OBJECTIVE:Muscle weakness is prevalent in rheumatoid arthritis (RA), osteoarthritis (OA) and sarcopenia (SARC). Endurance exercises may improve mitochondrial function and oxidative capacity, while strength exercises are thought to stimulate myofibrillar protein synthesis. This study aims to compare the effects of strength and endurance exercise and explore the association between muscle characteristics and exercise outcomes in patients with RA, OA and SARC. We hypothesize that responses to endurance and strength exercises in patients with muscle weakness are influenced by intramuscular pathology including muscle morphology, mitochondrial function, and systemic inflammation, based on their disease pathology, potentially requiring personalized training schedules. METHODS:This two-arm, parallel-group exploratory trial will enroll 69 patients (23 RA, 23 OA, 23 SARC), randomized to endurance (n = 35) or muscle strength exercises (n = 34), using minimization to balance disease type and gender. The 8-week intervention includes two supervised sessions per week using a controlled cable pulley device (Reforter™) and fitness equipment, plus one weekly home-based session. The primary outcome is isokinetic muscle strength (peak torque), measured with the Biodex system®. Secondary outcomes include muscle morphology, mitochondrial function, systemic inflammation and muscle endurance (by Biodex and 6 Minute Walk test). Muscle morphology will be assessed via 3D ultrasound imaging of the vastus lateralis. Mitochondrial function will be analyzed using high-resolution respirometry on muscle biopsies. Systemic inflammation will be measured using multiplex assays or ELISA on serum samples. DISCUSSION:This study will explore differential responses to muscle endurance and muscle strength exercises in patients with RA, OA, and SARC, offering novel insights into the molecular mechanisms of muscle weakness. The findings may help identify potential mechanisms underlying variability in exercise response and provide effect size estimates to guide future confirmatory studies and more targeted exercise interventions. TRIAL REGISTRATION:ClinicalTrials.gov NCT06480643 (date of registration28-06-24).

BACKGROUND:Ankle plantarflexion contracture is common in cerebral palsy (CP). Surgical gastrocsoleus aponeurotic lengthening can improve ankle dorsiflexion, but the effects on muscle morphology and gait remain unclear. This study aimed to explore the effects of Vulpius lengthening on gastrocnemius medialis (GM) morphology and gait in CP. METHODS:GM morphology was assessed in eight adolescents with CP (13-20 years) before and one year after gastrocsoleus lengthening, using 3D ultrasonography at 0 and 4 Nm dorsiflexion moments. GM extensibility was defined as the length change between 0 and 4 Nm. In addition, gait kinematics and kinetics were evaluated using gait analysis. FINDINGS:Post-intervention, passive ankle dorsiflexion increased by 12.5° [0:55°] (median [min:max]). At 0 Nm, muscle belly length decreased by 4.1% [-23.6:0.2%] and fascicle length shortened by 14.2% [-44.7:-5.5%], while tendon length increased by 11.4% [5.6:32.6%]. The physiological cross-sectional area increased by 37.5% [7.2:85.7%]. Muscle belly and fascicle extensibility decreased, by 37.3% [-73.1:18.5%] and 20.8% [-77.9:-1.4%], respectively. During gait, on average knee extension in late stance/pre-swing increased by 3.9° [-1.3:22.8°], and ankle power absorption in loading response was reduced by 0.9 Watt/kg [0.007:1.5 Watt/kg]. INTERPRETATION:Orthopedic Vulpius lengthening increased passive ankle dorsiflexion and improved aspects of gait mainly by elongating the Achilles tendon, but led to a shorter muscle belly and fascicles. This study provides insight into GM morphological changes and gait adaptations one year after Vulpius lengthening, and underscores the need to consider muscle morphology and function, rather than just passive joint range of motion, when planning and evaluating musculoskeletal procedures.

