Crosstalk among canonical Wnt and Hippo pathway members in skeletal muscle and at the neuromuscular junction

Skeletal muscles are essential for locomotion,posture,and metabolic regulation.To understand physiological processes,exercise adaptation,and muscle-related disorders,it is critical to understand the molecular pathways that underlie skeletal muscle function.The process of muscle contra ction,orchestrated by a complex interplay of molecular events,is at the core of skeletal muscle function.Muscle contraction is initiated by an action potential and neuromuscular transmission requiring a neuromuscular junction.Within muscle fibers,calcium ions play a critical role in mediating the interaction between actin and myosin filaments that generate force.Regulation of calcium release from the sarcoplasmic reticulum plays a key role in excitation-contraction coupling.The development and growth of skeletal muscle are regulated by a network of molecular pathways collectively known as myogenesis.Myogenic regulators coordinate the diffe rentiation of myoblasts into mature muscle fibers.Signaling pathways regulate muscle protein synthesis and hypertrophy in response to mechanical stimuli and nutrient availability.Seve ral muscle-related diseases,including congenital myasthenic disorders,sarcopenia,muscular dystrophies,and metabolic myopathies,are underpinned by dys regulated molecular pathways in skeletal muscle.Therapeutic interventions aimed at preserving muscle mass and function,enhancing regeneration,and improving metabolic health hold promise by targeting specific molecular pathways.Other molecular signaling pathways in skeletal muscle include the canonical Wnt signaling pathway,a critical regulator of myogenesis,muscle regeneration,and metabolic function,and the Hippo signaling pathway.In recent years,more details have been uncovered about the role of these two pathways during myogenesis and in developing and adult skeletal muscle fibers,and at the neuromuscular junction.In fact,research in the last few years now suggests that these two signaling pathways are interconnected and that they jointly control physiological and pathophysiological processes in muscle fibers.In this review,we will summarize and discuss the data on these two pathways,focusing on their concerted action next to their contribution to skeletal muscle biology.However,an in-depth discussion of the noncanonical Wnt pathway,the fibro/a dipogenic precursors,or the mechanosensory aspects of these pathways is not the focus of this review.

Low skeletal muscle mass and high visceral adiposity are associated with recurrence of acute cholecystitis after conservative management:A propensity score-matched cohort study

Background:Recurrent acute cholecystitis(RAC)can occur after non-surgical treatment for acute cholecystitis(AC),and can be more severe in comparison to the first episode of AC.Low skeletal muscle mass or adiposity have various effects in several diseases.We aimed to clarify the relationship between RAC and body parameters.Methods:Patients with AC who were treated at our hospital between January 2011 and March 2022 were enrolled.The psoas muscle mass and adipose tissue area at the third lumbar level were measured using computed tomography at the first episode of AC.The areas were divided by height to obtain the psoas muscle mass index(PMI)and subcutaneous/visceral adipose tissue index(SATI/VATI).According to median VATI,SATI and PMI values by sex,patients were divided into the high and low PMI groups.We performed propensity score matching to eliminate the baseline differences between the high PMI and low PMI groups and analyzed the cumulative incidence and predictors of RAC.Results:The entire cohort was divided into the high PMI(n=81)and low PMI(n=80)groups.In the propensity score-matched cohort there were 57 patients in each group.In Kaplan-Meier analysis,the low PMI group and the high VATI group had a significantly higher cumulative incidence of RAC than their counterparts(log-rank P=0.001 and 0.015,respectively).In a multivariate Cox regression analysis,the hazard ratios of low PMI and low VATI for RAC were 5.250(95%confidence interval 1.083-25.450,P=0.039)and 0.158(95%confidence interval:0.026-0.937,P=0.042),respectively.Conclusions:Low skeletal muscle mass and high visceral adiposity were independent risk factors for RAC.

