|  |  |  | | | | | TE-RegenMed-StemCell feed | | | | | | | | | | | | | | | | | | Scientist Martin Pera said tonight that he was departing as head of the USC stem cell research program for both personal reasons and an opportunity to help lead a national consortium in Australia.
Pera also said that disposition of the $7.4 million in grants from CIRM in which he is the principal investigator is under discussion with the agency, USC and himself.
Pera came to California in | | | | | | | | | | | | | | | | | | | | | | | | Internationally reknown stem cell researcher Martin Pera, who holds $7.4 million in California stem cell grants, is leaving the state to return to Australia to head the stem cell program at the University of Melbourne.
Martin Pera
USC Photo
In a March 7 memo to staff at USC's Keck School of Medicine, Dean Carmen Puliafito said that Pera will assume his new job in Australia on June 1 but plans | | | | | | | | | | | | | | | | | | | | | | | | | Protection of murine neural progenitor cells by the Hsp90 inhibitor 17-Allylamino-17-demethoxygeldanamycin in the low nanomolar concentration range. J Neurochem. 2011 Mar 11; Authors: Wang G, Krishnamurthy K, Tangpisuthipongsa D Stem cell-based approaches provide hope as a potential therapy for neurodegenerative diseases and stroke. One of the major scientific hurdles for stem cell therapy is the poor survival rate of the newly formed or transplanted neural stem cells. In this study, we found that low-dose treatment with the Hsp90 inhibitor 17-Allylamino-17-demethoxygeldanamycin (17-AAG), a heavily investigated anti-cancer drug, prevented neural progenitor cells from either naturally-occurring or stress-induced (β-amyloid and ceramide) apoptosis, although it induced apoptosis at higher doses. This stress adaptation (hormesis) effect mediated by low-dose 17-AAG is accompanied by activation of multiple cell survival pathways, including the stress response pathway (induction of Hsp70), the MAP kinase pathway, and the PI3K/Akt pathway. When administered in vivo, 17-AAG led to Akt and GSK-3β phosphorylation, and more BrDU positive cells in the mouse brain. These findings could have profound implications in stem cell therapy for neurodegenerative diseases and stroke. PMID: 21395580 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | The California Stem Cell Report has grumped mightily about the lackdaisical posting of important public information about matters that are to come before the directors of the $3 billion California stem agency.
Today, however, we are pleased to report that CIRM performed much better in advance of last week's meeting. Agency staffers should take some pride in that accomplishment.
We are | | | | | | | | | | | | | | | | | | | | | | | | | [The future of clinical medicine in new therapies: cell, gene and nanomedicine.] Med Clin (Barc). 2011 Mar 10; Authors: Gálvez P, Ruiz A, Clares B Advanced therapies provide a new concept of personalized medicament of autologous, allogeneic or xenogeneic origin, based on cells (cell therapy), genes (gene therapy) or tissues (tissue engineering), which, together with nanosystems, provide new advances in the diagnosis, prevention and treatment of diseases. The basis and different fields of action of cell therapy, gene therapy and nanomedicine are described in this review. PMID: 21397281 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Induced human pluripotent stem cells and advanced therapies Future perspectives for the treatment of haemophilia? Thromb Res. 2011 Mar 9; Authors: Liras A Human induced pluripotent stem cells (iPSCs) have revolutionized the stem cell field. These iPSCs from somatic cells have been reprogrammed with the introduction of transcription factors and are capable to differentiate into cells from all three germ layers. These strategies require retrovirus transduction or transfection of plasmid vectors strategy without viral transduction. Another promising strategy is based on direct delivery of the reprogramming proteins, addition of signal transduction inhibitors and chemical promoter cell survival. The main advantages of iPSCs cells are that they have not included in the debate over the ethics of embryonic stem cell. Current therapy of haemophilia is based on factor VIII (FVIII) or factor IX (FIX) replacement therapy including prophylactic or demand protocols of fixed-dose, and as future alternative, gene and cell therapy. Gene therapy can be made by using viral vectors, mainly lentiviral (LVV) and adeno-associated viruses (AAV) in adult stem cells and autologous fibroblasts, platelets or haematopoietic stem cells, and transfer using non-viral vectors (NVV). Cell therapy for haemophilia is based, mainly, in transplantation of healthy cells