Human Myoblasts Research Articles

Modelling Skeletal Muscle Ageing and Repair In Vitro

Healthy skeletal muscle can regenerate after ischaemic, mechanical, or toxin-induced injury, but ageing impairs that regeneration potential. This has been largely attributed to dysfunctional satellite cells and reduced myogenic capacity. Understanding which signalling pathways are associated with reduced myogenesis and impaired muscle regeneration can provide valuable information about the mechanisms driving muscle ageing and prompt the development of new therapies. To investigate this, we developed a high-throughput in vitro model to assess muscle regeneration in chemically injured C2C12 and human myotube-derived young and aged myoblast cultures. We observed a reduced regeneration capacity of aged cells, as indicated by an attenuated recovery towards preinjury myotube size and myogenic fusion index at the end of the regeneration period, in comparison with younger muscle cells that were fully recovered. RNA-sequencing data showed significant enrichment of KEGG signalling pathways, PI3K-Akt, and downregulation of GO processes associated with muscle development, differentiation, and contraction in aged but not in young muscle cells. Data presented here suggest that repair in response to in vitro injury is impaired in aged vs. young muscle cells. Our study establishes a framework that enables further understanding of the factors underlying impaired muscle regeneration in older age.

Inflammasome in Skeletal Muscle: NLRP3 Is an Inflammatory Cell Stress Component in Inclusion Body Myositis

Inclusion body myositis (IBM) is a chronic, mostly treatment-resistant, inflammatory myopathy with a pathology that centers around specific interactions between inflammation and protein accumulation. The study aimed to identify the inflammasome as a key event in the complex network of pathomechanisms. Regulation of the inflammasome was assessed in a well-established pro-inflammatory cell culture model using human myoblasts and primary human myotubes. By quantitative PCR, western blot and immunocytochemistry, inflammasome markers including NLRP3 were assessed in muscle cells exposed to the cytokines IL-1β and IFN-γ. The data were corroborated by analysis of muscle biopsies from patients with IBM compared to other myositis subtypes. In the cell culture model of IBM, the NLRP3 inflammasome was significantly overexpressed, as evidenced by western blot (p = 0.03) and quantitative PCR (p < 0.01). Target genes that play a role in inflammasome assembly, T-cell migration, and MHC-I expression (p = 0.009) were highly co-upregulated. NLRP3 was significantly overexpressed in muscle biopsies from IBM samples compared to disease controls (p = 0.049), including other inflammatory myopathies. Due to the extraordinary features of the pathogenesis and the pronounced upregulation of NLRP3 in IBM, the inflammasome could serve as a key molecule that drives the inflammatory cascade as well as protein accumulation in the muscle. These data can be useful for future therapeutic developments.

Nuclear Small Dystrophin Isoforms during Muscle Differentiation.

Mutations in the DMD gene can cause Duchenne or Becker muscular dystrophy (DMD/BMD) by affecting the giant isoform of dystrophin, a protein encoded by the DMD gene. The role of small dystrophin isoforms is not well investigated yet, and they may play a role in muscle development and molecular pathology. Here, we investigated the nuclear localization of short carboxy-terminal dystrophin isoforms during the in vitro differentiation of human, porcine, and murine myoblast cultures. We could not only confirm the presence of Dp71 in the nucleoplasm and at the nuclear envelope, but we could also identify the Dp40 isoform in muscle nuclei. The localization of both isoforms over the first six days of differentiation was similar between human and porcine myoblasts, but murine myoblasts behaved differently. This highlights the importance of the porcine model in investigating DMD. We could also detect a wave-like pattern of nuclear presence of both Dp71 and Dp40, indicating a direct or indirect involvement in gene expression control during muscle differentiation.

