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Satellite cells are generally quiescent in vivo. Once activated, progression through the cell cycle begins. Immortalised myoblasts from a single cell line are fairly homogenous in culture, but primary human myoblasts (PHMs) demonstrate heterogeneity. This phenomenon is poorly understood however may impact on PHM expansion. This study aimed to evaluate cell cycle transition from growth to synthesis phases of the cell cycle (G1 to S phase) and total mRNA relevant to this transition in PHM clones derived from 2 donor biopsies. Proportions of cells transitioning from G1 to S phase were evaluated at 2-hourly intervals for 24 h (n = 3 for each) and total mRNA quantified. Both PHM clones revealed an exponential transition from G1 to S phase over time, with a significantly slower rate for PHMs from S9.1 compared to S6.3, which had a higher proportion of PHMs in S phase for most time-points (p 0.05). After 24 h the proportion of PHMs in S phase was ∼13% (S6.3) compared to ∼22% (S9.1). Gene transcription increased as cells progressed from G1 to S phase. Although total RNA increased with similar linearity in both clones, S6.3 PHMs had consistently (10 out of 12 time points) significantly higher concentrations. Validating the 2-hourly assessment over 24 h, a 4-hourly assessment from 8 to 32 h revealed similar differences but included the beginning of a plateau. This study demonstrates that PHMs from different donors differ in both cell cycle progression and overall transcriptome revealing new aspects in the heterogeneity of isolated satellite cells in vitro.

Chronic wounds are a serious and debilitating complication of diabetes. A better understanding of the dysregulated healing responses following injury will provide insight into the optimal time frame for therapeutic intervention. In this study, a direct comparison was done between the healing dynamics and the proteome of acute and obese diabetic wounds on days 2 and 7 following injury. Full thickness excisional wounds were induced on obese diabetic (B6.Cg-lepob/J, ob/ob, n = 14) (blood glucose 423.25 ± 127.92 mg/dL) and WT control (C57BL/6J, n = 14) (blood glucose 186.67 ± 24.5 mg/dL) mice. Histological analysis showed no signs of healing in obese DM wounds whereas complete wound closure/re-epithelisation, the formation of granulation tissue and signs of re-vascularisation, was evident in acute wounds on day 7. In obese DM wounds, substance P deficiency and increased MMP-9 activity on day 2 coincided with increased cytokine/chemokine levels within wound fluid. LC-MS/MS identified 906 proteins, of which 23 (Actn3, Itga6, Epb41, Sncg, Nefm, Rsp18, Rsp19, Rpl22, Macroh2a1, Rpn1, Ppib, Snrnp70, Ddx5, Eif3g, Tpt1, FABP5, Cavin1, Stfa1, Stfa3, Cycs, Tkt, Mb, Chmp2a) were differentially expressed in wounded tissue on day 2 (P < 0.05; more than two-fold) and 6 (Cfd, Ptms, Hp, Hmga1, Cbx3, Syap1) (P < 0.05; more than two-fold) on day 7. A large number of dysregulated proteins on day 2 was associated with an inability to progress into the proliferative stage of healing and suggest that early intervention might be pivotal for effective healing outcomes. The proteomic approach highlighted the complexity of obese DM wounds in which the dysregulation involves multiple regulatory pathways and biological processes.

South Africa has one the highest TB and HIV burdens globally. TB preventive therapy (TPT) reduces the risk of TB disease and TB-related mortality in adults and children living with HIV and is indicated for use in TB-exposed HIV-negative individuals and children. TPT implementation in South Africa remains suboptimal.We conducted a pragmatic review of TPT implementation using multiple data sources, including informant interviews (TPT programme implementation was suboptimal, with inadequate monitoring even in health districts with well-functioning TB services. Health workers reported scepticism about TPT effectiveness, deprioritised TPT in practice and expressed divergent opinions about the cadres of staff responsible for implementation. Service- and facility-level barriers included ineffective contact tracing, resource shortages, lack of standardised reporting mechanisms and insufficient patient education on TPT. Patient-level barriers included socio-economic factors.Improving TPT implementation will require radically simplified and more feasible systems and training for all cadres of health workers. Partnership with communities to stimulate demand driven service uptake can potentially facilitate implementation.L’Afrique du Sud a l’une des charges de TB et de VIH les plus élevées au monde. La thérapie préventive contre la TB (TPT) réduit le risque de TB maladie et de mortalité liée à la TB chez les adultes et les enfants vivant avec le VIH et est indiquée chez les personnes et les enfants séronégatifs exposés à la TB. La mise en œuvre du TPT en Afrique du Sud reste sous-optimale.Nous avons procédé à un examen pragmatique de la mise en œuvre du TPT à l’aide de plusieurs sources de données, notamment des entretiens avec des informateurs (La mise en œuvre du programme TPT était sousoptimale, avec un suivi inadéquat, y compris dans les districts sanitaires où les services de lutte contre la TB fonctionnaient correctement. Les agents de santé ont fait part de leur scepticisme quant à l’efficacité de la TPT, n’ont pas accordé la priorité à la TPT dans la pratique et ont exprimé des opinions divergentes sur les cadres du personnel responsables de la mise en œuvre. Les obstacles au niveau des services et des établissements comprennent l’inefficacité de la recherche des contacts, la pénurie de ressources, l’absence de mécanismes de déclaration standardisés et l’insuffisance de l’éducation des patients sur la TPT. Les obstacles au niveau des patients comprenaient des facteurs socio-économiques.L’amélioration de la mise en œuvre des TPT nécessitera des systèmes radicalement simplifiés et plus réalisables ainsi qu’une formation pour tous les cadres du personnel de santé. Un partenariat avec les communautés pour stimuler l’adoption de services axés sur la demande peut potentiellement faciliter la mise en œuvre.

