| Genetically Engineered Mesenchymal Stem Cells: The Ongoing Research for Bone Tissue Engineering.
December 23, 2009 at 11:18 am
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| | Genetically Engineered Mesenchymal Stem Cells: The Ongoing Research for Bone Tissue Engineering. Anat Rec (Hoboken). 2009 Dec 21; Authors: Hong D, Chen HX, Ge R, Li JC Bone grafting is crucial in the surgical treatment of bone defects and nonunion fractures. Autogenous bone, allogenous bone, and biomaterial scaffold are three main sources of bone grafts. The biomaterial scaffold, both natural and synthetic, is widely accessible but weak in osteogenic potential. One approach to solve this problem is cell-based bone tissue engineering (BTE), established by growing living osteogenic cells on scaffold in vitro to build up its osteoinducitive capability. Mesenchymal stem cell (MSC) is suitable for use in cell-based BTE, but it remains a considerable challenge to induce MSCs to form solely bone and while preventing MSCs from differentiating into fats, muscles, and possibly neural elements in vivo. Recently, there is a drastic rise in use of genetically engineered MSCs, which can secrete growth factors or alter the transcription level, leading to osteoblast lineage commitment, bone formation, fracture repair, and spinal fusion. In this article, we reviewed the literatures regarding applications of genetically engineered MSCs in BTE. We addressed the currently applicable genes and candidate genes for MSCs modification, transduction efficiency and safety issues of the transfect vectors, and administration routes, and we briefly described in vivo tracking and potential clinical application of the genetically modified MSCs in BTE. Anat Rec, 2010. (c) 2009 Wiley-Liss, Inc. PMID: 20027644 [PubMed - as supplied by publisher] |
| Crosslinking of cell-derived 3D scaffolds up-regulates the stretching and unfolding of new extracellular matrix assembled by reseeded cells.
December 23, 2009 at 11:18 am
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| | Crosslinking of cell-derived 3D scaffolds up-regulates the stretching and unfolding of new extracellular matrix assembled by reseeded cells. Integr Biol (Camb). 2009 Dec;1(11-12):635-48 Authors: Kubow KE, Klotzsch E, Smith ML, Gourdon D, Little WC, Vogel V Elevated levels of tissue crosslinking are associated with numerous diseases (cancer stroma, organ fibrosis), and also eliminate the otherwise remarkable clinical successes of tissue-derived scaffolds, instead eliciting a foreign body reaction. Nevertheless, it is not well understood how the initial physical and biochemical properties of cellular microenvironments, stem cell niches, or of 3D tissue scaffolds guide the assembly and remodeling of new extracellular matrix (ECM) that is ultimately sensed by cells. Here, we incorporated FRET-based mechanical strain sensors, either into cell-derived ECM scaffolds or into the fibronectin (Fn) matrix assembled by reseeded fibroblasts, and demonstrated the following. Cell-generated tensile forces change the conformation of Fn in both 3D scaffolds and new matrix over time. The time course by which new matrix fibers are stretched by reseeded cells is accelerated by scaffold crosslinking. Importantly, stretching Fn fibers increases their elastic modulus (rigidity) and alters their biochemical display. Regulated by Fn fiber unfolding, more soluble Fn binds to the native than to the crosslinked scaffolds. Additionally, matrix assembly of fibroblasts is decreased by scaffold crosslinking. Taken together, scaffold crosslinking has a multifactorial impact on the microenvironment that reseeded cells assemble and respond to, with far-reaching implications for tissue engineering and disease physiology. PMID: 20027372 [PubMed - in process] |
| Reprogramming towards pluripotency requires AID-dependent DNA demethylation.
