Murry C E, Gipaya C T, Bartosek T, Benditt E P, Schwartz S M
Department of Pathology, University of Washington, Seattle 98195, USA.
Am J Pathol. 1997 Sep;151(3):697-705.
Atherosclerotic plaques contain a large monoclonal population of cells. Monoclonality could arise by somatic mutation, selection of a pre-existing lineage, or expansion of a pre-existing (developmental) clone. To determine the monoclonal cell type in plaque and learn when monoclonality arises, we studied X chromosome inactivation patterns using methylation of the X-linked human androgen receptor gene. Assays based on polymerase chain reaction were performed on samples of known cellular composition, microdissected from histological sections of human arteries. In atherosclerotic vessels, the majority of medial samples (7/11 coronary and 2/3 aortic) showed balanced (paternal and maternal) patterns of X inactivation, indicating polyclonality. In contrast, most samples of plaque smooth muscle cells showed a single pattern of X inactivation (3/4 aortic plaques and 9/11 coronary plaques; P < 0.01 versus media), indicating that plaque smooth muscle cells are monoclonal. Samples of plaque containing inflammatory or endothelial cells showed balanced X inactivation, also demonstrating polyclonality. Multiple plaques from a given patient showed no bias toward one allele, indicating there was no X-linked selection of cells during plaque growth. To determine whether plaques might arise from pre-existing clones (large X inactivation patches), we then studied 10 normal coronaries with diffuse intimal thickening. Six of the ten coronaries showed skewed X inactivation patterns in normal media and intima, suggesting the patch size in normal arteries is surprisingly large. Thus, smooth muscle cells constitute the monoclonal population in atherosclerotic plaques. The finding that normal arteries may have large X inactivation patches raises the possibility that plaque monoclonality may arise by expanding a pre-existing clone of cells rather than generating a new clone by mutation or selection.
动脉粥样硬化斑块包含大量单克隆细胞群体。单克隆性可能通过体细胞突变、对预先存在的谱系的选择或预先存在的（发育）克隆的扩增而产生。为了确定斑块中的单克隆细胞类型并了解单克隆性何时出现，我们使用X连锁的人类雄激素受体基因的甲基化研究了X染色体失活模式。基于聚合酶链反应的检测在已知细胞组成的样本上进行，这些样本是从人类动脉的组织学切片中显微切割得到的。在动脉粥样硬化血管中，大多数中膜样本（7/11的冠状动脉和2/3的主动脉）显示出平衡的（父本和母本）X失活模式，表明是多克隆性。相比之下，大多数斑块平滑肌细胞样本显示出单一的X失活模式（3/4的主动脉斑块和9/11的冠状动脉斑块；与中膜相比P < 0.01），表明斑块平滑肌细胞是单克隆的。含有炎症或内皮细胞的斑块样本显示出平衡的X失活，也证明是多克隆性。来自给定患者的多个斑块对一个等位基因没有偏向性，表明在斑块生长过程中没有对X连锁细胞的选择。为了确定斑块是否可能源自预先存在的克隆（大的X失活区域），我们随后研究了10个有弥漫性内膜增厚的正常冠状动脉。这10个冠状动脉中有6个在正常中膜和内膜中显示出偏态的X失活模式，表明正常动脉中的区域大小惊人地大。因此，平滑肌细胞构成了动脉粥样硬化斑块中的单克隆群体。正常动脉可能有大的X失活区域这一发现增加了斑块单克隆性可能通过扩增预先存在的细胞克隆而不是通过突变或选择产生新克隆的可能性。
