Corinne Barreau

Immunomodulatory effect of human adipose tissue-derived adult stem cells: comparison with bone marrow mesenchymal stem cells.

Like mesenchymal stem cells from bone marrow (BM‐MSCs), adipose tissue‐derived adult stem cells (ADAS cells) can differentiate into several lineages and present therapeutical potential for repairing damaged tissues. The use of allogenic stem cells can enlarge their therapeutical interest, provided that the grafted cells could be tolerated. We investigate here, for the first time, the immunosuppressive properties of ADAS cells compared with the well‐characterized immunosuppressive properties of BM‐MSCs. ADAS cells did not provoke in vitro alloreactivity of incompatible lymphocytes and, moreover, suppressed mixed lymphocyte reaction (MLR) and lymphocyte proliferative response to mitogens. The impairment of inhibition when ADAS cells and BM‐MSCs were separated from lymphocytes by a permeable membrane suggests that cell contact is required for a full inhibitory effect. Hepatocyte growth factor is secreted by both stem cells but, similar to interleukin‐10 and transforming growth factor‐β (TGF‐β), the levels of which were undetectable in supernatants of MLR inhibited by ADAS cells or BM‐MSCs, it did not seem implicated in the stem cell suppressive effect. These findings support that ADAS cells share immunosuppressive properties with BM‐MSCs. Therefore, ADAS cell‐based reconstructive therapy could employ allogenic cells and because of their immunosuppressive properties, ADAS cells could be an alternative source to BM‐MSCs to treat allogenic conflicts.

Human subcutaneous adipose cells support complete differentiation but not self-renewal of hematopoietic progenitors

Adipose tissue is now considered as an endocrine organ implicated in energy regulation, inflammation and immune response, and as a source of multipotent cells with a broad range of differentiation capacities. Some of these cells are of a mesenchymal type which can—like their bone marrow (BM) counterpart—support hematopoiesis, since in a previous study we were able to reconstitute lethally irradiated mice by cells isolated from adipose tissue. In the present study, we established that cells derived from the stroma‐vascular fraction of human subcutaneous fat pads support the complete differentiation of hematopoietic progenitors into myeloid and B lymphoid cells. However, these cells are unable to maintain the survival and self‐renewal of hematopoietic stem cells. These features, similar to those of BM adipocytes, are the opposite of those of other cell types derived from mesenchymal progenitors such as BM myofibroblasts or osteoblasts. Because it is abundant and accessible, adipose tissue could be a convenient source of cells for the short‐term reconstitution of hematopoiesis in man. J. Cell. Physiol. 208: 282–288, 2006.

Browning of White Adipose Cells by Intermediate Metabolites: An Adaptive Mechanism to Alleviate Redox Pressure

The presence of brown adipose tissue (BAT) in human adults opens attractive perspectives to treat metabolic disorders. Indeed, BAT dissipates energy as heat via uncoupling protein (UCP)1. Brown adipocytes are located in specific deposits or can emerge among white fat through the so-called browning process. Although numerous inducers have been shown to drive this process, no study has investigated whether it could be controlled by specific metabolites. Here, we show that lactate, an important metabolic intermediate, induces browning of murine white adipose cells with expression of functional UCP1. Lactate-induced browning also occurs in human cells and in vivo. Lactate controls Ucp1 expression independently of hypoxia-inducible factor-1α and PPARα pathways but requires active PPARγ signaling. We demonstrate that the lactate effect on Ucp1 is mediated by intracellular redox modifications as a result of lactate transport through monocarboxylate transporters. Further, the ketone body β-hydroxybutyrate, another metabolite that impacts redox state, is also a strong browning inducer. Because this redox-dependent increase in Ucp1 expression promotes an oxidative phenotype with mitochondria, browning appears as an adaptive mechanism to alleviate redox pressure. Our findings open new perspectives for the control of adipose tissue browning and its physiological relevance.

Adipose-derived cardiomyogenic cells: in vitro expansion and functional improvement in a mouse model of myocardial infarction

AIMS Cells derived from the stroma vascular fraction (SVF) of mouse adipose tissue can spontaneously give rise to rare, functional, cardiac-like cells in vitro. This study aimed to improve the production of adipose-derived cardiomyogenic cells (AD-CMG), to characterize them and to assess their cardiac fate and functional outcomes after their administration in a mouse model of acute myocardial infarction. METHODS AND RESULTS The culture process optimized to improve in vitro cardiac specification consisted of a primary culture of murine SVF cells in semi-solid methylcellulose medium, a selection of AD-CMG cell clusters, and a secondary culture and expansion in BHK21 medium. AD-CMG cells were CD29(+), CD31(-), CD34(-), CD44(+), CD45(-), CD81(+), CD90(-), CD117(-), and Flk-1(-) and expressed several cardiac contractile proteins. After 1, 2, and 4 weeks of their injection in mice having acute myocardial infarction, a strong presence of green fluorescent protein-positive cells was identified by immunohistochemistry as well as quantitative polymerase chain reaction. Echocardiography showed a significant reduction of remodelling and stability of left ventricle ejection fraction in the AD-CMG cell-treated group vs. controls. Vascular density analysis revealed that AD-CMG administration was also associated with stimulation of angiogenesis in peri-infarct areas. CONCLUSION Cardiomyogenic cells can be selected and expanded in large amounts from mouse adipose tissue. They can survive and differentiate in an acute myocardial infarction model, avoiding remodelling and impairment of cardiac function, and can promote neo-vascularization in the ischaemic heart.