December 23, 2009 at 11:18 am
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| | Reprogramming towards pluripotency requires AID-dependent DNA demethylation. Nature. 2009 Dec 21; Authors: Bhutani N, Brady JJ, Damian M, Sacco A, Corbel SY, Blau HM Reprogramming of somatic cell nuclei to yield induced pluripotent stem (iPS) cells makes possible derivation of patient-specific stem cells for regenerative medicine. However, iPS cell generation is asynchronous and slow (2-3 weeks), the frequency is low (<0.1%), and DNA demethylation constitutes a bottleneck. To determine regulatory mechanisms involved in reprogramming, we generated interspecies heterokaryons (fused mouse embryonic stem (ES) cells and human fibroblasts) that induce reprogramming synchronously, frequently and fast. Here we show that reprogramming towards pluripotency in single heterokaryons is initiated without cell division or DNA replication, rapidly (1 day) and efficiently (70%). Short interfering RNA (siRNA)-mediated knockdown showed that activation-induced cytidine deaminase (AID, also known as AICDA) is required for promoter demethylation and induction of OCT4 (also known as POU5F1) and NANOG gene expression. AID protein bound silent methylated OCT4 and NANOG promoters in fibroblasts, but not active demethylated promoters in ES cells. These data provide new evidence that mammalian AID is required for active DNA demethylation and initiation of nuclear reprogramming towards pluripotency in human somatic cells. PMID: 20027182 [PubMed - as supplied by publisher] |
| p38-{gamma}-dependent gene silencing restricts entry into the myogenic differentiation program.
December 23, 2009 at 11:18 am
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| | p38-{gamma}-dependent gene silencing restricts entry into the myogenic differentiation program. J Cell Biol. 2009 Dec 21; Authors: Gillespie MA, Le Grand F, Scimè A, Kuang S, von Maltzahn J, Seale V, Cuenda A, Ranish JA, Rudnicki MA The mitogen-activated protein kinase p38-gamma is highly expressed in skeletal muscle and is associated with the dystrophin glycoprotein complex; however, its function remains unclear. After induced damage, muscle in mice lacking p38-gamma generated significantly fewer myofibers than wild-type muscle. Notably, p38-gamma-deficient muscle contained 50% fewer satellite cells that exhibited premature Myogenin expression and markedly reduced proliferation. We determined that p38-gamma directly phosphorylated MyoD on Ser199 and Ser200, which results in enhanced occupancy of MyoD on the promoter of myogenin together with markedly decreased transcriptional activity. This repression is associated with extensive methylation of histone H3K9 together with recruitment of the KMT1A methyltransferase to the myogenin promoter. Notably, a MyoD S199A/S200A mutant exhibits markedly reduced binding to KMT1A. Therefore, p38-gamma signaling directly induces the assembly of a repressive MyoD transcriptional complex. Together, these results establish a hitherto unappreciated and essential role for p38-gamma signaling in positively regulating the expansion of transient amplifying myogenic precursor cells during muscle growth and regeneration. PMID: 20026657 [PubMed - as supplied by publisher] |
| Stem cell experiments and initial clinical trial of cellular cardiomyoplasty.
December 23, 2009 at 11:18 am
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| | Stem cell experiments and initial clinical trial of cellular cardiomyoplasty. Asian Cardiovasc Thorac Ann. 2009 Dec;17(6):581-6 Authors: Guhathakurta S, Subramanyan UR, Balasundari R, Das CK, Madhusankar N, Cherian KM Growing myocardial cells from human stem cells and stem cell transplantation to repair injured myocardium are new frontiers in cardiovascular research. The 1(st) stage of this study was conducted to determine whether transplantation of autologous bone marrow stem cells into infarcted myocardium of sheep could differentiate into beating cardiomyocytes. The 2(nd) stage was to demonstrate transdifferentiation of human bone marrow mesenchymal stem cells to precursor cardiomyocytes in vitro, using a novel conditioning medium. In the 3(rd) stage, a clinical trial of stem cell implantation in patients with severe myocardial dysfunction involved injection of peripheral blood-derived endothelial precursor cells in 11 patients and autologous bone marrow mononuclear cells in 29. A marginal improvement in myocardial function was noted at 3 months (mean increase in ejection fraction, 6% +/- 1%), although it plateaued at 6 months. The trial proved to be safe because there was no procedure-related mortality. There is growing optimism that stem cell therapy may delay heart transplantation. PMID: 20026532 [PubMed - in process] |
| Porous polycaprolactone scaffold for cardiac tissue engineering fabricated by selective laser sintering.