to replace the deficient function, for example, the transplantation of liver sinusoidal endothelial cells or endothelial progenitor cells derived from iPSCs. Recently, as first time in haemophilia, endothelial progenitor cells derived from iPSCs cells express FVIII protein effectively, engraft within the hepatic parenchyma, and functionally integrate to provide the therapeutic benefit for a phenotypic correction in haemophilia. Advanced therapies, gene and cell therapy and tissue engineering or iPSCs technology, can provide a potential clinical application in the treatment of haemophilia and other monogenic disorders. Because to date there are not relevant results for phenotypic correction in haemophilia, iPSCs technology could represent a potential alternative based on cellular therapy. PMID: 21396685 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Ectopic bone formation from mandibular osteoblasts cultured in a novel human serum-derived albumin scaffold. J Biomater Appl. 2010 Nov;25(4):367-81 Authors: Gallego L, Junquera L, Meana A, Alvarez-Viejo M, Fresno M The aim of this study was to evaluate the ectopic bone formation using a novel serum-derived albumin scaffold and cultured human mandibular osteoblasts in nude mice. Osteoblasts were cultured with 10% human serum and plated in a novel spongy noncalcified protein scaffold prepared with plasmatic albumin crossed with a glutaraldehyde type agent. Hematoxylin-eosin staining revealed a bone-like extracellular matrix and in vitro mineralization was confirmed by von Kossa staining. Histological and immunohistochemical evaluation showed progression of mineralization in vivo. These results suggest the clinical feasibility of alveolar cells and albumin scaffold as a good alternative for bone regeneration. PMID: 20008085 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | The Use of Poly(L-lactide-co-caprolactone) as a Scaffold for Adipose Stem Cells in Bone Tissue Engineering: Application in a Spinal Fusion Model. Macromol Biosci. 2011 Mar 11; Authors: Vergroesen PP, Kroeze RJ, Helder MN, Smit TH Since the early 1990s, tissue engineering has been heralded as a strategy that may solve problems associated with bone grafting procedures. The original concept of growing bone in the laboratory, however, has proven illusive due to biological, logistic, and regulatory problems. Fat-derived stem cells and synthetic polymers open new, more practicable routes for bone tissue engineering. In this paper, we highlight the potential of poly(L-lactide-co-caprolactone) (PLCL) to serve as a radiolucent scaffold in bone tissue engineering. It appears that PLCL quickly and preferentially binds adipose stem cells (ASCs), which proliferate rapidly and eventually differentiate into the osteogenic phenotype. An in vivo spinal fusion study in a goat model provides a preclinical proof-of-concept for a one-step surgical procedure with ASCs in bone tissue engineering. PMID: 21400658 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Electrospun scaffolds for bone tissue engineering. Musculoskelet Surg. 2011 Mar 12; Authors: Di Martino A, Liverani L, Rainer A, Salvatore G, Trombetta M, Denaro V Tissue engineering aims to regenerate native tissues and will represent the alternative choice of standard surgery for different kind of tissue damages. The fundamental basis of tissue engineering is the appropriate selection of scaffolds and their morphological, mechanical, chemical, and biomimetic properties, closely related to cell lines that will be seeded therein. The aim of this review is to summarize and report the innovative scientific contributions published in the field of orthopedic tissue engineering, in particular about bone tissue engineering. We have focused our attention on the electrospinning technique, as a scaffold fabrication method. Electrospun materials are being evaluated as scaffolds for bone tissue engineering, and the results of all these studies clearly indicate that they represent suitable potential substrates for cell-based technologies. PMID: 21399976 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Engineering of cartilage in recombinant human type II collagen gel in nude mouse model in vivo. Osteoarthritis Cartilage. 