Abstract 15249: Evidence for Clonal Proliferation of Smooth Muscle Cells in Unstable Human Atherosclerotic Lesions

Abstract

Background: Studies using techniques that relied on expression of an X-linked gene suggested predominant clones of smooth muscle cells (SMC) may exist in human atherosclerosis. These studies were limited by spatial resolution and nature of plaque types studied. We investigated whether clones of SMCs exist in unstable human atheroma. Methods and Results: We used a 25 nucleotide deletion in the 3’ UTR of the BGN gene, highly expressed by SMC and prevalent in 30% of females, to study clonal proliferation. Three different types of plaques (erosion, rupture, and adaptive intimal thickening) were selected from females heterozygous for the deletion mutant. Hybridization of target RNA-specific BaseScope probes was conducted to visualize the distribution of mutants and images displayed as a bubble plots. Clonality index was calculated as the percentage of each probe in each ROI. A clonality index equal to or exceeding the three times the standard deviation above the mean of the clonality index of the media in all plaques was considered clonal. In comparing clonality between media and intima, the mean percent ROI with clonality was significantly higher in the intima than in the media (42.3±18.2 vs 18.3±9.6%, P=0.003) and this was consistent for both eroded (27.0±9.8 vs 9.0±3.8%, P=0.04) and ruptured plaques (41.3±10.7 vs 20.0±3.5%, P=0.03). The relationship of dominant clone in the intima and media shows significant concordance in the majority of plaques studied (R=0.72, P<0.0001). Conclusions and Relevance: This novel approach suggests dominant clones exists within atherosclerotic lesions and may originate from the media.