Due to the abundance of lipoproteins in blood, it is challenging to characterize the biological functions and components of blood-derived extracellular vesicles. The aim of this study was to develop a multiple-step purification protocol to separate serum exosomes from serum proteins and lipoproteins and assess their regenerative potential. Exosomes were isolated by concentrating them in human serum using ultracentrifugation (UC), followed sequentially by density gradient (DG) UC and size exclusion chromatography (SEC). Purity and characterization were assessed by western blots, Lipoprint®, enzyme-linked immunosorbent assay, electron microscopy, mass spectrometry, and nanoparticle tracking analysis. Functionality was assessed by cell proliferation analysis and with an in vivo subcutaneous angiogenesis model. SEC alone isolated nano-sized vesicles possessing vesicle markers TSG101 and CD9, but there was a substantial presence of apolipoprotein B, predominantly derived from very-low- and intermediate-density lipoprotein particles. This was reduced to an undetectable level using the combined UC DG SEC approach. Mass spectrometry identified 224 proteins in UC DG SEC isolates relative to the 135 from SEC, with considerable increases in exosome-related proteins and reductions in lipoproteins. A consistent but limited increase in human dermal fibroblast proliferation and evidence of neovascularization enhancement were observed after exposure to UC DG SEC exosomes. An UC DG SEC purification protocol considerably improved the removal of lipoproteins during isolation of serum exosomes. The purified exosomes stimulated cell proliferation and potentially increased an in vivo angiogenic response. This multistep purification allows for more accurate identification of serum exosome functional activity and composition.

Skeletal muscle injury activates satellite cells to proliferate as myoblasts and migrate, differentiate and fuse with existing fibres at the site of injury. Nitric oxide (NO), a free radical produced by NO synthase, is elevated and supports healing after in vivo injury. NOS-independent elevation of NO levels in vitro is possible via donors such as molsidomine (SIN-1). We hypothesized that alterations in NO levels may directly influence myogenic processes critical for skeletal muscle wound healing. This study aimed to clarify the role of NO in myoblast proliferation, migration and differentiation. Baseline NO levels were established in vitro, whereafter NO levels were manipulated during myogenesis using l-NAME (NOS inhibitor) or SIN-1. Baseline NO levels generated by myoblasts in proliferation media did not change 1 h after stimulation. Addition of a pro-proliferative dose of HGF slightly elevated NO levels 1 h post-stimulation, whereas cell numbers assessed 24 h later increased significantly; l-NAME reduced the HGF-driven increase in NO and proliferation, reducing wound closure over 16 h. In differentiation media, NO levels increased significantly within 24 h, returning to baseline over several days. Regular addition of l-NAME to differentiating cells significantly reduced NO levels and fusion. SIN-1 increased NO levels in a dose-dependent manner, reaching maximal levels 16 h post-treatment. SIN-1, added at 0, 2 and 4 days, significantly increased myofiber area (26 ± 1.8% vs 18.6 ± 3.4% in control at 5 day, p 0.0001), without affecting proliferation or migration. In conclusion, this study demonstrates that, during skeletal muscle regeneration, increased NO specifically stimulates myoblast differentiation.

