Pig models in translational surgery.

Large mammals are required for surgical research since the small size of rodents does not allow the translation of the procedures to those of humans. The pig has a particularly high translational value due to its similar overall anatomy and physiology, thus used as a first choice in many fields of surgical research. In cardiovascular procedures, it contributed to stents development, coronary bypass grafting improvement and heart valve xenotransplantation. A particular focus will be done in the future to improve the models and consequently the reliability of the preclinical findings. In digestive surgery, the utility of pigs has been diverse, with the development of meshes for abdominal defects repair or improvement of surgical procedures aiming at compensate functional defects. A particular utilization has been made in liver regeneration and transplantation procedures, for which the future perspectives are wide, and in metabolic surgery research for metabolic diseases interventional therapy. In endocrine surgery, the use of the pig has mainly consisted in the development of pancreas and islets transplantation for type 1 diabetes therapy, whereas the research on the other glands is less represented. Osteoarticular and neurosurgery are fields where the use of the pig is increasing: for ethical reasons instead of non-human primate models in neurosurgery but also because the rapid growth of this species allows to test the biomechanical properties of orthopedic devices in context of skeletal growth. More generally, the pig has a particular present and future involvement for testing new surgical equipment or bioengineering solutions, developing new minimally invasive approaches and robotic surgery training, regardless of the field. Finally, pig-to-human organ xenotransplantation represents a major translational surgery challenge. If the research has reached a milestone with some living patients grafted with heart or kidney from pigs with multiple genetic modifications, additional findings are required to demonstrate the safety and the long-term benefit and to extend it to other organs like the liver. In summary, the pig model has led to many advances in surgical research, with future prospects focusing primarily on xenotransplantation. However, the use of the pig in biomedical research will have to deal with growing societal ethical expectations.