Myoblast transplantation: A possible surgical treatment for a severe pediatric disease

Duchenne muscular dystrophy (DMD) is a genetic X-linked recessive orphan disease that affects approximately 1 in 3 500 male births. Boys with DMD have progressive and predictable muscle destruction due to the absence of dystrophin, a protein present under the muscle fiber membrane. This absence induces contraction-related membrane damage and activation of inflammatory necrosis and fibrosis, leading to cardiac/diaphragmatic failure and death. The authors support the therapeutic role of myoblast transplantation in DMD, and describe the history and rationale for such an approach.     

Blood loss in Duchenne muscular dystrophy: vascular smooth muscle dysfunction?

Patients with Duchenne muscular dystrophy (DMD) tend to bleed more during surgery than do patients with other conditions. A retrospective analysis of blood loss after spinal surgery for scoliosis was therefore undertaken in 102 patients undergoing surgery in the senior author's unit. These included 48 patients with DMD, 26 patients with spinal muscular atrophy, and a miscellaneous group of 28 other patients most of whom had idiopathic scoliosis. For each patient the age at surgery, estimated blood volume, duration of operation, Cobb angle, and number of vertebrae fused were recorded and compared. Expression of dystrophin in skeletal muscle and the underlying gene mutation were also determined. The estimated blood loss in patients with DMD was significantly higher than that in patients with spinal muscular atrophy undergoing the same or similar procedure (P < 0.005) and was also significantly greater than that of the third group, which consisted mostly of patients with idiopathic scoliosis (P < 0.0005). Blood loss in the patient group with DMD showed a significant relationship with duration of surgery (P < 0.05). As most patients expressed no dystrophin, this did not correlate with the estimated blood loss. There was also no correlation between the estimated blood loss and the type of gene mutation found causing DMD. The authors' previous observations confirm the increased blood loss in patients with DMD who undergo scoliosis surgery. Because children with DMD lack dystrophin in all muscle types, including smooth muscle, the excessive blood loss may be because of a poor vascular smooth muscle vaso-constrictive response due to a lack of dystrophin.     

Growth Hormone Increases Bone Toughness and Decreases Muscle Inflammation in Glucocorticoid-Treated Mdx Mice,Model of Duchenne Muscular Dystrophy

The absence of functional dystrophin with mutations of the dystrophin-encoding gene in Duchenne muscular dystrophy (DMD) results in muscle inflammation and degeneration, as well as bone fragility. Long-term glucocorticoid therapy delays the muscular disease progression but suppresses growth hormone secretion, resulting in short stature and further deleterious effects on bone strength. This study evaluated the therapeutic potential of daily growth hormone therapy in growing mdx mice as a model of DMD. Growth hormone treatment on its own or in combination with glucocorticoids significantly improved muscle histology and function and decreased markers of inflammation in mdx mice. Glucocorticoid treatment thinned cortical bone and decreased bone strength and toughness. Despite the minimal effects of growth hormone on bone microarchitecture, it significantly improved biomechanical properties of femurs and vertebrae, even in the presence of glucocorticoid treatment. Together these studies suggest that the use of growth hormone in DMD should be considered for improvements to muscle and bone health. © 2019 American Society for Bone and Mineral Research.     

Dystrophin and utrophin “double knockout” dystrophic mice exhibit a spectrum of degenerative musculoskeletal abnormalities

Duchenne muscular dystrophy (DMD) is a degenerative muscle disorder characterized by the lack of dystrophin expression at the sarcolemma of muscle fibers. In addition, DMD patients acquire osteopenia, fragility fractures, and scoliosis indicating that a deficiency in skeletal homeostasis coexists but little is known about the effects of DMD on bone and other connective tissues within the musculoskeletal system. Recent evidence has emerged implicating adult stem cell dysfunction in DMD myopathogenesis. Given the common mesenchymal origin of muscle and bone, we sought to investigate bone and other musculoskeletal tissues in a DMD mouse model. Here, we report that dystrophin–utrophin double knockout (dko) mice exhibit a spectrum of degenerative changes, outside skeletal muscle, in bone, articular cartilage, and intervertebral discs, in addition to reduced lifespan, muscle degeneration, spinal deformity, and cardiomyopathy previously reported. We also report these mice to have a reduced capacity for bone healing and exhibit spontaneous heterotopic ossification in the hind limb muscles. Therefore, we propose the dko mouse as a model for premature musculoskeletal aging and posit that a similar phenomenon may occur in patients with DMD. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 343–349, 2013     

