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| State Lawmaker Says CIRM 'Accountable to No One'
February 18, 2010 at 7:00 PM
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| A leading California state senator said today that the state's $3 billion stem cell agency is "essentially accountable to no one" and declared that more accountability and transparency are needed.
Sen. Elaine Kontominas Alquist, D-San Jose and chair of the Senate Health Committee, made the statement in a news release touting her legislation to help ensure that Californians receive a "fair | | |
| Solid freeform fabrication and characterization of porous calcium polyphosphate structures for tissue engineering purposes.
February 18, 2010 at 7:03 AM
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| | Solid freeform fabrication and characterization of porous calcium polyphosphate structures for tissue engineering purposes. J Biomed Mater Res B Appl Biomater. 2010 Feb 16; Authors: Shanjani Y, De Croos JN, Pilliar RM, Kandel RA, Toyserkani E Solid freeform fabrication (SFF) enables the fabrication of anatomically shaped porous components required for formation of tissue engineered implants. This article reports on the characterization of a three-dimensional-printing method, as a powder-based SFF technique, to create reproducible porous structures composed of calcium polyphosphate (CPP). CPP powder of 75-150 mum was mixed with 10 wt % polyvinyl alcohol (PVA) polymeric binder, and used in the SFF machine with appropriate settings for powder mesh size. The PVA binder was eliminated during the annealing procedure used to sinter the CPP particles. The porous SFF fabricated components were characterized using scanning electron microscopy, micro-CT scanning, X-ray diffraction, and mercury intrusion porosimetry. In addition, mechanical testing was conducted to determine the compressive strength of the CPP cylinders. The 35 vol % porous structures displayed compressive strength on average of 33.86 MPa, a value! 57% higher than CPP of equivalent volume percent porosity made through conventional gravity sintering. Dimensional deviation and shrinkage analysis was conducted to identify anisotropic factors required for dimensional compensation during SFF sample formation and subsequent sintering. Cell culture studies showed that the substrate supported cartilage formation in vitro, which was integrated with the top surface of the porous CPP similar to that observed when chondrocytes were grown on CPP formed by conventional gravity sintering methods as determined histologically and biochemically. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. PMID: 20162726 [PubMed - as supplied by publisher] | | |
| Maintaining cell depth viability: on the efficacy of a trimodal scaffold pore architecture and dynamic rotational culturing.
February 18, 2010 at 7:03 AM
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| | Maintaining cell depth viability: on the efficacy of a trimodal scaffold pore architecture and dynamic rotational culturing. J Mater Sci Mater Med. 2010 Feb 17; Authors: Buckley CT, O'Kelly KU Tissue-engineering scaffold-based strategies have suffered from limited cell depth viability when cultured in vitro with viable cells typically existing at the fluid-scaffold interface. This is primarily believed to be due to the lack of nutrient delivery into and waste removal from the inner regions of the scaffold construct. This work focused on the assessment of a hydroxyapatite multi-domain porous scaffold architecture (i.e. a scaffold providing a discrete domain for cell occupancy and a separate domain for nutrient delivery). It has been demonstrated that incorporating unidirectional channels into a porous scaffold material significantly enhanced initial cell seeding distribution, while maintaining relatively high seeding efficiencies. In vitro static culturing showed that providing a discrete domain for nutrient diffusion and metabolic waste removal is insufficient to enhance or maintain homogeneous cell viability throughout the entire scaffold depth during ! a 7-day culture period. In contrast, scaffolds subjected to dynamic rotational culturing maintained uniform cell viability throughout the scaffold depth with increasing culturing time and enhanced the extent of cell proliferation (~2-2.4-fold increase) compared to static culturing. PMID: 20162335 [PubMed - as supplied by publisher] | | |
| Bioglass as a carrier for reindeer bone protein extract in the healing of rat femur defect.
