Tubular Heart Valves from Decellularized Engineered Tissue

A novel tissue-engineered heart valve (TEHV) was fabricated from a decellularized tissue tube mounted on a frame with three struts, which upon back-pressure cause the tube to collapse into three coapting “leaflets.” The tissue was completely biological, fabricated from ovine fibroblasts dispersed within a fibrin gel, compacted into a circumferentially aligned tube on a mandrel, and matured using a bioreactor system that applied cyclic distension. Following decellularization, the resulting tissue possessed tensile mechanical properties, mechanical anisotropy, and collagen content that were comparable to native pulmonary valve leaflets. When mounted on a custom frame and tested within a pulse duplicator system, the tubular TEHV displayed excellent function under both aortic and pulmonary conditions, with minimal regurgitant fractions and transvalvular pressure gradients at peak systole, as well as well as effective orifice areas exceeding those of current commercially available valve replacements. Short-term fatigue testing of one million cycles with pulmonary pressure gradients was conducted without significant change in mechanical properties and no observable macroscopic tissue deterioration. This study presents an attractive potential alternative to current tissue valve replacements due to its avoidance of chemical fixation and utilization of a tissue conducive to recellularization by host cell infiltration.     

Bioengineered Myelin Offers Potential to Regenerate Neural Tissue

Stem cell technology has long offered the hope of regenerating tissue to repair broken or damaged neural tissue. Findings have brought this dream a step closer by developing a method to generate functioning brain cells that produce myelin-a fatty, insulating sheath essential to normal neural conduction. The findings represent an important conceptual advance in stem cell research, which have bioengineered the first generation of myelin-producing cells with superior regenerative capacity.     

脱细胞基质水凝胶促组织再生的研究进展

脱细胞基质水凝胶是组织或器官通过物理、化学和酶解等手段去除其细胞的内容物,只保留细胞骨架结构和细胞外基质等成分,以实现促细胞黏附、增殖和分化并为其生长创造良好微环境的天然高分子生物材料。近年来,由于其良好的细胞相容性、生物可降解性和诱导组织再生能力,脱细胞基质水凝胶在组织修复、再生医学领域备受关注。首先,介绍该水凝胶的基本特点和材料特性,包括其内部的组成成分和结构、组织特异性以及潜在的免疫排斥反应;然后,从细胞水平的培养、临床前的研究和临床上的应用等三方面,重点阐述脱细胞基质水凝胶在组织工程学中的研究应用;最后,展望脱细胞基质材料运用的优势和需要克服的缺陷。总之,作为构建工程化组织以及修复组织缺损的新型生物活性材料,脱细胞基质水凝胶具有广阔的应用前景。     

Morphological Evaluation of the Tissue Reaction to Subcutaneous Implantation of Decellularized Matrices

Bulletin of Experimental Biology and Medicine - Based on the data of morphological analysis, we performed histological evaluation of rat tissue reaction to subcutaneous implantation of...     

一种新型的脱细胞组织工程血管支架的构建和评价

本研究的目的是制备一种免疫原性较小、生物相容性较好、力学性能优良的组织工程血管支架。新鲜获得的犬主动脉,置于三蒸水中4℃过夜，使血管细胞由于渗透压差较大而破裂；随后经过多聚环氧化合物家族的乙二醇缩水甘油醚（EX-810）的作用。进一步促进细胞破裂的同时。对血管支架的纤维结构起交联作用；最后应用物理超声的方法清除支架内的细胞碎片残留。用这种方法处理的犬主动脉内几乎没有可见的核染，基本消除了血管支架的免疫原性。同新鲜的血管相比较。这种组织工程血管支架的各种力学指标与新鲜的犬主动脉没有显著差异。说明处理后的支架仍然保持新鲜血管的力学特征。同时它还表现出极低的细胞毒性。分别在支架上种植内皮细胞和平滑肌细胞，扫描电镜检测结果表明，两种细胞在支架上生长良好，且局部已经融合成片。 相容性     

