3-羟基丁酸与3-羟基己酸共聚酯在心血管组织工程中的应用

为了研究可降解聚合材料3-羟基丁酸与3-羟基己酸共聚酯 (3-hydroxybutyrate-co-3-hydroxyhexanoate, PHBHHx)的血管内生物相容性, 采用脱细胞羊肺动脉为支架, 以PHBHHx涂层, 构建复合补片(Hybrid patch), 植入New Zealand兔腹主动脉内(12只), 以脱细胞未涂层羊肺动脉片(Uncoated patch)做为对照(12只)。分别于术后第1、4和12周处死动物, 取出移植补片进行组织学、免疫荧光染色、扫描电镜和钙含量测定。结果表明: hybrid patch管腔面光滑无血栓, 内膜增生适度, 再细胞化完全; 免疫荧光染色检测, 新生内膜组织中类内皮细胞呈CD31阳性反应, 单层连续排列, 间质细胞呈现SMA阳性反应; 钙含量测定, hybrid patch明显低于uncoated patch(P<0.05)。由此认为: PHBHHx的血管内生物相容性满意, 是心血管组织工程较为理想的腔内涂层材料。     

重组嗜水气单胞菌Aeromonas hydrophila 4AK4中3-羟基丁酸3-羟基己酸共聚酯PHBHHx的发酵生产

3-羟基丁酸和3-羟基己酸共聚酯(PHBHHx)是一种性能优良的新型生物可降解材料,其机械和加工性能与3-羟基己酸(3HHx)在共聚物中的含量密切相关。在嗜水气单孢菌Aeromonas hydrophila 4AK4中引入了编码β-酮基硫解酶(β-ketothiolase)的phbA基因和编码乙酰乙酰辅酶A还原酶(Acetoacetyl-CoA reductase)的phbB基因,使重组菌增加了一条利用乙酰辅酶A合成3-羟基丁酸-CoA的代谢途径,这使得利用非相关性碳源调控PHBHHx的单体组成比例成为可能。利用葡萄糖酸钠和月桂酸作为碳源,对重组Aeromonas hydrophila 4AK4进行了摇瓶培养及5L发酵罐培养的研究。在摇瓶实验中,通过改变碳源中两种组分的比例,可以使A,hydrophila 4AK4合成的PHBHHx中的3HHx摩尔含量由原来的15％左右降低到3％～12％,成功地实现了对PHBHHx单体组成的调控;当以月桂酸为唯一碳源时,在5L发酵罐中,经过56h的培养,获得了51．5g／L的细胞干重(CDW),其中62％为PHBHHx,3HHx在PHBHHx中的摩尔含量为9．7％;当以1：1的葡萄糖酸钠和月桂酸为碳源时,48h的5L发酵罐培养获得了32．8g／L的CDW和52％的PHBHHx含量,其中3HHx在PHBHHx中的摩尔含量为6．7％。结果证明了该重组菌在大规模生产单体组成可控PHBHHx方面具有很大的应用潜力。     

骨髓间充质干细胞与聚3-羟基丁酸酯-co-4-羟基丁酸酯生物材料共培养细胞补片的初步研究

目的:研究聚3-羟基丁酸酯-co-4-羟基丁酸酯[P(3HB-co-4HB)]这种新型高分子材料与骨髓间充质干细胞(BMSCs)共培养,观察材料对干细胞的存活及增殖的影响,形成细胞补片的效果;从而找到一种适合BMSCs生长、增殖的高分子生物材料,作为治疗心肌梗死,软骨损伤等多种组织损伤疾病的修复方法之一。方法:取清洁级雄性健康BSL-C57小鼠作为实验对象,通过分离培养获得小鼠BMSCs,并进行流式细胞仪鉴定表面标志物。BMSCs培养至5代后,将BMSCs与P(3HB-co-4HB)制成的生物材料薄膜共培养,24h后固定进行电镜扫描,并用DAPI荧光染料染色处理,在荧光显微镜下观察并进行细胞计数,并描绘生长曲线。结果:BMSCs流式细胞术鉴定:CD34、CD45阴性,CD90弱阳性,CD73阳性。扫描电镜下,P(3HB-co-4HB)材料与BMSCs共培养形成的细胞补片,其表面细胞数量多,细胞状态正常。荧光显微镜下,对其细胞补片表面的细胞进行计数,并绘制生长曲线,显示表面细胞有逐渐增多的趋势。结论:P(3HB-co-4HB)材料与BMSCs共培养制成的细胞补片表面有细胞存活及增殖,由于P(3HB-co-4HB)材料本身具有良好的生物组织相容性及可降解等性质,所以该新型高分子材料可以作为干细胞治疗多种疾病的支架材料之一。     

