A novel microtube culture system that enhances the in vitro development of parthenogenetic murine embryos

Oil is an indispensable material in micro-droplet culture; it prevents medium from evaporation, and its transparency facilitates monitoring. However, lipophilic factors in the medium can be absorbed into the oil overlay, and conversely, deleterious materials can diffuse into the medium. In the present study, we describe a novel oil-free microtube culture (MTC) system. Parthenogenetic mouse embryos were placed into 0.2-mL thin-wall flat cap PCR tubes and cultured to the blastocyst stage. Conventional drop culture was used as a control. Embryos in MTC had a higher blastocyst formation rate (89.2%) and larger population of cells in the blastocysts (92.0 ± 6.9; mean ± S.E.M.) compared with drop culture (78.3% and 74.7 ± 8.1; P < 0.05 for each). The large blastocyst cell population in MTC was due to higher numbers of trophectoderm (TE) cells (70.5 ± 5.9 versus 53.8 ± 7.4; P < 0.05) rather than inner cell mass cells. The presence of more TE cells was attributed to faster development in MTC. Embryos cultured in oil-covered MTC had fewer TE cells (61.5 ± 5.6) than oil-free cultures (70.5 ± 5.9; P < 0.05). In conclusion, oil-free MTC was an alternative to conventional micro-drops, without the deleterious effects of oil.