Role of apo (a) in atherogenesis. A study using transgenic rabbits expressing human apo (a)

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Transgenic rabbits expressing human apoprotein (a)1. Production of transgenic rabbits :We used liver-specific promoter mouse transferrin promoter and human apo (a) cDNA containing 17 copies of kringle 4. After microinjection of zygotes (2836 in total), we got 96 pups and found that 11 pups had human apo (a) transgene in their genome. After several breeding, we got 3 lines of transgenic rabbits that have detectable apo (a) in the plasma.2. Characterization of transgenic rabbits :Human apo (a) was expressed in the liver as confirmed by Northern blot analysis. Human apo (a) size was about 500kD as determined by SDS-PAGE.In transgenic rabbit plasma, human apo (a) was associated with rabbit apoB to form Lp (a) complex but lipoprotein profile was not effected by apo (a) expression. On a chow diet, transgenic rabbits do not develop any atherosclerotic lesions.3. Characterization of apo (a) transgenic rabbits fed a cholesterol diet for 16 weeks. When on a cholesterol diet, transgenic rabbits developed more atherosclerosis than did nontransgenic control. Increased lesions were found in all arterial trees in transgenic rabbits, including aorta, iliac and carotid arteries, and coronary artery. Immunohistochemical staining study showed that apo (a) may enhance the lesion development by modulating SMC phenotype changes.4. WHHL transgenic rabbits :After cross-breeding between WHHL and transgenic rabbits, we got WHHL transgenic rabbits to investigate whether LDL receptor is involved in Lp (a) catabolism. We found that in the setting of LDL receptor deficiency, Lp (a) was markedly accumulated in the plasma suggesting that Lp (a) clearance is controlled in part, by LDL receptor.