丁醇对发酵生产3-羟基丁酸与3-羟基己酸共聚酯(PHBHHx)单体组成的影响

3羟基丁酸与3羟基己酸共聚酯(PHBHHx)是由微生物合成的完全可降解高分子材料,其材料性能与3羟基己酸(3HHx)在共聚物中的含量有关。嗜水性气单孢菌A.hydrophila4AK4合成的PHBHHx中,3HHx含量通常都在12～15mol%之间。通过在培养基中添加正丁醇,降低了PHBHHx中3HHx的含量。在摇瓶培养中获得了含3HHx为58mol%的PHBHHx;在6L发酵罐中54h的发酵培养,获得40gL的细胞干重(CDW),并将3HHx的含量在发酵过程中有效地降低到5～10mol%。     

重组嗜水气单胞菌Aeromonas hydrophila 4AK4中3-羟基丁酸3-羟基己酸共聚酯PHBHHx的发酵生产

3-羟基丁酸和3-羟基己酸共聚酯（PHBHHx）是一种性能优良的新型生物可降解材料,其机械和加工性能与3-羟基己酸（3HHx）在共聚物中的含量密切相关。在嗜水气单孢菌Aeromonas hydrophila 4AK4中引入了编码β酮基硫解酶 (β-ketothiolase)的phbA基因和编码乙酰乙酰辅酶A还原酶(AcetoacetylCoA reductase)的phbB基因,使重组菌增加了一条利用乙酰辅酶A合成3羟基丁酸-CoA的代谢途径,这使得利用非相关性碳源调控PHBHHx的单体组成比例成为可能。利用葡萄糖酸钠和月桂酸作为碳源,对重组Aeromonas hydrophila 4AK4进行了摇瓶培养及5 L发酵罐培养的研究。在摇瓶实验中,通过改变碳源中两种组分的比例,可以使A. hydrophila 4AK4合成的PHBHHx中的3HHx摩尔含量由原来的15%左右降低到3%～12 %,成功地实现了对PHBHHx单体组成的调控;当以月桂酸为唯一碳源时,在5 L发酵罐中,经过56 h的培养,获得了51.5 g/L的细胞干重（CDW）,其中62 %为PHBHHx,3HHx在PHBHHx中的摩尔含量为9.7 %;当以1:1的葡萄糖酸钠和月桂酸为碳源时,48 h的5 L发酵罐培养获得了32.8 g/L的CDW和52 %的PHBHHx含量,其中3HHx在PHBHHx中的摩尔含量为6.7 %。结果证明了该重组菌在大规模生产单体组成可控PHBHHx方面具有很大的应用潜力。     

组织工程血管补片动物模型的建立及围术期处理

目的评估组织工程血管补片动物模型的可行性并总结模型建立的围手术期处理。方法10只成年杂种犬,用自身的骨髓细胞和高分子可降解材料构建的组织工程血管补片扩大肺动脉流出道。结果实验中有1例在术中出现心动过缓,暂停手术操作后,其余手术均逐渐恢复,未造成不良后果。术后实验动物均存活。术后5～10min撤离呼吸机,拔除胸引管。术后两周肺动脉造影示左肺动脉通畅,未见动脉瘤形成,移植物处稍狭窄;取出移植物观察,血管管腔通畅,腔面光滑,无血栓,无感染。结论通过自身的骨髓细胞和高分子可降解材料构建的组织工程血管补片扩大犬肺动脉流出道成功建立了组织工程血管补片动物模型。为了保证模型的成功建立,应使用右侧卧位、尽早进行心电监护、及时处理心律紊乱和尽早撤离呼吸机等围术期护理要点。     

