| Stabilization of Polymer-Hydrogel Capsules via Thiol-Disulfide Exchange.
September 23, 2009 at 9:55 am
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| | Stabilization of Polymer-Hydrogel Capsules via Thiol-Disulfide Exchange. Small. 2009 Sep 21; Authors: Chong SF, Chandrawati R, Städler B, Park J, Cho J, Wang Y, Jia Z, Bulmus V, Davis TP, Zelikin AN, Caruso F Polymer hydrogels are used in diverse biomedical applications including drug delivery and tissue engineering. Among different chemical linkages, the natural and reversible thiol-disulfide interconversion is extensively explored to stabilize hydrogels. The creation of macro-, micro-, and nanoscale disulfide-stabilized hydrogels commonly relies on the use of oxidizing agents that may have a detrimental effect on encapsulated cargo. Herein an oxidization-free approach to create disulfide-stabilized polymer hydrogels via a thiol-disulfide exchange reaction is reported. In particular, thiolated poly(methacrylic acid) is used and the conditions of polymer crosslinking in solution and on colloidal porous and solid microparticles are established. In the latter case, removal of the core particles yields stable, hollow, disulfide-crosslinked hydrogel capsules. Further, a procedure is developed to achieve efficient disulfide crosslinking of multilayered polymer films to obtain stable, liposome-loaded polymer-hydrogel capsules that contain functional enzymatic cargo within the liposomal subcompartments. This approach is envisaged to facilitate the development of biomedical applications of hydrogels, specifically those including fragile cargo. PMID: 19771568 [PubMed - as supplied by publisher] |
| Gef gene therapy enhances the therapeutic efficacy of doxorubicin to combat growth of MCF-7 breast cancer cells.
September 23, 2009 at 9:55 am
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| | Gef gene therapy enhances the therapeutic efficacy of doxorubicin to combat growth of MCF-7 breast cancer cells. Cancer Chemother Pharmacol. 2009 Sep 22; Authors: Prados J, Melguizo C, Rama AR, Ortiz R, Segura A, Boulaiz H, Vélez C, Caba O, Ramos JL, Aránega A PURPOSE: The potential use of combined therapy is under intensive study including the association between classical cytotoxic and genes encoding toxic proteins which enhanced the antitumour activity. The main aim of this work was to evaluate whether the gef gene, a suicide gene which has a demonstrated antiproliferative activity in tumour cells, improved the antitumour effect of chemotherapeutic drugs used as first-line treatment in the management of advanced breast cancer. METHODS: MCF-7 human breast cancer cells were transfected with gef gene using pcDNA3.1-TOPO expression vector. To determine the effect of the combined therapy, MCF-7 transfected and non-transfected cells were exposed to paclitaxel, docetaxel and doxorubicin at different concentrations. The growth-inhibitory effect of gef gene and/or drugs was assessed by MTT assay. Apoptosis modulation was determined by flow cytometric analysis, DNA fragmentation and morphological analysis. Multicellular tumour spheroids (MTS) from MCF-7 cells were used to confirm effectiveness of combined therapy (gef gene and drug). RESULTS: Our results demonstrate that combined therapy gef gene/drugs (paclitaxel, docetaxel or doxurubicin) caused a decrease in cell viability. However, only the gef-doxorubicin (10 muM) combination induced a greater enhancement in the antitumour activity in MCF-7 cells. Most importantly, this combined strategy resulted in a significant synergistic effect, thus allowing lower doses of the drug to be used to achieve the same therapeutic effect. These results were confirmed using MTS in which volume decrease with combined therapy was greater than obtained using the gene therapy or chemotherapy alone, or the sum of both therapies. CONCLUSIONS: The cytotoxic effect of gef gene in breast cancer cells enhances the chemotherapeutic effect of doxorubicin. This therapeutic approach has the potential to overcome some of the major limitations of conventional chemotherapy, and may therefore constitute a promising strategy for future applications in breast cancer therapy. PMID: 19771430 [PubMed - as supplied by publisher] |
| The hypoxic microenvironment maintains glioblastoma stem cells and promotes reprogramming towards a cancer stem cell phenotype.
