Endurance exercise training promotes medullary hematopoiesis

The Effect of Exercise on Mesenchymal Stem Cells and their Application in Obesity Treatment

Mesenchymal stem cells (MSCs) have demonstrated considerable potential in tissue repair and the treatment of immune-related diseases, but there are problems with homing efficiency during MSCs transplantation. Exercise, as an intervention, has been shown to have an important impact on the properties of MSCs. This review summarizes the effects of exercise on the properties (including proliferation, apoptosis, differentiation, and homing) of bone marrow-derived MSCs and adipose-derived MSCs. Studies indicated that exercise enhances bone marrow-derived MSCs proliferation, osteogenic differentiation, and homing while reducing adipogenic differentiation. For adipose-derived MSCs, exercise enhances proliferation and reduces adipogenic differentiation. In addition, studies have investigated the therapeutic effects of combined therapy of MSCs transplantation with exercise on diseases of the bone, cardiac, and nervous systems. The combined therapy improves tissue repair by increasing the homing of transplanted MSCs and cytokine secretion (such as neurotrophin 4). Furthermore, MSCs transplantation also has potential for the treatment of obesity. Although the effect is not significant in weight loss, MSCs transplantation shows effects in controlling blood glucose, improving dyslipidemia, reducing inflammation, and improving liver disease. Finally, the potential role of combined MSCs transplantation and exercise therapy in addressing obesity is discussed.

Effects of lifestyle factors on leukocytes in cardiovascular health and disease

Exercise, stress, sleep and diet are four distinct but intertwined lifestyle factors that influence the cardiovascular system. Abundant epidemiological, clinical and preclinical studies have underscored the importance of managing stress, having good sleep hygiene and responsible eating habits and exercising regularly. We are born with a genetic blueprint that can protect us against or predispose us to a particular disease. However, lifestyle factors build upon and profoundly influence those predispositions. Studies in the past 10 years have shown that the immune system in general and leukocytes in particular are particularly susceptible to environmental perturbations. Lifestyle factors such as stress, sleep, diet and exercise affect leukocyte behaviour and function and thus the immune system at large. In this Review, we explore the various mechanisms by which lifestyle factors modulate haematopoiesis and leukocyte migration and function in the context of cardiovascular health. We pay particular attention to the role of the nervous system as the key executor that connects environmental influences to leukocyte behaviour.

Translation of biophysical environment in bone into dynamic cell culture under flow for bone tissue engineering

Bone is a dynamic environment where osteocytes, osteoblasts, and mesenchymal stem/progenitor cells perceive mechanical cues and regulate bone metabolism accordingly. In particular, interstitial fluid flow in bone and bone marrow serves as a primary biophysical stimulus, which regulates the growth and fate of the cellular components of bone. The processes of mechano-sensory and -transduction towards bone formation have been well studied mainly in vivo as well as in two-dimensional (2D) dynamic cell culture platforms, which elucidated mechanically induced osteogenesis starting with anabolic responses, such as production of nitrogen oxide and prostaglandins followed by the activation of canonical Wnt signaling, upon mechanosensation. The knowledge has been now translated into regenerative medicine, particularly into the field of bone tissue engineering, where multipotent stem cells are combined with three-dimensional (3D) scaffolding biomaterials to produce transplantable constructs for bone regeneration. In the presence of 3D scaffolds, the importance of suitable dynamic cell culture platforms increases further not only to improve mass transfer inside the scaffolds but to provide appropriate biophysical cues to guide cell fate. In principle, the concept of dynamic cell culture platforms is rooted to bone mechanobiology. Therefore, this review primarily focuses on biophysical environment in bone and its translation into dynamic cell culture platforms commonly used for 2D and 3D cell expansion, including their advancement, challenges, and future perspectives. Additionally, it provides the literature review of recent empirical studies using 2D and 3D flow-based dynamic cell culture systems for bone tissue engineering.

Impact of exercise on brain-bone marrow interactions in chronic stress: potential mechanisms preventing stress-induced hypertension

We examined the effect of chronic restraint stress and the counteractive effects of daily exercise on the molecular basis of the brain-bone marrow (BM) interactions, by especially focusing on the paraventricular nucleus (PVN) of the hypothalamus. Male Wistar rats were assigned into control, restraint stress, and stress + daily spontaneous exercise (SE) groups. BM and hypothalamic gene expression profiles were examined through the undertaking of RT-PCR and microarrays, respectively. The inflammatory blood cell population was investigated through flow cytometry. Through the use of immunohistochemistry, we examined the presence of BM-derived C-C chemokine receptor type 2 (CCR2)-expressing microglial cells in the rat PVN. The gene expression levels of BM inflammatory factors such as those of interleukin 1 beta and CCR2, and the inflammatory blood cell population were found to be significantly higher in both restrained groups compared with control group. Interestingly, chronic restraint stress alone activated the recruitment of BM-derived CCR2-expressing microglial cells into the PVN, whereas daily spontaneous exercise prevented it. A notable finding was that restraint stress upregulated relative gene expression of hypothalamic matrix metalloproteinase 3 (MMP3), which increases the permeability of the blood-brain barrier (BBB), and that exercise managed to normalize it. Moreover, relative expression of some hypothalamic genes directly involved in the facilitation of cell migration was downregulated by daily exercise. Our findings suggest that daily spontaneous exercise can reduce the numbers of BM-derived CCR2-expressing microglial cells into the PVN through the prevention of stress-induced changes in the hypothalamic gene expression.NEW & NOTEWORTHY Chronic restraint stress can upregulate MMP3 gene expression in the rat hypothalamus, whereas daily spontaneous exercise can prevent this stress-induced effect. Stress-induced BM-derived inflammatory cell recruitment into the rat PVN can be prevented by daily spontaneous exercise. Stress-induced increase of hypothalamic MMP3 gene expression may be responsible for BBB injury, thereby allowing for BM-derived inflammatory cells to be recruited and to accumulate in the rat PVN, and to be subsequently involved in the onset of stress-induced hypertension.

Exercise sustains the hallmarks of health

Exercise has long been known for its active role in improving physical fitness and sustaining health. Regular moderate-intensity exercise improves all aspects of human health and is widely accepted as a preventative and therapeutic strategy for various diseases. It is well-documented that exercise maintains and restores homeostasis at the organismal, tissue, cellular, and molecular levels to stimulate positive physiological adaptations that consequently protect against various pathological conditions. Here we mainly summarize how moderate-intensity exercise affects the major hallmarks of health, including the integrity of barriers, containment of local perturbations, recycling and turnover, integration of circuitries, rhythmic oscillations, homeostatic resilience, hormetic regulation, as well as repair and regeneration. Furthermore, we summarize the current understanding of the mechanisms responsible for beneficial adaptations in response to exercise. This review aimed at providing a comprehensive summary of the vital biological mechanisms through which moderate-intensity exercise maintains health and opens a window for its application in other health interventions. We hope that continuing investigation in this field will further increase our understanding of the processes involved in the positive role of moderate-intensity exercise and thus get us closer to the identification of new therapeutics that improve quality of life.

