Sonic hedgehog promotes proliferation and differentiation of adult muscle cells: Involvement of MAPK/ERK and PI3K/Akt pathways

Interleukin 25 promotes muscle regeneration in sarcopenia by regulating macrophage-mediated Sonic Hedgehog signaling

OBJECTIVE

Sarcopenia manifests as a chronic, low-level inflammation along with multiple inflammatory cells infiltration. Interleukin (IL)-25 can regulate the function of macrophages. However, the specific role and mechanisms through which IL-25 functions in sarcopenia are still not fully understood and require further investigation.

METHODS

Aged mice were utilized as sarcopenia models and examined the expression of inflammatory factors. To investigate the effects of IL-25 on sarcopenia, the model mice received IL-25 treatment and underwent in vivo adoptive transfer of IL-25-induced macrophages. Meanwhile, RAW264.7 cells, bone marrow-derived macrophages, satellite cells and C2C12 cells were used in vitro. Shh insufficiency was induced through intramuscular administration of SHH-shRNA adenoviruses. Then, various assays including scratch wound, cell counting kit-8 and Transwell assays, as well as histological staining and molecular biological methods, were conducted.

RESULTS

Aged mice exhibited an accelerated decline in muscle strength and mass, along with an increased muscle lipid droplets and macrophage infiltration, and decreased IL-25 levels compared to the young group. IL-25 therapy and the transfer of IL-25-preconditioned macrophages could improve these conditions by promoting M2 macrophage polarization in vivo as well as in vitro. M2 macrophage conditioned medium enhanced satellite cell proliferation and migration, as well as the vitality, migration, and differentiation of C2C12 cells in vitro. Furthermore, IL-25 enhanced Shh expression in macrophages in vitro, and activated the Shh signaling pathway in muscle tissue of aged mice, which could be suppressed by either the inhibitor cyclopamine or Shh knockdown. Mechanistic studies showed that Shh insufficiency suppressed the activation of Akt/mTOR signaling pathway in muscle tissue of aged mice.

CONCLUSION

IL-25 promotes the secretion of Shh by M2 macrophages and activates the Shh/Akt/mTOR signaling pathway, which improves symptoms and function in sarcopenia mice. This suggests that IL-25 has potential as a therapeutic agent for treating sarcopenia.

Astaxanthin targets IL-6 and alleviates the LPS-induced adverse inflammatory response of macrophages

Numerous natural compounds are recognized for their anti-inflammatory properties attributed to antioxidant effects and the modulation of key inflammatory factors. Among them, astaxanthin (AST), a potent carotenoid antioxidant, remains relatively underexplored regarding its anti-inflammatory mechanisms and specific molecular targets. In this study, human monocytic leukemia cell-derived macrophages (THP-1) were selected as experimental cells, and lipopolysaccharides (LPS) served as inflammatory stimuli. Upon LPS treatment, the oxidative stress was significantly increased, accompanied by remarkable cellular damage. Moreover, LPSs escalated the expression of inflammation-related molecules. Our results demonstrate that AST intervention could effectively alleviate LPS-induced oxidative stress, facilitate cellular repair, and significantly attenuate inflammation. Further exploration of the anti-inflammatory mechanism revealed AST could substantially inhibit NF-κB translocation and activation, and mitigate inflammatory factor production by hindering NF-κB through the antioxidant mechanism. We further confirmed that AST exhibited protective effects against cell damage and reduced the injury from inflammatory cytokines by activating p53 and inhibiting STAT3. In addition, utilizing network pharmacology and in silico calculations based on molecular docking, molecular dynamics simulation, we identified interleukin-6 (IL-6) as a prominent core target of AST anti-inflammation, which was further validated by the RNA interference experiment. This IL-6 binding capacity actually enabled AST to curb the positive feedback loop of inflammatory factors, averting the onset of possible inflammatory storms. Therefore, this study offers a new possibility for the application and development of astaxanthin as a popular dietary supplement of anti-inflammatory or immunomodulatory function.

Comprehensive Analysis of miRNA and mRNA Expression Profiles during Muscle Development of the Longissimus Dorsi Muscle in Gannan Yaks and Jeryaks

A hybrid offspring of Gannan yak and Jersey cattle, the Jeryak exhibits apparent hybrid advantages over the Gannan yak in terms of production performance and other factors. The small non-coding RNAs known as miRNAs post-transcriptionally exert a significant regulatory influence on gene expression. However, the regulatory mechanism of miRNA associated with muscle development in Jeryak remains elusive. To elucidate the regulatory role of miRNAs in orchestrating skeletal muscle development in Jeryak, we selected longissimus dorsi muscle tissues from Gannan yak and Jeryak for transcriptome sequencing analysis. A total of 230 (DE) miRNAs were identified in the longissimus dorsi muscle of Gannan yak and Jeryak. The functional enrichment analysis revealed a significant enrichment of target genes from differentially expressed (DE)miRNAs in signaling pathways associated with muscle growth, such as the Ras signaling pathway and the MAPK signaling pathway. The network of interactions between miRNA and mRNA suggest that some (DE)miRNAs, including miR-2478-z, miR-339-x, novel-m0036-3p, and novel-m0037-3p, played a pivotal role in facilitating muscle development. These findings help us to deepen our understanding of the hybrid dominance of Jeryaks and provide a theoretical basis for further research on the regulatory mechanisms of miRNAs associated with Jeryak muscle growth and development.

Advanced glycation end products inhibit proliferation and primary cilia formation of myoblasts through receptor for advanced glycation end products pathway

The loss of skeletal muscle mass leads to various adverse conditions and shortened lifespan. The inhibition of myoblast proliferation is one of the causes that trigger muscle atrophy. Advanced glycation end products (AGEs) contribute to muscle atrophy. Since primary cilia are crucial organelles for proliferation, AGEs may inhibit primary cilia formation of myoblasts, thereby leading to impaired proliferation. Therefore, we aimed to clarify whether AGEs impeded the proliferation and formation of primary cilia of C2C12 skeletal muscle cells. AGE treatment inhibited the proliferation and formation of primary cilia. However, the inhibitor of the receptor for advanced glycosylation end products (RAGEs) abolished the inhibition of the proliferation and the primary cilia formation of C2C12 cells by AGEs, suggesting that AGEs cause these inhibitions through the RAGE pathway. In summary, our findings suggested that AGEs suppress the proliferation and formation of primary cilia of myoblasts through the RAGE pathway.

Absence of the primary cilia formation gene Talpid3 impairs muscle stem cell function

Skeletal muscle stem cells (MuSC) are crucial for tissue homoeostasis and repair after injury. Following activation, they proliferate to generate differentiating myoblasts. A proportion of cells self-renew, re-enter the MuSC niche under the basal lamina outside the myofiber and become quiescent. Quiescent MuSC have a primary cilium, which is disassembled upon cell cycle entry. Ex vivo experiments suggest cilia are important for MuSC self-renewal, however, their requirement for muscle regeneration in vivo remains poorly understood. Talpid3 (TA3) is essential for primary cilia formation and Hedgehog (Hh) signalling. Here we use tamoxifen-inducible conditional deletion of TA3 in MuSC (iSC-KO) and show that regeneration is impaired in response to cytotoxic injury. Depletion of MuSC after regeneration suggests impaired self-renewal, also consistent with an exacerbated phenotype in TA3iSC-KO mice after repeat injury. Single cell transcriptomics of MuSC progeny isolated from myofibers identifies components of several signalling pathways, which are deregulated in absence of TA3, including Hh and Wnt. Pharmacological activation of Wnt restores muscle regeneration, while purmorphamine, an activator of the Smoothened (Smo) co-receptor in the Hh pathway, has no effect. Together, our data show that TA3 and primary cilia are important for MuSC self-renewal and pharmacological treatment can efficiently restore muscle regeneration.

