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| Stem cell biologists sure play a mean pinball.
May 21, 2010 at 6:22 AM
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| | Stem cell biologists sure play a mean pinball. Nat Biotechnol. 2010 Apr;28(4):333-5 Authors: Sareen D, Svendsen CN PMID: 20379177 [PubMed - indexed for MEDLINE] | | |
| [Cellular engineering and biosensor technology for high through-put analysis on drug discovery]
May 21, 2010 at 6:22 AM
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| | [Cellular engineering and biosensor technology for high through-put analysis on drug discovery] Yakugaku Zasshi. 2010 Apr;130(4):559-64 Authors: Haruyama T Sensors have been developed to determine the concentration of specific compounds in situ. They are already widely employed as a practical technological tool in the clinical and healthcare fields. Recently, another concept of biosensing has been receiving attention: biosensing for the evaluation of molecular potency. The author described the idea as qualified analysis. The development of this novel concept has been supported by the development of related technologies, such as electrochemistry, molecular interface science, molecular design, molecular biology (genetic engineering), and cellular/tissual engineering. This study addresses this new concept of biosensing and its application to the evaluation of the potency of chemicals in biological systems, in the field of cellular/tissual engineering. Cellular biosensing will provide valuable information for both pharmaceutical research and chemical safety, and be applicable in drug discovery in vitro as a screening too! l. PMID: 20372001 [PubMed - indexed for MEDLINE] | | |
| The role of cell biology and leaflet remodeling in the progression of heart valve disease.
May 21, 2010 at 6:22 AM
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| | The role of cell biology and leaflet remodeling in the progression of heart valve disease. Methodist Debakey Cardiovasc J. 2010 Jan-Mar;6(1):2-7 Authors: Xu S, Grande-Allen KJ Heart valves are complex tri-layered structures that ensure the unidirectional flow of blood. Scientists are actively investigating how characteristics of the two major cell types, valvular endothelial cells (VECs) and valvular interstitial cells (VICs), and their mechanical relationships with the valvular extracellular matrix promote structural integrity and age-related remodeling. Abnormal changes in VECs, VICs, and the extracellular matrix at the molecular level lead to gross tissue malformations and dysfunction. This review addresses current advances in the field of valve biology, mechanisms underlying valvular leaflet remodeling, and common pathological manifestations. Improving our understanding of heart valve biology, the impact of cardiovascular drugs, and remodeling changes will be critical to the development of novel therapies for heart valve diseases. PMID: 20360651 [PubMed - indexed for MEDLINE] | | |
| Strategies in biologic augmentation of rotator cuff repair: a review.
May 21, 2010 at 6:22 AM
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| | Strategies in biologic augmentation of rotator cuff repair: a review. Clin Orthop Relat Res. 2010 Jun;468(6):1476-84 Authors: Cheung EV, Silverio L, Sperling JW BACKGROUND: Degenerative rotator cuff tears are increasing with the aging population, and healing is not uniform after surgery. Rotator cuffs may show improved healing when biologic factors are added during surgery. QUESTIONS/PURPOSES: We asked: (1) What cellular processes are involved in normal bone-to-tendon healing? (2) What approaches are being developed in tendon augmentation? (3) What approaches are being developed with the addition of growth factors? METHODS: We reviewed research in relating to biologic augmentation and cellular processes involved in rotator cuff repair, focusing on animal models of rotator cuff repair and nonrandomized human trials. RESULTS: Regular bone-to-tendon healing forms a fibrous junction between tendon and bone that is distinct from the original bone-to-tendon junction. Tendon augmentation with cellular components serves as scaffolding for fibroblastic cells and a possible source of growth factors and fibroblastic cells. Extracell! ular matrices provide a scaffold for incoming fibroblastic cells, although current research does not conclusively confirm which if any of these scaffolds enhance repair owing in part to intermanufacturer variations and the limited human research. Growth factors and platelet-rich-plasma are established in other fields of research and may enhance repair but have not been rigorously tested. CONCLUSIONS: There is potential application of biologic augmentation to improve healing after rotator cuff repair. However, research in this field is still inconclusive and has not been sufficiently demonstrated to merit regular clinical use. Future human trials can elucidate the use of biologic augmentation in rotator cuff repairs. PMID: 20352390 [PubMed - indexed for MEDLINE] | | |
| Derivation, propagation and controlled differentiation of human embryonic stem cells in suspension.
May 21, 2010 at 6:22 AM
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| | Derivation, propagation and controlled differentiation of human embryonic stem cells in suspension. Nat Biotechnol. 2010 Apr;28(4):361-4 Authors: Steiner D, Khaner H, Cohen M, Even-Ram S, Gil Y, Itsykson P, Turetsky T, Idelson M, Aizenman E, Ram R, Berman-Zaken Y, Reubinoff B Undifferentiated human embryonic stem cells (hESCs) are currently propagated on a relatively small scale as monolayer colonies. Culture of hESCs as floating aggregates is widely used for induction of differentiation into embryoid bodies. Here we show that hESC lines can be derived from floating inner cell masses in suspension culture conditions that do not involve feeder cells or microcarriers. This culture system supports prolonged propagation of the pluripotent stem cells as floating clusters without their differentiation into embryoid bodies. HESCs cultivated as aggregates in suspension maintain the expression of pluripotency markers and can differentiate into progeny of the three germ layers both in vitro and in vivo. We further show the controlled differentiation of hESC clusters in suspension into neural spheres. These results pave the way for large-scale expansion and controlled differentiation of hESCs in suspension, which would be valuable in basic and ap! plied research. PMID: 20351691 [PubMed - indexed for MEDLINE] | | |
| Wetting behaviour of laser synthetic surface microtextures on Ti-6Al-4V for bioapplication.
