中枢神经再生材料研究进展

首先介绍了目前中枢神经再生面临的问题和应对策略,然后系统地综述了脑再生和脊髓再生修复材料的发展。研究发现,成人中枢神经系统内存的神经干细胞和具有特定分化方向的前体细胞具有潜在的、巨大的修复功能;生物支架材料与神经干细胞的联合使用能够较好地控制细胞微环境,有望提高细胞移植后的存活状况,促进中枢神经再生。最后,结合现在中枢神经再生的研究热点——神经干细胞,阐述了中枢神经再生材料调控干细胞的研究进展和潜能,为联合应用生物材料与干细胞促进中枢再生提供了参考。     

三维成球培养优化间充质干细胞的研究进展

间充质干细胞(mesenchymal stem cells,MSCs)源于发育早期的中胚层,因其来源广泛、具有多向分化潜能、低免疫原性和自我更新能力,在组织工程和再生医学应用中显示出巨大的潜力,也是当前基础研究和临床研究中应用最多的一类干细胞。然而,间充质干细胞的临床应用面临许多挑战,比如治疗所需细胞数量巨大,细胞质量存在异质性,细胞体内移植后存活率低,以及二维(two-dimensional,2D)贴壁培养导致间充质干细胞特征衰减等。三维(three-dimensional,3D)成球培养可以更好地模拟体内微环境,且大量的研究证明,3D成球培养增强了间充质干细胞的细胞存活和因子分泌能力,促进了干细胞特征维持、细胞迁移和血管生成,在临床医学领域具有广阔的应用前景。基于此,综述了体外3D成球培养的方法、3D成球培养优化的间充质干细胞的生物学特性及应用,并对3D成球培养未来的研究方向进行展望。     

表达绿色荧光蛋白基因的花鲈胚胎干细胞株的建立及其体外分化

以带有绿色荧光标记的基因(pCMV-EGFP)为报告基因,用Genejammer、Genejuice和Metafectene三种脂质体介导花鲈胚胎干细胞(LJES1)的基因转移.实验发现,Genejammer介导的细胞转化效率最高,高达27.3%,其余分别为12.1%和5.3%.转移绿色荧光蛋白(GFP)基因的LJES1细胞经过药物筛选和单克隆化培养,获得了表达GFP基因的阳性克隆细胞株,经PCR对GFP阳性细胞株的基因组DNA及提取的RNA扩增,获得了目的条带,证实了GFP基因已经整合到LJES1细胞的基因组中,并获得了正常的表达.通过体外诱导,GFP阳性细胞能够分化为神经细胞、肌肉细胞、成纤维细胞等,用悬滴法培养获得了GFP阳性细胞的拟胚体,证实了经过长期的药物筛选后,LJES1细胞仍然保持着发育的多能性.这一研究,为进一步利用海水鱼类胚胎干细胞进行遗传操作及基因工程的研究提供了方法上的探索.     

干细胞命运示踪:一种新型近红外二区荧光/生物发光双模活体光学影像技术

正干细胞再生医学的发展正在为现代医学带来一场变革,并被认为是治疗人类组织、器官缺损和病变等重大疾病最具前景的方法。具有高度自我更新和多向分化潜能的干细胞是组织和器官再生所不可或缺的,是再生医学的基础。对于干细胞移植疗法,如何让移植干细胞准确分布到损伤部位并维持其高的存活率以保障干细胞疗法的疗效,以及如何保障     

建筑废弃物再生利用的相关性能及应用前景分析

近年来,我国城市化进程的推进和新农村建设的发展,不但使得国家能源负担日益加重,而且还随之产生了大量的建筑废弃物需进行处理,这些建筑废弃物已在城市固体垃圾中占有了一个相当大的比例,并且还在不断增长当中。对此,我国政府越来越重视节能和资源的回收利用问题,大力提倡和发展建筑废弃物的再利用。再生混凝土和再生砂浆作为新型的节约型建筑材料,对于保护环境、节约资源、发展生态建筑具有重要意义,近年来国内外学者开展了相关研究,并取得一定成果。本文通过分析再生混凝土、再生砂浆等主要再生建筑废弃物的力学性能及其破坏机理,以期为再生废弃物的进一步深入研究和应用提供更完善的科学依据。     

