Identification of Adipose Tissue as a Reservoir of Macrophages after Acute Myocardial Infarction.

Medullary and extra-medullary hematopoiesis has been shown to govern inflammatory cell infiltration and subsequently cardiac remodeling and function after acute myocardial infarction (MI). Emerging evidence positions adipose tissue (AT) as an alternative source of immune cell production. We, therefore, hypothesized that AT could act as a reservoir of inflammatory cells that participate in cardiac homeostasis after MI. To reveal the distinct role of inflammatory cells derived from AT or bone marrow (BM), chimeric mice were generated using standard repopulation assays. We showed that AMI increased the number of AT-derived macrophages in the cardiac tissue. These macrophages exhibit pro-inflammatory characteristics and their specific depletion improved cardiac function as well as decreased infarct size and interstitial fibrosis. We then reasoned that the alteration of AT-immune compartment in type 2 diabetes could, thus, contribute to defects in cardiac remodeling. However, in these conditions, myeloid cells recruited in the infarcted heart mainly originate from the BM, and AT was no longer used as a myeloid cell reservoir. Altogether, we showed here that a subpopulation of cardiac inflammatory macrophages emerges from myeloid cells of AT origin and plays a detrimental role in cardiac remodeling and function after MI. Diabetes abrogates the ability of AT-derived myeloid cells to populate the infarcted heart.

Driving regeneration, instead of healing, in adult mammals: the decisive role of resident macrophages through efferocytosis.

Tissue repair after lesion usually leads to scar healing and thus loss of function in adult mammals. In contrast, other adult vertebrates such as amphibians have the ability to regenerate and restore tissue homeostasis after lesion. Understanding the control of the repair outcome is thus a concerning challenge for regenerative medicine. We recently developed a model of induced tissue regeneration in adult mice allowing the comparison of the early steps of regenerative and scar healing processes. By using studies of gain and loss of function, specific cell depletion approaches, and hematopoietic chimeras we demonstrate here that tissue regeneration in adult mammals depends on an early and transient peak of granulocyte producing reactive oxygen species and an efficient efferocytosis specifically by tissue-resident macrophages. These findings highlight key and early cellular pathways able to drive tissue repair towards regeneration in adult mammals.

Tissue Regeneration: The Dark Side of Opioids.

Opioids are regarded as among the most effective analgesic drugs and their use for the management of pain is considered standard of care. Despite their systematic administration in the peri-operative period, their impact on tissue repair has been studied mainly in the context of scar healing and is only beginning to be documented in the context of true tissue regeneration. Indeed, in mammals, growing evidence shows that opioids direct tissue repair towards scar healing, with a loss of tissue function, instead of the regenerative process that allows for recovery of both the morphology and function of tissue. Here, we review recent studies that highlight how opioids may prevent a regenerative process by silencing nociceptive nerve activity and a powerful anti-inflammatory effect. These data open up new perspectives for inducing tissue regeneration and argue for opioid-restricted strategies for managing pain associated with tissue injury.

Lipodystrophy-like features after total body irradiation among survivors of childhood acute leukemia.

BACKGROUND/OBJECTIVE: The number of long-term survivors of childhood acute leukemia (AL) is substantially growing. These patients are at high risk for metabolic syndrome (MS), especially those who received total body irradiation (TBI). The consequences of children's irradiation on adipose tissue (AT) development in adulthood are currently unknown. The objective of this study is to assess the impact of TBI on AT of childhood AL survivors. DESIGN: We compared the morphological and functional characteristics of AT among survivors of childhood AL who developed MS and received (n = 12) or not received (n = 12) TBI. SUBJECTS/METHODS: Body fat distribution and ectopic fat stores (abdominal visceral and liver fat) were evaluated by DEXA, MRI and 1H-spectroscopy. Functional characteristics of subcutaneous AT were investigated by studying gene expression and pre-adipocyte differentiation in culture. RESULTS: Patients who have received TBI exhibited a lower BMI (minus 5 kg/m2) and a lower waist circumference (minus 14 cm), especially irradiated women. Despite the lower quantity of intra-abdominal AT, irradiated patient displayed a nearly two-fold greater content of liver fat when compared to non-irradiated patient (17 vs 9%, P = 0.008). These lipodystrophic-like features are supplemented by molecular abnormalities in subcutaneous AT of irradiated patients: decrease of gene expression of SREBP1 (minus 39%, P = 0.01) and CIDEA (minus 36%, P = 0.004) and a clear alteration of pre-adipocyte differentiation. CONCLUSIONS: These results strongly support the direct effect of irradiation on AT, especially in women, leading to specific nonalcoholic fatty liver disease, despite lower BMI. A long-term appropriate follow-up is necessary for these patients.

