UTRN as a potential biomarker in breast cancer: a comprehensive bioinformatics and in vitro study.

Utrophin (UTRN), known as a tumor suppressor, potentially regulates tumor development and the immune microenvironment. However, its impact on breast cancer's development and treatment remains unstudied. We conducted a thorough examination of UTRN using both bioinformatic and in vitro experiments in this study. We discovered UTRN expression decreased in breast cancer compared to standard samples. High UTRN expression correlated with better prognosis. Drug sensitivity tests and RT-qPCR assays revealed UTRN's pivotal role in tamoxifen resistance. Furthermore, the Kruskal-Wallis rank test indicated UTRN's potential as a valuable diagnostic biomarker for breast cancer and its utility in detecting T stage of breast cancer. Additionally, our results demonstrated UTRN's close association with immune cells, inhibitors, stimulators, receptors, and chemokines in breast cancer (BRCA). This research provides a novel perspective on UTRN's role in breast cancer's prognostic and therapeutic value. Low UTRN expression may contribute to tamoxifen resistance and a poor prognosis. Specifically, UTRN can improve clinical decision-making and raise the diagnosis accuracy of breast cancer.

Improved mitochondrial function in the hearts of sarcolipin-deficient dystrophin and utrophin double-knockout mice.

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease associated with cardiomyopathy. DMD cardiomyopathy is characterized by abnormal intracellular Ca2+ homeostasis and mitochondrial dysfunction. We used dystrophin and utrophin double-knockout (mdx:utrn-/-) mice in a sarcolipin (SLN) heterozygous-knockout (sln+/-) background to examine the effect of SLN reduction on mitochondrial function in the dystrophic myocardium. Germline reduction of SLN expression in mdx:utrn-/- mice improved cardiac sarco/endoplasmic reticulum (SR) Ca2+ cycling, reduced cardiac fibrosis, and improved cardiac function. At the cellular level, reducing SLN expression prevented mitochondrial Ca2+ overload, reduced mitochondrial membrane potential loss, and improved mitochondrial function. Transmission electron microscopy of myocardial tissues and proteomic analysis of mitochondria-associated membranes showed that reducing SLN expression improved mitochondrial structure and SR-mitochondria interactions in dystrophic cardiomyocytes. These findings indicate that SLN upregulation plays a substantial role in the pathogenesis of cardiomyopathy and that reducing SLN expression has clinical implications in the treatment of DMD cardiomyopathy.

Gene therapy delivered micro-dystrophins co-localize with transgenic utrophin in dystrophic skeletal muscle fibers.

Duchenne muscular dystrophy (DMD) is a devastating muscle disease caused by the absence of functional dystrophin. There are multiple ongoing clinical trials for DMD that are testing gene therapy treatments consisting of adeno-associated viral (AAV) vectors carrying miniaturized versions of dystrophin optimized for function, termed micro-dystrophins (µDys). Utrophin, the fetal homolog of dystrophin, has repeatedly been reported to be upregulated in human DMD muscle as a compensatory mechanism, but whether µDys displaces full-length utrophin is unknown. In this study, dystrophin/utrophin-deficient mice with transgenic overexpression of full-length utrophin in skeletal muscles were systemically administered low doses of either AAV6-CK8e-Hinge3-µDys (µDysH3) or AAV6-CK8e-µDys5 (µDys5). We used immunofluorescence to qualitatively assess the localization of µDys with transgenic utrophin and neuronal nitric oxide synthase (nNOS) in quadriceps muscles. µDys protein resulting from both gene therapies co-localized at myofiber membranes with transgenic utrophin. We also confirmed the sarcolemmal co-localization of nNOS with µDys5, but not with transgenic utrophin expression or µDysH3. Transgenic utrophin expression and µDys proteins produced from both therapies stabilize the dystrophin-glycoprotein complex as observed by sarcolemmal localization of ß-dystroglycan. This study suggests that µDys gene therapy will likely not inhibit any endogenous compensation by utrophin in DMD muscle.

Dystrophin- and Utrophin-Based Therapeutic Approaches for Treatment of Duchenne Muscular Dystrophy: A Comparative Review.

