Myogenic Cells Research Articles

Optimisation of cell fate determination for cultivated muscle differentiation.

Production of cultivated meat requires defined medium formulations for the robust differentiation of myogenic cells into mature skeletal muscle fibres in vitro. Although these formulations can drive myogenic differentiation levels comparable to serum-starvation-based protocols, the resulting cultures are often heterogeneous, with a significant proportion of cells not participating in myofusion, limiting maturation of the muscle. To address this problem, we employed RNA sequencing to analyse heterogeneity in differentiating bovine satellite cells at single-nucleus resolution, identifying distinct cellular subpopulations including proliferative cells that fail to exit the cell cycle and quiescent 'reserve cells' that do not commit to myogenic differentiation. Our findings indicate that the MEK/ERK, NOTCH, and RXR pathways are active during the initial stages of myogenic cell fate determination, and by targeting these pathways, we can promote cell cycle exit while reducing reserve cell formation. This optimised medium formulation consistently yields fusion indices close to 100% in 2D culture. Furthermore, we demonstrate that these conditions enhance myotube formation and actomyosin accumulation in 3D bovine skeletal muscle constructs, providing proof of principle for the generation of highly differentiated cultivated muscle with excellent mimicry to traditional muscle.

In Vitro Gene Therapy Using Human iPS-Derived Mesoangioblast-Like Cells (HIDEMs) Combined with Microdystrophin (μDys) Expression as the New Strategy for Duchenne Muscular Dystrophy (DMD) Experimental Treatment

Duchenne Muscular Dystrophy (DMD) is a genetic disorder characterized by disruptions in the dystrophin gene. This study aims to investigate potential a therapeutic approach using genetically modified human iPS-derived mesoangioblast-like cells (HIDEMs) in mdx mouse model. This study utilizes patient-specific myoblasts reprogrammed to human induced pluripotent stem cells (iPSCs) and then differentiated into HIDEMs. Lentiviral vectors carrying microdystrophin sequences have been employed to deliver the genetic construct to express a shortened, functional dystrophin protein in HIDEMs. The study indicated significant changes within redox potential between healthy and pathological HIDEM cells derived from DMD patients studied by catalase and superoxide dismutase activities. Microdystrophin expressing HIDEMs also improved expression of genes involved in STARS (striated muscle activator of Rho signaling) pathway albeit in selective DMD patients (with mild phenotype). Although in vivo observations did not bring progress in the mobility of mdx mice with HIDEMs, microdystrophin interventions this may argue against “treadmill test” as suitable for assessment of mdx mice recovery. Low-level signaling of the Rho pathway and inflammation-related factors in DMD myogenic cells can also contribute to the lack of success in a functional study. Overall, this research contributes to the understanding of DMD pathogenesis and provides insights into potential novel therapeutic strategy, highlighting the importance of personalized gene therapy.

Heterogeneity of extracellular vesicles in porcine myoblasts regulates adipocyte differentiation

sThe interactions between myogenic cells and adipocytes play an important role in improving carcass traits and the efficiency of energy utilization. However, there are few reports about the interaction between them mediated by small extracellular vesicles (sEV). In this study, sEV derived from porcine primary skeletal muscle stem cells (MuSCs) was found to be involved in the inhibition of porcine primary adipocyte viability, triglyceride content, Oil Red O enrichment and the expression of adipogenic genes. When the MuSCs were treated with insulin (INS) and oleic acid (OA), the effects of their secreted sEVs on adipose precursor cells were reversed, suggesting that the signaling effects of sEV are related to their own heterogeneity. Further by component heterogeneity analysis, miR-146a-5p was found to be enriched in sEVs of MuSCs and to regulate and suppress adipogenesis through its heterogeneity. This study provides an important mechanism and molecular target for small extracellular vesicles to regulate the interaction between muscle and adipose tissue and improve carcass traits at the intercellular level.