Rapid and Efficient Production of Human Functional Mast Cells through a Three-Dimensional Culture of Adipose Tissue-Derived Stromal Vascular Cells.

Mast cells (MC) are innate immune cells involved in many physiological and pathological processes. However, studies of MC function and biology are hampered by the difficulties to obtain human primary MC. To solve this problem, we established a new method to produce easily and rapidly high numbers of MC for in vitro studies using human adipose tissue, which is an abundant and easy access tissue. Stromal vascular fraction of adipose tissue, obtained from human abdominal dermolipectomy, was cultured as spheroids in serum free medium supplemented in stem cell factor. Using this method, we generated, within 3 wk, a highly pure population of connective tissue-type MC expressing MC typical peptidases (tryptase, chymase, and carboxypeptidase-A3) with a yield increasing over time. Stem cell factor was required for this culture, but unlike MC derived from CD34+ cells, this culture did not depend on IL-3 and -6. MC obtained with this method degranulated following FcεRI cross-linking or stimulation by C5a, compound 48/80, and substance P. Interestingly, activation by anti-IgE of both white adipose tissue-MC and MC obtained from peripheral blood-derived CD34+ pluripotent progenitor cells induced the production of PGs as well as proinflammatory cytokines (TNF-α, Il-6, and GM-CSF). In conclusion, we developed a new time saving and reproducible method to produce highly pure and functional human MC in 3 wk from human adipose tissue.

Opioids prevent regeneration in adult mammals through inhibition of ROS production.

Inhibition of regeneration and induction of tissue fibrosis are classic outcomes of tissue repair in adult mammals. Here, using a newly developed model of regeneration in adult mammals i.e. regeneration after massive resection of an inguinal fat pad, we demonstrate that both endogenous and exogenous opioids prevent tissue regeneration in adults, by inhibiting the early production of reactive oxygen species (ROS) that generally occurs after lesion and is required for regeneration. These effects can be overcome and regeneration induced by the use of an opioid antagonist. The results obtained in both our new model and the gold standard adult zebrafish demonstrate that this mechanism can be considered as a general paradigm in vertebrates. This work clearly demonstrates that ROS is required for tissue regeneration in adult mammals and shows the deleterious effect of opioids on tissue regeneration through the control of this ROS production. It thus raises questions about opioid-based analgesia in perioperative care.

Sex Differences in Stroke Attack, Incidence, and Mortality Rates in Northern France.

BACKGROUND: Age and sex have a major impact on stroke onset. AIMS: We aimed to compare the attack, incidence, and 28-day mortality rate for stroke as well as risk factors in men and women aged 35 and over. METHODS: Data were obtained between 2008 and 2015 from the stroke population-based registry covering the city of Lille (northern France). RESULTS: A total of 2426 strokes (1917 incident strokes) were recorded. The number of strokes was lower in women than in men when considering individuals under the age of 75 but was twice as high when considering individuals aged 75 or over. Overall, there were 25% more strokes in women than in men. The age-adjusted attack (P = .017) and incident (P = .027) rates of stroke were ~30% lower in women than in men (a ~30% lower risk of ischemic stroke (P = .02) and a ~40% lower risk of intracerebral hemorrhage (ICH) (P = .004)). The age-adjusted mortality rate after ICH was ~35% lower in women than in men (P = .014). With regard to cardiovascular risk factors, women with stroke were older, smoked less, and were more likely to have a history of migraine or atrial fibrillation than the men. CONCLUSION: The risk of stroke is lower in women than in men under the age of 75 but is similar when comparing women and men after that age. Nevertheless, the age structure of the population (with more elderly women than elderly men) translates into a higher absolute number of strokes in women than in men.

Corrupted adipose tissue endogenous myelopoiesis initiates diet-induced metabolic disease.

Activation and increased numbers of inflammatory macrophages, in adipose tissue (AT) are deleterious in metabolic diseases. Up to now, AT macrophages (ATM) accumulation was considered to be due to blood infiltration or local proliferation, although the presence of resident hematopoietic stem/progenitor cells (Lin-/Sca+/c-Kit+; LSK phenotype) in the AT (AT-LSK) has been reported. By using transplantation of sorted AT-LSK and gain and loss of function studies we show that some of the inflammatory ATM inducing metabolic disease, originate from resident AT-LSK. Transplantation of AT-LSK sorted from high fat diet-fed (HFD) mice is sufficient to induce ATM accumulation, and to transfer metabolic disease in control mice. Conversely, the transplantation of control AT-LSK improves both AT-inflammation and glucose homeostasis in HFD mice. Our results clearly demonstrate that resident AT-LSK are one of the key point of metabolic disease, and could thus constitute a new promising therapeutic target to fight against metabolic disease.