Fibrin gel improves the survival of transplanted myoblasts

Duchenne muscular dystrophy (DMD) is the most frequent muscular dystrophy in children and young adults. Currently, there is no cure for the disease. The transplantation of healthy myoblasts is an experimental therapeutic strategy, since it could restore the expression of dystrophin in DMD muscles. Nevertheless, this cellular therapy is limited by immune reaction, low migration of the implanted cells, and high early cell death that could be at least partially due to anoikis. To avoid the lack of attachment of the cells to an extracellular matrix after the transplantation, which is the cause of anoikis, we tested the use of a fibrin gel for myoblast transplantation. In vitro, three concentrations of fibrinogen were compared (3, 20, and 50 mg/ml) to form a fibrin gel. A stiffer fibrin gel leads to less degradability and less proliferation of the cells. A concentration of 3 mg/ml fibrin gel enhanced the differentiation of the myoblasts earlier as a culture in monolayer. Human myoblasts were also transplanted in muscles of Rag/mdx mice in a fibrin gel or in a saline solution (control). The use of 3 mg/ml fibrin gel for cell transplantation increased not only the survival of the cells as measured after 5 days but also the number of fibers expressing dystrophin after 21 days, compared to the control. Moreover, the fibrin gel was also compared to a prosurvival cocktail. The survival of the myoblasts at 5 days was increased in both conditions compared to the control but the efficacy of the prosurvival cocktail was not significantly higher than the fibrin gel.     

杜兴肌营养不良症治疗进展及前景

目的综述杜兴肌营养不良症（Duchenne muscular dystrophy，DMD）治疗的最新研究进展。方法广泛查阅近年来相关文献，对DMD治疗的研究进展进行综述。结果目前对DMD的治疗主要有基因治疗、细胞治疗和药理学治疗，基因治疗和细胞治疗通过传递正常基因或修正突变基因以及移植正常细胞，如干细胞来进行治疗；而药理学治疗主要针对dystrophin基因缺陷引起的下游事件，运用各种药物来减缓DMD病理进程，从而改善患者的生活质量，延长寿命。结论针对DMD的各种治疗手段均存在一定困难，目前尚不能有效治疗此病，还需要研究探索更有效的治疗浍格     

Duchenne muscular dystrophy: current knowledge,treatment, and future prospects

The cloning of the dystrophin gene has led to major advances in the understanding of the molecular genetic basis of Duchenne, Becker, and other muscular dystrophies associated with mutations in genes encoding members of the dystrophin-associated glycoprotein complex. The recent introduction of pharmaceutical agents such as prednisone has shown great promise in delaying the progression of Duchenne muscular dystrophy but there remains a need to develop more long-term therapeutic interventions. Knowledge of the nature of the dystrophin gene and the glycoprotein complex has led many researchers to think that somatic gene replacement represents the most promising approach to treatment. The potential use of this strategy has been shown in the mdx mouse model of Duchenne muscular dystrophy, where germ line gene transfer of either a full-length or a smaller Becker-type dystrophin minigene prevents necrosis and restores normal muscle function.     

Dystrophin deficient mdx muscle is not prone to MH susceptibility: an in vitro study

The association between malignant hyperthermia (MH) and neuromuscular disorders is controversial. An association between MH and Duchenne muscular dystrophy, a common and lethal disorder caused by deficiency of dystrophin, has been reported sporadically but is still not proved. To examine this problem, we performed halothane and caffeine in vitro contracture tests on skeletal muscles from dystrophin deficient mdx mice, an animal model for human Duchenne muscular dystrophy. As neither halothane nor caffeine triggered abnormal responses in mdx muscles, we conclude that dystrophin deficiency per se is not the primary cause of MH-like crises, as reported for patients with Duchenne muscular dystrophy.      