The role of exercise-and high fat diet-induced bone marrow extracellular vesicles in stress hematopoiesis

Exercise and obesity regulate hematopoiesis, in part through alterations in cellular and soluble components of the bone marrow niche. Extracellular vesicles (EVs) are components of the bone marrow niche that regulate hematopoiesis; however, the role of exercise training or obesity induced EVs in regulating hematopoiesis remains unknown. To address this gap, donor EVs were isolated from control diet-fed, sedentary mice (CON-SED), control diet-fed exercise trained mice (CON-EX), high fat diet-fed, sedentary mice (HFD-SED), and high fat diet-fed, exercise trained mice (HFD-EX) and injected into recipient mice undergoing stress hematopoiesis. Hematopoietic and niche cell populations were quantified, and EV miRNA cargo was evaluated. EV content did not differ between the four groups. Mice receiving HFD-EX EVs had fewer hematopoietic stem cells (HSCs) (p < 0.01), long-term HSC (p < 0.05), multipotent progenitors (p < 0.01), common myeloid progenitors (p<0.01), common lymphoid progenitors (p < 0.01), and granulocyte-macrophage progenitors (p < 0.05), compared to mice receiving HFD-SED EVs. Similarly, mice receiving EX EVs had fewer osteoprogenitor cells compared to SED (p < 0.05) but enhanced mesenchymal stromal cell (MSC) osteogenic differentiation in vitro (p < 0.05) compared to SED EVs. HFD EVs enhanced mesenchymal stromal cell (MSC) adipogenesis in vitro (p < 0.01) compared to CON EVs. HFD-EX EVs had lower microRNA-193 and microRNA-331-5p content, microRNAs implicated in inhibiting osteogenesis and leukemic cell expansion respectively, compared to HFD-SED EVs. The results identify alterations in EV cargo as a novel mechanism by which exercise training alters stress hematopoiesis and the bone marrow niche.

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.

Hematopoietic Stem Cell Factors: Their Functional Role in Self-Renewal and Clinical Aspects

Hematopoietic stem cells (HSCs) possess two important properties such as self-renewal and differentiation. These properties of HSCs are maintained through hematopoiesis. This process gives rise to two subpopulations, long-term and short-term HSCs, which have become a popular convention for treating various hematological disorders. The clinical application of HSCs is bone marrow transplant in patients with aplastic anemia, congenital neutropenia, sickle cell anemia, thalassemia, or replacement of damaged bone marrow in case of chemotherapy. The self-renewal attribute of HSCs ensures long-term hematopoiesis post-transplantation. However, HSCs need to be infused in large numbers to reach their target site and meet the demands since they lose their self-renewal capacity after a few passages. Therefore, a more in-depth understanding of ex vivo HSCs expansion needs to be developed to delineate ways to enhance the self-renewability of isolated HSCs. The multifaceted self-renewal process is regulated by factors, including transcription factors, miRNAs, and the bone marrow niche. A developed classical hierarchical model that outlines the hematopoiesis in a lineage-specific manner through in vivo fate mapping, barcoding, and determination of self-renewal regulatory factors are still to be explored in more detail. Thus, an in-depth study of the self-renewal property of HSCs is essentially required to be utilized for ex vivo expansion. This review primarily focuses on the Hematopoietic stem cell self-renewal pathway and evaluates the regulatory molecular factors involved in considering a targeted clinical approach in numerous malignancies and outlining gaps in the current knowledge.

Exercise to Mend Aged-tissue Crosstalk in Bone Targeting Osteoporosis & Osteoarthritis

Aging induces alterations in bone structure and strength through a multitude of processes, exacerbating common aging- related diseases like osteoporosis and osteoarthritis. Cellular hallmarks of aging are examined, as related to bone and the marrow microenvironment, and ways in which these might contribute to a variety of age-related perturbations in osteoblasts, osteocytes, marrow adipocytes, chondrocytes, osteoclasts, and their respective progenitors. Cellular senescence, stem cell exhaustion, mitochondrial dysfunction, epigenetic and intracellular communication changes are central pathways and recognized as associated and potentially causal in aging. We focus on these in musculoskeletal system and highlight knowledge gaps in the literature regarding cellular and tissue crosstalk in bone, cartilage, and the bone marrow niche. While senolytics have been utilized to target aging pathways, here we propose non-pharmacologic, exercise-based interventions as prospective "senolytics" against aging effects on the skeleton. Increased bone mass and delayed onset or progression of osteoporosis and osteoarthritis are some of the recognized benefits of regular exercise across the lifespan. Further investigation is needed to delineate how cellular indicators of aging manifest in bone and the marrow niche and how altered cellular and tissue crosstalk impact disease progression, as well as consideration of exercise as a therapeutic modality, as a means to enhance discovery of bone-targeted therapies.

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.

Exercise Improves Cancer-free Survival and Health Span in a Model of Radiation-induced Cancer

INTRODUCTION

Radiation therapy increases the risk of secondary malignancy and morbidity in cancer survivors. The role of obesity and exercise training in modulating this risk is not well understood. As such, we used a preclinical model of radiation-induced malignancy to investigate whether diet-induced obesity and/or endurance exercise training altered lifelong survival, cancer incidence, and morbidity.

METHODS

Male CBA mice were randomly divided into control diet/sedentary group (CTRL/SED), high-fat diet (45% fat)/sedentary group (HFD/SED), control diet/exercise group (2-3 d·wk-1; CTRL/EX), or high-fat diet/exercise group (HFD/EX) groups then exposed to whole-body radiation (3 Gy). End point monitoring and pathology determined mortality and cancer incidence, respectively. Health span index, a measure of morbidity, was determined by a composite measure of 10 anthropometric, metabolic, performance, and behavioral measures.

RESULTS

Overall survival was higher in HFD/SED compared with CTRL/SED (P < 0.05). The risk of cancer-related mortality by 18 months postradiation was 1.99 and 1.63 in HFD/SED compared with CTRL/EX (RR = 1.99, 95% confidence interval = 1.20-3.31, P = 0.0081) and CTRL/SED (RR = 1.63, 95% confidence interval = 1.06-2.49, P = 0.0250), respectively. The number of mice at end point with cancer was higher in HFD/SED compared with CTRL/EX and CTRL/SED (P < 0.05). Health span index was highest in CTRL/EX (score = +2.5), followed by HFD/EX (score = +1), and HFD/SED (score = -1) relative to CTRL/SED.

CONCLUSION

This work provides the basis for future preclinical studies investigating the dose-response relationship between exercise training and late effects of radiation therapy as well as the mechanisms responsible for these effects.

Stem cells and regenerative medicine in sport science

The estimated cost of acute injuries in college-level sport in the USA is ∼1.5 billion dollars per year, without taking into account the cost of follow up rehabilitation. In addition to this huge financial burden, without appropriate diagnosis and relevant interventions, sport injuries may be career-ending for some athletes. With a growing number of females participating in contact based and pivoting sports, middle aged individuals returning to sport and natural injuries of ageing all increasing, such costs and negative implications for quality of life will expand. For those injuries, which cannot be predicted and prevented, there is a real need, to optimise repair, recovery and function, post-injury in the sporting and clinical worlds. The 21st century has seen a rapid growth in the arena of regenerative medicine for sporting injuries, in a bid to progress recovery and to facilitate return to sport. Such interventions harness knowledge relating to stem cells as a potential for injury repair. While the field is rapidly growing, consideration beyond the stem cells, to the factors they secrete, should be considered in the development of effective, affordable treatments.

The Impact of Sedentary Lifestyle, High-fat Diet, Tobacco Smoke, and Alcohol Intake on the Hematopoietic Stem Cell Niches

Hematopoietic stem and progenitor cells maintain hematopoiesis throughout life by generating all major blood cell lineages through the process of self-renewal and differentiation. In adult mammals, hematopoietic stem cells (HSCs) primarily reside in the bone marrow (BM) at special microenvironments called “niches.” Niches are thought to extrinsically orchestrate the HSC fate including their quiescence and proliferation. Insight into the HSC niches mainly comes from studies in mice using surface marker identification and imaging to visualize HSC localization and association with niche cells. The advantage of mouse models is the possibility to study the 3-dimensional BM architecture and cell interactions in an intact traceable system. However, this may not be directly translational to human BM. Sedentary lifestyle, unhealthy diet, excessive alcohol intake, and smoking are all known risk factors for various diseases including hematological disorders and cancer, but how do lifestyle factors impact hematopoiesis and the associated niches? Here, we review current knowledge about the HSC niches and how unhealthy lifestyle may affect it. In addition, we summarize epidemiological data concerning the influence of lifestyle factors on hematological disorders and malignancies.

