| Biodegradable Polymeric Microcarriers with Controllable Porous Structure for Tissue Engineering.
October 13, 2009 at 8:59 am
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| | Biodegradable Polymeric Microcarriers with Controllable Porous Structure for Tissue Engineering. Macromol Biosci. 2009 Oct 9; Authors: Shi X, Sun L, Jiang J, Zhang X, Ding W, Gan Z Porous microspheres fabricated by biodegradable polymers show great potential as microcarriers for cell cultivation in tissue engineering. Herein biodegradable poly(DL-lactide) (PLA) was used to fabricate porous microspheres through a modified double emulsion solvent evaporation method. The influence of fabrication parameters, such as the stirring speed of the primary and secondary emulsion, the polymer concentration of the oil phase, and solvent type, as well as the post-hydrolysis treatment of the porous structure of the PLA microspheres are discussed. Good attachment and an active spread of MG-63 cells on the microspheres is observed, which indicates that the PLA microspheres with controllable porous structure are of great potential as cell delivery carriers for tissue engineering. PMID: 19821453 [PubMed - as supplied by publisher] |
| Post-culture treatment protocols for PLGA membrane scaffolds.
October 13, 2009 at 8:59 am
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| | Post-culture treatment protocols for PLGA membrane scaffolds. Biotechnol Lett. 2009 Oct 11; Authors: Ellis MJ, Forsey R, Chaudhuri JB The interactions of post-culture treatments reagents used for fixing, lysing and cell quantification on poly(lactide-co-glycolide) (PLGA) flat sheet membrane scaffolds are presented. Lysing with Alkaline buffer solution/Triton X-100/MilliQ water (ATM) and fixing with 10% Neutral Buffered Formalin (10% NBF) had no affect on membrane structure while fixing with 95% ethanol caused smoothing of the surface, shrinkage and a reduction in surface area of 55, 48 and 33, for 100:0, 75:25 and 50:50 (PLA:PGA), respectively. PicoGreen assay was selected for cell (560pZIPv.neo) quantification since the background noise would not affect readings for cell numbers over 3,000 cells/cm(2), while the background reading was too high for MTT and Methylene Blue (MB). MB at 0.5% (w/v) was, however, deemed suitable for visualising cell morphology on the membranes. Furthermore ATM buffer was suitable for the PicoGreen assay, which allows the same samples to be used for quantification of alkaline phosphatase activity. PMID: 19821075 [PubMed - as supplied by publisher] |
| Enhanced proliferation capacity of porcine tenocytes in low O(2) tension culture.
October 13, 2009 at 8:59 am
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| | Enhanced proliferation capacity of porcine tenocytes in low O(2) tension culture. Biotechnol Lett. 2009 Oct 11; Authors: Zhang Y, Wang B, Zhang WJ, Zhou G, Cao Y, Liu W Tenocytes reside in relatively avascular tissue and are difficult to expand due to phenotype drift and functional loss. Thus low O(2) tension culture was employed to enhance the expansion capability. The results demonstrated that low O(2) tension (2% O(2)) culture could significantly enhance the expansion of newborn pig tenocytes with 275-473% greater cell yield per cell passage that that of regular O(2) cultured (21% O(2)) cells. Importantly, low O(2) culture did not change the gene expression of functional molecule such as collagens I and III, decorin, prolyl 4-hydroxylase (P4H), lysyl oxidase (LOX), TIMP-1 and TIMP-2, but could significantly down regulate the gene expression of MMP-1 and IL-6. In conclusion, low O(2) tension culture can significantly enhance the expansion capacity of tenocytes without affecting their phenotype and functions. PMID: 19821074 [PubMed - as supplied by publisher] |
| Fibrin Sealant: Past, Present, and Future: A Brief Review.
