Therapeutic Pulsed Ultrasound Promotes Revascularization and Functional Recovery of Rat Skeletal Muscle after Contusion Injury

Low-intensity pulsed ultrasound (LIPUS) promotes skeletal muscle regeneration by regulating PGC-1α/AMPK/GLUT4 pathways in satellite cells/myoblasts

Low-Intensity Pulsed Ultrasound (LIPUS) holds therapeutic potential in promoting skeletal muscle regeneration, a biological process mediated by satellite cells and myoblasts. Despite their central roles in regeneration, the detailed mechanistic of LIPUS influence on satellite cells and myoblasts are not fully underexplored. In the current investigation, we administrated LIPUS treatment to injured skeletal muscles and C2C12 myoblasts over five consecutive days. Muscle samples were collected on days 6 and 30 post-injury for an in-depth histological and molecular assessment, both in vivo and in vitro with immunofluorescence analysis. During the acute injury phase, LIPUS treatment significantly augmented the satellite cell population, concurrently enhancing the number and size of newly formed myofibers whilst reducing fibrosis levels. At 30 days post-injury, the LIPUS-treated group demonstrated a more robust satellite cell pool and a higher myofiber count, suggesting that early LIPUS intervention facilitates satellite cell proliferation and differentiation, thereby promoting long-term recovery. Additionally, LIPUS markedly accelerated C2C12 myoblast differentiation, with observed increases in AMPK phosphorylation in myoblasts, leading to elevated expression of Glut4 and PGC-1α, and subsequent glucose uptake and mitochondrial biogenesis. These findings imply that LIPUS-induced modulation of myoblasts may culminate in enhanced cellular energy availability, laying a theoretical groundwork for employing LIPUS in ameliorating skeletal muscle regeneration post-injury. NEW & NOTEWORTHY: Utilizing the cardiotoxin (CTX) muscle injury model, we investigated the influence of LIPUS on satellite cell homeostasis and skeletal muscle regeneration. Our findings indicate that LIPUS promotes satellite cell proliferation and differentiation, thereby facilitating skeletal muscle repair. Additionally, in vitro investigations lend credence to the hypothesis that the regulatory effect of LIPUS on satellite cells may be attributed to its capability to enhance cellular energy metabolism.

Histological and biochemical changes in lymphatic vessels after skeletal muscle injury induced by lengthening contraction in male mice

Lymphatic vessels are actively involved in the recovery process of inflamed tissues. However, the changes in intramuscular lymphatic vessels during inflammation caused by skeletal muscle injury remain unclear. Therefore, the purpose of this study was to clarify the changes in lymphatic vessels after skeletal muscle injury. The left tibialis anterior muscles of male mice were subjected to lengthening contractions (LC) for inducing skeletal muscle injury, and samples were collected on Days 2, 4, and 7 for examining changes in both the skeletal muscles and intramuscular lymphatic vessels. With hematoxylin-eosin staining, the inflammatory response was observed in myofibers on Days 2 and 4 after LC, whereas regeneration of myofibers was found on Day 7 after LC. The number and area of intramuscular lymphatic vessels analyzed by immunohistochemical staining with an antibody against lymphatic vessel endothelial hyaluronan receptor 1 were significantly increased only on Day 4 after LC. Based on the abovementioned results, intramuscular lymphatic vessels undergo morphological changes such as increase under the state of muscle inflammation. This study demonstrated that the morphology of intramuscular lymphatic vessels undergoes significant changes during the initial recovery phase following skeletal muscle injury.

