The effect of chronic skeletal muscle stimulation on capillary growth in the rat: are sensory nerve fibres involved?

Electrotherapy for urethral modulation: Are extracellular matrix molecules and growth factors potential targets?

AIMS

To evaluate the expression of genes and proteins involved in the urethral components: vessels, nerves, and extracellular matrix, in female rats after trauma by vaginal distension (VD) and after electrical stimulation therapy (electrotherapy).

METHODS

We analyzed the urethras of three groups of 18 female rats 30 days posttrauma by VD: control (no interventions); trauma (animals that had VD); and electrotherapy group (those that had VD and were treated with electrical stimulation). We compared the expression of vascular endothelial growth factor (VEGF), nerve growth factor (NGF), collagen types I and III (COL1a1 and COL3a1), and lysyl-oxidase like 1 (LOXL1) among the groups. Real-time reverse transcription-polymerase chain reaction, Western blot, and immunohistochemistry were used for molecule quantification. We used the Kruskal-Wallis test and analysis of variance for statistical analyses with p < 0.05 for significance.

RESULTS

The COL1a1 gene expression was higher in the electrotherapy group than the trauma group (p = 0.036). COL3a1, VEGF, NGF, LOXL1 messenger RNA (mRNA) expression did not differ among the groups (p ≥ 0.05). COL1a1, COL3a1, VEGF, NGF, LOXL1 protein levels did not significantly differ among the groups (p ≥ 0.05) in Western blot analysis or immunohistochemistry assays.

CONCLUSIONS

Electrotherapy caused a long-term increase in the COL1a1 mRNA level but did not change COL1a1 protein expression or VEGF, NGF, COL3a1, and LOXL1 genes and proteins in the urethras of rats after trauma by VD.

Skeletal Muscle Microvascular Changes in Response to Short-Term Blood Flow Restricted Training-Exercise-Induced Adaptations and Signs of Perivascular Stress

Aim: Previous reports suggest that low-load muscle exercise performed under blood flow restriction (BFR) may lead to endurance adaptations. However, only few and conflicting results exist on the magnitude and timing of microvascular adaptations, overall indicating a lack of angiogenesis with BFR training. The present study, therefore, aimed to examine the effect of short-term high-frequency BFR training on human skeletal muscle vascularization.

Methods: Participants completed 3 weeks of high-frequency (one to two daily sessions) training consisting of either BFR exercise [(BFRE) n = 10, 22.8 ± 2.3 years; 20% one-repetition maximum (1RM), 100 mmHg] performed to concentric failure or work-matched free-flow exercise [(CON) n = 8, 21.9 ± 3.0 years; 20% 1RM]. Muscle biopsies [vastus lateralis (VL)] were obtained at baseline, 8 days into the intervention, and 3 and 10 days after cessation of the intervention to examine capillary and perivascular adaptations, as well as angiogenesis-related protein signaling and gene expression.

Results: Capillary per myofiber and capillary area (CA) increased 21–24 and 25–34%, respectively, in response to BFRE (P < 0.05–0.01), while capillary density (CD) remained unchanged. Overall, these adaptations led to a consistent elevation (15–16%) in the capillary-to-muscle area ratio following BFRE (P < 0.05–0.01). In addition, evaluation of perivascular properties indicated thickening of the perivascular basal membrane following BFRE. No or only minor changes were observed in CON.

Conclusion: This study is the first to show that short-term high-frequency, low-load BFRE can lead to microvascular adaptations (i.e., capillary neoformation and changes in morphology), which may contribute to the endurance effects previously documented with BFR training. The observation of perivascular membrane thickening suggests that high-frequency BFRE may be associated with significant vascular stress.

The Experimental Pathology at Ancona: 50 Years of Exciting and Pioneering Research on Human Pathology

Half century ago, a few academic pioneers founded the laboratories of experimental and ultrastructural pathology in Ancona. From this origin, a new phase of experimental studies developed aimed at translational and clinical research up to the present, when our group is internationally recognized for its fundamental contributions in gerontological research and molecular diagnostic pathology. Since the desire of immortality and of eternal youth seems to be as old as mankind, in the future we plan to focus our scientific research on Regenerative Medicine and Rejuvenation strategies. This is the most ambitious aim in the framework of the world aging population. We do not know whether we would achieve these results by ourselves. We are confident that, as in the past, new generations of scientist of the school of experimental pathology at Ancona will get the baton by the older one and lead the future with the same enthusiasm, love and commitment.