Due to atrophy, muscle weakness is a common occurrence in rheumatoid arthritis (RA). The majority of human studies are conducted on the vastus lateralis muscle—a muscle with mixed fiber type—but little comparative data between multiple muscles in either rodent or human models are available. The current study therefore assessed both muscle ultrastructure and selected redox indicators across various muscles in a model of collagen-induced rheumatoid arthritis in female Sprague-Dawley rats. Only three muscles, the gastrocnemius, extensor digitorum longus (EDL), and soleus, had lower muscle mass (38%, 27%, and 25% loss of muscle mass, respectively; all at least P<0.01), while the vastus lateralis muscle mass was increased by 35% (P<0.01) in RA animals when compared to non-RA controls. However, all four muscles exhibited signs of deterioration indicative of rheumatoid cachexia. Cross-sectional area was similarly reduced in gastrocnemius, EDL, and soleus (60%, 58%, and 64%, respectively; all P<0.001), but vastus lateralis (22% smaller, P<0.05) was less affected, while collagen deposition was significantly increased in muscles. This pathology was associated with significant increases in tissue levels of reactive oxygen species (ROS) in all muscles except the vastus lateralis, while only the gastrocnemius had significantly increased levels of lipid peroxidation (TBARS) and antioxidant activity (FRAP). Current data illustrates the differential responses of different skeletal muscles of the hindlimb to a chronic inflammatory challenge both in terms of redox changes and resistance to cachexia.

This cross-sectional study explored the differences in sociodemographics, dietary intake, and household foodways (cultural, socioeconomic practices that affect food purchase, consumption, and preferences) of food secure and food insecure older women living in a low-income urban setting in South Africa. Women (n = 122) aged 60–85 years old were recruited, a sociodemographic questionnaire was completed, and food security categories were determined. The categories were dichotomised into food secure (food secure and mild food insecurity) and food insecure (moderate and severe). A one-week quantified food frequency questionnaire was administered. Height and weight were measured to calculate body mass index (BMI, kg/m2). Most participants (&gt, 90%) were overweight/obese, unmarried/widowed, and breadwinners with a low monthly household income. Food insecure participants (36.9%) more frequently borrowed money for food (57.8% vs. 39.0%, p = 0.04), ate less so that their children could have more to eat (64.4%. vs. 27.3%, p = 0.001), and had higher housing density (1.2 vs. 1.0, p = 0.03), compared to their food-secure counterparts. Overall, &lt, 30% of participants met the WHO (Geneva, Switzerland) recommended daily servings of healthy foods (fruits, vegetables, and dairy products), but &gt, 60% perceived that they consumed an adequate amount of healthy foods. The overall low-quality diet of our cohort was associated with poor nutritional perceptions and choices, coupled with financial constraints.

Although rheumatoid arthritis affects 1% of the global population, the role of rheumatoid cachexia, which occurs in up to a third of patients, is relatively neglected as research focus, despite its significant contribution to decreased quality of life in patients. A better understanding of the cellular and molecular processes involved in rheumatoid cachexia, as well as its potential treatment, is dependent on elucidation of the intricate interactions of the cells involved, such as myoblasts, fibroblasts and macrophages. Persistent RA-associated inflammation results in a relative depletion of the capacity for regeneration and repair in the satellite cell niche. The repair that does proceed is suboptimal due to dysregulated communication from the other cellular role players in this multi-cellular environment. This includes the incomplete switch in macrophage phenotype resulting in a lingering pro-inflammatory state within the tissues, as well as fibroblast-associated dysregulation of the dynamic control of the extracellular matrix. Additional to this endogenous dysregulation, some treatment strategies for RA may exacerbate muscle wasting and no multi-cell investigation has been done in this context. This review summarizes the most recent literature characterising clinical RA cachexia and links these features to the roles of and complex communication between multiple cellular contributors in the muscle niche, highlighting the importance of a targeted approach to therapeutic intervention.

Regenerative medicine research and testing of new therapeutics for muscle-related human diseases call for a deeper understanding of how human myoblasts gain and maintain quiescence

