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| Surface expression of CXCR4 in unrestricted somatic stem cells and its regulation by growth factors.
March 4, 2010 at 7:42 AM
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| | Surface expression of CXCR4 in unrestricted somatic stem cells and its regulation by growth factors. Cell Biol Int. 2010 Mar 2; Authors: Ahmadbeigi N, Seyedjafari E, Gheisari Y, Atashi A, Omidkhoda A, Soleimani M Umbilical cord blood-drived unrestricted somatic stem cells (USSCs) have been recently considered as a potential source for stem cell therapy and transplantation due to their characteristics such as easy accessibility, low immunogenicity, self-renewing and multilineage differentiation potential. Stem cell homing is a key factor in successful transplantation which is regulated by CXCR4 in stem cells. In this study, we evaluated the expression of CXCR4 in USSCs different passages. Moreover, the effect of Vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF-1) on its expression was assessed. It was shown that the expression of CXCR4 in USSCs decreased with the increase in passage number. It was also revealed that VEGF increased surface expression and mRNA level of CXCR4 in USSCs while IGF-1 decreased its expression. When VEGF and IGF-1 were administered simultaneously, CXCR4 expression was increased but the expression level was less than VE! GF alone. Finally, it was shown that over-expression of CXCR4 enhanced the migratory capacity of USSCs. The increase of CXCR4 expression, here caused by VEGF in USSCs, can improve the efficacy of stem cell therapy and transplantation after long-term culture of stem cells before clinical use. PMID: 20196768 [PubMed - as supplied by publisher] | | |
| PHBV and predifferentiated human adipose-derived stem cells for cartilage tissue engineering.
March 4, 2010 at 6:47 AM
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| | PHBV and predifferentiated human adipose-derived stem cells for cartilage tissue engineering. J Biomed Mater Res A. 2010 Mar 2; Authors: Liu J, Zhao B, Zhang Y, Lin Y, Hu P, Ye C This study was conducted to investigate whether in vitro chondrogenic differentiated human adipose-derived stem cells (hASCs) can maintain the chondrogenic phenotype in (3-hydroxybutrate-co-3-hydroxyvalerate) (PHBV) scaffolds and whether differentiated hASCs/PHBV construct can produce neocartilage in a heterotopic animal model. hASCs were cultured with or without chondrogenic media in vitro and then seeded on PHBV foams. Differentiated cell/PHBV constructs were subcutaneously implanted in nude mice for 8 or 16 weeks; nondifferentiated cell/PHBV constructs were implanted in the control group. The results in the control group showed no cartilage formation and the disappearance of the scaffold at 8 weeks. Conversely, all differentiated hASCs/PHBV implants kept their original shape throughout 16 weeks. These implants at 16 weeks had stronger chondrocytes-specific histochemical staining than those at 8 weeks, with GAG, total collagen, and compressive moduli increased w! ith implantation time. Cartilage lacunae were observed in all retrieved implants at 16 weeks. The chondrocytes-specific genes were detected by RT-PCR at 16 weeks. The remnants of PHBV were observed in the implants throughout 16 weeks. This study demonstrates that chondrogenic predifferentiated hASCs have the ability to maintain a chondrogenic phenotype in PHBV and that cell/PHBV constructs can produce neocartilage in a heterotopic site, but the degradation rates of PHBV in different environments needs more investigation. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20198693 [PubMed - as supplied by publisher] | | |
| Tissue-engineered matrices as functional delivery systems: Adsorption and release of bioactive proteins from degradable composite scaffolds.
