Successful vitrification of stroke-prone spontaneously hypertensive and normal Wistar rat 2-cell embryos

Stroke-prone spontaneously hypertensive rats (SHRSPs) have been widely used as models of hypertension and cerebral apoplexy. They were obtained by selective sib-breeding of Wistar Kyoto rats with higher blood pressure than rats of the original Wistar Kyoto strain. For vitrification of SHRSP 2-cell embryos, DPS solution containing 2.75 M dimethylsulfoxide, 2.75 M propylene glycol and 1.0 M sucrose was prepared and diluted in a modified phosphate-buffered saline, PB1, containing 0.3% bovine serum albumin. Embryos were exposed to the resulting solution in one step at room temperature, kept in the solution for 15 s, vitrified in liquid nitrogen, and warmed rapidly. The post-warming survival rate as morphologically assessed was 70% (148/210), which was comparable (P > 0.05) to the rate of 88% (78/89) for the solution control. After vitrification, the embryos were transferred into recipient animals, and 62% (48/78) were normally delivered, comparable (P > 0.05) to the percentage for the solution control (68%, 57/84). These was no significant difference between pups from vitrified embryos and those from unvitrified control embryos in either the growth curve or degree of blood pressure increase. These findings demonstrate the effectiveness of the simple vitrification method we used for cryopreservation of SHRSP and Wistar rat 2-cell embryos, and also demonstrate that vitrification-mediated cryopreservation does not affect the phenotypic characteristics of SHRSPs.