Notch signaling regulates limb regeneration through Hes1 and HeyL in the Chinese mitten crab

Tissue regeneration is an efficient strategy developed by animals to compensate for damaged tissues, involving various types of progenitor cells. Deciphering the signal network that modulates the activity of these progenitors during regeneration is crucial for understanding the differences in regenerative capacities across species. In this study, we evaluated the expression profile and phenotypic function of Notch signaling during limb regeneration in arthropod Chinese mitten crabs. The expression of key components of the Notch signaling pathway was upregulated at 7-day post-autotomy (7 DPA), and declined later at 18-day post-autotomy (18 DPA). To assess the role of Notch, we injected dsRNA targeting the Notch gene into the automized area and evaluated the regeneration efficiency. Our results indicated that blocking Notch signaling led to regenerative defects, manifested by delays in the wound closure and blastema emergence processes. Furthermore, the expression of Notch target genes, Hes1 and HeyL, was significantly reduced following Notch knockdown by dsRNA. Knockdown of Hes1 specifically impaired the proliferation and expression of neural progenitor cell markers, without affecting myogenic cells. In contrast, blockage of HeyL inhibited the proliferation and expression of markers in both activated neurogenic and myogenic progenitor cells, while up-regulating markers of quiescent neural progenitor cells. These findings suggest that Notch signaling plays an important role in limb regeneration of E. sinensis by activating downstream effectors Hes1 and HeyL, regulating neurogenesis and myogenesis through distinct mechanisms.

Recent Advances of Exosomes Derived from Skeletal Muscle and Crosstalk with Other Tissues.

Skeletal muscle plays a crucial role in movement, metabolism, and energy homeostasis. As the most metabolically active endocrine organ in the body, it has recently attracted widespread attention. Skeletal muscle possesses the ability to release adipocytokines, bioactive peptides, small molecular metabolites, nucleotides, and other myogenic cell factors; some of which have been shown to be encapsulated within small vesicles, particularly exosomes. These skeletal muscle exosomes (SKM-Exos) are released into the bloodstream and subsequently interact with receptor cell membranes to modulate the physiological and pathological characteristics of various tissues. Therefore, SKM-Exos may facilitate diverse interactions between skeletal muscle and other tissues while also serving as biomarkers that reflect the physiological and pathological states of muscle function. This review delves into the pivotal role and intricate molecular mechanisms of SKM-Exos and its derived miRNAs in the maturation and rejuvenation of skeletal muscle, along with their intercellular signaling dynamics and physiological significance in interfacing with other tissues.

Development of Mesenchymal Stem Cell Encoded with Myogenic Gene for Treating Radiation-Induced Muscle Fibrosis.

Radiation therapy (RT) is a typical treatment for head and neck cancers. However, prolonged irradiation of the esophagus can cause esophageal fibrosis due to increased reactive oxygen species and proinflammatory cytokines. The objective of this study was to determine whether myogenic gene-transfected mesenchymal stem cells (MSCs) could ameliorate damage to esophageal muscles in a mouse model of radiation-induced esophageal fibrosis. We cloned esophageal myogenic genes (MyoD, MyoG, and Myf6) using plasmid DNA. Afterward, myogenic genes were transfected into Human Mesenchymal Stem Cells (hMSCs) using electroporation. Gene transfer efficiency, stemness, and myogenic gene profile were examined using flow cytometry, quantitative polymerase chain reaction, and RNA sequencing. In vivo efficacy of gene-transfected hMSCs was demonstrated through histological and gene expression analyses using a radiation-induced esophageal fibrosis animal model. We have confirmed that the gene transfer efficiency was high (∼75%). Pluripotency levels in gene-transfected MSCs were significantly decreased compared with those in the control (vector). Particularly, myogenesis-related genes such as OAS2, OAS3, and HSPA1A were overexpressed in the group transfected with three genes. At 4 weeks after injection, it was found that thickness collagen layer and esophageal muscle in MSCs transfected with all three genes were significantly reduced compared to those in the saline group. Muscularis mucosa was observed prominently in the gene combination group. Moreover, expression levels of myogenin, Myf6, calponin, and SM22α known to be specific markers of esophageal muscles tended to increase in the group transfected with three genes. Therefore, using gene-transfected MSCs has the potential as a promising therapy against radiation-induced esophageal fibrosis.

