Ultra-endurance exercise induces stress and inflammation and affects circulating hematopoietic progenitor cell function

Physical activity regulates the immune response to breast cancer by a hematopoietic stem cell-autonomous mechanism

Physical activity is a modifiable lifestyle factor that is associated with a decreased risk for the development of breast cancer. While the exact mechanisms for the reduction in cancer risk due to physical activity are largely unknown, it is postulated that the biological reduction in cancer risk is driven by improvements in inflammation and immune function with exercise. Hematopoietic stem cells (HSCs) are the progenitor for all of the cells of the immune system and are involved in cancer immunosurveillance through differentiation into cytotoxic cell population. In this study, we investigate the role of physical activity (PA) in a spontaneously occurring model of breast cancer over time, with a focus on tumor incidence, circulating and tumor-infiltrating immune cells as well gene expression profiles of tumors and hematopoietic stem cells. Furthermore, we show that, in addition to a direct effect of PA on the immune cells of tumor-bearing mice, PA reduces the oxidative stress in HSCs of wildtype and tumor-bearing mice, and by doing so, alters the differentiation of the HSCs towards T cells in order to enhance cancer immunosurveillance.

Does Physical Exercise Enhance the Immune Response after Vaccination? A Systematic Review for Clinical Indications of COVID-19 Vaccine

BACKGROUND

Stimulating protective immunity with vaccines appears to be the most promising option for providing widespread moderate to high protection against COVID-19 in people over the age of 18. Regular exercise improves the immune response, transmitting possible benefits against virus infections. The aim of this review is to study the effects of physical activity on vaccine injections, helping to develop new recommendations for COVID-19 vaccination campaigns.

METHODS

A comprehensive review of the existing literature was undertaken using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The internal quality of the studies was assessed according to the Physiotherapy Evidence Database (PEDro) scale. The outcomes analyzed were antibody titer, the level of lymphocytes CD4, CD8, InterLeukin 6 (IL6), leukocytes level, the visual analogue scale (VAS) for overall pain rating, arm and forearm circumferences and volume of oxygen (VO2) peak.

RESULTS

Fourteen articles were selected for the analysis. The majority of studies were randomized controlled trials (RCT) (n = 8) and controlled trials (CT) (n = 6). According to PEDro, the 'fair' category (n = 7) was the most represented, followed by 'good' (n = 6) and 'excellent' (n = 1). Physical training showed a positive effect on antibody titers of the vaccine; yet, different variables seem to influence antibody titers: higher new vs. old antigen in the vaccine, higher in younger vs. older individuals, and higher in females vs. males. After exercise, when analyzing variables of direct response to the vaccine, such as the amount of CD4, IL-6 and leukocytes, higher levels were observed in the patients who performed physical exercise compared to the control group. In the same way, better results were observed in physiological variables such as VO2 and limb circumferences, or subjective variables such as pain, which showed better results than the control group.

CONCLUSIONS

The immune response (antibody titers) depends on age, gender and the intensity of physical activity: long-term protocols at moderate intensity are the most recommended. All of these aspects also have to be carefully considered for the COVID-19 vaccination.

Pax7(+) Satellite Cells in Human Skeletal Muscle After Exercise: A Systematic Review and Meta-analysis

BACKGROUND

Skeletal muscle has extraordinary regenerative capabilities against challenge, mainly owing to its resident muscle stem cells, commonly identified by Pax7⁺, which expediently donate nuclei to the regenerating multinucleated myofibers. This local reserve of stem cells in damaged muscle tissues is replenished by undifferentiated bone marrow stem cells (CD34⁺) permeating into the surrounding vascular system.

OBJECTIVE

The purpose of the study was to provide a quantitative estimate for the changes in Pax7⁺ muscle stem cells (satellite cells) in humans following an acute bout of exercise until 96 h, in temporal relation to circulating CD34⁺ bone marrow stem cells. A subgroup analysis of age was also performed.

METHODS

Four databases (Web of Science, PubMed, Scopus, and BASE) were used for the literature search until February 2022. Pax7⁺ cells in human skeletal muscle were the primary outcome. Circulating CD34⁺ cells were the secondary outcome. The standardized mean difference (SMD) was calculated using a random-effects meta-analysis. Subgroup analyses were conducted to examine the influence of age, training status, type of exercise, and follow-up time after exercise.

