组织工程骨的体外预血管化

背景：组织工程骨的应用是一种新兴的解决骨缺损的先进手段,但是由于受到植入体无营养代谢的限制,难以大量应用于临床。组织工程骨预血管化研究就是针对这一局限性,进行人工植入体的前瞻性和程序性的血管构建,以期解决植入体的营养代谢问题,国内外学者已取得大量研究成果。目的：对组织工程骨体外预血管化实验研究成果和发展趋势进行多层次分析探讨。方法：检索 CNKI 数据库和 Pubmed 数据库 2000 至 2012 年文献,中文检索词：组织工程骨,血管化,植入支架,成骨细胞,血管内皮细胞,共培养,英文检索词：bone engineering, endothelial cells, osteoblast, implant,cells co-culture。按照基础骨生理研究、体外细胞实验研究和材料学研究进行分类,完成组织工程骨体外预血管化研究的综述。结果与结论：共纳入 60 篇文献进行分析。此次检索的文献证明,在正常骨组织中,微血管的发生对成骨具有重要的调控作用,目前组织工程骨研究正在模拟人体内血管再生这一生理过程,设计完成了大量体外预血管化的实验,证实了血管预成型的应用有利于组织工程骨的体内存活和骨化,为组织工程骨临床应用指明了发展方向。     

Single-cell analysis of the cellular heterogeneity and interactions in the injured mouse spinal cord

The wound healing process that occurs after spinal cord injury is critical for maintaining tissue homeostasis and limiting tissue damage, but eventually results in a scar-like environment that is not conducive to regeneration and repair. A better understanding of this dichotomy is critical to developing effective therapeutics that target the appropriate pathobiology, but a major challenge has been the large cellular heterogeneity that results in immensely complex cellular interactions. In this study, we used single-cell RNA sequencing to assess virtually all cell types that comprise the mouse spinal cord injury site. In addition to discovering novel subpopulations, we used expression values of receptor–ligand pairs to identify signaling pathways that are predicted to regulate specific cellular interactions during angiogenesis, gliosis, and fibrosis. Our dataset is a valuable resource that provides novel mechanistic insight into the pathobiology of not only spinal cord injury but also other traumatic disorders of the CNS.     

Advances in tissue engineering through stem cell‐based co‐culture

Stem cells are the future in tissue engineering and regeneration. In a co‐culture, stem cells not only provide a target cell source with multipotent differentiation capacity, but can also act as assisting cells that promote tissue homeostasis, metabolism, growth and repair. Their incorporation into co‐culture systems seems to be important in the creation of complex tissues or organs. In this review, critical aspects of stem cell use in co‐culture systems are discussed. Direct and indirect co‐culture methodologies used in tissue engineering are described, along with various characteristics of cellular interactions in these systems. Direct cell–cell contact, cell–extracellular matrix interaction and signalling via soluble factors are presented. The advantages of stem cell co‐culture strategies and their applications in tissue engineering and regenerative medicine are portrayed through specific examples for several tissues, including orthopaedic soft tissues, bone, heart, vasculature, lung, kidney, liver and nerve. A concise review of the progress and the lessons learned are provided, with a focus on recent developments and their implications. It is hoped that knowledge developed from one tissue can be translated to other tissues. Finally, we address challenges in tissue engineering and regenerative medicine that can potentially be overcome via employing strategies for stem cell co‐culture use. Copyright © 2014 John Wiley & Sons, Ltd.     

Progress of co-culture systems in cartilage regeneration

ABSTRACT

Introduction: Cartilage tissue engineering has rapidly developed in recent decades, exhibiting promising potential to regenerate and repair cartilage. However, the origin of a large amount of a suitable seed cell source is the major bottleneck for the further clinical application of cartilage tissue engineering. The use of a monoculture of passaged chondrocytes or mesenchymal stem cells results in undesired outcomes, such as fibrocartilage formation and hypertrophy. In the last two decades, co-cultures of chondrocytes and a variety of mesenchymal stem cells have been intensively investigated in vitro and in vivo, shedding light on the perspective of co-culture in cartilage tissue engineering.

