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| Characterization of poly(ethylene glycol) gels with added collagen for neural tissue engineering.
April 20, 2010 at 7:23 AM
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| | Characterization of poly(ethylene glycol) gels with added collagen for neural tissue engineering. J Biomed Mater Res A. 2010 Jun 1;93(3):817-23 Authors: Scott R, Marquardt L, Willits RK Over the past decade, it has been increasingly recognized that both chemical and mechanical properties of scaffolds influence neural cell behavior, ranging from growth to differentiation to migration. However, mechanical properties are difficult to control for in the design of scaffolds for nerve regeneration, as properties change over time for most biologically derived scaffolds. The focus of this project was to examine how the mechanical properties of a nondegradable scaffold, poly(ethylene glycol) (PEG) gels, influenced nerve cell behavior. Low concentration PEG gels, of 3, 4, or 5% PEG, with added collagen to alter chemical properties were examined for both their mechanical properties and their ability to support nerve expression and extension. Stiffness (G*) significantly increased with increased PEG concentration. The addition of chemically conjugated collagen significantly decreased the stiffness compared to plain gels. This phenomenon was confirmed to be a! n effect of the conjugate, and not the protein itself, as G* of gels containing conjugate, but no protein, was not significantly different than G* of gels with conjugated protein. PC12 cell neurite expression increased with decreasing PEG and increasing collagen concentration. At its best, the expression approached the value on collagen-coated tissue culture plastic, which is a substantial improvement over previous studies on PEG. Neurite extension of dorsal root ganglia was also improved on these same gels over gels with either higher PEG concentration or lower collagen amount. Overall, these results suggest that exploration of lower stiffness materials is necessary to improve neurite growth and extension in three-dimensional synthetic scaffolds. PMID: 20401966 [PubMed - in process] | | |
| Biomechanical and in vivo evaluation of experimental closure devices of the annulus fibrosus designed for a goat nucleus replacement model.
April 20, 2010 at 7:23 AM
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| | Biomechanical and in vivo evaluation of experimental closure devices of the annulus fibrosus designed for a goat nucleus replacement model. Eur Spine J. 2010 Apr 17; Authors: Bron JL, van der Veen AJ, Helder MN, van Royen BJ, Smit TH, , Promising strategies are being developed to replace or regenerate the herniated nucleus pulposus. However, clinical efficacy of these methods has still to be addressed, and the lack of appropriate annulus closure techniques is increasingly being recognised as a major limiting factor. In the current study, in vitro and in vivo evaluation of novel annulus closure devices (ACDs) was performed. These devices are intended to be used in adjunct to nucleus replacement therapies in an experimental goat study. After a standardised discectomy had been performed, different ACDs were implanted solely or in addition to a collagen nucleus replacement implant. Biomechanical effects and axial failure load were assessed in vitro and followed by in vivo evaluation in a goat model. On axial compression, the average axial failure load for ACDs with four barb rings was significantly higher compared to the implants with five barb rings. The increased range of flexion-extension and late! ro-flexion observed after discectomy were restored to the normal range after implantation of the implants. Positive findings with the four-ring ACD were confirmed in goats after a follow-up of 2 weeks in vivo. However, after 6 weeks most implants (n = 16) showed signs of destruction and displacement. Although there seemed to be a tendency towards better results when ACDs were placed in addition to the nucleus replacements, these differences were not statistically significant. Moreover, two endplate reactions extending into the subchondral bone were observed, most likely due to continuous friction between the ACD and the vertebrae. Although current results are encouraging first steps towards the development of an efficient ACD for animal models, further optimisation is necessary. Current results also show that one cannot rely on in vitro biomechanical studies with annulus closure techniques, and these should always be confirmed in vivo in a large animal model. PMID: 20401620 [PubMed - as supplied by publisher] | | |
| Naturally Occurring IgM Anti-Leukocyte Autoantibodies Inhibit T-Cell Activation and Chemotaxis.
