Connective tissue growth factor (CTGF/CCN2) is axiomatically necessary for proper skeletal development and function. We need not look further than the studies that have been done to date utilizing mice genetically engineered to lack CTGF production. These CTGF null or knockout (KO) mice fail to form a normal murine skeleton and instead yield one littered with bony dysmorphisms, including incompetent craniofacial development, kinked limb bones, and misshapen ribs that are not conducive to proper respiratory function. As a result, the global lack of CTGF is incompatible with postnatal life. A closer look at several sites demonstrated defects in physiologic processes necessary for bone formation - angiogenesis, chondrogenesis, and osteogenesis. Therefore, the dogma in the CCN protein field to date has been that systemic ablation of CTGF production in vivo results in global defects in bone development. We believe this dogma is an oversimplification of the role of CTGF on skeletal development. Our initial impetus leading us to this belief was the gross identification of the specific skeletal sites malformed in CTGF KO mice, in particular the bones of the limbs. While in the lower limb of CTGF KO mice the tibiae and fibulae are misshapen, the adjacent femora and digits are phenotypically normal. The same is true for the upper limb, in which the radii and ulnae are phenotypically abnormal while the humeri and digits are normal. Therefore, we believe that the role of CTGF in skeletogenesis is site-specific such that its loss affects local skeletal patterning and/or mechanobiological cues resulting in the unique phenotype seen in CTGF KO mice. The research of this dissertation constitutes a comprehensive skeletal analysis of CTGF KO mice and in so doing we determined the extent and location of skeletal abnormalities. We found skeletal site-specific changes in growth plate organization, bone microarchitecture and shape and gene expression levels in CTGF KO compared to wild-type (WT) mice. Growth plate malformations included reduced proliferation zone and increased hypertrophic zone lengths. Appendicular skeletal sites demonstrated decreased metaphyseal trabecular bone, while having increased mid-diaphyseal bone and osteogenic expression markers. Axial skeletal analysis showed decreased bone in caudal vertebral bodies, mandibles, and parietal bones in CTGF KO mice, with decreased expression of osteogenic markers. Analysis of skull phenotypes demonstrated global and regional differences in CTGF KO skull shape resulting from allometric (size-based) and non-allometric shape changes. Localized differences in skull morphology included increased skull width and decreased skull length. We further continued the skeletal characterization of CTGF KO bones with an analysis of bone cell ultrastructure and matrix composition. These studies demonstrated that, while CTGF is not necessary for complete morphologic maturation of bone cells, global ablation results in ultrastructural features not commonly seen in WT bones. Our findings include drastically dilated rough endoplasmic reticulum (RER) in osteoblasts of the tibial diaphyseal region, comprising the phenotypic kink in CTGF KO mice and ultrastructural dysmorphologies of CTGF KO osteoclasts including multi-layered, membranous inclusions, decreased vacuolization and ruffled border extents, and disproportionately large clear zones. Lastly, FT-IR analysis demonstrated heterogeneity in CTGF KO bone composition. The results of this dissertation have revealed a more complex role for CTGF in osteogenesis and have identified potential mechanisms and future research directions to fully understand this intricate story. / Cell Biology

L’apoptose des cellules endothéliales (CE) représente un évènement initial dans le développement de plusieurs pathologies fibrotiques telles que le rejet chronique d’allogreffe et la sclérose systémique. Nous avons démontré que les médiateurs issus des CE apoptotiques entraîne la différenciation myofibroblastique et la résistance à l’apoptose, deux mécanismes centraux à la fibrogénèse. L’activation de PI3K (phospatidylinositol-3 kinase) caractérise ces deux mécanismes. Un fragment C-terminal du perlécan (LG3) produit par les CE apoptotiques inhibe l’apoptose des fibroblastes. Les objectifs de ce travail étaient de : 1. définir les récepteurs et la signalisation impliqués dans la réponse anti-apoptotique et 2. caractériser les médiateurs fibrogéniques responsables de la différenciation myofibroblastique. En ce qui a trait à la réponse anti-apoptotique, l’inhibition des intégrines 21 ou des kinases de la famille Src (SFK) chez les fibroblastes prévient