Neuropathy of haematopoietic stem cell niche is essential for myeloproliferative neoplasms.

Myeloproliferative neoplasms (MPNs) are diseases caused by mutations in the haematopoietic stem cell (HSC) compartment. Most MPN patients have a common acquired mutation of Janus kinase 2 (JAK2) gene in HSCs that renders this kinase constitutively active, leading to uncontrolled cell expansion. The bone marrow microenvironment might contribute to the clinical outcomes of this common event. We previously showed that bone marrow nestin(+) mesenchymal stem cells (MSCs) innervated by sympathetic nerve fibres regulate normal HSCs. Here we demonstrate that abrogation of this regulatory circuit is essential for MPN pathogenesis. Sympathetic nerve fibres, supporting Schwann cells and nestin(+) MSCs are consistently reduced in the bone marrow of MPN patients and mice expressing the human JAK2(V617F) mutation in HSCs. Unexpectedly, MSC reduction is not due to differentiation but is caused by bone marrow neural damage and Schwann cell death triggered by interleukin-1ß produced by mutant HSCs. In turn, in vivo depletion of nestin(+) cells or their production of CXCL12 expanded mutant HSC number and accelerated MPN progression. In contrast, administration of neuroprotective or sympathomimetic drugs prevented mutant HSC expansion. Treatment with ß3-adrenergic agonists that restored the sympathetic regulation of nestin(+) MSCs prevented the loss of these cells and blocked MPN progression by indirectly reducing the number of leukaemic stem cells. Our results demonstrate that mutant-HSC-driven niche damage critically contributes to disease manifestation in MPN and identify niche-forming MSCs and their neural regulation as promising therapeutic targets.

Nestin-expressing progenitor cells: function, identity and therapeutic implications.

The neuroepithelial stem cell protein, or Nestin, is a cytoskeletal intermediate filament initially characterized in neural stem cells. However, current extensive evidence obtained in in vivo models and humans shows presence of Nestin+ cells with progenitor and/or regulatory functions in a number of additional tissues, remarkably bone marrow. This review presents the current knowledge on the role of Nestin in essential stem cell functions, including self-renewal/proliferation, differentiation and migration, in the context of the cytoskeleton. We further discuss the available in vivo models for the study of Nestin+ cells and their progeny, their function and elusive nature in nervous system and bone marrow, and their potential mechanistic role and promising therapeutic value in preclinical models of disease. Future improved in vivo models and detection methods will allow to determine the true essence of Nestin+ cells and confirm their potential application as therapeutic target in a range of diseases.

Multiple faces of succinate beyond metabolism in blood.

Succinate is an essential intermediate of the tricarboxylic acid cycle that exerts pleiotropic roles beyond metabolism in both physiological and pathological conditions. Recent evidence obtained in mouse models shows its essential role regulating blood cell function through various mechanisms that include pseudohypoxia responses by hypoxia-inducible factor-1α activation, post-translational modifications like succinylation, and communication mediated by succinate receptor 1. Hence, succinate links metabolism to processes like gene expression and intercellular communication. Interestingly, succinate plays key dual roles during inflammatory responses, leading to net inflammation or anti-inflammation depending on factors like the cellular context. Here, we further discuss current suggestions of the possible contribution of succinate to blood stem cell function and blood formation. Further study will be required in the future to better understand succinate biology in blood cells. This promising field may open new avenues to modulate inflammatory responses and to preserve blood cell homeostasis in the clinical setting.

Updates on Old and Weary Haematopoiesis.

Blood formation, or haematopoiesis, originates from haematopoietic stem cells (HSCs), whose functions and maintenance are regulated in both cell- and cell non-autonomous ways. The surroundings of HSCs in the bone marrow create a specific niche or microenvironment where HSCs nest that allows them to retain their unique characteristics and respond rapidly to external stimuli. Ageing is accompanied by reduced regenerative capacity of the organism affecting all systems, due to the progressive decline of stem cell functions. This includes blood and HSCs, which contributes to age-related haematological disorders, anaemia, and immunosenescence, among others. Furthermore, chronological ageing is characterised by myeloid and platelet HSC skewing, inflammageing, and expanded clonal haematopoiesis, which may be the result of the accumulation of preleukaemic lesions in HSCs. Intriguingly, haematological malignancies such as acute myeloid leukaemia have a high incidence among elderly patients, yet not all individuals with clonal haematopoiesis develop leukaemias. Here, we discuss recent work on these aspects, their potential underlying molecular mechanisms, and the first cues linking age-related changes in the HSC niche to poor HSC maintenance. Future work is needed for a better understanding of haematopoiesis during ageing. This field may open new avenues for HSC rejuvenation and therapeutic strategies in the elderly.

