Obesity-driven disruption of haematopoiesis and the bone marrow niche

Gene-environmental influence of space and microgravity on red blood cells with sickle cell disease

A fundamental question in human biology and for hematological disease is how do complex gene-environment interactions lead to individual disease outcome? This is no less the case for sickle cell disease (SCD), a monogenic disorder of Mendelian inheritance, both clinical course, severity, and treatment response, is variable amongst affected individuals. New insight and discovery often lie between the intersection of seemingly disparate disciplines. Recently, opportunities for space medicine have flourished and have offered a new paradigm for study. Two recent Nature papers have shown that hemolysis and oxidative stress play key mechanistic roles in erythrocyte pathogenesis during spaceflight. This paper reviews existing genetic and environmental modifiers of the sickle cell disease phenotype. It reviews evidence for erythrocyte pathology in microgravity environments and demonstrates why this may be relevant for the unique gene-environment interaction of the SCD phenotype. It also introduces the hematology and scientific community to methodological tools for evaluation in space and microgravity research. The increasing understanding of space biology may yield insight into gene-environment influences and new treatment paradigms in SCD and other hematological disease phenotypes.

27-Hydroxycholesterol Negatively Affects the Function of Bone Marrow Endothelial Cells in the Bone Marrow

Hematopoietic stem cells (HSCs) reside in specific microenvironments that facilitate their regulation through both internal mechanisms and external cues. Bone marrow endothelial cells (BMECs), which are found in one of these microenvironments, play a vital role in controlling the self-renewal and differentiation of HSCs during hematological stress. We previously showed that 27-hydroxycholesterol (27HC) administration of exogenous 27HC negatively affected the population of HSCs and progenitor cells by increasing the reactive oxygen species levels in the bone marrow. However, the effect of 27HC on BMECs is unclear. To determine the function of 27HC in BMECs, we employed magnetic-activated cell sorting to isolate CD31+ BMECs and CD31- cells. We demonstrated the effect of 27HC on CD31+ BMECs and HSCs. Treatment with exogenous 27HC led to a decrease in the number of BMECs and reduced the expression of adhesion molecules that are crucial for maintaining HSCs. Our results demonstrate that BMECs are sensitively affected by 27HC and are crucial for HSC survival.

Systemic deficits in lipid homeostasis promote aging-associated impairments in B cell progenitor development

Organismal aging has been associated with diverse metabolic and functional changes across tissues. Within the immune system, key features of physiological hematopoietic cell aging include increased fat deposition in the bone marrow, impaired hematopoietic stem and progenitor cell (HSPC) function, and a propensity towards myeloid differentiation. This shift in lineage bias can lead to pre-malignant bone marrow conditions such as clonal hematopoiesis of indeterminate potential (CHIP) or clonal cytopenias of undetermined significance (CCUS), frequently setting the stage for subsequent development of age-related cancers in myeloid or lymphoid lineages. At the systemic as well as sub-cellular level, human aging has also been associated with diverse lipid alterations, such as decreased phospholipid membrane fluidity that arises as a result of increased saturated fatty acid (FA) accumulation and a decay in n-3 polyunsaturated fatty acid (PUFA) species by the age of 80 years, however the extent to which impaired FA metabolism contributes to hematopoietic aging is less clear. Here, we performed comprehensive multi-omics analyses and uncovered a role for a key PUFA biosynthesis gene, ELOVL2 , in mouse and human immune cell aging. Whole transcriptome RNA-sequencing studies of bone marrow from aged Elovl2 mutant (enzyme-deficient) mice compared with age-matched controls revealed global down-regulation in lymphoid cell markers and expression of genes involved specifically in B cell development. Flow cytometric analyses of immune cell markers confirmed an aging-associated loss of B cell markers that was exacerbated in the bone marrow of Elovl2 mutant mice and unveiled CD79B, a vital molecular regulator of lymphoid progenitor development from the pro-B to pre-B cell stage, as a putative surface biomarker of accelerated immune aging. Complementary lipidomic studies extended these findings to reveal select alterations in lipid species in aged and Elovl2 mutant mouse bone marrow samples, suggesting significant changes in the biophysical properties of cellular membranes. Furthermore, single cell RNA-seq analysis of human HSPCs across the spectrum of human development and aging uncovered a rare subpopulation (<7%) of CD34 + HSPCs that expresses ELOVL2 in healthy adult bone marrow. This HSPC subset, along with CD79B -expressing lymphoid-committed cells, were almost completely absent in CD34 + cells isolated from elderly (>60 years old) bone marrow samples. Together, these findings uncover new roles for lipid metabolism enzymes in the molecular regulation of cellular aging and immune cell function in mouse and human hematopoiesis. In addition, because systemic loss of ELOVL2 enzymatic activity resulted in down-regulation of B cell genes that are also associated with lymphoproliferative neoplasms, this study sheds light on an intriguing metabolic pathway that could be leveraged in future studies as a novel therapeutic modality to target blood cancers or other age-related conditions involving the B cell lineage.

Bone marrow niches for hematopoietic stem cells

Hematopoietic stem cells (HSCs) are the cornerstone of the hematopoietic system. HSCs sustain the continuous generation of mature blood derivatives while self-renewing to preserve a relatively constant pool of progenitors throughout life. Yet, long-term maintenance of functional HSCs exclusively takes place in association with their native tissue microenvironment of the bone marrow (BM). HSCs have been long proposed to reside in fixed and identifiable anatomical units found in the complex BM tissue landscape, which control their identity and fate in a deterministic manner. In the last decades, tremendous progress has been made in the dissection of the cellular and molecular fabric of the BM, the structural organization governing tissue function, and the plethora of interactions established by HSCs. Nonetheless, a holistic model of the mechanisms controlling HSC regulation in their niche is lacking to date. Here, we provide an overview of our current understanding of BM anatomy, HSC localization, and crosstalk within local cellular neighborhoods in murine and human tissues, and highlight fundamental open questions on how HSCs functionally integrate in the BM microenvironment.

FATP2 regulates osteoclastogenesis by increasing lipid metabolism and ROS production

Lipid metabolism plays a crucial role in maintaining bone homeostasis, particularly in osteoclasts (OCs) formation. Here, we found that the expression level of FATP2, a transporter for long-chain and very-long-chain fatty acids, was significantly upregulated during OC differentiation and in the bone marrow of mice fed a high-fat diet (HFD). Notably, the use of FATP2 siRNA or a specific inhibitor (Lipofermata) resulted in significant inhibition of OC differentiation, while only slightly affecting osteoblasts. In pathological models of bone loss induced by LPS or ovariectomy, in vivo treatment with Lipofermata was able to rescue the loss of bone mass by inhibiting OC differentiation. RNA sequencing revealed that Lipofermata reduced fatty acid β-oxidation and inhibited energy metabolism, while regulating ROS metabolism to decrease ROS production, ultimately inhibiting OC differentiation. Treatment with Lipofermata, either in vivo or in vitro, effectively rescued the overactivation of OCs, indicating that FATP2 regulated OC differentiation by modulating fatty acid uptake and energy metabolism. These findings suggested that targeting FATP2 may represent a promising therapeutic approach for pathological osteoporosis.

