| Bone tissue engineering: A review in bone biomimetics and drug delivery strategies.
October 14, 2009 at 6:15 am
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| | Bone tissue engineering: A review in bone biomimetics and drug delivery strategies. Biotechnol Prog. 2009 Oct 12; Authors: Porter JR, Ruckh TT, Popat KC Critical-sized defects in bone, whether induced by primary tumor resection, trauma, or selective surgery have in many cases presented insurmountable challenges to the current gold standard treatment for bone repair. The primary purpose of a tissue-engineered scaffold is to use engineering principles to incite and promote the natural healing process of bone which does not occur in critical-sized defects. A synthetic bone scaffold must be biocompatible, biodegradable to allow native tissue integration, and mimic the multidimensional hierarchical structure of native bone. In addition to being physically and chemically biomimetic, an ideal scaffold is capable of eluting bioactive molecules (e.g., BMPs, TGF-betas, etc., to accelerate extracellular matrix production and tissue integration) or drugs (e.g., antibiotics, cisplatin, etc., to prevent undesired biological response such as sepsis or cancer recurrence) in a temporally and spatially controlled manner. Various biomaterials including ceramics, metals, polymers, and composites have been investigated for their potential as bone scaffold materials. However, due to their tunable physiochemical properties, biocompatibility, and controllable biodegradability, polymers have emerged as the principal material in bone tissue engineering. This article briefly reviews the physiological and anatomical characteristics of native bone, describes key technologies in mimicking the physical and chemical environment of bone using synthetic materials, and provides an overview of local drug delivery as it pertains to bone tissue engineering is included. (c) 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009. PMID: 19824042 [PubMed - as supplied by publisher] |
| In vitro liver model using microfabricated scaffolds in a modular bioreactor.
October 14, 2009 at 6:15 am
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| | In vitro liver model using microfabricated scaffolds in a modular bioreactor. Biotechnol J. 2009 Oct 12; Authors: Vinci B, Cavallone D, Vozzi G, Mazzei D, Domenici C, Brunetto M, Ahluwalia A Hepatocyte function on 3-D microfabricated polymer scaffolds realised with the pressure-activated microsyringe was tested under static and dynamic conditions. The dynamic cell culture was obtained using the multicompartment modular bioreactor system. Hepatocyte cell density, glucose consumption, and albumin secretion rate were measured daily over a week. Cells seeded on scaffolds showed an increase in cell density compared with monolayer controls. Moreover, in dynamic culture, cell metabolic function increased three times in comparison with static monolayer cultures. These results suggest that cell density and cell-cell interactions are mediated by the architecture of the substrate, while the endogenous biochemical functions are regulated by a sustainable supply of nutrients and interstitial-like flow. Thus, a combination of 3-D scaffolds and dynamic flow conditions are both important for the development of a hepatic tissue model for applications in drug testing and regenerative medicine. PMID: 19824019 [PubMed - as supplied by publisher] |
| Effects of exogenous glycosaminoglycans on human chondrocytes cultivated on type II collagen scaffolds.
