Short-Term Electrical Stimulation Impacts Cardiac Cell Structure and Function.

This investigation used a model of increased skeletal muscle contractile activity to evaluate whether the adenylate cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) pathway and/or the high-energy phosphate state of the muscle might be temporally related to the contraction-induced increase in skeletal muscle GLUT-4 protein concentration. Plantaris and gastrocnemius muscles of Sprague-Dawley rats were subjected to 3, 7, 14, or 28 days of chronic low-frequency electrical stimulation (10 Hz, 24 h/day). GLUT-4 protein concentration was slightly reduced after 3 days of electrical stimulation, similar to control values at 7 days and significantly elevated above control at 14 days (53%, P < 0.05) and 28 days (338%, P < 0.05) of stimulation. ATP, creatine phosphate, creatine, and P, were inversely related to GLUT-4 protein concentration. Adenylate cyclase activity increased with electrical stimulation and was significantly related to the increased GLUT-4 protein. cAMP was significantly increased at 14 days of stimulation and remained elevated through 28 days. These results demonstrate that both the adenylate cyclase-cAMP pathway and the high-energy phosphate state of the muscle are temporally related to elevations in skeletal muscle GLUT-4 protein concentration in response to chronic low-frequency electrical stimulation and, as such, suggest that both may comprise a component of the intracellular signal that regulates the contraction-induced increase in skeletal muscle GLUT-4 protein concentration.

Anatomical changes in chronically stimulated skeletal muscles.

1. We electrically stimulated the intermediate and deep layers of the superior colliculus (SC) in two rhesus macaques free to move their heads both vertically and horizontally (head unrestrained). Stimulation of the primate SC can elicit high-velocity, combined, eye-head gaze shifts that are similar to visually guided gaze shifts of comparable amplitude and direction. The amplitude of gaze shifts produced by collicular stimulation depends on the site of stimulation and on the parameters of stimulation (frequency, current, and duration of the stimulation train). 2. The maximal amplitude gaze shifts, produced by electrical stimulation at 56 sites in the SC of two rhesus monkeys, ranged in amplitude from approximately 7 to approximately 80 deg. Because the head was unrestrained, stimulation-induced gaze shifts often included movements of the head. Head movements produced at the 56 stimulation sites ranged in amplitude from 0 to approximately 70 deg. 3. The relationships between peak velocity and amplitude and between duration and amplitude of stimulation-induced head movements and gaze shifts were comparable with the relationships observed during visually guided gaze shifts. The relative contributions of the eyes and head to visually guided and stimulation-induced gaze shifts were also similar. 4. As was true for visually guided gaze shifts, the head contribution to stimulation-induced gaze shifts depended on the position of the eyes relative to the head at the onset of stimulation. When the eyes were deviated in the direction of the ensuing gaze shift, the head contribution increased and the latency to head movement onset was decreased. 5. We systematically altered the duration of stimulation trains (10-400 ms) while stimulation frequency and current remained constant. Increases in stimulation duration systematically increased the amplitude of the evoked gaze shift until a site specific maximal amplitude was reached. Further increases in stimulation duration did not increase gaze amplitude. There was a high correlation between the end of the stimulation train and the end of the evoked gaze shift for movements smaller than the site-specific maximal amplitude. 6. Unlike the effects of stimulation duration on gaze amplitude, the amplitude and duration of evoked head movements did not saturate for the range of durations tested (10-400 ms), but continued to increase linearly with increases in stimulation duration. 7. The frequency of stimulation was systematically varied (range: 63-1,000 Hz) while other stimulation parameters remained constant. The velocity of evoked gaze shifts was related to the frequency of stimulation; higher stimulation frequencies resulted in higher peak velocities. The maximal, site-specific amplitude was independent of stimulation frequency. 8. When stimulating a single collicular site using identical stimulation parameters, the amplitude and direction of stimulation-induced gaze shifts, initiated from different initial positions, were relatively constant. In contrast, the amplitude and direction of the eye component of these fixed vector gaze shifts depended upon the initial position of the eyes in the orbits; the endpoints of the eye movements converged on an orbital region, or "goal," that depended on the site of collicular stimulation. 9. When identical stimulation parameters were used and when the eyes were centered initially in the orbits, the gaze shifts produced by caudal collicular stimulation when the head was restrained were typically smaller than those evoked from the same site when the head was unrestrained. This attenuation occurred because stimulation drove the eyes to approximately the same orbital position when the head was restrained or unrestrained. Thus movements produced when the head was restrained were reduced in amplitude by approximately the amount that the head would have contributed if free to move. 10. When the head was restrained, only the eye component of the intended gaze shift