September 23, 2009 at 9:55 am
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| | The hypoxic microenvironment maintains glioblastoma stem cells and promotes reprogramming towards a cancer stem cell phenotype. Cell Cycle. 2009 Oct 3;8(20) Authors: Heddleston JM, Li Z, McLendon RE, Hjelmeland AB, Rich JN Glioblastomas are highly lethal cancers that contain cellular hierarchies with self-renewing cancer stem cells that can propagate tumors in secondary transplant assays. The potential significance of cancer stem cells in cancer biology has been demonstrated by studies showing contributions to therapeutic resistance, angiogenesis and tumor dispersal. We recently reported that physiologic oxygen levels differentially induce hypoxia inducible factor-2alpha (HIF2alpha) levels in cancer stem cells. HIF1alpha functioned in proliferation and survival of all cancer cells but also was activated in normal neural progenitors suggesting a potentially restricted therapeutic index while HIF2alpha was essential in only in cancer stem cells and was not expressed by normal neural progenitors demonstrating HIF2alpha is a cancer stem cell specific target. We now extend these studies to examine the role of hypoxia in regulating tumor cell plasticity. We find that hypoxia promotes the self-renewal capability of the stem and non-stem population as well as promoting a more stem-like phenotype in the non-stem population with increased neurosphere formation as well as upregulation of important stem cell factors, such as OCT4, NANOG and c-MYC. The importance of HIF2alpha was further supported as forced expression of non-degradable HIF2alpha induced a cancer stem cell marker and augmented the tumorigenic potential of the non-stem population. This novel finding may indicate a specific role of HIF2alpha in promoting glioma tumorigenesis. The unexpected plasticity of the nonstem glioma population and the stem-like phenotype emphasizes the importance of developing therapeutic strategies targeting the microenvironmental influence on the tumor in addition to cancer stem cells. PMID: 19770585 [PubMed - as supplied by publisher] |
| Layered implantation of myoblast sheets attenuates adverse cardiac remodeling of the infarcted heart.
September 23, 2009 at 9:55 am
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| | Layered implantation of myoblast sheets attenuates adverse cardiac remodeling of the infarcted heart. J Thorac Cardiovasc Surg. 2009 Oct;138(4):985-93 Authors: Sekiya N, Matsumiya G, Miyagawa S, Saito A, Shimizu T, Okano T, Kawaguchi N, Matsuura N, Sawa Y OBJECTIVE: We previously showed that autologous myoblast sheets constructed with tissue-engineering techniques improved the function of the impaired heart. In this study, we evaluated the effects of layered myoblast sheets to clarify whether increasing the number of sheets provides improvement of cardiac function. METHODS: Myoblast sheets were constructed in dishes that release confluent cells from the dish surface via temperature reduction. Sixty infarcted Lewis rats underwent implantation of myoblast sheets on the infarcted area. There were 4 groups (n = 15 in each group): S1: one layer, S3: three layers, S5: five layers, and a sham group. We examined cardiac function by echocardiography and catheterization, mRNA expression by real time reverse-transcriptase polymerase chain reaction, and histology. RESULTS: The ejection fraction and end-systolic pressure-volume relationship in the S5 and S3 groups were significantly improved. End-diastolic area was significantly reduced in the S5 group. The mRNAs for hepatocyte growth factor, vascular endothelial growth factor, and stromal cell-derived factor-1 were all up-regulated in dose-dependent fashion. On histologic examination, fibrosis was most decreased in S5, and vascular density was increased. Cellular hypertrophy was attenuated in both the S5 and S3 groups. Elastic fibers were massively up-regulated in the infarction and implanted sheets in the S5 and S3 groups, with expression of the elastin gene. CONCLUSIONS: Implantation of three- and five-layered myoblast sheets yields favorable results, with better improvement of cardiac function, induction of angiogenesis, more elastic fibers, and less fibrosis. Thus, layered myoblast sheets, in optimal numbers, may attenuate adverse cardiac remodeling of the infarcted heart. PMID: 19769884 [PubMed - in process] |
| The 'stem cell' concept: is it holding us back?
