In Vivo ZIMIR Imaging of Mouse Pancreatic Islet Cells Shows Oscillatory Insulin Secretion

Abstract

Appropriate insulin secretion is essential for maintaining euglycemia, and impairment or loss of insulin release represents a causal event leading to diabetes. There have been extensive efforts of studying insulin secretion and its regulation using a variety of biological preparations, yet it remains challenging to monitor the dynamics of insulin secretion at the cellular level in the intact pancreas of living animals, where islet cells are supplied with physiological blood circulation and oxygenation, nerve innervation, and tissue support of surrounding exocrine cells. Herein we presented our pilot efforts of ZIMIR imaging in pancreatic islet cells in a living mouse. The imaging tracked insulin/Zn2+ release of individual islet β-cells in the intact pancreas with high spatiotemporal resolution, revealing a rhythmic secretion activity that appeared to be synchronized among islet β-cells. To facilitate probe delivery to islet cells, we also developed a chemogenetic approach by expressing the HaloTag protein on the cell surface. Finally, we demonstrated the application of a fluorescent granule zinc indicator, ZIGIR, as a selective and efficient islet cell marker in living animals through systemic delivery. We expect future optimization and integration of these approaches would enable longitudinal tracking of beta cell mass and function in vivo by optical imaging.

Spatiotemporal Correlation Spectroscopy Reveals a Protective Effect of Peptide-Based GLP-1 Receptor Agonism against Lipotoxicity on Insulin Granule Dynamics in Primary Human β-Cells

“…To apply the present approach to intact islets, however, a few technical and methodological issues have to be addressed, the main being that proper fluorescence labeling shall be achieved in the intact islet. This step, in turn, implies the use of either virus-based technologies [ 43 , 44 ] or newly-developed organic dyes for granule labeling [ 45 , 46 ], thus avoiding the potentially perturbative effects of lipofection (i.e., Lipofectamine in the present work) on cells. Among organic dyes, ZIGIR, in particular, shows promising properties as a membrane-permeable, Zinc-chelating agent [ 45 ].…”

Glucose-dependent activation, activity, and deactivation of beta cell networks in acute mouse pancreas tissue slices

“…Most importantly, the tissue is removed from the animal during preparation, which inherently prevents signaling input and feedback from other tissues. Therefore, an integration of outcomes obtained with tissue slices with findings from in vivo studies on islets implanted into the anterior chamber of the eye (152,153) or in an exteriorized pancreas (154) should give a more complete understanding of glucose-dependent physiological properties of islets.…”

Sequentialin vivolabeling of insulin secretory granule pools in INS-SNAP transgenic pigs

“…Proteins tagged with self-labeling enzymes have so far been successfully used for in vivo studies in the mouse brain and in small animals (Masch et al, 2018;Poc et al, 2020;Campos et al, 2011;Yang et al, 2015) where application of the substrates is achieved by injection in the tissue. Administration of a single-color SNAP-or Halo-tag substrate via tail-vein injection has resulted in specific labeling in mice (Ivanova et al, 2013;Chen et al, 2021). This approach is less invasive and overcomes the substantial hurdles and potential severe complications, e.g.…”