Effects of Simulated Microgravity on the Internalization of Cerium Oxide Nanoparticles by Proliferating Human Skeletal Myoblasts

Spaceflight typically exerts detrimental effects on living organisms by promoting/accelerating some degenerative processes associated with aging and pathology onset on Earth, like muscle degeneration. As possible countermeasures to spaceflight effects, a few recent studies successfully tested the administration of nanomaterials for tuning of cellular activities and for promotion of certain cell phenotypes in microgravity, but largely missed investigation of early interactions of these nanomaterials with their cellular targets under altered gravity conditions. This study aims at filling this gap by elucidation of early interactions of a selected typology of redox-active nanoparticles (cerium oxide nanoparticles, also termed nanoceria, NC) with proliferating human skeletal myoblasts (HSkM) by concomitant exposure to simulated microgravity (achieved by a random positioning machine, RPM). To this purpose, NC were synthesized by a direct precipitation method and were chemically, structurally, and functionally characterized by several independent techniques prior to administration to skeletal muscle cell cultures and loading on the RPM. Confocal and electron microscopy evidence of nanoparticle internalization by several mechanisms (mostly involving macropinocytosis) in HSkM is provided, along with evidence of transcriptional regulation of key antioxidant response markers (Nos1, Sod2, and Sod3), promising oxidative stress alleviation and muscle protection under mechanical unloading conditions.

Contribution of peripheral blood mononuclear cells isolated by advanced filtration system to myogenesis of human bone marrow mesenchymal stem cells co-cultured with myoblasts

BackgroundContribution of peripheral blood mononuclear cells (PBMCs) in myogenesis is still under debate, even though blood filtration systems are commonly used in clinical practice for successfully management of critic limb ischemia. ObjectivesA commercial blood filter used for autologous human PBMC transplantation procedures is characterized and used to collect PBMCs, that are then added to well-established 2D in vitro myogenic models assembled with a co-culture of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) and skeletal myoblasts (hSkMs) whit the aim of investigating their potential contribution to stem cell myogenic commitment. MethodsA commercial blood filter was physically and chemically studied to understand its morphological characteristics and composition. PBMCs were concentrated using this system, further isolated by Ficoll-Paque density gradient centrifugation, and then added in an upper transwell chamber to a 2D co-culture of hBM-MSCs and hSkMs. Myogenic commitment was investigated by RT-PCR, immunofluorescence, and flow cytometry immunophenotyping. Cytokine levels were monitored by ELISA assay in culture media. ResultsThe blood filtration system was disassembled and appeared to be formed by twelve membranes of poly-butylene terephthalate fibers (diameters, 0.9–4.0 μm) with pore size distribution of 1–20 μm. Filter functional characterization was achieved by characterizing collected cells by flow cytometry. Subsequently, collected PBMCs fraction was added to an in-vitro model of hBM-MSC myogenic commitment. In the presence of PBMCs, stem cells significantly upregulated myogenic genes, such as Desmin and MYH2, as confirmed by qRT-PCR and expressed related proteins by immunofluorescence (IF) assay, while downregulated pro-inflammatory cytokines (IL12A at day 14) along the 21 days of culture. NoveltyOur work highlights chemical-physical properties of commercial blood filter and suggests that blood filtrated fraction of PBMC might modulate cytokine expression in response to muscle injury and promote myogenic events, supporting their clinical use in autologous transplantation.

Geroprotective Effect of the Mitochondrial-Targeted Antioxidant SkQBerb in a Model of the Chronological Aging of MB135 Human Myoblasts

Geroprotective Effect of the Mitochondrial-Targeted Antioxidant SkQBerb in a Model of the Chronological Aging of MB135 Human Myoblasts

Prime editing strategies to mediate exon skipping in DMD gene.

Duchenne muscular dystrophy is a rare and lethal hereditary disease responsible for progressive muscle wasting due to mutations in the DMD gene. We used the CRISPR-Cas9 Prime editing technology to develop different strategies to correct frameshift mutations in DMD gene carrying the deletion of exon 52 or exons 45 to 52. With optimized epegRNAs, we were able to induce the specific substitution of the GT nucleotides of the splice donor site of exon 53 in up to 32% of HEK293T cells and 28% of patient myoblasts. We also achieved up to 44% and 29% deletion of the G nucleotide of the GT splice site of exon 53, as well as inserted 17% and 5.5% GGG between the GT splice donor site of exon 51 in HEK293T cells and human myoblasts, respectively. The modification of the splice donor site for exon 51 and exon 53 provoke their skipping and allowed exon 50 to connect to exon 53 and allowed exon 44 to connect to exon 54, respectively. These corrections restored the expression of dystrophin as demonstrated by western blot. Thus, Prime editing was used to induce specific substitutions, insertions and deletions in the splice donor sites for exons 51 and 53 to correct the frameshift mutations in DMD gene carrying deletions of exon 52 and exons 45 to 52, respectively.

