PLA／PLGA共聚物在组织工程中的应用

聚乳酸（Polylactic acid,PLA）及其聚羟基乙酸共聚物[Poly（D,L—lactic—co—glycolic）acid]是一种生物相容性良好的可降解生物材料,具有支架和缓释的双重作用,目前针对性的研究主要集中于组织工程学和药学领域。本文对PLA／PLGA共聚物的代谢特征、降解机制,以及在组织工程中的应用等方面进行综述。     

可吸收性骨折内固定植入物

目前在骨折内固定材料所需的理化特性及能降解吸收的大分子复合材料中,最合适者为聚羟乙酸(PGA)、聚乳酸(PLA)和聚对二氧杂环己酮(PPDO),除此之外,各种由PGA及PLA的共聚物亦曾作过广泛试验。植入物的设计是用熔化模塑成针、棒、螺钉及小接骨板,同时用聚合物的基质加上同材料制成的纤维混凝物强化了其强度。实验研究已证明PGA、PLA和PPDO植入物在骨组织内能完全吸收,并在降解过程     

生物可降解材料聚乳酸在血管支架制备中的应用

第二代药物洗脱支架作为异物,对血管壁有长期炎症反应,这是导致支架术后远期血栓形成和支架内再狭窄的重要诱因。而生物可降解支架能克服这一缺陷。目前,生物可降解支架材料选择分为高分子聚合物材料和合金材料。在可降解高分子材料中,聚乳酸和其改性共聚物备受关注。聚乳酸是一种具有良好生物相容性和可降解性能的高分子材料,在血管支架的制备中具有广泛运用。聚乳酸既是一种很优秀的支架药物涂层的载体,也可以被开发作为支架骨架结构。     

组织工程技术预制血管实验研究的初步报告

目的:探讨利用组织工程技术,用自体血管壁组织培养预制血管的可行性。方法:取杂种犬12只,各切取右侧颈动脉2cm,将血管腔内残留血液冲洗干净,去除外膜纤维组织,用锐器切割和粉碎至匀浆状态,均匀种植于口径为3mm、长40mm的无纺聚羟基乙酸(polyglycolic acid,PGA)管状支架上;埋植于实验犬的腹直肌内。3月后,取出标本进行大体、组织学和超微结构观察。结果:PGA血管支架已完全被吸收和降解,种植的血管组织已完全生长成酷似血管的管状结构。电镜观察发现:外膜较薄,为疏松结缔组织;中膜较厚,主要由成纤维细胞、平滑肌细胞和胶原纤维等成分组成;内膜最薄,可见内皮细胞覆盖。结论:利用组织工程技术,将犬的动脉组织匀浆种植于PGA支架上,3月后支架完全降解和吸收,形成酷似血管的管状结构。     

生物合成支架材料的研究进展

皮肤组织工程就是应用组织工程学技术的基本方法 ,将组织细胞 (表皮细胞、成纤维细胞、内皮细胞等 )经体外培养扩增后 ,黏附于一种生物相容性良好并可被人体逐步降解吸收的真皮支架上 ,进行人工皮肤构建和培养。其中 ,真皮支架为细胞的增殖、繁衍提供三维空间 ,使之进行营养和气体交换、排除废物 ,因此真皮支架材料的性能直接影响着体外构建人工皮的质量和移植后的创面愈合质量。目前 ,用于制备真皮支架的材料种类较多 ,难以明确分类 ,一般多根据材料的来源大体分为天然生物材料和合成生物材料两大类。天然生物材料包括胶原、葡糖胺聚糖、壳聚糖、明胶等。合成生物材料主要由乳酸(LA)、羟基乙酸 (GA)、β 羟基丁酸、ε 羟基己酸等聚合而成 ,由于来源广泛、可塑性强、可生物降解、适合于规模化生产 ,因此其有可能成为组织工程的重要材料来源 ,可作为真皮支架应用于皮肤组织工程。本文就合成生物材料的种类和特点作一综述。一、合成生物支架材料的种类目前常用的合成生物支架材料主要是脂肪族聚酯类 ,包括聚乳酸 (PLA)、聚羟基乙酸 (PGA)、聚乳酸 羟基乙酸 (PLGA)、聚己内酯 (PCL)[1]。下面分别予以简要介绍。1.PLA:又称聚丙...     

