Peripheral arterial disease decreases muscle torque and functional walking capacity in elderly

ObjectivesThe aim of this study is to compare values of force–velocity and functional walking capacity in elderly patients with intermittent claudication with respect to the control group.Materials and methodsThe study involved 135 individuals: 85-peripheral arterial disease (PAD) group diagnosed with stage II chronic lower limb ischemia, according to Fontaine's classification, and 50-control group. The studies included an assessment of walking capacity using a six-minute walk test (6MWT) and measurement of force–velocity parameters (peak torque—PTQ, total work—TW, average power—AVGP) of the lower limbs obtained by means of a functional dynamometry under isokinetic conditions.ResultsThe peripheral arterial disease group is characterized by significantly lower values of force–velocity parameters compared to the control group (p < 0.005). Walking capacity in this group is significantly reduced due to significant differences in the distance covered (p < 0.0001), walking speed (p < 0.01), and its intensity (p < 0.01). Further, a positive correlation was found between the maximum distance specified in the six-minute walk test and lower limb muscle strength in the isokinetic test.ConclusionsMean values of all force–velocity parameters and walk distance were significantly higher in the control group than in the peripheral arterial disease group. In the PAD group, in both men and women, the value of the agonist/antagonist ratio of both lower limbs are lower in men and women comparing to the control group. A rehabilitation program for patients with intermittent claudication must consider exercises improving strength, exercise capacity, and endurance in patients with PAD.     

The impact of sarcopenia and exercise training on skeletal muscle satellite cells

It has been well-established that the age-related loss of muscle mass and strength, or sarcopenia, impairs skeletal muscle function and reduces functional performance at a more advanced age. Skeletal muscle satellite cells (SC), as precursors of new myonuclei, have been suggested to be involved in the development of sarcopenia. In accordance with the type II muscle fiber atrophy observed in the elderly, recent studies report a concomitant fiber type specific reduction in SC content. Resistance type exercise interventions have proven effective to augment skeletal muscle mass and improve muscle function in the elderly. In accordance, recent work shows that resistance type exercise training can augment type II muscle fiber size and reverse the age-related decline in SC content. The latter is supported by an increase in SC activation and proliferation factors that generally appear following exercise training. Present findings strongly suggest that the skeletal muscle SC control myogenesis and have an important, but yet unresolved, function in the loss of muscle mass with aging. This review discusses the contribution of skeletal muscle SC in the age-related loss of muscle mass and the efficacy of exercise training as a means to attenuate and/or reverse this process.     

Circuit resistance training is an effective means to enhance muscle strength in older and middle aged adults: A systematic review and meta-analysis

BackgroundPhysical exercise, particularly resistance training (RT), is proven treatment to reduce the accelerated decline in muscle strength exhibited by older adults, but its effect is hindered by low adherence rate, even under well-structured programs.Objective and data sourcesWe investigated the efficacy of circuit resistance training (CRT) on muscle strength, lean mass and aerobic capacity in older adults based on report in MEDLINE, EMBASE, ClinicalTrials.gov and Cochrane electronic (through 8/2016). Study eligibility criteria: middle and older aged men and/or women who followed a structured program, assigned to CRT. Study appraisal and synthesis methods: Out of 237 originally identified articles, 10 articles were included with a total of 362 patients with mean: age −64.5 ± 7.4 years; 3 ± 1.15 sessions/week; session duration 41.8 ± 15.9 min.ResultsUpper body strength modestly increased, by 1.14 kg (95% CI; 0.28–2.00), whereas larger increment was seen in lower body strength (11.99; 2.92–21.06). Higher program volume (>24 sessions) positively influenced upper body strength and aerobic capacity.Limitations(1) variability in the studies’ validity; (2) relatively low number of studies.ConclusionCRT is a valid alternative to conventional RT. Its shorter duration and lower intensity relative to traditional RT, may increase adherence to training in older adults.     