2010 Aug;18(8):1077-87 Authors: Pulkkinen HJ, Tiitu V, Valonen P, Jurvelin JS, Lammi MJ, Kiviranta I Our goal was to test the recombinant human type II collagen (rhCII) material as a gel-like scaffold for chondrocytes in a nude mouse model in vivo. PMID: 20472086 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | A Novel Nanoparticle-Enhanced Ph0toacoustic Stimulus for Bone Tissue Engineering. Tissue Eng Part A. 2011 Mar 12; Authors: Sitharaman B, Avti PK, Schaefer K, Talukdar Y, Longtin JP In this study, we introduce a novel nanoparticle-enhanced biophysical stimulus based on the photoacoustic (PA) effect. We demonstrate that the PA effect differentiates bone marrow-derived marrow stromal cells (MSCs) grown on poly(lactic-co-glycolic acid) (PLGA) polymer films towards osteoblasts. We further show that the osteodifferentiation of the MSCs due to PA stimulation is significantly enhanced by the presence of single-walled carbon nanotubes (SWCNTs) in the polymer. MSCs, without the osteogenic culture supplements (0.01 M β-glycerophosphate, 50 mg/L ascorbic acid, 10<sup>-8</sup> M dexamethasone), were seeded onto plain glass slides, glass slides coated with PLGA or glass slides coated with SWCNT-PLGA films and photoacoustically stimulated by a 527 nm Nd:YLF pulse laser, with a 200 ns pulse duration and 10 Hz pulse frequency for 10 minutes a day for 15 consecutive days. The study had four control groups; three baseline controls similar to the three experimental groups but without PA stimulation, and one positive control where MSCs were grown on glass slides without PA stimulation but with osteogenic culture supplements. The osteogenic differentiation of all the groups were evaluated using quantitative assays (alkaline phosphatase, calcium, osteopontin), and qualitative staining (alizarin red). After 15 days, the PA stimulated groups showed up to a 350% increase in calcium content when compared to the non-PA stimulated positive control. Further, within the PA stimulated group, the PLGA-SWCNT group had 130% higher calcium values than the PLGA film without SWCNTs. These results were further corroborated by the analysis of osteopontin secretion, alkaline phosphatase expression, and qualitative alizarin red staining of extracellular matrix calcification. The results indicate that PA stimulation holds promise for bone tissue engineering, and that the nanomaterials that enhance the PA effect should allow the development of biophysical rather than biochemical strategies to induce osteoinductive properties into tissue engineering scaffolds. PMID: 21395444 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Calcium phosphate nanoparticles as gene therapy vectors show the advantage for short-term hard tissue formation when compared with adenovirus. Acta Biomater. 2011 Mar 9; Authors: Yang X, Walboomers XF, Bian Z, Jansen JA, Fan M Calcium phosphate nanoparticles show potential as non-viral vectors for gene delivery. The aim of this study was to evaluate the feasibility and efficacy of this vector for hard tissue engineering, when compared with adenoviral vector. Nanoparticles encapsulating plasmid DNA (pEGFP-BMP2) were prepared. Then, dental pulp stem cells were transfected using nanoparticles or adenovirus and seeded onto a porous ceramic scaffold. The cell-scaffold complexes were implanted subcutaneously and then retrieved after 2, 4 and 8 weeks for histology evaluation. In vitro results indicated that nanoparticle was lower transfection efficiency but lower cytotoxicity compared with adenovirus. In vivo biocompatibility test showed minimal inflammatory response for nanoparticle group within 8 weeks' subcutaneous implantation in mice compared with adenovirus group. Histological observation demonstrated that the cultures with nanoparticle transfection can form hard tissue. Histomorphometrically, the nanoparticle group indicated higher (2 weeks) and similar (4 weeks) efficacy for hard tissue formation compared with adenovirus group, although less than that for 8 week's implantation period. In conclusion, pDNA-loaded calcium phosphate nanoparticles appear to be a candidate for gene therapy vector, and show the advantage for short-term hard tissue formation compared with adenovirus. PMID: 21397056 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Transcriptome-wide gene regulation by gentle treadmill walking during the progression of monoiodoacetate induced arthritis. Arthritis Rheum. 2011 Mar 11; Authors: Nam J, Perera P, Liu J, Wu LC, Rath B, Butterfield TA, Agarwal S OBJECTIVE.: Physiotherapies are the most widely recommended conservative treatment options for arthritic diseases. Here we examined the molecular mechanisms underlying the effects of gentle treadmill walking (GTW) on various stages of monoiodoacetate-induced arthritis (MIA) to unravel the basis for the success or failureof such therapies on the damaged joints. METHODS.: Rat knees were harvested from untreated control, MIA afflicted but not subjected to GTW, GTW regimens started one day post-MIA induction, or after cartilage damage had progressed to Grade 1 or Grade 2. The cartilage was examined by macroscopic, microscopic, µCT imaging and transcriptome-wide gene expression analysis. Microarray data was analyzed