Photobiomodulation mitigates Bothrops jararacussu venom-induced damage in myoblast cells by enhancing myogenic factors and reducing cytokine production.

BACKGROUND: Photobiomodulation has exhibited promise in mitigating the local effects induced by Bothrops snakebite envenoming; however, the mechanisms underlying this protection are not yet fully understood. Herein, the effectiveness of photobiomodulation effects on regenerative response of C2C12 myoblast cells following exposure to Bothrops jararacussu venom (BjsuV), as well as the mechanisms involved was investigated. METHODOLOGY/PRINCIPAL FINDINGS: C2C12 myoblast cells were exposed to BjsuV (12.5 µg/mL) and irradiated once for 10 seconds with laser light of 660 nm (14.08 mW; 0.04 cm2; 352 mW/cm2) or 780 nm (17.6 mW; 0.04 cm2; 440 mW/ cm2) to provide energy densities of 3.52 and 4.4 J/cm2, and total energies of 0.1408 and 0.176 J, respectively. Cell migration was assessed through a wound-healing assay. The expression of MAPK p38-α, NF-Кß, Myf5, Pax-7, MyoD, and myogenin proteins were assessed by western blotting analysis. In addition, interleukin IL1-ß, IL-6, TNF-alfa and IL-10 levels were measured in the supernatant by ELISA. The PBM applied to C2C12 cells exposed to BjsuV promoted cell migration, increase the expression of myogenic factors (Pax7, MyF5, MyoD and myogenin), reduced the levels of proinflammatory cytokines, IL1-ß, IL-6, TNF-alfa, and increased the levels of anti-inflammatory cytokine IL-10. In addition, PBM downregulates the expression of NF-kB, and had no effect on p38 MAKP. CONCLUSION/SIGNIFICANCE: These data demonstrated that protection of the muscle cell by PBM seems to be related to the increase of myogenic factors as well as the modulation of inflammatory mediators. PBM therapy may offer a new therapeutic strategy to address the local effects of snakebite envenoming by promoting muscle regeneration and reducing the inflammatory process.

(-)-Epicatechin modulates the expression of myomiRs implicated in exercise response in mouse skeletal muscle.

The flavanol (-)-epicatechin has exercise-mimetic properties. Besides, several miRNAs play a role in modulating the adaptation of the muscle to different training protocols. However, notwithstanding all information, few studies aimed to determine if (-)-epicatechin can modify the expression of miRNAs related to skeletal muscle development and regeneration. Mice were treated for fifteen days by oral gavage with the flavanol (-)-epicatechin. After treatment, the quadriceps of the mice was dissected, and total RNA was extracted. The expression level of miR-133, -204, -206, -223, -486, and -491 was analyzed by qRT-PCR. We also used bioinformatic analysis to predict the participation of these miRNAs in different skeletal muscle signal transduction pathways. Additionally, we analyzed the level of the myogenic proteins MyoD and myogenin by Western blot and measured the cross-sectional area of muscle fibers stained with E&H. (-)-Epicatechin upregulated the expression of miR-133, -204, -206, -223, and -491 significantly, which was associated with an increase in the level of the myogenic proteins MyoD and Myogenin and an augment in the fiber size. The bioinformatics analysis showed that the studied miRNAs might participate in different signal transduction pathways related to muscle development and adaptation. Our results showed that (-)-epicatechin upregulated miRNAs that participate in skeletal exercise muscle adaptation, induced muscle hypertrophy, and increased the level of myogenic proteins MyoD and MyoG.

Skeletal muscle heme oxygenase-1 activity regulates aerobic capacity.

Physical exercise has profound effects on quality of life and susceptibility to chronic disease; however, the regulation of skeletal muscle function at the molecular level after exercise remains unclear. We tested the hypothesis that the benefits of exercise on muscle function are linked partly to microtraumatic events that result in accumulation of circulating heme. Effective metabolism of heme is controlled by Heme Oxygenase-1 (HO-1, Hmox1), and we find that mouse skeletal muscle-specific HO-1 deletion (Tam-Cre-HSA-Hmox1fl/fl) shifts the proportion of muscle fibers from type IIA to type IIB concomitant with a disruption in mitochondrial content and function. In addition to a significant impairment in running performance and response to exercise training, Tam-Cre-HSA-Hmox1fl/fl mice show remarkable muscle atrophy compared to Hmox1fl/fl controls. Collectively, these data define a role for heme and HO-1 as central regulators in the physiologic response of skeletal muscle to exercise.

