D Benayahu

Tel Aviv University, Tell Afif, Tel Aviv, Israel

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Publications (92)282.74 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel collagen-based bio-composite was constructed from micro-crimped long collagen fiber bundles extracted from a soft coral embedded in alginate hydrogel matrix. The mechanical features of this bio-composite were studied for different fiber fractions and in longitudinal and transverse loading modes. The tensile modulus of the alginate hydrogel was 0.60±0.35MPa and in longitudinal collagen-reinforced construct it increased up to 9.71±2.80 for 50% fiber fraction. Ultimate tensile strength was elevated from 0.08±0.04MPa in matrix up to 1.21±0.29 for fiber fraction of 30%. The bio-composite demonstrated hyperelastic behavior similar to human native tissues. Additionally, a dedicated constitutive material model was developed to enable the prediction of the longitudinal mechanical behavior of the bio-composite. These findings will allow tailor-designed mechanical properties with a quantitatively controlled amount of fibers and their designed spatial arrangement. This unique bio-composite has the potential to be used for a wide range of engineered soft tissues.
    Journal of the mechanical behavior of biomedical materials. 04/2014; 36C:71-81.
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    ABSTRACT: Adipogenesis, a process of cell proliferation followed by the accumulation of lipid droplets (LDs), is accompanied by morphological changes in adipocytes, leading to a gradual rise in the structural stiffness of these cells. The increase in cellular structural stiffness can potentially influence the localized deformations of adjacent adipocytes in weight-bearing fat tissues, which, based on previous work, may accelerate intracytoplasmatic lipid production to form even larger and more tightly packed intracellular LDs. This process is based on mechanotransduction phenomena which are hypothesized (again, following empirical studies), to play a critical role in "en mass" adipocyte hypertrophy, and hence are important to characterize through computational modeling. Accordingly, we examined here how maturing adipocytes may affect localized loads acting on adjacent immature cells, using a set of finite element models of adipocytes embedded in an extracellular matrix. The peak strain energy density at the plasma membrane (PM) of the adipocytes, when constructs were externally loaded, was found to depend on the levels of lipid accumulation in the neighboring cells if the external compressive and shear deformations were large enough ([Formula: see text] and [Formula: see text], respectively). The mechanosignaling transduces through the PM and could therefore affect intracellular pathways to produce more lipid contents. Our results support the theory of deformation-induced differentiation in adipocytes. The findings are thus relevant in the context of a sedentary lifestyle, in which sustained deformations of weight-bearing adipose tissues may activate a positive feedback loop that promotes the "en mass" differentiation of cells, which subsequently increases the total mass of living fat tissues.
    Biomechanics and Modeling in Mechanobiology 04/2014; · 3.33 Impact Factor
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    ABSTRACT: Adipogenesis and increase in fat tissue mass are mechanosensitive processes and hence should be influenced by the mechanical properties of adipocytes. We evaluated subcellular effective stiffnesses of adipocytes using atomic force microscopy (AFM) and interferometric phase microscopy (IPM), and we verified the empirical results using finite element (FE) simulations. In the AFM studies, we found that the mean ratio of stiffnesses of the lipid droplets (LDs) over the nucleus was 0.83 ± 0.14, from which we further evaluated the ratios of LDs over cytoplasm stiffness, as being in the range of 2.5 to 8.3. These stiffness ratios, indicating that LDs are stiffer than cytoplasm, were verified by means of FE modeling, which simulated the AFM experiments, and provided good agreement between empirical and model-predicted structural behavior. In the IPM studies, we found that LDs mechanically distort their intracellular environment, which again indicated that LDs are mechanically stiffer than the surrounding cytoplasm. Combining these empirical and simulation data together, we provide in this study evidence that adipocytes stiffen with differentiation as a result of accumulation of LDs. Our results are relevant to research of adipose-related diseases, particularly overweight and obesity, from a mechanobiology and cellular mechanics perspectives.
