|  |  |  | | | | | TE-RegenMed-StemCell feed | | | | | | | | | | | | | | | | | | | Improved seeding of chondrocytes into polyglycolic acid scaffolds using semi-static and alginate loading methods. Biotechnol Prog. 2010 Sep 14; Authors: Shahin K, Doran PM Cell seeding and attachment in three-dimensional scaffolds is a key step in tissue engineering with implications for cell differentiation and tissue development. In this work, two new seeding methods were investigated using human chondrocytes and polyglycolic acid (PGA) fibrous mesh scaffolds. A simple semi-static seeding method using culture plates and tissue flasks was developed as an easy-to-perform modification of static seeding. An alginate-loading method was also studied, using alginate hydrogel as an adjuvant for entrapping cells within PGA scaffolds. Both the semi-static and PGA-alginate methods produced more homogeneous cell distributions than conventional static and dynamic seeding. Using 20 × 10(6) cells, whereas the seeding efficiency for static seeding was only 52%, all other techniques produced seeding efficiencies of ≥ 90%. With 40 × 10(6) cells, the efficiency of semi-static seeding declined to 74% while the dynamic and PGA-alginate methods retained their ability to accommodate high cell numbers. The seeded scaffolds were cultured in recirculation bioreactors to determine the effect of seeding method on cartilage production. Statically seeded scaffolds did not survive the 5-week cultivation period. Deposition of extracellular matrix in scaffolds seeded using the semi-static and PGA-alginate methods was more uniform compared with scaffolds seeded using the dynamic method. The new semi-static and PGA-alginate seeding methods developed in this work are recommended for tissue engineering because they provide substantial benefits compared with static seeding in terms of seeding efficiency, cell distribution, and cartilage deposition while remaining simple and easy to execute. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010. PMID: 21064180 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Co-electrospun fibrous scaffold-adsorbed DNA for substrate-mediated gene delivery. J Biomed Mater Res A. 2010 Nov 9; Authors: Zhang J, Duan Y, Wei D, Wang L, Wang H, Gu Z, Kong D Incorporation of gene into electrospun nanofibers for localized gene transfection of target cells represents a robust platform for tissue regeneration. In this study, a new two-step approach was explored to immobilize DNA onto electrospun nanofibers for effective gene delivery, that is, nonviral gene vector of polyethylene glycol (PEG)-modified polyethylenimine (PEI) was incorporated into scaffolds by electrospinning and then target DNA was adsorbed onto the electrospun nanofibers via electrostatic interaction between DNA and PEI-PEG. PEI-PEG/DNA particles formed from the released DNA, and PEI-PEG had a uniform particle size of approximately 200 nm. This nanofiber-based gene delivery system exhibited high transfection efficiency, in which >65% of human embryonic kidney 293 cells and >40% of mesenchymal stem cells were transfected with green fluorescent protein gene. Compared with PEI, PEG modification of PEI had improved the biocompatibility and further increased the transfection efficiency. These results suggest that the combination of nonviral gene carrier with electrospun nanofibers could be used for localized gene delivery, which has multifold potential applications in tissue engineering or as an in vivo substrate for tissue regeneration. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 21064119 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Tribocorrosion behaviour of nanostructured titanium substrates processed by high-pressure torsion. Nanotechnology. 2010 Dec 3;21(48):485703 Authors: Faghihi S, Li D, Szpunar JA Aseptic loosening induced by wear particles from artificial bearing materials is one of the main causes of malfunctioning in total hip replacements. With the increase in young and active patients, complications in revision surgeries and immense health care costs, there is considerable interest in wear-resistant materials that can endure longer in the harsh and corrosive body environment. Here, the tribological behaviour of nanostructured titanium substrates processed by high-pressure torsion (HPT) is investigated and compared with the coarse-grained samples. The high resolution transmission electron microscopy reveals that a nanostructured sample has a grain size of 5-10 nm compared to that of ∼ 10 µm and ∼ 50 µm for untreated and annealed substrates, respectively. Dry and wet wear tests were performed using a linear reciprocating ball-on-flat tribometer. Nanostructured samples show the best dry wear resistance and the lowest wear rate in the electrolyte. There was significantly lower plastic deformation and no change in preferred orientation of nanostructured samples attributable to the wear process. Electrochemical impedance spectroscopy (EIS) shows lower corrosion resistance for nanostructured samples. However, under the action of both wear and corrosion the nanostructured samples show superior performance and that makes them an attractive candidate for applications in which wear and corrosion act simultaneously. PMID: 21063052 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | Regenerative