|  |  |  | | | | | TERMSC | | | | | | | | | | | | | | | | | | | Mechanical evaluation of poly(vinyl alcohol)-based fibrous composites as biomaterials for meniscal tissue replacement. Acta Biomater. 2010 Dec;6(12):4716-24 Authors: Holloway JL, Lowman AM, Palmese GR In this study, poly(vinyl alcohol) (PVA) hydrogels were reinforced with ultrahigh molecular weight polyethylene (UHMWPE) and PP fibers and evaluated as potential nondegradable meniscal replacements. An investigation of hydrogel and composite mechanical properties indicates that fiber-reinforced PVA hydrogels could replicate the unique anisotropic modulus distribution present in the native meniscus; the most commonly damaged orthopedic tissue. More specifically, fibrous reinforcement successfully increased the tensile modulus of the biomaterial from 0.23±0.02MPa without any reinforcement to 258.1±40.1MPa at 29vol.% UHMWPE. Additionally, the molecular weight between cross-links, bound water and the microstructure of the PVA hydrogels were evaluated as a function of freeze-thaw cycles and polymer concentration to lend insight into the processes occurring during synthesis. These results suggest the presence of multiple mechanisms as causes for increasing hydrogel modulus with freeze-thaw cycling, including hydrogen bonding between amorphous and/or crystalline regions, and the formation of highly concentrated regions of mostly amorphous PVA chains. It is possible that the formation of regions with highly concentrated amounts of PVA increases the load-bearing ability of the hydrogels. PMID: 20601243 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Combined transplantation of pancreatic islets and adipose tissue-derived stem cells enhances the survival and insulin function of islet grafts in diabetic mice. Transplantation. 2010 Dec 27;90(12):1366-73 Authors: Ohmura Y, Tanemura M, Kawaguchi N, Machida T, Tanida T, Deguchi T, Wada H, Kobayashi S, Marubashi S, Eguchi H, Takeda Y, Matsuura N, Ito T, Nagano H, Doki Y, Mori M Overcoming significant loss of transplanted islet mass is important for successful islet transplantation. Adipose tissue-derived stem cells (ADSCs) seem to have angiogenic potential and antiinflammatory properties. We hypothesized that the inclusion of ADSCs with islet transplantation should enhance the survival and insulin function of the islet graft. PMID: 21076379 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Human artificial chromosome with a conditional centromere for gene delivery and gene expression. DNA Res. 2010;17(5):293-301 Authors: Iida Y, Kim JH, Kazuki Y, Hoshiya H, Takiguchi M, Hayashi M, Erliandri I, Lee HS, Samoshkin A, Masumoto H, Earnshaw WC, Kouprina N, Larionov V, Oshimura M Human artificial chromosomes (HACs), which carry a fully functional centromere and are maintained as a single-copy episome, are not associated with random mutagenesis and offer greater control over expression of ectopic genes on the HAC. Recently, we generated a HAC with a conditional centromere, which includes the tetracycline operator (tet-O) sequence embedded in the alphoid DNA array. This conditional centromere can be inactivated, loss of the alphoid(tet-O) (tet-O HAC) by expression of tet-repressor fusion proteins. In this report, we describe adaptation of the tet-O HAC vector for gene delivery and gene expression in human cells. A loxP cassette was inserted into the tet-O HAC by homologous recombination in chicken DT40 cells following a microcell-mediated chromosome transfer (MMCT). The tet-O HAC with the loxP cassette was then transferred into Chinese hamster ovary cells, and EGFP transgene was efficiently and accurately incorporated into the tet-O HAC vector. The EGFP transgene was stably expressed in human cells after transfer via MMCT. Because the transgenes inserted on the tet-O HAC can be eliminated from cells by HAC loss due to centromere inactivation, this HAC vector system provides important novel features and has potential applications for gene expression studies and gene therapy. PMID: 20798231 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Dechorionation of medaka embryos and cell transplantation for the generation of chimeras. J Vis Exp. 2010;(46): Authors: Porazinski SR, Wang H, Furutani-Seiki M Medaka is a small egg-laying freshwater fish that allows both genetic and embryological analyses and is one of the three vertebrate model organisms in which genome-wide phenotype-driven mutant screens were carried out (1). Divergence of functional overlap of related genes between medaka and zebrafish allows identification of novel phenotypes that are unidentifiable in a single species (2), thus medaka and zebrafish are complementary for genetic dissection of the vertebrate genome functions. Manipulation of medaka embryos, such as dechorionation, mounting embryos for imaging and cell transplantation, are key procedures to work on both medaka and zebrafish in a laboratory. Cell transplantation examines cell autonomy of medaka mutations. Chimeras are generated by transplanting labeled cells from donor embryos into unlabeled recipient embryos. Donor cells can be transplanted to specific areas of the recipient embryos based on the fate maps (3) so that clones from transplanted cells can be integrated in the tissue of interest during development. Due to the hard chorion and soft embryos, manipulation of medaka embryos is more involved than in zebrafish. In this video, we show detailed procedures to manipulate medaka embryos. PMID: 21206472 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | The role of the transient receptor potential (TRP) superfamily of cation-selective channels in the management of the overactive bladder. BJU Int. 2010 Oct;106(8):1114-27 Authors: Andersson KE, Gratzke C, Hedlund P • The pathophysiology of lower urinary tract symptoms (LUTS), detrusor overactivity (DO), and the overactive bladder (OAB) syndrome is multifactorial and remains poorly understood. • The transient receptor potential (TRP) channel superfamily has been shown to be involved in nociception and mechanosensory transduction in various organ systems, and studies of the LUT have indicated that several TRP channels, including TRPV1, TRPV2, TRPV4, TRPM8, and TRPA1, are expressed in the bladder, and may act as sensors of stretch and/or chemical irritation. • However, the roles of these individual channels for normal LUT function and in LUTS/DO/OAB, have not been established. • TRPV1 is the channel best investigated. It is widely distributed in LUT structures, but despite extensive information on morphology and function in animal models, the role of this channel in normal human bladder function is still controversial. Conversely, its role in the pathophysiology and treatment of particularly neurogenic DO is well established. • TRPV1 is co-expressed with TRPA1, and TRPA1 is known to be present on capsaicin-sensitive primary sensory neurones. Activation of this channel can induce DO in animal models. • TRPV4 is a Ca(2+)-permeable stretch-activated cation channel, involved in stretch-induced ATP release, and TRPV4-deficient mice exhibit abnormal frequencies of voiding and non-voiding contractions in cystometric experiments. • TRPM8 is a cool receptor expressed in the urothelium and suburothelial sensory fibres. It has been implicated in the bladder-cooling reflex and in idiopathic DO. • The occurrence of other members of the TRP superfamily in the LUT has