| Macro-alignment of electrospun fibers for vascular tissue engineering.
December 4, 2009 at 10:16 am
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| | Macro-alignment of electrospun fibers for vascular tissue engineering. J Biomed Mater Res B Appl Biomater. 2009 Dec 2; Authors: Zhu Y, Cao Y, Pan J, Liu Y Design of polymeric scaffolds with specific physical and biological properties is a key objective of tissue engineering research. Electrospinning generates loosely connected 3D porous mats simulating extra cellular matrix structure and therefore makes itself an excellent candidate for application in tissue engineering. Besides a high voltage generator and syringe pump, our electrospinning system was improved to add a programmable central controller which monitors system operation. The nozzles connected with syringe pump via silicon rubber tubing can move linearly with a step size of 0.1 mum or above while the mandrel collector rotates at a speed from 400 to 3000 revolutions per minute (rpm). Using this system, porous fiber sheets with fiber diameters ranging from 100 nm to several micrometers or meshes of macroscopically aligned fibers with diameter of approximately 10 mum have been fabricated under proper processing conditions. After biocompatible fibrin coating, oriented polycaprolactone (PCL) fibers were found to enhance the shifting of human umbilical artery smooth muscle cells from synthetic to contractile phenotype, and to maintain biological function of human umbilical vein endothelial cells. We believe that our electrospinning system will facilitate scaffold fabrication for vessel tissue engineering. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. PMID: 19957362 [PubMed - as supplied by publisher] |
| An injection molding process for manufacturing highly porous and interconnected biodegradable polymer matrices for use as tissue engineering scaffolds.
December 4, 2009 at 10:16 am
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| | An injection molding process for manufacturing highly porous and interconnected biodegradable polymer matrices for use as tissue engineering scaffolds. J Biomed Mater Res B Appl Biomater. 2009 Dec 2; Authors: Kramschuster A, Turng LS In this research, injection molding was combined with a novel material combination, supercritical fluid processing, and particulate leaching techniques to produce highly porous and interconnected structures that have the potential to act as scaffolds for tissue engineering applications. The foamed structures, molded with polylactide (PLA) and polyvinyl alcohol (PVOH) with salt as the particulate, were processed without the aid of organic solvents, which can be detrimental to tissue growth. The pore size in the scaffolds is controlled by salt particulates and interconnectivity is achieved by the co-continuous blending morphology of biodegradable PLA matrix with water-soluble PVOH. Carbon dioxide (CO(2)) at the supercritical state is used to serve as a plasticizer, thereby imparting moldability of blends even with an ultra high salt particulate content, and allows the use of low processing temperatures, which are desirable for temperature-sensitive biodegradable polymers. Interconnected pores of approximately 200 mum in diameter and porosities of approximately 75% are reported and discussed. (c) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. PMID: 19957359 [PubMed - as supplied by publisher] |
| Imaging and analysis of three-dimensional cell culture models.
December 4, 2009 at 10:16 am
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| | Imaging and analysis of three-dimensional cell culture models. Methods Mol Biol. 2010;591:211-27 Authors: Graf BW, Boppart SA Three-dimensional (3D) cell cultures are important tools in cell biology research and tissue engineering because they more closely resemble the architectural microenvironment of natural tissue, compared to standard two-dimensional cultures. Microscopy techniques that function well for thin, optically transparent cultures, however, are poorly suited for imaging 3D cell cultures. Three-dimensional cultures may be thick and highly scattering, preventing light from penetrating without significant distortion. Techniques that can image thicker biological specimens at high resolution include confocal microscopy, multiphoton microscopy, and optical coherence tomography. In this chapter, these three imaging modalities are described and demonstrated in the assessment of functional and structural features of 3D chitosin scaffolds, 3D micro-topographic substrates from poly-dimethyl siloxane molds, and 3D Matrigel cultures. Using these techniques, dynamic changes to cells in 3D microenvironments can be non-destructively assessed repeatedly over time. PMID: 19957133 [PubMed - in process] |
| Regenerative Medicine Special Feature: Enabling tools for engineering collagenous tissues integrating bioreactors, intravital imaging, and biomechanical modeling.