Arsenic disrupts extracellular vesicle-mediated signaling in regenerating myofibers

Chronic exposure to environmental arsenic is a public health crisis affecting hundreds of millions of individuals worldwide. Though arsenic is known to contribute to many pathologies and diseases, including cancers, cardiovascular and pulmonary diseases, and neurological impairment, the mechanisms for arsenic-promoted disease remain unresolved. This is especially true for arsenic impacts on skeletal muscle function and metabolism, despite the crucial role that skeletal muscle health plays in maintaining cardiovascular health, systemic homeostasis, and cognition. A barrier to researching this area is the challenge of interrogating muscle cell-specific effects in biologically relevant models. Ex vivo studies investigating mechanisms for muscle-specific responses to arsenic or other environmental contaminants primarily utilize traditional 2-dimensional culture models that cannot elucidate effects on muscle physiology or function. Therefore, we developed a contractile 3-dimensional muscle construct model-composed of primary mouse muscle progenitor cells differentiated in a hydrogel matrix-to study arsenic exposure impacts on skeletal muscle regeneration. Muscle constructs exposed to low-dose (50 nM) arsenic exhibited reduced strength and myofiber diameter following recovery from muscle injury. These effects were attributable to dysfunctional paracrine signaling mediated by extracellular vesicles (EVs) released from muscle cells. Specifically, we found that EVs collected from arsenic-exposed muscle constructs recapitulated the inhibitory effects of direct arsenic exposure on myofiber regeneration. In addition, muscle constructs treated with EVs isolated from muscles of arsenic-exposed mice displayed significantly decreased strength. Our findings highlight a novel model for muscle toxicity research and uncover a mechanism of arsenic-induced muscle dysfunction by the disruption of EV-mediated intercellular communication.

Hedgehog signaling in tissue homeostasis, cancers, and targeted therapies

The past decade has seen significant advances in our understanding of Hedgehog (HH) signaling pathway in various biological events. HH signaling pathway exerts its biological effects through a complex signaling cascade involved with primary cilium. HH signaling pathway has important functions in embryonic development and tissue homeostasis. It plays a central role in the regulation of the proliferation and differentiation of adult stem cells. Importantly, it has become increasingly clear that HH signaling pathway is associated with increased cancer prevalence, malignant progression, poor prognosis and even increased mortality. Understanding the integrative nature of HH signaling pathway has opened up the potential for new therapeutic targets for cancer. A variety of drugs have been developed, including small molecule inhibitors, natural compounds, and long non-coding RNA (LncRNA), some of which are approved for clinical use. This review outlines recent discoveries of HH signaling in tissue homeostasis and cancer and discusses how these advances are paving the way for the development of new biologically based therapies for cancer. Furthermore, we address status quo and limitations of targeted therapies of HH signaling pathway. Insights from this review will help readers understand the function of HH signaling in homeostasis and cancer, as well as opportunities and challenges of therapeutic targets for cancer.

Therapeutic implication of Sonic Hedgehog as a potential modulator in ischemic injury

Sonic Hedgehog (SHh) is a homology protein that is involved in the modeling and development of embryonic tissues. As SHh plays both protective and harmful roles in ischemia, any disruption in the transduction and regulation of the SHh signaling pathway causes ischemia to worsen. The SHh signal activation occurs when SHh binds to the receptor complex of Ptc-mediated Smoothened (Smo) (Ptc-smo), which initiates the downstream signaling cascade. This article will shed light on how pharmacological modifications to the SHh signaling pathway transduction mechanism alter ischemic conditions via canonical and non-canonical pathways by activating certain downstream signaling cascades with respect to protein kinase pathways, angiogenic cytokines, inflammatory mediators, oxidative parameters, and apoptotic pathways. The canonical pathway includes direct activation of interleukins (ILs), angiogenic cytokines like hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and hypoxia-inducible factor alpha (HIF-), which modulate ischemia. The non-canonical pathway includes indirect activation of certain pathways like mTOR, PI3K/Akt, MAPK, RhoA/ROCK, Wnt/-catenin, NOTCH, Forkhead box protein (FOXF), Toll-like receptors (TLR), oxidative parameters such as GSH, SOD, and CAT, and some apoptotic parameters such as Bcl2. This review provides comprehensive insights that contribute to our knowledge of how SHh impacts the progression and outcomes of ischemic injuries.

Identification of Differentially Expressed Genes in the Longissimus Dorsi Muscle of Luchuan and Duroc Pigs by Transcriptome Sequencing

The Duroc pig originated in the United States and is a typical lean-meat pig. The breed grows fast, and the body size is large, but the meat quality is poor. The Luchuan pig is one of eight excellent local breeds in China; it has tender meat but is small in size. To study the factors that determine growth, we selected the longissimus dorsi muscle of Luchuan and Duroc pigs for transcriptome sequencing. The results of the transcriptome showed that 3682 genes were differentially expressed (DEGs) in the longissimus dorsi muscle of Duroc and Luchuan pigs. We screened out genes related to muscle development and selected the MYL2 (Myosin light chain-2) gene to perform preliminary research. Gene Ontology (GO) enrichment of biological functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the gene products were mainly involved in the Akt/FoxO signaling pathway, fatty acid metabolism, arachidonic acid metabolism and glycine, serine and threonine metabolism. Such pathways contributed to skeletal muscle growth, fatty acid metabolism and intramuscular fat deposition. These results provide insight into the mechanisms underlying the formation of skeletal muscle and provide candidate genes to improve growth traits, as well as contribute to improving the growth and development traits of pigs through molecular breeding.

Multi-Omics Analysis of Transcriptomic and Metabolomics Profiles Reveal the Molecular Regulatory Network of Marbling in Early Castrated Holstein Steers

The intramuscular fat (IMF), or so-called marbling, is known as potential determinant of the high quality beef in China, Korea, and Japan. Of the methods that affect IMF content in cattle, castration is markedly regarded as an effective and economical way to improve the deposition of IMF but with little attention to its multi-omics in early-castrated cattle. The aim of this study was to investigate the liver transcriptome and metabolome of early-castrated Holstein cattle and conduct a comprehensive analysis of two omics associated with the IMF deposition using transcriptomics and untargeted metabolomics under different treatments: non−castrated and slaughtered at 16 months of age (GL16), castrated at birth and slaughtered at 16 months of age (YL16), and castrated at birth and slaughtered at 26 months of age (YL26). The untargeted metabolome was analyzed using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. The transcriptome of the hepatic genes was analyzed to identify marbling-related genes. Using untargeted metabolomics, the main altered metabolic pathways in the liver of cattle, including those for lipid and amino acid metabolism, were detected in the YL16 group relative to the GL16 and YL26 groups. Significant increases in the presence of betaine, alanine, and glycerol 3-phosphate were observed in the YL16 group (p < 0.05), which might have contributed to the improved beef-marbling production. Compared to the GL16 and YL26 groups, significant increases in the presence of glutathione, acetylcarnitine, and riboflavin but decreases in diethanolamine and 2-hydroxyglutarate were identified in YL16 group (p < 0.05), which might have been beneficial to the beef’s enhanced functional quality. The gene expressions of GLI1 and NUF2 were downregulated and that of CYP3A4 was upregulated in the YL16 group; these results were strongly correlated with the alanine, betaine, and leucine, respectively, in the liver of the cattle. In conclusion, implementation of early castration modified the hepatic metabolites and the related biological pathways by regulating the relevant gene expressions, which could represent a better rearing method for production of high marbled and healthier beef products.

Brewer's spent yeast replacement in carp diet leads to muscle biomass production, recycling, waste management and resource conservation

Brewer's spent yeast (BSY) is among the most voluminous by-products generated in brewery industry that adds to the waste; however, smart utilization of BSY could lead to edible biomass production besides waste management. To utilize it for biomass production, it is being used in fish feeds; however, its effect on the fish physiology has been scantily studied. The present study investigated the proteomic changes in muscle tissues of carp Labeo rohita fed with BSY-based diet, to understand its impact on muscle physiology and biomass. Six feeds were prepared with different grades of BSY (0, 20, 30, 40, 50, 100% replacement of fishmeal with BSY) and fishes were fed for 90 days. Highest weight gain%, feed conversion efficiency, specific growth rate% were observed in 30% BSY-replaced group and this group was considered for the proteomic study. Comparative shotgun proteomic analysis was carried out by LC-MS/MS and data generated have been deposited in ProteomeXchange Consortium with dataset identifier PXD020093. A total of 62 proteins showed differential abundance; 29 increased and 33 decreased in the 30% BSY-replaced group. Pathway analysis using IPA and Panther tools revealed that the proteins tyrosine protein kinase, PDGFα, PKRCB and Collagen promote muscle growth by inducing the PI3K-AKT pathway. Conversely, the proteins Serine/threonine-protein phosphatase, Phosphatidylinositol 3,4,5-trisphosphate5-phosphatase 2A and Ras-specific guanine- nucleotide-releasing factor inhibit muscle growth indicating that 30% BSY-replaced feed promote muscle growth in a highly controlled manner. Findings suggest that BSY could be recycled for carp feed production in large scale thereby leading to resource conservation, reducing environmental effects.