Post-Translational Modifications of the DUX4 Protein Impact Toxic Function in FSHD Cell Models.

Facioscapulohumeral muscular dystrophy (FSHD) is caused by abnormal de-repression of the myotoxic transcription factor DUX4. Although the transcriptional targets of DUX4 are known, the regulation of DUX4 protein and the molecular consequences of this regulation are unclear. Here, we used in vitro models of FSHD to identify and characterize DUX4 post-translational modifications (PTMs) and their impact on the toxic function of DUX4. We immunoprecipitated DUX4 protein and performed mass spectrometry to identify PTMs. We then characterized DUX4 PTMs and potential enzyme modifiers using mutagenesis, proteomics, and biochemical assays in HEK293 and human myoblast cell lines. We identified 17 DUX4 amino acids with PTMs, and generated 55 DUX4 mutants designed to prevent or mimic PTMs. Five mutants protected cells against DUX4-mediated toxicity and reduced the ability of DUX4 to transactivate FSHD biomarkers. These mutagenesis results suggested that DUX4 toxicity could be counteracted by serine/threonine phosphorylation and/or inhibition of arginine methylation. We therefore sought to identify modifying enzymes that could play a role in regulating DUX4 PTMs. We found several enzymes capable of modifying DUX4 protein in vitro, and confirmed that protein kinase A (PKA) and protein arginine methyltransferase (PRMT1) interact with DUX4. These results support that DUX4 is regulated by PTMs and set a foundation for developing FSHD drug screens based mechanistically on DUX4 PTMs and modifying enzymes. ANN NEUROL 2023;94:398-413.

Inhibiting de novo ceramide synthesis restores mitochondrial and protein homeostasis in muscle aging.

Disruption of mitochondrial function and protein homeostasis plays a central role in aging. However, how these processes interact and what governs their failure in aging remain poorly understood. Here, we showed that ceramide biosynthesis controls the decline in mitochondrial and protein homeostasis during muscle aging. Analysis of transcriptome datasets derived from muscle biopsies obtained from both aged individuals and patients with a diverse range of muscle disorders revealed that changes in ceramide biosynthesis, as well as disturbances in mitochondrial and protein homeostasis pathways, are prevalent features in these conditions. By performing targeted lipidomics analyses, we found that ceramides accumulated in skeletal muscle with increasing age across Caenorhabditis elegans, mice, and humans. Inhibition of serine palmitoyltransferase (SPT), the rate-limiting enzyme of the ceramide de novo synthesis, by gene silencing or by treatment with myriocin restored proteostasis and mitochondrial function in human myoblasts, in C. elegans, and in the skeletal muscles of mice during aging. Restoration of these age-related processes improved health and life span in the nematode and muscle health and fitness in mice. Collectively, our data implicate pharmacological and genetic suppression of ceramide biosynthesis as potential therapeutic approaches to delay muscle aging and to manage related proteinopathies via mitochondrial and proteostasis remodeling.