IntroductionSouth Africa (SA) is a developing country with an ageing population. Adequate nutrition and physical activity (PA) protect against the loss of muscle mass and physical function, both of which are important components of sarcopenia. This study aimed to measure the prevalence of sarcopenia in older black SA women and investigate its associations with PA and protein intake.Materials and MethodsOlder black SA women (age, 68 (range; 60–85 years) n = 122) completed sociodemographic questionnaires, 24 h urine collection (estimate protein intake), venous blood (hs-C-reactive protein (hs-CRP) and ferritin), functional tests (grip strength, 3 m timed-up-and-go (TUG), 10 m walk test) and PA monitoring (activPAL). Dual-energy x-ray absorptiometry whole-body scans assessed fat and fat-free soft tissue mass (FFSTM).ResultsAccording to the European Working group on Sarcopenia in Older People (EWGSOP)2, 2.5% (n = 3) had confirmed sarcopenia of a low severity based on normal physical function. Of the total cohort, 9% (n = 11) had low grip strength, 22.1% (n = 27) had a low appendicular skeletal muscle index (ASMI), and no women had low TUG (s) or gait speed (m/s). Higher ASMI was associated with lower hs-CRP (p = 0.05; Rho = -0.209) and higher ferritin (Rho = 0.252; p = 0.019), grip strength (kg, Rho = 0.223; p = 0.015), and gait speed (m/s, Rho = 0.180; p = 0.050). Protein intake suggested intake of 41.8g/day/ or 0.51 g/kg of body mass/day. Higher total protein intake (g/24h), was associated with higher FFSTM (kg) and ASMI (p < 0.001). PA outcomes were not correlated with FFSTM or ASMI (p > 0.05), however, there was a strong positive correlation of TUG (s) and gait speed (m/s) with time spent: 1) stepping per day (min) and; 2) at a high cadence (> 100 steps/min) (all p < 0.01). Daily step count was 7137 ± 3233 (mean ± Standard deviation), with 97.9 ± 38.7 min of total time spent stepping and 12.6 ± 16.8 min spent stepping at a high cadence (> 100 steps/min). Of note, 13.9% (n = 17) of women were completing > 10,000 steps/day.DiscussionBased on the EWGSOP2 criteria, there is a low prevalence of sarcopenia in older black SA women, explained by the maintenance of strength and physical function that directly related to PA, especially that performed at higher intensities. In contrast, low muscle mass was relatively prevalent (22.1%) and was associated with low dietary protein and not PA. Notably, it may be important to review the cut-points of EWGSOP2 criteria to be specific to the older SA women from disadvantaged communities.

IntroductionOsteoporosis was not a public health concern in black South African (SA) women, until recently when it was reported that the prevalence of vertebral fractures was 9.1% in black compared to 5.0% in white SA women. Accordingly, this study aimed to measure bone mineral density (BMD) of older black SA women and to investigate its association with risk factors for osteoporosis, including strength, muscle and fat mass, dietary intake and objectively measured physical activity (PA).Methods and materialsOlder black SA women (age, 68 (range; 60–85 years) n = 122) completed sociodemographic and quantitative food frequency questionnaires (QFFQ), fasting venous blood samples (25-hydroxycholecalciferol: Vitamin D-25), 24 h urine collection (estimate protein intake), grip strength and PA monitoring (activPAL). Dual-energy x-ray absorptiometry (DXA) scans of the hip (femoral neck and total) and lumbar spine determined BMD and whole-body scans for fat and fat-free soft tissue mass (FFSTM). WHO classifications were used to determine osteopenia (t-score -2.5 to -1), and osteoporosis (t-score < -2.5).ResultsAt the lumbar spine 34.4% of the women (n = 42) had osteopenia and 19.7% (n = 24) had osteoporosis. Osteopenia at the left femoral neck was 32% (n = 40) and osteoporosis was 13.1% (n = 16) of participants. The total left hip BMD indicated osteopenia in 27.9% (n = 34) and osteoporosis in 13.1% (n = 16) of participants. Multinomial regression revealed no differences in age (y) or frequency of falls in the past year between all groups (p = 0.727). Compared to those with normal BMD, participants with osteoporosis at the hip neck and lumbar spine were shorter, weighed less and had a lower body mass index (BMI) (all p < 0.05). When adjusted for height, the osteoporotic group (hip neck and lumbar spine) had lower trunk fat (% whole body), FFSTM (kg) and grip strength (kg), compared to those with normal BMD (p < 0.05). Only protein intake (g; 24 h urine analyses) was lower in women with osteoporosis (all sites) compared to those with normal BMD. Fat, carbohydrate and micronutrient intakes (relative to total daily energy intake), and vitamin D concentrations were not associated with BMD (all sites). Number of daily step count and stepping time (min) were inversely associated with BMI (p < 0.05), but not with BMD (all sites; p > 0.05).DiscussionA high prevalence of osteopenia and osteoporosis was evident at the lumbar spine and hip in older black SA women. This study highlights the importance of strength, body composition, and protein intake in maintaining BMD and preventing the development of osteoporosis in older women.

Additional file 1. Protocol for immunofluorescence staining, used in preparation of Figure 1.