February 18, 2010 at 7:03 AM
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| | Bioglass as a carrier for reindeer bone protein extract in the healing of rat femur defect. J Mater Sci Mater Med. 2010 Feb 17; Authors: Tölli H, Kujala S, Levonen K, Jämsä T, Jalovaara P Bioactive glasses have been developed as scaffolds for bone tissue engineering but combination with reindeer bone protein extract has not been evaluated. We investigated the effects of bone protein extract implants (5-40 mg dosages) with bioglass (BG) carrier on the healing of rat femur defects. Bioglass implants and untreated defects served as controls. All doses of extract increased bone formation compared with the control groups, and bone union was enhanced with doses of 10 mg or more. In comparison with untreated defect, mean cross-sectional bone area at the defect site was greater when implants with BG + 15 mg of extract or bioglass alone were used, bone density at the defect site was higher in all bioglass groups with and without bone extract, and the BG + 15 mg extract dosage marginally increased bone torsional stiffness in mechanical testing. Bioglass performed well as a carrier candidate for reindeer bone protein extract. PMID: 20162331 [PubMed - as supplied by publisher] | | |
| Glycine-spacers influence functional motifs exposure and self-assembling propensity of functionalized substrates tailored for neural stem cell cultures.
February 18, 2010 at 7:03 AM
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| | Glycine-spacers influence functional motifs exposure and self-assembling propensity of functionalized substrates tailored for neural stem cell cultures. Front Neuroengineering. 2010;3:1 Authors: Taraballi F, Natalello A, Campione M, Villa O, Doglia SM, Paleari A, Gelain F The understanding of phenomena involved in the self-assembling of bio-inspired biomaterials acting as three-dimensional scaffolds for regenerative medicine applications is a necessary step to develop effective therapies in neural tissue engineering. We investigated the self-assembled nanostructures of functionalized peptides featuring four, two or no glycine-spacers between the self-assembly sequence RADA16-I and the functional biological motif PFSSTKT. The effectiveness of their biological functionalization was assessed via in vitro experiments with neural stem cells (NSCs) and their molecular assembly was elucidated via atomic force microscopy, Raman and Fourier Transform Infrared spectroscopy. We demonstrated that glycine-spacers play a crucial role in the scaffold stability and in the exposure of the functional motifs. In particular, a glycine-spacer of four residues leads to a more stable nanostructure and to an improved exposure of the functional motif. Acco! rdingly, the longer spacer of glycines, the more effective is the functional motif in both eliciting NSCs adhesion, improving their viability and increasing their differentiation. Therefore, optimized designing strategies of functionalized biomaterials may open, in the near future, new therapies in tissue engineering and regenerative medicine. PMID: 20162033 [PubMed - in process] | | |
| Bridging the Divide between Neuroprosthetic Design, Tissue Engineering and Neurobiology.
February 18, 2010 at 7:03 AM
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| | Bridging the Divide between Neuroprosthetic Design, Tissue Engineering and Neurobiology. Front Neuroengineering. 2010;2:18 Authors: Leach JB, Achyuta AK, Murthy SK Neuroprosthetic devices have made a major impact in the treatment of a variety of disorders such as paralysis and stroke. However, a major impediment in the advancement of this technology is the challenge of maintaining device performance during chronic implantation (months to years) due to complex intrinsic host responses such as gliosis or glial scarring. The objective of this review is to bring together research communities in neurobiology, tissue engineering, and neuroprosthetics to address the major obstacles encountered in the translation of neuroprosthetics technology into long-term clinical use. This article draws connections between specific challenges faced by current neuroprosthetics technology and recent advances in the areas of nerve tissue engineering and neurobiology. Within the context of the device-nervous system interface and central nervous system implants, areas of synergistic opportunity are discussed, including platforms to present cells with! multiple cues, controlled delivery of bioactive factors, three-dimensional constructs and in vitro models of gliosis and brain injury, nerve regeneration strategies, and neural stem/progenitor cell biology. Finally, recent insights gained from the fields of developmental neurobiology and cancer biology are discussed as examples of exciting new biological knowledge that may provide fresh inspiration toward novel technologies to address the complexities associated with long-term neuroprosthetic device performance. PMID: 20161810 [PubMed - in process] | | |
| Biomedical applications of chemically-modified silk fibroin.