In vivo imaging and computational modeling of nonlinear shear waves in living skeletal muscles

How the state of living muscles modulates the features of nonlinear elastic waves generated by external dynamic loads remains unclear because of the challenge of directly observing and modeling nonlinear elastic waves in skeletal muscles in vivo,considering their active deformation behavior.Here,this important issue is addressed by combining experiments performed with an ultrafast ultrasound imaging system to track nonlinear shear waves(shear shock waves)in muscles in vivo and finite element analysis relying on a physically motivated constitutive model to study the effect of muscle activation level.Skeletal muscle was loaded with a deep muscle stimulator to generate shear shock waves(SSWs).The particle velocities,second and third harmonics,and group velocities of the SSWs in living muscles under both passive and active states were measured in vivo.Our experimental results reveal,for the first time,that muscle states have a pronounced effect on wave features;a low level of activation may facilitate the occurrence of both the second and third harmonics,whereas a high level of activation may inhibit the third harmonic.Finite element analysis was further carried out to quantitatively explore the effect of active muscle deformation behavior on the generation and propagation of SSWs.The simulation results at different muscle activation levels confirmed the experimental findings.The ability to reveal the effects of muscle state on the features of SSWs may be helpful in elucidating the unique dynamic deformation mechanism of living skeletal muscles,quantitatively characterizing diverse shock wave-based therapy instruments,and guiding the design of muscle-mimicking soft materials.

SWIR FluorescenceImaging In Vivo Monitoring and Evaluating Implanted M2 Macrophages in Skeletal Muscle Regeneration

Skeletal muscle has a robust regeneration ability that is impaired by severe injury,disease,and aging.resulting in a decline in skeletal muscle function.Therefore,improving skeletal muscle regeneration is a key challenge in treating skeletal muscle-related disorders.Owing to their significant role in tissue regeneration,implantation of M2 macrophages(M2MФ)has great potential for improving skeletal muscle regeneration.Here,we present a short-wave infrared(SWIR)fluorescence imaging technique to obtain more in vivo information for an in-depth evaluation of the skeletal muscle regeneration effect after M2MФtransplantation.SWIR fluorescence imaging was employed to track implanted M2MФin the injured skeletal muscle of mouse models.It is found that the implanted M2MФaccumulated at the injury site for two weeks.Then,SWIR fluorescence imaging of blood vessels showed that M2MФimplantation could improve the relative perfusion ratio on day 5(1.09±0.09 vs 0.85±0.05;p=0.01)and day 9(1.38±0.16 vs 0.95±0.03;p=0.01)post-injury,as well as augment the degree of skeletal muscle regencration on day 13 post-injury.Finally,multiple linear regression analyses determined that post-injury time and relative perfusion ratio could be used as predictive indicators to evaluate skeletal muscle regeneration.These results provide more in vivo details about M2MФin skeletal muscle regeneration and confirm that M2MФcould promote angiogenesis and improve the degree of skeletal muscle repair,which will guide the research and development of M2MФimplantation to improve skeletal muscle regeneration.

Temporal and spatial regulation of biomimetic vascularization in 3D-printed skeletal muscles

In the intricate skeletal muscle tissue,the symbiotic relationship between myotubes and their supporting vasculature is pivotal in delivering essential oxygen and nutrients.This study explored the complex interplay between skeletal muscle and endothelial cells in the vascularization ofmuscle tissue.By harnessing the capabilities of three-dimensional(3D)bioprinting and modeling,we developed a novel approach involving the co-construction of endothelial and muscle cells,followed by their subsequent differentiation.Our findings highlight the importance of the interaction dynamics between these two cell types.Notably,introducing endothelial cells during the advanced phases of muscle differentiation enhanced myotube assembly.Moreover,it stimulated the development of the vascular network,paving the way for the early stages of vascularized skeletal muscle development.The methodology proposed in this study indicates the potential for constructing large-scale,physiologically aligned skeletal muscle.Additionally,it highlights the need for exploring the delicate equilibrium and mutual interactions between muscle and endothelial cells.Based on the multicell-type interaction model,we can predict promising pathways for constructing even more intricate tissues or organs.

