A study of changes in levator muscle in congenital ptosis.

PURPOSE: To study microscopic and ultrastructural changes of levator palpebrae superioris (LPS) muscle in congenital ptosis. METHODS: In this prospective observational study, LPS muscle was studied in 77 eyelids with congenital ptosis; 35-simple congenital ptosis (SCP), 12-Marcus Gunn jaw winking phenomenon (MGJWP), and 30-blepharophimosis epicanthus inversus syndrome (BPES). Light microscopy, enzyme histochemistry, immunohistochemistry and electron microscopy were performed, and results were analyzed. RESULTS: Muscle fibers were detected in 83.33% of MGJWP, 22.86% of SCP and 16.67% of BPES eyelids. Fibers were detected significantly more in individuals with moderate ptosis, LPS action > 4 mm, present eyelid crease and eyelid fold. Severe endomysial and perimysial fibrosis was seen significantly more in individuals with MGJWP. Fat infiltration and nuclei internalization were seen in all three groups. The absence of degenerating or regenerating fibers and inflammatory cells, normal staining pattern on immunohistochemistry and absence of accumulation of any abnormal substance were found in all three groups. Abnormal mitochondrial staining pattern was seen occasionally in three groups. On electron microscopy, muscle was detected in 1 SCP eyelid and 8 MGJWP eyelids out of which 4 had myofibrillary disruption. All other eyelids where muscle fibers were not detected had only fibrocollagenous tissue. CONCLUSION: Fibrocollagenous tissue predominated in all the cases, and muscle fibers detected correlated inversely with the severity of ptosis. The absence of degenerating, regenerating fibers and inflammatory cells supported the theory of dysgenesis of muscle. However, internalization of nucleus seen in all the subtypes is a feature favoring dystrophy.

The impact of prolapse mesh on vaginal smooth muscle structure and function.

OBJECTIVE: To evaluate the impact of prolapse meshes on vaginal smooth muscle structure (VaSM) and function, and to evaluate these outcomes in the context of the mechanical and textile properties of the mesh. DESIGN: Three months following the implantation of three polypropylene prolapse meshes with distinct textile and mechanical properties, mesh tissue explants were evaluated for smooth muscle contraction, innervation, receptor function, and innervation density. SETTING: Magee-Womens Research Institute at the University of Pittsburgh. POPULATION: Thirty-four parous rhesus macaques of similar age, parity, and pelvic organ prolapse quantification (POP-Q) scores. METHODS: Macaques were implanted with mesh via sacrocolpopexy. The impact of Gynemesh(™)  PS (Ethicon; n = 7), Restorelle(®) (Coloplast; n = 7), UltraPro(™) parallel and UltraPro(™) perpendicular (Ethicon; n = 6 and 7, respectively) were compared with sham-operated controls (n = 7). Outcomes were analysed by Kruskal-Wallis ANOVA, Mann-Whitney U-tests and multiple regression analysis (P < 0.05). MEAN OUTCOME MEASURES: Vaginal tissue explants were evaluated for the maximum contractile force generated following muscle, nerve, and receptor stimulation, and for peripheral nerve density. RESULTS: Muscle myofibre, nerve, and receptor-mediated contractions were negatively affected by mesh only in the grafted region (P < 0.001, P = 0.002, and P = 0.008, respectively), whereas cholinergic and adrenergic nerve densities were affected in the grafted (P = 0.090 and P = 0.008, respectively) and non-grafted (P = 0.009 and P = 0.005, respectively) regions. The impact varied by mesh property, as mesh stiffness was a significant predictor of the negative affect on muscle function and nerve density (P < 0.001 and P = 0.013, respectively), whereas mesh and weight was a predictor of receptor function (P < 0.001). CONCLUSIONS: Mesh has an overall negative impact on VaSM, and the effects are a function of mesh properties, most notably, mesh stiffness. TWEETABLE ABSTRACT: Prolapse mesh affects vaginal smooth muscle.