The effects of locomotion on bone marrow mesenchymal stem cell fate: insight into mechanical regulation and bone formation

Bone marrow mesenchymal stem cells (BMSCs) refer to a heterogeneous population of cells with the capacity for self-renewal. BMSCs have multi-directional differentiation potential and can differentiate into chondrocytes, osteoblasts, and adipocytes under specific microenvironment or mechanical regulation. The activities of BMSCs are closely related to bone quality. Previous studies have shown that BMSCs and their lineage-differentiated progeny (for example, osteoblasts), and osteocytes are mechanosensitive in bone. Thus, a goal of this review is to discuss how these ubiquious signals arising from mechanical stimulation are perceived by BMSCs and then how the cells respond to them. Studies in recent years reported a significant effect of locomotion on the migration, proliferation and differentiation of BMSCs, thus, contributing to our bone mass. This regulation is realized by the various intersecting signaling pathways including RhoA/Rock, IFG, BMP and Wnt signalling. The mechanoresponse of BMSCs also provides guidance for maintaining bone health by taking appropriate exercises. This review will summarize the regulatory effects of locomotion/mechanical loading on BMSCs activities. Besides, a number of signalling pathways govern MSC fate towards osteogenic or adipocytic differentiation will be discussed. The understanding of mechanoresponse of BMSCs makes the foundation for translational medicine.

Exercise and Diet: Uncovering Prospective Mediators of Skeletal Fragility in Bone and Marrow Adipose Tissue

PURPOSE OF REVIEW

To highlight recent basic, translational, and clinical works demonstrating exercise and diet regulation of marrow adipose tissue (MAT) and bone and how this informs current understanding of the relationship between marrow adiposity and musculoskeletal health.

RECENT FINDINGS

Marrow adipocytes accumulate in the bone in the setting of not only hypercaloric intake (calorie excess; e.g., diet-induced obesity) but also with hypocaloric intake (calorie restriction; e.g., anorexia), despite the fact that these states affect bone differently. With hypercaloric intake, bone quantity is largely unaffected, whereas with hypocaloric intake, bone quantity and quality are greatly diminished. Voluntary running exercise in rodents was found to lower MAT and promote bone in eucaloric and hypercaloric states, while degrading bone in hypocaloric states, suggesting differential modulation of MAT and bone, dependent upon whole-body energy status. Energy status alters bone metabolism and bioenergetics via substrate availability or excess, which plays a key role in the response of bone and MAT to mechanical stimuli. Marrow adipose tissue (MAT) is a fat depot with a potential role in-as well as responsivity to-whole-body energy metabolism. Understanding the localized function of this depot in bone cell bioenergetics and substrate storage, principally in the exercised state, will aid to uncover putative therapeutic targets for skeletal fragility.

Exercise-Induced Circulating Hematopoietic Stem and Progenitor Cells in Well-Trained Subjects

It has been proposed that exercise-induced systemic oxidative stress increases circulating hematopoietic stem and progenitor cell (HPC) number in active participants, while HPC clonogenicity is reduced post-exercise. However, HPCs could be protected against exercise-induced reactive oxygen species in a trained state. Therefore, we characterized the acute exercise-induced HPC profile of well-trained participants including cell number, clonogenicity, and clearance. Twenty-one healthy, well-trained participants-12 runners, 9 cyclists; age 30.0 (4.3) years-performed a strenuous acute exercise session consisting of 4 bouts of 4-min high-intensity with 3-min low-intensity in-between, which is known to elicit oxidative stress. Average power/speed of intense phases was 85% of the peak achieved in a previous incremental test. Before and 10 min after exercise, CD34+/45dim cell number and clonogenicity, total oxidative (TOC), and antioxidative (TAC) capacities, as well as CD31 expression on detected HPCs were investigated. TOC significantly decreased from 0.093 (0.059) nmol/l to 0.083 (0.052) nmol/l post-exercise (p = 0.044). Although HPC proportions significantly declined below baseline (from 0.103 (0.037)% to 0.079 (0.028)% of mononuclear cells, p < 0.001), HPC concentrations increased post-exercise [2.10 (0.75) cells/μl to 2.46 (0.98) cells/μl, p = 0.002] without interaction between exercise modalities, while HPC clonogenicity was unaffected. Relating HPC concentrations and clonogenicity to exercise session specific (anti-) oxidative parameters, no association was found. CD31 median fluorescent intensity expression on detected HPCs was diminished post-exercise [from 1,675.9 (661.0) to 1,527.1 (558.9), p = 0.023] and positively correlated with TOC (r _rm = 0.60, p = 0.005). These results suggest that acute exercise-reduced oxidative stress influences HPC clearance but not mobilization in well-trained participants. Furthermore, a well-trained state protected HPCs' clonogenicity from post-exercise decline.

The effect of preconditioning with high-intensity training on tissue levels of G-CSF, its receptor and C-kit after an acute myocardial infarction in male rats

BACKGROUND

Exercise training is known as a practical way to increase cardioprotection against stress, and it seems that stem cell recruitment is one of its mechanisms. The purpose of the present study was to investigate the effect of preconditioning with High-intensity interval training (HIIT) on tissue levels of G-CSF, its receptor and C-Kit following acute myocardial infarction in male rats.

METHODS

Twenty Male Wistar rats were randomly divided into 4 groups of control, MI, HIIT, and HIIT+MI. Training groups performed 2 weeks of high intensity interval training in 4 sections. The first section consisted training in 3 days and 2 sessions in each day (4 × 2 min with 35-40 m/min and 3 × 2 min with 25-30 m/min between high intervals. The second part included 2 days of training (4 × 2 min with 40 to 45 m/min and 3 × 2 min with 28 to 32 m /min). The third part was performed in 3 days with one more repetition. The fourth section consisted 2 days of training and with one more repetition compared to section 3. For induction of myocardial infarction, subcutaneous injection of isoprenaline was used. CK, total CK, LDH, and troponin T were measured in serum and G-CSF, G-CSFR and C-Kit proteins were measured by the Western Blot method in the heart tissue.

RESULTS

The results of this study showed that enzymes of CK, total CK, LDH, troponin T had a significant increase in both MI and HIIT+MI groups compared to the other two groups (P < 0.001) and these indices in the MI group were significantly higher than the HIIT+MI group. Also, the results demonstrated that G-CSF, G-CSFR and C-Kit protein expression in the heart tissue significantly increased after MI. As well as, 2 weeks of HIIT training significantly increased G-CSF and C-kit in the training group compared to the control group, but the training caused that these proteins does not increase in HIIT+MI group as much as MI group.

CONCLUSIONS

Along with other protective pathways, high intensity interval training can increase cardioprotection and decrease heart injuries through the increase in G-CSF, G-CSFR and C-kit level.

Obesity-Induced Changes in Bone Marrow Homeostasis

Obesity is characterized by low-grade inflammation, which is accompanied by increased accumulation of immune cells in peripheral tissues including adipose tissue (AT), skeletal muscle, liver and pancreas, thereby impairing their primary metabolic functions in the regulation of glucose homeostasis. Obesity has also shown to have a detrimental effect on bone homeostasis by altering bone marrow and hematopoietic stem cell differentiation and thus impairing bone integrity and immune cell properties. The origin of immune cells arises in the bone marrow, which has been shown to be affected with the obesogenic condition via increased cellularity and shifting differentiation and function of hematopoietic and bone marrow mesenchymal stem cells in favor of myeloid progenitors and increased bone marrow adiposity. These obesity-induced changes in the bone marrow microenvironment lead to dramatic bone marrow remodeling and compromising immune cell functions, which in turn affect systemic inflammatory conditions and regulation of whole-body metabolism. However, there is limited information on the inflammatory secretory factors creating the bone marrow microenvironment and how these factors changed during metabolic complications. This review summarizes recent findings on inflammatory and cellular changes in the bone marrow in relation to obesity and further discuss whether dietary intervention or physical activity may have beneficial effects on the bone marrow microenvironment and whole-body metabolism.