Mast cells regulate myofilament calcium sensitization and heart function after myocardial infarction.

Acute myocardial infarction (MI) is a severe ischemic disease responsible for heart failure and sudden death. Inflammatory cells orchestrate postischemic cardiac remodeling after MI. Studies using mice with defective mast/stem cell growth factor receptor c-Kit have suggested key roles for mast cells (MCs) in postischemic cardiac remodeling. Because c-Kit mutations affect multiple cell types of both immune and nonimmune origin, we addressed the impact of MCs on cardiac function after MI, using the c-Kit-independent MC-deficient (Cpa3(Cre/+)) mice. In response to MI, MC progenitors originated primarily from white adipose tissue, infiltrated the heart, and differentiated into mature MCs. MC deficiency led to reduced postischemic cardiac function and depressed cardiomyocyte contractility caused by myofilament Ca(2+) desensitization. This effect correlated with increased protein kinase A (PKA) activity and hyperphosphorylation of its targets, troponin I and myosin-binding protein C. MC-specific tryptase was identified to regulate PKA activity in cardiomyocytes via protease-activated receptor 2 proteolysis. This work reveals a novel function for cardiac MCs modulating cardiomyocyte contractility via alteration of PKA-regulated force-Ca(2+) interactions in response to MI. Identification of this MC-cardiomyocyte cross-talk provides new insights on the cellular and molecular mechanisms regulating the cardiac contractile machinery and a novel platform for therapeutically addressable regulators.

Differential Hematopoietic Activity in White Adipose Tissue Depending on its Localization.

White adipose tissue (WAT) can be found in different locations in the body, and these different adipose deposits exhibit specific physiopathological importance according to the subcutaneous or abdominal locations. We have shown previously the presence of functional hematopoietic stem/progenitor cells (HSPC) in subcutaneous adipose tissue (SCAT). These cells exhibit a specific hematopoietic activity that contributes to the renewal of the immune cell compartment within this adipose deposit. In this study, we investigated whether HSPC can be found in visceral adipose tissue (VAT) and whether a putative difference in in situ hematopoiesis may be related to anatomical location and to site-specific immune cell content in VAT compared to SCAT. Therein, we identified for the first time the presence of HSPC in VAT. Using both in vitro assays and in vivo competitive repopulation experiments with sorted HSPC from VAT or SCAT, we showed that the hematopoietic activity of HSPC was lower in VAT, compared to SCAT. In addition, this altered hematopoietic activity of HSPC in VAT was due to their microenvironment, and may be related to a specific combination of secreted factors and extracellular matrix molecules expressed by adipose derived stromal cells. Our results indicate that WAT specific hematopoietic activity may be generalized to all adipose deposits, although with specificity according to the fat pad location. Considering the abundance of WAT in the body, this emphasizes the potential importance of this hematopoietic activity in physiopathological situations.

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.

[Recruitment and activation of brown and/or BRITE adipocytes : potential therapeutic against metabolic diseases]. / Le recrutement et l'activation d'adipocytes bruns et/ou BRITE - Une perspective réelle pour le traitement des maladies métaboliques ?

In mammals, typically two types of adipose tissues are described: the white and the brown adipose tissue (WAT and BAT respectively). Whereas WAT represents the main energy storage in the organism, BAT dissipates energy as heat through the expression of the uncoupling protein UCP1 (uncoupling protein-1) that uncouples the functioning of the respiratory chain from ATP synthase. While both white and brown adipocytes have been considered for a long time as two very close cellular types sharing a common precursor, recent data challenge these conclusions and propose the existence of a new possible type of adipocyte, the BRITE (brown-in-white) adipocyte. In parallel, the recent discovery of significant amounts of BAT in human adults has renewed the interest of the scientific community for this tissue. Given its considerable capacity to dissipate substrates, BAT appears again as a therapeutic target against metabolic diseases such as diabetes and obesity. This review's objective is to discuss recent literature and to highlight elements to be clarified.

In situ production of innate immune cells in murine white adipose tissue.

