新型生物可降解材料聚丁二酸丁二醇酯的生物安全性评价

目的通过对可降解材料聚丁二酸丁二醇酯(PBS)刺激和迟发超敏反应及血液相容性的研究,进一步评价PBS材料的生物安全性。方法选用新西兰白兔,通过单次接触实验法,研究原发刺激指数,以确定材料的刺激性。在实验用豚鼠上,采用最大剂量法,判定材料的迟发超敏反应性。采取新鲜兔血,通过溶血实验和血小板黏附实验,研究材料的血液相容性。结果 PBS局部刺激反应极轻微,无迟发超敏反应,材料的溶血率小于5.0%,血小板黏附性与聚乳酸材料相当。结论 PBS材料生物安全性良好,与皮肤接触无不良反应,溶血率低,血小板黏附性与聚乳酸材料相当。     

以聚羟基烷酸酯为支架同种异体工程化软骨构建

目的 探讨以聚羟基烷酸酯(polyhydroxyalkanotes,PHBV)为支架材料的同种异体软骨细胞构建组织工程化软骨的能力.方法 分离、培养、扩增、传代培养兔软骨细胞,接种在PHBV支架材料上,体外培养7 d后,将细胞-材料复合物种植在成年兔皮下,6周取材,对获得的同种异体工程化软骨进行组织学评价及扫描电镜观察.结果 组织学观察示PHBV有成熟软骨组织形成,软骨细胞形态正常,胶原形成较多;电镜观察示软骨基质内弹性纤维较丰富,在弹性纤维包绕中有散在的卵圆形软骨细胞.单纯PHBV体内培养无软骨组织形成.结论 以PHBV为支架材料同种异体软骨细胞在有免疫力的动物体内可形成工程化软骨.     

犬骨髓基质干细胞与聚羟基烷酸酯体外相容性的实验研究

目的：评价聚羟基烷酸酯（PHBV）作为组织工程支架与犬骨髓基质干细胞（BMSCs）的生物相容性。方法:原代培养犬BMSCs，传至3-4代后，接种至PHBV膜和泡沫样三维支架上，以接种至培养板上细胞为对照组，倒置显微镜下观察细胞形态；于培养1、2、3周分别采用4%多聚甲醛固定，常规组织切片，HE染色；在5、10、14 d用Hoechst33258荧光法定量测定细胞内DNA含量，BCA法测定蛋白质含量。结果:倒置显微镜观察PHBV 纤维较粗，且透光性差，在相差显微镜下不易观察。第3-4代BMSCs接种至PHBV膜上2 h后即大部黏附，3 d后伸展良好，呈纺锤形或梭形，在三维支架的孔隙内立体生长，1周开始细胞间连接，3周广泛连接，分泌大量基质；培养接种1周后，取二个膜状PHBV固定，HE染色后，见骨髓基质干细胞增殖。培养接种2周后，骨髓基质干细胞增殖明显，呈梭形密布于膜状PHBV上。培养接种3周后，骨髓基质干细胞增殖较第二周无明显变化。定量测定接种的细胞内DNA含量和蛋白质含量与对照组相比无显著差异。结论:PHBV作为BMSCs的组织工程支架材料，具有良好的生物相容性。     

成纤维细胞在聚羟基丁酸酯表面黏附与种植研究

可降解高分子聚合物广泛应用于组织工程,其表面的黏附特性影响细胞的种植与生长。我们研究了成纤维细胞系NIH3T3在可降解材料聚羟基丁酸酯（PHB）表面的黏附和生长。应用线性变剪切流槽研究NIH3T3细胞在材料表面的黏附力学特性,结果表明,由于在PHB表面的临界脱离剪应力较低,高密度接种时间细胞趋于聚集;在经多聚赖氨酸衣被的表面临界脱离剪应力提高,细胞铺展生长。对三维PHB多孔支架种植细胞实验表明,在PHB材料表面进行多聚赖氨酸衣被,可以有效地提高细胞种植效率。     