December 23, 2009 at 11:18 am
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| | Porous polycaprolactone scaffold for cardiac tissue engineering fabricated by selective laser sintering. Acta Biomater. 2009 Dec 18; Authors: Yeong WY, Sudarmadji N, Yu HY, Chua CK, Leong KF, Venkatraman SS, Freddy Boey YC, Tan LP An advanced manufacturing technique, Selective Laser Sintering (SLS), was utilized to fabricate porous polycaprolactone (PCL) scaffold designed with an automated algorithm in a parametric library system named "Computer Aided System for Tissue Scaffolds" (CASTS). Tensile stiffness of the sintered PCL strut was in the range of 0..43 +/- 0.15 MPa when a laser power of 3W and scanning speed of 150 in/s was used. A series of compressive mechanical characterization was performed on the parametric scaffold design and an empirical formula was presented to predict the compressive stiffness of the scaffold as a function of total porosity. In this work, the porosity of the scaffold was selected to be 85 % with micro-pores (40 mum -100 mum) throughout the scaffold. The compressive stiffness of the scaffold was 345 KPa. The feasibility of using the scaffold for cardiac tissue engineering was investigated by culturing C2C12 myoblast cells in vitro for 21 days. Fluorescence images showed cells were located throughout the scaffold. High density of cells at 1.2 X 10(6)cells/ml was recorded after 4 days of culture. Fusion and differentiation of C2C12 were observed as early as 6 days in vitro and was confirmed with myosin heavy chain immunostaining after 11 days of cell culture. A steady population of cells was then maintained throughout 21 days of culturing. This work demonstrated the feasibility of tailoring the mechanical property of the scaffold for soft tissue engineering using CASTS and SLS. The macro-architecture of the scaffold can be modified efficiently to fabricate scaffolds with different macro-pore size or changing the elemental cell design in CASTS. Further process and design optimization can be carried out in the future to fabricate scaffolds that match the tensile strength of native myocardium, which is in the order of tens of KPa. PMID: 20026436 [PubMed - as supplied by publisher] |
| In vivo degradation of calcium phosphate cement incorporated with biodegradable microspheres.
December 23, 2009 at 11:18 am
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| | In vivo degradation of calcium phosphate cement incorporated with biodegradable microspheres. Acta Biomater. 2009 Dec 17; Authors: Habraken WJ, Liao HB, Zhang Z, Wolke JG, Grijpma DW, Mikos AG, Feijen J, Jansen JA In this study we investigated the influence of the microsphere degradation or erosion mechanism on the in vivo degradation of microsphere/calcium phosphate cement composites (microsphere CPCs) for tissue engineering. Therefore, microspheres composed of poly(lactic-co-glycolic acid) (PLGA), gelatin and poly(trimethylene carbonate) (PTMC) were used as model and the resulting microsphere CPCs were implanted subcutaneously for 4, 8 and 12 weeks in the back of New Zealand white rabbits. Besides degradation, the soft tissue response to these formulations was evaluated. After retrieval, specimens were analyzed by physicochemical characterization and histological analysis. RESULTS: showed that all microsphere CPCs exhibited microsphere degradation after 12 weeks of subcutaneous implantation, which was accompanied by decreasing compression strength. The PLGA microspheres exhibited bulk erosion instantly through the whole composite, whereas with gelatin type B degradation of the microspheres proceeded from the outside to the center of the composite. High molecular weight PTMC microspheres exhibited surface erosion resulting in decreasing microsphere sizes. Furthermore, all composites showed a similar tissue response with a decreasing capsule thickness over time and a persisting moderate inflammatory response at the implant interface. In conclusion: microsphere CPCs can be used to generate porous scaffolds in an in vivo environment after degradation of microspheres with various degradation/erosion mechanisms. PMID: 20026289 [PubMed - as supplied by publisher] |
| Synthesis and characterization of hyaluronic acid-PEG hydrogels via Michael addition: An injectable biomaterial for cartilage repair.
