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| Osteogenic Differentiation of Marrow Stromal Cells on Random and Aligned Electrospun Poly(L: -lactide) Nanofibers.
June 26, 2010 at 8:16 AM
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| | Osteogenic Differentiation of Marrow Stromal Cells on Random and Aligned Electrospun Poly(L: -lactide) Nanofibers. Ann Biomed Eng. 2010 Jun 25; Authors: Ma J, He X, Jabbari E The fibrillar structure and sub-micron diameter of electrospun nanofibers can be used to reproduce the morphology and structure of the natural extracellular matrix (ECM). The objective of this work was to investigate the effect of fiber alignment on osteogenic differentiation of bone marrow stromal (BMS) cells. Random and aligned poly(L: -lactide) (PLLA) nanofibers were produced by collecting the spun fibers on a stationary plate and a rotating wheel, respectively, as the ground electrode. Morphology and alignment of the BMS cells seeded on the fibers were characterized by SEM. The effect of fiber orientation on osteogenic differentiation of BMS cells was determined by measuring alkaline phosphatase (ALPase) activity, calcium content, and mRNA expression levels of osteogenic markers. There was a strong correlation between the fiber and cell distributions for the random (p = 0.16) and aligned (p = 0.81) fibers. Percent deviation from ideal randomness (PDIR) values indicated that cells seeded on the random fibers (PDIR = 6.5%) were likely to be distributed randomly in all directions while cells seeded on the aligned fibers (PDIR = 86%) were highly likely to be aligned with the direction of fibers. BMS cell seeded on random and aligned fibers had similar cell count and ALPase activity with incubation time, but the calcium content on aligned fibers was significantly higher after 21 days compared to that of random fibers (p = 0.003). Osteopontin (OP) and osteocalcin (OC) expression levels of BMS cells on fibers increased with incubation time. However, there was no difference between the expression levels of OP and OC on aligned vs. random fibers. The results indicate that BMS cells aligned in the direction of PLLA fibers to form long cell extensions, and fiber orientation affected the extent of mineralization, but it had no effect on cell proliferation or mRNA expression of osteogenic markers. PMID: 20577811 [PubMed - as supplied by publisher] | | |
| Dual growth factor-releasing nanoparticle/hydrogel system for cartilage tissue engineering.
June 26, 2010 at 8:16 AM
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| | Dual growth factor-releasing nanoparticle/hydrogel system for cartilage tissue engineering. J Mater Sci Mater Med. 2010 Jun 25; Authors: Lim SM, Oh SH, Lee HH, Yuk SH, Im GI, Lee JH In order to induce the chondrogenesis of mesenchymal stem cells (MSCs) in tissue engineering, a variety of growth factors have been adapted and encouraging results have been demonstrated. In this study, we developed a delivery system for dual growth factors using a gelation rate controllable alginate solution (containing BMP-7) and polyion complex nanoparticles (containing TGF-beta(2)) to be applied for the chondrogenesis of MSCs. The dual growth factors (BMP-7/TGF-beta(2))-loaded nanoparticle/hydrogel system showed a controlled release of both growth factors: a faster release of BMP-7 and a slower release of TGF-beta(2), ca., approximately 80 and 30% release at the end of an incubation period (21 days), respectively, which may be highly desirable for chondrogenic differentiation of MSCs. On the contrary, the release of each growth factor from the dual growth factors-loaded hydrogel (without the nanoparticles) was much slower than that of the nanoparticle/hydrogel system, approximately 36% (BMP-7) and 16% (TGF-beta(2)) for 21 days, and this is more than likely attributed to the aggregation between growth factors during the hydrogel fabrication step. The nanoparticle/hydrogel system with separate growth factor loading may provide desirable growth factor delivery kinetics for cartilage regeneration, as well as the chondrogenesis of MSCs. PMID: 20577785 [PubMed - as supplied by publisher] | | |
| Towards computational prediction of microRNA function and activity.