December 4, 2009 at 10:16 am
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| | Regenerative Medicine Special Feature: Enabling tools for engineering collagenous tissues integrating bioreactors, intravital imaging, and biomechanical modeling. Proc Natl Acad Sci U S A. 2009 Dec 1; Authors: Niklason LE, Yeh AT, Calle EA, Bai Y, Valentín A, Humphrey JD Many investigators have engineered diverse connective tissues having good mechanical properties, yet few tools enable a global understanding of the associated formation of collagen fibers, the primary determinant of connective tissue stiffness. Toward this end, we developed a biomechanical model for collagenous tissues grown on polymer scaffolds that accounts for the kinetics of polymer degradation as well as the synthesis and degradation of multiple families of collagen fibers in response to cyclic strains imparted in a bioreactor. The model predicted well both overall thickness and stress-stretch relationships for tubular engineered vessels cultured for 8 weeks, and suggested that a steady state had not yet been reached. To facilitate future refinements of the model, we also developed bioreactors that enable intravital nonlinear optical microscopic imaging. Using these tools, we found that collagen fiber alignment was driven strongly by nondegraded polymer fibers at early times during culture, with subsequent mechano-stimulated dispersal of fiber orientations as polymer fibers degraded. In summary, mathematical models of growth and remodeling of engineered tissues cultured on polymeric scaffolds can predict evolving tissue morphology and mechanics after long periods of culture, and related empirical observations promise to further our understanding of collagen matrix development in vitro. PMID: 19955446 [PubMed - as supplied by publisher] |
| Long-term patency of small-diameter vascular graft made from fibroin, a silk-based biodegradable material.
December 4, 2009 at 10:16 am
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| | Long-term patency of small-diameter vascular graft made from fibroin, a silk-based biodegradable material. J Vasc Surg. 2009 Nov 30; Authors: Enomoto S, Sumi M, Kajimoto K, Nakazawa Y, Takahashi R, Takabayashi C, Asakura T, Sata M OBJECTIVE: There is an increasing need for vascular grafts in the field of surgical revascularization. However, smaller vascular grafts made from synthetic biomaterials, particularly those <5 mm in diameter, are associated with a high incidence of thrombosis. Fibroin is a biodegradable protein derived from silk. Silk fibroin from Bombyx mori provides an antithrombotic surface and serves as a scaffold for various cell types in tissue engineering. We evaluated the potential of fibroin to generate a vascular prosthesis for small arteries. METHODS: A small vessel with three layers was woven from silk fibroin thread. These fibroin-based grafts (1.5 mm diameter, 10 mm length) were implanted into the abdominal aorta of 10- to 14-week-old male Sprague-Dawley rats by end-to-end anastomosis. Polytetrafluoroethylene (PTFE)-based grafts were used as the control. To investigate the origin of the cells in the neointima and media, bone marrow transplantation was performed from green fluorescent protein (GFP) rats to wild-type rats. RESULTS: The patency of fibroin grafts at 1 year after implantation was significantly higher than that of PTFE grafts (85.1% vs 30%, P < .01). Endothelial cells and smooth muscle cells (SMCs) migrated into the fibroin graft early after implantation and became organized into endothelial and medial layers, as determined by anti-CD31 and anti-alpha-smooth muscle actin immunostaining. The total number of SMCs increased 1.6-fold from 1 month to 3 months. Vasa vasorum also formed in the adventitia. Sirius red staining of the fibroin grafts revealed that the content of collagen significantly increased at 1 year after implantation, with a decrease in fibroin content. GFP-positive cells contributed to organization of a smooth muscle layer. CONCLUSIONS: Small-diameter fibroin-based vascular grafts have excellent long-term patency. Bone marrow-derived cells contribute to vascular remodeling after graft implantation. Fibroin might be a promising material to engineer vascular prostheses for small arteries. PMID: 19954921 [PubMed - as supplied by publisher] |
| Molecular profiling of single cells in response to mechanical force: Comparison of chondrocytes, chondrons and encapsulated chondrocytes.