Duchenne muscular dystrophy is a devastating disease that leads to progressive muscle loss and premature death. While medical management focuses mostly on symptomatic treatment, decades of research have resulted in first therapeutics able to restore the affected reading frame of dystrophin transcripts or induce synthesis of a truncated dystrophin protein from a vector, with other strategies based on gene therapy and cell signaling in preclinical or clinical development. Nevertheless, recent reports show that potentially therapeutic dystrophins can be immunogenic in patients. This raises the question of whether a dystrophin paralog, utrophin, could be a more suitable therapeutic protein. Here, we compare dystrophin and utrophin amino acid sequences and structures, combining published data with our extended in silico analyses. We then discuss these results in the context of therapeutic approaches for Duchenne muscular dystrophy. Specifically, we focus on strategies based on delivery of micro-dystrophin and micro-utrophin genes with recombinant adeno-associated viral vectors, exon skipping of the mutated dystrophin pre-mRNAs, reading through termination codons with small molecules that mask premature stop codons, dystrophin gene repair by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (CRISPR/Cas9)-mediated genetic engineering, and increasing utrophin levels. Our analyses highlight the importance of various dystrophin and utrophin domains in Duchenne muscular dystrophy treatment, providing insights into designing novel therapeutic compounds with improved efficacy and decreased immunoreactivity. While the necessary actin and ß-dystroglycan binding sites are present in both proteins, important functional distinctions can be identified in these domains and some other parts of truncated dystrophins might need redesigning due to their potentially immunogenic qualities. Alternatively, therapies based on utrophins might provide a safer and more effective approach.

Exercise-induced circular RNA circUtrn is required for cardiac physiological hypertrophy and prevents myocardial ischaemia-reperfusion injury.

AIMS: Regular exercise training benefits cardiovascular health and effectively reduces the risk for cardiovascular disease. Circular RNAs (circRNAs) play important roles in cardiac pathophysiology. However, the role of circRNAs in response to exercise training and biological mechanisms responsible for exercise-induced cardiac protection remain largely unknown. METHODS AND RESULTS: RNA sequencing was used to profile circRNA expression in adult mouse cardiomyocytes that were isolated from mice with or without exercise training. Exercise-induced circRNA circUtrn was significantly increased in swimming-trained adult mouse cardiomyocytes. In vivo, circUtrn was found to be required for exercise-induced physiological cardiac hypertrophy. circUtrn inhibition abolished the protective effects of exercise on myocardial ischaemia-reperfusion remodelling. circUtrn overexpression prevented myocardial ischaemia-reperfusion-induced acute injury and pathological cardiac remodelling. In vitro, overexpression of circUtrn promoted H9 human embryonic stem cell-induced cardiomyocyte growth and survival via protein phosphatase 5 (PP5). Mechanistically, circUtrn directly bound to PP5 and regulated the stability of PP5 in a ubiquitin-proteasome-dependent manner. Hypoxia-inducible factor 1α-dependent splicing factor SF3B1 acted as an upstream regulator of circUtrn in cardiomyocytes. CONCLUSION: The circRNA circUtrn is upregulated upon exercise training in the heart. Overexpression of circUtrn can prevent myocardial I/R-induced injury and pathological cardiac remodelling.

Mimicking sarcolemmal damagein vitro: a contractile 3D model of skeletal muscle for drug testing in Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is the most prevalent neuromuscular disease diagnosed in childhood. It is a progressive and wasting disease, characterized by a degeneration of skeletal and cardiac muscles caused by the lack of dystrophin protein. The absence of this crucial structural protein leads to sarcolemmal fragility, resulting in muscle fiber damage during contraction. Despite ongoing efforts, there is no cure available for DMD patients. One of the primary challenges is the limited efficacy of current preclinical tools, which fail in modeling the biological complexity of the disease. Human-based three-dimensional (3D) cell culture methods appear as a novel approach to accelerate preclinical research by enhancing the reproduction of pathophysiological processes in skeletal muscle. In this work, we developed a patient-derived functional 3D skeletal muscle model of DMD that reproduces the sarcolemmal damage found in the native DMD muscle. These bioengineered skeletal muscle tissues exhibit contractile functionality, as they responded to electrical pulse stimulation. Sustained contractile regimes induced the loss of myotube integrity, mirroring the pathological myotube breakdown inherent in DMD due to sarcolemmal instability. Moreover, damaged DMD tissues showed disease functional phenotypes, such as tetanic fatigue. We also evaluated the therapeutic effect of utrophin upregulator drug candidates on the functionality of the skeletal muscle tissues, thus providing deeper insight into the real impact of these treatments. Overall, our findings underscore the potential of bioengineered 3D skeletal muscle technology to advance DMD research and facilitate the development of novel therapies for DMD and related neuromuscular disorders.

