Figure 3: Vascular Graft Maturation. Engineered grafts often require some form of treatment prior to use to expose tissues to the forces that will be encountered. Strategies for applying these forces include flow reactors, radial stretch, longitudinal stretch, and chemical factors. Though flow reactors are effective at mimicking the primary role of blood vessels, the transport of blood, this method primarily affects only the cells on the inner lumen [104]. Radial and longitudinal stretch may be applied to mimic the natural distension of blood vessels under pressure. The radial stretch is effective at impacting all cells throughout the entire vessel, while the longitudinal stretch primarily affects cells at the proximal and distal ends. Finally, chemical factors can be loaded into scaffolds for gradual release, or incubated with the surrounding solution to mimic the native biological chemical environment [126].