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Lrig1 is known to repress the epidermal growth through its inhibitory activity on EGFR, while CD44 promotes it. We analyzed the expression of these molecules in senescent atrophic human epidermis and in the epidermis of CD44KO mice. In normal human epidermis, Lrig1+ cells form clusters located in the basal layer in which CD44 expression is downregulated and Lef1 expression reflects an active Wnt signaling. In senescent atrophic human epidermis, we found retention of Lrig1high+ cells all along the basal layer, forming no clusters, with decrease of CD44 and lef1 expression. In vitro silencing of CD44 indicated that CD44 may be required for Wnt signaling. However, if looking at the ear epidermis of CD44KO mice, we only found a limited interfollicular epidermal atrophy and unchanged Lrig1high+ cells in the hair follicle. Cell lineage tracing further revealed that interfollicular epidermis did lost its self-renewing capacity but that its homeostasis relied on Lrig1-derived keratinocytes migrating from the hair follicle. Therefore, we conclude that CD44 downregulation is part of the phenotype of senescent atrophic human epidermis, and contributes to reduce Wnt signaling and to alter Lrig1high+ stem cell distribution.

Myocardial reperfusion injury is mediated by several processes including increase of reactive oxygen species (ROS). The aim of the study is to identify potential sources of ROS contributing to myocardial ischemia reperfusion injury. For this purpose we investigated myocardial ischemia/reperfusion pathology in mice deficient in various NADPH oxidase isoforms (Nox1 Nox2 Nox4 as well as Nox1/2 double knockout). Following 30. min of ischemia and 24. h of reperfusion a significant decrease in the size of myocardial infarct was observed in Nox1 Nox2 and Nox1/Nox2 but not in Nox4 deficient mice. However no protection was observed in a model of chronic ischemia suggesting that NOX1 and NOX2 mediated oxidative damage occurs during reperfusion. Cardioprotective effect of Nox1 and Nox2 deficiencies was associated with decrease of neutrophil invasion but on the other hand an improved reperfusion injury was also observed in isolated perfused hearts (Langendorff model) suggesting that inflammatory cells were not the major source of oxidative damage. A decrease in global post reperfusion oxidative stress was clearly detected in Nox2 but not in Nox1 deficient hearts. Analysis of key signaling pathways during reperfusion suggests distinct cardioprotective patterns: increased phosphorylation was seen for Akt and Erk in Nox1 deficient mice and for Stat3 and Erk in Nox2 deficient mice. Consequently NOX1 and NOX2 represent interesting drug targets for controlling reperfusion damage associated with revascularization in coronary disease. © 2013 Elsevier Ltd.

The Pax6 transcription factor is crucial for endocrine cell differentiation and function. Indeed, mutations of Pax6 are associated with a diabetic phenotype and a drastic decrease of insulin-positive cell number. Our aim was to better define the β-cell Pax6 transcriptional network and thus provide further information concerning the role of Pax6 in β-cell function. We developed a Pax6-deficient model in rat primary β-cells with specific small interfering RNA leading to a 75% knockdown of Pax6 expression. Through candidate gene approach, we confirmed that Pax6 controls the mRNA levels of the insulin 1 and 2, Pdx1, MafA, GLUT2, and PC1/3 genes in β-cells. Importantly, we identified new Pax6 target genes coding for GK, Nkx6.1, cMaf, PC2, GLP-1R and GIPR which are all involved in β-cell function. Furthermore, we demonstrated that Pax6 directly binds and activates specific elements on the promoter region of these genes. We also demonstrated that Pax6 knockdown led to decreases in insulin cell content, in insulin processing, and a specific defect of glucose-induced insulin secretion as well as a significant reduction of GLP-1 action in primary β-cells. Our results strongly suggest that Pax6 is crucial for β-cells through transcriptional control of key genes coding for proteins that are involved in insulin biosynthesis and secretion as well as glucose and incretin actions on β-cells. We provide further evidence that Pax6 represents a key element of mature β-cell function.

Chronic granulomatous disease (CGD), caused by a lack of reactive oxygen species (ROS) generation by the phagocyte NADPH oxidase NOX2, leads to massively increased inflammatory responses. In order to identify the type of phagocyte which requires NOX2 activity to limit inflammation, we investigated mice with a loss of function mutation in the Ncf1 gene coding for the p$47^{\rm{phox}}$ subunit of NOX2 and mice with transgenic rescue of Ncf1 under control of the CD68 promoter. To induce CGD hyperinflammation, different mouse genotypes were injected intradermally with β-glucan. Ncf1 mutant mice showed massive and prolonged hyperinflammation. Hyperinflammatory lesions were characterized by persistent neutrophilic infiltration, along with ulceration and necrosis. In contrast, in CD68 promoter rescue mice inflammation resolved within days, as seen in wild-type animals. Measurements of ROS in rescue mice demonstrated functional NOX2 in mononuclear phagocytes (macrophages and dendritic cells) but not in neutrophils. This absence of NOX2 function was also confirmed in inflammatory tissue neutrophils. Lack of functional NOX2 in mononuclear phagocytes increased the secretion of IL-1β at early time points and of IL-6 and TNFα at later time points. Thus, CGD hyperinflammation is a redox dysregulation in mononuclear phagocytes, demonstrating a cell type-specific anti-inflammatory function of NOX2.

The Spatial gene is expressed in highly polarized cell types such as testis germ cells, brain neurons and thymic epithelial cells (TEC). Its expression was documented in testis and brain but poorly characterized in thymus. Here, we characterize for the first time Spatial-expressing TEC throughout ontogeny and adult mouse thymus. Spatial is expressed in thymic-fated domain by embryonic day E10.5 and persists in subcapsular, cortical, medullary epithelial cells and in MTS24+ progenitor TEC. Using mouse strains in which thymocyte development is blocked at various stages, we show that Spatial expression is independent of thymocyte-derived signals during thymus organogenesis. Analyses on purified thymic cell subsets show that Spatial short isoforms are expressed in cortical TEC (cTEC) and mature medullary TEC (mTEC). Spatial long isoforms were detected in the same TEC population. Spatial presents a nuclear distribution specific to mature mTEC expressing UEA1 and Aire. Aire- and RANKL-deficientmice revealed that Spatial expression is drastically reduced in the thymus of these mutants. These findings reveal a critical function of Aire in regulating Spatial expression, which is compatible with promiscuous Spatial gene expression. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA., Funded by: Institut National de la Santé et de la Recherche Médicale (INSERM).