DNAJB6 isoform specific knockdown: Therapeutic potential for limb girdle muscular dystrophy D1

Dominant missense mutations in DNAJB6, a co-chaperone of HSP70, cause limb girdle muscular dystrophy (LGMD) D1. No treatments are currently available. Two isoforms exist, DNAJB6a and DNAJB6b, each with distinct localizations in muscle. Mutations reside in both isoforms, yet evidence suggests that DNAJB6b is primarily responsible for disease pathogenesis. Knockdown treatment strategies involving both isoforms carry risk, as DNAJB6 knockout is embryonic lethal. We therefore developed an isoform-specific knockdown approach using morpholinos. Selective reduction of each isoform was achieved invitro in primary mouse myotubes and human LGMDD1 myoblasts, as well as invivo in mouse skeletal muscle. To assess isoform specific knockdown in LGMDD1, we created primary myotube cultures from a knockin LGMDD1 mouse model. Using mass spectrometry, we identified an LGMDD1 protein signature related to protein homeostasis and myofibril structure. Selective reduction of DNAJB6b levels in LGMDD1 myotubes corrected much of the proteomic disease signature toward wild type levels. Additional invivo functional data is required to determine if selective reduction of DNAJB6b is a viable therapeutic target for LGMDD1.

Myogenic differentiation of human myoblasts and Mesenchymal stromal cells under GDF11 on Poly-ɛ-caprolactone-collagen I-Polyethylene-nanofibers

BackgroundFor the purpose of skeletal muscle engineering, primary myoblasts (Mb) and adipogenic mesenchymal stem cells (ADSC) can be co-cultured and myogenically differentiated. Electrospun composite nanofiber scaffolds represent suitable matrices for tissue engineering of skeletal muscle, combining both biocompatibility and stability Although growth differentiation factor 11 (GDF11) has been proposed as a rejuvenating circulating factor, restoring skeletal muscle function in aging mice, some studies have also described a harming effect of GDF11. Therefore, the aim of the study was to analyze the effect of GDF11 on co-cultures of Mb and ADSC on poly-ε-caprolactone (PCL)-collagen I-polyethylene oxide (PEO)-nanofibers.ResultsHuman Mb were co-cultured with ADSC two-dimensionally (2D) as monolayers or three-dimensionally (3D) on aligned PCL-collagen I-PEO-nanofibers. Differentiation media were either serum-free with or without GDF11, or serum containing as in a conventional differentiation medium. Cell viability was higher after conventional myogenic differentiation compared to serum-free and serum-free + GDF11 differentiation as was creatine kinase activity. Immunofluorescence staining showed myosine heavy chain expression in all groups after 28 days of differentiation without any clear evidence of more or less pronounced expression in either group. Gene expression of myosine heavy chain (MYH2) increased after serum-free + GDF11 stimulation compared to serum-free stimulation alone.ConclusionsThis is the first study analyzing the effect of GDF11 on myogenic differentiation of Mb and ADSC co-cultures under serum-free conditions. The results of this study show that PCL-collagen I-PEO-nanofibers represent a suitable matrix for 3D myogenic differentiation of Mb and ADSC. In this context, GDF11 seems to promote myogenic differentiation of Mb and ADSC co-cultures compared to serum-free differentiation without any evidence of a harming effect.

Constricted Migration of Human Myoblasts Impairs Motility, Nuclear Integrity and Differentiation

