Search

The success of rotator cuff tendon repair relies on both tendon healing and muscle recovery. The objective of this descriptive study was to investigate the regenerative potential of the supraspinatus muscle in rotator cuff tear conditions by quantifying the expression of Pax7, MyoD, and myogenin, basic factors that regulate myogenesis. Muscle biopsies were collected from thirty-three patients aged 34 to 73 years who underwent surgery for a rotator cuff tear affecting the supraspinatus muscle. Among these patients, twenty-seven percent were women, and the age of the lesions ranged from 2 to 72 months post-initial trauma. Biopsies were harvested from the supraspinatus muscle at the end closest to the tendon, and control biopsies were harvested from the ipsilateral deltoid muscle. The densities of immunohistochemically stained Pax7+, MyoD+, and myogenin+ nuclei/mm2 were used to estimate the myogenic potential of the muscle. Adjustments were made for patient age and lesion age. We found increased density of MyoD+ and myogenin+ cells in supraspinatus muscles compared to deltoid muscles (p < 0.001 and p = 0.003, respectively). Regression analyses that combined the density of positive nuclei with patient age showed a continuous increase in Pax7 with age but also a reduction of MyoD and myogenin in older patients. When combined with lesion age, there was a decline in the density of all myogenic markers after an initial rise. Pax7 density continued to be higher in supraspinatus compared to the deltoid muscle, but the density of MyoD and myogenin terminally dropped to a density lower than in the deltoid. Our findings suggest that the supraspinatus muscle in tear conditions showed signs of initial activation of muscle regeneration. When compared to the unaffected deltoid muscle, an apparent reduction in capacity to progress to full muscle fiber maturity was also demonstrated. This pattern of inhibited myogenesis seemed to increase with both patient age and lesion age. Our results on muscle regenerative capacity indicate that younger patients with rotator cuff tears have better chances of muscle recovery and may benefit from early surgical reconstruction. [ABSTRACT FROM AUTHOR]

To study the efficacy and possible mechanisms of radial extracorporeal shock wave (rESW) with different frequencies for the treatment of acute skeletal muscle injury in rabbits, 48 rabbits of acute injured biceps femoris were randomly divided into 4 groups. Except for the control group, the other groups were treated by rESW with 5 Hz, 10 Hz and 15 Hz, respectively. The injury symptom index scores (ISISs) in the rESW group were significantly lower than those in the control group, with the lowest in the 10 Hz rESW group. Histomorphological features demonstrated a decrease in mononuclear cells and an increase in new myocytes across all groups, with the rESW group showing the most significant changes. The concentrations of PGE2 and IL-1β were significantly lower in all rESW groups by ELISA compared to the control group. Additionally, the 10 Hz group had lower concentrations than the 5 Hz and 15 Hz group. Compared with the control group, MyoD of the rESW groups was significantly increased, and the expression level of the 10 Hz group was higher than that of the other groups. In conclusion, rESW with 5 Hz, 10 Hz and 15 Hz take certain curative effects on acute biceps femoris injury in rabbits, and the 10 Hz rESW takes advantage over 5 Hz and 15 Hz rESW. [ABSTRACT FROM AUTHOR]

The hybrids (BY) derived from blunt snout bream (Megalobrama amblycephala, BSB, ♀) and Bleeker’s yellow tai (Xenocypris davidi Bleeker, YT, ♂) have a fast growth rate and body thickness. However, the molecular mechanisms underlying the growth advantage of BY are still unclear. MSTN, a member of the TGF-β superfamily, is a negative regulator of muscle growth and development. MYOD, a member of the myogenic regulatory factor family (MRFs), is a positive regulator of muscle growth and development. MSTN and MYOD interact to coregulate muscle growth and development. In this study, we cloned the full-length cDNAs of mstn and myod in BY, analyzed differential expression of the two genes in muscle of BY and its parents, and observed the localization of the two genes during embryonic development of BY. Multiple sequence alignment of amino acids and phylogenetic analysis showed that mstn and myod were highly conserved in BY, BSB, YT, and other carp family fishes. Quantitative Real-time PCR (qRT-PCR) showed that mstn and myod were primarily expressed in muscle of BY, and there were significant differences in the expression of the two genes in the red and white muscles of BY, BSB, and YT at different age. The results of in situ hybridization of embryos showed an overlap in the temporal and spatial expression of mstn and myod in BY embryo development, suggesting that the two genes might interact to co-regulate embryo growth and development. This study provides a theoretical basis for further research on the mechanisms of mstn and myod in muscle growth of hybrid fishes. [ABSTRACT FROM AUTHOR]

Muscle regeneration depends on muscle stem cell (MuSC) activity. Myogenic regulatory factors, including myoblast determination protein 1 (MyoD), regulate the fate transition of MuSCs. However, the direct target of MYOD in the process is not completely clear. Using previously established MyoD knock-in (MyoD-KI) mice, we revealed that MyoD targets dual-specificity phosphatase (Dusp) 13 and Dusp27. In Dusp13 : Dusp27 double knock-out mice, the ability for muscle regeneration after injury was reduced. Moreover, single-cell RNA sequencing of MyoD-high expressing MuSCs from MyoD-KI mice revealed that Dusp13 and Dusp27 are expressed only in specific populations within MyoD-high MuSCs, which also express Myogenin. Overexpressing Dusp13 in MuSCs causes premature muscle differentiation. Thus, we propose a model where DUSP13 and DUSP27 contribute to the fate transition of MuSCs from proliferation to differentiation during myogenesis. [ABSTRACT FROM AUTHOR]

Abstract To study the efficacy and possible mechanisms of radial extracorporeal shock wave (rESW) with different frequencies for the treatment of acute skeletal muscle injury in rabbits, 48 rabbits of acute injured biceps femoris were randomly divided into 4 groups. Except for the control group, the other groups were treated by rESW with 5 Hz, 10 Hz and 15 Hz, respectively. The injury symptom index scores (ISISs) in the rESW group were significantly lower than those in the control group, with the lowest in the 10 Hz rESW group. Histomorphological features demonstrated a decrease in mononuclear cells and an increase in new myocytes across all groups, with the rESW group showing the most significant changes. The concentrations of PGE2 and IL-1β were significantly lower in all rESW groups by ELISA compared to the control group. Additionally, the 10 Hz group had lower concentrations than the 5 Hz and 15 Hz group. Compared with the control group, MyoD of the rESW groups was significantly increased, and the expression level of the 10 Hz group was higher than that of the other groups. In conclusion, rESW with 5 Hz, 10 Hz and 15 Hz take certain curative effects on acute biceps femoris injury in rabbits, and the 10 Hz rESW takes advantage over 5 Hz and 15 Hz rESW.

Abstract Background Numerous studies have shown that somite development is a necessary stage of myogenesis chondrogenesis and osteogenesis. Our previous study has established a stable presomitic mesoderm progenitor cell line (UiPSM) in vitro. Naturally, we wanted to explore whether UiPSM cell can develop bone and myogenic differentiation. Results Selective culture conditions yielded PAX3 and PAX7 positive skeletal muscle precursors from UiPSM cells. The skeletal muscle precursors undergo in vitro maturation resulting in myotube formation. MYOD effectively promoted the maturity of the skeletal myocytes in a short time. We found that UiPSM and MYOD mediated UiPSM cell-derived skeletal myocytes were viable after transplantation into the tibialis anterior muscle of MITRG mice, as assessed by bioluminescence imaging and scRNA-seq. Lack of teratoma formation and evidence of long-term myocytes engraftment suggests considerable potential for future therapeutic applications. Moreover, UiPSM cells can differentiate into osteoblast and chondroblast cells in vitro. Conclusions UiPSM differentiation has potential as a developmental model for musculoskeletal development research and treatment of musculoskeletal disorders.