September 23, 2009 at 9:55 am
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| | The 'stem cell' concept: is it holding us back? J Biol. 2009 Sep 21;8(8):70 Authors: Lander AD ABSTRACT: Developmental biology, regenerative medicine and cancer biology are increasingly occupied with the molecular characterization of stem cells. Yet recent work adds to a growing body of literature suggesting that 'stemness' cannot be reduced to the molecular features of cell types, and is instead an emergent property of cell lineages under feedback control. PMID: 19769787 [PubMed - as supplied by publisher] |
| Preliminary development of a diabetic foot ulcer database from a wound electronic medical record: A tool to decrease limb amputations.
September 23, 2009 at 9:55 am
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| | Preliminary development of a diabetic foot ulcer database from a wound electronic medical record: A tool to decrease limb amputations. Wound Repair Regen. 2009 Sep-Oct;17(5):657-65 Authors: Golinko MS, Margolis DJ, Tal A, Hoffstad O, Boulton AJ, Brem H Our objective was to create a practical standardized database of clinically relevant variables in the care of patients with diabetes and foot ulcers. Numerical clinical variables such as age, baseline laboratory values, and wound area were extracted from the wound electronic medical record (WEMR). A coding system was developed to translate narrative data, culture, and pathology reports into discrete, quantifiable variables. Using data extracted from the WEMR, a diabetic foot ulcer-specific database incorporated the following tables: (1) demographics, medical history, and baseline laboratory values; (2) vascular testing data; (3) radiology data; (4) wound characteristics; and (5) wound debridement data including pathology, culture results, and amputation data. The database contains variables that can be easily exported for analysis. Amputation was studied in 146 patients who had at least two visits (e.g., two entries in the database). Analysis revealed that 19 (13%) patients underwent 32 amputations (nine major and 23 minor) in 23 limbs. There was a decreased risk of amputation, 0.87 (0.78, 1.00), using a proportional hazards model, associated with an increased number of visits and entries in the WEMR. Further analysis revealed no significant difference in age, gender, HbA1c%, cholesterol, white blood cell count, or prealbumin at baseline, whereas hemoglobin and albumin were significantly lower in the amputee group (p<0.05) than the nonamputee group. Fifty-nine percent of amputees had histological osteomyelitis based on operating room biopsy vs. 45% of nonamputees. In conclusion, tracking patients with a WEMR is a tool that could potentially increase patient safety and quality of care, allowing clinicians to more easily identify a nonhealing wound and intervene. This report describes a method of capturing data relevant to clinical care of a patient with a diabetic foot ulcer, and may enable clinicians to adapt such a system to their own patient population. PMID: 19769719 [PubMed - in process] |
| Thermosensitive Chitosan-Gelatin-Glycerol Phosphate Hydrogels as a Cell Carrier for Nucleus Pulposus Regeneration: an In-vitro Study.
September 23, 2009 at 9:55 am
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| | Thermosensitive Chitosan-Gelatin-Glycerol Phosphate Hydrogels as a Cell Carrier for Nucleus Pulposus Regeneration: an In-vitro Study. Tissue Eng Part A. 2009 Sep 21; Authors: Cheng YH, Lin FH, Yang KC Injectable hydrogel is one of the great interests for tissue engineering and cell encapsulation. In the study, the gelatin molecules were added to the thermosensitive chitosan/ss-glycerol phosphate disodium salt hydrogels (C/GP hydrogels) as chitosan/gelatin/beta-glycerol phosphate disodium salt hydrogels (C/G/GP hydrogels) and applied as a cell carrier for nucleus pulposus (NP) regeneration. The