May 21, 2010 at 6:22 AM
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| | Wetting behaviour of laser synthetic surface microtextures on Ti-6Al-4V for bioapplication. Philos Transact A Math Phys Eng Sci. 2010 Apr 28;368(1917):1863-89 Authors: Dahotre NB, Paital SR, Samant AN, Daniel C Wettability at the surface of an implant material plays a key role in its success as it modulates the protein adsorption and thereby influences cell attachment and tissue integration at the interface. Hence, surface engineering of implantable materials to enhance wettability to physiological fluid under in vivo conditions is an area of active research. In light of this, in the present work, laser-based optical interference and direct melting techniques were used to develop synthetic microtextures on Ti-6Al-4V alloys, and their effects on wettability were studied systematically. Improved wettability to simulated body fluid and distilled water was observed for Ca-P coatings obtained by direct melting technique. This superior wettability was attributed to both the appropriate surface chemistry and the three-dimensional surface features obtained using this technique. To assert a better control on surface texture and wettability, a three-dimensional thermal model based! on COMSOL's multiphysics was employed to predict the features obtained by laser melting technique. The effect of physical texture and wetting on biocompatibility of laser-processed Ca-P coatings was evaluated in the preliminary efforts on culturing of mouse MC3T3-E1 osteoblast cells. PMID: 20308107 [PubMed - indexed for MEDLINE] | | |
| Bone repair by cell-seeded 3D-bioplotted composite scaffolds made of collagen treated tricalciumphosphate or tricalciumphosphate-chitosan-collagen hydrogel or PLGA in ovine critical-sized calvarial defects.
May 21, 2010 at 6:22 AM
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| | Bone repair by cell-seeded 3D-bioplotted composite scaffolds made of collagen treated tricalciumphosphate or tricalciumphosphate-chitosan-collagen hydrogel or PLGA in ovine critical-sized calvarial defects. J Biomed Mater Res B Appl Biomater. 2010 May;93(2):520-30 Authors: Haberstroh K, Ritter K, Kuschnierz J, Bormann KH, Kaps C, Carvalho C, Mülhaupt R, Sittinger M, Gellrich NC The aim of this study was to investigate the osteogenic effect of three different cell-seeded 3D-bioplotted scaffolds in a ovine calvarial critical-size defect model. The choice of scaffold-materials was based on their applicability for 3D-bioplotting and respective possibility to produce tailor-made scaffolds for the use in cranio-facial surgery for the replacement of complex shaped boneparts. Scaffold raw-materials are known to be osteoinductive when being cell-seeded [poly(L-lactide-co-glycolide) (PLGA)] or having components with osteoinductive properties as tricalciumphosphate (TCP) or collagen (Col) or chitosan. The scaffold-materials PLGA, TCP/Col, and HYDR (TCP/Col/chitosan) were cell-seeded with osteoblast-like cells whether gained from bone (OLB) or from periost (OLP). In a prospective and randomized design nine sheep underwent osteotomy to create four critical-sized calvarial defects. Three animals each were assigned to the HYDR-, the TCP/Col-, or the PL! GA-group. In each animal, one defect was treated with a cell-free, an OLB- or OLP-seeded group-specific scaffold, respectively. The fourth defect remained untreated as control (UD). Fourteen weeks later, animals were euthanized for histo-morphometrical analysis of the defect healing. OLB- and OLP-seeded HYDR and OLB-seeded TCP/Col scaffolds significantly increased the amount of newly formed bone (NFB) at the defect bottom and OLP-seeded HYDR also within the scaffold area, whereas PLGA-scaffolds showed lower rates. The relative density of NFB was markedly higher in the HYDR/OLB group compared to the corresponding PLGA group. TCP/Col had good stiffness to prepare complex structures by bioplotting but HYDR and PLGA were very soft. HYDR showed appropriate biodegradation, TCP/Col and PLGA seemed to be nearly undegraded after 14 weeks. 3D-bioplotted, cell-seeded HYDR and TCP/Col scaffolds increased the amount of NFB within ovine critical-size calvarial defects, but stiffness, res! pectively, biodegradation of materials is not appropriate for ! the appl ication in cranio-facial surgery and have to be improved further by modifications of the manufacturing process or their material composition. PMID: 20225216 [PubMed - indexed for MEDLINE] | | |
| Differential expression of biofunctional GM1 and GM3 gangliosides within the plastic-adherent multipotent mesenchymal stromal cell population.
