The present study was designed to determine the effect of skin-temperature-biofeedback training on cellular proliferation in three psoriasis patients. It was hypothesized that (a) psoriasis patients would be able to consciously decrease skin temperature of psoriatic tissue, and (b) there would be a positive correlation between rate of cellular proliferation and temperature change. Results obtained indicated biofeedback training to be effective in decreasing the surface temperature of psoriatic tissue. A 2 X 7 analysis of variance for two repeated measures indicated the change in skin temperatures as a function of sample period to be significant, F (6,26) = 3.29, p < .02. Generalization of temperature-training effects from the biofeedback to the no-feedback condition were observed. Rate of proliferation decreased from pretraining to posttraining biopsies.

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Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Electric fields, which are generated by the movement of charged ions across membranes, are found in all biological systems and can influence cellular components ranging from amino acids to biological macromolecules. Physiological field strengths range from 1 – 200 mV/mm, and these electric fields are especially elevated at sites of cellular growth during development and regeneration. It has previously been demonstrated that elevated electric fields induce alignment of astrocyte processes in vitro, enhancing the rate of neurite outgrowth. It is believed that electric fields of varying physiological strength affect other astrocytic responses associated with regeneration. To characterize the duration over which these changes emerge, cultured rat astrocytes were exposed to different direct-current electric field strengths. The resulting cellular behaviors were recorded every three minutes with an inverted microscope equipped with DIC optics and a stage incubator. Electric fields were found to induce astrocyte responses similar to those observed during periods of neurodevelopment and regeneration. Changes in astrocyte movement, proliferation, & morphology emerged within the first hour and persisted through the course of the electric field application, leading mammalian astrocytes to revert to an earlier maturation state resembling those seen in amphibian astrocytes associated with central nervous system regeneration. Collectively, these results suggest that applied electric fields lead to astrocyte dedifferentiation, with certain electric field strengths eliciting and enhancing specific cell responses.

Human immunodeficiency virus (HIV) infected patients with a history of injection opiate abuse have higher incidences of acquired immunodeficiency syndrome (AIDS) and neurological dysfunction. The use of combined anti-retroviral therapy has significantly reduced the prevalence of mortality and progression to AIDS. Due to extended life expectancy, these patients are still at a great risk for HIV-associated neurological disorders and impairment in their later life. Neural progenitor cells (NPCs) play critical roles in brain growth and repair after injury and insult. Pediatric HIV patients whose glial populations are still developing are especially at risk for central nervous system (CNS) damage. Our previous reports suggest that HIV-1 transactivator of transcription (Tat) can directly cause pathology in neural progenitors and oligodendroglia (OLs) (Hauser et al. 2009). Thus, we have hypothesized that NPCs and/or glial progenitors may be targets of HIV proteins ± opiates drugs of abuse. To determine whether progenitors are targets of HIV-1, a multi-plex assay was performed to assess chemokine/cytokine expression after treatment with viral proteins Tat or glycoprotein 120 (gp120) with/without morphine. Murine striatal progenitors released increased amount of the beta-chemokines CCL5/regulated upon activation, normal T cell expressed and secreted (RANTES), CCL3/macrophage inflammatory protein-1α (MIP-1α), and CCL4/macrophage inflammatory protein-1β (MIP-1β) after 12 h exposure to HIV-1 Tat, but no to gp120. Secreted factors from Tat-treated progenitors were chemoattractive towards microglia, an effect blocked by 2D7 anti- C-C chemokine receptor type 5 (CCR5) antibody pre-treatment. Tat and opiates have interactive effects on astroglial chemokine secretion, but this interaction did not occur in progenitors. We also examined effects of Tat and morphine on proliferation and lineage progression of NPCs in vitro and in vivo. In vitro, Tat and morphine independently reduced the proliferation and population of Sox2+ and Olig2+ cells in the absence of cell death. The interactive effects of morphine and either Tat or supernatant from HIV-1SF162 infected monocytes varied depending on outcome measure and time of exposure, but interactive effects occurred primarily on proliferation. In rare instances, viable human progenitors were associated with p24 immunolabeling suggesting that progenitors may be infected, a concept that is still controversial. To investigate effects of Tat and morphine on NPCs in vivo, we used a mouse model in which HIV-1 Tat1-86 is conditionally expressed in astroglia. In vivo results in neonatal striata were similar to those in cell cultures. We extended the experiments into adult mice with inducing Tat expression for 3 month and the effect of sexes was examined in these animals. Intriguingly, males showed more Tat-induced impairment in behavioral tests (rotarod, grip strength, light-dark box) than females. Tat+ males also showed a greater reduction in the proportion of NeuN+ cells and NeuN immunoreactivity in the striatum, accompanied by greater microglial activation (3-nitrotyrosine+/Iba-1+). Unbiased stereological estimation in Nissl staining revealed that the depletion of NeuN immunoreactivity in these mice was not due to neuron cell death or loss, because the total neuron number in striatum and total striatal volume were not affected by long-term Tat induction. Tat exposure appears to selectively reduce levels of NeuN in living neurons, although the reason is not known. Therefore, both the enhanced microglial reactivity and depletion of NeuN levels in males may help to explain sex-specific behavioral outcomes. Sox2+ and Olig2+ cells showed equivalent reduction in their population in both sexes. Overall, our findings show that CNS progenitors, including both undifferentiated NPCs and glial progenitors, are vulnerable to individual or combined effects of HIV-1 or Tat and opiates. Changes in progenitor dynamics may alter the balance of cell populations in both the developing and adult CNS. We speculate that such changes may contribute to the behavioral abnormalities that we observed in Tat+ mice and which appear to model aspects of motor, cognitive and anxiety deficits in HIV-infected patients.