    Biophysical Journal 03/2014; 106(6):1421-31. · 3.67 Impact Factor
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    ABSTRACT: A novel collagen-based bio-composite was constructed from micro-crimped long collagen fiber bundles extracted from a soft coral embedded in alginate hydrogel matrix. The mechanical features of this bio-composite were studied for different fiber fractions and in longitudinal and transverse loading modes. The tensile modulus of the alginate hydrogel was 0.60±0.35 MPa and in longitudinal collagen-reinforced construct it increased up to 9.71±2.80 for 50% fiber fraction. Ultimate tensile strength was elevated from 0.08±0.04 MPa in matrix up to 1.21±0.29 for fiber fraction of 30%. The bio-composite demonstrated hyperelastic behavior similar to human native tissues. Additionally, a dedicated constitutive material model was developed to enable the prediction of the longitudinal mechanical behavior of the bio-composite. These findings will allow tailor-designed mechanical properties with a quantitatively controlled amount of fibers and their designed spatial arrangement. This unique bio-composite has the potential to be used for a wide range of engineered soft tissues.
    Journal of the Mechanical Behavior of Biomedical Materials 01/2014; 36:71–81. · 2.37 Impact Factor
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    ABSTRACT: Promising treatment approaches in repairing tissue defects include implementation of regenerative medicine strategies, particularly delivery of preadipocytes to sites where adipose tissue damage needs to be repaired or where fat needs to be generated. In this study, we suggest that the injectable hyaluronic acid/adipic acid dihydrazide (HA/ADH) hydrogel may be an adipose-tissue-like material in terms of biological compatibility as well as mechanical behavior. First, we show that the hydrogel enables and supports growth, proliferation and differentiation of 3T3-L1 preadipocytes. Second, given that adipose tissue is a weight-bearing biological structure, we investigate the large deformation mechanical behavior of the hydrogel with and without embedded preadipocytes, by performing confined and unconfined compression tests and then calibrating a strain energy density (SED) function to the results. Four test groups were examined: (1) Hydrogel specimens right after the preparation without cells, (2) and (3) 3-days-cultured hydrogel specimens with and without cells, respectively, and (4) 6-days-cultured hydrogel specimens with cells. A one-term Ogden SED was found to adequately describe the hyperelastic behavior of the hydrogel specimens in all experimental groups. Importantly, we found that the mechanical properties of the hydrogel, when subjected to compression, are in good agreement with those of native adipose tissue, with the better fit occurring 3-6 days after preparation of the hydrogel. Third, computational finite element studies of the mechanical (stress-strain) behavior of the HA/ADH hydrogel when containing mature adipocytes indicated that the stiffnesses of the constructs were mildly affected by the presence of the adipocytes. Hence, we conclude that injectable HA/ADH hydrogel may serve as a vessel for protecting preadipocytes during, and at a short-term after delivery to native tissues, e.g. in research towards regenerative medicine in tissue reconstructions.
    Journal of the mechanical behavior of biomedical materials. 08/2013; 28C:320-331.
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    ABSTRACT: Satellite cells, myogenic progenitors located at the myofiber surface, are essential for repair of adult skeletal muscle. There is ample evidence for age-linked decline in satellite cell numbers and performance in limb muscles. Hence, effective means to activate and expand the satellite cell pool may enhance muscle maintenance and reduce the impact of age-associated muscle deterioration (sarcopenia). Toward this aim, we explored the potential beneficial effect of endurance exercise on satellite cells in young and old mice. Animals were subjected to an 8-week moderate-intensity treadmill running approach that does not inflict apparent muscle damage (0o inclination, 11.5 meter/min, 30 min/day, 6 days/week). Myofibers of extensor digitorum longus muscles were then isolated from exercised and sedentary mice and used for monitoring satellite cell numbers and for harvesting individual satellite cells for clonal growth assays. We specifically focused on satellite cell pools of single myofibers, with the view that daily ware of muscles is likely inflicting individual myofibers rather than causing overall muscle damage. We found an expansion of the satellite cell pool in the exercised groups compared with the sedentary groups, with the same increase factor (~1.6) in both age groups. Current results accord with our findings with rat gastrocnemius, attesting for the consistent effect of exercise running on satellite cell expansion in limb muscles. The experimental paradigm established here is useful for studying satellite cell dynamic at the myofiber niche and for broader investigation of the impact of physiologically and pathologically relevant factors on adult myogenesis. © 2013 The Authors Journal compilation © 2013 FEBS.