Skeletal muscle regeneration is a complex process influenced by non‐myogenic macrophages and fibroblasts, which acquire different phenotypes in response to changes in the injury milieu or changes in experimental conditions. In vitro, serum stimulates the differentiation of fibroblasts into myofibroblasts, while lipopolysaccharide (LPS) stimulates the polarization of unstimulated (M0) macrophages to acquire an M1 pro‐inflammatory phenotype. We characterized these phenotypes using morphology (with circularity as shape descriptor; perfect circularity = 1.0) and phenotype‐specific markers. Myofibroblasts (high α‐smooth muscle actin [SMA] expression) had high circularity (mean 0.60 ± 0.03). Their de‐differentiation to fibroblasts (low α‐SMA expression) significantly lessened circularity (0.47 ± 0.01 and 0.35 ± 0.02 in 2% or 0% serum culture media respectively (p, In the current study we established the exact conditions for generating, and tools for morphologically evaluating and characterizing, specific macrophage and fibroblast phenotypes. Subsequently, we used these conditions to investigate the effect of M1 macrophages on myofibroblast and myoblast numbers, and then screen for inhibitors that could abrogate the observed negative effect of the pro‐inflammatory macrophages on myofibroblasts.

Postnatal muscle growth and exercise- or injury-induced regeneration are facilitated by myoblasts. Myoblasts respond to a variety of proteins such as cytokines that activate various signaling cascades. Cytokines belonging to the interleukin 6 superfamily (IL-6) influence myoblasts&rsquo, proliferation but their effect on differentiation is still being researched. The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway is one of the key signaling pathways identified to be activated by IL-6. The aim of this study was to investigate myoblast fate as well as activation of JAK-STAT pathway at different physiologically relevant IL-6 concentrations (10 pg/mL, 100 pg/mL, 10 ng/mL) in the C2C12 mouse myoblast cell line and primary human myoblasts, isolated from eight young healthy male volunteers. Myoblasts&rsquo, cell cycle progression, proliferation and differentiation in vitro were assessed. Low IL-6 concentrations facilitated cell cycle transition from the quiescence/Gap1 (G0/G1) to the synthesis (S-) phases. Low and medium IL-6 concentrations decreased the expression of myoblast determination protein 1 (MyoD) and myogenin and increased proliferating cell nuclear antigen (PCNA) expression. In contrast, high IL-6 concentration shifted a larger proportion of cells to the pro-differentiation G0/G1 phase of the cell cycle, substantiated by significant increases of both MyoD and myogenin expression and decreased PCNA expression. Low IL-6 concentration was responsible for prolonged JAK1 activation and increased suppressor of cytokine signaling 1 (SOCS1) protein expression. JAK-STAT inhibition abrogated IL-6-mediated C2C12 cell proliferation. In contrast, high IL-6 initially increased JAK1 activation but resulted in prolonged JAK2 activation and elevated SOCS3 protein expression. High IL-6 concentration decreased interleukin-6 receptor (IL-6R) expression 24 h after treatment whilst low IL-6 concentration increased IL-6 receptor (IL-6R) expression at the same time point. In conclusion, this study demonstrated that IL-6 has concentration- and time-dependent effects on both C2C12 mouse myoblasts and primary human myoblasts. Low IL-6 concentration induces proliferation whilst high IL-6 concentration induces differentiation. These effects are mediated by specific components of the JAK/STAT/SOCS pathway.

Adult skeletal muscle stem cells, satellite cells, remain in an inactive or quiescent state in vivo under physiological conditions. Progression through the cell cycle, including activation of quiescent cells, is a tightly regulated process. Studies employing in vitro culture of satellite cells, primary human myoblasts (PHMs), necessitate isolation myoblasts from muscle biopsies. Further studies utilizing these cells should endeavour to represent their native in vivo characteristics as closely as possible, also considering variability between individual donors. This study demonstrates the approach of utilizing KnockOut™ Serum Replacement (KOSR)-supplemented culture media as a quiescence-induction media for 10 days in PHMs isolated and expanded from three different donors. Cell cycle analysis demonstrated that treatment resulted in an increase in G(1) phase and decreased S phase proportions in all donors (p 98% over time from day 0 to day 10. In contrast activation (CD56), proliferation (Ki67) and myogenic marker MyoD decreased, indicated de-differentiation. Induction of quiescence was accompanied in all three clones by fold change in p21 mRNA greater than 3.5 and up to tenfold. After induction of quiescence, differentiation into myotubes was not affected. In conclusion, we describe a method to induce quiescence in PHMs from different donors. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s10616-019-00365-8) contains supplementary material, which is available to authorized users.

CITATION: Smith, C. & Myburgh, K. H. 2005. Assessment of endocrine stress status in athletes – new twists to the tale. South African Journal of Sports Medicine, 17(3):19-29, doi:10.17159/5124.

