Title: 638. Combined LDL Receptor and ApoA-I Gene Therapy for Advanced Atherosclerosis in a Mouse Model of Familial Hypercholesterolemia
Abstract: Management of patients with autosomal dominant familial hypercholesterolemia continues to be a major challenge. Somatic gene therapy may offer an alternative treatment for these patients. We have previously reported that helper-dependent adenovirus (HDAd)-mediated LDL receptor (LDLR) gene transfer reversed hypercholesterolemia for over 108 weeks and markedly retarded development of atherosclerosis in LDLR-deficient mice (Gene Ther 11:1540-1548, 2004). We also reported that HDAd expressing apolipoprotein A-I (apoA-I) was effective in inhibition of progression of advanced atherosclerosis. After 24 weeks treatment, the lesions had a more stable-appearing phenotype with a decrease in subendothelial lipid deposits and a reduction in macrophage-derived cells and adhesion molecule expression (Circulation 107:2726-2732, 2003). ApoA-I and LDLR work via different mechanisms. ApoA-I elevates HDL, which has anti-inflammatory and anti-oxidative effects, and also promotes reverse cholesterol transfer. LDL works mainly by lowering atherogenic non-HDL lipoproteins. We, therefore, compared the efficacy of HDAd-mediated hepatic transfer of ApoA-I only, LDLR only, and ApoA-I + LDLR on atherosclerosis development in LDL-/- mice. LDLR-deficient mice (6-8 weeks of age) were fed a high cholesterol diet for 36 weeks and were separated into 5 groups (baseline, HDAd-0 empty vector, HDAd-AI + HDAd-0, HDAd-LDLR + HDAd-0, HDAd-AI + HDAd-LDLR). The baseline group was sacrificed, and the remaining mice were treated with 2 |[times]| 10E11 VP of HDAd vectors. The plasma cholesterol levels in HDAd-0 (n=6) or HDAd-AI + HDAd-0 (n=7) group were around 500 mg/dl throughout the experiment. Plasma cholesterol levels were reduced to 72 mg/dl 2 weeks after treatment in HDAd-LDLR group and gradually increased to 300 mg/dl over the next 28 weeks (n=7). The mice treated with both genes had a cholesterol level of 182 mg/dl at 2 weeks which gradually increased to 297 mg/dl at 28 weeks (n=8). FPLC analysis revealed that the prominent IDL/LDL fraction is reduced in HDAd-LDLR treated groups. Atherosclerotic lesion areas were measured by quantitative morphometry. Mean lesion area was 5.7 mm2 in the baseline group. It was 12.5 mm2 in the HDAd-0 group, 9.5 mm2 in the HDAd-AI group, 3.2 mm2 in the HDAd-LDLR group, and 3.3 mm2 in the HDAd-AI + HDAd-LDLR group. Compared with baseline and HDAd-0 group, HDAd-AI treatment inhibited the lesion progression by 25%, while HDAd-LDLR alone or combined treatment induced lesion regression by 44%. The combined treatment is very effective. However, our data suggest that LDLR gene transfer accounts for most of the effects in the combined treatment. Moreover, these results indicate that HDAd-mediated LDLR gene therapy is highly effective in inhibition of lesion progression as well as in inducing atherosclerotic lesion regression in a mouse model of familial hypercholesterolemia.