June 26, 2010 at 8:16 AM
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| | Towards computational prediction of microRNA function and activity. Nucleic Acids Res. 2010 Jun 24; Authors: Ulitsky I, Laurent LC, Shamir R While it has been established that microRNAs (miRNAs) play key roles throughout development and are dysregulated in many human pathologies, the specific processes and pathways regulated by individual miRNAs are mostly unknown. Here, we use computational target predictions in order to automatically infer the processes affected by human miRNAs. Our approach improves upon standard statistical tools by addressing specific characteristics of miRNA regulation. Our analysis is based on a novel compendium of experimentally verified miRNA-pathway and miRNA-process associations that we constructed, which can be a useful resource by itself. Our method also predicts novel miRNA-regulated pathways, refines the annotation of miRNAs for which only crude functions are known, and assigns differential functions to miRNAs with closely related sequences. Applying our approach to groups of co-expressed genes allows us to identify miRNAs and genomic miRNA clusters with functional importance in specific stages of early human development. A full list of the predicted mRNA functions is available at http://acgt.cs.tau.ac.il/fame/. PMID: 20576699 [PubMed - as supplied by publisher] | | |
| The retention of extracellular matrix proteins and angiogenic and mitogenic cytokines in a decellularized porcine dermis.
June 26, 2010 at 8:16 AM
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| | The retention of extracellular matrix proteins and angiogenic and mitogenic cytokines in a decellularized porcine dermis. Biomaterials. 2010 Jun 22; Authors: Hoganson DM, O'Doherty EM, Owens GE, Harilal DO, Goldman SM, Bowley CM, Neville CM, Kronengold RT, Vacanti JP Decellularized dermis materials demonstrate considerable utility in surgical procedures including hernia repair and breast reconstruction. A new decellularized porcine dermis material has been developed that retains many native extracellular matrix (ECM) proteins and cytokines. This material has substantial mechanical strength with maximum tensile strength of 141.7 +/- 85.4 (N/cm) and suture pull through strength of 47.0 +/- 14.0 (N). After processing, many ECM proteins remained in the material including collagen III, collagen IV, collagen VII, laminin and fibronectin. Glycosaminoglycans, including hyaluronic acid, were also preserved. Among several cytokines whose levels were quantified, more vascular endothelial growth factor (VEGF) and transforming growth factor beta (TGF-beta) were retained within this material than in comparable decellularized dermis materials. The retention of bioactivity was demonstrated in a cell culture assay. Because this decellularized porcine dermis material both retains significant strength and has substantial biological activity, it may promote rapid integration and repair in clinical applications. PMID: 20576289 [PubMed - as supplied by publisher] | | |
| Ureteral scrotal herniations after renal transplants.
June 26, 2010 at 8:16 AM
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| | Ureteral scrotal herniations after renal transplants. ANZ J Surg. 2010 Apr;80(4):296 Authors: Giuseppe O, Gianpiero G, Pierpaolo DC, Antonio F, Francesco P PMID: 20575970 [PubMed - in process] | | |
| Automatic Quantitative Micro-Computed Tomography Evaluation of Angiogenesis in an Axially Vascularized Tissue-Engineered Bone Construct.