October 13, 2009 at 8:59 am
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| | Fibrin Sealant: Past, Present, and Future: A Brief Review. World J Surg. 2009 Oct 10; Authors: Spotnitz WD BACKGROUND: Fibrin sealant is a two-component topical hemostat, sealant, and tissue adhesive consisting of fibrinogen and thrombin that has been used in the United States as a blood bank- or laboratory-derived product since the 1980s and has been commercially available since 1998. METHODS/RESULTS: Initially, surgeons employed hospital-based materials because of the lack of availability of a commercially produced agent. At present, there are five U.S. Food and Drug Administration (FDA)-approved forms including products derived from pooled or autologous human plasma as well as bovine plasma. On-label indications include hemostasis, colonic sealing, and skin graft attachment. Recent clinical and experimental uses include tissue or mesh attachment, fistula closure, lymphatic sealing, adhesion prevention, drug delivery, and tissue engineering. CONCLUSIONS: The modern literature on fibrin sealant now exceeds 3000 articles and continues to expand. This brief review presents the history of this material, its present clinical use, and its future applications. PMID: 19820991 [PubMed - as supplied by publisher] |
| Synchrotron X-ray microtomography for assessment of bone tissue scaffolds.
October 13, 2009 at 8:59 am
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| | Synchrotron X-ray microtomography for assessment of bone tissue scaffolds. J Mater Sci Mater Med. 2009 Oct 10; Authors: Yue S, Lee PD, Poologasundarampillai G, Yao Z, Rockett P, Devlin AH, Mitchell CA, Konerding MA, Jones JR X-ray microtomography (muCT) is a popular tool for imaging scaffolds designed for tissue engineering applications. The ability of synchrotron muCT to monitor tissue response and changes in a bioactive glass scaffold ex vivo were assessed. It was possible to observe the morphology of the bone; soft tissue ingrowth and the calcium distribution within the scaffold. A second aim was to use two newly developed compression rigs, one designed for use inside a laboratory based muCT machine for continual monitoring of the pore structure and crack formation and another designed for use in the synchrotron facility. Both rigs allowed imaging of the failure mechanism while obtaining stress-strain data. Failure mechanisms of the bioactive glass scaffolds were found not to follow classical predictions for the failure of brittle foams. Compression strengths were found to be 4.5-6 MPa while maintaining an interconnected pore network suitable for tissue engineering applications. PMID: 19820901 [PubMed - as supplied by publisher] |
| Regenerative Medicine Special Feature: Engineering anatomically shaped human bone grafts.
October 13, 2009 at 8:59 am
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| | Regenerative Medicine Special Feature: Engineering anatomically shaped human bone grafts. Proc Natl Acad Sci U S A. 2009 Oct 9; Authors: Grayson WL, Fröhlich M, Yeager K, Bhumiratana S, Chan ME, Cannizzaro C, Wan LQ, Liu XS, Guo XE, Vunjak-Novakovic G The ability to engineer anatomically correct pieces of viable and functional human bone would have tremendous potential for bone reconstructions after congenital defects, cancer resections, and trauma. We report that clinically sized, anatomically shaped, viable human bone grafts can be engineered by using human mesenchymal stem cells (hMSCs) and a "biomimetic" scaffold-bioreactor system. We selected the temporomandibular joint (TMJ) condylar bone as our tissue model, because of its clinical importance and the challenges associated with its complex shape. Anatomically shaped scaffolds were generated from fully decellularized trabecular bone by using digitized clinical images, seeded with hMSCs, and cultured with interstitial flow of culture medium. A bioreactor with a chamber in the exact shape of a human TMJ was designed for controllable perfusion throughout the engineered construct. By 5 weeks of cultivation, tissue growth was evidenced by the formation of confluent layers of lamellar bone (by scanning electron microscopy), markedly increased volume of mineralized matrix (by quantitative microcomputer tomography), and the formation of osteoids (histologically). Within bone grafts of this size and complexity cells were fully viable at a physiologic density, likely an important factor of graft function. Moreover, the density and architecture of bone matrix correlated with the intensity and pattern of the interstitial flow, as determined in experimental and modeling studies. This approach has potential to overcome a critical hurdle-in vitro cultivation of viable bone grafts of complex geometries-to provide patient-specific bone grafts for craniofacial and orthopedic reconstructions. PMID: 19820164 [PubMed - as supplied by publisher] |
| A small diameter elastic blood vessel wall prepared under pulsatile conditions from polyglycolic acid mesh and smooth muscle cells differentiated from adipose-derived stem cells.