December 4, 2009 at 10:16 am
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| | Molecular profiling of single cells in response to mechanical force: Comparison of chondrocytes, chondrons and encapsulated chondrocytes. Biomaterials. 2009 Nov 30; Authors: Wang QG, Nguyen B, Thomas CR, Zhang Z, El Haj AJ, Kuiper NJ A chondrocyte and its surrounding pericellular matrix (PCM) are defined as a chondron. The PCM plays a critical role in enhancing matrix production, protecting the chondrocyte during loading and transducing mechanical signals. Tissue engineering involves the design of artificial matrices which aim to mimic PCM function for mechanical strength and signalling motifs. We compare the mechanical performance and mechanoresponsiveness of chondrocytes with and without PCM, and encapsulated by alternate adsorption of two oppositely charged polyelectrolytes; chitosan and hyaluronan. Zeta potential measurements confirmed the success of the encapsulation. Encapsulation did not influence chondrocyte viability or metabolic activity. Cells were compressed by micromanipulation with final deformations to 30%, 50% and 70%. Force-displacement data showed that the larger the deformation at the end of compression, the greater the force on the cell. Mechanoresponsiveness of cells was studied by combining single cell PCR with dynamic compression at 20% and 40%. Aggrecan and Type II collagen gene expression were significantly increased in encapsulated chondrocytes and chondrons compared to chondrocytes whereas dynamic compression had no effect on SOX9 or lubricin gene expression. Our results demonstrate that although encapsulation can mimic responses of chondrocytes to biomechanical compression the molecular profile did not reach the enhanced levels observed with chondrons. PMID: 19954841 [PubMed - as supplied by publisher] |
| Effect of cell seeding and mechanical loading on vascularization and tissue formation inside a scaffold: A mechano-biological model using a lattice approach to simulate cell activity.
December 4, 2009 at 10:16 am
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| | Effect of cell seeding and mechanical loading on vascularization and tissue formation inside a scaffold: A mechano-biological model using a lattice approach to simulate cell activity. J Biomech. 2009 Nov 30; Authors: Checa S, Prendergast PJ Achieving successful vascularization remains one of the main problems in bone tissue engineering. After scaffold implantation, the growth of capillaries into the porous construct may be too slow to provide adequate nutrients to the cells in the scaffold interior and this inhibits tissue formation in the scaffold core. Often, prior to implantation, a controlled cell culture environment is used to stimulate cell proliferation and, once in place, the mechanical environment acting on the tissue construct is determined by the loading conditions at the implantation site. To what extent do cell seeding conditions and the construct loading environment have an effect on scaffold vascularization and tissue growth? In this study, a mechano-biological model for tissue differentiation and blood vessel growth was used to determine the influence of cell seeding on vascular network development and tissue growth inside a regular-structured bone scaffold under different loading conditions. It is predicted that increasing the number of cells seeded homogeneously reduces the rate of vascularization and the maximum penetration of the vascular network, which in turn reduces bone tissue formation. The seeding of cells in the periphery of the scaffold was predicted to be beneficial for vascularization and therefore for bone growth; however, tissue formation occurred more slowly during the first weeks after implantation compared to homogeneous seeding. Low levels of mechanical loading stimulated bone formation while high levels of loading inhibited bone formation and capillary growth. This study demonstrates the feasibility of computational design approaches for bone tissue engineering. PMID: 19954779 [PubMed - as supplied by publisher] |
| Evacuated calcium phosphate spherical microcarriers for bone regeneration.