Optimizing the structure and contractility of engineered skeletal muscle thin films

An experimental system was developed to tissue engineer skeletal muscle thin films with well-defined tissue architecture and to quantify the effect on contractility. Using the C2C12 cell line, the authors tested whether tailoring the width and spacing of micropatterned fibronectin lines can be used to increase myoblast differentiation into functional myotubes and maximize uniaxial alignment within a 2-D sheet. Using a combination of image analysis and the muscular thin film contractility assay, it was demonstrated that a fibronectin line width of 100 μm and line spacing of 20 μm is able to maximize the formation of anisotropic, engineered skeletal muscle with consistent contractile properties at the millimeter length scale. The engineered skeletal muscle exhibited a positive force–frequency relationship, could achieve tetanus and produced a normalized peak twitch stress of 9.4 ± 4.6 kPa at 1 Hz stimulation. These results establish that micropatterning technologies can be used to control skeletal muscle differentiation and tissue architecture and, in combination with the muscular thin film contractility, assay can be used to probe structure–function relationships. More broadly, an experimental platform is provided with the potential to examine how a range of microenvironmental cues such as extracellular matrix protein composition, micropattern geometries and substrate mechanics affect skeletal muscle myogenesis and contractility.     

Skeletal muscle regeneration and impact of aging and nutrition

After skeletal muscle injury a regeneration process takes place to repair muscle. Skeletal muscle recovery is a highly coordinated process involving cross-talk between immune and muscle cells. It is well known that the physiological activities of both immune cells and muscle stem cells decline with advancing age, thereby blunting the capacity of skeletal muscle to regenerate. The age-related reduction in muscle repair efficiency contributes to the development of sarcopenia, one of the most important factors of disability in elderly people. Preserving muscle regeneration capacity may slow the development of this syndrome. In this context, nutrition has drawn much attention: studies have demonstrated that nutrients such as amino acids, n-3 polyunsaturated fatty acids, polyphenols and vitamin D can improve skeletal muscle regeneration by targeting key functions of immune cells, muscle cells or both. Here we review the process of skeletal muscle regeneration with a special focus on the cross-talk between immune and muscle cells. We address the effect of aging on immune and skeletal muscle cells involved in muscle regeneration. Finally, the mechanisms of nutrient action on muscle regeneration are described, showing that quality of nutrition may help to preserve the capacity for skeletal muscle regeneration with age.     

Endurance training reduces exercise-induced acidosis and improves muscle function in a mouse model of sickle cell disease

Sickle cell disease (SCD) mice (Townes model of SCD) presented exacerbated exercise-induced acidosis and fatigability as compared to control animals. We hypothesize that endurance training could represent a valuable approach to reverse these muscle defects. Endurance-trained HbAA (HbAA-END, n = 10), HbAS (HbAS-END, n = 11) and HbSS (HbSS-END, n = 8) mice were compared to their sedentary counterparts (10 HbAA-SED, 10 HbAS-SED and 9 HbSS-SED mice) during two rest – exercise – recovery protocols during which muscle energetics and function were measured. In vitro analyses of some proteins involved in muscle energetics, pH regulation and oxidative stress were also performed. Exercise-induced acidosis was lower in HbSS-END mice as compared to their sedentary counterparts during both moderate (p < 0.001) and intense (p < 0.1) protocols. The total force production measured during both protocols was higher in trained mice compared to sedentary animals. In vitro analyses revealed that enolase/citrate synthase ratio was reduced in HbSS-END (p < 0.001) and HbAS-END (p < 0.01) mice compared to their sedentary counterparts. In addition, malondialdehyde concentration was reduced in trained mice (p < 0.05). In conclusion, endurance training would reverse the more pronounced exercise-induced acidosis, reduce oxidative stress and ameliorate some of the muscle function parameters in SCD mice.     

Regenerative function of immune system: Modulation of muscle stem cells

Ageing is characterised by progressive deterioration of physiological systems and the loss of skeletal muscle mass is one of the most recognisable, leading to muscle weakness and mobility impairments. This review highlights interactions between the immune system and skeletal muscle stem cells (widely termed satellite cells or myoblasts) to influence satellite cell behaviour during muscle regeneration after injury, and outlines deficits associated with ageing. Resident neutrophils and macrophages in skeletal muscle become activated when muscle fibres are damaged via stimuli (e.g. contusions, strains, avulsions, hyperextensions, ruptures) and release high concentrations of cytokines, chemokines and growth factors into the microenvironment. These localised responses serve to attract additional immune cells which can reach in excess of 1 × 10⁵ immune cell/mm³ of skeletal muscle in order to orchestrate the repair process. T-cells have a delayed response, reaching peak activation roughly 4 days after the initial damage. The cytokines and growth factors released by activated T-cells play a key role in muscle satellite cell proliferation and migration, although the precise mechanisms of these interactions remain unclear. T-cells in older people display limited ability to activate satellite cell proliferation and migration which is likely to contribute to insufficient muscle repair and, consequently, muscle wasting and weakness. If the factors released by T-cells to activate satellite cells can be identified, it may be possible to develop therapeutic agents to enhance muscle regeneration and reduce the impact of muscle wasting during ageing and disease.     