la résistance à l’apoptose et la phosphorylation d’Akt normalement induites par le milieu conditionné par des CE apoptotiques (SSC) ou le LG3. Ces résultats suggèrent que le LG3 produit par les CE apoptotiques initie un état de résistance à l’apoptose chez les fibroblastes par des voies α2β1integrines/SFK/PI3K dépendantes. Le LG3 n’induit cependant pas la différenciation myofibroblastique. Nous avons donc caractérisé le milieu SSC de façon à identifier les médiateurs responsables de la différenciation myofibroblastique. Les milieux conditionnés par des CE apoptotiques et non-apoptotiques (respectivement SSC et SSC-ZVAD) ont été analysés comparativement par chromatographie liquide bi-dimensionnelle, immunobuvardage et spectrométrie de masse. Le connective tissue growth factor (CTGF) est le seul facteur fibrogénique connu augmenté dans le milieu SSC. L’inhibition de la caspase-3 chez les CE prévient la relâche de CTGF. Au niveau du fibroblaste, l’inhibition de SFK ou de Pyk2 (proline-rich tyrosine kinase-2) prévient la différenciation myofibroblastique induite par le SSC ou le CTGF in vitro. L’anticorps neutralisant contre le TGF- (Transforming growth factor beta) n’est pas en mesure de bloquer la différenciation myofibroblastique induite par le SSC ou le CTGF. Des injections quotidiennes sous-cutanées de SSC chez la souris C3H pour 3 semaines entraîne une augmentation de l’épaisseur de la peau et des niveaux protéiques d’SMA, de vimentine et de collagène I. Cette réponse fibrogénique est réduite chez les souris qui ont reçu le SSC-ZVAD ou le SSC immunodéplété de son CTGF. Ces résultats apportent de nouvelles issues mécanistiques au niveau de la réponse fibrogénique activée par la mort des CE. L’activation des caspases chez les CE apoptotiques entraîne la production de LG3 et de CTGF qui, à leur tour, activent des voies de signalisation pro-fibrotiques SFK/PI3K dépendantes chez les fibroblastes, et ce indépendamment du TGF-. / Apoptosis of endothelial cells (EC) is an early event in various fibrotic diseases including chronic allograft vasculopathy and systemic sclerosis. We showed previously that mediators released by apoptotic EC activate myofibroblast differentiation and resistance to apoptosis, two mechanisms pivotal to fibrogenesis. PI3K (phospatidylinositol-3 kinase) activation was found to be central to these two mechanisms. A C-terminal fragment of perlecan (LG3) produced by apoptotic EC was found to inhibit apoptosis of fibroblasts. The aims of the present project were : 1. to define the receptors and pathways implicated in this anti-apoptotic response and 2. to characterize the fibrogenic mediators implicated in myofibroblast differentiation. Concerning the anti-apoptotic response, the inhibition of 21 integrin activity in fibroblasts exposed to either medium conditioned by apoptotic EC (SSC) or LG3 prevented resistance to apoptosis and was associated with decreased levels of Akt phosphorylation. Neutralizing Src family kinases (SFK) activity in fibroblasts produced the same effects. These results suggest that LG3 produced by apoptotic EC initiate a state of resistance to apoptosis in fibroblasts via an α2β1integrin/SFK/PI3K dependent pathway. LG3 did not induce myofibroblast differentiation. We went on to identify which mediators present in SSC are implicated in myofibroblast differentiation. Media conditioned by apoptotic and non-apoptotic EC (respectively SSC and SSC-ZVAD) were analyzed comparatively by 2-dimension liquid chromatography, western blotting and mass spectrometry. Connective tissue growth factor (CTGF) was the only known fibrogenic factor increased in SSC. Caspase-3 silencing of EC demonstrated that CTGF is released by apoptotic EC downstream of caspase-3 activation. In fibroblasts, blocking the activation of SFK or silencing the proline-rich tyrosine kinase 2 (Pyk2) blocked myofibroblast differentiation triggered by either SSC or recombinant CTGF in vitro. Exposure to a pan-transforming growth factor (TGF-β) neutralizing antibody failed to attenuate myofibroblast differentiation in fibroblasts exposed to either SSC or CTGF. Subcutaneous injection of mouse SSC to C3H mice daily for three weeks led to increased skin thickness, increased protein levels of αSMA, vimentin and collagen I. This fibrogenic response was blunted in mice injected with either SSC-ZVAD or SSC immunodepleted of CTGF. These results bring new mechanistic insights into the fibrogenic pathways activated by EC death. Caspase activation in apoptotic EC triggers the production of LG3 and CTGF which in turn activate SFK/PI3K dependant pathways in fibroblasts thus activating a TGF-β-independent fibrogenic response.