April 20, 2010 at 7:23 AM
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| | Naturally Occurring IgM Anti-Leukocyte Autoantibodies Inhibit T-Cell Activation and Chemotaxis. J Clin Immunol. 2010 Apr 17; Authors: Lobo PI, Schlegal KH, Vengal J, Okusa MD, Pei H INTRODUCTION: Naturally occurring IgM antileukocyte antoantibodies (IgM-ALA) are present from birth and increase during inflammatory processes of diverse etiologies. The clinical observation demonstrating a significant correlation (P < 01) between lack of acute rejections and presence of high levels of IgM-ALA in recipients of kidney allografts prompted us to study if IgM-ALA alters T-cell function and leukocyte chemotaxis. METHODS: In-vitro functional assays were performed using leucocytes isolated from human peripheral blood. In-vivo studies were performed in C57BL6 mice. RESULT: Human studies revealed that IgM-ALA consist of several different IgM, each with specificities for a different leukocyte receptor, e.g., CD3, CD4, CCR5, and CXCR4. We show that IgM inhibits T-cell activation, proliferation, and chemotaxis. Data on in vivo murine models of ischemia-reperfusion injury and cardiac transplantation support our hypothesis. CONCLUSION: The innate anti-inflam! matory mechanism of IgM-ALA can be exploited by using purified normal IgM to inhibit inflammatory states or by a vaccine approach to increase in vivo production of IgM-ALA (e.g., prior to a transplant). PMID: 20401525 [PubMed - as supplied by publisher] | | |
| Vascularised human tissue models: A new approach for the refinement of biomedical research.
April 20, 2010 at 7:23 AM
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| | Vascularised human tissue models: A new approach for the refinement of biomedical research. J Biotechnol. 2010 Apr 15; Authors: Schanz J, Pusch J, Hansmann J, Walles H Tissue engineering represents a biology driven approach by which bioartificial tissues are engineered through combining material technology and biotechnology. In order to ensure the functionality of in vitro cultured cells, culture conditions simulating the natural microenvironment must be created. Therefore, 1) sufficient nutrient supply of the cells, 2) co-culture of different cell types, 3) suitable carrier structures (scaffolds), and 4) advanced bioreactor technologies are needed. Bioreactors constitute and maintain physiological tissue conditions at desired levels, enhance mass transport rates, and expose cultured cells to specific stimuli. It has been shown that bioreactor technologies providing appropriate biochemical and physiological regulatory signals guide cell and tissue differentiation and influence tissue specific function of bioartificial 3-dimensional (3D) tissues. In addition, to safeguard sufficient nutrient supply of complex 3D-bioartificial tis! sue models, we developed the biological vascularized scaffold (BioVaSc((R))). The BioVaSc is generated from a decellularized porcine small bowl segment with preserved tubular structures of the capillary network within the collagen matrix. It is the prerequisite for the generation of bioartificial tissues endued with a functional artificial vascular network and has been realized in artificial human liver-, intestine-, trachea- and skin-models. These various human tissue models represent a new technology as alternative to animal experiments for pharmacokinetic (drug penetration, distribution and metabolisation) and pharmacodynamic studies. PMID: 20399817 [PubMed - as supplied by publisher] | | |
| The influence hydroxyapatite nanoparticle shape and size on the properties of biphasic calcium phosphate scaffolds coated with hydroxyapatite-PCL composites.
