Normal Muscle Function Research Articles

25OH Vitamin D Is No Associated with Muscle Function Loss in Adults and Elderly Patients Undergoing Hemodialysis.

In patients with chronic kidney disease, sarcopenia is associated with dialysis treatment, accelerated protein catabolism, and high energy demand. Thus, this study aimed to assess the association between 25-OH vitamin D concentrations and muscle function in patients undergoing hemodialysis. A cross-sectional study. Performed in a hemodialysis clinic. 79 adult and elderly patients undergoing hemodialysis. The sample was divided according to the SARC-F definition, being 55 patients allocated in the SARC-F <4 group and 24 in the SARC-F ≥4 group. Normal 25-OH vitamin D concentrations was considered when ≥30 ng/dL. Vitamin D concentrations and number of patients with low or normal muscle function did not differ between the groups. There was no correlation between SARC-F and 25-OH vitamin D levels (r: -0.09, p=0.42). 25-OH vitamin D has no association with muscle function loss in adults and elderly patients undergoing hemodialysis.

Effect of dry needling on lumbar muscle stiffness in patients with low back pain: A double blind, randomized controlled trial using shear wave elastography

ABSTRACT Background Dry needling treatment focuses on restoring normal muscle function in patients with musculoskeletal pain; however, little research has investigated this assertion. Shear wave elastography (SWE) allows quantification of individual muscle function by estimating both resting and contracted muscle stiffness. Objective To compare the effects of dry needling to sham dry needling on lumbar muscle stiffness in individuals with low back pain (LBP) using SWE. Methods Sixty participants with LBP were randomly allocated to receive one session of dry needling or sham dry needling treatment to the lumbar multifidus and erector spinae muscles on the most painful side and spinal level. Stiffness (shear modulus) of the lumbar multifidus and erector spinae muscles was assessed using SWE at rest and during submaximal contraction before treatment, immediately after treatment, and 1 week later. Treatment effects were estimated using linear mixed models. Results After 1 week, resting erector spinae muscle stiffness was lower in individuals who received dry needling than those that received sham dry needling. All other between-groups differences in muscle stiffness were similar, but non-significant. Conclusion Dry needling appears to reduce resting erector spinae muscle following treatment of patients with LBP. Therefore, providers should consider the use of dry needling when patients exhibit aberrant stiffness of the lumbar muscles.

A recurrent RYR1 mutation associated with early-onset hypotonia and benign disease course

The ryanodine receptor RyR1 is the main sarcoplasmic reticulum Ca2+ channel in skeletal muscle and acts as a connecting link between electrical stimulation and Ca2+-dependent muscle contraction. Abnormal RyR1 activity compromises normal muscle function and results in various human disorders including malignant hyperthermia, central core disease, and centronuclear myopathy. However, RYR1 is one of the largest genes of the human genome and accumulates numerous missense variants of uncertain significance (VUS), precluding an efficient molecular diagnosis for many patients and families. Here we describe a recurrent RYR1 mutation previously classified as VUS, and we provide clinical, histological, and genetic data supporting its pathogenicity. The heterozygous c.12083C>T (p.Ser4028Leu) mutation was found in thirteen patients from nine unrelated congenital myopathy families with consistent clinical presentation, and either segregated with the disease in the dominant families or occurred de novo. The affected individuals essentially manifested neonatal or infancy-onset hypotonia, delayed motor milestones, and a benign disease course differing from classical RYR1-related muscle disorders. Muscle biopsies showed unspecific histological and ultrastructural findings, while RYR1-typical cores and internal nuclei were seen only in single patients. In conclusion, our data evidence the causality of the RYR1 c.12083C>T (p.Ser4028Leu) mutation in the development of an atypical congenital myopathy with gradually improving motor function over the first decades of life, and may direct molecular diagnosis for patients with comparable clinical presentation and unspecific histopathological features on the muscle biopsy.