December 23, 2009 at 11:18 am
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| | Synthesis and characterization of hyaluronic acid-PEG hydrogels via Michael addition: An injectable biomaterial for cartilage repair. Acta Biomater. 2009 Dec 15; Authors: Jin R, Moreira Teixeira LS, Krouwels A, Dijkstra PJ, van Blitterswijk CA, Karperien M, Feijen J Injectable hydrogels based on hyaluronic acid (HA) and poly(ethylene glycol) (PEG) were designed as biodegradable matrices for cartilage tissue engineering. Solutions of HA conjugates containing thiol functional groups (HA-SH) and PEG-vinylsulfone (PEG-VS) macromers were crosslinked via Michael addition to form a three-dimensional network under physiological conditions. Gelation times varied from 14 min to less than 1 min, depending on the molecular weight of the HA-SH and PEG-VS, degree of substitution (DS) of the HA-SH and the total polymer concentration. In the presence of 100 U/mL of hyaluronidase, when the polymer concentration was increased from 2 to 6% (w/v), the degradation time increased from 3 to 15 days. Hydrogels with a homogeneous distribution of cells were obtained when chondrocytes were mixed with the precursor solutions. Culturing cell-hydrogel constructs, prepared from HA185k-SH with a DS of 28 and crosslinked with PEG5k-4VS for 3 weeks in vitro, revealed that the cells were viable and that cell division took place. Gel-cell matrices degraded in approximately 3 weeks as shown by a significant decrease in dry gel mass. At day 21, glycosaminoglycans and collagen type II were found to accumulate in hydrogels. These results indicate that these injectable hydrogels have a high potential for cartilage tissue engineering. PMID: 20025999 [PubMed - as supplied by publisher] |
| The N-terminal RASSF family: a new group of Ras-association-domaincontaining proteins, with emerging links to cancer formation.
December 23, 2009 at 11:18 am
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| | The N-terminal RASSF family: a new group of Ras-association-domaincontaining proteins, with emerging links to cancer formation. Biochem J. 2010 Jan 15;425(2):303-11 Authors: Sherwood V, Recino A, Jeffries A, Ward A, Chalmers AD The RASSF (Ras-association domain family) has recently gained several new members and now contains ten proteins (RASSF1-10), several of which are potential tumour suppressors. The family can be split into two groups, the classical RASSF proteins (RASSF1-6) and the four recently added N-terminal RASSF proteins (RASSF7-10). The N-terminal RASSF proteins have a number of differences from the classical RASSF members and represent a newly defined set of potential Ras effectors. They have been linked to key biological processes, including cell death, proliferation, microtubule stability, promoter methylation, vesicle trafficking and response to hypoxia. Two members of the N-terminal RASSF family have also been highlighted as potential tumour suppressors. The present review will summarize what is known about the N-terminal RASSF proteins, addressing their function and possible links to cancer formation. It will also compare the N-terminal RASSF proteins with the classical RASSF proteins and ask whether the N-terminal RASSF proteins should be considered as genuine members or imposters in the RASSF family. PMID: 20025613 [PubMed - in process] |
| Nanotechnology for treatment of stroke and spinal cord injury.
December 23, 2009 at 11:18 am
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| | Nanotechnology for treatment of stroke and spinal cord injury. Nanomed. 2010 Jan;5(1):99-108 Authors: Kubinová S, Syková E The use of nanotechnology in cell therapy and tissue engineering offers promising future perspectives for brain and spinal cord injury treatment. Stem cells have been shown to selectively target injured brain and spinal cord tissue and improve functional recovery. To allow cell detection, superparamagnetic iron-oxide nanoparticles can be used to label transplanted cells. MRI is then a suitable method for the in vivo tracking of grafted cells in the host organism. CNS, and particularly spinal cord, injury is accompanied by tissue damage and the formation of physical and biochemical barriers that prevent axons from regenerating. One aspect of nanomedicine is the development of biologically compatible nanofiber scaffolds that mimic the structure of the extracellular matrix and can serve as a permissive bridge for axonal regeneration or as a drug-delivery system. The incorporation of biologically active epitopes and/or the utilization of these scaffolds as stem cell carriers may further enhance their therapeutic efficacy. PMID: 20025468 [PubMed - in process] |
| Strategies for Articular Cartilage Lesion Repair and Functional Restoration.