gelation temperature, gelation time and gel strength of the C/G/GP hydrogels were analyzed by the rheometer. NP cells were then harvested from the intervertebral discs of the adult New Zealand white rabbits and cultured in monolayer or in C/G/GP hydrogel, respectively. The cell viability, material-mediated cytotoxicity, cell proliferation, production of sulfated glycosaminoglycans (GAGs) and extracellular matrix (ECM) related gene expressions of the NP cells were demonstrated. Results show that the sol/gel transition temperature of the C/G/GP hydrogel was in the range of 31.1-33.8 degrees C at neutral pH value, the gelation time was shortened and the gel strength also improved at body temperature when compared with the C/GP hydrogel. Among those, C/GP with 1% gelatin addition showed the most promising gelation time and gel strength and utilized in the later experiments. From the results of cell activity, cytotoxicity and cell proliferation assays, NP cells cultured in C/G/GP hydrogel had normal cell viability and cell proliferation that indicated the hydrogel was non-cytotoxicity. The amounts of sulfated GAGs of NP cells cultured in C/G/GP hydrogels were significantly higher than monolayer-cultured. Considering the ECM-related gene expression, type II collagen and aggrecan of NP cells cultured in the hydrogels greatly increased than those of in monolayer culture. On the contrary, the unfavorable gene expression such as type I collagen was decreased significantly. The results reveal that gelatin added into C/GP hydrogel significantly shortened the gelation time and improved the gel strength without influencing the biocompatibility. NP cells cultured in the C/G/GP hydrogel also displayed better gene expressions when compared with the monolayer culture. This study indicates that using chitosan/gelatin hydrogel for NP cell culture is feasible and may apply in minimal invasive intervertebral disc surgery in the future. PMID: 19769528 [PubMed - as supplied by publisher] |
| Bioprinted Nanoparticles for Tissue Engineering Applications.
September 23, 2009 at 9:55 am
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| | Bioprinted Nanoparticles for Tissue Engineering Applications. Tissue Eng Part C Methods. 2009 Sep 21; Authors: Buyukhatipoglu K, Chang RC, Sun W, Morss Clyne A Tissue engineering may require precise patterning and monitoring of cells and bioactive factors within the scaffold. We investigated a new hybrid nano-bioprinting technique that facilitates manipulation and tracking of cells and bioactive factors within a three-dimensional tissue construct. This technique combines the initial patterning capabilities of syringe-based cell deposition with the active patterning capabilities of superparamagnetic nanoparticles. Superparamagnetic iron oxide nanoparticles, either in the alginate biopolymer or loaded inside endothelial cells, were bioprinted using a solid freeform fabrication direct cell writing system. Bioprinting did not impact cell viability when nanoparticles were in the alginate. However, both control and printed samples with 0.1 or 1.0 mg/ml nanoparticles in the alginate showed a 16% or 35% viability loss 36 hours after printing, respectively. Nanoparticle loading in cells decreased cell viability 11% and bioprinting decreased viability an additional 29% at 36 hours. No changes were observed in any samples after 36 hours, suggesting that cell viability stabilized following the initial nanoparticle toxicity effect. Nanoparticles in the alginate and loaded in cells were moved using an external magnet, depending on biopolymer viscosity, and imaged by MicroCT. The hybrid nano-bioprinting method can non-invasively manipulate and track bioactive factors and cells within tissue engineering structures. PMID: 19769526 [PubMed - as supplied by publisher] |
| GOAT BONE TISSUE ENGINEERING:COMPARING AN INTRAMUSCULAR WITH A POSTEROLATERAL LUMBAR SPINE LOCATION.
