新型复合血管制备过程中胶原管成熟过程的观察

本文对新型生物－人工复合血管制备过程中胶原管的成熟过程进行了观察,确定了成熟时间为３个月。作者发现胶原管的成熟过程是聚酯网和硅胶棒刺激增生的纤维结缔组织在聚酯周围及内侧围绕硅胶棒不断塑开始以细胞成分为主,以后随着胶原成分不断增多,到３个月时以胶原成分为主,胶原纤维变得粗大且有序,以聚酯为骨架的胶原管成熟。     

聚酯网的缝接及其对复合血管形态结构的影响

本研究对生物——人工复合血管制备过程中聚酯网的缝接及其对复合血管形态结构的影响进行了探讨,作者通过对复合血管聚酯网缝接处的肉眼、LM和SEM观察,认为聚酯的缝接对复合血管形态结构的影响甚微,同时介绍了聚酯网缝接的原则和方法。     

旋转加压种植法在新型生物人工复合血管体外内皮化过程中的实验研究

目的：探讨在新型生物人工复合血管内腔面联合种植平滑肌细胞和内皮细胞的方法,比较研究旋转加压种植与普通灌注种植两种方法的内皮化效果,方法：先制备新型生物人工复合血管及获取培养鉴定平滑肌细胞和内皮细胞,再和旋转加压种植与普通灌注种植两种方法将平滑肌细胞和内皮细胞培养种植于新型复合血管内腔面,以光镜及扫描电镜等观察评价内皮化的效果。结果：旋转加压种植2小时末的复合血管腔内有大量内皮细胞,旋转加压种植9天后已形成完整的内皮细胞单层;普通灌注种植的复合血管内腔有内皮细胞附着,分布不均匀,未形成完整的内皮细胞层,结论：以旋转加压种植法在新型复合血管内腔面联合种植平滑肌细胞和内皮细胞效果满意,基本实现内皮化,可以满足复合血管内皮化的要求。     

人造血管的纺织设计与加工技术

1 引言 当人体内血管由于动脉硬化、血管瘤、血栓、血管老化或破损等原因不能正常工作时,需要进行血管移植。血管代用品的主要来源为生物血管、人造血管及复合血管。生物血管含自体血管、同种异体血管和异种血管3种。后两种由于通畅率低,易发生退行性变及强烈的排异作用,目前临床已经很少应用。自体血管在外周血管重建中,用作为小口径血管的优良代用品,但其来源少,口径和长度也受     

聚乳酸聚乙醇酸膜、聚β羟基丁酯膜和胶原膜三种材料的相容性探讨

目的 评价聚乳酸聚乙醇酸膜、聚β羟基丁酯膜和胶原膜的结构、生物相容性及其在组织工程血管中的应用前景.方法 HE、胶原染色,扫描电镜观察材料的结构.新西兰兔15只皮下植入材料,于4、6、8和12周取出观察其组织反应和降解情况.将犬股动脉间质细胞种植于聚乳酸聚乙醇酸膜、胶原膜上,观察其形态.结果 聚乳酸聚乙醇酸膜、聚β羟基...     

移植血管PC预处理反应条件初步探索

异体血管移植前必须经过预处理,以消除血管胶原上的异体抗原,戊二醛(Glutaraldehyde,GA)醛化作为经典的处理方法被广泛应用。但是,GA处理的生物材料仍有缺点;如钙化变性、耐久性差、组织僵硬等。为此,国外研究者已开始探索使用一种新的处理试剂——多聚环氧化合物(Polyepoxy compounds,PC)。文献报告PC处理的生物材料经体内及体外实验证实优于GA材     

复合血管内皮细胞的不同孔径磷酸钙陶瓷体内血管化的比较研究

目的:比较不同孔径多孔β-TCP材料复合血管内皮细胞后的体内血管化,探索孔隙大小对人工骨材料体内血管形成的作用。方法:血管内皮细胞与连通径均为100μM,而孔径分别为200-300μM和300~400μM两种不同孔隙结构β-TCP材料复合后包埋入36只成年新西兰兔的腿部肌肉内,相同结构的空白β-TCP材料作对照,术后2、4、8周对材料进行组织学观察、免疫组织化学分析,计算新生血管密度。结果:复合血管内皮细胞的材料血管形成启动过程早于空白对照组,术后第4周血管管腔已基本成形,并基本稳定,至第8周开始血管充盈,微血管密度高于对照组(P0.05)。而不同孔径的材料比较发现,不论是复合血管内皮细胞的材料还是空白材料,孔径300~400μM的材料内新生血管密度显著显著高于孔径200-300μM材料(P0.05)。结论:材料孔隙较大的材料更有利于材料体内的血管化,而复合血管内皮细胞后,更加快了其血管化进程,这一研究结果提示材料孔隙间的连通是影响材料体内血管化的关键因素,该研究结论将为改善人工骨材料体内血管化的方法提供新的思路,同时也为骨移植材料的最优结构的选择提供一定的借鉴。     