White adipose tissue (WAT) is the focus of new interest because of the presence of an abundant and complex immune cell population that is involved in key pathologies such as metabolic syndrome. Based on in vivo reconstitution assays, it is thought that these immune cells are derived from the bone marrow (BM). However, previous studies have shown that WAT exhibits specific hematopoietic activity exerted by an unknown subpopulation of cells. In the present study, we prospectively isolated a peculiar hematopoietic stem/progenitor cell population from murine WAT. The cells are phenotypically similar to BM hematopoietic stem cells and are able to differentiate into both myeloid and lymphoid lineages in vitro. In competitive repopulation assays in vivo, they reconstituted the innate immune compartment in WAT preferentially and more efficiently than BM cells, but did not reconstitute hematopoietic organs. They were also able to give rise to multilineage engraftment in both secondary recipients and in utero transplantation. Therefore, we propose that WAT hematopoietic cells constitute a population of immature cells that are able to renew innate immune cell populations. Considering the amount of WAT in adults, our results suggest that WAT hematopoietic activity controls WAT inflammatory processes and also supports innate immune responses in other organs.

Adipose-derived stromal cells: Their identity and uses in clinical trials, an update.

In adults, adipose tissue is abundant and can be easily sampled using liposuction. Largely involved in obesity and associated metabolic disorders, it is now described as a reservoir of immature stromal cells. These cells, called adipose-derived stromal cells (ADSCs) must be distinguished from the crude stromal vascular fraction (SVF) obtained after digestion of adipose tissue. ADSCs share many features with mesenchymal stem cells derived from bone marrow, including paracrine activity, but they also display some specific features, including a greater angiogenic potential. Their angiogenic properties as well as their paracrine activity suggest a putative tumor-promoting role for ADSCs although contradictory data have been published on this issue. Both SVF cells and ADSCs are currently being investigated in clinical trials in several fields (chronic inflammation, ischemic diseases, etc.). Apart from a phase III trial on the treatment of fistula, most of these are in phase I and use autologous cells. In the near future, the end results of these trials should provide a great deal of data on the safety of ADSC use.

Human adipose-derived stromal cells efficiently support hematopoiesis in vitro and in vivo: a key step for therapeutic studies.

Adipose-derived stromal cells (ADSCs) are close relatives of bone marrow mesenchymal stromal cells (BM-MSCs). The ease of access to subcutaneous fat pad and the abundance of stromal precursors make fat tissue an attractive source of stromal cells for clinicians. However, their ability to support hematopoietic stem cells in vitro and in vivo has not been established definitively. Thus, their usefulness in supporting hematopoietic stem cell engraftment is not as clear as with BM-MSCs. In this article, we show that human ADSCs, cultured with a good manufacturing practice medium, maintain in vitro human early and committed hematopoietic progenitors and support their complete differentiation toward myeloid and lymphoid lineages. Compared with BM-MSCs, ADSCs elicit a more precocious early progenitor formation and faster proliferation and differentiation of hematopoietic progenitors. Further, in vivo, when co-injected in NOD.Cg-Prkdc(scid) Il2(rgtm1Wjl)/SzJ (NSG) mice with a low number of human CD34(+) cells, ADSCs enabled the higher production of immature human hematopoietic progenitors and CD45(+) cells when compared with BM-MSCs. As a whole, our results indicate that human ADSCs, isolated and expanded under clinical-grade conditions, support hematopoiesis in vitro and in vivo and thus provide the rationale for their use in supporting hematopoietic reconstitution in clinical settings.

Adipose tissue as a dedicated reservoir of functional mast cell progenitors.

White adipose tissue (WAT) is a heterogeneous tissue, found in various locations throughout the body, containing mature adipocytes and the stroma-vascular fraction (SVF). The SVF includes a large proportion of immune hematopoietic cells, among which, mast cells that contribute to diet-induced obesity. In this study, we asked whether mast cells present in mice adipose tissue could derive from hematopoietic stem/progenitor cells (HSPC) identified in the tissue. We therefore performed both in vitro and in vivo experiments dedicated to monitoring the progeny of WAT-derived HSPC. The entire study was conducted in parallel with bone marrow-derived cells, considered the gold standard for hematopoietic-lineage studies. Here, we demonstrate that adipose-derived HSPC contain a precursor-cell population committed to the mast cell lineage, and able to efficiently home to peripheral organs such as intestine and skin, where it acquires properties of functional tissue mast cells. Additionally, WAT contains a significant mast cell progenitor population, suggesting that the entire mast cell lineage process take place in WAT. Considering the quantitative importance of WAT in the adult organism and the increasing roles recently assigned to mast cells in physiopathology, WAT may represent an important source of mast cells in physiological and pathological situations.

Vascular and endothelial regeneration.