February 18, 2010 at 7:03 AM
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| | Biomedical applications of chemically-modified silk fibroin. J Mater Chem. 2009 Jun 23;19(36):6443-6450 Authors: Murphy AR, Kaplan DL Silk proteins belong to a class of unique, high molecular weight, block copolymer-like proteins that have found widespread use in biomaterials and regenerative medicine. The useful features of these proteins, including self-assembly, robust mechanical properties, biocompatibility and biodegradability can be enhanced through a variety of chemical modifications. These modifications provide chemical handles for the attachment of growth factors, cell binding domains and other polymers to silk, expanding the range of cell and tissue engineering applications attainable. This review focuses on the chemical reactions that have been used to modify the amino acids in silk proteins, and describes their utility in biomedical applications. PMID: 20161439 [PubMed - as supplied by publisher] | | |
| Biodegradable Fibrous Scaffolds with Tunable Properties Formed from Photocrosslinkable Poly(glycerol sebacate).
February 18, 2010 at 7:03 AM
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| | Biodegradable Fibrous Scaffolds with Tunable Properties Formed from Photocrosslinkable Poly(glycerol sebacate). ACS Appl Mater Interfaces. 2009 Sep 30;1(9):1878-1892 Authors: Ifkovits JL, Devlin JJ, Eng G, Martens TP, Vunjak-Novakovic G, Burdick JA It is becoming increasingly apparent that the architecture and mechanical properties of scaffolds, particularly with respect to mimicking features of natural tissues, are important for tissue engineering applications. Acrylated poly(glycerol sebacate) (Acr-PGS) is a material that can be crosslinked upon exposure to ultraviolet light, leading to networks with tunable mechanical and degradation properties through simple changes during Acr-PGS synthesis. For example, the number of acrylate functional groups on the macromer dictates the concentration of crosslinks formed in the resulting network. Three macromers were synthesized that form networks that vary dramatically with respect to their tensile modulus (~30 kPa to 6.6 MPa) and degradation behavior (~20 to 100% mass loss at 12 weeks) based on the extent of acrylation (~1 to 24%). These macromers were processed into biodegradable fibrous scaffolds using electrospinning, with gelatin as a carrier polymer to facilita! te fiber formation and cell adhesion. The resulting scaffolds were also diverse with respect to their mechanics (tensile modulus ranging from ~60 kPa to 1 MPa) and degradation (~45 to 70% mass loss by 12 weeks). Mesenchymal stem cell adhesion and proliferation on all fibrous scaffolds was indistinguishable from controls. The scaffolds showed similar diversity when implanted on the surface of hearts in a rat model of acute myocardial infarction and demonstrated a dependence on scaffold thickness and chemistry in the host response. In summary, these diverse scaffolds with tailorable chemical, structural, mechanical and degradation properties are potentially useful for the engineering of a wide range of soft tissues. PMID: 20160937 [PubMed - as supplied by publisher] | | |
| The future: optimizing the healing environment in anterior cruciate ligament reconstruction.
February 18, 2010 at 7:03 AM
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| | The future: optimizing the healing environment in anterior cruciate ligament reconstruction. Sports Med Arthrosc. 2010 Mar;18(1):48-53 Authors: Sánchez M, Anitua E, Lopez-Vidriero E, Andía I The therapeutic use of autologous platelet-rich plasma constitutes a breakthrough in the stimulation and acceleration of soft-tissue healing and bone regeneration. Platelet-rich technologies seek to facilitate anterior cruciate ligament replacement by mimicking the native tissue and improving the adequacy of tissue function with appropriate cues, ultimately leading to better patient care. There are different technical protocols for preparing platelet-rich plasma, and the resultant products are typically heterogeneous; moreover, protocols for administrating the products in patients vary extensively. Poor standardization in the field makes full evaluation of different plasma products and establishing standards for the most beneficial applications of this technology difficult. This article presents the current data on the use of platelet-rich plasma in the reconstruction of the anterior cruciate ligament. Although the findings are not conclusive, the use of autologou! s platelet-rich plasma is shown to be safe, reproducible, and effective in mimicking the natural processes of soft tissue and bone healing. Platelet-rich technologies offer new opportunities for research and the application of anterior cruciate ligament tissue engineering. PMID: 20160631 [PubMed - in process] | | |
| Active multilayered capsules for in vivo bone formation.