Research Progress of Low-Intensity Pulsed Ultrasound in the Repair of Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a common disease that has profound impact on the health of patients, but has poor prognosis. The gold standard for the treatment of peripheral nerve defects is autologous nerve grafting; notwithstanding, due to the extremely high requirement for surgeons and medical facilities, there is great interest in developing better treatment strategies for PNI. Low-intensity pulsed ultrasound (LIPUS) is a noninterventional stimulation method characterized by low-intensity pulsed waves. It has good therapeutic effect on fractures, inflammation, soft tissue regeneration, and nerve regulation, and can participate in PNI repair from multiple perspectives. This review concentrates on the effects and mechanisms of LIPUS in the repair of PNI from the perspective of LIPUS stimulation of neural cells and stem cells, modulation of neurotrophic factors, signaling pathways, proinflammatory cytokines, and nerve-related molecules. In addition, the effects of LIPUS on nerve conduits are reviewed, as nerve conduits are expected to be a successful alternative treatment for PNI with the development of tissue engineering. Overall, the application advantages and prospects of LIPUS in the repair of PNI are highlighted by summarizing the effects of LIPUS on seed cells, neurotrophic factors, and nerve conduits for neural tissue engineering.

The therapeutic effects of low-intensity pulsed ultrasound in musculoskeletal soft tissue injuries: Focusing on the molecular mechanism

Musculoskeletal soft tissue injuries are very common and usually occur during both sporting and everyday activities. The intervention of adjuvant therapies to promote tissue regeneration is of great importance to improving people's quality of life and extending their productive lives. Though many studies have focused on the positive results and effectiveness of the LIPUS on soft tissue, the molecular mechanisms standing behind LIPUS effects are much less explored and reported, especially the intracellular signaling pathways. We incorporated all research on LIPUS in soft tissue diseases since 2005 and summarized studies that uncovered the intracellular molecular mechanism. This review will also provide the latest evidence-based research progress in this field and suggest research directions for future experiments.

Biochemical and Physiological Events Involved in Responses to the Ultrasound Used in Physiotherapy: A Review

Therapeutic ultrasound (TUS) is the ultrasound modality widely used in physical therapy for the treatment of acute and chronic injuries of various biological tissues. Its thermal and mechanical effects modify the permeability of the plasma membrane, the flow of ions and molecules and cell signaling and, in this way, promote the cascade of physiological events that culminate in the repair of injuries. This article is a review of the biochemical and physiological effects of TUS with parameters commonly used by physical therapists. Integrins can translate the mechanical signal of the TUS into a cellular biochemical signal for protein synthesis and modification of the active site of enzymes, so cell function and metabolism are modified. TUS also alters the permeability of the plasma membrane, allowing the influx of ions and molecules that modulate the cellular electrochemical signaling pathways. With biochemical and electrochemical signals tampered with, the cellular response to damage is then modified or enhanced. Greater release of pro-inflammatory factors, cytokines and growth factors, increased blood flow and activation of protein kinases also seem to be involved in the therapeutic response of TUS. Although a vast number of publications describe the mechanisms by which TUS can interact with the biological system, little is known about the metabolic possibilities of TUS because of the lack of standardization in its application.

Effect of Phonophoresis and Copaiba Oil on Oxidative Stress Biomarkers after Skeletal Muscle Injury in Rats

The objective of this study was to analyze the effectiveness of phonophoresis with copaiba oil gel, in comparison to therapeutic pulsed ultrasound alone or topical application of copaiba oil gel, on oxidative stress after a traumatic muscle injury. Forty male Wistar rats were divided into five groups: control, muscle injury, therapeutic pulsed ultrasound (TPU), copaiba oil gel (CO) and TPU plus CO. TPU and CO application occurred at 2, 12, 24, 48, 72 and 96 h after injury. The gastrocnemius muscle was injured by mechanical trauma. Malondialdehyde (a lipoperoxidation marker) and superoxide dismutase and catalase (antioxidant enzymes) were assessed 98 h after muscle injury. All were elevated in the muscle injury group. There was a significant difference among treatment groups favoring TPU plus CO for reducing malondialdehyde levels, but all treatments reduced superoxide dismutase and catalase activity, with no between-groups difference. In conclusion, phonophoresis-the application of TPU plus CO-was superior to TPU or CO alone for reducing lipoperoxidation. Phonophoresis, TPU alone and CO were all effective in decreasing antioxidant enzyme activity after a traumatic skeletal muscle injury.