Comparative genome-wide methylation analysis reveals epigenetic regulation of muscle development in grass carp (Ctenopharyngodon idellus) fed with whole faba bean

Crisp grass carp (CGC), the most representative improved varieties of grass carp (GC), features higher muscle hardness after feeding faba bean (Vicia faba L.) for 90-120 days. DNA methylation, a most widely studied epigenetic modification, plays an essential role in muscle development. Previous studies have identified numerous differentially expressed genes (DEGs) between CGC and GC. However, it remains unknown if the expression levels of these DEGs are influenced by DNA methylation. In the present study, we performed a comprehensive analysis of DNA methylation profiles between CGC and GC, and identified important candidate genes related to muscle development coupled with the transcriptome sequencing data. A total of 9,318 differentially methylated genes (DMGs) corresponding to 155,760 differentially methylated regions (DMRs) were identified between the two groups under the CG context in promoter regions. Combined with the transcriptome sequencing data, 14 key genes related to muscle development were identified, eight of which (gsk3b, wnt8a, wnt11, axin2, stat1, stat2, jak2, hsp90) were involved in muscle fiber hyperplasia, six of which (tgf-β1, col1a1, col1a2, col1a3, col4a1, col18a1) were associated with collagen synthesis in crisp grass carp. The difference of methylation levels in the key genes might lead to the expression difference, further resulting in the increase of muscle hardness in crisp grass carp. Overall, this study can help further understand how faba bean modulates muscle development by the epigenetic modifications, providing novel insights into the texture quality improvement in other aquaculture fish species by nutritional programming.

Lactate Activates AMPK Remodeling of the Cellular Metabolic Profile and Promotes the Proliferation and Differentiation of C2C12 Myoblasts

Lactate is a general compound fuel serving as the fulcrum of metabolism, which is produced from glycolysis and shuttles between different cells, tissues and organs. Lactate is usually accumulated abundantly in muscles during exercise. It remains unclear whether lactate plays an important role in the metabolism of muscle cells. In this research, we assessed the effects of lactate on myoblasts and clarified the underlying metabolic mechanisms through NMR-based metabonomic profiling. Lactate treatment promoted the proliferation and differentiation of myoblasts, as indicated by significantly enhanced expression levels of the proteins related to cellular proliferation and differentiation, including p-AKT, p-ERK, MyoD and myogenin. Moreover, lactate treatment profoundly regulated metabolisms in myoblasts by promoting the intake and intracellular utilization of lactate, activating the TCA cycle, and thereby increasing energy production. For the first time, we found that lactate treatment evidently promotes AMPK signaling as reflected by the elevated expression levels of p-AMPK and p-ACC. Our results showed that lactate as a metabolic regulator activates AMPK, remodeling the cellular metabolic profile, and thereby promoting the proliferation and differentiation of myoblasts. This study elucidates molecular mechanisms underlying the effects of lactate on skeletal muscle in vitro and may be of benefit to the exploration of lactate acting as a metabolic regulator.

Muscle cell-derived cytokines in skeletal muscle regeneration

Regeneration of the mammalian adult skeletal muscle is a well-orchestrated process regulated by multiple proteins and signalling pathways. Cytokines constitute a major class of regulators of skeletal myogenesis. It is well established that infiltrating immune cells at the site of muscle injury secrete cytokines, which play critical roles in the myofibre repair and regeneration process. In the past 10-15 years, skeletal muscle itself has emerged as a prolific producer of cytokines. Much attention in the field has been focused on the endocrine effects of muscle-secreted cytokines (myokines) on metabolic regulation. However, ample evidence suggests that muscle-derived cytokines also regulate myogenic differentiation and muscle regeneration in an autocrine manner. In this review, we survey cytokines that meet two criteria: (a) evidence of expression by muscle cells; (b) evidence demonstrating a myogenic function. Dozens of cytokines representing several major classes make up this group, and together they regulate all steps of the myogenic process. How such a large array of cytokines coordinate their signalling to form a regulatory network is a fascinating, pressing question. Functional studies that can distinguish the source of the cytokines in vivo are also much needed in order to facilitate exploration of their full therapeutic potential.

A Review of free fatty acid-induced cell signaling, angiopoietin-like protein 4, and skeletal muscle differentiation

Postnatal skeletal muscle differentiation from quiescent satellite cells is a highly regulated process, although our understanding of the contribution of nutritional factors in myogenesis is limited. Free fatty acids (FFAs) are known to cause detrimental effects to differentiated skeletal muscle cells by increasing oxidative stress which leads to muscle wasting and insulin resistance in skeletal muscle. In addition, FFAs are thought to act as inhibitors of skeletal muscle differentiation. However, the precise molecular mechanisms underlying the effects of FFAs on skeletal muscle differentiation remains to be elucidated. There is a clear relationship between dietary FFAs and their ability to suppress myogenesis and we propose the hypothesis that the FFA-mediated increase in angiopoietin-like protein 4 (ANGPTL4) may play a role in the inhibition of differentiation. This review discusses the role of FFAs in skeletal muscle differentiation to-date and proposes potential mechanisms of FFA-induced ANGPTL4 mediated inhibition of skeletal muscle differentiation.

Neuroprotective Effect of Sonic Hedgehog Mediated PI3K/AKT Pathway in Amyotrophic Lateral Sclerosis Model Mice

The Sonic Hedgehog (SHH) signaling pathway is related to the progression of various tumors and nervous system diseases. Still, its specific role in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), remains studied. This research investigates the role of SHH and PI3K/AKT signaling pathway proteins on ALS development in a SOD1-G93A transgenic mouse model. After injection of SHH and PI3K/AKT signaling pathway inhibitors or agonists in hSOD1-G93A (9 weeks of age) transgenic mice, we studied skeletal muscle pathology using immunohistochemical staining and Western blot methods. In addition, recorded data on rotation time, weight, and survival were analyzed for these mice. Our study showed that the expression of SHH, Gli-1 and p-AKT in ALS mice decreased with the progression of the disease. The expression of p-AKT changed together with Gli-1 while injecting PI3K/AKT signaling pathway inhibitor or agonist; SHH and Gli-1 protein expression remained unchanged; p-AKT protein expression significantly decreased while injecting PI3K/AKT signaling pathway inhibitor. These results indicate that SHH has a regulatory effect on PI3K/AKT signaling pathway. In behavioral experiments, we found that the survival time of hSOD1-G93A mice was prolonged by injection of SHH agonist while shortened by injection of SHH inhibitor. In conclusion, we confirmed that the SHH pathway played a neuroprotective role in ALS by mediating PI3K/AKT signaling pathway.

GLI3 regulates muscle stem cell entry into GAlert and self-renewal

Satellite cells are required for the growth, maintenance, and regeneration of skeletal muscle. Quiescent satellite cells possess a primary cilium, a structure that regulates the processing of the GLI family of transcription factors. Here we find that GLI3 processing by the primary cilium plays a critical role for satellite cell function. GLI3 is required to maintain satellite cells in a G0 dormant state. Strikingly, satellite cells lacking GLI3 enter the GAlert state in the absence of injury. Furthermore, GLI3 depletion stimulates expansion of the stem cell pool. As a result, satellite cells lacking GLI3 display rapid cell-cycle entry, increased proliferation and augmented self-renewal, and markedly enhanced regenerative capacity. At the molecular level, we establish that the loss of GLI3 induces mTORC1 signaling activation. Therefore, our results provide a mechanism by which GLI3 controls mTORC1 signaling, consequently regulating muscle stem cell activation and fate.

Muscle regeneration after high-dose radiation exposure: therapeutic potential of Hedgehog pathway modulation?

Purpose: Intentional or accidental exposure of relatively large as well as localized areas of the skin to ionizing radiation can lead to severe damage of many of its cellular components and cutaneous radiation syndrome. Patients can be treated with an invasive surgical procedure coupled with autologous cell therapy. However, this approach remains perfectible, especially for muscle repair. Indeed, a severe underlying muscle defect persists, in particular because of the damage to the satellite cells which ensure muscle regeneration. To overcome these shortcomings, a solution could be to develop new therapeutic strategies based on pharmacological treatments to improve post-irradiation muscle regeneration. In this study, we focus on the Hedgehog signaling pathway as a target, due to its involvement in myogenesis.Materials and methods: To evaluate the benefit of the pro-myogenic Hedgehog signaling pathway modulation, recombinant Sonic Hedgehog (rShh; agonist) or Cyclopamine (antagonist) were used in a stable cell line of mouse C2C12 myoblasts exposed to radiation (X-rays; 5 Gy). Our in vitro studies were carried out under either proliferation or differentiation conditions. Proliferation, migration, survival (apoptosis) and expression of myogenic genes/proteins were evaluated.Results: A high dose of radiation was shown to exert a serious negative impact in our in vitro model of mouse muscle progenitors after irradiation in proliferation or differentiation conditions. Interestingly, Hh pathway stimulation by rShh promotes the proliferation of myoblasts and their survival while its blockade by Cyclopamine significantly increases cell differentiation toward mature myotubes.Conclusion: These data suggest that, after irradiation, the sequence of activation and inhibition of the Hh pathway could allow rescue and proliferation of satellite cells, followed by their differentiation to regenerate new fibers. On the basis of these encouraging in vitro results, the second phase of our study will involve the in vivo validation of this treatment in a new murine model of ultra-localized muscle irradiation.

