Biology subjects

Lewis, M. P.

Publications and source records attributed to Lewis, M. P..

5 recordsLinked to original sources

bioRxiv2020

Zebrafish skeletal muscle cell cultures: Monolayer to three-dimensional tissue-engineered collagen constructs

Zebrafish (Danio rerio) are a commonly used model organism to study human muscular myopathies and dystrophies. To date, much of the work has been conducted in vivo due to limitations surrounding the consistent isolation and culture of zebrafish muscle progenitor cells (MPCs) in vitro and the lack of physiologically relevant models. Here we report a robust, repeatable, and cost-effective protocol for the isolation and culture of zebrafish MPCs in conventional monolayer (2D) and have successfully transferred these cells to 3D culture in collagen based three-dimensional (3D) tissue-engineered constructs. Zebrafish MPCs cultured in 2D were consistently reported to be Desmin positive reflecting their muscle specificity, with those demonstrating Desmin positivity in the 3D cultures. In addition, mRNA expression of muscle markers specific for proliferation, differentiation and maturation measured from both monolayer and 3D cultures at appropriate developmental stages were found consistent with previously published from other species in vitro and in vivo muscle data. Collagen constructs seeded with zebrafish MPCs were initially characterised for optimal seeding density, followed by macroscopic characterisation (three-fold contraction) of the matrix. Direct comparison between the morphological characteristics (proportion of cells) and gene expression profiles of cells cultured in collagen constructs revealed higher maturation and differentiation compared to monolayer cultures. In this regard, cells embedded in 3D collagen constructs revealed higher fusion index, Desmin positivity, hypertrophic growth, myotube maturity and myogenic mRNA expression when compared to in monolayer. In conclusion, these methods and models developed herein will facilitate in vitro experiments, which would complement in vivo zebrafish studies used to investigate the basic developmental, myopathies and dystrophies in skeletal muscle cells.

bioengineering↗

bioRxiv2020

Bioengineered model of the human motor unit with physiologically functional neuromuscular junctions

Investigations of the human neuromuscular junction (NMJ) have predominately utilised experimental animals and model organisms. Consequently, there remains a paucity of data regarding the development of the human NMJ and a lack of systems that enable temporal investigation of the motor unit. This work addresses this need, providing the methodologies to bioengineer 3D models of the human motor unit. Separate maturation of primary human skeletal muscle and iPSC derived motor neurons seeks to accurately represent neuromuscular development via controlled addition of motor axons following primary myogenesis. Spheroid cultures of motor neuron progenitors augmented the transcription of OLIG2, ISLET1 and SMI32 motor neuron mRNAs [~]400, [~]150 and [~]200-fold respectively. Axon projections of adhered motor neuron spheroids exceeded 1000m in monolayer, with transcription of SMI32 and VACHT mRNAs further enhanced in a concentration dependent manner within optimised 3D type I collagen extracellular matrices. Bioengineered skeletal muscles produce functional forces, demonstrate increased acetylcholine receptor (AChR) clustering, and transcription of MUSK and LRP4 mRNAs indicating enhanced organisation of the post-synaptic membrane. Dosed integration of motor neuron spheroids outlined the motor pool required to functionally innervate muscle tissues in 3D, generating physiologically functional human NMJs that evidence pre- and post-synaptic membrane and motor nerve terminal co-localisation. Spontaneous firing was significantly elevated in 3D motor units, confirmed to be driven by the motor nerve via antagonistic inhibition of the AChR. Finally, functional analyses outlined decreased time to peak twitch and half relaxation times, indicating enhanced physiology of excitation contraction coupling of NMJs within innervated motor units.

bioengineering↗

bioRxiv2020

Bioengineered human skeletal muscle with a Pax7+ satellite cell niche capable of functional regeneration