交联I型胶原复合生物玻璃在兔股骨远端缺损中的成骨作用

摘要 目的：评价交联度不同的I型胶原复合生物玻璃后作为人工骨移植物在兔股骨髁部骨缺损中的修复作用,以研究一种成骨性能优秀,降解速度令人满意,且具有可塑性,便于术中使用的新型人工骨移植材料。方法：本研究设置实验组及对照组,实验组为交联度70%的高交联I型胶原复合生物玻璃以及交联度为45%的低交联I型胶原复合生物玻璃。对照组为普通未交联I型胶原复合生物玻璃。于9只新西兰大白兔双下肢股骨髁部制备动物骨缺损模型,将随机分组后的三种骨移植物分别植入股骨髁部骨缺损模型中。术后6周取材行组织学分析研究,比较3种骨移植物在骨缺损中的新骨生成率。结果：组织学分析结果显示,高交联组的新骨生成率为5.23 0.87%,其成骨性能显著低于低交联组13.23 1.13%以及未交联组的12.63 0.92%（P<0.05）。而低交联组的新骨生成率与未交联组之间无统计学差异（P>0.05）。结论：交联度为45%的低交联I型胶原复合生物玻璃具有更好的成骨能力,作为骨移植材料在临床应用中具有更广阔的发展前景。     

生物血管异种移植的初步研究

目的为了寻求一种新的小口径血管代用品,建立异种移植的动物实验模型,以观察异种移植物的安全性、可靠性、通畅性及组织学改变。方法共采用17只杂种雌性犬,实验组10只,植入经环氧化物处理的猪血管移植物;对照组7只,植入人造血管。手术方法为右侧股动静脉瘘。术后通过超声和血管造影方法来观察移植血管的通畅性,并在术后3月将移植物取出,进行病理学检查,观察移植前后移植物的组织学改变。结果术后第一周、二周行Doppler超声检查结果,两组动静脉瘘均通畅,2周内血管通畅率为100%。术后3个月动脉造影检查后,生物血管组(PG)通畅5只,通畅率62.5%,e-PTFE组通畅4只,通畅率66.7%。两组数据统计学处理,差异无显著性(P>0.05)。术后3月对移植物取材,进行光镜及扫描电镜病理学检查,通畅的生物血管吻合口无狭窄,吻合部位有新的内膜覆盖,周围组织无钙化,有新生的内皮细胞覆盖。结论经环氧化物处理的猪的血管移植物(PG)生物血管作为异种移植物,生物相容性好,具有一定的可行性。     

内皮抑素研究进展

新生血管的生成 (Angiogenesis)与多种生理过程相关 ,受多种促进和抑制因子的调节 ,细胞外基质蛋白经酶解产生的小片段中很多都参与了这一过程的调节。内皮抑素 (Endostatin)是 1997年首先从小鼠血管内皮瘤EOMA细胞培养上清中发现的 ,是细胞外基质蛋白胶原XVⅢα1链NC1结构域C末端 184个Aa的片段。可抑制bFGF和VEGF刺激的血管内皮细胞的增殖和迁移 ,抑制新生血管的形成 ,抑制肿瘤的形成和转移。由于其作用对象是血管内皮细胞 ,而不是转化的肿瘤细胞本身 ,长期反复治疗中不会引起耐药性。它在肿瘤治疗中的应用前景引起多方关注 ,相关研究广泛开展起来。本文综述了近几年在其生物功能、作用机理及应用等方面的研究进展     

A periadventitial sirolimus-releasing mesh decreased intimal hyperplasia in a rabbit model