含内皮祖细胞的组织工程皮肤体外构建及裸鼠移植研究

目的构建含内皮祖细胞（EPC）和成纤维细胞的组织工程复合皮，初步研究EPC在组织工程皮肤移植中促血管发生的作用。方法采用免疫磁珠法从人脐血中分离培养CD133＋血管内皮祖细胞，以聚羟基乙酸（PGA）为真皮基质，接种EPC和成纤维细胞，其上覆盖表皮细胞膜片，构建组织工程复合皮，覆盖裸鼠背部全层皮肤缺损创面。结果EPC和成纤维细胞能均匀贴附于PGA支架纤维材料上，并逐渐伸展为梭形或多极状。裸鼠移植实验表职，实验组创面愈合早于对照组，可见EPC参与大量新生小血管形成，真皮支架5周完全降解。结论EPC参与血管重建，具有促进血管新生，加速缺血组织血管化的作用。应用PGA＋纤维蛋白凝胶，制备含EPC和成纤维细胞的活性真皮替代物，具有良好的生物相容性、降解特性。     

可降解材料对外周神经的毒性作用研究

目的 研究聚乳酸、聚羟基乙酸和壳聚糖等可降解材料对正常外周神经有无毒性作用，为研制组织工程化神经筛选相容性好的支架材料。方法 取15只SD大鼠，随机分成3组，打开坐骨神经外膜后，分别将聚乳酸、聚羟基乙酸和壳聚糖植入神经束之间。术后7周取材，观察坐骨神经组织结构的变化以及材料在神经组织内引起的异物反应。结果各组的神经干内均有纤维结缔组织轻度增生，但神经束的形态结构无明显变化；各种材料周围均有纤维假膜形成，假膜内有淋巴细胞和巨噬细胞浸润，而包裹壳聚糖的假膜最厚，细胞浸润最明显。结论 聚乳酸、聚羟基乙酸和壳聚糖对外周神经均无毒性，可作为组织工程化神经的支架材料，但壳聚糖引起的异物反应较聚乳酸和聚羟基乙酸明显。     

构建带内支撑组织工程睾丸假体的实验研究

目的探讨以医用多孔高密度聚乙烯(high-density polyethylene,HDPE,商品名为Medpor)为内支撑,外裹聚羟基乙酸(polyglycolic acid,PGA)的支架,接种软骨细胞后,于裸鼠体内构建组织工程睾丸假体的可行性及特点。方法取新生雌性长枫杂交仔猪1只,取四肢大关节表面软骨,制备密度为5×107/ml的软骨细胞悬液。将其接种于长短半径分别为6mm和4mm的Medpor,外裹2mm PGA的支架,体外培养2周。取4周龄BALB/C裸鼠10只,随机分为两组(n=5)。实验组:采用制备的细胞-支架复合物植入裸鼠背部皮下;对照组:采用Medpor-PGA复合支架植入裸鼠皮下。8周后处死裸鼠取材,行大体观察、组织学及免疫组织化学观察。结果大体观察:实验组标本形状与体积未发生变化,色泽及弹性与正常软骨相似,软骨与Medpor接合紧密;对照组无软骨形成,外包裹纤维样组织。实验组:HE染色见软骨内存在大量成熟的软骨陷窝,无血管长入,部分PGA尚未降解完全;甲苯胺蓝染色示细胞外基质具有异染特性;藏红花染色示基质中大量蛋白聚糖沉积;型胶原免疫组织化学染色呈强阳性表达。对照组:Medpor被大量富含血管的纤维组织包裹。结论利用Medpor与PGA复合的支架,接种软骨细胞后,可于体内构建出具有预构睾丸形态且组织学良好的Medpor-软骨复合体。     

