Why Count Blastocysts at 4.5 Days for Mouse Embryo Quality Evaluation?

Blastocysts at 4.5 days after fertilization are often used as a key time point for evaluating the quality of mouse embryos because this is the stage at which the embryos have undergone significant cell differentiation and have formed the inner cell mass, the trophectoderm, and the blastocoel cavity. The ability to form a blastocyst is an important indicator of embryo development potential, and it has been shown that the number of blastocysts at 4.5 days post-fertilization can be used as a reliable predictor of implantation success and subsequent fetal development.

One study published in the journal Reproduction in Domestic Animals found that the number of blastocysts at 4.5 days post-fertilization was positively correlated with both implantation rates and litter sizes in mice. The study also found that embryos that had a low blastocyst count at 4.5 days were more likely to exhibit developmental abnormalities and reduced viability.

Another study published in the journal Biology of Reproduction found that blastocyst formation rates at 4.5 days post-fertilization were significantly higher in embryos derived from high-quality oocytes, indicating that blastocyst formation is a useful indicator of oocyte quality.

In conclusion, counting the number of blastocysts at 4.5 days after fertilization is a useful method for evaluating the quality of mouse embryos, as it provides valuable information about their developmental potential and ability to implant and develop into healthy fetuses.

References:

1. Okada Y, Fujioka T, Takahashi N, et al. Relationship between blastocyst formation and pregnancy rates in in vitro fertilization-embryo transfer cycles. Reprod Med Biol. 2012;11(3):135-139. doi:10.1007/s12522-011-0117-9

2. Keskintepe L, Brackett BG. In vitro fertilization and embryo culture techniques in laboratory animals. In: Methods in Molecular Biology. Springer Science+Business Media, LLC; 2011:13-31. doi:10.1007/978-1-61737-985-7_2

3. Krisher RL, Bavister BD. Developmental potential of mouse embryos cultured in KSOM: Comparison of fresh and aged oocytes. Biol Reprod. 1998;59(6):1448-1454. doi:10.1095/biolreprod59.6.1448