Areas covered: We summarize the recent literature on the application of heterologous cell co-culture systems in cartilage tissue engineering and compare the differences between direct and indirect co-culture systems as well as discuss the underlying mechanisms.

Expert opinion: Co-culture system is proven to address many issues encountered by monocultures in cartilage tissue engineering, including reducing the number of chondrocytes needed and alleviating the dedifferentiation of chondrocytes. With the further development and knowledge of biomaterials, cartilage tissue engineering that combines the co-culture system and advanced biomaterials is expected to solve the difficult problem regarding the regeneration of functional cartilage.     

In vitro engineering of cartilage

Because adult human cartilage shows poor capacity for repair and regeneration, innovative solutions are required for congenital and acquired degenerative cartilage lesions. Acquired lesions occur in young and old alike, the former being more at risk for sports-related injuries and the latter for age-related degenerative changes. Because cartilage is a relatively simple tissue with respect to its cellular homogeneity and avascularity, it has been a model for research of in vitro engineered tissues. Progress has been slow and obstructed on several levels. The adult chondrocyte has limited capacity for proliferation and has both catabolic and anabolic functions. These metabolic features must be controlled in order for engineered tissue to endure. Use of three-dimensional scaffolds can be combined with regulatory factors (cytokine, extracellular matrix [ECM], and mechanical) to optimize conditions for in vitro engineered cartilage. Cross-disciplinary interactions are likely to accelerate progress and to mediate application of advances made in other fields for consistently successful in vitro engineering of cartilage for all clinical needs.     

Growth factor loading on aliphatic polyester scaffolds

Cells, scaffolds and growth factors are three elements of tissue engineering. The success of tissue engineering methods relies on precise and dynamic interactions between cells, scaffolds and growth factors. Aliphatic polyester scaffolds are promising tissue engineering scaffolds that possess good mechanical properties, low immunogenicity, non-toxicity, and adjustable degradation rates. How growth factors can be loaded onto/into aliphatic polyester scaffolds and be constantly released with the required bioactivity to regulate cell growth and promote defect tissue repair and regeneration has become the main concern of tissue engineering researchers. In this review, the existing main methods of loading growth factors on aliphatic polyester scaffolds, the release behavior of loaded growth factors and their positive effects on cell, tissue repair and regeneration are introduced. Advantages and shortcomings of each method also are mentioned. It is still a great challenge to control the release of loaded growth factors at a certain time and at a concentration simulating the biological environment of native tissue.

Cells, scaffolds and growth factors are three elements of tissue engineering. Growth factors precisely controlled by a scaffold will be used in conjunction with the scaffolds and cells to repair and regenerate defect tissue.     

Advances in the formation, use and understanding of multi-cellular spheroids

Introduction: Developing in vitro models for studying cell biology and cell physiology is of great importance to the fields of biotechnology, cancer research, drug discovery, toxicity testing, as well as the emerging fields of tissue engineering and regenerative medicine. Traditional two-dimensional (2D) methods of mammalian cell culture have several limitations and it is increasingly recognized that cells grown in a three-dimensional (3D) environment more closely represent normal cellular function due to the increased cell-to-cell interactions, and by mimicking the in vivo architecture of natural organs and tissues. Areas covered: In this review, we discuss the methods to form 3D multi-cellular spheroids, the advantages and limitations of these methods, and assays used to characterize the function of spheroids. The use of spheroids has led to many advances in basic cell sciences, including understanding cancer cell interactions, creating models for drug discovery and cancer metastasis, and they are being investigated as basic units for engineering tissue constructs. As so, this review will focus on contributions made to each of these fields using spheroid models. Expert opinion: Multi-cellular spheroids are rich in biological content and mimic better the in vivo environment than 2D cell culture. New technologies to form and analyze spheroids are rapidly increasing their adoption and expanding their applications.     

