Resolving spatiotemporal electrical signaling within the islet via CMOS microelectrode arrays

Glucose-stimulated beta-cells exhibit synchronized calcium dynamics across the islet that recruit beta-cells to enhance insulin secretion. Compared to calcium dynamics, the formation and cell-to-cell propagation of electrical signals within the islet are poorly characterized. To determine factors that influence the propagation of electrical activity across the islet underlying calcium oscillations and beta-cell synchronization, we used high-resolution CMOS multielectrode arrays (MEA) to measure voltage changes associated with the membrane potential of individual cells within intact C57BL6 mouse islets. We measured fast (milliseconds, spikes) and slow (seconds, waves) voltage dynamics. Single spike activity and wave signal velocity were both glucose-dependent, but only spike activity was influenced by NMDA receptor activation or inhibition. A repeated glucose stimulus revealed a highly responsive subset of cells in terms of spike activity. When islets were pretreated for 72 hours with glucolipotoxic medium, the wave velocity was significantly reduced. Network analysis confirmed that in response to glucolipotoxicity the synchrony of islet cells was affected due to slower propagating electrical waves and not due to altered spike activity. In summary, this approach provided novel insight regarding the propagation of electrical activity and the disruption of cell-to-cell communication due to excessive stimulation.