Acupotomy ameliorates knee osteoarthritis-related collagen deposition and fibrosis in rabbit skeletal muscle through the TGF-β/Smad pathway

Objective:To investigate the effects of acupotomy on skeletal muscle fibrosis and collagen deposition in a rabbit knee osteoarthritis(KOA)model.Methods: Rabbits(n=18)were randomly divided into control,KOA,and KOA+acupotomy(Apo)groups(n=6).The rabbits in the KOA and Apo groups were modeled using the modified Videman's method for 6 weeks.After modeling,the Apo group was subjected to acupotomy once a week for 3 weeks on the vastus medialis,vastus lateralis,rectus femoris,biceps femoris,and anserine bursa tendons around the knee.The behavior of all animals was recorded,rectus femoris tissue was obtained,and histomorphological changes were observed using Masson staining and transmission electron microscopy.The expression of transforming growth factor-β1(TGF-β1),Smad 3,Smad 7,fibrillar collagen types I(Col-I)and III(Col-III)was detected using Western blot and real-time polymerase chain reaction(RT-PCR).Results: Histological analysis revealed that acupotomy improved the microstructure and reduced the collagen volume fraction of rectus femoris,compared with the KOA group(P=.034).Acupotomy inhibited abnormal collagen deposition by modulating the expression of fibrosis-related proteins and mRNA,thus preventing skeletal muscle fibrosis.Western blot and RT-PCR analysis revealed that in the Apo group,Col-I,and Col-III protein levels were significantly lower than those in the KOA group(both P<.01),same as Col-I and Col-III mRNA levels(P=.0031;P=.0046).Compared with the KOA group,the protein levels of TGF-β1 and Smad 3 were significantly reduced(both P<.01),as were the mRNA levels of TGF-β1 and Smad 3(P=.0007;P=.0011).Conversely,the levels of protein and mRNA of Smad 7 were significantly higher than that in the KOA group(P<.01;P=.0271).Conclusion: Acupotomy could alleviate skeletal muscle fibrosis and delay KOA progress by inhibiting collagen deposition through the TGF-β/Smad pathway in the skeletal muscle of KOA rabbits.

Catalpa bignonioides extract improves exercise performance through regulation of growth and metabolism in skeletal muscles

Objective:To evaluate the effects of Catalpa bignonioides fruit extract on the promotion of muscle growth and muscular capacity in vitro and in vivo.Methods:Cell viability was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.Cell proliferation was assessed using a 5-bromo-2’-deoxyuridine(BrdU)assay kit.Western blot analysis was performed to determine the protein expressions of related factors.The effects of Catalpa bignonioides extract were investigated in mice using the treadmill exhaustion test and whole-limb grip strength assay.Chemical composition analysis was performed using high-performance liquid chromatography(HPLC).Results:Catalpa bignonioides extract increased the proliferation of C2C12 mouse myoblasts by activating the Akt/mTOR signaling pathway.It also induced metabolic changes,increasing the number of mitochondria and glucose metabolism by phosphorylating adenosine monophosphate-activated protein kinase.In an in vivo study,the extract-treated mice showed improved motor abilities,such as muscular endurance and grip strength.Additionally,HPLC analysis showed that vanillic acid may be the main component of the Catalpa bignonioides extract that enhanced muscle strength.Conclusions:Catalpa bignonioides improves exercise performance through regulation of growth and metabolism in skeletal muscles,suggesting its potential as an effective natural agent for improving muscular strength.

Mitochondrial dysfunction in type 2 diabetes:A neglected path to skeletal muscle atrophy

Over the course of several decades,robust research has firmly established the significance of mitochondrial pathology as a central contributor to the onset of skeletal muscle atrophy in individuals with diabetes.However,the specific intricacies governing this process remain elusive.Extensive evidence highlights that individuals with diabetes regularly confront the severe consequences of skeletal muscle degradation.Deciphering the sophisticated mechanisms at the core of this pathology requires a thorough and meticulous exploration into the nuanced factors intricately associated with mitochondrial dysfunction.

In vivo measurement of NADH fluorescence lifetime in skeletal muscle via -ber-coupled time-correlated single photon counting

