Neural agrin controls maturation of the excitation-contraction coupling mechanism in human myotubes developing in vitro.
The aim of this study was to elucidate the mechanisms responsible for the effects of innervation on the maturation of excitation-contraction coupling apparatus in human skeletal muscle. For this purpose, we compared the establishment of the excitation-contraction coupling mechanism in myotubes differentiated in four different experimental paradigms: 1) aneurally cultured, 2) cocultured with fetal rat spinal cord explants, 3) aneurally cultured in medium conditioned by cocultures, and 4) aneurally cultured in medium supplemented with purified recombinant chick neural agrin. Ca(2+) imaging indicated that coculturing human muscle cells with rat spinal cord explants increased the fraction of cells showing a functional excitation-contraction coupling mechanism. The effect of spinal cord explants was mimicked by treatment with medium conditioned by cocultures or by addition of 1 nM of recombinant neural agrin to the medium. The treatment with neural agrin increased the number of human muscle cells in which functional ryanodine receptors (RyRs) and dihydropyridine-sensitive L-type Ca(2+) channels were detectable. Our data are consistent with the hypothesis that agrin, released from neurons, controls the maturation of the excitation-contraction coupling mechanism and that this effect is due to modulation of both RyRs and L-type Ca(2+) channels. Thus, a novel role for neural agrin in skeletal muscle maturation is proposed.
Bandi
Elena
E
Department of Physiology and Pathology and Centre for Neuroscience B.R.A.I.N., University of Trieste, Trieste, Italy.
Jevsek
Marko
M
Mars
Tomaz
T
Jurdana
Mihaela
M
Formaggio
Elena
E
Sciancalepore
Marina
M
Fumagalli
Guido
G
Grubic
Zoran
Z
Ruzzier
Fabio
F
Lorenzon
Paola
P
D018171:Agrin / Q000378:metabolism*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects; D002454:Cell Differentiation; D002478:Cells, Cultured; D002645:Chickens; D002648:Child; D002675:Child, Preschool; D018920:Coculture Techniques; D017077:Culture Media, Conditioned / Q000378:metabolism; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000254:growth & development / Q000294:innervation / Q000378:metabolism*; D019899:Paracrine Communication; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D013116:Spinal Cord / Q000196:embryology / Q000378:metabolism*; D013997:Time Factors; D046509:Tissue Culture Techniques
D018171:Agrin; D020746:Calcium Channels, L-Type; D017077:Culture Media, Conditioned; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D002110:Caffeine