Purpose: We investigated the effects of mouse-derived DFAT on the myogenic differentiation of a mouse-derived myoblast cell line (C2C12) and examined the therapeutic effects of rat-derived DFAT on anal sphincter injury using a rat model. Methods: C2C12 cells were cultured using DMEM and DFAT-conditioned medium (DFAT-CM), evaluating MyoD and Myogenin gene expression via RT-PCR. DFAT was locally administered to model rats with anorectal sphincter dysfunction 3 days post-CTX injection. Therapeutic effects were assessed through functional assessment, including anal pressure measurement using solid-state manometry pre/post-CTX, and on days 1, 3, 7, 10, 14, 17, and 21 post-DFAT administration. Histological evaluation involved anal canal excision on days 1, 3, 7, 14, and 21 after CTX administration, followed by hematoxylin–eosin staining. Results: C2C12 cells cultured with DFAT-CM exhibited increased MyoD and Myogenin gene expression compared to control. Anal pressure measurements revealed early recovery of resting pressure in the DFAT-treated group. Histologically, DFAT-treated rats demonstrated an increase in mature muscle cells within newly formed muscle fibers on days 14 and 21 after CTX administration, indicating enhanced muscle tissue repair. Conclusion: DFAT demonstrated the potential to enhance histological and functional muscle tissue repair. These findings propose DFAT as a novel therapeutic approach for anorectal sphincter dysfunction treatment. [ABSTRACT FROM AUTHOR]

Background: Numerous studies have shown that somite development is a necessary stage of myogenesis chondrogenesis and osteogenesis. Our previous study has established a stable presomitic mesoderm progenitor cell line (UiPSM) in vitro. Naturally, we wanted to explore whether UiPSM cell can develop bone and myogenic differentiation. Results: Selective culture conditions yielded PAX3 and PAX7 positive skeletal muscle precursors from UiPSM cells. The skeletal muscle precursors undergo in vitro maturation resulting in myotube formation. MYOD effectively promoted the maturity of the skeletal myocytes in a short time. We found that UiPSM and MYOD mediated UiPSM cell-derived skeletal myocytes were viable after transplantation into the tibialis anterior muscle of MITRG mice, as assessed by bioluminescence imaging and scRNA-seq. Lack of teratoma formation and evidence of long-term myocytes engraftment suggests considerable potential for future therapeutic applications. Moreover, UiPSM cells can differentiate into osteoblast and chondroblast cells in vitro. Conclusions: UiPSM differentiation has potential as a developmental model for musculoskeletal development research and treatment of musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

Heart failure (HF) prognosis depends on various regulatory factors; microRNA‐128 (miR‐128) is identified as a regulator of cardiac fibrosis, contributing to HF. MyoD family inhibitor (MDFI), which is reported to be related with Wnt/β‐catenin pathway, is supposed to be regulated by miR‐128. This study investigates the interaction between miR‐128 and MDFI in cardiomyocyte development and elucidates its role in heart injury. Gene expression profiling assessed miR‐128's effect on MDFI expression in HF using qPCR and Western blot analysis. Luciferase assays studied the direct interaction between miR‐128 and MDFI. MTT, transwell, and immunohistochemistry evaluated the effects of miR‐128 and MDFI on myocardial cells in mice HF. Genescan and luciferase assays validated the interaction between miR‐128 and MDFI sequences. miR‐128 mimics significantly reduced MDFI expression at mRNA and protein levels with decrease rate of 55%. Overexpression of miR‐128 promoted apoptosis with the increase rate 65% and attenuated cardiomyocyte proliferation, while MDFI upregulation significantly enhanced proliferation. Elevated miR‐128 levels upregulated Wnt1 and β‐catenin expression, whereas increased MDFI levels inhibited these expressions. Histological analysis with haematoxylin and eosin staining revealed that miR‐128 absorption reduced MDFI expression, hindering cell proliferation and cardiac repair, with echocardiography showing corresponding improvements in cardiac function. Our findings suggest miR‐128 interacts with MDFI, playing a crucial role in HF management by modulating the Wnt1/β‐catenin pathway. Suppression of miR‐128 could promote cardiomyocyte proliferation, highlighting the potential value of the miR‐128/MDFI interplay in HF treatment. [ABSTRACT FROM AUTHOR]

During embryogenesis, basic fibroblast growth factor (bFGF) is released from neural tube and myotome to promote myogenic fate in the somite, and is routinely used for the culture of adult skeletal muscle (SKM) stem cells (MuSC, called satellite cells). However, the mechanism employed by bFGF to promote SKM lineage and MuSC proliferation has not been analyzed in detail. Furthermore, the question of if the post-translational modification (PTM) of bFGF is important to its stemness-promoting effect has not been answered. In this study, GST-bFGF was expressed and purified from E.coli, which lacks the PTM system in eukaryotes. We found that both GST-bFGF and commercially available bFGF activated the Akt–Erk pathway and had strong cell proliferation effect on C2C12 myoblasts and MuSC. GST-bFGF reversibly compromised the myogenesis of C2C12 myoblasts and MuSC, and it increased the expression of Myf5, Pax3/7, and Cyclin D1 but strongly repressed that of MyoD, suggesting the maintenance of myogenic stemness amid repressed MyoD expression. The proliferation effect of GST-bFGF was conserved in C2C12 over-expressed with MyoD (C2C12-tTA-MyoD), implying its independence of the down-regulation of MyoD. In addition, the repressive effect of GST-bFGF on myogenic differentiation was almost totally rescued by the over-expression of MyoD. Together, these evidences suggest that (1) GST-bFGF and bFGF have similar effects on myogenic cell proliferation and differentiation, and (2) GST-bFGF can promote MuSC stemness and proliferation by differentially regulating MRFs and Pax3/7, (3) MyoD repression by GST-bFGF is reversible and independent of the proliferation effect, and (4) GST-bFGF can be a good substitute for bFGF in sustaining MuSC stemness and proliferation. [ABSTRACT FROM AUTHOR]

Cellular therapy holds immense promise to remuscularize the damaged myocardium but is practically hindered by limited allogeneic sources of cardiac-committed cells that engraft stably in the recipient heart after transplantation. Here, we demonstrate that the pericardial tissue harbors myogenic stem cells (pSCs) that are activated in response to inflammatory signaling after myocardial infarction (MI). The pSCs derived from the MI rats (MI-pSCs) show in vivo and in vitro cardiac commitment characterized by cardiac-specific Tnnt2 expression and formation of rhythmic contraction in culture. Bulk RNA-seq analysis reveals significant upregulation of a panel of genes related to cardiac/myogenic differentiation, paracrine factors, and extracellular matrix in the activated pSCs compared to the control pSCs (Sham-pSCs). Notably, we define MyoD as a key factor that governs the process of cardiac commitment, as siRNA-mediated MyoD gene silencing results in a significant reduction of myogenic potential. Injection of the cardiac-committed cells into the infarcted rat heart leads to long-term survival and stable engraftment in the recipient myocardium. Therefore, these findings point to pericardial myogenic progenitors as an attractive candidate for cardiac cell-based therapy to remuscularize the damaged myocardium. [ABSTRACT FROM AUTHOR]

The transcriptional regulation of skeletal muscle (SKM) development (myogenesis) has been documented for over 3 decades and served as a paradigm for tissue-specific cell type determination and differentiation. Myogenic stem cells (MuSC) in embryos and adult SKM are regulated by the transcription factors Pax3 and Pax7 for their stem cell characteristics, while their lineage determination and terminal differentiation are both dictated by the myogenic regulatory factors (MRF) that comprise Mrf4, Myf5, Myogenin, and MyoD. The myocyte enhancer factor Mef2c is activated by MRF during terminal differentiation and collaborates with them to promote myoblast fusion and differentiation. Recent studies have found critical regulation of these myogenic transcription factors at mRNA level, including subcellular localization, stability, and translational regulation. Therefore, the regulation of Pax3/7, MRFs and Mef2c mRNAs by RNA-binding factors and non-coding RNAs (ncRNA), including microRNAs and long non-coding RNAs (lncRNA), will be the focus of this review and the impact of this regulation on myogenesis will be further addressed. Interestingly, the stem cell characteristics of MuSC has been found to be critically regulated by ncRNAs, implying the involvement of ncRNAs in SKM homeostasis and regeneration. Current studies have further identified that some ncRNAs are implicated in the etiology of some SKM diseases and can serve as valuable tools/indicators for prediction of prognosis. The roles of ncRNAs in the MuSC biology and SKM disease etiology will also be discussed in this review. [ABSTRACT FROM AUTHOR]