Nicotinamide adenine dinucleotide(NADH)is a cofactor that serves to shuttle electrons during metabolic processes such as glycolysis,the tricarboxylic acid cycle,and oxidative phosphorylation(OXPHOS).NADH is autofluorescent,and itsfluorescence lifetime can be used to infer metabolic dynamics in living cells.Fiber-coupled time-correlated single photon counting(TCSPC)equipped with an implantable needle probe can be used to measure NADH lifetime in vivo,enabling investigation of changing metabolic demand during muscle contraction or tissue regeneration.This study illustrates a proof of concept for point-based,minimally-invasive NADHfluorescence lifetime measurement in vivo.Volumetric muscle loss(VML)injuries were created in the left tibialis anterior(TA)muscle of male Sprague Dawley rats.NADH lifetime measurements were collected before,during,and after a 30 s tetanic contraction in the injured and uninjured TA muscles,which was subsequently-t to a biexponential decay model to yield a metric of NADH utilization(cytoplasmic vs protein-bound NADH,the A11/A22 ratio).On average,this ratio was higher during and after contraction in uninjured muscle compared to muscle at rest,suggesting higher levels of free NADH in contracting and recovering muscle,indicating increased rates of glycolysis.In injured muscle,this ratio was higher than uninjured muscle overall but decreased over time,which is consistent with current knowledge of inflammatory response to injury,suggesting tissue regeneration has occurred.These data suggest that-ber-coupled TCSPC has the potential to measure changes in NADH binding in vivo in a minimally invasive manner that requires further investigation.

Exploring the therapeutic effect of Xiaoyan d ecoction on lung cancer cachexia skeletal muscle atrophy based on L3-SMI

Background:Lung cancer cachexia has received widespread attention as one of the most common complications in patients with advanced lung cancer.As a multifactorial syndrome,lung cancer cachexia is characterized by a persistent decline in muscle mass that cannot be reversed by conventional nutrition Xiaoyan d ecoction can promote appetite and improve skeletal muscle mass in patients with lung cancer cachexia,while the third lumbar skeletal muscle index(L3-SMI)is able to determine whole-body skeletal muscle mass.To analyze the relationship between L3-SMI and hematological indexes and lung cancer cachexia,and to study the clinical efficacy of Xiaoyan decoction on skeletal muscle atrophy in lung cancer cachexia patients,with the aim of providing a reference basis for the early diagnosis and treatment of lung cancer cachexia patients and skeletal muscle atrophy.Methods:148 patients who were diagnosed with lung cancer in the Department of Oncology of the First Affiliated Hospital of Tianjin University of Traditional Chinese Medicine from January 2020 to December 2022 were included,and were divided into cachexia and non-cachexia groups according to the diagnostic criteria of cachexia,and analyzed the differences of hematological indexes and L3-SMI between cachexia patients and non-cachexia patients.And the patients with cachexia were divided into control group and treatment group,analyzed and compared the changes of body mass index(BMI),L 3-SMI,Karnofsky functional status score,albumin and other hematological indexes of the two groups before and after the treatment,and evaluated the safety of the Xiaoyan decoction in the treatment of cachexia.Results:A total of 148 lung cancer patients were included in this study,including 67 patients in the cachexia group and 81 patients in the non-cachexia group.According to the pre-treatment statistical analysis,the BMI of patients in the cachexia group was lower than that of patients in the non-cachexia group(P<0.05);among the biochemical function indexes,the proportions of creatinine(P<0.05),total protein(P<0.05),The levels of albumin in the cachexia group were significantly lower(P<0.05)compared to the non-cachexia group;in the cachexia group,both males and females had lower L3-SMIs than in the non-cachexia group(P<0.05).A total of 62 cases of lung cancer cachexia were studied,30 cases in the control group and 32 cases in the treatment group,according to statistical analysis,BMI was significantly different before and after treatment(P<0.05);L3-SMI was significantly different in the treatment group before and after treatment(P<0.05);Karnofsky significantly differed in the treatment group before and after treatment(P<0.05);and there was a significant difference in albumin before and after(P<0.05).Conclusion:Cachexia patients had significantly lower third lumbar skeletal muscle mass than non-cachexia patients,according to this study;Xiaoyan decoction was able to improve skeletal muscle mass,nutritional status as well as functional status of patients with cachexia in lung cancer,among others.