June 26, 2010 at 8:16 AM
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| | Automatic Quantitative Micro-Computed Tomography Evaluation of Angiogenesis in an Axially Vascularized Tissue-Engineered Bone Construct. Tissue Eng Part C Methods. 2010 Jun 24; Authors: Arkudas A, Beier JP, Pryymachuk G, Hoereth T, Bleiziffer O, Polykandriotis E, Hess A, Gulle H, Horch RE, Kneser U Introduction: We invented an automatic observer-independent quantitative method to analyze vascularization using micro-computed tomography (CT) along with three-dimensional (3D) reconstruction in a tissue engineering model. Materials and Methods: An arteriovenous loop was created in the medial thigh of 30 rats and was placed in a particulated porous hydroxyapatite and beta-tricalcium phosphate matrix, filled with fibrin (10 mg/mL fibrinogen and 2 IU/mL thrombin) without (group A) or with (group B) application of fibrin-gel-immobilized angiogenetic growth factors vascular endothelial growth factor (VEGF(165)) and basic fibroblast growth factor (bFGF). The explantation intervals were 2, 4, and 8 weeks. Specimens were investigated by means of micro-CT followed by an automatic 3D analysis, which was correlated to histomorphometrical findings. Results: In both groups, the arteriovenous loop led to generation of dense vascularized connective tissue with differentiated and functional vessels inside the matrix. Quantitative analysis of vascularization using micro-CT showed to be superior to histological analysis. The micro-CT analysis also allows the assessment of different other, more complex vascularization parameters within 3D constructs, demonstrating an early improvement of vascularization by application of fibrin-gel-immobilized VEGF(165) and bFGF. Conclusions: In this study quantitative analysis of vascularization using micro-CT along with 3D reconstruction and automatic analysis exhibit to be a powerful method superior to histological evaluation of cross sections. PMID: 20575690 [PubMed - as supplied by publisher] | | |
| The Osteoconductivity of Biomaterials Is Regulated by Bone Morphogenetic Protein 2 Autocrine Loop Involving alpha2beta1 Integrin and Mitogen-Activated Protein Kinase/Extracellular Related Kinase Signaling Pathways.
June 26, 2010 at 8:16 AM
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| | The Osteoconductivity of Biomaterials Is Regulated by Bone Morphogenetic Protein 2 Autocrine Loop Involving alpha2beta1 Integrin and Mitogen-Activated Protein Kinase/Extracellular Related Kinase Signaling Pathways. Tissue Eng Part A. 2010 Jun 24; Authors: Lu Z, Zreiqat H It is critical to understand the complex interactions between cells and scaffolds for a successful tissue engineering approach for bone regeneration. Beyond providing structural support for the cells, synthetic scaffolds act together with some soluble biofactors through intracellular signaling pathways to provide the appropriate clues for cells to form bone tissue. The aim of this study was to investigate the mechanism by which beta-tricalcium phosphate (beta-TCP), a clinically used bone graft substitute, exerts its osteoconductivity on primary human osteoblasts. Culturing human osteoblasts on beta-TCP scaffold for 1 and 7 days induced gene expression of bone morphogenetic protein 2 (BMP2) and its receptors and activated its downstream Smad1/5 signaling pathway, which were orchastrated with induced osteoblastic differentiation. Blocking BMP2 activity by its inhibitor (Noggin) led to the abrogation of osteoblastic differentiation and partially inhibited Smad1/5 signaling pathway. Finally, blocking alpha2beta1 integrin or inhibiting mitogen-activated protein kinase/extracellular related kinase signaling pathway attenuated the induction of gene expression of BMP2 and its receptors and the activation of Smad1/5 signaling pathway. We concluded that beta-TCP scaffold promotes osteoblastic differentiation by a BMP2 autocrine loop, a process involving alpha2beta1 integrin and mitogen-activated protein kinase/extracellular related kinase signaling pathways. The findings of this study might provide a useful principle for fabricating or designing an ideal scaffold for bone tissue engineering. PMID: 20575676 [PubMed - as supplied by publisher] | | |
| Luciferase labeling for MSC tracking in spinal fusion versus ectopic bone tissue engineering in mice and rats.