Association of osteoporosis with sarcopenia and its components among community-dwelling older Chinese adults with different obesity levels: A cross-sectional study

We aimed to investigate whether sarcopenia and its components are associated with osteoporosis in community-dwelling older Chinese adults with different obesity levels. This cross-sectional study included 1938 participants (42.1% male) with a mean age of 72.1 ± 5.9 years. The categorization of individuals into various weight categories was based on the Working Group on Obesity in China's criteria, utilizing the body mass index (BMI) as follows: underweight, BMI < 18.5 kg/m2; normal weight, 18.5 ≤ BMI < 24 kg/m2; overweight, 24 ≤ BMI < 28 kg/m2; and obesity, BMI ≥ 28 kg/m2. In this research, the osteoporosis definition put forth by the World Health Organization (bone mineral density T-score less than or equal to -2.5 as assessed by Dual-energy X-ray absorptiometry (DXA)). Sarcopenia was defined according to the diagnostic criteria of the Asian Working Group for Sarcopenia. The prevalence of osteoporosis was highest in the underweight group and gradually decreased with increasing BMI (Underweight: 55.81% vs Normal weight: 45.33% vs Overweight: 33.69% vs Obesity: 22.39). Sarcopenia was associated with elevated odds of osteoporosis in normal-weight subjects independent of potential covariates (OR = 1.70, 95% CI = 1.22-2.35, P = .002). In normal-weight participants, a higher appendicular skeletal muscle mass index (ASMI) was associated with a reduced risk of osteoporosis (OR = 0.56, 95% CI = 0.42-0.74, P < .001). In this study, we found that the prevalence of osteoporosis was highest in the underweight group and gradually decreased with increasing BMI. Sarcopenia, body fat percentage, and ASMI were associated with elevated odds of osteoporosis in normal-weight subjects independent of potential covariates, and higher percent body fat (PBF) was associated with an increased risk of osteoporosis in overweight people, and no such association was found in other weight groups. Different amounts of adipose tissue and muscle mass may alter bone biology. Further longitudinal follow-up studies are required to more accurately assess the risk of osteoporosis and sarcopenia in different weight populations. This cross-sectional study found that the prevalence of osteoporosis was highest in the underweight group and gradually decreased with increasing BMI. Sarcopenia was associated with elevated odds of osteoporosis in normal-weight subjects independent of potential covariates.

The role of adiposity, adipokines and polymorphisms of leptin and adiponectin in myelodysplastic syndromes

The aim of the present study was to investigate the relationship between leptin and adiponectin gene polymorphisms, circulating levels of leptin and adiponectin, adiposity and clinical markers in patients with myelodysplastic syndrome (MDS). This cross-sectional study was conducted with 102 adults and elderly MDS patients and 102 age- and sex-matched controls. Clinical characteristics, co-morbidities, anthropometric data, laboratory evaluation and genetic analysis (polymorphisms -2548G > A/rs7799039 of the LEP gene and +276G > T/rs1501299 of the ADIPOQ gene) were investigated. Serum leptin was higher and adiponectin lower in MDS when compared with controls. There was a significant positive correlation between serum leptin levels and BMI (r = 0·264, P = 0·025), waist circumference (r = 0·235, P = 0·047), body fat percentage (BF %) (r = 0·373, P = 0·001) and the fat mass index (FMI) (r = 0·371, P < 0·001). A lower mean adiponectin was found among patients with high BF %, higher visceral adiposity index and metabolic syndrome. A significant association was found between the AA genotype (mutant) of the LEP polymorphism rs7799039 and male sex and blast excess (≥ 5 %). In addition, a significant association was observed between the TT genotype (mutant) of the ADIPOQ rs1501299 polymorphism and Fe overload. These results demonstrate the importance of a comprehensive and systematic evaluation in patients with MDS in order to identify and control negative factors not related to the disease at an early stage.

Mitochondria: the gatekeepers between metabolism and immunity

Metabolism and immunity are crucial monitors of the whole-body homeodynamics. All cells require energy to perform their basic functions. One of the most important metabolic skills of the cell is the ability to optimally adapt metabolism according to demand or availability, known as metabolic flexibility. The immune cells, first line of host defense that circulate in the body and migrate between tissues, need to function also in environments in which nutrients are not always available. The resilience of immune cells consists precisely in their high adaptive capacity, a challenge that arises especially in the framework of sustained immune responses. Pubmed and Scopus databases were consulted to construct the extensive background explored in this review, from the Kennedy and Lehninger studies on mitochondrial biochemistry of the 1950s to the most recent findings on immunometabolism. In detail, we first focus on how metabolic reconfiguration influences the action steps of the immune system and modulates immune cell fate and function. Then, we highlighted the evidence for considering mitochondria, besides conventional cellular energy suppliers, as the powerhouses of immunometabolism. Finally, we explored the main immunometabolic hubs in the organism emphasizing in them the reciprocal impact between metabolic and immune components in both physiological and pathological conditions.

Effect of laparoscopic sleeve gastrectomy on platelet count and mean platelet volume

Objective

Several studies have reported an increase in platelet (PLT) count with chronic inflammation in the presence of obesity. Mean platelet volume (MPV) is an important marker for PLT activity. Our study aims to demonstrate if laparoscopic sleeve gastrectomy (LSG) has any effect on PLT, MPV and white blood cells (WBCs).

Methods

A total of 202 patients undergoing LSG for morbid obesity between January 2019 and March 2020 who completed at least 1 year of follow-up were included in the study. Patients' characteristics and laboratory parameters were recorded preoperatively and were compared in the 6th and 12th months.

Results

Two hundred and two patients (50% - female) with a mean age of 37.5 ± 12.2 years and mean pre-operative body mass index (BMI) of 43 (34.1-62.5) kg/m2 underwent LSG. BMI regressed to 28.2 ± 4.5 kg/m2 at 1 year after LSG (P < 0.001). The mean PLT count, MPV and WBC during the pre-operative period were 293.2 ± 70.3 103 cells/μL, 10.22 ± 0.9 fL and 7.8 ± 1.9 103 cells/μL, respectively. A significant decrease was seen in mean PLT count, with 257.3 ± 54.2 103cell/μL (P < 0.001) at 1 year post-LSG. The mean MPV was increased at 6 months 10.5 ± 1.2 fL (P < 0.001) and remained unchanged at 1 year 10.3 ± 1.3 fL (P = 0.9). The mean WBC levels were significantly decreased with 6.5 ± 1.7 103 cells/μL (P < 0.001) at 1 year. At the end of the follow-up, weight loss showed no correlation with PLT and MPV (P = 0.42, P = 0.32).

Conclusion

Our study has shown a significant decrease in circulating PLT and WBC levels while MPV remained unchanged after LSG.

Bone marrow microenvironment: roles and therapeutic implications in obesity-associated cancer

Obesity is increasing globally and has been closely linked to the initiation and progression of multiple human cancers. These relationships, to a large degree, are mediated through obesity-driven disruption of physiological homeostasis characterized by local and systemic endocrinologic, inflammatory, and metabolic changes. Bone marrow microenvironment (BMME), which evolves during obesity, has been implicated in multiple types of cancer. Growing evidence shows that physiological dysfunction of BMME with altered cellular composition, stromal and immune cell function, and energy metabolism, as well as inflammation and hypoxia, in the context of obesity contributes to cancer initiation and progression. Nonetheless, the mechanisms underlying the obesity-BMME-cancer axis remain elusive. In this review, we discuss the recent advances in understanding the evolution of BMME during obesity, its contributions to cancer initiation and progression, and the implications for cancer therapy.

Obesity and Fibrosis: Setting the Stage for Breast Cancer

Obesity is a rising health concern and is linked to a worsened breast cancer prognosis. Tumor desmoplasia, which is characterized by elevated numbers of cancer-associated fibroblasts and the deposition of fibrillar collagens within the stroma, may contribute to the aggressive clinical behavior of breast cancer in obesity. A major component of the breast is adipose tissue, and fibrotic changes in adipose tissue due to obesity may contribute to breast cancer development and the biology of the resulting tumors. Adipose tissue fibrosis is a consequence of obesity that has multiple sources. Adipocytes and adipose-derived stromal cells secrete extracellular matrix composed of collagen family members and matricellular proteins that are altered by obesity. Adipose tissue also becomes a site of chronic, macrophage-driven inflammation. Macrophages exist as a diverse population within obese adipose tissue and mediate the development of fibrosis through the secretion of growth factors and matricellular proteins and interactions with other stromal cells. While weight loss is recommended to resolve obesity, the long-term effects of weight loss on adipose tissue fibrosis and inflammation within breast tissue are less clear. Increased fibrosis within breast tissue may increase the risk for tumor development as well as promote characteristics associated with tumor aggressiveness.

