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| Preparation and characterization of lectin-conjugated chitosan fluorescent nanoparticles.
April 10, 2010 at 6:53 AM
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| | Preparation and characterization of lectin-conjugated chitosan fluorescent nanoparticles. Mol Biosyst. 2010 Apr 8; Authors: Liu J, Zhang L, Wang C, Xu H, Zhao X The purpose of this study was to design and evaluate a novel target nanoparticle for disease detection and drug delivery using the biotin-avidin binding system. The formed lectin-conjugated chitosan fluorescent nanoparticles were of spherical shape (100-200 nm in diameter), which were more stable under light than pure fluorescein isothiocyanate (FITC). PMID: 20379582 [PubMed - as supplied by publisher] | | |
| How to become immortal: let MEFs count the ways.
April 10, 2010 at 6:53 AM
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| | How to become immortal: let MEFs count the ways. Aging (Albany NY). 2010 Mar 18;2(3) Authors: Odell A, Askham J, Whibley C, Hollstein M Understanding the molecular mechanisms and biological consequences of genetic changes occurring during bypass of cellular senescence spans a broad area of medical research from the cancer field to regenerative medicine. Senescence escape and immortalisation have been intensively studied in murine embryonic fibroblasts as a model system, and are known to occur when the p53/ARF tumour suppressor pathway is disrupted. We showed recently that murine fibroblasts with a humanised p53 gene (Hupki cells, from a human p53 knock-in mouse model) first senesce, and then become immortalised in the same way as their homologues with normal murine p53. In both cell types, immortalised cultures frequently sustain either a p53 gene mutation matching a human tumour mutation and resulting in loss of p53 transcriptional transactivation, or a biallelic deletion at the p19/ARF locus. Whilst these genetic events were not unexpected, we were surprised to find that a significant proportion! of immortalised cell cultures apparently had neither a p53 mutation nor loss of p19/ARF. Here we consider various routes to p53/ARF disruption in senescence bypass, and dysfunction of other tumour suppressor networks that may contribute to release from tenacious cell cycle arrest in senescent cultures. PMID: 20378935 [PubMed - as supplied by publisher] | | |
| Embryonic and adult stem cell therapy.
April 10, 2010 at 6:53 AM
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| | Embryonic and adult stem cell therapy. J Allergy Clin Immunol. 2010 Feb;125(2 Suppl 2):S336-44 Authors: Brignier AC, Gewirtz AM There are many types of stem cells. All share the characteristics of being able to self-renew and to give rise to differentiated progeny. Over the last decades, great excitement has been generated by the prospect of being able to exploit these properties for the repair, improvement, and/or replacement of damaged organs. However, many hurdles, both scientific and ethical, remain in the path of using human embryonic stem cells for tissue-engineering purposes. In this report we review current strategies for isolating, enriching, and, most recently, inducing the development of human pluripotent stem cells. In so doing, we discuss the scientific and ethical issues associated with this endeavor. Finally, progress in the use of stem cells as therapies for type 1 diabetes mellitus, congestive heart failure, and various neurologic and immunohematologic disorders, and as vehicles for the delivery of gene therapy, is briefly discussed. PMID: 20061008 [PubMed - indexed for MEDLINE] | | |
| Osteochondral Interface Tissue Engineering Using Macroscopic Gradients of Bioactive Signals.
April 10, 2010 at 6:17 AM
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| | Osteochondral Interface Tissue Engineering Using Macroscopic Gradients of Bioactive Signals. Ann Biomed Eng. 2010 Apr 9; Authors: Dormer NH, Singh M, Wang L, Berkland CJ, Detamore MS Continuous gradients exist at osteochondral interfaces, which may be engineered by applying spatially patterned gradients of biological cues. In the present study, a protein-loaded microsphere-based scaffold fabrication strategy was applied to achieve spatially and temporally controlled delivery of bioactive signals in three-dimensional (3D) tissue engineering scaffolds. Bone morphogenetic protein-2 and transforming growth factor-beta(1)-loaded poly(D: ,L: -lactic-co-glycolic acid) microspheres were utilized with a gradient scaffold fabrication technology to produce microsphere-based scaffolds containing opposing gradients of these signals. Constructs were then seeded with human bone marrow stromal cells (hBMSCs) or human umbilical cord mesenchymal stromal cells (hUCMSCs), and osteochondral tissue regeneration was assessed in gradient scaffolds and compared to multiple control groups. Following a 6-week cell culture, the gradient scaffolds produced regionalized ex! tracellular matrix, and outperformed the blank control scaffolds in cell number, glycosaminoglycan production, collagen content, alkaline phosphatase activity, and in some instances, gene expression of major osteogenic and chondrogenic markers. These results suggest that engineered signal gradients may be beneficial for osteochondral tissue engineering. PMID: 20379780 [PubMed - as supplied by publisher] | | |
| Physicochemical control of adult stem cell differentiation: shedding light on potential molecular mechanisms.