Menopausal transition alters female skeletal muscle transcriptome

Objectives Although skeletal muscle is a target of hormonal regulation,the muscle transcriptome,including messenger-RNA(mRNA),long non-coding RNAs(lncRNAs),and microRNAs(miRNAs)has not previously been studied across the menopausal transition.Thus,we took a multi-RNA-omics approach to get insight into transcriptome-wide events of menopause.Methods We included baseline and follow-up muscle samples from seven early(EarlyMT)and 17 late perimenopausal(LateMT)women transitioning to early postmenopause during the study.Total RNA was sequenced and differential expression(DE)of the transcriptome was investigated.Gene functions were investigated with pathway analyses and protein level expression with Western Blot.Results We found 30 DE mRNA genes in EarlyMT and 19 in LateMT participating in pathways controlling cell death,growth,and interactions with the external environment.Lack of protein level changes may indicate a specific role of the regulatory RNAs during menopause.10 DE lncRNA transcripts but no DE lncRNA genes were identified.No DE miRNAs were found.We identified putative regulatory networks likely to be affected by estradiol availability.Changes in gene expression were correlated with changes in body composition variables,indicating that muscularity and adiposity regulators are affected by menopausal transition.We also found correlations between gene expression and physical activity levels.Conclusions The observed DE genes and their regulatory networks offer novel mechanistic insights into factors affecting body composition during and after menopause.Our results imply that physiological deteriorations orchestrated by the muscle transcriptome likely depend on the magnitude of hormonal change and are influenced by physical activity.

Heat shock protein 90 is a potential therapeutic target for ameliorating skeletal muscle abnormalities in Parkinson's disease

Previous studies have confirmed that heat shock protein 90 overexpression can lead to dopami- nergic neuronal death. This study was designed to further investigate what effects are produced by heat shock protein 90 after endurance exercise training. Immunohistochemistry results showed that exercise training significantly inhibited heat shock protein 90 overexpression in the soleus and gastrocnemius in Parkinson＇s disease rats, which is a potential therapeutic target for ameliorating skeletal muscle abnormalities in Parkinso^s disease.

Pickering emulsion transport in skeletal muscle tissue:A dissipative particle dynamics simulation approach

Lymph node targeting is a commonly used strategy for particulate vaccines,particularly for Pickering emulsions.However,extensive research on the internal delivery mechanisms of these emulsions,especially the complex intercellular interactions of deformable Pickering emulsions,has been surprisingly sparse.This gap in knowledge holds significant potential for enhancing vaccine efficacy.This study aims to address this by summarizing the process of lymph-node-targeting transport and introducing a dissipative particle dynamics simulation method to evaluate the dynamic processes within cell tissue.The transport of Pickering emulsions in skeletal muscle tissue is specifically investigated as a case study.Various factors impacting the transport process are explored,including local cellular tissue environmental factors and the properties of the Pickering emulsion itself.The simulation results primarily demonstrate that an increase in radial repulsive interaction between emulsion particles can decrease the transport efficiency.Additionally,larger intercellular gaps also diminish the transport efficiency of emulsion droplet particles due to the increased motion complexity within the intricate transport space compared to a single channel.This study sheds light on the nuanced interplay between engineered and biological systems influencing the transport dynamics of Pickering emulsions.Such insights hold valuable potential for optimizing transport processes in practical biomedical applications such as drug delivery.Importantly,the desired transport efficiency varies depending on the specific application.For instance,while a more rapid transport might be crucial for lymph-node-targeted drug delivery,certain applications requiring a slower release of active components could benefit from the reduced transport efficiency observed with increased particle repulsion or larger intercellular gaps.

Effect of berberine on glucolipid metabolization in diabetic skeletal muscle and its mechanism

Aim To investigate the effect of berberine on damaged morphology and glucolipid metabolization in skeletal muscle of diabetic rat and the relationship between peroxisome proliferator-activated receptor （PPARs） α/γ/δ protein expression. Methods Type 2 diabetes mellitus rats were induced by an injection of 35 mg.kg^-1 streptozotocin （STZ） and a high-carbohydrate/ high-fat diet for 16 weeks. From week 17 to 32, diabetic rats were given low-, middle-, high-dose berberine （75, 150, 300 mg.kg^-1）, fenofibrate （100 mg.kg^-1） and rosiglitazone （4 mg.kg^-1） by oral administration, respectively. The skeletal muscle structure was observed with hematoxylin-eosin （HE） staining, glycogen and triglyceride contents were measured by spectrophotometry and PPAR α/γ/δ protein expressions were detected by immunohistochemistry. Results Fiber distribution remained normal in skeletal muscles of all the groups, middle-, high-dose berberine partly improved diabetic fibre atrophy, increased glycogen and decreased triglyceride levels in diabetic muscle （P〈 0.01）. Middle-, high-dose berberine and rosiglitazone all significantly reduced PPARy protein level in diabetic skeletal muscle （P 〈 0.01）; middle-, high-dose berberine and fenofibrate strikingly increased both PPARu and PPAR8 expression （P〈 0.01）. Conclusion Berberine modulates PPAR α/γ/δ protein expression in diabetic skeletal muscle which may contribute to ameliorate fibre damage and glucolipid metabolization.