Treacher Collins syndrome (TCS) is an autosomal dominant craniofacial development disorder and is caused by mutations in the TCOF1 gene. The TCOFl protein treacle is a nucleolar protein and may function in ribosome biogenesis.Previously, we identified downstream candidate genes using microarray analysis after manipulating Tcofl levels in a murine neuroblastoma (NB) cell line. The list of genes includes cell cycle genes as well as the transcription factors Cnbp and Tbx2, which are known to affect the cell cycle through the c-myc and p19-Mdm2-p53-p21 pathways respectively. To further characterize the cellular effects of Tcofl, stably transfected NB cell lines with overexpression or knockdown of Tcofl were generated. Growth curves were generated by counting cell numbers. BrdU incorporation and TUNEL assays were used to determine proliferation and apoptosis levels. Western blot analysis was used to detect protein level changes of candidate downstream pathway genes. Bothoverexpression and knockdown of Tcofl are detrimental to cell growth. Overexpression of Tcofl causes increased apoptosis and knockdown of Tcofl causes reduced cell proliferation and increased apoptosis. Western blot analysis shows that Cnbp and Tbx2 protein levels change with Tcofl, c-myc level is decreased in Tcofl knockdown cells and p19 (Cdkn2d), p53 and p21 (Cdkn1a) levels are increased in Tcofl overexpressing cells. Our results suggest that an optimal Tcofl level is required for cell proliferation and survival, and that overexpression and knockdown of Tcofl may affect cell proliferation and apoptosis through the p19-Mdm2-p53-p21 and Cnbp-c-myc pathways respectively.Heterozygous Tcofl knock out mice are neonatal lethal, which circumvents further analysis of the heterozygous and homozygous mice. In this study, we generated Tcofl conditional allele mice with loxP sites flanking exon 1. These mice were crossed with Wntl-Cre transgenic mice to generate a conditional knockout of Tcofl specifically in neural crest (NC) cells. Homozygous conditional knockout mice show craniofacial abnormalities resembling TCS patients. Heterozygous conditional knockout mice are phenotypically normal, which suggests that Tcofl functions in tissues other than NC cells during development. Cnbp expression is decreased in a proportion of the homozygous conditional knockout mouse embryos. Our results suggest that Tcofl may affect craniofacial development through Cnbp by maintaining cell growth.