A New Surgical Model of Skeletal Muscle Injuries in Rats Reproduces Human Sports Lesions.

Skeletal muscle injuries are the most common sports-related injuries in sports medicine. In this work, we have generated a new surgically-induced skeletal muscle injury in rats, by using a biopsy needle, which could be easily reproduced and highly mimics skeletal muscle lesions detected in human athletes. By means of histology, immunofluorescence and MRI imaging, we corroborated that our model reproduced the necrosis, inflammation and regeneration processes observed in dystrophic mdx-mice, a model of spontaneous muscle injury, and realistically mimicked the muscle lesions observed in professional athletes. Surgically-injured rat skeletal muscles demonstrated the longitudinal process of muscle regeneration and fibrogenesis as stated by Myosin Heavy Chain developmental (MHCd) and collagen-I protein expression. MRI imaging analysis demonstrated that our muscle injury model reproduces the grade I-II type lesions detected in professional soccer players, including edema around the central tendon and the typically high signal feather shape along muscle fibers. A significant reduction of 30% in maximum tetanus force was also registered after 2 weeks of muscle injury. This new model represents an excellent approach to the study of the mechanisms of muscle injury and repair, and could open new avenues for developing innovative therapeutic approaches to skeletal muscle regeneration in sports medicine.

Molecular basis of carcinogenicity of tungsten alloy particles.

The tungsten alloy of 91% tungsten, 6% nickel and 3% cobalt (WNC 91-6-3) induces rhabdomyosarcoma when implanted into a rat thigh muscle. To investigate whether this effect is species-specific human HSkMc primary muscle cells were exposed to WNC 91-6-3 particles and responses were compared with those from a rat skeletal muscle cell line (L6-C11). Toxicity was assessed by the adenylate kinase assay and microscopy, DNA damage by the Comet assay. Caspase 3 enzyme activity was measured and oligonucleotide microarrays were used for transcriptional profiling. WNC 91-6-3 particles caused toxicity in cells adjacent to the particles and also increased DNA strand breaks. Inhibition of caspase 3 by WNC 91-6-3 occurred in rat but not in human cells. In both rat and human cells, the transcriptional response to WNC 91-6-3 showed repression of transcripts encoding muscle-specific proteins with induction of glycolysis, hypoxia, stress responses and transcripts associated with DNA damage and cell death. In human cells, genes encoding metallothioneins were also induced, together with genes related to angiogenesis, dysregulation of apoptosis and proliferation consistent with pre-neoplastic changes. An alloy containing iron, WNF 97-2-1, which is non-carcinogenic in vivo in rats, did not show these transcriptional changes in vitro in either species while the corresponding cobalt-containing alloy, WNC 97-2-1 elicited similar responses to WNC 91-6-3. Tungsten alloys containing both nickel and cobalt therefore have the potential to be carcinogenic in man and in vitro assays coupled with transcriptomics can be used to identify alloys, which may lead to tumour formation, by dysregulation of biochemical processes.

ACTN3 R577X genotypes associate with Class II and deepbite malocclusions.

INTRODUCTION: α-Actinins are myofibril anchor proteins that influence the contractile properties of skeletal muscles. ACTN2 is expressed in slow type I and fast type II fibers, whereas ACTN3 is expressed only in fast fibers. ACTN3 homozygosity for the 577X stop codon (ie, changing 577RR to 577XX, the R577X polymorphism) results in the absence of α-actinin-3 in about 18% of Europeans, diminishes fast contractile ability, enhances endurance performance, and reduces bone mass or bone mineral density. We have examined ACTN3 expression and genetic variation in the masseter muscle of orthognathic surgery patients to determine the genotype associations with malocclusion. METHODS: Clinical information, masseter muscle biopsies, and saliva samples were obtained from 60 subjects. Genotyping for ACTN3 single nucleotide polymorphisms, real-time polymerase chain reaction quantitation of muscle gene message, and muscle morphometric fiber type properties were compared to determine statistical differences between genotype and phenotype. RESULTS: Muscle mRNA expression level was significantly different for ACTN3 single nucleotide polymorphism genotypes (P <0.01). The frequency of ACTN3 genotypes was significantly different for the sagittal and vertical classifications of malocclusion, with the clearest association being elevated 577XX genotype in skeletal Class II malocclusion (P = 0.003). This genotype also resulted in significantly smaller diameters of fast type II fibers in masseter muscles (P = 0.002). CONCLUSION: ACTN3 577XX is overrepresented in subjects with skeletal Class II malocclusion, suggesting a biologic influence during bone growth. ACTN3 577XX is underrepresented in subjects with deepbite malocclusion, suggesting that muscle differences contribute to variations in vertical facial dimensions.