    FEBS Journal 03/2013; · 4.25 Impact Factor
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    ABSTRACT: We studied the effects of chronic angiotensin 1-7 (Ang 1-7) treatment in an experimental model of the metabolic syndrome, i.e., rats given high-fructose/low-magnesium diet (HFrD). Rats were fed on HFrD for 24 weeks with and without Ang 1-7 (576 µg/kg/day, s.c., Alzet pumps). After 6 months, Ang 1-7-treated animals had lower body weight (-9.5%), total fat mass (detected by magnetic resonance imaging), and serum triglycerides (-51%), improved glucose tolerance, and better insulin sensitivity. Similar metabolic effects were also evident, albeit in the absence of weight loss, in rats first exposed to HFrD for 5 months and then subjected to short-term (4 weeks) treatment with Ang 1-7. Six months of Ang 1-7 treatment were associated with lower plasma renin activity (-40%) and serum aldosterone (-48%), less hepatosteatatitis, and a reduction in epididymal adipocyte volume. The marked attenuation of macrophage infiltration in white adipose tissue (WAT) was associated with reduced levels of the pP65 protein in the epididymal fat tissue, suggesting less activation of the nuclear factor-kB (NFkB) pathway in Ang1-7-treated rats. WAT from Ang 1-7-treated rats showed reduced NADPH-stimulated superoxide production. In single muscle fibers (myofibers) harvested and grown ex vivo for 10 days, myofibers from HFrD rats gave rise to 20% less myogenic cells than the Ang 1-7-treated rats. Fully developed adipocytes were present in most HFrD myofiber cultures but entirely absent in cultures from Ang 1-7-treated rats. In summary, Ang 1-7 had an ameliorating effect on insulin resistance, hypertriglyceridemia, fatty liver, obesity, adipositis, and myogenic and adipogenic differentiation in muscle tissue in the HFrD rats.
    Diabetes 12/2012; · 7.90 Impact Factor
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    ABSTRACT: SVEP1 is a multi-domain protein recognized as a cell adhesion molecule (CAM). In this study, we focused on the activity regulation of an alternative promoter (AP) and the expression of alternative splice forms of mRNA from SVEP1 gene. The expression of SVEP1 isoforms was analyzed on RNA isolated from pre-osteoblastic MBA-15 and mammary adenocarcinoma DA3 cells grown alone or following co-culture between these cells. The co-culture system aimed to mimic the cellular cross talk that exists in the bone microenvironment once the mammary cells invade the bone. We demonstrated that SVEP1 isoforms were differentially expressed between these cells. The various isoforms levels were affected by co-culturing or in cells treated with TNFα or estrogen. Both cell lines exhibited an increase of message levels of a and e isoforms following the co-culture conditions. A novel aspect presented here is related to existence of an alternative promoter (AP) in SVEP1 gene. The AP was in silico predicted and analyzed for binding by specific transcription factors (TFIIB, ERα, NF-κB, Sp1 and pcJUN) using Chromatin immunoprecipitation (ChIP) assay. The binding of these TFs results in a non uniform binding pattern when comparing between the DA3 and MBA-15 cells. Using the demethylation agent, 5'-aza-deoxycitidine and histone deacetylase inhibitor, Trichostatin-A allowed to study the methylation level of the AP and the message expression. This study provides insights into alternative splice forms of SVEP1 and their regulation that may play a role within the bone niche with invading carcinoma cells.
    Gene 05/2012; 505(1):137-45. · 2.20 Impact Factor
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    ABSTRACT: The relationships between cancer cells and the microenvironment play a critical role in cancer growth and development. The bone stroma consists of mesenchymal stem cells and mature osteoblasts that promote cancer growth. Yet it is not completely understood what are the molecular processes guiding cancer cells progression to the bone. In this study, a coculture assay and subsequent gene profiling arrays were used to compare the gene expression profile of a pre-osteoblastic (PO) cell line (MBA-15) with that of a mammary adenocarcinoma (DA3) cells. After coculture, cells were separated by magnetic beads based on the expression of CD326 antigen. RNA was purified and hybridized on gene expression array. The gene expression pattern changes were followed by qRT-PCR. We demonstrate that cocultured DA3 cells express elevated levels of genes that regulate growth and responses to both hormonal stimulus and wounding, as well as reduced expression of genes related to lipid metabolism. Also, cocultured PO cells showed reduced expression of cell junction genes. The study presents a simplified model system, composed of PO and mammary cancer cells, that potentially mimics the molecular interactions in the tumor microenvironment which contribute to tumor progression.