March 4, 2010 at 6:47 AM
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| | Tissue-engineered matrices as functional delivery systems: Adsorption and release of bioactive proteins from degradable composite scaffolds. J Biomed Mater Res A. 2010 Mar 2; Authors: Cushnie EK, Khan YM, Laurencin CT A tissue-engineered bone graft should imitate the ideal autograft in both form and function. However, biomaterials that have appropriate chemical and mechanical properties for grafting applications often lack biological components that may enhance regeneration. The concept of adding proteins such as growth factors to scaffolds has therefore emerged as a possible solution to improve overall graft design. In this study, we investigated this concept by loading porous hydroxyapatite-poly(lactide-co-glycolide) (HA-PLAGA) scaffolds with a model protein, cytochrome c, and then studying its release in a phosphate-buffered saline solution. The HA-PLAGA scaffold has previously been shown to be bioactive, osteoconductive, and to have appropriate physical properties for tissue engineering applications. The loading experiments demonstrated that the HA-PLAGA scaffold could also function effectively as a substrate for protein adsorption and release. Scaffold protein adsorptive l! oading (as opposed to physical entrapment within the matrix) was directly related to levels of scaffold HA-content. The HA phase of the scaffold facilitated protein retention in the matrix following incubation in aqueous buffer for periods up to 8 weeks. Greater levels of protein retention time may improve the protein's effective activity by increasing the probability for protein-cell interactions. The ability to control protein loading and delivery simply via composition of the HA-PLAGA scaffold offers the potential of forming robust functionalized bone grafts. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010. PMID: 20198692 [PubMed - as supplied by publisher] | | |
| The Current Status of Engineering Myocardial Tissue.
March 4, 2010 at 6:47 AM
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| | The Current Status of Engineering Myocardial Tissue. Stem Cell Rev. 2010 Mar 3; Authors: Sui R, Liao X, Zhou X, Tan Q Myocardial infarction (MI) remains a common fatal disease all over the world. The adult cardiac myocytes regenerative capability is very limited after infarct injury. Heart transplantation would be the best therapeutic option currently but is restricted due to the lack of donor organs and the serious side effects of immune suppression. The emerging of tissue engineering has evolved to provide solutions to tissue repair and replacement. Engineering myocardial tissue is considered to be a new therapeutic approach to repair infarcted myocardium and ameliorate cardiac function after MI. Engineering myocardial tissue is the combination of biodegradable scaffolds with viable cells and has made much progress in the experimental phase. However, the largest challenge of this field is the revascularization of the engineering constructs to provide oxygen and nutrients for cells. This review will give an overview on the current evolution of engineering myocardial tissue and a! ddress a new method to improve the vascularization of myocardium tissue in vivo. PMID: 20198517 [PubMed - as supplied by publisher] | | |
| A novel collagen scaffold supports human osteogenesis-applications for bone tissue engineering.
March 4, 2010 at 6:47 AM
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| | A novel collagen scaffold supports human osteogenesis-applications for bone tissue engineering. Cell Tissue Res. 2010 Mar 3; Authors: Keogh MB, O' Brien FJ, Daly JS Collagen glycosaminoglycan (CG) scaffolds have been clinically approved as an application for skin regeneration. The goal of this study has been to examine whether a CG scaffold is a suitable biomaterial for generating human bone tissue. Specifically, we have asked the following questions: (1) can the scaffold support human osteoblast growth and differentiation and (2) how might recombinant human transforming growth factor-beta (TGF-beta(1)) enhance long-term in vitro bone formation? We show human osteoblast attachment, infiltration and uniform distribution throughout the construct, reaching the centre within 14 days of seeding. We have identified the fully differentiated osteoblast phenotype categorised by the temporal expression of alkaline phosphatase, collagen type 1, osteonectin, bone sialo protein, biglycan and osteocalcin. Mineralised bone formation has been identified at 35 days post-seeding by using von Kossa and Alizarin S Red staining. Both gene express! ion and mineral staining suggest the benefit of introducing an initial high treatment of TGF-beta(1) (10 ng/ml) followed by a low continuous treatment (0.2 ng/ml) to enhance human osteogenesis on the scaffold. Osteogenesis coincides with a reduction in scaffold size and shape (up to 70% that of original). A notable finding is core degradation at the centre of the tissue-engineered construct after 49 days of culture. This is not observed at earlier time points. Therefore, a maximum of 35 days in culture is appropriate for in vitro studies of these scaffolds. We conclude that the CG scaffold shows excellent potential as a biomaterial for human bone tissue engineering. PMID: 20198386 [PubMed - as supplied by publisher] | | |
| The mechanical stress-strain properties of single electrospun collagen type I nanofibers.