GRADING OF RABBIT SKELETAL MUSCLE TRAUMA BY DIFFUSION TENSOR IMAGING AND TRACTOGRAPHY ON MAGNETIC RESONANCE IMAGING

Objective To distinguish the edema, injury, or rupture in the traumatic skeletal muscle fiber in vivo using diffusion tensor imaging （DTI） and tractography on magnetic resonance imaging （MRI）. Methods The skeletal muscle trauma models were made in 4 rabbits （ eight hindlimbs） by iron discus （ weight 1. 0 kg, diameter 6 cm） falling down vertically from 45 cm height to rabbits＇ thighs. Conventional sequences and two-dimensional （2D） diffusion-weighted （DW） spin-echo （SE） echo planar imaging （EPI） sequence with fat suppression （ b = 600 s/mm^2 ） were performed on 1.5T MRI scanner. The grading of edema, injury, and fiber rupture in the damaged muscle were made according to their histopathological views, which was consistent with the images. The mean apparent diffusion coefficient （ADC） values and fractional anisotropy （FA） values were measured from the region of interests （ROIs） of all groups on 2D DW images used for tractography. Analysis of variance test was performed to analyze all data. Results ADC values of the areas in normal muscle, edema muscle, injury muscle, and ruptured muscle were （6. 12±1.34 ） × 10^-3, （ 6.38±1.30 ） × 10^-3, （ 8.06±0. 97 ） × 10^-3, and （ 9. 57±0. 93 ） × 10^-3 mm^2/s, respectively. There was significant difference among groups （P 〈0. 001 ）, but no difference between edema muscle and normal muscle group （P 〉0. 05）. The FA values of normal muscle, edema muscle, injury muscle, and ruptured muscle were 0. 42±0. 12, 0. 36±0. 12, 0. 26±0. 09, 0. 12±0. 08, respectively, with a significant difference among groups （ P 〈 0. 001 ）. In the edema muscle, the tracking cross-fiber could be seen but it decreased slightly. In the injury muscle, the tracking fiber decreased markedly. In the ruptured muscle, the transverse-orientation tracking fiber vanished, yet some interrupted longitudinal-orientation tracking fiber could be found. Conclsion The edema, injury, and rupture of muscle fiber in rabbit damaged skeletal muscle can be verified according to the ADC and the FA on DTI and tractography.

Molecular cloning and mRNA expression analysis of myosin heavy chain(MyHC)from fast skeletal muscle of grass carp,Ctenopharyngodon idella

The myosin heavy chain(MyHC)is one of the major structural and contracting proteins of muscle.We have isolated the cDNA clone encoding MyHC of the grass carp,Ctenopharyngodon idella. The sequence comprises 5 934 bp,including a 5 814 bp open reading frame encoding an amino acid sequence of 1 937 residues.The deduced amino acid sequence showed 69%homology to rabbit fast skeletal MyHC and 73%–76%homology to the MyHCs from the mandarin fish,walleye pollack,white croaker,chum salmon,and carp.The putative sequences of subfragment-1 and the light meromyosin region showed 61.4%–80%homology to the corresponding regions of other fish MyHCs.The tissue-specific and developmental stage-specific expressions of the MyHC gene were analyzed by quantitative real-time PCR.The MyHC gene showed the highest expression in the muscles compared with the kidney,spleen and intestine.Developmentally,there was a gradual increase in MyHC mRNA expression from the neural formation stage to the tail bud stage.The highest expression was detected in hatching larva.Our work on the MyHC gene from the grass carp has provided useful information for fish molecular biology and fish genomics.

Impact of Bovine Skeletal Muscle Satellite Cell Differentiation by Small Interfering RNA Targeting Myogenin Gene

To examine the effect of myogenin gene on the differentiation of bovine skeletal muscle satellite cell, we constructed small interfering RNA plasmid vector to obtain myogenin knockdown bovine skeletal muscle cells, then used cell transfection, real time RCR and Western Blot to detect the influence of myogenin to cell differentiation. Results showed that the knockdown of myogenin significantly decreased its expression and other muscle-specific genes. Compared to the control, it could differentiate into few myotubes when challenged by low serum in the medium. These findings provided an important theoretical basis for further explore of the genetic mechanism in adult skeletal muscle, the remedy of muscle injuries and the cultivation of high-yield transgenic cattle.