RESULTS

The final search identified 20 studies for Pax7⁺ cells comprising a total of 370 participants between the average age of 21 and 74 years and 26 studies for circulating CD34⁺ bone marrow stem cells comprising 494 participants between the average age of 21 and 67 years. Only one study assessed Pax7⁺ cells immediately after aerobic exercise and showed a 32% reduction in exercising muscle followed by a fast repletion to pre-exercise level within 3 h. A large effect on increasing Pax7⁺ cell content in skeletal muscles was observed 24 h after resistance exercise (SMD = 0.89, p < 0.001). Pax7⁺ cells increased to ~ 50% above pre-exercise level 24-72 h after resistance exercise. For a subgroup analysis of age, a large effect (SMD = 0.81, p < 0.001) was observed on increasing Pax7⁺ cells in exercised muscle among adults aged > 50 years, whereas adults at younger age presented a medium effect (SMD = 0.64, p < 0.001). Both resistance exercise and aerobic exercise showed a medium overall effect in increasing circulating CD34⁺ cells (SMD = 0.53, p < 0.001), which declined quickly to the pre-exercise baseline level after exercise within 6 h.

CONCLUSIONS

An immediate depletion of Pax7⁺ cells in exercising skeletal muscle concurrent with a transient release of CD34⁺ cells suggest a replenishment of the local stem cell reserve from bone marrow. A protracted Pax7⁺ cell expansion in the muscle can be observed during 24-72 h after resistance exercise. This result provides a scientific basis for exercise recommendations on weekly cycles allowing for adequate recovery time. Exercise-induced Pax7⁺ cell expansion in muscle remains significant at higher age, despite a lower stem cell reserve after age 50 years. More studies are required to confirm whether Pax7⁺ cell increment can occur after aerobic exercise.

CLINICAL TRIAL REGISTRATION

Registered at the International Prospective Register of Systematic Reviews (PROSPERO) [identification code CRD42021265457].

Molecular mechanisms of exercise contributing to tissue regeneration

Physical activity has been known as an essential element to promote human health for centuries. Thus, exercise intervention is encouraged to battle against sedentary lifestyle. Recent rapid advances in molecular biotechnology have demonstrated that both endurance and resistance exercise training, two traditional types of exercise, trigger a series of physiological responses, unraveling the mechanisms of exercise regulating on the human body. Therefore, exercise has been expected as a candidate approach of alleviating a wide range of diseases, such as metabolic diseases, neurodegenerative disorders, tumors, and cardiovascular diseases. In particular, the capacity of exercise to promote tissue regeneration has attracted the attention of many researchers in recent decades. Since most adult human organs have a weak regenerative capacity, it is currently a key challenge in regenerative medicine to improve the efficiency of tissue regeneration. As research progresses, exercise-induced tissue regeneration seems to provide a novel approach for fighting against injury or senescence, establishing strong theoretical basis for more and more "exercise mimetics." These drugs are acting as the pharmaceutical alternatives of those individuals who cannot experience the benefits of exercise. Here, we comprehensively provide a description of the benefits of exercise on tissue regeneration in diverse organs, mainly focusing on musculoskeletal system, cardiovascular system, and nervous system. We also discuss the underlying molecular mechanisms associated with the regenerative effects of exercise and emerging therapeutic exercise mimetics for regeneration, as well as the associated opportunities and challenges. We aim to describe an integrated perspective on the current advances of distinct physiological mechanisms associated with exercise-induced tissue regeneration on various organs and facilitate the development of drugs that mimics the benefits of exercise.

