Abstract:

BACKGROUND: Human embryonic stem cells (hESCs) are pluripotent cells which may differentiate into tissues of all three germ layers. Such research as the feeder-free growth of hESCs is few in China. Fibroblast growth factor (FGF) is a major factor to maintain the undifferentiated state of hESCs.

OBJECTIVE: To evaluate the ability of FGF at different concentrations in maintaining the undifferentiated state and pluripotency of hESC lines in the long-term culture.

METHODS: Two cell lines of hES-8 and hES-18 were cultured with mouse embryonic fibroblast condition medium for 3 passages and then transferred into mouse embryonic fibroblast condition medium containing different concentrations of FGF: 100, 160, 250 μg/L for 8 passages. The hESCs were removed from the petri dish, cell clusters were digested with collagenase IV and gathered. Cell differentiation and pluripotency were observed. The eighth generation of the hESCs were collected and incubated into severe combined immunodeficiency mice, so as to observe teratoma formation. Morphologies of the cells were evaluated. Alkaline phosphatase staining, surface labeling immunocytochemical analysis and RT-PCR assay method were utilized to determine the OCT-4 expression and tumorigenesis in vivo.

RESULTS AND CONCLUSION: Cultured in mouse embryonic fibroblast condition medium containing 160 and 250 μg/L FGF, two cell lines of hESC could maintain undifferentiated state: Clones were round with a high ratio of nucleus to cytoplasm. Large areas in the center of clones were undifferentiated cells, while surrounding the clones were differentiated cells; Strong positive expression for alkaline phosphatase staining was observed; Two cell lines showed high levels of OCT-4 transcription factor protein; The surface markers SSEA-4, TRA-1-60, TRA-1-81 were all positive on both two lines; The hESC clusters could form embryoid body in vivo 10 days later; 3 germ layers of teratomas were also obtained after implanted into severe combined immunodeficiency mice. Mouse embryonic fibroblast condition medium containing 100 μg/L FGF was not sufficient to maintain the long-term proliferation of hESCs, and most of the cells differentiated and died after 4 passages. Alone with concentration 160 μg/LbFGF or more could maintain two hESC lines undifferentiated stably in vitro, has no influence on the differentiation and totipotency of two cell lines.