The proliferation and differentiation of skeletal muscle stem cells are enhanced in a bioreactor.

Skeletal muscle (SKM) is the largest organ in mammalian body and it can repair damages by using the residential myogenic stem cells (MuSC), but this repairing capacity reduces with age and in some genetic muscular dystrophy. Under these circumstances, artificial amplification of autologous MuSC in vitro might be necessary to repair the damaged SKM. The amplification of MuSC is highly dependent on myogenic signals, such as sonic hedgehog (Shh), Wnt3a, and fibroblast growth factors, so formulating an optimum myogenic kit composed of specific myogenic signals might increase the proliferation and differentiation of MuSC efficiently. In this study, various myogenic signals have been tested on C2C12 myoblasts and primary MuSC, and a myogenic kit consists of insulin, lithium chloride, T3, and retinoic acid has been formulated, and we found it significantly increased the fusion index and MHC expression level of both C2C12 and MuSC myotubes. A novel bioreactor providing cyclic stretching (CS) and electrical stimulation (ES) has been fabricated to enhance the myogenic differentiation of both C2C12 and MuSC. We further found that coating the bioreactor substratum with collagen gave the best effect on proliferation and differentiation of MuSC. Furthermore, combining the collagen coating and physical stimuli (CS + ES) in the bioreactor can generate more proliferative primary MuSC cells. Our results have demonstrated that the combination of myogenic kit and bioreactor can provide environment for efficient MuSC proliferation and differentiation. These MuSC and mature myotubes amplified in the bioreactor might be useful for clinical grafting into damaged SKM in the future.

9291 Hypothyroidism impairs skeletal muscle regeneration after injury

Abstract Disclosure: P. Aguiari: None. V. Villani: None. K.Y. Liu: None. G.A. Brent: None. L. Perin: None. A. Milanesi: None. Thyroid hormone (TH) signaling plays an essential role in muscle development and function, in the maintenance of muscle mass, and in regeneration after injury. Disruption of TH signaling results in an abnormal skeletal muscle phenotype, impaired regeneration, and sarcopenia with aging, reflecting the myopathic changes described in hypothyroid patients. Muscle stem cells (MuSCs) are the mediators of post-natal skeletal muscle plasticity. Normally quiescent, in response to injury they enter the cell cycle (myoblasts) and proliferate. Myoblasts then exit the cell cycle and differentiate into myocytes that will fuse with existing myofibers to restore tissue architecture and function. Via TH receptor alpha, TH regulates all the stages of the regeneration program and regulates the expression of multiple myogenic genes. Despite all this evidence, to date there are no studies investigating MuSCs behavior in response to injury during hypothyroidism. We characterized injury-induced regeneration of the tibialis anterior muscle (TAM) in euthyroid and hypothyroid mice, fed a low iodine + 0.15% propylthiouracil diet. To investigate the cell cycle dynamics of MuSCs, we generated Pax7-Fucci mice carrying the fluorescent ubiquitination-based cell-cycle indicator (Fucci) system under the Pax7 promoter. Muscle injury was induced via cardiotoxin injection in the TAM of 3-month-old Pax7-Fucci mice. Hypothyroid mice present signs of impaired regeneration compared to euthyroid mice. From histological analysis, at different time points, we observed smaller fiber diameters, myofibers with central nuclei, and a significantly reduced number of fast glycolytic type IIb fibers, the prevalent muscle fiber type in the TA muscle. ScRNAseq analysis shows that at a late phase of regeneration (14 days after injury) hypothyroid MuSCs and myoblasts are still in the activation state and overexpress genes related to DNA replication and cell proliferation, while genes related to myogenic differentiation and cell cycle exit are downregulated. Differentiated myocytes in the hypothyroid fibers present an immature phenotype and are characterized by overexpression of embryonic/temporary and slow myosin genes and downregulation of mature fast myosins. Cell cycle analysis of the Fucci signal through Flow Cytometry confirmed a higher number of activated hypothyroid MuSCs at 4, 7, and 28 days after injury. These cells accumulate in the S phase and are unable to exit the cell cycle and differentiate towards myocytes. These data demonstrate that hypothyroidism impairs muscle tissue regeneration halting MuSCs progression through the cell cycle, myoblast cell cycle exit, and fiber maturation. Investigating muscle stem cell behavior and response to injury during hypothyroidism is crucial to understanding the mechanism behind thyroid hormone-induced myopathies and identifying possible therapeutical targets. Presentation: 6/2/2024