April 10, 2010 at 6:17 AM
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| | Physicochemical control of adult stem cell differentiation: shedding light on potential molecular mechanisms. J Biomed Biotechnol. 2010;2010:743476 Authors: Titushkin I, Sun S, Shin J, Cho M Realization of the exciting potential for stem-cell-based biomedical and therapeutic applications, including tissue engineering, requires an understanding of the cell-cell and cell-environment interactions. To this end, recent efforts have been focused on the manipulation of adult stem cell differentiation using inductive soluble factors, designing suitable mechanical environments, and applying noninvasive physical forces. Although each of these different approaches has been successfully applied to regulate stem cell differentiation, it would be of great interest and importance to integrate and optimally combine a few or all of the physicochemical differentiation cues to induce synergistic stem cell differentiation. Furthermore, elucidation of molecular mechanisms that mediate the effects of multiple differentiation cues will enable the researcher to better manipulate stem cell behavior and response. PMID: 20379388 [PubMed - in process] | | |
| Low-Power Ultrasounds as a Tool to Culture Human Osteoblasts inside Cancellous Hydroxyapatite.
April 10, 2010 at 6:17 AM
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| | Low-Power Ultrasounds as a Tool to Culture Human Osteoblasts inside Cancellous Hydroxyapatite. Bioinorg Chem Appl. 2010;:456240 Authors: Fassina L, Saino E, Cusella De Angelis MG, Magenes G, Benazzo F, Visai L Bone graft substitutes and cancellous biomaterials have been widely used to heal critical-size long bone defects due to trauma, tumor resection, and tissue degeneration. In particular, porous hydroxyapatite is widely used in reconstructive bone surgery owing to its biocompatibility. In addition, the in vitro modification of cancellous hydroxyapatite with osteogenic signals enhances the tissue regeneration in vivo, suggesting that the biomaterial modification could play an important role in tissue engineering. In this study, we have followed a tissue-engineering strategy where ultrasonically stimulated SAOS-2 human osteoblasts proliferated and built their extracellular matrix inside a porous hydroxyapatite scaffold. The ultrasonic stimulus had the following parameters: average power equal to 149 mW and frequency of 1.5 MHz. In comparison with control conditions, the ultrasonic stimulus increased the cell proliferation and the surface coating with bone proteins (dec! orin, osteocalcin, osteopontin, type-I collagen, and type-III collagen). The mechanical stimulus aimed at obtaining a better modification of the biomaterial internal surface in terms of cell colonization and coating with bone matrix. The modified biomaterial could be used, in clinical applications, as an implant for bone repair. PMID: 20379359 [PubMed - in process] | | |
| Effects of sintering temperature on physical and compositional properties of alpha-tricalcium phosphate foam.
April 10, 2010 at 6:17 AM
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| | Effects of sintering temperature on physical and compositional properties of alpha-tricalcium phosphate foam. Dent Mater J. 2010 Mar;29(2):154-9 Authors: Udoh K, Munar ML, Maruta M, Matsuya S, Ishikawa K Effects of sintering temperature on the physical and compositional properties of alpha-TCP foam fabricated using the polyurethane foam method were examined. When a polyurethane foam coated with alpha-TCP slurry was sintered at 1,400-1,550 degrees C, alpha-TCP foam having basically the same fully interconnected porous structure was produced although shrinkage occurred with increasing sintering temperature. On porosity of the alpha-TCP foam, a higher foam porosity of 95% was obtained when sintered at 1,400 degrees C as compared to the 90% porosity obtained at a higher sintering temperature of 1,550 degrees C. Further, at 1,500 degrees C or higher temperature, frame became dense with disappearance of micropores. On compressive strength, it increased from approximately 50 to 250 kPa when sintering temperature was increased from 1,400 to 1,550 degrees C. Nonetheless, no compositional changes were observed even when the alpha-TCP foam was cooled in the furnace without q! uenching process. In light of the results obtained, it was concluded that alpha-TCP foam fabricated using the polyurethane method was useful as a bone substitute and/or scaffolding material for tissue engineering. Besides, alpha-TCP foam could be useful as a precursor for the fabrication of other calcium phosphate foams. PMID: 20379025 [PubMed - in process] | | |
| Creation of highly functional CO(3)Ap-collagen scaffold biomaterials.