去细胞牛颈静脉构建组织工程右心带瓣管道体内实验初步研究

目的：将体外构建的组织工程右心带瓣管道,以带瓣补片的形式移植于犬主肺动脉,观测带瓣管道材料体内情况。方法：去细胞处理牛颈静脉体,无菌处理后种植标记过的犬骨髓间质干细胞,构建组织工程带瓣管道,犬开胸手术,将体外构建的组织工程右心带瓣管道,以带瓣补片的形式移植于犬主肺动脉,术后4、8、12行胸部B超检查;取出补片,HE染色;荧光显微镜下标记细胞检测;样本钙含量测定。结果：术后犬胸部B超观察：瓣叶无增厚,钙化,管道血流通畅,无血栓及钙化。术后4、8、12周除了瓣叶逐渐缩小外,补片无动脉瘤形成,瓣膜表面光滑,无血栓形成,弹性良好,血管壁内面光滑,无血栓形成。种植种子细胞牛颈静脉带瓣补片成活。4周钙含量增加,8周时候,钙含量又有增加,12周时钙含量与8周相比无明显变化。结论：组织工程技术构建组织工程右心带瓣管道有可行之处。     

去细胞牛颈静脉构建组织工程右心带瓣管道体内 实验初步研究

目的:将体外构建的组织工程右心带瓣管道,以带瓣补片的形式移植于犬主肺动脉,观测带瓣管道材料体内情况。方法:去细胞处理牛颈静脉体,无菌处理后种植标记过的犬骨髓间质干细胞,构建组织工程带瓣管道,犬开胸手术,将体外构建的组织工程右心带瓣管道,以带瓣补片的形式移植于犬主肺动脉,术后4、8、12行胸部B超检查;取出补片,HE染色;荧光显微镜下标记细胞检测;样本钙含量测定。结果:术后犬胸部B超观察:瓣叶无增厚,钙化,管道血流通畅,无血栓及钙化。术后4、8、12周除了瓣叶逐渐缩小外,补片无动脉瘤形成,瓣膜表面光滑,无血栓形成,弹性良好,血管壁内面光滑,无血栓形成。种植种子细胞牛颈静脉带瓣补片成活。4周钙含量增加,8周时候,钙含量又有增加,12周时钙含量与8周相比无明显变化。结论:组织工程技术构建组织工程右心带瓣管道有可行之处。     

去细胞牛颈静脉构建组织工程右心带瓣管道体内实验初步研究

目的:将体外构建的组织工程右心带瓣管道,以带瓣补片的形式移植于犬主肺动脉,观测带瓣管道材料体内情况.方法:去细胞处理牛颈静脉体,无菌处理后种植标记过的犬骨髓间质干细胞,构建组织工程带瓣管道,犬开胸手术,将体外构建的组织工程右心带瓣管道,以带瓣补片的形式移植于犬主肺动脉,术后4、8、12行胸部B超检查;取出补片,HE染色;荧光显微镜下标记细胞检测;样本钙含量测定.结果:术后犬胸部B超观察:瓣叶无增厚,钙化,管道血流通畅,无血栓及钙化.术后4、8、12周除了瓣叶逐渐缩小外,补片无动脉瘤形成,瓣膜表面光滑,无血栓形成,弹性良好,血管壁内面光滑,无血栓形成.种植种子细胞牛颈静脉带瓣补片成活.4周钙含量增加,8周时候,钙含量又有增加,12周时钙含量与8周相比无明显变化.结论:组织工程技术构建组织工程右心带瓣管道有可行之处.     

代谢工程技术调控3-羟基丁酸与3-羟基己酸共聚酯PHBHHx的微生物合成

3-羟基丁酸和3-羟基己酸共聚酯(PHBHHx)是一种新型生物可降解材料,其性能与3-羟基己酸(3HHx)在共聚物中的摩尔百分含量密切相关。本研究在两株嗜水性气单孢菌Aeromonas hydrophila WQ和Aeromonas hydrophila 4AK4中分别引入了编码酯酰辅酶A脱氢酶的yafH基因和编码合成3-羟基丁酸-CoA的phbA和phbB基因,将A.hydrophila WQ合成的PHBHHx中的3HHx的摩尔含量由3％—5％提高到20％以上;而A.hydrophila 4AK4合成的PHBHHx中的3HHx摩尔含量则由15％左右降低到3％-12％。成功地实现了对PHBHHx单体组成的调控。     