聚谷氨酸苄酯/聚乙二醇嵌段共聚物膜的血液相容性研究

使用凝血时间实验、血小板的黏附和变形实验、血浆蛋白的吸附实验来评价聚谷氨酸苄酯 /聚乙二醇(PBL G/PEG)嵌段共聚物膜的血液相容性 ,PEG嵌段的引入对共聚物血液相容性的影响。结果表明 ,均聚物的血液相容性优于玻璃和硅油 ,共聚物的血液相容性优于均聚物 ,且随着 PEG含量增加 ,其血液相容性更好。     

胚胎干细胞与聚3-羟基丁酸酯-co-4-羟基丁酸酯共培养细胞补片的初步研究

目的干细胞移植是具有治疗心血管疾病潜力的有效方法,但是细胞移植过程中缺乏有效的载体会大大影响其成活和增殖。聚3-羟基丁酸酯-co-4-羟基丁酸酯P(3HB-co-4HB)是一种能够完全降解的,具有良好物理特性的高分子材料。探讨P(3HB-co-4HB)这种三维材料是否适合胚胎干细胞在上面生长,并生成细胞补片。方法复苏小鼠胚胎干细胞,传代培养,消化离心后重悬细胞,用悬滴法形成拟胚体(embryid bodies,EB),将拟胚体与P(3HB-co-4HB)膜共培养;72 h共培养后固定并进行扫描电镜和共聚焦显微镜观察细胞黏附情况,DAPI荧光染色观察细胞在P(3HB-co-4HB)膜上形态。结果胚胎干细胞在培养皿中贴壁生长良好,形态正常;拟胚体同P(3HB-co-4HB)膜共培养72 h后,所有拟胚体都在三维材料表面良好生长,爬膜率为100%;Confocal显微镜和扫描电镜观察到在2 mm的三维膜上,拟胚体生长贴附在生物膜上,细胞形态正常。结论 ESC在P(3HB-co-4HB)表面生长、增殖形成细胞补片。P(3HB-co-4HB)可作为干细胞治疗多种疾病的支架材料之一。     

聚羟基丁酸及其共聚物在组织工程心脏瓣膜中应用的初步研究

应用组织工程支架 ,将活细胞种植于可生物降解的瓣膜支架上 ,制造出一种组织相容性好 ,不需抗凝 ,具有修复能力 ,且支持患者终生的理想心脏瓣膜。对照进行聚羟基丁酸 (polyhydroxybutyrate ,PHB)、聚羟基丁酸 /聚羟基戊酸共聚物 (Poly-hydroxybutyrate/hydroxyvalerate ,PHBV)皮下包埋和种植细胞生长研究实验。结果表明PHBV皮下包埋 8周仍基本保持膜状结构 ,10周完全降解 ,且生物相容性优于PHB。PHBV更适于组织工程心脏瓣膜支架材料的应用。     

用复合诱导型骨修复材料修复兔桡骨缺损的实验研究

以不同的载药方式构建4种壳聚糖/聚羟基丁酸酯-羟基戊酸酯(PHBV)复合诱导型骨修复材料,检测并比较4种支架材料对兔桡骨缺损的修复效果,筛选出最佳骨修复材料并确定最佳药物控释方式。以淫羊藿苷为诱导因子,采用两相混合冷冻干燥技术以微球载药、改性药物微球(W/O法制得并表征)、改性药物与材料共价结合等药物添加方式及不加药制得4种支架材料,并对其进行显微结构以及载药支架药物缓释表征,后将4种材料分别植入兔桡骨缺损处,于1、3、6个月进行X射线及三维CT观察支架材料对兔桡骨缺损的修复情况,HE,Masson染色观察其诱导成骨效果。结果表明,支架材料呈网络状串珠状的显微结构,载药微球粒径分布在3～11 μm,载药支架材料有着良好的药物缓释,其中共价结合组药物释放峰值时间较其他组推迟,为72 h,且峰值后药物缓释量迅速平稳为75 μg左右。X射线及三维CT观察显示,最终共价结合组支架材料骨缺损处连通,且骨密度高于其他3组。HE、Masson染色结果显示,共价结合组成骨效果优于其他组。共价结合的药物添加方式能使支架具有良好的药物缓释效果,进而对兔桡骨缺损表现出良好的修复效果。     