Autologous vein grafts used as aortocoronary bypasses are often prone to intimal hyperplasia, which results in stenosis and occlusion of the vein. The aim of this study was to prevent intimal hyperplasia using a newly developed perivascular system with sustained release of sirolimus. This system of controlled drug release consists of a polyester mesh coated with a copolymer of L-lactic acid and epsilon-caprolactone that releases sirolimus. The mesh is intended for wrapping around the vein graft during surgery. The mesh releasing sirolimus was implanted in periadventitial position onto arteria carotis communis of rabbits, and neointimal hyperplasia was then assessed. We found that implanted sirolimus-releasing meshes reduced intima thickness by 47+/-10 % compared to a vein graft after 3 weeks. The pure polyester mesh decreased vein intima thickness by 35+/-9 %. Thus, our periadventitial system for controlled release of sirolimus prevented the development of intimal hyperplasia in autologous vein grafts in vivo in rabbits. A perivascularly applied mesh releasing sirolimus is a promising device for preventing stenosis of autologous vein grafts.     

Behaviour of a New Composite Mesh for the Repair of Full-Thickness Abdominal Wall Defects in a Rabbit Model

Introduction

Composite biomaterials designed for the repair of abdominal wall defects are composed of a mesh component and a laminar barrier in contact with the visceral peritoneum. This study assesses the behaviour of a new composite mesh by comparing it with two latest-generation composites currently used in clinical practice.

Methods

Defects (7x5cm) created in the anterior abdominal wall of New Zealand White rabbits were repaired using a polypropylene mesh and the composites: Physiomesh^TM; Ventralight^TM and a new composite mesh with a three-dimensional macroporous polyester structure and an oxidized collagen/chitosan barrier. Animals were sacrificed on days 14 and 90 postimplant. Specimens were processed to determine host tissue incorporation, gene/protein expression of neo-collagens (RT-PCR/immunofluorescence), macrophage response (RAM-11-immunolabelling) and biomechanical resistance. On postoperative days 7/14, each animal was examined laparoscopically to quantify adhesions between the visceral peritoneum and implant.

Results

The new composite mesh showed the lowest incidence of seroma in the short term. At each time point, the mesh surface covered with adhesions was greater in controls than composites. By day 14, the implants were fully infiltrated by a loose connective tissue that became denser over time. At 90 days, the peritoneal mesh surface was lined with a stable mesothelium. The new composite mesh induced more rapid tissue maturation than Physiomesh^TM, giving rise to a neoformed tissue containing more type I collagen. In Ventralight^TM the macrophage reaction was intense and significantly greater than the other composites at both follow-up times. Tensile strengths were similar for each biomaterial.

Conclusions

All composites showed optimal peritoneal behaviour, inducing good peritoneal regeneration and scarce postoperative adhesion formation. A greater foreign body reaction was observed for Ventralight^TM. All composites induced good collagen deposition accompanied by optimal tensile strength. The three-dimensional macroporous structure of the new composite mesh may promote rapid tissue regeneration within the mesh.     

In vivo study of a model tissue-engineered small-diameter vascular bypass graft

Conventionally used vascular grafts such as polyester (Dacron) or expanded polytetrafluoroethylene perform inadequately as small-diameter vascular bypass grafts (SDBGs). SDBGs, which can maintain long-term patency and those that could potentially evolve with the somatic growth, are highly desirable in vascular surgery and thus research into tissue-engineered blood vessels (TEBVs) is of keen interest. A TEBV was developed by seeding endothelial cells onto a collagen matrix that was cross-linked and contracted by smooth muscle cells (SMCs). A polyester graft served as a scaffold. Recovery studies (12 TEBVs and seven controls) were carried out to assess in vivo endothelialization and long-term patency of TEBVs. Hemodynamic observations indicated para-anastomotic turbulences and high shear stress at anastomosis. Recovery studies demonstrated confluent endothelialization, thrombus-free surfaces, and patent TEBVs in all cases. Graft incorporation and neovascularization of the scaffold occurred in both hybrid and control grafts. However, thickened neointima formation occurred in TEBV grafts, which was most likely caused by the rigidity of polyester scaffold. Significant perigraft inflammatory changes could be observed in both TEBVs and control grafts at 1, 4, and 8 weeks. In conclusion, the TEBVs demonstrated satisfactory performance as an infra-renal-aortic graft in a porcine model. The TEBV serves as a promising model and facilitates the development of a TEBV in a clinical setting, potentially with human stem cells and with more biocompatible, biodegradable scaffolds that are mechanically more compliant with natural vessels.     

