Muscle atrophy-related myotube-derived exosomal microRNA in neuronal dysfunction: Targeting both coding and long noncoding RNAs.

In mammals, microRNAs can be actively secreted from cells to blood. miR-29b-3p has been shown to play a pivotal role in muscle atrophy, but its role in intercellular communication is largely unknown. Here, we showed that miR-29b-3p was upregulated in normal and premature aging mouse muscle and plasma. miR-29b-3p was also upregulated in the blood of aging individuals, and circulating levels of miR-29b-3p were negatively correlated with relative appendicular skeletal muscle. Consistently, miR-29b-3p was observed in exosomes isolated from long-term differentiated atrophic C2C12 cells. When C2C12-derived miR-29b-3p-containing exosomes were uptaken by neuronal SH-SY5Y cells, increased miR-29b-3p levels in recipient cells were observed. Moreover, miR-29b-3p overexpression led to downregulation of neuronal-related genes and inhibition of neuronal differentiation. Interestingly, we identified HIF1alpha-AS2 as a novel c-FOS targeting lncRNA that is induced by miR-29b-3p through down-modulation of c-FOS and is required for miR-29b-3p-mediated neuronal differentiation inhibition. Our results suggest that atrophy-associated circulating miR-29b-3p may mediate distal communication between muscle cells and neurons.