A Novel Gutless Adenoviral Vector Encoding Sphingosine Kinase Promotes Arteriogenesis and Improves Perfusion in a Rabbit Hindlimb Ischemia Model

Abstract

Background: We previously demonstrated that sphingosine kinase (SPK) increases the level of extracellular sphingosine-1-phosphate and promotes arteriogenesis in a mouse matrigel model. The present study was designed to test the hypothesis that SPK gene transfer using a novel “gutless” adenoviral vector (AGV) can enhance arteriogenesis in a rabbit hindlimb ischemia model. Methods and Results: Thirty five male New Zealand white rabbits were randomized to AGV-SPK group (n=13), AGV-Null group (n=13, vector without SPK gene), and control group (n=9). At day 10 after the induction of unilateral hind-limb ischemia, gene vectors or buffer were introduced and the effect examined at day 30, using calf blood pressure, quantitative angiographic analysis, and histology. Calf systolic blood pressure ratios of the ischemic limb to the normal limb at day 30 were 0.75 ? 0.15 in control group, 0.76 ? 0.13 AGV-Null group, and 0.89 ? 0.14 in AGV-SPK group (p<0.05 for AGV-SPK versus controls or AGV-Null). Angiographic vessel counts were significantly increased (8.0±2.1 at baseline and 11.8±3.2 on day 30, p<0.001) in AGV-SPK group. There was a significant increase in flow capacity of AGV-SPK group (day 0; 0.07±0.05, day 30; 0.17±0.11, p=0.004). Histologic analysis showed that microscopic total vessel counts at day 30 were 3.5?1.8/field in Control and AGV-Null group, 5.4?1.0/field in AGV-SPK group. Arterioles (AGV-SPK; 3.0?0.8 versus Control and AGV-Null; 2.1?1.1, p=0.044) and veins (AGV-SPK;2.4?0.8 versus Control and AGV-Null; 1.8?2.0, p=0.038) were significantly increased in AGV-SPK group. Conclusions: This study shows that SPK promotes arteriogenesis, as evidenced by the maximal improvement in the blood pressure restoration and collateral vessel counts. SPK may be an important angiogenic target to improve perfusion in ischemic tissues