Life-long endurance exercise in humans: Circulating levels of inflammatory markers and leg muscle size

Human aging is associated with a loss of skeletal muscle and an increase in circulating inflammatory markers. It is unknown whether endurance training (Tr) can prevent these changes. Therefore we studied 15 old trained (O-Tr) healthy males and, for comparison, 12 old untrained (O-Un), 10 Young-Tr (Y-Tr) and 12 Young-Un (Y-Un). Quadriceps size, VO₂ peak, CRP, IL-6, TNF-α and its receptors, suPAR, lipid profile, leucocytes and glucose homeostasis were measured. Tr was associated with an improved insulin profile (p < 0.05), and lower leucocyte (p < 0.05) and triglyceride levels (p < 0.05), independent of age. Aging was associated with poorer glucose control (p < 0.05), independent of training. The age-related changes in waist circumference, VO₂ peak, cholesterol, LDL, leg muscle size, CRP and IL-6 were counteracted by physical activity (p < 0.05). A significant increase in suPAR with age was observed (p < 0.05). Most importantly, life-long endurance exercise was associated with a lower level of the inflammatory markers CRP and IL-6 (p < 0.05), and with a greater thigh muscle area (p < 0.05), compared to age-matched untrained counterparts. These findings in a limited group of individuals suggest that regular physical endurance activity may play a role in reducing some markers of systemic inflammation, even within the normal range, and in maintaining muscle mass with aging.     

Age-related changes in resting energy expenditure in normal weight,overweight and obese men and women

ObjectivesAging is associated with changes in resting energy expenditure (REE) and body composition. We investigated the association between age and changes in REE in men and women stratified by body mass index (BMI) categories (normal weight, overweight and obesity). We also examined whether the age-related decline in REE was explained by concomitant changes in body composition and lifestyle factors.Study designCross-sectional.Main outcome measures3442 adult participants (age range: 18–81 y; men/women: 977/2465) were included. The BMI range was 18.5–60.2 kg/m². REE was measured by indirect calorimetry in fasting conditions and body composition by bioelectrical impedance. Regression models were used to evaluate age-related changes in REE in subjects stratified by sex and BMI. Models were adjusted for body composition (fat mass, fat free mass), smoking, disease count and physical activity.ResultsIn unadjusted models, the rate of decline in REE was highest in obese men (slope = −8.7 ± 0.8 kcal/day/year) whereas the lowest rate of decline was observed in normal weight women (−2.9 ± 0.3 kcal/day/year). Gender differences were observed for the age of onset of REE adaptive changes (i.e., not accounted by age related changes in body composition and lifestyle factors). In women, adaptive changes appeared to occur in middle-age (∼47 y) across all BMI groups whereas changes seemed to be delayed in obese men (∼54 y) compared to overweight (∼43 y) and normal weight (∼39 y) men.ConclusionsSex and BMI influenced the rate and degree of the age-related decline in REE. Critical age windows have been identified for the onset of putative mechanisms of energy adaptation. These findings require confirmation in prospective studies.     

Sarcopenic obesity or obese sarcopenia: A cross talk between age-associated adipose tissue and skeletal muscle inflammation as a main mechanism of the pathogenesis

Sarcopenia, an age-associated decline in skeletal muscle mass coupled with functional deterioration, may be exacerbated by obesity leading to higher disability, frailty, morbidity and mortality rates. In the combination of sarcopenia and obesity, the state called sarcopenic obesity (SOB), some key age- and obesity-mediated factors and pathways may aggravate sarcopenia. This review will analyze the mechanisms underlying the pathogenesis of SOB. In obese adipose tissue (AT), adipocytes undergo hypertrophy, hyperplasia and activation resulted in accumulation of pro-inflammatory macrophages and other immune cells as well as dysregulated production of various adipokines that together with senescent cells and the immune cell-released cytokines and chemokines create a local pro-inflammatory status. In addition, obese AT is characterized by excessive production and disturbed capacity to store lipids, which accumulate ectopically in skeletal muscle. These intramuscular lipids and their derivatives induce mitochondrial dysfunction characterized by impaired β-oxidation capacity and increased reactive oxygen species formation providing lipotoxic environment and insulin resistance as well as enhanced secretion of some pro-inflammatory myokines capable of inducing muscle dysfunction by auto/paracrine manner. In turn, by endocrine manner, these myokines may exacerbate AT inflammation and also support chronic low grade systemic inflammation (inflammaging), overall establishing a detrimental vicious circle maintaining AT and skeletal muscle inflammation, thus triggering and supporting SOB development. Under these circumstances, we believe that AT inflammation dominates over skeletal muscle inflammation. Thus, in essence, it redirects the vector of processes from “sarcopenia → obesity” to “obesity → sarcopenia”. We therefore propose that this condition be defined as “obese sarcopenia”, to reflect the direction of the pathological pathway.     

