Cross-talk between motor neurons and myotubes via endogenously secreted neural and muscular growth factors.

Saini, Jasdeep, Faroni, Alessandro, Reid, Adam J, Mouly, Vincent, Butler-Browne, Gillian, Lightfoot, Adam P, McPhee, Jamie S, Degens, Hans ORCID: https://orcid.org/0000-0001-7399-4841 and Al-Shanti, Nasser ORCID: https://orcid.org/0000-0002-4215-2649 (2021) Cross-talk between motor neurons and myotubes via endogenously secreted neural and muscular growth factors. Physiological Reports, 9 (8). ISSN 2051-817X

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Abstract

Neuromuscular junction (NMJ) research is vital to advance the understanding of neuromuscular patho-physiology and development of novel therapies for diseases associated with NM dysfunction. In vivo, the micro-environment surrounding the NMJ has a significant impact on NMJ formation and maintenance via neurotrophic and differentiation factors that are secreted as a result of cross-talk between muscle fibers and motor neurons. Recently we showed the formation of functional NMJs in vitro in a co-culture of immortalized human myoblasts and motor neurons from rat-embryo spinal-cord explants, using a culture medium free from serum and neurotrophic or growth factors. The aim of this study was to assess how functional NMJs were established in this co-culture devoid of exogenous neural growth factors. To investigate this, an ELISA-based microarray was used to compare the composition of soluble endogenously secreted growth factors in this co-culture with an a-neural muscle culture. The levels of seven neurotrophic factors brain-derived neurotrophic factor (BDNF), glial-cell-line-derived neurotrophic factor (GDNF), insulin-like growth factor-binding protein-3 (IGFBP-3), insulin-like growth factor-1 (IGF-1), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and vascular endothelial growth factor (VEGF) were higher (p < 0.05) in the supernatant of NMJ culture compared to those in the supernatant of the a-neural muscle culture. This indicates that the cross-talk between muscle and motor neurons promotes the secretion of soluble growth factors contributing to the local microenvironment thereby providing a favourable regenerative niche for NMJs formation and maturation.