The regulatory light chain mediates inactivation of myosin motors during active shortening of cardiac muscle

The normal function of heart muscle depends on its ability to contract more strongly at longer length. Increased venous filling stretches relaxed heart muscle cells, triggering a stronger contraction in the next beat- the Frank-Starling relation. Conversely, heart muscle cells are inactivated when they shorten during ejection, accelerating relaxation to facilitate refilling before the next beat. Although both effects are essential for the efficient function of the heart, the underlying mechanisms were unknown. Using bifunctional fluorescent probes on the regulatory light chain of the myosin motor we show that its N-terminal domain may be captured in the folded OFF state of the myosin dimer at the end of the working-stroke of the actin-attached motor, whilst its C-terminal domain joins the OFF state only after motor detachment from actin. We propose that sequential folding of myosin motors onto the filament backbone may be responsible for shortening-induced de-activation in the heart.

The Assessment of Muscle Mass and Function in Patients with Long-Standing Rheumatoid Arthritis.

Muscular dysfunction in rheumatoid arthritis (RA) can affect the quality of life and comorbidities. We enrolled 320 patients with RA, and evaluated their muscle mass, grip strength, and physical performance. Seven (2.2%) and 21 RA patients (6.6%) had sarcopenia, as defined by the European and Asian Working Group for Sarcopenia (EWGS and AWGS), respectively; 54 patients (16.9%) were determined to have low muscle mass with normal muscle function, as defined by the EWGS; 38 patients (11.9%) reported sarcopenia by SARC-F questionnaire. Male sex (odds ratio (OR) 140.65), low body mass index (BMI) (OR 0.41), and use of tumor necrosis factor (TNF) inhibitors (OR 4.84) were associated with a low muscle mass as defined by the EWGS, while male sex, old age, and low BMI were associated with sarcopenia as defined by the AWGS. Old age (OR 1.11), high BMI (OR 1.13), and a high Disease Activity Score 28 (OR 1.95) were associated with sarcopenia as reported on the SARC-F. Male, low BMI, and use of TNF inhibitors were associated with a low muscle mass, while male sex, old age, and low BMI were associated with sarcopenia in patients with long-standing RA.

Altered Ca2+ Handling and Oxidative Stress Underlie Mitochondrial Damage and Skeletal Muscle Dysfunction in Aging and Disease.

Skeletal muscle contraction relies on both high-fidelity calcium (Ca2+) signals and robust capacity for adenosine triphosphate (ATP) generation. Ca2+ release units (CRUs) are highly organized junctions between the terminal cisternae of the sarcoplasmic reticulum (SR) and the transverse tubule (T-tubule). CRUs provide the structural framework for rapid elevations in myoplasmic Ca2+ during excitation–contraction (EC) coupling, the process whereby depolarization of the T-tubule membrane triggers SR Ca2+ release through ryanodine receptor-1 (RyR1) channels. Under conditions of local or global depletion of SR Ca2+ stores, store-operated Ca2+ entry (SOCE) provides an additional source of Ca2+ that originates from the extracellular space. In addition to Ca2+, skeletal muscle also requires ATP to both produce force and to replenish SR Ca2+ stores. Mitochondria are the principal intracellular organelles responsible for ATP production via aerobic respiration. This review provides a broad overview of the literature supporting a role for impaired Ca2+ handling, dysfunctional Ca2+-dependent production of reactive oxygen/nitrogen species (ROS/RNS), and structural/functional alterations in CRUs and mitochondria in the loss of muscle mass, reduction in muscle contractility, and increase in muscle damage in sarcopenia and a wide range of muscle disorders including muscular dystrophy, rhabdomyolysis, central core disease, and disuse atrophy. Understanding the impact of these processes on normal muscle function will provide important insights into potential therapeutic targets designed to prevent or reverse muscle dysfunction during aging and disease.