Endogenous IL-1 receptor antagonist restricts healthy and malignant myeloproliferation.

Here we explored the role of interleukin-1ß (IL-1ß) repressor cytokine, IL-1 receptor antagonist (IL-1rn), in both healthy and abnormal hematopoiesis. Low IL-1RN is frequent in acute myeloid leukemia (AML) patients and represents a prognostic marker of reduced survival. Treatments with IL-1RN and the IL-1ß monoclonal antibody canakinumab reduce the expansion of leukemic cells, including CD34+ progenitors, in AML xenografts. In vivo deletion of IL-1rn induces hematopoietic stem cell (HSC) differentiation into the myeloid lineage and hampers B cell development via transcriptional activation of myeloid differentiation pathways dependent on NFκB. Low IL-1rn is present in an experimental model of pre-leukemic myelopoiesis, and IL-1rn deletion promotes myeloproliferation, which relies on the bone marrow hematopoietic and stromal compartments. Conversely, IL-1rn protects against pre-leukemic myelopoiesis. Our data reveal that HSC differentiation is controlled by balanced IL-1ß/IL-1rn levels under steady-state, and that loss of repression of IL-1ß signaling may underlie pre-leukemic lesion and AML progression.

The Hematology of Tomorrow Is Here-Preclinical Models Are Not: Cell Therapy for Hematological Malignancies.

The purpose of this review is to present the current knowledge on the clinical use of several forms of cell therapy in hematological malignancies and the preclinical models available for their study. In the context of allogeneic hematopoietic stem cell transplants, mesenchymal stromal cells are pursued to help stem cell engraftment and expansion, and control graft versus host disease. We further summarize the status of promising forms of cellular immunotherapy including CAR T cell and CAR NK cell therapy aimed at eradicating the cells of origin of leukemia, i.e., leukemia stem cells. Updates on other forms of cellular immunotherapy, such as NK cells, CIK cells and CAR CIK cells, show encouraging results in AML. The considerations in available in vivo models for disease modelling and treatment efficacy prediction are discussed, with a particular focus on their strengths and weaknesses for the study of healthy and diseased hematopoietic stem cell reconstitution, graft versus host disease and immunotherapy. Despite current limitations, cell therapy is a rapidly evolving field that holds the promise of improved cure rates, soon. As a result, we may be witnessing the birth of the hematology of tomorrow. To further support its development, improved preclinical models including humanized microenvironments in mice are urgently needed.

Crosstalk between AML and stromal cells triggers acetate secretion through the metabolic rewiring of stromal cells.

Acute myeloid leukaemia (AML) cells interact and modulate components of their surrounding microenvironment into their own benefit. Stromal cells have been shown to support AML survival and progression through various mechanisms. Nonetheless, whether AML cells could establish beneficial metabolic interactions with stromal cells is underexplored. By using a combination of human AML cell lines and AML patient samples together with mouse stromal cells and a MLL-AF9 mouse model, here we identify a novel metabolic crosstalk between AML and stromal cells where AML cells prompt stromal cells to secrete acetate for their own consumption to feed the tricarboxylic acid cycle (TCA) and lipid biosynthesis. By performing transcriptome analysis and tracer-based metabolic NMR analysis, we observe that stromal cells present a higher rate of glycolysis when co-cultured with AML cells. We also find that acetate in stromal cells is derived from pyruvate via chemical conversion under the influence of reactive oxygen species (ROS) following ROS transfer from AML to stromal cells via gap junctions. Overall, we present a unique metabolic communication between AML and stromal cells and propose two different molecular targets, ACSS2 and gap junctions, that could potentially be exploited for adjuvant therapy.

Ovariectomy causes immunosenescence and oxi-inflamm-ageing in peritoneal leukocytes of aged female mice similar to that in aged males.

Immunosenescence involves age-associated restructuring changes of innate and adaptative immune functions. We have suggested that these changes of the immune system participate in the rate of ageing through modulating oxi-inflamm-ageing. Thus, age-related changes in the immune system can be biological age markers and predictors of longevity. Gender differences in oxidation status and immune functions have been observed in rats, with males showing higher oxidation and immunosenescence than females of the same age. Oestrogens are sex hormones that actively participate in modulating the mammalian immune function and, therefore, the age-related impairment of the immune response is drastically accelerated in females during the menopausal transition. Ovariectomy in rodents constitutes a good model for mimicking human oestrogen loss and thus the menopausal situation. Recently, we have shown the deleterious effects of oestrogen loss on several functions of leukocytes from immune organs in rats and mice. In addition, ovariectomised rats show similar levels in these immune functions to those in males. The present work studied several functions as well as inflammatory and oxidative stress parameters in mouse peritoneal macrophages and lymphocytes from old sham and ovariectomised females, as well as in males of the same age. In general, the results show that females, which have a higher immune response and a lower oxidation and inflammation than males, appear similar to males in the parameters studied when they have lost oestrogens by ovariectomy. Thus, these data support the positive role of oestrogens in the immune function through the ageing process.