April 20, 2010 at 7:23 AM
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| | The influence hydroxyapatite nanoparticle shape and size on the properties of biphasic calcium phosphate scaffolds coated with hydroxyapatite-PCL composites. Biomaterials. 2010 Apr 14; Authors: Roohani-Esfahani SI, Nouri-Khorasani S, Lu Z, Appleyard R, Zreiqat H We developed a composite biphasic calcium phosphate (BCP) scaffold by coating a nanocomposite layer, consisting of hydroxyapatite (HA) nanoparticles and polycaprolactone (PCL), over the surface of BCP. The effects of HA particle size and shape in the coating layer on the mechanical and biological properties of the BCP scaffold were examined. Micro-computerized tomography studies showed that the prepared scaffolds were highly porous ( approximately 91%) with large pore size (400-700 mum) and an interconnected porous network of approximately 100%. The HA nanoparticle (needle shape)-composite coated scaffolds displayed the highest compressive strength (2.1 +/- 0.17 MPa), compared to pure HA/beta-TCP (0.1 +/- 0.05 MPa) and to the micron HA - composite coated scaffolds (0.29 +/- 0.07 MPa). These needle shaped scaffolds also showed enhanced elasticity and similar stress-strain profile to natural bone. Needle shaped coated HA/PCL particles induced the differentiation of ! primary human bone derived cells, with significant upregulation of osteogenic gene expression (Runx2, collagen type I, osteocalcin and bone sialoprotein) and alkaline phosphatase activity compared to other groups. These properties are essential for enhancing bone ingrowth in load-bearing applications. The developed composite scaffolds possessed superior physical, mechanical, elastic and biological properties rendering them potentially useful for bone tissue regeneration. PMID: 20398935 [PubMed - as supplied by publisher] | | |
| Characterization of the complete fiber network topology of planar fibrous tissues and scaffolds.
April 20, 2010 at 7:23 AM
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| | Characterization of the complete fiber network topology of planar fibrous tissues and scaffolds. Biomaterials. 2010 Apr 14; Authors: D'Amore A, Stella JA, Wagner WR, Sacks MS Understanding how engineered tissue scaffold architecture affects cell morphology, metabolism, phenotypic expression, as well as predicting material mechanical behavior has recently received increased attention. In the present study, an image-based analysis approach that provides an automated tool to characterize engineered tissue fiber network topology is presented. Micro-architectural features that fully defined fiber network topology were detected and quantified, which include fiber orientation, connectivity, intersection spatial density, and diameter. Algorithm performance was tested using scanning electron microscopy (SEM) images of electrospun poly(ester urethane)urea (ES-PEUU) scaffolds. SEM images of rabbit mesenchymal stem cell (MSC) seeded collagen gel scaffolds and decellularized rat carotid arteries were also analyzed to further evaluate the ability of the algorithm to capture fiber network morphology regardless of scaffold type and the evaluated size ! scale. The image analysis procedure was validated qualitatively and quantitatively, comparing fiber network topology manually detected by human operators (n = 5) with that automatically detected by the algorithm. Correlation values between manual detected and algorithm detected results for the fiber angle distribution and for the fiber connectivity distribution were 0.86 and 0.93 respectively. Algorithm detected fiber intersections and fiber diameter values were comparable (within the mean +/- standard deviation) with those detected by human operators. This automated approach identifies and quantifies fiber network morphology as demonstrated for three relevant scaffold types and provides a means to: (1) guarantee objectivity, (2) significantly reduce analysis time, and (3) potentiate broader analysis of scaffold architecture effects on cell behavior and tissue development both in vitro and in vivo. PMID: 20398930 [PubMed - as supplied by publisher] | | |
| Porous nanocrystalline silicon membranes as highly permeable and molecularly thin substrates for cell culture.
April 20, 2010 at 7:23 AM
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| | Porous nanocrystalline silicon membranes as highly permeable and molecularly thin substrates for cell culture. Biomaterials. 2010 Apr 14; Authors: Agrawal AA, Nehilla BJ, Reisig KV, Gaborski TR, Fang DZ, Striemer CC, Fauchet PM, McGrath JL Porous nanocrystalline silicon (pnc-Si) is new type of silicon nanomaterial with potential uses in lab-on-a-chip devices, cell culture, and tissue engineering. The pnc-Si material is a 15nm thick, freestanding, nanoporous membrane made with scalable silicon manufacturing. Because pnc-Si membranes are approximately 1000 times thinner than any polymeric membrane, their permeability to small solutes is orders-of-magnitude greater than conventional membranes. As cell culture substrates, pnc-Si membranes can overcome the shortcomings of membranes used in commercial transwell devices and enable new devices for the control of cellular microenvironments. The current study investigates the feasibility of pnc-Si as a cell culture substrate by measuring cell adhesion, morphology, growth and viability on pnc-Si compared to conventional culture substrates. Results for immortalized fibroblasts and primary vascular endothelial cells are highly similar on pnc-Si, polystyrene and ! glass. Significantly, pnc-Si dissolves in cell culture media over several days without cytotoxic effects and stability is tunable by modifying the density of a superficial oxide. The results establish pnc-Si as a viable substrate for cell culture and a degradable biomaterial. Pnc-Si membranes should find use in the study of molecular transport through cell monolayers, in studies of cell-cell communication, and as biodegradable scaffolds for three-dimensional tissue constructs. PMID: 20398927 [PubMed - as supplied by publisher] | | |
| Cell delivery therapeutics for musculoskeletal regeneration.