Effects of Obesity and Exercise on Bone Marrow Progenitor Cells after Radiation

INTRODUCTION

The late effects of radiation therapy can have significant consequences for the health and quality of life of long-term cancer survivors. Radiation induces persistent alterations in hematopoietic stem and progenitor cells (HSPC) and the bone marrow environment; however, how relevant host factors such as obesity and exercise differentially regulate HSPC content and the bone marrow environment after radiation exposure remains unknown. The purpose of this investigation was to evaluate how the combination of obesity and exercise training modulates HSPC and their niche after sublethal radiation exposure in mice.

METHODS

Mice fed either a control or a high-fat diet to induce obesity remained sedentary or underwent a progressive treadmill exercise program. At 13 wk of age, mice were irradiated (3 Gy) and continued their specific diets and exercise program for four more weeks.

RESULTS

Exercise-trained mice had significantly higher quantities of several HSPC subpopulations and bone marrow stromal cell populations, whereas HSPC subpopulations were significantly lower in obese mice after radiation. Reactive oxygen species content was significantly decreased in HSPC with exercise training. Proteomics analysis of bone marrow supernatant revealed clustering of biologically relevant changes in exercise-trained mice. Functional evaluation of bone marrow supernatant revealed a significant increase in leukemia blast viability in obese mice but not in the exercise-trained mice (P < 0.05).

CONCLUSION

Together, these data suggest that exercise training partially restores the negative effects of obesity on HSPC and their niche after radiation exposure. As such, exercise training should be considered to mitigate the late effects of radiation therapy on the hematopoietic system for cancer survivors with or without obesity who have undergone radiation therapy.

Exercise reduces inflammatory cell production and cardiovascular inflammation via instruction of hematopoietic progenitor cells

A sedentary lifestyle, chronic inflammation and leukocytosis increase atherosclerosis; however, it remains unclear whether regular physical activity influences leukocyte production. Here we show that voluntary running decreases hematopoietic activity in mice. Exercise protects mice and humans with atherosclerosis from chronic leukocytosis but does not compromise emergency hematopoiesis in mice. Mechanistically, exercise diminishes leptin production in adipose tissue, augmenting quiescence-promoting hematopoietic niche factors in leptin-receptor-positive stromal bone marrow cells. Induced deletion of the leptin receptor in Prrx1-creER^T2; Lepr^fl/fl mice reveals that leptin's effect on bone marrow niche cells regulates hematopoietic stem and progenitor cell (HSPC) proliferation and leukocyte production, as well as cardiovascular inflammation and outcomes. Whereas running wheel withdrawal quickly reverses leptin levels, the impact of exercise on leukocyte production and on the HSPC epigenome and transcriptome persists for several weeks. Together, these data show that physical activity alters HSPCs via modulation of their niche, reducing hematopoietic output of inflammatory leukocytes.

Correlations of C-Reactive Protein and Folate with Smoking, Sport, Hematological Inflammation Biomarkers and Anthropometrics in Syrian University Female Students Cross-Sectional Study

In Syria, high-Sensitive C-Reactive (hsCRP), folate, and, other health risk data in young women are limited. This cross-sectional study evaluates hsCRP and folate levels along with anthropometric characteristics, lifestyle factors and some biomarkers linked to cardiovascular disease (CVD) risk factors in healthy female students (n = 207, 18-25 years old). Among participants, hsCRP level was at average or high risk of CVD in 20.7% and 2.5% respectively and it was significantly higher in participants who had high body mass index (BMI) (Nonparametric statistical tests, p value < 0.05). Unexpectedly, it did not vary significantly between smokers and nonsmokers. And, it correlated positively with anthropometric and erythrocyte sedimentation rate (ESR) measurements. While folate level was low in 3.4% of participants, no association between hsCRP and folate levels was found. Finally, low hemoglobin level and habit of waterpipe smoking are spreading; and, sport practicing is shrinking. After reviewing similar works, this study suggests that the possible correlation between hsCRP and folate could be displayed in patients older than 30 years. Also, the marked decrease in hemoglobin level needs more attention. Finally, young females in Syria are advised to consider a lifestyle free of smoking and packed with physical activity.

Use of adult mesenchymal stromal cells in tissue repair: impact of physical exercise

Physical exercise (PE) has unquestionable beneficial effects on health, which likely extend into several organ-to-cell physiological processes. At the cell scale, endogenous mesenchymal stromal cells (MSCs) contribute to tissue repair, although their repair capacities may be insufficient in paucicellular or severely damaged tissues. For this reason, MSC transplantation holds great promise for tissue repair. With the goals of understanding if PE has beneficial effects on MSC biology and if PE potentiates their role in tissue repair, we reviewed literature reports regarding the effects of PE on MSC properties (specifically, proliferation, differentiation, and homing) and of a combination of PE and MSC transplantation on tissue repair (specifically neural, cartilage, and muscular tissues). Contradictory results have been reported; interpretation is complicated because various and different species, cell sources, and experimental protocols, specifically exercise programs, have been used. On the basis of these data, the effects of exercise on MSC proliferation and differentiation depend on exercise characteristics (type, intensity, duration, etc.) and on the characteristics of the tissue from which the MSCs were collected. For the in vitro studies, the level of strain (and other details of the mechanical stimulus), the time elapsed between the end of exposure to strain and MSC collection, the age of the donors, as well as the passage number at which the MSCs are evaluated also play a role. The combination of PE and MSC engraftment improves neural, cartilage, and muscular tissue recovery, but it is not clear whether the effects of MSCs and exercise are additive or synergistic.

Supplementary Nitric Oxide Donors and Exercise as Potential Means to Improve Vascular Health in People with Type 1 Diabetes: Yes to NO?

Type 1 diabetes (T1D) is associated with a greater occurrence of cardiovascular pathologies. Vascular dysfunction has been shown at the level of the endothelial layers and failure to maintain a continuous pool of circulating nitric oxide (NO) has been implicated in the progression of poor vascular health. Biochemically, NO can be produced via two distinct yet inter-related pathways that involve an upregulation in the enzymatic activity of nitric oxide synthase (NOS). These pathways can be split into an endogenous oxygen-dependent pathway i.e., the catabolism of the amino acid L-arginine to L-citrulline concurrently yielding NO in the process, and an exogenous oxygen-independent one i.e., the conversion of exogenous inorganic nitrate to nitrite and subsequently NO in a stepwise fashion. Although a body of research has explored the vascular responses to exercise and/or compounds known to stimulate NOS and subsequently NO production, there is little research applying these findings to individuals with T1D, for whom preventative strategies that alleviate or at least temper vascular pathologies are critical foci for long-term risk mitigation. This review addresses the proposed mechanisms responsible for vascular dysfunction, before exploring the potential mechanisms by which exercise, and two supplementary NO donors may provide vascular benefits in T1D.

Effects of obesity and exercise on colon cancer induction and hematopoiesis in mice

Obesity-induced inflammation is associated with increased risk for colorectal cancer (CRC). The role of diet and exercise in modulating increased CRC risk in obesity and the potential role of altered hematopoiesis as a contributor to these effects remain unknown. The purpose of this study was to examine how weight loss induced during CRC induction with or without exercise alters CRC initiation and its relationship to altered hematopoiesis. Mice consumed either a control (CON) or a high-fat diet to induce obesity. All mice were then placed on the control diet during CRC induction with azoxymethane (AOM). Following AOM injection, mice originally on the high-fat diet were randomized into sedentary (HF-SED) or exercise trained (HF-EX) conditions. At euthanasia, body weight and fat mass were similar among all three groups ( P < 0.05). Compared with CON and HF-EX, HF-SED developed increased content of preneoplastic lesions ( P < 0.05), and HF-SED had significantly increased markers of colon inflammation compared with CON. Compared with both CON and HF-EX, HF-SED had decreased content of short-term hematopoietic stem cells and increased content of common myeloid progenitor cells (both P < 0.05). Similarly, HF-SED had increased bone marrow adiposity compared with CON and HF-EX ( P < 0.05), and proteomics analysis revealed an increased marker of bone marrow inflammation in HF-SED compared with CON and HF-EX. Our results suggest that the early removal of a high-fat diet reduces CRC incidence when combined with an exercise training intervention. This reduction in risk was related to lower colon inflammation with anti-inflammatory changes in hematopoiesis induced by exercise.