Female Mice Reaching Exceptionally High Old Age Have Preserved 20S Proteasome Activities.

Oxidized, damaged and misfolded proteins accumulate during aging and contribute to impaired cell function and tissue homeodynamics. Damaged proteins are degraded by cellular clearance mechanisms like the 20S proteasome. Aging relates to low 20S proteasome function, whereas long-lived species show high levels. However, contradictory results exist depending on the tissue or cell type and it is unknown how the 20S proteasome functions in exceptionally old mice. The aim of this study was to investigate two proteasome activities (caspase-like and chymotrypsin-like) in several tissues (lung, heart, axillary lymph nodes, liver, kidney) and cells (peritoneal leukocytes) from adult (28 ± 4 weeks, n = 12), old (76 ± 4 weeks, n = 9) and exceptionally old (128 ± 4 weeks, n = 9) BALB/c female mice. The results show different age-related changes depending on the tissue and the activity considered, so there is no universal decline in proteasome function with age in female mice. Interestingly, exceptionally old mice displayed better maintained proteasome activities, suggesting that preserved 20S proteasome is associated with successful aging.

Accelerated immunosenescence, oxidation and inflammation lead to a higher biological age in COPD patients.

Chronic obstructive pulmonary disease (COPD) is characterised by inflammatory and oxidative alterations in the lung and extrapulmonary compartments, through involvement of the immune system. Several leukocyte functions are health markers and good predictors of longevity, and high pro-inflammatory and oxidative states are related to more aged profiles. Here, we aimed to investigate the aging rate in terms of immunosenescence in COPD men with respect to healthy age-matched controls. Several neutrophil (adherence, chemotaxis, phagocytosis, superoxide anion stimulated production) and lymphocyte (adherence, chemotaxis, lymphoproliferation, natural killer activity) functions, cytokine concentrations released in response to lipopolysaccharide (tumor necrosis factor-alpha, interleukin (IL)-6, IL-8, IL-10) and redox parameters (intracellular glutathione content, basal superoxide anion level) were assessed in circulating leukocytes of men with moderate and severe stages of COPD, and compared to healthy age-matched volunteers. The biological age or aging rate in each participant was determined using the values of leukocyte functions. The results indicated impairment of immune functions in COPD patients, both in innate and adaptive immunity, and higher pro-inflammatory and oxidative states in peripheral leukocytes than controls. In general, these changes were more remarkable at the severe stage of airway obstruction. Importantly, COPD patients were found to be aging at a faster rate than age-matched healthy counterparts.

Differential expression of Toll-like receptor 2 and 4 on peritoneal leukocyte populations from long-lived and non-selected old female mice.

The aim of the present study was to determine Toll-like receptor (TLR)-2 and TLR-4 membrane expression on the major peritoneal leukocyte populations throughout the aging process, including subjects that had achieved exceptional longevity. ICR (CD1) female mice of different ages: adult (44 +/- 4 weeks), old (69 +/- 4), very old (92 +/- 4) and extreme long-lived (125 +/- 4), were used. Peritoneal leukocytes were collected, and percentages of CD11b, CD11c, CD3CD4, CD3CD8 and CD19 cells present in the samples were analysed, as well as the expression of TLR-2 and TLR-4 on them, by flow cytometry. The results showed increased TLR expression on CD11b+ cells from animals at very old ages and especially in the extreme long-lived. Old subjects showed lower percentage of CD11c+ cells, but no age-related changes were found in the TLR expression on these cells. TLRs on CD3CD4+ and CD3CD8+ cells from very old animals were increased as compared to the adults, whereas long-lived subjects showed preserved levels. However, TLR expression on CD19+ cells was higher in long-lived individuals with respect to subjects at all the other younger ages. These data suggest that differential age-related changes in the expression of TLR-2 and TLR-4 on leukocyte populations from long-lived and non-selected younger old mice could contribute to a different age-related immune remodelling in long-lived subjects, which could allow better preservation of their immune responses.