原卟啉钠对急性肝损伤小鼠肝组织SOD、MDA的影响

 目的 探讨原卟啉钠对四氯化碳（CCl4）致急性肝损伤小鼠血清转氨酶和肝组织超氧化物歧化酶（SOD）、脂质过氧化产物丙二醛（MDA）的影响。方法 60只ICR小鼠随机分为正常对照组、CCl4模型组、联苯双酯组、原卟啉钠低、中、高剂量组。各治疗组每天灌胃给药及造模16h后,摘眼球取血测定血清中谷丙转氨酶（ALT）和谷草转氨酶（AST）活性,剖腹取肝测定肝脏SOD活力和MDA含量。结果 CCl4模型组小鼠血清ALT和AST活力分别为（1879±1219）、（2210±1585）U/L,与正常对照组比较,降低显著（P<0.01）;联苯双酯组、原卟啉钠低、中、高剂量组的SOD活力和MDA含量分别为（207.61±16.02）、（184.35±13.42）、（190.88±17.77）、（199.38±14.43）U/mgprot和（1.08±0.15）、（1.35±0.26）、（1.07±0.16）、（0.92±0.18）nmol/mgprot,与CCl4模型组比较,差异有统计学意义（P<0.05～P<0.01）。结论 原卟啉钠能有效阻止CCl4致急性肝损伤小鼠肝组织SOD活性降低,脂质过氧化产物MDA含量升高,具有一定的保肝降酶作用。     

Immunogenicity of surfactant. II. Porcine and bovine surfactants.

Protein-containing surfactants of human and animal origin are being used increasingly to treat neonatal and adult respiratory distress syndromes. This trend led us to examine the antigenicity of two important preparations of animal surfactant, cow lung surfactant extract (CLSE) and a porcine surfactant preparation, Curosurf. We describe here 15 monoclonal antibodies against Curosurf and four against CLSE. Antibodies were studied by Western blot analysis to determine their ability to recognize protein components of their respective surfactant preparations. They were also tested for their ability to inactivate surfactant in vitro, assayed using the pulsating bubble surfactometer. Several antibodies directed against CLSE or Curosurf functionally inactivate the surfactant to which they were raised. We determined the degree of immunologic cross-reactivity between antibodies directed to CLSE and Curosurf against the other surfactant and also against human surfactant, both by Western blot and by examining functional inactivation in vitro. Antibodies to these animal surfactants that are commonly used therapeutically may inactivate the specific animal surfactant to which they were raised, as well as human and other surfactants. Generally, when antibodies inactivate surfactant from more than one animal species, they inactivate heterologous surfactants comparably to the extent to which they inactivate the surfactant to which they are directed. Immune complexes between anti-surfactant antibodies and surfactant have been described in the course of neonatal respiratory distress syndrome. The potential pathophysiological importance of anti-surfactant antibodies may therefore lie in their ability to inactivate administered surfactant, other similar surfactants and endogenous surfactant. In so doing, these antibodies may potentiate surfactant deficiency or pulmonary injury initiated by other stimuli.     

Bioengineered scaffolds for spinal cord repair

Spinal cord injury can lead to devastating and permanent loss of neurological function, affecting all levels below the site of trauma. Unfortunately, the injured adult mammalian spinal cord displays little regenerative capacity and little functional recovery in large part due to a tissue environment that is nonpermissive for regenerative axon growth. Artificial tissue repair scaffolds may provide a physical guide to allow regenerative axon growth that bridges the lesion cavity and restores functional neural connectivity. By integrating different strategies, including the use of various biomaterials and microstructures as well as incorporation of bioactive molecules and living cells, combined or synergistic effects for spinal cord repair through regenerative axon growth may be achieved. This article briefly reviews the development of bioengineered scaffolds for spinal cord repair, focusing on spinal cord injury and the subsequent cellular response, scaffold materials, fabrication techniques, and current therapeutic strategies. Key issues and challenges are also identified and discussed along with recommendations for future research.     

