On defining the islet micro-electrogram with a focus on translational aspects.

An ability to measure the electrical activity arising from whole tissues such as the heart (electrocardiogram), brain (electroencephalogram), and muscle (electromyogram) in vivo have proved to be valuable research and clinical tools in the understanding of these organs physiology and pathology. As electrode technology has developed, it has become possible to design custom systems that are able to measure the electrical activity of biopsies, cell clusters and tissue fragments in vitro. These tissues include so-called brain organoids and other stem cell derived tissue clusters such as cardiospheroids. There, electrical activity has been measured as a way of determining functionality, though with (so far) little clinical impact. In contrast, the electrical responses of isolated pancreatic islets have been well documented and it has been suggested that this electrical activity is a prerequisite for insulin secretion. Here we define the islet-electrogram (IE) by comparing whole islet electrical responses using both single and custom planar electrode arrays. We argue from our data that important islet ‘health’ information such as islet quality, beta cell responses and coupling, can be demonstrated in multiple electrode configurations and can be inferred accurately from single electrode recording. Our proposal lays the basis for accurate non labelled electrical assessment of islet quality to inform clinical decision making in type I diabetes transplants.