Reparative properties of infrared laser exposure are well known, but the effects of green laser light are little studied. We analyzed the effects of short (60 sec) and longer (180 sec) exposure to infrared (980 nm) and green (520 nm) laser on the number of activated myosatellite cells in the regenerating m. gastrocnemius of Wistar rats after infliction of an incision wound. Histological preparations were used for morphometric evaluation of myosatellite cells with MyoD+ nuclei. Increased numbers of MyoD+ nuclei were observed on days 3 and 7 after 60-sec exposure to infrared and green laser. [ABSTRACT FROM AUTHOR]

Background: Skeletal muscle fibers form through the fusion of myoblasts, a process regulated by Racl, a small G-protein crucial for actin dynamics. Understanding Rac1's role in muscle stem cell distribution is essential for elucidating muscle regeneration mechanisms. Aim: This study aims to investigate the significance of Rac1 in muscle stem cell distribution and myogenesis using conditional knockout mice. Methods: Conditional Rac1 mutant mice were generated, and the distribution of Pax7-positive stem cells was assessed. Comparative analysis of mutant myogenic cells was conducted to elucidate Rac1's role throughout the fusion process. Immunofluorescence staining and transmission electron microscopy were employed for cellular and ultrastructural analysis. Results: Rac1-lacking muscle exhibited a reduction in Pax7-positive satellite cells, indicating its importance in muscle stem cell distribution. Comparative analysis of mutant myogenic cells revealed distinct roles for Rac1 throughout the fusion process. Transmission electron microscopy studies demonstrated irregularities in muscle cell layers in Rac1-deficient mice. Conclusion: Our study highlights the critical role of Rac1 in myogenesis and muscle stem cell distribution. Rac1 deficiency led to fewer Pax7-positive satellite cells, emphasizing its importance in muscle regeneration. These findings provide insights into potential therapeutic interventions for muscle-related disorders. [ABSTRACT FROM AUTHOR]

The principles of myogenesis play crucial roles in the production of cultured meat, and identifying protein stimulators associated with myogenesis holds great potential to enhance the efficiency of this process. In this study, we used surface plasmon resonance (SPR)-based screening of a natural product library to discover ligands for Pax7 and MyoD, key regulators of satellite cells (SCs), and performed cell-based assays on Hanwoo SCs (HWSCs) to identify substances that promote cell proliferation and/or differentiation. Through an SPR analysis, we found that six chemicals, including one Pax7+/MyoD− chemical, four Pax7+/MyoD+ chemicals, and one Pax7−/MyoD+ chemical, bound to Pax7 and/or MyoD proteins. Among four Pax7+/MyoD+ chemicals, parthenolide (0.5 and 1 µM) and rutin (100 and 200 µM) stimulated cell proliferation in the medium with 10% FBS similar to the medium with 20% FBS, without affecting differentiation. Adenosine, a Pax7−/MyoD+ chemical, accelerated differentiation. These chemicals could be potential additives to reduce the reliance of FBS required for HWSC proliferation and differentiation in cultured meat production. [ABSTRACT FROM AUTHOR]

ObjectiveTo observe effects of electroacupuncture at Fengchi acupoint on expression of myosatellite cells, myogenic determining factor (MyoD), proliferating cell nuclear antigen (PCNA), Toll-like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (MyD88) and nuclear factor-kappa B p65 (NF-κBp65) protein in rat with chronic cervical muscle injury, so as to explore possible mechanism of electroacupuncture in promoting the repair of chronic cervical muscle injury.MethodsTen Wistar rats were selected from 45 Wistar rats as blank group, and the remaining rats were divided into model group, electroacupuncture group (EA group) and meloxicam group according to random number table method, with 10 rats in each group (5 rats were unsuccessful in modeling). Chronic cervical muscle injury model of rats was established by long-term head flexion fixation and hypertonic saline injection. After 3 months of modeling, the morphological changes of posterior cervical muscle were observed by ultrasonic diagnostic detector. The success of modeling was verified by EMG. The EA group received electroacupuncture at Fengchi acupoint on both sides, 25 min each time, once a day, for 10 consecutive days as one course of treatment, with an interval of two days between courses of treatment, for 2 courses of treatment. After intervention, the posterior cervical muscle tissue of rats in each group was collected and the morphological changes of posterior cervical muscle tissue were observed under electron microscope. The protein contents of PCNA, MyoD, TLR4, MyD88 and NF-κBp65 were detected by immunohistochemistry.Results1) Morphological detection: Compared with the blank group, ultrasonic diagnosis results of the model group showed that tissue of posterior cervical muscle of rats was discontinuous and thickness was significantly narrower. Electrophysiological test results showed that amplitude and frequency of electromyographic significantly decreased in the model group. Compared with the blank group, muscle electron microscopy results of the model group showed that the arrangement of myofibrils was discontinuous, some mitochondria were swollen, and there were breaks between muscle fibers and muscle segments, and there were vacuoles. Compared with the model group, the EA group showed that myofibrils were clearly visible, cross-section of the myofibrils was punctured, sarcomere and serosa were intact, some mitochondria were swollen, and a few of them had vacuoles at the fracture of myofibrils. Myofibril structure of the meloxicam group was occasionally irregular, with vacuoles at the fracture of myofibril and a small amount of mitochondrial swelling. 2) Immunohistochemistry: Compared with the blank group, expression of PCNA and MyoD in model group was weakly positive, and protein expression of TLR4, MyD88 and NF-κBp65 significantly increased (PPPP>0.05).ConclusionThe treatment of chronic cervical muscle injury by electroacupuncture at Fengchi acupoint may be related to promoting the proliferation and differentiation of myosatellite cells, and the mechanism may be achieved by regulating the TLR4/MyD88/NF-κB signal transduction pathway.

Long non-coding RNAs (lncRNAs) are involved in the process of muscle cell differentiation and play an important role. Previous studies have shown that lncRNA-MEG3 promotes the differentiation of porcine skeletal muscle satellite cells (PSCs), but the regulatory mechanism of MEG3 interaction with target protein has not been well studied. We demonstrated that MEG3 can bind dihydrolipoamide succinyltransferase (DLST) by RNA pull down and RIP-qPCR. Subsequently, knockdown and overexpression experiments showed that DLST promotes PSCs differentiation. Rescue experiments showed that the expression of DLST protein was significantly increased with MEG3 overexpression and decreased with MEG3 knockdown, while its mRNA expression was not changed. Furthermore, we have successfully predicted and validated that the transcription factor myogenic differentiation (MYOD) binds to the MEG3 core promoter though utilizing chromatin immunoprecipitation (CHIP) and luciferase reporter assays. The results indicated that MYOD acts as a transcription factor of MEG3 to promote MEG3 transcription. Knockdown of MEG3 in vivo indicated that MEG3 is involved in skeletal muscle regeneration. It is concluded that MYOD acts as a transcription factor to induce MEG3 expression. MEG3 acts as a molecular scaffold to bind and promote DLST protein expression. This paper provides a new molecular mechanism for MEG3 to promote the differentiation of PSCs.

