Abstract 146: Expression of Axl, a Receptor Tyrosine Kinase, Regulates Vein Graft Remodeling

Introduction: We recently found that expression of Axl, a receptor tyrosine kinase, in non-bone marrow derived cells is important for carotid thickening in response to low flood flow. We hypothesize that Axl plays a role in smooth muscle cell functions during vein graft remodeling. Methods and Results: A segment of inferior vena cava was harvested from male Axl wild type (Axl+/+) or knockout (Axl-/-) mice and anastomosed to a carotid artery in female Axl+/+ mice under isoflurane anesthesia. Ultrasound Vevo2100 system was used to evaluate successful engraftment of the veins. Initial assessments of the blood flow through the graft were done at 1week after the surgery. A 3-dimensional high-resolution imaging was performed in mice after 3weeks after surgery. We found similar mean blood flow velocity ~110mm/s in the vein grafts between Axl+/+ >Axl+/+ and Axl-/- >Axl+/+ mice. There were no differences in the length of the graft between the groups in reconstruction of 3D-Mode imaging. However, graft volumes had a tendency (p~0.1) to be lower in Axl-/- >Axl+/+ vs. Axl+/+ >Axl+/+ mice (5.3±0.2 vs. 5.8±0.4mm3). We also observed ~20% reduction of graft wall thickness in Axl-/- >Axl+/+ mice. Finally, pulsatility and resistive indexes of vein grafts were ~10% lower in Axl-/- >Axl+/+ mice. Conclusions: This is the first study to demonstrate contribution of Axl to vein graft remodeling. Although, to confirm ultrasound differences between experimental groups vein graft wall changes are being evaluated by histology.