Early effects of exogenous arginine after the implantation of prosthetic material into the rat abdominal wall

We have investigated the effects of high arginine (Arg) levels (7.5 mg/100 g body weight per hour) on the early integration of biocompatible mesh grafts into the rat abdominal wall. Studies were performed over implantation intervals of 6, 12, 24 or 48 hours (n=12, each). Arginine and related compounds were quantified in plasma, wound fluids and multiple tissues. Plasma nitric oxide (NO) production was studied. Strips were taken from the polypropylene fiber-host tissue interfaces (PTIs) for optical microscopic analysis and for immunohistochemical analysis using rat-specific antibodies against type I and type III collagens. Exogenous Arg was metabolized at the peripheral tissues but reliably reached the wound space. High amounts of Arg and ornithine (Orn) were detected in the specimens considered. No changes on citrulline (Ctr) or NO concentrations were observed, overall suggesting that, during the period studied, the arginase pathway predominated. The acute scarring response differed significantly in the two placements considered. The P-SS interface evidenced more extensive new tissue growth than the P-DS interface. Forty-eight hours after mesh implantation cellular infiltration, fibroblast proliferation, and mesh-surrounding angiogenesis were higher in the arginine-treated rats. Type III collagen staining was related to arginine treatment, being higher (++) in the study group. In conclusion, and independently of the site of mesh placement, supplemental Arg seemed to favorably affect early local collagen deposition. This could be potentially helpful to ameliorate the integration of biomaterials into the tissues and, consequently, to allow for the design of more selective therapeutic strategies to prevent hernia recurrence rates.     

Take percentage and conditions of cultured epithelium were improved when basement membrane of the graft was maintained and anchoring mesh was added

To achieve a higher take rate for epithelial grafts, this study investigated grafting techniques. Seventy-seven nude mice received flap grafting in which cultured human epithelium was grafted inside the flap, and 55 nude rats received transplantation of epithelium to a full-thickness skin defect. In each group, four models were studied, including model 1, in which epithelium was cultured with the conventional method; model 2, in which epithelium was cultured with fibrin gel to avoid sheet damage, then absorptive mesh was incorporated into the epithelium for anchoring to the graft bed; model 3, in which epithelium was cultured with fibrin gel and combined with absorptive mesh and artificial dermis containing fibroblasts; and model 4, in which the model 2 epithelium was grafted after artificial dermis was transplanted. The take for these models was evaluated grossly and histologically. The results show that the take percentage of models 2 and 3 was significantly higher than that of model 1 (conventional epithelium) and that there was no significant difference between model 3 (simultaneous grafting) and model 4 (two-step grafting). The difference in the take percentages of the grafts to the flap and to the full-thickness skin defect was also insignificant. In immunohistochemistry, human keratin appeared in all epidermis layers and diversification of the layer was observed in models 2, 3, and 4. In these three models, type IV collagen appeared in the basal layer and the formation of basal membrane was confirmed. These findings suggest that epithelia cultured on fibrin gel and combined with absorptive mesh could be used in a new technique for better, more stable take.     

A Silk Fibroin/Collagen Nerve Scaffold Seeded with a Co-Culture of Schwann Cells and Adipose-Derived Stem Cells for Sciatic Nerve Regeneration

As a promising alternative to autologous nerve grafts, tissue-engineered nerve grafts have been extensively studied as a way to bridge peripheral nerve defects and guide nerve regeneration. The main difference between autogenous nerve grafts and tissue-engineered nerve grafts is the regenerative microenvironment formed by the grafts. If an appropriate regenerative microenvironment is provided, the repair of a peripheral nerve is feasible. In this study, to mimic the body’s natural regenerative microenvironment closely, we co-cultured Schwann cells (SCs) and adipose-derived stem cells (ADSCs) as seed cells and introduced them into a silk fibroin (SF)/collagen scaffold to construct a tissue-engineered nerve conduit (TENC). Twelve weeks after the three different grafts (plain SF/collagen scaffold, TENC, and autograft) were transplanted to bridge 1-cm long sciatic nerve defects in rats, a series of electrophysiological examinations and morphological analyses were performed to evaluate the effect of the tissue-engineered nerve grafts on peripheral nerve regeneration. The regenerative outcomes showed that the effect of treatment with TENCs was similar to that with autologous nerve grafts but superior to that with plain SF/collagen scaffolds. Meanwhile, no experimental animals had inflammation around the grafts. Based on this evidence, our findings suggest that the TENC we developed could improve the regenerative microenvironment and accelerate nerve regeneration compared to plain SF/collagen and may serve as a promising strategy for peripheral nerve repair.     