Introduction: Upon injury, muscle stem cells (MuSCs) undergo activation, proliferation, migration, differentiation and fusion to regenerate muscle. MuSCs sense and respond to the mechanical microenvironment of the tissue while migrating through the interstitial matrix to the cell niche. In fibrosis, a common manifestation of injury, the mechanical microenvironment of the tissue is modified. The extracellular matrix (ECM) has increased stiffness and decreased porosity which may decrease the mobility and differentiation ability of MuSCs. The objective of this study was to determine the capacity of human myoblast to undergo constricted migration through small rigid pores and the deficits in their regenerative capacity following constricted migration. We hypothesized that fewer cells would undergo constricted migration and those that did would incur greater nuclear rupture, increased DNA damage, and impaired differentiation capacity. Methods: Immortalized human myoblasts were allowed to migrate through transwell inserts of pores with 3μm (constricted migration) and 8μm diameter (unconstricted migration) or in 2D conditions (control). Live cell imaging techniques over a period 24 hours were used to quantify relative cell migration. The extent of nuclear rupture and DNA damage were quantified using immunofluorescent imaging of cells on transwell inserts. Differentiation index was calculated by removing the cells from the transwell and placing in differentiation conditions prior to immunofluorescent imaging. Results: Cells migrated more rapidly through large pores than the constrictive pores. For 3μm protrusions through the pores resulted in migration in ~46 % cells compared to 68% for 8μm pores. Following migration through the pores there was no difference in 2D migration, but it was significantly slower than cells that remained in 2D conditions. Human myoblasts undergoing 3μm migration incurred nuclear rupture in ~85% of cells while cells migrating through 8μm or non-migrating cells rarely had ruptured nuclei (<2%). 3μm migration was also related to a significant ~80% increase in DNA damage from cells undergoing 8μm migration. The human myoblasts undergoing 3μm migration maintained impaired differentiation of ~30% compared to 8μm migration or non-migrating cells. Conclusions: The study results support the hypothesis that constricted environments impair migration, cause substantial nuclear rupture, induce DNA damage, and impair differentiation. The use of human myoblasts with different migration speeds than previously used mouse myoblasts had substantially more profound impacts on nuclear rupture and persistence of differentiation defects. Thus, the constrictive environment presented by muscle fibrosis could be a critical aspect of impaired regeneration in fibrotic conditions. Funding sources: This work was supported by grants from NIH NIAMS R01 AR079545 and R00 AR067867 to LRS. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A new immunodeficient Duchenne muscular dystrophy rat model to evaluate engraftment after human cell transplantation.

Duchenne muscular dystrophy (DMD) is an X-linked fatal muscular disease, affecting one in 3,500 live male births worldwide. Currently, there is no cure for this disease, except for steroid-based treatment to attenuate disease progression. Cell transplantation therapy is a promising therapeutic approach, however, there is a lack of appropriate animal models to conduct large-scale preclinical studies using human cells, including biochemical and functional tests. Here, we established an immunodeficient DMD rat model and performed exhaustive pathological analysis and transplantation efficiency evaluation to assess its suitability to study DMD. Our DMD rat model exhibited histopathological characteristics similar to those observed in human patients with DMD. Human myoblasts demonstrated successful engraftment following transplantation into these rats. Therefore, this immunodeficient DMD rat model would be useful in preclinical studies to develop cellular transplantation therapies for DMD.

Specific miRNAs are associated with human cancer cachexia in an organ-specific manner.

Cancer cachexia (CCx) is a complex and multi-organ wasting syndrome characterized by substantial weight loss and poor prognosis. An improved understanding of the mechanisms involved in the onset and progression of cancer cachexia is essential. How microRNAs contribute to the clinical manifestation and progression of CCx remains elusive. The aim of this study was to identify specific miRNAs related to organ-specific CCx and explore their functional role in humans. miRNA patterns in serum and in cachexia target organs (liver, muscle and adipose tissue) from weight stable (N≤12) and cachectic patients (N≤23) with gastrointestinal cancer were analysed. As a first step, a miRNA array (158 miRNAs) was performed in pooled serum samples. Identified miRNAs were validated in serum and corresponding tissue samples. Using in silico prediction, related genes were identified and evaluated. The findings were confirmed in vitro by siRNA knock-down experiments in human visceral preadipocytes and C2C12 myoblast cells and consecutive gene expression analyses. Validating the results of the array, a 2-fold down-regulation of miR-122-5p (P=0.0396) and a 4.5-fold down-regulation of miR-194-5p (P<0.0001) in serum of CCx patients in comparison with healthy controls were detected. Only miR-122-5p correlated with weight loss and CCx status (P=0.0367). Analysing corresponding tissues six muscle and eight visceral adipose tissue (VAT) cachexia-associated miRNAs were identified. miR-27b-3p, miR-375 and miR-424-5p were the most consistently affected miRNAs in tissues of CCx patients correlating negatively with the severity of body weight loss (P=0.0386, P=0.0112 and P=0.0075, respectively). We identified numerous putative target genes of the miRNAs in association with muscle atrophy and lipolysis pathways. Knock-down experiments in C2C12 myoblast cells revealed an association of miR-27b-3p and the in silico predicted atrophy-related target genes IL-15 and TRIM63. Both were up-regulated in miR-27b-3p knock-down cells (P<0.05). Concordantly, in muscle tissue of CCx individuals, significant higher expression levels of IL-15 (P=0.0237) and TRIM63 (P=0.0442) were detected. miR-424-5p was identified to regulate the expression of lipase genes. Knock-down experiments in human visceral preadipocytes revealed an inverse association of miR-424-5p with its predicted target genes LIPE, PNPLA2, MGLL and LPL (P<0.01). The identified miRNAs, in particular miR-122-5p, miR-27b-3p, miR-375 and miR-424-5p, represent features of human CCx and may contribute to tissue wasting and skeletal muscle atrophy through the regulation of catabolic signals. Further studies are needed to explore the potential of the identified miRNAs as a screening tool for early detection of cancer cachexia.