8670 Hypothyroidism impairs skeletal muscle regeneration after injury

Abstract Disclosure: P. Aguiari: None. V. Villani: None. K.Y. Liu: None. G.A. Brent: None. L. Perin: None. A. Milanesi: None. Thyroid hormone (TH) signaling plays an essential role in muscle development and function, in the maintenance of muscle mass, and in regeneration after injury. Disruption of TH signaling results in an abnormal skeletal muscle phenotype, impaired regeneration, and sarcopenia with aging, reflecting the myopathic changes described in hypothyroid patients. Muscle stem cells (MuSCs) are the mediators of post-natal skeletal muscle plasticity. Normally quiescent, in response to injury they enter the cell cycle (myoblasts) and proliferate. Myoblasts then exit the cell cycle and differentiate into myocytes that will fuse with existing myofibers to restore tissue architecture and function. Via TH receptor alpha, TH regulates all the stages of the regeneration program and regulates the expression of multiple myogenic genes. Despite all this evidence, to date there are no studies investigating MuSCs behavior in response to injury during hypothyroidism. We characterized injury-induced regeneration of the tibialis anterior muscle (TAM) in euthyroid and hypothyroid mice, fed a low iodine + 0.15% propylthiouracil diet. To investigate the cell cycle dynamics of MuSCs, we generated Pax7-Fucci mice carrying the fluorescent ubiquitination-based cell-cycle indicator (Fucci) system under the Pax7 promoter. Muscle injury was induced via cardiotoxin injection in the TAM of 3-month-old Pax7-Fucci mice. Hypothyroid mice present signs of impaired regeneration compared to euthyroid mice. From histological analysis, at different time points, we observed smaller fiber diameters, myofibers with central nuclei, and a significantly reduced number of fast glycolytic type IIb fibers, the prevalent muscle fiber type in the TA muscle. ScRNAseq analysis shows that at a late phase of regeneration (14 days after injury) hypothyroid MuSCs and myoblasts are still in the activation state and overexpress genes related to DNA replication and cell proliferation, while genes related to myogenic differentiation and cell cycle exit are downregulated. Differentiated myocytes in the hypothyroid fibers present an immature phenotype and are characterized by overexpression of embryonic/temporary and slow myosin genes and downregulation of mature fast myosins. Cell cycle analysis of the Fucci signal through Flow Cytometry confirmed a higher number of activated hypothyroid MuSCs at 4, 7, and 28 days after injury. These cells accumulate in the S phase and are unable to exit the cell cycle and differentiate towards myocytes. These data demonstrate that hypothyroidism impairs muscle tissue regeneration halting MuSCs progression through the cell cycle, myoblast cell cycle exit, and fiber maturation. Investigating muscle stem cell behavior and response to injury during hypothyroidism is crucial to understanding the mechanism behind thyroid hormone-induced myopathies and identifying possible therapeutical targets. Presentation: 6/2/2024

Prenatal and progressive coenzyme Q10 administration to mitigate muscle dysfunction in mitochondrial disease.

