Pancreatic islets are micro-organs composed of a mixture of endocrine and non-endocrine cells, where the former secrete hormones and peptides necessary for metabolic homeostasis. Through vasculature and innervation the cells within the islets are in communication with the rest of the body, while they interact with each other through juxtacrine, paracrine and autocrine signals, resulting in fine-tuned sensing and response to stimuli. In this context, cellular protrusion in islet cells, such as primary cilia and filopodia, have gained attention as potential signaling hubs. During the last decade, several pieces of evidence have shown how the primary cilium is required for islet vascularization, function and homeostasis. These findings have been possible thanks to the development of ciliary/basal body specific knockout models and technological advances in microscopy, which allow longitudinal monitoring of engrafted islets transplanted in the anterior chamber of the eye in living animals. Using this technique in combination with optogenetics, new potential paracrine interactions have been suggested. For example, reshaping and active movement of filopodia-like protrusions of δ-cells were visualized in vivo, suggesting a continuous cell remodeling to increase intercellular contacts. In this review, we discuss these recent discoveries regarding primary cilia and filopodia and their role in islet homeostasis and intercellular islet communication.
Bibliographical noteCopyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.
This work was supported by funding from Karolinska Institutet, the Strategic Research Program in Diabetes at Karolinska Institutet,
the Swedish Research Council, the Novo Nordisk Foundation, the Swedish Diabetes Association, the Family Knut and Alice Wallenberg
Foundation, the Jonas & Christina af Jochnick Foundation, the Family Erling-Persson Foundation, Berth von Kantzow’s Foundation,
the Swedish Foundation for Strategic Research and the European Research Council grant ERC-2018-AdG 834860 EYELETS.