聚羟基丁酸及其共聚物在组织工程心脏瓣膜中应用的初步研究

应用组织工程支架，将活细胞种植于可生物降解的瓣膜支架上，制造出一种组织相容性好，不需抗凝，具有修复能力，且支持患终生的理想心脏瓣膜。对照进行聚羟基丁酸（polyhydroxybutyrate,PHB)、聚羟基丁酸／聚羟基戊酸共聚物（Polyhydroxybutyrate/hydroxyvalerate,PHBV)皮下包埋和种植细胞生长研究实验。结果表明PHBV皮下包埋8周仍基本保持膜状结构，10周完全降解，且生物相容性优于PHB。PHBV更适于组织工程心脏瓣膜支架材料的应用。     

聚羟基烷酸酯聚合物负载软骨细胞修复同种异体喉软骨缺损

背景：软骨组织工程基础研究相当深入,但在耳鼻咽喉科实际应用研究颇少,探索组织工程技术简便实用的喉软骨修复方法是值得研究的课题。 目的：比较多孔海绵状聚羟基丁酸酯与聚羟基己酸酯共聚物生物材料负载软骨细胞体外培养形成的初期组织工程软骨组织与体内植入一定时期形成的较成熟组织工程软骨组织修复同种异体甲状软骨缺损的效果。 方法：收集体外培养第3代乳兔(3 d龄)软骨细胞,以多孔海绵状聚羟基丁酸酯与聚羟基己酸酯共聚物生物材料为细胞外基质,采用组织工程技术制备细胞-材料复合物,共同体外培养形成初级组织工程软骨组织后直接应用于成兔甲状软骨缺损的修复(实验组A,n=5)或将初级组织工程软骨组织体内植入一定时期形成较成熟组织工程软骨再应用于甲状软骨缺损的修复(实验组B,n=5)。设单纯聚羟基丁酸酯与聚羟基己酸酯共聚物材料修复组(对照A组,n=4)和单纯软骨细胞修复组(对照B组,n=4)作为对照。分别于术后4周(实验B组)和8周(实验A组、对照A组、对照B组)取材,对甲状软骨缺损修复效果进行大体和组织学评价。 结果与结论：两者大体支架形态基本一致,修复区与原有软骨均相续平坦,无凹陷及缺损。但实验A组存在界面无细胞区,修复区基质分泌不丰富;实验B组界面区有细胞生长,基质分泌良好。两者炎细胞浸润均不明显。对照组修复区凹陷,呈暗红色软组织充填,组织学及特殊染色检查未发现软骨样结构及其分泌的基质成分。结果表明在有免疫力的动物体内,初级组织工程软骨组织直接应用与体内植入后再应用均能有效修复同种异体甲状软骨缺损,无明显免疫反应;相同时期内,应用较成熟组织工程软骨组织修复效果优于应用初级组织工程软骨组织。然而,直接应用初级组织工程软骨组织可节省时间、成本、工作量及操作环节,避免二次皮下手术的痛苦,是比较实用的方法之一。     

Poly I:C primes the suppressive function of human palatine tonsil-derived MSCs against Th17 differentiation by increasing PD-L1 expression

It has been established that mesenchymal stem cells (MSCs) can have a suppressive effect on T cells, yet much remains unknown about the underlying mechanisms that support this effect. The T cell co-stimulatory pathway involving the programmed death-1 (PD-1) receptor and its ligand PD-L1 regulates T cell activation, tolerance, and subsequent immune-mediated tissue damage. In this study, human palatine tonsil-derived MSCs (T-MSCs) constitutively expressed PD-L1 and exhibited a suppressive activity that specifically targeted murine Th17 differentiation. Additionally, polyinosinic–polycytidylic acid (poly I:C), a Toll-like receptor 3 (TLR3) ligand, increased PD-L1 expression on T-MSCs. The elevated PD-L1 levels enhanced the suppressive functions of T-MSCs on Th17 differentiation. Therefore, pre-stimulation of T-MSCs with poly I:C may serve as an effective therapeutic priming step for modulating Th17-dominant immune responses.     