Wearing of complete dentures reduces slow fibre and enhances hybrid fibre fraction in masseter muscle.

Edentulous conditions and use of complete dentures alter the function of jaw muscles, which is presumably reflected in the myosin heavy chain (MyHC) isoform composition. This study is the first dealing with MyHC isoforms expression in edentulous persons with the aim to clarify to which extent the decreased functional load following teeth loss contributes to the changed muscle phenotype during ageing. We analysed MyHC expression in old masseter muscle at decreased and full functional load by comparing age-matched edentulous and dentate subjects. Edentulous subjects had upper and lower complete dentures. Dentate subjects had at least 24 natural teeth in continuous dental arches with two molars present in each quadrant and normal intermaxillary relationship. The adaptive response to the reduced masticatory load was lower numerical and area proportion of MyHC-1 expressing fibres and higher numerical proportion of hybrid fibres in edentulous compared with dentate subjects with no significant difference in the proportion of MyHC-neo-expressing fibres between both groups. We conclude that the observed differences in the proportion of fibre types between denture wearers and dentate subjects cannot be ascribed to degenerative changes intrinsic to the ageing muscle, but to functional differences in muscle activity and to morphological alterations of stomatognathic system accompanying the complete teeth loss.

Myotubes differentiate optimally on substrates with tissue-like stiffness: pathological implications for soft or stiff microenvironments.

Contractile myocytes provide a test of the hypothesis that cells sense their mechanical as well as molecular microenvironment, altering expression, organization, and/or morphology accordingly. Here, myoblasts were cultured on collagen strips attached to glass or polymer gels of varied elasticity. Subsequent fusion into myotubes occurs independent of substrate flexibility. However, myosin/actin striations emerge later only on gels with stiffness typical of normal muscle (passive Young's modulus, E approximately 12 kPa). On glass and much softer or stiffer gels, including gels emulating stiff dystrophic muscle, cells do not striate. In addition, myotubes grown on top of a compliant bottom layer of glass-attached myotubes (but not softer fibroblasts) will striate, whereas the bottom cells will only assemble stress fibers and vinculin-rich adhesions. Unlike sarcomere formation, adhesion strength increases monotonically versus substrate stiffness with strongest adhesion on glass. These findings have major implications for in vivo introduction of stem cells into diseased or damaged striated muscle of altered mechanical composition.

The use of established skeletal muscle cell lines to assess potential toxicity from embedded metal fragments.

The use of novel materials on the modern battlefield, both in military munitions as well as in Improvised Explosive Devices, opens the possibility of wounds with embedded fragments whose health effects and toxicity characteristics have not been fully investigated, if at all. The costly and time-consuming nature of standard two-year lifespan studies prohibits the testing of many materials. In this report, we describe an in vitro system for rapidly assessing potential toxicity of metals and metal mixtures. Using rat L6 and mouse C2C12 skeletal muscle cells and tests for cellular viability, we have shown that two militarily relevant tungsten alloy mixtures (W/Ni/Co and W/Ni/Fe) significantly decreased the metabolic viability of rat L6 cells, whereas the viability of mouse C2C12 cells was not affected by W/Ni/Co and only slightly affected by W/Ni/Fe. In addition, viability assessed through lysosomal uptake of neutral red dye was not affected by either mixture in either cell line indicating that the mitochondria may be the target organelle of these unique metal mixtures. Development of this in vitro screening system may provide a procedure by which the potential toxicities of embedded metal fragments can be rapidly assessed.

