Comparison of Single-step and Sequential Embryo Culture Systems: Replacement of Serum with Platelet Lysate

 More understanding of the physiological needs of the embryo during its growth from the zygote to the blastocyst stage, as well as the composition of the uterine and fallopian tubal secretions, has led to the development of single-step or sequential culture media.

 The present study aimed to investigate the utilization of mCR2aa culture medium as a sequential culture medium for embryo development, supplemented with platelet lysate (PL) to decrease the concentration of fetal bovine serum (FBS) in the embryo culture medium.

 After maturation and fertilization of sheep oocytes obtained from a slaughterhouse, potential zygotes were cultured in mCR2aa medium without FBS for two days (C1, 1 - 3 days of culture). In the second two days of culture (C2, 3 - 5 days of culture), 2.5% or 5% of FBS and 5% or 10% of PL were used. In the remaining days of culture (C3, 5 - 9 days of culture), 2.5%, 5%, or 10% of FBS, and 0%, 2.5%, 5%, or 10% of PL were used. These percentages were compared to the commercial BO-IVC™ medium and mCR2aa medium, both of which contained 10% of FBS.

 No significant difference was observed in the number of produced blastocysts between different treatments and the control. However, the number of hatched blastocysts in BO-IVC™, as a single-step culture medium, significantly differed from that of the other treatments. The number of hatched blastocysts in the sequential culture medium was higher in media supplemented with 2.5% FBS and 10% PL in the C2 mCR2aa medium, and 2.5% FBS without PL in the C3 mCR2aa medium, but no significant difference was observed in other treatments. However, increasing the concentration of FBS and PL in the C3 mCR2aa medium significantly decreased the number of hatched blastocysts.

 An increase in the percentage of PL to 10% necessitated a decrease in FBS to 2.5% in the C2 mCR2aa medium, while PL in the C3 mCR2aa medium was not required in the presence of 2.5% FBS.