Non‐invasive long‐term and real‐time analysis of endocrine cells on micro‐electrode arrays

Abstract

Key points• Pancreatic islet cells are required for glucose homeostasis and their dysfunction leads to diabetes mellitus.• The electrical activity of these cells is regulated by nutrients as well as hormones and this provides the first integrative read-out reflecting their function.• Non-invasive recording of their electrical activity and its analysis in real time would provide the possibility of long-term and repetitive investigations or testing of multiple drugs.• Combining electrophysiology and microelectronics, we now demonstrate such an approach with multiple (up to 60) electrodes and including on-line signal analysis on the two major cell types present in islets, α-and β-cells.• This method should be applicable to other endocrine cells and may serve in the long-run as the basis for a novel biosensor.Abstract Non-invasive high-throughput and long-term monitoring of endocrine cells is important for drug research, phenotyping, tissue engineering and pre-transplantation quality control. Here we report a novel approach to obtain simultaneous long-term electrical recordings of different islet cell types using multi-electrode arrays. We implemented wavelet transforms to resolve the low signal/noise ratio inherent to these measurements and extracted on-line a signature specific of cell activity. The architecture employed allows multiplexing a large number of electrodes for high-throughput screening. This method should be of considerable advantage in endocrine research and may be extended to other excitable cells previously not accessible to the technique. Abbreviations ASIC, Application-specific integrated circuit; FPGA, field-programmable gate array; MEA, multi-electrode array; SWT, stationary wavelet transform.

Slow potentials encode intercellular coupling and insulin demand in pancreatic beta cells

“…Probably due to their small amplitude, APs were not visible in 32.2±3.7% of electrodes with SPs (n=20 experiments). When present, APs were downward on the majority of recordings but upward in a few cases (96% vs 4%, respectively) as in our previous report [10]. Temporal correlations between the two signals showed that APs mainly occurred during the falling (69%) rather than the rising phase (31%) of SPs (Fig.…”

“…A higher temporal resolution of this glucose-induced activity ( Fig. 1d) revealed the presence of two distinct and superimposed signals: rapid spikes of small amplitude (40-60 ms in duration, 10-50 μV), which have previously been characterised as APs [10]. In addition, we found slower oscillations of larger amplitude (800-1,500 ms period, 50-350 μV peak-to-peak), we refer to as SPs.…”

“…2). We also tested the stress hormone adrenaline, an inhibitor of electrical signals in beta cells and an activator of alpha cells, at relatively high concentrations to ensure safe discrimination between the two cell types [10,[15][16][17]. SPs induced by glucose were reversibly inhibited by adrenaline (Fig.…”

“…The relative angular position of 4,400 action potentials (APs) on their respective SPs was determined for four independent experiments in mouse islets recorded at 3-11 mmol/l glucose. SPs were extracted by determining their positive and negative extremes, APs were isolated using the wavelet transforms method [10]. The angular position of each AP was then computed between 0°and 180°(rising phase of SPs) or between 180°and 360°( falling phase).…”

“…These techniques are time-consuming and restricted to the observation of individual cells for a limited time. By contrast, extracellular recordings on multielectrode arrays (MEAs) offer a novel approach for physiological experiments with intact and native islet cells in a multicellular context [7,9,10].…”