The molecular effects of electrical stimulation on the muscle components of the urethra of female rats after trauma by vaginal distention.

AIMS: To evaluate the expression of genes and proteins related to the urethral muscles of female rats after trauma by vaginal distention (VD) and after electrical stimulation therapy (EST). METHODS: We compared the urethras of four groups of 20 animals each: control without trauma (C), 7 (recent-trauma) and 30 days (late-trauma) post-VD, and VD-treated with EST. We evaluated the expression of myogenic regulatory factors MYOD1 and myogenin (MYOG); skeletal muscle myosin heavy chain 1, 2, and 3 (MYH1, MYH2, and MYH3); smooth muscle MYH11; and myosin light chain 9 (MYL9). We used real-time quantitative polymerase chain reaction, Western blot analysis, and immunohistochemistry. RESULTS: MYOD1 and MYOG genes were overexpressed in the recent-trauma group compared with the other groups (P < .05). MYH1 and MYH3 genes were upregulated in the recent-trauma group compared with the control and EST groups (P < .05). The MYH2 gene was overexpressed in the late-trauma group (P < .05), while the MYH2 protein was significantly increased in the EST group compared with control, recent-trauma and late-trauma groups by 5-, 3-, and 2.7-fold change, respectively (P < .05). MYL9 and MYH11 messenger RNA were overexpressed in both trauma groups compared with control and EST groups (P < .05). MYH11 protein was not different among the study groups (P > .05). CONCLUSIONS: EST enhances the recovery of the damaged urethral tissue of rats mainly by acting on the striated-muscle components. The MYH2 pathway underlies the positive effects of EST in the external urethral sphincter.

Activation of protein synthesis, regeneration, and MAPK signaling pathways following repeated bouts of eccentric cycling.

The aim of this study was to examine the activation of skeletal muscle signaling pathways related to protein synthesis and the gene expression of regeneration/degradation markers following repeated bouts of eccentric cycling. Nine untrained men (25.4 ± 1.9 yr) performed two 30-min eccentric cycling bouts (ECC1, ECC2) at 85% of maximal concentric workload, separated by 2 wk. Muscle biopsies were taken from the vastus lateralis before and 2 h after each bout. Indirect markers of muscle damage were assessed before and 24-48 h after exercise. Changes in the Akt/mammalian target of rapamycin (mTOR)/rbosomal protein S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) and MAPK signaling pathways were measured by Western blot and changes in mRNA expression of IL-6 and IL-1ß, and myogenic regulatory factors (MRFs) were measured by real-time PCR. ECC1 induced greater increases in indirect markers of muscle damage compared with ECC2. Phosphorylation of S6K1 and rpS6 increased after both exercise bouts (P < 0.05), whereas phosphorylation of mTOR increased after ECC2 only (P = 0.03). Atrogin-1 mRNA expression decreased after ECC1 and ECC2 (P < 0.05) without changes in muscle RING-finger protein-1 mRNA. Basal mRNA levels of myoblast determination protein-1 (MyoD), MRF4, and myogenin were higher 2 wk after ECC1 (P < 0.05). MRF4 mRNA increased after ECC1 and ECC2 (P < 0.05), whereas MyoD mRNA expression increased only after ECC1 (P = 0.03). Phosphorylation of JNK and p38 MAPK increased after both exercise bouts (P < 0.05), similar to IL-6 and IL-1ß mRNA expression. All together, these results suggest that differential regulation of the mTOR pathway and MRF expression could mediate the repeated bout effect observed between an initial and secondary bout of eccentric exercise.

Chromatin Immunoprecipitation in Early Mouse Embryos.