Exodontia-induced muscular hypofunction by itself or associated to chronic stress impairs masseter muscle morphology and its mitochondrial function.

Stress is associated with orofacial pain sensitivity and is qualified as a temporomandibular disorder risk factor. During stressful periods, painful thresholds of masticatory muscles in individuals suffering muscle facial pain are significantly lower than in controls, but the exact physiologic mechanism underlying this relation remains unclear. Our hypothesis is that chronic unpredictable stress and masticatory hypofunction induce morphologic and metabolic masseter muscle changes in rats. For test this hypothesis, adult Wistar rats were submitted to chronic unpredictable stress and/or exodontia of left molars and the left masseter muscle was removed for analysis. The parameters evaluated included ultrastructure, oxidative level, metabolism activity and morphological analysis in this muscle. Our data show by histological analysis, that stress and exodontia promoted a variation on diameters and also angled contours in masseter fibers. The masticatory hypofunction increased oxidative metabolism as well as decreased reactive species of oxygen in masseter muscle. The ultrastructural analysis of muscle fibers showed disruption of the sarcoplasmic reticulum cisterns in certain regions of the fiber in stress group, and the disappearance of the sarcoplasmic reticulum membrane in group with association of stress and exodontia. Our findings clarify mechanisms by which chronic stress and masticatory hypofunction might be involved in the pathophysiology of muscular dysfunctions. Masticatory hypofunction influenced oxidative stress and induced oxidative metabolism on masseter muscle, as well as altered its fiber morphology. Chronic stress presented malefic effect on masseter morphology at micro and ultra structurally. When both stimuli were applied, there were atrophic fibers and a complete mitochondrial derangement.

POLG1 mutations manifesting as autosomal recessive axonal Charcot-Marie-Tooth disease.

BACKGROUND: Although a molecular diagnosis is possible in most patients having Charcot-Marie-Tooth disease (CMT), recessively inherited and axonal neuropathies still present a diagnostic challenge. OBJECTIVE: To determine the cause of axonal CMT type 2 in 3 siblings. DESIGN: Case report. SETTING: Academic research. PARTICIPANTS: Three siblings who subsequently developed profound cerebellar ataxia. MAIN OUTCOME MEASURES: Muscle biopsy specimen molecular genetic analysis of the POLG1 (polymerase gamma-1) gene, as well as screening of control subjects for POLG1 sequence variants. RESULTS: Cytochrome c oxidase deficient fibers and multiple deletions of mitochondrial DNA were detected in skeletal muscle. Three compound heterozygous substitutions were detected in POLG1. CONCLUSION: Even in the absence of classic features of mitochondrial disease, POLG1 should be considered in patients having axonal CMT that may be associated with tremor or ataxia.

Biocompatibility of four common orthopedic biomaterials following neuroelectromyostimulation: An in-vivo study.

