Abstract 13754: RNA Interference and Inhibition of Stem Cell Factor (SCF)/c-Kit Signaling Prevent Stenosis of Arteriovenous Fistulae
Background: Neointimal hyperplasia (NIH) is the most common cause of vein graft and arteriovenous fistula (AVF) failure. This study demonstrates the essential role of Stem Cell Factor (SCF)/c-Kit signaling in neointimal cell mobilization and venous stenosis.
Methods and Results: Discarded human AVFs with neointimal hyperplasia ranging from minimal to severe were immunostained for SCF and c-Kit. SCF and c-Kit+ cells were abundant in fistulae with proliferating neointimas but rare those with minimal or advanced NIH. This biphasic pattern of expression was also observed in a rat experimental fistulae created by anastomosing the left renal vein to the abdominal aorta after unilateral nephrectomy. In this model, c-Kit+ cells were detectable at day 3 (125 ± 23 cells/mm2) reaching its maximum at day 14 (435±72 cells/mm2) and then, decreased to a non-significant level at day 30 (35±15 cells/mm2). c-Kit+ cells turned positive for SMA, a smooth muscle cell/myofibroblast marker, only in the media and neointima. The venous wall of sham operated rats didn’t show staining for SCF or c-Kit. In agreement with a previous work, c-Kit+ cells were also found incorporated in the adventitial neovasculature. The up-regulation of SCF signaling molecules was further confirmed by qRT-PCR and by placing fistulae in a transgenic c-Kit GFP reporter mouse. Interestingly, adventitial c-Kit+ cells did not derive from bone marrow (BM) because they were mostly GFP negative in chimeric rats that were created by reconstituting wildtype rats with GFP+ bone marrow (GFP BM Lewis WT). Finally, we used Gleevec, a specific c-Kit inhibitor (5mg/Kg/d for 7d) and a lentiviral vector carrying a small hairpin RNA that decreases SCF gene expression in cultured smooth muscle cells to assess the therapeutic effect of SCF/c-Kit signaling inhibition on venous NIH. Gleevec produced a 3-folds reduction in neointimal thickness in treated versus control groups (0.093±0.006 vs. 0.030±0.0008, p=0.0026) while the SCF shRNA vector abolish the development of NIH in experimental fistulae (0.067±0.003 vs. 0.0180±0.0008, p=0.036).
Conclusion: Our results demonstrate the SCF deficiency protects veins from developing NIH.
- © 2011 by American Heart Association, Inc.