Turning the spotlight on bone marrow adipocytes in haematological malignancy and non-malignant conditions

Whilst bone marrow adipocytes (BMAd) have long been appreciated by clinical haemato-pathologists, it is only relatively recently, in the face of emerging data, that the adipocytic niche has come under the watchful eye of biologists. There is now mounting evidence to suggest that BMAds are not just a simple structural entity of bone marrow microenvironments but a bona fide driver of physio- and pathophysiological processes relevant to multiple aspects of health and disease. Whilst the truly multifaceted nature of BMAds has only just begun to emerge, paradigms have shifted already for normal, malignant and non-malignant haemopoiesis incorporating a view of adipocyte regulation. Major efforts are ongoing, to delineate the routes by which BMAds participate in health and disease with a final aim of achieving clinical tractability. This review summarises the emerging role of BMAds across the spectrum of normal and pathological haematological conditions with a particular focus on its impact on cancer therapy.

Vertebrae but not femur marrow fat transiently decreases in response to body weight loss in an 18-month randomized control trial

BACKGROUND

Increased levels of bone marrow adipose tissue (BMAT) are negatively associated with skeletal health and hematopoiesis. BMAT is known to increase with age; however, the effect of long-term weight loss on BMAT is still unknown.

OBJECTIVE

In this study, we examined BMAT response to lifestyle-induced weight loss in 138 participants (mean age 48 y; mean body mass index 31 kg/m²), who participated in the CENTRAL-MRI trial.

METHODS

Participants were randomized for dietary intervention of low-fat or low-carb, with or without physical activity. Magnetic resonance imaging (MRI) was used to quantify BMAT and other fat depots at baseline, six and eighteen months of intervention. Blood biomarkers were also measured at the same time points.

RESULTS

At baseline, the L3 vertebrae BMAT is positively associated with age, HDL cholesterol, HbA1c and adiponectin; but not with other fat depots or other metabolic markers tested. Following six months of dietary intervention, the L3 BMAT declined by an average of 3.1 %, followed by a return to baseline after eighteen months (p < 0.001 and p = 0.189 compared to baseline, respectively). The decrease of BMAT during the first six months was associated with a decrease in waist circumference, cholesterol, proximal-femur BMAT, and superficial subcutaneous adipose tissue (SAT), as well as with younger age. Nevertheless, BMAT changes did not correlate with changes in other fat depots.

CONCLUSIONS

We conclude that physiological weight loss can transiently reduce BMAT in adults, and this effect is more prominent in younger adults. Our findings suggest that BMAT storage and dynamics are largely independent of other fat depots or cardio-metabolic risk markers, highlighting its unique functions.

Maternal Western-style diet remodels the transcriptional landscape of fetal hematopoietic stem and progenitor cells in rhesus macaques

Maternal obesity adversely impacts the in utero metabolic environment, but its effect on fetal hematopoiesis remains incompletely understood. During late development, the fetal bone marrow (FBM) becomes the major site where macrophages and B lymphocytes are produced via differentiation of hematopoietic stem and progenitor cells (HSPCs). Here, we analyzed the transcriptional landscape of FBM HSPCs at single-cell resolution in fetal macaques exposed to a maternal high-fat Western-style diet (WSD) or a low-fat control diet. We demonstrate that maternal WSD induces a proinflammatory response in FBM HSPCs and fetal macrophages. In addition, maternal WSD consumption suppresses the expression of B cell development genes and decreases the frequency of FBM B cells. Finally, maternal WSD leads to poor engraftment of fetal HSPCs in nonlethally irradiated immunodeficient NOD/SCID/IL2rγ^-/- mice. Collectively, these data demonstrate for the first time that maternal WSD impairs fetal HSPC differentiation and function in a translationally relevant nonhuman primate model.

Inflammatory-driven NK cell maturation and its impact on pathology

NK cells are innate lymphocytes involved in a large variety of contexts and are crucial in the immunity to intracellular pathogens as well as cancer due to their ability to kill infected or malignant cells. Thus, they harbor a strong potential for clinical and therapeutic use. NK cells do not require antigen exposure to get activated; their functional response is rather based on a balance between inhibitory/activating signals and on the diversity of germline-encoded receptors they express. In order to reach optimal functional status, NK cells go through a step-wise development in the bone marrow before their egress, and dissemination into peripheral organs via the circulation. In this review, we summarize bone marrow NK cell developmental stages and list key factors involved in their differentiation before presenting newly discovered and emerging factors that regulate NK cell central and peripheral maturation. Lastly, we focus on the impact inflammatory contexts themselves can have on NK cell development and functional maturation.

Hematologic dysfunction in cancer: Mechanisms, effects on antitumor immunity, and roles in disease progression

With the major advances in cancer immunology and immunotherapy, it is critical to consider that most immune cells are short-lived and need to be continuously replenished from hematopoietic stem and progenitor cells. Hematologic abnormalities are prevalent in cancer patients, and many ground-breaking studies over the past decade provide insights into their underlying cellular and molecular mechanisms. Such studies demonstrate that the dysfunction of hematopoiesis is more than a side-effect of cancer pathology, but an important systemic feature of cancer disease. Here we review these many advances, covering the cancer-associated phenotypes of hematopoietic stem and progenitor cells, the dysfunction of myelopoiesis and erythropoiesis, the importance of extramedullary hematopoiesis in cancer disease, and the developmental origins of tumor associated macrophages. We address the roles of many secreted mediators, signaling pathways, and transcriptional and epigenetic mechanisms that mediate such hematopoietic dysfunction. Furthermore, we discuss the important contribution of the hematopoietic dysfunction to cancer immunosuppression, the possible avenues for therapeutic intervention, and highlight the unanswered questions and directions for future work. Overall, hematopoietic dysfunction is established as an active component of the cancer disease mechanisms and an important target for therapeutic intervention.

The skeleton in a physical world

All organisms exist within a physical space and respond to physical forces as part of daily life. In higher organisms, the skeleton is critical for locomotion in the physical environment, providing a carapace upon which the animal can move to accomplish functions necessary for living. As such, the skeleton has responded evolutionarily, and does in real-time, to physical stresses placed on it to ensure that its structure supports its function in the sea, in the air, and on dry land. In this article, we consider how those cells responsible for remodeling skeletal structure respond to mechanical force including load magnitude, frequency, and cyclicity, and how force rearranges cellular structure in turn. The effects of these forces to balance the mesenchymal stem cell supply of bone-forming osteoblasts and energy storing adipocytes are addressed. That this phenotypic switching is achieved at the level of both gene transactivation and alteration of structural epigenetic controls of gene expression is considered. Finally, as clinicians, we consider this information as it applies to a prescriptive for intelligent exercise.

Comorbidities, Associated Diseases, and Risk Assessment in COVID-19-A Systematic Review

It is considered that COVID-19's pandemic expansion is responsible for the particular increase in deaths, especially among the population with comorbidities. The health system is often overwhelmed by the large number of cases of patients addressing it, by the regional limitation of funds, and by the gravity of cases at subjects suffering from this pathology. Several associated conditions including diabetes, cardiovascular illnesses, obesity, persistent lung condition, neurodegenerative diseases, etc., increase the mortality risk and hospitalization of subjects suffering from COVID-19. The rapid identification of patients with increased risk of death from the SARS-CoV-2 virus, the stratification in accordance with the risk and the allocation of human, financial, and logistical resources in proportion must be a priority for health systems worldwide.

How Does Lifestyle Affect Hematopoiesis and the Bone Marrow Microenvironment?