Despite the worldwide high prevalence of total joint arthroplasty (TJA), life expectancy of prosthesis remains limited by mechanical and chemical constraint which promote wear debris production, surrounding tissues damage and finally prosthesis loosening. Such results could be amplified by neuro-myoelectrostimulation (NMES; widely used to reduce neuromuscular deficits observed following TJA surgery). It was previously described in an in vivo experiment that interactions between NMES and Ti6Al4V implant are deleterious for both implant and surrounding muscles. The purpose of the present study was to compare the biocompatibility of four common orthopedic biomaterials, two metallic (Ti6Al4V, CrCo) and two nonmetallic (PEEK, Al2 O3 ) alloys, fixed on rat tibial crest in which the surrounding muscles were electrostimulated. Muscle cell death rate was not found significantly increased, with or without electrical stimulation for nonmetallic implants. Contrary to Ti6Al4V alloy, the CrCo implant did not induce destruction of the surrounding muscle. However, cell viability decreased for both metallic alloys when NMES was applied but within a greater significant extent for Ti6Al4V implant. Otherwise, when NMES was applied, implant-to-bone adhesion significantly decreased for Ti6Al4V while no significant difference was found for PEEK, Al2 O3 , and CrCo. Statistical analyses reveal also a lesser adhesion strength for Ti6Al4V compared with CrCo when NMES was applied. Selecting the most suitable material in term of biocompatibility remains a major concern and non-metallic materials seems to be more appropriated in regard to electrical currents used for post TJA care. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1156-1164, 2018.

Breaking biological barriers with a toothbrush.

Toothbrushing exposes epithelia and other tissues of the oral cavity to mechanical stress. Here, we investigated whether brushing induces cell wounding--plasma membrane disruption--in epithelial and other cell types in the oral cavity. Brushing of the gingivae and tongues of rats resulted in a striking increase in the number of cells positive for a marker of disruption injury. These cells included those in all strata of the gingival epithelium, and in the skeletal muscle of the tongue. Additionally, we found that brushing resulted in an increase in c-fos expression by junctional epithelial and skeletal muscle cells. Epithelial barrier function, however, was not overtly affected by brushing, despite the observed individual injuries to cells. We concluded that brushing disrupts cell plasma membrane barriers in the oral cavity and activates gene expression events that may lead to local adaptive changes in tissue architecture beneficial to gingival health.

Leiomyomatous hamartoma presenting as a congenital epulis.

An otherwise-healthy 11-month-old white girl presented with a polyp-like lesion on the anteromedial part of the maxillary alveolar ridge. It looked like a congenital epulis, but histological examination showed fascicles of smooth muscle cells dispersed in collagenous stroma with a few peripheral nerve bundles that were intermingled with smooth muscle fibres. The muscle cells stained strongly for desmin and alpha-smooth-muscle actin. However, S-100 was found only in peripheral nerve bundles. It was therefore a leiomyomatous hamartoma.

An interesting case report of Morvan's syndrome from the Indian subcontinent.

The French physician Augustine Marie Morvan first used the term 'la choriotae fibrillare' to describe a syndrome characterized by peripheral nerve hyperexcitability, dysautonomia, insomnia and fluctuating delirium. There are no published reports of the condition from the Indian subcontinent. We report the first such case from the region. Our patient, a 24-year-old male, presented with easy fatigability and stiffness in both the calves for 18 months; continuous twitching of muscles of all four limbs and jaw for two months; hyperhydrosis, palpitations, urinary symptoms, burning dysesthesia in hands, insomnia and abnormal sleep behavior for about a month. Patient had bilateral hyper-reflexia with extensor plantar on the right and equivocal response on the left. Electromyography revealed continuous muscle fiber activity. Thyroid function test, electroencephalography, computerized tomography scan (head) and routine cerebrospinal fluid analysis were normal. The patient showed marked clinical and electrophysiological improvement on prednisolone along with symptomatic therapy over the next two months.

Preventive Effects of Poloxamer 188 on Muscle Cell Damage Mechanics Under Oxidative Stress.