Effects of Shiga Toxin Type 2 on a Bioengineered Three-Dimensional Model of Human Renal Tissue

Shiga toxins (Stx) are a family of cytotoxic proteins that can cause hemolytic-uremic syndrome (HUS), a thrombotic microangiopathy, following infections by Shiga toxin-producing Escherichia coli (STEC). Renal failure is a key feature of HUS and a major cause of childhood renal failure worldwide. There are currently no specific therapies for STEC-associated HUS, and the mechanism of Stx-induced renal injury is not well understood primarily due to a lack of fully representative animal models and an inability to monitor disease progression on a molecular or cellular level in humans at early stages. Three-dimensional (3D) tissue models have been shown to be more in vivo-like in their phenotype and physiology than 2D cultures for numerous disease models, including cancer and polycystic kidney disease. It is unknown whether exposure of a 3D renal tissue model to Stx will yield a more in vivo-like response than 2D cell culture. In this study, we characterized Stx2-mediated cytotoxicity in a bioengineered 3D human renal tissue model previously shown to be a predictor of drug-induced nephrotoxicity and compared its response to Stx2 exposure in 2D cell culture. Our results demonstrate that although many mechanistic aspects of cytotoxicity were similar between 3D and 2D, treatment of the 3D tissues with Stx resulted in an elevated secretion of the kidney injury marker 1 (Kim-1) and the cytokine interleukin-8 compared to the 2D cell cultures. This study represents the first application of 3D tissues for the study of Stx-mediated kidney injury.     

Bioengineered glial strands for nerve regeneration

Nerve guide implants approved for human application in the peripheral nervous system generally fail to bridge lesion gaps longer than 2 cm and cannot match the clinical performance of autologous nerve transplants. Since current synthetic implants are simply hollow tubes, we aim to recreate the native microarchitecture of nerves inside the tubular implants. Most importantly, in the regenerating nerve, dedifferentiated Schwann cells align to form thousands of long glial strands, which act as guiding structures for the regrowing axons. In order to artificially induce the formation of Schwann cell strands, 28 μm thick, endless poly-p-dioxanone filaments (PDO) were synthesized with longitudinal grooves. A polycationic coating on the PDO filaments rendered the polymer surface cell-permissive and induced the growth of highly oriented Schwann cells with polarized expression of N-cadherin at cell–cell contact sites. In vitro cell proliferation on three-dimensional PDO filaments was significantly increased in comparison to planar PDO substrates. Time lapse video recordings revealed high Schwann cell motility, which is advantageous for the repopulation of cell-free implants after implantation. In a pilot study we employed a novel microsurgical technique in vivo. All axon fascicles were selectively dissected from sciatic rat nerves, and the remaining epineural tube was filled with hundreds of PDO filaments. Histological analysis 6 weeks postoperatively showed no fibrosis or encapsulation but instead longitudinal cell alignment and axonal regrowth. The data suggest that the addition of microstructured PDO filaments to the lumen of synthetic tubular implants might significantly improve performance.     

Decellularized placental matrices for adipose tissue engineering

A tissue-engineered adipose substitute would be invaluable to plastic surgeons for reconstructive, corrective, and cosmetic procedures. This work involves the design of a scaffold for soft tissue augmentation incorporating the decellularized extracellular matrix (ECM) of human placenta. We have developed a protocol to decellularize an intact, large segment (8 cm by 8 cm) of the human placenta. To facilitate the complete decellularization of the dense matrix, a system was designed to perfuse the required chemicals into the placenta via the existing vasculature. Following processing, the original architecture of the placental ECM was preserved, including an intact vascular network. Histological, immunohistochemical, and scanning electron microscopic analyses confirmed the removal of the cells and cellular debris and characterized the composition and structure of the matrix. In vitro cell culture experimentation showed that the placental decellular matrix (PDM) could facilitate the adhesion of primary human adipose precursor cells at early time points. The PDM has great potential for use as a scaffold for adipose tissue engineering, as the placenta is a rich source of human ECM components that can be readily harvested without harm to the donor.     