Mitochondrial dynamics-related genes DRP1 and OPA1 contributes to early diagnosis of cognitive impairment in diabetes.

BACKGROUND AND AIM: DRP1 and OPA1 play important roles in mitochondrial fusion and fission. However, the role of DRP1 and OPA1 amplification in mitochondrial cognitive impairment has not been reported. This study aimed to investigate the relationship between DRP1 and OPA1 and the risk of cognitive impairment. METHODS: In this study, 45 elderly patients with diabetes admitted to the Lianyungang Second People's Hospital from September 2020 to January 2021 were included. The patients were divided into normal group, mild cognitive impairment group and dementia group by using MMSE score, and the clinical characteristics of the three groups were compared. The amplification multiples of the two genes' DNA were calculated by ΔΔCT and defined as 2- K. Spearman rank correlation was used to analyze the correlation between the DNA amplification multiples of patients' DRP1 and OPA1 and AD8 and MoCA scores. The sensitivity and specificity of DNA amplification multiples of DRP1 and OPA1 to predict clinical outcomes of diabetic cognitive impairment were evaluated using Receiver operator characteristic (ROC) curves. Multiple logistic regression was used to evaluate the relationship between DNA amplification factor of DRP1 and OPA1 and cognitive function. RESULTS: DRP1(2- K) and OPA1(2- K) significantly increased and decreased in dementia and MCI groups compared with the normal group (P ≤ 0.001). The DNA amplification factor of DRP1 was positively correlated with AD8 score and negatively correlated with MoCA score (P < 0.001). The DNA amplification factor of OPA1 was positively correlated with the MoCA score (P = 0.0002). Analysis of ROCs showed that the DNA amplification factor of OPA1 had a higher predictive value for dementia (P < 0.0001), and that it had a higher predictive value when used in combination with DRP1. Multiple logistic regression results showed that increased DNA amplification in DRP1 was associated with increased risk of dementia (OR 1.149;95%CI,1.035-1.275), and increased DNA amplification in OPA1 was associated with decreased risk of MCI (OR 0.004;95%CI,0.000-0.251) and dementia (OR 0.000;95%CI,0.000-0.134). CONCLUSION: DNA amplification multiples of DRP1 and OPA1 are associated with the risk of dementia in elderly patients and may serve as potential biomarkers.

Increasing muscle contractility through low-frequency stimulation alters tibial bone geometry and reduces bone strength in mdx and dko dystrophic mice.

Duchenne muscular dystrophy (DMD) is a severe muscle wasting disease caused by mutations or deletions in the dystrophin gene, for which there remains no cure. As DMD patients also develop bone fragility because of muscle weakness and immobilization, better understanding of the pathophysiological mechanisms of dystrophin deficiency will help develop therapies to improve musculoskeletal health. Since alterations in muscle phenotype can influence bone structure, we investigated whether modifying muscle contractile activity through low-frequency stimulation (LFS) could alter bone architecture in mouse models of DMD. We tested the hypothesis that increasing muscle contractile activity could influence bone mass and structure in dystrophin-deficient (mdx) and dystrophin- and utrophin-deficient (dko) dystrophic mice. Tibial bone structure in dko mice was significantly different from that in mdx and wild-type (C57BL/10) control mice. Effects of LFS on bone architecture differed between dystrophic and healthy mice, with LFS thinning cortical bone in both dystrophic models. Bone mass was maintained in LFS-treated healthy mice, with a reduced proportion of high-density bone and concomitant increase in low-density bone. LFS-treated dko mice exhibited a net deficit in cortical thickness and reduced high-density bone but no equivalent increase in low-density bone. These alterations in bone structure and mineral density reduced mechanical strength in mdx and dko mice. The findings reveal that muscle activity can regulate bone mass, structure, mineral accrual, and strength, especially in the context of dystrophin and/or utrophin deficiency. The results provide unique insights into the development of bone fragility in DMD and for devising interventions to improve musculoskeletal health.NEW & NOTEWORTHY Patients with Duchenne muscular dystrophy (DMD) develop bone fragility because of muscle weakness and immobilization. We investigated whether increasing muscle contractile activity through low-frequency stimulation (LFS) could alter bone architecture in dystrophin-deficient (mdx) or dystrophin- and utrophin-deficient (dko) mouse models of DMD. Chronic LFS reduced tibial diaphysis cross sections in mdx and dko mice, without affecting bone shape in healthy mice. LFS affected the distribution of bone mineral density across all phenotypes, with the magnitude of effect being dependent on disease severity.

