Study Of Biodegradable Endovascular Stent

Purpose1, To investigate the feasibility and reliability of fabricating the sirolimus-incorporated biodegradable endovascular stent by means of adding drug into solution and to study the difference of mechanical performance among naed, ASODN-coated and sirolimus- incorporated BES.2, To demonstrate the role of sirolimus-incorporated BES in preventing the neointimal hyperplasia of porcine balloon-injuried renal artery.3, To demonstrate the role of ASODN-coted BES in surpressing the expression of c-myc gene and the prevention of neointimal hyperplasia of porcine balloon-injureud renal artery.Matietial and Methods1, Biodegradable endovascular stent was fabricated using macromolecular PLLA. Sirolimus-eluting BES was fabricated by means of adding drug into solution and its durg-loading capacity was measured by HPLC. ASODN-coated BES was fabricated by means of surface coating. Radial strength of three kinds of BES was measured and was compared with that of metal stent.2, Sirolimus-eluting BES and naked BES were implanted into bilateral balloon-injrued renal artry of 6 pigs respectively and specimen were harvested 8 weeks later. The neointimal thickness, neintimal area, lumen area and PCNA index were measured and compared between two kinds of BES.3, ASODN-coated BES and naked BES were implanted into bilateral balloon-injrued renal artry of 16 pigs respectively and each 4 animals were sacrificed 24 hours, 1 week, 4 weeks and 12 weeks after BES implantation.The c-myc gene expression was analysed by Western Blot and neointimal thickness, neointimal area, lumen area and PCNA index of the specimens of all the time intervals were measured and compared between two kinds of BES.Results1, The diameter of BES was 4.0 or 5.0mm with strut diameter of 0.5mm and stent length of 15mm. There were on differences in appearance among three kinds of BES. The average loading-capacity of sirolimus-eluting BES was 181^g, which was consistent with the design. Radial strength of three kinds of BES were inferior to that of mateal stent. The naked BES showed similar radial strength to coated BES, both of which were slightly higher than that of sirolimus-eluting BES.2> All the BES were fully expanded 8 weeks after implantation. The neointimal thickness, neointimal area and PCNA index were obviously smaller than that of naked BES while lumen area was larger than the latter.3 >. The neointima of vessels implanted with naked BES and ASODN coated BES showed continuous healing process. The c-myc expression of ASODN-coated BES was similar to that of healthy vessel, both of which were obviously lower than that of naked BES and the difference sustained 4 weeks after injury. All specimens showed low expression of c-myc 12 weeks after injury. Neointimal hyperplasia and PCNA index, especially around the BES strut, of ASODN-coated BES was lower compared with that of naked BES and the lumen area was larger than that of the latter on all the time intervals after vessel injury except for 24hours.Conclusion 1 -. Radial strength of naked BES, drug-incoperating BES and coating BES werelower than that of metal stent and radial strength of drug-incoperationg BES wasslightly lower than that of naked BES and coating BES. The method of addingsirolimus into solution was reliable and can take the place of surface remodeltechnics.2, BES could fulfill the supporting misson and surpress the neointimalhyperplasia of porcine renal artery effectively afer vessel injury compared withnaked BES.3 ^ C-myc gene expression of balloon injured porcine reanal artery andsuccedental neointimal hyperplasia could be surpressesed by ASODN-coatingBES and PLLA stent was an optimal vehicle for antiproliferational genereliesing.