Microelectrode electrode array studies of spinal motor neurons
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Abstract
Co-cultures are a traditional method for studying the cellular properties of cell to cell interactions among different cell types. How network properties in these multicellular synthetic systems vary from monocultures are of particular interest. Understanding the changes in the functional output of these in vitro spiking neural networks can provide new insights into in vivo systems and how to develop biological system models that better reflect physiological conditions - something of paramount importance to the progress of synthetic biology. Culture models of spinal motor neurons have been customarily studied as a monoculture, and the overwhelming consensus is that in culture they are different in nature from their in vivo counterparts. I studied the electrophysiological properties of spinal ventral horn networks cocultured with myocytes or astrocytes using a 64 channel microelectrode array system to record extracellular voltage measurements. When compared over a period of 40 days, significant differences were found between coculture types in metrics of spiking, bursting, and network bursting. Myocyte cocultures, when compared with simple ventral horn cultures, showed significant decreases in spikes, spike amplitudes, spike energy, number of units in network burst, and an increase in interspike interval. Astrocyte cocultures, when compared with simple ventral horn cultures showed decreases in sorted units, burst duration, mean interspike interval, and network burst duration but increases in spikes, energy of spikes, bursts, spikes per burst, network bursts, and number of units per network burst. This suggests that traditional culturing techniques involving a uniform cell type might not be the best way to functionally model in vivo neural networks. Concerning an in vitro model system for lower motor neurons, the most accurate model would most likely be a combination of spinal motor neurons cultured with myocytes as well as increased levels of astrocytes. A synthetic ecosystem of various cell types is beneficial to replicating cell behavior in vitro, thus is a necessary refinement to the commonly used technique of cell culture. With a more physiological model system, hypotheses about interacting systems can be better addressed and the outcomes will have greater relevancy.