    Genes to Cells 03/2012; 17(4):302-15. · 2.73 Impact Factor
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    ABSTRACT: Fundamental aspects of embryonic and post-natal development, including maintenance of the mammalian female germline, are largely unknown. Here we employ a retrospective, phylogenetic-based method for reconstructing cell lineage trees utilizing somatic mutations accumulated in microsatellites, to study female germline dynamics in mice. Reconstructed cell lineage trees can be used to estimate lineage relationships between different cell types, as well as cell depth (number of cell divisions since the zygote). We show that, in the reconstructed mouse cell lineage trees, oocytes form clusters that are separate from hematopoietic and mesenchymal stem cells, both in young and old mice, indicating that these populations belong to distinct lineages. Furthermore, while cumulus cells sampled from different ovarian follicles are distinctly clustered on the reconstructed trees, oocytes from the left and right ovaries are not, suggesting a mixing of their progenitor pools. We also observed an increase in oocyte depth with mouse age, which can be explained either by depth-guided selection of oocytes for ovulation or by post-natal renewal. Overall, our study sheds light on substantial novel aspects of female germline preservation and development.
    PLoS Genetics 02/2012; 8(2):e1002477. · 8.52 Impact Factor
  • C Glait-Santar, D Benayahu
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    ABSTRACT: Breast cancer is one of several tumors, including prostate, thyroid and kidney, which display a remarkable predilection for metastasis to bone. The preference to metastasize to bone by tumor cells relies on specific interactions among tumor cells, bone marrow microenvironment and bone cells. Osteomimicry is postulated to enable the survival of tumor cells in the bone tissue. Using gene profiling array and RT-PCR we demonstrated the message expression of few bone matrix proteins in mammary adenocarcinoma cells as well as that of cell adhesion molecules (CAMs). A CAM molecule, named SVEP1, was previously shown to be expressed in osteoblastic cells both in vivo and in vitro mediating cell adhesion in the bone-marrow niches. Both estradiol (17βE(2)) and TNFα regulate the expression of adhesion molecules and act in bone-cancer-crosstalk. We focused on differential regulation of SVEP1 gene comparing pre-osteoblastic MBA-15 and mammary adenocarcinoma DA3 cells. 17βE(2) and TNFα activated SVEP1 promoter, increased its message and protein levels in both cell types. Using chromatin immunoprecipitation assay, we quantified SVEP1 promoter occupancy by transcription factors; TFIIB, ERα, NF-κB, Sp1 and their binding was also regulated by both factors. By comparing pre-osteoblastic with mammary adenocarcinoma cells, the study expands our understanding of SVEP1 gene expression regulation and it sheds light on its involvement in bone-cancer-microenvironment interactions.
    The Journal of steroid biochemistry and molecular biology 01/2012; 130(1-2):36-44. · 3.98 Impact Factor
  • Gabi Shefer, Dafna Benayahu
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    ABSTRACT: Skeletal muscles are able to adapt to over - or under-use. In response to enhanced use, such as exercise, skeletal muscles undergo morphological and physiological changes possibly including injury and regeneration of muscle fibers (myofibers). The regeneration process includes addition or replacement of myofiber nuclei (myonuclei) (1). Myonuclei are terminally differentiated, thus maintenance and repair of myofibers are attributed to satellite cells, the myogenic stem cells. Up to date little is known about the differential effects of different growth factors on satellite cell and their subsequent contribution in exercise. The adaptation of skeletal muscles to altered use is governed by three major processes: satellite (stem) cell activity, gene transcription, and protein translation. A defect in any of these processes could interfere with muscle maintenance and regeneration. This review focuses on current understanding of the effects of resistance and endurance exercise on skeletal muscle fibers (myofibers) and on the skeletal muscle stem cells, satellite cells. We first summarize in brief the basic biology of skeletal satellite cells; the types of exercise and the basic biology of IGF-I. We then discuss the interplay between IGF skeletal muscle and satellite cells.