Survival and integration of tissue-engineered corneal stroma in a model of corneal ulcer

Tissue-engineered replacement of diseased or damaged tissue has become a reality for some types of tissue, such as skin and cartilage. Tissue-engineered corneal stroma represents a promising concept to overcome the limitations of cornea replacement with allograft. In this study, porcine cornea was decellularized by a series of extraction methods, and the in vivo biocompatibility of the scaffold was measured subcutaneously in rabbits (n = 8). These were not acutely rejected and no abscesses were observed by hematoxylin and eosin staining at the 8th week, indicating that the scaffolds had good biocompatibility. To investigate the potential value of clinical applications, rabbit stromal keratocytes were implanted onto decellularized scaffolds to fabricate tissue-engineered corneal stroma. Allograft, tissue-engineered corneal stroma, or scaffolds were implanted into a model of corneal ulcer. The survival and reconstruction of corneal transplantation were morphologically evaluated by light and electron microscopy until the 32nd week after implantation. Experiments involving transplantation indicated that the epithelial and stromal defect healed quickly, with improvement in corneal clarity. The integration of the graft was accompanied by neurite ingrowth from the host tissue. By 16 weeks after transplantation, the cornea had gradually regained an intact state similar to that of normal cornea. Our results demonstrate that the tissue-engineered corneal stroma with allogenetic cells is a promising therapeutic method for corneal injury. This study was supported by the Nature Science Foundation of China (project no. 30572046) and the Development of High and New Science and Technology (863 Project) of China (2002AA205041, 2005AA205241).     

The Effect of Heparin-VEGF Multilayer on the Biocompatibility of Decellularized Aortic Valve with Platelet and Endothelial Progenitor Cells

The application of polyelectrolyte multilayer films is a new, versatile approach to surface modification of decellularized tissue, which has the potential to greatly enhance the functionality of engineered tissue constructs derived from decellularized organs. In the present study, we test the hypothesis that Heparin- vascular endothelial growth factor (VEGF) multilayer film can not only act as an antithrombotic coating reagent, but also induce proliferation of endothelial progenitor cells (EPCs) on the decellularized aortic heart valve. SEM demonstrated the adhesion and geometric deformation of platelets. The quantitative assay of platelet activation was determined by measuring the production of soluble P-selectin. Binding and subsequent release of heparin and VEGF from valve leaflets were assessed qualitatively by laser confocal scanning microscopy and quantitatively by ELISA methods. Human blood derived EPCs were cultured and the adhesion and growth of EPCs on the surface modified valvular scaffolds were assessed. The results showed that Heparin-VEGF multilayer film improved decellularized valve haemocompatibility with respect to a substantial reduction of platelet adhesion. Release of VEGF from the decellularized heart valve leaflets at physiological conditions was sustained over 5 days. In vitro biological tests demonstrated that EPCs achieved better adhesion, proliferation and migration on the coatings with Heparin-VEGF multilayer film. Combined, these results indicate that Heparin-VEGF multilayer film could be used to cover the decellularized porcine aortic valve to decrease platelet adhesion while exhibiting excellent EPCs biocompatibility.     

Development of biodegradable scaffolds based on patient-specific arterial configuration

Biodegradable scaffolds are of great value in tissue engineering. We have developed a method for fabricating patient-specific vascular scaffolds from a biocompatible and biodegradable polymer, poly(L-lactide-co-epsilon-caprolactone). This method's usefulness is due to flexibility in the choice of materials and vascular configurations. Here, we present a way to fabricate scaffolds of human carotid artery by combining processes of rapid prototyping, lost wax, dip coating, selective dissolution, and salt leaching. The result was the successful development of porous biodegradable scaffolds, with mechanical strength covering the range of human blood vessels (1-3 MPa). Human umbilical vein endothelial cells were also cultured on the scaffolds and their biocompatibility was confirmed by cell growth. The Young's modulus of scaffolds could be controlled by changing polymer concentration and porosity. The wall thickness of the tubular scaffold was also controllable by adjusting polymer concentration and pull-up velocity during dip coating. We believe that this fabrication technique can be applied to patient-specific regeneration of blood vessels.     

