Bioengineering dermo-epidermal skin grafts with blood and lymphatic capillaries.

The first bioengineered, autologous, dermo-epidermal skin grafts are presently undergoing clinical trials; hence, it is reasonable to envisage the next clinical step at the forefront of plastic and burn surgery, which is the generation of autologous skin grafts that contain vascular plexuses, preformed in vitro. As the importance of the blood, and particularly the lymphatic vascular system, is increasingly recognized, it is attractive to engineer both human blood and lymphatic vessels in one tissue or organ graft. We show here that functional lymphatic capillaries can be generated using three-dimensional hydrogels. Like normal lymphatics, these capillaries branch, form lumen, and take up fluid in vitro and in vivo after transplantation onto immunocompromised rodents. Formation of lymphatic capillaries could be modulated by both lymphangiogenic and anti-lymphangiogenic stimuli, demonstrating the potential usefulness of this system for in vitro testing. Blood and lymphatic endothelial cells never intermixed during vessel development, nor did blood and lymphatic capillaries anastomose under the described circumstances. After transplantation of the engineered grafts, the human lymphatic capillaries anastomosed to the nude rat's lymphatic plexus and supported fluid drainage. Successful preclinical results suggest that these skin grafts could be applied on patients suffering from severe skin defects.