A cell leakproof PLGA‐collagen hybrid scaffold for cartilage tissue engineering

A cell leakproof porous poly(DL ‐lactic‐co‐glycolic acid) (PLGA)‐collagen hybrid scaffold was prepared by wrapping the surfaces of a collagen sponge except the top surface for cell seeding with a bi‐layered PLGA mesh. The PLGA‐collagen hybrid scaffold had a structure consisting of a central collagen sponge formed inside a bi‐layered PLGA mesh cup. The hybrid scaffold showed high mechanical strength. The cell seeding efficiency was 90.0% when human mesenchymal stem cells (MSCs) were seeded in the hybrid scaffold. The central collagen sponge provided enough space for cell loading and supported cell adhesion, while the bi‐layered PLGA mesh cup protected against cell leakage and provided high mechanical strength for the collagen sponge to maintain its shape during cell culture. The MSCs in the hybrid scaffolds showed round cell morphology after 4 weeks culture in chondrogenic induction medium. Immunostaining demonstrated that type II collagen and cartilaginous proteoglycan were detected in the extracellular matrices. Gene expression analyses by real‐time PCR showed that the genes encoding type II collagen, aggrecan, and SOX9 were upregulated. These results indicated that the MSCs differentiated and formed cartilage‐like tissue when being cultured in the cell leakproof PLGA‐collagen hybrid scaffold. The cell leakproof PLGA‐collagen hybrid scaffolds should be useful for applications in cartilage tissue engineering. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

A comparison of oxidized LDL-induced collagen secretion by graft and aortic SMCs: role of PDGF

Smooth muscle cells (SMCs) from prosthetic vascular grafts constitutively secrete higher levels of collagen than aortic SMCs. Lipid oxidation products accumulate in grafts, and we postulated that they stimulate SMC production of collagen. The effect of oxidized low-density lipoprotein (oxLDL) on type I collagen secretion by aortic and graft SMCs was compared. SMCs isolated from the canine thoracic aorta or Dacron thoracoabdominal grafts (n = 10) were incubated with native LDL or oxLDL (0-400 microg cholesterol/ml) for 72 h. Type I collagen in the conditioned medium was measured by ELISA. OxLDL increased collagen production by graft SMCs from 4.1 +/- 0.3 to 11.0 +/- 0.4 ng/microg DNA and by aortic SMCs from 2.3 +/- 0.1 to 3.5 +/- 0.2 ng/microg DNA. Native LDL had little effect. LY-83583, a superoxide generator, stimulated a dramatic increase in collagen secretion by graft SMCs and a smaller but significant elevation by aortic SMCs. OxLDL has been shown to increase PDGF production by graft SMCs, and PDGF can stimulate collagen production. Anti-PDGF antibody inhibited the increase in collagen production by graft SMCs that was stimulated by oxLDL, implicating PDGF as one mechanism of oxLDL-induced collagen production. Lipid oxidation products that accumulate in prosthetic vascular grafts can cause an oxidative stress that stimulates PDGF production by graft SMCs that in turn stimulates collagen production, contributing to the progression of intimal hyperplasia.     

A critical assessment of standard processing methods for the preparation of palynological samples

Standard processing techniques for the isolation of organic walled dinoflagellate cysts from geological samples are examined, with particular attention to the size and type of sieve mesh used. Variations within the ‘standard’ processing techniques used by different laboratories are identified, and an assessment of the retention capacities of meshes of different sizes and different materials is carried out. Some dinoflagellate cysts and large numbers of Lycopodium spores, used for the calculations of absolute abundance data, were found to pass through 20 μm meshes. This is due to a combination of factors including: the diagonal aperture diameter of a 20 μm mesh measuring over 28 μm; the three-dimensional properties of different mesh weaves (nylon and polyester); and the non-spherical shape of the particles. Experiments demonstrate that the maximum mesh size that should be used in palynological processing is 15 μm. Nylon mesh is more practical to use than polyester as processing time is reduced, but nylon is degraded by contact with acid solutions. Meshes with apertures < 15 μm may be used, though this may be impractical for large samples containing significant quantities of fine siliciclastic or organic material.