Examination of bone marrow mesenchymal stem cells seeded onto poly(3-hydroxybutyrate-co-4-hydroxybutyrate) biological materials for myocardial patch

The implantation of bone marrow mesenchymal stem cells (BMSCs) into the heart has been reported to be effective for myocardial infarction; however, it is unknown what methods are most suitable for supporting stem cell growth in a myocardial patch. This study used a new polymer material composed of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] co-cultured with BMSCs to create a myocardial patch. Bone marrow mesenchymal stem cells were obtained from healthy male BSL-C57 mice. The cells were treated with 5-azacytidine to investigate their differentiation into cardiomyocytes. The cells were seeded for 24-hours onto P(3HB-co-4HB) biological material films (n?=?8). Cell-biomaterial constructs were fixed and analyzed using different methods. Bone marrow mesenchymal stem cells were CD34, CD45^??, CD90⁺ (low), and CD73⁺. The cells were stained with anti-cardiac troponin T (anti-cTnT) and anti-connexin 43 (anti-CX43) antibodies after 5-azacytidine treatment. Scanning electron microscopy showed that BMSC morphology was normal, and cell numbers were more abundant on the P(3HB-co-4HB) material surfaces. The growth curve of BMSCs on the biomaterial patches showed that the P(3HB-co-4HB) material permitted good stem cell growth. Owing to its excellent biocompatibility and biodegradability properties, in particular its porosity, P(3HB-co-4HB) is highlighted as an optimal material to support myocardial cell growth and myocardial patch formation in patients with myocardial infarction.     

Emulating native periosteum cell population and subsequent paracrine factor production to promote tissue engineered periosteum-mediated allograft healing

Emulating autograft healing within the context of decellularized bone allografts has immediate clinical applications in the treatment of critical-sized bone defects. The periosteum, a thin, osteogenic tissue that surrounds bone, houses a heterogenous population of stem cells and osteoprogenitors. There is evidence that periosteum-cell derived paracrine factors, specifically vascular endothelial growth factor (VEGF) and bone morphogenetic protein 2 (BMP2), orchestrate autograft healing through host cell recruitment and subsequent tissue elaboration. In previous work, we demonstrated that the use of poly(ethylene glycol) (PEG) hydrogels as a tissue engineered (T.E.) periosteum to localize mesenchymal stem cells (MSCs) to the surface of decellularized bone enhances allograft healing and integration. Herein, we utilize a mixed population of 50:50 MSCs and osteoprogenitor cells to better mimic native periosteum cell population and paracrine factor production to further promote allograft healing. This mixed cell population was localized to the surface of decellularized allografts within degradable hydrogels and shown to expedite allograft healing. Specifically, bone callus formation and biomechanical graft–host integration are increased as compared to unmodified allografts. These results demonstrate the dual importance of periosteum-mediated paracrine factors orchestrating host cell recruitment as well as new bone formation while developing clinically translatable strategies for allograft healing and integration.     

Immunomodulation by mesenchymal stem cells combats the foreign body response to cell-laden synthetic hydrogels