Finite element analysis of the stress released by buccinator muscle in the mandibular dental arch during sucking habits

ObjectivesThe effect of buccinator muscle on the mandible need to be more clarified. Finite element method used to estimate the effect of the buccinator during abnormal function on the size and shape of the mandible. MethodsThree-dimensional model of human mandible using Finite element analysis referring to dry normal mandible with teeth as a template, The mechanical characteristic of the materials were supposed to be homogenous, isotropic, and linear elastic. Auto mesh order used to discredit the model under analysis to numerous elements; every element includes numbers of apexes called nodes; the association of elements and nodes called the finite element mesh. The force of (2 ​gm/cm2) had been applied perpendicular to buccal surface of posterior teeth within the mandible representing normal buccinators muscle function on the mandible. While for simulation of abnormal suckling, buccinators muscle force (21 ​gm∖cm2) applied to the same area. Resultsabnormal size and shape of the mandible with malocclusion especially at the posterior teeth area in transverse direction in addition to backward pressure on the chin and anterior teeth result from abnormal suckling force. ConclusionIt could be concluded that abnormal function of buccinators during growth and development could result in size and shape variation of the mandible with concomitant malocclusion.

Heterochronic Plasma Transfer Alters Proteostatic Maintenance in Skeletal Muscle

Studies using heterochronic blood transfer (HBT) and heterochronic plasma transfer (HPT) show that circulating factors in young blood and plasma can rejuvenate the ability of aged skeletal muscle to respond to damage. Additionally, the transfer of old blood and plasma to young mice inhibits skeletal muscle regeneration. These changes in the ability of skeletal muscle to regenerate in response to modifications in the systemic environment are largely mediated by satellite cells. However, the role of satellite cells in maintaining normal muscle function is unclear. Therefore, how the systemic environment influences skeletal muscle in the absence of extreme muscle damage is still unknown. Proteostatic maintenance, which includes protein synthesis and breakdown, is necessary for cellular stability in skeletal muscle. One measure of proteostatic maintenance is protein:DNA ratio (i.e. how much protein is synthesized for cellular maintenance verses cellular proliferation). Here we determined if altering the systemic environment of old mice with young plasma and the systemic environment of young mice with old plasma would change proteostatic maintenance of skeletal muscle. We hypothesized that compared to old mice that receive old plasma (OOp), old mice that underwent HPT from young mice (OYp) would improve proteostatic maintenance. Additionally, we hypothesized that compared to young mice that receive young plasma (YYp), young mice that underwent HPT from old mice (YOp) would decrease proteostatic maintenance. To test this, we implanted young (5-month, n=3 YYp and 5 YOp) and old (24-months, n=5 OOp, and 5 OYp) C57BL/6J mice with a jugular catheter. All mice underwent heterochronic plasma transfer (HPT), receiving 100μl plasma injections, every three days for 24 days. The day before HPT, mice began stable isotope labeling with a bolus injection of 99% deuterium oxide (D2O) followed by 8% D2O-enriched drinking water. After 4 weeks, the quadriceps, gastrocnemius, and tibialis anterior muscles were harvested and analyzed for DNA and protein synthesis to calculate the protein:DNA ratios. The protein:DNA ratio for the mitochondrial fraction trended toward a higher ratio in the tibialis anterior of the OYp versus OOp (11.93 ± 1.161 and 8.928 ± 1.128, respectively: p=0.10). The protein:DNA ratio for the myofibrillar fraction trended toward being lower in the gastrocnemius of the YOp compared to YYp (8.338 ± 0.429 and 6.281 ± 0.737, respectively: p=0.06). These results suggest that manipulating the systemic environment with young or old plasma can change proteostatic maintenance of skeletal muscle so that the muscle reflects the systemic environment. Therefore, strategies to improve the systemic environment, like with exercise, may be a feasible strategy to improve proteostatic maintenance in aged skeletal muscle. Further research is needed to determine what circulating factors alter protein and DNA turnover in skeletal muscle.

Evolving Roles of Muscle-Resident Fibro-Adipogenic Progenitors in Health, Regeneration, Neuromuscular Disorders, and Aging.