Unilateral muscle overuse causes bilateral changes in muscle fiber composition and vascular supply

Unilateral strength training can cause cross-transfer strength effects to the homologous contralateral muscles. However, the impact of the cross-over effects on the muscle tissue is unclear. To test the hypothesis that unilateral muscle overuse causes bilateral alterations in muscle fiber composition and vascular supply, we have used an experimental rabbit model with unilateral unloaded overstrain exercise via electrical muscle stimulation (E/EMS). The soleus (SOL) and gastrocnemius (GA) muscles of both exercised (E) and contralateral non-exercised (NE) legs (n = 24) were morphologically analyzed after 1 w, 3 w and 6 w of EMS. Non-exercised rabbits served as controls (n = 6). After unilateral intervention the muscles of both E and NE legs showed myositis and structural and molecular tissue changes that to various degrees mirrored each other. The fiber area was bilaterally smaller than in controls after 3 w of E/EMS in both SOL (E 4420 and NE 4333 µm2 vs. 5183 µm2, p<0.05) and GA (E 3572 and NE 2983 µm2 vs. 4697 µm2, p<0.02) muscles. After 6 w of E/EMS, the percentage of slow MyHCI fibers was lower than in controls in the NE legs of SOL (88.1% vs. 98.1%, p<0.009), while the percentage of fast MyHCIIa fibers was higher in the NE legs of GA (25.7% vs. 15.8%, p = 0.02). The number of capillaries around fibers in the E and NE legs was lower (SOL 13% and 15%, respectively, GA 25% and 23%, respectively, p<0.05) than in controls. The overall alterations were more marked in the fast GA muscle than in the slow SOL muscle, which on the other hand showed more histopathological muscle changes. We conclude that unilateral repetitive unloaded overuse exercise via EMS causes myositis and muscle changes in fiber type proportions, fiber area and fiber capillarization not only in the exercised leg, but also in the homologous muscles in the non-exercised leg.

Intussusceptive angiogenesis: expansion and remodeling of microvascular networks

Intussusceptive angiogenesis is a dynamic intravascular process capable of dramatically modifying the structure of the microcirculation. The distinctive structural feature of intussusceptive angiogenesis is the intussusceptive pillar--a cylindrical microstructure that spans the lumen of small vessels and capillaries. The extension of the intussusceptive pillar appears to be a mechanism for pruning redundant or inefficient vessels, modifying the branch angle of bifurcating vessels and duplicating existing vessels. Despite the biological importance and therapeutic potential, intussusceptive angiogenesis remains a mystery, in part, because it is an intravascular process that is unseen by conventional light microscopy. Here, we review several fundamental questions in the context of our current understanding of both intussusceptive and sprouting angiogenesis. (1) What are the physiologic signals that trigger pillar formation? (2) What endothelial and blood flow conditions specify pillar location? (3) How do pillars respond to the mechanical influence of blood flow? (4) What biological influences contribute to pillar extension? The answers to these questions are likely to provide important insights into the structure and function of microvascular networks.

Circulating angiogenic biomolecules at rest and in response to upper-limb exercise in individuals with spinal cord injury

OBJECTIVE

Individuals with spinal cord injury (SCI) show structural and functional vascular maladaptations and muscle loss in their lower limbs. Angiogenic biomolecules play important roles in physiological and pathological angiogenesis, and are implicated in the maintenance of muscle mass. This study examined the responses of angiogenic molecules during upper-limb aerobic exercise in patients with SCI and in able-bodied (AB) individuals.

METHODS

Eight SCI patients with thoracic lesions (T6-T12, ASIA A) and eight AB individuals performed an arm-cranking exercise for 30 minutes at 60% of their VO2max. Plasma concentrations of vascular endothelial growth factor (VEGF-A165), VEGF receptor 1 (sVEGFr-1), VEGF receptor 2 (sVEGFr-2), metalloproteinase 2 (MMP-2), and endostatin were measured at rest, after exercise, and at 1.5 and 3.0 hours during recovery.

RESULTS

The two-way analysis of variance showed non-significant main effects of "group" and significant main effects of "time/exercise" for all angiogenic biomolecules examined (P < 0.01-0.001). The arm-cranking exercise significantly increased plasma concentrations of VEGF, sVEGFr-1, sVEGFr-2, MMP-2, and endostatin in both groups (P < 0.001-0.01). The magnitude of the increase was similar in both patients with SCI and AB individuals, as shown by the non-significant group × time interaction for all angiogenic parameters.