December 23, 2009 at 11:18 am
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| | Strategies for Articular Cartilage Lesion Repair and Functional Restoration. Tissue Eng Part B Rev. 2009 Dec 21; Authors: Ahmed TA, Hincke MT Injury of articular cartilage due to trauma or pathological conditions is the major cause of disability worldwide, especially in North America. The increasing number of patients suffering from joint-related conditions leads to a concomitant increase in the economic burden. In this review article, we focus on strategies to repair and replace knee joint cartilage, since knee-associated disabilities are more prevalent than any other joint. Due to inadequacies associated with widely used approaches, the orthopaedic community has an increasing tendency to develop biological strategies, which include transplantation of autologous (i.e. mosaicplasty) or allogeneic osteochondral grafts, autologous chondrocytes (ACT), or tissue-engineered cartilage substitutes. Tissue-engineered cartilage constructs represent a highly promising treatment option for knee injury as they mimic the biomechanical environment of the native cartilage and have superior integration capabilities. Currently, a wide range of tissue engineering - based strategies are established and investigated clinically as an alternative to the routinely used techniques (i.e. knee replacement and ACT). Tissue engineering-based strategies include implantation of autologous chondrocytes in combination with collagen I, collagen I/III (matrix - induced autologous chondrocyte implantation, MACI), HYAFF(R) 11 (Hyalograft(R) C), and fibrin glue (Tissucol(R)) or implantation of minced cartilage in combination with copolymers of polyglycolic acid along with polycaprolactone PGA/PCL (cartilage autograft implantation system, CAIS), and fibrin glue (DeNovo NT graft). Tissue-engineered cartilage replacements show better clinical outcomes in the short-term, and with advances that have been made in orthopaedics they can be introduced arthroscopically in a minimally invasive fashion. Thus, the future is bright for this innovative approach to restore function. PMID: 20025455 [PubMed - as supplied by publisher] |
| Impact of biological agents and tissue engineering approaches in the treatment of rheumatic diseases.
December 23, 2009 at 11:18 am
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| | Impact of biological agents and tissue engineering approaches in the treatment of rheumatic diseases. Tissue Eng Part B Rev. 2009 Dec 21; Authors: Alves da Silva M, Martins A, Teixeira A, Reis RL, Neves NM The treatment of rheumatic diseases has been the focus of many clinical studies aiming to achieve the best combination of drugs for symptoms reduction. Although improved understanding of the pathophysiology of rheumatic diseases has led to the identification of effective therapeutic strategies, its cure remains unknown. Biological agents were a breakthrough in the treatment of these diseases. They proved to be more effective than the other conventional therapies in refractory inflammatory rheumatic diseases. Among them, TNF-inhibitors are widely used, namely Etanercept, Infliximab or Adalimumab, alone or in combination with disease modifying anti-rheumatic drugs (DMARDs). Nevertheless, severe adverse effects have been detected in patients with history of recurrent infections, including cardiac failure or malignancy. Currently, most of the available therapies for rheumatic diseases do not have sufficient tissue specificity. Consequently, high drug doses must be administrated systemically, leading to adverse side effects associated with its possible toxicity. Drug delivery systems, by its targeted nature, are excellent solutions to overcome this problem. In this review, we will describe the state-of-the-art in clinical studies on the treatment of rheumatic diseases, emphasising the use of biological agents and target drug delivery systems. Some alternative novel strategies of regenerative medicine and its implications for rheumatic diseases will also be discussed. PMID: 20025434 [PubMed - as supplied by publisher] |
| Concurrent extraction of proteins and RNA from cell-laden hydrogel scaffold free of polysaccharide interference.
December 23, 2009 at 11:18 am
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| | Concurrent extraction of proteins and RNA from cell-laden hydrogel scaffold free of polysaccharide interference. J Chromatogr B Analyt Technol Biomed Life Sci. 2009 Nov 1;877(29):3762-6 Authors: Wang C, Li X, Yao Y, Wang DA Concurrent extractions of proteins and RNA from cell-laden scaffolds would be of great help to biomaterialists and tissue engineers. Here we describe a procedure to extract proteins from the discard solution generated during the RNA isolation from polysaccharide-rich hydrogel scaffolds. This approach allows to obtain proteins and RNA from same sample while eliminating the polysaccharide interference. PMID: 19782009 [PubMed - indexed for MEDLINE] | | | 
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