Abstract 2721: Sustained delivery of low-dose anti-CTLA-4 by genetically engineered encapsulated cells to the tumor microenvironment drives tumor response and prolongs survival in a colorectal cancer model

Abstract Introduction: Systemic therapy with CTLA-4 blocking antibody (aCTLA-4) restores endogenous antitumor immunity and induces remarkable long-term clinical benefits in patients with melanoma. Yet immune-related side effects remain a major hurdle to extending its label to many more types of cancer. Intra- and peritumoral administration of aCTLA-4 has recently emerged as a means to optimize its dose/efficacy ratio while preventing its off-target, systemic toxicities. Sustained peritumoral delivery of low-dose aCTLA-4 by genetically engineered encapsulated cells could offer a promising option for cancer treatment addressing the shortcomings of systemic therapy. Material and Methods: The efficacy of sustained, low-dose aCTLA-4 delivered by genetically engineered encapsulated cells was assessed in human CTLA4 knock-in mice subcutaneously engrafted with MC38 colon adenocarcinoma cells. In a therapeutic model, mice were treated with either encapsulated human myoblast cells secreting aCTLA-4 (MVX-3) in the vicinity of the tumor, or i.p. injections of Ipilimumab (10mg/kg BIW x 4). Encapsulated wild-type cells (WT) and PBS were used as respective controls. A subgroup of mice was terminated at day 7 post-treatment for early pharmacological characterization. Tumor size and survival were measured to evaluate the efficacy. Secretion of aCTLA-4 by MVX-3 and aCTLA-4 titer in plasma was quantified by ELISA. Tumors, spleens, and draining lymph nodes were collected for flow cytometry analyses. Results: Peritumoral administration of MVX-3 induced durable complete tumor rejection (2/7) and tumor growth control (4/7) when administered at doses 1’000 times lower than i.p ipilimumab, whereas rapid tumor growth without any tumor rejection was observed in mice treated with control vehicles. I.p. ipilimumab induced durable complete tumor rejection (9/12), while treatment-related toxicities upon dosing led to premature mice termination (3/12). MVX-3 was found as equally effective as i.p. ipilimumab in decreasing the proportion of CTLA4+ helper and regulatory T cells in the tumor at Day 7 post-treatment. Survival was also improved by MVX-3 compared to control vehicles. Conclusions: These findings suggest that sustained delivery of low-dose aCTLA-4 by genetically engineered encapsulated cells to the tumor microenvironment could achieve similar therapeutic benefits as systemic therapy, without the commonly associated toxicities. The safety and biological efficacy profile of MVX-3 encourage further preclinical and clinical explorations. Citation Format: Julien Grogg, Emily Charrier, Remi Vernet, Muriel Urwyler, Olivier Von Rohr, Valentin Saingier, Fabien Courtout, Aurelien Lathuiliere, Adrien Engel, Nicolas Mach. Sustained delivery of low-dose anti-CTLA-4 by genetically engineered encapsulated cells to the tumor microenvironment drives tumor response and prolongs survival in a colorectal cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2721.

Harnessing the synergy of perfusable muscle flap matrix and adipose-derived stem cells for prevascularization and macrophage polarization to reconstruct volumetric muscle loss.