Exercise-Mobilized Platelet-Rich Plasma: Short-Term Exercise Increases Stem Cell and Platelet Concentrations in Platelet-Rich Plasma

PURPOSE

To evaluate the effects of vigorous short-term exercise on the platelet and other cellular components of 2 point-of-care blood-processing devices: a buffy coat-based platelet-rich plasma (PRP) product and a plasma-based PRP product.

METHODS

Twenty healthy subjects (aged 21-45 years) participated in a 20-minute vigorous exercise regimen on an upright stationary bike at 70% to 85% of maximum target heart rate. Pre- and post-exercise blood was processed in either a plasma-based or automated buffy coat-based PRP system. Complete blood counts were used to compare the cellular components in whole blood and the PRP products.

RESULTS

Exercise significantly increased the concentrations of platelets by over 20% in whole blood (P < .001) and in both PRP products (P = .002 and P = .018). Both devices performed consistently with pre- and post-exercise blood. Buffy coat-based PRP prepared after exercise was also significantly larger in volume and had a significantly higher concentration of mobilized hematopoietic stem cells (hematopoietic progenitor cells [HPCs], from 1.7/μL to 2.7/μL, P = .043). The concentrations of all white blood cell types were increased, which could be differentially collected in the devices studied.

CONCLUSIONS

Exercise can be used to consistently alter the composition of PRP. Twenty minutes of vigorous exercise can increase platelet concentrations in plasma-based and buffy coat-based PRP products and can increase HPC concentrations and volume in buffy coat-based PRP.

CLINICAL RELEVANCE

This study shows a nonpharmacologic method to increase platelet and HPC harvests from peripheral blood. This is important because it highlights a method for altering biological therapies with limited comorbidity.

Effects of 10 weeks of regular running exercise with and without parallel PDTC treatment on expression of genes encoding sarcomere-associated proteins in murine skeletal muscle

Physical exercise can induce various adaptation reactions in skeletal muscle tissue, such as sarcomere remodeling. The latter involves degradation of damaged sarcomere components, as well as de novo protein synthesis and sarcomere assembly. These processes are controlled by specific protease systems in parallel with molecular chaperones that assist in folding of newly synthesized polypeptide chains and their incorporation into sarcomeres. Since acute exercise induces oxidative stress and inflammation, leading to activation of the transcription factor NFκB (nuclear factor kappa B), we speculated that this transcription factor might also play a role in the regulation of long-term adaptation to regular exercise. Thus, we studied skeletal muscle adaptation to running exercise in a murine model system, with and without parallel treatment with the NFκB-inhibitory, anti-oxidant and anti-inflammatory drug pyrrolidine dithiocarbamate (PDTC). In control mice, 10 weeks of uphill (15° incline) treadmill running for 60 min thrice a week at a final speed of 14 m/min had differential, but only minor effects on many genes encoding molecular chaperones for sarcomere proteins, and/or factors involved in the degradation of the latter. Furthermore, there were marked differences between individual muscles. PDTC treatment modulated gene expression patterns as well, both in sedentary and exercising mice; however, most of these effects were also modest and there was little effect of PDTC treatment on exercise-induced changes in gene expression. Taken together, our data suggest that moderate-intensity treadmill running, with or without parallel PDTC treatment, had little effect on the expression of genes encoding sarcomere components and sarcomere-associated factors in murine skeletal muscle tissue.

Effects of endurance exercise training on inflammatory circulating progenitor cell content in lean and obese adults

KEY POINTS

Chronic inflammation underlies many of the health decrements associated with obesity. Circulating progenitor cells can sense and respond to inflammatory stimuli, increasing the local inflammatory response within tissues. Here we show that 6 weeks of endurance exercise training significantly decreases inflammatory circulating progenitor cells in obese adults. These findings provide novel cellular mechanisms for the beneficial effects of exercise in obese adults.

ABSTRACT

Circulating progenitor cells (CPCs) and subpopulations are normally found in the bone marrow, but can migrate to peripheral tissues to participate in local inflammation and/or remodelling. The purpose of this study was to compare the CPC response, particularly the inflammatory-primed haematopoietic stem and progenitor (HSPC) subpopulation, to a 6 week endurance exercise training (EET) intervention between lean and obese adults. Seventeen healthy weight (age: 23.9 ± 5.4 years, body mass index (BMI): 22.0 ± 2.6 kg m^-2 ) and 10 obese (age: 29.0 ± 8.0 years, BMI: 33.1 ± 6.0 kg m^-2 ) previously sedentary adults participated in an EET. Blood was collected before and after EET for quantification of CPCs and subpopulations via flow cytometry, colony forming unit assays and plasma concentrations of C-X-C motif chemokine 12 (CXCL12), granulocyte-colony stimulating factor (G-CSF), and chemokine (C-C motif) ligand 2 (CCL2). Exercise training reduced the number of circulating HSPCs and adipose tissue-derived mesenchymal stem cells (AT-MSCs). EET increased the colony forming potential of granulocytes and macrophages irrespective of BMI. EET reduced the number of HSPCs expressing the chemokine receptor CCR2 and the pro-inflammatory marker TLR4. EET-induced changes in adipose tissue-derived MSCs and bone marrow-derived MSCs were negatively related to changes in absolute fitness. Our results indicate that EET, regardless of BMI status, decreases CPCs and subpopulations, particularly those primed for contribution to tissue inflammation.

Exercise training differentially alters axial and appendicular marrow cellularity in old mice

Aging gradually renders bone marrow hematopoietically inactive. Endurance exercise reverses this phenotype in young mice. Here, we determine the effects in aged mice. Twenty-two month old mice (n = 6) underwent a progressive exercise training protocol. In appendicular bones, marrow cellularity increased by 51% (p < 0.05) and marrow CFU, CFU-GM, and CAFC increased by 12%, 71%, and 86%, respectively (p < 0.05). Vertebral cellularity remained unchanged. The mechanical forces associated with treadmill exercise training may be responsible for these observations.

Marrow Adiposity and Hematopoiesis in Aging and Obesity: Exercise as an Intervention

PURPOSE OF REVIEW

Changes in the bone marrow microenvironment, which accompany aging and obesity, including increased marrow adiposity, can compromise hematopoiesis. Here, we review deleterious shifts in molecular, cellular, and tissue activity and consider the potential of exercise to slow degenerative changes associated with aging and obesity.

RECENT FINDINGS

While bone marrow hematopoietic stem cells (HSC) are increased in frequency and myeloid-biased with age, the effect of obesity on HSC proliferation and differentiation remains controversial. HSC from both aged and obese environment have reduced hematopoietic reconstitution capacity following bone marrow transplant. Increased marrow adiposity affects HSC function, causing upregulation of myelopoiesis and downregulation of lymphopoiesis. Exercise, in contrast, can reduce marrow adiposity and restore hematopoiesis. The impact of marrow adiposity on hematopoiesis is determined mainly through correlations. Mechanistic studies are needed to determine a causative relationship between marrow adiposity and declines in hematopoiesis, which could aid in developing treatments for conditions that arise from disruptions in the marrow microenvironment.

Exercise-dependent regulation of the tumour microenvironment

The integrity and composition of the tumour microenvironment (TME) is highly plastic, undergoing constant remodelling in response to instructive signals derived from alterations in the availability and nature of systemic host factors. This 'systemic milieu' is directly modulated by host exposure to modifiable lifestyle factors such as exercise. Host exposure to regular exercise markedly reduces the risk of the primary development of several cancers and might improve clinical outcomes following a diagnosis of a primary disease. However, the molecular mechanisms that underpin the apparent antitumour effects of exercise are poorly understood. In this Opinion article, we explore the putative effects of exercise in reprogramming the interaction between the host and the TME. Specifically, we speculate on the possible effects of exercise on reprogramming 'distant' tissue microenvironments (those not directly involved in the exercise response) by analysing how alterations in the systemic milieu might modulate key TME components to influence cancer hallmarks.