March 4, 2010 at 6:47 AM
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| | The mechanical stress-strain properties of single electrospun collagen type I nanofibers. Acta Biomater. 2010 Feb 27; Authors: Carlisle CR, Coulais C, Guthold M Knowledge of the mechanical properties of electrospun fibers is important for their successful application to tissue engineering, material composites, filtration and drug delivery. In particular, electrospun collagen has great potential for biomedical applications due to its biocompatibility and promotion of cell growth and adhesion. Using a combined atomic force/optical microscopy technique, we determined the single fiber mechanical properties of dry, electrospun collagen type I. The fibers were electrospun from a 80 mg/ml collagen solution in 1,1,1,3,3,3-hexafluro-2-propanol and collected on a striated surface suitable for lateral force manipulation by the AFM. The small strain modulus, calculated from three point bending analysis, was 2.82 GPa. The modulus showed significant softening as strain increased. The average extensibility of the fibers was 33% of their initial length and the average maximum stress (rupture stress) was 25 MPa. The fibers displayed signi! ficant energy loss and permanent deformations above 2% strain. PMID: 20197123 [PubMed - as supplied by publisher] | | |
| Differential expression of biofunctional GM1 and GM3 gangliosides within the plastic-adherent multipotent mesenchymal stromal cell population.
March 4, 2010 at 6:47 AM
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| | Differential expression of biofunctional GM1 and GM3 gangliosides within the plastic-adherent multipotent mesenchymal stromal cell population. Cytotherapy. 2010 Apr;12(2):131-42 Authors: Freund D, Fonseca AV, Janich P, Bornhäuser M, Corbeil D Abstract Background aims. It is unclear whether the plastic-adherent multipotent mesenchymal stromal cells (MSC) isolated from human bone marrow (BM) represent a uniform cell population or are heterogeneous in terms of cell-surface constituents and hence functionality. Methods. We investigated the expression profile of certain biofunctional lipids by plastic-adherent MSC, focusing particularly on two membrane microdomain (lipid raft)-associated monosialogangliosides, GM1 and GM3, using indirect confocal laser scanning fluorescence microscopy and flow cytometry. Results. Phenotypically, we observed a differential expression where certain MSC subsets exhibited GM1, GM3 or both at the plasma membrane. Furthermore, disialoganglioside GD2 detection increased the complexity of the expression patterns, giving rise to seven identifiable cell phenotypes. Variation of standard culture conditions, such as the number of cell passage and period in culture, as well as donors, d! id not influence the heterologous ganglioside expression profile. In contrast, the binding of various lectins appeared homogeneous throughout the MSC population, indicating that the general glycosylation pattern remained common. Morphologically, the expression of a given ganglioside-based phenotype was not related to a cell with particular size or shape. Interestingly, a segregation of GM1 and GM3 clusters was observed, GM3 being mostly excluded from the highly curved plasma membrane protrusions. Conclusions. These data highlight the phenotypic heterogeneity of plastic-adherent MSC in terms of certain lipid constituents of the plasma membrane, and the presence and/or absence of distinct ganglioside-based membrane microdomains suggest their potential functional diversity. PMID: 20196693 [PubMed - in process] | | |
| Congenital anomalies of soft tissues: Birth defects depending on tissue engineering solutions and present advances in regenerative medicine.