been reported, but information on their effects on LUT functions is scarce. There seem to be several links between activation of different members of the TRP superfamily and LUTS/DO/OAB, and further exploration of the involvement of these channels in LUT function, normally and in dysfunction, may be rewarding. PMID: 21156013 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Current concepts for the use of platelet-rich plasma in the foot and ankle. Clin Podiatr Med Surg. 2011 Jan;28(1):155-70 Authors: Soomekh DJ Platelet-rich plasma (PRP) injections have been used and studied since the 1970s. Its use has become more popularized over the last several years in the treatment of foot and ankle injuries. Platelets are a normal product found in the clotting cascade and inflammatory process of healing. They produce granules that release growth factors that promote healing. PRP works by increasing the concentration of platelets, thereby increasing the concentration of growth factors and increasing healing potential. PRP has an advantage over many tissue engineering products in that it is autologous. It has been studied and used for the treatment of tendon injuries, chronic wounds, ligamentous injuries, cartilage injuries, muscle injuries, and bone augmentation. The results from in vitro and in vivo studies in foot and ankle injuries are promising. The applications for treatment in the foot and ankle may be broader than once thought. PMID: 21276524 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | Transient receptor potential A1 and cannabinoid receptor activity in human normal and hyperplastic prostate: relation to nerves and interstitial cells. Eur Urol. 2010 May;57(5):902-10 Authors: Gratzke C, Weinhold P, Reich O, Seitz M, Schlenker B, Stief CG, Andersson KE, Hedlund P Ion channel transient receptor potential A1 (TRPA1) and cannabinoid (CB) receptors are involved in mechanoafferent signaling from the bladder and the urethra. PMID: 19733001 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Bioresorbable electrospun fibers for immobilization of thiol-containing compounds. Macromol Biosci. 2010 Oct 8;10(10):1177-83 Authors: Lösel R, Grafahrend D, Möller M, Klee D For the reconstruction of functional tissue, biodegradable scaffolds providing specific surface functionality and a three-dimensional structure matching that of the damaged tissue are needed. Fibers capable of controlling cell-fiber interaction were produced by electrospinning of PDLLA-block-PEG with thiol-reactive end groups from a solvent mixture. The hydrophilic fibers uniquely combine minimized non-specific protein adsorption and well-defined surface reactivity allowing controlled immobilization of peptides and proteins. Human dermal fibroblasts show adherence and proliferation on the surface of RGDC-functionalized electrospun PDLLA-block-PEG fibers. PMID: 20572276 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Mutations in GDF5 presenting as semidominant brachydactyly A1. Hum Mutat. 2010 Oct;31(10):1155-62 Authors: Byrnes AM, Racacho L, Nikkel SM, Xiao F, MacDonald H, Underhill TM, Bulman DE Brachydactyly A1 (BDA1) is an autosomal dominant disorder characterized by shortness of all middle phalanges of the hands and toes, shortness of the proximal phalanges of the first digit, and short stature. Missense mutations in the Indian Hedgehog gene (IHH) are known to cause BDA1, and a second locus has been mapped to chromosome 5p. In a consanguineous French Canadian kindred with BDA1, both IHH and the 5p locus were excluded. Microsatellites flanking GDF5 on chromosome 20q were found to cosegregate with the disease. Sequencing of the GDF5 coding region revealed that a mildly affected individual in the family was heterozygous, and that all of the severely affected individuals were homozygous for a novel missense c.1195C>T mutation that predicts a p.Arg399Cys substitution at a highly conserved amino acid. Functional analysis demonstrated that although the p.Arg399Cys mutant is able to stimulate chondrogenesis, it is much less effective than wild-type GDF5. This data confirms genetic heterogeneity in BDA1, demonstrates that mutations upstream of IHH can result in BDA1, and shows that BDA1 can result from semidominant mutations in GDF5. PMID: 20683927 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Treat the graft to improve the regenerative ability of the host. Med Hypotheses. 2011 Jan 28; Authors: Mamidi MK, Pal R, Govindasamy V, Zakaria Z, Bhonde R The staggering number of publications featuring the use of stem cells has revolutionized regenerative medicine research. Preclinical studies indicate that allogeneic human mesenchymal stem cells (MSCs) may be useful for the treatment of several clinical disorders, including sepsis, acute renal failure, acute myocardial infarction, and more recently, acute lung injury (ALI). However, considerable success would not be obtained in clinical trials due to poor survival of transplanted cells under the influence of inflammatory conditions. Despite robust approaches like cellular reprogramming, scaffolds and conditioned media have been tested to overcome this problem; however the success rate of these approaches remain questionable. Recently, pretreatment of bioactive compounds in vitro have been shown to suppress cell apoptosis and promote cell survival. Quite likely a similar phenomenon can take place in vivo. Based on such studies, we hypothesize that MSCs derived from human post-natal tissues could be conditioned and prepared for targeted disease therapy. Depending on the disease condition, the MSCs could be treated prior to delivery with appropriate bioactive compounds to allow them survive longer and perform a better role as biocatalyst. The advantage of this approach could be the tailor made availability of MSCs preconditioned with appropriate bioactive compounds for disease specific therapy. Therefore, the choice of suitable bioactive molecule is likely to enhance the efficacy of targeted stem cell therapy and preconditioning may provide a novel strategy in maximizing biological and functional properties of MSCs. PMID: 21277690 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Mesenchymal Lineage Stem Cells Have Pronounced Anti-Inflammatory Effects in the Twitcher Mouse Model of Krabbe's Disease. Stem Cells. 