Experimental Approaches to Controlled Diapause in Mammals

Abstract

Diapause is a coping strategy characteristic to many invertebrates and vertebrates including more than 100 mammalian species. Preserving the genetic diversity of rare and endangered diapausing species is important for maintaining ecological systems. The purpose of this work was to compare the surgical model of diapause and the pharmacological model based on injecting DL-α-difluoromethylornithine (DL-α-DFMO) into mice. Another goal was to investigate the intriguing possibility of controlling the state of diapause in vitro by exposing murine embryos to putrescine and/or DL-α-DFMO. Although the pharmacological model a priori seems to be attractive for applying it to other mammalian species besides mice, since it does not require surgical intervention, our results on mice demonstrated that this model is less effective compared to the traditional surgical model of diapause. Our data indicates that the effects of DL-α-DFMO on mouse embryos are mediated via its effect on the uterus, as it was not possible to maintain dormancy state in diapausing embryos in vitro by this agent. Meanwhile, in vitro exposure to putrescine facilitates the re-activation of diapausing embryos, as evidenced by the higher rate of blastocysts adhesion and the more advanced stages of ICM outgrowth compared to controls. Our results on mice presented hereby indicate that the surgical model is more reliable than DL-α-DFMO diapause model. Moreover, our results proved that putrescine is a potent tool to re-activate murine diapausing embryos in vitro; this may be considered an ecologically important issue relevant to the conservation problem.