Lifestyle factors are modifiable behavioral factors that have a significant impact on health and longevity. Diet-induced obesity and physical activity/exercise are two prevalent lifestyle factors that have strong relationships to overall health. The mechanisms linking obesity to negative health outcomes and the mechanisms linking increased participation in physical activity/exercise to positive health outcomes are beginning to be elucidated. Chronic inflammation, due in part to overproduction of myeloid cells from hematopoietic stem cells (HSCs) in the bone marrow, is an established mechanism responsible for the negative health effects of obesity. Recent work has shown that exercise training can reverse the aberrant myelopoiesis present in obesity in part by restoring the bone marrow microenvironment. Specifically, exercise training reduces marrow adipose tissue, increases HSC retention factor expression, and reduces pro-inflammatory cytokine levels in the bone marrow. Other, novel mechanistic factors responsible for these exercise-induced effects, including intercellular communication using extracellular vesicles (EVs), is beginning to be explored. This review will summarize the recent literature describing the effects of exercise on hematopoiesis in individuals with obesity and introduce the potential contribution of EVs to this process.

Bone marrow adipocytes drive the development of tissue invasive Ly6Chigh monocytes during obesity

During obesity and high fat-diet (HFD) feeding in mice, sustained low-grade inflammation includes not only increased pro-inflammatory macrophages in the expanding adipose tissue, but also bone marrow (BM) production of invasive Ly6C^high monocytes. As BM adiposity also accrues with HFD, we explored the relationship between the gains in BM white adipocytes and invasive Ly6C^high monocytes by in vivo and ex vivo paradigms. We find a temporal and causal link between BM adipocyte whitening and the Ly6C^high monocyte surge, preceding the adipose tissue macrophage rise during HFD in mice. Phenocopying this, ex vivo treatment of BM cells with conditioned media from BM adipocytes or bona fide white adipocytes favoured Ly6C^high monocyte preponderance. Notably, Ly6C^high skewing was preceded by monocyte metabolic reprogramming towards glycolysis, reduced oxidative potential and increased mitochondrial fission. In sum, short-term HFD changes BM cellularity, resulting in local adipocyte whitening driving a gradual increase and activation of invasive Ly6C^high monocytes.

Obesity, Bone Loss, and Periodontitis: The Interlink

Obesity and periodontitis are both common health concerns that have given rise to considerable economic and societal burden worldwide. There are established negative relationships between bone metabolism and obesity, obesity and diabetes mellitus (DM), and DM and periodontitis, to name a few, with osteoporosis being considered a long-term complication of obesity. In the oral cavity, bone metabolic disorders primarily display as increased risks for periodontitis and alveolar bone loss. Obesity-driven alveolar bone loss and mandibular osteoporosis have been observed in animal models without inoculation of periodontopathogens. Clinical reports have also indicated a possible association between obesity and periodontitis. This review systematically summarizes the clinical periodontium changes, including alveolar bone loss in obese individuals. Relevant laboratory-based reports focusing on biological interlinks in obesity-associated bone remodeling via processes like hyperinflammation, immune dysregulation, and microbial dysbiosis, were reviewed. We also discuss the potential mechanism underlying obesity-enhanced alveolar bone loss from both the systemic and periodontal perspectives, focusing on delineating the practical considerations for managing periodontal disease in obese patients.

Exercise suppresses tumor growth independent of high fat food intake and associated immune dysfunction

Epidemiological data suggest that exercise training protects from cancer independent of BMI. Here, we aimed to elucidate mechanisms involved in voluntary wheel running-dependent control of tumor growth across chow and high-fat diets. Access to running wheels decreased tumor growth in B16F10 tumor-bearing on chow (− 50%) or high-fat diets (− 75%, p < 0.001), however, tumor growth was augmented in high-fat fed mice (+ 53%, p < 0.001). Tumor growth correlated with serum glucose (p < 0.01), leptin (p < 0.01), and ghrelin levels (p < 0.01), but not with serum insulin levels. Voluntary wheel running increased immune recognition of tumors as determined by microarray analysis and gene expression analysis of markers of macrophages, NK and T cells, but the induction of markers of macrophages and NK cells was attenuated with high-fat feeding. Moreover, we found that the regulator of innate immunity, ZBP1, was induced by wheel running, attenuated by high-fat feeding and associated with innate immune recognition in the B16F10 tumors. We observed no effects of ZBP1 on cell cycle arrest, or exercise-regulated necrosis in the tumors of running mice. Taken together, our data support epidemiological findings showing that exercise suppresses tumor growth independent of BMI, however, our data suggest that high-fat feeding attenuates exercise-mediated immune recognition of tumors.

Hematopoietic Progenitors and the Bone Marrow Niche Shape the Inflammatory Response and Contribute to Chronic Disease

It is now well understood that the bone marrow (BM) compartment can sense systemic inflammatory signals and adapt through increased proliferation and lineage skewing. These coordinated and dynamic alterations in responding hematopoietic stem and progenitor cells (HSPCs), as well as in cells of the bone marrow niche, are increasingly viewed as key contributors to the inflammatory response. Growth factors, cytokines, metabolites, microbial products, and other signals can cause dysregulation across the entire hematopoietic hierarchy, leading to lineage-skewing and even long-term functional adaptations in bone marrow progenitor cells. These alterations may play a central role in the chronicity of disease as well as the links between many common chronic disorders. The possible existence of a form of “memory” in bone marrow progenitor cells is thought to contribute to innate immune responses via the generation of trained immunity (also called innate immune memory). These findings highlight how hematopoietic progenitors dynamically adapt to meet the demand for innate immune cells and how this adaptive response may be beneficial or detrimental depending on the context. In this review, we will discuss the role of bone marrow progenitor cells and their microenvironment in shaping the scope and scale of the immune response in health and disease.

Hemolysis contributes to anemia during long-duration space flight

Anemia in astronauts has been noted since the first space missions, but the mechanisms contributing to anemia in space flight have remained unclear. Here, we show that space flight is associated with persistently increased levels of products of hemoglobin degradation, carbon monoxide in alveolar air and iron in serum, in 14 astronauts throughout their 6-month missions onboard the International Space Station. One year after landing, erythrocytic effects persisted, including increased levels of hemolysis, reticulocytosis and hemoglobin. These findings suggest that the destruction of red blood cells, termed hemolysis, is a primary effect of microgravity in space flight and support the hypothesis that the anemia associated with space flight is a hemolytic condition that should be considered in the screening and monitoring of both astronauts and space tourists.

Bone marrow adipose tissue content in Latino adolescents with prediabetes and obesity

OBJECTIVE

This study aimed to examine whether total, regional, and organ fat predicts bone marrow adipose tissue (BMAT) fat content and to explore whether BMAT fat content differs by sex among Latino youth.

METHODS

Latino youth (n = 86; age 13.6 [1.4] years, 62% male) with obesity (BMI percentile = 98.5% [1.2%]) underwent a dual-energy x-ray absorptiometry scan to assess body composition and a magnetic resonance imaging scan to determine abdominal adiposity, liver fat, and vertebral BMAT fat content in the thoracic (average of T8-T12) and lumbar (average of L1-L5) spine.

RESULTS

Male youth exhibited significantly greater thoracic (male youth = 30.8% [1.4%] vs. female youth = 24.5% [2.1%], p = 0.027) and lumbar (male youth = 36.3% [1.5%] vs. female youth = 30.2% [2.2%], p = 0.038) BMAT fat content compared with female youth. Visceral adipose tissue was a significant predictor of thoracic (β = 0.434, t[86] = 3.016, p = 0.003) and lumbar (β = 0.389, t[86] = 2.677, p = 0.009) BMAT fat content, explaining 8.9% and 6.9% of the variance, respectively. Liver fat was a significant predictor of both thoracic (β = 0.487, t[86] = 4.334, p < 0.001) and lumbar (β = 0.436, t[86] = 3.793, p < 0.001) BMAT fat content, explaining 17.6% and 13.8% of the variance, respectively.