September 23, 2009 at 9:55 am
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| | GOAT BONE TISSUE ENGINEERING:COMPARING AN INTRAMUSCULAR WITH A POSTEROLATERAL LUMBAR SPINE LOCATION. Tissue Eng Part A. 2009 Sep 21; Authors: van Gaalen SM, Dhert W, Kruyt M, Yuan H, Oner FC, van Blitterswijk CA, Verbout A, de Bruijn J The aim of this study was to investigate the effect of implant location on bone formation in goats using autologous bone marrow derived stromal cells (BMSC's) in porous calcium phosphate scaffolds. Intramuscular locations were compared to posterolateral spine fusion locations in 8 goats. As scaffolds we used Biphasic Calcium Phosphate (BCP) porous blocks of 5x5x5 mm. Cell-seeded implants were compared to empty controls. BMSC's were seeded at 8 million cells per cm3 scaffold and cultured for one week. The follow-up time was 12 weeks. Fluorochromes were administered intravenously at 4, 6 and 8 weeks. Ectopic implants showed 21 +/- 3.6 % bone formation for the cell-seeded and 2.0 +/- 3.0 % for the controls (p<0.001). Paraspinal implants however, showed 0.10 +/- 0.13 % in the cell seeded as compared to a 0.023 +/- 0.027 % in the control group (p=0.09). A benefit of the cells was only found in the area closest to the paraspinal muscles (p<0.01). Bone formation in the control samples was of later onset as compared to the cell-seeded implants. In conclusion, cell based bone tissue engineering in an ectopic environment was clearly effective. Similar constructs implanted in a posterolateral spine fusion location, hardly showed any effect. PMID: 19769525 [PubMed - as supplied by publisher] |
| [Biocompatibility of new bone tissue engineering scaffolds in vivo]
September 23, 2009 at 9:55 am
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| | [Biocompatibility of new bone tissue engineering scaffolds in vivo] Hua Xi Kou Qiang Yi Xue Za Zhi. 2009 Aug;27(4):447-50 Authors: Li Y, Ran W, Wang GL, Jing XD OBJECTIVE: To investigate the biocompatibility of new bone tissue engineering scaffolds, A:D, L-polylactic acid (PDLLA)/polylactic acid-polyethylene glycol-polylactic acid-polylactic acid (PLA-PEG-PLA)/Tricalcium phosphate and B: PDLLA/PLA-PEG-PLA in vivo, compared with PDLLA in repair of a rabbit mandibular body defect. METHODS: 24 New Zealand adult rabbits were divided into 4 groups randomly. 15 mm x 6 mm defects were made surgically in the bilateral mandibular bodies and each hemi-mandible was assigned as an experimental unit. The defects were randomly repaired with scaffold materials in each group. Specimens obtained were evaluated with general observation, X-ray, histomorphology and computerized graphical analysis at 2, 4 , 8, 12 weeks after surgery. RESULTS: Compared with PDLLA, the new scaffold materials B showed biocompatibility. At the same time the quantity of new bone produced was much more than that in control group (P<0.05). The new scaffold materials A showed the clear chronic granulomatous inflammation. CONCLUSION: New scaffold material B had sound biocompatibility. It was much better than PDLLA. So it may be an ideal bone tissue engineering scaffold material. A is not adapted to be used as scaffold material. PMID: 19769271 [PubMed - in process] |
| A split-face, double-blind, randomized and placebo-controlled pilot evaluation of a novel oligopeptide for the treatment of recalcitrant melasma.
September 23, 2009 at 9:55 am
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| | A split-face, double-blind, randomized and placebo-controlled pilot evaluation of a novel oligopeptide for the treatment of recalcitrant melasma. J Drugs Dermatol. 2009 Aug;8(8):732-5 Authors: Hantash BM, Jimenez F Melasma is a cutaneous disorder associated with an overproduction of melanin by the tyrosinase enzyme. A proprietary oligopeptide (Lumixyl) was previously shown to competitively inhibit mushroom and human tyrosinase without the associated toxicity of hydroquinone. The aim of this split-face, randomized, double-blind and placebo-controlled pilot study was to determine the effect of twice-daily topical application of this oligopeptide (0.01% w/w) on moderate, recalcitrant melasma over a 16-week course. Five female participants with Fitzpatrick phototype IV and moderate recalcitrant melasma enrolled and completed the study. Improvement in melasma and overall facial aesthetics as well as assessment of volunteer satisfaction was measured using 10- and five-point grading scales, respectively. Treatment was well tolerated with no visible signs of irritation or allergy. All five participants demonstrated statistically significant improvement in the appearance of melasma and overall facial aesthetics with high patient satisfaction. Results suggest that the oligopeptide may be useful in the treatment of melasma and warrants further evaluation. PMID: 19663110 [PubMed - indexed for MEDLINE] |
| Naive rat amnion-derived cell transplantation improved left ventricular function and reduced myocardial scar of postinfarcted heart.
