Effects of Mouse Strain on Establishment of Embryonic Stem Cell Lines

Purpose: Embryonic stem (ES) cells are derived from the inner cell mass of blastocysts with self-renewal and pluripotency characteristics. These cells have potential for studies of in vitro differentiation, gene function, etc. This study was, therefore, initiated to establish new ES lines and evaluate the effects of strain on ES cell production. Materials and Methods: 3-5 day blastocysts were recovered from BALB/C, C57BL/6, NMRI and/or hybrid of NMRI (male) and BALB/C (female). The inner cell masses were cultured in embryonic stem cell medium, supplemented with 5000iu/m1 leukemia inhibitor factor (UF).The established lines were evaluated by morphology, passaging, freezing and thawing, alkaline phosphatase, Oct-4 expression, karyotype and spontaneous differentiation. Results: One and two ES cell lines were derived from 260 blastocysts of BALB/C and 70 blastocysts of hybrid of NMRI/BALB/C, respectively. The lines remained undifferentiated in morphology during continuous passaging, maintained a normal XY karyotype and expressed alkaline phosphatase and Oct-4.These cells differentiated in vitro in the absence of a feeder layer and UF, and they produced embryoid bodies that could further differentiate into beating cardiomyocytes as well as neurons. Conclusion: These data, in addition to showing the establishment of 3 new ES cell lines, demonstrated that the efficiency of the ES establishment was more in the hybrids (NRMI, BALB/C) than the inbred (BALB/C) strains.