Valproic acid reduces muscle susceptibility to contraction-induced functional loss but increases weakness in two murine models of Duchenne muscular dystrophy.

Skeletal muscles in animal models of Duchenne muscular dystrophy (DMD) are more susceptible to contraction-induced functional loss, which is not related to fatigue. Valproic acid (VPA) reportedly improves serological and histological markers of damage in dystrophin-deficient murine muscle. Here, we tested whether VPA would reduce the susceptibility to contraction-induced functional loss in two murine DMD models. Adult female mdx (mild) and D2-mdx (severe) DMD murine models were administered VPA (240 mg/kg) or saline for 7 days. Some VPA-treated mdx mice also performed voluntary running in a wheel, which is known to reduce the susceptibility to contraction-induced functional loss; that is, isometric force drop following eccentric contractions. In situ muscle function was assessed before, during and after eccentric contractions. Muscle utrophin and desmin expression were also evaluated using immunoblotting. Interestingly, VPA reduced the isometric force drop following eccentric contractions in both murine models, without change in the relative eccentric maximal force and in the expression of utrophin and desmin. VPA for 7 days combined with voluntary running had no additive effect compared to VPA alone. Furthermore, VPA reduced the absolute isometric maximal force before eccentric contractions in both murine models. The results of our study indicated that VPA in both murine DMD models reduced the susceptibility to contraction-induced functional loss but increased muscle weakness.

Acute, next-generation AMPK activation initiates a disease-resistant gene expression program in dystrophic skeletal muscle.

Duchenne muscular dystrophy (DMD) is a life-limiting neuromuscular disorder characterized by muscle weakness and wasting. Previous proof-of-concept studies demonstrate that the dystrophic phenotype can be mitigated with the pharmacological stimulation of AMP-activated protein kinase (AMPK). However, first-generation AMPK activators have failed to translate from bench to bedside due to either their lack of potency or toxic, off-target effects. The identification of safe and efficacious molecules that stimulate AMPK in dystrophic muscle is of particular importance as it may broaden the therapeutic landscape for DMD patients regardless of their specific dystrophin mutation. Here, we demonstrate that a single dose of the next generation, orally-bioactive AMPK agonist MK-8722 (MK) to mdx mice evoked skeletal muscle AMPK and extensive downstream stimulation within 12 h post-treatment. Specifically, MK elicited a gene expression profile indicative of a more disease-resistant slow, oxidative phenotype including increased peroxisome proliferator-activated receptor É£ coactivator-1⍺ activity and utrophin levels. In addition, we observed augmented autophagy signaling downstream of AMPK, as well as elevations in critical autophagic genes such as Map1lc3 and Sqstm1 subsequent to the myonuclear accumulation of the master regulator of the autophagy gene program, transcription factor EB. Lastly, we show that pharmacological AMPK stimulation normalizes the expression of myogenic regulatory factors and amends activated muscle stem cell content in mdx muscle. Our results indicate that AMPK activation via MK enhances disease-mitigating mechanisms in dystrophic muscle and prefaces further investigation on the chronic effects of novel small molecule AMPK agonists.

Utrophin correlates with disease severity in Duchenne muscular dystrophy.

This month in Med, the description of an unusually severely affected DMD patient suffering from a large deletion in the dystrophin gene confirms that absence of utrophin worsens the dystrophy and supports the concept that utrophin upregulation ameliorates the pathology. This study may guide the development of dystrophin-based gene therapies.