October 14, 2009 at 6:15 am
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| | Effects of exogenous glycosaminoglycans on human chondrocytes cultivated on type II collagen scaffolds. J Mater Sci Mater Med. 2009 Oct 13; Authors: Wu CH, Ko CS, Huang JW, Huang HJ, Chu IM Cartilage extracellular matrix (ECM) is composed primarily of type II collagen (COL II) and large, networks of proteoglycans (PGs) that contain glycosaminoglycans such as hyaluronic acid (HA) and chondroitin sulfate (CS). Since cartilage shows little tendency for self-repair, injuries are kept unhealed for years and can eventually lead to further degeneration. During the past decades, many investigations have pursued techniques to stimulate articular cartilage repair or regeneration. The current study assessed the effects of exogenous glycosaminoglycans (GAGs) including CS-A, CS-B, CS-C, heparan sulfate and HA, administration on human chondrocytes in terms of proliferation and matrix synthesis, while the cells were seeded and grown on the genipin-crosslinked collagen type II (COL II) scaffold. DNA content was measured by Hoechst dye intercalation, matrix deposition was evaluated by DMMB dye. Expression of collagen II and aggrecan mRNAs was assessed by RT-PCR, followed by gel electrophoresis. In a 28-day in vitro culture, administration of 5 mug/ml CS-A, 50 mug/ml CS-B, 50 mug/ml CS-C, 5 mug/ml HS, and 500 kDa HA led to significant increase in biosynthesis rate of PGs. Gene expression of aggrecan and collagen II were upregulated by CS-A, CS-C and HA. These results showed considerable relevance of GAGs to the issue of in vitro/ex vivo neo-cartilage synthesis for tissue engineering and regenerative medical applications. PMID: 19823917 [PubMed - as supplied by publisher] |
| Dynamic distribution and stem cell characteristics of Sox1-expressing cells in the cerebellar cortex.
October 14, 2009 at 6:15 am
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| | Dynamic distribution and stem cell characteristics of Sox1-expressing cells in the cerebellar cortex. Cell Res. 2009 Oct 13; Authors: Alcock J, Sottile V Bergmann glia cells are a discrete radial glia population surrounding Purkinje cells in the cerebellar cortex. Although Bergmann glia are essential for the development and correct arborization of Purkinje cells, little is known about the regulation of this cell population after the developmental phase. In an effort to characterize this population at the molecular level, we have analyzed marker expression and established that adult Bergmann glia express Sox1, Sox2 and Sox9, a feature otherwise associated with neural stem cells (NSCs). In the present study, we have further analyzed the developmental pattern of Sox1-expressing cells in the developing cerebellum. We report that before becoming restricted to the Purkinje cell layer, Sox1-positive cells are present throughout the immature tissue, and that these cells show characteristics of Bergmann glia progenitors. Our study shows that these progenitors express Sox1, Sox2 and Sox9, a signature maintained throughout cerebellar maturation into adulthood. When isolated in culture, the Sox1-expressing cerebellar population exhibited neurosphere-forming ability, NSC-marker characteristics, and demonstrated multipotency at the clonal level. Our results show that the Bergmann glia population expresses Sox1 during cerebellar development, and that these cells can be isolated and show stem cell characteristics in vitro, suggesting that they could hold a broader potential than previously thought. PMID: 19823196 [PubMed - as supplied by publisher] |
| Characteristics and management of diaphragm involvement in patients with primary advanced-stage ovarian, fallopian tube, or peritoneal cancer.
October 14, 2009 at 6:15 am
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| | Characteristics and management of diaphragm involvement in patients with primary advanced-stage ovarian, fallopian tube, or peritoneal cancer. Int J Gynecol Cancer. 2009 Oct;19(7):1288-97 Authors: Einenkel J, Ott R, Handzel R, Braumann UD, Horn LC OBJECTIVES:: The aim of this study was to determine the frequency of diaphragm involvement (DI) in cases of International Federation of Gynecology and Obstetrics (FIGO) stage IIIC and IV primary epithelial ovarian, fallopian tube, or peritoneal cancer; the frequency of use of different surgical techniques in managing diaphragm implants; and the procedure-associated morbidity. METHODS:: A retrospective analysis of consecutive patients undergoing primary surgery by a single surgical team between January 2005 and June 2007 was accomplished. Patients with tumors of low malignant potential and nonepithelial histologic diagnosis and those who received neoadjuvant chemotherapy were excluded. RESULTS:: Thirty-three patients met the inclusion criteria. Diaphragm involvement was found in 91% of the cases. Whereas the left hemidiaphragm is never involved alone, the right side is significantly affected more extensively (P = 0.002) and frequently (alone, 20%; both sides, 80%). The frequency of use of procedures varies considerably in the literature, whereas full-thickness diaphragm resection (DR) had to be performed in 53% of our patients with DI. Diaphragm resection at the left hemidiaphragm and bilateral DRs are very rare in primary cases. A specific histopathologic examination of the DR preparation is desirable. A simple 4-tiered classification of the infiltration depth is proposed. The most frequent complication is serothorax, but a generous indication for intraoperative chest tube placement is solely recommended in cases of DR. CONCLUSIONS:: Surgical effort in achieving an optimum cytoreduction could be evaluated more precisely with parameters of DI and diaphragm-related treatment procedures. The usual quality criteria for ovarian cancer surgery, such as residual tumor state and morbidity, are more marked by subjectivity and inconsistent definitions. PMID: 19823067 [PubMed - in process] |
| microRNAs regulate human embryonic stem cell division.