May 21, 2010 at 6:22 AM
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| | Differential expression of biofunctional GM1 and GM3 gangliosides within the plastic-adherent multipotent mesenchymal stromal cell population. Cytotherapy. 2010 Apr;12(2):131-42 Authors: Freund D, Fonseca AV, Janich P, Bornhäuser M, Corbeil D BACKGROUND AIMS: It is unclear whether the plastic-adherent multipotent mesenchymal stromal cells (MSC) isolated from human bone marrow (BM) represent a uniform cell population or are heterogeneous in terms of cell-surface constituents and hence functionality. METHODS: We investigated the expression profile of certain biofunctional lipids by plastic-adherent MSC, focusing particularly on two membrane microdomain (lipid raft)-associated monosialogangliosides, GM1 and GM3, using indirect confocal laser scanning fluorescence microscopy and flow cytometry. RESULTS: Phenotypically, we observed a differential expression where certain MSC subsets exhibited GM1, GM3 or both at the plasma membrane. Furthermore, disialoganglioside GD2 detection increased the complexity of the expression patterns, giving rise to seven identifiable cell phenotypes. Variation of standard culture conditions, such as the number of cell passage and period in culture, as well as donors, did not in! fluence the heterologous ganglioside expression profile. In contrast, the binding of various lectins appeared homogeneous throughout the MSC population, indicating that the general glycosylation pattern remained common. Morphologically, the expression of a given ganglioside-based phenotype was not related to a cell with particular size or shape. Interestingly, a segregation of GM1 and GM3 clusters was observed, GM3 being mostly excluded from the highly curved plasma membrane protrusions. CONCLUSIONS: These data highlight the phenotypic heterogeneity of plastic-adherent MSC in terms of certain lipid constituents of the plasma membrane, and the presence and/or absence of distinct ganglioside-based membrane microdomains suggest their potential functional diversity. PMID: 20196693 [PubMed - indexed for MEDLINE] | | |
| The mobility of chondroitin sulfate in articular and artificial cartilage characterized by 13C magic-angle spinning NMR spectroscopy.
May 21, 2010 at 6:22 AM
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| | The mobility of chondroitin sulfate in articular and artificial cartilage characterized by 13C magic-angle spinning NMR spectroscopy. Biopolymers. 2010 Jun;93(6):520-32 Authors: Scheidt HA, Schibur S, Magalhães A, de Azevedo ER, Bonagamba TJ, Pascui O, Schulz R, Reichert D, Huster D We have studied the molecular dynamics of one of the major macromolecules in articular cartilage, chondroitin sulfate. Applying (13)C high-resolution magic-angle spinning NMR techniques, the NMR signals of all rigid macromolecules in cartilage can be suppressed, allowing the exclusive detection of the highly mobile chondroitin sulfate. The technique is also used to detect the chondroitin sulfate in artificial tissue-engineered cartilage. The tissue-engineered material that is based on matrix producing chondrocytes cultured in a collagen gel should provide properties as close as possible to those of the natural cartilage. Nuclear relaxation times of the chondroitin sulfate were determined for both tissues. Although T(1) relaxation times are rather similar, the T(2) relaxation in tissue-engineered cartilage is significantly shorter. This suggests that the motions of chondroitin sulfate in natural and artificial cartilage are different. The nuclear relaxation times o! f chondroitin sulfate in natural and tissue-engineered cartilage were modeled using a broad distribution function for the motional correlation times. Although the description of the microscopic molecular dynamics of the chondroitin sulfate in natural and artificial cartilage required the identical broad distribution functions for the correlation times of motion, significant differences in the correlation times of motion that are extracted from the model indicate that the artificial tissue does not fully meet the standards of the natural ideal. This could also be confirmed by macroscopic biomechanical elasticity measurements. Nevertheless, these results suggest that NMR is a useful tool for the investigation of the quality of artificially engineered tissue. PMID: 20091673 [PubMed - indexed for MEDLINE] | | |
| Pharmacotherapy of the overactive bladder.
May 21, 2010 at 6:22 AM
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| | Pharmacotherapy of the overactive bladder. Discov Med. 2009 Oct;8(42):118-24 Authors: Andersson KE Lower urinary tract symptoms (LUTS), the overactive bladder syndrome (OAB), and detrusor overactivity (DO) are all conditions that can have major effects on quality of life and social functioning. Antimuscarinic drugs are first-line treatment--they often have good initial response rates, but adverse effects and decreasing efficacy cause long-term compliance problems, and alternatives are needed. The recognition of the functional contribution of the urothelium, the spontaneous myocyte activity during bladder filling, and the diversity of nerve transmitters involved has sparked interest in both peripheral and central modulation of LUTS/OAB/DO pathophysiology. There may be several new possibilities to treat LUTS/OAB/DO. For example, beta3-adrenoceptor (AR) agonists (mirabegron), phosphodiesterase type 5 inhibitors (sildenafil, tadalafil, vardenafil), combinations (alpha1-AR antagonist+antimuscarinic), and drugs with a central mode of action (tramadol, gabapentin) all! have positive proof of concept documented in randomized, controlled trials. Which of these therapeutic principles will be developed to become clinically useful treatments remain to be established. PMID: 19833057 [PubMed - indexed for MEDLINE] | | |
| [Reconstruction and transplantation of the composite skin comprising epithelial growth factor gene-transfected keratinocytes]
May 21, 2010 at 6:22 AM
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| | [Reconstruction and transplantation of the composite skin comprising epithelial growth factor gene-transfected keratinocytes] Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2007 Aug;29(4):506-9 Authors: Xiao SC, Zhu SH, Xia ZF, Wang GQ, Wang YS, Liu ZG OBJECTIVE: To investigate the epithelial growth factor (EGF) expression of EGF gene-transfected keratinocytes and its effect on cell proliferation after grafting. METHODS: Newborn Balb/c mouse keratinocytes and gene transfected keratinocytes were seeded on the surface of acellular dermal matrix and cocultured in different ratios as follows: 1:1, 1:3, or 1:5 1 week after culture. The composite skin was grafted onto the full-thickness wound in Balb/c mouse. Specimen was harvested at interval after grafting and underwent the immunohistochemistry staining for EGF and proliferating cell nuclear antigen (PCNA). RESULTS: Immunohistochemical staining showed EGF was expressed in the newly generated epidermis 1-2 week after grafting of the composite skin comprising Balb/c mouse keratinocytes and gene-transfected keratinocytes (at the ratio of 1:5). One week after surgery, Anti-PCNA positive basal cells were more than that in composite skin containing Balb/c mouse keratinocy! tes alone (P<0.01). CONCLUSION: The gene-transfected keratinocytes expresses EGF and promotes the proliferation of keratinocytes in the early stage after transplantation. PMID: 19209794 [PubMed - indexed for MEDLINE] | | |
| Gene delivery by surface immobilization of plasmid to tissue-engineering scaffolds.