October 13, 2009 at 8:59 am
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| | A small diameter elastic blood vessel wall prepared under pulsatile conditions from polyglycolic acid mesh and smooth muscle cells differentiated from adipose-derived stem cells. Biomaterials. 2009 Oct 9; Authors: Wang C, Cen L, Yin S, Liu Q, Liu W, Cao Y, Cui L Smooth muscle layer plays an important role in maintaining homeostasis of blood vessels, thus generating a functional smooth muscle layer is a prerequisite for successful construction of blood vessels via tissue-engineering approach. In this study, we investigated the feasibility of constructing an elastic vessel wall in small diameter (less than 6 mm) using smooth muscle cells (SMCs) differentiated from human adipose-derived stem cells (hASCs) under pulsatile stimulation in a bioreactor. With the induction of transforming growth factor-beta1 (TGF-beta1) and bone morphogenetic protein-4 (BMP4) in combination for 7 days, hASCs were found to acquire an SMC phenotype characterized by the expression of SMC-related markers including smooth muscle alpha actin (alpha-SMA), calponin, and smooth muscle myosin heavy chain (SM-MHC). The SMCs derived from hASCs were seeded in polyglycolic acid (PGA) unwoven mesh and the cell-scaffold complex were subjected to pulsatile stimulation in a bioreactor for 8 weeks. The vessel walls engineered under the dynamic stimulation for 8 weeks showed a dense and well-organized structure similar to that of native vessels. The differentiated hASCs with dynamic loading were found to maintain their SMC phenotype within 3-dimensional PGA scaffold with a high level of collagen deposition close to that of native ones. Vessels constructed in the static condition showed a loose histological structure with less expression of contractile proteins. More importantly, the engineered vessel under pulsatile stimulation exhibited significant improvement in biomechanical properties over that generated from static conditions. Our results demonstrated that hASCs can serve as a new cell source for SMCs in blood vessel engineering, and an elastic small-diameter vessel wall could be engineered by in vitro culture of SMC-differentiated hASCs on the PGA scaffold with matchable biomechanical strength to that of normal blood vessels under pulsatile stimulation. PMID: 19819545 [PubMed - as supplied by publisher] |
| Enhancement of chondrogenesis of human adipose derived stem cells in a hyaluronan-enriched microenvironment.
October 13, 2009 at 8:59 am
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| | Enhancement of chondrogenesis of human adipose derived stem cells in a hyaluronan-enriched microenvironment. Biomaterials. 2009 Oct 9; Authors: Wu SC, Chang JK, Wang CK, Wang GJ, Ho ML Microenvironment plays a critical role in guiding stem cell differentiation. We investigated the enhancing effect of a hyaluronan (HA)-enriched microenvironment on human adipose derived stem cell (hADSC) chondrogenesis for articular cartilage tissue engineering. The hADSCs were obtained from patients undergoing hip replacement. HA-coated wells and HA-modified poly-(lactic-co-glycolic acid) (HA/PLGA) scaffolds were used as the HA-enriched microenvironment. The mRNA expressions of chondrogenic (SOX-9, aggrecan and collagen type II), fibrocartilage (collagen type I), and hypertrophic (collagen type X) marker genes were quantified by real-time polymerase chain reaction. Sulfated glycosaminoglycan (sGAG) deposition was detected by Alcian blue, safranin-O staining, and dimethylmethylene blue (DMMB) assays. Localized collagen type II was detected by immunohistochemistry. The hADSCs cultured in HA-coated wells (0.005-0.5mg/cm(2)) showed enhanced aggregation and mRNA expressions (SOX-9, collagen type II, and aggrecan) after 24h, and sGAG content was also significantly increased after 9 days of culture. The HA-modified PLGA did not change the cell adherence and viability of hADSCs. The mRNA expressions of chondrogenic marker genes were significantly enhanced in hADSCs cultured in HA/PLGA rather than those cultured in the PLGA scaffold after 1, 3, and 5 days of culture. The hADSCs cultured in HA/PLGA produced higher levels of sGAG and collagen type II, compared to those in the PLGA scaffold after 4 weeks of cultures. Our results suggest that HA-enriched microenvironment induces chondrogenesis in hADSCs, which may be beneficial in articular cartilage tissue engineering. PMID: 19819543 [PubMed - as supplied by publisher] |
| High-throughput Laser Printing of Cells and Biomaterials for Tissue Engineering.