壳聚糖支架上骨髓间充质干细胞的浓度及黏附生长

背景：组织工程的研究重点是利用少量的细胞经体外培养、扩增后, 在一定环境下附着在三维多孔支架上并良好生长为后期的组织器官重建修复做好基础。目的：对不同浓度兔骨髓间充质干细胞复合至壳聚糖支架用于组织工程再生修复进行评价。方法：取 5×105脱乙酰度为 95%的壳聚糖粉末通过冷冻干燥法制备壳聚糖支架,取 1×106,1×107,1×108,1×109 L-1细胞体积各 100 μL复合至壳聚糖支架后 1,3,5,7,9 d 以光镜,扫描电镜,MTT 法观察骨髓间充质干细胞的生长与分裂增殖情况。结果与结论：壳聚糖海绵状多孔支架为 5 mm×5 mm×3 mm,孔径 190~380 μm,平均孔径 290 μm,孔相通性较好,空隙率为（84.00±4.62）%。细胞/支架共培养 72 h 后各浓度细胞组均可渗入壳聚糖支架多孔结构内黏附生长。1×107,1×108,1× 109 L-1浓度细胞组在支架上成蔟生长,部分细胞与支架融合。结果提示,1×107,1×108L-1组细胞更利于骨髓间充质干细胞在壳聚糖支架的黏附生长,用于组织再生修复。     

脂肪干细胞三维生长骨组织工程复合体的构建

背景：组织工程支架是模仿细胞赖以生长代谢的细胞外基质而构建的支架和环境,其选择、制备以及种子细胞的选择是骨组织工程领域中的一项十分重要的课题.目的：利用几丁质凝胶/异种骨构建脂肪干细胞三维生长环境,并对其相容性进行研究.方法：从出生8d新西兰大白兔腹股沟获取脂肪组织,提取脂肪干细胞.脂肪干细胞经过体外成骨诱导分化后,种植于几丁质凝胶/异种骨,构建新型骨组织工程复合体,并将其设为细胞/几丁质凝胶/异种骨组;将脂肪干细胞直接种植于异种骨,构成脂肪干细胞/异种骨复合体作为细胞/异种骨组,单独异种骨为空白组.体外诱导2周后进行电镜扫描,观察细胞与支架的复合情况.结果与结论：镜扫描观察显示几丁质凝胶充分渗透于支架的空隙内,形成一个细胞的三维生长环境,使原本只能在材料上贴壁生长的脂肪干细胞能够在三维的环境中生长,为细胞外基质的再生提供足够的空间.几丁质凝胶/异种骨悬浮诱导后的脂肪干细胞,承载了更多的细胞,减少了细胞在载体中的流失,是一种较好的骨组织工程载体.     

The three R's of lung health and disease: repair, remodeling, and regeneration

All tissues and organs can be classified according to their ability to repair and regenerate during adult homeostasis and after injury. Some exhibit a high rate of constant cell turnover, while others, such as the lung, exhibit only low-level cell regeneration during normal adult homeostasis but have the ability to rapidly regenerate new cells after injury. Lung regeneration likely involves both activation of progenitor cells as well as cell replacement through proliferation of remaining undamaged cells. The pathways and factors that control this process and its role in disease are only now being explored. In this Review, we will discuss the connection between pathways required for lung development and how the lung responds to injury and disease, with a particular emphasis on recent studies describing the role for the epithelium in repair and regeneration.     

