The Study Of Biodegradable Intravascular Stents

Purpose1 To prepare biodegradable intravascular stents (BIS) with biodegradable materials poly- L -acid (PLLA), the capability of BIS is similar to metallic stents.2 To investigate BIS's biocompatibility, and evaluate the histopathological findings at a fixed timetable after the BIS implanted so as to determine the possibility of BIS implanted into arteries.3 To prepare drug eluting BIS with antiproliferation agent-paclitaxel, and both the drug release BIS and bare BIS (without any drug) be implanted into the aorta of canine models of restenosis, to assess the effect of paclitaxel releasing drug BIS at preventing neointimal hyperplasia.Materials and Methods1 BIS were prepared with PLLA, porous structures were fabricated and the films were coated at the strut of BIS. The stringent physical and mechanical properties of the BIS were tested.2 Appropriately sized zigzag BISs were implanted into the aorta and iliac arteries of 11 canines, the animals were euthanized according to a fixed timetable forhistopathological assessment.3 Both paclitaxel eluting BIS and bare BIS were implanted into the infrarenal aortas of the canine models of restenosis, the animals were euthanized 6 weeks after implantation for histopathological and immunohistochemical assessment.Results1 Two types of spiral and zigzag BIS were prepared with PLLA (MW^IOOOOOD), the strut of BIS is from 0.1-0.6, the diameter of BIS from 6-15mm, and the length from 3-8cm.2 Fibrosis was evidence surrounded the struts of BIS Iwk days after implantation, and scarce blood platelets were deposited on it. At 2wk, endothelialization of the BIS was not completed. At 4wk, the struts were covered completely by neointima. At 8 wk, the neointima seemed not to be thickening, the arteries' wall were smooth and intact.3 Some significant differences were noted between the paclitaxel BIS group and bare BIS group. The mean lumen area (LA) of bare BIS was smaller than that of the paclitaxel BIS group(77586 n m2 vs 113 435 u m2, pO.OOl). And the mean intimal area (IA) of bare BIS was larger than that of paclitaxel BIS group (24 803 u m2 vs 12 931 u m2 , pO.OOl).4 The PCNA positive ratio of bare BIS group was higher than that of paclitaxel group (38%?15% vs 11%?.31%, PO.01).Conclusion1 The mechanical characteristics of BIS could fulfill the stringent physical, mechanical and chemical properties for the stents implanting to arteries.2 The type of zigzag BIS is convenient to be deployed with stringent mechanical properties and good biocompatibility. After implanted into arteries, the BIS do not induce severe inflammatory or foreign body reaction. At 4wk, BISs were covered completely by neointima, after 8 wk, the neointima thickening seem reduced.3 BIS as a vehicle of loading and releasing drugs could be inhibit significantly the VSMC and neointimal hyperplasia with antiproliferation agent- paclitaxel.4 BIS is promising and a new strategy in preventing restenosis.