Background:The development of multifunctional dressings capable of actively orchestrating the complex wound microenvironment remains a critical challenge in regenerative medicine. Although leucocyte cell-derived chemotaxin-2 (LECT2) has been implicated in inflammation and angiogenesis, its therapeutic potential in wound healing remains unexplored. Results:Here, we report a novel, portable coaxial electrospinning system for the in situ fabrication of a bioactive nanofiber dressing that continuously delivers functional LECT2. This dressing features a unique polyvinyl butyral (PVB)/polyvinylpyrrolidone (PVP) core and a polyvinyl alcohol (PVA)/PVP shell, which together ensure sustained LECT2 release. We demonstrate that LECT2 acts as a potent multi-target agent: it directly scavenges reactive oxygen species by upregulating the NRF2/SOD axis in keratinocytes and fibroblasts, promotes angiogenesis under oxidative stress, and exerts antimicrobial activity against S. aureus and Methicillin-resistant Staphylococcus aureus. Crucially, LECT2 drives immune reprogramming by polarizing macrophages toward a pro-regenerative M2 phenotype. The resulting dressing exhibits excellent mechanical properties and air permeability, and facilitates rapid wound closure in vivo by simultaneously enhancing re-epithelialization, neovascularization, and M2 macrophage polarization. Conclusions: This work not only unveils LECT2 as a master regulator of wound healing but also establishes a versatile platform for in situ fabrication of advanced dressings, with great promise for the treatment of complex skin wounds.

Abstract Patients with long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) suffer from post-exertional malaise. The accompanying physical inactivity may contribute to a lower aerobic capacity and may explain skeletal muscle adaptations in these patients. Here, we compare whole-body exercise responses and skeletal muscle adaptations after strict 60-day bed rest in healthy people with those in long COVID and ME/CFS patients, and healthy age- and sex-matched controls. Bed rest alters respiratory and cardiovascular responses to maximal exercise, which are dissimilar in patients. Bed rest causes muscle atrophy without altering fiber type. Both patient groups have more glycolytic fibers, and ME/CFS patients display type I-specific atrophy. Only after bed rest is oxidative phosphorylation capacity associated with maximal oxygen uptake. As skeletal muscle characteristics differ between patients and healthy individuals after bed rest, physical inactivity cannot solely explain the lower exercise capacity and skeletal muscle adaptations in long COVID and ME/CFS patients.

When not treated adequately, neuromusculoskeletal, tendinous, and joint tissue injuries may become chronic, leading to impaired tissue function due to fibrosis, extracellular matrix densification, and fatty connective tissue accumulation, ultimately resulting in reduced joint and muscle mobility. Timely treatment involving the mobilization of fascia and targeted muscle exercise has been shown to enhance and promote tissue regeneration. Key phases in tissue regeneration after injury include the activation of the innate immune system, followed by its resolution. Although several treatment modalities are effective in restoring tissue function, their success rate and time to recovery may still need optimization. Over recent decades, increasing attention has been given to the role of fascia in neuromuscular tissue function, adaptation, and regeneration. However, the complex interactions between fasciae, myofibers, and the immune system remain insufficiently understood, particularly regarding the mechanisms underlying fibrosis, extracellular matrix densification, and chronic pain. Fasciae are interconnected connective tissue sheaths that maintain anatomical organization, allow tissue gliding, and facilitate mechanical force transmission between structures. Because of their mediating role in mechanical and biochemical signalling, fascial tissues are also involved in injury and regeneration processes. Pathological stiffening of fascial connections may impair regeneration by limiting mobility and disrupting mechanotransduction. Therefore, treatment strategies that target both muscle and fascial tissues may offer improved outcomes in the recovery of neuromusculoskeletal function.