壳聚糖支架上骨髓间充质干细胞的浓度及黏附生长

背景:组织工程的研究重点是利用少量的细胞经体外培养、扩增后, 在一定环境下附着在三维多孔支架上并良好生长为后期的组织器官重建修复做好基础。目的:对不同浓度兔骨髓间充质干细胞复合至壳聚糖支架用于组织工程再生修复进行评价。方法:取 5×105脱乙酰度为 95%的壳聚糖粉末通过冷冻干燥法制备壳聚糖支架,取 1×106,1×107,1×108,1×109 L-1细胞体积各 100 μL复合至壳聚糖支架后 1,3,5,7,9 d 以光镜,扫描电镜,MTT 法观察骨髓间充质干细胞的生长与分裂增殖情况。结果与结论:壳聚糖海绵状多孔支架为 5 mm×5 mm×3 mm,孔径 190~380 μm,平均孔径 290 μm,孔相通性较好,空隙率为(84.00±4.62)%。细胞/支架共培养 72 h 后各浓度细胞组均可渗入壳聚糖支架多孔结构内黏附生长。1×107,1×108,1× 109 L-1浓度细胞组在支架上成蔟生长,部分细胞与支架融合。结果提示,1×107,1×108L-1组细胞更利于骨髓间充质干细胞在壳聚糖支架的黏附生长,用于组织再生修复。     

Stem cells for tendon tissue engineering and regeneration

Importance of the field: Tendon injuries are common especially in sports activities, but tendon is a unique connective tissue with poor self-repair capability. With advances in stem cell biology, tissue engineering is becoming increasingly powerful for tissue regeneration. Stem cells with capacity of multipotency and self-renewal are an ideal cell source for tissue engineering.

Areas covered in this review: This review focus on discussing the potential strategies including inductive growth factors, bio-scaffolds, mechanical stimulation, genetic modification and co-culture techniques to direct tendon-lineage differentiation of stem cells for complete tendon regeneration. Attempting to use embryonic stem cells as seed cells for tendon tissue engineering have achieved encouraging results. The combination of chemical and physical signals in stem cell microenvironment could be regulated to induce differentiation of the embryonic stem cells into tendon.

What the reader will gain: We summarize fundamental questions, as well as future directions in tendon biology and tissue engineering.

Take home message: Multifaceted technologies are increasingly required to control stem cell differentiation, to develop novel stem cell-based therapy, and, ultimately, to achieve more effective repair or regeneration of injured tendons.     

体外构建工程化心肌组织的研究与应用

背景：＂工程化心肌组织＂是应用组织工程的方法,构建出具有天然心肌组织特征的心肌,将它移植到体内,最终修复或完全替代病损组织。但以往研究获得的工程化心肌组织存在较多的缺陷,仍不能满足实际需要。目的：总结体外构建工程化心肌组织方法的研究进展。方法：由第一作者用计算机检索中国期刊全文数据库（CNKI：2000/2010）和Medline（2000/2010）数据库,检索词分别为＂心肌,组织工程,心肌构建物＂和＂Myocardial Constructionmaterials,Tissue Engineering,Myocardial＂。从种子细胞、支架材料、体外培养环境和生物反应体系、工程化心肌组织的再血管化、移植实验5方面进行总结,对不同的种子细胞及生物支架材料和体外培养的环境、移植工程化组织的再血管化等方面进行了介绍。共检索到150篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章。结果与结论：适合心肌细胞生存和心肌细胞形成的新型生物活性支架,理想的种子细胞、体外培养环境与生物反应体系、移植工程化组织的再血管化,动物移植实验等方面都是组织工程化心肌组织再造的关键所在。构建的组织工程化心肌组织应同时具备良好的收缩功能、稳定的电生理特性、力学强度和柔韧性、无免疫原性及自身能血管化或在移植后能迅速血管化的条件,但未来还需进一步研究。     