The implantation of non-biological materials, including scaffolds for tissue engineering, ubiquitously leads to a foreign body response (FBR). We recently reported that this response negatively impacts fibroblasts encapsulated within a synthetic hydrogel and in turn leads to a more severe FBR, suggesting a cross-talk between encapsulated cells and inflammatory cells. Given the promise of mesenchymal stem cells (MSCs) in tissue engineering and recent evidence of their immunomodulatory properties, we hypothesized that MSCs encapsulated within poly(ethylene glycol) (PEG) hydrogels will attenuate the FBR. In vitro, murine MSCs encapsulated within PEG hydrogels attenuated classically activated primary murine macrophages by reducing gene expression and protein secretion of pro-inflammatory cytokines, most notably tumor necrosis factor-α. Using a COX2 inhibitor, prostaglandin E2 (PGE2) was identified as a mediator of MSC immunomodulation of macrophages. In vivo, hydrogels laden with MSCs, osteogenically differentiating MSCs, or no cells were implanted subcutaneously into C57BL/6 mice for 28 days to assess the impact of MSCs on the fibrotic response of the FBR. The presence of encapsulated MSCs reduced fibrous capsule thickness compared to acellular hydrogels, but this effect diminished with osteogenic differentiation. The use of MSCs prior to differentiation in tissue engineering may therefore serve as a dynamic approach, through continuous cross-talk between MSCs and the inflammatory cells, to modulate macrophage activation and attenuate the FBR to implanted synthetic scaffolds thus improving the long-term tissue engineering outcome.     

Mesenchymal stem cells attenuated PLGA-induced inflammatory responses by inhibiting host DC maturation and function

The poly lactic-co-glycolic acid (PLGA) bio-scaffold is a biodegradable scaffold commonly used for tissue repair. However, implanted PLGA scaffolds usually cause serious inflammatory responses around grafts. To improve PLGA scaffold-based tissue repair, it is important to control the PLGA-mediated inflammatory responses. Recent evidence indicated that PLGA induce dendritic cell (DC) maturation in vitro, which may initiate host immune responses. In the present study, we explored the modulatory effects of mesenchymal stem cells (MSC) on PLGA-induced DCs (PLGA-DC). We found that mouse MSCs inhibited PLGA-DC dendrite formation, as well as co-stimulatory molecule and pro-inflammatory factor expression. Functionally, MSC-educated PLGA-DCs promoted Th2 and regulatory T cell differentiation but suppressed Th1 and Th17 cell differentiation. Mechanistically, we determined that PLGA elicited DC maturation via inducing phosphorylation of p38/MAPK and ERK/MAPK pathway proteins in DCs. Moreover, MSCs suppressed PLGA-DCs by partially inactivating those pathways. Most importantly, we found that the MSCs were capable of suppressing DC maturation and immune function in vivo. Also, the proportion of mature DCs in the mice that received MSC-PLGA constructs greatly decreased compared with that of their PLGA-film implantation counterparts. Additionally, MSCs co-delivery increased regulatory T and Th2 cells but decreased the Th1 and Th17 cell numbers in the host spleens. Histological analysis showed that MSCs alleviated the inflammatory responses around the grafted PLGA scaffolds. In summary, our findings reveal a novel function for MSCs in suppressing PLGA-induced host inflammatory response and suggest that DCs are a new cellular target in improving PLGA scaffold-based tissue repair.     

Spontaneous osteogenesis of MSCs cultured on 3D microcarriers through alteration of cytoskeletal tension

3-dimensional microcarrier (3D-MC) cell culture systems are often used for expansion of stem cells including mesenchymal stem cells (MSCs) for high cell volumes required in clinical applications. However, compared to 2-dimensional (2D) cell culture, effects of 3D-MC systems on MSC differentiation have not been well studied. In this study, the behavior of various sources of MSCs from two species was observed and compared on 3D collagen I-coated-MCs (COL-MC) versus 2D culture. Proliferation of all MSCs cultured on 3D COL-MC was much decreased compared to 2D culture. Unexpectedly, COL-MC-cultured MSCs underwent spontaneous osteogenesis without exogenous addition of biochemical factors, as evidenced by increased osteogenic genes expression, ALP activity, calcium deposition, and collagen I secretion. Furthermore, MSCs cultured on 3D-MC alone without collagen I coating is sufficient to induce osteogenesis. The spontaneous lineage commitment induced by 3D-MC culture was mediated by increased cytoskeletal tension and actomyosin contraction of MSCs, which could be prevented by latrunculin B and blebbistatin, inhibitors of cytoskeletal tension and actomyosin contraction respectively. Our findings show that the combination of bioengineered MC and MSCs alone can induce specific lineage commitment very efficiently. These data have strong implications in simplifying tissue engineering strategies for therapeutic applications.     