December 4, 2009 at 10:16 am
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| | Evacuated calcium phosphate spherical microcarriers for bone regeneration. Tissue Eng Part A. 2009 Dec 2; Authors: Park JS, Hong SJ, Kim HY, Yu HS, Jeong I, Lee YI, Kim CH, Kwak SJ, Lee HH, Kim HW Microparticulates are an effective 3D matrix for the culture of stem cells to be used in tissue engineering of bone. Herein, bioactive calcium phosphate microparticles with an evacuated morphology were prepared and their potential to support stem cells for bone tissue engineering was addressed. Spherical particles with sizes of hundreds of micrometers were produced using the emulsification method, during which the internal portion was evacuated with the aid of solvent evaporation. The evacuated portion of the microspheres, which is considered to enhance cell population and be replaced with new bone, was found to comprise approximately 65-70 % of the total volume. Stem cells derived from human adipose (hASCs) and rat bone marrow (rBMSCs) were isolated and cultured on the evacuated microspheres. When compared to a 2D culture dish, the 3D spherical substrate provided cells with more space to adhere and populate, which became more evident as the cell seeding quantity increased. Moreover, better cell proliferation was observed on the evacuated microspheres than on the conventional filled microspheres, suggesting that evacuation of the internal part of the microspheres was useful for generating a large cell population. The differentiation of cells cultured on the 3D evacuated microspheres into osteoblasts with appropriate osteogenic cues was also more effective when compared to cells cultured on 2D dish. When implanted within a rabbit calvarium, the evacuated microspheres induced rapid bone formation at 6 weeks with a typical lamella pattern. Based on the results, the evacuated CaP microspheres are considered to be an effective 3D matrix for direct-filling of bone defects as well as for bone tissue engineering using stem cells. PMID: 19954329 [PubMed - as supplied by publisher] |
| Practical barriers to delivering autologous bone marrow stem cell therapy as an adjunct to liver resection.
December 4, 2009 at 10:16 am
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| | Practical barriers to delivering autologous bone marrow stem cell therapy as an adjunct to liver resection. Stem Cells Dev. 2009 Dec 2; Authors: Stutchfield BM, Rashid S, Forbes SJ, Wigmore SJ Liver resection has been associated with significant morbidity and mortality due to hepatic dysfunction or hepatic failure in the postoperative period. Autologous bone marrow stem cell therapies may offer the potential to enhance hepatic regeneration in this setting, perhaps increasing the safety of the procedure. Preclinical models and initial translational studies have suggested that autologous bone marrow stem cell administration can facilitate hepatic regeneration following both acute and chronic liver disease. While translational studies have begun in chronic hepatic disease, translation to hepatic surgical indications has been limited. This review explores the practical barriers currently restricting the delivery of autologous stem cell therapies to enhance hepatic regeneration following liver resection including selection of cell type, cell isolation, therapy delivery, trial design and assessment of efficacy. PMID: 19954303 [PubMed - as supplied by publisher] |
| Modification of Polylactide Surfaces with Lactide-Ethylene Oxide Functional Block Copolymers: Accessibility of Functional Groups.
December 4, 2009 at 10:16 am
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| | Modification of Polylactide Surfaces with Lactide-Ethylene Oxide Functional Block Copolymers: Accessibility of Functional Groups. Biomacromolecules. 2009 Dec 2; Authors: Třesohlavá E, Popelka S, Machová L, Rypáček F Feasibility of using amphiphilic block copolymers composed of polylactide (PLA) and poly(ethylene oxide) (PEO) blocks for biomimetic surface modification of polylactide-based biomaterials for tissue engineering was investigated. PEO-b-PLA copolymers were deposited on the PLA surface from a solution in PEO-selective solvent. Copolymers with a neutral omega-methoxy end group of the PEO block (mPEO-b-PLA) were used to provide hydrophilic surface of PLLA, which exhibited suppressed nonspecific protein adsorption. Their analogues, containing biotin group at the end of PEO block (bPEO-b-PLA), were used as a model of functional copolymers, carrying a biomimetic group, for example, a cell-adhesion fibronectine-derived peptide sequence. The surface topography of functional groups on the modified surface and their accessibility for interaction with a protein receptor was investigated, taking advantage of specific biotin-avidin interaction, on surfaces modified with a combination of mPEO-b-PLA and bPEO-b-PLA copolymers. The accessibility of model biotin groups for interaction with their protein counterpart was proven through visualization of avidin or avidin-labeled nanospheres with atomic force microscopy. PMID: 19954220 [PubMed - as supplied by publisher] |