2011 Jan;29(1):67-77 Authors: Ripoll CB, Flaat M, Klopf-Eiermann J, Fisher-Perkins JM, Trygg CB, Scruggs BA, McCants ML, Leonard HP, Lin AF, Zhang S, Eagle ME, Alvarez X, Li YT, Li SC, Gimble JM, Bunnell BA The twitcher mouse is an animal model of Krabbe's disease (KD), which is a neurodegenerative lysosomal storage disorder resulting from the absence of functional lysosomal enzyme galactocerebrosidase (GALC). This disease affects the central and peripheral nervous systems and in its most severe form results in death before the age of 2 in humans and approximately 30-40 days in mice. This study evaluates the effect of intracerebroventricular administration of mesenchymal stem cells derived from adipose tissue (ASCs) and bone marrow (BMSCs) on the pathology of KD. Subsequent to the intracerebroventricular injection of ASCs or BMSCs on postnatal day (PND) 3-4, body weight, lifespan, and neuromotor function were evaluated longitudinally beginning on PND15. At sacrifice, tissues were harvested for analysis of GALC activity, presence of myelin, infiltration of macrophages, microglial activation, inflammatory markers, and cellular persistence. Survival analysis curves indicate a statistically significant increase in lifespan in stem cell-treated twitcher mice as compared with control twitcher mice. Body weight and motor function were also improved compared with controls. The stem cells may mediate some of these benefits through an anti-inflammatory mechanism because the expression of numerous proinflammatory markers was downregulated at both transcriptional and translational levels. A marked decrease in the levels of macrophage infiltration and microglial activation was also noted. These data indicate that mesenchymal lineage stem cells are potent inhibitors of inflammation associated with KD progression and offer potential benefits as a component of a combination approach for in vivo treatment by reducing the levels of inflammation. STEM CELLS 2011;29:67-77. PMID: 21280158 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | Development of Osteogenic Cell Sheets for Bone Tissue Engineering Applications. Tissue Eng Part A. 2011 Jan 30; Authors: Pirraco R, Obokata H, Iwata T, Marques A, Tsuneda S, Yamato M, Reis RL, Okano T The use of scaffolds in combination with osteogenic cells has been the gold standard in Bone Tissue Engineering strategies. These strategies have, however, in many cases failed to produce the desired results due to issues such as the immunogenicity of the biomaterials used and cell necrosis at the bulk of the scaffold related to deficient oxygen and nutrients diffusion. Here, we originally propose the use of cell sheet (CS) engineering as a possible way to overcome some of these obstacles. Osteogenic CSs were fabricated by culturing rat bone marrow stromal cells in thermo-responsive culture dishes. The CSs were recovered from the dishes using a low temperature treatment and then were implanted subcutaneously in nude mice. New bone formation was verified from day 7 post transplantation using x-ray, µ-CT and histological analysis. The presence of a vascularized marrow was also verified in the new formed bone after 6 weeks of transplantation. Furthermore, osteocytes were found in this newly formed tissue, supporting the conclusion that mature bone was formed after ectopically transplanting osteogenic CSs. These results therefore confirm the great potentiality of CS engineering to be used in bone tissue engineering applications. PMID: 21275832 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Temperature-dependent higher order structures of the (Pro-Pro-Gly)(10) -modified dendrimer. Biopolymers. 2011 Apr;95(4):270-7 Authors: Suehiro T, Tada T, Waku T, Tanaka N, Hongo C, Yamamoto S, Nakahira A, Kojima C Collagen is the most abundant protein in mammals and is widely used as a biomaterial for tissue engineering and drug delivery. We previously reported that dendrimers and linear polymers, modified with collagen model peptides (Pro-Pro-Gly)(5) , form a collagen-like triple-helical structure; however, its triple helicity needs improvement. In this study, a collagen-mimic dendrimer modified with the longer collagen model peptides, (Pro-Pro-Gly)(10) , was synthesized and named PPG10-den. Circular dichroism analysis shows that the efficiency of the triple helix formation in PPG10-den was much improved over the original. The X-ray diffraction analysis suggests that the higher order structure was similar to the collagen triple helix. The thermal stability of the triple helix in PPG10-den was higher than in the PPG10 peptide itself and our previous collagen-mimic polymers using (Pro-Pro-Gly)(5) . Interestingly, PPG10-den also assembled at low temperatures. Self-assembled structures with spherical and rod-like shapes were observed by transmission electron microscopy. Furthermore, a hydrogel of PPG10-den was successfully prepared which exhibited the sol-gel transition around 45°C. Therefore, the collagen-mimic dendrimer is a potential temperature-dependent biomaterial. © 2010 Wiley Periodicals, Inc. Biopolymers 95: 270-277, 2011. PMID: 21280022 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | The application of exosomes as a nanoscale cancer vaccine. Int J Nanomedicine. 2010;5:889-900 Authors: Tan A, De La Peña H, Seifalian AM Cancer is a leading cause of death globally, and it is predicted and projected to continue rising as life expectancy increases. Although patient survival rates for some forms of cancers are high due to clinical advances in treatment protocols, the search for effective cancer vaccines remains the ultimate Rosetta Stone in oncology. Cervarix(®), Gardasil(®), and hepatitis B vaccines are currently employed in preventing certain forms of viral cancers. However, they are, strictly speaking, not 'true' cancer vaccines as they are prophylactic rather than therapeutic, are only effective against the oncogenic viruses, and do not kill the actual cancer cells. On April 2010, a new prostate cancer vaccine Provenge(®) (sipuleucel-T) was approved by the US FDA, and it is the first approved therapeutic vaccine that utilizes antigen-presenting cell technology involving dendritic cells in cancer immunotherapy. Recent evidence suggests that the use of nanoscale particles like exosomes in immunotherapy could form a viable basis for the development of novel cancer vaccines, via antigen-presenting cell technology, to prime the immune system to recognize and kill cancer cells. Coupled with nanotechnology, engineered exosomes are emerging as new and novel avenues for cancer vaccine development. Here, we review the current knowledge pertaining to exosome technology in immunotherapy and also seek to address the challenges and future directions associated with it, in hopes of bringing this exciting application a step closer toward an effective clinical reality. PMID: 21116329 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Stem cell and peripheral nerve injury and repair. Facial Plast Surg. 2010 Oct;26(5):421-7 Authors: Dong MM, Yi TH Peripheral motor nerve injuries are a significant source of morbidity. Neural stem cells (NSCs), a group of relatively primitive cells, possess self-renewal ability and multidifferentiation potential. NSCs may be successfully separated from the human embryo and central nervous system (CNS) and differentiated into mature neurons and gliacytes by in vitro induction or transplantation into the body and may be differentiated into Schwann-like cells under specific conditions. It has been demonstrated that the ability of peripheral nerves to regenerate is mainly attributable to Schwann cells. NSC transplantation can promote peripheral nerve regeneration and provide a new means for treatment of peripheral nerve injury. In recent years, the study of NSCs has become a focus of many laboratories, but the biological characteristics and differentiation regulation mechanisms are not fully clear. In this article, we provide a brief review of NSC characteristics, cultivation, oriented differentiation, and clinical application. PMID: 20853234 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | An introduction to stem cell biology. Facial Plast Surg. 2010 Oct;26(5):343-9 Authors: Hemmat S, Lieberman DM, Most SP The field of stem cell biology has undergone tremendous expansion over the past two decades. Scientific investigation has continued to expand our understanding of these complex cells at a rapidly increasing rate. This understanding has produced a vast array of potential clinical applications. This article will serve as an overview of the current state of stem cell research as it applies to scientific and medical applications. Included in the discussion is a review of the many different types of stem cells, including but not limited to adult, embryonic, and perinatal stem cells. Also, this article describes somatic cell nuclear transfer, an exciting technology that allows the production of totipotent stem cells from fully differentiated cells, thereby eliminating the use of embryonic sources. This discussion should serve as a review of the field of stem cell biology and provide a foundation for the reader to better understand the interface of stem cell technology and facial plastic and reconstructive surgery. PMID: 20853224 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Adipose-derived stem cells for clinical applications: a review. Cell Prolif. 