We used successfully human foreskin fibroblasts as feeder cells for derivation and continued undifferentiated growth of hES cells. These feeder cells are convenient for IVF units, because no fetal human tissues or tissue from operations are needed.

The International Stem Cell Initiative characterized 59 human embryonic stem cell lines from 17 laboratories worldwide. Despite diverse genotypes and different techniques used for derivation and maintenance, all lines exhibited similar expression patterns for several markers of human embryonic stem cells. They expressed the glycolipid antigens SSEA3 and SSEA4, the keratan sulfate antigens TRA-1-60, TRA-1-81, GCTM2 and GCT343, and the protein antigens CD9, Thy1 (also known as CD90), tissue-nonspecific alkaline phosphatase and class 1 HLA, as well as the strongly developmentally regulated genes NANOG, POU5F1 (formerly known as OCT4), TDGF1, DNMT3B, GABRB3 and GDF3. Nevertheless, the lines were not identical: differences in expression of several lineage markers were evident, and several imprinted genes showed generally similar allele-specific expression patterns, but some gene-dependent variation was observed. Also, some female lines expressed readily detectable levels of XIST whereas others did not. No significant contamination of the lines with mycoplasma, bacteria or cytopathic viruses was detected.

2005;23:544-549

Information concerning the development and differentiation of human embryonic stem (hES) cells in vivo is limited. The present study has focused on the in vivo outcome and differentiation of the hESC line HS181, after injection into SCID/beige mice. hES cell-derived teratomas were explored using histological evaluation and by the identification of markers for differentiated cells and tissues. The analyses identified predominant differentiation along a neuronal lineage, the formation of bone/cartilage and epithelia. Fluorescent in situ hybridization (FISH) analysis with a human-specific probe showed the teratomas to be mainly of human origin, with the most organized areas being exclusively human. Importantly, the study revealed interactions between mouse and human tissues, most notably in the formation of vessels. Both mouse and human cells contributed to specific microstructures in which mouse cells could be observed to take on the appropriate histiotypic appearance. Hence, HS181 cells were able to develop into defined mature tissues, supporting the relevant use of this hES cells model for studies of early human development, given the use of appropriate controls for host contribution. Although extensive mitotic activity implicated progenitor cell activity, no detectable multipotent or malignant areas were observed during the observation period. Persisting undifferentiated hESC were not detected.