October 14, 2009 at 6:15 am
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| | microRNAs regulate human embryonic stem cell division. Cell Cycle. 2009 Nov 10;8(22) Authors: Qi J, Yu JY, Shcherbata HR, Mathieu J, Wang AJ, Seal S, Zhou W, Stadler BM, Bourgin D, Wang L, Nelson A, Ware C, Raymond C, Lim LP, Magnus J, Ivanovska I, Diaz R, Ball A, Cleary MA, Ruohola-Baker H microRNAs (miRNAs) regulate numerous physiological processes such as cell division and differentiation in many tissue types including stem cells. To probe the role that miRNAs play in regulating processes relevant to embryonic stem cell biology, we used RNA interference to silence DICER and DROSHA, the two main miRNA processing enzymes. Consistent with a role for miRNAs in maintaining normal stem cell division and renewal, we found that perturbation of miRNA pathway function in human embryonic stem cells (hESCs) attenuates cell proliferation. Normal cell growth can be partially restored by introduction of the mature miRNAs miR-195 and miR-372. These miRNAs regulate two tumor suppressor genes, respectively: WEE1, which encodes a negative G2/M kinase modulator of the CycB/CDK complex and CDKN1A, which encodes p21, a CycE/CDK cyclin dependent kinase inhibitor that regulates the G1/S transition. We show that in wild-type hESCs, WEE 1 levels control the rate of hESC division, whereas p21 levels must be maintained at a low level for hESC division to proceed. These data support a model for hESC cell cycle control in which miRNAs regulate negative cell cycle modulators at two phases of the cell cycle to ensure proper replenishment of the stem cell population. PMID: 19823043 [PubMed - as supplied by publisher] |
| Dual role for the methyltransferase G9a in the maintenance of {beta}-globin gene transcription in adult erythroid cells.
October 14, 2009 at 6:15 am
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| | Dual role for the methyltransferase G9a in the maintenance of {beta}-globin gene transcription in adult erythroid cells. Proc Natl Acad Sci U S A. 2009 Oct 12; Authors: Chaturvedi CP, Hosey AM, Palii C, Perez-Iratxeta C, Nakatani Y, Ranish JA, Dilworth FJ, Brand M Using a proteomics screen, we have identified the methyltransferase G9a as an interacting partner of the hematopoietic activator NF-E2. We show that G9a is recruited to the beta-globin locus in a NF-E2-dependent manner and spreads over the entire locus. While G9a is often regarded as a corepressor, knocking down this protein in differentiating adult erythroid cells leads to repression of the adult beta(maj) globin gene and aberrant reactivation of the embryonic beta-like globin gene E(y). While in adult cells G9a maintains E(y) in a repressed state via dimethylation of histone H3 at lysines 9 and 27, it activates beta(maj) transcription in a methyltransferase-independent manner. Interestingly, the demethylase UTX is recruited to the beta(maj) (but not the E(y)) promoter where it antagonizes G9a-dependent H3K27 dimethylation. Collectively, these results reveal a dual role for G9a in maintaining proper expression (both repression and activation) of the beta-globin genes in differentiating adult erythroid cells. PMID: 19822740 [PubMed - as supplied by publisher] |
| Effect of fiber diameter, pore size and seeding method on growth of human dermal fibroblasts in electrospun poly(varepsilon-caprolactone) fibrous mats.