October 13, 2009 at 8:59 am
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| | High-throughput Laser Printing of Cells and Biomaterials for Tissue Engineering. Acta Biomater. 2009 Oct 8; Authors: Guillemot F, Souquet A, Catros S, Guillotin B, Lopez J, Faucon M, Pippenger B, Bareille R, Rémy M, Bellance S, Chabassier P, Fricain JC, Amédée J Parallel to inkjet printing and bioplotting, Biological Laser Printing (BioLP) using Laser-Induced Forward Transfer (LIFT) has emerged as an alternative method in the assembly and micropatterning of biomaterials and cells. In this paper, we present results on the high-throughput laser printing of a biopolymer (sodium alginate), biomaterials (nano-sized HA synthesized by wet precipitation) and human endothelial cells (EA.hy926), thus demonstrating the interest of this technique in 3D tissue construction. A rapid prototyping workstation equipped with an infra-red pulsed laser (tau=30 ns, gamma=1064nm, f=1-100kHz), galvanometric mirrors (scanning speed up to 2,000mm/s) and micrometric translation stages (x,y,z) has been set up. The droplet generation process have been controlled by monitoring laser fluence, focalization conditions and writing speed, to take into account its mechanism which is mainly driven by bubble dynamics. Droplets of 70mum in diameter and containing around 5-7 living cells per droplet have been obtained, thereby minimizing the dead volume of the hydrogel that surrounds the cells. In addition to cell transfer, we have demonstrated the potential of using high throughput BioLP for creating well defined nano-sized HA patterns. Finally, we discuss bioprinting efficiency criteria (speed, volume, resolution, integrability) for the purpose of tissue engineering. PMID: 19819356 [PubMed - as supplied by publisher] |
| Novel microencapsulation of potential drugs with low molecular weight and high hydrophilicity: hydrogen peroxide as a candidate compound.
October 13, 2009 at 8:59 am
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| | Novel microencapsulation of potential drugs with low molecular weight and high hydrophilicity: hydrogen peroxide as a candidate compound. Int J Pharm. 2009 Oct 8; Authors: Ng SM, Choi JY, Han HS, Huh JS, Lim JO Microencapsulation of drugs into solid biodegradable polymeric microspheres via solvent evaporation technique remains challenging especially with those having low molecular weight and high hydrophilicity nature. This paper presents an efficient encapsulation protocol for this group of drugs, demonstrated using hydrogen peroxide as a model compound that is encapsulated into poly(lactic-co-glycolic acid) microspheres. Hydrogen peroxide can be employed as antiseptic agent or its decomposed form into oxygen can be useful in various pharmaceutical applications. The new encapsulation technique was developed based on the modification of conventional double emulsion and solvent evaporation protocol with a backward concentration gradient of hydrogen peroxide. This was achieved by adding and controlling the concentration of hydrogen peroxide at the continuous phase during the solidification stage of the microspheres. Parameters involved in the production and the formulation aspect were optimized to achieve the best protocol having controlled efficiency of encapsulation that is simple, safe, practical, and economical. Evaluation on the encapsulation efficiency and the release profile has been made indirectly by monitoring the dissolved oxygen level of the solution in where the microspheres were incubated. Morphology of the microspheres was investigated using scanning electron microscopy. This proposed method has successfully used to prepare batches of microspheres having different encapsulation efficiencies and its potential applications have been demonstrated accordingly. PMID: 19819316 [PubMed - as supplied by publisher] |
| Gene expression profile of mouse masseter muscle after repetitive electrical stimulation.