Hippocampal neurons are vulnerable to injury, as indicated by the prevalence of learning and memory deficits following traumatic brain injury. Research indicates that proliferation of neural precursor cells increases following brain injury, which implies that there is an endogenous response in the hippocampus to replenish neurons and restore cognitive function. Studies show that mitogenic growth factors may drive this proliferative response; one of which is epidermal growth factor. Because adults and the elderly manifest the most enduring deficits following TBI, it is critical to investigate how EGF expression following injury may relate to injury-induced cell proliferation and the degree of cognitive recovery observed with aging. In the current study, we assessed the temporal and spatial expression of EGF in the injured hippocampus with age. Our results suggest that EGF expression increases following TBI, and this increase is more significant in the younger brain. Additionally, we investigated the phenotype and localization of cells that express EGF following injury.

Cell proliferation and contact inhibition play a major role in maintaining epithelial cell homeostasis. A hallmark of epithelial cells is strong cell-cell junctions. These junctions include E-Cadherin, a type of adherens junction that is critical for both barrier function and contact inhibition. Prior experiments by other groups have shown that adherens junctions are subject to mechanical tension. Externally applied forces (e.g. stretch) results in changes in E-Cadherin forces that coordinate proliferation. My current work tests the hypothesis that E-Cadherin forces mediate the spatial regulation of cell proliferation even in the absence of externally applied forces.

Nous avons au cours de notre travail de thèse tenté de préciser les outils nécessaires àamplifier le potentiel lymphocytaire T de précurseurs hématopoïétiques chez l’Homme. Aucours de la différenciation lymphoïde T deux facteurs semblent importants, Notch et l’IL7.Nous avons étudié le rôle de l’IL7 et de Notch au cours de la différenciation T humaine. Nousavons montré que seule l’IL7 est indispensable à la différenciation des thymocytes immatureshumains. L’activation de la voie Notch potentialise la survie et la prolifération induite parl’IL7 des CD34+TN et des CD4 ISP. Notch maintien l’expression de la chaîne α de l’IL7Rmalgré la présence de l’IL7. Une étude épigénétique a montré que Notch est capable d’induirela déméthylation du promoteur de l’IL-7Rα permettant son expression.Les résultats obtenus avec les cellules CD34+ de sang de cordon ont montré que Notch etnon l’IL7 était indispensable à la différenciation au moins dans les stades précoces. Lesdifférences entre les thymocytes et les CD34+ de sang de cordon ne semblent pas êtreexpliquées par une expression différente des récepteurs Notch. Le système de différenciationdes cellules CD34+ de sang de cordon permet aussi d’augmenter le potentiel T in vitro.Nos données confirment le rôle indispensable de Notch et de l’IL7 dans la différenciationT avec toutefois des implications différentes selon l’origine des précurseurs et du stade dedifférenciation. La poursuite de l’étude du rôle de ces deux signaux au cours de l’ontogénie Thumaine permettrait de définir les conditions de culture optimale à l’amplification dupotentiel T des précurseurs CD34+ dans une optique d’utilisation en thérapeutique humaine / In this work, we have attempted to define tools for amplifying the T lymphocyte potentialof hematopoietic precursor cells in man. Notch and IL7 are important factors for Tlymphocyte differentiation. We have studied the roles of IL7 and Notch during human T celldifferentiation. We have shown that only IL7 is essential for differentiation of humanimmature thymocytes. Notch pathway activation potentiates IL7 induced CD34+ TN and CD4ISP survival and proliferation. Notch maintains IL7Rαchain expression in spite of thepresence of IL7. Epigenetic study showed that Notch is able to induce IL7RαpromoterdemethylationOur results on cord blood CD34+ cells showed that Notch, but not IL7, was essential fordifferentiation, at least in early stages. Differences between thymocytes and cord blood cellsCD34+ cells do not seem to be accounted for by different Notch receptor expression. Inaddition, cord blood CD34+ cell differentiation system increases in vitro T lymphocytepotential.Our data confirm the essential role of Notch and IL7 in T cell differentiation, with somediffferences between these two factors according to precursor origin and differentiation stage.Continuation of this study on the role of these signals in human T cell ontogeny would help indefining optimal culture conditions fot T lymphocyte potential amplification from CD34+precursors, in the perspective of therapeutical use in man