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Figure 4 Photomicrographs of rabbit iliac arteries after stent implantation. Serial sections from four arteries stained for collagen (picrosirius red), fibrin (Mallory’s PTAH) and hyaluronan (b-PG). In arteries with uncoated stents, collagen deposition within the neointima (yellow-orange viewed under polarized light) intensifies between 28 days (A) and 180 days (D). With paclitaxel-releasing stents, although medial collagen is present, neointimal collagen is sparse after 28 (G) and 180 days (J). Neointimal fibrin (extracellular blue staining) is sparse in arteries receiving uncoated stents after 28 (B) and 180 days (E). In contrast, intense extracellular fibrin persists in vessels receiving paclitaxel-releasing stents at 28 (H) and 180 days (K). Hyaluronan (brown staining) diminishes in arteries with uncoated stents between 28 (C) and 180 days (F). In paclitaxel-releasing stents, hyaluronan persists without change between 28 (I) and 180 (L) days. *Sites of stent struts. Original magnification 120x.