell Biology. Cold Spring Harbor Laboratory Press, New york; Eridani 2002. J. Roy. Soc. Med. 95: 5-8; Borge and Evers 2003. Cytotechnology 41: 59-68; Sgaramella 2003. Cytotechnology 41: 69-73), however, the bonanza of experimental data recently accumulating have raised such an amount of controversial views and discussions that time perhaps has come for a reassessment of the basic facts in this peculiar area of research and an evaluation of possible, not unrealistic, implications.