Muscle flaps must have a strong vascular network to support a large tissue volume and ensure successful engraftment. We developed porcine stomach musculofascial flap matrix (PDSF) comprising extracellular matrix (ECM) and intact vasculature. PDSF had a dominant vascular pedicle, microcirculatory vessels, a nerve network, well-retained 3-dimensional (3D) nanofibrous ECM structures, and no allo- or xenoantigenicity. In-depth proteomic analysis demonstrated that PDSF was composed of core matrisome proteins (e.g., collagens, glycoproteins, proteoglycans, and ECM regulators) that, as shown by Gene Ontology term enrichment analysis, are functionally related to musculofascial biological processes. Moreover, PDSF-human adipose-derived stem cell (hASC) synergy not only induced monocytes towards IL-10-producing M2 macrophage polarization through the enhancement of hASCs' paracrine effect but also promoted the proliferation and interconnection of both human skeletal muscle myoblasts (HSMMs) and human umbilical vein endothelial cells (HUVECs) in static triculture conditions. Furthermore, PDSF was successfully prevascularized through a dynamic perfusion coculture of hASCs and HUVECs, which integrated with PDSF and induced the maturation of vascular networks in vitro. In a xenotransplantation model, PDSF demonstrated myoconductive and immunomodulatory properties associated with the predominance of M2 macrophages and regulatory T cells. In a volumetric muscle loss (VML) model, prevascularized PDSF augmented neovascularization and constructive remodeling, which was characterized by the predominant infiltration of M2 macrophages and significant musculofascial tissue formation. These results indicate that hASCs' integration with PDSF enhances the cells' dual function in immunomodulation and angiogenesis. Owing in part to this PDSF-hASC synergy, our platform shows promise for vascularized muscle flap engineering for VML reconstruction.

Dystrophin Expressing Chimeric (DEC) Cell Therapy for Duchenne Muscular Dystrophy: A First-in-Human Study with Minimum 6 Months Follow-up.

Duchenne Muscular Dystrophy (DMD) is a X-linked progressive lethal muscle wasting disease for which there is no cure. We present first-in-human study assessing safety and efficacy of novel Dystrophin Expressing Chimeric (DEC) cell therapy created by fusion of patient myoblasts with myoblasts of normal donor origin. We report here on safety and functional outcomes of the first 3DMD patients. No study related adverse events (AE) and no serious adverse events (SAE) were observed up to 14months after systemic-intraosseous administration of DEC01. Ambulatory patients showed improvements in functional tests (6-Minute Walk Test (6MWT), North Star Ambulatory Assessment (NSAA)) and both, ambulatory and non-ambulatory in PUL, strength and fatigue resistance which correlated with improvement of Electromyography (EMG) parameters. DEC01 therapy does not require immunosuppression, involves no risks of off target mutations, is not dependent upon the causative mutation and is therefore a universal therapy that does not use viral vectors and therefore can be readministered, if needed. This study was approved by the Bioethics Committee (approvalNo. 46/2019). Mechanism of action of the Dystrophin Expressing Chimeric Cell (DEC) cells created via ex vivo fusion of human myoblast from normal and DMD-affected donors. Following systemic-intraosseous administration, DEC engraft and fuse with the myoblasts of DMD patients, deliver dystrophin and improve muscle strength and function. (Created with BioRender.com).

Bioactive Ingredients in K. pinnata Extract and Synergistic Effects of Combined K. pinnata and Metformin Preparations on Antioxidant Activities in Diabetic and Non-Diabetic Skeletal Muscle Cells.