by Ingenuity Pathways Analysis to construct molecular functional networks regulated by GTW. RESULTS.: GTW intervention started on day 1 post-MIA induction significantly prevented the MIA progression, but its efficacy was reduced when implemented on the knees exhibiting close to Grade 1 cartilage damage. However, GTW accelerated damage in the knees with close to Grade 2 cartilage pathologies. Transcriptome-wide gene expression analysis revealed that GTW intervention started one day post-MIA inception significantly suppressed inflammation-associated genes and upregulated matrix associated gene networks. However, delayed GTW intervention following Grade 1 damage was less effectivein suppressing proinflammatory genes or upregulating matrix synthesis. CONCLUSION.: The findings suggest that GTW suppresses proinflammatory gene networks and upregulates matrix synthesis to prevent progression of cartilage damage in MIA afflicted knees. However, the extent of cartilage damage at the initiation of GTW may be an important determinant for the success or failure of such therapies. PMID: 21400474 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Multiphoton microscopy of engineered dermal substitutes: assessment of 3-D collagen matrix remodeling induced by fibroblast contraction. J Biomed Opt. 2010 Sep-Oct;15(5):056018 Authors: Pena AM, Fagot D, Olive C, Michelet JF, Galey JB, Leroy F, Beaurepaire E, Martin JL, Colonna A, Schanne-Klein MC Dermal fibroblasts are responsible for the generation of mechanical forces within their surrounding extracellular matrix and can be potentially targeted by anti-aging ingredients. Investigation of the modulation of fibroblast contraction by these ingredients requires the implementation of three-dimensional in situ imaging methodologies. We use multiphoton microscopy to visualize unstained engineered dermal tissue by combining second-harmonic generation that reveals specifically fibrillar collagen and two-photon excited fluorescence from endogenous cellular chromophores. We study the fibroblast-induced reorganization of the collagen matrix and quantitatively evaluate the effect of Y-27632, a RhoA-kinase inhibitor, on dermal substitute contraction. We observe that collagen fibrils rearrange around fibroblasts with increasing density in control samples, whereas collagen fibrils show no remodeling in the samples containing the RhoA-kinase inhibitor. Moreover, we show that the inhibitory effects are reversible. Our study demonstrates the relevance of multiphoton microscopy to visualize three-dimensional remodeling of the extracellular matrix induced by fibroblast contraction or other processes. PMID: 21054112 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Epidermal differentiation governs engineered skin biomechanics. J Biomech. 2010 Dec 1;43(16):3183-90 Authors: Ebersole GC, Anderson PM, Powell HM Engineered skin must be mechanically strong to facilitate surgical application and prevent damage during the early stages of engraftment. However, the evolution of structural properties during culture, the relative contributions of the epidermis and dermis, and any correlation with tissue morphogenesis are not well known. These aspects are investigated by assessing the mechanical properties of engineered skin (ES) and engineered dermis (ED) during a 21-day culture period, including correlations with cellular metabolism, cellular organization and epidermal differentiation. During culture, the epidermis differentiates and begins to cornify, as evidenced by immunostaining and surface electrical capacitance. Tensile testing reveals that the ultimate tensile strength and linear stiffness increase linearly with time for ES, but are relatively unchanged for ED. ES strength correlates significantly with epidermal differentiation (p < 0.001) and a composite strength model indicates that strength is largely determined by the epidermis. These data suggest that strategies to improve ES biomechanics should target the dermis. Additionally, time-dependant changes in average ES strength and percent elongation can be used to set upper bound limits on mechanical stimulation profiles to avoid tissue damage. PMID: 20723899 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Vascularization is the key challenge in tissue engineering. Adv Drug Deliv Rev. 2011 Mar 8; Authors: Novosel EC, Kleinhans C, Kluger PJ The main limitation in engineering in vitro tissues is the lack of a sufficient blood vessel system - the vascularization. In vivo almost all tissues are supplied by these endothelial cell coated tubular networks. Current strategies to create vascularized tissues are discussed in this review. The first strategy is based on the endothelial cells and their ability to