    Frontiers in bioscience (Elite edition) 01/2012; 4:230-9.
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    ABSTRACT: Understanding mechanotransduction in adipocytes is important for research of obesity and related diseases. We cultured 3T3-L1 preadipocytes on elastic substrata and applied static tensile strains of 12% to the substrata while inducing differentiation. Using an image processing method, we monitored lipid production for a period of 3-4 wk. The ratio of %-lipid area per field of view (FOV) in the stretched over nonstretched cultures was significantly greater than unity (P < 0.05), reaching ∼1.8 on average starting from experimental day ∼10. The superior coverage of the FOV by lipids in the stretched cultures was due to significantly greater sizes of lipid droplets (LDs) with respect to nonstretched cultures, starting from experimental day ∼10 (P < 0.05), and due to significantly more LDs per cell between days ∼10 and ∼17 (P < 0.05). The statically stretched cells also differentiated significantly faster than the nonstretched cells within the first ∼10 days (P < 0.05). Adding peroxisome proliferator-activated receptor-γ (PPARγ) antagonist did not change these trends, as the %-lipid area per FOV in the stretched cultures that received this treatment was still significantly greater than in the nonstretched cultures without the PPARγ antagonist (14.44 ± 1.96% vs. 10.21 ± 3%; P < 0.05). Hence, the accelerated adipogenesis in the stretched cultures was not mediated through PPARγ. Nonetheless, inhibiting the MEK/MAPK signaling pathway reduced the extent of adipogenesis in the stretched cultures (13.53 ± 5.63%), bringing it to the baseline level of the nonstretched cultures without the MEK inhibitor (10.21 ± 3.07%). Our results hence demonstrate that differentiation of adipocytes can be enhanced by sustained stretching, which activates the MEK signaling pathway.
    AJP Cell Physiology 01/2012; 302(2):C429-41. · 3.71 Impact Factor
  • Uri David Akavia, Rina Socher, Dafna Benayahu
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    ABSTRACT: We isolated cells from their native in vivo microenvironment using the Laser Capture Micro dissection (LCM). Bone and cartilage tissues were studied from mouse embryonic (18dpc) processed by cry sections enabled the cell isolation from anatomical complexity of skeletal tissues using the LCM technique. RNA was purified from the isolated cells and followed with amplification stage to hybridize on gene array for high through (HT) put analysis to profile the tissues gene expression. Bioinformatics profiling of the differential expression performed according to the tissue origin highlighted the common and divergent genes in the regulation of these tissues. Specifically, we identified that genes related to cell replication and cell metabolism were more prominent in bone, while organic acid metabolism was more prominent in cartilage. This study has demonstrated the utility of applying HT microarray analysis using RNA from small number of cells isolated by LCM from skeletal tissues. The bioinformatics provides insight which has not yet been explored for the developing skeletal tissues. The power of LCM application provides a platform to make a broad molecular analysis using transcriptom analysis to reveal the molecular signature of tissues in their nature environment.
    Frontiers in bioscience (Elite edition) 01/2012; 4:1941-50.
