FGF-signalling in the differentiation of mouse ES cells towards ...

2008). Lineage tracing of these cells has not yet been performed but will elucidate whether theincreases in β cell mass are truly by neogenesis of ductal cells. Acinar cells cultured in vitroshow dedifferentiation, possibly to the stage of the common acinar and endocrine cell which isfound during pancreas development. They can subsequently be re-specified into hepatocytes inhuman cultures and β cells in mouse cultures, showing a large amount of plasticity of thesecells (Lardon et al. 2004; Okuno et al. 2007).Whether it is possible to circumvent the patient’s auto-immune response towards these β cells isstill to be seen. For the moment, life-long treatment with immune-suppressors represents theonly alternative and is not desirable due to inherent side effects.Concluding remarksThe reason for putting a large effort into differentiation in a 2-dimensional, serum and feederfreeprotocol is first of all to be able to better control the signalling events going on in the dishand thereby better direct differentiation into the cell types of desire. A second and not lessimportant point is that cell culture with animal products is not desirable due to fear of spread ofdisease. The latter especially has major implications in xeno-transplantations. Recently, apublication showing derivation and culture of a xeno-free hES cell line was published(Ellerstrom et al. 2006). In the future, this could very well be the only material we arecomfortable with using for transplantation and it will as such have major impact on theapplication of the various differentiation protocols applicable to clinical work.88