2011 Feb;44(1):86-98 Authors: Wilson A, Butler PE, Seifalian AM The use of stem cells derived from adipose tissue as an autologous and self-replenishing source for a variety of differentiated cell phenotypes, provides a great deal of promise for reconstructive surgery. In this article, we review available literature encompassing methods of extraction of pluripotent adipose stem cells (ASCs) from lipoaspirate locations, their storage, options for culture, growth and differentiation, cryopreservation and its effect on stem cell survival and proliferation, and new technologies involving biomaterials and scaffolds. We will conclude by assessing potential avenues for developing this incredibly promising field. PMID: 21199013 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | De novo formation and ultra-structural characterization of a fiber-producing human hair follicle equivalent in vitro. J Biotechnol. 2011 Jan 27; Authors: Lindner G, Horland R, Wagner I, Ata B, Lauster R Across many tissues and organs, the ability to create an organoid, the smallest functional unit of an organ, in vitro is the key both to tissue engineering and preclinical testing regimes. The hair follicle is an organoid that has been much studied based on its ability to grow quickly and to regenerate after trauma. But hair follicle formation in vitro has been elusive. Replacing hair lost due to pattern baldness or more severe alopecia, including that induced by chemotherapy, remains a significant unmet medical need. By carefully analyzing and recapitulating the growth conditions of hair follicle formation, we recreated human hair follicles in tissue culture that were capable of producing hair. Our microfollicles contained all relevant cell types and their structure and orientation resembled in some ways excised hair follicle specimens from human skin. This finding offers a new window onto hair follicle development. Having a robust culture system for hair follicles is an important step towards improved hair regeneration as well as to an understanding of how marketed drugs or drug candidates, including cancer chemotherapy, will affect this important organ. PMID: 21277344 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | [Effect of tannic acid treatment on the physico-chemical properties of glutaraldehyde-fixed bovine jugular vein]. Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2009 Feb;31(1):65-7 Authors: De W, Zhou JY, Hu SS, Jiang H, Wang S, Li J To evaluate the effects of tannic acid (TA) treatment on the physico-chemical properties of glutaraldehyde (Glut)-fixed bovine jugular vein (BJV). PMID: 19317063 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Finite Element Method (FEM), Mechanobiology and Biomimetic Scaffolds in Bone Tissue Engineering. Int J Biol Sci. 2011;7(1):112-32 Authors: Boccaccio A, Ballini A, Pappalettere C, Tullo D, Cantore S, Desiate A Techniques of bone reconstructive surgery are largely based on conventional, non-cell-based therapies that rely on the use of durable materials from outside the patient's body. In contrast to conventional materials, bone tissue engineering is an interdisciplinary field that applies the principles of engineering and life sciences towards the development of biological substitutes that restore, maintain, or improve bone tissue function. Bone tissue engineering has led to great expectations for clinical surgery or various diseases that cannot be solved with traditional devices. For example, 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 bone tissue engineering is to apply engineering principles to incite and promote the natural healing process of bone which does not occur in critical-sized defects. The total market for bone tissue regeneration and repair was valued at $1.1 billion in 2007 and is projected to increase to nearly $1.6 billion by 2014.Usually, temporary biomimetic scaffolds are utilized for accommodating cell growth and bone tissue genesis. The scaffold has to promote biological processes such as the production of extra-cellular matrix and vascularisation, furthermore the scaffold has to withstand the mechanical loads acting on it and to transfer them to the natural tissues located in the vicinity. The design of a scaffold for the guided regeneration of a bony tissue requires a multidisciplinary approach. Finite element method and mechanobiology can be used in an integrated approach to find the optimal parameters governing bone scaffold performance.In this paper, a review of the studies that through a combined use of finite element method and mechano-regulation algorithms described the possible patterns of tissue differentiation in biomimetic scaffolds for bone tissue engineering is given. Firstly, the generalities of the finite element method of structural analysis are outlined; second, the issues related to the generation of a finite element model of a given anatomical site or of a bone scaffold are discussed; thirdly, the principles on which mechanobiology is based, the principal theories as well as the main applications of mechano-regulation models in bone tissue engineering are described; finally, the limitations of the mechanobiological models and the future perspectives are indicated. PMID: 21278921 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | Microinjection of medaka embryos for use as a model genetic organism. J Vis Exp. 2010;(46): Authors: Porazinski SR, Wang H, Furutani-Seiki M In this video, we demonstrate the technique of microinjection into one-cell stage medaka embryos. Medaka is a small egg-laying freshwater fish that allows both genetic and embryological analyses and is one of the vertebrate model organisms in which genome-wide phenotype-driven mutant screens were carried out (1), as in zebrafish and the mouse. Divergence of functional overlap of related genes between medaka and zebrafish allows identification of novel phenotypes that are unidentifiable in a single species (2), thus medaka and zebrafish are complementary for genetic dissection of vertebrate genome functions. To take advantage of medaka fish whose embryos are transparent and develop externally, microinjection is an essential technique to inject cell-tracers for labeling cells, mRNAs or anti-sense oligonucleotides for over-expressing and knocking-down genes of interest, and DNAs for making transgenic lines. PMID: 21206471 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Unbiased screening of polymer libraries to define novel substrates for functional hepatocytes with inducible drug metabolism. Stem