title: Long-term effect of stents eluting 6-mercaptopurine in porcine coronary arteries.
abstract: BACKGROUND
  Drug-eluting stents (DES) have dramatically reduced restenosis rates compared to bare metal stents and are widely used in coronary artery angioplasty. The anti-proliferative nature of the drugs reduces smooth muscle cell (SMC) proliferation effectively, but unfortunately also negatively affects endothelialization of stent struts, necessitating prolonged dual anti-platelet therapy. Cell-type specific therapy may prevent this complication, giving rise to safer stents that do not require additional medication. 6-Mercaptopurine (6-MP) is a drug with demonstrated cell-type specific effects on vascular cells both in vitro and in vivo, inhibiting proliferation of SMCs while promoting survival of endothelial cells. In rabbits, we demonstrated that DES locally releasing 6-MP during 4 weeks reduced in-stent stenosis by inhibiting SMC proliferation and reducing inflammation, without negatively affecting endothelialization of the stent surface. The aim of the present study was to investigate whether 6-MP-eluting stents are similarly effective in preventing stenosis in porcine coronary arteries after 3 months, in order to assess the eligibility for human application.
  
  
  METHODS
  6-MP-eluting and polymer-only control stents (both n = 7) were implanted in porcine coronary arteries after local balloon injury to assess the effect of 6-MP on vascular lesion formation. Three months after implantation, stented coronary arteries were harvested and analyzed.
  
  
  RESULTS
  Morphometric analyses revealed that stents were implanted reproducibly and with limited injury to the vessel wall. Unexpectedly, both in-stent stenosis (6-MP: 41.1 ± 10.3 %; control: 29.6 ± 5.9 %) and inflammation (6-MP: 2.14 ± 0.51; control: 1.43 ± 0.45) were similar between the groups after 3 months.
  
  
  CONCLUSIONS
  In conclusion, although 6-MP was previously found to potently inhibit SMC proliferation, reduce inflammation and promote endothelial cell survival, thereby effectively reducing in-stent restenosis in rabbits, stents containing 300 μg 6-MP did not reduce stenosis and inflammation in porcine coronary arteries.
authors.affiliation: Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.|Present address: Unit of Tissue Engineering, Monzino Cardiologic Center, Milan, Italy.
authors.forename: Matthijs S
authors.initials: MS
authors.lastname: Ruiter
authors.affiliation: InnoCore Pharmaceuticals, Groningen, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Doornbos
authors.affiliation: Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands.
authors.forename: Vivian
authors.initials: V
authors.lastname: de Waard
authors.affiliation: Department of Cardiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: de Winter
authors.affiliation: Central Laboratory Animal Research Facility, Faculty of Veterinary Medicine, University of Utrecht, Utrecht, The Netherlands.
authors.forename: Nico J M
authors.initials: NJ
authors.lastname: Attevelt
authors.affiliation: InnoCore Pharmaceuticals, Groningen, The Netherlands.
authors.forename: Rob
authors.initials: R
authors.lastname: Steendam
authors.affiliation: Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ, Amsterdam, The Netherlands. c.j.devries@amc.nl.
authors.forename: Carlie J M
authors.initials: CJ
authors.lastname: de Vries
mesh_terms: D000818:Animals; D019917:Blood Vessel Prosthesis Implantation; D003331:Coronary Vessels / Q000187:drug effects*; D054855:Drug-Eluting Stents; D005260:Female; D007249:Inflammation / Q000473:pathology; D015122:Mercaptopurine / Q000494:pharmacology*; D034421:Sus scrofa; D013997:Time Factors
chemical_list: D015122:Mercaptopurine