title: Heterogeneity and nearest-neighbor coupling can explain small-worldness and wave properties in pancreatic islets.
abstract: Many multicellular systems consist of coupled cells that work as a syncytium. The pancreatic islet of Langerhans is a well-studied example of such a microorgan. The islets are responsible for secretion of glucose-regulating hormones, mainly glucagon and insulin, which are released in distinct pulses. In order to observe pulsatile insulin secretion from the β-cells within the islets, the cellular responses must be synchronized. It is now well established that gap junctions provide the electrical nearest-neighbor coupling that allows excitation waves to spread across islets to synchronize the β-cell population. Surprisingly, functional coupling analysis of calcium responses in β-cells shows small-world properties, i.e., a high degree of local coupling with a few long-range "short-cut" connections that reduce the average path-length greatly. Here, we investigate how such long-range functional coupling can appear as a result of heterogeneity, nearest-neighbor coupling, and wave propagation. Heterogeneity is also able to explain a set of experimentally observed synchronization and wave properties without introducing all-or-none cell coupling and percolation theory. Our theoretical results highlight how local biological coupling can give rise to functional small-world properties via heterogeneity and wave propagation.
authors.affiliation: Department of Information Engineering, University of Padua, Via Gradenigo 6/B, 35131 Padua, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Cappon
authors.affiliation: Department of Information Engineering, University of Padua, Via Gradenigo 6/B, 35131 Padua, Italy.
authors.forename: Morten Gram
authors.initials: MG
authors.lastname: Pedersen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002450:Cell Communication; D007515:Islets of Langerhans / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D018408:Patch-Clamp Techniques
chemical_list: D002118:Calcium