基于基因芯片的人参作用脑组织抗衰老基因表达谱的研究

针对D-半乳糖造成的小鼠亚急性衰老模型,采用Cy3和Cy5两种不同的荧光染料通过逆转录反应将人参作用前后的小鼠脑组织细胞mRNA分别标记成两种探针,混合后与小鼠基因芯片杂交。借助计算机分析扫描芯片荧光信号图像,寻找出经人参作用后表达有差异的基因。据此研究人参水煎剂对衰老模型小鼠脑组织细胞基因表达的影响,以深入探讨其作用的分子机制。研究表明,微矩阵基因芯片在研究人参作用前后衰老模型小鼠脑细胞基因表达的改变时,具有快速、高通量、高敏度等特点,为运用生物芯片技术研究中药抗衰老机理提供了有价值的方法。     

RAC材料应用现状及研究进展

介绍了建筑废弃物定义、时代特征以及再生骨料混凝土的应用现状;通过评析再生骨料特性探讨了再生骨料的引入对混凝土材料基本力学性能、干缩性能的影响;并在总结再生骨料混凝土国内外研究现状的基础上指出,再生骨料混凝土未来研究重点应该还是主要攻克建筑废弃物循环利用的技术难题和继续研究再生骨料微观结构对再生骨料混凝土性能的影响。     

转轮除湿空调系统及吸附剂再生特性研究进展

转轮除湿空调系统可实现温湿独立控制,与传统空调相比具有舒适、节能、环保等优点。本文阐述了转轮除湿空调系统及其吸附剂再生特性的研究进展,包括转轮除湿空调系统形式及其特性、转轮除湿性能和吸附剂再生方式及再生特性等内容。最后,指出了目前转轮除湿空调系统的研究不足,并对转轮除湿空调系统进一步研究方向提出了建议。     

砂率对高强再生混凝土的力学及干燥收缩性能影响研究

再生混凝土的综合利用可缓解矿石资源压力,实现低碳循环可持续经济。该研究采用砂率（34%,36%,38%,40%）和再生骨料替代率（0,30%,50%）为控制变量,以抗压强度、抗拉强度、抗折强度及干燥收缩变形为指标,详细探讨砂率和再生骨料替代率对高强再生混凝土的性能影响规律。研究表明：高强再生混凝土的力学强度均随着再生粗骨料的增加而逐渐降低,适量的砂率会产生高强度的再生混凝土坍落度,可以提升再生混凝土的密实度,脆性和塑性变形能力,并提高其力学强度。高强度再生混凝土的干缩率变化率在90 d后逐渐趋于稳定,砂率和干缩率的变化呈良好的线性关系。增加砂的比例能在一定程度上降低再生粗骨料对高强度再生混凝土干缩的影响。     

吸附材料再生机理研究进展

随着吸附材料日趋广泛的应用,其后处理成为重要议题。再生是处理吸附材料的有效途径,具有节约资源、减少环境污染等现实意义。再生机理作为再生技术的重要内容,已得到关注。阐述了热再生、生物再生、电化学再生、微波加热再生、超临界流体再生、超声波再生、光催化再生和等离子体再生等几种再生方法机理,总结了研究人员对各再生方法机理的不同认识,指出了各再生技术的优缺点。最后,从机理角度展望了未来再生研究的方向。     

人组织型纤溶酶原激活剂乳腺定位表达载体的构建及其表达

将编码人组织型纤溶酶原激活剂的１７６６ｂｐ基因片段插入大鼠β－乳酪蛋白启动子的下游及ｐＳＶＬ质粒的ＰｏｌｙＡ上游。构建了ｐβ－Ｃａｓｅｉｎ－ＰＡ、,ｐβ－Ｃａｓｅｉｎ－ＰＡ２两个乳腺定位表达载体。将其分别与脂质体混合制备转染液后,直接注入妊娠２９天的青紫蓝母兔乳腺中。结果表明：两种载体均能在乳腺中表达,且具有溶纤活性,表达量在２００￣５００ｇｎ／ｍｌ之间,这不仅证明了所构建载体可用于转基因乳腺生物     