May 21, 2010 at 6:22 AM
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| | Gene delivery by surface immobilization of plasmid to tissue-engineering scaffolds. Gene Ther. 2010 May 20; Authors: Salvay DM, Zelivyanskaya M, Shea LD Biomaterial scaffolds that serve as vehicles for gene delivery to promote expression of inductive factors have numerous regenerative medicine applications. In this report, we investigate plasmid delivery from biomaterial scaffolds using a surface immobilization strategy. Porous scaffolds were fabricated from poly(D,L-lactide-co-glycolide) (PLG), and plasmids were immobilized by drying. In vitro plasmid release indicated that the majority (>70%) of adsorbed plasmids were released within 24 h and >98% within 3 days; however, in vivo implantation of the scaffolds at the subcutaneous site yielded transgene expression that persisted for at least 28 weeks and was localized to the site of implantation. Histological analysis of DNA-adsorbed scaffolds indicated that macrophages at the scaffold were transfected in the first 2 weeks after implantation, whereas muscle cells adjacent to the implant primarily expressed the transgene at 4 weeks. In addition to localized ge! ne expression, a secreted protein (human factor IX) was retained at the implant site and not available systemically after 3 days, indicating minimal off-target effects. These findings show that surface immobilization of plasmid onto microporous PLG scaffolds can produce localized and long-term gene expression in vivo, which may be used to enhance the bioactivity of scaffolds used for regenerative medicine.Gene Therapy advance online publication, 20 May 2010; doi:10.1038/gt.2010.79. PMID: 20485383 [PubMed - as supplied by publisher] | | |
| Mouse models of periventricular leukomalacia.
May 21, 2010 at 6:22 AM
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| | Mouse models of periventricular leukomalacia. J Vis Exp. 2010;(39): Authors: Shen Y, Plane JM, Deng W We describe a protocol for establishing mouse models of periventricular leukomalacia (PVL). PVL is the predominant form of brain injury in premature infants and the most common antecedent of cerebral palsy. PVL is characterized by periventricular white matter damage with prominent oligodendroglial injury. Hypoxia/ischemia with or without systemic infection/inflammation are the primary causes of PVL. We use P6 mice to create models of neonatal brain injury by the induction of hypoxia/ischemia with or without systemic infection/inflammation with unilateral carotid ligation followed by exposure to hypoxia with or without injection of the endotoxin lipopolysaccharide (LPS). Immunohistochemistry of myelin basic protein (MBP) or O1 and electron microscopic examination show prominent myelin loss in cerebral white matter with additional damage to the hippocampus and thalamus. Establishment of mouse models of PVL will greatly facilitate the study of disease pathogenesis us! ing available transgenic mouse strains, conduction of drug trials in a relatively high throughput manner to identify candidate therapeutic agents, and testing of stem cell transplantation using immunodeficiency mouse strains. PMID: 20485263 [PubMed - in process] | | |
| Mandible reconstruction.
May 21, 2010 at 6:22 AM
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| | Mandible reconstruction. Curr Opin Otolaryngol Head Neck Surg. 2010 May 18; Authors: Miles BA, Goldstein DP, Gilbert RW, Gullane PJ PURPOSE OF REVIEW: The purpose of this article is to review current microvascular mandibular reconstruction techniques and recent literature on the advances of tissue engineering as they relate to mandibular reconstruction. RECENT FINDINGS: Microvascular reconstruction continues to be the standard of care for complicated mandibular reconstruction in major ablative defects of the head and neck. Several recent modifications of current microvascular techniques offer significant improvement in the quality of reconstructions currently being performed. Advances in tissue engineering are currently not widely applicable clinically due to a number of factors; however, the technology offers promising advances in the management of mandibular continuity defects in the future. SUMMARY: Microvascular reconstruction of the mandible represents the most significant advancement in technique in the current era. Tissue engineering offers a promising future to improve outcomes and dec! rease patient morbidity. Future investigations regarding this new technology will provide information on the utility and feasibility of tissue engineering in mandibular reconstruction. PMID: 20485172 [PubMed - as supplied by publisher] | | |
| Key issues in nasal reconstruction.