Normal skeletal muscle functions are affected following trauma, chronic diseases, inherited neuromuscular disorders, aging, and cachexia, hampering the daily activities and quality of life of the affected patients. The maladaptive accumulation of fibrous intramuscular connective tissue and fat are hallmarks of multiple pathologies where chronic damage and inflammation are not resolved, leading to progressive muscle replacement and tissue degeneration. Muscle-resident fibro-adipogenic progenitors are adaptable stromal cells with multilineage potential. They are required for muscle homeostasis, neuromuscular integrity, and tissue regeneration. Fibro-adipogenic progenitors actively regulate and shape the extracellular matrix and exert immunomodulatory functions via cross-talk with multiple other residents and non-resident muscle cells. Remarkably, cumulative evidence shows that a significant proportion of activated fibroblasts, adipocytes, and bone-cartilage cells, found after muscle trauma and disease, descend from these enigmatic interstitial progenitors. Despite the profound impact of muscle disease on human health, the fibrous, fatty, and ectopic bone tissues’ origins are poorly understood. Here, we review the current knowledge of fibro-adipogenic progenitor function on muscle homeostatic integrity, regeneration, repair, and aging. We also discuss how scar-forming pathologies and disorders lead to dysregulations in their behavior and plasticity and how these stromal cells can control the onset and severity of muscle loss in disease. We finally explore the rationale of improving muscle regeneration by understanding and modulating fibro-adipogenic progenitors’ fate and behavior.

Ca2+-mediated coupling between neuromuscular junction and mitochondria in skeletal muscle

The volitional movement of skeletal is controlled by the motor neuron at the site of neuromuscular junction (NMJ) where the retrograde signals are also passed back from muscle to the motor neuron. As the normal function of muscle largely depends on mitochondria that determine the fate of a skeletal muscle myofiber, there must exist a fine-controlled functional coupling between NMJ and mitochondria in myofibers. This mini-review discusses recent publications that reveal how spatiotemporal profiles of intracellular free Ca2+ could couple mitochondrial function with the activity of NMJ in skeletal muscle myofibers.

Costs and health resource use in patients with X-linked myotubular myopathy: insights from US commercial claims.

BACKGROUND: In X-linked myotubular myopathy (XLMTM), mutations in the MTM1 gene result in absence or dysfunction of myotubularin, a protein required for normal development, maintenance, and function of skeletal muscle. Extreme muscle weakness results in severe respiratory failure that is fatal for approximately half of XLMTM-affected children by age 18 months. Most surviving patients require invasive mechanical ventilation, feeding tubes, and wheelchairs for mobility, due to profoundly impaired motor function. Little is known about the costs of care for this rare disease. Currently, there are no approved therapies for XLMTM. OBJECTIVE: To quantify the direct medical costs and health care resource utilization (HRU) incurred by XLMTM patients and paid by commercial insurers. METHODS: A retrospective, longitudinal study was conducted using the IQVIA PharMetrics Plus commercial database of adjudicated claims for more than 140 million individuals with commercial insurance coverage in the United States. An algorithm based on demographic information, diagnosis and procedure codes, and medications was used to identify XLMTM patients younger than aged 2 years during the study period from January 1, 2006, through September 30, 2018. All-cause direct medical costs and HRU during each month were calculated. Costs were grouped as inpatient hospital admissions (including the intensive care unit or neonatal intensive care unit [NICU]); emergency department visits; outpatient services (outpatient hospital visits, office visits, physician/provider office visits, ambulatory surgeries and procedures, laboratory tests, and imaging tests); and prescription medications. Monthly costs and HRU over time were stratified by age and use of mechanical ventilation. RESULTS: 49 patients met the study criteria. All had at least 1 inpatient hospital admission, and 36 (73%) had at least 1 NICU stay. All patients received ventilation at some time during the study period, including 40 (82%) treated with invasive ventilation. Mean monthly per patient direct medical costs were highest in the first year of life ($74,831), including costs for inpatient admissions ($69,025), outpatient services ($5,266), and prescription medication ($540). Mean monthly costs were lower in the second, third, and fourth years of life ($23,207, $13,044, and $9,440, respectively). When annualized, these all-cause monthly medical costs totaled $897,978 per patient in the first year of life and nearly $1.5 million total for patients who survived the first 4 years of life. Costs were consistently highest when patients were receiving invasive ventilation and lowest when they were not receiving ventilation (i.e., before they started on ventilator support). CONCLUSIONS: This direct health care cost and HRU analysis demonstrates the substantial economic burden associated with XLMTM. Costs are highest in the first year of life and are particularly significant for patients receiving invasive ventilation. DISCLOSURES: This study was funded by Audentes Therapeutics, an Astellas Company, and was conducted by PRECISIONheor with funding from Audentes Therapeutics, an Astellas Company. Slocomb is an employee of Audentes Therapeutics, an Astellas Company; James was an employee at the time of the study. Sacks, Healey, and Cyr are employees of PRECISIONheor. Graham participated in the medical/scientific advisory board for Audentes as part of a clinical trial design for XLMTM but declares no vested interest or holdings that would represent a conflict of interest. Beggs received consulting fees from Audentes Therapeutics, for work on this study, and has received grants from Alexion Pharmaceuticals, Audentes Therapeutics, Dynacure SAS, Pfizer Pharmaceuticals, along with personal fees from Asklepios Biopharmaceutical, Inc., Ballard Biologics, Biogen, F. Hoffmann-La Roche AG, GLG, Guidepoint Global, and Kate Therapeutics, unrelated to this study. In addition, Beggs has a patent (Patent number: 10736945) for systemic gene replacement therapy for treatment of X-linked myotubular myopathy (XLMTM) licensed to Audentes Therapeutics.