Preconditioning by Mitochondrial Reactive Oxygen Species Improves the Proangiogenic Potential of Adipose-Derived Cells-Based Therapy

Objective—Transplantation of adipose-derived stroma cells (ADSCs) stimulates neovascularization after experimental ischemic injury. ADSC proangiogenic potential is likely mediated by their ability to differentiate into endothelial cells and produce a wide array of angiogenic and antiapoptotic factors. Mitochondrial reactive oxygen species (ROS) have been shown to control ADSC differentiation. We therefore hypothesized that mitochondrial ROS production may change the ADSC proangiogenic properties. Methods and Results—The use of pharmacological strategies (mitochondrial inhibitors, antimycin, and rotenone, with or without antioxidants) allowed us to specifically and precisely modulate mitochondrial ROS generation in ADSCs. We showed that transient stimulation of mitochondrial ROS generation in ADSCs before their injection in ischemic hindlimb strongly improved revascularization and the number of ADSC-derived CD31-positive cells in ischemic area. Mitochondrial ROS generation increased the secretion of the proangiogenic and antiapoptotic factors, VEGF and HGF, but did not affect ADSC ability to differentiate into endothelial cells, in vitro. Moreover, mitochondrial ROS-induced ADSC preconditioning greatly protect ADSCs against oxidative stress–induced cell death. Conclusion—Our study demonstrates that in vitro preconditioning by moderate mitochondrial ROS generation strongly increases in vivo ADSC proangiogenic properties and emphasizes the crucial role of mitochondrial ROS in ADSC fate.

Metabolic endotoxemia directly increases the proliferation of adipocyte precursors at the onset of metabolic diseases through a CD14-dependent mechanism

Metabolic endotoxemia triggers inflammation, targets cells from the stroma-vascular fraction of adipose depots, and metabolic disease. To identify these cells we here infused mice with lipopolysaccharides and showed by FACS analyses and BrdU staining that the number of small subcutaneous adipocytes, preadipocytes and macrophages increased in wild type but not in CD14-knockout (KO) mice. This mechanism was direct since in CD14KO mice grafted subcutaneously and simultaneously with fat pads from CD14KO and wild-type mice the concentration of cytokine mRNA was increased in the wild-type fat pad only. Conversely, the mRNA concentration of genes involved in glucose and lipid metabolism and the number of large adipocytes was reduced. Eventually, a pretreatment with LPS enhanced HFD-induced metabolic diseases. Altogether, these results show that metabolic endotoxemia increases the proliferation of preadipocytes through a CD14-dependent mechanism directly, without recruiting CD14-positive cells from non-adipose depot origin. This mechanism could precede the onset of metabolic diseases.

Xenobiotic-Metabolizing Cytochromes P450 in Human White Adipose Tissue: Expression and Induction

Lipophilic pollutants can accumulate in human white adipose tissue (WAT), and the consequences of this accumulation are still poorly understood. Cytochromes P450 (P450s) have recently been found in rat WAT and shown to be inducible through mechanisms similar to those in the liver. The aim of our study was to describe the cytochrome P450 pattern and their induction mechanisms in human WAT. Explants of subcutaneous and visceral WAT and primary culture of subcutaneous adipocytes were used as WAT models, and liver biopsies and primary culture of hepatocytes were used as liver models to characterize P450 expression in both tissues. The WAT and liver models were then treated with typical P450 inducers (rifampicin, phenobarbital, and 2,3,7,8-tetrachlorodibenzo-p-dioxin) and lipophilic pollutants (lindane, prochloraz, and chlorpyrifos), and the effects on P450 expression were studied. P450 expression was considerably lower in WAT than in the liver, except for CYP1B1 and CYP2U1, which were the most highly expressed adipose P450s in all individuals. 2,3,7,8-Tetrachlorodibenzo-p-dioxin and prochloraz induced CYP1A1 and CYP1B1 expression in both tissues. The aryl hydrocarbon receptor was also present in WAT. In contrast, neither phenobarbital nor rifampicin treatment induced CYP2 or CYP3 mRNA in WAT, and constitutive androstane receptor and pregnane X receptor were almost undetectable. These results suggest that the mechanisms by which P450s of family 1 are regulated in the liver are also functional in human WAT, but those regulating CYP2 and CYP3 expression are not.