March 4, 2010 at 6:47 AM
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| | Congenital anomalies of soft tissues: Birth defects depending on tissue engineering solutions and present advances in regenerative medicine. Tissue Eng Part B Rev. 2010 Mar 2; Authors: Saxena AK Congenital anomalies encompass a wide range of malformations that could affect various organs and tissues in the newborn and infant population. These disorders that involve defects in or injury to a developing fetus may be a result of genetic abnormalities or mutations, alterations in the intrauterine environment, irregularities in morphogenesis or chromosomal aberration. The outcome of these defects could lead to minor anomalies or major malformations which are dependent on the complex processes between the pre-natal deficit and post-natal environment. Often multiple malformations occur within the same fetus and give rise to a malformation syndrome. Since congenital anomalies are evident at birth, solutions must be found to improve the clinical state and quality of life that a newborn has to lead from infancy through adolescence into adulthood. Transplantation options in this age group are limited due to the shortage of organs and the discrepancy in adult donor s! ize mismatch. Over the past 2 decades tremendous strides have been made in the research of biomaterials, stem cells, organ generation and tissue engineering to provide viable solutions to a wide range of organ and tissue losses focusing on the adult population. This review intends to highlight the shortage of tissue and organs in neonates and infants with congenital malformations. This is also the first monograph which presents estimation of incidences of the congenital malformations based on an extensive literature search. It also outlines the challenges in clinical management of these entities and presents an organ-based demand for engineered tissues. PMID: 20196647 [PubMed - as supplied by publisher] | | |
| THE EARLY FRACTURE HEMATOMA AND ITS POTENTIAL ROLE IN FRACTURE HEALING.
March 4, 2010 at 6:47 AM
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| | THE EARLY FRACTURE HEMATOMA AND ITS POTENTIAL ROLE IN FRACTURE HEALING. Tissue Eng Part B Rev. 2010 Mar 2; Authors: Kolar P, Schmidt-Bleek K, Schell H, Gaber T, Toben D, Schmidtmaier G, Perka C, Buttgereit F, Duda G Abstract Research regarding the potency and potential of the fracture hematoma has begun to receive increasing attention. However, currently there is a paucity of relevant literature on the capability and composition of the fracture hematoma. This review briefly summarizes the regenerative fracture healing process and the close interplay between the skeletal and immune systems. The role of immune cells in wound healing is also discussed to clarify their involvement in immunological processes during regeneration. We attempt to describe the current state of knowledge regarding the fracture hematoma as the initial stage of the regenerative process of fracture healing. The review discusses how a better understanding of immune reactions in the hematoma may have implications for bone tissue engineering strategies. We conclude the review by emphasizing how additional investigations of the initial phase of healing will allow us to better differentiate between deleterious ! and beneficial aspects of inflammation, thereby facilitating improved fracture treatment strategies. PMID: 20196645 [PubMed - as supplied by publisher] | | |
| Parameters in 3D "Osteospheroids" of telomerized human mesenchymal (stromal) stem cells grown on osteoconductive scaffolds that predict in vivo bone forming potential.
March 4, 2010 at 6:47 AM
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| | Parameters in 3D "Osteospheroids" of telomerized human mesenchymal (stromal) stem cells grown on osteoconductive scaffolds that predict in vivo bone forming potential. Tissue Eng Part A. 2010 Mar 2; Authors: Burns JS, Rasmussen PL, Larsen KH, Schrøder HD, Kassem M Osteoblastic differentiation of human mesenchymal stem cells (hMSC) in monolayer culture is artefactual, lacking an organized bone-like matrix. We present a highly reproducible microwell protocol generating 3D ex vivo multicellular aggregates of telomerized hMSC (hMSC-TERT) with improved mimicry of in vivo tissue engineered bone. In osteogenic induction medium the hMSC transitioned with time-dependent specification towards the osteoblastic lineage characterised by production of alkaline phosphatase, type I collagen, osteonectin and osteocalcin. Introducing a 1-2 mm3 crystalline hydroxyapatite/tricalcium phosphate (HA/ss-TCP) scaffold generated "Osteospheroids" with upregulated gene expression of transcription factors RUNX2/CBFA1, Msx-2 and Dlx-5. An organized lamellar bone-like collagen matrix, evident by birefringence of polarized light, was deposited in the scaffold concavities. Here, mature osteoblasts, stained positively for differentiated osteoblast markers: ! TAZ, biglycan, osteocalcin, and phospho-AKT. Quantification of collagen birefringence and relatively high expression of matrix proteins, including type I collagen, bigylcan, decorin, lumican, elastin, MFAP2, MFAP5, periostin and tetranectin in vitro correlated predictively with in vivo bone formation. The 3D hMSC-TERT/HA-TCP osteospheroid cultures recapitulated many characteristics of in vivo bone formation, providing a highly reproducible and resourceful platform for improved in vitro modelling of osteogenesis and refinement of bone tissue engineering. PMID: 20196644 [PubMed - as supplied by publisher] | | |
| The role of organ level conditioning on the promotion of engineered heart valve tissue development in-vitro using mesenchymal stem cells.