June 26, 2010 at 8:16 AM
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| | Luciferase labeling for MSC tracking in spinal fusion versus ectopic bone tissue engineering in mice and rats. Tissue Eng Part A. 2010 Jun 24; Authors: Geuze R, Prins HJ, Oner FC, Helm van der YJ, Schuijff L, Martens AC, Kruyt M, Alblas J, Dhert W Tissue engineering of bone, by combining multipotent stromal cells (MSCs) with osteoconductive scaffolds, has not yet yielded any clinically useful applications so far. The fate and contribution of the seeded cells are not sufficiently clarified, especially at clinically relevant locations. Therefore we investigated cell proliferation around the spine and at ectopic sites using noninvasive in vivo bioluminescence imaging (BLI) in relation to new bone formation. Goat MSCs were lentivirally transduced to express luciferase. After showing both correlation between MSC viability and BLI signal as well as survival and osteogenic capacity of these cells ectopically in mice, they were seeded on ceramic scaffolds and implanted in immunodeficient rats at two levels in the spine for spinal fusion as well as subcutaneously. Non-transduced MSCs were used as a control group. All rats were monitored at day one and after that weekly until termination at week 7. In mice a BLI signal was observed during the whole observation period indicating survival of the seeded MSCs, which was accompanied by osteogenic differentiation in vivo. However, these same MSCs showed a different response in the rat model, where the BLI signal was present until day 14, both in the spine and ectopically, indicating that MSCs were able to survive at least two weeks of implantation. Only when the signal was still present after the total implantation period ectopically, which only occurred in one rat, new bone was formed extensively and the implanted MSCs were responsible for this bone formation. Ectopically, neither a reduced proliferative group (irradiated), nor a group in which the cells were devitalized by liquid nitrogen and the produced extracellular matrix remained (matrix group) resulted in bone formation. This suggests that the release of soluble factors or the presence of an extracellular matrix is not enough to induce bone formation. For the spinal location, the question remains whether the implanted MSCs contribute to the bone regeneration or that the principal mechanism of MSC activity is through the release of soluble mediators. PMID: 20575656 [PubMed - as supplied by publisher] | | |
| Thermally Responsive Injectable Hydrogel Incorporating Methacrylate-Polylactide for Hydrolytic Lability.
June 26, 2010 at 8:16 AM
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| | Thermally Responsive Injectable Hydrogel Incorporating Methacrylate-Polylactide for Hydrolytic Lability. Biomacromolecules. 2010 Jun 24; Authors: Ma Z, Nelson DM, Hong Y, Wagner WR Injectable thermoresponsive hydrogels are of interest for a variety of biomedical applications, including regional tissue mechanical support as well as drug and cell delivery. Within this class of materials there is a need to provide options for gels with stronger mechanical properties as well as variable degradation profiles. To address this need, the hydrolytically labile monomer, methacrylate-polylactide (MAPLA), with an average 2.8 lactic acid units, was synthesized and copolymerized with N-isopropylacrylamide (NIPAAm) and 2-hydroxyethyl methacrylate (HEMA) to obtain bioabsorbable thermally responsive hydrogels. Poly(NIPAAm-co-HEMA-co-MAPLA) with three monomer feed ratios (84/10/6, 82/10/8, and 80/10/10) was synthesized and characterized with NMR, FTIR, and GPC. The copolymers were soluble in saline at reduced temperature (<10 degrees C), forming clear solutions that increased in viscosity with the MAPLA feed ratio. The copolymers underwent sol-gel transition at lower critical solution temperatures of 12.4, 14.0, and 16.2 degrees C, respectively, and solidified immediately upon being placed in a 37 degrees C water bath. The warmed hydrogels gradually excluded water to reach final water contents of approximately 45%. The hydrogels as formed were mechanically strong, with tensile strengths as high as 100 kPa and shear moduli of 60 kPa. All three hydrogels were completely degraded (solubilized) in PBS over a 6-7 month period at 37 degrees C, with a higher MAPLA feed ratio resulting in a faster degradation period. Culture of primary vascular smooth muscle cells with degradation solutions demonstrated a lack of cytotoxicity. The synthesized hydrogels provide new options for biomaterial injection therapy where increased mechanical strength and relatively slow resorption rates would be attractive. PMID: 20575552 [PubMed - as supplied by publisher] | | |
| Remodeling of buccal mucosa by bladder microenvironment.