form new vessels known as neoangiogenesis. Herein prevascularization techniques are compared to approaches in which biomolecules, such as growth factors, cytokines, peptides and proteins as well as cells are applied to generate new vessels. The second strategy is focused on scaffold-based techniques. Naturally-derived scaffolds, which contain vessels, are distinguished from synthetically manufactured matrices. Advantages and pitfalls of the approaches to create vascularized tissues in vitro are outlined and feasible future strategies are discussed. PMID: 21396416 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Development of a total atherosclerotic occlusion with cell-mediated calcium deposits in a rabbit femoral artery using tissue-engineering scaffolds. J Tissue Eng Regen Med. 2011 Mar 13; Authors: Zhu B, Bailey SR, Elliott J, Li X, Escobar GP, Rodriguez EM, Agrawal CM This study sought to establish a chronic total occlusion (CTO) model with cell-mediated calcium deposits in rabbit femoral arteries. CTO is the most severe case in atherosclerosis and contains calcium deposits. Previous animal models of CTO do not mimic the gradual occlusion of arteries or have calcium in physiological form. In the present study we tested the strategy of placing tissue-engineering scaffolds preloaded with cells in arteries to develop a novel CTO model. Primary human osteoblasts (HOBs) were first cultured in vitro on polycaprolactone (PCL) scaffolds with 5 ng TGFβ1 loading for 28 days for precalcification. The HOB-PCL construct was then implanted into a rabbit femoral artery for an additional 3, 10 or 28 days. At the time of sacrifice, angiograms and gross histology of arteries were captured to examine the occlusion of arteries. Fluorescent staining of calcium and EDS detection of calcium were used to evaluate the presence and distribution of calcium inside arteries. Rabbit femoral arteries were totally occluded over 28 days. Calcium was presented at CTO sites at 3, 10 and 28 days, with the day 10 specimens showing the maximum calcium. Chronic inflammatory response and recanalization were observed in day 28 CTO sites. A novel CTO model with cell-mediated calcium has been successfully established in a rabbit femoral artery. This model can be used to develop new devices and therapies to treat severe atherosclerotic occlusion. Copyright © 2011 John Wiley & Sons, Ltd. PMID: 21400666 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Spherical N-carboxyethylchitosan/hydroxyapatite nanoparticles prepared by ionic diffusion process in a controlled manner. J Mater Sci Mater Med. 2010 Dec;21(12):3095-101 Authors: Zhu A, Lu Y, Zhou Y, Dai S The nanocomposites containing hydroxyapatite (HA) and biomacromolecules have attracted considerable research interest in implants, tissue scaffolds and drug controlled delivery. In this study, the N-carboxyethylchitosan/hydroxyapatite (NCECS/HA) nanoparticles were prepared by the ionic diffusion process in a controlled manner. The crystallization, particle size, size distribution and aggregation morphology of the NCECS/HA nanocomposites were dependent on the mole ratio of the glucosamine unit in NCECS to the Ca(2+). Fourier transform-infrared spectroscopic (FTIR) result indicated that there are chemical bonds formed between NCECS and HA. X-ray diffraction (XRD) analysis showed that the crystallization of HA in NCECS matrix was significantly retarded. Transmission electron microscopy (TEM) results revealed that NCECS/HA nanocomposites have the spherical morphology with the diameter ranging from 10 to 40 nm. The NCECS mineralization is driven by the self-assembly of NCECS and HA. These NCECS/HA nanocomposites have potential applications as the carrier for the controlled delivery of growth factors and drugs. PMID: 20890642 [PubMed - indexed for MEDLINE] | | | | | | | | | | | | | | | | | | | | | | | | | Accelerating Vascularization in Polycaprolactone Scaffolds by Endothelial Progenitor Cells. Tissue Eng Part A. 2011 Mar 12; Authors: Singh S, Wu B, Dunn J Vascularization is a major challenge in tissue engineering. The purpose of this study is to expedite the formation of blood vessels in porous polycaprolactone (PCL) scaffolds by the delivery of endothelial progenitor cells (EPCs). To establish a pro-angiogenic and pro-vasculogenic microenvironment, we employed EPCs seeded in PCL scaffold with surface-immobilized heparin and vascular endothelial growth factor (VEGF). EPCs seeded on scaffolds with VEGF exhibited phosphorylation of the receptor. After 7 days of subcutaneous implantation in immunodeficient mice, heparin-immobilized PCL scaffolds with VEGF induced significantly high density of blood vessel formation. The anastomosis of EPC-derived vessels with