Abstract 1862: Inhibition of the Effects of Cell Therapy by Endothelial Dysfunction and Rescue by L-Arginine Supplementation in a Rat Hindlimb Ischemia Model
OBJECTIVE: Myocardial cell therapy in humans has been less effective than in animal models. This could be due to the target clinical population consisting of patients who have endothelial dysfunction, whose inhibitory effects on protein angiogenesis have been shown, but remain unknown with cell therapy. We examined whether hypercholesterolemia (HC) inhibits cell-based angiogenesis after transplantation of endothelial progenitor cells (EPCs) in a rat model of hindlimb ischemia, and whether L-arginine prevents this HC-related impairment of angiogenesis.
METHODS: Thirty-six athymic male Sprague-Dawley rats were fed either a normal (NORM, n=12) or high cholesterol diet, with (CHOL-ARG, n=12) or without (CHOL, n=12) L-arginine. At 2 weeks of diet intervention, rats underwent unilateral femoral artery ligation and IM injection of 4-day cultured human EPCs into the adductor muscle distal to the ligation. Laser Doppler Perfusion Analysis was performed pre and postoperatively, and on days 7, 14 and 21 post-treatment. Hindlimb muscle was collected for immunohistochemistry and serum for biochemistry.
RESULTS: HC decreased serum nitrite levels by 33±5% (P=0.02). Perioperative ischemic/normal hindlimb blood perfusion did not differ among groups. Complete normalization of tissue perfusion within 21 days of femoral artery ligation was observed in the NORM group. However, this did not occur in the CHOL group (perfusion 40±12% less than NORM at 21 days; P<0.0001), where no functional increase in perfusion was noted. Perfusion in the CHOL-ARG group was higher than the CHOL group at day 14 (P<0.0005) and 21 (P<0.0001), and similar to the NORM group. Histology revealed lower ischemic/normal hindlimb arteriolar density in CHOL rats (density ratio: 0.81±0.33) compared NORM rats (1.23±0.51; P=0.01), and L-arginine markedly increased arteriolar density (1.31±0.57; P=0.01) compared to CHOL rats.
CONCLUSIONS: In a rat model of hindlimb ischemia, HC-induced endothelial dysfunction resulted in impaired cell-based angiogenesis, which L-arginine restored to normal levels. To our knowledge, this indicates for the first time that endothelial dysfunction inhibits cell therapy in vivo, and suggests a role for substrate modification to improve its results in patients.