Metformin is the first-line therapy for type 2 diabetes mellitus and is commonly co-administered with statins for cardiovascular risk reduction. However, statins can cause statin-associated muscle symptoms, while metformin itself exerts complex effects on skeletal muscle. Because both drugs influence cellular energy metabolism and stress-response pathways in skeletal muscle, their combined effects on muscle cells warrant investigation. C2C12 myotubes were treated with metformin (50 or 1000 μM) in the absence or presence of simvastatin (10 μM) for 24 h. Myotube morphology, differentiation, and fusion indices, myoblast proliferation, and expression of atrophy-, stress-, and metabolism-related genes were assessed. Phosphorylation of key metabolic and anabolic signaling proteins (AMPK/ACC and Akt/mTOR-p70S6K) was analyzed. Mitochondrial respiration was measured using Seahorse respirometry, and mitochondrial network organization was quantified by live-cell imaging. Simvastatin significantly reduced myotube diameter (p < 0.0001), impaired myogenic progression in differentiated myotubes (differentiation index, p < 0.0001; fusion index, p = 0.0152), and inhibited myoblast proliferation (p = 0.003). Simvastatin increased the atrophy markers (Trim63, Fbxo32), stress marker (Perk), and concurrently suppressed myogenic (Myod) and anabolic (p-p70s6k/p70s6k) activity. Simvastatin also induced a broad suppression of mitochondrial and glycolytic metabolism, accompanied by reduced expression of the metabolic genes (Glut4, Hk2) and disruption of mitochondrial network connectivity. Co-exposure with metformin significantly attenuated simvastatin-induced effects, increasing myotube diameter (1.43-fold at low dose, p = 0.0223, and 1.48-fold at high dose, p = 0.0131), differentiation index (low dose: 1.63-fold; high dose: 1.80-fold; both p < 0.0001), and fusion index (low dose: 1.35; high dose: 1.50-fold; both p < 0.01). Compared with simvastatin alone, co-treatment with high-dose metformin increased AMPK and ACC phosphorylation and further suppressed mTOR signaling without amplifying atrophy-related gene expression. Despite deeper suppression of metabolic parameters (routine respiration, ATP production, Hk2 expression), metformin preserved mitochondrial network structure, increased Ppargc1a expression, and reduced cellular stress markers (Hri, Perk, Atf4). Simvastatin induced metabolic suppression, mitochondrial dysfunction, and atrophy-related responses in skeletal muscle cells. Metformin partially attenuated these alterations by preserving myotube structural integrity and reducing cellular stress signaling despite further metabolic suppression. These findings suggest that metformin may promote adaptive metabolic responses that enhance cellular resilience during simvastatin-induced metabolic stress.

Conventional two-dimensional (2D) dental pulp culture models are limited by their inability to recapitulate native tissue complexity and their frequent dependence on exogenous scaffolds. Here, we engineer scaffold-free, assembloid-like microspheroids that integrate stem cells from human exfoliated deciduous teeth (SHED) with human umbilical vein endothelial cells (HUVECs) to model physiological odontogenic-angiogenic coupling. Three-dimensional (3D) SHED micro-spheroids significantly upregulate key odontogenic markers (DMP1, DSPP) and the angiogenic factor VEGFA compared to 2D cultures. When co-assembled with HUVECs, the resulting microspheroids further amplify the expression of angiogenic markers (CD31, EMCN) and the osteo/odontogenic transcription factor RUNX2. Subcutaneous transplantation in nude mice reveals that these SHED–HUVEC microspheroids generate robust type H vascular networks and extensive mineralized dentin-like structures, outperforming SHED-only constructs. Mechanistically, 3D self-assembly activates the gap junction protein connexin 26 (CX26) and the immediate-early transcription factor CFOS in SHED. CX26/CFOS signaling collectively promote the upregulation of VEGFA, DMP1, and DSPP, a regulatory axis validated through loss-of-function studies. Our findings establish a potent, scaffold-free micro-spheroid platform for functional dental pulp regeneration and uncover the CX26/CFOS pathway as a master regulator of vascularized dental tissue formation, offering a translatable strategy for clinical pulp engineering.