medicine as applied to solid organ transplantation: current status and future challenges. Transpl Int. 2010 Nov 10; Authors: Orlando G, Baptista P, Birchall M, De Coppi P, Farney A, Guimaraes-Souza NK, Opara E, Rogers J, Seliktar D, Shapira-Schweitzer K, Stratta RJ, Atala A, Wood KJ, Soker S In the last two decades, regenerative medicine has shown the potential for "bench-to-bedside" translational research in specific clinical settings. Progress made in cell and stem cell biology, material sciences and tissue engineering enabled researchers to develop cutting-edge technology which has lead to the creation of nonmodular tissue constructs such as skin, bladders, vessels and upper airways. In all cases, autologous cells were seeded on either artificial or natural supporting scaffolds. However, such constructs were implanted without the reconstruction of the vascular supply, and the nutrients and oxygen were supplied by diffusion from adjacent tissues. Engineering of modular organs (namely, organs organized in functioning units referred to as modules and requiring the reconstruction of the vascular supply) is more complex and challenging. Models of functioning hearts and livers have been engineered using "natural tissue" scaffolds and efforts are underway to produce kidneys, pancreata and small intestine. Creation of custom-made bioengineered organs, where the cellular component is exquisitely autologous and have an internal vascular network, will theoretically overcome the two major hurdles in transplantation, namely the shortage of organs and the toxicity deriving from lifelong immunosuppression. This review describes recent advances in the engineering of several key tissues and organs. PMID: 21062367 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Nanoparticles: Functionalization and Multifunctional Applications in Biomedical Sciences. Curr Med Chem. 2010 Nov 10; Authors: Subbiah R, Veerapandian M, Yun KS Rapid innovations in nanomedicine have increased the likelihood that engineered nanomaterials will eventually come in contact with humans and the environment. The advent of nanotechnology has created strong interest in many fields such as biomedical sciences and engineering field. Central to any significant advances in nanomaterial based applications will be the development of functionalized nanoparticles, which are believed to hold promise for use in fields such as pharmaceutical and biomedical sciences. Early clinical results have suggested that functionalization of nanoparticles with specific recognition chemical moieties indeed yields multifunctional nanoparticles with enhanced efficacy, while simultaneously reducing side effects, due to properties such as targeted localization in tumors and active cellular uptake. A prerequisite for advancing this area of research is the development of chemical methods to conjugate chemical moieties onto nanoparticles in a reliable manner. In recent years a variety of chemical methods have been developed to synthesize functionalized nanoparticles specifically for drug delivery, cancer therapy, diagnostics, tissue engineering and molecular biology, and the structure-function relationship of these functionalized nanoparticles has been extensively examined. With the growing understanding of methods to functionalize nanoparticles and the continued efforts of creative scientists to advance this technology, it is likely that functionalized nanoparticles will become an important tool in the above mentioned areas. Therefore, the aim of this review is to provide basic information on nanoparticles, describe previously developed methods to functionalize nanoparticles and discuss their potential applications in biomedical sciences. The information provided in this review is important in regards to the safe and widespread use of functionalized nanoparticles particularly in the biomedicine field. PMID: 21062250 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Functional neovascularization in tissue engineering with porcine acellular dermal matrix and human umbilical vein endothelial cells. Tissue Eng Part C Methods. 2010 Nov 10; Authors: Zhang X, Yang J, Li Y, Liu S, Long K, Zhao Q, Zhang Y, Deng Z, Jin Y Endothelial cells-matrix interactions play an important role in promoting and controlling network formation. In this study, porcine acellular dermal matrix (PADM) was used to guide human umbilical vein endothelial cells (HUVECs) adhesion and proliferation as a potential system for vascularization of engineered tissues. We fabricated PADM using a modified protocol and assessed their composition and ultrastructures. Subsequently, the viability of HUVECs and the formation of capillary-like networks were evaluated by seeding cells directly on PADM scaffolds or PADM digests in vitro. We further investigated the function of the HUVECs seeded on the PADM scaffolds after subcutaneous transplantation in athymic mice. Moreover, the function of the neovessels formed in the PADM scaffolds were assessed by implantation into cutaneous wounds on the backs of mice. The results showed that PADM scaffolds significantly increased proliferation of HUVECs, and the PADM digest induced HUVECs formed many tube-like structures. Moreover, HUVECs seeded on the PADM scaffolds formed numerous