October 14, 2009 at 6:15 am
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| | Effect of fiber diameter, pore size and seeding method on growth of human dermal fibroblasts in electrospun poly(varepsilon-caprolactone) fibrous mats. Biomaterials. 2009 Oct 10; Authors: Lowery JL, Datta N, Rutledge GC Nonwoven fiber mats of poly(varepsilon-caprolactone) (PCL) and PCL blended with poly(ethylene oxide) (PEO) were generated by electrospinning. Differential scanning calorimetry, scanning electron microscopy, and gravimetric measurement confirm the removal of PEO after immersion in water, as well as an increase in the PCL crystallinity. The reorganization of PCL resulted in the macroscopic alteration of the electrospun mat, decreasing the peak pore diameter up to a factor of 3 while only minimally affecting the fiber diameter. This technique was used to create electrospun PCL scaffolds with similar fiber diameters but different pore diameters to examine the effect of pore diameter on cell growth. Human Dermal Fibroblasts (HDF) were seeded into multiple samples using a perfusion seeding technique to guarantee successful cell deposition. Fluorescence analysis at 7, 14, and 21 days found that cells proliferated at a faster rate on scaffolds with peak pore diameters greater than 6mum, as determined by mercury porosimetry. Cell conformation was also found to change as the peak pore diameter grew from 12 to 23mum; cells began aligning along single fibers instead of attaching to multiple fibers. Knowledge of the effect of void architecture on cell proliferation and conformation could lead to the development of more effective scaffolds for tissue engineering. PMID: 19822363 [PubMed - as supplied by publisher] |
| Some properties of keratin biomaterials: Kerateines.
October 14, 2009 at 6:15 am
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| | Some properties of keratin biomaterials: Kerateines. Biomaterials. 2009 Oct 10; Authors: Sierpinski-Hill P, Brantley H, Van Dyke M Keratins are a family of structural proteins that can be isolated from a variety of tissues. "Soft" keratins are cytoskeletal elements found in epithelial tissues while protective tissues such as nails, hooves, and hair are composed of "hard" keratins. Hard keratins have been the subject of biomaterials investigations for more than three decades. Numerous methods exist for denaturing these proteins which are characterized by a high sulfur content and extensive disulfide bonding, under either oxidative or reductive conditions, extracting them from tissue and processing them into various physical states such as gels, films, coatings, and fibers. Kerateines or keratoses (oxidatively or reductively derived, respectively), alone or in combination with other biomaterials, have been tested in a small number of systems to demonstrate feasibility for medical applications such as wound healing, bone regeneration, hemostasis, and peripheral nerve repair. These investigations have shown generally good compatibility with cells and tissues, but the focus of prior investigations has been fairly narrow, and as a result there is relatively little published data on the general behavior of keratin biomaterials in biological systems beyond cell culture assays. The goal of this study was to produce a reduced form of keratin biomaterial, kerateine, using a typical and well-published technique, and characterize several aspects of its behavior that may have implications to its general use as a biomaterial. Kerateines were extracted from human hair, fabricated into gels and porous scaffolds, characterized, and placed into biological systems to determine their interactions with cells and tissue. Initially, the proteins were analyzed for molecular weight and amino acid content, as well as their ability to facilitate cell adhesion and proliferation. Crosslinked hydrogels were investigated for their hydrolytic stability in vitro; the micro-architecture and in vivo tissue response of lyophilized gels was also studied. These experiments both confirmed and expanded earlier findings that kerateines demonstrate excellent compatibility in biological systems. PMID: 19822360 [PubMed - as supplied by publisher] |
| Bone Morphogenetic Protein-6-loaded Chitosan Scaffolds Enhance the Osteoblastic Characteristics of MC3T3-E1 Cells.