High oxidative stress can occur during ischemic reperfusion and chronic inflammation. It has been hypothesized that such oxidative challenges could contribute to clinical risks such as deep tissue pressure ulcers. Skeletal muscles can be challenged by inflammation-induced or reperfusion-induced oxidative stress. Oxidative stress reportedly can lower the compressive damage threshold of skeletal muscles cells, causing actin filament depolymerization, and reduce membrane sealing ability. Skeletal muscles thus become easier to be damaged by mechanical loading under prolonged oxidative exposure. In this study, we investigated the preventive effect of poloxamer 188 (P188) on skeletal muscle cells against extrinsic oxidative challenges (H2O2). It was found that with 1 mM P188 pre-treatment for 1 h, skeletal muscle cells could maintain their compressive damage threshold. The actin polymerization dynamics largely remained stable in term of the expression of cofilin, thymosin beta 4 and profilin. Laser photoporation demonstrated that membrane sealing ability was preserved even as the cells were challenged by H2O2. These findings suggest that P188 pre-treatment can help skeletal muscle cells retain their normal mechanical integrity in oxidative environments, adding a potential clinical use of P188 against the combined challenge of mechanical-oxidative stresses. Such effect may help to prevent deep tissue ulcer development.

Poloxamer 188 failed to prevent exercise-induced membrane breakdown in mdx skeletal muscle fibers.

We sought to determine the effectiveness of poloxamer 188 (P188) in protecting dystrophin-deficient, mdx skeletal muscle fiber membrane against exercise-induced breaches. mdx mice were treated with either P188 or placebo via intraperitoneal injections and run on a treadmill for 60-90 min. Membrane breakdown was quantified in cross-sections of rectus femoris muscle pretreated with Evans blue dye (in vivo). The mean % dye-penetrated muscle in the P188 and placebo groups was not significantly different in each of three trials. These results contrast with a recent report of P188 being highly effective in protecting the stretch- and dobutamine-stressed mdx heart muscle. The most likely explanations for the disparity are: (1) the exercise stress we used was beyond the protective range of P188, (2) P188 delivery and serum concentration were sub-optimal, or (3) the mdx skeletal myopathy and cardiomyopathy have fundamentally different responses to treatment.

In vitro cellular response to oxidized collagen-PLLA hybrid scaffolds designed for the repair of muscular tissue defects and complex incisional hernias.

Unique poly(l-lactic acid) (PLLA)-based scaffolds were constructed by embedding knitted PLLA yarns within a bioresorbable and differentially crosslinked three-dimensional (3D) oxidized collagen scaffold. The scaffolds were designed specifically for the repair of complex incisional abdominal wall hernias and the repair of defects within planar muscular tissues, such as the bladder. The chemical composition of the collagen matrix and the percentage of scaffold infiltration were compared for the different scaffold compositions. The results demonstrate that the incorporation of the collagen sponge within the PLLA scaffold facilitated bladder smooth muscle cell (bSMC) adhesion and proliferation. The highest dose of oxidized collagen (Oxicol) demonstrated better cell adhesion, resulting in the largest cell densities and most uniform distribution throughout the 3D collagen sponge. This formulation promoted the greatest α-smooth muscle actin (αSMA) expression detected through immunohistochemical staining and western blotting. For abdominal wall repair applications, the proliferation and differentiation of C2C12 myoblasts and myotube formation were studied. Following 7 days of myogenic induction, the greatest expression of mRNA of the myogenic markers myogenin and MRF4 was observed within the scaffolds with the highest dose of oxidized collagen, 1.5- and 3.85-fold greater expressions, respectively, compared to PLLA with unmodified collagen. Furthermore, in vitro myotube formation and MyMC expression were enhanced in the Oxicol scaffolds. We conclude that the Oxicol scaffold formulation with a high-dose oxidized collagen ratio provides enhanced myogenesis and αSMA, and the biological induction cues necessary to achieve better tissue integration, than standard PLLA scaffolds in the treatment of complex abdominal wall hernias. Copyright © 2013 John Wiley & Sons, Ltd.

Impaired primary mouse myotube formation on crosslinked type I collagen films is enhanced by laminin and entactin.

