## 4 Clinical Study in Arterial Model  
Historically, the development of TEVGs in the arterial system has faced many difficulties as the currently available materials have been unable to withstand high arterial pressures while simultaneously allowing for graft degradation and host remodeling. The human acellular TEVG for dialysis access in patients with End-Stage Renal Disease ( is a promising new technology that has been developed by [PERSON] et al. of [9]. In their approach organ donor-derived SMCs are seeded onto PGA scaffolds and then cultured in a pulsatile bioreactor to stimulate extracellular matrix production. The ester hydrolysis which occurs on the PGA fiber surface results in increased hydrophilicity with an increase in the adsorption of serum proteins and contributes to SMC adhesion. After the initial SMC seeding period of 30 minutes, the bioreactor was filled with medium and the SMCs were cultured for eight weeks under conditions of beating radial stress. The histological examination suggests that pulsatile stimulation is required to promote smooth muscle cell migration. [69]. After the successful creation of an ECM rich scaffold, the grafts were decellularized to remove allogeneic antigens and implanted as vascular scaffolds within baboons and canines to evaluate their in vivo function and remodeling over time. Figure 4: Macroscopic and histological images of explanted human TEVG. A female patient with a single right ventricle underwent TCPC with common atrioventricular valve plasty at age 4 years. A 12-mm-diameter biodegradable synthetic TEVG with BM-MNCs was implanted between the hepatic vein and pulmonary artery. Unfortunately, she died 12 years later and an autopsy was performed. **(A)** Macroscopic imaging of the TEVG. No difference appears between native PA and TEVG. **(B)** Cross-section view of the border between native PA and TEVG. **(C)** Hematoxylin-eosin staining. **(D)** Masson trichrome staining. **(E)** Victoria blue-van Gieson staining. **(F)** Factor VIII-positive cells (brown). **(G)**\(\alpha\)-Smooth muscle actin–positive cells (brown). **(H)** Calponim-positive cells (brown). LPA, left pulmonary artery; PA, pulmonary artery; RPA, right pulmonary artery; SVC, superior vena cava; TCPC, total cavopulmonary connection; TEVG, tissue engineered vascular graft. Modified from [PERSON], [PERSON] [PERSON] First report of histological evaluation of human tissue-engineered vasculature. J Biotechnol Biomater 2015; 5:200 Adopted with permission from [PERSON] et al. Their first set of animal experiments evaluated a small diameter (3-4 mm) TEVG in a canine peripheral arterial and coronary bypass model. The graft was created as detailed above with the requirement that cells were sourced from a canine in order to avoid cellular rejection after implantation. It should be noted that following the decellularization process they additionally seeded the grafts with ECs over an additional two days [69]. After excluding for surgical mortality in the setting of patent grafts, they demonstrated long-term patency in five out of six grafts at one month [69]. A baboon model preclinical evaluation was undertaken to evaluate the graft as an arteriovenous shunt. Briefly, grafts 6 mm in diameter were implanted as arteriovenous shunts between an axillary artery and brachial vein. A total of eight grafts were implanted, followed by routine ultrasound to determine patency and evaluated at explant of one, three, or six months. patency rates were 100%, 66%, and 100% at one, two, and six month explants, respectively. Only one graft showed thrombosis at three months, likely because of technical difficulties with access, which required prolonged manual pressure that led to graft clotting. Hence, the sum total patency of the arteriovenous 6 mm TEVGs in the baboon was 88% (seven of eight) [70]. Following these encouraging preclinical results, human clinical trials were conducted. Two phase two clinical trials were conducted in a total of 60 patients with the graft implanted as an arteriovenous shunt.