October 13, 2009 at 8:59 am
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| | Gene expression profile of mouse masseter muscle after repetitive electrical stimulation. J Prosthodont Res. 2009 Oct 8; Authors: Ono T, Maekawa K, Sonoyama W, Kojima S, Tanaka T, Clark GT, Kuboki T PURPOSE: To examine gene expression profile changes in the mouse masseter muscle tissue after repetitive electrical stimulation by using a DNA microarray technique. METHODS: Nine male ICR mice aged 10 weeks were used. Each anesthetized mouse was secured on a platform in a supine position and the masseter muscle tissues on both sides were exposed. Bipolar electrodes were set on the right masseteric fascia to electrically stimulate the masseter muscle (8V, 10Hz, 20ms) for 30min. After cessation of stimulation bilateral masseter muscle tissues were sampled at 0h (n=3), 1h (n=3), 2h (n=3). Total RNA was isolated from the homogenized muscle tissues and purified mRNA samples (50mug) were processed and hybridized with microarray slides. Probe arrays were then scanned and analyzed to calculate the signal density. Gene expression profiles were compared at each time point between the right (stimulation side) and left (control side) masseter. When the gene expression levels were different more than 2-fold, the difference was regarded as positive. RESULTS: Of the 6400 genes assessed, 1733 genes were up-regulated and 515 genes were down-regulated in the stimulation side at least once during the experimental time course. These up- or down-regulated genes were associated with autoimmune/inflammatory disease (28/114), cardiovascular disease (17/61), neuroscience (12/50), apoptosis (27/93), diabetes/obesity (9/28), signal transduction (66/250) and others. 28 genes were up-regulated and 25 genes were down-regulated at all time points. CONCLUSIONS: Dramatic gene expression changes were induced by the repetitive electrical muscle stimulation in mouse masseter. PMID: 19819208 [PubMed - as supplied by publisher] |
| The intervertebral disc: From pathophysiology to tissue engineering.
October 13, 2009 at 8:59 am
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| | The intervertebral disc: From pathophysiology to tissue engineering. Joint Bone Spine. 2009 Oct 8; Authors: Clouet J, Vinatier C, Merceron C, Pot-Vaucel M, Hamel O, Weiss P, Grimandi G, Guicheux J PMID: 19819178 [PubMed - as supplied by publisher] |
| Tailoring the surface functionalities of titania nanotube arrays.
October 13, 2009 at 8:59 am
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| | Tailoring the surface functionalities of titania nanotube arrays. Biomaterials. 2009 Oct 8; Authors: Vasilev K, Poh Z, Kant K, Chan J, Michelmore A, Losic D Nanotubular titanium oxide (TiO(2)) produced by self-ordering processes using electrochemical anodization have been extensively explored in recent years as a new biomaterial for implants, drug delivery systems, cell growth, biosensors, immunoisolations, bioartificial organs and tissue engineering. Chemical inertness is the main weakness of this material when placed in contact with biological systems and surface modification is a possible solution of this problem. The aim of this study is to develop a flexible and facile method for surface modification of TiO(2) nanotubes to tailor new interfacial properties important in many biomedical applications. TiO(2) nanotubes were prepared by electrochemical anodization of titanium foil using ethylene glycol: NH(4)F electrolyte (2% water and 0.3% NH(4)F). Plasma surface modification using allylamine (AA) as a precursor has been applied to generate a thin and chemically reactive polymer (AAPP) film rich in amine groups on top of the TiO(2) nanotube surface. This initial polymer film was used for further surface functionalization by attachment of desired molecules. Two modification techniques were used to demonstrate the flexibility for building of new functionalities on titania nanotube surface: electrostatic adsorption of poly(sodium styrenesulfonate) (PSS) as an example of layer-by-layer assembly (LbL), and covalent coupling of poly(ethylene glycol) (PEG) as an example of creating a protein-resistant surface. These approaches for tailoring the surface chemistry and wettability of TiO(2) nanotubes offer considerable prospects for advancing their interfacial properties to improve existing and develop new functional biomaterials for diverse biomedical applications. PMID: 19819014 [PubMed - as supplied by publisher] |
| The effect of mean pore size on cell attachment, proliferation and migration in collagen-glycosaminoglycan scaffolds for bone tissue engineering.