ADCK genesencode aarF domain-containing mitochondrial kinases involved in coenzyme Q (CoQ) biosynthesis and regulation. Haploinsufficiency of ADCK2 in humans leads to adult-onset physical incapacity with reduced mitochondrial CoQ levels in skeletal muscle, resulting in mitochondrial myopathy and alterations in fatty acid β-oxidation. The sole current treatment for CoQ deficiencies is oral administration of CoQ10, which causes only partial recovery with postnatal treatment, underscoring the importance of early diagnosis for successful intervention. We used Adck2 heterozygous mice to examine the influence of this gene on muscle structure, function and regeneration throughout development, growth and ageing. This investigation involved techniques including immunohistochemistry, analysis of CoQ levels, mitochondrial respiratory content, muscle transcriptome analysis and functional tests. We demonstrated that Adck2 heterozygous mice exhibit defects from embryonic development, particularly in skeletal muscle (1102 genes deregulated). Adck2 heterozygous embryos were 7% smaller in size and displayed signs of delayed development. Prenatal administration of CoQ10 could mitigate these embryonic defects. Heterozygous Adck2 mice also showed a decrease in myogenic cell differentiation, with more severe consequences in 'aged' mice (41.63% smaller) (P<0.01). Consequently, heterozygous Adck2 mice displayed accelerated muscle wasting associated with ageing in muscle structure (P<0.05), muscle function (less grip strength capacity) (P<0.001) and muscle mitochondrial respiration (P<0.001). Furthermore, progressive CoQ10 administration conferred protective effects on mitochondrial function (P<0.0001) and skeletal muscle (P<0.05). Our work uncovered novel aspects of CoQ deficiencies, revealing defects during embryonic development in mammals for the first time. Additionally, we identified the gradual establishment and progression of the deleterious Adck2 mouse phenotype. Importantly, CoQ10 supplementation demonstrated a protective effect when initiated during development.

Bioactive MXene hydrogel promotes structural and functional regeneration of skeletal muscle through improving autophagy and muscle innervation

Complete skeletal muscle regeneration after traumatic injuries remains a challenge due to impaired regenerative capability and dysregulated microenvironments. Autophagy plays a crucial role in the muscle regeneration process by regulating myogenic and non-myogenic cells. Herein, we report a bioactive MXene hydrogel (FPGM) capable of upregulating autophagy and increasing muscle innervation to restore skeletal muscle structure and function. FPGM possessed excellent electrical conductivity, tissue adhesive ability and antioxidation, which could eliminate excess reactive oxygen species to reduce oxidative stress and decrease the secretion of pro-inflammatory cytokine. FPGM upregulated the autophagy level of myoblasts and promoted the migration and tube formation of endothelial cells as well as myogenic differentiation with negligible toxicity. FPGM accelerated muscle fiber formation and skeletal muscle regeneration by improving autophagy, which could regulate microenvironment through raising M2 macrophages to alleviate excessive inflammation, facilitating angiogenesis and decreasing fibrous scar tissue formation in vivo. Importantly, FPGM could efficiently restore muscle function by improving muscle innervation, tibialis anterior compound muscle action potential amplitude and neuromuscular conduction. This work demonstrates that bioactive MXene hydrogel should be a promising candidate for complete skeletal muscle regeneration.

Optimization of Exon-Skipping Riboswitches and Their Applications to Control Mammalian Cell Fate.

Mammalian riboswitches that can regulate transgene expression via RNA-small molecule interaction have promising applications in medicine and biotechnology, as they involve no protein factors that can induce immunogenic reactions and are not dependent on specially engineered promoters. However, the lack of cell-permeable and low-toxicity small molecules and cognate aptamers that can be exploited as riboswitches and the modest switching performance of mammalian riboswitches have limited their applications. In this study, we systematically optimized the design of a riboswitch that regulates exon skipping via an RNA aptamer that binds ASP2905. We examined two design strategies to modulate the stability of the aptamer base stem that blocks the 5' splice site to fine-tune the riboswitch characteristics. Furthermore, an optimized riboswitch was used to generate a mouse embryonic stem cell line that can be chemically induced to differentiate into myogenic cells by activating Myod1 expression and a human embryonic kidney cell line that can be induced to trigger apoptosis by activating BAX expression. The results demonstrate the tight chemical regulation of transgenes in mammalian cells to control their phenotype without exogenous protein factors.

In vitro immuno-prevention of nitration/dysfunction of myogenic stem cell activator HGF, towards developing a strategy for age-related muscle atrophy.