基于三维打印和组织工程技术构建人阴茎形态软骨支撑体

目的探讨基于三维打印和组织工程技术构建人阴茎形态软骨支撑体的可行性。方法应用三维打印技术制备人阴茎形态聚己内酯/羟基磷灰石(PCL/HA)内核,并在外层包被聚羟基乙酸/聚乳酸(PGA/PLA)细胞支架,组装成人阴茎形态三维复合支架。获取乳猪关节软骨细胞,培养、扩增至第1代,收取细胞,接种至复合支架,体外培养4周后植入裸鼠皮下,体内8周后取材,进行大体及组织学观察。结果人阴茎形态复合支架形态逼真,植入裸鼠体内8周后,再生出人阴茎形态的软骨支撑体,支撑体表面形成均质、成熟的软骨层,软骨层与内核支架融合良好。结论基于三维打印和组织工程技术,可形成内核为PCL/HA支架,外层包被成熟软骨的人阴茎形态软骨支撑体。     

不同比例的PLA—PGA支架对软骨细胞复合的影响

目的研究经聚乳酸（PLA）包埋后的不同比例PLA-聚羟基乙酸（PGA）组织工程支架对软骨细胞复合的影响及原因。方法分离培养小猪软骨细胞，并以5×10^7cells／mL的密度接种在经PLA包埋的不同比例PGA—PLA支架材料上，4h后检测软骨细胞在支架材料上的流失率。24h后检测软骨细胞在支架材料上的粘附率，并对支架材料进行电镜扫描，分析原因。结果随着支架材料中PLA比例的提高，软骨细胞的接种流失率上升，支架材料的接种负荷下降，24h时软骨细胞粘附率无明显差异。扫描电镜证实其原因。结论PLA包埋的PGA支架材料会降低对软骨细胞的接种负荷，但细胞粘附率无变化。     

复合可降解基质膜片制备及血管内皮细胞在其吸附生长的实验研究

目的　制备几种复合可降解基质膜片 ,观察血管内皮细胞在其上的生长情况。方法　用胶原酶消化法分离牛主动脉血管内皮细胞 (VEC) ,另采用两步盐析法提取牛骨 型胶原。将交联胶原包埋处理聚羟基乙酸 (PGA)、聚乳酸 (PL A)及聚β羟基丁酸 (PHB)形成可降解基质材料膜片 ,并接种牛 VEC,采用 MTT法比较 VEC在几种可降解基质材料膜片的生长情况。结果　胶原、PGA/胶原、PL A/胶原膜质地均匀柔韧 ,固定成形 ,具有一定弹性和吸水性 ;MTT比色实验表明 VEC在胶原、PGA/胶原、PL A/胶原上均生长良好 ,优于 PHB/胶原组。尤以 PGA/胶原所形成的基质材料固定成形 ,弹性和韧性好 ,VEC在其上贴附生长良好。结论　通过生物材料与人工可降解材料有机结合 ,PGA/胶原物理性能互补 ,是组织工程再造血管较理想的基质材料之一。     

Preliminary experience with tissue engineering of a venous vascular patch by using bone marrow-derived cells and a hybrid biodegradable polymer scaffold

OBJECTIVE: Currently available synthetic polymer vascular patches used in cardiovascular surgery have shown serious shortcomings, including thrombosis, calcification, infection, and lack of growth potential. These problems may be avoided by vascular patches tissue-engineered with autologous stem cells and biodegradable polymeric materials. The objective of this study was to develop a tissue-engineered vascular patch by using autologous bone marrow-derived cells (BMCs) and a hybrid biodegradable polymer scaffold. METHODS: Hybrid biodegradable polymer scaffolds were fabricated from poly(lactide-co-epsilon-caprolactone) (PLCL) copolymer reinforced with poly(glycolic acid) (PGA) fibers. Canine bone marrow mononuclear cells were induced in vitro to differentiate into vascular smooth muscle cells and endothelial cells. Tissue-engineered vascular patches (15 mm wide x 30 mm long) were fabricated by seeding vascular cells onto PGA/PLCL scaffolds and implanted into the inferior vena cava of bone marrow donor dogs. RESULTS: Compared with PLCL scaffolds, PGA/PLCL scaffolds exhibited tensile mechanical properties more similar to those of dog inferior vena cava. Eight weeks after implantation of vascular patches tissue-engineered with BMCs and PGA/PLCL scaffolds, the vascular patches remained patent with no sign of thrombosis, stenosis, or dilatation. Histological, immunohistochemical, and scanning electron microscopic analyses of the retrieved vascular patches revealed regeneration of endothelium and smooth muscle, as well as the presence of collagen. Calcium deposition on tissue-engineered vascular patches was not significantly different from that on native blood vessels. Immunofluorescent double staining confirmed that implanted BMCs survived after implantation and contributed to regeneration of endothelium and vascular smooth muscle in the implanted vascular patches. CONCLUSIONS: This study demonstrates that vascular patches can be tissue-engineered with autologous BMCs and hybrid biodegradable polymer scaffolds.     