May 21, 2010 at 6:22 AM
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| | Key issues in nasal reconstruction. Curr Opin Otolaryngol Head Neck Surg. 2010 May 18; Authors: Asaria J, Pepper JP, Baker SR PURPOSE OF REVIEW: To review recent research and advances in nasal reconstruction over the last 12 months. RECENT FINDINGS: Although the major principles of replacing surgically ablated tissues with like tissue and respecting the nasal aesthetic subunits have not changed, recent advances in nasal reconstruction have focused on producing superior aesthetic and functional results, while minimizing deformity and morbidity. Future directions may also include the application of allotransplantation and tissue engineering. SUMMARY: A large variety of sophisticated techniques continue to emerge with the goal of producing increasingly natural results for patients undergoing nasal reconstruction. PMID: 20485171 [PubMed - as supplied by publisher] | | |
| Biomimetic coatings for bone tissue engineering of critical-sized defects.
May 21, 2010 at 6:22 AM
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| | Biomimetic coatings for bone tissue engineering of critical-sized defects. J R Soc Interface. 2010 May 19; Authors: Liu Y, Wu G, de Groot K The repair of critical-sized bone defects is still challenging in the fields of implantology, maxillofacial surgery and orthopaedics. Current therapies such as autografts and allografts are associated with various limitations. Cytokine-based bone tissue engineering has been attracting increasing attention. Bone-inducing agents have been locally injected to stimulate the native bone-formation activity, but without much success. The reason is that these drugs must be delivered slowly and at a low concentration to be effective. This then mimics the natural method of cytokine release. For this purpose, a suitable vehicle was developed, the so-called biomimetic coating, which can be deposited on metal implants as well as on biomaterials. Materials that are currently used to fill bony defects cannot by themselves trigger bone formation. Therefore, biological functionalization of such materials by the biomimetic method resulted in a novel biomimetic coating onto differen! t biomaterials. Bone morphogenetic protein 2 (BMP-2)-incorporated biomimetic coating can be a solution for a large bone defect repair in the fields of dental implantology, maxillofacial surgery and orthopaedics. Here, we review the performance of the biomimetic coating both in vitro and in vivo. PMID: 20484228 [PubMed - as supplied by publisher] | | |
| Ras controls melanocyte expansion during zebrafish fin stripe regeneration.
May 21, 2010 at 6:22 AM
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| | Ras controls melanocyte expansion during zebrafish fin stripe regeneration. Dis Model Mech. 2010 May 18; Authors: Lee Y, Nachtrab G, Klinsawat PW, Hami D, Poss KD Regenerative medicine for complex tissues like limbs will require the provision or activation of precursors for different cell types, in the correct number, and with the appropriate instructions. These strategies can be guided by what is learned from spectacular events of natural limb or fin regeneration in urodele amphibians and teleost fish. Following zebrafish fin amputation, melanocyte stripes faithfully regenerate in tandem with complex fin structures. Distinct populations of melanocyte precursors emerge and differentiate to pigment regenerating fins, yet the regulation of their proliferation and patterning is incompletely understood. Here, we found that transgenic increases in active Ras dose-dependently hyperpigmented regenerating zebrafish fins. Lineage tracing and marker analysis indicated that increases in active Ras stimulated the in situ amplification of undifferentiated melanocyte precursors expressing mitfa and kita. Active Ras also hyperpigmented ea! rly fin regenerates of kita mutants, which are normally devoid of primary regeneration melanocytes, suppressing defects in precursor function and survival. By contrast, this protocol had no noticeable impact on pigmentation by secondary regulatory melanocyte precursors in late-stage kita regenerates. Our results provide evidence that Ras activity levels control the repopulation and expansion of adult melanocyte precursors after tissue loss, enabling the recovery of patterned melanocyte stripes during zebrafish appendage regeneration. PMID: 20483996 [PubMed - as supplied by publisher] | | |
| Getting back at nature: understanding thymic development and overcoming its atrophy.
May 21, 2010 at 6:22 AM
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| | Getting back at nature: understanding thymic development and overcoming its atrophy. Curr Opin Pharmacol. 2010 May 17; Authors: Heng TS, Chidgey AP, Boyd RL T cell development is a complex and tightly regulated process involving reciprocal interactions between the thymic stroma and differentiating thymocytes. Normal thymic function is critical for immunity and microenvironmental defects predispose to dysregulation in the T cell compartment. Thymic structure and function are also severely damaged by chemotherapy and pre-transplant conditioning. Furthermore, poor immune competence with ageing is closely linked to thymic atrophy. Overcoming such thymic defects would have immediate application in many diseases, especially the recovery of cancer patients from cytotoxic treatment. Reversing the thymus ageing process via inhibition of atrophic factors such as sex steroids or administration of thymopoietic growth factors is one possible approach. Moreover, it is becoming clear a common thymic epithelial progenitor exists, raising the possibility for de novo thymus generation using emerging stem cell and tissue engineering tec! hnologies. Achievement of this goal will open up many avenues for the application of thymus-based immune rejuvenation and manipulation. PMID: 20483662 [PubMed - as supplied by publisher] | | |
| Reinforcement of a Porous Collagen Scaffold with Surface-Activated PLA Fibers.