September 23, 2009 at 9:55 am
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| | Naive rat amnion-derived cell transplantation improved left ventricular function and reduced myocardial scar of postinfarcted heart. Cell Transplant. 2009;18(4):477-86 Authors: Fujimoto KL, Miki T, Liu LJ, Hashizume R, Strom SC, Wagner WR, Keller BB, Tobita K Stem cells contained in the amniotic membrane may be useful for cellular repair of the damaged heart. Previously, we showed that amnion-derived cells (ADCs) express embryonic stem cell surface markers and pluripotent stem cell-specific transcription factor genes. These ADCs also possess the potential for mesoderm (cardiac) lineage differentiation. In the present study we investigated whether untreated naive ADC transplantation into the injured left ventricular (LV) myocardium is beneficial as a cell-based cardiac repair strategy in a rat model. ADCs were isolated from Lewis rat embryonic day 14 amniotic membranes. FACS analysis revealed that freshly isolated ADCs contained stage-specific embryonic antigen-1 (SSEA-1), Oct-4-positive cells, and mesenchymal stromal cells, while hematopoietic stem cell marker positive cells were absent. Reverse transcription-PCR revealed that naive ADCs expressed cardiac and vascular specific genes. We injected freshly isolated ADCs (2 x 10(6) cells suspended in PBS, ADC group) into acutely infarcted LV myocardium produced by proximal left coronary ligation. PBS was injected in postinfarction controls (PBS group). Cardiac function was assessed at 2 and 6 weeks after injection. ADC treatment attenuated LV dilatation and sustained LV contractile function at 2 and 6 weeks in comparison to PBS controls (p < 0.05, ANOVA). LV peak systolic pressure and maximum dP/dt of ADC-treated heart were higher and LV end-diastolic pressure and negative dP/dt were lower than in PBS controls (p < 0.05). Histological assessment revealed that infarcted myocardium of the ADC-treated group had less fibrosis, thicker ventricular walls, and increased capillary density (p < 0.05). The fate of injected ADCs was confirmed using ADCs derived from EGFP(+) transgenic rats. Immunohistochemistry at 6 weeks revealed that EGFP(+) cells colocalized with von Willebrand factor, alpha-smooth muscle actin, or cardiac troponin-I. Our results suggest that naive ADCs are a potential cell source for cellular cardiomyoplasty. PMID: 19622235 [PubMed - indexed for MEDLINE] |
| ERas is expressed in primate embryonic stem cells but not related to tumorigenesis.
September 23, 2009 at 9:55 am
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| | ERas is expressed in primate embryonic stem cells but not related to tumorigenesis. Cell Transplant. 2009;18(4):381-9 Authors: Tanaka Y, Ikeda T, Kishi Y, Masuda S, Shibata H, Takeuchi K, Komura M, Iwanaka T, Muramatsu S, Kondo Y, Takahashi K, Yamanaka S, Hanazono Y The ERas gene promotes the proliferation of and formation of teratomas by mouse embryonic stem (ES) cells. However, its human orthologue is not expressed in human ES cells. This implies that the behavior of transplanted mouse ES cells would not accurately reflect the behavior of transplanted human ES cells and that the use of nonhuman primate models might be more appropriate to demonstrate the safety of human ES cell-based therapies. However, the expression of the ERas gene has not been examined in nonhuman primate ES cells. In this study, we cloned the cynomolgus homologue and showed that the ERas gene is expressed in cynomolgus ES cells. Notably, it is also expressed in cynomolgus ES cell-derived differentiated progeny as well as cynomolgus adult tissues. The ERas protein is detectable in various cynomolgus tissues as assessed by immunohistochemisty. Cynomolgus ES cell-derived teratoma cells, which also expressed the ERas gene at higher levels than the undifferentiated cynomolgus ES cells, did not develop tumors in NOD/Shi-scid, IL-2Rgamma(null) (NOG) mice. Even when the ERas gene was overexpressed in cynomolgus stromal cells, only the plating efficiency was improved and the proliferation was not promoted. Thus, it is unlikely that ERas contributes to the tumorigenicity of cynomolgus cells. Therefore, cynomolgus ES cells are more similar to human than mouse ES cells despite that ERas is expressed in cynomolgus and mouse ES cells but not in human ES cells. PMID: 19622226 [PubMed - indexed for MEDLINE] |
| Doppler optical coherence tomography imaging of local fluid flow and shear stress within microporous scaffolds.
