<i>In vivo</i> Ca²⁺ imaging analysis of pancreatic β-cells and islets using transgenic mice expressing a high-sensitivity ratiometric Ca²⁺ indicator

Abstract

Pancreatic β-cells release insulin in a Ca 2+ -dependent pulsatile manner to control blood glucose levels. Although the Ca 2+ signaling mechanism in β-cells has been extensively studied using in vitro and ex vivo preparations, its analysis in living animals remains challenging. Therefore, while β-cell activities in vivo are under the influence of the autonomic nervous system, various hormones and other bioactive substances, Ca 2+ responses of β-cells under physiological conditions have not been clarified. We here report a method to monitor and analyze in vivo β-cell Ca 2+ activities using a transgenic mouse line expressing a genetically encoded ratiometric Ca 2+ indicator, YC-Nano50.Using the method, we visualized β-cell Ca 2+ signals in laparotomized mice under anesthesia, and observed synchronized Ca 2+ oscillations in β-cells within individual islets. Furthermore, we succeeded in monitoring Ca 2+ activities in multiple islets simultaneously, which may clarify the basis for a pulsatile insulin secretion. Further studies in living animals using the new method is expected to help elucidate the mechanism of insulin secretion and the etiology of diabetes.