May 21, 2010 at 6:22 AM
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| | Reinforcement of a Porous Collagen Scaffold with Surface-Activated PLA Fibers. J Biomater Sci Polym Ed. 2010;21(6):963-77 Authors: Liu X, Huang C, Feng Y, Liang J, Fan Y, Gu Z, Zhang X A hybrid porous collagen scaffold mechanically reinforced with surface-activated poly(lactic acid) (PLA) fiber was prepared. PLA fibers, 20 mum in diameter and 1 mm in length, were aminolyzed with hexanediamine to introduce free amino groups on the surfaces. After the amino groups were transferred to aldehyde groups by treatment with glutaraldehyde, different amounts (1.5, 3, 5 and 8 mg) of surface-activated PLA fibers were homogeneously mixed with 2 ml type-I collagen solution (pH 2.8, 0.6 wt%). This mixture solution was then freeze-dried and cross-linked to obtain collagen sponges with surface-activated PLA fiber. Scanning electron microscopy observation indicated that the collagen sponges had a highly interconnected porous structure with an average pore size of 170 mum, irrespective of PLA fiber incorporation. The dispersion of surface-activated PLA fibers was homogeneous in collagen sponge, in contrast to unactivated PLA fibers. The compression modulus test re! sults showed that, compared with unactivated PLA fibers, the surface-activated PLA fibers enhanced the resistance of collagen sponge to compression more significantly. Cytotoxicity assay by MTT test showed no cytotoxicity of these collagen sponges. L929 mouse fibroblast cell-culture studies in vitro revealed that the number of L929 cells attached to the collagen sponge with surface-activated PLA fibers, both 6 h and 24 h after seeding, was higher than that in pure collagen sponge and sponge with unactivated PLA fibers. In addition, a better distribution of cells infiltrated in collagen sponge with surface-activated PLA fibers was observed by histological staining. These results indicated that the collagen sponge reinforced with surface-activated PLA fibers is a promising biocompatible scaffold for tissue engineering. PMID: 20482996 [PubMed - in process] | | |
| Solid Free-Form Fabrication-Based PCL/HA Scaffolds Fabricated with a Multi-head Deposition System for Bone Tissue Engineering.
May 21, 2010 at 6:22 AM
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| | Solid Free-Form Fabrication-Based PCL/HA Scaffolds Fabricated with a Multi-head Deposition System for Bone Tissue Engineering. J Biomater Sci Polym Ed. 2010;21(6):951-62 Authors: Kim JY, Lee TJ, Cho DW, Kim BS In this study, we fabricated polycaprolactone/hydroxyapatite (PCL/HA) scaffolds with a multi-head deposition system, a solid free-form fabrication technology that was developed in our previous study. The bone regeneration potential of the scaffolds was compared with that of PCL scaffolds fabricated with the same system. The fabricated scaffolds had a pore size of 400 mum and a porosity of 66.7%. The PCL/HA scaffolds had higher mechanical strength and modulus than the PCL scaffolds. To compare the osteogenic potential, the two types of scaffolds were seeded with rat osteoblasts and cultured in vitro or implanted subcutaneously into athymic mice. The cells cultured on PCL/HA scaffolds expressed higher levels of osteopontin and osteonectin, both of which are osteogenic proteins. The PCL/HA scaffolds resulted in larger bone area and calcium deposition in the implants compared to the PCL scaffolds. PMID: 20482995 [PubMed - in process] | | |
| Cross-Linking and Depolymerisation of gamma-Irradiated Fish Gelatin and Porcine Gelatin Studied by SEC-MALLS and SDS-PAGE: A Comparative Study.
May 21, 2010 at 6:22 AM
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| | Cross-Linking and Depolymerisation of gamma-Irradiated Fish Gelatin and Porcine Gelatin Studied by SEC-MALLS and SDS-PAGE: A Comparative Study. J Biomater Sci Polym Ed. 2010;21(6):877-92 Authors: Hara M, Koshimizu N, Yoshida M, Haug IJ, Ulset AS, Christensen BE gamma-Irradiation of gelatin and collagen hydrogels can be used for sterilization and mechanical stabilization, providing biomaterials suitable for both tissue engineering and drug-delivery systems. Controversial results have been reported regarding the extent of irradiation-induced cross-linking and degradation, which depend on both protein concentration and irradiation dose. In this work the relative contributions of these processes were studied for irradiation doses between 0 and 1.0 kGy and concentrations between 0.3% and 5% using size-exclusion chromatography (SEC) with multi-angle laser light scattering (MALLS) and viscosity detection, as well as SDS-PAGE. It was demonstrated that chain degradation and cross-linking occur simultaneously in fish gelatin (FG), porcine gelatin (PG) and porcine collagen (PC), by the gradual appearance of protein fragments (10-80) x 10(3) concomitant with the formation of structures of high molecular weight. FG and PG behaved rat! her similarly, despite the fact they were irradiated and analyzed above and below their denaturation temperatures, respectively, suggesting little or no influence of molecular ordering under the conditions used. PC showed an increasing amount of degradation products following heat treatment prior to SEC-MALLS, suggesting that chain cleavage may occur within ordered collagen structures without complete release of the protein fragments. PMID: 20482990 [PubMed - in process] | | |
| Development of biodegradable polyurethane scaffolds using amino Acid and dipeptide-based chain extenders for soft tissue engineering.