Analyses of the differentiation potential of satellite cells from <Emphasis Type="Italic">myoD</Emphasis><Superscript>-/-</Superscript>, <Emphasis Type="Italic">mdx</Emphasis>, and <Emphasis Type="Italic">PMP22</Emphasis> C22 mice

Background  

Sporadic and sometimes contradictory studies have indicated changes in satellite cell behaviour associated with the progressive nature of human Duchenne muscular dystrophy (DMD). Satellite cell proliferation and number are reportedly altered in DMD and the mdx mouse model. We recently found that satellite cells in MSVski transgenic mice, a muscle hypertrophy model showing progressive muscle degeneration, display a severe ageing-related differentiation defect in vitro. We tested the hypothesis that similar changes contribute to the gradual loss of muscle function with age in mdx and PMP22 mice, a model of human motor and sensory neuropathy type 1A (HMSN1A).     

Autotransplantation in mdx mice of mdx myoblasts genetically corrected by an HSV-1 amplicon vector

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder, characterized by a lack of dystrophin. To eliminate the need for immunosuppressive drugs, transplantation of genetically modified autologous myoblasts has been proposed as a possible therapy for this myopathy. An HSV-1 amplicon vector (HSVDGN), containing a 17.3-kb full-length MCK-driven mouse dystrophin cDNA, an eGFP gene, and a neomycin resistance gene driven by CMV or SV40 promoters, respectively, was constructed and used to transduce mdx primary myoblasts. The presence of the eGFP and neomycin resistance genes facilitated the evaluation of the initial transduction efficiency and the permanent transduction frequency. At low multiplicities of infection (MOI 1-5), the majority of myoblasts (60-90%) expressed GFP. The GFP-positive mdx myoblasts were sorted by FACS and selected with neomycin (300 microg/ml) for 2 weeks. Up to 2% of initially infected mdx myoblasts stably expressed the three transgenes without further selection at that time. These altered cells were grafted into the tibialis anterior muscles of 18 mdx mice. Some of the mice were immunosuppressed with FK506 due to the anticipation that eGFP and the product of neomycin resistance gene might be immunogenic. One month after transplantation, numerous muscle fibers expressing mouse dystrophin were detected by immunohistochemistry, in both immunosuppressed (10-50%) and nonimmunosuppressed (5-25%) mdx mice. Our results demonstrated the capability of permanently expressing a full-length dystrophin in dystrophic myoblasts with HSV-1 amplicon vector and raised the possibility of an eventual treatment of DMD based on the transplantation of genetically modified autologous myoblasts.     

Inhibiting myostatin with follistatin improves the success of myoblast transplantation in dystrophic mice

Duchenne muscular dystrophy is a recessive disease due to a mutation in the dystrophin gene. Myoblast transplantation permits to introduce the dystrophin gene in dystrophic muscle fibers. However, the success of this approach is reduced by the short duration of the regeneration following the transplantation, which reduces the number of hybrid fibers. Our aim was to verify whether the success of the myoblast transplantation is enhanced by blocking the myostatin signal with an antagonist, follistatin. Three different approaches were studied to overexpress follistatin in the muscles of mdx mice transplanted with myoblasts. First, transgenic follistatin/mdx mice were generated; second, a follistatin plasmid was electroporated in mdx muscles, and finally, follistatin was induced in mdx mice muscles by a treatment with a histone deacetylase inhibitor. The three approaches improved the success of the myoblast transplantation. Moreover, fiber hypertrophy was also observed in all muscles, demonstrating that myostatin inhibition by follistatin is a good method to improve myoblast transplantation and muscle function. Myostatin inhibition by follistatin in combination with myoblast transplantation is thus a promising novel therapeutic approach for the treatment of muscle wasting in diseases such as Duchenne muscular dystrophy.     

