Regulation of mouse embryo development by autocrine throphic factors

Embryo development depends on maternal and embryonic factors. When occurs in vitro, embryos secrete factors that stimulate their development. The purpose of this study was to investigate the possible effects of embryos at morula stage on mouse embryo development in vitro. To obtain conditioned media (CM), morulas were cultured in groups of 5 (CM5) or 10 (CM10) in microdrops of Ham-F10 culture medium during 24 h and later they were removed. Subsequently, 365 morulas were cultured in CM5 and CM10 or in Ham-F10 media (as control group). No differences in blastocyst formation could be found between embryos cultured for 24h in Ham-F10, CM5 or CM10 (49.66, 53.04, 60.00% respectively). However, CM5 significantly increased differentiation in embryos cultured for 48h as compared to Ham-F10 medium (80.00% and 64.14 respectively). The CM5 caused a significant increase in the hatching rate compared to Ham-F10 evaluated at 78 and 96 h of culture (66.96 vs. 52.41% and 70.43 vs. 55.17%, respectively). After 72, 78 and 96h of culture the hatching rate for embryos cultured in CM10 was significantly higher than that in Ham-F10 (64.76 vs. 47.59%, 67.62 vs. 52.41% and 73.33 vs. 55.17%, respectively). At 48h of culture, differences between CM5, CM10 and Ham-F10 were not observed. These results suggest that preimplantational mouse embryos produce trophic factor/factors that enhance the differentiation and hatching process.