Neural network tissue and myocytes co-culture system reveals effects of different myocytes on postnatal development of spinal cord neural network.

The interaction between spinal cord neural networks and myocytes in postnatal mammals plays a crucial role in development, and the neural regulation of motor and visceral functions. Here, spinal cord neural network tissue (SC-NNT) was constructed with neonatal rat spinal cord neural stem cells (SC-NSCs) and co-cultured with skeletal muscle cells (SkMCs) and corpus cavernosum smooth muscle cells (CC-SmMCs). The mechanisms by which these two types of myocytes influence postnatal SC-NSC differentiation and SC-NNT formation were explored. Both SkMCs and CC-SmMCs promoted SC-NSC differentiation towards neurons rather than neuroglia cells. Excitatory neurons were predominant in co-culture, with significantly increased synaptic protein expression. CC-SmMCs more strongly promoted SC-NSC differentiation into DβH-positive neurons, while SkMCs more strongly promoted axonal extension of neurons. Moreover, SkMCs formed neuromuscular junction-like specialized structures, enabling the SC-NNT to control SkMC contraction. Although human-induced pluripotent stem cell-derived neuromuscular organoids avoid embryo-related ethical concerns, they remain subject to strict cell source regulations. Neonatal rat cells avoid such ethical issues. In addition, rat SC-NSCs differentiate into neurons more rapidly and establish neural control over muscles faster. They also offer insights into how different myocyte types affect the postnatal development and function of spinal cord neural networks.