Skeletal muscle contractility is preserved in COPD patients with normal fat‐free mass

Aim: Peripheral muscle dysfunction often occurs in patients with chronic obstructive pulmonary disease (COPD). The muscle dysfunction may be caused by a loss of force‐generating capacity, resulting from a loss of muscle mass, as well as by other alterations in contractile properties of skeletal muscle. Methods: The maximal isometric voluntary strength and fatigability were determined in hand‐grip and quadriceps muscles from nine male COPD patients (FEV₁ 30–50% predicted) and control subjects matched for fat‐free mass (FFM), physical activity level and age. Contractile properties and fatigability of the quadriceps muscle were also studied with electrically evoked isometric contractions. Results: The maximal voluntary force (MVC) and fatigability of the handgrip muscle did not differ between the COPD patients and control subjects. Also the MVC of the quadriceps muscle and the rate of force rise, contraction time, force–frequency relationship and fatigability, as determined with electrically evoked contractions, were similar in patients with COPD and control subjects. Conclusion: Skeletal muscle strength, contractile properties and fatigability are preserved in patients with moderate COPD and a normal FFM and activity level. This suggests that skeletal muscle dysfunction does not take place during moderate COPD until cachexia and/or a decline in physical activity occur.     

The effect of vertical whole-body vibration on lower limb muscle activation in elderly adults: Influence of vibration frequency,amplitude and exercise

ObjectiveThis study aimed to investigate how whole-body vibration (WBV) and exercise and their interactions influenced leg muscle activity in elderly adults.Study designAn experimental study with repeated measures design that involved a group of ambulatory, community-dwelling elderly adults (n = 30; 23 women; mean age = 61.4 ± 5.3 years).Main outcome measuresMuscle activity of the vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius (GS) was measured by surface electromyography (EMG), while participants were performing seven different exercises during 4 WBV conditions (condition 1: frequency = 30 Hz, amplitude = 0.6 mm, intensity = 2.25 units of Earth’s gravity (g); condition 2: 30 Hz, 0.9 mm, 3.40 g; condition 3: 40 Hz, 0.6 mm, 3.65 g; condition 4: 40 Hz, 0.9 mm, 5.50 g) and a no-WBV condition in a single experimental session.ResultsSignificantly greater muscle activity was recorded in VL (3%–148%), BF (16%–202%), and GS (19% –164%) when WBV was added to the exercises, compared with the same exercises without WBV (p ≤ 0.015). The effect of vibration intensity on EMG amplitude was exercise-dependent in VL (p = 0.002), and this effect was marginally significant in GS (p = 0.052). The EMG activity induced by the four WBV intensities was largely similar, and was the most pronounced during static erect standing and static single-leg standing.ConclusionsThe EMG amplitude of majority of leg muscles tested was significantly greater during WBV exposure compared with the no-WBV condition. Low-intensity WBV can induce muscle activity as effectively as higher-intensity protocols, and may be the preferred choice for frail elderly adults.     