  • C Glait-Santar, D Benayahu
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    ABSTRACT: SVEP1 gene encodes a cell adhesion molecule (CAM) that was previously shown to be expressed by cells related to skeletal tissues. Here we focus on SVEP1 expression regulation in pre-osteoblastic MBA-15 and mammary adenocarcinoma DA3 cells. We show that SVEP1 message and protein are highly expressed by MBA-15 when compared with DA3 cells. DNA methylation of CpGs sites is an epigenetic mechanism associated with gene silencing. Therefore, we analyzed the methylation status of a region potentially harbors SVEP1 promoter and further activity alterations induced by estrogen (17βE(2)) and TNFα. We also mapped in silico the transcription binding sites namely TFIIB, NF-κB, ERE, AP1 and Sp1 at the putative promoter. Treatments with demethylation reagents, 5'-aza-deoxy-Cytidine (5'-aza-dC), or histone deacetylase inhibitor, Trichostatin A (TSA) resulted with an elevation of SVEP1 mRNA expression in both cell types. Methylation levels of specific CpGs sites located at transcription binding sites were assessed using sodium bisulfite genomic DNA sequencing, methylated DNA immunoprecipitation (meDIP) and Methylation-Specific PCR (MSP). Our results show that the putative promoter of SVEP1 is hypermethylated in DA3- compared with MBA-15 cells, thus regulating SVEP1 expression levels. In addition, by affecting SVEP1 promoter methylation status, 17βE(2) and TNFα regulate ectopic SVEP1 promoter and mRNA expression. Our data sheds light on understanding the cell-type specific promoter status for regulation of the SVEP1. Since SVEP1 protein mediates cellular adhesion, this data might be beneficial for the future characterization of SVEP1 expression in the interactions existing in bone.
    Gene 09/2011; 490(1-2):6-14. · 2.20 Impact Factor
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    ABSTRACT: Myofiber cultures give rise to myogenic as well as to non-myogenic cells. Whether these myofiber-associated non-myogenic cells develop from resident stem cells that possess mesenchymal plasticity or from other stem cells such as mesenchymal stem cells (MSCs) remain unsolved. To address this question, we applied a method for reconstructing cell lineage trees from somatic mutations to MSCs and myogenic and non-myogenic cells from individual myofibers that were cultured at clonal density.Our analyses show that (i) in addition to myogenic progenitors, myofibers also harbor non-myogenic progenitors of a distinct, yet close, lineage; (ii) myofiber-associated non-myogenic and myogenic cells share the same muscle-bound primordial stem cells of a lineage distinct from bone marrow MSCs; (iii) these muscle-bound primordial stem-cells first part to individual muscles and then differentiate into myogenic and non-myogenic stem cells.
    PLoS ONE 01/2011; 6(10):e25605. · 3.73 Impact Factor
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    ABSTRACT: Tissue engineering is attempting to recreate the complexity of living tissues. In order to test a variety of scaffolds or cells that are constantly being developed, we describe here a model where tissue engineering of bone in a non-osseous environment at subcutaneous thoracic site of DA rats generates. In this model, cell - matix interactions can mimic the normal cascade of bone development into a well organized ossicle like structure including newly formed bone marrow, during 3-4 weeks. Histogenesis of cartilage, bone and bone marrow is closely related to changes in molecular expression of essential early transcriptional regulators of osteoblast differentiation. We tested different organic, anorganic and polymeric scaffolds and their interaction with mesenchymal stem cells present in fresh bone marrow. In another series of experiments we tested mesenchymal populations separated from cultures of calvaria and periosteum for their ability to form bone in the same rat model. It is concluded that this in vivo model is very potent in studying cell-scaffold interactions affecting the temporal and spatial tissue engineering of bone.
    Frontiers in bioscience (Scholar edition) 01/2011; 3:61-8.
  • Gabi Shefer, Dafna Benayahu
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    ABSTRACT: In this study we explored the expression pattern of SVEP1, a novel cell adhesion molecule (CAM), in bona fide satellite cells and their immediate progeny. We show that SVEP1 is expressed in activated satellite cells prior to their determination to the myogenic lineage. SVEP1 was also expressed during early phases of myogenic differentiation through the initial stage of myoblast fusion and myotube formation. The expression of SVEP1 was shown by immunostaining two cell culture systems: freshly isolated myofibers and primary myoblasts. Pax7 was used to pinpoint satellite cells situated in their niche on myofibers, and activated satellite cells were determined based on BrdU incorporation (Pax7(+)/BrdU(+)cells). MyoD marked satellite cells fated to undergo myogenesis as well as proliferating and differentiating myoblasts. Differentiating myoblasts and myotubes were identified based on their sarcomeric myosin expression. We showed that SVEP1 was specifically expressed in pre-determined activated satellite cells (Pax7(+)/ BrdU(+) /MyoD(-)) accounting for about 24% of total satellite cells. On the other hand, SVEP1 expression was absent in quiescent satellite cells (Pax7(+)/BrdU(-)/MyoD(-)). Moreover, based on MyoD/sarcomeric myosin co-expression SVEP1 was shown to be expressed throughout the early phases of myogenesis up until myoblast fusion and myotube formation. A decline in SVEP1 expression occurred upon myotube maturation. We suggest SVEP1 as a potential biomarker for pre-fated satellite cells. The impact of this finding is that it may allow scrutinizing signals that affect differentiation commitment. Thus, holds a therapeutic potential for maladies that involve deregulated stem cell fate-decision.
