Utilization of the Rat Tibial Nerve Transection Model to Evaluate Cellular and Molecular Mechanisms Underpinning Denervation-Mediated Muscle Injury.

Peripheral nerve injury denervates muscle, resulting in muscle paralysis and atrophy. This is reversible if timely muscle reinnervation occurs. With delayed reinnervation, the muscle's reparative ability declines, and muscle-resident fibro-adipogenic progenitor cells (FAPs) proliferate and differentiate, inducing fibro-fatty muscle degradation and thereby physical disability.

MicroRNA regulatory networks associated with abnormal muscle repair in survivors of critical illness.

Background: Intensive care unit (ICU)-acquired weakness is characterized by muscle atrophy and impaired contractility that may persist after ICU discharge. Dysregulated muscle repair and regeneration gene co-expression networks are present in critical illness survivors with persistent muscle wasting and weakness. We aimed to identify microRNAs (miRs) regulating the gene networks and determine their role in the self-renewal of muscle in ICU survivors.

Identification, Isolation, and Characterization of Fibro-Adipogenic Progenitors (FAPs) and Myogenic Progenitors (MPs) in Skeletal Muscle in the Rat.

Fibro-adipogenic Progenitors (FAPs) are resident interstitial cells in skeletal muscle that, together with myogenic progenitors (MPs), play a key role in muscle homeostasis, injury, and repair. Current protocols for FAPs identification and isolation use flow cytometry/fluorescence-activated cell sorting (FACS) and studies evaluating their function in vivo to date have been undertaken exclusively in mice. The larger inherent size of the rat allows for a more comprehensive analysis of FAPs in skeletal muscle injury models, especially in severely atrophic muscle or when investigators require substantial tissue mass to conduct multiple downstream assays.

Mechanisms of Chronic Muscle Wasting and Dysfunction after an Intensive Care Unit Stay. A Pilot Study.

Rationale: Critical illness survivors often experience permanent functional disability due to intensive care unit (ICU)-acquired weakness. The mechanisms responsible for long-term weakness persistence versus resolution are unknown.

Objectives: To delineate cellular mechanisms underlying long-term weakness persistence in ICU survivors.

PDLIM7 is a novel target of the ubiquitin ligase Nedd4-1 in skeletal muscle.

Skeletal muscle atrophy remains a complication occurring both as a natural response to muscle disuse and as a pathophysiological response to illness such as diabetes mellitus and nerve injury, such as traumatic muscle denervation. The ubiquitin-proteasome system (UPS) is the predominant proteolytic machinery responsible for atrophy of skeletal muscle, and Nedd4-1 (neural precursor cell-expressed developmentally down-regulated 4-1) is one of a series of E3 ubiquitin ligases identified to mediate inactivity-induced muscle wasting. Targets of Nedd4-1 mediated ubiquitination in skeletal muscle remain poorly understood.

Skeletal muscle dysfunction in idiopathic pulmonary arterial hypertension.

Despite improvements in survival with disease-targeted therapies, the majority of patients with pulmonary arterial hypertension (PAH) have persistent exercise intolerance that results from impaired cardiac function and skeletal muscle dysfunction. Our intent was to understand the molecular mechanisms mediating skeletal muscle dysfunction in PAH. A total of 12 patients with PAH and 10 matched control subjects were assessed.

The ubiquitin ligase Nedd4-1 participates in denervation-induced skeletal muscle atrophy in mice.

Skeletal muscle atrophy is a consequence of muscle inactivity resulting from denervation, unloading and immobility. It accompanies many chronic disease states and also occurs as a pathophysiologic consequence of normal aging. In all these conditions, ubiquitin-dependent proteolysis is a key regulator of the loss of muscle mass, and ubiquitin ligases confer specificity to this process by interacting with, and linking ubiquitin moieties to target substrates through protein:protein interaction domains.

Hypertrophic airway smooth muscle mass correlates with increased airway responsiveness in a murine model of asthma.

The increase of airway smooth muscle (ASM) mass in asthma results from hypertrophic and hyperplastic stimuli, and leads to an increase in cellular contractile proteins. However, little evidence correlates the relative contributions of hypertrophic and hyperplastic muscle with functional effects on airway resistance. We performed a ventilator-based assessment of respiratory mechanics and responsiveness to methacholine in a murine model of acute (3-week) ovalbumin (OVA)-induced airway inflammation, compared with a chronic (12-week) model.

Cellular markers of muscle atrophy in chronic obstructive pulmonary disease.

Skeletal muscle atrophy in individuals with advanced chronic obstructive pulmonary disease (COPD) is associated with diminished quality of life, increased health resource use, and worsened survival. Muscle wasting results from an imbalance between protein degradation and synthesis, and is enhanced by decreased regenerative repair. We investigated the activation of cellular signaling networks known to mediate muscle atrophy and regulate muscle regenerative capacity in rodent models, in individuals with COPD (FEV(1) < 50% predicted).

Absence of caspase-3 protects against denervation-induced skeletal muscle atrophy.

The ubiquitin-proteasome system is a key proteolytic pathway activated during skeletal muscle atrophy. The proteasome, however, cannot degrade intact myofibrils or actinomyosin complexes. In rodent models of diabetes mellitus and uremia, caspase-3 is involved in actinomyosin cleavage, generating fragments that subsequently undergo ubiquitin-proteasome-mediated degradation.

The inositol phosphatase MTMR4 is a novel target of the ubiquitin ligase Nedd4.

The inositol phosphatase, MTMR4 (myotubularin-related protein 4), was identified as a novel interactor of the ubiquitin ligase Nedd4 (neural-precursor-cell-expressed developmentally down-regulated 4). hMTMR4 (human MTMR4) and Nedd4 co-immunoprecipitated and co-localized to late endosomes. The PY (Pro-Tyr) motif of hMTMR4 binds to WW (Trp-Trp) domains of hNedd4.