Duchenne muscular dystrophy

Duchenne muscular dystrophy is an X-linked disease of muscle caused by an absence of the protein dystrophin. Affected boys begin manifesting signs of disease early in life, cease walking at the beginning of the second decade, and usually die by age 20 years. Until treatment of the basic genetic defect is available, medical, surgical, and rehabilitative approaches can be used to maintain patient function and comfort. Corticosteroids, including prednisone and a related compound, deflazacort, have recently been shown to markedly delay the loss of muscle strength and function in boys with Duchenne muscular dystrophy. Surgical release of lower extremity contractures may benefit some patients. Approximately 90% of boys with Duchenne muscular dystrophy will develop severe scoliosis, which is not amenable to control by nonsurgical means such as bracing or adaptive seating. The most effective treatment for severe scoliosis is prevention by intervening with early spinal fusion utilizing segmental instrumentation as soon as curves are ascertained and before the onset of severe pulmonary or cardiac dysfunction.     

Systemic human minidystrophin gene transfer improves functions and life span of dystrophin and dystrophin/utrophin‐deficient mice

Duchenne muscular dystrophy (DMD) is the most common and lethal genetic muscle disease, caused by mutations in the dystrophin gene. No efficacious treatment is currently available. Here we report AAV vector systemic delivery and therapeutic benefits of the functional human minidystrophin gene in a severe and more reliable DMD mouse model, the dystrophin/utrophin double deficiency mouse (dys?/?:utrn?/?, dKO). These mice show many pathologic and phenotypic signs typical of DMD in humans including kyphosis and shorter life span, all of which are not seen in the mdx mice due to their utrophin upregulation that partially compensates the loss of dystrophin functions and leads to mild phenotypes. The therapeutic value of this new approach was demonstrated in both mdx and dKO murine models, in which we observed highly efficient minidystrophin gene expression, ameliorated muscle pathologies, improvement in growth and motility, inhibition of spine and limb deformation, and prolongation of life span. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 421–426, 2009     

Anesthesia with sevoflurane for tonsillectomy in a boy with Duchenne muscular dystrophy

A 6-year-old boy with Duchenne muscular dystrophy (DMD) and foreseen difficult tracheal intubation underwent tonsillectomy under general inhaled anesthesia with sevoflurane. No neuromuscular blockers were administered and no perioperative complications emerged. In spite of advances in genetic diagnosis there continue to be patients with DMD because of spontaneous mutation of the dystrophin gene. Late detection leaves them vulnerable to administration of drugs like succinylcholine that can trigger fatal reactions involving hyperpotassemia, rhabdomyolysis, and malignant hyperthermia. Total intravenous anesthesia seems the best way to provide general anesthesia for a patient with DMD. Inhaled anesthesia is an alternative. Although halogenated agents can lead to rhabdomyolysis and malignant hyperthermia, the frequency seems low if we bear in mind that the use of sevoflurane is widespread in pediatrics. In this case sevoflurane induction facilitated safe tracheal intubation.     

Duchenne muscular dystrophy: an old anesthesia problem revisited

Patients with Duchenne and Becker muscular dystrophy suffer from a progressive deterioration in muscle secondary to a defect in the dystrophin gene. As such, they are susceptible to perioperative respiratory, cardiac and other complications, such as rhabdomyolysis. Inhalational anesthetic agents have been implicated as a cause of acute rhabdomyolysis that can resemble malignant hyperthermia (MH). This article reviews perioperative 'MH-like' reactions reported in muscular dystrophy patients and groups them into three categories according to clinical presentation. The etiology and underlying pathophysiological process responsible for these reactions is discussed and recommendations are proposed for the safe anesthetic management of these patients.     

Dystrophin deficiency in canine X-linked muscular dystrophy in Japan (CXMDJ) alters myosin heavy chain expression profiles in the diaphragm more markedly than in the tibialis cranialis muscle

Background  

Skeletal muscles are composed of heterogeneous collections of muscle fiber types, the arrangement of which contributes to a variety of functional capabilities in many muscle types. Furthermore, skeletal muscles can adapt individual myofibers under various circumstances, such as disease and exercise, by changing fiber types. This study was performed to examine the influence of dystrophin deficiency on fiber type composition of skeletal muscles in canine X-linked muscular dystrophy in Japan (CXMD_J), a large animal model for Duchenne muscular dystrophy.     

