Giuriato L, Scatena M, Chiavegato A, Zanellato A M, Guidolin D, Pauletto P, Sartore S
Department of Biomedical Sciences, University of Padova, Italy.
Arterioscler Thromb. 1993 Mar;13(3):347-59. doi: 10.1161/01.atv.13.3.347.
Morphological techniques (histology and electron microscopy), as well as immunofluorescence assays, were applied to the study of the localization and smooth muscle cell (SMC) composition of atherosclerotic lesions in Watanabe heritable hyperlipidemic (WHHL) rabbits during a 4.5-month period. Vascular segments from different arteries (carotid, coronary, and iliac arteries) or from the same vessel at different levels (aorta) of animals at days 7, 15, 30, 40, 60, 90, and 135 showed that the atherosclerotic lesion first became visible at the level of the aortic arch in 60-day-old WHHL animals. Histological examination of serial cryosections from this vascular region indicated that the vascular lesion arose from a cavity in the media layer, located anatomically at the level of the juncture of the ligamentum arteriosum with the aortic arch. This aortic arch cavity is formed during the postnatal closure of the ductus arteriosus and is characterized by the presence of a thickened intima, which was absent in the other vascular regions examined. Immunofluorescence comparison of normal and atherosclerotic tissues from the aortic arch cavity wall with the use of monoclonal antibodies specific for smooth muscle and nonmuscle myosin isoforms revealed the existence of distinct SMC populations. SMCs in the thickened intima showed a myosin isoform pattern peculiar to cells with a degree of maturation intermediate between the fully differentiated and the developing (fetal) aortic SMCs. By contrast, SMCs present in atherosclerotic lesions displayed a predominant fetal-type pattern of myosin isoform expression. The achievement of this myosin isoform content seems to be correlated with the accumulation of lipids in the intima. In the media subjacent to the intimal thickening or atherosclerotic lesion, SMCs primarily displayed an intermediate degree of maturation. In older WHHL animals and at this aortic level, the SMC composition of the atherosclerotic lesion did not change, whereas in the subjacent media, the cells of intermediate type almost disappeared. In the vascular regions in which the atherosclerotic lesion appeared at later stages, such as near the aortic bifurcation, the distribution of fetal and intermediate cell types in the atherosclerotic wall was similar to that taken at the aortic arch level. These results indicate that there is 1) a preferential anatomic site from which atherogenesis initiates in WHHL rabbits; 2) a time correlation between the accumulation of lipids in the wall and the phenotypic change of SMCs toward a poorly differentiated cell type; and 3) the tendency for SMCs to follow the same differentiation pattern in early atherosclerotic lesions, irrespective of the site and time at which they develop.
运用形态学技术（组织学和电子显微镜）以及免疫荧光分析，对渡边遗传性高脂血症（WHHL）兔在4.5个月期间动脉粥样硬化病变的定位和平滑肌细胞（SMC）组成进行了研究。在第7、15、30、40、60、90和135天，取自不同动脉（颈动脉、冠状动脉和髂动脉）或同一血管不同水平（主动脉）的血管段显示，在60日龄的WHHL动物中，动脉粥样硬化病变首先在主动脉弓水平可见。对该血管区域连续冰冻切片的组织学检查表明，血管病变起源于中膜层的一个腔隙，该腔隙在解剖学上位于动脉韧带与主动脉弓交界处的水平。这个主动脉弓腔隙是在出生后动脉导管关闭期间形成的，其特征是内膜增厚，而在其他检查的血管区域则不存在这种情况。使用针对平滑肌和非肌肉肌球蛋白同工型的单克隆抗体，对主动脉弓腔壁的正常组织和动脉粥样硬化组织进行免疫荧光比较，发现存在不同的SMC群体。增厚内膜中的SMC显示出一种肌球蛋白同工型模式，这种模式在完全分化的和发育中的（胎儿）主动脉SMC之间的成熟程度的细胞中较为独特。相比之下，动脉粥样硬化病变中存在的SMC表现出主要为胎儿型的肌球蛋白同工型表达模式。这种肌球蛋白同工型含量的实现似乎与内膜中脂质的积累相关。在内膜增厚或动脉粥样硬化病变下方的中膜中，SMC主要表现出中等程度的成熟。在年龄较大的WHHL动物中，在这个主动脉水平，动脉粥样硬化病变的SMC组成没有变化，而在下方的中膜中，中间类型的细胞几乎消失。在动脉粥样硬化病变出现较晚的血管区域，如主动脉分叉附近，动脉粥样硬化壁中胎儿型和中间型细胞类型的分布与主动脉弓水平相似。这些结果表明：1）在WHHL兔中存在动脉粥样硬化发生的优先解剖部位；2）壁中脂质积累与SMC向低分化细胞类型的表型变化之间存在时间相关性；3）在早期动脉粥样硬化病变中，SMC倾向于遵循相同的分化模式，而不论它们发生的部位和时间。