Skeletal muscle injury elicits the activation of satellite cells and their migration to the wound area for subsequent terminal differentiation and tissue integration. However, interstitial fibroblasts recruited to the site of injury promote deposition of fibrotic tissue, which hampers myoblast-mediated muscle regeneration. Currently, analysis of myoblast migration in vitro can be accomplished using chemotactic, cell-exclusion, or wound healing assays. Yet, to investigate cell motility following skeletal muscle damage more accurately, migration assays need to better simulate the repair process. Here we present a protocol for the simultaneous isolation of myoblasts and fibroblasts from the same muscle tissue, ensuring the consistent generation of enriched, purified, and matched cell populations at a low passage number. We then describe a wound assay that uses a novel approach to the co-culture of myoblasts and fibroblasts to mimic the injured environment more closely than other established methods. Using this assay, we demonstrate that fibroblasts are able to increase myoblast migration significantly, validating our new in vitro method. As the observed effect on migration is most likely mediated by secreted factors, our assay could easily be extended to include antibody-based protein analysis of secreted factors in animal or human systems.

Purpose: The purpose of this study was to investigate skeletal muscle changes induced by an acute bout of plyometric exercise (PlyEx) both before and after PlyEx training, to understand if titin is affected differently after PlyEx training. Methods: Healthy untrained individuals (N=11) completed the 1stPlyEx (10x10 squat-jumps, 1min rest). Thereafter, 6 subjects completed 8 weeks of PlyEx, while 5 controls abstained from any jumping activity. Seven days after the last training session all subjects completed the 2ndPlyEx. Blood samples were collected before, 6 hours and 1, 2, 3 and 4 days after each acute bout of PlyEx, and muscle biopsies 4 days before and 3 days after each acute bout of PlyEx. Results: The 1stPlyEx induced an increase in circulating myoglobin concentration. Muscle sample analysis revealed Z-disk streaming, a stretch or a fragmentation of titin (immunogold), and increased calpain-3 autolysis. After training, 2ndPlyEx did not induce Z-disk streaming, or calpain-3 activation. The previously observed post-1stPlyEx positional change of the titin c-terminus was still present pre-2ndPlyEx, in all trained and all control subjects. Only 2 controls presented with Z-disk streaming after 2ndPlyEx, while calpain-3 activation was absent in all controls. Discussion: Eccentric explosive exercise induced a stretch or fragmentation of titin, which presented as a positional change of the c-terminus. Calpain-3 activation does not occur when titin is already stretched before explosive jumping. Enzymatic digestion results in titin fragmentation, but since an increase in calpain-3 autolysis was visible only after the 1stPlyEx acute bout, fragmentation cannot explain the prolonged positional change.

Satellite cell migration is critical for skeletal muscle growth and regeneration. Controlled cell migration is dependent on the formation of mature focal adhesions between the cell and the underlying extracellular matrix (ECM). These cell-ECM interactions trigger the activation of signalling events such as the Rho/ROCK pathway. We have previously identified a specific role for ROCK-2 during myoblast migration. In this study we report that ROCK inhibition with Y-27632 increases C2C12 myoblast velocity, but at the expense of directional migration. In response to Y-27632 an increased number of smaller focal adhesions were distributed across adhesion sites that in turn were clearly larger than sites in untreated cells, suggesting a reduction in focal adhesion maturation. We also confirm ROCK-2 localisation to the focal adhesion sites in migrating myoblasts and demonstrate a change in the distribution of these ROCK-2 containing adhesions in response to Y-27632. Taken together, our observations provide further proof that ROCK-2 regulates directional myoblast migration through focal adhesion formation and maturation.

Fruit and vegetable flavonoids, including proanthocyanidins, anthocyanidins to an extent and anthocyanins (anthocyanidins with sugar moieties attached to the hydroxyl groups) are found in reasonably high quantities in cocoa, berries, cinnamon and red grapes and have proved to be protective against many cardiovascular risk factors. After summarising the biokinetic properties of anthocyanins and proanthocyanidins, we review basic science and clinical evidence for the effectiveness of these flavonoids against cardiovascular disease and discuss the possible mechanisms of action and cellular signalling pathways involved in this effect.