the host circulatory system was evident by the presence of murine erythrocytes in the lumen of human-CD31 positive vessels. A more uniform distribution of blood vessels was achieved within 2-mm thick scaffolds by seeding an optimal density of EPCs. The seeding of a higher density of EPC resulted in an increase in apoptosis and a concomitant decline in blood vessel formation at the scaffold's inner core. When co-seeded with other cells, the EPCs maintained the ability to accelerate vessel formation. The excessive expansion of EPCs in vitro was associated with a decline in their in vivo vasculogenic potential. EPCs accelerated the vascularization of heparin-immobilized PCL scaffolds in the presence of VEGF. PMID: 21395445 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | The effect of matrix stiffness on the differentiation of mesenchymal stem cells in response to TGF-β Biomaterials. 2011 Mar 11; Authors: Park JS, Chu JS, Tsou AD, Diop R, Tang Z, Wang A, Li S Bone marrow mesenchymal stem cells (MSCs) are a valuable cell source for tissue engineering and regenerative medicine. Transforming growth factor β (TGF-β) can promote MSC differentiation into either smooth muscle cells (SMCs) or chondrogenic cells. Here we showed that the stiffness of cell adhesion substrates modulated these differential effects. MSCs on soft substrates had less spreading, fewer stress fibers and lower proliferation rate than MSCs on stiff substrates. MSCs on stiff substrates had higher expression of SMC markers α-actin and calponin-1; in contrast, MSCs on soft substrates had a higher expression of chondrogenic marker collagen-II and adipogenic marker lipoprotein lipase (LPL). TGF-β increased SMC marker expression on stiff substrates. However, TGF-β increased chondrogenic marker expression and suppressed adipogenic marker expression on soft substrates, while adipogenic medium and soft substrates induced adipogenic differentiation effectively. Rho GTPase was involved in the expression of all aforementioned lineage markers, but did not account for the differential effects of substrate stiffness. In addition, soft substrates did not significantly affect Rho activity, but inhibited Rho-induced stress fiber formation and α-actin assembly. Further analysis showed that MSCs on soft substrates had weaker cell adhesion, and that the suppression of cell adhesion strength mimicked the effects of soft substrates on the lineage marker expression. These results provide insights of how substrate stiffness differentially regulates stem cell differentiation, and have significant implications for the design of biomaterials with appropriate mechanical property for tissue regeneration. PMID: 21397942 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | Endothelial Smad4 Maintains Cerebrovascular Integrity by Activating N-Cadherin through Cooperation with Notch. Dev Cell. 2011 Mar 15;20(3):291-302 Authors: Li F, Lan Y, Wang Y, Wang J, Yang G, Meng F, Han H, Meng A, Wang Y, Yang X Cerebrovascular dysfunction is strongly associated with neonatal intracranial hemorrhage (ICH) and stroke in adults. Cerebrovascular endothelial cells (ECs) play important roles in maintaining a stable cerebral circulation in the central nervous system by interacting with pericytes. However, the genetic mechanisms controlling the functions of cerebral ECs are still largely unknown. Here, we report that disruption of Smad4, the central intracellular mediator of transforming growth factor-β (TGF-β) signaling, specifically in the cerebral ECs, results in perinatal ICH and blood-brain barrier breakdown. Furthermore, the mutant vessels exhibit defective mural cell coverage. Smad4 stabilizes cerebrovascular EC-pericyte interactions by regulating the transcription of N-cadherin through associating with the Notch intracellular complex at the RBP-J binding site of the N-cadherin promoter. These findings uncover a distinct role of endothelial Smad4 in maintaining cerebrovascular integrity and suggest important implications for genetic or functional deficiencies in TGF-β/Smad signaling in the pathogenesis of cerebrovascular dysfunction. PMID: 21397841 [PubMed - in process] | | | | | | | | | | | | | | | | | | | | | | | | | Bypassing the patient: Comparison of biocompatible models for the future of vascular tissue engineering. Cell Transplant. 