肝脏组织工程纳米纤维支架材料的比较研究

探讨海藻酸钠、壳聚糖和PLGA纳米纤维支架的机械稳定性、生物相容性及细胞在其表面的生长规律,寻找合适的肝脏组织工程支架材料。用静电纺丝的方法分别制备海藻酸钠、壳聚糖和PLGA纳米纤维支架,观察材料的机械稳定性及肝细胞在材料表面的活性和生长情况。接种后0.5 h内,肝细胞在壳聚糖和海藻酸钠材料表面贴壁,生长良好。第二天起,肝细胞在壳聚糖表面逐渐聚集生长,形成聚集体,而在海藻酸钠材料表面无聚集。第三天后,海藻酸钠材料发生溶胀,纳米结构破坏,而壳聚糖纳米支架保持完好。在观察期间,PLGA材料表面一直没有肝细胞黏附。肝脏细胞不能在PLGA纳米材料表面黏附生长;壳聚糖具有良好的生物相容性,且肝细胞在壳聚糖纳米材料表面能形成球形聚集体;海藻酸钠生物相容性好,但机械稳定性差,容易降解,不能单独作为肝脏组织工程的纳米支架材料。     

改良Pringle肝血流阻断法在肝癌切除术中的应用

目的：探讨改良Pringle法阻断人肝血流行肝切除术治疗肝癌合并肝硬化的效果。方法：回顾分析32例原发性肝癌合并肝硬化患采用改良Pringle法阻断人肝血流行肝癌切除的病例资料。结果：32例肿瘤均获完整切除，术后恢复良好。结论：肝叶切除时采用改良Pringle人肝血流阻断技术简便、安全，特别适用于原发性肝癌合并肝硬化患。     

Decellularized ureter for tissue-engineered small-caliber vascular graft

Previous attempts to create small-caliber vascular prostheses have been limited. The aim of this study was to generate tissue-engineered small-diameter vascular grafts using decellularized ureters (DUs). Canine ureters were decellularized using one of four different chemical agents [Triton-X 100 (Tx), deoxycholate (DCA), trypsin, or sodium dodecyl sulfate (SDS)] and the histology, residual DNA contents, and immunogenicity of the resulting DUs were compared. The mechanical properties of the DUs were evaluated in terms of water permeability, burst strength, tensile strength, and compliance. Cultured canine endothelial cells (ECs) and myofibroblasts were seeded onto DUs and evaluated histologically. Canine carotid arteries were replaced with the EC-seeded DUs (n = 4). As controls, nonseeded DUs (n = 5) and PTFE prostheses (n = 4) were also used to replace carotid arteries. The degree of decellularization and the maintenance of the matrix were best in the Tx-treated DUs. Tx-treated and DCA-treated DUs had lower remnant DNA contents and immunogenicity than the others. The burst strength of the DUs was more than 500 mmHg and the maximum tensile strength of the DUs was not different to that of native ureters. DU compliance was similar to that of native carotid artery. The cell seeding test resulted in monolayered ECs and multilayered alpha-smooth muscle actin-positive cells on the DUs. The animal implantation model showed that the EC-seeded DUs were patent for at least 6 months after the operation, whereas the nonseeded DUs and PTFE grafts become occluded within a week. These results suggest that tissue-engineered DUs may be a potential alternative conduit for bypass surgery.     

肝组织工程的研究概况

综述了肝组织工程的研究概况及发展前景。     

肝静脉在背驮式肝移植术中的应用

按背驮式原位肝移植术要求,对17例成人肝和肝短静脉进行解剖观察与测量。结果显示:左、中、右肝静脉主干长为22.8±8.8mm,50.98±23.94mm,22.8±9.5mm;管径分别为10.74±2.86mm,9.5±3.75mm,15.6±4.05mm。右肝静脉除1例外,都以单独1支形式注入下腔静脉。中肝静脉和左肝静脉分三种形式注入下腔静脉:Ⅰ型4例,占23.5％,Ⅱ型12例,占70.6>6％;Ⅲ型1例,占5.9％。它们不在同一个平面注入下腔静脉。右、中肝静脉之间距离7～23mm,平均15.6mm。文章结合解剖学发现着重讨论了病肝切除和肝静脉成形术中的有关问题。