    Stem cell reviews 03/2010; 6(1):42-9. · 5.08 Impact Factor
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    ABSTRACT: BACKGROUND: Muscle regeneration depends on satellite cells, myogenic stem cells that reside on the myofiber surface. Reduced numbers and/or decreased myogenic aptitude of these cells may impede proper maintenance and contribute to the age-associated decline in muscle mass and repair capacity. Endurance exercise was shown to improve muscle performance; however, the direct impact on satellite cells in aging was not yet thoroughly determined. Here, we focused on characterizing the effect of moderate-intensity endurance exercise on satellite cell, as possible means to attenuate adverse effects of aging. Young and old rats of both genders underwent 13 weeks of treadmill-running or remained sedentary. METHODOLOGY: Gastrocnemius muscles were assessed for the effect of age, gender and exercise on satellite-cell numbers and myogenic capacity. Satellite cells were identified in freshly isolated myofibers based on Pax7 immunostaining (i.e., ex-vivo). The capacity of individual myofiber-associated cells to produce myogenic progeny was determined in clonal assays (in-vitro). We show an age-associated decrease in satellite-cell numbers and in the percent of myogenic clones in old sedentary rats. Upon exercise, there was an increase in myofibers that contain higher numbers of satellite cells in both young and old rats, and an increase in the percent of myogenic clones derived from old rats. Changes at the satellite cell level in old rats were accompanied with positive effects on the lean-to-fat Gast muscle composition and on spontaneous locomotion levels. The significance of these data is that they suggest that the endurance exercise-mediated boost in both satellite numbers and myogenic properties may improve myofiber maintenance in aging.
    PLoS ONE 01/2010; 5(10):e13307. · 3.73 Impact Factor
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    ABSTRACT: Nanosecond pulsed electric fields applied to biological cells are now well recognized to induce a series of intracellular responses. These evidences have paved the route toward the use of electro-manipulation techniques to noninvasively altering the biochemical state of many intracellular functions. Although of the vast experimental progress, the more fundamental understanding of these electrostatic effects is quite controversial. Recently, several models which are based on the core–shell representation have been proposed in order to clarify these effects. However, since most sub-cellular organelles generally “exhibit” much complex and convoluted morphology, these models might be quite restricted in predicting the more native intracellular responses. Given these realizations, this study aims to theoretically explore the nature of induced cellular potentials in a more realistic model. For this purpose, a 3D cytoplasmic-embedded mitochondrion model has been constructed in order to imitate the morphological structure of a native cellular system. Based on finite numerical simulations, the electrically induced transmembrane potential gradients have been computed and examined against the responses obtained based on the approximated shell models. The prominent deviations obtained between the realistic and the approximated models arouse serious thoughts regarding the compatibility of these models to the analysis of sub-cellular organelles.
    Journal of Electroanalytical Chemistry - J ELECTROANAL CHEM. 01/2010; 638(1):59-69.

Publication Stats

2k Citations
282.74 Total Impact Points

Institutions

  • 1989–2014
    • Tel Aviv University
      • • Department of Cell and Developmental Biology
      • • Department of Biomedical Engineering
      • • Faculty of Engineering
      • • Department of Physiology and Pharmacology
      • • Department of Orthopedics
      Tell Afif, Tel Aviv, Israel
  • 1993–2012
    • Weizmann Institute of Science
      • • Department of Biological Regulation
      • • Department of Computer Science and Applied Mathematics
      • • Department of Biological Chemistry
      Israel
  • 1996
    • Agricultural Research Organization ARO
      • Institute of Animal Science
      Bet Dagan, Central District, Israel