Epigenetic regulation is achieved at many levels by different factors such as tissue-specific transcription factors, members of the basal transcriptional apparatus, chromatin-binding proteins, and noncoding RNAs. Importantly, chromatin structure dictates the availability of a specific genomic locus for transcriptional activation as well as the efficiency with which transcription can occur. Chromatin immunoprecipitation (ChIP) is a method that allows elucidating gene regulation at the molecular level by assessing if chromatin modifications or proteins are present at a specific locus. Initially, the majority of ChIP experiments were performed on cultured cell lines and more recently this technique has been adapted to a variety of tissues in different model organisms. Using ChIP on mouse embryos, it is possible to document the presence or absence of specific proteins and chromatin modifications at genomic loci in vivo during mammalian development and to get biological meaning from observations made on tissue culture analyses. We describe here a ChIP protocol on freshly isolated mouse embryonic somites for in vivo analysis of muscle specific transcription factor binding on chromatin. This protocol has been easily adapted to other mouse embryonic tissues and has also been successfully scaled up to perform ChIP-Seq.

High final energy of gallium arsenide laser increases MyoD gene expression during the intermediate phase of muscle regeneration after cryoinjury in rats.

The aim of this study was to determine the effects of gallium arsenide (GaAs) laser on IGF-I, MyoD, MAFbx, and TNF-α gene expression during the intermediate phase of muscle regeneration after cryoinjury 21 Wistar rats were divided into three groups (n = 7 per group): untreated with no injury (control group), cryoinjury without GaAs (injured group), and cryoinjury with GaAs (GaAs-injured group). The cryoinjury was induced in the central region of the tibialis anterior muscle (TA). The region injured was irradiated once a day during 14 days using GaAs laser (904 nm; spot size 0.035 cm2, output power 50 mW; energy density 69 J cm-2; exposure time 4 s per point; final energy 4.8 J). Twenty-four hours after the last application, the right and left TA muscles were collected for histological (collagen content) and molecular (gene expression of IGF-I, MyoD, MAFbx, and TNF-α) analyses, respectively. Data were analyzed using one-way ANOVA at P < 0.05. There were no significant (P > 0.05) differences in collagen density and IGF-I gene expression in all experimental groups. There were similar (P < 0.05) decreases in MAFbx and TNF-α gene expression in the injured and GaAs-injured groups, compared to control group. The MyoD gene expression increased (P = 0.008) in the GaAs-injured group, but not in the injured group (P = 0.338), compared to control group. GaAs laser therapy had a positive effect on MyoD gene expression, but not IGF-I, MAFbx, and TNF-α, during intermediary phases (14 days post-injury) of muscle repair.

Effect of MSTN propeptide protein on the growth and development of Altay lamb muscle.

Prokaryotic expression technology was used to express maltose-binding protein binding myostatin (MSTN) propeptide fusion protein. Six disease-free Altay lambs were used in this study. The right leg gastrocnemii were injected with MSTN recombinant propeptide protein. The left leg gastrocnemii (the control group) were injected with the same dose of phosphate based saline. The lambs were fed during four months under the same conditions and then slaughtered. Gastrocnemius samples were hematoxylin-eosin stained and the size of the muscle fibers was measured. A real-time polymerase chain reaction (RT-PCR) showed that single gastrocnemius cells in the experimental group had an average area of 1163.01 µm(2), while it was 845.09 µm(2) in the control group (P < 0.05). This indicates that the MSTN propeptide biological agents had an inhibitory effect on MSTN. In order to reveal its mechanism, RT-PCR was conducted to detect the expression of the differentiation-associated genes MyoD, Myf5, Myogenin, p21, and Smad3. The results showed that, in the MSTN propeptide biological agent injected group, expression levels of MSTN, Smad3, and p21 were lower than the control group, while Myf5, MyoD, and Myogenin were higher compared to the control group. This indicates that, when expression of the MSTN gene was inhibited, muscle cell differentiation and growth can be promoted by Smad3 up-regulated expression of Myf5, MyoD, and Myogenin.

Modulation of MAPK and NF-954;B Signaling Pathways by Antioxidant Therapy in Skeletal Muscle of Heart Failure Rats.