Biocompatibility of nano-hydroxyapatite/Mg-Zn-Ca alloy composite scaffolds to human umbilical cord mesenchymal stem cells from Wharton’s jelly in vitro

Seeding cells and scaffolds play pivotal roles in bone tissue engineering and regenerative medicine.Wharton’s jelly-derived mesenchymal stem cells(WJCs)from human umbilical cord represent attractive and promising seeding cells in tissue regeneration and engineering for treatment applications.This study was carried out to explore the biocompatibility of scaffolds to seeding cells in vitro.Rod-like nano-hydroxyapatite(RN-HA)and flake-like micro-hydroxyapatite(FM-HA)coatings were prepared on Mg-Zn-Ca alloy substrates using micro-arc oxidation and electrochemical deposition.WJCs were utilized to investigate the cellular biocompatibility of Mg-Zn-Ca alloys after different surface modifications by observing the cell adhesion,morphology,proliferation,and osteoblastic differentiation.The in vitro results indicated that the RN-HA coating group was more suitable for cell proliferation and cell osteoblastic differentiation than the FM-HA group,demonstrating better biocompatibility.Our results suggested that the RN-HA coating on Mg-Zn-Ca alloy substrates might be of great potential in bone tissue engineering.     

The effect of a silk Fibroin/Polyurethane blend patch on rat Vessels

Patch grafts are widely used in various kind of vascular surgeries such as detect repair or dilation of vascular stenosis. Expanded polytetrafluoroethylene (ePTFE) patches are flexible and handle well, but have shown problems with calcification as they are non-bioabsorbable and therefore permanently remain in the body. It is important to develop an alternative biocompatible patch. Silk fibroin (SF) was developed as a biocompatible material, but it lacks of the elasticity required for surgery as a patch. Polyurethane (PU) is also a well-known elastomer so this study focused on the SF and the PU blend materials with a weight ratio of 5:5 (SF/PU). To evaluate the SF/PU patch, the patches were implanted into the abdominal aortas of rats, using the ePTFE patch in the control group. Because it was more flexible the SF/PU patch was easier to implant than the ePTFE patch. At 1 week after implantation, the SF/PU patch had been infiltrated with cells and collagen fiber. The ePTFE control patch did not accumulate collagen fiber until 3 months and calcification occurred at 4 weeks. The SF/PU patch did not present any signs of calcification for 3 months. This study addressed the problems associated with using SF in isolation and showed that the SF/PU patch can be considered as a useful alternative to the ePTFE to overcome the problem of calcification.     

冻融联合灌注法优化大鼠肾脏脱细胞支架的制备

本研究旨在探索优化肾脏脱细胞支架的制备方法,为肾脏组织工程及肾脏体外病理、毒理研究提供实验基础。取大鼠肾脏灌注PBS作为对照组 (Control组),在不同流速下分别以十二烷基磺酸钠 (Sodium dodecyl sulfate,SDS) 灌注 (S组),Triton X-100联合SDS灌注 (TS组),反复冻融后Triton X-100联合SDS灌注(FTS组),制备肾脏脱细胞支架,并测定其流体分布及脉管阻力。HE染色、DAPI染色、DNA定量检测脱细胞支架脱细胞程度,Masson染色、PAS染色、免疫组织化学染色检测脱细胞支架主要成分的保留和结构的完整,扫描电镜检测支架的超微结构,MTT法检测支架的细胞毒性,ELISA检测支架中生长因子的含量。结果显示,FTS组脱细胞用时较S组、TS组少,10 mL/min组支架脉管阻力较低,S组、TS组、FTS组流体分布与Control组存在差异。HE染色和DAPI染色显示各组支架未见细胞成分残留,DNA含量＜50 ng/mg。Masson染色和PAS染色可见细胞外网状胶原及多糖,免疫组织化学染色见Ⅰ型胶原 (CollagenⅠ)、Ⅳ型胶原蛋白 (Collagen Ⅳ)、纤维连接蛋白 (Fibronectin)、层粘连蛋白 (Laminin) 表达。扫描电镜见支架呈蜂窝状结构。MTT法检测支架细胞毒性分级在0–1级之间。ELISA检测提示FTS组VEGF、EGF、IGF-1、PDGF含量明显高于S组和TS组。综上,联合冻融和灌注法能够制备更为理想且有效的大鼠肾脏整器官脱细胞支架,为肾脏组织工程及肾脏体外病理、毒理学研究奠定基础。     

