Individual assessment of bovine embryo development using a homemade chamber reveals kinetic patterns of success and failure to reach blastocyst stage.

Most early developmental data are lost in bovine embryo culture systems. We developed and validated a method for culture of bovine embryos in groups that allow individual assessment. An autoclavable low-cost multiembryo chamber (MEC) was prepared using a polyester mesh fixed to a glass coverslip. Embryonic development was not affected by MEC. Compared to conventional bovine culture system (oil-covered drops, control), cleavage (C, 71.2 +/- 7.8%; MEC, 74.3 +/- 6.0%), blastocyst rate (C, 29.9 +/- 4.4%; MEC, 28.3 +/- 5.0%) and blastocyst cell number (C, 94.1 +/- 9.7; MEC, 92.9 +/- 5.3) were similar. Caspase 3 positive cell index in blastocysts was increased in MEC group, but apoptosis rate was below 5% (C, 2.9 +/- 0.5; MEC, 4.6 +/- 0.6). Using MEC, we performed a retrospective analysis for 'failure' and 'success' embryos, based on their ability to reach the blastocyst stage. We detected the majority of 'success' embryos displayed 8 cells at 48 h post-insemination (hpi) (48.7%), but blastocysts derived from this pattern presented lower cell numbers (91.3 +/- 4.2 vs. 107.9 +/- 4.9) and higher apoptosis index (6.2 +/- 0.6 vs. 4.4 +/- 0.5) than blastocysts from 4-cell embryos at 48 hpi. Most (72.0%) embryos that were at morula stage 120 hpi reached blastocyst stage at 168 hpi. Those blastocysts presented more number of cells than blastocysts derived from embryos exhibiting 16 cells at 120 hpi (108.6 +/- 4.1 vs. 83.9 +/- 4.8). Combination of embryo kinetics data at 48 and 120 hpi revealed high chances of blastocyst formation for patterns: 8 cells/morula, 4 cells/morula, 8 cells/16 cells and 4 cells/16 cells. Blastocysts formed from 4-cell/morula and 8-cell/morula patterns represented 69% of all 168 hpi blastocysts. Blastocysts derived from 4 cells/16 cells displayed decreased apoptosis (3.1 +/- 0.6). Our results suggest that MEC can be used for bovine embryo culture without detrimental effects on development and can help to predict blastocyst formation and quality of in vitro fertilization (IVF) embryos.