Supplement use among athletes is widespread, including non-traditional and biological compounds. Despite increasing research, a comprehensive and critical review on polyphenol supplementation and exercise is still lacking. This review is relevant for researchers directly involved in the topic, as well as those with a broad interest in athletic performance enhancement and sports nutrition. The purpose of this review is to present background information on groups of polyphenols and their derivatives because their differing chemical structures influence mechanisms of action; to discuss the potential of plant, fruit and vegetable-based biological supplements, high in polyphenol content, to affect exercise performance and biomarkers of oxidative stress and exercise-induced muscle damage; and to critically discuss the exercise studies and biomarkers used. Subjects in the studies reviewed were either sedentary, healthy individuals, or active, recreationally trained or well-trained athletes. Polyphenol supplementation in exercise studies included mainly extracts (multicomponent or purified), juices, infusions or an increased intake of polyphenol-rich foods. This review includes details of supplement doses and exercise test protocols. Many studies considered only the performance or one or two selected biomarkers of antioxidant capacity instead of a comprehensive choice of biomarkers to assess damage to lipids or proteins. Evidence is insufficient to make recommendations for or against the use of polyphenol supplementation (neither specific polyphenols nor specific doses) for either recreational, competitive or elite athletes. Polyphenols have multiple biological effects, and future exercise studies must be designed appropriately and specifically to determine physiological interactions between exercise and the selected supplement, rather than considering performance alone.

This study aimed to compare the response of performance-matched black and white runners during maximal and sub-maximal running in normoxic and hypoxic conditions. 14 well-trained runners (8 black, 6 white) performed 2 incremental maximal exercise tests and 2 fatigue resistance tests at 21% O2 (normoxia) or 14% O2 (hypoxia). Respiratory parameters, heart rate (HR), lactate concentration ([La-]) as well as arterial saturation (SpO2) were measured. Enzyme activities and myosin heavy chain content (MHC) were also measured. White runners reached a significantly greater peak treadmill speed and a higher HRmax than black runners in hypoxia (p

Stem cells have an inherent capacity to facilitate regeneration; this has led to unprecedented growth in their experimental use in various clinical settings, particularly in patients with diseases with few alternative treatment options. However, their approved clinical use has to date been restricted largely to haematological diseases and epidermal transplantation to treat severe burns. After thorough searching of two databases, this review illuminates the role of stem cell therapy for treatment of musculoskeletal diseases. Research suggests that successful application of stem cells as regenerative mediators is in all likelihood dependent on the ability of endogenous tissue-resident reparative mediators to respond to paracrine signals provided by the applied stem cells. Therefore, an understanding of how the pathological environment influences this process is crucial for the ultimate success of stem cell therapies. The current review presents both the progress and limitations of stem cells as regenerative mediators in the context of musculoskeletal disorders.

Individual responses in creatine kinase (CK) release after eccentric exercise are divergent. This study aimed to identify whether this could be related to selected humoral or intramuscular inflammatory factors. Twenty-three subjects were divided into non-exercising (n = 5) and downhill run (DHR; n = 18) groups (12 × 5 min, 10% decline at 15 km/h). Blood samples were analyzed for white blood cell differential count, CK, myoglobin, tumor necrosis factor-α, granulocyte colony-stimulating factor, interleukin (IL)-1β, IL-6, and IL-10. Muscle biopsies were analyzed for signal transducer and activator of transcription-3 (STAT3), IκBα, and myeloperoxidase (MPO). DHR participants clustered as early (DHR1) recovery, biphasic response (DHR2), or classic delayed exaggerated CK response (DHR3), with a delayed CK peak (4784 ± 1496 U/L) on day 4. For DHR1 and DHR2, CK peaked on day 1 (DHR1: 1198 ± 837 U/L) or on day 1 and day 4 (DHR2: 1583 ± 448 U/L; 1878 ± 427 U/L), respectively. Immediately post-DHR, IL-6 increased in DHR2 and DHR3 whereas IL-10 increased in all DHR groups. STAT3 signaling increased for DHR1 and DHR2 at 4 h, but MPO at day 2 only in DHR2. Objective cluster analysis uncovered a group of subjects with a characteristic biphasic CK release after DHR. The second elevation was related to their early cytokine response. The results provide evidence that early responses following eccentric exercise are indicative of later variation.