BACKGROUND/AIMS: Although increased oxidative stress plays a role in heart failure (HF)-induced skeletal myopathy, signaling pathways involved in muscle changes and the role of antioxidant agents have been poorly addressed. We evaluated the effects of N-acetylcysteine (NAC) on intracellular signaling pathways potentially modulated by oxidative stress in soleus muscle from HF rats. METHODS AND RESULTS: Four months after surgery, rats were assigned to Sham, myocardial infarction (MI)-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. Oxidative stress was evaluated in serum and soleus muscle; malondialdehyde was higher in MI-C than Sham and did not differ between MI-C and MI-NAC. Oxidized glutathione concentration in soleus muscle was similar in Sham and MI-C, and lower in MI-NAC than MI-C (Sham 0.168 ± 0.056; MI-C 0.223 ± 0.073; MI-NAC 0.136 ± 0.023 nmol/mg tissue; p = 0.014). Western blot showed increased p-JNK and decreased p38, ERK1/2, and p-ERK1/2 in infarcted rats. NAC restored ERK1/2. NF-954;B p65 subunit was reduced; p-Ser276 in p65 and I954;B was increased; and p-Ser536 unchanged in MI-C compared to Sham. NAC did not modify NF-954;B p65 subunit, but decreased p-Ser276 and p-Ser536. CONCLUSION: N-acetylcysteine modulates MAPK and NF-954;B signaling pathways in soleus muscle of HF rats.

Variation in myogenic differentiation 1 mRNA abundance is associated with beef tenderness in Nelore cattle.

The myogenic differentiation 1 gene (MYOD1) has a key role in skeletal muscle differentiation and composition through its regulation of the expression of several muscle-specific genes. We first used a general linear mixed model approach to evaluate the association of MYOD1 expression levels on individual beef tenderness phenotypes. MYOD1mRNA levels measured by quantitative polymerase chain reactions in 136 Nelore steers were significantly associated (P ≤ 0.01) with Warner-Bratzler shear force, measured on the longissimus dorsi muscle after 7 and 14 days of beef aging. Transcript abundance for the muscle regulatory gene MYOD1 was lower in animals with more tender beef. We also performed a co-expression network analysis using whole transcriptome sequence data generated from 30 samples of longissimus muscle tissue to identify genes that are potentially regulated by MYOD1. The effect of MYOD1 gene expression on beef tenderness may emerge from its function as an activator of muscle-specific gene transcription such as for the serum response factor (C-fos serum response element-binding transcription factor) gene (SRF), which determines muscle tissue development, composition, growth and maturation.

Comparative effects of low-level laser therapy pre- and post-injury on mRNA expression of MyoD, myogenin, and IL-6 during the skeletal muscle repair.

This study analyzed the effect of pre-injury and post-injury irradiation with low-level laser therapy (LLLT) on the mRNA expression of myogenic regulatory factors and interleukin 6 (IL-6) during the skeletal muscle repair. Male rats were divided into six groups: control group, sham group, LLLT group, injury group; pre-injury LLLT group, and post-injury LLLT group. LLLT was performed with a diode laser (wavelength 780 nm; output power 40 mW' and total energy 3.2 J). Cryoinjury was induced by two applications of a metal probe cooled in liquid nitrogen directly onto the belly of the tibialis anterior (TA) muscle. After euthanasia, the TA muscle was removed for the isolation of total RNA and analysis of MyoD, myogenin, and IL-6 using real-time quantitative PCR. Significant increases were found in the expression of MyoD mRNA at 3 and 7 days as well as the expression of myogenin mRNA at 14 days in the post-injury LLLT group in comparison to injury group. A significant reduction was found in the expression of IL-6 mRNA at 3 and 7 days in the pre-injury LLLT and post-injury LLLT groups. A significant increase in IL-6 mRNA was found at 14 days in the post-injury LLLT group in comparison to the injury group. LLLT administered following muscle injury modulates the mRNA expression of MyoD and myogenin. Moreover, the both forms of LLLT administration were able to modulate the mRNA expression of IL-6 during the muscle repair process.

Differentiated evolutionary relationships among chordates from comparative alignments of multiple sequences of MyoD and MyoG myogenic regulatory factors.

