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

表达人载脂蛋白（a）1的转基因兔。转基因兔的制备：我们使用肝脏特异性启动子、小鼠转铁蛋白启动子和含有17个拷贝的kringle 4的人apo（a）cDNA。显微注射受精卵（共2836个）后，我们得到96只幼崽，发现11只幼崽的基因组中有人apo（a）转基因。经过多次选育，获得了3个转基因兔品系，血浆中检测到载脂蛋白（a）.转基因兔的表征：通过北方印迹分析证实人apo（a）在肝脏中表达。经SDS-PAGE检测，人apo（a）分子量约为500 kD，在转基因兔血浆中，人apo（a）与兔apoB形成Lp（a）复合物，但apo（a）的表达对脂蛋白谱无影响。在普通饲料中，转基因兔子不会出现任何动脉粥样硬化病变。喂饲胆固醇饲料16周的载脂蛋白（a）转基因兔的特征。在胆固醇饮食中，转基因兔子比非转基因对照组发生更多的动脉粥样硬化。在转基因兔的所有动脉树中发现了增加的病变，包括主动脉、髂动脉和颈动脉以及冠状动脉。免疫组化研究显示apo（a）可能通过调节SMC表型的改变而促进病变的发展. WHHL转基因兔：将WHHL转基因兔与转基因兔杂交，获得转基因兔，以研究LDL受体是否参与Lp（a）催化。我们发现，在LDL受体缺乏的情况下，Lp（a）在血浆中显著蓄积，表明Lp（a）清除部分受LDL受体控制。

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.