capillary-like networks and some perfused vascular structures following implantation into mice. PADM seeded with HUVECs and fibroblasts were also able to form many capillary-like networks in vitro. Furthermore, these neovessels could inosculate with the murine vasculature after implantation into cutaneous wounds in mice. The advantage of this method is that the decellularized matrix not only provides signals to maintain the viability of endothelial cells but also serves as the template structure for regenerated tissue. These findings indicate that PADM seeded with HUVECs may be a potential system for successful engineering of large, thick and complex tissues. PMID: 21062229 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Epithelial-Mesenchymal Interactions As a Working Concept for Oral Mucosa Regeneration. Tissue Eng Part B Rev. 2010 Nov 10; Authors: Liu J, Mao J, Chen L Oral mucosa consists of two tissue layers, the superficial epithelium and the underlying lamina propria. Together, oral mucosa functions as a barrier against exogenous substances and pathogens. In development, interactions of stem/progenitor cells of the epithelium and mesenchyme are crucial to the morphogenesis of oral mucosa. Previous work in oral mucosa regeneration has yielded important clues for several meritorious proof of concept approaches. Tissue engineering offers a broad array of novel tools for oral mucosa regeneration with reduced donor site trauma and accelerated clinical translation. However, the developmental concept of epithelial-mesenchymal interactions is rarely considered in oral mucosa regeneration. Epithelial-mesenchymal interactions in postnatal oral mucosa regeneration likely will not be a simple recapitulation of prenatal oral mucosa development. Biomaterial scaffolds play an indispensible role for oral mucosa regeneration and should provide a conducive environment for pivotal epithelial-mesenchymal interactions. Autocrine and paracrine factors, either exogenously delivered or innately produced, have rarely been and should be harnessed to promote oral mucosa regeneration. This review focuses on a working concept of epithelial and mesenchymal interactions in oral mucosa regeneration. PMID: 21062224 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Carbon nanotubes in animal models: a systematic review on toxic potential. Tissue Eng Part B Rev. 2010 Nov 10; Authors: van der Zande M, Junker R, Walboomers XF, Jansen J Amongst the engineered nanomaterials, especially carbon nanotubes (CNTs) have received considerable attention for application in tissue engineering scaffolds. CNTs are considered promising on behalf of their physicochemical properties, yet such nanomaterials also have been associated with potentially hazardous effects on human health. To gain insight in the toxicity aspects of CNTs <i>in vivo</i>, the current study presents a systematic review of literature. After screening of literature through defined inclusion and exclusion criteria, and subsequent data extraction, it can be concluded that pulmonary administered CNTs have the capacity to induce toxicity in the lung area. However, conclusions for other organs, or on systemic toxicity, are yet premature. In addition, the carcinogenic potential of CNTs is also still ambiguous, since contradictive results are presented. Intrinsic factors, like material characteristics and associated distribution- and agglomeration patterns are of influence on the toxic potential of CNTs. Similarly, environmental factors like the exposure route, pre-existing allergies, pathological infections, or air pollutant exposure are significant. In spite of the many reports published currently, more studies will be required to gain full understanding of the toxic potential of CNTs and especially the underlying mechanisms. For this end, development of standardized protocols and reliable nanodetection techniques will form prerequisites. PMID: 21062222 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Definition and validation of operating equations for poly(vinyl alcohol)-poly(lactide-co-glycolide) microfiltration membrane-scaffold bioreactors. Biotechnol Bioeng. 2010 Oct 1;107(2):382-92 Authors: Shipley RJ, Waters SL, Ellis MJ The aim of this work is to provide operating data for biodegradable hollow fiber membrane bioreactors. The physicochemical cell culture environment can be controlled with the permeate flowrate, so this aim necessitates the provision of operating equations that enable end-users to set the pressures and feed flowrates to obtain their desired culture environment. In this paper, theoretical expressions for the pure water retentate and permeate flowrates, derived using lubrication theory, are compared against experimental data for a single fiber poly(vinyl alcohol)-poly(lactide-co-glycolide) crossflow module to give values for the membrane permeability and slip. Analysis of the width of the boundary layer region where slip effects are important, together with the sensitivity of the retentate and permeate equations to the slip parameter, show that slip is insignificant for these membranes, which have a mean pore diameter of 1.1 microm. The experimental data is used to determine a membrane permeability, of k = 1.86 x 10(-16) m(2), and to validate the model. It was concluded that the operating equation that relates the permeate to feed ratio, c, lumen inlet flowrate, Q (l,in), lumen outlet pressure, P (1), and ECS outlet pressure, P (0), is P(1) - P(0) = Q(l),in (Ac + B) where A and B are constants that depend on the membrane permeability and geometry (and are given explicitly). Finally, two worked examples are presented to demonstrate how a tissue engineer can use Equation (1) to specify operating conditions for their bioreactor. PMID: 20641054 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Multi-lineage differentiation of hMSCs encapsulated in thermo-reversible hydrogel using a co-culture system with differentiated cells. Biomaterials. 