Time-dependent gene expression analysis after mouse skeletal muscle contusion

Background:Though the mechanisms of skeletal muscle regeneration are deeply understood,those involved in muscle contusion,one of the most common muscle injuries in sports medicine clinics,are not.The objective of this study is to explore the mechanisms involved in muscle regeneration after contusion injury.Methods:In this study,a total of 72 mice were used.Eight of them were randomly chosen for the control group,while the rest were subjected to muscle contusion.Subsequently,their gastrocnemius muscles were harvested at different time points.The changes in muscle morphology were assessed by hematoxylin and eosin(HE) stain.In addition,the gene expression was analyzed by real-time polymerase chain reaction.Results:The data showed that the expression of many genes,i.e.,specific markers of immune cells and satellite cells,regulatory factors for muscle regeneration,cytokines,and chemokines,increased in the early stages of recovery,especially in the first 3 days.Furthermore,there were strict rules in the expression of these genes.However,almost all the genes returned to normal at 14 days post-injury.Conclusion:The sequence of immune cells invaded after muscle contusion was neutrophils,M1 macrophages and M2 macrophages.Some CC(CCL2,CCL3,and CCL4) and CXC(CXCL10) chemokines may be involved in the chemotaxis of these immune cells.HGF may be the primary factor to activate the satellite cells after muscle contusion.Moreover,2 weeks are needed to recover when acute contusion happens as used in this study.

Effects of plyometric vs.resistance training on skeletal muscle hypertrophy:A review

Objective:In this review,we critically evaluate studies directly comparing the effects of plyometric vs.resistance training on skeletal muscle hypertrophy.Methods:We conducted electronic searches of PubMed/MEDLINE,Scopus,SPORTDiscus,and Web of Science to find studies that explored the effects of plyometric vs.resistance training on muscle hypertrophy.Results:Eight relevant studies were included in the review.Six studies compared the effects of plyometric vs.resistance training on muscle hypertrophy,while 2 studies explored the effects of combining plyometric and resistance training vs.isolated resistance training on acute anabolic signaling or muscle hypertrophy.Based on the results of these studies,we conclude that plyometric and resistance training may produce similar effects on whole muscle hypertrophy for the muscle groups of the lower extremities.Therefore,it seems that plyometric training has a greater potential for inducing increases in muscle size than previously thought.Despite the findings observed at the whole muscle level,the evidence for the effects of plyometric training on hypertrophy on the muscle fiber level is currently limited for drawing inferences.Compared to isolated resistance training,combining plyometric and resistance exercise does not seem to produce additive effects on anabolic signaling or muscle growth;however,this area requires future study.The limitations of the current body of evidence are that the findings are specific to(a)musculature of the lower extremities,(b)short-term training interventions that lasted up to 12 weeks,and(c)previously untrained or recreationally active participants.Conclusion:This review highlights that plyometric and resistance training interventions may produce similar effects on whole muscle hypertrophy,at least for the muscle groups of the lower extremities,in untrained and recreationally trained individuals,and over short-term(i.e.,≤12 weeks)intervention periods.

Disruption of bone and skeletal muscle in severe burns

Severe burn injury triggers the body＇s nonspecific adaptive responses to acute insult, including the systemic inflammatory and stress responses, as well as the sympathetic response to immobilization. These responses trigger inflammatory bone resorption followed by glucocorticoid-induced apoptosis of osteoblasts and probably osteocytes. Because these patients are catabolic, they suffer concomitant muscle wasting and negative nitrogen balance. The use of anabolic agents such as recombinant human growth hormone and oxandrolone results in improved bone mineral content and muscle strength after approximately I year. Use of bisphosphonates within the first 10 days of a severe burn completely blocks the resorptive bone loss and has the added advantage of appearing to preserve muscle protein from excessive breakdown. The mechanism for the protective effect on muscle is not currently known. However, if the effect of bisphosphonates on muscle can be confirmed, it raises the possibility that bone communicates with muscle.