诱导性多潜能干细胞(iPS)研究：现状与展望

通过特定的基因组合与转染可以将已分化的体细胞诱导重编程为多潜能干细胞(iPS),是近年来干细胞研究领域最令人瞩目的一项新的干细胞制造技术.与胚胎干细胞(ES)不同,iPS细胞的制造不需要毁损胚胎,因而不会涉及更多的伦理学问题.iPS的出现不仅为体细胞重编程去分化机制的研究注入了新的活力,而且为疾病发生发展相关机制研究与特异的细胞治疗,特别是再生医学带来新的曙光.目前,iPS的研究尚处于初级阶段,文章就iPS的研究现状与应用前景进行综述和展望.     

Artificial stem cell niches

Stem cells are characterized by their dual ability to reproduce themselves (self-renew) and specialize (differentiate), yielding a plethora of daughter cells that maintain and regenerate tissues. In contrast to their embryonic counterparts, adult stem cells retain their unique functions only if they are in intimate contact with an instructive microenvironment, termed stem cell niche. In these niches, stem cells integrate a complex array of molecular signals that, in concert with induced cell-intrinsic regulatory networks, control their function and balance their numbers in response to physiologic demands. This progress report provides a perspective on how advanced materials technologies could be used (i) to engineer and systematically analyze specific aspects of functional stem cells niches in a controlled fashion in vitro and (ii) to target stem cell niches in vivo. Such "artificial niches" constitute potent tools for elucidating stem cell regulatory mechanisms with the capacity to directly impact the development of novel therapeutic strategies for tissue regeneration.     

Genomic expression of mesenchymal stem cells to altered nanoscale topographies.

The understanding of cellular response to the shape of their environment would be of benefit in the development of artificial extracellular environments for potential use in the production of biomimetic surfaces. Specifically, the understanding of how cues from the extracellular environment can be used to understand stem cell differentiation would be of special interest in regenerative medicine.In this paper, the genetic profile of mesenchymal stem cells cultured on two osteogenic nanoscale topographies (pitted surface versus raised islands) are compared with cells treated with dexamethasone, a corticosteroid routinely used to stimulate bone formation in culture from mesenchymal stem cells, using 19k gene microarrays as well as 101 gene arrays specific for osteoblast and endothelial biology.The current studies show that by altering the shape of the matrix a cell response (genomic profile) similar to that achieved with chemical stimulation can be elicited. Here, we show that bone formation can be achieved with efficiency similar to that of dexamethasone with the added benefit that endothelial cell development is not inhibited. We further show that the mechanism of action of the topographies and dexamethasone differs. This could have an implication for tissue engineering in which a simultaneous, targeted, development of a tissue, such as bone, without the suppression of angiogenesis to supply nutrients to the new tissue is required. The results further demonstrate that perhaps the shape of the extracellular matrix is critical to tissue development.     

Stem cell homing-based tissue engineering using bioactive materials

Tissue engineering focuses on repairing tissue and restoring tissue functions by employing three elements: scaffolds, cells and biochemical signals. In tissue engineering, bioactive material scaffolds have been used to cure tissue and organ defects with stem cell-based therapies being one of the best documented approaches. In the review, different biomaterials which are used in several methods to fabricate tissue engineering scaffolds were explained and show good properties (biocompatibility, biodegradability, and mechanical properties etc.) for cell migration and infiltration. Stem cell homing is a recruitment process for inducing the migration of the systemically transplanted cells, or host cells, to defect sites. The mechanisms and modes of stem cell homing-based tissue engineering can be divided into two types depending on the source of the stem cells: endogenous and exogenous. Exogenous stem cell-based bioactive scaffolds have the challenge of long-term culturing in vitro and for endogenous stem cells the biochemical signal homing recruitment mechanism is not clear yet. Although the stem cell homing-based bioactive scaffolds are attractive candidates for tissue defect therapies, based on in vitro studies and animal tests, there is still a long way before clinical application.     