MyoD and MyoG are transcription factors that have essential roles in myogenic lineage determination and muscle differentiation. The purpose of this study was to compare multiple amino acid sequences of myogenic regulatory proteins to infer evolutionary relationships among chordates. Protein sequences from Mus musculus (P10085 and P12979), human Homo sapiens (P15172 and P15173), bovine Bos taurus (Q7YS82 and Q7YS81), wild pig Sus scrofa (P49811 and P49812), quail Coturnix coturnix (P21572 and P34060), chicken Gallus gallus (P16075 and P17920), rat Rattus norvegicus (Q02346 and P20428), domestic water buffalo Bubalus bubalis (D2SP11 and A7L034), and sheep Ovis aries (Q90477 and D3YKV7) were searched from a non-redundant protein sequence database UniProtKB/Swiss-Prot, and subsequently analyzed using the Mega6.0 software. MyoD evolutionary analyses revealed the presence of three main clusters with all mammals branched in one cluster, members of the order Rodentia (mouse and rat) in a second branch linked to the first, and birds of the order Galliformes (chicken and quail) remaining isolated in a third. MyoG evolutionary analyses aligned sequences in two main clusters, all mammalian specimens grouped in different sub-branches, and birds clustered in a second branch. These analyses suggest that the evolution of MyoD and MyoG was driven by different pathways.

Effects of Pax3 and Pax7 expression on muscle mass in the Pekin duck (Anas platyrhynchos domestica).

This study aimed to investigate whether the differential expression of muscle development-related genes is one of the reasons why muscle development differs between Pekin, Jianchang, and Heiwu ducks, which are all domesticated duck breeds (Anas platyrhynchos domestica) breeds. At 2 weeks of age, the RNA expression of paired box 7 (Pax7), paired box 3 (Pax3), myogenic differentiation antigen (MYOD), and myogenin (MYOG) genes were measured by quantitative polymerase chain reaction, and Pax3 and Pax7 protein levels were detected by western blot assay. Myofiber morphology was investigated using paraffin-embedded muscle sections. At 8 weeks of age, 30 ducks of each breed were slaughtered for meat quality determination. The results revealed that Pax3 and Pax7 expression levels at both the RNA and protein levels were high in the Pekin duck. In addition, MYOG expression levels in the Jianchang duck were significantly higher than in the other two duck breeds (P < 0.05). There were no significant differences in MYOD expression levels between the breeds (P > 0.05). Myofiber diameter and cross-sectional area were the largest in the Pekin duck and the smallest in the Heiwu duck. There were significant differences in slaughter data between these breeds, and muscle content was greatest in the Pekin duck. The results indicate that the muscle content of three different duck breeds is associated with the expression of satellite-cell marker genes.

Association of MyoD1a and MyoD1b gene polymorphisms and meat quality traits in rainbow trout.

In this study, we identified myogenic regulatory factors (MRFs) and analyzed the correlation between MRFs and meat quality in rainbow trout. The MyoD1a and MyoD1b genes were cloned from rainbow trout using a homology cloning method. Introns 1 and 2 in the MyoD1a and MyoD1b genes were cloned and submitted to GenBank (accession Nos. FJ623462 and FJ793566). Polymorphisms of MyoD1a and MyoD1b genes were analyzed using single-strand conformation polymorphism and sequencing, respectively. Two single nucleotide polymorphisms were detected in the MyoD1 gene, located at 129G→A in exon 1 and 37 G→A in exon 2. The 37 G→A mutation in exon 2 induced the R185K amino acid change in the polypeptide chain. Seven single nucleotide polymorphisms in the MyoD2 gene were detected, including 218T→C, 224T→C, 242A→C, 246T→A, 248T→C, 305T→C, and 329C→T. The 246T→A mutation in exon 1 induced the R83K change in the polypeptide chain. In the S3 fragment, meat quality traits of genotypes AA and AB significantly differed from those of genotype BB (P < 0.05). In the S5 fragment, meat quality traits of the genotypes AA and AC were significantly different from the genotypes BB and BC (P < 0.05). These results indicate that the MyoD1a and MyoD1b genes have an important influence on meat quality or were linked to the major genes in these strains. These genes can be used to control muscle fiber traits in rainbow trout, and the mutations in the S3 and S5 fragments can be used as molecular markers for selecting rainbow trout with better meat quality traits.