February 18, 2010 at 7:03 AM
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| | Active multilayered capsules for in vivo bone formation. Proc Natl Acad Sci U S A. 2010 Feb 16; Authors: Facca S, Cortez C, Mendoza-Palomares C, Messadeq N, Dierich A, Johnston AP, Mainard D, Voegel JC, Caruso F, Benkirane-Jessel N Interest in the development of new sources of transplantable materials for the treatment of injury or disease has led to the convergence of tissue engineering with stem cell technology. Bone and joint disorders are expected to benefit from this new technology because of the low self-regenerating capacity of bone matrix secreting cells. Herein, the differentiation of stem cells to bone cells using active multilayered capsules is presented. The capsules are composed of poly-L-glutamic acid and poly-L-lysine with active growth factors embedded into the multilayered film. The bone induction from these active capsules incubated with embryonic stem cells was demonstrated in vitro. Herein, we report the unique demonstration of a multilayered capsule-based delivery system for inducing bone formation in vivo. This strategy is an alternative approach for in vivo bone formation. Strategies using simple chemistry to control complex biological processes would be particularly p! owerful, as they make production of therapeutic materials simpler and more easily controlled. PMID: 20160118 [PubMed - as supplied by publisher] | | |
| Apatite Containing Aspartic Acid for Selective Protein Loading.
February 18, 2010 at 7:03 AM
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| | Apatite Containing Aspartic Acid for Selective Protein Loading. J Dent Res. 2010 Feb 16; Authors: Hafiz Uddin M, Matsumoto T, Ishihara S, Nakahira A, Okazaki M, Sohmura T Physico-chemical modifications of hydroxyapatite (HAp) materials are considered as pre-requisites for the development of new bioactive carrier materials for drug delivery and tissue engineering applications. Since acidic amino acids have well-documented affinities to both HAp and basic proteins, HAp modified by aspartic acid (Asp, acidic amino acid) might be one of the candidate substrates for a basic protein carrier. Here, we synthesized HAp in the presence of various concentrations of Asp and observed that HAp crystallinity and other physico-chemical properties were effectively modulated. Detailed studies indicated that Asp was not incorporated in the HAp crystal lattice, but rather was trapped in HAp crystals. Protein adsorption studies indicated that the HAp particles modified by Asp had a selective loading capacity for basic protein. Therefore, HAp particles containing Asp might have potential in drug delivery applications, especially as the carrier of basic ! proteins including bFGF and BMP. PMID: 20160067 [PubMed - as supplied by publisher] | | |
| Biomimetic Branched Hollow Fibers Templated by Self-Assembled Fibrous Polyvinylpyrrolidone Structures in Aqueous Solution.
February 18, 2010 at 7:03 AM
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| | Biomimetic Branched Hollow Fibers Templated by Self-Assembled Fibrous Polyvinylpyrrolidone Structures in Aqueous Solution. ACS Nano. 2010 Feb 16; Authors: Qiu P, Mao C Branched hollow fibers are common in nature, but to form artificial fibers with a similar branched hollow structure is still a challenge. We discovered that polyvinylpyrrolidone (PVP) could self-assemble into branched hollow fibers in an aqueous solution after aging the PVP solution for about two weeks. On the basis of this finding, we demonstrated two approaches by which the self-assembly of PVP into branched hollow fibers could be exploited to template the formation of branched hollow inorganic fibers. First, inorganic material such as silica with high affinity against the PVP could be deposited on the surface of the branched hollow PVP fibers to form branched hollow silica fibers. To extend the application of PVP self-assembly in templating the formation of hollow branched fibers, we then adopted a second approach where the PVP molecules bound to inorganic nanoparticles (using gold nanoparticles as a model) co-self-assemble with the free PVP molecules in an aqu! eous solution, resulting in the formation of the branched hollow fibers with the nanoparticles embedded in the PVP matrix constituting the walls of the fibers. Heating the resultant fibers above the glass transition temperature of PVP led to the formation of branched hollow gold fibers. Our work suggests that the self-assembly of the PVP molecules in the solution can serve as a general method for directing the formation of branched hollow inorganic fibers. The branched hollow fibers may find potential applications in microfluidics, artificial blood vessel generation, and tissue engineering. PMID: 20158250 [PubMed - as supplied by publisher] | | |
| Self-Assembling Multidomain Peptide Hydrogels: Designed Susceptibility to Enzymatic Cleavage Allows Enhanced Cell Migration and Spreading.
