In vitro development of bison embryos using interspecies somatic cell nuclear transfer

Area of Science:

• Reproductive biology
• Animal biotechnology
• Conservation genetics

Background:

• Interspecies somatic cell nuclear transfer (SCNT) is a key technique in animal reproduction.
• Challenges in SCNT development are often linked to species-specific nuclear-cytoplasmic incompatibilities.
• Bison embryo production via SCNT remains underexplored.

Purpose of the Study:

• To establish interspecies SCNT for producing bison embryos in vitro.
• To evaluate the developmental potential and quality of resulting bison embryos.
• To compare SCNT-derived embryos with in vitro fertilization (IVF) and control SCNT embryos.

Main Methods:

• Wood bison, plains bison, and wisent oocytes were used for SCNT with cattle cytoplasts.
• Control groups included cattle in vitro fertilization (IVF) and cattle SCNT.
• Embryo development was assessed by cleavage and blastocyst rates.
• Blastocyst quality was evaluated by total cell number, apoptosis, and mitochondrial gene expression (NRF1, MT-CYB, TFAM).

Main Results:

• Successful production of bison embryos via interspecies SCNT across all tested species/subspecies, with blastocyst rates ranging from 13.34% to 33.54%.
• Bison SCNT blastocysts exhibited higher apoptosis incidence (10.45-12.69%) and lower cell numbers (80-87 cells) compared to cattle SCNT controls (8.76% and >100 cells).
• No significant differences in the expression of NRF1, MT-CYB, and TFAM were observed between bison and cattle SCNT blastocysts.

Conclusions:

• Interspecies SCNT is a viable method for producing bison embryos in vitro, yielding higher blastocyst rates than previous IVF studies.
• While SCNT enables bison embryo production, developmental competence and quality require improvement, indicated by increased apoptosis and reduced cell counts.
• Further research is essential to understand and overcome the factors limiting blastocyst quality and viability in bison SCNT embryos.