The Sonic Hedgehog signaling pathway regulates autophagy and migration in ovarian cancer

Background

The Sonic Hedgehog (SHH) signaling pathway plays an important role in various types of human cancers including ovarian cancer; however, its function and underlying mechanism in ovarian cancer are still not entirely understood.

Methods

We detected the expressions of SHH and SQSTM1 in borderline ovarian tumor tissues, epithelial ovarian cancer (EOC) tissues and benign ovarian tumor tissues. Cyclopamine (Cyp, a well‐known inhibitor of SHH signaling pathway) and chloroquine (CQ, the pharmaceutical inhibitor of autophagy) were used in vivo and in vitro (autophagic flux, CCK‐8 assay, wound healing assay, transwell assay, tumor xenograft model). The mechanism of action was explored through Quantitative RT‐PCR and Western Blot.

Results

We found up‐regulation of SHH and accumulation of SQSTM1/P62 in epithelial ovarian cancer. Cyp induced autophagy through the PI3K/AKT signaling pathway. Moreover, low‐dose Cyp and chloroquine (CQ) significantly promoted the migratory ability of SKOV3 cells.

Conclusions

Our findings suggest that inhibition of the SHH pathway and autophagy may be a potential and effective therapy for the treatment of ovarian cancer.

The Role of Embryonic Chick Muscle Cell Culture in the Study of Skeletal Myogenesis

The mechanisms involved in the development of skeletal muscle fibers have been studied in the last 70 years and yet many aspects of this process are still not completely understood. A myriad of in vivo and in vitro invertebrate and vertebrate animal models has been used for dissecting the molecular and cellular events involved in muscle formation. Among the most used animal models for the study of myogenesis are the rodents rat and mouse, the fruit fly Drosophila, and the birds chicken and quail. Here, we describe the robustness and advantages of the chick primary muscle culture model for the study of skeletal myogenesis. In the myoblast culture obtained from embryonic chick pectoralis muscle it is possible to analyze all the steps involved in skeletal myogenesis, such as myoblast proliferation, withdrawal from cell cycle, cell elongation and migration, myoblast alignment and fusion, the assembly of striated myofibrils, and the formation of multinucleated myotubes. The fact that in vitro chick myotubes can harbor hundreds of nuclei, whereas myotubes from cell lines have only a dozen nuclei demonstrates the high level of differentiation of the autonomous chick myogenic program. This striking differentiation is independent of serum withdrawal, which points to the power of the model. We also review the major pro-myogenic and anti-myogenic molecules and signaling pathways involved in chick myogenesis, in addition to providing a detailed protocol for the preparation of embryonic chick myogenic cultures. Moreover, we performed a bibliometric analysis of the articles that used this model to evaluate which were the main explored topics of interest and their contributors. We expect that by describing the major findings, and their advantages, of the studies using the embryonic chick myogenic model we will foster new studies on the molecular and cellular process involved in muscle proliferation and differentiation that are more similar to the actual in vivo condition than the muscle cell lines.

Effects of 20(S)-hydroxycholesterol on satellite cell proliferation and differentiation of broilers

In the modern poultry industry, with increasing product demand, muscle growth rate and meat yield in chickens have tremendously changed. Understanding the regulation of muscle development is important to maintain efficient growth and development in meat-type chickens. 20(S)-hydroxycholesterol (20S) is known as one of the naturally occurring osteogenic cholesterol derivatives due to its ability to induce osteogenic differentiation; however, no studies have evaluated myogenic response to 20S in chicken muscle cells. To determine the use of 20S in vitro for the proliferation and differentiation of chicken satellite cells, satellite cells were isolated from pectoralis major muscle of 4-week-old Ross 708 male chickens and subjected to 0.25, 0.5, and 1.0 μmol of 20S during their proliferation and differentiation stages. Cell proliferation and differentiation were measured every 24 h for 72 h by determining DNA concentration, the activity of creatine kinase, and the expressions of myogenic regulatory transcription factors. Together these results suggested that a lower concentration of 20S did not affect myogenesis but a high concentration of 1.0 μmol 20S can negatively affect proliferation and differentiation in chicken satellite cells.

Hedgehog Signaling: Implications in Cancers and Viral Infections

The hedgehog (SHH) signaling pathway is primarily involved in embryonic gut development, smooth muscle differentiation, cell proliferation, adult tissue homeostasis, tissue repair following injury, and tissue polarity during the development of vertebrate and invertebrate organisms. GLIoma-associated oncogene homolog (GLI) family of zinc-finger transcription factors and smoothened (SMO) are the signal transducers of the SHH pathway. Both SHH ligand-dependent and independent mechanisms activate GLI proteins. Various transcriptional mechanisms, posttranslational modifications (phosphorylation, ubiquitination, proteolytic processing, SUMOylation, and acetylation), and nuclear-cytoplasmic shuttling control the activity of SHH signaling pathway proteins. The dysregulated SHH pathway is associated with bone and soft tissue sarcomas, GLIomas, medulloblastomas, leukemias, and tumors of breast, lung, skin, prostate, brain, gastric, and pancreas. While extensively studied in development and sarcomas, GLI family proteins play an essential role in many host-pathogen interactions, including bacterial and viral infections and their associated cancers. Viruses hijack host GLI family transcription factors and their downstream signaling cascades to enhance the viral gene transcription required for replication and pathogenesis. In this review, we discuss a distinct role(s) of GLI proteins in the process of tumorigenesis and host-pathogen interactions in the context of viral infection-associated malignancies and cancers due to other causes. Here, we emphasize the potential of the Hedgehog (HH) pathway targeting as a potential anti-cancer therapeutic approach, which in the future could also be tested in infection-associated fatalities.

MEK/ERK Signaling Regulates Reconstitution of the Dopaminergic Nerve Circuit in the Planarian Dugesia japonica

Planarian Dugesia japonica is a flatworm that can autonomously regenerate its own body after an artificial amputation. A recent report showed the role of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) pathway in the head morphogenesis during the planarian regeneration process after amputation; however, neuron-specific regeneration mechanisms have not yet been reported. Here, whether MEK/ERK pathway was involved in the dopaminergic neuronal regeneration in planarians was investigated. Planarians regenerated their body within 14 days after amputation; however, the head region morphogenesis was inhibited by MEK inhibitor U0126 (3 or 10 μM). Furthermore, the number of planarian tyrosine hydroxylase (DjTH)-positive dopaminergic neurons in the regenerated head region was also decreased by U0126. The 6-hydroxydopamine (6-OHDA), a dopaminergic neurotoxin, can decrease the number of dopaminergic neurons; however, planarians can regenerate dopaminergic neurons after injecting 6-OHDA into the intestinal tract. MEK inhibitor PD98059 (30 μM) or U0126 (10 μM) significantly decreased dopaminergic neurons 5 days after the 6-OHDA injection. During the regeneration process of dopaminergic neurons, phosphorylated histone H3 (H3P)-positive stem cells known as "neoblasts" were increased in the head region; however, MEK inhibitors significantly decreased the number of H3P-positive neoblasts. These results suggested that dopaminergic neuronal regeneration in planarian was regulated by the MEK/ERK pathway.

Impressic Acid Attenuates the Lipopolysaccharide-Induced Inflammatory Response by Activating the AMPK/GSK3β/Nrf2 Axis in RAW264.7 Macrophages

Inflammatory diseases are caused by excessive inflammation from pro-inflammatory mediators and cytokines produced by macrophages. The Nrf2 signaling pathway protects against inflammatory diseases by inhibiting excessive inflammation via the regulation of antioxidant enzymes, including HO-1 and NQO1. We investigated the anti-inflammatory effect of impressic acid (IPA) isolated from Acanthopanax koreanum on the lipopolysaccharide (LPS)-induced inflammation and the underlying molecular mechanisms in RAW264.7 cells. IPA attenuated the LPS-induced production of pro-inflammatory cytokines and reactive oxygen species, and the activation of the NF-κB signaling pathway. IPA also increased the protein levels of Nrf2, HO-1, and NQO1 by phosphorylating CaMKKβ, AMPK, and GSK3β. Furthermore, ML385, an Nrf2 inhibitor, reversed the inhibitory effect of IPA on LPS-induced production of pro-inflammatory cytokines in RAW264.7 cells. Therefore, IPA exerts an anti-inflammatory effect via the AMPK/GSK3β/Nrf2 signaling pathway in macrophages. Taken together, the findings suggest that IPA has preventive potential for inflammation-related diseases.