In skeletal muscle, the stem cell niche is important for controlling the quiescent, proliferation and differentiation states of satellite cells, which are key for skeletal muscle regeneration after wounding. It has been shown that type I collagen, often used as 3D-scaffolds for regenerative medicine purposes, impairs myoblast differentiation. This is most likely due to the absence of specific extracellular matrix proteins providing attachment sites for myoblasts and/or myotubes. In this study we investigated the differentiation capacity of primary murine myoblasts on type I collagen films either untreated or modified with elastin, laminin, type IV collagen, laminin/entactin complex, combinations thereof, and Matrigel as a positive control. Additionally, increased reactive oxygen species (ROS) and ROCK signaling might also be involved. To measure ROS levels with live-cell microscopy, fibronectin-coated glass coverslips were additionally coated with type I collagen and Matrigel onto which myoblasts were differentiated. On type I collagen-coated coverslips, myotube formation was impaired while ROS levels were increased. However, anti-oxidant treatment did not enhance myotube formation. ROCK inhibition, which generally improve cellular attachment to uncoated surfaces or type I collagen, enhanced myoblast attachment to type I collagen-coated coverslips and -films, but slightly enhanced myotube formation. Only modification of type I collagen films by Matrigel and a combination of laminin/entactin significantly improved myotube formation. Our results indicate that type I collagen scaffolds can be modified by satellite cell niche factors of which specifically laminin and entactin enhanced myotube formation. This offers a promising approach for regenerative medicine purposes to heal skeletal muscle wounds. STATEMENT OF SIGNIFICANCE: In this manuscript we show for the first time that impaired myotube formation on type I collagen scaffolds can be completely restored by modification with laminin and entactin, two extracellular proteins from the satellite cell niche. This offers a promising approach for regenerative medicine approaches to heal skeletal muscle wounds.

The construction of three-dimensional composite fibrous macrostructures with nanotextures for biomedical applications.

The development of modern biomedical nanotechnology requires three-dimensional macrostructures with nanotextures to meet the requirements for practical applications in intricate biological systems. Additionally, the restoration and regeneration of some specific body tissues and organs rely on the function of conductive polymers, which can provide electrical cues for cells. In this study, we fabricated three-dimensional composite nanofibre macrostructures of polycaprolactone (PCL) with different concentrations of polyaniline (PANi) by employing an improved electrospinning technology with a specially designed collector. The 3D structures possessed cap-like macrostructures with centimetre-scale thickness and interconnected pore nanotextures with nanometre-scale nanofibres. To estimate the biocompatibility of the 3D PCL/PANi composite nanofibre macrostructures, mouse myoblasts (C2C12 cells) were cultured as model cells. The initial responses of C2C12 cells to the 3D PCL/PANi composite macrostructures were significantly superior to those to pure PCL, that is, the cells exhibited typical myoblast-like morphologies with obvious pseudopodia and the moderate incorporation (less than 2.0 wt%) of conductive PANi facilitated cell proliferation, which indicated that PANi has appreciable cell affinity. Moreover, the addition of conductive PANi to the 3D composite nanofibre macrostructures considerably enhanced myoblast differentiation and myotube maturation. These results suggest that electrospun 3D PCL/PANi composite nanofibre macrostructures would have promising applications in tissue engineering.

Mice Hemizygous for a Pathogenic Mitofusin-2 Allele Exhibit Hind Limb/Foot Gait Deficits and Phenotypic Perturbations in Nerve and Muscle.

Charcot-Marie-Tooth disease type 2A (CMT2A), the most common axonal form of hereditary sensory motor neuropathy, is caused by mutations of mitofusin-2 (MFN2). Mitofusin-2 is a GTPase required for fusion of mitochondrial outer membranes, repair of damaged mitochondria, efficient mitochondrial energetics, regulation of mitochondrial-endoplasmic reticulum calcium coupling and axonal transport of mitochondria. We knocked T105M MFN2 preceded by a loxP-flanked STOP sequence into the mouse Rosa26 locus to permit cell type-specific expression of this pathogenic allele. Crossing these mice with nestin-Cre transgenic mice elicited T105M MFN2 expression in neuroectoderm, and resulted in diminished numbers of mitochondria in peripheral nerve axons, an alteration in skeletal muscle fiber type distribution, and a gait abnormality.