Effect of Citrus aurantium L. essential oil on muscle regeneration in mdx mice / Efecto del aceite esencial de Citrus aurantium L. en la regeneración muscular en ratones mdx

Duchenne muscular dystrophy (DMD) is a severe X-linked recessive disorder characterized by the progressive loss of muscular strength. Mdx mutant mice show a marked deficiency in dystrophin, which was related to muscle membrane stability. The aim of this study was to verify the possible protective anti-inflammatory effect of citrus oil on mdx muscle fibers. Thus, adult male and female mdx mice (014/06-CEEA) were divided into control and citrus-treated. After 60 days of treatment, one ml of blood was collected for creatine kinase (CK) test. Diaphragm, sternomastoideus, anterior tibial and gastrocnemius muscles were removed and processed according to histological routine methods. The observed alterations indicate a direct effect of citrus. Recent studies have improved the diagnosis of muscular diseases but with no definitions of efficient treatments. Intervention with several therapies is important to many patients presenting muscular dystrophy, which enables them to live longer and be more active, while there is no development of gene therapies.

La distrofia muscular de Duchenne (DMD) es una enfermedad grave ligada al cromosoma X, trastorno recesivo que se caracteriza por la pérdida progresiva de fuerza muscular. Mdx ratones mutantes muestran una marcada deficiencia en la distrofina, que está relacionada con la estabilidad de la membrana muscular. El objetivo de este estudio fue comprobar el posible efecto protector, antiinflamatorio del aceite de cítricos en las fibras musculares mdx. Los ratones mdx adultos machos y hembras (014/06-CEEA) se dividieron en control y cítricos tratados. Después de 60 días de tratamiento, un ml de sangre fue recogida para cuantificar la creatina quinasa (CK) de prueba. Fueron retirados y procesados los músculos diafragma, esternomastoideo, tibial anterior y gastrocnemio de acuerdo con los métodos de rutina histológica. Las alteraciones observadas indican un efecto directo de los cítricos. Estudios recientes han mejorado el diagnóstico de enfermedades musculares, pero sin definiciones de tratamientos eficaces. Intervención con varias terapias es importante para muchos pacientes que presentan distrofia muscular, lo que les permite vivir más y ser más activos, mientras no exista desarrollo de terapias génicas.

Terminal schwann cell distribution at the neuromuscular junction of the dystrophin-deficient MDX mice

The murine model of muscular dystrophy, the mdx mice, is widely used to study the pathogenesis of muscular dystrophies. These mice suffer an X-linked dystrophin deficiency and present cycles of muscle fiber degeneration-regeneration beginning at 21 days of age. At the present, we studied neuromuscular junction organization in the sternomastoid muscle of mdx mice, focusing on the distribution of terminal Schwann cells during early development and adults. Seven and 14 days after birth (n=200 endplates for each age), before the onset of muscle degeneration-regeneration, fluorescence confocal microscopy showed that there were no detectable differences in the pattern of Schwann cell distribution in the mdx compared to controls of the same age. Schwann cells had a diffuse pattern of distribution, covering the plaques of acetylcholine receptors. In adult mdx muscles, terminal Schwann cell processes filled the center of acetylcholine receptors islands, similar to nerve terminal distribution, at the majority of the junctions (n=200; 100%). Conversely, all of the adult control junctions (n=200) showed continuous processes of Schwann cells covering the continuous branches of acetylcholine receptors. These observations indicate that remodeling of the three components of the neuromuscular junction occurs only after the onset of the cycles of muscle fiber degeneration-regeneration, in the mdx mice.

Sstructural biology of the dystrophin-deficient muscle fiver

The discovery of dystrophin and its gene had led to major advances in our understanding of the molecular basis of Duchenne, Becker and other muscular dystrophies related to the dystrophin-associated protein complex. The concept that dystrophin has a mechanical function in stabilizing the muscle fiber membrane has expanded in the last five years. The dystrophin-glycoprotein complex is now considered a multifunctional complex that contains molecules involved in signal transduction cascades important for cell survival. The roles of dystrophin and the dystrophin-glycoprotein complex in positioning and anchoring receptors and ion channels is also important, and much of what is known about these functions is based on studies of the neuromuscular synapse. In this review, we discuss the components and the cellular signaling molecules associated with the dystrophin-glycoprotein complex. We then focus on the molecular organization of the neuromuscular junction and its structural organization in the dystrophin-deficient muscle fibers of mdx mice, a well-established experimental model of Duchenne muscular dystrophy.

Correlation between ultrastructural and molecular changes in denervated muscle: a paradigm based on functional eletrical stomulation

Soon after denervation, skeletal muscle undergoes ultrastructural and molecular changes that ultimately lead to muscle atrophy and cell death. Functional electrical stimulation (FES) is effective in preventing the artrophy of denervated muscles, but it is unclear whether FES can prevent the progression of ultrastructural changes in the sarcotubular system and cell death after denervation. In this work, we developed a model to study the effects of FES on the ultrastructural changes in the sarcotubular system and the cell death which follow skeletal muscle denervation. The right sciatic nerve of adult rats was sectioned and after 1 day, and 1, 2 and 3 weeks the tibialis anterioris muscle was electricall stimulated. FES was done for 1, 2, 3, 10 and 20 weeks after denervation. The stimuli (10 Hz) were given for 10s followed by a 10s rest for a total of 30 min/day. Transmission electron microscopy showed that progressive dilatation of the sarcotubular system, as well as signs of cell death, were prevented when stimulation was started one day or one week after denervation. This model could be useful for undertanding the correlation between the structural changes and the molecules involved in the dilatation of the sarcotubular system or cell death.

An ultrastructural study of the temporal progress of neuromuscular junction regeneration after sciatic nerve transection and tubulization repair

The aim of this investigation was to study the timecourse of motor endplates in the extensor digitorum logus (EDL) muscle after peripheral nerve transection and tubulization repair. Adult male C57BL/6J mice received sciatic nerve transection at midhigh level and both proximal and distal nerve stumps were stured into a 5-mm long polyethylene tube to bridge a final nerve gap distance of 3mm. At 2 to 40 weeks postoperatively the EDL muscle on the operated side was fixed in situ and processed histochemically for visualization of cholinesterase-rich sites. Groups of muscle fibers containing motor endplates were then processed for electron microscopy (EM). Two weeks after tubulization the EDL muscle was entirely denervated: Schwann cells came into contact with the post-synaptic folds of the muscle fibers; there was an increase in concentration of collagen and fibroblasts at the synaptic sites. Reinnervation began 4 weeks after tube implantation, when the first axon terminals established contact with a small portion of the specialized subneural region, many synaptic folds were still covered by collagen fibers and, in some cases, Schwann cells remained interposed between the folds and the synaptic terminals. Twelve weeks after surgery all the neuromuscular junctions examined were reinnervated and looked normal; motor terminals were alawys located at the primary synaptic clefts, although rarely some subneural folds lacking nerve terminals were seen. At 12 to 40 weeks all motor endplates appeared normally innervated by EM criteria.