Barbara St. Pierre Schneider

Neutrophil Infiltration in Exercise-Injured Skeletal Muscle How Do We Resolve the Controversy?

Neutrophils have not consistently been detected in exercise-injured skeletal muscle and, therefore, neutrophil infiltration in this muscle has become a controversial issue. Thirty-eight animal and human studies that assessed injured muscle for neutrophils and employed acute exercise (e.g. level, uphill or downhill running, eccentric contractions, or swimming) were analysed to help clarify the relationship between neutrophil infiltration and exercise-induced muscle injury. Findings from nearly three-quarters of the reviewed studies suggest that neutrophil accumulation follows exercise-induced muscle injury. Intramuscular neutrophil infiltration was present in 85% and 55% of the animal and human studies, respectively. However, no consistent relationship between the potential damaging effect of the exercise type and neutrophil infiltration can be conclusively established from these studies. Specific animal-related factors that could influence these results include age, animal strain, catecholamines, corticosterone, acute stressors and muscle type, whereas a specific human-related influencing factor is physical activity status. Factors affecting both animal and human studies could include sex hormones, muscle sampling techniques and neutrophil detection approaches. General categories of methods that have been used to detect neutrophil infiltration are microscopy, myeloperoxidase (MPO) biochemical assay, antibody staining and white blood cell radionuclide imaging. Only studies employing white blood cell radionuclide imaging have consistently detected neutrophil infiltration. However, antibody staining with a quantitative analysis is currently the most feasible, valid and sensitive method. Research recommendations, therefore, are warranted to resolve the neutrophil infiltration controversy. We propose two approaches for animal studies. The first approach encompasses (i) studying or measuring factors that could influence neutrophil infiltration; (ii) using quantitative antibody staining analysis (in all studies and employing a panel of anti-neutrophil antibodies); (iii) examining the relationship between fibre morphological changes and neutrophil antigen expression; and (iv) developing a neutrophil antibody-radionuclide imaging technique. The second approach will yield animal findings complementing or addressing the gaps from the human exercise studies. For human studies, we suggest that (i) physical activity status is investigated; (ii) quantitative antibody staining analysis is performed (including staining injured muscle with a panel of antibodies such as anti-elastase, anti-MPO, anti-CD11b and anti-CD15 or assessing injured muscle using both immunohistochemistry and the MPO biochemical assay); and (iii) the relationship between fibre morphological changes and neutrophil antigen expression is examined. Studies that incorporate these recommendations could lead to an increased understanding of whether neutrophils are essential for the recovery from an exerciseinduced muscle injury.

Time course of chemokine expression and leukocyte infiltration after acute skeletal muscle injury in mice

Innate pro-inflammatory processes, such as chemokine signaling and leukocyte infiltration, predominate during the first 48 h after an acute skeletal muscle injury. However, the time course of chemokine expression and its relationship to leukocyte infiltration after acute muscle injury within this early post-injury time period has not been investigated. In this study, 46 anesthetized female C57BL/6NHsd mice underwent a closed crush injury of the gastrocnemius muscle and were euthanized 4, 8, 24 and 48 h post-injury. Microarray analysis found 14 chemokine genes to be up-regulated during this period, 12 of which are involved in macrophage or neutrophil chemotaxis, with up-regulation peaking at either 8 or 48 h. RT-PCR analysis on select chemokines confirmed the microarray activation pattern. Neutrophil infiltration patterns mirrored the time course of neutrophil-related chemokines with Gr-1-, 1A8- and 7/4-positive neutrophils infiltrating the muscle 4 h after injury, decreasing at 48 h. Conversely, gene expression and relative quantification levels of macrophage-related chemokines Ccl2 and Ccl7 peaked at 8 h, preceding the infiltration of CD68- and F4/80-positive macrophages, and protein expression of Ccl2 in the muscle. The up-regulation of other macrophage-related chemokines and their receptors peaked at 48 h post-injury.

