Early mammalian embryo development depends on cumulus removal technique

Abstract

Cumulus removal (CR) at the zygote stage is necessary for most mammalian in vitro production (IVP). Present techniques use high fluidic stresses (vortexing) or mechanical stress with enzymatic treatment (pipetting) to remove cumulus. Herein a recently developed microfluidic device for cumulus removal from zygotes is compared with traditional vortexing. Microfluidic CR (µFCR) increased development on day 2 (20 ± 4% to 35 ± 6%, p < 0.01) and blastocyst formation at day 8 (33 ± 1% to 57 ± 5%, p < 0.01) when compared to vortex CR. Vortexing effects on embryo development were studied; 15, 30 and 120 s vortex doses. Development at day 2 was inversely proportional to duration of vortexing. An in situ transcription assay was used to assess biochemical activity of zygotes after cumulus removal. There was a spike of RNA transcription of vortexed zygotes at 2 h post CR not seen in the microfluidic treatment. These results suggest the potential for microfluidic methods to enhance production efficiencies while providing insight into basic developmental mechanisms.