Kinetics of circulating progenitor cell mobilization during submaximal exercise

Circulating progenitor cells (CPCs) are a heterogeneous population of stem/progenitor cells in peripheral blood that includes hematopoietic stem and progenitor cells (HSPCs and HSCs), endothelial progenitor cells (EPCs), and mesenchymal stem cells (MSCs) that are involved in tissue repair and adaptation. CPC mobilization during exercise remains uncharacterized in young adults. The purpose of this study was to investigate the kinetics of CPC mobilization during and after submaximal treadmill running and their relationship to mobilization factors. Seven men [age = 25.3 ± 2.4 yr, body mass index = 23.5 ± 1.0 kg/m2, peak O2uptake (V̇o2peak) = 60.9 ± 2.74 ml·kg−1·min−1] ran on a treadmill for 60 min at 70% V̇o2peak. Blood sampling occurred before (Pre), during [20 min (20e), 40 min (40e), 60 min (60e)], and after exercise [15 min (15p), 60 min (60p), 120 min (120p)] for quantification of CPCs (CD34+), HSPCs (CD34+/CD45low), HSCs (CD34+/CD45low/CD38−), CD34+MSCs (CD45−/CD34+/CD31−/CD105+), CD34−MSCs (CD45−/CD34−/CD31−/CD105+), and EPCs (CD45−/CD34+/CD31+) via flow cytometry. CPC concentration increased compared with Pre at 20e and 40e (2.7- and 2.4-fold, respectively, P < 0.05). HSPCs and HSCs increased at 20e compared with 60p (2.7- and 2.8-fold, respectively, P < 0.05), whereas EPCs and both MSC populations did not change. CXC chemokine ligand (CXCL) 12 (1.5-fold; P < 0.05) and stem cell factor (1.3-fold; P < 0.05) were increased at 40e and remained elevated postexercise. The peak increase in CPCs was positively correlated to concentration of endothelial cells during exercise with no relationship to CXCL12 and SCF. Our data show the kinetics of progenitor cell mobilization during exercise that could provide insight into cellular mediators of exercise-induced adaptations, and have implication for the use of exercise as an adjuvant therapy for CPC collection in hematopoietic stem cell transplant.

NEW & NOTEWORTHY Using a comprehensive evaluation of circulating progenitor cells (CPCs), we show that CPC mobilization during exercise is related to tissue damage, and not plasma concentrations of CXC chemokine ligand 12 and stem cell factor. These data have implications for the use of exercise interventions as adjuvant therapy for CPC mobilization in the context of hematopoietic stem cell transplant and also support the role of mobilized progenitor cells as cellular mediators of systemic adaptations to exercise.

Aerobic exercise in humans mobilizes HSCs in an intensity-dependent manner

Hematopoietic stem and progenitor cells are necessary to maintain, repair, and reconstitute the hematopoietic blood cell system. Mobilization of these cells from bone marrow to blood can be greatly increased under certain conditions, one such being exercise. The purpose of this study was to identify the importance of exercise intensity in hematopoietic mobilization, to better understand the mobilization kinetics postexercise, and to determine if exercise is capable of mobilizing several specific populations of hematopoietic cells that have clinical relevance in a transplant setting. Healthy individuals were exercised on a cycle ergometer at 70% of their peak work rate (WRpeak) until volitional fatigue and at 30% of their WRpeak work matched to the 70% WRpeak bout. Blood was collected before, immediately post, and 10, 30, and 60 min postexercise. Total blood cells, hematocrit, and mononuclear cells isolated by density gradient centrifugation were counted. Specific populations of hematopoietic stem cells were analyzed by flow cytometry. Mononuclear cells, CD34+, CD34+/CD38-, CD34+/CD110+, CD3-/CD16+/CD56+, CD11c+/CD123-, and CD11c-/CD123+ cells per millilter of blood increased postexercise. Overall, the 70% WRpeak exercise group showed greater mobilization immediately postexercise, while there was no observable increase in mobilization in the work matched 30% WRpeak exercise group. Mobilization of specific populations of hematopoietic cells mirrored changes in the general mobilization of mononuclear cells, suggesting that exercise serves as a nonspecific mobilization stimulus. Evidently, higher intensity exercise is capable of mobilizing hematopoietic cells to a large extent and immediately postexercise is an ideal time point for their collection.

NEW & NOTEWORTHY

Here we demonstrate for the first time that mobilization of hematopoietic stem cells (HSCs) through exercise is intensity dependent, with the greatest mobilization occurring immediately after high-intensity exercise. As well, we show that exercise is a general stimulus for mobilization: increases in specific HSC populations are reliant on general mononuclear cell mobilization. Finally, we demonstrate no differences in mobilization between groups with different aerobic fitness.

Pretransplantation Exercise and Hematopoietic Cell Transplantation Survival: A Secondary Analysis of Blood and Marrow Transplant Clinical Trials Network (BMT CTN 0902)

Blood and Marrow Transplant Clinical Trials Network (BMT CTN) protocol 0902 evaluated whether exercise and stress management training before hematopoietic cell transplantation (HCT) improved physical and mental functioning after HCT. Neither overall survival nor other patient-reported transplantation outcomes were improved by the training intervention. In some animal studies of HCT, moderate-intensity exercise for 8 weeks before HCT has been associated with positive effects on hematopoietic progenitors, resulting in improved donor engraftment and improved survival. Accordingly, we performed a secondary analysis of data from BMT CTN 0902 to determine whether exercise engagement before HCT was associated with engraftment and survival. We found no significant associations between self-reported pre-HCT exercise levels and engraftment or survival. There was also no effect of pretransplantation exercise on either neutrophil or platelet engraftment. These findings do not support the observations in animal models but are limited by several shortcomings that do not refute the hypothesis that exercise before HCT may be beneficial.

A potential role for genome structure in the translation of mechanical force during immune cell development

Immune cells react to a wide range of environments, both chemical and physical. While the former has been extensively studied, there is growing evidence that physical and in particular mechanical forces also affect immune cell behavior and development. In order to elicit a response that affects immune cell behavior or development, environmental signals must often reach the nucleus. Chemical and mechanical signals can initiate signal transduction pathways, but mechanical forces may also have a more direct route to the nucleus, altering nuclear shape via mechanotransduction. The three-dimensional organization of DNA allows for the possibility that altering nuclear shape directly remodels chromatin, redistributing critical regulatory elements and proteins, and resulting in wide-scale gene expression changes. As such, integrating mechanotransduction and genome architecture into the immunology toolkit will improve our understanding of immune development and disease.

Exercise as an Adjuvant Therapy for Hematopoietic Stem Cell Mobilization

Hematopoietic stem cell transplant (HSCT) using mobilized peripheral blood hematopoietic stem cells (HSPCs) is the only curative strategy for many patients suffering from hematological malignancies. HSPC collection protocols rely on pharmacological agents to mobilize HSPCs to peripheral blood. Limitations including variable donor responses and long dosing protocols merit further investigations into adjuvant therapies to enhance the efficiency of HSPCs collection. Exercise, a safe and feasible intervention in patients undergoing HSCT, has been previously shown to robustly stimulate HSPC mobilization from the bone marrow. Exercise-induced HSPC mobilization is transient limiting its current clinical potential. Thus, a deeper investigation of the mechanisms responsible for exercise-induced HSPC mobilization and the factors responsible for removal of HSPCs from circulation following exercise is warranted. The present review will describe current research on exercise and HSPC mobilization, outline the potential mechanisms responsible for exercise-induced HSPC mobilization, and highlight potential sites for HSPC homing following exercise. We also outline current barriers to the implementation of exercise as an adjuvant therapy for HSPC mobilization and suggest potential strategies to overcome these barriers.