Common Biochemical and Magnetic Resonance Imaging Biomarkers of Early Knee Osteoarthritis and of Exercise/Training in Athletes: A Narrative Review

Knee osteoarthritis (OA) is the most common joint disease of the world population. Although considered a disease of old age, OA also affects young individuals and, more specifically among them, those practicing knee-joint-loading sports. Predicting OA at an early stage is crucial but remains a challenge. Biomarkers that can predict early OA development will help in the design of specific therapeutic strategies for individuals and, for athletes, to avoid adverse outcomes due to exercising/training regimens. This review summarizes and compares the current knowledge of fluid and magnetic resonance imaging (MRI) biomarkers common to early knee OA and exercise/training in athletes. A variety of fluid biochemical markers have been proposed to detect knee OA at an early stage; however, few have shown similar behavior between the two studied groups. Moreover, in endurance athletes, they are often contingent on the sport involved. MRI has also demonstrated its ability for early detection of joint structural alterations in both groups. It is currently suggested that for optimal forecasting of early knee structural alterations, both fluid and MRI biomarkers should be analyzed as a panel and/or combined, rather than individually.

Changes in Circulating Stem and Progenitor Cell Numbers Following Acute Exercise in Healthy Human Subjects: a Systematic Review and Meta-analysis

Despite of the increasing number of investigations on the effects of acute exercise on circulating stem and progenitor cell (SC) numbers, and in particular on respective subgroups, i.e. endothelial (ESC), hematopoietic (HSC), and mesenchymal (MSC) stem and progenitor cells, a consensus regarding mechanisms and extent of these effects is still missing. The aim of this meta-analysis was to systematically evaluate the overall-effects of acute exercise on the different SC-subgroups and investigate possible subject- and intervention-dependent factors affecting the extent of SC-mobilization in healthy humans. Trials assessing SC numbers before and at least one timepoint after acute exercise, were identified in a systematic computerized search. Compared to baseline, numbers were significantly increased for early and non-specified SCs (enSCs) until up to 0.5 h after exercise (0–5 min: +0.64 [Standardized difference in means], p < 0.001; 6–20 min: +0.42, p < 0.001; 0.5 h: +0.29, p = 0.049), for ESCs until 12–48 h after exercise (0–5 min: +0.66, p < 0.001; 6–20 min: +0.43 p < 0.001; 0.5 h: +0.43, p = 0.002; 1 h: +0.58, p = 0.001; 2 h: +0.50, p = 0.002; 3–8 h: +0.70, p < 0.001; 12–48 h: +0.38, p = 0.003) and for HSCs at 0–5 min (+ 0.47, p < 0.001) and at 3 h after exercise (+ 0.68, p < 0.001). Sex, intensity and duration of the intervention had generally no influence. The extent and kinetics of the exercise-induced mobilization of SCs differ between SC-subpopulations. However, also definitions of SC-subpopulations are non-uniform. Therefore, finding a consensus with a clear definition of cell surface markers defining ESCs, HSCs and MSCs is a first prerequisite for understanding this important topic.

Acute Exercise-Induced Oxidative Stress Does Not Affect Immediate or Delayed Precursor Cell Mobilization in Healthy Young Males

Exercise is known to acutely and transiently mobilize precursor cells to the peripheral blood. To date, the underlying mechanisms have not yet been fully elucidated and we hypothesized that exercise-induced oxidative stress could be a mobilizing agent, either directly or via circulating apoptotic cells as mediators. The aim of the study was to assess the effect of acute exercise-induced oxidative stress on numbers of circulating angiogenic precursor cells (CACs), circulating non-angiogenic precursor cells (nCACs), mesenchymal precursor cells (MPCs), mature endothelial cells (ECs), and mononuclear cells (MNCs), as well as their apoptotic subsets. Healthy, young males (n = 18, age: 24.2 ± 3.5 years) completed two identical, standardized incremental cycling tests. The first, un-supplemented control test was followed by a 7-day-long supplementation of vitamin C (1,000 mg/day) and E (400 I.U./day), immediately preceding the second test. Blood samples were collected before, directly after, 30, 90, 180, and 270 min after exercise, and aforementioned circulating cell numbers were determined by flow cytometry and a hematology analyzer. Additionally, total oxidative capacity (TOC) and total antioxidative capacity (TAC) were measured in serum at all timepoints. Antioxidative supplementation abolished the exercise-induced increase in the oxidative stress index (TOC/TAC), and reduced baseline concentrations of TOC and TOC/TAC. However, it did not have any effect on CACs, nCACs, and MPC numbers or the increase in apoptotic MNCs following exercise. Our results indicate that exercise-induced oxidative stress is neither a main driver of lymphocyte and monocyte apoptosis, nor one of the mechanisms involved in the immediate or delayed mobilization of precursor cells.