Small activating RNA induces myogenic differentiation of rat adipose-derived stem cells by upregulating MyoD.

PURPOSE: RNA activation (RNAa) is a mechanism of gene activation triggered by promoter-targeted small double stranded RNAs (dsRNAs), also known as small activating RNAs (saRNAs). Myogenic regulatory factor MyoD is regarded as the master activator of myogenic differentiation cascade by binding to enhancer of muscle specific genes. Stress urinary incontinence (SUI) is a condition primarily resulted from urethral sphincter deficiency. It is thus expected that by promoting differentiation of adipose-derived stem cells (ADSCs) into myoblasts by activating MyoD gene through RNAa may offer benefits to SUI. MATERIALS AND METHODS: Rats ADSCs were isolated, proliferated in vitro, and identified by flow cytometry. Purified ADSCs were then transfected with a MyoD saRNA or control transfected. Real-time polymerase chain reaction (RT-PCR) and western blotting were used to detect MyoD mRNA and protein expression, respectively. Immunocytochemical staining was applied to determine the expression of desmin protein in transfected cells. Cell viability was measured by using CellTiter 96R AQueous One Solution Cell Proliferation Assay kit. RESULTS: Transfection of a MyoD saRNA (dsMyoD) into ADSCs significantly induced the expression of MyoD at both the mRNA and protein levels, and inhibited cell proliferation. Desmin protein expression was detected in dsMyoD treated ADSCs 2 weeks later. CONCLUSION: Our findings show that RNAa mediated overexpression of MyoD can promote transdifferentiation of ADSCs into myoblasts and may help treat stress urinary incontinence (SUI)-a condition primarily resulted from urethral sphincter deficiency.

Small activating RNA induces myogenic differentiation of rat adipose-derived stem cells by upregulating MyoD

ABSTRACTPurpose:RNA activation (RNAa) is a mechanism of gene activation triggered by promoter-targeted small double stranded RNAs (dsRNAs), also known as small activating RNAs (saRNAs). Myogenic regulatory factor MyoD is regarded as the master activator of myogenic differentiation cascade by binding to enhancer of muscle specific genes. Stress urinary incontinence (SUI) is a condition primarily resulted from urethral sphincter deficiency. It is thus expected that by promoting differentiation of adipose-derived stem cells (ADSCs) into myoblasts by activating MyoD gene through RNAa may offer benefits to SUI.Materials and Methods:Rats ADSCs were isolated, proliferated in vitro, and identified by flow cytometry. Purified ADSCs were then transfected with a MyoD saRNA or control transfected. Real-time polymerase chain reaction (RT-PCR) and western blotting were used to detect MyoD mRNA and protein expression, respectively. Immunocytochemical staining was applied to determine the expression of desmin protein in transfected cells. Cell viability was measured by using CellTiter 96® AQueous One Solution Cell Proliferation Assay kit.Results:Transfection of a MyoD saRNA (dsMyoD) into ADSCs significantly induced the expression of MyoD at both the mRNA and protein levels, and inhibited cell proliferation. Desmin protein expression was detected in dsMyoD treated ADSCs 2 weeks later.Conclusion:Our findings show that RNAa mediated overexpression of MyoD can promote transdifferentiation of ADSCs into myoblasts and may help treat stress urinary incontinence (SUI)–a condition primarily resulted from urethral sphincter deficiency.

Expression and variation of Myf5 and MyoD1 genes in different tissues of Wuzhishan pigs.

The myogenic regulatory factor (MRF) family includes Myf5, MyoD1, Myf4, and Mfy6 genes. This experiment assessed the variation of Myf5 and MyoD1 genes from birth to maturity (30, 210, and 360 days) in the back muscle tissue of Wuzhishan pigs (WZSP), and the expression of Myf5 and MyoD1 mRNA in the heart, liver, lung, spleen, kidney, muscle, stomach, and intestine tissues were also examined. The results indicate that the expression level of mRNA for Myf5 and MyoD1 genes in the back muscle tissue is directly proportional to age (P < 0.05). Furthermore, of the eight adult pig tissue types that were tested, the expression of Myf5 and MyoD1 was highest in the muscle tissue.