Macrophage Colony Stimulating Factor-Induced Macrophage Differentiation Influences Myotube Elongation

Background: Unaccustomed exercise, high-intensity dynamic sports activities, or the resumption of normal weight-bearing after a period of disuse can induce skeletal muscle injury, which activates an inflammatory response followed by muscle regeneration. Specific subsets of macrophages are involved in muscle regeneration. But the exact role of macrophage differentiation during muscle regeneration remains to be elucidated. Objective: The objective of the study was to examine the effect of macrophage colony stimulating factor (M-CSF)-differentiated, lipopolysaccharides (LPS)-stimulated-macrophage-conditioned medium on muscle-cell proliferation, fusion, and elongation, which are key events during muscle regeneration and myogenesis. Method: Murine C2C12 myoblasts were cultured in conditioned medium obtained from PU5-1R macrophages that were (a) undifferentiated, unstimulated; (b) M-CSF-differentiated, unstimulated; (c) undifferentiated, LPS-stimulated; or (d) M-CSF-differentiated, LPS-stimulated. Myoblast proliferation ratio, nuclei number, and length were measured. Results: C2C12 cells cultured in conditioned medium from M-CSF-differentiated, LPS-stimulated macrophages had significantly more nuclei and greater length than cells cultured in conditioned medium from undifferentiated, LPS-stimulated macrophages. Dilution and denaturization of the M-CSF-differentiated, LPS-stimulated-macrophage medium prevented a marked increase in C2C12 nuclei number and length. However, the C2C12 myoblast proliferation ratio was significantly greater in conditioned medium from undifferentiated, LPS-stimulated macrophages than in conditioned medium from M-CSF-differentiated, LPS-stimulated macrophages. Conclusions: M-CSF-differentiated, LPS-stimulated macrophages may influence myogenesis and the early and terminal stages of muscle regeneration. This knowledge may aid in developing therapies that will directly expedite muscle repair and lead to faster rehabilitation and reduced rehabilitation costs.

Nursing's leadership in positioning human health at the core of urban sustainability

The United Nations predicts that by 2050 nearly three fourths of the worlds population will live in urban areas, including cities. People are attracted to cities because these urban areas offer diverse opportunities, including the availability of goods and services and a higher quality of life. Cities, however, may not be sustainable with this population boom. To address sustainability, urban developers and engineers are building green structures, and businesses are creating products that are safe for the environment. Additionally, efforts are needed to place human health at the core of urban sustainability. Without human health, cities will not survive for future generations. Nursing is the discipline that can place human health in this position. Nursings initiatives throughout history are efforts of sustainability-improving human health within the physical, economic, and social environments. Therefore, nursing must take a leadership role to ensure that human health is at the core of urban sustainability.

Time Course of Inflammatory Gene Expression Following Crush Injury in Murine Skeletal Muscle

Background Early inflammation and secretion of proinflammatory cytokines such as IL-1&bgr;, IL-6, and TNF-&agr; act as the key drivers to regulate inflammation after muscle injury. However, the effects of these key proinflammatory drivers in a noninvasive crush injury model are not well known. Understanding these effects is important for treating crush injuries that occur during natural disasters and military conflicts. Purpose We studied the timed mRNA expression of IL-1&bgr;, IL-6, and TNF-&agr; in a noninvasive murine crush injury model to further understand their impact on proinflammatory cytokine pathways that are activated within the first 48 hours after a crush muscle injury. Methods A total of 25 mice were anesthetized and placed on a crush injury apparatus platform with the apparatus piston situated in direct contact with intact skin overlying the right gastrocnemius muscle. Pressure at 45 psi was applied to the piston for 30 seconds for two applications. The mice recovered for either 4, 8, 24, or 48 hours postinjury, after which we harvested the gastrocnemius muscle of both legs. Microarray, confirmatory real-time polymerase chain reaction, and immunolabeling experiments were followed by a microarray time-course analysis. Results Muscle IL-1&bgr; mRNA rose 270-fold within 4 hours and declined rapidly at 8 hours to 196-fold, 24 hours to 96-fold, and 48 hours to 10-fold. Muscle IL-6 followed the same pattern, with a 34-fold increase at 4 hours, 29-fold increase at 8 hours, 10-fold increase at 24 hours, and 5-fold increase at 48 hours. Ingenuity Pathway Analysis of IL-6 identified activation of two major downstream signaling pathways (IL-6/Stat3 and IL-1&bgr;/Egr1) as key activators of inflammation, regeneration, and fibrosis. Discussion Closed crush muscle injury produced robust muscle cytokine expression levels, and the microarray findings allowed us to generate our most novel hypothesis: that high expression of IL-1&bgr;, IL-6, and TNF-&agr; may be related to the downregulation of mitochondrial genes early after injury and triggers activation of genes in the repair and fibrosis machinery. The significance of these findings and the identified expression pathways of IL1-&bgr;, IL-6, and TNF-&agr; and their downstream targets in skeletal muscle will allow us to further investigate targets for improved muscle recovery and limb-saving interventions.

