The potential role of tissue‐engineered urethral substitution: clinical and preclinical studies

Urethral strictures and anomalies remain among the difficult problems in urology, with urethroplasty procedures being the most effective treatment options. The two major types of urethroplasty are anastomotic urethroplasty and widening the urethral lumen using flaps or grafts (i.e. substitution urethroplasty). However, no ideal material for the latter has been found so far. Designing and selecting such a material is a necessary and challenging endeavour, driving the need for further bioengineered urethral tissue research. This article reviews currently available studies on the potentialities of tissue engineering in urethral reconstruction, in particular those describing the use of both acellular and recellularized tissue‐engineered constructs in animal and human models. Possible future developments in this field are also discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Multi‐modal imaging for assessment of tissue‐engineered bone in a critical‐sized calvarial defect mouse model

Tissue‐engineered bone (TEB) analysis in vivo relies heavily on tissue histological and end‐point evaluations requiring the sacrifice of animals at specific time points. Due to differences in animal response to implanted tissues, the conventional analytical methods to evaluate TEB can introduce data inconsistencies. Additionally, the conventional methods increase the number of animals required to provide an acceptable statistical power for hypothesis testing. Alternatively, our non‐invasive optical imaging allows for the longitudinal analysis of regenerating tissue, where each animal acts as its own control, thus reducing overall animal numbers. In our 6 month feasibility study, TEB, consisting of a silk protein scaffold with or without differentiated mesenchymal stem cells, was implanted in a critical‐sized calvarial defect mouse model. Osteogenesis of the TEB was monitored through signal variation, using magnetic resonance imaging (MRI) and near‐infrared (NIR) optical imaging with IRDye® 800CW BoneTag^TM (800CW BT, a bone‐specific marker used to label osteogenically differentiated mesenchymal stem cells and mineralization). Histological endpoint measurements and computed tomography (CT) were used to confirm imaging findings. Anatomical MRI revealed decreased signal intensity, indicating mineralization, in the TEB compared to the control (i.e. silk scaffold only) at various growth stages. NIR optical imaging results demonstrated a signal intensity increase of the TEB compared to control. Interpretation of the imaging results were confirmed by histological analysis. Specifically, haematoxylin and eosin staining revealing de novo bone in TEB showed that 80% of the defect was covered by TEB, while only 40% was covered for the control. Taken together, these results demonstrate the potential of multi‐modal non‐invasive imaging to visualize and quantify TEB for the assessment of regenerative medicine strategies. Copyright © 2015 John Wiley & Sons, Ltd.     

The immunology of corneal xenotransplantation: a review of the literature

As the worldwide demand for human donor corneas far exceeds supply, there is a need for a new source of corneas for clinical transplantation. Genetically engineered pigs may prove to be that new source, particularly as current evidence indicates that the anatomical and biomechanical properties of human and pig corneas are similar. Experience with clinical and experimental corneal xenotransplantation has been comprehensively reviewed and is summarized. Studies in small and large animal models have documented that both humoral and cellular immune responses play roles in xenograft rejection. Recent progress in the genetic manipulation of pigs has led to the prospect that clinical corneal xenotransplantation, in the absence of exogenous immunosuppressive therapy, may become successful in the foreseeable future.     

Screening for Oxidative Stress Elicited by Engineered Nanomaterials: Evaluation of Acellular DCFH Assay

The DCFH assay is commonly used for measuring free radicals generated by engineered nanomaterials (ENM), a well-established mechanism of ENM toxicity. Concerns exist over susceptibility of the DCFH assay to: assay conditions, adsorption of DCFH onto ENM, fluorescence quenching and light scattering. These effects vary in magnitude depending on ENM physiochemical properties and concentration. A rigorous evaluation of this method is still lacking. The objective was to evaluate performance of the DCFH assay for measuring ENM-induced free radicals. A series of diverse and well-characterized ENM were tested in the acellular DCFH assay. We investigated the effect of sonication conditions, dispersion media, ENM concentration, and the use of horseradish peroxidase (HRP) on the DCFH results. The acellular DCFH assay suffers from high background signals resulting from dye auto-oxidation and lacks sensitivity and robustness. DCFH oxidation is further enhanced by HRP. The number of positive ENM in the assay and their relative ranking changed as a function of experimental conditions. An inverse dose relationship was observed for several Carbon-based ENM. Overall, these findings indicate the importance of having standardized assays for evaluating ENM toxicity and highlights limitations of the DCFH assay for measuring ENM-induced free radicals.     

组织工程皮肤细胞对朗格汉斯细胞表型的影响

目的:研究异体组织工程皮肤种子细胞(角质形成细胞、成纤维细胞)对朗格汉斯细胞的表型影响.方法:外周血单个核细胞在粒细胞巨噬细胞集落刺激因子(GM-CSF)、白介素4(IL-4)和转化生长因子β1(TGF-β1)的诱导下培养出朗格汉斯细胞.培养的朗格汉斯细胞与异体组织工程皮肤种子细胞共同培养后,检测其表型变化情况.随后将朗格汉斯细胞与淋巴细胞共培养后检测淋巴细胞的增殖程度.结果:诱导培养的朗格汉斯细胞低表达HLA-DR、CD80和CD86,不表达CD83.与异体组织工程皮肤种子细胞共培养后朗格汉斯细胞表型无明显变化,共培养后的朗格汉斯细胞无法刺激自体淋巴细胞增殖.结论:与异体组织工程皮肤种子细胞共培养后,朗格汉斯细胞仍保持不成熟的状态,这提示组织工程皮肤种子细胞免疫原性较低,移植后不易引起宿主的免疫排斥反应.     