CONCLUSIONS

Male youth had significantly greater thoracic and lumbar BMAT fat content than female youth. Greater BMAT fat content is associated with greater liver fat and visceral adipose tissue among youth with obesity. Further investigation of the mechanistic underpinnings of BMAT may help to differentiate its metabolic and bone-related functions.

Gentiopicroside promotes the osteogenesis of bone mesenchymal stem cells by modulation of β-catenin-BMP2 signalling pathway

Osteoporosis is characterized by increased bone fragility, and the drugs used at present to treat osteoporosis can cause adverse reactions. Gentiopicroside (GEN), a class of natural compounds with numerous biological activities such as anti‐resorptive properties and protective effects against bone loss. Therefore, the aim of this work was to explore the effect of GEN on bone mesenchymal stem cells (BMSCs) osteogenesis for a potential osteoporosis therapy. In vitro, BMSCs were exposed to GEN at different doses for 2 weeks, whereas in vivo, ovariectomized osteoporosis was established in mice and the therapeutic effect of GEN was evaluated for 3 months. Our results in vitro showed that GEN promoted the activity of alkaline phosphatase, increased the calcified nodules in BMSCs and up‐regulated the osteogenic factors (Runx2, OSX, OCN, OPN and BMP2). In vivo, GEN promoted the expression of Runx2, OCN and BMP2, increased the level of osteogenic parameters, and accelerated the osteogenesis of BMSCs by activating the BMP pathway and Wnt/β‐catenin pathway, effect that was inhibited using the BMP inhibitor Noggin and Wnt/β‐catenin inhibitor DKK1. Silencing the β‐catenin gene and BMP2 gene blocked the osteogenic differentiation induced by GEN in BMSCs. This block was also observed when only β‐catenin was silenced, although the knockout of BMP2 did not affect β‐catenin expression induced by GEN. Therefore, GEN promotes BMSC osteogenesis by regulating β‐catenin‐BMP signalling, providing a novel strategy in the treatment of osteoporosis.

Autophagic Mediators in Bone Marrow Niche Homeostasis

The bone marrow serves as a reservoir for a multifunctional assortment of stem, progenitor, and mature cells, located in functional anatomical micro-areas termed niches. Within the niche, hematopoietic and mesenchymal progenies establish a symbiotic relationship characterized by interdependency and interconnectedness. The fine-tuned physical and molecular interactions that occur in the niches guarantee physiological bone turnover, blood cell maturation and egression, and moderation of inflammatory and oxidative intramural stressful conditions. The disruption of bone marrow niche integrity causes severe local and systemic pathological settings, and thus bone marrow inhabitants have been the object of extensive study. In this context, research has revealed the importance of the autophagic apparatus for niche homeostatic maintenance. Archetypal autophagic players such as the p62 and the Atg family proteins have been found to exert a variety of actions, some autophagy-related and others not; they moderate the essential features of mesenchymal and hematopoietic stem cells and switch their operational schedules. This chapter focuses on our current understanding of bone marrow functionality and the role of the executive autophagic apparatus in the niche framework. Autophagic mediators such as p62 and Atg7 are currently considered the most important orchestrators of stem and mature cell dynamics in the bone marrow.

Patient Age and Cell Concentration Influence Prevalence and Concentration of Progenitors in Bone Marrow Aspirates: An Analysis of 436 Patients

BACKGROUND

Connective tissue progenitors (CTPs) resident in native tissues serve as biological building blocks in tissue repair and remodeling processes. Methods for analysis and reporting on CTP quantity and quality are essential for defining optimal cell sources and donor characteristics and the impact of cell processing methods for cell therapy applications. The present study examines the influence of donor characteristics and cell concentration (nucleated cells/mL) on CTP prevalence (CTPs/million nucleated cells) and CTP concentration (CTPs/mL) in bone marrow aspirates (BMAs).

METHODS

Iliac crest bone marrow was aspirated from 436 patients during elective total knee or hip arthroplasty. Bone marrow-derived nucleated cells were plated at a density of 1.19 × 105 cells/cm2. Colony-forming unit analysis was performed on day 6.

RESULTS

Large variation was seen between donors. Age (p < 0.05) and cell concentration (p < 0.001) significantly influenced CTP prevalence and CTP concentration. For every 1-year increase in age, the odds of having at least an average CTP prevalence and CTP concentration decreased by 1.5% and 1.6%, respectively. For every 1 million cells/mL increase in cell concentration, the odds of having at least an average CTP prevalence and CTP concentration increased by 2.2% and 7.9%, respectively. Sex, race, body mass index (BMI), and the presence of osteoporosis did not influence CTP prevalence or CTP concentration.

CONCLUSIONS

BMA-derived CTPs were obtained from all patient groups. CTP prevalence and CTP concentration decreased with age. Cell concentration decreased with age and positively correlated with total CTP prevalence and CTP concentration. The mean CTP concentration in patients >60 years of age was a third of the CTP concentration in patients <30 years of age.

CLINICAL RELEVANCE

Proper BMA techniques are necessary to obtain a high-quality yield and composition of cells and CTPs. The reduced CTP concentration and CTP prevalence in the elderly may be mitigated by the use of cell processing methods that increase CTP concentration and CTP prevalence (e.g., by removing red blood cells, serum, and non-CTPs or by increasing aspirate volumes). Cell concentration in the BMA can be measured at the point of care and is an appropriate initial assessment of the quality of BMA.

MUFAs in High-Fat Diets Protect against Obesity-Induced Bias of Hematopoietic Cell Lineages

SCOPE

The role of dietary fatty acids in the generation of bone marrow (BM) immune cells and their trafficking to extramedullary compartments in the obesity is not yet fully understood.

METHODS AND RESULTS

C57BL/6J mice are randomly assigned to isocaloric high-fat diets (HFDs) formulate with dietary fats rich in saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) or MUFAs fortified with eicosapentaenoic and docosahexaenoic acids for 20 weeks, followed by profiling of the obese metabolic phenotype and immunophenotypic features of immune cells in blood, spleen, and BM. All HFDs induce an obese phenotype, but it becomes largely less disruptive after the HFDs are enriched in MUFAs, which also induce signs of granulopoiesis and an expansion of long-term hematopoietic stem and granulocyte-macrophage progenitor cells in BM. In contrast, a HFD enriched in SFAs disturbs the fitness of medullary lymphocytes and promotes monopoiesis in favor of pro-inflammatory activated subsets.

CONCLUSION

The reshaping of the fatty acid pools with MUFAs from the diet serves to manipulate the generation and trafficking of immune cells that are biased during obesity. These findings reveal a novel strategy by which dietary MUFAs may be instrumental in combating HFD-induced dysfunctional immune systems.

Novel insights into the pathological mechanisms of metabolic related dyslipidemia

Due to the technological advances, it has been well-established that obesity is strongly correlated with various health problems. Among these problems, dyslipidemia is one of the most important concomitant symptoms under obese status which is the main driving force behind the pathological progression of cardio-metabolic disorder diseases. Importantly, the type of dyslipidemia, arising from concerted action of obesity, has been identified as "metabolic related dyslipidemia", which is characterized by increased circulating levels of Low density lipoprotein cholesterol (LDL-C), Triglycerides (TG) accompanied by lower circulating levels of High density lipoprotein cholesterol (HDL-C). On the other hand, the metabolic related dyslipidemia is being verified as a vital link between obesity and hypertension, diabetes mellitus, and Cardiovascular disease (CVD). In this review, we summarized the current understanding of metabolic related dyslipidemia and the potential mechanisms which lead to the pathogenesis of obesity. Meanwhile, we also summarized the emerging results which focused on several novel lipid bio-markers in metabolic related dyslipidemia, such as pro-protein convertase subtilisin/kexin type 9 (PCSK9) and sphingosine-1-phosphate (S1P), and their potential use as biomarkers of metabolic related dyslipidemia.