May 21, 2010 at 6:22 AM
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| | Development of biodegradable polyurethane scaffolds using amino Acid and dipeptide-based chain extenders for soft tissue engineering. J Biomater Sci Polym Ed. 2010;21(6):843-62 Authors: Parrag IC, Woodhouse KA The inherent flexibility of polyurethane (PU) chemistry allows the incorporation of specific chemical moieties into the backbone structure conferring a unique biological function to these synthetic polymers. We describe here the synthesis and characterization of a PU containing a Gly-Leu linkage, the cleavage site of several matrix metalloproteinases. A Gly-Leu dipeptide was introduced into the chain extender of the polyurethane through the reaction with 1,4-cyclohexane dimethanol. PUs synthesized with the Gly-Leu-based chain extender had a high weight-average molecular weight (M(w) > 125 x 10(3)) and were phase segregated, semi-crystalline polymers with a low soft-segment glass-transition temperature (T(g) < -50 degrees C). Uniaxial tensile testing of PU films indicated that the polymer could withstand high ultimate tensile strengths (approx. 13 MPa) and were flexible with breaking strains of approx. 900%. The Gly-Leu PU had a significantly higher initial m! odulus, yield stress and ultimate stress compared to a PU previously developed in our laboratory containing a phenylalanine-based chain extender (Phe PU). The Gly-Leu-based chain extender allowed for better hard segment packing and hydrogen bonding leading to enhanced mechanical properties. Electrospinning was used to form scaffolds with randomly organized fibers and an average fiber diameter of approx. 3.6 mum for both the Gly-Leu and Phe PUs. Mouse embryonic fibroblasts were successfully cultured on the PU scaffolds out to 28 days. Further investigations into cell-mediated polymer degradation will help to identify the suitability of this new biomaterial as scaffolds for soft tissue applications. PMID: 20482988 [PubMed - in process] | | |
| Tissue engineered tumor models.
May 21, 2010 at 6:22 AM
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| | Tissue engineered tumor models. Biotech Histochem. 2010 May 20; Authors: Ingram M, Techy G, Ward B, Imam S, Atkinson R, Ho H, Taylor C Abstract Many research programs use well-characterized tumor cell lines as tumor models for in vitro studies. Because tumor cells grown as three-dimensional (3-D) structures have been shown to behave more like tumors in vivo than do cells growing in monolayer culture, a growing number of investigators now use tumor cell spheroids as models. Single cell type spheroids, however, do not model the stromal-epithelial interactions that have an important role in controlling tumor growth and development in vivo. We describe here a method for generating, reproducibly, more realistic 3-D tumor models that contain both stromal and malignant epithelial cells with an architecture that closely resembles that of tumor microlesions in vivo. Because they are so tissue-like we refer to them as tumor histoids. They can be generated reproducibly in substantial quantities. The bioreactor developed to generate histoid constructs is described and illustrated. It accommodates disposable ! culture chambers that have filled volumes of either 10 or 64 ml, each culture yielding on the order of 100 or 600 histoid particles, respectively. Each particle is a few tenths of a millimeter in diameter. Examples of histological sections of tumor histoids representing cancers of breast, prostate, colon, pancreas and urinary bladder are presented. Potential applications of tumor histoids include, but are not limited to, use as surrogate tumors for pre-screening anti-solid tumor pharmaceutical agents, as reference specimens for immunostaining in the surgical pathology laboratory and use in studies of invasive properties of cells or other aspects of tumor development and progression. Histoids containing nonmalignant cells also may have potential as "seeds" in tissue engineering. For drug testing, histoids probably will have to meet certain criteria of size and tumor cell content. Using a COPAS Plus flow cytometer, histoids containing fluorescent tumor cells were analyzed suc! cessfully and sorted using such criteria. PMID: 20482463 [PubMed - as supplied by publisher] | | |
| Recombinant Human Collagen and Biomimetic Variants Using a De Novo Gene Optimized for Modular Assembly.