2010 Oct;31(28):7275-87 Authors: Park JS, Yang HN, Woo DG, Kim H, Na K, Park KH The micro-environment is an important factor in the differentiation of cultured stem cells for the purpose of site specific transplantation. In an attempt to optimize differentiation conditions, co-culture systems composed of both stem cells and primary cells or cell lines were used in hydrogel with in vitro and in vivo systems. Stem cells encapsulated in hydrogel, under certain conditions, can undergo increased differentiation both in vitro and in vivo; therefore, reconstruction of transplanted stem cells in a hydrogel co-culture system is important for tissue regeneration. In order to construct such a co-culture system, we attempted to create a hydrogel scaffold which could induce neo-tissue growth from the recipient bed into the material. This material would enable encapsulation of stem cells in vitro after which they could be transferred to an in vivo system utilizing nude mice. In this case, the hydrogel was implanted in the subfascial space of nude mice and excised 4 weeks later. Cross-sections of the excised samples were stained with von Kossa or safranin-O and tubular formations into the gel were observed with and tested by doppler imaging. The data showed that the hydrogel markedly induced growth of osteogenic, chondrogenic, and vascular-rich tissue into the hydrogel by 4 weeks, which surpassed that after transplantation in a co-culture system. Further, a co-culture system with differentiated cells and stem cells potentially enhanced chondrogenesis, osteogenesis, and vascularization. These findings suggest that a co-culture system with hydrogel as scaffold material for neo-tissue formation is a useful tools for multi-lineage stem cell differentiation. PMID: 20619450 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Laser assisted bioprinting of engineered tissue with high cell density and microscale organization. Biomaterials. 2010 Oct;31(28):7250-6 Authors: Guillotin B, Souquet A, Catros S, Duocastella M, Pippenger B, Bellance S, Bareille R, Rémy M, Bordenave L, Amédée J, Guillemot F Over this decade, cell printing strategy has emerged as one of the promising approaches to organize cells in two and three dimensional engineered tissues. High resolution and high speed organization of cells are some of the key requirements for the successful fabrication of cell-containing two or three dimensional constructs. So far, none of the available cell printing technologies has shown an ability to concomitantly print cells at a cell-level resolution and at a kHz range speed. We have studied the effect of the viscosity of the bioink, laser energy, and laser printing speed on the resolution of cell printing. Accordingly, we demonstrate that a laser assisted cell printer can deposit cells with a microscale resolution, at a speed of 5 kHz and with computer assisted geometric control. We have successfully implemented such a cell printing precision to print miniaturized tissue like layouts with de novo high cell density and micro scale organization. PMID: 20580082 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Extent of cell differentiation and capacity for cartilage synthesis in human adult adipose-derived stem cells: comparison with fetal chondrocytes. Biotechnol Bioeng. 2010 Oct 1;107(2):393-401 Authors: Mahmoudifar N, Doran PM This study evaluated the extent of differentiation and cartilage biosynthetic capacity of human adult adipose-derived stem cells relative to human fetal chondrocytes. Both types of cell were seeded into nonwoven-mesh polyglycolic acid (PGA) scaffolds and cultured under dynamic conditions with and without addition of TGF-beta1 and insulin. Gene expression for aggrecan and collagen type II was upregulated in the stem cells in the presence of growth factors, and key components of articular cartilage such as glycosaminoglycan (GAG) and collagen type II were synthesized in cultured tissue constructs. However, on a per cell basis and in the presence of growth factors, accumulation of GAG and collagen type II were, respectively, 3.4- and 6.1-fold lower in the stem cell cultures than in the chondrocyte cultures. Although the stem cells synthesized significantly higher levels of total collagen than the chondrocytes, only about 2.4% of this collagen was collagen type II. Relative to cultures without added growth factors, treatment of the stem cells with TGF-beta1 and insulin resulted in a 59% increase in GAG synthesis, but there was no significant change in collagen production even though collagen type II gene expression was upregulated 530-fold. In contrast, in the chondrocyte