Pathology of metabolically-related dyslipidemia

It is well established that overweight/obesity is closely associated with multiple health problems. Among these, dyslipidemia is the most important and main driving force behind pathologic development of cardio-metabolic disorders such as diabetes mellitus, atherosclerotic-related cardiovascular disease and hypertension. Notably, a subtype of dyslipidemia, metabolic related dyslipidemia, is now recognized as a vital link between obesity and multiple different cardiovascular diseases. This condition is characterized by increased low density lipoprotein cholesterol (LDL-C) and triglyceride (TG) and very low density lipoprotein cholesterol (VLDL-C) as well as decreased high density lipoprotein cholesterol (HDL-C) in serum. In this review, we summarize the current understanding of metabolic related dyslipidemia and the potential mechanisms which lead to the pathogenesis of obesity/overweight. We focus on several novel lipid biomarkers such as pro-protein convertase subtilisin/kexin type 9 (PCSK9) and sphingosine-1-phosphate (S1P) and their potential use as biomarkers of metabolic related dyslipidemia.

Macrophage Related Chronic Inflammation in Non-Healing Wounds

Persistent hyper-inflammation is a distinguishing pathophysiological characteristic of chronic wounds, and macrophage malfunction is considered as a major contributor thereof. In this review, we describe the origin and heterogeneity of macrophages during wound healing, and compare macrophage function in healing and non-healing wounds. We consider extrinsic and intrinsic factors driving wound macrophage dysregulation, and review systemic and topical therapeutic approaches for the restoration of macrophage response. Multidimensional analysis is highlighted through the integration of various high-throughput technologies, used to assess the diversity and activation states as well as cellular communication of macrophages in healing and non-healing wound. This research fills the gaps in current literature and provides the promising therapeutic interventions for chronic wounds.

Malfunctioning CD106-positive, short-term hematopoietic stem cells trigger diabetic neuropathy in mice by cell fusion

Diabetic neuropathy is an incurable disease. We previously identified a mechanism by which aberrant bone marrow-derived cells (BMDCs) pathologically expressing proinsulin/TNF-α fuse with residential neurons to impair neuronal function. Here, we show that CD106-positive cells represent a significant fraction of short-term hematopoietic stem cells (ST-HSCs) that contribute to the development of diabetic neuropathy in mice. The important role for these cells is supported by the fact that transplantation of either whole HSCs or CD106-positive ST-HSCs from diabetic mice to non-diabetic mice produces diabetic neuronal dysfunction in the recipient mice via cell fusion. Furthermore, we show that transient episodic hyperglycemia produced by glucose injections leads to abnormal fusion of pathological ST-HSCs with residential neurons, reproducing neuropathy in nondiabetic mice. In conclusion, we have identified hyperglycemia-induced aberrant CD106-positive ST-HSCs underlie the development of diabetic neuropathy. Aberrant CD106-positive ST-HSCs constitute a novel therapeutic target for the treatment of diabetic neuropathy.

Katagi et al. show that abnormal bone marrow-derived cells originated from hematopoietic stem cells (CD106-positive short-term HSCs) aberrantly fuse with neurons to develop diabetic neuropathy. This study suggests that the pathological abnormality is memorized in the bone marrow and that it cannot be erased by conventional therapy.

Adipocyte Fatty Acid Transfer Supports Megakaryocyte Maturation

Megakaryocytes (MKs) come from a complex process of hematopoietic progenitor maturation within the bone marrow that gives rise to de novo circulating platelets. Bone marrow microenvironment contains a large number of adipocytes with a still ill-defined role. This study aims to analyze the influence of adipocytes and increased medullar adiposity in megakaryopoiesis. An in vivo increased medullar adiposity in mice caused by high-fat-diet-induced obesity is associated to an enhanced MK maturation and proplatelet formation. In vitro co-culture of adipocytes with bone marrow hematopoietic progenitors shows that delipidation of adipocytes directly supports MK maturation by enhancing polyploidization, amplifying the demarcation membrane system, and accelerating proplatelet formation. This direct crosstalk between adipocytes and MKs occurs through adipocyte fatty acid transfer to MKs involving CD36 to reinforce megakaryocytic maturation. Thus, these findings unveil an influence of adiposity on MK homeostasis based on a dialogue between adipocytes and MKs.

Effect of Lipids and Lipoproteins on Hematopoietic Cell Metabolism and Commitment in Atherosclerosis

Hematopoiesis is the process that leads to multiple leukocyte lineage generation within the bone marrow. This process is maintained throughout life thanks to a nonstochastic division of hematopoietic stem cells (HSCs), where during each division, one daughter cell retains pluripotency while the other differentiates into a restricted multipotent progenitor (MPP) that converts into mature, committed circulating cell. This process is tightly regulated at the level of cellular metabolism and the shift from anaerobic glycolysis, typical of quiescent HSC, to oxidative metabolism fosters HSCs proliferation and commitment. Systemic and local factors influencing metabolism alter HSCs balance under pathological conditions, with chronic metabolic and inflammatory diseases driving HSCs commitment toward activated blood immune cell subsets. This is the case of atherosclerosis, where impaired systemic lipid metabolism affects HSCs epigenetics that reflects into increased differentiation toward activated circulating subsets.

Aim of this review is to discuss the impact of lipids and lipoproteins on HSCs pathophysiology, with a focus on the molecular mechanisms influencing cellular metabolism. A better understanding of these aspects will shed light on innovative strategies to target atherosclerosis-associated inflammation.

Targeting reactive oxygen species in stem cells for bone therapy

Reactive oxygen species (ROS) have emerged as key players in regulating the fate and function of stem cells from both non-hematopoietic and hematopoietic lineages in bone marrow, and thus affect the osteoblastogenesis-osteoclastogenesis balance and bone homeostasis. Accumulating evidence has linked ROS and associated oxidative stress with the progression of bone disorders, and ROS-based therapeutic strategies have appeared to achieve favorable outcomes in bone. We review current knowledge of the multifactorial roles and mechanisms of ROS as a target in bone pathology. In addition, we discuss emerging ROS-based therapeutic strategies that show potential for bone therapy. Finally, we highlight the opportunities and challenges facing ROS-targeted stem cell therapeutics for improving bone health.

The Chemokine Receptor CCR3 Is Potentially Involved in the Homing of Prostate Cancer Cells to Bone: Implication of Bone-Marrow Adipocytes

Bone metastasis remains the most frequent and the deadliest complication of prostate cancer (PCa). Mechanisms leading to the homing of tumor cells to bone remain poorly characterized. Role of chemokines in providing navigational cues to migrating cancer cells bearing specific receptors is well established. Bone is an adipocyte-rich organ since 50 to 70% of the adult bone marrow (BM) volume comprise bone marrow adipocytes (BM-Ads), which are likely to produce chemokines within the bone microenvironment. Using in vitro migration assays, we demonstrated that soluble factors released by human primary BM-Ads are able to support the directed migration of PCa cells in a CCR3-dependent manner. In addition, we showed that CCL7, a chemokine previously involved in the CCR3-dependent migration of PCa cells outside of the prostate gland, is released by human BM-Ads. These effects are amplified by obesity and ageing, two clinical conditions known to promote aggressive and metastatic PCa. In human tumors, we found an enrichment of CCR3 in bone metastasis vs. primary tumors at mRNA levels using Oncomine microarray database. In addition, immunohistochemistry experiments demonstrated overexpression of CCR3 in bone versus visceral metastases. These results underline the potential importance of BM-Ads in the bone metastatic process and imply a CCR3/CCL7 axis whose pharmacological interest needs to be evaluated.