April 20, 2010 at 7:23 AM
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| | Cell delivery therapeutics for musculoskeletal regeneration. Adv Drug Deliv Rev. 2010 Apr 13; Authors: Nöth U, Rackwitz L, Steinert AF, Tuan RS The last decade has witnessed the development of cell-based therapy as a major biomedical research area, including the treatment of musculoskeletal diseases. Both differentiated and undifferentiated stem cells have been used as starting cell sources. In particular, the use of multipotent adult mesenchymal stem cells holds great promise for future therapeutic strategies. In addition to the cell type used, the cell delivery system is also of critical importance in cell-based therapy. Cell delivery may be achieved by direct cell injection or by grafting engineered constructs derived by cell seeding into natural or synthetic biomaterial scaffolds. While direct injection is the most direct and convenient means of cell delivery, the latter approach is capable of producing three-dimensional engineered tissues with mechanical properties compatible with those of various musculoskeletal tissues. This review will focus on the functional approach of using biomaterial scaffold! materials as cell carriers for musculoskeletal applications, as well as the use of cell-based gene therapy for tissue engineering and regeneration. PMID: 20398712 [PubMed - as supplied by publisher] | | |
| Combination stem cell therapy for heart failure.
April 20, 2010 at 7:23 AM
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| | Combination stem cell therapy for heart failure. Int Arch Med. 2010 Apr 14;3(1):5 Authors: Ichim TE, Solano F, Lara F, Paz Rodriguez J, Cristea O, Minev B, Ramos F, Woods EJ, Murphy MP, Alexandrescu DT, Patel AN, Riordan NH ABSTRACT: Patients with congestive heart failure (CHF) that are not eligible for transplantation have limited therapeutic options. Stem cell therapy such as autologous bone marrow, mobilized peripheral blood, or purified cells thereof has been used clinically since 2001. To date over 1000 patients have received cellular therapy as part of randomized trials, with the general consensus being that a moderate but statistically significant benefit occurs. Therefore, one of the important next steps in the field is optimization. In this paper we discuss three ways to approach this issue: a) increasing stem cell migration to the heart; b) augmenting stem cell activity; and c) combining existing stem cell therapies to recapitulate a "therapeutic niche". We conclude by describing a case report of a heart failure patient treated with a combination stem cell protocol in an attempt to augment beneficial aspects of cord blood CD34 cells and mesenchymal-like stem cells. PMID: 20398245 [PubMed - as supplied by publisher] | | |
| Biomedical applications of photochemistry.
April 20, 2010 at 7:23 AM
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| | Biomedical applications of photochemistry. Tissue Eng Part B Rev. 2010 Apr 16; Authors: Chan BP Photochemistry is a study of photochemical reactions between light and molecules. Recently, there is increasing interests in using photochemical reactions in the fields of biomaterials and tissue engineering. This work revisits the components and mechanisms of photochemistry, reviews biomedical applications of photochemistry in various disciplines including oncology, molecular biology and biosurgery, with particular emphasis on tissue engineering. Finally, potential toxicities and research opportunities in this field are discussed. PMID: 20397818 [PubMed - as supplied by publisher] | | |
| The relationship between temporomandibular joint pathosis and muscle tenderness in the orofacial and neck/shoulder region.