SERINC3, a member of the serine incorporator protein family, is known for its roles in viral resistance and tumorigenesis, however, its function in osteogenesis remains unexplored. Lentivirus infection, alkaline Phosphatase/Alizarin Red S Staining, and RT-qPCR were used to evaluate the osteogenic differentiation of mesenchymal stem cells mediated by SERINC3. MicroCT, H E, and Masson staining were performed to investigate the bone formation and bone defect repair via Serinc3 knockout (KO) mice and nude mice. RNA sequencing, Co-IP, Western blotting, and Seahorse energy metabolism analysis were performed to elucidate the regulatory mechanism of SERINC3. Here, we identify SERINC3 as a critical regulator of osteogenic differentiation of bone marrow-derived stem cells (BMSCs) and bone regeneration. SERINC3 expression was significantly upregulated during osteogenic differentiation of BMSCs and stem cells from human exfoliated deciduous teeth (SHED). Functional assays revealed that SERINC3 overexpression enhanced osteogenic differentiation, proliferation, and migration of MSCs, while Serinc3-KO impaired these processes and led to osteopenia in mice. In a calvarial defect model, Serinc3-KO mice exhibited 42

To explore segment-specific associations between lumbodorsal epimuscular fat (EMF FF

Abstract Micro-nano bioactive glass (MNBG) has bone regenerative potential. However, the difficulty of MNBG molding restricts its clinical applications in bone regeneration. Exosomes carry proteins, lipids, and nucleic acids for communication between cells. In this study, we adhered human exfoliated deciduous teeth (SHED)-derived exosomes (SHED-Exos) to electrospun micro-nano bioactive glass/polycaprolactone (MNBG/PCL) membrane to control inflammation and promote bone regeneration. MNBG/PCL membrane showed biocompatibility and osteogenic ability. Next, we demonstrated that SHED-Exos internalized into macrophages attenuated LPS-induced expression of M1-macrophage markers iNOS, IL-6, and IL-1β and upregulated M2-macrophage marker IL-10 expression, indicating a switch from M1 to M2 macrophage phenotype. MNBG/PCL-loaded SHED-Exos membrane supported the survival and growth of mouse bone marrow stromal cells (mBMSCs). When M1 macrophages were co-cultured with mBMSCs on the membrane, the SHED-Exos-loaded membrane showed higher Runx2, Alp, and Ocn gene expression. Our findings indicate that SHED-Exos-functionalized MNBG/PCL membrane has anti-inflammatory and osteoinductive potential, suggesting its potential as a candidate material for bone regeneration.

Transforming growth factor-β (TGF-β) signaling is associated with progressive skeletal muscle wasting. It is unknown whether myofibre-specific knockout of TGF-β type I receptors affects muscle transcriptome, mass, contractile force and oxidative metabolism. Here we show that 3 months after myofibre-specific knockout of TGF-β type I receptors (dKO) in male mice, transcriptomics demonstrate substantially more differentially expressed genes in gastrocnemius medialis (GM) than in soleus, mainly related to muscle contraction, hypertrophy and oxidative metabolism. GM mass of dKO mice increases substantially more than maximal force. Conversely, soleus mass of dKO mice increases in proportion to maximal force. Myofibre hypertrophy in dKO mice is accompanied by a proportional increase in succinate dehydrogenase enzyme activity. These adaptations are associated with a simultaneous decrease in β1-syntrophin and increases in sarcolipin, hepatocyte growth factor gene expression and anabolic signalling. Single receptor knockout causes minor phenotypical and transcriptional alterations. Our study highlights that myofibre-specific interference with both TGF-β type I receptors concurrently stimulates myofibre hypertrophy, enhances absolute force and simultaneously augments oxidative capacity.

