DIFFERENTIATION OF THE MOUSE EMBRYOID BODIES GRAFTED ON THE CHORIOALLANTOIC MEMBRANE OF THE CHICK-EMBRYO

In order to test the developmental potential of the mouse embryonic-st ern-cell-derived embryoid bodies as chorioallantoic grafts, the embryo id bodies were transplanted to the chorioallantoic membrane (CAM) of t he chick embryo. The graft implantation was achieved if the embryoid b odies were transferred to the CAM into the blood drop created by gentl e laceration of a CAM blood vessel. The resulting tumors were recovere d after 10 days, when they were rounded white elevations, up to 1 mm b ig. Histological analysis showed that they were made of groups of comp acted epithelial-like cells and fibroblast-like spindle shaped cells d ivided by the CAM mesenchyme. The grafting caused angiogenic response of the CAM. Blood vessels converged toward the tumor and spread throug h the CAM mesenchyme among the groups of condensed cells. Although the embryonic bodies were able to implant to the CAM of the chick, their differentiation did not result in a wide variety of differentiated cel l types or in the formation of complex structures resembling morphogen esis. Thus in comparison with in vitro differentiation of embryoid bod ies on an adhesive substrate, or in vivo differentiation under the mou se kidney capsule, the differentiation potential of embryoid bodies as chorioallantoic grafts appeared restricted. However, we suggest that the accessibility of the chorioallantoic graft can be an advantage for future experiments.