Six degrees head-down tilt bed rest caused low-grade hemolysis: a prospective randomized clinical trial

This study aimed to measure hemolysis before, during and after 60 days of the ground-based spaceflight analog bed rest and the effect of a nutritional intervention through a prospective randomized clinical trial. Twenty male participants were hospitalized for 88 days comprised of 14 days of ambulatory baseline, 60 days of 6° head-down tilt bed rest and 14 days of reambulation. Ten participants each received a control diet or daily polyphenol associated with omega-3, vitamin E, and selenium supplements. The primary outcome was endogenous carbon monoxide (CO) elimination measured by gas chromatography. Hemolysis was also measured with serial bilirubin, iron, transferrin saturation blood levels and serial 3-day stool collections were used to measure urobilinoid excretion using photometry. Total hemoglobin mass (tHb) was measured using CO-rebreathing. CO elimination increased after 5, 11, 30, and 57 days of bed rest: +289 ppb (95% CI 101-477 ppb; p = 0.004), +253 ppb (78-427 ppb; p = 0.007), +193 ppb (89-298 ppb; p = 0.001) and +858 ppb (670-1046 ppb; p < 0.000), respectively, compared to baseline. Bilirubin increased after 20 and 49 days of bed rest +0.8 mg/l (p = 0.013) and +1.1 mg/l (p = 0.012), respectively; and iron increased after 20 days of bed rest +10.5 µg/dl (p = 0.032). The nutritional intervention did not change CO elimination. THb was lower after 60 days of bed rest -0.9 g/kg (p = 0.001). Bed rest enhanced hemolysis as measured through all three by-products of heme oxygenase. Ongoing enhanced hemolysis over 60 days contributed to a 10% decrease in tHb mass. Modulation of red blood cell control towards increased hemolysis may be an important mechanism causing anemia in astronauts.

Tissue-Specific Effects of Leptin on Glucose and Lipid Metabolism

The discovery of leptin was intrinsically associated with its ability to regulate body weight. However, the effects of leptin are more far-reaching and include profound glucose-lowering and anti-lipogenic effects, independent of leptin's regulation of body weight. Regulation of glucose metabolism by leptin is mediated both centrally and via peripheral tissues and is influenced by the activation status of insulin signaling pathways. Ectopic fat accumulation is diminished by both central and peripheral leptin, an effect that is beneficial in obesity-associated disorders. The magnitude of leptin action depends upon the tissue, sex, and context being examined. Peripheral tissues that are of particular relevance include the endocrine pancreas, liver, skeletal muscle, adipose tissues, immune cells, and the cardiovascular system. As a result of its potent metabolic activity, leptin is used to control hyperglycemia in patients with lipodystrophy and is being explored as an adjunct to insulin in patients with type 1 diabetes. To fully understand the role of leptin in physiology and to maximize its therapeutic potential, the mechanisms of leptin action in these tissues needs to be further explored.

Obesity and COVID-19: what makes obese host so vulnerable?

The disease (COVID-19) novel coronavirus pandemic has so far infected millions resulting in the death of over a million people as of Oct 2020. More than 90% of those infected with COVID-19 show mild or no symptoms but the rest of the infected cases show severe symptoms resulting in significant mortality. Age has emerged as a major factor to predict the severity of the disease and mortality rates are significantly higher in elderly patients. Besides, patients with underlying conditions like Type 2 diabetes, cardiovascular diseases, hypertension, and cancer have an increased risk of severe disease and death due to COVID-19 infection. Obesity has emerged as a novel risk factor for hospitalization and death due to COVID-19. Several independent studies have observed that people with obesity are at a greater risk of severe disease and death due to COVID-19. Here we review the published data related to obesity and overweight to assess the possible risk and outcome in Covid-19 patients based on their body weight. Besides, we explore how the obese host provides a unique microenvironment for disease pathogenesis, resulting in increased severity of the disease and poor outcome.

FOXO activity adaptation safeguards the hematopoietic stem cell compartment in hyperglycemia

Hematopoietic stem cell (HSC) activity is tightly controlled to ensure the integrity of the hematopoietic system during the organism's lifetime. How the HSC compartment maintains its long-term fitness in conditions of chronic stresses associated with systemic metabolic disorders is poorly understood. In this study, we show that obesity functionally affects the long-term function of the most immature engrafting HSC subpopulation. We link this altered regenerative activity to the oxidative stress and the aberrant constitutive activation of the AKT signaling pathway that characterized the obese environment. In contrast, we found minor disruptions of the HSC function in obese mice at steady state, suggesting that active mechanisms could protect the HSC compartment from its disturbed environment. Consistent with this idea, we found that FOXO proteins in HSCs isolated from obese mice become insensitive to their normal upstream regulators such as AKT, even during intense oxidative stress. We established that hyperglycemia, a key condition associated with obesity, is directly responsible for the alteration of the AKT-FOXO axis in HSCs and their abnormal oxidative stress response. As a consequence, we observed that HSCs isolated from a hyperglycemic environment display enhanced resistance to oxidative stress and DNA damage. Altogether, these results indicate that chronic metabolic stresses associated with obesity and/or hyperglycemia affect the wiring of the HSCs and modify their oxidative stress response. These data suggest that the uncoupling of FOXO from its environmental regulators could be a key adaptive strategy that promotes the survival of the HSC compartment in obesity.

Implications of metabolism-driven myeloid dysfunctions in cancer therapy

Immune homeostasis is maintained by an adequate balance of myeloid and lymphoid responses. In chronic inflammatory states, including cancer, this balance is lost due to dramatic expansion of myeloid progenitors that fail to mature to functional inflammatory neutrophils, macrophages, and dendritic cells (DCs), thus giving rise to a decline in the antitumor effector lymphoid response. Cancer-related inflammation orchestrates the production of hematopoietic growth factors and cytokines that perpetuate recruitment and activation of myeloid precursors, resulting in unresolved and chronic inflammation. This pathologic inflammation creates profound alterations in the intrinsic cellular metabolism of the myeloid progenitor pool, which is amplified by competition for essential nutrients and by hypoxia-induced metabolic rewiring at the tumor site. Therefore, persistent myelopoiesis and metabolic dysfunctions contribute to the development of cancer, as well as to the severity of a broad range of diseases, including metabolic syndrome and autoimmune and infectious diseases. The aims of this review are to (1) define the metabolic networks implicated in aberrant myelopoiesis observed in cancer patients, (2) discuss the mechanisms underlying these clinical manifestations and the impact of metabolic perturbations on clinical outcomes, and (3) explore new biomarkers and therapeutic strategies to restore immunometabolism and differentiation of myeloid cells towards an effector phenotype to increase host antitumor immunity. We propose that the profound metabolic alterations and associated transcriptional changes triggered by chronic and overactivated immune responses in myeloid cells represent critical factors influencing the balance between therapeutic efficacy and immune-related adverse effects (irAEs) for current therapeutic strategies, including immune checkpoint inhibitor (ICI) therapy.

Emerging functions of adipokines in linking the development of obesity and cardiovascular diseases

Increasing evidence shows that obesity is the critical factor in shaping cardio-metabolic phenotypes. However, the pathogenic mechanisms remain incompletely clarified. According to the published reports, adipose tissue communicates with several diverse organs, such as heart, lungs, and kidneys through the secretion of various cytokines named adipokines. The adipocytes isolated from obese mice or humans are dysfunctional with aberrant production of pro-inflammatory adipokines, which subsequently induce both acute and chronic inflammatory reaction and facilitate the process of cardio-metabolic disorder complications. Furthermore, the microenvironment within adipose tissue under obese status also influence the secretion of adipokines. Recently, given that several important adipokines have been completely researched and causally involved in various diseases, we could make a conclusion that adipokines play an essential role in modulating the development of cardio-metabolic disorder diseases, whereas several novel adipokines continue to be explored and elucidated. In the present review, we summarized the current knowledge of the microenvironment of adipose tissue and the published mechanisms whereby adipocytes affects obesity and cardiovascular diseases. On the other hand, we also provide the evidence to elucidate the functions of adipokines in controlling and regulating the inflammatory reactions which contribute to obesity and cardiovascular disease.