With healthcare costs rising, many affected by ailments are turning to alternative medicine for treatment. More people are choosing to complement their pharmacological regimen with dietary supplements from natural products. In this study, the compound composition of Kalanchoe Pinnata (K. pinnata) and the effects of combined preparations of K. pinnata and metformin on antioxidant activity in human skeletal muscle myoblasts (HSMMs) and human diabetic skeletal muscle myoblasts (DHSMMs) were investigated. Ultraperformance liquid chromatography fusion orbitrap mass spectrometry (UPLC-OT-FTMS) identified biologically active flavanols in K. pinnata. The main compounds identified in locally grown K. pinnata were quercetin, kaempferol, apigenin, epigallocatechin gallate (EGCG), and avicularin. Antioxidant results indicated that a combinatorial preparation of K. pinnata with metformin may modulate antioxidant responses by increasing the enzymatic activity of superoxide dismutase and increasing levels of reduced glutathione. A combination of 50 μM and 150 μg/mL of metformin and K. pinnata, respectively, resulted in a significant increase in reduced glutathione levels in non-diabetic and diabetic human skeletal muscle myoblasts and H2O2-stress-induced human skeletal muscle myoblasts. Additionally, a K. pinnata treatment (400 µg/mL) alone significantly increased catalase (CAT) activity for non-diabetic and diabetic human skeletal muscle myoblasts and a H2O2-stress-induced human skeletal muscle myoblast cell line, while significantly lowering malondialdehyde (MDA) levels. However, the treatment options were more effective at promoting cell viability after 24 h versus 72 h and did not promote cell viability after 72 h in H2O2-stress-induced HSMM cells. These treatment options show promise for treating oxidative-stress-mediated pathophysiological complications associated with type II diabetes.

Development of three-dimensional primary human myospheres as culture model of skeletal muscle cells for metabolic studies.

Introduction: Skeletal muscle is a major contributor to whole-body energy homeostasis and the utilization of fatty acids and glucose. At present, 2D cell models have been the most used cellular models to study skeletal muscle energy metabolism. However, the transferability of the results to in vivo might be limited. This project aimed to develop and characterize a skeletal muscle 3D cell model (myospheres) as an easy and low-cost tool to study molecular mechanisms of energy metabolism. Methods and results: We demonstrated that human primary myoblasts form myospheres without external matrix support and carry structural and molecular characteristics of mature skeletal muscle after 10days of differentiation. We found significant metabolic differences between the 2D myotubes model and myospheres. In particular, myospheres showed increased lipid oxidative metabolism than the 2D myotubes model, which oxidized relatively more glucose and accumulated more oleic acid. Discussion and conclusion: These analyses demonstrate model differences that can have an impact and should be taken into consideration for studying energy metabolism and metabolic disorders in skeletal muscle.

Cellular senescence and disrupted proteostasis induced by myotube atrophy are prevented with low-dose metformin and leucine cocktail.

Aging coincides with the accumulation of senescent cells within skeletal muscle that produce inflammatory products, known as the senescence-associated secretory phenotype, but the relationship of senescent cells to muscle atrophy is unclear. Previously, we found that a metformin + leucine (MET+LEU) treatment had synergistic effects in aged mice to improve skeletal muscle structure and function during disuse atrophy. Therefore, the study's purpose was to determine the mechanisms by which MET+LEU exhibits muscle atrophy protection in vitro and if this occurs through cellular senescence. C2C12 myoblasts differentiated into myotubes were used to determine MET+LEU mechanisms during atrophy. Additionally, aged mouse single myofibers and older human donor primary myoblasts were individually isolated to determine the translational potential of MET+LEU on muscle cells. MET+LEU (25 + 125 μM) treatment increased myotube differentiation and prevented myotube atrophy. Low concentration (0.1 + 0.5 μM) MET+LEU had unique effects to prevent muscle atrophy and increase transcripts related to protein synthesis and decrease transcripts related to protein breakdown. Myotube atrophy resulted in dysregulated proteostasis that was reversed with MET+LEU and individually with proteasome inhibition (MG-132). Inflammatory and cellular senescence transcriptional pathways and respective transcripts were increased following myotube atrophy yet reversed with MET+LEU treatment. Dasatinib + quercetin (D+Q) senolytic prevented myotube atrophy similar to MET+LEU. Finally, MET+LEU prevented loss in myotube size in alternate in vitro models of muscle atrophy as well as in aged myofibers while, in human primary myotubes, MET+LEU prevented reductions in myonuclei fusion. These data support that MET+LEU has skeletal muscle cell-autonomous properties to prevent atrophy by reversing senescence and improving proteostasis.