Leukemia Stem Cell Release From the Stem Cell Niche to Treat Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a heterogeneous, complex, and deadly disease, whose treatment has hardly evolved for decades and grounds on the use of intensive chemotherapy regimens. Chemotherapy helps reduce AML bulk, but promotes relapse in the long-run by selection of chemoresistant leukemia stem cells (LSC). These may diversify and result in progression to more aggressive forms of AML. In vivo models suggest that the bone marrow stem cell niche helps LSC stay dormant and protected from chemotherapy. Here, we summarize relevant changes in stem cell niche homing and adhesion of AML LSC vs. healthy hematopoietic stem cells, and provide an overview of clinical trials aiming at targeting these processes for AML treatment and future directions within this field. Promising results with various non-mutation-targeted novel therapies directed to LSC eradication via interference with their anchoring to the stem cell niche have encouraged on-going or future advanced phase III clinical trials. In the coming years, we may see a shift in the focus of AML treatment to LSC-directed therapies if the prospect of improved cure rates holds true. In the future, AML treatment should lean toward personalized therapies using combinations of these compounds plus mutation-targeted agents and/or targeted delivery of chemotherapy, aiming at LSC eradication with reduced side effects.

Impaired immune function in a homeless population with stress-related disorders.

OBJECTIVE: Homeless people suffer high levels of psychological distress. The aim of the present work was to study the immune function in a group of homeless people with stress-related disorders and compare it with that of healthy non-homeless controls. METHODS: We included in the study 40 homeless persons and 40 housed controls recruited from the population of Madrid and matched for age and gender. Samples from peripheral blood were collected and we studied several leukocyte functions previously described as good health and survival markers [adherence, chemotaxis, phagocytosis, superoxide anion levels, lymphocyte proliferation in response to phytohemagglutinin, NK activity and cytokine (IL-2, TNF-alpha) levels], as well as other related parameters, such as plasma cortisol levels and total antioxidant capacity. RESULTS: There was a strongly suppressed immune response in the homeless group, with decreased adherence, chemotaxis, phagocytosis, superoxide levels, lymphoproliferation and NK activity. IL-2 and plasma antioxidant levels were also impaired. CONCLUSIONS: These findings suggest an altered immune function in the homeless population that might be responsible for the higher morbidity and mortality of homeless people. In addition, the present work points out directions for future research attempting to increase the quality of life and health status of homeless individuals, since it shows that oxidative stress seems to play a key role in this immune function impairment.

[Social isolation during old age worsens cognitive, behavioral and immune impairment]. / El aislamiento social durante la vejez empeora el deterioro cognitivo, conductual e inmunitario.

INTRODUCTION: Several studies by the World Health Organization indicate that widows and widowers show lower physical and mental health indexes than the age-matched general population. In addition, widowhood and social isolation are common in the elderly, with women being more affected than men due to their longer life span. Thus, the aim of the present study was to create an animal model of solitude in old age to study the behavioral, cognitive and immunological changes induced by social isolation at this late stage of life. MATERIAL AND METHODS: Twenty female C57b/129sv mice, housed in groups of 4-5 until their old age (18 months), remained in groups (controls, n=10) or were isolated after reaching the age of 18 months and until they reached the age of 24 months (isolated, n=10). At this advanced age, the animals were submitted to a battery of tests to assess neophobia (corner test), anxiety (open-field test), and learning and memory (Morris water maze). Thereafter, the animals were sacrificed and the thymus was removed. The natural killer (NK) activity of the thymic cells against the YAC-1 murine tumor cell line was evaluated. RESULTS: Animals isolated during old age showed functional and cognitive decline, with increased neophobia and anxiety as well as learning and memory deficits. In addition, isolation reduced the NK activity of thymic cells. CONCLUSIONS: We demonstrate the importance of social isolation and solitude during old age. Both social isolation and solitude exacerbate mental and immunological involution during this period, despite normal social life during previous stages of life.

Bone Marrow Adipocytes: The Enigmatic Components of the Hematopoietic Stem Cell Niche.

Bone marrow adipocytes (BMA) exert pleiotropic roles beyond mere lipid storage and filling of bone marrow (BM) empty spaces, and we are only now beginning to understand their regulatory traits and versatility. BMA arise from the differentiation of BM mesenchymal stromal cells, but they seem to be a heterogeneous population with distinct metabolisms, lipid compositions, secretory properties and functional responses, depending on their location in the BM. BMA also show remarkable differences among species and between genders, they progressively replace the hematopoietic BM throughout aging, and play roles in a range of pathological conditions such as obesity, diabetes and anorexia. They are a crucial component of the BM microenvironment that regulates hematopoiesis, through mechanisms largely unknown. Previously considered as negative regulators of hematopoietic stem cell function, recent data demonstrate their positive support for hematopoietic stem cells depending on the experimental approach. Here, we further discuss current knowledge on the role of BMA in hematological malignancies. Early hints suggest that BMA may provide a suitable metabolic niche for the malignant growth of leukemic stem cells, and protect them from chemotherapy. Future in vivo functional work and improved isolation methods will enable determining the true essence of this elusive BM hematopoietic stem cell niche component, and confirm their roles in a range of diseases. This promising field may open new pathways for efficient therapeutic strategies to restore hematopoiesis, targeting BMA.

