To improve the culture conditions for in vitro production of porcine embryos, we evaluated the effect of knockout serum replacement (KSR), a substitute for serum or albumin, on the viability and development of porcine blastocysts. The addition of 5% (v/v) KSR to porcine blastocyst medium (PBM) on day 5 (day 0 = in vitro fertilization) significantly increased the survival and hatching rates of blastocysts and the total cell number of blastocysts on day 7 when compared with those in culture without KSR. Furthermore, the ATP content of blastocysts cultured with 5% KSR was significantly higher on day 7 than that of blastocysts cultured without KSR. The mRNA expression of a rate-limiting enzyme in β-oxidation, carnitine palmitoyltransferase 1, in blastocysts on day 6 and a serine proteinase, urokinase-type plasminogen activator, in blastocysts on day 7 cultured in 5% KSR-PBM was significantly higher than that of blastocysts cultured in PBM alone. Four of eight porcine recipients (50%), in which blastocysts treated with 5% KSR on day 5 were transferred non-surgically, became pregnant. The present study demonstrated that the addition of KSR to PBM enhanced the in vitro viability of porcine blastocysts. In addition, our data suggest that KSR improved development to the hatching stage and blastocyst quality by increasing ATP content and hatching-related mRNA expression in blastocysts.
(Pathology and Physiopathology Research Division)
Sakurai M. et al (2015) Theriogenology 83:679-686