February 18, 2010 at 7:03 AM
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| | Self-Assembling Multidomain Peptide Hydrogels: Designed Susceptibility to Enzymatic Cleavage Allows Enhanced Cell Migration and Spreading. J Am Chem Soc. 2010 Feb 16; Authors: Galler KM, Aulisa L, Regan KR, D'Souza RN, Hartgerink JD Multidomain peptides are a class of amphiphilic self-assembling peptides with a modular ABA block motif in which the amphiphilic B block drives self-assembly while the flanking A blocks, which are electrostatically charged, control the conditions under which assembly takes place. Previously we have shown that careful selection of the amino acids in the A and B blocks allow one to control the self-assembled fiber length and viscoelastic properties of formed hydrogels. Here we demonstrate how the modular nature of this peptide assembler can be designed for biological applications. With control over fiber length and diameter, gelation conditions, and viscoelastic properties, we can develop suitable materials for biological applications. Going beyond a simple carrier for cell delivery, a biofunctional scaffold will interact with the cells it carries, promoting advantageous cell-matrix interactions. We demonstrate the design of a multidomain peptide into a bioactive va! riant by incorporation of a matrix metalloprotease 2 (MMP-2) specific cleavage site and cell adhesion motif. Gel formation and rheological properties were assessed and compared to related peptide hydrogels. Proteolytic degradation by collagenase IV was observed in a gel weight loss study and confirmed by specific MMP-2 degradation monitored by mass spectrometry and cryo-transmission electron microscopy (cryo-TEM). Combination of this cleavage site with the cell adhesion motif RGD resulted in increased cell viability and cell spreading and encouraged cell migration into the hydrogel matrix. Collectively the structural, mechanical, and bioactive properties of this multidomain peptide hydrogel make it suitable as an injectable material for a variety of tissue engineering applications. PMID: 20158218 [PubMed - as supplied by publisher] | | |
| Flk-1+ mesenchymal stem cells aggravate collagen-induced arthritis by up-regulating interleukin-6.
February 18, 2010 at 7:03 AM
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| | Flk-1+ mesenchymal stem cells aggravate collagen-induced arthritis by up-regulating interleukin-6. Clin Exp Immunol. 2010 Mar;159(3):292-302 Authors: Chen B, Hu J, Liao L, Sun Z, Han Q, Song Z, Zhao RC The immunomodulatory ability of mesenchymal stem cells (MSCs) may be used to develop therapies for autoimmune diseases. Flk-1(+) MSCs are a population of MSCs with defined phenotype and their safety has been evaluated in Phase 1 clinical trials. We designed this study to evaluate whether Flk-1(+) MSCs conferred a therapeutic effect on collagen-induced arthritis (CIA), an animal model of rheumatic arthritis, and to explore the underlying mechanisms. Flk-1(+) MSCs, 1-2 x 10(6), were injected into CIA mice on either day 0 or day 21. The clinical course of arthritis was monitored. Serum cytokine profile was determined by cytometric bead array kit or enzyme-linked immunosorbent assay. Flk-1(+) MSCs and splenocytes co-culture was conducted to explore the underlying mechanisms. Flk-1(+) MSCs did not confer therapeutic benefits. Clinical symptom scores and histological evaluation suggested aggravation of arthritis in mice treated with MSCs at day 21. Serum cytokine profil! e analysis showed marked interleukin (IL)-6 secretion immediately after MSC administration. Results of in vitro culture of splenocytes confirmed that the addition of Flk-1(+) MSCs promoted splenocyte proliferation and increased IL-6 and IL-17 secretion. Moreover, splenocyte proliferation was also enhanced in mice treated with MSCs at day 21. Accordingly, MSCs at low concentrations were found to promote lipopolysaccharide-primed splenocytes proliferation in an in vitro co-culture system. We propose that Flk-1(+) MSCs aggravate arthritis in CIA model by at least up-regulating secretion of IL-6, which favours Th17 differentiation. When Flk-1(+) MSCs are used for patients, we should be cautious about subjects with rheumatoid arthritis. PMID: 20002448 [PubMed - indexed for MEDLINE] | | |
| Biomaterial mediated epithelial-mesenchymal interaction of salivary tissue under serum free condition.