Cell Res. 2010 Dec 10; Authors: Hay DC, Pernagallo S, Diaz-Mochon JJ, Medine CN, Greenhough S, Hannoun Z, Schrader J, Black JR, Fletcher J, Dalgetty D, Thompson AI, Newsome PN, Forbes SJ, Ross JA, Bradley M, Iredale JP Maintaining stable differentiated somatic cell function in culture is essential to a range of biological endeavors. However, current technologies, employing, for example, primary hepatic cell culture (essential to the development of a bio-artificial liver and improved drug and toxicology testing), are limited by supply, expense, and functional instability even on biological cell culture substrata. As such, novel biologically active substrates manufacturable to GMP standards have the potential to improve cell culture-based assay applications. Currently hepatic endoderm (HE) generated from pluripotent stem cells is a genotypically diverse, cheap, and stable source of "hepatocytes"; however, HE routine applications are limited due to phenotypic instability in culture. Therefore a manufacturable subcellular matrix capable of supporting long-term differentiated cell function would represent a step forward in developing scalable and phenotypically stable hESC-derived hepatocytes. Adopting an unbiased approach we screened polymer microarrays and identified a polyurethane matrix which promoted hepatic endoderm viability, hepatocellular gene expression, drug-inducible metabolism, and function. Moreover, the polyurethane supported, when coated on a clinically approved bio-artificial liver matrix, long-term hepatocyte function and growth. In conclusion, our data suggest that an unbiased screening approach can identify cell culture substrate(s) that enhance the phenotypic stability of primary and stem cell-derived cell resources. PMID: 21277274 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Repair of peripheral nerve defects in rabbits using keratin hydrogel scaffolds. Tissue Eng Part A. 2011 Jan 30; Authors: Hill P, Apel PJ, Barnwell J, Smith TL, Koman LA, Atala A, Van Dyke M Entubulation of transected nerves using bioabsorbable conduits is a promising alternative to sural nerve autografting, but full functional recovery is rarely achieved. Numerous studies have suggested that scaffold-based conduit fillers may promote axon regeneration, but no neuroinductive biomaterial filler has been identified. We previously showed that a nerve guide filled with keratin hydrogel actively stimulates regeneration in a mouse model, and results in functional outcomes superior to empty conduits at early time points. The goal of the present study was to develop a peripheral nerve defect model in a rabbit and assess the effectiveness of a keratin hydrogel filler. Although repairs with keratin-filled conduits were not as consistently successful as autograft overall, the use of keratin resulted in a significant improvement in conduction delay compared to both empty conduits and autograft, as well as a significant improvement in amplitude recovery compared to empty conduits when measurable regeneration did occur. Taking into account all study animals (i.e. regenerated and non-regenerated), histological assessment showed that keratin treated nerves had significantly greater myelin thickness compared to empty conduits. These data support the findings of our earlier study and suggest that keratin hydrogel fillers have the potential to be used clinically to improve conduit repair. PMID: 21275820 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Characterization and quantification of biological micropatterns using Cluster-SIMS. Surf Interface Anal. 2011;43(1-2):555-558 Authors: Chen LJ, Shah SS, Verkhoturov SV, Revzin A, Schweikert EA Micropatterning is used widely in biosensor development, tissue engineering and basic biology. Creation of biological micropatterns typically involves multiple sequential steps that may lead to cross-contamination and may contribute to sub-optimal performance of the surface. Therefore, there is a need to develop novel strategies for characterizing location-specific chemical composition of biological micropatterns. In this paper, C(60) (+) ToF-SIMS operating in the event-by-event bombardment-detection mode was used for spatially resolved chemical analysis of micropatterned indium tin oxide (ITO) surfaces. Fabrication of the micropatterns involved multiple steps including self-assembly of poly (ethylene glycol) (PEG)-silane, patterning of photoresist, treatment with oxygen plasma and adsorption of collagen (I). The ITO surfaces were analyzed with 26 keV C(60) (+)SIMS run in the event-by-event bombardment-detection mode at different steps of the modification process. We were able to evaluate the extent of cross-contamination between different steps and quantify coverage of the immobilized species. The methodology described here provides a novel means for characterizing the composition of biological micropatterns in a quantitative and spatially-resolved manner. PMID: 21278908 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Primary human hepatocytes on biodegradable poly(l-lactic acid) matrices: A promising model for improving transplantation efficiency with tissue engineering. Liver Transpl. 2011 Feb;17(2):104-14 Authors: Török E, Lutgehetmann M, Bierwolf J, Melbeck S, Düllmann J, Nashan B, Ma PX, Pollok JM Liver transplantation is an established treatment for acute and chronic liver disease. However, because of the shortage of donor organs, it does not fulfill the needs of all patients. Hepatocyte transplantation is promising as an alternative method for the treatment of end-stage liver disease and as bridging therapy until liver transplantation. Our group has been working on the optimization of matrix-based hepatocyte transplantation. In order to increase cell survival after transplantation, freshly isolated human hepatocytes were seeded onto biodegradable poly(l-lactic acid) (PLLA) polymer scaffolds and were cultured in a flow bioreactor. PLLA discs were seeded with human hepatocytes and exposed to a recirculated medium flow for 6 days. Human hepatocytes formed spheroidal aggregates with a liver-like morphology and active metabolic function. Phase contrast microscopy showed increasing numbers of spheroids of increasing diameter during the culture period. Hematoxylin and eosin histology showed viable and intact hepatocytes inside the spheroids. Immunohistochemistry confirmed sustained hepatocyte function and a preserved hepatocyte-specific cytoskeleton. Albumin, alpha-1-antitrypsin, and urea assays showed continued production during the culture period. Northern blot analysis demonstrated increasing albumin signals. Scanning electron micrographs showed hepatocyte spheroids with relatively smooth undulating surfaces and numerous microvilli. Transmission electron micrographs revealed intact hepatocytes and junctional complexes with coated pits and vesicles inside the spheroids. Therefore, we conclude that primary human hepatocytes, precultured in a flow bioreactor on a PLLA scaffold, reorganize to form morphologically intact liver neotissue, and this might offer an optimized method for hepatocyte transplantation because of the expected reduction of the initial cell loss, the high regenerative potential in vivo, and the preformed functional integrity. Liver Transpl 17:104-114, 2011. © 2011 AASLD. PMID: 21280182 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | Substrates for cardiovascular tissue