April 10, 2010 at 6:17 AM
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| | Creation of highly functional CO(3)Ap-collagen scaffold biomaterials. Dent Mater J. 2010 Jan;29(1):1-8 Authors: Okazaki M Physicochemical properties of apatites are affected dramatically by the substitution of trace elements. Especially, biological apatites constituting bone and teeth contain several wt% of CO(3)(2- )ions, which are related to the crystallinity and solubility. Recently, scaffold biomaterials are being developed with a shape-maintaining property in addition to large pores and high porosity, into which cells can easily invade. To develop a new biodegradable scaffold biomaterial, bone-like carbonate apatites (CO(3)Ap) were synthesized and CO(3)Ap-collagen scaffolds were created. This scaffold biomaterial is useful for regions with bone regeneration ability. When these sponge-frame complexes with rh-BMP2 were implanted beneath the periosteum cranii of rats, sufficient new bone was created at the surface of the periosteum cranii after 4 weeks' implantation. Furthermore, when a CO(3)Ap-collagen sponge containing SVVYGLR peptide was implanted as a graft into a tissue defect! created in rat tibia, the migration of numerous vascular endothelial cells, as well as prominent angiogenesis inside the graft, could be detected after 1 week. Thus, the modification of higher functions such as cytokine and angiogenesis factors is effective for low regeneration regions using tissue engineering biomaterials. PMID: 20379005 [PubMed - in process] | | |
| An in vitro model of chronic wound biofilms to test wound dressings and assess antimicrobial susceptibilities.
April 10, 2010 at 6:17 AM
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| | An in vitro model of chronic wound biofilms to test wound dressings and assess antimicrobial susceptibilities. J Antimicrob Chemother. 2010 Apr 8; Authors: Hill KE, Malic S, McKee R, Rennison T, Harding KG, Williams DW, Thomas DW Objectives The targeted disruption of biofilms in chronic wounds is an important treatment strategy and the subject of intense research. In the present study, an in vitro model of chronic wound biofilms was developed to assess the efficacy of antimicrobial treatments for use in the wound environment. Methods Using chronic wound isolates, assays of bacterial coaggregation established that aerobic and anaerobic wound bacteria were able to coaggregate and form biofilms. A constant depth film fermenter (CDFF) was used to develop wound biofilms in vitro, which were analysed using light microscopy and scanning electron microscopy. The susceptibility of bacteria within these biofilms was examined in response to the most frequently prescribed 'chronic wound' antibiotics and a series of iodine- and silver-containing commercial antimicrobial products and lactoferrin. Results Defined biofilms were rapidly established within 1-2 days. Antibiotic treatment demonstrated that mi! xed Pseudomonas and Staphylococcus biofilms were not affected by ciprofloxacin (5 mg/L) or flucloxacillin (15 mg/L), even at concentrations equivalent to twice the observed peak serum levels. The results contrasted with the ability of povidone-iodine (1%) to disrupt the wound biofilm; an effect that was particularly pronounced in the dressing testing where iodine-based dressings completely disrupted established 7 day biofilms. In contrast, only two of six silver-containing dressings exhibited any effect on 3 day biofilms, with no effect on 7 day biofilms. Conclusions This wound model emphasizes the potential role of the biofilm phenotype in the observed resistance to antibiotic therapies that may occur in chronic wounds in vivo. PMID: 20378671 [PubMed - as supplied by publisher] | | |
| Defined high protein content surfaces for stem cell culture.