cultures, synthesis of collagen type II and levels of collagen type II as a percentage of total collagen more than doubled after growth factors were applied. Although considerable progress has been achieved to develop differentiation strategies and scaffold-based culture techniques for adult mesenchymal stem cells, the extent of differentiation of human adipose-derived stem cells in this study and their capacity for cartilage synthesis fell considerably short of those of fetal chondrocytes. PMID: 20506225 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Genipin-crosslinked microcarriers mediating hepatocellular aggregates formation and functionalities. J Biomed Mater Res A. 2010 Nov 9; Authors: Lau TT, Wang C, Png SW, Su K, Wang DA In engineered regenerative medicine, various types of scaffolds have been customized to pursue the optimal environment for different types of therapeutic cells. In liver therapeutic research, hepatocytes require attachment to solid anchors for survival and proliferation before they could grow into cellular aggregates with enhanced functionalities. Among the various biomaterials scaffolds and vehicles, microspherical cell carriers are suited to these requirements. Individual spheres may provide two-dimensional (2D) cell-affinitive surfaces for cell adhesion and spreading; whereas multiple microcarriers may form three-dimensional (3D) matrices with inter-spherical space for cell expansion and multicellular aggregation. In this study, we culture human liver carcinoma cell line (HepG2) cells on genipin-crosslinked gelatin microspheres of two different sizes. Results suggest that both microcarriers support cell adhesion, proliferation, and spontaneous formation of hepatocellular aggregates, among which the spheres with bigger size (200-300 μm) seem more favorable than the smaller ones in terms of aggregate formation and liver specific functionalities. These findings suggest that the genipin-crosslinked microcarrier is a competent vehicle for liver cell delivery. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 21064126 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Regenerative medicine as applied to solid organ transplantation: current status and future challenges. Transpl Int. 2010 Nov 10; Authors: Orlando G, Baptista P, Birchall M, De Coppi P, Farney A, Guimaraes-Souza NK, Opara E, Rogers J, Seliktar D, Shapira-Schweitzer K, Stratta RJ, Atala A, Wood KJ, Soker S In the last two decades, regenerative medicine has shown the potential for "bench-to-bedside" translational research in specific clinical settings. Progress made in cell and stem cell biology, material sciences and tissue engineering enabled researchers to develop cutting-edge technology which has lead to the creation of nonmodular tissue constructs such as skin, bladders, vessels and upper airways. In all cases, autologous cells were seeded on either artificial or natural supporting scaffolds. However, such constructs were implanted without the reconstruction of the vascular supply, and the nutrients and oxygen were supplied by diffusion from adjacent tissues. Engineering of modular organs (namely, organs organized in functioning units referred to as modules and requiring the reconstruction of the vascular supply) is more complex and challenging. Models of functioning hearts and livers have been engineered using "natural tissue" scaffolds and efforts are underway to produce kidneys, pancreata and small intestine. Creation of custom-made bioengineered organs, where the cellular component is exquisitely autologous and have an internal vascular network, will theoretically overcome the two major hurdles in transplantation, namely the shortage of organs and the toxicity deriving from lifelong immunosuppression. This review describes recent advances in the engineering of several key tissues and organs. PMID: 21062367 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Molecular physiology of cardiac regeneration. Ann N Y Acad Sci. 2010 Nov;1211(1):113-26 Authors: Bolli P, Chaudhry HW Heart disease is the leading cause of death in the industrialized world. This is partially attributed to the inability of cardiomyocytes to divide in a significant manner, and therefore the heart responds to injury through scar formation. One of the challenges of modern medicine is to develop novel therapeutic strategies to facilitate regeneration of cardiac muscle in the diseased heart. Numerous methods have been studied and a wide variety of cell types have been considered. To date, bone marrow stem cells, endogenous populations of cardiac stem cells, embryonic stem cells, and induced pluripotent stem cells have been investigated for their ability to regenerate infarcted myocardium, although stem cell transplantation has produced ambiguous results in human clinical trials. Several studies support another approach that seems very appealing: enhancing the limited endogenous regenerative capacity of the heart. The recent advances in stem cell and regenerative biology are giving rise to the view that cardiac regeneration, although not quite ready for clinical treatment, may translate into therapeutic reality in the not too distant future. PMID: 21062300 [PubMed - in process] | | | | | | | | | |  | |  | |  |
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