Author/Editor		Marš, Tomaž; Miš, Katarina; Meznarič, Marija; Prpar Mihevc, Sonja; Jan, Vid; Haugen, Fred; Rogelj, Boris; Rustan, Arild C.; Thoresen, G. Hege; Pirkmajer, Sergej; Nikolić, Nataša
Title		Innervation and electrical pulse stimulation - in vitro effects on human skeletal muscle cells
Type		članek
Publication year		2020
Volume		str. str.
ISSN		1715-5312 - Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme
Language		eng
Abstract		Contraction-induced adaptations in skeletal muscles are well characterized in vivo, but the underlying cellular mechanisms are still not completely understood. Cultured human myotubes represent an essential model system for human skeletal muscle which can be modulated ex vivo, but they are quiescent and do not contract unless being stimulated. Stimulation can be achieved by innervation of human myotubes in vitro by co-culturing with embryonic rat spinal cord, or by replacing motor neuron activation by electrical pulse stimulation (EPS). Effects of these two in vitro approaches, innervation and EPS, were characterized with respects to the expression of myosin heavy chains (MyHCs) and metabolism of glucose and oleic acid in cultured human myotubes. Adherent human myotubes were either innervated with rat spinal-cord segments or exposed to EPS. The expression pattern of MyHCs was assessed by qPCR, immunoblotting, and immunofluorescence, while the metabolism of glucose and oleic acid were studied using radiolabeled substrates. Innervation and EPS promoted differentiation towards different fiber types in human myotubes. Expression of the slow MyHC-1 isoform was reduced in innervated myotubes, whereas it remained unaltered in EPS-treated cells. Expression of both fast isoforms (MyHC-2A and MyHC-2X) tended to decrease in EPS-treated cells. Both approaches induced a more oxidative phenotype, reflected in increased CO2 production from both glucose and oleic acid. Novelty: Innervation and EPS favour differentiation into different fiber types in human myotubes. Both innervation and EPS promote a metabolically more oxidative phenotype in human myotubes.
Keywords		skeletal muscles electrical pulse stimulation innervation skeletne mišice stimulacija električnega impulza inervacija