Endogenous bioluminescent reporters reveal a sustained increase in utrophin gene expression upon EZH2 and ERK1/2 inhibition.

Duchenne muscular dystrophy (DMD) is an X-linked disorder caused by loss of function mutations in the dystrophin gene (Dmd), resulting in progressive muscle weakening. Here we modelled the longitudinal expression of endogenous Dmd, and its paralogue Utrn, in mice and in myoblasts by generating bespoke bioluminescent gene reporters. As utrophin can partially compensate for Dmd-deficiency, these reporters were used as tools to ask whether chromatin-modifying drugs can enhance Utrn expression in developing muscle. Myoblasts treated with different PRC2 inhibitors showed significant increases in Utrn transcripts and bioluminescent signals, and these responses were independently verified by conditional Ezh2 deletion. Inhibition of ERK1/2 signalling provoked an additional increase in Utrn expression that was also seen in Dmd-mutant cells, and maintained as myoblasts differentiate. These data reveal PRC2 and ERK1/2 to be negative regulators of Utrn expression and provide specialised molecular imaging tools to monitor utrophin expression as a therapeutic strategy for DMD.

Unusually severe muscular dystrophy upon in-frame deletion of the dystrophin rod domain and lack of compensation by membrane-localized utrophin.

BACKGROUND: Utrophin, a dystrophin homolog, is consistently upregulated in muscles of patients with Duchenne muscular dystrophy (DMD) and is believed to partially compensate for the lack of dystrophin in dystrophic muscle. Even though several animal studies support the idea that utrophin can modulate DMD disease severity, human clinical data are scarce. METHODS: We describe a patient with the largest reported in-frame deletion in the DMD gene, including exons 10-60 and thus encompassing the entire rod domain. FINDINGS: The patient presented with an unusually early and severe progressive weakness, initially suggesting congenital muscular dystrophy. Immunostaining of his muscle biopsy showed that the mutant protein was able to localize at the sarcolemma and stabilize the dystrophin-associated complex. Strikingly, utrophin protein was absent from the sarcolemmal membrane despite the upregulation of utrophin mRNA. CONCLUSIONS: Our results suggest that the internally deleted and dysfunctional dystrophin lacking the entire rod domain may exert a dominant-negative effect by preventing upregulated utrophin protein from reaching the sarcolemmal membrane and thus blocking its partial rescue of muscle function. This unique case may set a lower size limit for similar constructs in potential gene therapy approaches. FUNDING: This work was supported by a grant from MDA USA (MDA3896) and by grant number R01AR051999 from NIAMS/NIH to C.G.B.

Phosphorylation alters the mechanical stiffness of a model fragment of the dystrophin homologue utrophin.

Duchenne muscular dystrophy is a lethal muscle wasting disease caused by the absence of the protein dystrophin. Utrophin is a dystrophin homologue currently under investigation as a protein replacement therapy for Duchenne muscular dystrophy. Dystrophin is hypothesized to function as a molecular shock absorber that mechanically stabilizes the sarcolemma. While utrophin is homologous with dystrophin from a molecular and biochemical perspective, we have recently shown that full-length utrophin expressed in eukaryotic cells is stiffer than what has been reported for dystrophin fragments expressed in bacteria. In this study, we show that differences in expression system impact the mechanical stiffness of a model utrophin fragment encoding the N terminus through spectrin repeat 3 (UtrN-R3). We also demonstrate that UtrN-R3 expressed in eukaryotic cells was phosphorylated while bacterial UtrN-R3 was not detectably phosphorylated. Using atomic force microscopy, we show that phosphorylated UtrN-R3 exhibited significantly higher unfolding forces compared to unphosphorylated UtrN-R3 without altering its actin-binding activity. Consistent with the effect of phosphorylation on mechanical stiffness, mutating the phosphorylated serine residues on insect eukaryotic protein to alanine decreased its stiffness to levels not different from unphosphorylated bacterial protein. Taken together, our data suggest that the mechanical properties of utrophin may be tuned by phosphorylation, with the potential to improve its efficacy as a protein replacement therapy for dystrophinopathies.

