Abstract:

Objective To explore the residual undifferentiated mouse embryonic stem cells (ESCs) in embryoid bodies. Methods Mouse R1 and Oct-4-GFP transgenic ESCs were firstly cultured in suspension to form embryoid bodies (EBs). Twenty days later, EBs were digested into single cells and then  re-plated in standard ESC culture condition. The morphology of residual undifferentiated cells in EBs was observed, and surface makers and in vitro redifferentiation potency of residual cells were examined by flow cytometry and immunofluorescent staining. The residual cells were expanded and subcutaneously injected into nude mice, and the specimens were  harvested from the injection site for histological analysis 6 weeks after injection. Results There were residual undifferentiated ESCs in EBs differentiated for 20 days, which displayed clonal morphology and expressed undifferentiated cell markers of ESCs, including SSEA1, CD31, CD9 and Oct-4. The cells could be differentiated to form EBs again, and could be re-expanded from secondary EBs. The residual cells were able to form teratoma at the injection site, and mature endoderm, mesoderm and ectoderm tissues could be found in teratoma tissues. Conclusion There are residual undifferentiated ESCs after differentiation of ESCs into EBs. The residual ESCs can differentiate again in vitro and in vivo, and can residue again in the in vitro differentiation.

Key words: embryonic stem cell, differentiation, embryoid body, residue