Comparative Transcriptome Profile Analysis of Longissimus dorsi Muscle Tissues From Two Goat Breeds With Different Meat Production Performance Using RNA-Seq

Carcass weight, meat quality and muscle components are important traits economically and they underpin most of the commercial return to goat producers. In this study, the Longissimus dorsi muscle tissues were collected from five Liaoning cashmere (LC) goats and five Ziwuling black (ZB) goats with phenotypic difference in carcass weight, some meat quality traits and muscle components. The histological quantitative of collagen fibers and the transcriptome profiles in the Longissimus dorsi muscle tissues were investigated using Masson-trichrome staining and RNA-Seq, respectively. The percentage of total collagen fibers in the Longissimus dorsi muscle tissues from ZB goats was less than those from LC goats, suggesting that these ZB goats had more tender meat. An average of 15,919 and 15,582 genes were found to be expressed in Longissimus dorsi muscle tissues from LC and ZB goats, respectively. Compared to LC goats, the expression levels of 78 genes were up-regulated in ZB goats, while 133 genes were down-regulated. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the differentially expressed genes (DEGs) were significantly enriched in GO terms related to the muscle growth and development and the deposition of intramuscular fat and lipid metabolism, hippo signaling pathway and Jak-STAT signaling pathway. The results provide an improved understanding of the genetic mechanisms regulating meat production performance in goats, and will help us improve the accuracy of selection for meat traits in goats using marker-assisted selection based on these differentially expressed genes obtained.

Mechanisms of IGF-1-Mediated Regulation of Skeletal Muscle Hypertrophy and Atrophy

Insulin-like growth factor-1 (IGF-1) is a key growth factor that regulates both anabolic and catabolic pathways in skeletal muscle. IGF-1 increases skeletal muscle protein synthesis via PI3K/Akt/mTOR and PI3K/Akt/GSK3β pathways. PI3K/Akt can also inhibit FoxOs and suppress transcription of E3 ubiquitin ligases that regulate ubiquitin proteasome system (UPS)-mediated protein degradation. Autophagy is likely inhibited by IGF-1 via mTOR and FoxO signaling, although the contribution of autophagy regulation in IGF-1-mediated inhibition of skeletal muscle atrophy remains to be determined. Evidence has suggested that IGF-1/Akt can inhibit muscle atrophy-inducing cytokine and myostatin signaling via inhibition of the NF-κΒ and Smad pathways, respectively. Several miRNAs have been found to regulate IGF-1 signaling in skeletal muscle, and these miRs are likely regulated in different pathological conditions and contribute to the development of muscle atrophy. IGF-1 also potentiates skeletal muscle regeneration via activation of skeletal muscle stem (satellite) cells, which may contribute to muscle hypertrophy and/or inhibit atrophy. Importantly, IGF-1 levels and IGF-1R downstream signaling are suppressed in many chronic disease conditions and likely result in muscle atrophy via the combined effects of altered protein synthesis, UPS activity, autophagy, and muscle regeneration.

Transcriptomic changes in bovine skeletal muscle cells after resveratrol treatment

Skeletal muscles constitute a high proportion of the cellular mass that is essential for the growth traits in cattle. Resveratrol (RSV) is a natural polyphenol compound involved in pleiotropic biological activities of muscle. Therefore, the aim of our study was to investigate the transcriptome-level effects of RSV on bovine primary myoblast to reveal differentially expressed genes (DEGs). We treated three replicates of primary myoblasts with 20 μM mother solution containing RSV, whereas three other replicates without RSV were used as control group. Then, we conducted genome-wide transcriptome analysis for the two groups. The results of expression analysis identified 3856 DEGs of which 1805 genes were up-regulated and 2051 genes were down-regulated (adjusted P < 0.05). In addition, qRT-PCR analysis of 19 selected DEGs were consistent with the expression levels observed in the transcriptome data. Gene Ontology (GO) and pathway enrichment analysis showed 72 and 66 significant GO terms and KEGG pathways, respectively (adjusted P < 0.05). The most significant GO term was actin cytoskeleton organization (GO:0030036). The top significant KEGG pathway was focal adhesion (bta04510). Predicted protein-protein interactions (PPIs) showed that CDKN1A encoding cyclindependent kinase inhibitor 1A connects several larger protein complexes. In conclusion, our results found a list of DEGs, significant GO terms and pathways, and provided an improved and expanded understanding of the impact of RSV on cattle muscle cells at the transcriptomic level. The study elucidates the potential of using the genes enriched in pathways mediating resveratrol effects as targets in genomic selection for muscle development and growth in beef cattle.

Hedgehog pathway inhibition as a therapeutic target in acute myeloid leukemia

Introduction: The Hedgehog (HH) pathway constitutes a collection of signaling molecules which critically influence embryogenesis. In adults, however, the HH pathway remains integral to the proliferation, maintenance, and apoptosis of adult stem cells including hematopoietic stem cells. Areas covered: We discuss the current understanding of the HH pathway as it relates to normal hematopoiesis, the pathology of acute myeloid leukemia (AML), the rationale for and data from combination therapies including HH pathway inhibitors, and ultimately the prospects that might offer promise in targeting this pathway in AML. Expert opinion: Efforts to target the HH pathway have been focused on impeding this disposition and restoring chemosensitivity to conventional myeloid neoplasm therapies. The year 2018 saw the first approval of a HH pathway inhibitor (glasdegib) for AML, though for an older population and in combination with an uncommonly-used therapy. Several other clinical trials with agents targeting modulators of HH signaling in AML and MDS are underway. Further study and understanding of the interplay between the numerous aspects of HH signaling and how it relates to the augmented survival of AML will provide a more reliable substrate for therapeutic strategies in patients with this poor-risk disease.

GLI1 activation by non-classical pathway integrin αvβ3/ERK1/2 maintains stem cell-like phenotype of multicellular aggregates in gastric cancer peritoneal metastasis

Peritoneal metastasis is one of the most important causes of postoperative death in patients with gastric cancer, and the exact mechanism remains unclear. The proliferation of multicellular aggregates of exfoliated malignant gastric cells in the abdominal cavity is the focus of current research. However, the mechanism how gastric cancer multicellular aggregates survive remains unclear. In this study, we demonstrated that multicellular aggregates of exfoliated gastric cancer cells in the abdominal cavity expressed a stem cell-Like phenotype. We found that Integrin α_vβ₃ not only mediated adhesion of gastric cancer multicellular aggregates to form independent functional units, but also maintained their stem cell-like phenotype by the non-classical pathway Integrin α_vβ₃/ERK1/2/GLI1. In addition, ERK1/2 directly regulates the transcriptional activity of GLI1. GLI1 is a key effector of the Integrin α_vβ₃ pathway in regulating stem cell-like phenotype in multicellular aggregates. Our data indicates that although there is a crosstalk between the non-classical Integrin α_vβ₃ pathway and the classical Hedgehog pathway, the activation of GLI1 is almost independent of the Hedgehog pathway in multicellular aggregates of gastric cancer cells. Our study provides a basis for blocking GLI1 activity in the prevention and treatment of peritoneal metastases of gastric cancer.

Smoothened receptor inhibitor vismodegib for the treatment of basal cell carcinoma: a retrospective analysis of efficacy and side effects

Background: Smoothened receptor inhibitor vismodegib is indicated to treat locally advanced basal cell carcinoma (laBCC) and lesions in nevoid basal cell carcinoma syndrome (NBCCS).Methods: We treated 11 patients - including four NBCCS and seven laBCC patients - with vismodegib at our department.Results: Complete remission was achieved in three cases, without relapse after discontinuation. Two of the aforementioned patients had NBCCS, in their cases further treatment might be needed. Two patients showed improvement, but later passed away due to unrelated conditions. Two patients with laBCC initially showed remission, then the treatment was suspended due to side effects. After re-administration of the drug, loss of efficacy was observed. We did not observe therapy resistance in our NBCCS group. The rest of the patients showed good response to therapy, but have not reached full remission yet. The main side effects of vismodegib were muscle cramps, dysgeusia, nausea and alopecia. The frequency of adverse events did not show significant differences between the patient groups.Conclusions: Our results show that vismodegib therapy is effective in the treatment of BCC; however, side effects are often severe. Since the suspension of treatment can lead to therapy resistance, the management of side effects is of great importance.