October 13, 2009 at 8:59 am
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| | The effect of mean pore size on cell attachment, proliferation and migration in collagen-glycosaminoglycan scaffolds for bone tissue engineering. Biomaterials. 2009 Oct 8; Authors: Murphy CM, Haugh MG, O'Brien FJ In the literature there are conflicting reports on the optimal scaffold mean pore size required for successful bone tissue engineering. This study set out to investigate the effect of mean pore size, in a series of collagen-glycosaminoglycan (CG) scaffolds with mean pore sizes ranging from 85mum to 325mum, on osteoblast adhesion and early stage proliferation up to 7 days post-seeding. The results show that cell number was highest in scaffolds with the largest pore size of 325mum. However, an early additional peak in cell number was also seen in scaffolds with a mean pore size of 120mum at time points up to 48h post-seeding. This is consistent with previous studies from our laboratory which suggest that scaffold specific surface area plays an important role on initial cell adhesion. This early peak disappears following cell proliferation indicating that while specific surface area may be important for initial cell adhesion, improved cell migration provided by scaffolds with pores above 300mum overcomes this effect. An added advantage of the larger pores is a reduction in cell aggregations that develop along the edges of the scaffolds. Ultimately scaffolds with a mean pore size of 325mum were deemed optimal for bone tissue engineering. PMID: 19819008 [PubMed - as supplied by publisher] |
| Feeder-free self-renewal of human embryonic stem cells in 3D porous natural polymer scaffolds.
October 13, 2009 at 8:59 am
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| | Feeder-free self-renewal of human embryonic stem cells in 3D porous natural polymer scaffolds. Biomaterials. 2009 Oct 8; Authors: Li Z, Leung M, Hopper R, Ellenbogen R, Zhang M Human embryonic stem cells (hESCs) are routinely cultured on fibroblast feeder layers or in fibroblast-conditioned medium, which requires continued supply of feeder cells and poses the risks of xenogenic contamination and other complications such as feeder-dependent outcome. Here, we demonstrate a strategy that supports sustained self-renewal of hESCs in a three-dimensional porous natural polymer scaffold, comprised of chitosan and alginate, without the support of feeder cells or conditioned medium. We assessed the pluripotency of the renewed hESCs both in vitro by evaluation of cellular proliferation, functionality, and gene activities for 21 days, and in vivo by implantation of the stem cell populated scaffolds in an immunodeficient mouse model to induce teratoma formation. The self-renewed stem cells can be easily recovered for subculture by decomposing the scaffold under a mild condition. We further subcultured recovered hESCs for 14 days and verified their pluripotency. In addition to providing a clean environment for stem cell renewal, this strategy, with the demonstrated biocompatibility and biodegradability of chitosan and alginate, may potentially allow for the direct implantation of stem cell populated scaffolds for a broad spectrum of applications in tissue engineering and regenerative medicine. PMID: 19819007 [PubMed - as supplied by publisher] |
| Modeling collagen remodeling.
October 13, 2009 at 8:59 am
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| | Modeling collagen remodeling. J Biomech. 2009 Oct 8; Authors: Baaijens F, Bouten C, Driessen N Collagen is the main load bearing protein in many soft tissues, and in cardiovascular tissues in particular. In many tissues collagen has a specific architecture that is crucial for the biomechanical function of the tissue. Typical examples are the hammock-shaped collagen architecture in heart valves and a helical pattern in arteries. One of the objectives in cardiovascular tissue engineering is the reconstitution of this architecture. It is hypothesized that the architecture is mediated by mechanical stimulation. Computational models were developed to predict the mechanoregulation of the collagen architecture. This review recapitulates the key modeling assumptions and results achieved to date. PMID: 19818962 [PubMed - as supplied by publisher] |
| Characterisation of Human Bone Marrow Stromal Cell heterogeneity for skeletal regeneration strategies using a two-stage colony assay and computational modeling.
October 13, 2009 at 8:59 am
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| | Characterisation of Human Bone Marrow Stromal Cell heterogeneity for skeletal regeneration strategies using a two-stage colony assay and computational modeling. Bone. 2009 Oct 7; Authors: Sengers BG, Dawson JI, Oreffo RO Skeletal regeneration and tissue engineering strategies rely critically on the efficient expansion of progenitor cell populations while simultaneously preserving multipotentiality and the ability to induce differentiation towards bone and cartilage. Cell population heterogeneity has a significant impact on this process, but is currently poorly quantified, hampering the interpretation of experimental results and the design of optimised expansion protocols. The objective of this study was to characterise individual Human Bone Marrow Stromal Cell heterogeneity in terms of colony expansion potential. For this purpose, a novel two stage CFU-F assay was developed in which cells from primary single cell derived colonies were detached and reseeded again at clonal density as single cells to form new secondary colonies. This clearly demonstrated how secondary colony growth potential varies markedly both between and within primary colonies. Depending on the primary colony, cells either generated small secondary colonies only, or else a wide range of colony sizes. Using computational modelling it was shown how such colony heterogeneity could arise from hierarchical progenitor cell populations and what the limits of such a population structure were in explaining the experimental data. In addition the model demonstrated the significant potential impact of cell mobility on expansion potential and its implications for inducing population heterogeneity. This combined experimental-computational approach will ascertain the impact of cell culture protocols on the expansion potential and functional composition of heterogeneous progenitor populations. Such insights are likely to be of crucial importance for the success of skeletal regeneration strategies. PMID: 19818885 [PubMed - as supplied by publisher] |
| Flexible and elastic porous poly(trimethylene carbonate) structures for use in vascular tissue engineering.