Report from the fifth National Cancer Institute Mouse Models of Human Cancers Consortium Nervous System Tumors Workshop

Cancers of the nervous system are clinically challenging tumors that present with varied histopathologies and genetic etiologies. While the prognosis for the most malignant of these tumors is essentially unchanged despite decades of basic and translational science research, the past few years have witnessed the identification of numerous targetable molecular alterations in these cancers. With the advent of advanced genomic sequencing methodologies and the development of accurate small-animal models of these nervous system cancers, we are now ideally positioned to develop personalized therapies that target the unique cellular and molecular changes that define their formation and drive their continued growth. Recently, the National Cancer Institute convened a workshop to advance our understanding of nervous system cancer mouse models and to inform clinical trials by reconsidering these neoplasms as complex biological systems characterized by heterogeneity at all levels.     

兔骨髓基质干细胞复合珊瑚修复兔骨缺损的实验研究

目的：对天然珊瑚（natural coral，NC）的细胞相容性进行研究，观察其与兔骨髓基质干细胞（bone marrow stem cells．BMSCs）复合后修复兔桡骨缺损的能力。方法：从兔股骨转子窝抽取骨髓，体外培养扩增，将其接种于珊瑚上，一组分别于1、3、7、14天取材，扫描电镜（SEM）观察细胞在支架上的生长情况，另一组进行诱导，培养5天后接种于兔桡骨1cm缺损中．以珊瑚填充桡骨缺损组作为对照。结果：从第1天开始，珊瑚表面即有细胞贴壁，随时间延长，细胞数量增多，到14天时有大量胶原形成。种植于兔桡骨缺损者4周时珊瑚降解不明显，骨组织形成较少，8周时见珊瑚部分降解．骨组织形成较多，20周时珊瑚完全降解，骨折愈合。结论：BMSCs与NC复合可构建组织工程骨，能修复骨缺损，并具有成骨可靠、来源广泛、成本低廉等特点．     

聚二乙醇酸与Degrapol对肌成纤维细胞粘附、生长的影响

目的　寻找一种更加理想的人工降解材料 ,为改进人工降解材料提供理论依据。方法　比较聚二乙醇酸( PGA)与 Degrapol对肌成纤维细胞粘附、生长、繁殖及产生胶原的影响。结果　 1细胞种植 2周和 6周 ,PGA组的细胞计数明显多于 Degrapol组 ( P<0 .0 1) ;2 6周 PGA组胶原含量明显高于 Degrapol组 ( P<0 .0 1) ;3 2周肌成纤维细胞粘附于 PGA上 ,分布广泛 ;6周后 PGA降解 ,胶原含量丰富。而 Degrapol则部分降解 ,胶原含量较少。结论　Degrapol作为一种新型人工降解材料 ,若用于构建组织工程心脏瓣膜 ,在细胞亲和力等方面尚有待进一步改进     

Neural tissue engineering options for peripheral nerve regeneration

Tissue engineered nerve grafts (TENGs) have emerged as a potential alternative to autologous nerve grafts, the gold standard for peripheral nerve repair. Typically, TENGs are composed of a biomaterial-based template that incorporates biochemical cues. A number of TENGs have been used experimentally to bridge long peripheral nerve gaps in various animal models, where the desired outcome is nerve tissue regeneration and functional recovery. So far, the translation of TENGs to the clinic for use in humans has met with a certain degree of success. In order to optimize the TENG design and further approach the matching of TENGs with autologous nerve grafts, many new cues, beyond the traditional ones, will have to be integrated into TENGs. Furthermore, there is a strong requirement for monitoring the real-time dynamic information related to the construction of TENGs. The aim of this opinion paper is to specifically and critically describe the latest advances in the field of neural tissue engineering for peripheral nerve regeneration. Here we delineate new attempts in the design of template (or scaffold) materials, especially in the context of biocompatibility, the choice and handling of support cells, and growth factor release systems. We further discuss the significance of RNAi for peripheral nerve regeneration, anticipate the potential application of RNAi reagents for TENGs, and speculate on the possible contributions of additional elements, including angiogenesis, electrical stimulation, molecular inflammatory mediators, bioactive peptides, antioxidant reagents, and cultured biological constructs, to TENGs. Finally, we consider that a diverse array of physicochemical and biological cues must be orchestrated within a TENG to create a self-consistent coordinated system with a close proximity to the regenerative microenvironment of the peripheral nervous system.     

蚕丝组织工程肌腱修复肌腱缺损的实验性研究

[目的]探讨用蚕丝与同种异体肌腱细胞联合培养植入体内,构建组织工程化肌腱的可行性。[方法]以罗曼鸡为实验对象分两组,术后第2、4、6、8周进行病理学检查、生物力学和拉伸度的测定。数据采用SPSS 13.0进行统计分析。[结果]细胞组在胶原的合成以及力学检测均明显优于非细胞组(P0.05)。[结论]本实验的结果说明蚕丝材料对肌腱细胞的吸附明显,降解缓慢,抗拉性能优越,构成组织工程化肌腱,可能会在肌腱缺损的治疗方面发挥出巨大潜能。