RhoA phosphorylation mediated by Rho/RhoA-associated kinase pathway improves the anti-freezing potentiality of murine hatched and diapaused blastocysts.

Embryonic cryopreservation has a relatively low survival rate because of cytoskeletal damage. However, molecular anti-freezing mechanisms have been largely unexplored. This study investigated the significance of RhoA, involved in embryonic development, and the Rho/RhoA-associated kinase (ROCK) signalling pathway in cryopreservation. The anti-freezing mechanism in murine dormant embryos, compared with normal blastocysts, was assessed by combining molecular, physiological and pharmacological approaches. Real-time PCR and western blotting experiments showed high RhoA expression in cryo-dormant and dormant embryos. RhoA GTPases were overexpressed on the surface of trophectoderm cells in dormant embryos. Treatment with Y-27632, a ROCK antagonist, decreased survival of both normal and dormant blastocysts, while recombinant RhoA protein remarkably increased survival, after freeze-thawing, of normal hatched blastocysts. Our findings elucidated the molecular mechanism of anti-freezing, involving RhoA phosphorylation, meditated by the Rho/ROCK signalling pathway, in hatched and diapaused murine blastocysts. In addition, evidence for a potentially protective additive suggests a new method for improving the anti-freezing potential of mammalian embryos, without protecting the zona pellucida.