Adipose tissue is the final tissue to develop and is strongly involved in energy homeostasis. It can represent up to 50% of body weight in obesity. Beside its metabolic role, endocrine functions appeared to play a key role in interconnecting adipose tissue with other tissues of the organism and in numerous physiological functions. The presence of adipocyte progenitors has long been demonstrated throughout life in the stromal fraction of adipose tissue. Now, it appears that these cells are multipotent and share numerous features with mesenchymal stem cells (MSC) derived from bone marrow. They also display some specificities and a strong pro-angiogenic potential. Altogether, these data emphasize the need to reconsider the potential of adipose tissue. Moreover, since fat pads are easy to sample, numerous and promising perspectives are now opening up in regenerative medicine, particularly in ischemic situations.

Adult stromal cells derived from human adipose tissue provoke pancreatic cancer cell death both in vitro and in vivo.

BACKGROUND: Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. Disrupting this homeostasis can induce aberrant cell proliferation, adhesion, function and migration that might promote malignant behavior. Indeed, aberrant stromal-epithelial interactions contribute to pancreatic ductal adenocarcinoma (PDAC) spread and metastasis, and this raises the possibility that novel stroma-targeted therapies represent additional approaches for combating this malignant disease. The aim of the present study was to determine the effect of human stromal cells derived from adipose tissue (ADSC) on pancreatic tumor cell proliferation. PRINCIPAL FINDINGS: Co-culturing pancreatic tumor cells with ADSC and ADSC-conditioned medium sampled from different donors inhibited cancer cell viability and proliferation. ADSC-mediated inhibitory effect was further extended to other epithelial cancer-derived cell lines (liver, colon, prostate). ADSC conditioned medium induced cancer cell necrosis following G1-phase arrest, without evidence of apoptosis. In vivo, a single intra-tumoral injection of ADSC in a model of pancreatic adenocarcinoma induced a strong and long-lasting inhibition of tumor growth. CONCLUSION: These data indicate that ADSC strongly inhibit PDAC proliferation, both in vitro and in vivo and induce tumor cell death by altering cell cycle progression. Therefore, ADSC may constitute a potential cell-based therapeutic alternative for the treatment of PDAC for which no effective cure is available.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 deficiency reduces leukocyte infiltration into adipose tissue and favors fat deposition.

Obesity is associated with low-grade inflammation and leukocyte infiltration in white adipose tissue (WAT) and is linked to diabetic complications. Semicarbazide-sensitive amine oxidase, also known as vascular adhesion protein-1 (SSAO/VAP-1), is a membrane protein that is highly expressed in adipocytes and is also present on the endothelial cell surface where it is involved in leukocyte extravasation. We studied fat deposition and leukocyte infiltration in WAT of mice with a null mutation in the amine oxidase copper-containing-3 (AOC3) gene encoding SSAO/VAP-1. Both epididymal and inguinal WATs were larger in 6-month-old AOC3-KO males than in age-matched wild-type controls. However, WAT from AOC3-KO mice contained lower CD45 mRNA levels and fewer CD45(+) leukocytes. Subpopulation analyses revealed a diminished infiltration of WAT by T cells, macrophages, natural killer, and natural killer T cells. A decrease in leukocyte content in WAT was also detected in female AOC3-KO mice as early as 2 months of age, whereas increased fat mass was evident by 6 months of age. Reduced CD45(+) populations in WAT of AOC3-KO mice was not rescued by human SSAO/VAP-1 expression on adipocytes under the control of aP2, suggesting the importance of vascular AOC3 in leukocyte entrance into fat. Our results indicate that SSAO/VAP-1 is instrumental for the presence of leukocytes in WAT. Therefore, AOC3-KO mice present a unique model of mild obesity, characterized by increased WAT devoid of low-grade inflammation.

Comparative proteomic analysis of human mesenchymal and embryonic stem cells: towards the definition of a mesenchymal stem cell proteomic signature.

Mesenchymal stem cells (MSC) are adult multipotential progenitors which have a high potential in regenerative medicine. They can be isolated from different tissues throughout the body and their homogeneity in terms of phenotype and differentiation capacities is a real concern. To address this issue, we conducted a 2-DE gel analysis of mesenchymal stem cells isolated from bone marrow (BM), adipose tissue, synovial membrane and umbilical vein wall. We confirmed that BM and adipose tissue derived cells were very similar, which argue for their interchangeable use for cell therapy. We also compared human mesenchymal to embryonic stem cells and showed that umbilical vein wall stem cells, a neo-natal cell type, were closer to BM cells than to embryonic stem cells. Based on these proteomic data, we could propose a panel of proteins which were the basis for the definition of a mesenchymal stem cell proteomic signature.