Acute exercise mobilizes hematopoietic stem and progenitor cells and alters the mesenchymal stromal cell secretome

Transplantation of hematopoietic stem and progenitor cells (HSPC), collected from peripheral blood, is the primary treatment for many hematological malignancies; however, variable collection efficacy with current protocols merits further examination into factors responsible for HSPC mobilization. HSPCs primarily reside within the bone marrow and are regulated by mesenchymal stromal cells (MSC). Exercise potently and transiently mobilizes HSPCs from the bone marrow into peripheral circulation. Thus the purpose of the present study was to evaluate potential factors in the bone marrow responsible for HSPC mobilization, investigate potential sites of HSPC homing, and assess changes in bone marrow cell populations following exercise. An acute exercise bout increased circulating HSPCs at 15 min (88%, P < 0.001) that returned to baseline at 60 min. Gene expression for HSPC homing factors (CXCL12, vascular endothelial growth factor-a, and angiopoietin-1) were increased at 15 min in skeletal muscle and HSPC content was increased in the spleen 48 h postexercise (45%, P < 0.01). Acute exercise did not alter HSPCs or MSCs quantity in the bone marrow; however, proliferation of HSPCs (40%, P < 0.001), multipotent progenitors (40%, P < 0.001), short-term hematopoietic stem cells (61%, P < 0.001), long-term hematopoietic stem cells (55%, P = 0.002), and MSCs (20%, P = 0.01) increased postexercise. Acute exercise increased the content of the mobilization agent granulocyte-colony stimulating factor, as well as stem cell factor, interleukin-3, and thrombopoeitin in conditioned media collected from bone marrow stromal cells 15 min postexercise. These findings suggest that the MSC secretome is responsible for HSPC mobilization and proliferation; concurrently, HSPCs are homing to extramedullary sites following exercise.

Endurance Exercise Mobilizes Developmentally Early Stem Cells into Peripheral Blood and Increases Their Number in Bone Marrow: Implications for Tissue Regeneration

Endurance exercise has been reported to increase the number of circulating hematopoietic stem/progenitor cells (HSPCs) in peripheral blood (PB) as well as in bone marrow (BM). We therefore became interested in whether endurance exercise has the same effect on very small embryonic-like stem cells (VSELs), which have been described as a population of developmentally early stem cells residing in BM. Mice were run daily for 1 hour on a treadmill for periods of 5 days or 5 weeks. Human volunteers had trained in long-distance running for one year, six times per week. FACS-based analyses and RT-PCR of murine and human VSELs and HSPCs from collected bone marrow and peripheral blood were performed. We observed that endurance exercise increased the number of VSELs circulating in PB and residing in BM. In parallel, we observed an increase in the number of HSPCs. These observations were subsequently confirmed in young athletes, who showed an increase in circulating VSELs and HSPCs after intensive running exercise. We provide for the first time evidence that endurance exercise may have beneficial effects on the expansion of developmentally early stem cells. We hypothesize that these circulating stem cells are involved in repairing minor exercise-related tissue and organ injuries.

Exercise and Stem Cells

Stem cells are traditionally studied in the context of embryonic development, yet studies confirm that a fraction remains in the adult organism for the purpose of daily remodeling and rejuvenation of multiple tissues following injury. Adult stem cells (ASCs) are found in close proximity to vessels and respond to tissue-specific cues in the microenvironment that dictate their fate and function. Exercise can dramatically alter strain sensing, extracellular matrix composition, and inflammation, and such changes in the niche likely alter ASC quantity and function postexercise. The field of stem cell biology is still in its infancy and identification and terminology of ASCs continues to evolve; thus, current information regarding exercise and stem cells is lacking. This chapter summarizes the literature that reports on the ASC response to acute exercise and exercise training, with particular emphasis on hematopoietic stem cells, endothelial progenitor cells, and mesenchymal stem cells.

Effects of physical exercise on survival after allogeneic stem cell transplantation

Observational studies have suggested that physical activity may be associated with improved survival after cancer treatment. However, data from controlled clinical trials are required. We analyzed survival data of 103 patients from a previously published randomized controlled trial in allogeneic stem cell transplant patients who were randomized to either an exercise intervention (EX) or to a social contact control group. EX patients trained prior to hospital admission, during inpatient treatment, and for 6-8 weeks after discharge. Survival analyses were used to compare both total mortality (TM) and non-relapse mortality (NRM) after discharge and transplantation during an observation period of 2 years after transplantation. Analyses were corroborated with Cox and Fine & Gray regression models adjusting for potential confounders. After discharge, EX patients had a significantly lower TM rate than controls (12.0 vs. 28.3%, p = 0.030) and a numerically lower NRM rate (4.0 vs. 13.5%, p = 0.086). When the inpatient period was included, absolute risk reductions were similar but not significantly different (TM: 34.0 vs. 50.9%, p = 0.112; NRM: 26.0 vs. 36.5%, p = 0.293). The number needed to treat (NNT) to prevent one death with EX was about 6. Furthermore, regression analyses revealed that baseline fitness was protective against mortality. The data suggest that exercise might improve survival in patients undergoing allo-HCT. However, the results should be interpreted with caution as the study was not designed to detect differences in survival rates, and as no stratification on relevant prognostic factors was carried out.

Physical Activity Increases the Total Number of Bone-Marrow-Derived Mesenchymal Stem Cells, Enhances Their Osteogenic Potential, and Inhibits Their Adipogenic Properties

Aging and sedentary lifestyle are common nowadays and are associated with the increasing number of chronic diseases. Thus, physical activity is recommended as one of three healthy behavior factors that play a crucial role in health prophylaxis. In the present study, we were interested whether physical activity influences the number and potential of bone-marrow-derived mesenchymal stem cells BMMSCs. In this study, four-week-old male C57Bl/6 mice were trained on a treadmill at progressive speeds over a 5-week period. Comparisons made between exercised (EX) and sedentary animal groups revealed (i) significantly higher number of MSCs in EX animals, (ii) elevated alkaline phosphatase (ALP) activity, (iii) increased level of osteopontin (OPN) and osteocalcin (OCL), and (iv) reduced marrow cavity fat. The results obtained support the thesis that EX may play a substantial role in the regeneration of mesenchymal tissues. Therefore, EX may represent a novel, nonpharmacological strategy of slowing down age-related decline of the musculoskeletal functions.

Apoptotic lymphocytes induce progenitor cell mobilization after exercise

There is evidence that apoptotic cells and their components have immunmodulatory properties and signaling function. The present study investigated first whether exercise-induced apoptosis and exercise-induced mobilization of progenitor cells are similarly affected by subjects' training status and, second, whether the appearance of dying cells in the circulation might mobilize progenitor cells. CD1 SWISS mice were subjected to a 10-wk endurance training using free wheel running or served as untrained controls. Mice of both groups performed an intensive exercise test after the training period at a velocity corresponding to 80% maximal oxygen uptake for 30 min. Cells from blood and bone marrow were analyzed, and apoptosis and number of progenitor cells determined via flow cytometry. In a second experiment, apoptotic cells were transferred into recipient mice, and mobilization of progenitor cells was analyzed while vital cells served as controls. In untrained animals, the exhaustive exercise was followed by an enhanced rate of annexin V positive CD3(+) cells in blood and bone marrow (P < 0.05), whereas no increase was found in trained mice. Similarly, exercise mobilized Sca-1(+)/c-kit(+) and Sca-1(+)/Flk(+) cells in untrained (P < 0.05) but not trained mice. Furthermore, application of apoptotic cells and their supernatant mobilized Sca-1(+)/c-kit(+) cells into the blood (P < 0.05), whereas Sca-1(+)/Flk(+) cells were not affected. The present study demonstrated that both lymphocyte apoptosis, as well as mobilization of progenitor cells are similarly related to training status. Furthermore, apoptotic cells seem to induce signals that effectively mobilize hematopoietic progenitor cells. The relevance of this effect for the adaptation to exercise stimuli remains to be shown.