Importance of mitochondrial dynamin-related protein 1 in hypothalamic glucose sensitivity in rats.

AIMS Hypothalamic mitochondrial reactive oxygen species (mROS)-mediated signaling has been recently shown to be involved in the regulation of energy homeostasis. However, the upstream signals that control this mechanism have not yet been determined. Here, we hypothesize that glucose-induced mitochondrial fission plays a significant role in mROS-dependent hypothalamic glucose sensing. RESULTS Glucose-triggered translocation of the fission protein dynamin-related protein 1 (DRP1) to mitochondria was first investigated in vivo in hypothalamus. Thus, we show that intracarotid glucose injection induces the recruitment of DRP1 to VMH mitochondria in vivo. Then, expression was transiently knocked down by intra-ventromedial hypothalamus (VMH) DRP1 siRNA (siDRP1) injection. 72 h post siRNA injection, brain intracarotid glucose induced insulin secretion, and VMH glucose infusion-induced refeeding decrease were measured, as well as mROS production. The SiDRP1 rats decreased mROS and impaired intracarotid glucose injection-induced insulin secretion. In addition, the VMH glucose infusion-induced refeeding decrease was lost in siDRP1 rats. Finally, mitochondrial function was evaluated by oxygen consumption measurements after DRP1 knock down. Although hypothalamic mitochondrial respiration was not modified in the resting state, substrate-driven respiration was impaired in siDRP1 rats and associated with an alteration of the coupling mechanism. INNOVATION AND CONCLUSION Collectively, our results suggest that glucose-induced DRP1-dependent mitochondrial fission is an upstream regulator for mROS signaling, and consequently, a key mechanism in hypothalamic glucose sensing. Thus, for the first time, we demonstrate the involvement of DRP1 in physiological regulation of brain glucose-induced insulin secretion and food intake inhibition. Such involvement implies DRP1-dependent mROS production.

Native Adipose Stromal Cells Egress from Adipose Tissue In Vivo: Evidence During Lymph Node Activation†‡§

Adipose tissue (AT) has become accepted as a source of multipotent progenitor cells, the adipose stromal cells (ASCs). In this regard, considerable work has been performed to harvest and characterize this cell population as well as to investigate the mechanisms by which transplanted ASCs mediate tissue regeneration. In contrast the endogenous release of native ASCs by AT has been poorly investigated. In this work, we show that native ASCs egress from murine AT. Indeed, we demonstrated that the release of native ASCs from AT can be evidenced both using an ex vivo perfusion model that we set up and in vivo. Such a mobilization process is controlled by CXCR4 chemokine receptor. In addition, once mobilized from AT, circulating ASCs were found to navigate through lymph fluid and to home into lymph nodes (LN). Therefore, we demonstrated that, during the LN activation, the fat depot encapsulating the activated LN releases native ASCs, which in turn invade the activated LN. Moreover, the ASCs invading the LN were visualized in close physical interaction with podoplanin and ER‐TR7 positive structures corresponding to the stromal network composing the LN. This dynamic was impaired with CXCR4 neutralizing antibody. Taken together, these data provide robust evidences that native ASCs can traffic in vivo and that AT might provide stromal cells to activated LNs. STEM Cells2013;31:1309–1320

Age-related changes in the features of porcine adult stem cells isolated from adipose tissue and skeletal muscle

A better understanding of the control of body fat distribution and muscle development is of the upmost importance for both human and animal physiology. This requires a better knowledge of the features and physiology of adult stem cells in adipose tissue and skeletal muscle. Thus the objective of the current study was to determine the type and proportion of these cells in growing and adult pigs. The different cell subsets of stromal vascular cells isolated from these tissues were characterized by flow cytometry using cell surface markers (CD11b, CD14, CD31, CD34, CD45, CD56, and CD90). Adipose and muscle cells were predominantly positive for the CD34, CD56, and CD90 markers. The proportion of positive cells changed with age especially in intermuscular adipose tissue and skeletal muscle where the percentage of CD90(+) cells markedly increased in adult animals. Further analysis using coimmunostaining indicates that eight populations with proportions ranging from 12 to 30% were identified in at least one tissue at 7 days of age, i.e., CD90(+)/CD34(+), CD90(+)/CD34(-), CD90(+)/CD56(+), CD90(+)/CD56(-), CD90(-)/CD56(+), CD56(+)/CD34(+), CD56(+)/CD34(-), and CD56(-)/CD34(+). Adipose tissues appeared to be a less heterogeneous tissue than skeletal muscle with two main populations (CD90(+)/CD34(-) and CD90(+)/CD56(-)) compared with five or more in muscle during the studied period. In culture, cells from adipose tissue and muscle differentiated into mature adipocytes in adipogenic medium. In myogenic conditions, only cells from muscle could form mature myofibers. Further studies are now needed to better understand the plasticity of those cell populations throughout life.