Hyperplasia and accelerated hypertrophy of marrow adipocytes with knee immobilization were sustained despite remobilization

Skeletal disuse can cause an accumulation of bone marrow adipose tissue (MAT) characterized by a combination of marrow adipocyte hyperplasia and/or hypertrophy. The malleability of MAT accumulation and of the hyperplasia and hypertrophy upon remobilization is unknown. In this study, we showed extensive hyperplasia and accelerated hypertrophy of bone marrow adipocytes in the proximal tibia epiphysis of rat knees immobilized for durations between 1 and 32 wk. Similar histomorphometric measures of adipocytes carried out in unoperated controls allowed distinguishing the effects of immobilization from the effects of aging. Although both knee immobilization and aging led to adipocyte hypertrophy, adipocyte hyperplasia was the hallmark signature effect of immobilization on MAT. Both bone marrow adipocyte hyperplasia and hypertrophy were sustained despite knee remobilization for durations up to four times the duration of immobilization. These results suggest that adipocyte hyperplasia is the predominant mechanism explaining MAT accumulation in skeletal disuse. In this model, the changes were unremitting for the investigated time points. Investigating the cellular and molecular mechanisms of marrow adipocyte mechanoregulation will be important to better understand how adipocytes adapt to changes in mechanical environments.NEW & NOTEWORTHY This longitudinal study elucidates the response of marrow adipose tissue adipocytes in weight-bearing joints to changes in different mechanical environments, and we provide insight on the malleability of the changes over time. In a rat animal model, knee immobilization induced hyperplasia and accelerated the age-dependent hypertrophy of adipocytes. Changes in adipocyte number and size were sustained despite unassisted remobilization. Multimodal distributions of cell size were characteristic of bone marrow adipocytes.

Obesity-Associated Hypermetabolism and Accelerated Senescence of Bone Marrow Stromal Stem Cells Suggest a Potential Mechanism for Bone Fragility

Obesity is associated with increased risk for fragility fractures. However, the cellular mechanisms are unknown. Using a translational approach combining RNA sequencing and cellular analyses, we investigated bone marrow stromal stem cells (BM-MSCs) of 54 men divided into lean, overweight, and obese groups on the basis of BMI. Compared with BM-MSCs obtained from lean, obese BM-MSCs exhibited a shift of molecular phenotype toward committed adipocytic progenitors and increased expression of metabolic genes involved in glycolytic and oxidoreductase activity. Interestingly, compared with paired samples of peripheral adipose tissue-derived stromal cells (AT-MSCs), insulin signaling of obese BM-MSCs was enhanced and accompanied by increased abundance of insulin receptor positive (IR+) and leptin receptor positive (LEPR+) cells in BM-MSC cultures. Their hyper-activated metabolic state was accompanied by an accelerated senescence phenotype. Our data provide a plausible explanation for the bone fragility in obesity caused by enhanced insulin signaling leading to accelerated metabolic senescence of BM-MSCs.

Daily Ethanol Drinking Followed by an Abstinence Period Impairs Bone Marrow Niche and Mitochondrial Function of Hematopoietic Stem/Progenitor Cells in Rhesus Macaques

BACKGROUND

Unhealthy consumption of alcohol is a major public health crisis with strong associations between immunological dysfunctions, high vulnerability to infectious disease, anemia, and an increase in the risk of hematological malignancies. However, there is a lack of studies addressing alcohol-induced changes in bone marrow (BM) and hematopoiesis as fundamental aspects of immune system function.

METHODS

To address the effect of chronic alcohol consumption on hematopoietic stem and progenitor cells (HSPCs) and the BM niche, we used an established rhesus macaque model of voluntary alcohol drinking. A cohort of young adult male rhesus macaques underwent a standard ethanol self-administration protocol that allowed a choice of drinking alcohol or water 22 hours/day with periods of forced abstinence that elevated subsequent intakes when alcohol availability resumed. Following the last month of forced abstinence, the monkeys were euthanized. HSPCs and bone samples were collected and analyzed in functional assays and by confocal microscopy.

RESULTS

HSPCs from alcohol animals exhibited reduced ability to form granulocyte-monocyte and erythroid colonies in vitro. HSPCs also displayed a decrease in mitochondrial oxygen consumption linked to ATP production and basal respiratory capacity. Chronic alcohol use led to vascular remodeling of the BM niche, a reduction in the number of primitive HSPCs, and a shift in localization of HSPCs from an adipose to a perivascular niche.

CONCLUSIONS

Our study demonstrates, for the first time, that chronic voluntary alcohol drinking in rhesus macaque monkeys leads to the long-term impairment of HSPC function, a reduction in mitochondrial respiratory activity, and alterations in the BM microenvironment. Further studies are needed to determine whether these changes in hematopoiesis are persistent or adaptive during the abstinent period and whether an initial imprinting to alcohol primes BM to become more vulnerable to future exposure to alcohol.

Spatial and biochemical interactions between bone marrow adipose tissue and hematopoietic stem and progenitor cells in rhesus macaques

Recent developments in in situ microscopy have enabled unparalleled resolution of the architecture of the bone marrow (BM) niche for murine hematopoietic stem and progenitor cells (HSPCs). However, the extent to which these observations can be extrapolated to human BM remains unknown. In humans, adipose tissue occupies a significant portion of the BM medullary cavity, making quantitative immunofluorescent analysis difficult due to lipid-mediated light scattering. In this study, we employed optical clearing, confocal microscopy and nearest neighbor analysis to determine the spatial distribution of CD34+ HSPCs in the BM in a translationally relevant rhesus macaque model. Immunofluorescent analysis revealed that femoral BM adipocytes are associated with the branches of vascular sinusoids, with half of HSPCs localizing in close proximity of the nearest BM adipocyte. Immunofluorescent microscopy and flow cytometric analysis demonstrate that BM adipose tissue exists as a multicellular niche consisted of adipocytes, endothelial cells, granulocytes, and macrophages. Analysis of BM adipose tissue conditioned media using liquid chromatography-tandem mass spectrometry revealed the presence of multiple bioactive proteins involved in regulation of hematopoiesis, inflammation, and bone development, with many predicted to reside inside microvesicles. Pretreatment of purified HSPCs with BM adipose tissue conditioned media, comprising soluble and exosomal/microvesicle-derived factors, led to enhanced proliferation and an increase in granulocyte-monocyte differentiation potential ex vivo. Our work extends extensive studies in murine models, indicating that BM adipose tissue is a central paracrine regulator of hematopoiesis in nonhuman primates and possibly in humans.

Bone marrow adipose cells - cellular interactions and changes with obesity

The bone marrow is a spatially restricted niche, housing cells of the hematopoietic and mesenchymal lineages in various hierarchical commitment states. Although highly localized, cells within this niche are also subject to regulation by environmental and/or circulatory changes through extensive vascularization. Bone marrow adipocytes, derived from mesenchymal stem cells and once known as marrow space fillers, are a heterogeneous population. These cells reside in distinct niches within the bone marrow and interact with proximal cells, such as hematopoietic precursors and lineage-committed cells. In this diverse cellular milieu, bone marrow adipocytes influence commitment decisions and cellular lineage selection by interacting with stem and progenitor cells. In addition, bone marrow adipocytes respond to environmental changes, such as obesity, by undergoing hypertrophy, hyperplasia or adoption of characteristics resembling those of peripheral brown, beige or white adipocytes. Here, we review recent findings and concepts on the influence of bone marrow adipocytes on hematopoietic and other cellular lineages within this niche. We discuss how changes in local, systemic, cellular and secreted signals impact on mesenchymal stem cell expansion, differentiation and lineage commitment. Furthermore, we highlight that bone marrow adipocytes may be intermediaries conveying environmental cues to influence hematopoietic cellular survival, proliferation and preferential differentiation.