engineering. Adv Drug Deliv Rev. 2011 Jan 25; Authors: Bouten CV, Dankers PY, Driessen-Mol A, Pedron S, Brizard AM, Baaijens FP Cardiovascular tissue engineering aims to find solutions for the suboptimal regeneration of heart valves, arteries and myocardium by creating 'living' tissue replacements outside (in vitro) or inside (in situ) the human body. A combination of cells, biomaterials and environmental cues of tissue development is employed to obtain tissues with targeted structure and functional properties that can survive and develop within the harsh hemodynamic environment of the cardiovascular system. This paper reviews the up-to-date status of cardiovascular tissue engineering with special emphasis on the development and use of biomaterial substrates. Key requirements and properties of these substrates, as well as methods and readout parameters to test their efficacy in the human body, are described in detail and discussed in the light of current trends toward designing biologically inspired microenviroments for in situ tissue engineering purposes. PMID: 21277921 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Intravenous Administration of Human ES-derived Neural Precursor Cells Attenuates Cuprizone-induced CNS Demyelination. Neuropathol Appl Neurobiol. 2011 Jan 28; Authors: Crocker SJ, Bajpai R, Moore CS, Frausto RF, Brown GD, Pagarigan RR, Whitton JL, Terskikh AV Aims: Previous studies have demonstrated the therapeutic potential for human embryonic stem cell-derived neural precursor cells (hES-NPCs) in autoimmune and genetic animal models of demyelinating diseases. Herein, we tested whether intravenous (i.v) administration of hES-NPCs would impact central nervous system (CNS) demyelination in a cuprizone model of demyelination. Methods: C57Bl/6 mice were fed cuprizone (0.2%) for two weeks and then separated into two groups that either received an i.v. injection of hES-NPCs or i.v. administration of media without these cells. After an additional two weeks of dietary cuprizone treatment, CNS tissues were analyzed for detection of transplanted cells and differences in myelination in the region of the corpus callosum (CC). Results: Cuprizone-induced demyelination in the CC was significantly reduced in mice treated with hES-NPCs compared with cuprizone-treated controls that did not receive stem cells. hES-NPCs were identified within the brain tissues of treated mice and revealed migration of transplanted cells into the CNS. A limited number of human cells were found to express the mature oligodendrocyte marker, O1, or the astrocyte marker, GFAP. Reduced apoptosis and attenuated microglial and astrocytic responses were also observed in the CC of hES-NPC-treated mice. Conclusions: These findings indicated that systemically-administered hES-NPCs migrated from circulation into a demyelinated lesion within the CNS and effectively reduced demyelination. Observed reductions in astrocyte and microglial responses, and (c) the benefit of hES-NPC treatment in this model of myelin injury was not obviously accountable to tissue replacement by exogenously administered cells. PMID: 21276029 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Taking a lesson from the past in organ biology. Cell Transplant. 2010;19(6):645-7 Authors: Kobayashi N, Amemiya H, Nagao T, Takahara S PMID: 20525432 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Successful anatomic repair of fetoscopic access sites in the mid-gestational rabbit model using amnion cell engineering. In Vivo. 2010 Sep-Oct;24(5):745-50 Authors: Papadopulos NA, Kyriakidis DI, Schillinger U, Totis A, Henke J, Kovacs L, Horch RE, Schneider KT, Machens HG, Biemer E Our aim was to evaluate the impact of in vitro cultured amnion cells, injected and/or seeded in different scaffolds, on in vivo fetal membrane repair. PMID: 20952743 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | The Wnt receptor Ryk controls specification of GABAergic neurons versus oligodendrocytes during telencephalon development. Development. 2011 Feb;138(3):409-19 Authors: Zhong J, Kim HT, Lyu J, Yoshikawa K, Nakafuku M, Lu W GABAergic neurons and oligodendrocytes originate from progenitors within the ventral telencephalon. However, the molecular mechanisms that control neuron-glial cell-fate segregation, especially how extrinsic factors regulate cell-fate changes, are poorly understood. We have discovered that the Wnt receptor Ryk promotes GABAergic neuron production while repressing oligodendrocyte formation in the ventral telencephalon. We demonstrate that Ryk controls the cell-fate switch by negatively regulating expression of the intrinsic oligodendrogenic factor Olig2 while inducing expression of the interneuron fate determinant Dlx2. In addition, we demonstrate that Ryk is required for GABAergic neuron induction and oligodendrogenesis inhibition caused by Wnt3a stimulation. Furthermore, we showed that the cleaved intracellular domain of Ryk is sufficient to regulate the cell-fate switch by regulating the expression of intrinsic cell-fate determinants. These results identify Ryk as a multi-functional receptor that is able to transduce extrinsic cues into progenitor cells, promote GABAergic neuron formation, and inhibit oligodendrogenesis during ventral embryonic brain development. PMID: 21205786 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Cranial bone defects: current and future strategies. Neurosurg Focus. 2010 Dec;29(6):E8 Authors: Szpalski C, Barr J, Wetterau M, Saadeh PB, Warren SM Bony defects in the craniomaxillofacial skeleton remain a major and challenging health concern. Surgeons have been trying for centuries to restore functionality and aesthetic appearance using autografts, allografts, and even xenografts without entirely satisfactory results. As a result, physicians, scientists, and engineers have been trying for the past few decades to develop new techniques to improve bone growth and bone healing. In this review, the authors summarize the advantages and limitations of current animal models; describe current materials used as scaffolds, cell-based, and protein-based therapies; and lastly highlight areas for future investigation. The purpose of this review is to highlight the major scaffold-, cell-, and protein-based preclinical tools that are currently being developed to repair cranial defects. PMID: 21121722 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Tissue engineering on matrix: future of autologous tissue replacement. Semin Immunopathol. 