Pulsed ultrasound prevents lipopolysaccharide-induced muscle atrophy through inhibiting p38 MAPK phosphorylation in C2C12 myotubes

OBJECTIVE

Inflammation contributes to skeletal muscle atrophy via protein degradation induced by p38 mitogen-activated protein kinase (MAPK) phosphorylation. Meanwhile, pulsed ultrasound irradiation provides the mechanical stimulation to the target tissue, and has been reported to show anti-inflammatory effects. This study investigated the preventive effects of pulsed ultrasound irradiation on muscle atrophy induced by lipopolysaccharide (LPS) in C2C12 myotubes.

METHODS

C2C12 myotubes were used in this research. The pulsed ultrasound (a frequency of 3 MHz, duty cycle of 20%, intensity of 0.5 W/cm²) was irradiated to myotube before LPS administration.

RESULTS

The LPS increased phosphorylation of p38 MAPK and decreased the myofibril and myosin heavy chain protein (P < 0.05), followed by atrophy in C2C12 myotubes. The pulsed ultrasound irradiation attenuated p38 MAPK phosphorylation and myotube atrophy induced by LPS (P < 0.05).

CONCLUSIONS

Pulsed ultrasound irradiation has the preventive effects on inflammation-induced muscle atrophy through inhibiting phosphorylation of p38 MAPK.

Effects of Physical Agents on Muscle Healing with a Focus on Animal Model Research

Skeletal muscle injury is caused by a variety of events, such as muscle laceration, contusions, or strain. Muscle fibers respond to minor damage with immediate repair mechanisms that reseal the cell membrane. On the other hand, repair of irreversibly damaged fibers is achieved by activation of muscle precursor cells. Muscle repair is not always perfect, especially after severe damage, and can lead to excessive fibroblast proliferation that results in the formation of scar tissue within muscle fibers. Remaining scar tissue can impair joint movement, reduce muscular strength, and inhibit exercise ability; therefore, to restore muscle function, minimizing the extent of injury and promoting muscle regeneration are necessary. Various physical agents, such as cold, thermal, electrical stimulation, and low-intensity pulsed ultrasound therapy, have been reported as treatments for muscle healing. Although approaches based on the muscle regeneration process have been under development, the most efficacious physiological treatment for muscle injury remains unclear. In this review, the influence of these physical agents on muscle injury is described with a focus on research using animal models.

A novel quercetin/β-cyclodextrin transdermal gel, combined or not with therapeutic ultrasound, reduces oxidative stress after skeletal muscle injury

A gel containing the inclusion complex of quercetin and β-cyclodextrin was developed in order to verify its effects, isolated or using phonophoresis, on oxidative biomarkers after skeletal muscle injury. 30 male rats were divided into one of five groups: Control (CTRL), Muscle Injury (MI), Therapeutic Pulsed Ultrasound (TPU), Therapeutic Pulsed Ultrasound plus Quercetin (TPU plus gel-QUE) or Quercetin gel (QUE). Quercetin gel was complexed with β-Cyclodextrin (β-CD) using chromatography (HPLC). TPU and quercetin application occurred with 2, 12, 24, 48, 72, 96 hours intervals after injury. Gastrocnemius muscle was injured by mechanical trauma. Lipid peroxidation, superoxide dismutase activity, and catalase activity were assessed. The inclusion complex exhibited adequate entrapment efficiency, relative density and pH. The viscosity of the complex showed a non-Newtonian pseudoplastic behavior. Quercetin/β-cyclodextrin gel reduced lipid peroxidation, superoxide dismutase activity and catalase activity compared to muscle injury group. Similarly, phonophoresis and TPU also reduced the levels of these oxidative biomarkers. In conclusion, quercetin/β-cyclodextrin transdermal gel reduces oxidative stress biomarkers after skeletal muscle injury irrespective of using phonophoresis.

A gel containing the inclusion complex of quercetin and β-cyclodextrin was developed in order to verify its effects, isolated or using phonophoresis, on oxidative biomarkers after skeletal muscle injury.