| [Effect on cochlea function by tissue-engineering ossicle prothesis containing controlled release bone morphogenetic protein 2 transplanted into acoustic bulla in guinea pig]
December 4, 2009 at 10:16 am
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| | [Effect on cochlea function by tissue-engineering ossicle prothesis containing controlled release bone morphogenetic protein 2 transplanted into acoustic bulla in guinea pig] Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2009 Jun;44(6):490-3 Authors: Li XS, Sun JJ, Jiang W, Liu X OBJECTIVE: To prepare the tissue-engineering ossicle prothesis which contained controlled release BMP-2 and implant into the acoustic bulla of guinea-pig, and observed the osteogenesis of the prothesis in the bulla and the effect of the prothesis on the cochlea. METHODS: The acellular bony microtubule filled with collagen containing BMP-2 as tissue-engineering prothesis was implanted into the acoustic bulla of the guinea-pig through the retroauricular approach. The prothesis without BMP-2 was implanted into the contralateral bulla as control. ABR of the animals was checked after surgery at different time to observe the variation of the hearing threshold. After 3 months, the osteogenesis of the prothesis and its effect on the structure of bulla, cochlea and hair cells was observed by histological technique and silver nitrate staining method. RESULTS: The animals were recovered soon after surgery. The hearing threshold of the animals [(15.5 +/- 2.8) dB SPL] were increased slightly just after the surgery [(28.3 +/- 4.8) dB SPL, P<0.05], and come back completely after 3 month [(16.1 +/- 4.0) dB, P>0.05]. The prothesis was covered with mucosa finally while the bulla and cochlea were normal in shape. The osteogenesis was occurred at the inner side of the acellular bony tube. There wasn't any abnormal hyperplasia of bone in the bulla and cochlea. The articulation between the stapes and oval window wasn't merged. The shape of the hair cells were normal and there wasn't obvious deletion of the hair cells compared with control group. CONCLUSIONS: The tissue-engineering ossicle prothesis contained controlled release BMP-2 can induce osteogenesis in the bulla of the animals. This kind of material doesn't affect the shape of the bulla and the hearing threshold of the cochlea, moreover, they doesn't induce the abnormal hyperplasia of bone in the bulla and might be used to reconstruct the defects of ossicles. PMID: 19954021 [PubMed - in process] |
| A Tissue Engineering Approach for Prenatal Closure of Myelomeningocele with gelatin sponges incorporating basic fibroblast growth factor.
December 4, 2009 at 4:16 am
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| | A Tissue Engineering Approach for Prenatal Closure of Myelomeningocele with gelatin sponges incorporating basic fibroblast growth factor. Tissue Eng Part A. 2009 Dec 2; Authors: Watanabe M, Jo JI, Radu A, Kaneko M, Tabata Y, Flake A Myelomeningocele (MMC) is a common and devastating malformation. While, fetal surgical closure may improve outcome, a less invasive approach that can be applied earlier in gestation is desirable. The objective of this study is to evaluate the therapeutic feasibility of a tissue engineering approach for prenatal coverage of MMC. A Gelatin hydrogel composite combining a gelatin sheet and gelatin sponge was prepared with or without basic fibroblast growth factor (bFGF) incorporation, and applied prenatally to retinoic acid induced fetal MMC in the rat model. Most of the composites were adherent to the MMC within the amniotic fluid environment with the help of Cyanoacrylate adhesive. Histological examination revealed cells layered over the composites with associated extracellular matrix (ECM) as well as cellular ingrowth into the sponges. The layer over the composite was composed of mixed non-epithelial and epithelial cells with the ECM consisting of collagen type I and hyaluronic acid. The tissue inside the sponge consisted of non-epithelial cells and hyaluronic acid. Epidermal ingrowth underneath the sponges and neovascularization into the sponges occurred and was significantly increased by the incorporation of bFGF. Although further development is needed, this study supports the therapeutic potential of a tissue engineering approach for prenatal coverage of MMC. PMID: 19954327 [PubMed - as supplied by publisher] | | | 
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