Sperm cryopreservation is essential for cattle in vitro embryo production (IVP). However, many sperm are rendered unviable post-thaw [1]. Granulocyte macrophage colony stimulating factor (GM-CSF) is present in seminal plasma and the female reproductive tract and its receptors are found on bovine sperm [2-4]. Whether GM-CSF can improve the health of post-thaw bovine sperm is unknown. The present study aimed to determine if in vitro addition of GM-CSF to frozen/thawed bovine sperm could improve sperm function, fertilisation and embryo development outcomes following IVP.
Thawed bovine sperm (N=4 bulls/4reps) were treated with 0, 0.1, 1, 2 or 10 ng/ml of recombinant bovine GM-CSF at 38.5C for 45 min and assessed for motility on CASA and quality parameters: glucose uptake, mitochondrial ROS, intracellular Ca+, and mitochondrial membrane potential (MMP) by flow cytometry. Capacitation as measured by chlortetracycline staining, and DNA integrity (HALO sperm) were examined following 5 h. IVP was performed on in vitro matured oocytes (N=200/5rep/group), fertilised with post-thaw bovine sperm treated with 2 ng/ml GM-CSF. Presumptive zygotes were cultured in 6% CO2; 7% O2; N2 balance, and day 8 blastocyst development examined. Cell numbers were determined by differential staining.
GM-CSF (2 and 10 ng/ml) increased progressive and rapid motility (10%), and glucose uptake (13%), while 1, 2, and 10 ng increased capacitation (17%) of post-thaw treated sperm (P<0.05), but had no effect on mitochondrial ROS, intracellular Ca+, MMP or DNA integrity. Oocytes fertilised with treated sperm had increased fertilisation rates (69.6 vs 81.7, P=0.006), hatching blastocyst rates (5.6% vs 7.8%, P= 0.048), and blastocyst inner cell mass numbers (35.3 vs 41.8, P=0.026) compared with control.
Our data suggest that GM-CSF treatment of frozen/thawed bovine sperm increases sperm function and improves IVP embryo quality and could be a useful addition to cattle IVP protocols to increase embryo yield and quality.