Use of human tissue specimens obtained by directional atherectomy to study restenosis

Directional atherectomy has provided the opportunity to study the pathology of restenosis in human tissue specimens from live patients. The restenosis lesion is characterized by two distinctive features: a focus of hypercellularity, comprised of cells with phenotypic features of proliferative vascular smooth muscle cells (SMCs), and a rich, loose extracellular matrix (ECM). Analysis of restenosis lesions by in situ hybridization, immunohistochemistry, and cell culture has disclosed evidence of activated SMCs, and in many cases-particularly lesions from the peripheral vasculature-ongoing cellular proliferation. The ECM of restenosis lesions is biglycan rich and decorin poor, a finding that is associated with increased expression of transforming growth factor beta (TGF-β). While certain restenosis lesions contain foci of microangiogenesis, the pathogenetic significance of this feature remains uncertain.