Skeletal muscle myoblastic cell lines can provide a valuable new in vitro model for the exploration of the mechanisms that control skeletal muscle development and its associated molecular regulation. In this study, the skeletal muscle tissues of grass carp were digested with trypsin and collagenase I to obtain the primary myoblast cell culture. Myoblast cells were obtained by differential adherence purification and further analyzed by cryopreservation and resuscitation, chromosome analysis, immunohistochemistry, and immunofluorescence. A continuous grass carp myoblast cell line (named CIM) was established from grass carp (Ctenopharyngodon idellus) muscle and has been subcultured > 100 passages in a year and more. The CIM cells revived at 79.78–95.06% viability after 1–6 months of cryopreservation, and shared a population doubling time of 27.24 h. The number of modal chromosomes of CIM cells was 48, and the mitochondrial 12S rRNA sequence of the CIM cell line shared 99% identity with those of grass carp registered in GenBank. No microorganisms (bacteria, fungi, or mycoplasma) were detected during the whole study. The cell type of CIM cells was proven to be myoblast by immunohistochemistry of specific myogenic protein markers, including CD34, desmin, MyoD, and MyHC, as well as relative expression of key genes. And the myogenic rate and fusion index of this cell line after 10 days of induced differentiation were 8.96 ~ 9.42% and 3–24%, respectively. The telomerase activity and transfection efficiency of CIM cell line were 0.027 IU/mgprot and 23 ~ 24%, respectively. These results suggest that a myoblast cell line named CIM with normal biological function has been successfully established, which may provide a valuable tool for related in vitro studies. [ABSTRACT FROM AUTHOR]

Abstract Background Brachial Plexus Injury (BPI) is one of the peripheral nerve injuries which causes severe functional impairment and disability. Without prompt treatment, prolonged denervation will cause severe muscle atrophy. MyoD, which is expressed by satellite cells, is one of the parameters that relate to the regeneration process in post-injury muscle and it is presumed to determine the clinical outcome following neurotization procedure. This study aims to understand the correlation between time to surgery (TTS) and MyoD expression in satellite cells in the biceps muscle of adult brachial plexus injury patients. Methods Analytic observational study with a cross-sectional design was conducted at Dr. Soetomo General Hospital. All patients with BPI who underwent surgery between May 2013 and December 2015 were included. Muscle biopsy was taken and stained using immunohistochemistry for MyoD expression. Pearson correlation test was used to assess the correlation between MyoD expression with TTS and with age. Results Twenty-two biceps muscle samples were examined. Most patients are males (81.8%) with an average age of 25.5 years. MyoD expression was found to be highest at TTS of 4 months and then dropped significantly (and plateau) from 9 to 36 months. MyoD expression is significantly correlated with TTS (r=-0.895; p = 0.00) but not with age (r=-0.294; p = 0.184). Conclusion Our study found, from the cellular point of view, that treatment of BPI needs to be done as early as possible before the regenerative potential - as indicated by MyoD expression – declined.

Labeo rohita is a widely cultivated tropical freshwater carp and found in rivers of South Asian region. A new cell line, designated LRM, has been developed from the muscle tissue of L. rohita. Muscle cells were subcultured up to 38 passages in a Leibovitz's-15 (L-15) supplemented with 10% FBS (Fetal Bovine Serum) and 10 ng/ml bFGF. The LRM cells exhibited fibroblastic morphology with a doubling time of 28 h, and a plating efficiency of 17%. A maximum growth rate was observed for LRM cells at 28 °C, 10% FBS and 10 ng/ml bFGF. A cytochrome C oxidase subunit I (COI) gene sequence was used to authenticate the developed cell line. Chromosome analysis revealed 50 diploid chromosomes. The fibroblastic characteristics of the of the LRM cells was confirmed by immunocytochemistry. The expression of MyoD gene in LRM cells was analyzed by quantitative PCR in comparison with passages 3, 18 and 32. The expression of MyoD was higher at passage 18 compared to the passages 3 and 32. The LRM cells attached properly onto the 2D scaffold and the expression of the F-actin filament protein was confirmed by phalloidin staining followed by counter staining with DAPI to observe the distribution of the muscle cell nuclei and the cytoskeleton protein. A revival rate of 70–80% was achieved when the LRM cells were cryopreserved at − 196 °C using liquid nitrogen. This study would further contribute to understanding the in vitro myogenesis and progress toward cultivated fish meat production. [ABSTRACT FROM AUTHOR]

Herein, we review a unique and versatile lineage composed of Myo/Nog cells that may be beneficial or detrimental depending on their environment and nature of the pathological stimuli they are exposed to. While we will focus on the lens, related Myo/Nog cell behaviors and functions in other tissues are integrated into the narrative of our research that spans over three decades, examines multiple species and progresses from early stages of embryonic development to aging adults. Myo/Nog cells were discovered in the embryonic epiblast by their co-expression of the skeletal muscle-specific transcription factor MyoD, the bone morphogenetic protein inhibitor Noggin and brain-specific angiogenesis inhibitor 1. They were tracked from the epiblast into the developing lens, revealing heterogeneity of cell types within this structure. Depletion of Myo/Nog cells in the epiblast results in eye malformations arising from the absence of Noggin. In the adult lens, Myo/Nog cells are the source of myofibroblasts whose contractions produce wrinkles in the capsule. Eliminating this population within the rabbit lens during cataract surgery reduces posterior capsule opacification to below clinically significant levels. Parallels are drawn between the therapeutic potential of targeting Myo/Nog cells to prevent fibrotic disease in the lens and other ocular tissues. [ABSTRACT FROM AUTHOR]

E3 ubiquitin ligases are closely related to cell division, differentiation, and survival in all eukaryotes and play crucial regulatory roles in multiple biological processes and diseases. While Deltex2, as a member of the DELTEX family ubiquitin ligases, is characterized by a RING domain followed by a C-terminal domain (DTC), its functions and underlying mechanisms in myogenesis have not been fully elucidated. Here, we report that Deltex2, which is highly expressed in muscles, positively regulates myoblast proliferation via mediating the expression of Pax7. Meanwhile, we find that Deltex2 is translocated from the nucleus into the cytoplasm during myogenic differentiation, and further disclose that Deltex2 inhibits myoblast differentiation and interacts with MyoD, resulting in the ubiquitination and degradation of MyoD. Altogether, our findings reveal the physiological function of Deltex2 in orchestrating myogenesis and delineate the novel role of Deltex2 as a negative regulator of MyoD protein stability.

Objective: Satellite cells play an important role in muscle regeneration, which this process can be affected by differentgenes including PAX7 and MyoD. Exercise training known as an important strategy for mediating the satellite cell’sfunction. Therefore, the main purpose of the present study is to investigate the changes in PAX7 and MyoD proteinexpression in response to eccentric and concentric resistance exercise in healthy young men.Materials and Methods: In this semi-experimental and cross-sectional study, 10 healthy men (age range 18-30 yearsold) participated. They were randomly divided into two equal groups (n=5) to perform one of two high-intensity eccentricor concentric knee extensions muscle contraction protocols. The contractions included a maximum of 12 sets of 10repetitions, with a 30 second rest time interval between sets. PAX7 and MyoD protein expression was assessed usingImmunohistochemistry analysis from the Vastus Lateralis muscle needle biopsy samples that have been taken 24hours before and 3 to 4 hours after the end of the exercise protocol.Results: We observed that the PAX7 protein expression level increased significantly after eccentric (47.75%) andconcentric (39.21%) (P=0.01) intervention. While, the MyoD protein expression level reduced (38.14%) significantlyfollowing acute eccentric resistance exercise (P=0.01).Conclusion: It seems that eccentric or concentric muscular contraction modulates the expression of PAX7 and MyoDprotein expression in the skeletal muscle, with further effects observed in eccentric resistance exercise.

