Paternal effect does not affect in vitro embryo morphokinetics but modulates molecular profile.
Level 5 - mechanism / opinion, no new human data
Level 5 by design analogy; non-clinical in vitro animal laboratory study.
PubMed 34775199 · doi:10.1016/j.theriogenology.2021.10.027
What was done
Ten bulls were selected from a commercial database ranking 140 sires based on retrospective in vitro embryo production records, categorized into high-fertility (HF; n = 5) and low-fertility (LF; n = 5) groups. Embryos produced in vitro from both groups were evaluated for developmental kinetics at 24, 36, 48, 60, and 72 hours post-insemination (hpi), pronuclei formation at 24 hpi, day 3 cleavage rate, day 7 blastocyst and development rates, blastocyst morphology, and the abundance of 96 targeted transcripts at the 8–16 cell and blastocyst stages.
What was found
Early embryo kinetics (P > 0.05) and cleavage rates (HF = 86.7% vs. LF = 84.9%; P = 0.25) did not differ significantly between groups. HF bulls had higher fertilization rates (72% vs. 62%) and lower polyspermy rates (16.2% vs. 29.2%) compared to LF bulls. HF bulls also achieved higher blastocyst rates (29.4% vs. 16.0%; P < 0.0001) and development rates (33.9% vs. 18.9%; P < 0.0001). At the 8–16 cell stage, 22 transcripts were differentially expressed (P ≤ 0.05); only PGK1 and TFAM were higher in HF, while stress-related (6/22), proliferation (6/22), and lipid metabolism (5/22) transcripts were elevated in LF. At the blastocyst stage, 9 transcripts differed (P ≤ 0.05), with only ACSL3 and ELOV1 higher in HF.
Why it matters
Paternal in vitro fertility status in cattle affects polyspermy rates and alters embryonic gene expression pathways during genome activation rather than changing the speed of initial cell cleavages.
Limits
The study included only 10 bulls selected retrospectively, and total counts of oocytes and embryos analyzed per assay are not stated in the abstract. Gene expression analysis was restricted to a targeted panel of 96 transcripts rather than an unbiased whole-transcriptome assessment, and findings in an in vitro bovine model may not generalize to in vivo settings.
Cited by
- partial In IVF, embryos failing to develop past day three into a blastocyst are typically attributed to sperm quality.