L’apoptose des cellules endothéliales (CE) représente un évènement initial dans le développement de plusieurs pathologies fibrotiques telles que le rejet chronique d’allogreffe et la sclérose systémique. Nous avons démontré que les médiateurs issus des CE apoptotiques entraîne la différenciation myofibroblastique et la résistance à l’apoptose, deux mécanismes centraux à la fibrogénèse. L’activation de PI3K (phospatidylinositol-3 kinase) caractérise ces deux mécanismes. Un fragment C-terminal du perlécan (LG3) produit par les CE apoptotiques inhibe l’apoptose des fibroblastes. Les objectifs de ce travail étaient de : 1. définir les récepteurs et la signalisation impliqués dans la réponse anti-apoptotique et 2. caractériser les médiateurs fibrogéniques responsables de la différenciation myofibroblastique. En ce qui a trait à la réponse anti-apoptotique, l’inhibition des intégrines 21 ou des kinases de la famille Src (SFK) chez les fibroblastes prévient la résistance à l’apoptose et la phosphorylation d’Akt normalement induites par le milieu conditionné par des CE apoptotiques (SSC) ou le LG3. Ces résultats suggèrent que le LG3 produit par les CE apoptotiques initie un état de résistance à l’apoptose chez les fibroblastes par des voies α2β1integrines/SFK/PI3K dépendantes. Le LG3 n’induit cependant pas la différenciation myofibroblastique. Nous avons donc caractérisé le milieu SSC de façon à identifier les médiateurs responsables de la différenciation myofibroblastique. Les milieux conditionnés par des CE apoptotiques et non-apoptotiques (respectivement SSC et SSC-ZVAD) ont été analysés comparativement par chromatographie liquide bi-dimensionnelle, immunobuvardage et spectrométrie de masse. Le connective tissue growth factor (CTGF) est le seul facteur fibrogénique connu augmenté dans le milieu SSC. L’inhibition de la caspase-3 chez les CE prévient la relâche de CTGF. Au niveau du fibroblaste, l’inhibition de SFK ou de Pyk2 (proline-rich tyrosine kinase-2) prévient la différenciation myofibroblastique induite par le SSC ou le CTGF in vitro. L’anticorps neutralisant contre le TGF- (Transforming growth factor beta) n’est pas en mesure de bloquer la différenciation myofibroblastique induite par le SSC ou le CTGF. Des injections quotidiennes sous-cutanées de SSC chez la souris C3H pour 3 semaines entraîne une augmentation de l’épaisseur de la peau et des niveaux protéiques d’SMA, de vimentine et de collagène I. Cette réponse fibrogénique est réduite chez les souris qui ont reçu le SSC-ZVAD ou le SSC immunodéplété de son CTGF. Ces résultats apportent de nouvelles issues mécanistiques au niveau de la réponse fibrogénique activée par la mort des CE. L’activation des caspases chez les CE apoptotiques entraîne la production de LG3 et de CTGF qui, à leur tour, activent des voies de signalisation pro-fibrotiques SFK/PI3K dépendantes chez les fibroblastes, et ce indépendamment du TGF-. / Apoptosis of endothelial cells (EC) is an early event in various fibrotic diseases including chronic allograft vasculopathy and systemic sclerosis. We showed previously that mediators released by apoptotic EC activate myofibroblast differentiation and resistance to apoptosis, two mechanisms pivotal to fibrogenesis. PI3K (phospatidylinositol-3 kinase) activation was found to be central to these two mechanisms. A C-terminal fragment of perlecan (LG3) produced by apoptotic EC was found to inhibit apoptosis of fibroblasts. The aims of the present project were : 1. to define the receptors and pathways implicated in this anti-apoptotic response and 2. to characterize the fibrogenic mediators implicated in myofibroblast differentiation. Concerning the anti-apoptotic response, the inhibition of 21 integrin activity in fibroblasts exposed to either medium conditioned by apoptotic EC (SSC) or LG3 prevented