Non-coding RNAs, including piwi-interacting RNAs (piRNAs), are known to regulate osteogenic differentiation in bone marrow-derived mesenchymal stem cells (BMSCs); their role in mesenchymal stem cells (MSCs) from diverse origins remains unclear. In this study, we identified piR48444 as a key regulator that is downregulated during the osteogenic differentiation of stem cells from exfoliated deciduous teeth (SHED) but is upregulated in inflamed and aged BMSCs. Functionally, piR48444 inhibited, while its knockdown enhanced osteogenic differentiation across MSCs from multiple sources. Notably, piR48444-depleted MSCs exhibited superior bone defect repair capacity. PiR48444 antagomir promoted bone regeneration in LPS-induced osteolysis mice and aging mice. Mechanistically, we demonstrated that piR48444 targets METTL7A, suppressing BMP2 mRNA m6A methylation. Furthermore, we discovered that the METTL7A/eIF4E complex binds to BMP2 mRNA, thereby enhancing its translational efficiency. Our findings establish piR48444 as a negative regulator of MSC osteogenesis through METTL7A-mediated BMP2 m6A methylation, highlighting its potential as a therapeutic target to enhance MSC-based bone regeneration strategies. piR48444 targets METTL7A to inhibit BMP2 mRNA m6A methylation and METTL7A/eIF4E complex-mediated BMP2 mRNA stability and translation, ultimately inhibiting osteogenic differentiation of MSCs and bone regeneration.

Osteogenesis imperfecta (OI) is a genetic disorder characterized by bone fragility. It is one of the most prevalent rare skeletal dysplasias. The mildest form, OI type 1, predominantly results from collagen type I haploinsufficiency due to pathogenic variants in the COL1A1 gene, leading to reduced collagen type I. Despite OI type 1 representing approximately half of the OI population, the lack of an effective mouse model has hindered research and therapy development. To address this gap, we developed a genetically engineered mouse model harboring a heterozygous deletion of the Col1a1 allele using the CRISPR/Cas system. The bone phenotype was characterized in 8- and 24-wk-old mice, assessing transcriptomics and serum markers for bone formation (procollagen type I N-terminal propeptide) and resorption (tartrate-resistant acid phosphatase 5b). Bone volume, microarchitecture, and strength were evaluated by micro-CT, histomorphometry, and three-point bending test. We showed that the decreased Col1a1 to Col1a2 mRNA ratio determines reduced collagen type I production in OI mice bones as the underlying mechanism of haploinsufficient OI. This was supported by COL1A1 to COL1A2 mRNA ratio findings in human OI cell models, including fibroblasts and induced mesenchymal stem cells, as well as in induced pluripotent and mesenchymal stem cell models that were edited to carry a heterozygous COL1A1 allele. Our findings indicate for the first time that reduced bone volume and altered bone microarchitecture in haploinsufficient OI depends on the Col1a1 to Col1a2 mRNA ratio regulation. This novel mouse model faithfully recapitulates OI type 1 and provides a vital tool for investigating the disease mechanism and developing targeted therapeutic strategies for this large neglected OI patient population.

The assessment of skeletal muscle volume is valuable for fundamental research and clinical practice, but remains limited in larger cohorts due to its time-consuming nature. Here, we developed a method to accurately estimate vastus lateralis (VL) muscle volume based on a single measurement of anatomical cross-sectional area (ACSA) or tissue thickness. Sixty-nine healthy participants (20–91 years) volunteered. In a subgroup (n = 34) we measured VL volume and ACSAs at 10% intervals along the muscle length to derive a VL muscle shape factor. We subsequently estimated VL volume by multiplying this muscle shape factor with muscle length and a single measure of ACSA at 50% muscle length (ACSAVL50%) or an estimated ACSAVL50% from a single ultrasound scan of tissue thickness in an independent cohort (n = 35). VL muscle shape factor was determined by integrating a fourth-order polynomial of muscle length and ACSA, and was dependent on muscle size. Estimating muscle volume had a high accuracy (R²=0.976, CCC = 0.987), low bias and error (< 8.5%) in both the main cohort and an independent validation group. Estimating muscle volume from stitching 2D images at 50% muscle length or estimating ACSA with a geometric model explained 91–95% of variance in measured volumes, with high accuracy and concordance correlation coefficients. VL muscle volume can be estimated by multiplying a muscle shape factor with muscle length and ACSAVL50% from a single ultrasound image. We present a novel, cost-effective, rapid, yet accurate assessment of VL muscle mass for (large-scale) studies and clinical practice.