March 4, 2010 at 6:47 AM
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| | The role of organ level conditioning on the promotion of engineered heart valve tissue development in-vitro using mesenchymal stem cells. Biomaterials. 2010 Feb;31(6):1114-25 Authors: Ramaswamy S, Gottlieb D, Engelmayr GC, Aikawa E, Schmidt DE, Gaitan-Leon DM, Sales VL, Mayer JE, Sacks MS We have previously shown that combined flexure and flow (CFF) augment engineered heart valve tissue formation using bone marrow-derived mesenchymal stem cells (MSC) seeded on polyglycolic acid (PGA)/poly-L-lactic acid (PLLA) blend nonwoven fibrous scaffolds (Engelmayr, et al., Biomaterials 2006; vol. 27 pp. 6083-95). In the present study, we sought to determine if these phenomena were reproducible at the organ level in a functional tri-leaflet valve. Tissue engineered valve constructs (TEVC) were fabricated using PGA/PLLA nonwoven fibrous scaffolds then seeded with MSCs. Tissue formation rates using both standard and augmented (using basic fibroblast growth factor [bFGF] and ascorbic acid-2-phosphate [AA2P]) media to enhance the overall production of collagen were evaluated, along with their relation to the local fluid flow fields. The resulting TEVCs were statically cultured for 3 weeks, followed by a 3 week dynamic culture period using our organ level bioreactor! (Hildebrand et al., ABME, Vol. 32, pp. 1039-49, 2004) under approximated pulmonary artery conditions. Results indicated that supplemented media accelerated collagen formation (approximately 185% increase in collagen mass/MSC compared to standard media), as well as increasing collagen mass production from 3.90 to 4.43 pg/cell/week from 3 to 6 weeks. Using augmented media, dynamic conditioning increased collagen mass production rate from 7.23 to 13.65 pg/cell/week (88.8%) during the dynamic culture period, along with greater preservation of net DNA. Moreover, when compared to our previous CFF study, organ level conditioning increased the collagen production rate from 4.76 to 6.42 pg/cell/week (35%). Newly conducted CFD studies of the CFF specimen flow patterns suggested that oscillatory surface shear stresses were surprisingly similar to a tri-leaflet valve. Overall, we found that the use of simulated pulmonary artery conditions resulted in substantially larger collagen mass! production levels and rates found in our earlier CFF study. M! oreover, given the fact that the scaffolds underwent modest strains (approximately 7% max) during either CFF or physiological conditioning, the oscillatory surface shear stresses estimated in both studies may play a substantial role in eliciting MSC collagen production in the highly dynamic engineered heart valve fluid mechanical environment. PMID: 19944458 [PubMed - indexed for MEDLINE] | | |
| The relationship between fibroblast growth and the dynamic stiffnesses of a DNA crosslinked hydrogel.
March 4, 2010 at 6:47 AM
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| | The relationship between fibroblast growth and the dynamic stiffnesses of a DNA crosslinked hydrogel. Biomaterials. 2010 Feb;31(6):1199-212 Authors: Jiang FX, Yurke B, Schloss RS, Firestein BL, Langrana NA The microenvironment of cells is dynamic and undergoes remodeling with time. This is evident in development, aging, pathological processes, and at tissue-biomaterial interfaces. But in contrast, the majority of the biomimetic materials have static properties. Here, we show that a previously developed DNA crosslinked hydrogel circumvents the need of environmental factors and undergoes controlled stiffness change via DNA delivery, a feasible approach to initiate property changes in vivo, different from previous attempts. Two types of fibroblasts, L929 and GFP, were subject to the alterations in substrate rigidity presented in the hydrogels. Our results show that exogenous DNA does not cause appreciable cell shape change. Cells do respond to mechanical alterations as demonstrated in the cell projection area and polarity (e.g., Soft vs. Soft-->Medium), and the responses vary depending on magnitude (e.g., Soft-->Medium vs. Soft-->Stiff) and range of stiffness ! changes (e.g., Soft-->Medium vs. Medium-->Stiff). The two types of fibroblasts share specific responses in common (e.g., Soft-->Medium), while differ in others (e.g., Medium-->Stiff). For each cell type, the projection area and polarity respond differently. This approach provides insight into pathology (e.g., cancer) and tissue functioning, and assists in designing biomaterials with controlled dynamic stiffness by choosing the range and magnitude of stiffness change. PMID: 19931905 [PubMed - indexed for MEDLINE] | | |
| Engineering integrin signaling for promoting embryonic stem cell self-renewal in a precisely defined niche.