September 23, 2009 at 9:55 am
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| | Doppler optical coherence tomography imaging of local fluid flow and shear stress within microporous scaffolds. J Biomed Opt. 2009 May-Jun;14(3):034014 Authors: Jia Y, Bagnaninchi PO, Yang Y, Haj AE, Hinds MT, Kirkpatrick SJ, Wang RK Establishing a relationship between perfusion rate and fluid shear stress in a 3D cell culture environment is an ongoing and challenging task faced by tissue engineers. We explore Doppler optical coherence tomography (DOCT) as a potential imaging tool for in situ monitoring of local fluid flow profiles inside porous chitosan scaffolds. From the measured fluid flow profiles, the fluid shear stresses are evaluated. We examine the localized fluid flow and shear stress within low- and high-porosity chitosan scaffolds, which are subjected to a constant input flow rate of 0.5 ml min(-1). The DOCT results show that the behavior of the fluid flow and shear stress in micropores is strongly dependent on the micropore interconnectivity, porosity, and size of pores within the scaffold. For low-porosity and high-porosity chitosan scaffolds examined, the measured local fluid flow and shear stress varied from micropore to micropore, with a mean shear stress of 0.49+/-0.3 dyn cm(-2) and 0.38+/-0.2 dyn cm(-2), respectively. In addition, we show that the scaffold's porosity and interconnectivity can be quantified by combining analyses of the 3D structural and flow images obtained from DOCT. PMID: 19566307 [PubMed - indexed for MEDLINE] |
| Effect of low-level laser treatment of tissue-engineered skin substitutes: contraction of collagen lattices.
September 23, 2009 at 9:55 am
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| | Effect of low-level laser treatment of tissue-engineered skin substitutes: contraction of collagen lattices. J Biomed Opt. 2009 May-Jun;14(3):034002 Authors: Ho G, Barbenel J, Grant MH Fibroblast-populated collagen lattices (FPCL) are widely used in tissue-engineered artificial skin substitutes, but their main drawback is that interaction of fibroblasts and matrix causes contraction of the lattice, reducing it to about 20% of its original area. The effect of low-level laser treatment (LLLT) on the behavior of 3T3 fibroblasts seeded in collagen lattices containing 20% chondroitin-6-sulphate was investigated to determine whether LLLT could control the contraction of FPCL. A He-Ne laser was used at 632.8 nm to deliver a 5-mW continuous wave with fluences from 1 to 4 J/cm(2). Laser treatment at 3 J/cm(2) increased contraction of collagen lattices in the absence of cells but decreased contraction of cell seeded lattices over a 7-day period. The effect was energy dependent and was not observed at 1, 2, or 4 J/cm(2). There was no alteration in fibroblast viability, morphology, or mitochondrial membrane potential after any laser treatments, but the distribution of actin fibers within the cells and collagen fibers in the matrices was disturbed at 3 J/cm(2). These effects contribute to the decrease in contraction observed. LLLT may offer a means to control contraction of FPCL used as artificial skin substitutes. PMID: 19566296 [PubMed - indexed for MEDLINE] |
| Definitive proof for direct reprogramming of hematopoietic cells to pluripotency.
September 23, 2009 at 9:55 am
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| | Definitive proof for direct reprogramming of hematopoietic cells to pluripotency. Blood. 2009 Aug 27;114(9):1764-7 Authors: Okabe M, Otsu M, Ahn DH, Kobayashi T, Morita Y, Wakiyama Y, Onodera M, Eto K, Ema H, Nakauchi H Generation of induced pluripotent stem cells (iPSCs) generally uses fibroblastic cells, but other cell sources may prove useful in both research and clinical settings. Although proof of cellular origin requires genetic-marker identification in both target cells and established iPSCs, somatic cells other than mature lymphocytes mostly lack such markers. Here we show definitive proof of direct reprogramming of murine hematopoietic cells with no rearranged genes. Using iPSC factor transduction, we successfully derived iPSCs from bone marrow progenitor cells obtained from a mouse whose hematopoiesis was reconstituted from a single congenic hematopoietic stem cell. Established clones were demonstrated to be genetically identical to the transplanted single hematopoietic stem cell, thus proving their cellular origin. These hematopoietic cell-derived iPSCs showed typical characteristics of iPSCs, including the ability to contribute to chimerism in mice. These results will prompt further use of hematopoietic cells for iPSC generation while enabling definitive studies to test how cellular sources influence characteristics of descendant iPSCs. PMID: 19564635 [PubMed - indexed for MEDLINE] |
| Comment on "A novel strategy for prefabrication of large and axially vascularized tissue engineered bone by using an arteriovenous loop".