Sonic hedgehog pathway activation is associated with cetuximab resistance and EPHB3 receptor induction in colorectal cancer

A major problem of colorectal cancer (CRC) targeted therapies is relapse caused by drug resistance. In most cases of CRC, patients develop resistance to anticancer drugs. Cetuximab does not show many of the side effects of other anticancer drugs and improves the survival of patients with metastatic CRC. However, the molecular mechanism of cetuximab resistance is not fully understood.

Methods: EPHB3-mediated cetuximab resistance was confirmed by in vitro western blotting, colony-forming assays, WST-1 colorimetric assay, and in vivo xenograft models (n = 7 per group). RNA-seq analysis and receptor tyrosine kinase assays were performed to identify the cetuximab resistance mechanism of EPHB3. All statistical tests were two-sided.

Results: The expression of EFNB3, which upregulates the EPHB3 receptor, was shown to be increased via microarray analysis. When resistance to cetuximab was acquired, EPHB3 protein levels increased. Hedgehog signaling, cancer stemness, and epithelial-mesenchymal transition signaling proteins were also increased in the cetuximab-resistant human colon cancer cell line SW48R. Despite cells acquiring resistance to cetuximab, STAT3 was still responsive to EGF and cetuximab treatment. Moreover, inhibition of EPHB3 was associated with decreased STAT3 activity. Co-immunoprecipitation confirmed that EGFR and EPHB3 bind to each other and this binding increases upon resistance acquisition, suggesting that STAT3 is activated by the binding between EGFR and EPHB3. Protein levels of GLI-1, SOX2, and Vimentin, which are affected by STAT3, also increased. Similar results were obtained in samples from patients with CRC.

Conclusion: EPHB3 expression is associated with anticancer drug resistance.

Dynamic membrane proteome of adipogenic and myogenic precursors in skeletal muscle highlights EPHA2 may promote myogenic differentiation through ERK signaling

The balance of myogenic and adipogenic differentiation is crucial for skeletal muscle homeostasis. Given the vital role of membrane proteins (MBPs) in cell signal perception, membrane proteomics was conducted to delineate mechanisms regulating differentiation of adipogenic and myogenic precursors in skeletal muscle. Adipogenic and myogenic precursors with divergent differentiation potential were isolated from the longissimus dorsi muscle of neonatal pigs by the preplate method. A total of 85 differentially expressed MBPs (P < 0.05 and fold change ≥1.2 or ≤0.83) between 2 precursors were detected via isobaric tags for relative and absolute quantitation (iTRAQ) assay, including 67 up-regulated and 18 down-regulated in myogenic precursors. Functional enrichment analysis uncovered that myogenic and adipogenic precursors showed significant differences in cytoskeleton organization, syncytium formation, environmental information processing, and organismal systems. Furthermore, key MBPs in regulating cell differentiation were also characterized, including ITGB3, ITGAV, ITPR3, and EPHA2. Noteworthily, EPHA2 was required for myogenic differentiation, and it may promote myogenic differentiation through ERK signaling. Collectively, our study provided an insight into the distinct MBP profile between myogenic and adipogenic precursors in skeletal muscle and served as a solid basis for supporting the role of MBPs in regulating differentiation.—Zhang, X., Wang, L., Qiu, K., Xu, D., Yin, J. Dynamic membrane proteome of adipogenic and myogenic precursors in skeletal muscle highlights EPHA2 may promote myogenic differentiation through ERK signaling.

Mir-215-5p induces autophagy by targeting PI3K and activating ROS-mediated MAPK pathways in cardiomyocytes of chicken

Our previous study revealed that selenium (Se) deficiency can cause myocardial injury through triggering autophagy. MicroRNAs (miRNAs) play crucial roles in autophagic cell death. However, the relationship between miRNAs and myocardial autophagy injury caused by Se deficiency remains unclear. We selected differential microRNA-215-5p (miR-215-5p) in Se-deficient myocardial tissue using high-throughput miRNA-sequencing. To further explore the role of miR-215-5p in myocardial injury, overexpression/knockdown of miR-215-5p in primary cardiomyocyte model was established by miRNAs interference technology. In this study, we report that miR-215-5p can promote myocardial autophagy by directly binding to the 3'untranslated region (3'UTR) of phosphatidylinositol-4, 5-bisphosphate 3-kinase (PI3K). Its target gene PI3K was confirmed by dual luciferase reporter assay, quantitative real-time polymerase chain reaction (qRT-PCR) and western blot in cardiomyocytes. Our results showed that overexpression of miR-215-5p could trigger myocardial autophagy through PI3K-threonine-protein kinase (AKT)-target of rapamycin (TOR) pathway. Further studies revealed that autophagic cell death was dependent on the activation of extracellular signal-regulated kinase1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38 kinase (p38) and generation of reactive oxygen species (ROS) in overexpression of miR-215-5p in cardiomyocytes. On the contrary, miR-215-5p inhibitor can enhance cell survival capacity against autophagy by inhibiting ROS-mitogen-activated protein kinase (MAPK) pathways and activating the PI3K/AKT/TOR pathway in cardiomyocytes. Together, our findings support that miR-215-5p may modulate cell survival programs by regulating autophagy, and miR-215-5p acts as an autophagic regulator in the regulatory feedback loop that regulates cardiomyocyte survival by modulating the PI3K/AKT/TOR pathway and ROS-dependent MAPK pathways.

Sonic Hedgehog Signaling Pathway Mediates Proliferation and Migration of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis via MAPK/ERK Signaling Pathway

Fibroblast-like synoviocytes (FLSs) are the major effector cells that lead to rheumatoid arthritis (RA) synovitis and joint destruction. Our previous studies showed that Sonic Hedgehog (SHH) signaling pathway is involved in aberrant activation of RA-FLSs and inhibition of SHH pathway decreases proliferation and migration of RA-FLSs. The objective of this study was to investigate if the SHH pathway mediates proliferation and migration of RA-FLSs via the mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) signaling pathway. SHH signaling was studied by using SHH agonist (Purmorphamine) and antagonist (Cyclopamine) targeting the Smoothened (SMO) in FLSs. U0126-EtOH was used to inhibit the MAPK/ERK signaling pathway. The phosphorylation of ERK 1/2 (p-ERKl/2) was examined by western blot. Cell viability was detected using cell proliferation and cytotoxicity kit-8 (CCK8), and cell cycle distribution and proliferating cells were evaluated by the flow cytometry. Cell migration was examined by Transwell assay. Results showed that, compared with the control group, Purmorphamine increased the levels of p-ERK1/2 in concentration-and time-dependent manners (P < 0.01). Co-treated with Purmorphamine and U0126-EtOH or Cyclopamine both decreased the levels of p-ERK1/2 (P < 0.05). RA-FLSs treated with Purmorphamine resulted in alteration of cell cycle distribution, increasing of proliferating cells, cell viability, and migration cells compared to controls (P < 0.01). However, the above phenomenon can be abolished by U0126-EtOH (P < 0.05). The findings suggest that SHH signaling pathway mediates proliferation and migration of RA-FLSs via MAPK/ERK pathway and may contribute to progression of RA. Targeting SHH signaling may have a therapeutic potential in patients with RA.