In response to peroxynitrite (ONOO-) generation, myogenic stem satellite cell activator HGF (hepatocyte growth factor) undergoes nitration of tyrosine residues (Y198 and Y250) predominantly on fast IIa and IIx myofibers to lose its binding to the signaling receptor c-met, thereby disturbing muscle homeostasis during aging. Here we show that rat anti-HGF monoclonal antibody (mAb) 1H41C10, which was raised in-house against a synthetic peptide FTSNPEVRnitroY198EV, a site well-conserved in mammals, functions to confer resistance to nitration dysfunction on HGF. 1H41C10 was characterized by recognizing both nitrated and non-nitrated HGF with different affinities as revealed by Western blotting, indicating that the paratope of 1H41C10 may bind to the immediate vicinity of Y198. Subsequent experiments showed that 1H41C10-bound HGF resists peroxynitrite-induced nitration of Y198. A companion mAb-1H42F4 presented similar immuno-reactivity, but did not protect Y198 nitration, and thus served as the control. Importantly, 1H41C10-HGF also withstood Y250 nitration to retain c-met binding and satellite cell activation functions in culture. The Fab region of 1H41C10 exerts resistivity to Y250 nitration possibly due to its localization in the immediate vicinity to Y250, as supported by an additional set of experiments showing that the 1H41C10-Fab confers Y250-nitration resistance which the Fc segment does not. Findings highlight the invitro preventive impact of 1H41C10 on HGF nitration-dysfunction that strongly impairs myogenic stem cell dynamics, potentially pioneering cogent strategies for counteracting or treating age-related muscle atrophy with fibrosis (including sarcopenia and frailty) and the therapeutic application of investigational HGF drugs.

Epicatechin ameliorates palmitate-induced insulin resistance in C2C12 myogenic cells by alleviating oxidative stress and activating the AMPK/ACC pathway

ABSTRACT Epicatechin (EC) is a water-soluble natural organic compound belonging to the flavanol class of compounds. It exhibits various physiological activities such as anti-inflammatory, antioxidant, treatment of mitochondrial diseases, and prevention of cardiovascular diseases.To examineEC’s impact and mechanism on adult myoblasts’ insulin resistance. The effects of various EC concentrations on the viability of C2C12 adult myoblasts were measured, as were glucose consumption and glycogen content; in vitro antioxidant activity of EC was measured; cellular oxidative marker content and apoptosis were measured; and protein expression was detected by Western blot. A model of insulin resistance in C2C12 myogenic cells was established using palmitic acid. EC significantly increased the glucose consumption and glycogen content; EC increased the levels of CAT, SOD and GSH and decreased the levels of NO, MDA and ROS; EC decreased the apoptosis rate of cells; EC treatment upregulated the levels of GLUT4, p-AMPK, p-ACC, NRF2, and HO-1 proteins. These results suggest that EC can regulate the NRF2/HO-1 signaling pathway, enhance GLUT4 transport, activate AMPK/ACC pathway, enhance cellular uptake of glucose, thus effectively improving insulin resistance in C2C12 cells.

