March K L, Mohanraj S, Ho P P, Wilensky R L, Hathaway D R
Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis 46202-4800.
Circulation. 1994 May;89(5):1929-33. doi: 10.1161/01.cir.89.5.1929.
Smooth muscle cell proliferation plays a major role in the genesis of restenosis after angioplasty or vascular injury. Local application of agents capable of modulating vascular responses, including smooth muscle cell proliferation, has been achieved, but difficulty in maintaining active levels locally has been a factor limiting the efficacy of such approaches. One strategy to maintain adequate levels is the local delivery of microspheres that release active agents over sustained time periods.
We incorporated a colchicine analogue into biodegradable microspheres composed of a lactic acid/glycolic acid copolymer and characterized their drug release behavior as well as their effects on bovine aortic smooth muscle cells (BASMCs) in culture. Drug release was evaluated by spectrophotometric assay. Drug effects on DNA synthesis were measured by thymidine incorporation after addition of serum to subconfluent cells synchronized by serum withdrawal as well as in asynchronous cell populations. Polymeric microspheres incorporating 10% to 17% drug by weight and averaging 6 microns in size were found to release the colchicine analog in buffered saline solutions over more than several weeks. Drug-loaded particles inhibited DNA synthesis completely, with EC50 values ranging from 0.001 to 0.005 g% (wt/wt). Morphological changes suggesting microtubule depolymerization were observed after drug particle treatment, with similar EC50 values. Microspheres allowed to contact the cell surface demonstrated effects similar to those seen with microspheres suspended in the nutrient medium by porous polycarbonate filters, at EC50 values approximately fivefold lower. In contrast, control microspheres composed only of polymer with no incorporated active drug demonstrated no observable toxicity to BASMCs and < 40% inhibition of thymidine incorporation even in suspensions containing up to 0.5 g% particles.
Biodegradable microspheres were fashioned that release a colchicine analogue and inhibit DNA synthesis in smooth muscle cells. Drug-loaded polymeric particles are candidates for local delivery at sites of arterial injury to decrease restenosis.
平滑肌细胞增殖在血管成形术或血管损伤后再狭窄的发生中起主要作用。已经实现了局部应用能够调节血管反应（包括平滑肌细胞增殖）的药物，但在局部维持有效水平方面存在困难，这一直是限制此类方法疗效的一个因素。维持适当水平的一种策略是局部递送能在持续时间段内释放活性剂的微球。
我们将一种秋水仙碱类似物掺入由乳酸/乙醇酸共聚物组成的可生物降解微球中，并对其药物释放行为以及对培养的牛主动脉平滑肌细胞（BASMCs）的影响进行了表征。通过分光光度法测定评估药物释放。在向通过血清饥饿同步化的亚汇合细胞以及非同步细胞群体中添加血清后，通过胸苷掺入来测量药物对DNA合成的影响。发现掺入10%至17%（重量）药物且平均尺寸为6微米的聚合物微球在缓冲盐溶液中能在数周以上的时间内释放秋水仙碱类似物。载药颗粒完全抑制DNA合成，EC50值范围为0.001至0.005 g%（重量/重量）。药物颗粒处理后观察到提示微管解聚的形态学变化，EC50值相似。允许与细胞表面接触的微球显示出与通过多孔聚碳酸酯滤器悬浮在营养培养基中的微球类似的效果，EC50值约低五倍。相比之下，仅由不含活性药物的聚合物组成的对照微球即使在含有高达0.5 g%颗粒的悬浮液中对BASMCs也未显示出可观察到的毒性，且胸苷掺入抑制率<40%。
制备了可生物降解的微球，其能释放秋水仙碱类似物并抑制平滑肌细胞中的DNA合成。载药聚合物颗粒可作为在动脉损伤部位进行局部递送以减少再狭窄的候选物。
