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Differential Healing Responses in Polymer- and Nonpolymer-Based Sirolimus-Eluting Stents

Michael C. John, MPH^_*, Rainer Wessely, MD, Adnan Kastrati, MD, Albert Schömig, MD, Michael Joner, MD, Mayu Uchihashi, BA^_*, Johanna Crimins, BA^_*, Scott Lajoie^_*, Frank D. Kolodgie, PhD, Herman K. Gold, MD^_*, Renu Virmani, MD, Aloke V. Finn, MD^_*,_*

^_* Cardiac Unit, Department of Internal Medicine, Massachusetts General Hospital, Boston, Massachusetts
CVPath, International Registry of Pathology, Gaithersburg, Maryland
Deutsches Herzzentrum and Med. Klinik rechts der Isar, Technische Universität, Munich, Germany

^_* Reprint requests and correspondence: Dr. Aloke V. Finn, Department of Internal Medicine, Emory University School of Medicine, Emory Crawford Long Hospital, 550 Peachtree Street NE, Atlanta, Georgia 30308 (Email: avfinn{at}emory.edu).

Objectives: We compared the healing and inflammatory responses of polymer-free bare-metal stents (BMS), polymer-free sirolimus-eluting stents (SES) and polymer-free sirolimus-eluting stents plus estradiol (SES+ED) to Cypher drug-eluting stents (CDES) in a rabbit model of overlapping stent placement.

Background: Inflammatory responses to polymers and delayed healing remain important safety issues associated with CDES. Whether nonpolymeric stents that elute sirolimus or sirolimus and estradiol provoke less inflammation and heal better is unknown.

Methods: Twenty-eight rabbits received 2 overlapping stents in each iliac artery: SES, SES+ED, BMS, or CDES, and vessels were harvested at 28 days for histology and scanning electron microscopy.

Results: Although similar at nonoverlapping segments, neointimal thickness within the overlap site of CDES was significantly less than in SES, SES+ED, and BMS (0.07 ± 0.04 mm vs. 0.16 ± 0.03 mm, 0.14 ± 0.03 mm, and 0.15 ± 0.03 mm, p < 0.0001). Endothelialization was greater in SES, SES+ED, and BMS compared with CDES in nonoverlapping sections (80.0 ± 5.0% vs. 95.3 ± 5.0%, 97.5 ± 2.5%, and 96.7 ± 3.8%; p = 0.0028) and overlapping sections (85.8 ± 2.9% vs. 90.8 ± 6.3%, 89.2 ± 6.3%, and 48.3 ± 2.9%; p < 0.0001). The number of luminal eosinophils was also less in overlapping sections of SES, SES+ED, and BMS versus CDES but was similar in nonoverlapping sections.

Conclusions: Polymer-free stents coated with SES or SES+ED result in less robust neointimal suppression but markedly improved arterial healing compared with CDES in the rabbit model.

Key Words: stents • endothelium • polymer

Abbreviations and Acronyms   BMS = bare-metal stent(s)   CDES = Cypher drug-eluting stent(s)   DES = drug-eluting stent(s)   IL = interleukin   ISAR = individualizable drug-eluting stent system to abrogate restenosis   LM = light microscopy   OC = organoid culture   SEM = scanning electron microscopy   SES = sirolimus-eluting stent(s)   SES+ED = sirolimus-eluting stent(s) plus estradiol   VEGF = vascular endothelial growth factor