October 14, 2009 at 6:15 am
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| | Bone Morphogenetic Protein-6-loaded Chitosan Scaffolds Enhance the Osteoblastic Characteristics of MC3T3-E1 Cells. Artif Organs. 2009 Oct 11; Authors: Akman AC, Seda Tığlı R, Gümüşderelioğlu M, Nohutcu RM Abstract The purpose of this study is to investigate the convenience of bone morphogenetic protein-6 (BMP-6)-loaded chitosan scaffolds with preosteoblastic cells for bone tissue engineering. MC3T3-E1 cells were seeded into three different groups: chitosan scaffolds, BMP-6-loaded chitosan scaffolds, and chitosan scaffolds with free BMP-6 in culture medium. Tissue-engineered constructs were characterized by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide assay, scanning electron microscopy (SEM), mineralization assay (von Kossa), alkaline phosphatase (ALP) activity, and osteocalcin (OCN) assays. BMP-6-loaded chitosan scaffolds supported proliferation of the MC3T3-E1 mouse osteogenic cells in a similar pattern as the unloaded chitosan scaffolds group and as the chitosan scaffolds with free BMP-6 group. SEM images of the cell-seeded scaffolds revealed significant acceleration of extracellular matrix synthesis in BMP-6-loaded chitosan scaffolds. Both levels of ALP and OCN were higher in BMP-6-loaded chitosan scaffold group compared with the other two groups. In addition, BMP-6-loaded scaffolds showed strong staining in mineralization assays. These findings suggest that BMP-6-loaded chitosan scaffold supports cellular functions of the osteoblastic cells; therefore, this scaffold is considered as a new promising vehicle for bone tissue engineering applications. PMID: 19821811 [PubMed - as supplied by publisher] |
| Bone-marrow-derived mesenchymal stem cell therapy for neurodegenerative diseases.
October 14, 2009 at 6:15 am
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| | Bone-marrow-derived mesenchymal stem cell therapy for neurodegenerative diseases. Expert Opin Biol Ther. 2009 Oct 13; Authors: Sadan O, Melamed E, Offen D Background: Stem-cell-based therapy is a promising new approach to handling neurodegenerative diseases. One of the most promising cellular sources is bone-marrow-derived mesenchymal stem cells (MSCs) also termed multipotent stromal cells. MSCs represent an autologous source and are abundant and non-tumorigenic. Additionally, MSCs possess the useful characteristics of homing and chemokine secretion. Objective/methods: Since neurodegenerative diseases have many pathological processes in common, a specific therapeutic agent could potentially ameliorate the symptoms of several distinct neurodegenerative diseases. In this review we demonstrate the wide variety of mechanisms by which MSCs can influence neurodegenerative processes. Results/conclusions: The mechanisms by which transplanted MSCs influence neurodegenerative diseases can be broadly classified as cellular replacement or paracrine secretion, with the latter subdivided into trophic factor secretion or immunomodulation by cytokines. Emerging research suggests that genetic manipulations before transplantation could enhance the therapeutic potential of MSCs. Such manipulation could turn the cells into a 'Trojan horse', to deliver specific proteins, or promote reprogramming of the MSCs into the neural lineage. Clinical trials testing MSC-based therapies for familial amyotrophic lateral sclerosis and multiple sclerosis are in progress. PMID: 19821796 [PubMed - as supplied by publisher] |
| Photopatterned thiol surfaces for biomolecule immobilization.