2011 Jan 29; Authors: Weber B, Emmert MY, Schoenauer R, Brokopp C, Baumgartner L, Hoerstrup SP Tissue engineering aims at the creation of living neo-tissues identical or close to their native human counterparts. As basis of this approach, temporary biodegradable supporter matrices are fabricated in the shape of a desired construct, which promote tissue strength and provide functionality until sufficient neo-tissue is formed. Besides fully synthetic polymer-based scaffolds, decellularized biological tissue of xenogenic or homogenic origin can be used. In a second step, these scaffolds are seeded with autologous cells attaching to the scaffold microstructure. In order to promote neo-tissue formation and maturation, the seeded scaffolds are exposed to different forms of stimulation. In cardiovascular tissue engineering, this "conditioning" can be achieved via culture media and biomimetic in vitro exposure, e.g., using flow bioreactors. This aims at adequate cellular differentiation, proliferation, and extracellular matrix production to form a living tissue called the construct. These living autologous constructs, such as heart valves or vascular grafts, are created in vitro, comprising a viable interstitium with repair and remodeling capabilities already prior to implantation. In situ further in vivo remodeling is intended to recapitulate physiological vascular architecture and function. The remodeling mechanisms were shown to be dominated by monocytic infiltration and chemotactic host-cell attraction leading into a multifaceted inflammatory process and neo-tissue formation. Key molecules of these processes can be integrated into the scaffold matrix to direct cell and tissue fate in vivo. PMID: 21279358 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | HIF-1α is essential for hypoxia-induced mesenchymal stem cell mobilization into the peripheral blood. Stem Cells Dev. 2011 Jan 30; Authors: Liu L, Yu Q, Lin J, Lai X, Cao W, Du K, Wang Y, Wu K, Hu Y, Zhang L, Xiao H, Duan Y, Huang H Mobilization of mesenchymal stem cells (MSCs) is a promising strategy for tissue repair and regenerative medicine. The establishment of an appropriate animal model and clarification of the underlying mechanisms are beneficial to develop the mobilization regimens for therapeutic use. In this study, we therefore provided a rat MSC-mobilization model and investigated the related mechanisms, using continuous hypoxia as the mobilizing stimulus. We found that MSCs could be mobilized into peripheral blood (PB) of rats exposed to short-term hypoxia (2 days) and the mobilization efficiency increased in a time-dependent manner (2-14 days). Hypoxia-inducible factor 1α (HIF-1α) was upregulated during hypoxic exposure, and was expressed continuously in bone marrow (BM). Inhibition of HIF-1α expression by YC-1 remarkably reduced the number of mobilized MSCs, suggesting that HIF-1α is essential for hypoxia-induced MSC mobilization. Furthermore, we investigated the potential role of HIF-1α target genes, vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1α (SDF-1α). VEGF expression was elevated from days 2-7 of hypoxia, stimulating an increase in BM sinusoidal vessels and possibly facilitating the egress of MSCs. SDF-1α protein levels were increased in PB of rats during MSC mobilization, and promoted the migration of MSCs under hypoxic conditions in vitro. These results suggest that HIF-1α plays a pivotal role in hypoxia-induced MSC mobilization, possibly acting via its downstream genes VEGF and SDF-1α. These data provide a novel insight into the mechanisms responsible for MSC mobilization and may help in the development of clinically useful therapeutic agents. PMID: 21275821 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Transplantation of adipose-derived stem cells promotes formation of prefabricated flap in a rat model. Tohoku J Exp Med. 2010;222(2):131-40 Authors: Li H, Zan T, Li Y, Weng R, Yang M, Du Z, Zhong S, Li Q Flap prefabrication is started with transposition of a vascular pedicle into a donor area that lacks an axial blood supply. Adipose-derived stem cells (ASCs) have been proven beneficial for promoting neovascularization and tissue regeneration in several animal models. Here we investigated the feasibility of applying ASCs as a novel strategy to promote flap prefabrication, which involves the processes of neovascularization and regeneration. Prefabricated flaps were performed by two-stage procedure in a rat model. At stage one, the right femoral vascular pedicle was dissected and embedded underneath the abdominal flap to form a man-made axial flap. At stage two, the prefabricated abdominal flap was elevated as an island flap based on the implanted femoral vessel. Ninety rats were randomly divided into 3 groups and received allogeneic ASCs, chondrocytes and phosphate-buffered saline (PBS), respectively during the first operation. Eighteen flaps of each group were harvested for vascular endothelial growth factor-A (VEGF-A) protein assay after the first surgery. The other flaps were processed for flap viability measurements by flap survival rate and capillary density after the second surgery. Results demonstrated that the ASCs treated group had higher survival percentage and capillary density of flap as compared with either PBS group or chondrocyte group. Furthermore, the ASC group had the highest level of in vivo VEGF-A among three groups, while the chondrocyte group had the lowest. These results indicate that ASCs are capable of promoting flap prefabrication, and its therapeutic potential is correlated with the angiogenic cytokines such as VEGF-A. PMID: 20944441 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Neural crest origin of olfactory ensheathing glia. Proc Natl Acad Sci U S A. 2010 Dec 7;107(49):21040-5 Authors: Barraud P, Seferiadis AA, Tyson LD, Zwart MF, Szabo-Rogers HL, Ruhrberg C, Liu KJ, Baker CV Olfactory ensheathing cells (OECs) are a unique class of glial cells with exceptional translational potential because of their ability to support axon regeneration in the central nervous system. Although OECs are similar in many ways to immature and nonmyelinating Schwann cells, and can myelinate large-diameter axons indistinguishably from myelination by Schwann cells, current dogma holds that OECs arise from the olfactory epithelium. Here, using fate-mapping techniques in chicken embryos and genetic lineage tracing in mice, we show that OECs in fact originate from the neural crest and hence share a common developmental heritage with Schwann cells. This explains the similarities between OECs and Schwann cells and overturns the existing dogma on the developmental origin of OECs. Because neural crest stem cells persist in adult tissue, including skin and hair follicles, our results also raise the possibility that patient-derived neural crest stem cells could in the future provide an abundant and accessible source of autologous OECs for cell transplantation therapy for the injured central nervous system. PMID: 21078992 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Engineering of an hepatic organoid to develop liver assist devices. Cell Transplant. 2010;19(6):815-22 Authors: Soto-Gutierrez A, Navarro-Alvarez N, Yagi H, Nahmias Y, Yarmush ML, Kobayashi N Cell-based technologies to support/restore liver function represent one of the most promising opportunities in the treatment of acute liver failure. However, the understanding of the constituent cell types that interact to achieve liver-specific structure and function has not been achieved in the development of liver assist devices (LADs). Here we show that hepatocytes migrated toward and adhered and formed sinusoids-like structures in conjunction with liver nonparenchymal cells, and that this liver organoid formed sophisticated tissue after 7 days in an implanted LAD in rodents. Hepatocytes only or in combination with human nonparenchymal liver cell lines (endothelial, cholangiocytes, and stellate cells) were cultured in Matrigel. Ultrastructural analysis showed that the hepatocyte-decorated endothelial vascular structures resemble in vivo sinusoids containing plate-like structures, bile canaliculi, and lumen. The sinusoid-like structures retained albumin secretion and drug metabolism capabilities. In addition, LADs containing cocultures of human liver nonparenchymal cells were transplanted