Background: Brachial Plexus Injury (BPI) is one of the peripheral nerve injuries which causes severe functional impairment and disability. Without prompt treatment, prolonged denervation will cause severe muscle atrophy. MyoD, which is expressed by satellite cells, is one of the parameters that relate to the regeneration process in post-injury muscle and it is presumed to determine the clinical outcome following neurotization procedure. This study aims to understand the correlation between time to surgery (TTS) and MyoD expression in satellite cells in the biceps muscle of adult brachial plexus injury patients. Methods: Analytic observational study with a cross-sectional design was conducted at Dr. Soetomo General Hospital. All patients with BPI who underwent surgery between May 2013 and December 2015 were included. Muscle biopsy was taken and stained using immunohistochemistry for MyoD expression. Pearson correlation test was used to assess the correlation between MyoD expression with TTS and with age. Results: Twenty-two biceps muscle samples were examined. Most patients are males (81.8%) with an average age of 25.5 years. MyoD expression was found to be highest at TTS of 4 months and then dropped significantly (and plateau) from 9 to 36 months. MyoD expression is significantly correlated with TTS (r=-0.895; p = 0.00) but not with age (r=-0.294; p = 0.184). Conclusion: Our study found, from the cellular point of view, that treatment of BPI needs to be done as early as possible before the regenerative potential - as indicated by MyoD expression – declined. [ABSTRACT FROM AUTHOR]

Sarcopenia associated with aging and obesity is characterized by the atrophy of fast-twitch muscle fibers and an increase in intramuscular fat deposits. However, the mechanism of fast-twitch fiber-specific atrophy remains unclear. In this study, we aimed to assess the effect of palmitic acid (PA), the most common fatty acid component of human fat, on muscle fiber type, focusing on the expression of fiber-type-specific myosin heavy chain (MHC). Myotubes differentiated from C2C12 myoblasts were treated with PA. The PA treatment inhibited myotube formation and hypertrophy while reducing the gene expression of MHC IIb and IIx, specific isoforms of fast-twitch fibers. Consistent with this, a significant suppression of MHC IIb protein expression in PA-treated cells was observed. A reporter assay using plasmids containing the MHC IIb gene promoter revealed that the PA-induced reduction in MHC IIb gene expression was caused by the suppression of MyoD transcriptional activity through its phosphorylation. Treatment with a specific protein kinase C (PKC) inhibitor recovered the reduction in MHC IIb gene expression levels in PA-treated cells, suggesting the involvement of the PA-induced activation of PKC. Thus, PA selectively suppresses the mRNA and protein expression of fast-twitch MHC by modulating MyoD activity. This finding provides a potential pathogenic mechanism for age-related sarcopenia. [ABSTRACT FROM AUTHOR]

The principles of myogenesis play crucial roles in the production of cultured meat, and identifying protein stimulators associated with myogenesis holds great potential to enhance the efficiency of this process. In this study, we used surface plasmon resonance (SPR)-based screening of a natural product library to discover ligands for Pax7 and MyoD, key regulators of satellite cells (SCs), and performed cell-based assays on Hanwoo SCs (HWSCs) to identify substances that promote cell proliferation and/or differentiation. Through an SPR analysis, we found that six chemicals, including one Pax7+/MyoD− chemical, four Pax7+/MyoD+ chemicals, and one Pax7−/MyoD+ chemical, bound to Pax7 and/or MyoD proteins. Among four Pax7+/MyoD+ chemicals, parthenolide (0.5 and 1 µM) and rutin (100 and 200 µM) stimulated cell proliferation in the medium with 10% FBS similar to the medium with 20% FBS, without affecting differentiation. Adenosine, a Pax7−/MyoD+ chemical, accelerated differentiation. These chemicals could be potential additives to reduce the reliance of FBS required for HWSC proliferation and differentiation in cultured meat production.

Delving into porcine embryonic myogenesis is the key to elucidate the complex regulation of breed-specific differences in growth performance and meat production. Increasing evidence proves that pigs with less meat production show earlier embryonic myogenesis, but little is known about the underlying mechanisms. In this study, we examine the longissimus dorsi muscle (LDM) by immunohistochemistry and confirm that the differentiation of myogenic progenitors is increased (P–/MyoD+) and less (P+/MyoD–) in LT pigs at 35 days post-conception (35dpc). Additionally, embryonic myogenic progenitors isolated from LT pigs show greater (P

Vertebrate ATP1B4 genes represent a rare instance of orthologous gene co-option, resulting in radically different functions of the encoded BetaM proteins. In lower vertebrates, BetaM is a Na, K-ATPase β-subunit that is a component of ion pumps in the plasma membrane. In placental mammals, BetaM lost its ancestral role and, through structural alterations of the N-terminal domain, became a skeletal and cardiac muscle-specific protein of the inner nuclear membrane, highly expressed during late fetal and early postnatal development. We previously determined that BetaM directly interacts with the transcriptional co-regulator SKI-interacting protein (SKIP) and is implicated in the regulation of gene expression. This prompted us to investigate a potential role for BetaM in the regulation of muscle-specific gene expression in neonatal skeletal muscle and cultured C2C12 myoblasts. We found that BetaM can stimulate expression of the muscle regulatory factor (MRF), MyoD, independently of SKIP. BetaM binds to the distal regulatory region (DRR) of MyoD, promotes epigenetic changes associated with activation of transcription, and recruits the SWI/SNF chromatin remodeling subunit, BRG1. These results indicate that eutherian BetaM regulates muscle gene expression by promoting changes in chromatin structure. These evolutionarily acquired new functions of BetaM might be very essential and provide evolutionary advantages to placental mammals. [ABSTRACT FROM AUTHOR]

Objective: Satellite cells play an important role in muscle regeneration, which this process can be affected by different genes including PAX7 and MyoD. Exercise training known as an important strategy for mediating the satellite cell’s function. Therefore, the main purpose of the present study is to investigate the changes in PAX7 and MyoD protein expression in response to eccentric and concentric resistance exercise in healthy young men. Materials and Methods: In this semi-experimental and cross-sectional study, 10 healthy men (age range 18-30 years old) participated. They were randomly divided into two equal groups (n=5) to perform one of two high-intensity eccentric or concentric knee extensions muscle contraction protocols. The contractions included a maximum of 12 sets of 10 repetitions, with a 30 second rest time interval between sets. PAX7 and MyoD protein expression was assessed using Immunohistochemistry analysis from the Vastus Lateralis muscle needle biopsy samples that have been taken 24 hours before and 3 to 4 hours after the end of the exercise protocol. Results: We observed that the PAX7 protein expression level increased significantly after eccentric (47.75%) and concentric (39.21%) (P=0.01) intervention. While, the MyoD protein expression level reduced (38.14%) significantly following acute eccentric resistance exercise (P=0.01). Conclusion: It seems that eccentric or concentric muscular contraction modulates the expression of PAX7 and MyoD protein expression in the skeletal muscle, with further effects observed in eccentric resistance exercise. [ABSTRACT FROM AUTHOR]

Introduction: Although exercise training and herbs consumption have protective effects on many diseases, the mechanism of action of exercise training with different intensities and citrus aurantium (CA) extract consumption on the autophagy-dependent MyoD activation pathway is not yet known. The aim of this study was to investigate the effect of eight weeks of moderate intensity continuous training (MICT) and high intensity interval training (HIIT) with CA consumption on the expression of LC3-II, Beclin-1 and MyoD as autophagy related markers in the muscle tissue of elderly rats. Methods: In this experimental study, 42 elderly female rats were randomly assigned to (1) control (C) (2) MICT, (3) HIIT, (4) MICT + CA, (5) HIIT + CA, (6) CA and (7) sham (normal saline) groups. HIIT was performed at 85-110% VO2max intensity and 15-25 m / min speed and MICT at 65% VO2max intensity and 20-25 m / min speed; 300 mg / kg / day CA was received peritoneally. One-way analysis of variance with Tukey's post hoc test was used to analyze the findings. Findings were analyzed using Graph Pad Prism 8.3.0 software (p ≤ 0.05). Results: MICT and HIIT increased LC3II, Bclin1 and MyoD gene expression (p ≤ 0.05); The effect of HIIT on MyoD increase was greater than MICT (p ≤ 0.05). CA increased the expression of LC3II and Bclin1 (p ≤ 0.05). MICT + CA and HIIT + CA increased the expression of LC3II, Bclin1 and MyoD in the muscle tissue of elderly rats (p ≤ 0.05). Conclusion: It seems that exercise training and CA consumption with different mechanism of action activate autophagy in the soleus muscle tissue, however the simultaneous use of HIIT, MICT and CA also has favorable effects on the autophagy-dependent MyoD activation pathway.