April 20, 2010 at 7:23 AM
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| | The relationship between temporomandibular joint pathosis and muscle tenderness in the orofacial and neck/shoulder region. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010 Jan;109(1):86-90 Authors: Inoue E, Maekawa K, Minakuchi H, Nagamatsu-Sakaguchi C, Ono T, Matsuka Y, Clark GT, Kuboki T OBJECTIVE: The objective of this study was to investigate the association between TMJ pain/disk pathosis and the muscle tenderness pattern in the orofacial and neck/shoulder region. STUDY DESIGN: One hundred seventy-one TMD patients were divided into 4 groups, including group 1: patients with painful unilateral TMJ disk displacement (DD); group 2: patients with painless unilateral TMJ DD; group 3: patients with painless bilateral TMJ DD; and group 4: patients with a bilateral normal TMJ disk position (n = 41). Each subject underwent muscle palpation and the side-by-side number of muscle tenderness points was combined as the number of muscle tenderness points on each side. Within each group, DD with and without reduction subjects were separated into subgroups and then were analyzed. RESULTS: In group 1, the median muscle tenderness points on the side with painful TMJ DD without reduction was significantly higher than on the normal side (P = .019), whereas the palpa! tion scores for painless DD patients showed no significant difference between the DD and normal sides. CONCLUSIONS: These results indicated painful disk displacement to possibly be correlated with ipsilateral muscle tenderness. PMID: 20123380 [PubMed - indexed for MEDLINE] | | |
| Recovery process of sciatic nerve defect with novel bioabsorbable collagen tubes packed with collagen filaments in dogs.
April 20, 2010 at 7:23 AM
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| | Recovery process of sciatic nerve defect with novel bioabsorbable collagen tubes packed with collagen filaments in dogs. J Biomed Mater Res A. 2010 Mar 1;92(3):859-68 Authors: Okamoto H, Hata K, Kagami H, Okada K, Ito Y, Narita Y, Hirata H, Sekiya I, Otsuka T, Ueda M Autologous nerve graft is the most commonly applied treatment for the patients with peripheral nerve defect, while application is limited because of tissue availability and unfavorable donor site morbidity. To overcome this problem, peripheral nerve regeneration using a nerve conduit has been studied. Especially, nerve conduit using biodegradable materials has been considered promising. In this study, a potential of collagen nerve conduit has been studied with special reference to the regenerating process of a peripheral nerve. Twelve adult female Beagle dogs weighting 10-12 kg were used. The peroneal nerve was cut to make a 30-mm defect. The nerve defect was bridged by the collagen artificial nerve conduit. Comprehensive functional, electrophysiological, morphometrical, and histological analyses were performed until one year after operation. The wet weight of tibialis anterior muscles was only 32.4% of the healthy side at 24 weeks, which was recovered to 77.4% at! 52 weeks after denervation. Electrophysiological evaluation of tibialis anterior muscle belly showed polyphasic wave at 52 weeks after implantation, which was almost half amplitude as compared with that of control. The diameters of myelinated nerve fibers thickened day by day, and the average diameter was 5.16 microm at PFN, 3.91 microm at CG, and 3.75 microm at DFN, and average thickness of myelin sheath was 0.94 microm at PFN, 0.46 microm at CG, and 0.55 microm at DFN after 52 weeks. The distribution of myelinated nerve fiber size in the 52 weeks group was distinctly bimodal with the major peak at approximately 2-4 microm and the minor peak at 10-12 microm. These findings were consistent with the distribution of the normal nerve fiber. This study proves the feasibility of the collagen artificial nerve conduit for promoting nerve regeneration, raises new possibilities of seeking alternatives to autograft for nerve repair. The results from this study showed detailed proces! s of morphological, electrophysiological, and functional recov! ery of t he regenerated nerve, which would provide scientific background for this novel therapy. PMID: 19280630 [PubMed - indexed for MEDLINE] | | | | 
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