2011 Mar 9; Authors: Phd KL The objective of vascular tissue engineering is to develop tissue-engineered, biocompatible, small-diameter vessels suitable to withstand in vivo systolic pressures as well as be immunologically compatible with the patient, in order to minimize graft rejection. In this study, we present and compare two models of biocompatible, tissue-engineered vascular grafts (TEVG), using chitosan and acellularized rat aortas as options for scaffolds. Human aortic adventitial smooth muscle cells and fibroblasts were seeded onto a fibrin gel and subsequently wrapped around either of the two scaffolds. After several weeks of maturation in standard culturing conditions, the graft models were analyzed and compared by mechanical testing, cell viability, and histology. Histological and viability data showed that both models were viable and developed similarly, with a scaffold surrounded by two layers of cells, the fibroblasts lying on top of the smooth muscle cells. Both models responded to 200mM potassium chloride (KCl) (tensions of 38 ± 3μN, 78 ± 13μN, and 52 ± 7μN) and 25mM 8-bromo-cyclic AMP (tensions of -23 ± 4μN, -39 ± 10μN, and -31 ± 12μN) stimulation by vasoconstriction and vasorelaxation (n=3), respectively; however, the chitosan model was unable to maintain the contracted and relaxed tension. Because the acellularized-aorta TEVGs were able to maintain stimulated tension better than chitosan TEVGs, we concluded that the acellularized aorta model was better suited for further development. PMID: 21396173 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | EFfect of PCL Scaffold Permeability on Bone Regeneration In Vivo. Tissue Eng Part A. 2011 Mar 12; Authors: Mitsak AG, Kemppainen JM, Harris MT, Hollister S Successful bone tissue engineering depends on the scaffold's ability to deliver nutrients to the regeneration site, remove waste products and provide an appropriate mechanical environment. Since bone is highly vascularized, scaffolds that provide greater mass transport may support increased bone regeneration. Permeability encompasses the salient features of 3D porous scaffold architecture effects on scaffold mass transport. We hypothesized that higher permeability scaffolds will enhance bone regeneration for a given cell seeding density. We manufactured poly-ε-caprolactone scaffolds, designed to have the same internal pore design and either a "low" permeability (0.688 x 10^-7 m^4/N-s) or a "high" permeability (3.991 x 10^-7 m^4/N-s). Scaffolds were seeded with BMP-7-transduced human gingival fibroblasts and implanted subcutaneously into immuno-compromised mice for four and eight weeks. Micro-CT evaluation showed better bone penetration into high permeability scaffolds, with blood vessel infiltration visible at 4 weeks. Compression testing showed that scaffold design had more influence on elastic modulus than time point did and that bone tissue infiltration increased the mechanical properties of the high permeability scaffolds at eight weeks. These results suggest that for polycaprolactone, a more permeable scaffold with regular architecture is best for in vivo bone regeneration. This finding is an important step toward the end goal of optimizing a scaffold for bone tissue engineering. PMID: 21395465 [PubMed - as supplied by publisher] | | | | | | | | | | | | | | | | | | | | | | | | | The effect of poly (L-lactic acid) nanofiber orientation on osteogenic responses of human osteoblast-like MG63 cells. J Mech Behav Biomed Mater. 2011 May;4(4):600-9 Authors: Wang B, Cai Q, Zhang S, Yang X, Deng X In this study, poly (L-lactic acid) (PLLA)/trifluoroethanol (TFE) solution was electrospun to fabricate fibrous scaffolds with different fiber orientations. Random and parallel PLLA nanofiber alignments were achieved by using a metal plate and a rolling rod as the receiver, respectively. The parallel PLLA fibrous scaffolds were further hot-stretched to obtain hyperparallel PLLA fibrous scaffolds. The PLLA fibrous scaffolds were characterized by fiber diameter, interfiber distance, fiber array angle, water contact angle, morphology and mechanical strength. The tensile strength of hyperparallel nano-fibers was approximately 5- and 14-times the parallel and random fibers, respectively. Osteoblast-like MG63 cells were cultured on the PLLA scaffolds to study the effects of fiber orientation on cell morphology, proliferation and differentiation. The cells on the randomly-oriented scaffolds showed irregular forms, while the cells exhibited shuttle-like shapes on the parallel scaffolds and had larger aspect ratios along the fiber direction of the hyperparallel scaffolds. Alkaline phosphatase (ALP) activity and collagen I (placeStateCol I) and osteocalcin (OC) deposition exhibited fiber orientation dependence. With an increase in parallelism of the fibers, there was a decrease in ALP activity and placeStateCol I and OC production. These results suggest that exploitation of PLLA fiber orientation may be used to control osteoblast-like cell responses. PMID: 21396609 [PubMed - in process] | | | | | | | | | |  | |  | |  |
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