October 13, 2009 at 8:59 am
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| | Flexible and elastic porous poly(trimethylene carbonate) structures for use in vascular tissue engineering. Acta Biomater. 2009 Oct 6; Authors: Song Y, Kamphuis MM, Zhang Z, Sterk LM, Vermes I, Poot AA, Feijen J, Grijpma DW Biocompatible and elastic porous tubular structures based on poly(1,3-trimethylene carbonate) (PTMC) were developed as scaffolds for tissue engineering of small-diameter blood vessels. High molecular weight PTMC (M(n) = 4.37x105) was crosslinked by gamma irradiation in an inert nitrogen atmosphere. The resulting networks (50-70% gel content) were elastic and creep-resistant. The PTMC materials were highly biocompatible as determined by cell adhesion and proliferation studies using various relevant cells types (human umbilical vein endothelial cells (HUVECs), smooth muscle cells (SMCs) and mesenchymal stem cells (MSCs)). Dimensionally stable, tubular scaffolds with an interconnected pore network were prepared by particulate leaching. Different crosslinked porous PTMC specimens with average pore sizes between 55 mum and 116 mum, and porosities ranging from 59 to 83%. were prepared. These scaffolds were highly compliant and flexible, with high elongations at break. Furthermore, their resistance to creep was excellent and under cyclic loading conditions (20 deformation cycles to 30% elongation) no permanent deformation occurred. Seeding of SMCs into the wall of the tubular structures was done by carefully perfusing cell suspensions with syringes from the lumen through the wall. The cells were then cultured for 7 days. Upon proliferation of the SMCs, the formed blood vessel constructs had excellent mechanical properties. Their radial tensile strengths had increased from 0.23 to 0.78 MPa, which is close to that of natural blood vessels. PMID: 19818420 [PubMed - as supplied by publisher] |
| [Progress on scaffold of vascular tissue engineering]
October 13, 2009 at 8:59 am
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| | [Progress on scaffold of vascular tissue engineering] Zhongguo Xiu Fu Chong Jian Wai Ke Za Zhi. 2009 Sep;23(9):1134-7 Authors: Xue Z, Li M OBJECTIVE: To introduce the materials, preparative technique and endothelialization modification of scaffold. METHODS: The recent original articles about vascular tissue engineering were extensively reviewed and analyzed. RESULTS: The materials including natural materials, biodegradable polymers and composite materials were studied in the field of scaffold. The ways of casting, cell self-assembly, gel spinning and electrospinning were applied to prepare the scaffold of vascular tissue engineering. The modification of scaffold was one of the most important elements for vascular tissue engineering. CONCLUSION: The recent researchs about scaffold of vascular tissue engineering focus on composite material and electrospinning, the modification of scaffold can improve the ability of adhesion to endothelial cells. PMID: 19817305 [PubMed - in process] |
| Tissue assembly and organization: developmental mechanisms in microfabricated tissues.