Assessing the immune status of critically ill trauma patients by flow cytometry.

BackgroundUnintentional injury or trauma remains the leading cause of death among young adults. About one fifth of these trauma patients require care in an intensive care unit (ICU) because of severity of injuries and comorbidities. Patients hospitalized in an ICU are at increased risk for nosocomial infections, such as urinary tract infections, pneumonia, bacteremia, and wound infections. Many of these patients will develop sepsis or septic shock, and some will progress to multiple organ failure and death. The balance between the proinflammatory and counterinflammatory immune response appears to be a driving factor in this progression. At present, there is no proposed method for the timely detection of the immune status in trauma patients, making rational decisions to use immune-altering therapies difficult. ObjectiveWe demonstrate that flow cytometry, with its capabilities to characterize and/or enumerate (a) leukocyte subtypes, (b) leukocyte activation markers, (c) leukocyte-derived cytokines and microvesicles, and (d) leukocyte function is well suited to monitor the immune status of critically ill trauma patients. MethodsInformation for the review was obtained from the extant literature. DiscussionWe suggest that flow cytometry is a research method that might aid nurse scientists in investigating the immune status of critically ill patients, the recovery status of conditions such as hemorrhagic shock and tissue injury and the relationship between cancer disease progression and symptoms. Therefore, flow cytometry has the potential to broaden nursing research priority areas so that a comprehensive approach to understanding the cellular response is attained.

Comparison of Methodologic Quality and Study/Report Characteristics Between Quantitative Clinical Nursing and Nursing Education Research Articles

AIM To compare the methodologic quality and study/report characteristics between quantitative clinical nursing and nursing education research articles. BACKGROUND The methodologic quality of quantitative nursing education research needs to advance to a higher level. Clinical research can provide guidance for nursing education to reach this level. METHOD One hundred quantitative clinical research articles from high impact journals published in 2007 and 37 education research articles from high impact journals published in 2006 to 2007 were chosen for analysis. RESULTS Clinical articles had significantly higher quality scores than education articles in three domains: number of institutions studied, type of data, and outcomes. CONCLUSION The findings indicate three ways in which nursing education researchers can strengthen the methodologic quality of their quantitative research. With this approach, greater funding may be secured for advancing the science of nursing education.

Body weight and leukocyte infiltration after an acute exercise-related muscle injury in ovariectomized mice treated with estrogen and progesterone.