Resistance training, and IGF involvement in the maintenance of muscle mass during the aging process

Sarcopenia is the decline of muscle mass and strength with age. Sarcopenia leads to significant impairment in the ability to carry out normal daily function and thus there is a great need for interventions that will lead to muscle regeneration and repair in the aging population. Age-related sarcopenia in humans, characterized by loss of type I and type II muscle fibers and a decrease in fiber cross-sectional area primarily in type II fibers, can be attenuated by mechanical load on the muscle, which increases cross-sectional area of the remaining fibers, but does not restore fiber numbers characteristic of young muscle. Considerable evidence also implicates age-related declines in muscle insulin-like growth factor action in sarcopenia. IGF-I promotes myoblast proliferation, differentiation, and protein accretion in muscle through multiple signaling mechanisms, including the PI3-kinase, MAP kinase and calcineurin pathways. Exercise and injury induce increases in IGF-I, IGF-I receptors and IGF-I-activated signaling pathways. Although there is evidence that aging muscle retains the ability to synthesize IGF-I, there is also evidence that aging may be associated with attenuation of the ability of exercise to induce an isoform of IGF-I that promotes satellite cell proliferation. Moreover, aging muscle may be resistant to IGF-I, an effect that is reversed by exercise. However, it is clear that over-expression of IGF-I in muscle can protect against age-related sarcopenia.     

Gender differences in strength and muscle fiber characteristics

Summary Strength and muscle characteristics were examined in biceps brachii and vastus lateralis of eight men and eight women. Measurements included motor unit number, size and activation and voluntary strength of the elbow flexors and knee extensors. Fiber areas and type were determined from needle biopsies and muscle areas by computerized tomographical scanning. The women were approximately 52% and 66% as strong as the men in the upper and lower body respectively. The men were also stronger relative to lean body mass. A significant correlation was found between strength and muscle cross-sectional area (CSA; P0.05). The women had 45, 41, 30 and 25% smaller muscle CSAs for the biceps brachii, total elbow flexors, vastus lateralis and total knee extensors respectively. The men had significantly larger type I fiber areas (4597 vs 3483 m²) and mean fiber areas (6632 vs 3963 m²) than the women in biceps brachii and significantly larger type II fiber areas (7700 vs 4040 m²) and mean fiber areas (7070 vs 4290 m²) in vastus lateralis. No significant gender difference was found in the strength to CSA ratio for elbow flexion or knee extension, in biceps fiber number (180 620 in men vs 156 872 in women), muscle area to fiber area ratio in the vastus lateralis 451 468 vs 465 007) or any motor unit characteristics. Data suggest that the greater strength of the men was due primarily to larger fibers. The greater gender difference in upper body strength can probably be attributed to the fact that women tend to have a lower proportion of their lean tissue distributed in the upper body. It is difficult to determine the extent to which the larger fibers in men represent a true biological difference rather that a difference in physical activity, but these data suggest that it is largely an innate gender difference.     

Effects of age and nerve-repair grafts on reinnervation and fiber type distribution of rat medial gastrocnemius muscles

Aging is associated with a decline in skeletal muscle function. Previous research suggests that this decline in skeletal muscle function may, in part, be explained by an age-associated decline in the ability of skeletal muscle to reinnervate and/or age-associated changes in fiber types and distribution during reinnervation. This study used a nerve-repair graft model to investigate age-associated changes in the ability to reinnervate via expression of neural cell adhesion molecule (NCAM), a marker of denervated and recently reinnervated muscle fibers and changes in fiber type and Type I fiber grouping in medial gastrocnemius (MG) muscles of 6-, 12- and 24-month-old male Fischer 344 rats. Age had no effect on total MG muscle fiber number. Aging and nerve-repair grafting led to an increase in percent Type I and a decrease in percent Type IIB fibers. Aging and nerve-repair grafting led to an increase in NCAM positive fibers and an increase in the percentage of enclosed Type I muscle fibers, which was greatest in the 24 month nerve-repair grafted group. Thus, we conclude that diminished contractile function of aged and/or nerve-repair grafted MG muscle may be explained, in part, by an increase in the percentage of denervated fibers.     

Muscular architecture of the popliteus muscle and the basic science implications

BackgroundThe function of the popliteus muscle is largely treated as a static stabilizer and has a lack of basic muscular architectural data to enable study of its dynamic function. A large volume of literature supports its static function and the essential need for reconstruction in the posterolateral knee when injured to restore knee stability.Hypothesis/purposeWe hypothesize that the popliteus muscle is more significant as a dynamic presence in the knee.MethodsA collection of popliteus architectural data was collected from 28 cadaver specimens (mean (SD) 76 years (11)). Physiological cross-sectional area of the popliteus and semimembranosus muscles were calculated from muscle volume and fiber length to power future muscle force prediction models. Posterior knee muscle trajectories were measured with respect to the longitudinal axis of the tibia. A 2-tailed T test was performed.ResultsSignificant differences between males and females were found for both the popliteus (p = 1.1E − 05) and semimembranosus (p = 2.0E–05) muscle volumes. Significant differences between males and females were also found in PCSA for the popliteus (p = 0.005) and semimembranosus (p = 4.1E–05) muscles. There were no significant differences in fiber length, overall muscle length (with tendon removed), age, and orientation.ConclusionFurther consideration should be given to include the popliteus muscle as a dynamic entity in the knee given its mechanical properties, trajectory, and prior biomechanical evidence showing when and how it is activated. The present study provides data that may shape future directions of research and treatment with regard to posterolateral corner injuries and ligamentous balancing of the knee.     