Introduction: We investigated changes in satellite cell (SC) pool size after an acute bout of strenuous exercise and evaluated the influence of baseline SC count and fiber type. Methods: Participants completed a downhill running (DHR) intervention (5 × 8 min, 2-min rest; 80% VO2max; −10% gradient). Muscle biopsies were taken 7 days before VO2max and 7–9 days after the DHR intervention. Delayed-onset muscle soreness (DOMS) and creatine kinase activity (CK) were measured on days 1, 2, 7, and 9 post-DHR. SCs were identified by Pax7 and laminin staining. Relative distribution of MHC isoforms was determined by electrophoresis. Results: DOMS and CK peaked on day 1 post-DHR (P < 0.01). The SC pool increased (26%) after DHR (P = 0.005). SCs/total myonuclei after recovery correlated with baseline SCs (r = 0.979, P = 0.003) and VO2max (r = 0.956, P = 0.011), whereas change in SC pool (Pax7+ cells/total myonuclei: recovery minus baseline) tended to correlate with percent MHC II (r = 0.848; P = 0.06). Conclusion: Interindividual physiological characteristics affect SC pool expansion after a single bout of DHR and are influenced by VO2max. Muscle Nerve, 2013

Sport is recognized as playing a relevant societal role to promote education, health, intercultural dialogue, and the individual development, regardless of an individual’s gender, race, age, ability, religion, political affiliation, sexual orientation, and socioeconomic background. Yet, it was not until the 2012 Summer Olympic Games in London that every country’s delegation included a female competitor. The gender gap in sport, although closing, remains, due to biological differences affecting performance, but it is also influenced by reduced opportunity and sociopolitical factors that influence full female participation across a range of sports around the world. Until the cultural environment is equitable, scientific discussion related to physiological differences using methods that examine progression in male and female world-record performances is limited. This commentary is intended to provide a forum to discuss issues underlying gender differences in sport performance from a global perspective and acknowledge the influence of cultural and sociopolitical factors that continue to ultimately affect female performance.

Acute skeletal muscle damage results in fiber disruption, oxidative stress and inflammation. We investigated cell-specific contributions to the regeneration process after contusion-induced damage (rat gastrocnemius muscle) with or without chronic grape seed-derived proanthocyanidolic oligomer (PCO) administration. In this placebo-controlled study, male Wistar rats were subjected to PCO administration for 2 weeks, after which they were subjected to a standardised contusion injury. Supplementation was continued after injury. Immune and satellite cell responses were assessed, as well as oxygen radical absorption capacity and muscle regeneration. PCO administration resulted in a rapid satellite cell response with an earlier peak in activation (Pax7⁺, CD56⁺, at 4 h post-contusion) vs. placebo groups (PLA) (P.001: CD56⁺ on Day 5 and Pax7⁺ on Day 7). Specific immune-cell responses in PLA followed expected time courses (neutrophil elevation on Day 1; sustained macrophage elevation from Days 3 to 5). PCO dramatically decreased neutrophil elevation to nonsignificant, while macrophage responses were normal in extent, but significantly earlier (peak between Days 1 and 3) and completely resolved by Day 5. Anti-inflammatory cytokine, IL-10, increased significantly only in PCO (Day 3). Muscle fiber regeneration (MHC(f) content and central nuclei) started earlier and was complete by Day 14 in PCO, but not in PLA. Thus, responses by three crucial cell types involved in muscle recovery were affected by in vivo administration of a specific purified polyphenol in magnitude (neutrophil), time course (macrophages), or time course and activation state (satellite cell), explaining faster effective regeneration in the presence of proanthocyanidolic oligomers.

Context: Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. Objective: To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Intervention(s): Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Main Outcome Measure(s): Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Results: Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). Conclusions: We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle fibers.

(2012). Chapter 9 - Understanding the dominance of African endurance runners: Exercise biology and an integrative model. Routledge Online Studies on the Olympic and Paralympic Games: Vol. 1, East African Running: toward a cross-disciplinary perspective, pp. 134-158.

Satellite cells (SCs) are responsible for muscle repair following strenuous exercise or injury. SC responses to intervention have been studied, but most studies do not discuss or take into account the substantial variability in SC number among young individuals. We hypothesized that an active lifestyle reflected in higher VO(2max) may be associated with greater SC number. As training alters basal p38-mitogen-activated protein kinase (MAPK) activity, which is associated with SC proliferation, SC count may also correlate with this stress signaling kinase. Muscle biopsies from vastus lateralis of eight male participants were analyzed for fiber type, myogenin, and p38/phospho-p38 MAPK using SDS-PAGE and Western blotting. Immunofluorescence was used to detect Pax7(+) SCs. Two weeks following the biopsy, subjects underwent an incremental treadmill test to determine VO(2max) . A strong positive correlation (P = 0.0087) was found between the number of Pax7(+) nuclei and VO(2max) . Pax7(+) cell number correlated negatively with phospho-p38/p38 MAPK (P = 0.0006), but had no correlation with fiber type or myogenin. SC number is proportional to VO(2max) , and hence it can be postulated that higher levels of physical activity activate SC proliferation but not fusion, underlining the relevance of exercise in stimulating SC pool size even without injury.