蒸汽灭菌对聚醚酯材料及其血管细胞相容性的影响

探讨了蒸汽灭菌对聚乙二醇对苯二甲酸酯/聚对苯二甲酸丁二醇酯多嵌段共聚物(PEGT/PBT)性能的改变而导致对血管细胞相容性的影响.血管细胞能在紫外辐照灭菌的PEGT/PBT膜片上较好地黏附生长,而在蒸汽灭菌的膜片表面几乎无法黏附生长.使用差示扫描量热分析、静态接触角、光电子能谱、表面羧基测定、核磁共振和扫描电镜等分析测试方法对灭菌前后膜片的本体性能和表面性能进行表征.结果表明,蒸汽灭菌没有改变材料表面形貌和材料的组成.但是在蒸汽灭菌过程中PEGT/PBT链段发生重新取向,亲水性软段PEGT和材料的端羧基在表面富集,使得材料表面亲水性增加、硬段的结晶度有所增加.可能由于端羧基和表面聚乙二醇增多导致蛋白在材料表面的吸附减少,而致使血管细胞无法在蒸汽灭菌的膜片上黏附生长.     

Preparation of Poly(3-hydroxybutyrate) Porous Films by Microemulsion Templates Method

INTRODUCTION　　 The nature poly(3 -hydroxybutyrate) (PHB) is a biodegradable polyester pro-duced by a numberof bacteria as a reserve of carbon and energy. Due to its excellentproperties,for example,biodegradability,biocompatibility,optical activity,piezo…     

犬骨髓间充质干细胞定向分化为内皮细胞的研究

应用密度梯度离心法分离狗骨髓间充质干细胞,建立诱导分化内皮细胞的方法及条件。密度梯度离心法分离狗骨髓间充质干细胞后,在体外经血管内皮细胞生长因子(Vascular endothelial growth factor,VEGF)、内皮细胞生长因子(Endothelial growth factor,EGF)等诱导后,分化形成内皮样细胞。结果表明:光镜下细胞单层融合生长,呈铺路石样形态,单个核位于中央。电镜下可见到Weibel-Palade小体,在细胞胞浆vWF染色阳性。骨髓间质干细胞,在体外可诱导分化成内皮细胞。     

Mesenchymal stem cell stimulation of tissue growth depends on differentiation state

The osteochondral microenvironment involves a complex milieu of cues that facilitate proper tissue development, homeostasis, and repair. This environment is disrupted in disease states such as osteoarthritis. Mesenchymal stem cells (MSCs) are under clinical investigation for the treatment of osteoarthritis given their capacity to differentiate into chondrocytes as well as to secrete a wide array of biologically active factors that support cell proliferation and tissue formation. In fact, the therapeutic action of these cells in many clinical applications is now thought to be at least partially dependent on their secretory capacity. Previous work demonstrated that MSCs were capable of stimulating chondrocyte growth and tissue production, whereas tissue-derived osteoblasts were not stimulatory. This study investigated the stimulatory capacity of MSCs during osteogenesis and the impact of MSC phenotype on cartilage stimulation. Cell interactions were examined in 3 coculture systems to confirm that trends were not dependent on material: traditional cell culture insert coculture, bilayered poly(ethylene glycol) gels, and a scaffold comprised of a layer of poly(ethylene glycol) polymerized onto a poly(lactic-co-glycolic) acid-based scaffold. Results demonstrated that MSCs predifferentiated toward an osteogenic phenotype for 3 days exhibited enhanced stimulation of chondrocyte extracellular matrix production, whereas longer periods of predifferentiation decreased the magnitude of observed stimulation. Further, tissue formation by the MSCs themselves showed greater dependence on the coculture system than the presence of other cells or length of predifferentiation.