October 13, 2009 at 8:59 am
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| | Tissue assembly and organization: developmental mechanisms in microfabricated tissues. Biomaterials. 2009 Oct;30(28):4851-8 Authors: Rivron NC, Rouwkema J, Truckenmüller R, Karperien M, De Boer J, Van Blitterswijk CA In vitro-generated tissues hold significant promise in modern biology since they can potentially mimic physiological and pathological tissues. However, these are currently structurally and functionally of limited complexity and necessitate self-organization and recapitulation of tissue development mechanisms in vitro. Tools derived from nano- and microfabrications along with bottom-up strategies are emerging to allow the fabrication of primitive tissues structures that can remodel overtime. Subsequently, clues are accumulating to show that, beyond genetic material, both intrinsic tissue architectures and microenvironmental cues can lead to morphogenesis related mechanisms in vitro. The question arises, however, as how we may design and assemble structures prone to adequate tissue remodeling, predict and manipulate those developmental mechanisms in vitro? Systems integrating architectural, physical and molecular cues will allow more systematic investigation of basic principles of tissue morphogenesis, differentiation or maintenance and will feedback to reproduce the dynamic of tissue development in vitro and form more complex tissues. PMID: 19592088 [PubMed - indexed for MEDLINE] |
| Chitosan/polyglycolic acid nerve grafts for axon regeneration from prolonged axotomized neurons to chronically denervated segments.
October 13, 2009 at 8:59 am
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| | Chitosan/polyglycolic acid nerve grafts for axon regeneration from prolonged axotomized neurons to chronically denervated segments. Biomaterials. 2009 Oct;30(28):5004-18 Authors: Jiao H, Yao J, Yang Y, Chen X, Lin W, Li Y, Gu X, Wang X Peripheral nerve regeneration for long-term delayed injuries is usually unsatisfied. Here we attempted to use a chitosan/polyglycolic acid (PGA) artificial nerve graft to bridge a long-term delayed 10-mm defect in SD rats based on the previous studies on the graft used for immediate repair of 30-mm-long dog sciatic nerve defects and for clinical treatment of a 35-mm-long median nerve defect at elbow of a human patient. In this study, for experimental groups, the rat sciatic nerve had been transected leaving a 10-mm defect, which was maintained for 3 or 6 months before implantation with the chitosan/PGA artificial nerve graft. The animals non-grafted or grafted with autograft served as negative or positive control group. In experiment groups, nerve regeneration with functional recovery was achieved as measured by electrophysiological and histological techniques, although differences in the quantity and the quality of the regenerated nerve were observed between the 3- and 6-month delayed subgroups. The results showed that: (1) a few denervated Schwann cells survived and sustained their ability to myelinate axons at least 6 months, and (2) the atrophic denervated muscle could be reinnervated by regenerated axons through new muscle-nerve connections. These observations provide the possibility of guiding regenerated axons from survived axotomized neurons to distal nerve stump by the chitosan/PGA artificial nerve graft. PMID: 19540584 [PubMed - indexed for MEDLINE] |
| Anterior cruciate ligament regeneration using mesenchymal stem cells and silk scaffold in large animal model.
October 13, 2009 at 8:59 am
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| | Anterior cruciate ligament regeneration using mesenchymal stem cells and silk scaffold in large animal model. Biomaterials. 2009 Oct;30(28):4967-77 Authors: Fan H, Liu H, Toh SL, Goh JC Although in vivo studies in small animal model show the ligament regeneration by implanting mesenchymal stem cells (MSCs) and silk scaffold, large animal studies are still needed to evaluate the silk scaffold before starting a clinical trial. The aim of this study is to regenerate anterior cruciate ligament (ACL) in pig model. The micro-porous silk mesh was fabricated by incorporating silk sponges into knitted silk mesh with lyophilization. Then the scaffold was prepared by rolling the micro-porous silk mesh around a braided silk cord to produce a tightly wound shaft. In vitro study indicated that MSCs proliferated profusely on scaffold and differentiated into fibroblast-like cells by expressing collagen I, collagen III and tenascin-C genes in mRNA level. Then the MSCs-seeded scaffold was implanted in pig model to regenerate ACL. At 24 weeks postoperatively, the MSCs in regenerated ligament exhibited fibroblast morphology. The key ligament-specific extracellular matrix components were produced prominently and indirect ligament-bone insertion with three zones (bone, Sharpey's fibers and ligament) was observed. Although there was remarkable scaffold degradation, the maximum tensile load of regenerated ligament could be maintained after 24 weeks of implantation. In conclusion, the results imply that silk-based material has great potentials for clinical applications. PMID: 19539988 [PubMed - indexed for MEDLINE] | | | 
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