Sonic Hedgehog signaling and Gli-1 during embryonic chick myogenesis

The Sonic Hedgehog signaling (Shh) pathway has been implicated in both proliferation of myoblast cells and terminal differentiation of muscle fibers, and contradictory results of these effects have been described. To clarify the role of Shh during myogenesis, we decided to study the effects of recombinant Shh and the distribution of Gli-1 during in vitro and in situ embryonic chick skeletal muscle differentiation at later stages of development. Gli-1 was found in small aggregates near the nucleus in mononucleated myoblasts and in multinucleated myotubes both in vitro and in situ chick muscle cells. Some Gli-1 aggregates colocalized with gamma-tubulin positive-centrosomes. Gli-1 was also found in striations and at the subsarcolemmal membrane in muscle fibers in situ. Recombinant Shh added to in vitro grown muscle cells induced the nuclear translocation of Gli-1, as well as an increase in the number of myoblasts and in the number of nuclei within myotubes. We suggest that Gli-1 aggregates observed in chick muscle cells near the nuclei of myoblasts and myotubes could be a storage site for the rapid cellular redistribution of Gli-1 upon specific signals during muscle differentiation.

miR-423-5p inhibits myoblast proliferation and differentiation by targeting Sufu

Myoblast proliferation and terminal differentiation are the key steps of myogenesis. MicroRNAs are a class of small noncoding RNAs that play important roles in gene expression regulation. They negatively regulate gene expression by causing messenger RNA translational repression or target messenger RNA degradation. Here, we found that microRNA-423-5p (miR-423-5p) is highly expressed in both slow and fast muscles. Our gain-of-function study indicated that miR-423-5p actually plays a negative role in regulating myoblast proliferation and differentiation. We also found that miR-423-5p is able to inhibit the expression of suppressor of fused homolog to inactivate the expression of the marker genes in myoblast proliferation and differentiation. Taken together, our findings indicated miR-423-5p as a potential inhibitor of myogenesis by targeting suppressor of fused homolog in myoblast, and it also contributes to a better understanding of the microRNAs-target gene regulatory network in different types of porcine muscle types and may benefit the practice of improving the meat quality in animal husbandry.

The effect of QTL-rich region polymorphisms identified by targeted DNA-seq on pig production traits

The aim of the present study was to analyse the effect of PLCD4, PECR, FN1 and PNKD mutations on pig productive traits and tested the usefulness of targeted enrichment DNA sequencing method as tool for preselection of genetic markers. The potential genetic markers for pig productive traits were identified by using targeted enrichment DNA sequencing of chromosome 15 region that is QTL-rich. The selected mutations were genotyped by using HRM, Sanger sequencing and PCR-ACRS methods. The association study was performed by using GLM model in SAS program and included over 500 pigs of 5 populations maintained in Poland. The variation (C/T) of PLCD4 gene affected feed conversion, intramuscular fat and water exudation. The PNKD mutations were associated with texture parameters measured after cooking. In turn, the variation rs792423408 (C/T) in the FN1 gene influenced toughness measured in semimembranosus muscle and growth traits that was observed particularly in Duroc breed. Summarizing, the investigated gene variants delivered valuable information that could be used during developing SNP microarray for genomic estimated breeding value procedure in pigs. Moreover, the study showed that the TEDNA-seq method could be used to preselect the molecular markers associated with pig traits. However, the further association study that included large number animal populations is necessary.

Clinical and mutational spectrum of highly differentiated, paired box 3:forkhead box protein o1 fusion-negative rhabdomyosarcoma: A report from the Children's Oncology Group

BACKGROUND

Pediatric paired box 3:forkhead box protein O1 fusion-negative (PF-) rhabdomyosarcoma (RMS) represents a diverse spectrum of tumors with marked differences in histology, myogenic differentiation, and clinical behavior.

METHODS

This study sought to evaluate the clinical and mutational spectrum of 24 pediatric PF- human RMS tumors with high levels of myogenic differentiation. Tumors were sequenced with OncoPanel v.2, a panel consisting of the coding regions of 504 genes previously linked to human cancer.

RESULTS

Most of the tumors (19 of 24) arose at head/neck or genitourinary sites, and the overall survival rate was 100% with a median follow-up time of 4.6 years (range, 1.4-8.6 years). RAS pathway gene mutations were the most common mutations in PF-, highly differentiated RMS tumors. In addition, Hedgehog (Hh) and mechanistic target of rapamycin (mTOR) gene mutations with evidence for functional relevance (high-impact) were identified in subsets of tumors. The presence of Hh and mTOR pathway gene mutations was mutually exclusive and was associated with high-impact RAS pathway gene mutations in 3 of 4 Hh-mutated tumors and in 1 of 6 mTOR-mutated tumors.

CONCLUSIONS

Interestingly, Hh and mTOR gene mutations were previously associated with rhabdomyomas, which are also known to preferentially arise at head/neck and genitourinary sites. Findings from this study further support the idea that PF-, highly differentiated RMS tumors and rhabdomyomas may represent a continuous spectrum of tumors. Cancer 2018;124:1973-81. © 2018 American Cancer Society.

Sonic hedgehog signaling mediates resveratrol to improve maturation of pig oocytes in vitro and subsequent preimplantation embryo development

The beneficial effects of resveratrol on in vitro maturation (IVM) have been explained mainly by indirect antioxidant effects and limited information is available on the underlying mechanism by which resveratrol acts directly on porcine cumulus oocyte complexes (COCs). Recently, several studies reported that sonic hedgehog (SHH) signaling mediates resveratrol to exert its biological activities. Furthermore, SHH is an important signaling molecule for follicle development, oocyte maturation, and embryo development. Therefore, to elucidate the relationship between resveratrol and SHH signaling, we designed three groups: (i) control; (ii) resveratrol; and (iii) resveratrol with cyclopamine (SHH signaling inhibitor). We evaluated the effects of these agents on cumulus expansion, oocyte maturation, embryo development after parthenogenetic activation, expression levels of mRNAs in cumulus cells, oocytes and blastocysts, and protein expression in COCs. Resveratrol significantly increased the proportion of COCs exhibiting complete cumulus expansion (degree 4), oocyte nuclear maturation, cleavage and blastocyst formation rates and total cell numbers, which were blocked in the presence of cyclopamine. At the same time, a significant increase in the expression levels of mRNAs related to cumulus expansion, oocyte maturation and SHH signaling-related mRNAs and proteins from the resveratrol treatment group was also inhibited by simultaneous addition of cyclopamine. In conclusion, our results indicate that SHH signaling mediates resveratrol to improve porcine cumulus expansion, oocyte maturation, and subsequent embryo development.

A compartmentalized phosphoinositide signaling axis at cilia is regulated by INPP5E to maintain cilia and promote Sonic Hedgehog medulloblastoma

Sonic Hedgehog (SHH) signaling at primary cilia drives the proliferation and progression of a subset of medulloblastomas, the most common malignant paediatric brain tumor. Severe side effects associated with conventional treatments and resistance to targeted therapies has led to the need for new strategies. SHH signaling is dependent on primary cilia for signal transduction suggesting the potential for cilia destabilizing mechanisms as a therapeutic target. INPP5E is an inositol polyphosphate 5-phosphatase that hydrolyses PtdIns(4,5)P₂ and more potently, the phosphoinositide (PI) 3-kinase product PtdIns(3,4,5)P₃. INPP5E promotes SHH signaling during embryonic development via PtdIns(4,5)P₂ hydrolysis at cilia, that in turn regulates the cilia recruitment of the SHH suppressor GPR161. However, the role INPP5E plays in cancer is unknown and the contribution of PI3-kinase signaling to cilia function is little characterized. Here, we reveal INPP5E promotes SHH signaling in SHH medulloblastoma by negatively regulating a cilia-compartmentalized PI3-kinase signaling axis that maintains primary cilia on tumor cells. Conditional deletion of Inpp5e in a murine model of constitutively active Smoothened-driven medulloblastoma slowed tumor progression, suppressed cell proliferation, reduced SHH signaling and promoted tumor cell cilia loss. PtdIns(3,4,5)P₃, its effector pAKT and the target pGSK3β, which when non-phosphorylated promotes cilia assembly/stability, localized to tumor cell cilia. The number of PtdIns(3,4,5)P₃/pAKT/pGSK3β-positive cilia was increased in cultured Inpp5e-null tumor cells relative to controls. PI3-kinase inhibition or expression of wild-type, but not catalytically inactive HA-INPP5E partially rescued cilia loss in Inpp5e-null tumor cells in vitro. INPP5E mRNA and copy number were reduced in human SHH medulloblastoma compared to other molecular subtypes and consistent with the murine model, reduced INPP5E was associated with improved overall survival. Therefore our study identifies a compartmentalized PtdIns(3,4,5)P₃/AKT/GSK3β signaling axis at cilia in SHH-dependent medulloblastoma that is regulated by INPP5E to maintain tumor cell cilia, promote SHH signaling and thereby medulloblastoma progression.