The only curative therapy for many endstage diseases is allograft organ transplantation. Due to the limited supply of donor organs, relatively few patients are recipients of a transplanted organ. Therefore, new strategies are warranted to address this unmet need. Using gene editing technologies, somatic cell nuclear transfer and human induced pluripotent stem cell technologies, interspecies chimeric organs have been pursued with promising results. In this review, we highlight the overall technical strategy, the successful early results and the hurdles that need to be addressed in order for these approaches to produce a successful organ that could be transplanted in patients with endstage diseases.

End stage heart failure is a terminal disease, and the only curative therapy is orthotopic heart transplantation. Due to limited organ availability, alternative strategies have received intense interest for treatment of patients with advanced heart failure. Recent studies using gene-edited porcine organs suggest that cardiac xenotransplantation may provide a future source of organs. In this review, we highlight the historical milestones for cardiac xenotransplantation and the gene editing strategies designed to overcome immunological barriers, which have culminated in a recent cardiac pig-to-human xenotransplant. We also discuss recent results of studies on the engineering of human-porcine chimeric organs that may provide an alternative and complementary strategy to overcome some of the major immunological barriers to producing a new source of transplantable organs. • There is a limited organ supply for orthotopic heart transplantation. • Gene edited porcine hearts have been used as xenografts in nonhuman primates, with prolonged survival. • A gene edited porcine heart has been transplanted with 2-month survival into a patient with end-stage heart failure. • Blastocyst complementation using hiPSCs in an organ depleted porcine embryo results in the development of humanized organs. [ABSTRACT FROM AUTHOR]

The discovery of the skeletal muscle-specific transcription factor MyoD represents a milestone in the field of transcriptional regulation during differentiation and cell-fate reprogramming. MyoD was the first tissue-specific factor found capable of converting non-muscle somatic cells into skeletal muscle cells. A unique feature of MyoD, with respect to other lineage-specific factors able to drive trans-differentiation processes, is its ability to dramatically change the cell fate even when expressed alone. The present review will outline the molecular strategies by which MyoD reprograms the transcriptional regulation of the cell of origin during the myogenic conversion, focusing on the activation and coordination of a complex network of co-factors and epigenetic mechanisms. Some molecular roadblocks, found to restrain MyoD-dependent trans-differentiation, and the possible ways for overcoming these barriers, will also be discussed. Indeed, they are of critical importance not only to expand our knowledge of basic muscle biology but also to improve the generation skeletal muscle cells for translational research. [ABSTRACT FROM AUTHOR]

The vertebrate embryonic midline vasculature forms in close proximity to the developing skeletal muscle, which originates in the somites. Angioblasts migrate from bilateral positions along the ventral edge of the somites until they meet at the midline, where they sort and differentiate into the dorsal aorta and the cardinal vein. This migration occurs at the same time that myoblasts in the somites are beginning to differentiate into skeletal muscle, a process which requires the activity of the basic helix loop helix (bHLH) transcription factors Myod and Myf5. Here we examined vasculature formation in myod and myf5 mutant zebrafish. In the absence of skeletal myogenesis, angioblasts migrate normally to the midline but form only the cardinal vein and not the dorsal aorta. The phenotype is due to the failure to activate vascular endothelial growth factor ligand vegfaa expression in the somites, which in turn is required in the adjacent angioblasts for dorsal aorta specification. Myod and Myf5 cooperate with Hedgehog signaling to activate and later maintain vegfaa expression in the medial somites, which is required for angiogenic sprouting from the dorsal aorta. Our work reveals that the early embryonic skeletal musculature in teleosts evolved to organize the midline vasculature during development. [Display omitted] • Myod and Myf5 are required for dorsal aorta and intersegmental vessel formation. • Myod and Myf5 are required for somitic expression of the VEGF ligand vegfaa. • Restoring vegfaa expression in Myod/Myf5 double mutants rescues aortic fate. • Myod and Myf5 function cooperatively with Hedgehog signaling to induce vegfaa. • vegfaa maintenance requires continued bHLH activity in muscle cells. Summary statement: The myogenic transcription factors Myod and Myf5 have a novel function in inducing the artery through regulation of VEGF. [ABSTRACT FROM AUTHOR]

Paired box 3 (Pax3) is a critical upstream regulator of the onset of myogenesis. We have previously identified two spliced isoforms of pax3a (pax3a-1 and pax3a-2) and three spliced isoforms of -pax3b (pax3b-1, pax3b-2, and pax3b-3) in olive flounder, but their roles in myogenesis are unknown. In this study, we investigated their cellular localization, transcriptional activity on myod gene regulation, and roles in myogenesis. Different Pax3a and Pax3b isoforms revealed various subcellular localizations, which were related to their corresponding protein structures. Pax3a-1, Pax3a-2, and Pax3b-1 promoted the transcriptional activity of myod to different degrees, whereas Pax3b-2 and Pax3b-3 had a slight inhibitory or no effect. The pairwise interaction analysis demonstrated the synergistic effect of Pax3b-1 and Pax3b-3 on myod transcriptional activity. The overexpression of different pax3a and pax3b isoforms differentially altered the spatial expression patterns of myod and differentially regulated the expression levels of their target genes (myod, myf5, and c-met) in zebrafish embryonic myogenesis. In addition, the different flounder myod promoter-driven pax3a/3b isoform expression vectors were successfully introduced into the skeletal muscles of juvenile flounder by electroporation. However, none of them could change the mRNA expression levels of mstn, myf5, myod, myogenin, pax7a, and pax7b in the electroporated muscles. These results suggest that different Pax3a and Pax3b isoforms may precisely and collaboratively regulate embryonic myogenesis, but their roles in juvenile myogenesis are uncertain. [ABSTRACT FROM AUTHOR]

The basic helix-loop-helix (bHLH) family is one of the most conserved transcription factor families that plays an important role in regulating cell growth, differentiation and tissue development. Typically, members of this family form homo- or heterodimers to recognize specific motifs and activate transcription. MyoD is a vital transcription factor that regulates muscle cell differentiation. However, it is necessary for MyoD to form a heterodimer with E-proteins to activate transcription. Even though the crystal structure of the MyoD homodimer has been determined, the structure of the MyoD heterodimer in complex with the E-box protein remains unclear. In this study, we determined the crystal structure of the bHLH domain of the MyoD-E47 heterodimer at 2.05 Å. Our structural analysis revealed that MyoD interacts with E47 through a hydrophobic interface. Moreover, we confirmed that heterodimerization could enhance the binding affinity of MyoD to E-box sequences. Our results provide new structural insights into the heterodimer of MyoD and E-box protein, suggesting the molecular mechanism of transcription activation of MyoD upon binding to E-box protein. • Purification of the MyoD and E47 heterodimer at 1:1 stoichiometry. • Crystal structure of MyoD and E47 heterodimer. • (MyoD:E47) bHLH heterodimer exhibits stronger DNA binding affinity. [ABSTRACT FROM AUTHOR]

Background & aim: The increase of myoD gene expression is the characteristic of activation and proliferation of satellite cells due to induced stimulus in skeletal muscle. But it seems the fast and slow skeletal muscle response and the appearance of this marker due to stimulus are not similar. Accordingly, the present study aimed to evaluate the effect of endurance training on myoD gene expression in fast and slow skeletal muscle in Wistar male rats. Methods: In the present study conducted in 2020, 14 rats (weight 234±24g) provided from Pasteur Institute and housed under natural conditions (temperature, light/dark (12-h) cycle, with ad Libitum access to food and water). The rats randomly divided to two groups experimental (n=7) and control (n=7); the experimental group performed an endurance training program (30 m/min, 50 min, 6 sessions per week for 14-weeks) on a motorized treadmill, and 48 hours after the end of the last session of endurance activity with the control group were anesthetized and sacrificed, then the soleus and extensor digitorum longus (EDL) muscles were removed. Real-time RT-PCR was used to determine if expression levels of myoD gene. To conclude, the data were analyzed by independent t-test. Results: endurance training induced a significant increase (p=0.022) in EDL myoD gene expression; correspondingly, this modification was observed in soleus muscles (p=0.001) Conclusion: it appeared that endurance training increased the myoD gene expression in soleus (slow-twitch muscle) and EDL (fast-twitch muscle).