Autologous bone marrow cell (BMC) transplantation has been shown as a potential approach to treat ischemic disease. However, BMC dysfunction has been reported in several conditions, leading to poor cell engraftment and failure in tissue revascularization. We have previously shown that skeletal muscle angiogenesis induced by electrical stimulation (ES) is impaired in the SS/Mcwi rats and this effect seems to be related to an impaired regulation in the renin angiotensin system (RAS). The present study explored the role of the RAS on BMC function and its impact on skeletal muscle angiogenesis induced by ES. SS/Mcwi rats were randomized to receive BMC from: SS/Mcwi; SS‐13BN/Mcwi; SS/Mcwi rats infused with saline or ANGII (3 ng.kg‐1.min‐1). BMC were injected in the stimulated tibialis anterior muscle of SS/Mcwi rats. After 7 days of ES, unstimulated and stimulated muscles were harvested and the vessel density was evaluated. BMC isolated from SS/Mcwi or SS/Mcwi rats infused with saline failed to restore angiogenesis induced by ES. However, cells isolated from SS‐13BN/Mcwi consomic rats as well as from SS/Mcwi rats infused with ANGII showed a significant increase in vessel density after 7 days of ES. This study suggests that an impaired RAS regulation may be associated with a significant BMC dysfunction and have profound effects on the angiogenesis response induced by ES in SS/Mcwi rats. (Support NIH HL‐29587, N01 HV‐28182).

Chondrogenic potential of animal adult stem cells through electrical stimulation

Background: Tinnitus-the perception of sound despite the absence of an external source-can be a debilitating condition for which there are currently no pharmacological remedies. Our proof of concept study focused on the immediate effects of non-invasive electrical stimulation through the ear canal on loudness and tinnitus-induced distress. In addition, we aimed to identify variables that may affect the simulation outcomes. Methods: Sixty-six patients (29 women and 37 men, mean age 54.4 ± 10.4) with chronic tinnitus were recruited to the tertiary referral hospital between December 2019 and December 2021. They underwent 10 min of electrical stimulation through the ear canal for three consecutive days. Visual analog scales measured loudness and tinnitus-induced distress immediately before and after stimulation. Results: After three days of electrical stimulation, tinnitus loudness decreased in 47% of patients, 45.5% reported no change, and 7.6% reported worsening. Tinnitus severity decreased in 36.4% of cases, 59.1% of patients reported no change, and 4.5% reported worsening. Women responded positively to therapy earlier than men. In addition, tinnitus distress decreased in patients with compensated tinnitus but not in those with uncompensated tinnitus. Finally, patients with bilateral tinnitus improved earlier than those with unilateral tinnitus, and the age of the patients did not influence the stimulation results. Conclusions: Our proof of concept study confirms the potential of non-invasive electrical stimulation of the ear as a promising screening approach to identifying patients for more advanced electrostimulation treatment, such as an extracochlear anti-tinnitus implant. These findings have practical implications for tinnitus management, offering hope for improved patient care.

Direct electrical stimulation of rat soleus during denervation-reinnervation

Engineered cardiomyocytes made of human-induced pluripotent stem cells (iPSC) present phenotypical characteristics similar to human fetal cardiomyocytes. There are different factors that are essential for engineered cardiomyocytes to be functional, one of them being that their mechanical properties must mimic those of adult cardiomyocytes. Techniques, such as electrical stimulation, have been used to improve the extracellular matrix's alignment and organization and improve the intracellular environment. Therefore, electrical stimulation could potentially be used to enhance the mechanical properties of engineered cardiac tissue. The goal of this study is to establish the effects of electrical stimulation on the elastic modulus of engineered cardiac tissue. Nanoindentation tests were performed on engineered cardiomyocyte constructs under seven days of electrical stimulation and engineered cardiomyocyte constructs without electrical stimulation. The tests were conducted using BioSoft™ In-Situ Indenter through displacement control mode with a 50 µm conospherical diamond fluid cell probe. The Hertzian fit model was used to analyze the data and obtain the elastic modulus for each construct. This study demonstrated that electrically stimulated cardiomyocytes (6.98 ± 0.04 kPa) present higher elastic modulus than cardiomyocytes without electrical stimulation (4.96 ± 0.29 kPa) at day 7 of maturation. These results confirm that electrical stimulation improves the maturation of cardiomyocytes. Through this study, an efficient nanoindentation method is demonstrated for engineered cardiomyocyte tissues, capable of capturing the nanomechanical differences between electrically stimulated and non-electrically stimulated cardiomyocytes.