Effects of Hyperbaric Oxygen Therapy on Inflammation, Oxidative/Antioxidant Balance, and Muscle Damage after Acute Exercise in Normobaric, Normoxic and Hypobaric, Hypoxic Environments: A Pilot Study

The purpose of this study was to investigate the effects of hyperbaric oxygen therapy (HBOT) on inflammation, the oxidative/antioxidant balance, and muscle damage after acute exercise in normobaric, normoxic (NN) and hypobaric, hypoxic (HH) environments. Eighteen healthy males were selected and randomly assigned to three groups: exercise in NN conditions (NN group, n = 6), HBOT treatment after exercise in NN conditions (HNN group, n = 6), and HBOT treatment after exercise in HH conditions (HHH group, n = 6). All subjects performed treadmill running for 60 min at 75–80% maximum heart rate (HRmax) exercise intensity under each condition. The HBOT treatments consisted of breathing 100% oxygen at 2.5 atmosphere absolute (ATA) for 60 min. Blood samples were collected before exercise (BE), after exercise (AE), and after HBOT (AH) to examine inflammation (fibrinogen, interleukin-6 [IL-6], and tumor necrosis factor-α (TNF-α)), the oxidative/antioxidant balance (derivatives of reactive oxygen metabolites (d-ROMs) and the biological antioxidant potential (BAP)), and muscle damage (creatine kinase (CK) and lactate dehydrogenase (LDH)). Plasma fibrinogen, serum IL-6, CK, and LDH levels were significantly increased AE compared to BE in all groups (p < 0.05). Plasma fibrinogen levels were significantly decreased AH compared to AE in all groups (p < 0.05), and the HNN group had a significantly lower AH compared to BE (p < 0.05). Serum IL-6 levels were significantly decreased AH compared to AE in the HNN and HHH groups (p < 0.05). Serum CK levels were significantly decreased AH compared to AE in the HHH group (p < 0.05). Serum LDH levels were significantly decreased AH compared to AE in the HNN and HHH groups (p < 0.05), and the NN and HNN groups had significantly higher AH serum LDH levels compared to BE (p < 0.05). These results suggest that acute exercise in both the NN and HH environments could induce temporary inflammatory responses and muscle damage, whereas HBOT treatment may be effective in alleviating exercise-induced inflammatory responses and muscle damage.

Inflammatory Effects of High and Moderate Intensity Exercise-A Systematic Review

Background: Exercise leads to a robust inflammatory response mainly characterized by the mobilization of leukocytes and an increase in circulating inflammatory mediators produced by immune cells and directly from the active muscle tissue. Both positive and negative effects on immune function and susceptibility to minor illness have been observed following different training protocols. While engaging in moderate activity may enhance immune function above sedentary levels, excessive amounts of prolonged, high-intensity exercise may impair immune function. Thus, the aim of the present review was to clarify the inflammatory effects in response to different exercise intensities. Methods: Search was performed on PubMed and was completed on July 31st, 2017. The studies were eligible if they met the predefined inclusion criteria: a) observational or interventional studies, b) conducted in healthy adults (18-65 years), c) written in Portuguese, English or Spanish, d) including moderate and/or intense exercise. Eighteen articles were included. The specific components that were examined included circulating blood levels of cytokines, leukocytes, creatine kinase (CK) and C-reactive protein (CRP). The methodological quality of the included studies was assessed. Results: Most of the intervention studies showed changes in the assessed biomarkers, although these changes were not consistent. White blood cells (WBC) had an increase immediately after intensive exercise (> 64% VO_2max), without alteration after moderate exercise (46-64% VO_2max). The results suggested an elevation of the pro-inflammatory cytokines, namely IL-6, followed by an elevation of IL-10 that were more evident after intense exercise bouts. CRP increased both after intense and moderate exercise, with peak increases up to 28 h. CK increased only after intensive and long exercising. Conclusion: In summary, intense long exercise can lead, in general, to higher levels of inflammatory mediators, and thus might increase the risk of injury and chronic inflammation. In contrast, moderate exercise or vigorous exercise with appropriate resting periods can achieve maximum benefit.

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.

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.