Presence or Absence of Skeletal Muscle Dysfunction in Chronic Obstructive Pulmonary Disease is Associated With Distinct Phenotypes

IntroductionReduced skeletal muscle function and cognitive performance are common extrapulmonary features in Chronic Obstructive Pulmonary Disease (COPD) but their connection remains unclear. Whether presence or absence of skeletal muscle dysfunction in COPD patients is linked to a specific phenotype consisting of reduced cognitive performance, comorbidities and nutritional and metabolic disturbances needs further investigation. MethodsThirty-seven patients with COPD (grade II–IV) were divided into two phenotypic cohorts based on the presence (COPD dysfunctional, n=25) or absence (COPD functional, n=12) of muscle dysfunction. These cohorts were compared to 28 healthy, age matched controls. Muscle strength (dynamometry), cognitive performance (Trail Making Test and STROOP Test), body composition (Dual-energy X-Ray Absorptiometry), habitual physical activity, comorbidities and mood status (questionnaires) were measured. Pulse administration of stable amino acid tracers was performed to measure whole body production rates. ResultsPresence of muscle dysfunction in COPD was independent of muscle mass or severity of airflow obstruction but associated with impaired STROOP Test performance (p=0.04), reduced resting O2 saturation (p=0.003) and physical inactivity (p=0.01), and specific amino acid metabolic disturbances (enhanced leucine (p=0.02) and arginine (p=0.06) production). In contrast, COPD patients with normal muscle function presented with anxiety, increased fat mass, plasma glucose concentration, and metabolic syndrome related comorbidities (hypertension and dyslipidemia). ConclusionCOPD patients with muscle dysfunction show characteristics of a cognitive – metabolic impairment phenotype, influenced by the presence of hypoxia, whereas those with normal muscle function present a phenotype of metabolic syndrome and mood disturbances.

Optimizing the Femoral Offset for Restoring Physiological Hip Muscle Function in Patients With Total Hip Arthroplasty.

ObjectiveFemoral offset (FO) restoration is significantly correlated with functional recovery following total hip arthroplasty (THA). Accurately assessing the effects of FO changes on hip muscles following THA would help improve function and optimize functional outcomes. The present study aimed to (1) identify the impact of FO side difference on the hip muscle moment arms following unilateral THA during gait and (2) propose the optimal FO for a physiological hip muscle function.MethodsIn vivo hip kinematics from eighteen unilateral THA patients during gait were measured with a dual-fluoroscopic imaging system. The moment arms of thirteen hip muscles were calculated using CT-based 3D musculoskeletal models with the hip muscles’ lines of actions. The correlation coefficient (R) between FO and hip muscle moment arm changes compared with the non-implanted hip was calculated. We considered that the FO reconstruction was satisfactory when the abductor moment arms increased, while the extensor, adductor, and flexor moment arms decreased less than 5%.ResultsA decreased FO following THA was significantly correlated with a decrease of the abductor and external rotator moment arms during the whole gait (R > 0.5) and a decrease of extensor moment arms during the stance phase (R > 0.4). An increased FO following THA was significantly associated with shorter flexor moment arms throughout the gait (R < −0.5) and shorter adductor moment arms in the stance phase (R < −0.4). An increase in FO of 2.3–2.9 mm resulted in increased abductor moment arms while maintaining the maximum decrease of the hip muscles at less than 5.0%.ConclusionAn increase of 2–3 mm in FO could improve the abductor and external rotator function following a THA. Accurate surgical planning with optimal FO reconstruction is essential to restoring normal hip muscle function in THA patients.

