Hybrid synthetic grafts and embodiments of systems and methods for producing hybrid vascular grafts that can yield implantable grafts that combine synthetic grafts with living cells. Embodiments of systems can include a pressure/flow loop subsystem having an external flow loop system coupled to a specimen holder where the pressure/flow loop subsystem is capable of adjusting at least two dynamic conditions in the specimen holder or a diameter of a specimen in the specimen holder. Embodiments of methods can coat a hybrid lower limb artery bypass vascular graft with a confluent monolayer of endothelial cells by immobilizing a plurality of endothelial cells on the hybrid lower limb artery bypass vascular graft and placing the hybrid lower limb artery bypass vascular graft in a system embodiment according to the invention under conditions effective to promote the endothelial cells to form a confluent monolayer on the surface of the hybrid vascular graft.