Herein, we review a unique and versatile lineage composed of Myo/Nog cells that may be beneficial or detrimental depending on their environment and nature of the pathological stimuli they are exposed to. While we will focus on the lens, related Myo/Nog cell behaviors and functions in other tissues are integrated into the narrative of our research that spans over three decades, examines multiple species and progresses from early stages of embryonic development to aging adults. Myo/Nog cells were discovered in the embryonic epiblast by their co-expression of the skeletal muscle-specific transcription factor MyoD, the bone morphogenetic protein inhibitor Noggin and brain-specific angiogenesis inhibitor 1. They were tracked from the epiblast into the developing lens, revealing heterogeneity of cell types within this structure. Depletion of Myo/Nog cells in the epiblast results in eye malformations arising from the absence of Noggin. In the adult lens, Myo/Nog cells are the source of myofibroblasts whose contractions produce wrinkles in the capsule. Eliminating this population within the rabbit lens during cataract surgery reduces posterior capsule opacification to below clinically significant levels. Parallels are drawn between the therapeutic potential of targeting Myo/Nog cells to prevent fibrotic disease in the lens and other ocular tissues.

Intramuscular fat (IMF) content is a key determinant of beef quality, making it a key topic of research interest. ATP5B serves as the catalytic component of the mitochondrial ATP synthase complex and plays essential roles in controlling fat contents and oxidative metabolism in bovine skeletal muscle. In this study, we determined that bovine ATP5B was highly expressed in longissimus thoracis. To elucidate the molecular mechanisms involved in bovine ATP5B regulation, we cloned and characterized the promoter region of ATP5B. Applying 5'-rapid amplification of cDNA end analysis (RACE), we identified two transcriptional start sites (TSSs) in its promoter region. Using a series of 5'-deletion promoter plasmids in luciferase reporter assay, we found that the proximal minimal promoter of ATP5B was located within the region −539/220 relative to the TSS. Site-directed mutation in combination with chromatin immunoprecipitation (ChIP) assays demonstrated that MyoD and GATA1 binding to the promoter region drives bovine ATP5B transcription. Taken together, these results provide new insight into the regulatory mechanisms of ATP5B transcription in mediating the IMF content of beef. [ABSTRACT FROM AUTHOR]

Background: Understanding how gene regulatory networks (GRNs) control developmental progression is a key to the mechanistic understanding of morphogenesis. The sea urchin larval skeletogenesis provides an excellent platform to tackle this question. In the early stages of sea urchin skeletogenesis, skeletogenic genes are uniformly expressed in the skeletogenic lineage. Yet, during skeletal elongation, skeletogenic genes are expressed in distinct spatial sub‐domains. The regulation of differential gene expression during late skeletogenesis is not well understood. Results: Here we reveal the dynamic expression of the skeletogenic regulatory genes that define a specific regulatory state for each pair of skeletal rods, in the sea urchin Paracentrotus lividus. The vascular endothelial growth factor (VEGF) signaling, essential for skeleton formation, specifically controls the migration of cells that form the postoral and distal anterolateral skeletogenic rods. VEGF signaling also controls the expression of regulatory genes in cells at the tips of the postoral rods, including the transcription factors Pitx1 and MyoD1. Pitx1 activity is required for normal skeletal elongation and for the expression of some of VEGF target genes. Conclusions: Our study illuminates the fine‐tuning of the regulatory system during the transition from early to late skeletogenesis that gives rise to rod‐specific regulatory states. Key Findings: The skeletogenic transcription factors form specific regulatory states in various skeletogenic sub‐populations.Late VEGF signaling controls the regulatory states at the tips of the post‐oral and anterolateral skeletal rods.VEGF signaling controls the expression of the transcription factors, MyoD1 and Pitx1.Pitx1 activity is required for normal skeletal elongation and for the expression of some of VEGF target genes. [ABSTRACT FROM AUTHOR]

Stem cells functions are regulated by different factors and non-conding RNAs, such as microRNA. MiRNAsplay an important role in modulating the expression of genes involved in the commitment and differentiation of progenitor cells. MiRNAs are post transcriptional regulators which may be modulated by physical exercise. MiRNAs, by regulating different signaling pathways, play an important role in myogenesis as well as in muscle activity. MiRNAs quantification may be considered for evaluating physical performance or muscle recovery. With the aim to identify specific miRNAs potentially involved in myogenesis and modulated by physical activity, we investigated miRNAs expression following physical performance in Peripheral Blood Mononuclear Cells (PBMCs) and in sera of half marathon (HM) runnners. The effect of runners sera on Myogenesis in in vitro cellular models was also explored. Therefore, we performed Microarray Analysis and Real Time PCR assays, as well as in vitro cell cultures analysis to investigate myogenic differentiation. Our data demonstrated gender-specific expression patterns of PBMC miRNAs before physical performance. In particular, miR223-3p, miR26b-5p, miR150-5p and miR15-5p expression was higher, while miR7a-5p and miR7i-5p expression was lower in females compared to males. After HM, miR152-3p, miR143-3p, miR27a-3p levels increased while miR30b-3p decreased in both females and males: circulating miRNAs mirrored these modulations. Furthermore, we also observed that the addition of post-HM participants sera to cell cultures exerted a positive effect in stimulating myogenesis. In conclusion, our data suggest that physical activity induces the modulation of myogenesis-associated miRNAs in bothfemales and males, despite the gender-associated different expression of certain miRNAs, Noteworthy, these findings might be useful for evaluating potential targets for microRNA based-therapies in diseases affecting the myogenic stem cells population. [ABSTRACT FROM AUTHOR]

Objective The growth rate of pigs is related to differentiation and proliferation of muscle cells, which are regulated by growth factors and expression of growth-related genes. Thus, the objective of this study was to establish optimal culture conditions for Jeju black pig (JBP) muscle cells and determine the relationship of various factors involved in muscle growth with the proliferation of JBP muscle cells. Methods Muscles were taken from the femur skeletal muscle of JBP embryos. After isolation of the muscle cells, cells were cultured in a 6-well plate under four different culture conditions to optimize culture conditions for JBP muscle cells. To analyze proliferation rate of JBP muscle cells, these muscle cells were seeded into 6-well plates at a density of 1.5×105 cells per well and cultured for 3 days. Western blot and quantitative real-time polymerase chain reaction were applied to verify the myogenic differentiation 1 (MyoD) expression and growth-related gene expression in JBP muscle cells, respectively. Results We established a muscle cell line from JBP embryos and optimized its culture conditions. These muscle cells were positive for MyoD, but not for paired box 7. The proliferation rate of these muscle cells was significantly higher in a culture medium containing bFGF and epidermal growth factor + basic fibroblast growth factor (EGF+bFGF) than that without a growth factor or containing EGF alone. Treatment with EGF and bFGF significantly induced the expression of MyoD protein, an important transcription factor in muscle cells. Moreover, we checked the changes of expression of growth-related genes in JBP muscle cells by presence or absence of growth factors. Expression level of collagen type XXI alpha 1 gene was changed only when EGF and bFGF were added together to culture media for JBP muscle cells. Conclusion Concurrent use of EGF and bFGF increased the expression of MyoD protein, thus regulating the proliferation of JBP muscle cells and the expression of growth-related genes.