October 14, 2009 at 6:15 am
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| | Photopatterned thiol surfaces for biomolecule immobilization. Langmuir. 2009 Oct 20;25(20):12275-82 Authors: Chen S, Smith LM The ability to pattern small molecules and proteins on artificial surfaces is of importance for the development of new tools including tissue engineering, cell-based drug screening, and cell-based sensors. We describe here a novel "caged" thiol-mediated strategy for the fabrication of planar substrates patterned with biomolecules using photolithography. A thiol-bearing phosphoramidite (3-(2'-nitrobenzyl)thiopropyl (NBTP) phosphoramidite) was synthesized and coupled to a hydroxyl-terminated amorphous carbon substrate. A biocompatible oligo(ethylene glycol) spacer was used to resist nonspecific adsorption of protein and DNA and enhance flexibility of attached biomolecules. Thiol functionalities are revealed by UV irradiation of NBTP-modified surfaces. Both the surface coupling and photodeprotection were monitored by Polarization Modulation Fourier Transform Infrared Reflection Absorption Spectroscopy (PM-FTIRRAS) and X-ray Photoelectron Spectroscopy (XPS) measurements. The newly exposed thiols are chemically very active and react readily with a wide variety of groups. A series of molecules including biotin, DNA, and proteins were attached to the surfaces with retention of their biological activities, demonstrating the utility and generality of the approach. PMID: 19821627 [PubMed - in process] |
| Banking stem cells from human exfoliated deciduous teeth (SHED): saving for the future.
October 14, 2009 at 6:15 am
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| | Banking stem cells from human exfoliated deciduous teeth (SHED): saving for the future. J Clin Pediatr Dent. 2009;33(4):289-94 Authors: Arora V, Arora P, Munshi AK Tooth derived cells are readily accessible and provide an easy and minimally invasive way to obtain and store stem cells for future use. Banking ones own tooth-derived stem cells is a reasonable and simple alternative to harvesting stem cells from other tissues. Obtaining stem cells from human exfoliated deciduous teeth (SHED) is simple and convenient, with little or no trauma. Every child loses primary teeth, which creates the perfect opportunity to recover and store this convenient source of stem cells--should they be needed to treat future injuries or ailments and presents a far better alternative to simply discarding the teeth or storing them as mementos from the past. Furthermore, using ones own stem cells poses few, if any, risks for developing immune reactions or rejection following transplantation and also eliminates the potential of contracting disease from donor cells. Stem cells can also be recovered from developing wisdom teeth and permanent teeth. Individuals have different opportunities at different stages of their life to bank these valuable cells. It is best to recover stem cells when a child is young and healthy and the cells are strong and proliferative. The purpose of this review is to discuss the present scenario as well as the technical details of tooth banking as related to SHED cells. PMID: 19725233 [PubMed - indexed for MEDLINE] |
| Effects of cyclic stretch on proliferation of mesenchymal stem cells and their differentiation to smooth muscle cells.
October 14, 2009 at 6:15 am
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| | Effects of cyclic stretch on proliferation of mesenchymal stem cells and their differentiation to smooth muscle cells. Biochem Biophys Res Commun. 2009 Oct 23;388(3):601-5 Authors: Ghazanfari S, Tafazzoli-Shadpour M, Shokrgozar MA Bone marrow mesenchymal stem cells (MSCs) are capable of differentiating into a variety of cell types such as vascular smooth muscle cells (SMCs). In this study, we investigated influence of cyclic stretch on proliferation of hMSCs for different loading conditions, alignment of actin filaments, and consequent differentiation to SMCs. Isolated cells from bone marrow were exposed to cyclic stretch utilizing a customized device. Cell proliferation was examined by MTT assay, alignment of actin fibers by a designed image processing code, and cell differentiation by fluorescence staining. Results indicated promoted proliferation of hMSCs by cyclic strain, enhanced by elevated strain amplitude and number of cycles. Such loading regulated smooth muscle alpha-actin, and reoriented actin fibers. Cyclic stretch led to differentiation of hMSCs to SMCs without addition of growth factor. It was concluded that applying appropriate loading treatment on hMSCs could enhance proliferation capability, and produce functional SMCs for engineered tissues. PMID: 19695226 [PubMed - indexed for MEDLINE] | | | 
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