June 26, 2010 at 8:16 AM
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| | Remodeling of buccal mucosa by bladder microenvironment. Urology. 2010 Jun;75(6):1514.e7-14 Authors: Lu M, Zhou G, Liu W, Wang Z, Zhu Y, Yu B, Zhang W, Cao Y OBJECTIVES: The optimal cell source for bladder mucosa reconstruction is in question. This study explored the feasibility of phenotype transformation of oral mucosa towards bladder urothelium by transplanting the oral mucosa into bladder local microenvironment. METHODS: Porcine oral mucosa grafts were transplanted into autologous bladder mucosa defects, and the specific marker expressions of both oral epithelium and bladder urothelium were examined by immunohistochemistry and RT-PCR at 3, 6, and 12 months to detect a potential phenotype transformation. RESULTS: The grafts could retain the phenotype and structure of oral mucosa within 3 months with positive expression of cytokeratin 14 (CK 14, a specific marker of oral epithelium) and negative expression of uroplakin II (UPII, a urothelium-specific marker). However, after 6 months of transplantation, the grafts expressed UPII at both protein and mRNA levels and the phenotype persisted at 12 months postsurgery. All the grafts continuously retained the positive expression of CK 14 at all time points. CONCLUSIONS: These findings, for the first time, revealed the transdifferential potential of oral keratinocytes toward urothelial cells and the important role of bladder local microenvironment for remodeling oral mucosa epithelium. These results support the hypothesis that oral keratinocytes can serve as a potential cell source for reconstructing bladder mucosa. PMID: 20394977 [PubMed - indexed for MEDLINE] | | |
| Plasticity and physiological role of stem cells derived from skeletal muscle interstitium: contribution to muscle fiber hyperplasia and therapeutic use.
June 26, 2010 at 8:16 AM
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| | Plasticity and physiological role of stem cells derived from skeletal muscle interstitium: contribution to muscle fiber hyperplasia and therapeutic use. Curr Pharm Des. 2010;16(8):956-67 Authors: Tamaki T, Uchiyama Y, Akatsuka A Stem cells other than satellite cells that can give rise to primary myoblasts, which are able to form additional new fibers postnatally, are present in the interstitial spaces of skeletal muscle. These cells are sorted into CD34(+)/45(-) (Sk-34) and CD34(-)/45(-) (Sk-DN) cell fractions, and they are wholly (>99%) negative for Pax7 at initial isolation. Colony-forming units of these cells typically include non-adherent type myogenic cells, while satellite cells are known to be adherent in cell culture. In addition, both Pax7(-) and Pax7(+) cells are produced, depending on asymmetric cell division. A large number of myotubes are also formed in each colony, thus suggesting that putative Pax7(+) satellite cells also present in each colony. Interestingly, interstitial myogenic cells show basal lamina formation at early stages of myogenesis in response to various types of stimulation in compensatory enlarged muscle, a property that satellite cells do not possess in the parent fiber basal lamina cylinder. Basal lamina formation and production of satellite cells are essential before muscle fiber establishment in vivo. It is therefore likely that myogenic cells in skeletal muscle can be divided into two populations: 1) basal lamina-producing myogenic cells; and 2) basal lamina-non-producing myogenic cells. The latter population may be Pax7(+) satellite cells showing adherent capacity in cell culture, while the lamina-producing myogenic population derived from interstitial multipotent stem cells, which is predominant among Sk-34 and Sk-DN cells, plays a role in primary myoblast generation and shows non-adherent behavior in culture. Therefore, the physiological role of interstitial myogenic cells is as a source for new postnatal muscle fiber formation, and multinucleated muscle fibers (cells) are potentially formed clonally. PMID: 20041822 [PubMed - indexed for MEDLINE] | | | | 
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