Canine embryo-derived stem cells and models for human diseases.

Embryonic stem (ES) cells are pluripotent and permanent cell lines which can differentiate into cell types of all the three germ layers. These features imply multiple opportunities for clinical applications in tissue engineering and regenerative medicine. Most of our knowledge on the biology and technology of ES cells is derived from studies with mouse ES cells. While appropriate for proof-of-principle studies, the mouse model has limitations in its application in translational, pre-clinical studies. This is particularly true for studies evaluating the safety and efficacy of stem cell therapies. For this purpose, large animal models more closely mimicking important aspects of human anatomy, physiology and pathology than mouse models are urgently needed. In this context, the dog is an excellent candidate: the plethora of different dog breeds offer a large phenotypic and genetic variability, which can be exploited increasingly well due to the advanced status of the dog genome project and the rapidly growing box of genomic tools. Recently, the first pluripotent canine embryo-derived stem cells have been described, further increasing the potential of the dog as a model system for regenerative medicine. Although these cells express alkaline phosphatase, NANOG and OCT4, and can be differentiated in vitro towards endoderm-, mesoderm- and ectoderm-lineages (typical features of human and mouse ES cells), their in vivo differentiation capability, i.e. formation of teratomas in immunodeficient mice or contribution to chimeric animals, remains to be demonstrated. Here, we discuss the features of reported canine embryo-derived cells and their potential applications in basic and translational biomedical research.