resistance to apoptosis and was associated with decreased levels of Akt phosphorylation. Neutralizing Src family kinases (SFK) activity in fibroblasts produced the same effects. These results suggest that LG3 produced by apoptotic EC initiate a state of resistance to apoptosis in fibroblasts via an α2β1integrin/SFK/PI3K dependent pathway. LG3 did not induce myofibroblast differentiation. We went on to identify which mediators present in SSC are implicated in myofibroblast differentiation. Media conditioned by apoptotic and non-apoptotic EC (respectively SSC and SSC-ZVAD) were analyzed comparatively by 2-dimension liquid chromatography, western blotting and mass spectrometry. Connective tissue growth factor (CTGF) was the only known fibrogenic factor increased in SSC. Caspase-3 silencing of EC demonstrated that CTGF is released by apoptotic EC downstream of caspase-3 activation. In fibroblasts, blocking the activation of SFK or silencing the proline-rich tyrosine kinase 2 (Pyk2) blocked myofibroblast differentiation triggered by either SSC or recombinant CTGF in vitro. Exposure to a pan-transforming growth factor (TGF-β) neutralizing antibody failed to attenuate myofibroblast differentiation in fibroblasts exposed to either SSC or CTGF. Subcutaneous injection of mouse SSC to C3H mice daily for three weeks led to increased skin thickness, increased protein levels of αSMA, vimentin and collagen I. This fibrogenic response was blunted in mice injected with either SSC-ZVAD or SSC immunodepleted of CTGF. These results bring new mechanistic insights into the fibrogenic pathways activated by EC death. Caspase activation in apoptotic EC triggers the production of LG3 and CTGF which in turn activate SFK/PI3K dependant pathways in fibroblasts thus activating a TGF-β-independent fibrogenic response.

Dysregulated wound healing is commonly associated with excessive fibrosis. Connective tissue growth factor (CTGF/CCN2) is characteristically overexpressed in fibrotic diseases and stimulated by transforming growth factor-β (TGF-β) in dermal fibroblasts. Reepithelialisation and epidermal wound coverage counteract excessive scar formation. We have previously shown that interleukin-1α (IL-1α) derived from keratinocytes conteracts TGF-β-stimulated CTGF-expression. The aim of this thesis was to further explore the effects of keratinocytes and IL-1α on gene and protein expression, as well as pathways, in TGF-β stimulated fibroblasts. Fibroblasts were studied in vitro by conventional two dimensional cell culture models and in a three dimensional keratinocyte-fibroblast organotypic skin culture model. The results showed that IL-1 suppresses basal and TGF-β-induced CTGF mRNA and protein, involving a possible TAK1 mechanism. Keratinocytes regulate the expression of fibroblast genes important for the turnover of the extracellular matrix. Most of the genes analysed (11/13) were regulated by TGF-β and counter regulated by keratinocytes. The overall results support a view that keratinocytes regulate fibroblasts to act catabolically (anti-fibrotic) on the extracellular matrix. Transcriptional microarray and gene set enrichment analysis showed that antagonizing effects of IL-1α on TGF-β were much more prominent than the synergistic effects. The most confident of these pathways was the interferon signaling, which were inhibited by TGF-β and activated by IL-1α. A proteomics study confirmed that IL-1α preferentially conteracts TGF-β effects. Six new fibroblast proteins involved in synthesis/ regulation were identified, being regulated by TGF-β and antagonized by IL-1α. Pathway analysis confirmed counter-regulation of interferon signaling by the two cytokines. These findings have implications for understanding the role of fibroblasts for inflammatory responses and development of fibrosis in the skin.