March 4, 2010 at 6:47 AM
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| | Engineering integrin signaling for promoting embryonic stem cell self-renewal in a precisely defined niche. Biomaterials. 2010 Feb;31(6):1219-26 Authors: Lee ST, Yun JI, Jo YS, Mochizuki M, van der Vlies AJ, Kontos S, Ihm JE, Lim JM, Hubbell JA We present development and use of a 3D synthetic extracellular matrix (ECM) analog with integrin-specific adhesion ligands to characterize the microenvironmental influences in embryonic stem cell (ESC) self-renewal. Transcriptional analysis of 24 integrin subunits followed by confirmation at the translational and functional levels suggested that integrins alpha(5)beta(1), alpha(v)beta(5), alpha(6)beta(1) and alpha(9)beta(1) play important roles in maintenance of stemness in undifferentiated mouse ESCs. Using the well-defined matrix as a tool to activate integrins alpha(5)beta(1) plus alpha(v)beta(5), alpha(6)beta(1) and alpha(9)beta(1), individually and in combination, differential integrin activation was demonstrated to exert exquisite control over ESC fate decisions. Simultaneous ligation of these four integrin heterodimers promoted self-renewal, as evidence by prolonged SSEA-1, Oct4 and Nanog expression, and induced Akt1 kinase signaling along with translationa! l regulation of other stemness-related genes. The biofunctional network we have designed based on this knowledge may be useful as a defined niche for regulating ESC pluripotency through selective cell-matrix interactions, and the method we present may be more generally useful for probing matrix interactions in stem cell self-renewal and differentiation. PMID: 19926127 [PubMed - indexed for MEDLINE] | | |
| The effect of VEGF on the myogenic differentiation of adipose tissue derived stem cells within thermosensitive hydrogel matrices.
March 4, 2010 at 6:47 AM
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| | The effect of VEGF on the myogenic differentiation of adipose tissue derived stem cells within thermosensitive hydrogel matrices. Biomaterials. 2010 Feb;31(6):1213-8 Authors: Kim MH, Hong HN, Hong JP, Park CJ, Kwon SW, Kim SH, Kang G, Kim M We investigated the combination of human adipose tissue derived stem cells (ADSC) and in vivo gel-forming methoxy poly (ethyleneglycol)-poly (epsilon-caprolactone) (MPEG-PCL) as a muscle regeneration matrix, with and without inclusion of vascular endothelial cell growth factor (VEGF). VEGF(165)-treated stem cell grafts showed significant proliferation and differentiation into muscle tissue in vivo. Importantly, the inclusion of VEGF enhanced vascularization. This scaffold supported preconditioned ADSC, and allowed them to differentiate into mature muscle tissues in vivo, indicating that ADSC of human origin and MPEG-PCL scaffolds provided an appropriate environment for cellular growth and expansion. Our results thus provide a potential solution to the major obstacle encountered in the engineering of thick complex tissues, which require an adequate blood supply to maintain cell viability during tissue growth and to induce appropriate structural organization. Theref! ore, the combination of ADSC and in vivo gel-forming MPEG-PCL with VEGF(165) might serve as a suitable non-invasive biomaterial for clinical muscle regeneration applications. PMID: 19914711 [PubMed - indexed for MEDLINE] | | |
| Immunological response to tissue-engineered cartilage derived from auricular chondrocytes and a PLLA scaffold in transgenic mice.