in animals for a week; the liver tissue formed sophisticated structures resembling the liver. These results demonstrate the importance of nonparenchymal cells in the cellular composition of LADs. The novelty of the culture's sinusoid-like organization and function strongly support the integration of liver nonparenchymal units into hepatocyte coculture-based LADs as a potential destination therapy for liver failure. PMID: 20573303 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Embryonic progenitor cells in adipose tissue engineering. Facial Plast Surg. 2010 Oct;26(5):405-12 Authors: Hillel AT, Elisseeff JH Adipose tissue is extensively used in facial plastic surgery as a soft tissue filler for small-to-large facial defects. Variable results with autologous fat grafting and lipoinjection has led to interest in alternative forms of adipose tissue, including tissue engineered adipose tissue. Tissue engineering combines cells, scaffolds, and bioactive signals to regenerate organs or tissue. Cell sources include preadipocytes, adult stem cells, and embryonic stem cells. Although adult cells may be easily accessible from a patient, embryonic progenitor cells have comparative advantages over adult stem cells including indefinite self-renewal (high proliferative and expansion capacity) and strong tissue-forming capacity. This article will describe the types of embryonic progenitor cells and the cell culture conditions, common biomaterials, signaling factors, and biomechanical forces used in adipose tissue engineering. We will identify optimal conditions to generate functional, long-lasting adipose-like tissue. Lastly, we will propose potential future directions for the rapidly expanding field of adipose tissue engineering. PMID: 20853232 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Controlling cell behavior through the design of polymer surfaces. Small. 2010 Oct 18;6(20):2208-20 Authors: Alves NM, Pashkuleva I, Reis RL, Mano JF Polymers have gained a remarkable place in the biomedical field as materials for the fabrication of various devices and for tissue engineering applications. The initial acceptance or rejection of an implantable device is dictated by the crosstalk of the material surface with the bioentities present in the physiological environment. Advances in microfabrication and nanotechnology offer new tools to investigate the complex signaling cascade induced by the components of the extracellular matrix and consequently allow cellular responses to be tailored through the mimicking of some elements of the signaling paths. Patterning methods and selective chemical modification schemes at different length scales can provide biocompatible surfaces that control cellular interactions on the micrometer and sub-micrometer scales on which cells are organized. In this review, the potential of chemically and topographically structured micro- and nanopolymer surfaces are discussed in hopes of a better understanding of cell-biomaterial interactions, including the recent use of biomimetic approaches or stimuli-responsive macromolecules. Additionally, the focus will be on how the knowledge obtained using these surfaces can be incorporated to design biocompatible materials for various biomedical applications, such as tissue engineering, implants, cell-based biosensors, diagnostic systems, and basic cell biology. The review focusses on the research carried out during the last decade. PMID: 20848593 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Effects of Cryopreservation on the Transcriptome of Human Embryonic Stem Cells After Thawing and Culturing. Stem Cell Rev. 2011 Jan 29; Authors: Wagh V, Meganathan K, Jagtap S, Gaspar JA, Winkler J, Spitkovsky D, Hescheler J, Sachinidis A Human embryonic stem cells (hESCs) can be propagated indefinitely in vitro in an undifferentiated pluripotent state, can differentiate into derivatives of all three germ layers and are of considerable interest for applications in regenerative medicine. Clinical application of hESCs, however, requires reliable protocols for cryopreservation. Current protocols for cryopreservation of hESCs suffer from low recovery rates of hESCs and loss of pluripotency after thawing. We therefore studied the effects of cryopreservation on the viability, proliferation potential, and the pluripotency status of hESCs by combining cellular readouts and transcriptomics. We identified biological processes and pathways affected by cryopreservation in order to understand the limited survival rate of hESCs by comparing transcriptomes of hESCs at different time points after thawing with cells that did not undergo cryopreservation. While the transcriptomes of cells post thawing were very similar to those of control non-frozen hESCs for the early time points, we observed increased expression of genes involved in apoptosis, embryonic morphogenesis, ossification, tissue morphogenesis, regeneration, vasculature development and cell death at later time points. Our data suggest that inhibition of anoikis apoptosis and the stress-induced differentiation pathways are promising targets for improving the survival rate and maintaining pluripotency of hESCs after cryopreservation. PMID: 21279480 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | The Effect of Cell Seeding Density on the Cellular and Mechanical Properties of a Mechanostimulated Tissue Engineered Tendon. Tissue Eng Part A. 2011 Jan 30; Authors: Issa RI, Engebretson B, Rustom L, McFetridge PS, Sikavitsas VI The initial seeding density is a critical variable in functional tissue engineering. A sufficient number of cells uniformly distributed throughout the scaffold is a key requirement to achieve homogeneous extra cellular matrix (ECM) deposition <i>in vitro</i>. However, high initial seeding densities might have negative repercussions on nutrient availability, cellular metabolism, and cell viability. In the current study, our aim was to understand the implications of using high seeding densities (3, 5, and 10 million cells/ml) in a human umbilical vein (HUV) tendon model subjected to 1 hour of cyclic stretching per day at 2% strain and a frequency of 0.0167 Hz in a mechanostimulating bioreactor, on nutrient availability, cell viability and metabolism, and construct properties. Mechanostimulated constructs seeded with 3 million cells/ml had significantly higher cell number than the static controls and resulted in a 20 fold increase in proliferation rates and a 3 fold increase in tensile strength values after one week of culture in the bioreactor. However, higher seeding densities resulted in cell death, degraded ECM, and poorer mechanical properties. Nutrient and growth factor mass transport limitations are implicated in the inability of the decellularized HUV to support high cell numbers. The effective diffusion coefficient for glucose was measured to be 0.21 ± 0.04 cm<sup>2</sup>/day. In the absence of convective flow, proteins and growth factors with a molecular radius larger than 4.9 nm could not diffuse through the HUV. Cells seeded in the HUV consumed 10.5±0.5 ng/cell/day of glucose. Glucose diffusion coefficient and glucose consumption rates in the HUV indicated the presence of glucose mass transport limitations when cell seeding densities exceed 3 million cells/ml. PMID: 21275843 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |  | |  | |  |
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