968-23 Evaluation of Proliferation in Human Atherectomy Specimens Using In Situ Hybridization for Histone H3

Abstract

Previously, using immunocytochemistry for the proliferating cell nuclear antigen, we detected low levels of replication (≤ 1%) in 100 restenotic coronary atherectomy specimens. Histone H3 mRNA increases 30-50-fold as cells pass through S phase of the cell cycle and can be used as an independent marker of cell replication. Therefore, using in situ hybridization for histone H3 mRNA we examined the proliferative profile of: i) coronary atherectomy specimens (n = 12) obtained within the first 60 days after a previous interventional procedure, and ii) primary (n = 13) and restenotic (n = 10) peripheral atherectomy specimens because of their larger tissue sample size. For these respective tissue groups, the number of specimens that had any cells expressing histone mRNA on a slide were 2/12, 5/13 and 7/10. The total number of cells per slide expressing histone H3 mRNA ranged from 0 to 23.0 to 82 and 0 to 118 for these 3 groups of specimens. Typical coronary and peripheral atherectomy specimens contain 4,500 and 10,200 cells per slide, respectively. Therefore, the highest replication profiles (0.5%, 1.2%) were seen in restenotic coronary and peripheral artery specimens obtained 1 and 2 days post-atherectomy, respectively. Smooth muscle and endothelial cells expressed histone H3 mRNA. These results suggest that: 1) replication is a modest event in human atherosclerosis and restenosis; 2) replication may be more prevalent in peripheral compared to coronary atherectomy specimens; and 3) anecdotally, an important time window for proliferation may be in the days immediately post-intervention.