Bone tissue and muscle dystrophin deficiency in mdx mice

Duchenne muscular dystrophy is a neuromuscular disease caused by the lack of dystrophin that affects skeletal muscles, causing degeneration of muscle fibers and replacing them with fibrous and adipose tissue, events that gradually lead to functional loss. Patients with Duchenne muscular dystrophy have shown that bones become more fragile with age and with advancement of the disease. Muscle weakness and reduced mobility have been suggested to be the factors that promote bone deterioration. However, it seems that this does not occur in mdx mice. It has been identified in mdx mice the existence of a factor related or not to the lack of dystrophin that also participates in the impairment of bone quality. Mdx mice also exhibit muscle degeneration, but unlike human, it is compensated by muscle regeneration. In consequence, there is an increase in the muscle mass, but not necessarily of muscle contractile strength. The accommodation of this increased muscle mass promotes bone formation at specific sites, such as at tendo-osseous junctions. In addition, the inflammatory response to muscle injury may be responsible for the increase in angiogenesis and regeneration observed in mdx mice, inducing the release of cytokines and chemokines that play an important role in the recruitment of leukocytes and macrophages. Then, mdx mice may possess compensatory mechanisms in bone in response to a genetic defect.     

Central tolerance to myogenic cell transplants does not include muscle neoantigens

BACKGROUND: Duchenne muscular dystrophy is a fatal genetic disease caused by lack of dystrophin. Myogenic cell transplantation (MT), a potential therapy for Duchenne muscular dystrophy, can restore dystrophin expression in muscles. Because allogeneic MT is highly resistant to peripheral tolerance, we proposed to induce central tolerance. However, given its immunogenicity, we asked whether central tolerance to donor major histocompatibility complex would allow long-term expression of dystrophin, a tissue-specific neoantigen in dystrophic recipients. METHODS: Central tolerance was induced in C57BL/10J mdx (dystrophic) mice by allogeneic bone marrow transplantation (BMT) after conditioning with either lethal total body irradiation (TBI) or an established nonmyeloablative protocol (anti-CD154, anti-CD8 mAbs, and low-dose TBI). Recipients subsequently received donor-strain MT or skin grafts. RESULTS: Long-term hematopoietic chimeras generated using either lethal TBI or the nonmyeloablative regimen were tolerant to donor skin grafts and both primary and secondary donor MT (>90 days). Myogenic cell transplantation survival was decreased when chimerism was transient, which was most common with nonmyeloablative conditioning and fully rather than haplo-mismatched donors. Interestingly, regardless of conditioning, MT was associated with localized muscle infiltration with Foxp3CD4, CD25CD4, and PerforinCD8 cells, whereas skin grafts lacked infiltration. CONCLUSIONS: Central tolerance achieved using regimens that eliminate nearly all endogenous peripheral lymphocytes (i.e., lethal irradiation) or a nonmyeloablative protocol that depleted peripheral CD8 cells, results in lymphocytic infiltration in muscles that received MT but not in skin allografts. This suggests that muscle-specific infiltration may result from lack of negative selection for peripheral neoantigens in the thymus after BMT and that tolerance after MT may rely on peripheral regulatory mechanisms.     

Hyperkalemic cardiac arrest after cardiopulmonary bypass in a child with unsuspected duchenne muscular dystrophy

Adverse reactions to volatile anesthetics and depolarizing muscle relaxants can occur in patients with Duchenne muscular dystrophy (DMD) resulting in acute rhabdomyolysis and hyperkalemia. We report a case of hyperkalemic cardiac arrest after cardiac surgery using cardiopulmonary bypass in a child with unsuspected DMD. Early diagnosis and management of hyperkalemia resulted in a successful outcome. Genetic testing confirmed the diagnosis of DMD. We recommend a thorough preoperative investigation, including creatine kinase estimation, in children with a history of unexplained motor delay.