May 21, 2010 at 6:22 AM
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| | Recombinant Human Collagen and Biomimetic Variants Using a De Novo Gene Optimized for Modular Assembly. Biomacromolecules. 2010 May 18; Authors: Chan SW, Hung SP, Raman SK, Hatfield GW, Lathrop RH, Da Silva NA, Wang SW A collagen-mimetic polymer that can be easily engineered with specific cell-responsive and mechanical properties would be of significant interest for fundamental cell-matrix studies and applications in regenerative medicine. However, oligonucleotide-based synthesis of full-length collagen has been encumbered by the characteristic glycine-X-Y sequence repetition, which promotes mismatched oligonucleotide hybridizations during de novo gene assembly. In this work, we report a novel, modular synthesis strategy that yields full-length human collagen III and specifically defined variants. We used a computational algorithm that applies codon degeneracy to design oligonucleotides that favor correct hybridizations while disrupting incorrect ones for gene synthesis. The resulting recombinant polymers were expressed in Saccharomyces cerevisiae engineered with prolyl-4-hydroxylase. Our modular approach enabled mixing-and-matching domains to fabricate different combinations of! collagen variants that contained different secretion signals at the N-terminus and cysteine residues imbedded within the triple-helical domain at precisely defined locations. This work shows the flexibility of our strategy for designing and assembling specifically tailored biomimetic collagen polymers with re-engineered properties. PMID: 20481478 [PubMed - as supplied by publisher] | | |
| [Cell sources for engineered temporomandibular joint disc tissue: present and future]
May 21, 2010 at 6:22 AM
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| | [Cell sources for engineered temporomandibular joint disc tissue: present and future] Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2010 Apr;27(2):463-6 Authors: Su X, Kang H The purpose of this review is to provide a reference for researchers in investigating the tissue engineering of the temporomandibular joint (TMJ) disc. Currently tissue engineering of the TMJ disc is in its infancy, and cell source is one of the key factors that define the development of the tissue engineering of TMJ disc. In this paper, 6 kinds of cells: the TMJ disc native cells, chondrocytes, dermal fibroblasts, bone marrow-derived mesenchymal stem cells, adipose-derived stem cells, and embryonic stem cells are introduced. In addition, the possibility that these cells can be used as cell sources for TMJ disc tissue engineering is described. PMID: 20481340 [PubMed - in process] | | |
| [Human preterm amnion cells cultured in three-dimensional collagen I matrix]
May 21, 2010 at 6:22 AM
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| | [Human preterm amnion cells cultured in three-dimensional collagen I matrix] Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2010 Apr;27(2):384-8 Authors: Liu F, Qi H For the purpose of fetal membrane healing, amnion mesenchymal cells were embedded in three-dimensional (3D) collagen I, and amnion epithelial cells were placed on top of it to build the amniotic cells/collagen I matrix complex to simulate the architecture of native amnion. Morphology of cell cultured on 3D collagen I was visualized by F-actin filaments incubated with rhodamine-labelled phalloidin. Cell ultrastructure of amnion epithelial cells and amnion mesenchymal cells was visualized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Results show amnion epithelial and mesenchymal cells cultured in collagen I matrix assume cell morphologies similar to those observed in vivo. CONCLUSION: Collagen I might be useful in amnion cell tissue engineering, Three-dimensional cell-matrix system might be useful in the study of preterm premature rupture of the membrane (PPROM) and be a therapeutic strategy for PPROM. PMID: 20481324 [PubMed - in process] | | |
| [Investigation of polyanhydride-glucan as stem cell carriers]
May 21, 2010 at 6:22 AM
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| | [Investigation of polyanhydride-glucan as stem cell carriers] Sheng Wu Yi Xue Gong Cheng Xue Za Zhi. 2010 Apr;27(2):348-53 Authors: Yu M, Du Z, Zhu Z, Gao Y, Gao Q The purpose of this study with regard to the effects of polyanhydride--three-dimensional vector-glucan material on the fetal liver stem cell adhesion and proliferation was to find a new carrier. The methods of two-step collagenase perfusion digestion and liquid Percoll discontinuous density gradient centrifugation were used for the separation of fetal liver stem cells. The fetal liver stem cells were selected and cultivated in the polyanhydride-three-dimensional vector-glucan material. Inverted microscope was used to observe cell adhesion and growth status. Also performed were: Calculation of the rate of cell adhesion; MTT assay of the cells in each group absorbance value (OD value); collecting and counting the cells on the carrier scaffold. Then the cell carriers histological sections (HE staining) were observed. On the 7th day of cell culture, the cells were subjected to immunofluorescence staining and flow cytometry. Results: polyanhydride-three-dimensional vec! tor-glucan promoted liver stem cells growth and adhesion. There were active functions of the liver stem cells within carrier materials. In the three-dimensional surface and the internal culture of liver stem cell, proliferation was sustained. After 40 days, the polyanhydride co-culture-three-dimensional vector-glucan showed no sign of toxicity to stem cells. Human fetal liver stem cells attached to the polyanhydride--three-dimensional vector-glucan stent. The cell proliferation went on well and exhibited sustained expression of markers; 7 days training led up to an increase of 19.7 percent in the number of cells. Conclusively, polyanhydride-three-dimensional vector-glucan can be used for promoting the proliferation of liver stem cells, and liver stem cells can be used as vectors in liver tissue engineering. PMID: 20481317 [PubMed - in process] | | |
| A model for genetic and epigenetic regulatory networks identifies rare pathways for transcription factor induced pluripotency.
May 21, 2010 at 1:22 AM
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| | A model for genetic and epigenetic regulatory networks identifies rare pathways for transcription factor induced pluripotency. PLoS Comput Biol. 2010;6(5):e1000785 Authors: Artyomov MN, Meissner A, Chakraborty AK With relatively low efficiency, differentiated cells can be reprogrammed to a pluripotent state by ectopic expression of a few transcription factors. An understanding of the mechanisms that underlie data emerging from such experiments can help design optimal strategies for creating pluripotent cells for patient-specific regenerative medicine. We have developed a computational model for the architecture of the epigenetic and genetic regulatory networks which describes transformations resulting from expression of reprogramming factors. Importantly, our studies identify the rare temporal pathways that result in induced pluripotent cells. Further experimental tests of predictions emerging from our model should lead to fundamental advances in our understanding of how cellular identity is maintained and transformed. PMID: 20485562 [PubMed - in process] | | | | 
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