Loss of H3K27me3 occurs in a large subset of embryonal rhabdomyosarcomas: Immunohistochemical and molecular analysis of 25 cases

Loss of histone 3 lysine 27 trimethylation (H3K27me3) has been described as a diagnostic marker for malignant peripheral nerve sheath tumor (MPNST), also discriminating MPNST with rhabdomyoblastic differentiation (malignant Triton tumor) from rhabdomyosarcoma (RMS).We studied the immunohistochemical expression of H3K27me3 in embryonal RMSs (ERMSs), performed methylation profiling in order to support the diagnosis and RNA-sequencing for comparison of the transcriptome of H3K27me3-positive and -negative cases.Of the 25 ERMS patients, 17 were males and 8 were females with an age range from 1 to 67 years (median, 6 years). None were known with neurofibromatosis type 1. One patient had Li-Fraumeni syndrome. Tumor localization included paratesticular (n = 9), genitourinary (n = 6), head/neck (n = 5), retroperitoneal (n = 4) and lower arm (n = 1). Five MPNSTs served as reference group. All ERMS had classical features including a variable spindle cell component. Immunohistochemical loss (partial or complete) of H3K27me3 was detected in 18/25 cases (72%). Based on methylation profiling, 22/22 cases were classified as ERMS. Using RNA sequencing, the ERMS group (n = 14) had a distinct gene expression profile in contrast to MPNSTs, confirming that the H3K27me3 negative ERMS cases do not represent malignant Triton tumors. When comparing H3K27me3-negative and -positive ERMSs, gene set enrichment analysis revealed differential expression of genes related to histone acetylation and normal muscle function with H3K27me3 negative ERMSs being associated with acetylation.Conclusion: Loss of H3K27me3 frequently occurs in ERMSs and correlates with H3K27 acetylation. H3K27me3 is not a suitable marker to differentiate ERMS (with spindle cell features) from malignant Triton tumor.

Levator ani and puborectalis muscle rupture: diagnosis and repair for perineal instability.

Puborectalis muscle rupture usually arises from peri-partum perineal trauma and may result in anterior, middle compartment prolapses, posterior compartment prolapse which includes rectocele and rectal prolapse, with or without associated anal sphincter damage. Patients with puborectalis muscle and levator ani rupture may present some form of incontinence or evacuation disorder, sexual dysfunction or pelvic organ descent. However, the literature on this subject is scarce. The aim of our study was to evaluate management and treatment of functional disorders associated with puborectalis and/or pubococcygei rupture at the level of the insertion in the pubis in a cohort of patients referred to a tertiary care coloproctology center. We conducted a prospective cohort study of patients with levator ani and puborectalis muscle avulsion in the Proctology and Pelvic Floor Unit, Division of Digestive Surgery of the University Hospitals of Geneva from January 2001 to November 2018. Clinical examination, anoscopy and ultrasound were performed on a routine basis. Rupture of the levator ani muscle was diagnosed by clinical examination and ultrasound. A Wexner incontinence score was completed before and 6months after surgery. Levator ani muscle repair was performed using a transvaginal approach. Fifty-two female patients (median age 56 ± 11.69 SD years, range 38-86years) were included in the study. Thirty-one patients (59.6%) had anal incontinence, 25 (48.1%) urinary incontinence, 28 (53.9%) dyschezia (obstructive defecation or excessive straining to defecate), 20 (38.5%) dyspareunia, 17 (32.7%) colpophony, and 13 (25.0%) impaired sensation during sexual intercourse. Deviation of the anus on the side opposite the lesion was observed in 50 patients (96.2%), confirmed with clinical examination and both endoanal and perineal ultrasound. Out of these 52 patients, levator ani rupture (including puborectalis rupture) were categorized into right sided, 43 (82.69%), left sided, 7 (13.46%) and bilateral, 2 (3.85%). Levator ani muscle repair was performed in all patients, associated with posterior repair and levatorplasty in 26 patients (50%) andwith sphincteroplasty in 34 patients (63.4%). Four patients (7.7%) experienced postoperative complications: significant postoperative pain (n = 3; 5.77%), urinary retention (n = 2; 3.85%), hematoma (n = 1; 1.92%), and perineal abscess (n = 1; 1.92%). Forty-one patients (78.8%) had full restoration of normal puborectalis muscle function (Wexner score: 0/20) after surgery, and overall, all patients had an improvement in the Wexner score and in sexual function.Dyschezia was reported by 28 patients (53.9%) preoperatively, resolved in 18 (64.3%) and improved by50%or morein 10 (35.71%). Diagnosis of levator ani and puborectalis muscle rupture requires careful history taking, clinical examination, endoanal and perineal ultrasound. Surgical repair improved anal continence as well as sexual function in all patients. Transvaginal levator ani repair seems to be well tolerated with good short-term results.