Preparation and Characterization of an Advanced Medical Device for Bone Regeneration

Tridimensional scaffolds can promote bone regeneration as a framework supporting the migration of cells from the surrounding tissue into the damaged tissue and as delivery systems for the controlled or prolonged release of cells, genes, and growth factors. The goal of the work was to obtain an advanced medical device for bone regeneration through coating a decellularized and deproteinized bone matrix of bovine origin with a biodegradable, biocompatible polymer, to improve the cell engraftment on the bone graft. The coating protocol was studied and set up to obtain a continuous and homogeneous polylactide-co-glycolide (PLGA) coating on the deproteinized bone matrix Orthoss® block without occluding pores and decreasing the scaffold porosity. The PLGA-coated scaffolds were characterized for their morphology and porosity. The effects of PLGA polymer coating on cell viability were assessed with the 3-(4,5-dimethyl-2-thiazolyl)-2,5 diphenyl-2H-tetrazolium assay. The polymer solution concentration and the number of polymeric layers were the main variables affecting coating efficiency and porosity of the original decellularized bone matrix. The designed polymer coating protocol did not affect the trabecular structure of the original decellularized bone matrix. The PLGA-coated decellularized bone matrix maintained the structural features, and it improved the ability in stimulating fibroblasts attachment and proliferation.     

Morphofunctional characterization of decellularized vena cava as tissue engineering scaffolds

Clinical experience for peripheral arterial disease treatment shows poor results when synthetic grafts are used to approach infrapopliteal arterial segments. However, tissue engineering may be an option to yield surrogate biocompatible neovessels. Thus, biological decellularized scaffolds could provide natural tissue architecture to use in tissue engineering, when the absence of ideal autologous veins reduces surgical options. The goal of this study was to evaluate different chemical induced decellularization protocols of the inferior vena cava of rabbits. They were decellularized with Triton X100 (TX100), sodium dodecyl sulfate (SDS) or sodium deoxycholate (DS). Afterwards, we assessed the remaining extracellular matrix (ECM) integrity, residual toxicity and the biomechanical resistance of the scaffolds. Our results showed that TX100 was not effective to remove the cells, while protocols using SDS 1% for 2 h and DS 2% for 1 h, efficiently removed the cells and were better characterized. These scaffolds preserved the original organization of ECM. In addition, the residual toxicity assessment did not reveal statistically significant changes while decellularized scaffolds retained the equivalent biomechanical properties when compared with the control. Our results concluded that protocols using SDS and DS were effective at obtaining decellularized scaffolds, which may be useful for blood vessel tissue engineering.     

PHBHHx膜表面亲水改性及其与神经干细胞生物相容性

对羟基丁酸-羟基己酸共聚酯(PHBHHx)膜进行表面改性,研究神经干细胞(NSCs)在改性后的PHBHHx膜表面的贴附、增殖及分化情况,为开发新型脑组织工程支架材料奠定基础。采用溶剂挥发法制备PHBHHx膜,扫描电镜观察其表面性状;分别通过脂肪酶处理,NaOH处理的方法对PHBHHx膜进行表面改性,测量接触角以检测膜表面亲水性。分离培养孕14.5 d大鼠胚胎大脑皮质NSCs,接种在表面改性后的PHBHHx膜表面进行体外培养,扫描电镜观察膜表面细胞形态,MTT法检测细胞活力,免疫细胞化学染色观察NSCs存活和分化情况。结果显示,与未处理的PHBHHx膜相比,脂肪酶、NaOH处理能够显著提高PHBHHx膜表面亲水性,增加NSCs在PHBHHx膜表面贴附数量;NSCs在改性后的PHBHHx膜表面能够良好地存活并分化为神经元和胶质细胞。结果提示PHBHHx膜表面碱处理通过提高材料表面亲水性和粗糙程度,增加其与NSCs的生物相容性,改性后的PHBHHx材料是一种非常有潜力的新型脑组织工程支架材料,有望在NSCs移植修复脑损伤中发挥作用。