Artificial extracellular matrix for embryonic stem cell cultures: a new frontier of nanobiomaterials

Abstract

Nanobiomaterials can play a central role in regenerative medicine and tissue engineering by facilitating cellular behavior and function, such as those where extracellular matrices (ECMs) direct embryonic stem (ES) cell morphogenesis, proliferation, differentiation and apoptosis. However, controlling ES cell proliferation and differentiation using matrices from natural sources is still challenging due to complex and heterogeneous culture conditions. Moreover, the systemic investigation of the regulation of self-renewal and differentiation to lineage specific cells depends on the use of defined and stress-free culture conditions. Both goals can be achieved by the development of biomaterial design targeting ECM or growth factors for ES cell culture. This targeted application will benefit from expansion of ES cells for transplantation, as well as the production of a specific differentiated cell type either by controlling the differentiation in a very specific pathway or by elimination of undesirable cell types.     

Self-assembling peptide nanofiber hydrogels for central nervous system regeneration

Central nervous system (CNS) presents a complex regeneration problem due to the inability of central neurons to regenerate correct axonal and dendritic connections. However, recent advances in developmental neurobiology, cell signaling, cell--matrix interaction, and biomaterials technologies have forced a reconsideration of CNS regeneration potentials from the viewpoint of tissue engineering and regenerative medicine. The applications of a novel tissue regeneration-inducing biomaterial and stem cells are thought to be critical for the mission. The use of peptide nanofiber hydrogels in cell therapy and tissue engineering offers promising perspectives for CNS regeneration. Self-assembling peptide undergo a rapid transformation from liquid to gel upon addition of counterions or pH adjustment, directly integrating with the host tissue. The peptide nanofiber hydrogels have mechanical properties that closely match the native central nervous extracellular matrix, which could enhance axonal growth. Such materials can provide an optimal three dimensional microenvironment for encapsulated cells. These materials can also be tailored with bioactive motifs to modulate the wound environment and enhance regeneration. This review intends to detail the recent status of self-assembling peptide nanofiber hydrogels for CNS regeneration.     

Constrained optimization of divisional load in hierarchically organized tissues during homeostasis

It has been hypothesized that the structure of tissues and the hierarchy of differentiation from stem cell to terminally differentiated cell play a significant role in reducing the incidence of cancer in that tissue. One specific mechanism by which this risk can be reduced is by minimizing the number of divisions—and hence the mutational risk—that cells accumulate as they divide to maintain tissue homeostasis. Here, we investigate a mathematical model of cell division in a hierarchical tissue, calculating and minimizing the divisional load while constraining parameters such that homeostasis is maintained. We show that the minimal divisional load is achieved by binary division trees with progenitor cells incapable of self-renewal. Contrary to the protection hypothesis, we find that an increased stem cell turnover can lead to lower divisional load. Furthermore, we find that the optimal tissue structure depends on the time horizon of the duration of homeostasis, with faster stem cell division favoured in short-lived organisms and more progenitor compartments favoured in longer-lived organisms.     

Human dental follicle precursor cells of wisdom teeth: isolation and differentiation towards osteoblasts for implants with and without scaffolds

The human dental follicle is a developmental precursor for essential periodontal tissues such as periodontal ligament and root development. These cells can be expected to differentiate into several lineages, since they are derived from mesoderm. Especially the differentiation towards the osteogenic lineage could be interesting for tissue regeneration with or without growing on scaffold biomaterials in autologous transplantation for reconstruction of large bone defects and incorporation of teeth implants. Here we demonstrate a fast and efficient method to isolate stem cells out of the dental follicle of wisdom teeth and their more determined lineage specific commitment into the osteogenic direction. Typical markers confirmed the stem cell character of the isolated and differentiated cells and the successful differentiation has been verified in addition after lineage specific induction using corresponding stainings. In order to evaluate the quality of the cells microbiological investigations were performed and showed that all samples contained microbial species. Pre‐treatment of patients with antibiotics reduced the number of microorganisms to a minimum but did not suffice to eliminate all bacteria. The predominantly found species were gram‐positive cocci being either catalase‐positive and oxidase‐negative or catalase‐ and oxidase‐negative. Most microorganisms belonged to the families of Streptococcaceae and Staphylococcaceae. During cultivation of the stem cells, the contamination with microorganisms could be easily suppressed by usage of standard cell culture conditions with penicillin and streptomycin.