Specificity of Molecular Fragments Binding to S100B versus S100A1 as Identified by NMR and Site Identification by Ligand Competitive Saturation (SILCS).

S100B, a biomarker of malignant melanoma, interacts with the p53 protein and diminishes its tumor suppressor function, which makes this S100 family member a promising therapeutic target for treating malignant melanoma. However, it is a challenge to design inhibitors that are specific for S100B in melanoma versus other S100-family members that are important for normal cellular activities. For example, S100A1 is most similar in sequence and structure to S100B, and this S100 protein is important for normal skeletal and cardiac muscle function. Therefore, a combination of NMR and computer aided drug design (CADD) was used to initiate the design of specific S100B inhibitors. Fragment-based screening by NMR, also termed “SAR by NMR,” is a well-established method, and was used to examine spectral perturbations in 2D [1H, 15N]-HSQC spectra of Ca2+-bound S100B and Ca2+-bound S100A1, side-by-side, and under identical conditions for comparison. Of the 1000 compounds screened, two were found to be specific for binding Ca2+-bound S100A1 and four were found to be specific for Ca2+-bound S100B, respectively. The NMR spectral perturbations observed in these six data sets were then used to model how each of these small molecule fragments showed specificity for one S100 versus the other using a CADD approach termed Site Identification by Ligand Competitive Saturation (SILCS). In summary, the combination of NMR and computational approaches provided insight into how S100A1 versus S100B bind small molecules specifically, which will enable improved drug design efforts to inhibit elevated S100B in melanoma. Such a fragment-based approach can be used generally to initiate the design of specific inhibitors for other highly homologous drug targets.

Pelvic floor muscle function recovery using biofabricated tissue constructs with neuromuscular junctions

Damages in pelvic floor muscles often cause dysfunction of the entire pelvic urogenital system, which is clinically challenging. A bioengineered skeletal muscle construct that mimics structural and functional characteristics of native skeletal muscle could provide a therapeutic option to restore normal muscle function. However, most of the current bioengineered muscle constructs are unable to provide timely innervation necessary for successful grafting and functional recovery. We previously have demonstrated that post-synaptic acetylcholine receptors (AChR) clusters can be pre-formed on cultured skeletal muscle myofibers with agrin treatment and suggested that implantation of AChR clusters containing myofibers could accelerate innervation and recovery of muscle function. In this study, we develop a 3-dimensional (3D) bioprinted human skeletal muscle construct, consisting of multi-layers bundles with aligned and AChR clusters pre-formed human myofibers, and investigate the effect of pre-formed AChR clusters in bioprinted skeletal muscle constructs and innervation efficiency in vivo. Agrin treatment successfully pre-formed functional AChR clusters on the bioprinted muscle constructs in vitro that increased neuromuscular junction (NMJ) formation in vivo in a transposed nerve implantation model in rats. In a rat model of pelvic floor muscle injury, implantation of skeletal muscle constructs containing the pre-formed AChR clusters resulted in functional muscle reconstruction with accelerated construct innervation. This approach may provide a therapeutic solution to the many challenges associated with pelvic floor reconstruction resulting from the lack of suitable bioengineered tissue for efficient innervation and muscle function restoration.

