Pluripotency describes the ability of stem cells to differentiate into derivatives of the three germ layers. In reporting new human pluripotent stem cell lines, their clonal derivatives or the... Show morePluripotency describes the ability of stem cells to differentiate into derivatives of the three germ layers. In reporting new human pluripotent stem cell lines, their clonal derivatives or the safety of differentiated derivatives for transplantation, assessment of pluripotency is essential. Historically, the ability to form teratomas in vivo containing different somatic cell types following injection into immunodeficient mice has been regarded as functional evidence of pluripotency. In addition, the teratomas formed can be analyzed for the presence of malignant cells. However, use of this assay has been subject to scrutiny for ethical reasons on animal use and due to the lack of standardization in how it is used, therefore questioning its accuracy. In vitro alternatives for assessing pluripotency have been developed such as ScoreCard and PluriTest. However, it is unknown whether this has resulted in reduced use of the teratoma assay. Here, we systematically reviewed how the teratoma assay was reported in publications between 1998 (when the first human embryonic stem cell line was described) and 2021. Our analysis of >400 publications showed that in contrast to expectations, reporting of the teratoma assay has not improved: methods are not yet standardized, and malignancy was examined in only a relatively small percentage of assays. In addition, its use has not decreased since the implementation of the ARRIVE guidelines on reduction of animal use (2010) or the introduction of ScoreCard (2015) and PluriTest (2011). The teratoma assay is still the preferred method to assess the presence of undifferentiated cells in a differentiated cell product for transplantation since the in vitro assays alone are not generally accepted by the regulatory authorities for safety assessment. This highlights the remaining need for an in vitro assay to test malignancy of stem cells. Show less
Chapter 2 investigated the generation of knockin mESC line in order to study the biallelic distribution of Nanog expression at the protein level. Chapter 3 investigated the generation of human ECs... Show moreChapter 2 investigated the generation of knockin mESC line in order to study the biallelic distribution of Nanog expression at the protein level. Chapter 3 investigated the generation of human ECs from hESCs using a spin-EB differentiation approach. Chapter 4 described the rst derivation of three human iPS cell lines in the Netherlands: two from healthy individuals and one from a patient with HHT. Chapter 5 investigated the use of hiPSC-EC as a model for studying HHT1 in vitro.Chapter 6 investigated the role of Gja5 that encodes for the gap junction protein Cx40 in the development of AVMs in the HHT2 mouse model. Show less
