In the light of a careful preclinical evaluation of AFCs for cardiovascular tissue engineering applications, the characterization of amniotic fluid harvested from an ovine preclinical model—representing the standard model in cardiovascular medicine—has recently been reported [61]. Several biochemical parameters, like total protein amount or electrolytes, have been suggested as possible indicators for a specific isolation of amniotic fluid in sheep. Moreover, isolated cells showed a stable karyotype with expression of common mesenchymal stem cell surface markers as well as of some stem cell factors like NANOG and STAT-3. In contrast to the successful sorting of human amniotic fluid-derived cells based on AC133.1 [38], isolation of sheep endothelial cells was not possible using this technique. Nevertheless functional in vitro fabrication of tissue engineered vascular grafts and cardiovascular patches could be shown using amniotic fluid-derived cells (Fig. 9.3). However, more in vivo experiments in preclinical models are indispensable to evaluate this cell source for a possible human clinical translation. The exact in vivo fate of the cells needs to be defined in order to guarantee safety and exclude adverse effects for a potential prenatal therapy. In conclusion, amniotic fluid-derived cells represent an effective cell source for the treatment of congenital defects. In particular their early availability via low-risk procedures as well as their wide differentiation capacities hold great potential for autologous tissue engineering applications.