No description available.

No description available.

L'utérus est un organe hautement dynamique, qui subit des changements morphologiques durant le cycle œstral sous l'influence des hormones sexuelles. Ces adaptations sont essentielles à l’homéostasie utérine et résultent d’une régulation minutieuse de la prolifération, de la différenciation et de la survie cellulaire par de nombreuses voies de signalisation. Nous avons émis l'hypothèse que la voie Hippo est impliquée dans l'homéostasie utérine chez l’espèce bovine, et nous avons tenté de déterminer les variations de ses constituants. Des biopsies de l'endomètre et des échantillons de sang ont été obtenus aux jours 0, 3 et 10 du cycle chez 14 vaches. Les concentrations sanguines de progestérone et d’œstrogène ont confirmé la progression du cycle œstral chez cinq vaches. Des analyses immunohistochimiques, Western Blot et RT-PCR ont été réalisées sur les biopsies afin d’évaluer la variation des composantes de la voie Hippo et de ses gènes cibles. Nous avons démontré la présence de YAP et de TAZ dans l'endomètre bovin à tous les moments du cycle œstral. Elles présentaient une expression cytoplasmique dans l'épithélium glandulaire, et présentaient une expression nucléaire dans le stroma à J0 et J10 et dans l'épithélium luminal à J3. Nous avons également noté une tendance à l'augmentation des concentrations de la forme phosphorylée de YAP au jour 3 du cycle œstral par rapport aux jours 0 et 10. Cette augmentation a été corrélée à une diminution de l'expression du gène CTGF au jour 3 par rapport aux autres jours du cycle œstral. En conclusion, nous avons démontré que la voie Hippo est exprimée différentiellement dans l'utérus bovin au cours du cycle œstral. / The uterus is a highly dynamic organ that changes morphologically under the influence of sexual hormones during the estrous cycle. These adaptations are essential for the proper function of the uterus and are due to the careful regulation of cell proliferation, differentiation, and apoptosis by numerous signaling pathways. We hypothesized that the Hippo pathway is implicated in uterine homeostasis in cattle, and we aimed to determine the variation of its canonical constituents during the bovine cycle. Endometrial biopsies and blood samples were obtained on days 0, 3, and 10 of the cycle in 14 cows. Progesterone and estrogens blood concentrations were measured and confirmed the status of the oestrus cycle in five cows. Immunohistochemistry, western blot, and RT-PCR were then performed on their endometrial biopsies to evaluate the Hippo components and targeted genes. Our results showed the presence of YAP and TAZ in the bovine endometrium at all time point. Both proteins displayed cytoplasmic expression in the glandular epithelium while exhibiting nuclear expression in the stroma on D0 and D10 and in the luminal epithelium on D3. We also noted a tendency for an increased amount of phosphorylated YAP during day 3 of the estrous cycle compared to days 0 and 10. It was correlated with a decreased expression of CTGF (Hippo target gene) on day 3 compared to the other day of the cycle. In conclusion, we can confirm that Hippo is differentially expressed in the bovine uterus during the estrous cycle.

No description available.