Animal models for prenatal gene therapy: the sheep model.

Large animal experiments are vital in the field of prenatal gene therapy, to allow translation from small animals into man. Sheep provide many advantages for such experiments. They have been widely used in research into fetal physiology and pregnancy and the sheep fetus is a similar size to that in the human. Sheep are tolerant to in utero manipulations such as fetoscopy or even hysterotomy, and they are cheaper and easier to maintain than non-human primates. In this chapter, we describe the animal husbandry involved in generating time-mated sheep pregnancies, the large number of injection routes in the fetus that can be achieved using ultrasound or fetoscopic-guided injection, and laparotomy when these more minimally invasive routes of injection are not feasible.