February 18, 2010 at 7:03 AM
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| | Biomaterial mediated epithelial-mesenchymal interaction of salivary tissue under serum free condition. Biomaterials. 2010 Jan;31(2):288-95 Authors: Yang TL, Hsiao YC, Lin SJ, Lee HW, Lou PJ, Ko JY, Young TH Many organs develop from epithelial-mesenchymal interactions such that in order to regenerate these organs, it might be a preferable strategy to recapitulate this process. However, in the current culture system designed for tissue interaction, the supplement of serum is required. The aim of this study is to explore the possibility of reproducing epithelial-mesenchymal interaction and ensuing morphogenesis in a serum-free condition. In accordance with the previous studies, by using a standard model of murine fetal submandibular gland (SMG), the tissue interaction and the morphogenesis were largely dependent on serum. Nonetheless, when tissue recombinants were cultivated on polyvinylidene fluoride (PVDF), but not on other biomaterials, the serum-deprived effect could be rescued. On PVDF, SMG tissue recombinant was able to increase epithelial size, de novo synthesize basement membrane, and develop new branches without serum. Although the gene expression levels of sel! ected morphogens were not significantly altered, the precise localization of morphogenetic-decisive extracellular matrix such as type III collagen and the superior adsorbing capacity of essential diffusible factors like fibroblast growth factor 7 (FGF7) might account for PVDF effect. Accordingly, the result demonstrates that it is possible to establish a serum-free system that is competent in facilitating epithelial-mesenchymal interaction of salivary tissue. With PVDF, the crosstalk between SMG epithelia and mesenchyme could be sustained without serum. PMID: 19853295 [PubMed - indexed for MEDLINE] | | |
| The development of a tissue-engineered artery using decellularized scaffold and autologous ovine mesenchymal stem cells.
February 18, 2010 at 7:03 AM
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| | The development of a tissue-engineered artery using decellularized scaffold and autologous ovine mesenchymal stem cells. Biomaterials. 2010 Jan;31(2):296-307 Authors: Zhao Y, Zhang S, Zhou J, Wang J, Zhen M, Liu Y, Chen J, Qi Z Alternatives to using native arteries in vascular surgery are urgently needed. Vessels made from synthetic polymers have shortcomings such as thrombosis, rejection, intimal hyperplasia, calcification, infection, chronic inflammation and no growth potential. Tissue-engineered blood vessels (TEBV) may overcome these problems. We developed a tissue-engineered artery using autologous bone marrow derived mesenchymal stem cells (MSCs) and a decellularized arterial scaffold. Vascular smooth muscle cell (SMCs)-like cells and endothelial cell (ECs)-like cells were differentiated from MSCs in vitro. We constructed TEBV by seeding these autologous cells onto decellularized ovine carotid arteries and interposed into the carotid arteries in an ovine host models. The scaffold retained the main structural components of a blood vessel, such as collagen and elastin. The TEBVs were patent, anti-thrombogenic, and mechanically stable for 5 months in vivo, whereas non-seeded grafts oc! cluded within 2 weeks. Histological, immunohistochemical, and electron microscopic analyses of the TEBVs demonstrated the existence of endothelium, smooth muscle and the presence of collagen and elastin both at 2 and 5 months, respectively. MSCs labeled with a fluorescent dye prior to implantation were detected in the harvested TE artery 2 months after implantation, indicating that the MSCs survived and contributed to the vascular tissue regeneration. Therefore, TEBVs can be assembled from autologous MSCs and decellularized bioscaffold. PMID: 19819544 [PubMed - indexed for MEDLINE] | | |
| Scaffolds with covalently immobilized VEGF and Angiopoietin-1 for vascularization of engineered tissues.