March 4, 2010 at 6:47 AM
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| | Immunological response to tissue-engineered cartilage derived from auricular chondrocytes and a PLLA scaffold in transgenic mice. Biomaterials. 2010 Feb;31(6):1227-34 Authors: Fujihara Y, Takato T, Hoshi K The immune response against biomaterials in tissue-engineered constructs could potentially worsen the outcome of tissue regeneration, but immunological reactions between host and donor in tissue-engineered constructs remain to be clarified. In the present study, we syngenically transplanted tissue-engineered cartilage constructs consisting of C57BL/6 mice auricular chondrocytes and poly-l-lactic acid scaffolds (MW:200,000) into EGFP transgenic mice of C57BL/6 background, and evaluated the response by the localization of donor-derived and host-derived cells, the latter of which were distinguished by the presence of EGFP. While donor-derived cells constituted the areas of regenerated cartilage, host-derived cells were increased in number for the initial two weeks, and then decreased and excluded to non-cartilage areas thereafter. Furthermore, EGFP positivity was mostly co-localized with that of F4/80, suggesting most of the host-derived cells in the tissue-engineere! d constructs could be macrophages. Immunohistochemical staining of the tissue-engineered cartilage constructs revealed expression of factors related to immune privilege in chondrocytes, such as macrophage migration inhibitory factor (MIF), fas ligand (FasL) and others. Co-culture of chondrocytes and macrophages in vitro increased the expression of MIF and FasL in the chondrocytes, suggesting that chondrocytes in tissue-engineered cartilage constructs could regulate the actions of host-derived macrophages by expressing factors related to immune privilege. PMID: 19913296 [PubMed - indexed for MEDLINE] | | |
| The effect of timing in the administration of hepatocyte growth factor to modulate BMP-2-induced osteoblast differentiation.
March 4, 2010 at 6:47 AM
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| | The effect of timing in the administration of hepatocyte growth factor to modulate BMP-2-induced osteoblast differentiation. Biomaterials. 2010 Feb;31(6):1191-8 Authors: Kawasaki T, Niki Y, Miyamoto T, Horiuchi K, Matsumoto M, Aizawa M, Toyama Y Development of bone morphogenetic protein (BMP) signaling modulators may provide useful therapeutic options for the treatment of large bony defects in clinical settings. Controversy remains over whether hepatocyte growth factor (HGF) is a positive or negative modulator of BMP-induced osteogenesis. This study analyzed osteogenic properties of HGF, particularly during BMP-2-induced bone formation. Using a mouse model of ectopic bone formation, HGF-impregnated gelatin sponges displayed significantly reduced bone formation induced by BMP-2, both radiologically and histologically. Abrogation of endogenous HGF production by knockdown of HGF mRNA resulted in upregulation of BMP-2-induced ALP activity for C2C12 myoblasts in vitro. In contrast, addition of exogenous HGF inhibited BMP-2-induced ALP activity and osteocalcin production by mouse embryonic fibroblasts (MEFs) through HGF-c-Met interactions. Inhibition of ALP activity by HGF was rescued by U0126, a MEK1/2 inhibit! or, indicating that HGF suppresses the BMP-2-Smad axis via activation of ERK1/2. Importantly, treatment with HGF prior to administration of BMP-2 induced cellular proliferation of MEFs and did not influence subsequent osteoblast differentiation induced by BMP-2. The effects of HGF may differ according to the differentiation stage of mesenchymal stem cells, which would explain the inconsistencies seen in osteogenic properties of HGF in previous reports. The timing of HGF treatment is critical and should be carefully determined for successful induction of bone formation by BMPs. PMID: 19913294 [PubMed - indexed for MEDLINE] | | |
| Injectable biodegradable hydrogels with tunable mechanical properties for the stimulation of neurogenesic differentiation of human mesenchymal stem cells in 3D culture.
