Microelectrode Array based Functional Testing of Pancreatic Islet Cells.

Ahmad Alassaf,Matthew Ishahak,Annie Bowles,Ashutosh Agarwal

doi:10.3390/mi11050507

Abstract

Electrophysiological techniques to characterize the functionality of islets of Langerhans have been limited to short-term, one-time recordings such as a patch clamp recording. We describe the use of microelectrode arrays (MEAs) to better understand the electrophysiology of dissociated islet cells in response to glucose in a real-time, non-invasive method over prolonged culture periods. Human islets were dissociated into singular cells and seeded onto MEA, which were cultured for up to 7 days. Immunofluorescent imaging revealed that several cellular subtypes of islets; β, δ, and γ cells were present after dissociation. At days 1, 3, 5, and 7 of culture, MEA recordings captured higher electrical activities of islet cells under 16.7 mM glucose (high glucose) than 1.1 mM glucose (low glucose) conditions. The fraction of the plateau phase (FOPP), which is the fraction of time with spiking activity recorded using the MEA, consistently showed distinguishably greater percentages of spiking activity with high glucose compared to the low glucose for all culture days. In parallel, glucose stimulated insulin secretion was measured revealing a diminished insulin response after day 3 of culture. Additionally, MEA spiking profiles were similar to the time course of insulin response when glucose concentration is switched from 1.1 to 16.7 mM. Our analyses suggest that extracellular recordings of dissociated islet cells using MEA is an effective approach to rapidly assess islet functionality, and could supplement standard assays such as glucose stimulate insulin response.

Highlights

Islets of Langerhans are three-dimensional (3D) multicellular clusters that range from 50 to 500 μm in diameter [1,2]
The fraction of a plateau phase (FOPP), which is the fraction of time with spiking activity recorded using the Microelectrode arrays (MEAs) was developed as a metric for beta-cell function [9]
We demonstrated that extracellular recordings of dissociated islet cells using MEA is an effective approach to rapidly assess islet functionality, and could supplement standard assays such as glucose stimulate insulin response

Summary

Introduction

Islets of Langerhans are three-dimensional (3D) multicellular clusters that range from 50 to 500 μm in diameter [1,2]. The disadvantages to performing the patch clamp technique are the invasiveness to the sample, technical complexity, and limited recording time (hours) [8]. Pfeiffer et al performed extracellular recordings of whole islets using MEA, a glass holding pipette angled at 30◦, and a micromanipulator to control the islet location on top of the recording electrode. They were able to show continuous bursts of spikes at high glucose concentration (15 mM) and concluded that the length of the bursts correlated with the amount of insulin released. Cells in the dissociated human and rat islet cell monolayers (α, β, δ, and γ) were in proportions similar to native 3D islets [15]

Methods

Results

Conclusion