February 18, 2010 at 7:03 AM
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| | Scaffolds with covalently immobilized VEGF and Angiopoietin-1 for vascularization of engineered tissues. Biomaterials. 2010 Jan;31(2):226-41 Authors: Chiu LL, Radisic M The aim of this study was to engineer a biomaterial capable of supporting vascularization in vitro and in vivo. We covalently immobilized vascular endothelial growth factor (VEGF) and Angiopoietin-1 (Ang1) onto three-dimensional porous collagen scaffolds using 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) chemistry. Over both 3 and 7 days in vitro, seeded endothelial cells (ECs) had increased proliferation on scaffolds with immobilized VEGF and/or Ang1 compared to unmodified scaffolds and soluble growth factor controls. Notably, the group with co-immobilized VEGF and Ang1 showed significantly higher cell number (P=0.0079), higher overall lactate production rate (P=0.0044) and higher overall glucose consumption rate (P=0.0034) at Day 3, compared to its corresponding soluble control for which growth factors were added to culture medium. By Day 7, hematoxylin and eosin, live/dead, CD31, and von Willebrand factor staining all showed improved tube f! ormation by ECs when cultivated on scaffolds with co-immobilized growth factors. Interestingly, scaffolds with co-immobilized VEGF and Ang1 showed increased EC infiltration in the chorioallantoic membrane (CAM) assay, compared to scaffolds with independently immobilized VEGF/Ang1. This study presents an alternative method for promoting the formation of vascular structures, via covalent immobilization of angiogenic growth factors that are more stable than soluble ones and have a localized effect. PMID: 19800684 [PubMed - indexed for MEDLINE] | | |
| Fabrication and characterization of porous tubular silk fibroin scaffolds.
February 18, 2010 at 7:03 AM
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| | Fabrication and characterization of porous tubular silk fibroin scaffolds. J Biomater Sci Polym Ed. 2009;20(13):1961-74 Authors: Min S, Gao X, Liu L, Tian L, Zhu L, Zhang H, Yao J Silk fibroin (SF) has been one of promising resources of biotechnology and biomedical materials due to its unique properties. Here, different sizes of porous tubular scaffolds were fabricated from a SF aqueous solution with the addition of poly(ethylene glycol diglycidyl ether) (PGDE). The scaffolds were generally flexible and transparent at the wet state with a pore size of 81-128 mum and porosity of 90-96%, depending on the concentrations of SF and PGDE. The mechanical properties measurement showed that the tubular SF scaffolds had satisfying tensile and compression properties, especially the excellent deformation-recovery ability. FT-IR spectra indicated that the SF in the tubular scaffolds was in a beta-sheet structure, and no PGDE characteristic band was observed, suggesting that the PGDE could be removed from the scaffolds by soaking in deionized water. The cell compatibility of scaffolds was evaluated, and no obvious cytotoxicity to mouse L-929 fibroblasts ! was detected. PMID: 19793450 [PubMed - indexed for MEDLINE] | | |
| Impact of RGD micro-patterns on cell adhesion.