Mitochondrial DNA mutations, energy metabolism and apoptosis in aging muscle

Locomotor functional decline and loss in muscle mass with age is virtually a universal characteristic that has been documented in several species, including worms, fruit flies, rodents, non-human primates and humans. The age-related loss of muscle mass and strength (sarcopenia) represents an important risk factor for disability and mortality in older subjects and has been linked with cellular energy deficit and increased apoptosis at old age. Many key theories on aging describing the mechanisms underlying sarcopenia are now focused on the mitochondria because of their dichotomous role in controlling life and death processes within myocytes. Mitochondria represent the main producers of cellular energy in the form of adenosine triphosphate, but are also considered a key regulatory center of apoptosis. Unknown factors leading to a decrease in aerobic energy efficiency are linked with mitochondrial mutations which may result into apoptosis. Moreover, deregulation of autophagy (degradation and recycling of long-lived protein and organelles, such as the mitochondria) in post-mitotic tissue might also be responsible for the age-associated cellular energy failure. Alterations in specific signaling pathways, such as AMP-activated protein kinases, play a role in both cell survival response and apoptotic response depending on energy depletion. Evidence supports that apoptosis occurring in aging skeletal muscle may be due, in part, to the progressive decline in mitochondrial function and the resulting energy depletion within the cell. In turn, mitochondrial dysfunction is partly due to the accumulation of oxidative damage to macromolecules, including mitochondrial DNA, RNA and proteins, essential components for optimal functioning of mitochondria. Evidence concerning these series of events leading to energy depletion and apoptosis are discussed.     

Migration of dendritic cells from murine skeletal muscle

To better understand the role of dendritic cells (DCs) in skeletal muscle, we investigated the migration of DCs from murine skeletal muscle and compared that to previously studied footpad (FP) DC trafficking. We adoptively transferred carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled mature DCs to syngeneic mice and followed them in various lymphatic tissues at different time points. Injection of DCs into the tibialis anterior muscle resulted in the peak number of CFSE⁺ DCs recovered in spleen at 12 h, not at 24 h, when the largest number of these cells appeared in the draining lymph nodes. Interestingly, this result for adoptive transfer of DCs to skeletal muscle differs with what is previously reported for adoptive transfer to the FP, a result that we also confirmed in parallel studies. These findings could have a significant impact on (1) understanding muscle diseases with immunological complications such as muscular dystrophies and (2) the immunologic effects of treatments for muscle diseases.     

The effect of the nonionic block copolymer pluronic P85 on gene expression in mouse muscle and antigen-presenting cells

DNA vaccines can be greatly improved by polymer agents that simultaneously increase transgene expression and activate immunity. We describe here Pluronic P85 (P85), a triblock copolymer of ethylene oxide (EO) and propylene oxide (PO) EO₂₆–PO₄₀–EO₂₆. Using a mouse model we demonstrate that co-administration of a bacterial plasmid DNA with P85 in a skeletal muscle greatly increases gene expression in the injection site and distant organs, especially the draining lymph nodes and spleen. The reporter expression colocalizes with the specific markers of myocytes and keratinocytes in the muscle, as well as dendritic cells (DCs) and macrophages in the muscle, lymph nodes and spleen. Furthermore, DNA/P85 and P85 alone increase the systemic expansion of CD11c⁺ (DC), and local expansion of CD11c⁺, CD14⁺ (macrophages) and CD49b⁺ (natural killer) cell populations. DNA/P85 (but not P85) also increases maturation of local DC (CD11c + CD86⁺, CD11c + CD80⁺, and CD11c + CD40⁺). We suggest that DNA/P85 promotes the activation and recruitment of the antigen-presenting cells, which further incorporate, express and carry the transgene to the immune system organs.