Beta cells in fresh pancreatic slices: applying physiology on functional networks
Jurij Dolenšek, Institute of Physiology, University of Maribor
Oscillatory electrical activity is regarded as a hallmark of the pancreatic beta cell glucose-dependent excitability pattern. Electrophysiologically recorded membrane potential oscillations in beta cells are associated with in-phase oscillatory cytosolic calcium activity ([Ca2+]i) measured with fluorescent probes. Jurij Dolensek recently introduced functional multicellular [Ca2+]i imaging to study [Ca2+]i changes in a large number of beta cells from all layers of an islet in acute pancreas tissue slices, an approach unique to his laboratory.
Glucose stimulation of beta cells in intact islets within acute tissue slices produces a [Ca2+]i change with initial transient phase followed by a plateau phase with highly synchronized [Ca2+]i oscillations. Glucose modulates both the basal [Ca2+]i response and the superimposed [Ca2+]i oscillations. Increasing glucose concentrations recruits cells within an islet in a concentration and time dependent manner. At physiological levels of glucose, recruitment of beta cells is an important mechanism of response to increasing concentrations of glucose. To further decipher beta-cell physiology, we recently introduced high resolution voltage-sensitive dye based confocal imaging in pancreatic tissue. Glucose-evoked membrane potential oscillations spread over the islet in a wave-like manner, with membrane potential and [Ca2+]i having tight but nevertheless limited coupling. Ultimately, [Ca2+]i oscillatory activity was used to construct functional complex networks of beta cells. The extracted connectivity networks are sparse for low glucose concentrations, whereas for higher stimulatory levels they become more densely connected. Beta cells within the islets form locally clustered functional sub-compartments exhibiting a modular nature. Furthermore, cells in the network that are most interconnected have higher dissipation rates, i.e. consuming more energy, indicating a potential risk for pathological changes in the tissue. Currently we have an ongoing project on applying high temporal and spatial resolution calcium imaging on human tissue which displays some important structural differences compared with the mouse pancreas.Contact person: Christina Bark