CONCLUSIONS

Upper-limb exercise (arm-cranking for 30 minutes at 60% of VO2max) is a sufficient stimulus to trigger a coordinated circulating angiogenic response in patients with SCI. The response of angiogenic molecules to upper-limb aerobic exercise in SCI appears relatively similar to that observed in AB individuals.

Bilateral increase in expression and concentration of tachykinin in a unilateral rabbit muscle overuse model that leads to myositis

Background

Tachykinins can have pro-inflammatory as well as healing effects during tissue reorganization and inflammation. Recent studies report an up-regulation in the expression of the substance P (SP)-preferred receptor, the neurokinin-1 receptor, in marked muscle inflammation (myositis). There is, however, only very little information on the expression patterns and levels of tachykinins in this situation.

Methods

The tachykinin system was analyzed using a rabbit experimental model of muscle overuse, whereby unilateral muscle exercise in combination with electrical stimulation led to muscle derangement and myositis in the triceps surae muscle (experimental length 1–6 weeks). Evaluations were made for both parts of the muscle (soleus and gastrocnemius muscles) in experimental and non-experimental (contralateral) sides. Morphologic evaluation, immunohistochemistry, in situ hybridization and enzyme immunoassay (EIA) analyses were applied.

Results

Myositis and muscle derangement occurred focally not only in the experimental side but also in the non-experimental side. In the inflammatory areas (focal myositis areas), there were frequent nerve fibers showing tachykinin-like immunoreactivity and which were parts of nerve fascicles and which were freely dispersed in the tissue. Cells in the inflammatory infiltrates showed tachykinin-like immunoreactivity and tachykinin mRNA expression. Specific immunoreactivity and mRNA expression were noted in blood vessel walls of both sides, especially in focally affected areas. With increasing experimental length, we observed an increase in the degree of immunoreactivity in the vessel walls. The EIA analyses showed that the concentration of tachykinin in the tissue on both sides increased in a time-dependent manner. There was a statistical correlation in the concentration of tachykinin and the level of tachykinin immunoreactivity in the blood vessel walls between experimental and non-experimental sides.

Conclusions

The observations show an up-regulation of the tachykinin system bilaterally during muscle derangement/myositis in response to pronounced unilateral muscle overuse. This up-regulation occurred in inflammatory areas and was related not only to increased tachykinin innervation but also to tachykinin expression in blood vessel walls and inflammatory cells. Importantly, the tachykinin system appears to be an important factor not only ipsilaterally but also contralaterally in these processes.

Marked Effects of Tachykinin in Myositis Both in the Experimental Side and Contralaterally: Studies on NK-1 Receptor Expressions in an Animal Model

Muscle injury and inflammation (myositis) in a rabbit model of an unilateral muscle overuse were examined. It is unknown if the tachykinin system has a functional role in this situation. In this study, therefore, the neurokinin-1 receptor (NK-1R) expression patterns were evaluated. White blood cells, nerve fascicles, fine nerve fibers, and blood vessel walls in myositis areas showed NK-1R immunoreaction. NK-1R mRNA reactions were observable for white blood cells and blood vessel walls of these areas. NK-1R immunoreaction and NK-1R mRNA reactions were also seen for muscle fibers showing degenerative and regenerative features. There were almost no NK-1R immunoreactions in normal muscle tissue. Interestingly, marked NK-1R expressions were seen for myositis areas of both the experimental side and the contralateral nonexperimental side. EIA analyses showed that the concentration of substance P in the muscle tissue was clearly increased bilaterally at the experimental end stage, as compared to the situation for normal muscle tissue. These observations show that the tachykinin system is very much involved in the processes that occur in muscle injury/myositis. The effects can be related to proinflammatory effects and/or tissue repair. The fact that there are also marked NK-1R expressions contralaterally indicate that the tachykinin system has crossover effects.