Glycosaminoglycan Modification of Decorin Depends on MMP14 Activity and Regulates Collagen Assembly.

Proper processing of collagens COL1 and COL6 is required for normal function of adipose tissue and skeletal muscle. Proteoglycan decorin (DCN) regulates collagen fiber formation. The amino-terminus of DCN is modified with an O-linked glycosaminoglycan (GAG), the function of which has remained unclear. Previously, non-glycanated DCN (ngDCN) was identified as a marker of adipose stromal cells. Here, we identify MMP14 as the metalloprotease that cleaves DCN to generate ngDCN. We demonstrate that mice ubiquitously lacking DCN GAG (ngDCN mice) have reduced matrix rigidity, enlarged adipocytes, fragile skin, as well as skeletal muscle hypotrophy, fibrosis, and dysfunction. Our results indicate that DCN deglycanation results in reduced intracellular DCN—collagen binding and increased production of truncated COL6 chains, leading to aberrant procollagen processing and extracellular localization. This study reveals that the GAG of DCN functions to regulate collagen assembly in adipose tissue and skeletal muscle and uncovers a new mechanism of matrix dysfunction in obesity and aging.

Carnosine synthase deficiency is compatible with normal skeletal muscle and olfactory function but causes reduced olfactory sensitivity in aging mice

Carnosine (β-alanyl-l-histidine) and anserine (β-alanyl-3-methyl-l-histidine) are abundant peptides in the nervous system and skeletal muscle of many vertebrates. Many in vitro and in vivo studies demonstrated that exogenously added carnosine can improve muscle contraction, has antioxidant activity, and can quench various reactive aldehydes. Some of these functions likely contribute to the proposed anti-aging activity of carnosine. However, the physiological role of carnosine and related histidine-containing dipeptides (HCDs) is not clear. In this study, we generated a mouse line deficient in carnosine synthase (Carns1). HCDs were undetectable in the primary olfactory system and skeletal muscle of Carns1-deficient mice. Skeletal muscle contraction in these mice, however, was unaltered, and there was no evidence for reduced pH-buffering capacity in the skeletal muscle. Olfactory tests did not reveal any deterioration in 8-month-old mice lacking carnosine. In contrast, aging (18-24-month-old) Carns1-deficient mice exhibited olfactory sensitivity impairments that correlated with an age-dependent reduction in the number of olfactory receptor neurons. Whereas we found no evidence for elevated levels of lipoxidation and glycation end products in the primary olfactory system, protein carbonylation was increased in the olfactory bulb of aged Carns1-deficient mice. Taken together, these results suggest that carnosine in the olfactory system is not essential for information processing in the olfactory signaling pathway but does have a role in the long-term protection of olfactory receptor neurons, possibly through its antioxidant activity.

The Drosophila CG1674 gene encodes a synaptopodin 2-like related protein that localizes to the Z-disc and is required for normal flight muscle development and function.

To identify novel myofibrillar components of the Drosophila flight muscles, we carried out a proteomic analysis of chemically demembranated flight muscle myofibrils, and characterized the knockdown phenotype of a novel gene identified in the screen, CG1674. The CG1674 protein has some similarity to vertebrate synaptopodin 2-like, and when expressed as a FLAG-tagged fusion protein, it was localized during development to the Z-disc and cytoplasm. Knockdown of CG1674 expression affected the function of multiple muscle types, and defective flight in adults was accompanied by large actin-rich structures in the flight muscles that resembled overgrown Z-discs. Localization of CG1674 to the Z-disc depended predominantly upon presence of the Z-disc component alpha-actinin, but also depended upon other Z-disc components, including Mask, Zasp52, and Sals. We also observed re-localization of FLAG-CG1674 to the nucleus in Alpha-actinin and sals knockdown animals. These studies identify and characterize a previously unreported myofibrillar component of Drosophila muscle that is necessary for proper myofibril assembly during development.