TGFbeta Family Members Are Key Mediators in the Induction of Myofibroblast Phenotype of Human Adipose Tissue Progenitor Cells by Macrophages

International audienceOBJECTIVE: The present study was undertaken to characterize the remodeling phenotype of human adipose tissue (AT) macrophages (ATM) and to analyze their paracrine effects on AT progenitor cells. RESEARCH DESIGN AND METHODS: The phenotype of ATM, immunoselected from subcutaneous (Sc) AT originating from subjects with wide range of body mass index and from paired biopsies of Sc and omental (Om) AT from obese subjects, was studied by gene expression analysis in the native and activated states. The paracrine effects of ScATM on the phenotype of human ScAT progenitor cells (CD34(+)CD31(-)) were investigated. RESULTS: Two main ATM phenotypes were distinguished based on gene expression profiles. For ScAT-derived ATM, obesity and adipocyte-derived factors favored a pro-fibrotic/remodeling phenotype whereas the OmAT location and hypoxic culture conditions favored a pro-angiogenic phenotype. Treatment of native human ScAT progenitor cells with ScATM-conditioned media induced the appearance of myofibroblast-like cells as shown by expression of both α-SMA and the transcription factor SNAIL, an effect mimicked by TGFβ1 and activinA. Immunohistochemical analyses showed the presence of double positive α-SMA and CD34 cells in the stroma of human ScAT. Moreover, the mRNA levels of SNAIL and SLUG in ScAT progenitor cells were higher in obese compared with lean subjects. CONCLUSIONS: Human ATM exhibit distinct pro-angiogenic and matrix remodeling/fibrotic phenotypes according to the adiposity and the location of AT, that may be related to AT microenvironment including hypoxia and adipokines. Moreover, human ScAT progenitor cells have been identified as target cells for ScATM-derived TGFβ and as a potential source of fibrosis through their induction of myofibroblast-like cells

Régulations croisées entre signalisation lipidique et signalisation dépendant des nucléotides cycliques dans l\u27activation lymphocytaire : rôle de l\u27acide phosphatidique

L\u27activation mitogénique des cellules mononuclééés de sang périphérique humain (PBMC) augmente la production d\u27acide phosphatidique (PA) et stimule l\u27activité phosphodiestérase (PDE) des nucléotides cycliques. De plus, en système acellulaire, le PA stimule directement l\u27activité PDE. L\u27effet mitogénique du PA pourrait donc être dû à une activation des PDE conduisant à une diminution du taux intracellulaires d\u27AMPc, signal inhibiteur de la lymphoprolifération. Ce travail montre que la lectine mitogénique Concanavaline A (Con A) augmente significativement la synthèse de PA dans les PBMC dès 5 min de stimulation, majoritairement par la voie PI-PLC/DAG-Kinase. D\u27autre part, l\u27étude en parallèle de la production de PA, des activités PDE et des taux d\u27AMPc induits par différents mitogènes dans une population cellulaire issue d\u27un même donneur montre qu\u27il existe une corrélation étroite entre les taux de PA et les activités PDE. De plus, les drogues diminuant la synthèse de PA suppriment l\u27activation des PDE et la réponse proliférative des cellules aux mitogènes. Enfin, les taux d\u27AMPc sont modestement, mais significativement diminués en réponse aux mitogènes. Le lien entre PA et réponse mitogènique a aussi été étudié dans un modèle expérimental mimant une situation physiologique particulière : le vieillissement. Il s\u27agit de PBMC enrichies en 12-HETE, dérivé monohydroxylé issu de l\u27acide arachidonique par la voie 12-lipoxygénasique, caractérisées par une réponse proliférative diminuée. Le 12-HETE étant décrit comme un inhibiteur de DAG-Kinase, notre hypothèse était qu\u27il pouvait diminuer les taux de PA. Au contraire, nous avons montré une synthèse accrue de PA, par un mécanisme impliquant l\u27activation d\u27une PLD. De plus, cette activation ne dépend pas de PKC, met en jeu des tyrosine-phosphorylations, et probablement des sites de liaison du 12-HETE de faible affinité, couplés à une protéine G

Immune cells in adipose tissue: Key players in metabolic disorders.

International audienceObesity, defined as the excess development of adipose tissue, is an important risk factor for metabolic and cardiovascular diseases such as type 2 diabetes, hypertension and atherosclerosis. Over the past few years, metabolic inflammation has emerged as a major process underlying the link between obesity and its associated pathologies. Adipose tissue appears to play a primary and crucial role as a source and site of inflammation. Accumulation of immune cells within adipose tissue occurs in obese conditions. The present review focuses on the relationship between adipose tissue and immune cells, including macrophages, dendritic cells, T and B lymphocytes, and natural killer cells, in both the physiological state and under obese conditions. The factors involved in the accumulation of both myeloid and lymphoid cells in adipose tissue are also described. In addition, the role of adipose-tissue immune cells on adipocyte metabolism and cells of the adipose tissue stromal-vascular fraction are discussed, with particular emphasis on the cross-talk between macrophages and adipocytes, together with recent reports of T lymphocytes in adipose tissue

Adipose-derived stromal cells: cytokine expression and immune cell contaminants.

International audienceThe present method describes an immunoselection/depletion approach to isolate the native human adipose tissue-derived progenitor cells that are free from endothelial cells and immune cells by the use of magnetic nanobeads and microbeads coupled to antibodies. Moreover, methods to isolate and to analyse the distinct cell populations that constitute the microenvironment of the human adipose tissue progenitor cells, i.e. mature adipocytes, endothelial cells, and macrophages, are mentioned

Evidence of in situ proliferation of adult adipose tissue-derived progenitor cells: influence of fat mass microenvironment and growth.

International audienceCONTEXT: Adipocyte formation in human adult adipose tissue (hAT) originates from resident progenitor cell differentiation in the stroma vascular fraction of the AT. The processes involved in the self-renewal of this cell population remain to be defined. OBJECTIVE: The objective was to study in situ and in vitro hAT progenitor cell (defined as CD34(+)/CD31(-) cells) proliferation. DESIGN AND PARTICIPANTS: In situ progenitor cell proliferation was assessed by immunohistochemistry and flow cytometry analyses on hAT from lean to obese subjects using the proliferation marker Ki-67. The effects of adipokines, hypoxia, and conditioned media (CM) from adipocytes, capillary endothelial cells, and macrophages isolated by an immunoselection approach were studied on hAT progenitor cell growth. Cell death in hAT was assessed by the terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein end labeling method. RESULTS: Ki-67-positive staining was observed in AT progenitor cells. Fat mass enlargement in obese patients was associated with an increased Ki-67(+) progenitor cell population together with a new fraction of small adipocytes and increased cell death. HIF-1alpha mRNA expression in freshly harvested progenitor cells was positively correlated with body mass index. Adipocyte- and capillary endothelial cell-CM, hypoxia, leptin, IL-6, lysophosphatidic acid, and vascular endothelial growth factor, all increased hAT progenitor cell proliferation in vitro. Macrophage-CM had an antiproliferative effect that was suppressed by an antioxidant. CONCLUSIONS: The fraction of proliferative progenitor cells in adult hAT is modulated by the degree of adiposity. Changes in the progenitor cell microenvironment involving adipokines, hypoxia, and oxidative stress might play a key role in the control of the self-renewal of the local pool of AT progenitor cells