Aging and brain rejuvenation as systemic events

The effects of aging were traditionally thought to be immutable, particularly evident in the loss of plasticity and cognitive abilities occurring in the aged central nervous system (CNS). However, it is becoming increasingly apparent that extrinsic systemic manipulations such as exercise, caloric restriction, and changing blood composition by heterochronic parabiosis or young plasma administration can partially counteract this age-related loss of plasticity in the aged brain. In this review, we discuss the process of aging and rejuvenation as systemic events. We summarize genetic studies that demonstrate a surprising level of malleability in organismal lifespan, and highlight the potential for systemic manipulations to functionally reverse the effects of aging in the CNS. Based on mounting evidence, we propose that rejuvenating effects of systemic manipulations are mediated, in part, by blood-borne ‘pro-youthful’ factors. Thus, systemic manipulations promoting a younger blood composition provide effective strategies to rejuvenate the aged brain. As a consequence, we can now consider reactivating latent plasticity dormant in the aged CNS as a means to rejuvenate regenerative, synaptic, and cognitive functions late in life, with potential implications even for extending lifespan.

Exercise-induced norepinephrine decreases circulating hematopoietic stem and progenitor cell colony-forming capacity

A recent study showed that ergometry increased circulating hematopoietic stem and progenitor cell (CPC) numbers, but reduced hematopoietic colony forming capacity/functionality under normoxia and normobaric hypoxia. Herein we investigated whether an exercise-induced elevated plasma free/bound norepinephrine (NE) concentration could be responsible for directly influencing CPC functionality. Venous blood was taken from ten healthy male subjects (25.3+/-4.4 yrs) before and 4 times after ergometry under normoxia and normobaric hypoxia (FiO2<0.15). The circulating hematopoietic stem and progenitor cell numbers were correlated with free/bound NE, free/bound epinephrine (EPI), cortisol (Co) and interleukin-6 (IL-6). Additionally, the influence of exercise-induced NE and blood lactate (La) on CPC functionality was analyzed in a randomly selected group of subjects (n = 6) in vitro under normoxia by secondary colony-forming unit granulocyte macrophage assays. Concentrations of free NE, EPI, Co and IL-6 were significantly increased post-exercise under normoxia/hypoxia. Ergometry-induced free NE concentrations found in vivo showed a significant impairment of CPC functionality in vitro under normoxia. Thus, ergometry-induced free NE was thought to trigger CPC mobilization 10 minutes post-exercise, but as previously shown impairs CPC proliferative capacity/functionality at the same time. The obtained results suggest that an ergometry-induced free NE concentration has a direct negative effect on CPC functionality. Cortisol may further influence CPC dynamics and functionality.

Bone and fat: a relationship of different shades

Environmental and behavioral changes which occurred over the last century led simultaneously to a remarkable increase in human lifespan and to the development of health problems associated with functional impairment of organs either regulating or dependent on balanced energy metabolism. Diseases such as diabetes, obesity and osteoporosis are prevalent in our society and pose major challenges with respect to the overall health and economy. Therefore, better understanding of regulatory axes between bone and fat may provide the basis for development of strategies which will treat these diseases simultaneously and improve health and life quality of elderly.

Exercise promotes bone marrow cell survival and recipient reconstitution post-bone marrow transplantation, which is associated with increased survival

Bone marrow transplantation (BMT) is associated with a high risk of mortality, partially because of the harmful effects of the preconditioning myeloablative regimens. We have recently demonstrated increased bone marrow cell survival and proliferation in response to exercise training, which may be attributable to increased quality of the niche. The purpose of the present study was to determine the extent to which exercise preconditioning of recipients could increase the success of BMT. Recipient mice remained sedentary (SED) or were exercise-trained (EX) on a treadmill (3 d/wk for 8 weeks) before reconstitution with green fluorescent protein (GFP)-labeled donor marrow. Recipient survival, both donor-derived and total (donor- and recipient-derived) blood reconstitution were measured by flow cytometry. The first and fourth day after BMT apoptosis, cellularity and donor cell homing were determined in the recipients' bone marrow cavity by flow cytometry. Whereas only 25% of SED mice survived, 82% of EX recipients survived the BMT. Homing of donor-derived marrow cells to the recipients' marrow cavity acutely after BMT was not altered in EX, but EX mice displayed decreased levels (10%; p < 0.05) of activated caspase-3/-7 one day after BMT, leading to a maintenance of marrow cellularity in mice preconditioned with exercise. The acute inhibition of marrow cell apoptosis in EX mice resulted in increased total blood cell reconstitution at 1 and 3.5 months after BMT in EX mice (42% and 43%, respectively; both p < 0.05). Short- and long-term donor-derived engraftment was not different between EX and SED recipients. Exercise training increases recipient survival after BMT with increased total blood cell reconstitution.

Characterization of the effects of exercise training on hematopoietic stem cell quantity and function

The effect of exercise training on hematopoietic stem cells (HSC) is largely unknown. The aim of the present investigation was to determine whether exercise training could expand the bone marrow HSC pool and influence various aspects of HSC function. Mice were either exercise trained (EX; 1 h/day, 3 days/wk, for 8 wk) or remained sedentary (SED). Bone marrow (BM) from SED or EX mice was extracted from different HSC niches for cell cycle analysis, HSC (lineage(-), Sca-1(+), c-Kit(+)) quantification, and differentiation along various hematopoietic lineages via flow cytometry. Serum was collected for evaluation of cytokines known to regulate HSC. To determine HSC function, BM from EX and SED mice was transplanted into primary and secondary recipients in a BM transplant assay. EX increased HSC quantity in the vascular BM niche 20% vs. SED (P < 0.05) and increased the proportion of whole BM cells in G(2)/M phase of cell cycle (P < 0.05). The number of spleen colonies was 48% greater (P < 0.05) in recipients transplanted with BM from EX. Serum IL-6 levels were decreased 38% in EX, and differentiation along the lineage trended to increase (16%, P = 0.053 and 16%, P = 0.061, respectively). Short- or long-term engraftment and homing in primary recipients were not altered in EX. HSC self-renewal as analyzed by hematopoietic regeneration in secondary recipients was also unaffected by EX. Here we demonstrate that HSC quantity is increased in the BM niche associated with more activated, differentiated HSC, and that this expansion does not improve or impair HSC function.

Impaired transcriptional activity of Nrf2 in age-related myocardial oxidative stress is reversible by moderate exercise training

Aging promotes accumulation of reactive oxygen/nitrogen species (ROS/RNS) in cardiomyocytes, which leads to contractile dysfunction and cardiac abnormalities. These changes may contribute to increased cardiovascular disease in the elderly. Inducible antioxidant pathways are regulated by nuclear erythroid 2 p45-related factor 2 (Nrf2) through antioxidant response cis-elements (AREs) and are impaired in the aging heart. Whereas acute exercise stress (AES) activates Nrf2 signaling and promotes myocardial antioxidant function in young mice (∼2 months), aging mouse (>23 months) hearts exhibit significant oxidative stress as compared to those of the young. The purpose of this study was to investigate age-dependent regulation of Nrf2-antioxidant mechanisms and redox homeostasis in mouse hearts and the impact of exercise. Old mice were highly susceptible to oxidative stress following high endurance exercise stress (EES), but demonstrated increased adaptive redox homeostasis after moderate exercise training (MET; 10m/min, for 45 min/day) for ∼6 weeks. Following EES, transcription and protein levels for most of the ARE-antioxidants were increased in young mice but their induction was blunted in aging mice. In contrast, 6-weeks of chronic MET promoted nuclear levels of Nrf2 along with its target antioxidants in the aging heart to near normal levels as seen in young mice. These observations suggest that enhancing Nrf2 function and endogenous cytoprotective mechanisms by MET, may combat age-induced ROS/RNS and protect the myocardium from oxidative stress diseases.