The glutathione precursor N-acetylcysteine improves immune function in postmenopausal women.

Aging is a chronic oxidation process in which the immune system is involved. Because leukocyte functions is a good health marker and longevity predictor, the effects of daily oral administration of N-acetylcysteine (NAC, 600 mg) on several lymphocyte (adherence, chemotaxis, proliferation, natural killer activity) and neutrophil (adherence, chemotaxis, phagocytosis, superoxide) functions, as well as cytokine levels (interleukin-2, tumor necrosis factor alpha, interleukin-8), were studied in 36 healthy postmenopausal women: 18 aged 50-69 years and 18 aged > 69 years. In addition, plasma and leukocyte oxidative stress markers (glutathione, superoxide, malondialdehyde) were evaluated. These parameters were analyzed within 2 and 4 months of of NAC intake and 3 months after the end of the supplementation. In parallel, samples from 18 healthy adult women aged 30-49 years were used as a control age group. the results showed general impairment of immune function and increased oxidation markers in postmenopausal women as compared with the control group; however, NAC administration significantly improved the parameters studied, bringing their values closer to those of younger women and thus exerting a modulatory, rather than a merely stimulatory, action on the immune system. These effects were also observed 3 months after the end of supplementation. The present finding suggest that a short period of NAC supply (i.e., 2-4 months) at the dose used may lead to prolonged strengthening of immune defence in postmenopausal women, likely by increasing the leukocyte glutathione pool. Thus, NAC could contribute to maintenance of good health and quality of life in postmenopausal women by decreasing the probability of immune system-related diseases, such as infections, in aging.

Gender-specific neuroimmunoendocrine aging in a triple-transgenic 3xTg-AD mouse model for Alzheimer's disease and its relation with longevity.

In the present work, we briefly review the evidence on the key role played by the neuroimmunoendocrine network in the etiopathogenesis of Alzheimer's disease (AD) and provide new behavioral, immune and endocrinological data obtained on old male and female triple-transgenic 3xTg-AD mice harboring PS1(M146V), APP(Swe) and tau(P301L) transgenes in contrast to wild-type animals. The results indicate that several aspects of the impairment of the neuroimmunoendocrine network that occurs with aging are more evident in the 3xTg-AD mice, especially in males. This supports the hypothesis of a premature immunosenescence as a pathogenically relevant factor in AD which was found to be enhanced in the 3xTg-AD males, suggesting that this could also be responsible for the increased morbidity and mortality of these subjects. Therefore, future research on strategies that could improve the immune system and the other regulatory systems, such as the nervous and the endocrine system, as well as their communication, could have preventive and/or therapeutical effects on that disease. The results also show the relevance of gender differences that should be taken into consideration in both basic and clinical research for assessing new strategies for the control of AD.

IL-1ß Promotes a New Function of DNase I as a Transcription Factor for the Fas Receptor Gene.

Recently we described that endonuclease inactive DNase I translocated into the nucleus in response to increased endogenous IL-1ß expression. Here, we demonstrate impact and function of translocated DNase I in tubular cells. Effect of cytokines on expression level and nuclear localisation of DNase I and corresponding levels of Fas receptor (FasR) and IL-1ß were determined by confocal microscopy, qPCR and western blot analyses, in presence or absence of siRNA against IL-1ß and DNase I mRNA. Nuclear DNase I bound to the FAS promotor region as determined by chromatin immuno-precipitation analysis. Data demonstrate that; (i) translocation of DNase I depended on endogenous de novo-expressed IL-1ß, (ii) nuclear DNase I bound FAS DNA, (iii) FasR expression increased after translocation of DNase I, (iv) interaction of exogenous Fas ligand (FasL) with upregulated FasR induced apoptosis in human tubular cells stimulated with TNFα. Thus, translocated DNase I most probably binds the promoter region of the FAS gene and function as a transcription factor for FasR. In conclusion, DNase I not only executes chromatin degradation during apoptosis and necrosis, but also primes the cells for apoptosis by enhancing FasR expression.