In utero and exo utero surgery on rodent embryos

Mammalian development has been best characterized using the mouse model. Direct intervention of the postimplantation mouse embryo in utero represents one of many experimental approaches that can be used to probe mammalian embryogenesis. Experimental access to the mouse embryo is difficult, but techniques have been developed to circumvent some of the challenges of operating on the embryo in vivo. Experimental studies have been carried out on postimplantation stage embryos from E8.5 to term, so much of the gestational period is accessible for experimentation. One approach that has helped to enhance embryo accessibility was the development of surgical techniques based on the finding that embryonic development continued normally exo utero. Exo utero development refers to the surgically created condition in which the embryo develops outside of the uterine cavity, yet within the female abdominal cavity and attached, via the placenta, to the uterus. Using this approach it is feasible to carry out precise surgical manipulations of the mouse embryo without compromising embryo viability associated with postsurgery uterine contractions. In this chapter we review technical aspects of both in utero and exo utero surgical approaches and how these surgeries are used in conjunction with other experimental applications.