Muscle proteostasis is shaped by the myogenic transcription factor MyoD which regulates the expression of chaperones during muscle differentiation. Whether MyoD can also modulate chaperone expression in terminally differentiated muscle cells remains open. Here we utilized a temperature-sensitive (ts) conditional knockdown nonsense mutation in MyoD ortholog in C. elegans, HLH-1, to ask whether MyoD plays a role in maintaining muscle proteostasis post myogenesis. We showed that hlh-1 is expressed during larval development and that hlh-1 knockdown at the first, second, or third larval stages resulted in severe defects in motility and muscle organization. Motility defects and myofilament organization were rescued when the clearance of hlh-1(ts) mRNA was inhibited, and hlh-1 mRNA levels were restored. Moreover, hlh-1 knockdown modulated the expression of chaperones with putative HLH-1 binding sites in their promoters, supporting HLH-1 role in muscle maintenance during larval development. Finally, mild disruption of hlh-1 expression during development resulted in earlier dysregulation of muscle maintenance and function during adulthood. We propose that the differentiation transcription factor, HLH-1, contributes to muscle maintenance and regulates cell-specific chaperone expression post differentiation. HLH-1 may thus impact muscle proteostasis and potentially the onset and manifestation of sarcopenia.

Abstract Background Meat from Jeju native pigs (JNPs) is highly popular among Korean consumers; however, the production efficiency is limited due to the low adult body weight. In contrast, the Berkshire breed, which has a genetic background closely related to Asian native pigs, gains weight more efficiently. Objectives This study focused on the differential expression of genes related to muscle growth in postnatal myogenesis between Berkshire and JNPs, specifically the myogenic regulatory factor (MRF) genes (MyoD, Pax7, Myf5, Myf6 and MyBPH). The MRF family is primarily involved in the proliferation and development of muscle. Methods Qualitative reverse transcription‐polymerase chain reaction and western blot analyses revealed that expression of MyoD and Pax7 was significantly higher in Berkshire pigs than in JNPs. In addition, co‐expression of MyoD and Pax7 was observed in myotubes formed in cultured C2C12 cells. ToppCluster was used to elucidate the relationship between biological processes of the MRFs and muscle‐related signalling pathways. Results MyoD and Pax7 are factors essential for the activation of satellite cell during myogenesis. However, the mRNA and protein levels of MyBPH (which is responsible for meat quality, e.g. water content, colour and tenderness) are significantly higher in both 1‐day‐old piglets and adult JNPs than in Berkshire pigs. Conclusions This study provides a genetic understanding of myogenesis in the postnatal and adult stages of Berkshire pigs and JNPs. Moreover, these results will help identify marker genes related to muscle mass, growth performance and meat quality in indigenous Korean pig breeds.

MyoD, Myf5, myogenin, and MRF4 (also known as Myf6 or herculin) are myogenic regulatory factors (MRFs). MRFs are regarded as master transcription factors that are upregulated during myogenesis and influence stem cells to differentiate into myogenic lineage cells. In this review, we summarize MRFs, their regulatory factors, such as TLE3, NF-κB, and MRF target genes, including non-myogenic genes such as taste receptors. Understanding the function of MRFs and the physiology or pathology of satellite cells will contribute to the development of cell therapy and drug discovery for muscle-related diseases. [ABSTRACT FROM AUTHOR]

Long noncoding RNA (lncRNA) plays a crucial part in all kinds of life activities, especially in myogenesis. SMARCD3 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily d, member 3) is a member of the SWI/SNF protein complex and was reported to be required for cell proliferation and myoblast differentiation. In this study, we identified a new lncRNA named SMARCD3-OT1 (SMARCD3overlappinglncRNA), which strongly regulated the development of myogenesis by improving the expression of SMARCD3X4 (SMARCD3transcripts4). We overexpressed and knockdown the expression of SMARCD3-OT1 and SMARCD3X4 to investigate their function on myoblast proliferation and differentiation. Cell experiments proved that SMARCD3-OT1 and SMARCD3X4 promoted myoblast proliferation through the CDKN1A pathway and improved differentiation of differentiated myoblasts through the MYOD pathway. Moreover, they upregulated the fast-twitch fiber-related genes and downregulated the slow-twitch fiber-related genes, which indicated that they facilitated the slow-twitch fiber to transform into the fast-twitch fiber. The animals' experiments supported the results above, demonstrating that SMARCD3-OT1 could induce muscle hypertrophy and fast-twitch fiber transformation. In conclusion, SMARCD3-OT1 can improve the expression of SMARCD3X4, thus inducing muscle hypertrophy. In addition, SMARCD3-OT1 can facilitate slow-twitch fibers to transform into fast-twitch fibers. [ABSTRACT FROM AUTHOR]

We investigate the underlying biological effects and mechanisms of rESWT on myogenic contracture and muscle atrophy in a rabbit model of extending knee joint contracture. In group control, the knee joint was not fixed. In group I-4w, the knee joint was only fixed for 4 weeks. In groups SR-1 w, SR-2 w, and SR-4 w, the knee joint was fixed for 4 weeks before the rabbits underwent 1, 2, and 4 weeks of self-recovery, respectively. In groups rESWT-1 w, rESWT 2 w, and rESWT-4 w, the knee joint was fixed for 4 weeks before the rabbits underwent 1, 2, and 4 weeks of rESWT, respectively. The myogenic contracture was measured, the cross-sectional area and key protein levels for NF-κB/HIF-1α signaling pathway and myogenic regulatory factors were evaluated. During the recovery period, biological findings showed that the levels of myogenic contracture and muscle atrophy were milder in group rESWT by compared with group SR after 2 weeks. Molecular biological analysis showed that MyoD protein levels in the group rESWT was significantly higher than those in the group SR, and importantly, phospho-NF-κB p65 and HIF-1α protein levels in the group rESWT were significantly lower than those in the group SR at the same time point. This is the first study demonstrated that rESWT has the potential to reduce myogenic contracture and muscle atrophy after long-term immobilization in animal model. It is a possible mechanism that changing the low oxygen environment in skeletal muscle through rESWT may inhibit activation of NF-κB/HIF-1α signaling pathway. [ABSTRACT FROM AUTHOR]

Satellite cells (SATC), the most abundant skeletal muscle stem cells, play a main role in muscle plasticity, including the adaptive response following physical activity. Thus, we investigated how long-term phenotype selection of male mice for high running performance (Dummerstorf high Treadmill Performance; DUhTP) affects abundance, creatine kinase activity, myogenic marker expression (Pax7, MyoD), and functionality (growth kinetics, differentiation) of SATC and their progeny. SATC were isolated from sedentary male DUhTP and control (Dummerstorf Control; DUC) mice at days 12, 43, and 73 of life and after voluntary wheel running for three weeks (day 73). Marked line differences occur at days 43 and 73 (after activity). At both ages, analysis of SATC growth via xCELLigence system revealed faster activation accompanied by a higher proliferation rate and lower proportion of Pax7+ cells in DUhTP mice, indicating reduced reserve cell formation and faster transition into differentiation. Cultures from sedentary DUhTP mice contain an elevated proportion of actively proliferating Pax7+/MyoD+ cells and have a higher fusion index leading to the formation of more large and very large myotubes at day 43. This robust hypertrophic response occurs without any functional load in the donor mice. Thus, our selection model seems to recruit myogenic precursor cells/SATC with a lower activation threshold that respond more rapidly to external stimuli and are more primed for differentiation at the expense of more primitive cells. [ABSTRACT FROM AUTHOR]