Development of Microfluidic Stretch System for Studying Recovery of Damaged Skeletal Muscle Cells

The skeletal muscle occupies about 40% mass of the human body and plays a significant role in the skeletal movement control. Skeletal muscle injury also occurs often and causes pain, discomfort, and functional impairment in daily living. Clinically, most studies observed the recovery phenomenon of muscle by massage or electrical stimulation, but there are limitations on quantitatively analyzing the effects on recovery. Although additional efforts have been made within in vitro biochemical research, some questions still remain for effects of the different cell microenvironment for recovery. To overcome these limitations, we have developed a microfluidic system to investigate appropriate conditions for repairing skeletal muscle injury. First, the muscle cells were cultured in the microfluidic chip and differentiated to muscle fibers. After differentiation, we treated hydrogen peroxide and 18% axial stretch to cause chemical and physical damage to the muscle fibers. Then the damaged muscle fibers were placed under the cyclic stretch condition to allow recovery. Finally, we analyzed the damage and recovery by quantifying morphological change as well as the intensity change of intracellular fluorescent signals and showed the skeletal muscle fibers recovered better in the cyclic stretched condition. In total, our in situ generation of muscle damage and induction recovery platform may be a key system for investigating muscle recovery and rehabilitation.

Nonoperative treatment of muscle injuries - recommendations from the GOTS expert meeting

BACKGROUND

Muscle injuries are some of the most common injuries in sports; they have a high recurrence rate and can result in the loss of ability to participate in training or competition. In clinical practice, a wide variety of treatment strategies are commonly applied. However, a limited amount of evidence-based data exists, and most therapeutic approaches are solely based on "best practice". Thus, there is a need for consensus to provide strategies and recommendations for the treatment of muscle injuries.

METHODS

The 2016 GOTS Expert Meeting, initiated by the German-Austrian-Swiss Society for Orthopaedic Traumatologic Sports Medicine (GOTS), focused on the topic of muscle and tendon injuries and was held in Spreewald/Berlin, Germany. The committee was composed of twenty-two medical specialists. Nine of them were delegated to a subcommittee focusing on the nonoperative treatment of muscle injuries. The recommendations and statements that were developed were reviewed by the entire consensus committee and voted on by the members.

RESULTS

The committee reached a consensus on the utility and effectiveness of the management of muscle injuries.

MAIN RESULTS

the "PRICE" principle to target the first inflammatory response is one of the most relevant steps in the treatment of muscle injuries. Haematoma aspiration may be considered in the early stages after injury. There is presently no clear evidence that intramuscular injections are of use in the treatment of muscle injuries. The ingestion of non-steroidal anti-inflammatory drugs (NSAIDs) should be regarded critically because there is currently no hard evidence to support their use, although they are appropriate in exceptional cases.

CONCLUSIONS

The present work provides a structured overview of the various nonoperative treatment strategies of muscle injuries and evaluates their effectiveness with respect to the existing scientific evidence and clinical expertise in the context of basic science on the healing process of muscle injuries. The committee agreed that there is a compelling need for further studies, including high-quality randomized investigations to completely evaluate the effectiveness of the existing therapeutic approaches. The given recommendations may be updated and adjusted as further evidence will be generated.

Low-Intensity Pulsed Ultrasound Promotes Exercise-Induced Muscle Hypertrophy

The purpose of this study was to investigate whether low-intensity pulsed ultrasound (LIPUS) promotes exercise-induced muscle hypertrophy. Twenty-four adult Sprague-Dawley (SD) rats were randomly assigned to three groups (n = 8 per group): normal control group (NC), treadmill exercise group (TE) and treadmill exercise + LIPUS group (TE + LIPUS). The TE + LIPUS group received a LIPUS treatment (1 MHz, 30 mW/cm²) at the gastrocnemius for 20 min/d after treadmill exercise. The TE group was sham-treated. Eight weeks of treadmill training successfully established the exercise-induced muscle hypertrophy model. Muscle strength, muscle mass and muscle fiber cross-sectional area were significantly increased in the TE + LIPUS group compared with the TE group. Moreover, LIPUS treatment significantly upregulated the expression of Akt, mTOR, p-Akt and p-mTOR and significantly downregulated the expression of MSTN, ActRIIB, FoxO1 and its phosphorylation. The results indicated that LIPUS promotes exercise-induced muscle hypertrophy by facilitating protein synthesis and inhibiting the protein catabolism pathway.