Skeletal muscle (SkM) regenerates following injury, replacing damaged tissue with high fidelity. However, in serious injuries non-regenerative defects leave patients with loss of function, increased re-injury risk and often chronic pain. Progress in treating these non-regenerative defects has been slow, with advances only occurring where a comprehensive understanding of regeneration has been gained. Tissue engineering has allowed the development of bioengineered models of SkM which regenerate following injury to support research in regenerative physiology. To date however, no studies have utilised human myogenic precursor cells (hMPCs) to closely mimic human physiology due to difficulties generating sufficient cell numbers and the relatively low myogenic potential of hMPCs. Here we address problems associated with cell number and hMPC mitogenicity using magnetic association cell sorting (MACS), for the marker CD56, and media supplementation with fibroblast growth factor 2 (FGF-2) and B-27 supplement. Cell sorting allowed extended expansion of myogenic cells and supplementation was shown to improve myogenesis within engineered tissues and force generation at maturity. In addition, these engineered human SkM contained a Pax7+ niche and regenerated following Barium Chloride (BaCl2) injury. Following injury, reductions in function (87.5%) and myotube number (33.3%) were observed, followed by a proliferative phase with increased MyoD+ cells and a subsequent recovery of function and myotube number. An expansion of the Pax7+ cell population was observed across recovery suggesting an ability to generate Pax7+ cells within the tissue, similar to the self-renewal of satellite cells seen in vivo. This work outlines an engineered human SkM capable of functional regeneration following injury, built upon an open source system adding to the pre-clinical testing toolbox to improve the understanding of basic regenerative physiology.

cell biology↗

bioRxiv2019

γ-Linolenic acid increases expression of key regulators of lipid metabolism in human skeletal muscle cells.

Control of skeletal muscle fat metabolism is regulated acutely through Peroxisome Proliferator Activated Receptor (PPAR) {delta} activation and its downstream intracellular targets. The purpose of this study was to determine whether fatty acids with high binding affinity for PPAR{delta} can elevate the expression of genes related to fatty acid oxidation and indicators of mitochondrial biogenesis in cultured human skeletal myotubes. Myotubes were treated for 72 hours with one of four conditions: (i) Control (CON); (ii) Eicosapentaenoic acid (EPA 250M); (iii) {gamma}-linolenic acid ({gamma}-LA 250M); (iv) PPAR{delta} Agonist (GW501516 10nM). Incubation with {gamma}-LA induced increases in the gene expression of CD36 (p= 0.005), HADHA (p= 0.022) and PDK4 (p=0.025) in comparison with CON, with no further differences observed between conditions. Furthermore, intensity of MitoTracker(R) Red immunostaining in myotubes increased following incubation with {gamma}-LA (p[≤] 0.001) and EPA (p= 0.005) however these trends were not mirrored in the expression of PGC-1 as might be expected. Overall, {gamma}-LA elevates levels the transcription of key intracellular regulators of lipid metabolism and transport in human myotubes, which may be clinically beneficial in the control of metabolic diseases.

cell biology↗

bioRxiv2019

Monosodium Iodoacetate delays regeneration and inhibits hypertrophy in skeletal muscle cells in vitro

ObjectiveOsteoarthritis (OA) is a musculoskeletal disease which contributes to severe morbidity. The monosodium iodoacetate (MIA) rodent model of OA is now well established, however the effect of MIA on surrounding tissues post injection has not been investigated and as such the impact on phenotypic development is unknown. The aim of this investigation was to examine the impact of MIA incubation on skeletal muscle cells in vitro, to provide an indication as to the potential influence of MIA administration of skeletal muscle in vivo.\n\nMethodsC2C12 skeletal muscle myotubes were treated with either 4.8M MIA or 10M Dexamethasone (DEX, positive atrophic control) up to 72hrs post differentiation and sampled for morphological and mRNA analyses.\n\nResultsSignificant morphological effects (fusion index, number of myotubes and myotube width, p<0.05) were evident, demonstrating a hypertrophic phenotype in control (CON) compared to a hyperplasic phenotype in MIA and DEX. Increases in MAFbx mRNA were also evident between conditions, with post-hoc analysis demonstrating significance between CON and DEX (p<0.001), but not between CON and MIA (p>0.05).\n\nConclusionsThese data indicate a significant impact of both DEX and MIA on regeneration and hypertrophy in vitro and suggest differential activating mechanisms. Future investigations should determine whether skeletal muscle regeneration and hypertrophy is affected in the in vivo rodent model and the potential impact this has on the OA phenotypic outcome.

cell biology↗