In both rats and mice, an acute skeletal muscle injury leads to leukocyte infiltration in which the leukocytes remove dead fibers and cellular debris, induce a secondary injury, and/or promote myofiber regeneration. Short-term exogenous estrogen treatment attenuates this leukocyte infiltration and prevents body weight gain in rat exercise-induced skeletal muscle injury models. But these estrogen effects may not occur in mice because body weight gain does not consistently occur in ovariectomized mice treated with estrogen. Additionally, progesterone may also attenuate this leukocyte infiltration without affecting body weight. The aim of the current study was to compare body weight and leukocyte infiltration in exercise-injured skeletal muscle of ovariectomized mice treated with exogenous estrogen and progesterone for the short period of 17 days with that of ovariectomized-placebo-treated mice and gonadal-intact male and female mice. There was no significant difference in body weight between the ovariectomized-estrogen-treated and the ovariectomized-placebo-treated mice. The amount of intramuscular leukocyte infiltration of ovariectomized mice treated with estrogen or progesterone was not significantly different from that of ovariectomized-placebo-treated mice. However, in the injured muscle, the mean area of the leukocyte antigen, 7/4, of the ovariectomized-estrogen-treated group was 2-3-fold greater than that of the ovariectomized-placebo-treated, ovariectomized-estrogen-progesterone-treated, and intact male groups (p<.05), suggesting that the 7/4-positive leukocytes of the ovariectomized-estrogen-treated group were larger or had more antigen. In conclusion, ovariectomized mice demonstrate a different body weight and leukocyte response to short-term estrogen treatment than that of ovariectomized rats, and short-term estrogen treatment modulates leukocyte phenotype. These data broaden our understanding of estrogens effects on body weight and leukocyte infiltration, and may aid in increasing our understanding of how males and females differ in response to acute muscle injury.

A Rodent Model to Advance the Field Treatment of Crush Muscle Injury During Earthquakes and Other Natural Disasters

Approximately 170 earthquakes of 6.0 or higher magnitude occur annually worldwide. Victims often suffer crush muscle injuries involving impaired blood flow to the affected muscle and damage to the muscle fiber membrane. Current rescue efforts are directed toward preventing acute kidney injury (AKI), which develops upon extrication and muscle reperfusion. But field-usable, muscle-specific interventions may promote muscle regeneration and prevent or minimize the pathologic changes of reperfusion. Although current rodent crush injury models involve reperfusion upon removal of the crush stimulus, an analysis of their methodological aspects is needed to ensure adequate simulation of the earthquake-related crush injury. The objectives of this systematic review are to (a) describe rodent crush muscle injury models, (b) discuss the benefits and limitations of these models, and (c) offer a recommendation for animal models that would increase our understanding of muscle recovery processes after an earthquake-induced crush muscle injury. The most commonly used rodent model uses a clamping or pressing crush stimulus directly applied to murine hindlimb muscle. This model has increased our understanding of muscle regeneration but its open approach does not adequately represent the earthquake-related crush injury. The model we recommend for developing field-usable, muscle-specific interventions is a closed approach that involves a nonclamping crush stimulus. Findings from studies employing this recommended model may have greater relevance for developing interventions that lessen the earthquake’s devastating impact on individual and community health and quality of life, especially in developing countries.

Simulated flight, muscle genetics, and inflammatory indicators in mice.

INTRODUCTION Skeletal muscle discomfort commonly occurs during long-distance air travel. Although the effects of high altitude on muscle have been well-studied, the effects of short-term exposure to the altitude at which aircraft cabins are pressurized, 2438 m, have not. The primary aim of this study was to examine global gene expression in the gastrocnemius muscle after simulated flight. Inflammatory indicators were also assessed in the muscle. METHODS Thirty-five mice were evenly exposed to normobaria or hypobaria (2438 m) for -8-9 h. Microarray and ribonucleic acid (RNA) analyses were performed. Additionally, macrophage and neutrophil presence was examined. RESULTS Fourteen genes were downregulated in females after hypobaria. These genes included those related to epithelial homeostasis, such as the keratins, and genes activated by cellular insult. In contrast, four noncoding, regulatory RNAs were upregulated in males. No difference in proinflammatory cytokine gene and messenger RNA (mRNA) expression was detected between normobaria and hypobaria. The mean number of CD68-positive leukocytes per mm2 and mean area percentage of the CD68 antigen in muscle of normobaric (NB) and hypobaric (HB) mice were 53-54 and -0.2%, respectively. DISCUSSION Simulated flight does not activate a proinflammatory response in healthy muscle. However, epithelial and cellular defense genes may be downregulated in females, whereas regulatory RNAs may be upregulated in males.