Low-level laser irradiation modulates cell viability and creatine kinase activity in C2C12 muscle cells during the differentiation process.

Low-level laser irradiation (LLLI) is increasingly used to treat musculoskeletal disorders, with satisfactory results described in the literature. Skeletal muscle satellite cells play a key role in muscle regeneration. The aim of the present study was to evaluate the effect of LLLI on cell viability, creatine kinase (CK) activity, and the expression of myogenic regulatory factors in C2C12 myoblasts during the differentiation process. C2C12 cells were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 2% horse serum and submitted to irradiation with GaAlAs diode laser (wavelength, 780 nm; output power, 10 mW; energy density, 5 J/cm2). Cell viability and the expression of myogenic regulatory factors were assessed 24, 48, and 72 h after irradiation by 3-(4,5-dimethylthiazol-2-yl)-2,5,-diphenyltetrazolium bromide (MTT) assay and quantitative real-time polymerase chain reaction (RT-qPCR), respectively. CK activity was analyzed at 24 and 72 h. An increase in cell viability was found in the laser group in comparison to the control group at all evaluation times. CK activity was significantly increased in the laser group at 72 h. Myogenin messenger RNA (mRNA) demonstrated a tendency toward an increase in the laser group, but the difference in comparison to the control group was non-significant. In conclusion, LLLI was able to modulate cell viability and CK activity in C2C12 myoblasts during the differentiation process.

Low-level laser therapy (LLLT) (660nm) alters gene expression during muscle healing in rats.

INTRODUCTION: The effects of LLLT were studied during muscle regeneration through gene expression. METHODS: It was evaluated 10 and 50J/cm(2) doses during 7, 14 and 21days post cryoinjury, through histopathological analysis and mRNA MyoD, Myogenin, Vegf and Cox-2 expression. RESULTS: Irradiated groups presented less inflammatory process than control group after 14 and 21days. Cox-2 levels were downregulated in all irradiated groups after 7, 14 and 21days. On day 7, both treated groups had a downregulation of Vegf levels, and an upregulation after 14 and 21days, mainly with 50J/cm(2). The MyoD levels were upregulated with high dose in all periods and with low dose after 21days. Myogenin expression was downregulated in both treated groups after 7days, and was upregulated with 10J/cm(2) after 21days. CONCLUSION: These responses suggest that LLLT can improve the skeletal muscle regeneration through the gene expression stimulation.

Polymorphism of MyoD1 and Myf6 genes and associations with carcass and meat quality traits in beef cattle.

Myogenic determination factor 1 (MyoD1) and myogenic factor 6 (Myf6) genes belong to the myogenic differentiation (MyoD) gene family, which play key roles in growth and muscle development. The study aimed to investigate the effects of variants in cattle MyoD1 and Myf6 on carcass and meat traits. We screened single nucleotide polymorphisms (SNPs) of both genes in 8 cattle populations, including Simmental, Angus, Hereford, Charolais, Limousin, Qinchuan, Luxi, and Jinnan by sequencing. The G782A locus was identified in exon 1 of MyoD1 (MyoD1-BglI) as well as the T186C locus in exon 1 of Myf6 (Myf6-ApaLI). For the two SNPs, the A allele was significantly more frequent than the B allele in the populations tested. The χ(2) test showed that the MyoD1-BglI locus conformed to Hardy-Weinberg equilibrium in the 8 populations, as did the Myf6-ApaLI locus, with the exception of the Simmental population (P > 0.05). Association analysis revealed that the MyoD1-BglI locus was significantly associated with loin muscle area (LMA) (P < 0.05), and the Myf6-ApaLI locus was significantly associated with carcass length (CL) (P < 0.05). Animals with BB and AB genotypes for the MyoD1-BglI locus had larger LMAs compared to animals with AA genotype. Individuals with BB genotype had longer CLs compared to those with AA and AB genotypes. We conclude that the two SNPs might provide useful genetic markers, opening up new possibilities for cattle breeding and improvements in gene-assisted selection.