The present study investigated whether alterations in the muscle high energy phosphate state initiates the contraction-induced increase in skeletal muscle GLUT4 protein concentration. Sprague-Dawley rats were provided either a normal or a 2% beta-guanidinoproprionic acid (beta-GPA) diet for 8 weeks and then the gastrocnemius of one hind limb was subjected to 0, 14 or 28 days of chronic (24 h day-1) low-frequency electrical stimulation (10 Hz). The beta-GPA diet, in the absence of electrical stimulation, significantly reduced ATP, creatine phosphate, creatine and inorganic phosphate and elevated GLUT4 protein concentration by 60% without altering adenylate cyclase activity or cAMP concentration. Following 14 days of electrical stimulation, GLUT4 protein concentration was elevated above non-stimulated muscle in both groups but was significantly more elevated in the beta-GPA group. Concurrent with this greater rise in GLUT4 protein concentration was a greater decline in the high energy phosphates and a greater rise in cAMP. After 28 days of electrical stimulation, GLUT4 protein concentration and cAMP stabilized and was not different between diet treatments. However, the high energy phosphates were significantly higher in the normal diet rats as opposed to the beta-GPA rats. These findings therefore suggest that a reduction in cellular energy supply initiates the contraction-induced increase in muscle GLUT4 protein concentration, but that a rise in cAMP may potentiate this effect.

Changes in skeletal muscle morphology and metabolism are associated with limited functional capacity in heart failure, which can be attenuated by neuromuscular electrical stimulation (ES). The purpose of the present study was to analyse the effects of ES upon GLUT-4 protein content, fibre structure and vessel density of the skeletal muscle in a rat model of HF subsequent to myocardial infarction. Forty-four male Wistar rats were assigned to one of four groups: sham (S), sham submitted to ES (S+ES), heart failure (HF) and heart failure submitted to ES (HF+ES). The rats in the ES groups were submitted to ES of the left leg during 20 days (2.5 kHz, once a day, 30 min, duty cycle 50%- 15 s contraction/15 s rest). After this period, the left tibialis anterior muscle was collected from all the rats for analysis. HF+ES rats showed lower values of lung congestion when compared with HF rats (P = 0.0001). Although muscle weight was lower in HF rats than in the S group, thus indicating hypotrophy, 20 days of ES led to their recovery (P < 0.0001). In both groups submitted to ES, there was an increase in muscle vessel density (P < 0.04). Additionally, heart failure determined a 49% reduction in GLUT-4 protein content (P < 0.03), which was recovered by ES (P < 0.01). In heart failure, ES improves morphological changes and raises GLUT-4 content in skeletal muscle.

Microfluidics embedded with microelectrodes for electrostimulation of neural stem cells proliferation