138 Regulation of post protein translational modification in adipogenesis and fat accumulation in pigs

Abstract In this study, we explored the role of protein transcriptional modification (PTM) in the adipogenesis and fat accumulation of intramuscular adipocytes. Intramuscular fat (IMF) is mainly stored in adipocytes interspersed in the perimysial space or within fascicles, and its content is a key factor attributing to meat quality in farm animals, especially in terms of tenderness, flavor and juiciness. The early stage from the fetus to the neonate is crucial for skeletal muscle development involving myogenesis, adipogenesis, and fibrogenesis, and is susceptible to environmental factors. Previous studies have been subjected to explore the molecular mechanism involved in IMF development. However, it was obscured by muscular background of IMF adipocytes. Therefore, we investigated PTM dynamics from three aspects: 1) first analyzed PTM levels of lysine acetylation (Kac), 2-hydroxyisobutyrylation (Khib), crotonylation (Kcr) and succinylation (Ksu) in three distinct differentiation potenctial primary stem cells, including myogenic precursor cells (MPCs), fibro-adipogenic progenitors (FAPs) and MSCs isolated from neonatal longissimus dorsi muscle of pigs within 3-d of age; 2) Comparing the Khib levels of proliferative and differentiated FAPs; and 3) Exploring the role of Khib modification in the adipose tissue of obese- and lean-types of pigs. We found that only Khib level in FAPs was significantly greater than MSCs. During adipogenic differentiation of FAPs, the modification level of Khib was significantly increased quadratically in parallel with protein levels of acylation regulatory enzymes KAT5 (writer) and HDAC2 (Eraser). In comparison of Khib levels in FAPs in proliferation and in differentiation and Khib levels in backfat tissues from obese pigs (Laiwu pigs) and lean pigs (Duroc pigs), we also demonstrated that Khib modification level was positive correlated with adipogenic differentiation and fat accumulation. Accordingly, the expression patterns of KAT5 and HDAC2 were parallel to the degree of lipid accumulation in the backfat adipose tissue of finishing pigs. Furthermore, we showed that KAT5 knockdown in FAPs inhibited adipogenic differentiation, while HDAC2 knockdown enhanced adipogenic differentiation of FAPs. By employing C3H10T1/2 cells, we identified EON1 involved in Khib modification in regulation of adipo gesis and fat accumulation with analysis of Liquid chromatography-tandem mass spectrometry (LC-MS/MS) using the Tandem Mass Tag (TMT Through conditional loss- and gain-of-function mutations, we further demonstrated that khib modification of ENO1 is necessary for preadipocyte differentiation and subsequent fat accumulation by mediating cellular glycolysis. In conclusion, we are the first to reveal the role of Khib modification in adipogenesis and fat deposition in pigs, and provided new clues for the improvement of fat accumulation and distribution via genetic selection and nutritional strategy in pigs.

137 Possible mechanisms underlying enhanced intramuscular adipogenesis in Wagyu cattle

Abstract The quality of beef hinges significantly on the abundance of intramuscular fat and tenderness. Intramuscular fat accumulation results directly from intramuscular adipogenesis, while tenderness is adversely affected by collagenous intramuscular connective tissue. Both intramuscular fat and connective tissue originate from fibro/adipogenic progenitors (FAPs), a group of bipotent progenitors. Wagyu cattle are renowned for their tender beef with rich intramuscular fat, likely owing to the distinctive features of Wagyu FAPs. Our study has identified fewer myogenic cells but more FAPs with greater adipogenic potential in Wagyu compared with Angus muscle. Furthermore, single-cell transcriptomic analysis identified that Wagyu FAPs exhibit greater adipogenic and decreased fibrogenic characteristics compared with FAPs in Brahman cattle, which generally produce low-quality beef with limited intramuscular fat and tenderness. Interestingly, Wagyu muscle also contains more abundant vascular cells, crucial for supporting adipogenesis. Mechanistic studies have unveiled several signaling pathways, including the bone morphogenetic protein signaling and the alternative complement pathway of the complement system, which likely contributes to the heightened adipogenic programming of Wagyu FAPs and is subject to epigenetic regulation.

Correction of exon 2, exon 2–9 and exons 8–9 duplications in DMD patient myogenic cells by a single CRISPR/Cas9 system

Duchenne Muscular dystrophy (DMD), a yet-incurable X-linked recessive disorder that results in muscle wasting and loss of ambulation is due to mutations in the dystrophin gene. Exonic duplications of dystrophin gene are a common type of mutations found in DMD patients. In this study, we utilized a single guide RNA CRISPR strategy targeting intronic regions to delete the extra duplicated regions in patient myogenic cells carrying duplication of exon 2, exons 2–9, and exons 8–9 in the DMD gene. Immunostaining on CRISPR-corrected derived myotubes demonstrated the rescue of dystrophin protein. Subsequent RNA sequencing of the DMD cells indicated rescue of genes of dystrophin related pathways. Examination of predicted close-match off-targets evidenced no aberrant gene editing at these loci. Here, we further demonstrate the efficiency of a single guide CRISPR strategy capable of deleting multi-exon duplications in the DMD gene without significant off target effect. Our study contributes valuable insights into the safety and efficacy of using single guide CRISPR strategy as a potential therapeutic approach for DMD patients with duplications of variable size.

