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David Israeli

Publications and source records attributed to David Israeli.

8 recordsLinked to original sources
PubMed2005

Global transcriptional characterization of SP and MP cells from the myogenic C2C12 cell line: effect of FGF6.

With the use of Hoechst staining techniques, we have previously shown that the C2C12 myogenic cell line contains a side population (SP) that is largely increased in the presence of fibroblast growth factor 6 (FGF6). Here, we compared transcriptional profiles from SP and main population (MP) cells from either C2C12 or FGF6-expressing C2C12. Expression profiles of SPs show that these cells are less differentiated than MPs and display some similarities to stem cells. Moreover, principal component analysis made it possible to distinguish specific contributions of either FGF6 or differentiation effects on gene expression profiles. This demonstrated that FGF6-expanded SPs were similar to parental C2C12-derived SPs. Conversely, FGF6-treated MPs differed from parental MPs and were more related to SP cells. These results show that FGF6 pushed committed myogenic cells toward a more immature phenotype resulting in the accumulation of cells with a SP phenotype. We propose that FGF6 conditioning could provide a way to expand the pool of immature cells by myoblast dedifferentiation.

Animals↗
PubMed2005

A proposal for the physiological significance of mdr1 and Bcrp1/Abcg2 gene expression in normal tissue regeneration and after cancer therapy.

Cellular multi-drug resistance (MDR), which often develops in cancer cells of patients subjected to anti-cancer treatment, remains a significant barrier to successful cancer therapy. One of the principal causes of cellular MDR development is an increased expression of ABC-transporter genes such as mdr1 and Bcrp1/Abcg2. Despite many years of intensive research, the natural biological role of mdr1 in the context of cancer has remained elusive. Some hints about this role came, however, from an observation that P-gp, the mdr1 encoded protein, is expressed widely in stem cells and from the discovery that P-gp possesses an anti-apoptotic activity independently of exogenous drug application. Here, we discuss our own and other groups' recently published works and propose an integrated view of mdr1 and Bcrp1/Abcg2 activity during tissue regeneration in normal tissues as part of a stress-induced regeneration genetic program and in cancerous tissues in response to cancer therapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Intraoperative complications of phacoemulsification in eyes with and without pseudoexfoliation.

PURPOSE: To determine the intraoperative complications in a large series of phacoemulsification procedures, including patients with and without pseudoexfoliation, excluding those with marked phacodonesis or lens subluxation. SETTING: Department of Ophthalmology, Carmel Medical Centre, Haifa, Israel. METHODS: This institutional case-control study included 1501 consecutive phacoemulsification procedures: 137 eyes with pseudoexfoliation and 1364 eyes without this condition. Baseline demographics and clinical factors were collected from the medical files. A comparative analysis of the incidence of intraoperative complications in eyes with or without pseudoexfoliation was calculated. Univariate analysis and multiple logistic regression were used to identify ocular factors that predicted intraoperative complications. RESULTS: There was no significant difference (P>.05) in the rate of intraoperative complications between the pseudoexfoliation (5.8%) and control (4.0%) groups. There were no significant differences in the incidence of capsular breaks, vitreous loss, and zonular ruptures without vitreous loss in the 2 groups. Pseudoexfoliation did not confer a statistically higher risk for intraoperative complications (odds ratio 1.62, 95% confidence interval 0.74-3.55). CONCLUSION: Phacoemulsification by experienced surgeons is safe in eyes with pseudoexfoliation without marked phacodonesis or lens subluxation.

Aged↗
PubMed2004

Evidence for a resident subset of cells with SP phenotype in the C2C12 myogenic line: a tool to explore muscle stem cell biology.

Muscle satellite cells are heterogeneous and present functional disparities, some of them behaving as multipotent stem cells. Yet their phenotype is obscure and their isolation remains elusive. The ability to purify stem cells from a wide variety of tissues by using Hoechst 33342 staining/FACS methods has permitted access to this category of cells (side population, or SP) in a manner independent of antibodies. Here, we show that the C2C12 myogenic line comprises a minor population of cells with SP phenotype. These cells are growth-arrested and delayed in their ability to differentiate. Dye efflux in C2C12-derived SPs is likely mediated by mdr1a, whose overexpression results in increased dedifferentiation. Interestingly, growth-arrested SPs rapidly appear in purified MP populations, thus suggesting a dynamic equilibrium among different states of differentiation. Finally, transcriptional profiling of C2C12-derived SP and MP cells corroborates the many similarities of SP to stem cells.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2004

FGF6 mediated expansion of a resident subset of cells with SP phenotype in the C2C12 myogenic line.