Effects on contralateral muscles after unilateral electrical muscle stimulation and exercise

It is well established that unilateral exercise can produce contralateral effects. However, it is unclear whether unilateral exercise that leads to muscle injury and inflammation also affects the homologous contralateral muscles. To test the hypothesis that unilateral muscle injury causes contralateral muscle changes, an experimental rabbit model with unilateral muscle overuse caused by a combination of electrical muscle stimulation and exercise (EMS/E) was used. The soleus and gastrocnemius muscles of both exercised and non-exercised legs were analyzed with enzyme- and immunohistochemical methods after 1, 3 and 6 weeks of repeated EMS/E. After 1 w of unilateral EMS/E there were structural muscle changes such as increased variability in fiber size, fiber splitting, internal myonuclei, necrotic fibers, expression of developmental MyHCs, fibrosis and inflammation in the exercised soleus muscle. Only limited changes were found in the exercised gastrocnemius muscle and in both non-exercised contralateral muscles. After 3 w of EMS/E, muscle fiber changes, presence of developmental MyHCs, inflammation, fibrosis and affections of nerve axons and AChE production were observed bilaterally in both the soleus and gastrocnemius muscles. At 6 w of EMS/E, the severity of these changes significantly increased in the soleus muscles and infiltration of fat was observed bilaterally in both the soleus and the gastrocnemius muscles. The affections of the muscles were in all three experimental groups restricted to focal regions of the muscle samples. We conclude that repetitive unilateral muscle overuse caused by EMS/E overtime leads to both degenerative and regenerative tissue changes and myositis not only in the exercised muscles, but also in the homologous non-exercised muscles of the contralateral leg. Although the mechanism behind the contralateral changes is unclear, we suggest that the nervous system is involved in the cross-transfer effects.

Physiological factors influencing capillary growth

(1) Angiogenesis (growth of new capillaries from an existing capillary bed) may result from a mismatch in microvascular supply and metabolic demand (metabolic error signal). Krogh examined the distribution and number of capillaries to explore the correlation between O(2) delivery and O(2) consumption. Subsequently, the heterogeneity in angiogenic response within a muscle has been shown to reflect either differences in fibre type composition or mechanical load. However, local control leads to targetted angiogenesis in the vicinity of glycolytic fibre types following muscle stimulation, or oxidative fibres following endurance training, while heterogeneity of capillary spacing is maintained during ontogenetic growth. (2) Despite limited microscopy resolution and lack of specific markers, Krogh's interest in the structure of the capillary wall paved the way for understanding the mechanisms of capillary growth. Angiogenesis may be influenced by the response of perivascular or stromal cells (fibroblasts, macrophages and pericytes) to altered activity, likely acting as a source for chemical signals modulating capillary growth such as vascular endothelial growth factor. In addition, haemodynamic factors such as shear stress and muscle stretch play a significant role in adaptive remodelling of the microcirculation. (3) Most indices of capillarity are highly dependent on fibre size, resulting in possible bias because of scaling. To examine the consequences of capillary distribution, it is therefore helpful to quantify the area of tissue supplied by individual capillaries. This allows the spatial limitations inherent in most models of tissue oxygenation to be overcome generating an alternative approach to Krogh's tissue cylinder, the capillary domain, to improve descriptions of intracellular oxygen diffusion.

Attenuation of changes in capillary fine structure and leukocyte adhesion improves muscle performance following chronic ischaemia in rats

Acute ischaemia-reperfusion disrupts capillary fine structure and increases leukocyte adhesion in postcapillary venules. We determined whether chronic muscle ischaemia has similar consequences, and whether it is possible to ameliorate its effect on muscle performance. Following ischaemia (unilateral ligation, common iliac artery) rat hindlimb muscles were examined without other intervention or following treatment with an xanthine oxidase inhibitor (allopurinol), a Na(+)/H(+) exchange blocker (amiloride), or an oxygen free radical scavenger (vitamin E). No significant leukocyte adhesion or rolling, nor changes in capillary fine structure were observed 3 days postsurgery, when limb use was limited. However, leukocyte rolling and adhesion almost trebled by 7 days (P < 0.001), when normal gait was largely restored. Capillary fine structure was disturbed over a similar time course, e.g. relative endothelial volume (control 46%, 7 days 61%; P < 0.05), that resolved by 5 weeks. Where activity was increased by mild electrical stimulation 3 days after ligation muscles showed enhanced capillary swelling (endothelial volume 66% versus 50%, P < 0.005), but improved fatigue index (52% versus 16%, P < 0.001) as a result of greater blood flow. Muscle fatigue after ligation was related to the extent of contraction-induced hyperaemia (R(2) = 0.725), but not capillary swelling. Amiloride, and to a lesser extent allopurinol but not vitamin E, significantly decreased leukocyte rolling and adhesion, as well as capillary endothelial swelling. We conclude that increased activity of ischaemic muscles on recovery is likely to accentuate acidosis accompanying changes in microcirculation and contribute to enhanced muscle fatigue, whereas formation of oxygen free radicals may be attenuated by endogenous protective mechanisms.

