Objective(s) The clinical translation of tissue-engineered vascular grafts has been demonstrated in children. growth and remodeling was quantified using X-ray computed tomography angiography. Methods Cell-seeded and unseeded scaffolds were implanted in lambs (n=5) as inferior vena cava interposition grafts. At 2 and 6 months post-implantation angiography assessed graft morphology. and single photon emission tomography/X-ray computed tomography imaging was performed with a radiolabeled compound targeting matrix metalloproteinase activity at 6 months. Neotissue was examined Spry4 CGI1746 at 6 months using qualitative histologic and immunohistochemical staining and quantitative biochemical analysis. Results Seeded grafts demonstrated significant luminal and longitudinal growth from 2 to 6 months. imaging revealed subjectively higher matrix metalloproteinase activity in grafts vs. native tissue. imaging confirmed a quantitative increase in matrix metalloproteinase activity and demonstrated higher activity in unseeded vs. seeded grafts. Glycosaminoglycan content was increased in seeded grafts vs. unseeded grafts without significant differences in collagen content. Conclusions Matrix metalloproteinase activity remains elevated in tissue-engineered grafts 6 months post-implantation and may indicate remodeling. Optimization of imaging to noninvasively evaluate matrix metalloproteinase activity may assist in serial assessment of vascular graft remodeling. Introduction Our research team developed the first tissue engineered vascular graft (TEVG) to be used in humans 1 and applied this technology in a clinical trial for congenital CGI1746 heart surgery.2 We are currently conducting the first FDA approved clinical trial examining the safety and efficacy of TEVG implantation in children within the United States.3 The TEVGs are constructed with autologous bone marrow mononuclear cells (BM-MNCs) seeded onto a biodegradable scaffold 4 and demonstrate growth potential and SPECT/CT imaging of MMP activity within TEVGs in a clinically relevant large animal model 6 months following TEVG implantation CGI1746 and evaluated serial changes in TEVG morphology using CT angiography. Materials and Methods Graft scaffold Scaffolds were constructed using a polyglycolic acid nonwoven sheet coated with a 50:50 copolymer solution of poly (L-lactic acid-64-slice X-ray CT angiography with iodinated contrast (350 mgI/ml Omnipaque GE Healthcare) was performed (Discovery NM-CT 570c GE Healthcare) in lambs at 2 and 6 months following TEVG implantation to assess graft luminal and longitudinal growth. Following sedation animals were intubated and mechanically ventilated CGI1746 (Venturi Cardiopulmonary Incorporated) with 35% oxygen 65 nitrous oxide and 1-3% isoflurane. Blood pressure oxygen saturation and an electrocardiogram signal were continuously monitored during each imaging session (IntelliVue MP50 Philips). Peripheral vein access was established and a 5F polyethylene catheter was placed for the administration of fluids CT contrast agent and radioisotope. Prior to imaging all animals were fasted overnight and given an intravenous 500 cc bolus of normal saline to attain euvolemia. CT images were acquired at a slice thickness of 0.625 mm at 300 mA and 120 kVp. Intravenous contrast injections were performed with a power injector (Stellant D MEDRAD) at a constant rate of 3 cc/sec and total CGI1746 volume of 30 cc followed by a 20 cc saline flush at 3 cc/sec. TEVG luminal volume and length were quantified using commercially available software (Advanced Workstation v4.4 GE Healthcare). Measurement of TEVG length was standardized by selecting the mid-point of each marker that was attached to the distal and proximal anastomoses. Stenosis was defined as a decrease in luminal CGI1746 diameter that was greater than 50% of initial diameter at the time of implantation. In vivo hybrid SPECT/CT imaging single isotope imaging was performed 6 months after IVC graft implantation for qualitative assessment of MMP activity using hybrid SPECT/CT with 99mTc-RP805 (Lantheus Medical Imaging Inc.). 99mTc-RP805 is a broad-spectrum MMP-targeted compound that binds to the activated exposed catalytic domain of MMPs -2 -3 -7 -9 -12 and -13. Previous work in our lab has demonstrated various binding characteristics associated with this radiotracer for each of these MMPs.16 SPECT imaging was performed 60 minutes following intravenous injection of radiotracer at rest (1468.9 ± 159.1 MBq). All images were acquired with a dedicated cardiac SPECT.