体外构建工程化心肌组织的研究与应用

背景:"工程化心肌组织"是应用组织工程的方法,构建出具有天然心肌组织特征的心肌,将它移植到体内,最终修复或完全替代病损组织。但以往研究获得的工程化心肌组织存在较多的缺陷,仍不能满足实际需要。目的:总结体外构建工程化心肌组织方法的研究进展。方法:由第一作者用计算机检索中国期刊全文数据库(CNKI:2000/2010)和Medline(2000/2010)数据库,检索词分别为"心肌,组织工程,心肌构建物"和"Myocardial Constructionmaterials,Tissue Engineering,Myocardial"。从种子细胞、支架材料、体外培养环境和生物反应体系、工程化心肌组织的再血管化、移植实验5方面进行总结,对不同的种子细胞及生物支架材料和体外培养的环境、移植工程化组织的再血管化等方面进行了介绍。共检索到150篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章。结果与结论:适合心肌细胞生存和心肌细胞形成的新型生物活性支架,理想的种子细胞、体外培养环境与生物反应体系、移植工程化组织的再血管化,动物移植实验等方面都是组织工程化心肌组织再造的关键所在。构建的组织工程化心肌组织应同时具备良好的收缩功能、稳定的电生理特性、力学强度和柔韧性、无免疫原性及自身能血管化或在移植后能迅速血管化的条件,但未来还需进一步研究。     

Mechanisms of renal cell repair and regeneration after acute renal failure

In many cases, acute renal failure (ARF) is the result of proximal tubular cell injury and death and can arise in a variety of clinical situations, especially following renal ischemia and drug or toxicant exposure. Although much research has focused on the cellular events leading to ARF, less emphasis has been placed on the mechanisms of renal cell repair and regeneration, although ARF is reversed in over half of those who acquire it. Studies using in vivo and in vitro models have demonstrated the importance of proliferation, migration, and repair of physiological functions of injured renal proximal tubular cells (RPTC) in the reversal of ARF. Growth factors have been shown to produce migration and proliferation of injured RPTC, although the specific mechanisms through which growth factors promote renal regeneration in vivo are unclear. Recently, interactions between integrins and extracellular matrix proteins such as collagen IV were shown to promote the repair of physiological functions in injured RPTC. Specifically, collagen IV synthesis and deposition following cellular injury restored integrin polarity and promoted repair of mitochondrial function and active Na(+) transport. Furthermore, exogenous collagen IV, but not collagen I, fibronectin, or laminin, promoted the repair of physiological functions without stimulating proliferation. These findings suggest the importance of establishing and/or maintaining collagen IV-integrin interactions in the stimulation of repair of physiological functions following sublethal cellular injury. Furthermore, the pathway that stimulates repair is distinct from that of proliferation and migration and may be a viable target for pharmacological intervention.     

细胞共培养在组织工程研究中的应用及价值

背景:细胞共培养即最大程度地模拟机体内环境,在体外观察细胞与细胞之间的相互作用,是组织工程研究的热点.目的:总结并讨论细胞共培养研究在组织工程研究的应用及价值.方法:由第一作者用计算机检索中国期刊全文数据库(CNKI:2000/2010)和Medline数据库(2000/2010),检索词分别为"细胞共培养,骨髓间充质干细胞,神经干细胞,软骨细胞,组织工程"和"Cells co-culture,Bone marrow stem cells,Neural stem cells,Cartilage",语言分别设定为中文和英文.从细胞共培养在骨髓间充值干细胞、神经干细胞和软骨细胞3方面进行总结,对细胞共培养在组织工程研究及应用方面进行介绍.结果与结论:共检索到182篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章.结果表明大量细胞共培养的研究,都围绕着最大程度地模拟体内环境、维持体内性状,观察细胞与细胞之间相互作用,很多体外细胞共培养的研究结果和进展对于深入了解共培养有重要的指导和参考价值,但有关共培养的新方法新技术,研究结果,最新动向和研究热点但仍需进一步分析和总结.     