April 10, 2010 at 6:17 AM
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| | Defined high protein content surfaces for stem cell culture. Biomaterials. 2010 Apr 6; Authors: Doran MR, Frith JE, Prowse AB, Fitzpatrick J, Wolvetang EJ, Munro TP, Gray PP, Cooper-White JJ Unlocking the clinical potential of stem cell based therapies requires firstly elucidation of the biological mechanisms which direct stem cell fate decisions and thereafter, technical advances which allow these processes to be driven in a fully defined culture environment. Strategies for the generation of defined surfaces for human embryonic stem cell (hESC) and mesenchymal stem cell (MSC) culture remain in their infancy. In this paper we outline a simple, effective and efficient method for presenting proteins or peptides on an otherwise non-fouling Layer-by-Layer (LbL) self-assembled surface of hyaluronic acid (HA) and chitosan (CHI). We are able to generate a surface that has both good temporal stability and the ability to direct biological outcomes based on its defined surface composition. Surface functionalization is achieved through suspending the selected extracellular matrix (ECM) protein domain or extracted full-length protein in buffer containing a cross-! linking agent (N-hydroxysulfosuccinimide/N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride) over the LbL HA-CHI surface and then allowing the solvent to evaporate overnight. This simple, but important step results in remarkable protein deposition efficiencies often exceeding 50%, whereas traditional cross-linking methods result in such poor deposition of non-collagenous proteins that a.) quantification of bound amounts of protein is outside the resolution of commonly utilized protein assays, and b.) these surfaces are both unable to support cell attachment and growth. The utility of the protein-modified HA-CHI surfaces is demonstrated through the identification of specific hESC attachment efficiencies and through directing MSC osteogenic outcomes on these fully defined surfaces. This simple and scalable method is shown to enable the development of defined stem cell culture conditions, as well as the elucidation of the fundamental biological processes necessary fo! r the realization of stem cell based therapies. PMID: 20378164 [PubMed - as supplied by publisher] | | |
| The effect of 3D hydrogel scaffold modulus on osteoblast differentiation and mineralization revealed by combinatorial screening.
April 10, 2010 at 6:17 AM
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| | The effect of 3D hydrogel scaffold modulus on osteoblast differentiation and mineralization revealed by combinatorial screening. Biomaterials. 2010 Apr 6; Authors: Chatterjee K, Lin-Gibson S, Wallace WE, Parekh SH, Lee YJ, Cicerone MT, Young MF, Simon CG Cells are known to sense and respond to the physical properties of their environment and those of tissue scaffolds. Optimizing these cell-material interactions is critical in tissue engineering. In this work, a simple and inexpensive combinatorial platform was developed to rapidly screen three-dimensional (3D) tissue scaffolds and was applied to screen the effect of scaffold properties for tissue engineering of bone. Differentiation of osteoblasts was examined in poly(ethylene glycol) hydrogel gradients spanning a 30-fold range in compressive modulus ( approximately 10 kPa to approximately 300 kPa). Results demonstrate that material properties (gel stiffness) of scaffolds can be leveraged to induce cell differentiation in 3D culture as an alternative to biochemical cues such as soluble supplements, immobilized biomolecules and vectors, which are often expensive, labile and potentially carcinogenic. Gel moduli of approximately 225 kPa and higher enhanced osteogenes! is. Furthermore, it is proposed that material-induced cell differentiation can be modulated to engineer seamless tissue interfaces between mineralized bone tissue and softer tissues such as ligaments and tendons. This work presents a combinatorial method to screen biological response to 3D hydrogel scaffolds that more closely mimics the 3D environment experienced by cells in vivo. PMID: 20378163 [PubMed - as supplied by publisher] | | |
| Intermittent dosing of G-CSF to ameliorate carbon tetrachloride-induced liver fibrosis in mice.
April 10, 2010 at 6:17 AM
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| | Intermittent dosing of G-CSF to ameliorate carbon tetrachloride-induced liver fibrosis in mice. Toxicology. 2010 Mar 30;270(1):43-8 Authors: Fang B, Luo S, Song Y, Li N, Li H, Zhao RC On the basis of the recent report that granulocyte colony-stimulating factor (G-CSF) administration after rats' partial orthotopic liver transplantation greatly improved survival rate and liver regeneration of partial graft, we here evaluated the effect of intermittent administration of G-CSF on fibrosis formation induced by carbon tetrachloride (CCl(4)). Bone marrow chimeric female C57BL/6 mice were treated with G-CSF at days 1, 7, 14, 21, and 28 after CCl(4) challenge. At day 35 after CCl(4) administration, we found that G-CSF treatment significantly reduced CCl(4)-induced liver damage and collagen deposition. In addition, levels of hepatic hydroxyproline and serum fibrosis markers in mice receiving G-CSF administration after CCl(4) challenge were significantly lower compared to those of control mice. Histological examination suggested that hepatic damage recovery was much better in these G-CSF-treated mice. Immunofluorescence and fluorescence in situ hybridizat! ion (FISH) analysis revealed that donor cells engrafted into host liver, had epithelium-like morphology and expressed albumin, although at low frequency. These results suggest that intermittent G-CSF treatment might initiate endogenous hepatic tissue regeneration in response to CCl(4) injury and ameliorate its fibrogenic effects. PMID: 20005281 [PubMed - indexed for MEDLINE] | | | | 
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