Fibroblast growth factor 6 (FGF6) is selectively expressed during muscle development and regeneration. We examined its effect on muscle precursor cells (mpc) by forcing stable FGF6 expression in C2C12 cells in vitro. FGF6 produced in genetically engineered mpc was active, inducing strong morphological changes, altering cell adhesion and compromising their ability to differentiate into myotubes. Expression of MyoD and myogenin, but not of Myf5, was abrogated in FGF6 engineered mpc. These effects were reversed by FGF inhibitors. Ectopic expression of MyoD also restored fiber formation indicating that FGF6 interferes with the myogenic differentiation pathway upstream of MyoD. We also report that in the presence of FGF6, the minor (0.5-2%) subpopulation of cells actively excluding Hoechst 33342 in a verapamil-dependent manner (SP phenotype) was increased to 15-20% and the expression of the mdr1a gene (but not mdr1b) was upregulated by 400-fold. Our data establish a previously undescribed link between FGF6--a muscle specific growth factor--and a multidrug resistance gene expressed in stem cells, and suggest a role for FGF6 in the maintenance of a reserve pool of progenitor cells in the skeletal muscle.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2004

Transactivator and structurally optimized inducible lentiviral vectors.

Lentiviral vectors offer well-recognized advantages as a gene delivery system both for the analysis of gene function and as a vehicle for gene therapy. In the present study optimized HIV-1-based vector systems that display efficient doxycycline (Dox)-dependent transgene expression in vitro and in vivo have been developed through the modification of factors that contribute to basal activity levels. Dissection of HIV-1 vectors harboring a tTA-dependent transgene expression cassette revealed several mechanisms that account for Dox-independent transgene expression, including those mediated by an internal CMV promoter, as well as a potential contribution from fusion proteins generated by translational readthrough. A precipitous reduction in basal activity levels was accomplished by separating the transactivator and the transgene cassettes into a binary vector system and by relocating the inducible promoter to the U3 region of the LTR. In addition, substituting the VP16 portion of tTA with the human p65 transactivating domain improved Dox-dependent transgene expression in a number of cell types. Optimizing HIV-1-based vectors culminated in a "toolbox" of vectors suitable for transgene delivery in vitro and in vivo, as conveyed by our ability to control the Dox-dependent differentiation of embryonic fibroblasts into muscle cells in vitro and transgene expression in rat brains.

Animals↗
PubMed2002

Induction of immune tolerance toward tumor-associated-antigens enables growth of human hepatoma in mice.

Adoptive transfer of immunity against hepatitis B surface antigen (HBsAg) was previously shown to facilitate suppression of experimental human hepatocellular carcinoma (HCC) expressing HBsAg in athymic mice. We have shown that oral tolerance induces antigen-specific immune suppression of HBsAg by feeding hepatitis B virus (HBV) antigens. In the present study we evaluated the effect of oral tolerance induction toward HBV or HCC antigens on the growth of experimental HCC-expressing HBsAg in mice. Tolerance induction was induced in mice by 5 oral feedings of 1 microg HBV antigens or HCC-extracted proteins (50 microg protein) before vaccination with recombinant HBsAg. Splenocytes (2 x 10(6)) from these mice were transferred to sublethally irradiated athymic BALB/c mice previously transplanted subcutaneously with 10(7) human hepatoma Hep3B cells. Adoptive transfer of splenocytes immunized toward HBsAg prevented tumor growth. At 4 weeks after splenocyte transplantation, tumor volume and serum alpha-fetoprotein (AFP) levels in athymic mice transplanted with splenocytes immunized to HBsAg were undetectable as compared with 1,048 +/- 738 mm(3) and 2,500 +/- 1,431 ng/ml in recipients of naïve splenocytes (p < 0.0001). Mice receiving splenocytes tolerized toward Hep3B cells, as manifested by reduced serum HBs antibody levels, reduced HBV-specific stimulation index and reduced HBV-specific-IFN gamma spot-forming cells, had early tumor growth evident by elevated AFP serum levels, weight loss and mortality, which were suppressed at 6 weeks. Mice transplanted with splenocytes tolerized toward HBV antigens did not have direct evidence of tumor growth. Induction of oral tolerance toward HCC-extracted proteins enabled transient tumor growth in this model. This effect was mediated through downregulation of the anti-HBV immune response.

Adoptive Transfer↗