Hedgehog-Gli1 signaling regelates differentiation of chicken (Gallus gallus) embryonic stem cells to male germ cells

Gli1 is an important signaling molecular in Hedgehog signaling pathway. In our study, we explored the adjustment effect of Hedgehog-Gli1 signaling pathway on chicken male germ cells differentiation based on the transcriptome-wide analyses of chicken ESCs, primordial germ cells (PGCs) and spermatogonia stem cells (SSCs) that were associated with male germ cell differentiation. We screened out Hedgehog signaling pathway and identified 8 candidated differentially expressed genes (DEGs), Wnt3a, Wnt16, Wnt8a, HHIPL1, Gli1, BMP6, BMP7 and TTLL4. These DEGs expression change trend among blastoderm, genital ridge and testes, from which ESCs, PGCs and SSCs were isolated was the same as RNA-Seq data with quantitative RT-PCR evaluation. Based on retinoic acid (RA) induction of ESCs to SSCs in vitro, Gli1 overexpression has the ability to induce ESCs differentiation and SSCs-like cells formation and high expression of related reproductive genes, like Cvh, C-kit, Blamp1, Prmd14, Stra8, Dazl, integrin α6 and integrin β1 and so on in vitro. While RNAi knockdown of Gli1 can protect ESCs from differentiating into SSCs and correspondingly reduce the expression of the associated reproductive gene in vivo and vitro. Immunochemistry results showed that Gli1 overexpression could increase the expression of PGCs markers Cvh and C-kit and SSCs markers integrin α6 and integrin β1 in vivo, while Gli1 knockdown can have the opposite effect in vivo and in vitro. PAS stain and flow cytometry (FCM) evaluation results indicated the quantity of germ cells is decrease or increase with Gli1 knockdown or overexpression. Collectively, these results uncovered a novel function of Gli1 and demonstrated Hedgehog-Gli1 signaling pathway involved in chicken male germ cell differentiation, where it acts as a facilitator.

Sonic Hedgehog Promotes Cementoblastic Differentiation via Activating the BMP Pathways

Although sonic hedgehog (SHH), an essential molecule in embryogenesis and organogenesis, stimulates proliferation of human periodontal ligament (PDL) stem cells, the effects of recombinant human SHH (rh-SHH) on osteoblastic differentiation are unclear. To reveal the role of SHH in periodontal regeneration, expression of SHH in mouse periodontal tissues and its effects on the osteoblastic/cementoblastic differentiation in human cementoblasts were investigated. SHH is immunolocalized to differentiating cementoblasts, PDL cells, and osteoblasts of the developing mouse periodontium. Addition of rh-SHH increased cell growth, ALP activity, and mineralization nodule formation, and upregulated mRNA expression of osteoblastic and cementoblastic markers. The osteoblastic/cementoblastic differentiation of rh-SHH was abolished by the SHH inhibitor cyclopamine (Cy) and the BMP antagonist noggin. rh-SHH increased the expression of BMP-2 and -4 mRNA, as well as levels of phosphorylated Akt, ERK, p38, and JNK, and of MAPK and NF-κB activation, which were reversed by noggin, Cy, and BMP-2 siRNA. Collectively, this study is the first to demonstrate that SHH can promote cell growth and cell osteoblastic/cementoblastic differentiation via BMP pathway. Thus, SHH plays important roles in the development of periodontal tissue, and might represent a new therapeutic target for periodontitis and periodontal regeneration.

Translating Hedgehog in Cancer: Controlling Protein Synthesis

Developmental Hedgehog (Hh) signaling is found deregulated in a broad spectrum of human malignancies and, thus, is an attractive target for cancer therapy. Currently available Hh inhibitors have shown the rapid occurrence of drug resistance, due to altered signaling in collateral pathways. Emerging observations suggest that Hh signaling regulates protein translation in pathways that depend both on Cap- and IRES-mediated translation. In addition, translational regulators have been shown to modulate Hh function. In this opinion, we describe this novel Hh/translation crosstalk and argue that it plays a relevant role in Hh-mediated tumorigenesis and drug resistance. As such, we suggest that drugs targeting translation might be introduced in novel protocols aimed at treating malignancies driven by aberrant Hh signaling.

Ion Current-Based Proteomic Profiling for Understanding the Inhibitory Effect of Tumor Necrosis Factor Alpha on Myogenic Differentiation

Despite a demonstrated role for TNF-α in promoting muscle wasting and cachexia, the associated molecular mechanisms and signaling pathways of myoblast differentiation dysregulated by TNF-α remain poorly understood. This study presents well-controlled proteomic profiling as a means to investigate the mechanisms of TNF-α-regulated myogenic differentiation. Primary human muscle precursor cells (MPCs) cultured in growth medium (GM), differentiation medium (DM) to induce myogenic differentiation, and DM with 20 ng/mL of TNF-α (n = 5/group) were comparatively analyzed by an ion current-based quantitative platform consisting of reproducible sample preparation/on-pellet digestion, a long-column nano-LC separation, and ion current-based differential analysis. The inhibition of myogenic differentiation by TNF-α was confirmed by reduced formation of multinucleated myotubes and the recovered expression of altered myogenic proteins such as MYOD and myogenin during myogenic differentiation. Functional analysis and validation by immunoassay analysis suggested that the cooperation of NF-κB and STAT proteins is responsible for dysregulated differentiation in MPCs by TNF-α treatment. Increased MHC class I components such as HLA-A, HLA-B, HLA-C, and beta-2-microglobulin were also observed in cultures in DM treated with TNF-α. Interestingly, inhibition of the cholesterol biosynthesis pathway during myogenic differentiation induced by serum starvation was not recovered by TNF-α treatment, which combined with previous reports, implies that this process may be an early event of myogenesis. This finding could lay the foundation for the potential use of statins in modulating myogenesis through cholesterol, for example, in stem cell-based myocardial infarction treatment, where differentiation of myoblasts and stem cells into force-generating mature muscle cells is a key step to the therapeutic capacity. In conclusion, the landscapes of altered transcription regulators, metabolic processes, and signaling pathways in MPCs are revealed in the regulation of myogenic differentiation by TNF-α, which is valuable for myogenic cellular therapeutics.

Skeletal muscle wasting and renewal: a pivotal role of myokine IL-6

Adult skeletal tissue is composed of heterogeneous population of cells that constantly self-renew by means of a controlled process of activation and proliferation of tissue-resident stem cells named satellite cells. Many growth factors, cytokines and myokines produced by skeletal muscle cells play critical roles in local regulation of the inflammatory process and skeletal muscle regeneration during different pathological conditions. IL-6 is a pleiotropic cytokine released in large amount during infection, autoimmunity and cancer. Low levels of IL-6 can promote activation of satellite cells and myotube regeneration while chronically elevated production promote skeletal muscle wasting. These distinct effects may be explained by a crosstalk of the IL-6/IL-6 receptor and gp130 trans-signaling pathway that oppose to regenerative and anti-inflammatory of the classical IL-6 receptor signaling pathway. Here we discuss on potential therapeutic strategies using monoclonal antibodies to IL-6R for the treatment of skeletal muscle wasting and cachexia. We also highlight on the IL-6/JAK/STAT and FGF/p38αβ MAPK signaling pathways in satellite cell activation and the use of protein kinase inhibitors for tailoring and optimizing satellite cell proliferation during the skeletal muscle renewal. Future investigations on the roles of the IL-6 classical and trans-signaling pathways in both immune and non-immune cells in skeletal muscle tissue will provide new basis for therapeutic approaches to reverse atrophy and degeneration of skeletal muscles in cancer and inflammatory diseases.

Effect of purmorphamine on the mRNA expression of Sonic Hedgehog signaling downstream molecules in ovine embryo

Abstract. Sonic Hedgehog (SHH) is a signaling pathway mediated through a receptor system which seems to have effects on oocyte maturation and embryonic development. Purmorphamine is an SHH agonist that performs a crucial role in the regulation of the activity of SHH receptors and downstream transcription factors. The aim of this study was to analyze the effect of purmorphamine on the mRNA expression of SHH signaling downstream molecules (Patched1, Glioma-Associated Oncogene1, Smoothened, Histone Deacetylase1, Histone Deacetylase2 and Histone Deacetylase3) in ovine two-cell embryo. Ovaries were obtained from a slaughterhouse, and cumulus–oocyte complexes were aspirated and cultured in maturation media containing 0, 250 or 500 ng mL−1 purmorphamine. Then, oocytes were fertilized and cultured in a CR1 culture medium and after 24 h, two-cell embryos were collected for RNA extraction. Gene expression was evaluated by real-time polymerase chain reaction (PCR). Results indicated that in 250 ng mL−1 purmorphamine, Smo, Ptch1 and Hdac3 expression reduced, Hdac1 expression increased, and Gli1 and Hdac2 expression levels did not change. In 500 ng mL−1 purmorphamine, Gli1 and Smo transcripts increased, while Ptch1, Hdac2 and Hdac3 transcripts decreased. Regarding to the presence of SHH signaling molecules in two-cell embryos and their response to purmorphamine, it can be suggested that SHH signaling is probably active before embryonic genome activation in ovine embryos.