Biological and genetic therapies for the treatment of Duchenne muscular dystrophy.

INTRODUCTION: Duchenne muscular dystrophy is a lethal genetic disease which currently has no cure, and poor standard treatment options largely focused on symptom relief. The development of multiple biological and genetic therapies is underway across various stages of clinical progress which could markedly affect how DMD patients are treated in the future. AREAS COVERED: The purpose of this review is to provide an introduction to the different therapeutic modalities currently being studied, as well as a brief description of their progress to date and relative advantages and disadvantages for the treatment of DMD. This review discusses exon skipping therapy, microdystrophin therapy, stop codon readthrough therapy, CRISPR-based gene editing, cell-based therapy, and utrophin upregulation. Secondary therapies addressing nonspecific symptoms of DMD were excluded. EXPERT OPINION: Despite the vast potential held by gene replacement therapy options such as microdystrophin production and utrophin upregulation, safety risks inherent to the adeno-associated virus delivery vector might hamper the clinical viability of these approaches until further improvements can be made. Of the mutation-specific therapies, exon skipping therapy remains the most extensively validated and explored option, and the cell-based CAP-1002 therapy may prove to be a suitable adjunct therapy filling the urgent need for cardiac-specific therapies.

Cardiac and Skeletal Muscle Pathology in the D2/mdx Mouse Model and Caveats Associated with the Quantification of Utrophin.

Duchenne muscular dystrophy (DMD) (the most common form of muscular dystrophy) is caused by a lack of dystrophin protein. Currently, although many therapeutic strategies are under investigation, there is no cure for DMD and unfortunately, patients succumb to respiratory and/or cardiac failure in their second or third decade of life. Preclinical work has focused on the mouse model C57BL/10ScSn-Dmdmdx/J (BL10/mdx), which does not exhibit a robust pathophenotype. More recently, the D2.B10-Dmdmdx/J (D2/mdx) mouse has been utilized, which presents a more severe pathology and therefore more closely mimics the human pathophenotype, particularly in the heart. Here, we outline important considerations when utilizing the D2/mdx model by highlighting the differences between these models in addition to describing histological and immunohistochemical methods utilized in Kennedy et al. (Mol Ther Methods Clin Dev 11:92-105, 2018) for both cardiac and skeletal muscle, which can quantify these differences. These considerations are particularly important when investigating treatment strategies that may be affected by regeneration; such is the case for upregulation of the dystrophin paralogue, utrophin.

Identifying FDA-Approved Drugs that Upregulate Utrophin A as a Therapeutic Strategy for Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is a neuromuscular disease caused by mutations and deletions within the DMD gene, which result in a lack of dystrophin protein at the sarcolemma of skeletal muscle fibers. The absence of dystrophin fragilizes the sarcolemma and compromises its integrity during cycles of muscle contraction, which, progressively, leads to reductions in muscle mass and function. DMD is thus a progressive muscle-wasting disease that results in a loss of ambulation, cardiomyopathy , respiratory impairment, and death. Although there is presently no cure for DMD, recent advances have led to many promising treatments. One such approach entails increasing expression of a homologous protein to dystrophin, named utrophin A, which is endogenously expressed in both healthy and DMD muscle fibers. Upregulation of utrophin A all along the sarcolemma of DMD muscle fibers can, in part, compensate for the absence of dystrophin. Over the years, our laboratory has focused a significant portion of our efforts in identifying and characterizing drugs and small molecules for their ability to target utrophin A and cause its overexpression. As part of these efforts, we have recently developed a novel ELISA-based high-throughput drug screen, to identify FDA-approved drugs that increase the expression of utrophin A in muscle cells in culture as well as in dystrophic mice. Here, we describe our overall strategy to identify and characterize several FDA-approved drugs that upregulate utrophin A expression and provide details on all experimental approaches. Such strategy has the potential to lead to the rapid development of novel therapeutics for DMD.

Strategies for Bottlenecks of rAAV-Mediated Expression in Skeletal and Cardiac Muscle of Duchenne Muscular Dystrophy.