P204 To evaluate the importance of the renin angiotensin system (RAS) in VEGF expression and angiogenesis in skeletal muscle, we compared the angiogenic response to electrical stimulation in congenic strains of SS/Jr/Hsd rats using a complementation test design. We have previously demonstrated that both increases in VEGF expression and angiogenesis induced by electrical stimulation of skeletal muscle were absent in inbred Dahl S rats having a wildtype renin allele (S/ren ss ). In contrast, the congenic S/ren rr in which a 10 cM segment of chromosome 13 containing the normally functioning salt resistant renin allele was transferred onto the Dahl S background, exhibit the expected changes in renin. In the present study we investigate the effects of electrical stimulation on VEGF expression and angiogenesis in these rats. Congenic S/ren rr and S/ren ss rats, fed a 0.4% salt diet were surgically prepared by chronic implantation of an electrical stimulator. Another group of S/ren rr rats was treated with lisinopril, 2 days before the surgery and throughout the stimulation protocol. Rats without any drug treatment were used as control. The right tibialis anterior (TA) and extensor digitorum longus (EDL) were stimulated (10 Hz, 0.3 ms duration) for 8 hours per day for 7 days. The contralateral muscles served as controls. Western blot analysis was performed to identify VEGF protein expression in these muscles. Seven days of electrical stimulation of the skeletal muscles produced no change in vessel density of S/ren ss (Δ=5.50 ± 3.8 % and 8.14 ± 2.0 % for EDL and TA respectively). Transfer of the resistant renin allele (S/ren rr ) restored the angiogenic response (Δ=16% and 30% for EDL and TA, respectively) despite a significantly higher blood pressure (113.5 ± 2.25 mmHg and 148.67 ± 1.12 mmHg for S/ren ss and S/ren rr , respectively). Blockade of the RAS in S/ren rr restored the phenotype observed in the S/ren ss (Δ=1.46% and 1.9% to EDL and TA, respectively, p rr . These results demonstrate that RAS plays an important role in the regulation of VEGF expression and angiogenesis in skeletal muscle.

Reason for the increased electroactivity of extracellular polymeric substances with electrical stimulation: Structural change of α-helix peptide of protein

A single-case study design. To examine the effect of electrical stimulation of the vastus medialis muscle on stiffness, pain and function for a patient with delayed functional progress following a lateral patellar retinacular release. Five months after an arthroscopic lateral patellar retinacular release, the patient, although highly motivated, had made little progress using routine exercises and taping. An electrical stimulation program producing approximately 300 contractions daily of the vastus medialis muscle was implemented. The electrical stimulation applied for 33 of the 36 days was a rectangular and balanced biphasic pulse of 625-micros duration, 70-Hz frequency, 8-second peak on-time, 3-second off-time, 1-second ramp-up, and 0.5-second ramp-down. Objective measures of stair climbing and hopping, together with the subjective measure of therapist-palpated superomedial patella displacement force, were recorded for each treatment visit. Other subjective measures were the patient's daily recordings of knee pain and stiffness. Patient-reported stiffness reduced rapidly as the actual and cumulative number of daily contractions of the vastus medialis muscle increased. After 8 days of electrical stimulation, the patient was able to ascend stairs unassisted and after another 21 days to hop unsupported. Stiffness rapidly reduced and function started to improve once the electrical stimulation program was implemented. Recovery during the 36 days of treatment with electrical stimulation was greater than during the previous 5 months using other methods. Compliance was not an issue, nor was muscle soreness.

Electrical stimulation of peripheral nerves produces acute analgesic effects. This randomized, sham-controlled, crossover study was designed to evaluate the effect of differing durations of electrical stimulation on the analgesic response to percutaneous electrical nerve stimulation in 75 consenting patients with low back pain. All patients received electrical stimulation for four different time intervals (0, 15, 30, and 45 min) in a random sequence over the course of an 11-week study period. All active percutaneous electrical nerve stimulation treatments were administered using alternating frequencies of 15 and 30 Hz three times per week for 2 consecutive weeks. The prestudy assessments included the health status survey short form questionnaire and 10-cm visual analog scale scores for pain, physical activity, and quality of sleep, with 0 being the best and 10 being the worst. The pain scoring was repeated 5-10 min after each 60-min study session and 24 h after the last treatment session with each of the four methods. The daily oral analgesic requirements were assessed during each of the four treatment blocks. At the end of each 2-week treatment block, the questionnaire was repeated. Electrical stimulation using percutaneously placed needles produced short-term improvements in the visual analog scale pain, physical activity, and quality of sleep scores, and a reduction in the oral analgesic requirements. The 30-min and 45-min durations of electrical stimulation produced similar hypoalgesic effects (48+/-21% and 46+/-19%, respectively) and were significantly more effective than either 15 min (21+/-17%) or 0 min (10+/-11%). The 30- and 45-min treatments were also more effective in improving physical activity and sleep scores over the course of the 2-week treatment period. In contrast to the sham treatment (0 min), the health status survey short form revealed that electrical stimulation for 15 to 45 min three times per week for 2 weeks improved patient function. The recommended duration of electrical stimulation with percutaneous electrical nerve stimulation therapy is 30 min.