Eletroestimulação muscular: alternativa de tratamento coadjuvante para pacientes com doença arterial obstrutiva periférica

A doença arterial periférica faz parte de um grupo de patologias vasculares que evolui de forma lenta e progressiva. A proposta deste artigo foi avaliar, por meio de revisão bibliográfica, os possíveis benefícios da eletroestimulação crônica como tratamento coadjuvante para pacientes arteriopatas. De acordo com a literatura analisada, concluímos que a eletroestimulação é capaz de provocar alterações importantes no perfil metabólico das fibras musculares, convertendo-as do tipo II para o tipo I, o que induz o crescimento capilar, a densidade capilar e o suprimento de oxigênio. Desta forma, este recurso terapêutico aumenta a capacidade aeróbica oxidativa e a resistência à fadiga dos músculos isquêmicos. Assim, a eletroestimulação é mais um recurso terapêutico capaz de melhorar a habilidade para caminhar destes pacientes, diminuindo gastos com cirurgias de revascularização e complicações maiores.

Application of Animal Models: Chronic Electrical Stimulation-Induced Contractile Activity

Unilateral, chronic low-frequency electrical stimulation (CLFS) is an experimental model that evokes numerous biochemical and physiological adaptations in skeletal muscle. These occur within a short time frame and are restricted to the stimulated muscle. The humoral effects of whole body exercise are eliminated and the nonstimulated contralaterai limb can often be used as a control muscle, if possible effects on the contralateral side are considered. CLFS induces a fast-to-slow transformation of muscle because of alterations in calcium dynamics and myofibrillar proteins, and a white-to-red transformation because of changes in mitochondrial enzymes, myoglobin, and the induction of angiogenesis. These adaptations occur in a coordinated time-dependent manner and result from altered gene expression, including transcriptional and posttranscriptional processes. CLFS techniques have also been applied to myocytes in cell culture, which provide a greater opportunity for the delivery of pharmacological agents or for the application of gene transfer methodologies. Clinical applications of the CLFS technique have been limited, but they have shown potential therapeutic value in patients in whom voluntary muscle contraction is not possible due to debilitating disease and/or injury. Thus the CLFS technique has great value for studying various aspects of muscle adaptation, and its wider scientific application to a variety of neuromuscular-based disorders in humans appears to be warranted. Key words: skeletal muscle, muscle plasticity, endurance training, mitochondrial biogenesis, fiber types

High-frequency, low-magnitude vibrations suppress the number of blood vessels per muscle fiber in mouse soleus muscle

Extremely low-magnitude (0.3 g), high-frequency (30-90 Hz), whole body vibrations can stimulate bone formation and are hypothesized to provide a surrogate for the oscillations of muscle during contraction. Little is known, however, about the potential of these mechanical signals to stimulate adaptive responses in other tissues. The objective of this study was to determine whether low-level mechanical signals produce structural adaptations in the vasculature of skeletal muscle. Eight-week-old male BALB/cByJ (BALB) mice were divided into two experimental groups: mice subjected to low-level, whole body vibrations (45 Hz, 0.3 g) superimposed on normal cage activities for 15 min/day (n = 6), and age-matched controls (n = 7). After the 6-wk experimental protocol, sections from end and mid regions of the soleus muscles were stained with lectin from Bandeiraea Simplicifolia, an endothelial cell marker, and smooth muscle (SM) alpha-actin, a perivascular cell marker. Six weeks of this low-level vibration caused a 29% decrease in the number of lectin-positive vessels per muscle fiber in the end region of the soleus muscle, indicating a significant reduction in the number of capillaries per muscle fibers. Similarly, these vibrations caused a 36% reduction in SM alpha-actin-positive vessels per muscle fiber, indicating a reduction in the number of arterioles and venules. The decreases in lectin- and SM alpha-actin-positive vessels per muscle fiber ratios were not significant in the mid muscle sections. These results demonstrate the sensitivity of the vasculature in mouse skeletal muscle to whole body, low-level mechanical signals.