Temporäre Implantate für die endovaskuläre Applikation

Although vascular intervention using metal stents has become the gold standard of care for stenotic vessels, the lifelong persistence of metal stents within the arteries might induce long-term effects, bearing the risk of late thrombosis finally resulting in neointimal hyperplasia. However, since the vessel wall may undergo positive remodeling after stenting, the need for mechanical scaffolding of an artery may be only temporary. Thus, the use of biodegradable devices, which eventually degrade and leave only the remodeled vessel, might decrease restenosis rates. Polymeric biodegradable polylactide stents have demonstrated this potential as an alternative to standard metal stents, but to date, the human experiences with these devices are limited. The aim of this study was therefore to summarize our experiences in dealing with a biodegradable slotted tube stent made of poly-L-lactide (PLLA) with incorporation of Sirolimus (polymeric drug eluting stent).     

利用组织工程技术再生软骨组织的实验研究

目的 在有免疫力的动物体兔体内探索组织工程化软骨生成的影响因素。 方法 经不同物质修猸的聚羟基乙酸支架与软骨细胞体外培养,观察基质产生情况,并将细胞支架复合物体内回植,观察软骨的生成,并进行组织学及超微结构评价。结果 以孵磷脂、多聚赖氨酸及聚乳酸共同修饰的聚羟基乙酸与软骨细胞体外培养,结果基质产生旺盛,体内回植后软骨生成良好。 结论 细胞支架复合物体外培养期间有基质产生,是组织工程化软骨生成的前提     

Urethral in situ biocompatibility of new drug‐eluting biodegradable stents: an experimental study in the rabbit

OBJECTIVE

To assess the effect of drug‐eluting properties on the degradation process and the biocompatibility of biodegradable drug‐eluting urethral stents.

MATERIALS AND METHODS

Braided biodegradable 80 L/20D‐PLGA (copolymer of polylactide and polyglycolide) stents with drug‐eluting properties were used as the test material. The drugs analysed were indomethacin, dexamethasone and ciprofloxacine. 80 L/20D‐PLGA stents without a drug coating served as controls. In all, 16 male rabbits were used and divided into four groups. The stents were inserted under general anaesthesia into the posterior urethra. After 1 month, the rabbits were killed and the urethra removed for histological and optic microscopy analyses.

RESULTS

Control stents and the dexamethasone‐eluting stents degraded totally during the follow‐up period. Conversely, in both indomethacin‐ and ciprofloxacine‐eluting stent groups, the degradation process was significantly delayed and they induced an increase in epithelial hyperplasia. Histological analysis showed that all the stents induced eosinophilia, but there were no significant differences in the intensity of acute or chronic inflammatory reactions and fibrosis.

CONCLUSIONS

A drug‐eluting capacity can be added to biodegradable stents. The addition of a drug influences the biodegradation time of PLGA urethral stents. Further studies are needed, to find the proper concentrations and releasing profiles of the drugs to achieve the desired bioactivity and biocompatibility properties.     