February 18, 2010 at 7:03 AM
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| | Impact of RGD micro-patterns on cell adhesion. Colloids Surf B Biointerfaces. 2010 Jan 1;75(1):107-14 Authors: Chollet C, Lazare S, Guillemot F, Durrieu MC In order to avoid the problems related to biomaterial use (inflammation, infections, aseptic loosening, etc.), a new approach consisting of associating the material and autologous cells before implantation is being developed, thus requiring a perfect cooperation between the material's surface and the cell. To improve cell adhesion to biomaterials, a suitable method is to functionalize their surface by pro-adhesive ligand grafting. The aim of this study was to covalently graft RGD containing peptides onto a poly-(ethylene terephthalate) surface in well-defined microstructures in order to control MC3T3 cell adhesion. We followed two different routes for obtaining micro-patterned materials: (1) a photoablation technique using an excimer laser and (2) a photolithography process. The resulting patterns were characterized by optical microscopy, scanning electron microscopy, optical profilometry and high resolution mu-imager. The biological evaluation of cell adhesion on! to the micro-patterned surfaces was carried out using optical microscopy, scanning electron microscopy and fluorescence microscopy. Cells seeded onto photolithographical or photoablated micro-patterned PET exhibited an alignment with the RGD domains and appear to be connecting through pseudopods extending towards each other. Whatever the technique used to create micro-patterns, a cell alignment occurs once the thickness of the RGD line reaches approximately 100 microm. These results prove the importance of microstructured surfaces for the elaboration of tissue engineered biomaterials. PMID: 19775874 [PubMed - indexed for MEDLINE] | | |
| A novel three-dimensional tubular scaffold prepared from silk fibroin by electrospinning.
February 18, 2010 at 7:03 AM
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| | A novel three-dimensional tubular scaffold prepared from silk fibroin by electrospinning. Int J Biol Macromol. 2009 Dec 1;45(5):504-10 Authors: Zhou J, Cao C, Ma X Effects of electrospinning parameters (including voltage, collection distance, solution concentration and flow rate) on the morphology and diameter distribution of regenerated SF (silk fibroin) fiber were investigated. Afterward, SF tubular scaffold composed of homogenous fibers was fabricated at voltage of 18kV, collection distance of 18cm, concentration of 37%, and flow rate of 0.15mL/min. After methanol treatment, SF tubular scaffold showed tensile strength of 3.57MPa and porosity of 80.85%. It is satisfied that our work offers a simple method to fabricate seamless and porous tubular scaffold from SF without any additives and organic solvents. Furthermore, the results suggest that this tubular scaffold shows promising applications in small-diameter vascular graft. PMID: 19772871 [PubMed - indexed for MEDLINE] | | |
| Release characteristics and osteogenic activity of recombinant human bone morphogenetic protein-2 grafted to novel self-assembled poly(lactide-co-glycolide fumarate) nanoparticles.
February 18, 2010 at 7:03 AM
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| | Release characteristics and osteogenic activity of recombinant human bone morphogenetic protein-2 grafted to novel self-assembled poly(lactide-co-glycolide fumarate) nanoparticles. J Control Release. 2009 Dec 3;140(2):148-56 Authors: Mercado AE, Ma J, He X, Jabbari E Functionalized biodegradable nanoparticles (NPs) provide reactive groups and large surface area for grafting recombinant human bone morphogenetic protein-2 (rhBMP-2) to reduce protein diffusion and maintain sufficient concentration for recruitment and differentiation of osteoprogenitor cells. The objective of this work was to investigate release characteristics and osteogenic activity of rhBMP-2, grafted to biodegradable NPs based on succinimide-terminated poly(lactide fumarate) (PLAF-NHS) and poly(lactide-co-glycolide fumarate) (PLGF-NHS) macromers. The release of rhBMP-2 from the NPs, measured by enzyme-linked immunosorbent assay, was linear with time in the first two weeks, and 24.70+/-1.30% and 48.7+/-0.7% of the protein grafted to PLGF-NHS and PLAF-NHS NPs, respectively, was released in the enzymatically active conformation after complete degradation/erosion of the NPs. After 14 days of incubation with bone marrow stromal (BMS) cells, rhBMP-2 grafted to PLAF-! NHS and PLGF-NHS NPs was as effective in inducing mineralization as the native rhBMP-2 that was directly added to the cell culture media. At any incubation time, rhBMP-2 grafted to PLAF had the highest expression of osteopontin (OP) and osteocalcin (OC), followed by rhBMP-2 grafted to PLGF and rhBMP-2 directly added to media. Higher OP and OC expression for BMP-gPLAF and BMP-gPLGF groups may be related to other factors in the cascade of osteogenesis, such as differentiation of BMS cells to the vasculogenic lineage and formation of a vascularized/mineralized matrix. PMID: 19699244 [PubMed - indexed for MEDLINE] | | | | 
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