Lysosomes accumulate at the perinuclear region of muscle cells during chick myogenesis.

Lysosomes are involved in a myriad of cellular functions, such as degradation of macromolecules, endocytosis and exocytosis, modulation of several signaling pathways, and regulation of cell metabolism. To fulfill these diverse functions, lysosomes can undergo several dynamic changes in their content, size, pH, and location within cells. Here, we studied some of these parameters during embryonic chick skeletal muscle cells. We used an anti-lysosome-associated membrane protein 2 (LAMP2) antibody to specifically determine the intracellular localization of lysosomes in these cells. Our data shows that lysosomes are highly enriched in the perinuclear region of chick embryonic muscle cells. We also showed that the wingless signaling pathway (Wnt)/β-catenin signaling pathway can modulate the location of LAMP2 in chick myogenic cells. Our results highlight the role of lysosomes during muscle differentiation and particularly the presence of a subcellular population of lysosomes that are concentrated in the perinuclear region of muscle cells.

Spatial Transcriptomics Analysis: Maternal Obesity Impairs Myogenic Cell Migration and Differentiation during Embryonic Limb Development.

Limb muscle is responsible for physical activities and myogenic cell migration during embryogenesis is indispensable for limb muscle formation. Maternal obesity (MO) impairs prenatal skeletal muscle development, but the effects of MO on myogenic cell migration remain to be examined. C57BL/6 mice embryos were collected at E13.5. The GeoMx DSP platform was used to customize five regions along myogenic cell migration routes (myotome, dorsal/ventral limb, limb stroma, limb tip), and data were analyzed by GeomxTools 3.6.0. A total of 2224 genes were down-regulated in the MO group. The GO enrichment analysis showed that MO inhibited migration-related biological processes. The signaling pathways guiding myogenic migration such as hepatocyte growth factor signaling, fibroblast growth factor signaling, Wnt signaling and GTPase signaling were down-regulated in the MO E13.5 limb tip. Correspondingly, the expression levels of genes involved in myogenic cell migration, such as Pax3, Gab1, Pxn, Tln2 and Arpc, were decreased in the MO group, especially in the dorsal and ventral sides of the limb. Additionally, myogenic differentiation-related genes were down-regulated in the MO limb. MO impedes myogenic cell migration and differentiation in the embryonic limb, providing an explanation for the impairment of fetal muscle development and offspring muscle function due to MO.

Role and Regulatory Mechanism of circRNA_14820 in the Proliferation and Differentiation of Goat Skeletal Muscle Satellite Cells.

Skeletal muscle satellite cells (SMSCs), a type of myogenic stem cell, play a pivotal role in postnatal muscle regeneration and repair in animals. Circular RNAs (circRNAs) are a distinct class of non-coding RNA molecules capable of regulating muscle development by modulating gene expression, acting as microRNAs, or serving as protein decoys. In this study, we identified circ_14820, an exonic transcript derived from adenosine triphosphatase family protein 2 (ATAD2), through initial RNA-Seq analysis. Importantly, overexpression of circ_14820 markedly enhanced the proliferation of goat SMSCs while concomitantly suppressing their differentiation. Moreover, circ_14820 exhibited predominant localization in the cytoplasm of SMSCs. Subsequent small RNA and mRNA sequencing of circ_14820-overexpressing SMSCs systematically elucidated the molecular regulatory mechanisms associated with circ_14820. Our preliminary findings suggest that the circ_14820-miR-206-CCND2 regulatory axis may govern the development of goat SMSCs. These discoveries contribute to a deeper understanding of circRNA-mediated mechanisms in regulating skeletal muscle development, thereby advancing our knowledge of muscle biology.