Koronare Stents, duale Antiplättchentherapie und die perioperative Problematik

Up to 90% of all percutaneous coronary interventions include coronary artery stenting. Dual antiplatelet therapy, usually involving acetylsalicyl acid combined with clopidogrel, is mandatory for patients with coronary artery stents. The duration of antiplatelet therapy for bare metal stents is 3–4 weeks, for drug eluting stents 6–12 months. Preoperative discontinuation of both drugs increases the risk of stent thrombosis, continuation the risk of relevant bleeding. According to the recommendations of anaesthesiological and cardiological societies, perioperative management has to balance the risk of bleeding vs stent thrombosis. Surgery involving a high risk of bleeding can require the discontinuance of both substances. In cases of high thrombosis risk, at least the acetylsalicyl acid should be continued until the day of surgery. For patients under antiplatelet therapy scheduled for local anaesthesia, national recommendations exist. A close collaboration between the anaesthesiologist, cardiologist and surgeon is essential for appropriate pre-, intra- and postoperative management.     

Coronary stents, dual antiplatelet therapy and peri-operative problems

Up to 90% of all percutaneous coronary interventions include coronary artery stenting. Dual antiplatelet therapy, usually involving acetylsalicyl acid combined with clopidogrel, is mandatory for patients with coronary artery stents. The duration of antiplatelet therapy for bare metal stents is 3-4 weeks, for drug eluting stents 6-12 months. Preoperative discontinuation of both drugs increases the risk of stent thrombosis, continuation the risk of relevant bleeding. According to the recommendations of anaesthesiological and cardiological societies, perioperative management has to balance the risk of bleeding vs stent thrombosis. Surgery involving a high risk of bleeding can require the discontinuance of both substances. In cases of high thrombosis risk, at least the acetylsalicyl acid should be continued until the day of surgery. For patients under antiplatelet therapy scheduled for local anaesthesia, national recommendations exist. A close collaboration between the anaesthesiologist, cardiologist and surgeon is essential for appropriate pre-, intra- and postoperative management.     

新型冠状动脉支架应用现状及展望

采用裸金属支架植入治疗冠心病疗效显著,但内膜增生引起支架内再狭窄风险高。采用药物洗脱支架可降低支架内再狭窄发生率,但患者需长期接受双联抗血小板治疗来预防血管愈合延迟和内皮功能紊乱引起的支架内血栓形成。第二代药物洗脱支架和无载药涂层洗脱支架、载药涂层可降解支架、完全可降解支架等新概念支架已投入临床应用。这些新型支架具有良好的安全性和有效性。本文对新型冠状动脉支架的临床应用、研究现状及发展方向进行综述。     

包埋后的聚羟基乙酸与软骨细胞体外培养实验研究

目的:通过卵磷脂和多聚赖氨酸分别和共同包埋以聚乳酸固定成形的聚羟基乙酸支架与软骨细胞体外培养,来观察其亲水性和对细胞吸附力的改变以及对细胞功能的影响。方法:将软骨细胞种于上述支架体外培养,通过倒置显微镜及扫描电镜观察支架的亲水性、对细胞的吸附力及基质产生情况。结果:支架以卵磷脂包埋后细胞悬液易浸入到支架内;以多聚赖氨酸包埋后细胞易吸附在支架纤维表面;以卵磷脂和多聚赖氨酸共同包埋后细胞均匀分布于支架纤维之间及吸附在支架纤维表面,且基质产生旺盛。结论:卵磷脂具有增强支架亲水性作用;而多聚赖氨酸除增加支架对细胞的吸附力外,还具有促进细胞功能的作用。以卵磷脂和多聚赖氨酸共同包埋支架可能是组织工程技术中较理想的支架之一。     

Coronary stents and anaesthesia

The coronary stents are widely used to prevent coronary restenosis after percutaneous coronary intervention. Dual antiplatelet therapy (acetyl salicylic acid and a thienopyridine-clopidogrel or ticlopidine) are prescribed at least during six weeks after conventional stent and six months after drug eluting stent insertion to prevent stent thrombosis. When an invasive procedure is required, a risk of stent thrombosis arises after stopping antiplatelet therapy and a risk of bleeding when continuing this treatment. Therefore, cardiologists should choose carefully the type of coronary stent before insertion and concerned physicians (anaesthesiologists, surgeons, cardiologists) should decide a perioperative strategy in these high-risk patients.