Gene therapy using the adeno-associated virus (rAAV) to deliver mini/micro- dystrophin is the current promising strategy for Duchenne Muscular Dystrophy (DMD). However, the further transformation of this strategy still faces many "bottlenecks". Most gene therapies are only suitable for infants with strong muscle cell regeneration and immature immune system, and the treatment depends heavily on the high dose of rAAV. However, high-dose rAAV inevitably causes side effects such as immune response and acute liver toxicity. Therefore, how to reduce the degree of fibrosis and excessive immune response in older patients and uncouple the dependence association between therapeutic effect and high dose rAAV are crucial steps for the transformation of rAAV-based gene therapy. The article analyzes the latest research and finds that the application of utrophin, the homologous protein of dystrophin, could avoid the immune response associated with dystrophin, and the exploration of methods to improve the expression level of mini/micro-utrophin in striated muscle, combined with the novel MyoAAV with high efficiency and specific infection of striated muscle, is expected to achieve the same therapeutic efficacy under the condition of reducing the dose of rAAV. Furthermore, the delivery of allogeneic cardio sphere-derived cells (CDCs) with anti-inflammatory and anti-fibrotic characteristics combined with immune suppression can provide a continuous and appropriate "window period" for gene therapy. This strategy can expand the number of patients who could benefit from gene therapy.

Macroglossia and less advanced dystrophic change in the tongue muscle of the Duchenne muscular dystrophy rat.

BACKGROUND: Duchenne muscular dystrophy (DMD) is an X-linked muscle disease caused by a complete lack of dystrophin, which stabilizes the plasma membrane of myofibers. The orofacial function is affected in an advanced stage of DMD and this often leads to an eating disorder such as dysphagia. Dysphagia is caused by multiple etiologies including decreased mastication and swallowing. Therefore, preventing the functional declines of mastication and swallowing in DMD is important to improve the patient's quality of life. In the present study, using a rat model of DMD we generated previously, we performed analyses on the masseter and tongue muscles, both are required for proper eating function. METHODS: Age-related changes of the masseter and tongue muscle of DMD rats were analyzed morphometrically, histologically, and immunohistochemically. Also, transcription of cellular senescent markers, and utrophin (Utrn), a functional analog of dystrophin, was examined. RESULTS: The masseter muscle of DMD rats showed progressive dystrophic changes as observed in their hindlimb muscle, accompanied by increased transcription of p16 and p19. On the other hand, the tongue of DMD rats showed macroglossia due to hypertrophy of myofibers with less dystrophic changes. Proliferative activity was preserved in the satellite cells from the tongue muscle but was perturbed severely in those from the masseter muscle. While Utrn transcription was increased in the masseter muscle of DMD rats compared to WT rats, probably due to a compensatory mechanism, its level in the tongue muscle was comparable between WT and DMD rats and was similar to that in the masseter muscle of DMD rats. CONCLUSIONS: Muscular dystrophy is less advanced in the tongue muscle compared to the masseter muscle in the DMD rat.

Senolytic elimination of senescent macrophages restores muscle stem cell function in severely dystrophic muscle.

The aging of the immune system, or immunosenescence, was recently verified to have a causal role in driving the aging of solid organs, while the senolytic elimination of senescent immune cells was found to effectively delay systemic aging. Our recent study also showed that immune cells in severely dystrophic muscles develop senescence-like phenotypes, including the increased expression of senescence-associated secretory phenotype (SASP) factors and senescence markers. Here we further investigated whether the specific clearance of senescent immune cells in dystrophic muscle may effectively improve the function of muscle stem cells and the phenotypes of dystrophic muscle. We observed increased percentage of senescent cells in macrophages from mdx/utro(-/-) mice (a murine model for muscular dystrophy disease, dystrophin-/-; utrophin-/-), while the treatment of mdx/utro(-/-) macrophages with senolytic drug fisetin resulted in reduced number of senescent cells. We administrated fisetin to mdx/utro(-/-) mice for 4 weeks, and observed obviously reduced number of senescent immune cells, restored number of muscle cells, and improve muscle phenotypes. In conclusion, our results reveal that senescent immune cells, such as macrophages, are greatly involved in the development of muscle dystrophy by impacting the function of muscle stem cells, and the senolytic ablation of these senescent cells with fisetin can be an effective therapeutic strategy for improving function of muscle stem cells and phenotypes of dystrophic muscles.