September 23, 2009 at 9:55 am
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| | Comment on "A novel strategy for prefabrication of large and axially vascularized tissue engineered bone by using an arteriovenous loop". Med Hypotheses. 2009 Sep;73(3):461-2 Authors: Jiang X, Wang D, Jin D, Pei G PMID: 19409712 [PubMed - indexed for MEDLINE] |
| Novel biological/biohybrid prostheses for the ossicular chain: fabrication feasibility and preliminary functional characterization.
September 23, 2009 at 9:55 am
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| | Novel biological/biohybrid prostheses for the ossicular chain: fabrication feasibility and preliminary functional characterization. Biomed Microdevices. 2009 Aug;11(4):783-93 Authors: Danti S, Stefanini C, D'Alessandro D, Moscato S, Pietrabissa A, Petrini M, Berrettini S Alternatives for ossicular replacements were fabricated in order to overcome persisting rejections in middle ear prosthetization. Unlike the synthetic prostheses in fashion, we propose biological and biohybrid replacements containing extra cellular matrix (ECM) molecules to improve biointegration. In this study, ECM-containing devices shaped as Partial Ossicular Replacement Prostheses (PORPs) were fabricated reproducing the current synthetic models. Biological PORPs were obtained from human decellularized cortical bone allografts by computer numerically controlled ultraprecision micromilling. Moreover, porous PORP-like scaffolds were produced and cultured with osteoinduced human mesenchymal stromal cells to generate in vitro bone ECM within the scaffold porosity (biohybrid PORPs). The acoustic responses of such devices were investigated and compared to those of commercial prostheses. Results showed that biological PORPs transmit mechanical signals with appropriate frequencies, amplitudes, and with early extinction time. Although signal transmission in biohybrid PORPs showed insufficient amplitude, we believe that tissue engineered constructs represent the new challenge in ossiculoplasty. PMID: 19294514 [PubMed - indexed for MEDLINE] |
| Controlled cellular orientation on PLGA microfibers with defined diameters.
September 23, 2009 at 9:55 am
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| | Controlled cellular orientation on PLGA microfibers with defined diameters. Biomed Microdevices. 2009 Aug;11(4):739-46 Authors: Hwang CM, Park Y, Park JY, Lee K, Sun K, Khademhosseini A, Lee SH In this study, we investigated the effects of the diameter of microfibers on the orientation (angle between cells' major axis and the substrate fiber long axis) of adhered cells. For this purpose, mouse fibroblast L929 cells were cultured on the surface of PLGA fibers of defined diameters ranging from 10 to 242 mum, and their adhesion and alignment was quantitatively analyzed. It was found that the mean orientation of cells and the spatial variation of cell alignment angle directly related to the microfiber diameter. Cells that were cultured on microfibrous scaffolds oriented along the long axis of the microfiber and the orientation increased as the fiber diameter decreased. For the fiber diameter of 10 microm, the mean orientation was 3.0 +/- 0.2 degrees (mean +/- SE), whereas for a diameter of 242 microm, it decreased to 37.7 +/- 2.1 degrees . Using these studies we demonstrate that fibroblasts have a characteristic alignment on microscale fibers and that the microscale fiber diameter plays a critical role in cellular orientation. The ability to control cellular alignment on engineered tissue scaffold can be a potentially powerful approach to recreate the microscale architecture of engineered tissues. This may be important for engineering a variety of human tissues such as tendon, muscle and nerves as well as applications in 3D tissue culture and drug screening. PMID: 19242806 [PubMed - indexed for MEDLINE] | | | 
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