Nanomaterial-mediated macrophage immune response plays a crucial role in bone regeneration microenvironment. Mesoporous silica nanoparticles are widely used as nano-drug carriers, imaging agents, and bioactivity regulators for potential tissue regeneration. It is known that surface topography features of nanomaterials play an important regulatory role in the immune response. In this study, it was found that the pollen-like surface morphology of mesoporous silica nanoparticles (PMSNs) inhibited the expression of pro-inflammatory markers at gene and protein levels in macrophages (RAW 264.7 cells) compared to the smooth surface morphology of mesoporous silica nanoparticles (MSNs). Scanning electron microscopy images showed distinct macrophage membrane surface binding patterns of MSNs and PMSNs. MSNs were more evenly dispersed across the macrophage cell membrane, while PMSNs were aggregated on the membrane and prevented the M1 polarization of macrophages. PMSNs-induced macrophage anti-inflammatory responses were associated with up-regulation of the cell surface receptor CD28 and inhibition of ERK phosphorylation. TEM images showed that macrophages phagocytosed both MSNs and PMSNs while inhibiting nanoparticle phagocytosis did not affect the expression of anti-inflammatory genes and proteins. Moreover, PMSNs-induced conditioned medium from macrophages promoted osteogenic differentiation of mouse bone marrow-derived stromal cells (mBMSCs), evidenced by increased mineralization and osteogenic marker BMP2 expression via Alizarin Red S and LSCM assays compared to MSNs-induced conditioned medium. Moreover, a lipopolysaccharide (LPS)-induced osteolysis model in mouse cranial bone further demonstrated that PMSNs prevent bone resorption by mitigating LPS-induced inflammation. Our results revealed that PMSNs-mediated macrophage immunomodulation promotes bone regeneration via surface topology-related physical contact cues. STATEMENT OF SIGNIFICANCE: Nanomaterials have been widely used in bone regeneration. The immune response of macrophages induced by nanomaterials, plays a crucial role in bone regeneration. However, most nanomaterial immunomodulatory research focus on macrophage internalization or phagocytosis. The early contact between the cell membrane and nanomaterials is often easily overlooked. To clarify how early contact between nanomaterial-cell membrane regulates macrophage immune response. We developed MSN particles with special pollen-like surface morphology and studied the impact of nanoparticle morphology on the early contact between materials and macrophage cell membranes, as well as the subsequent impact on macrophage immune response and bone regeneration and related regulatory mechanisms. The results can provide new guidance for the design and development of osteoimmunomodulatory nanomaterials.

Backgrounds Periodontitis-induced alveolar bone loss is a primary cause of tooth loss. Porphyromonas gingivalis (P. gingivalis) is the primary pathogenic bacterium of periodontitis. Outer membrane vesicles (OMVs) derived from P. gingivalis (P.g-OMVs) contain various bioactive molecules, and several studies have suggested that P.g-OMVs may participate in alveolar bone loss caused by periodontitis.Materials and Methods P.g-OMVs were isolated and characterized. The effect of P.g-OMVs on BMSCs proliferation and osteogenic differentiation was analyzed. High-throughput sequencing, RT-qPCR, and Western blot analysis were performed in BMSCs to unravel the underlying molecular mechanism.Results P.g-OMVs promoted proliferation but inhibited osteogenic differentiation of BMSCs. High-throughput sequencing results showed that serum amyloid A (SAA), especially SAA3, was robustly upregulated in P.g-OMVs-treated BMSCs. Upregulated SAA3 promoted TLR4, MyD88, and NF-κB p65 and inhibited osteogenic differentiation of P.g-OMVs-treated BMSCs. The knockdown of SAA3 in BMSCs downregulated P.g-OMVs-induced TLR4, MyD88, and NF-κB p65 and rescued P.g-OMVs-inhibited osteogenic differentiation.Conclusions Our results indicate that P.g-OMVs inhibit osteogenic differentiation of BMSCs via the SAA3-mediated TLR4/MyD88/NF-κB axis, providing novel targets for the treatment of periodontitis-induced alveolar bone loss.