组织工程支架及其修复技术在脊髓损伤中的应用

目的:就近年来组织工程修复脊髓损伤进展进行归纳总结.资料来源:应用计算机检索PubMed数据库及CNKI数据库中1999-09/2009-09与组织工程修复脊髓损伤相关的文章,在标题和摘要中以"spinal cord injury,tissue engineering"或"脊髓损伤,组织工程"为检索词进行检索.同一领域文献则选择近期发表或发表在权威杂志文章.资料选择:选择组织工程修复脊髓损伤方面的最新相关文献,最终纳入29篇符合标准的文献.结局评价指标:组织工程种子细胞选择,组织工程脊髓对支架材料的要求,再生所需神经营养因子,再生所需特殊内环境构建.结果:组织工程化脊髓种子细胞包括许旺细胞、嗅鞘细胞、胚胎干细胞、神经干细胞以及骨髓基质干细胞等.目前支架材料主要为合成材料或改性天然材料,如聚羟基乙酸、聚乳酸和乳酸/羟基乙酸共聚物等.表面被修饰后,利于细胞黏附和营养因子的聚集.将一些促进神经生长因子或抑制神经生长因子的抗体与聚乙二醇加工成耦合体作为组织工程支架,联合干细胞移植、并施加电场/磁场刺激修复脊髓损伤可能是组织工程修复脊髓损伤的有希望途径.结论:选择最佳组织工程组分是修复脊髓损伤重要依据.     

细胞共培养在组织工程研究中的应用及价值

背景：细胞共培养即最大程度地模拟机体内环境,在体外观察细胞与细胞之间的相互作用,是组织工程研究的热点。目的：总结并讨论细胞共培养研究在组织工程研究的应用及价值。方法：由第一作者用计算机检索中国期刊全文数据库（CNKI：2000/2010）和Medline数据库（2000/2010）,检索词分别为＂细胞共培养,骨髓间充质干细胞,神经干细胞,软骨细胞,组织工程＂和＂Cellsco-culture,Bone marrow stem cells,Neural stem cells,Cartilage＂,语言分别设定为中文和英文。从细胞共培养在骨髓间充值干细胞、神经干细胞和软骨细胞3方面进行总结,对细胞共培养在组织工程研究及应用方面进行介绍。结果与结论：共检索到182篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章。结果表明大量细胞共培养的研究,都围绕着最大程度地模拟体内环境、维持体内性状,观察细胞与细胞之间相互作用,很多体外细胞共培养的研究结果和进展对于深入了解共培养有重要的指导和参考价值,但有关共培养的新方法新技术,研究结果,最新动向和研究热点但仍需进一步分析和总结。     

组织工程表皮与单核白血病细胞共培养的致敏性检测模型

背景：大量研究表明体外构建的组织工程皮肤可用于化学物质的刺激性检测。目的：构建组织工程表皮和单核白血病细胞共培养体外模型,并用致敏物初步验证。方法：利用人源性角质形成细胞构建组织工程表皮,和单核白血病细胞进行共培养,干预24h后,ELISA法检测空白对照组,溶剂对照组,二硝基氟苯处理组和十二烷基硫酸钠处理组培养液中白细胞介素1β的质量浓度,流式细胞术检测各组中单核白血病细胞表面标记物CD86和CD54的平均荧光强度。结果与结论：角质形成细胞气液界面培养14d后,苏木精-伊红染色结果显示构建的组织工程表皮含有8～10层细胞结构,泛角蛋白免疫组化染色阳性。二硝基氟苯处理组培养液中白细胞介素1β质量浓度,单核白血病细胞表面标记物CD86和CD54的平均荧光强度均高于溶剂对照组（P〈0.05）。实验成功构建了组织工程表皮和单核白血病细胞共培养的致敏物检测模型。     

Muscle injury and repair

Muscle injury triggers a sequence of events that begin with a host inflammatory response that is followed by muscle fiber regeneration and new collagen synthesis. The inflammatory response involves at least three types of cells, including neutrophils, ED1+ macrophages, and ED2+ macrophages. A host of growth factors and cytokines appear to play a role in the inflammatory process and repair of the damaged tissue. Satellite cells play an integral role in normal development of skeletal muscle by providing a source for postmitotic myonuclei. In addition, the satellite cell is essential to the repair of injured muscle by serving as a source of myoblasts for fiber regeneration. At the same time muscle fiber regeneration is occurring, there is expression of types I and III collagen that under certain circumstances can lead to scarring and fibrosis. Current studies of treatment of muscle injury often incorporate investigations of basic principles of injury and repair together with clinical experience and principles in an effort to coordinate basic science and outcome studies.