March 4, 2010 at 6:47 AM
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| | Injectable biodegradable hydrogels with tunable mechanical properties for the stimulation of neurogenesic differentiation of human mesenchymal stem cells in 3D culture. Biomaterials. 2010 Feb;31(6):1148-57 Authors: Wang LS, Chung JE, Chan PP, Kurisawa M We report an injectable hydrogel scaffold system with tunable stiffness for controlling the proliferation rate and differentiation of human mesenchymal stem cells (hMSCs) in a three-dimensional (3D) context in normal growth media. The hydrogels composed of gelatin-hydroxyphenylpropionic acid (Gtn-HPA) conjugate were formed using the oxidative coupling of HPA moieties catalyzed by hydrogen peroxide (H(2)O(2)) and horseradish peroxidase (HRP). The stiffness of the hydrogels was readily tuned by varying the H(2)O(2) concentration without changing the concentration of polymer precursor. We found that the hydrogel stiffness strongly affected the cell proliferation rates. The rate of hMSC proliferation increased with the decrease in the stiffness of the hydrogel. Also, the neurogenesis of hMSCs was controlled by the hydrogel stiffness in a 3D context without the use of any additional biochemical signal. These cells which were cultured in hydrogels with lower stiffness f! or 3 weeks expressed much more neuronal protein markers compared to those cultured within stiffer hydrogels for the same period of time. PMID: 19892395 [PubMed - indexed for MEDLINE] | | |
| Engineering a scaffold-free 3D tumor model for in vitro drug penetration studies.
March 4, 2010 at 6:47 AM
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| | Engineering a scaffold-free 3D tumor model for in vitro drug penetration studies. Biomaterials. 2010 Feb;31(6):1180-90 Authors: Ong SM, Zhao Z, Arooz T, Zhao D, Zhang S, Du T, Wasser M, van Noort D, Yu H Three-dimensional (3D) in vitro cultures are recognized for recapitulating the physiological microenvironment and exhibiting high concordance with in vivo conditions. In cancer research, the multi-cellular tumor spheroid (MCTS) model is an established 3D cancer model that exhibits microenvironmental heterogeneity close to that of tumors in vivo. However, the established process of MCTS formation is time-consuming and often uncontrolled. Here, we report a method for engineering MCTS using a transient inter-cellular linker which facilitates cell-cell interaction. Using C3A cells (a hepatocellular carcinoma cell line) as a model, we formed linker-engineered spheroids which grew to a diameter of 250 microm in 7 days, as compared to 16 days using conventional non-adherent culture. Seven-day old linker-engineered spheroids exhibited characteristics of mature MCTS, including spheroid morphology, gene expression profile, cell-cell interaction, extracellular matrix secreti! on, proliferation and oxygen concentration gradients, and cellular functions. Linker-engineered spheroids also displayed a resistance to drug penetration similar to mature MCTS, with dose-dependent extracellular accumulation of the drug. The linker-engineered spheroids thus provide a reliable accelerated 3D in vitro tumor model for drug penetration studies. PMID: 19889455 [PubMed - indexed for MEDLINE] | | |
| The mechanically enhanced phase separation of sprayed polyurethane scaffolds and their effect on the alignment of fibroblasts.
March 4, 2010 at 6:47 AM
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| | The mechanically enhanced phase separation of sprayed polyurethane scaffolds and their effect on the alignment of fibroblasts. Biomaterials. 2010 Feb;31(6):1126-32 Authors: Kennedy JP, McCandless SP, Lasher RA, Hitchcock RW This paper reports a method to fabricate anisotropic scaffolds of tunable porosity and mechanical properties. Scaffolds were fabricated using a computer controlled sprayed phase separation technique. Following fabrication, the sheets were elongated 0, 35 or 70% of their original length to induce varying degrees of scaffold alignment and anisotropy. The nonsolvent used in the phase separation was shown to affect porosity and the elastic modulus. Mouse embryo NIH-3T3 fibroblasts were cultured on the scaffolds to investigate cell response to the anisotropy of the scaffold. A 2D FFT method was used to quantify cellular alignment. Cells were shown to align themselves with the scaffold. This sheet-like scaffold material can be used in single plys or can be laminated to form porous 3D composite scaffolds. PMID: 19878993 [PubMed - indexed for MEDLINE] | | | | 
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