Interspecies chimeras: an experimental approach for studies on embryonic angiogenesis.

Most studies on the growth of vessels have so far focused on the tumour vascularization or that occurring in the area of inflammation. The mechanisms of embryonic angiogenesis have not been characterized in such a detail and only relatively few experimental studies have been carried out to analyse the origin and development of the embryonic vasculature. It is not known if the vessels develop in situ in each organ rudiment or by invasion of earlier committed vascular cells. Because morphological analyses of in vivo tissues have proved to be unreliable for judging the origin of vascular cells, new methods have been presented. Nuclear differences between of some species can be used to trace the origin of cells in interspecies transplantation experiments. This review presents data on the biology of vasculogenesis and shows how interspecies chimeras can be used in studies on angiogenesis. For example, the transplantation experiments with embryonic kidneys are described in more detail.