br Conclusions and future perspectives Due

Conclusions and future perspectives Due to the extraordinary speed that stem cell research is proceeding, scientists rarely have time to improve or replace assay systems that are working. For industrial and clinical applications the differentiation potential assessed by in vitro differentiation would be sufficient, as often only one specific cell type is needed. Therefore, if proof of pluripotency is not essential, teratoma models should not be used. In fact, directed differentiation of stem kras-pdeδ inhibitor in monolayers or as EBs, provides much more detailed information on the development and function of those cells. The influence of growth factors, transcription factor expression, and cytokines can be studied on the molecular and cellular levels from the very beginning of differentiation until terminal differentiation of a somatic cell using the EB system. Secondly, the differentiation process based on a standardized EB model is highly reproducible and allows the study of molecular mechanisms guiding the differentiation process (Barbaric et al., 2010). Studying the transcriptional networks regulating differentiation of stem cells in combination with the external signals and their respective signaling pathways will help to define conditions, that will result in the improvement of the model of directed differentiation. This model might indicate that aggregation of stem cells will no longer be a prerequisite for the generation of a specific type of somatic cell. In parallel, models based on cell–cell and cell–matrix interactions need to be established, to provide knowledge from which more complex in vitro models will be developed and validated for clinical, pharmacological, and toxicological applications (Andrews et al., 2010; Laustriat et al., 2010). To broaden the acceptance of in vitro as well as in silico models as valid pluripotency tests, more research needs to be performed on stem cell aggregates, on directed differentiation of stem cells without prior aggregation, and global correlates of these processes in high content formats such as RNA-seq or Methyl-seq. It is also essential to investigate the fundamental molecular and cellular processes taking place in EBs and somatic stem cell aggregates. It is important to understand these molecular and morphological changes seen in EBs and to correlate them with bona fide embryogenesis. There are a number of alternative in vitro approaches available to the stem cell community for the assessment of pluripotency. If an objective analysis of the intended use of a cell line suggests that in vivo testing can be excluded, the latter should be dropped altogether. There is no ethical and academic justification to test cell lines universally in a teratoma assay in order to generate results that prove to be less informative than those generated by in vitro approaches.
Disclosures The central aim of the SET Foundation is to reduce and replace animal experimentation. The Foundation is made up of representatives from industry, animal welfare, science and government. Their role is the transparent, interdisciplinary allocation of funds to eligible projects researching and implementing methods to replace and complement experiments on animals (www.stiftung-set.de).
Introduction The initial success of the Edmonton protocol highlighted the potential of cell replacement therapy in type 1 diabetes (Shapiro et al., 2000). However, wider application of this approach is severely limited by the shortage of transplantable pancreatic β-cells (de Kort et al., 2011). In addition, the transplantation of cadaveric islets requires life-long immune suppression (Ricordi and Strom, 2004). Ideally, therefore, a source of transplantable β-cells would be both autologous and abundant. Because of their in vitro growth capacity, pluripotent stem cells (PSCs) are an attractive potential source of transplantable β-cells. While significant progress has been made, the generation of true β-cells in vitro has remained elusive thus far (Alipio et al., 2010; D\'Amour et al., 2006; Nostro et al., 2011). In addition, PSCs are capable of forming teratomas and represent an unknown risk in terms of tumorigenesis (Fujikawa et al., 2005; Kroon et al., 2008).