BackgroundLow Back Pain (LBP) is a global musculoskeletal disorder affecting quality of life, with 90% of cases categorized as nonspecific, indicating that the underlying cause is unknown. One of the current treatment modalities that physiotherapists use are fascia tissue manipulations (FTMs), such as soft tissue mobilization, myofascial release, and elastic tape, to enhance joint mobility and muscle flexibility in LBP individuals.PurposeThis review and experimental research explore the hypothetical mechanisms of FTMs using Skin Displacement (SKD), either by hand or with elastic tape.MethodsSeveral hypotheses regarding the working mechanisms of FTMs are discussed through inductive reasoning based on literature and new experimental results using ultrasonography and cadaver dissection. In this paper, stiffness is defined as the ratio of the applied force to the resulting strain, based on Hooke’s law. We focus on the role of lumbar fasciae and skeletal muscles, as well as the linkages between skin, fasciae, skeletal muscles, and joints, including the SKD-induced stress transmission between these structures. Furthermore, we discuss how the mechanical properties and stiffness of these structures can be altered.ResultsThe skin connects densely to the fasciae, back muscles, and spine, contributing to the stiffness of structures in the lumbar region. SKD maneuvers transmit stress to deeper tissues, causing strain and displacement of the thoracolumbar fascia, back muscles, and arthrofascia. These deformations may alter the active and passive mechanical properties of deeper tissues including fascia and muscle, by triggering stress-relaxation as well as structural adaptation.ConclusionThis paper provides indications that the skin is strongly connected to the thoracolumbar fascia, back muscles, and spine. These connections are possibly enhanced in patients with LBP. Stress applied to the skin by SKD maneuvers is shown to be transmitted to the underlying anatomical structures via these connections and can alter the stiffness of fasciae and skeletal muscles. The working mechanisms of FTMs potentially alter the quantity and composition of matrix components, as well as the contractile activity of muscle fibers, and traction forces of (myo)fibroblasts and other cells within the matrices. FTM-induced stress and alterations in anatomical structures not only improve joint mobility but also promote regeneration and tissue adaptation via various mechanisms resulting in pain relief.

The antibiotic streptomycin is an integral part of cell culture medium. Because streptomycin inhibits bacterial protein synthesis, streptomycin might also have off‐target effects on muscle cell function. Here, we studied the effect of streptomycin on C2C12 myoblasts, myofiber growth, and metabolism. C2C12 myoblasts were cultured with or without streptomycin. The control condition consisted of carbenicillin and ampicillin. Streptomycin did not impair myoblast proliferation rate. Streptomycin exposure led to a ~ 40% reduction in myotube diameter and reduced protein synthesis rate. Myotubes with streptomycin showed a 25% lower differentiation and 60% lower fusion index. Expression of cell stress markers was upregulated by streptomycin. Mitochondrial respiration rate was unaffected by streptomycin, but gene expression levels of Myh3 and Acta1 were lower, as well as the protein content of mitochondrial complex I subunits. Myotubes cultured in the presence of streptomycin showed fragmentation of the mitochondrial network, a smaller mitochondrial footprint (−64%), and shorter branch lengths (−34%). Streptomycin does not alter C2C12 myoblast proliferation but reduces global protein synthesis rates in differentiating myotubes. The routine use of streptomycin in muscle cell cultures should be carefully evaluated, particularly when investigating muscle growth, metabolism, or protein synthesis, where off‐target effects may confound experimental outcomes.