Neuroendocrinology and Neuroimmunology
Author: Ivana Maria Gomez | Email: firstname.lastname@example.org
Ivana Maria Gomez 1°, Franco Barrile 1°, Gimena Fernandez 1°, Daniel Castrogiovanni 1°, Maia Uriarte 1°, Mario Perelló 1°, Pablo Nicolás De Francesco 1°
1° Laboratorio de Neurofisiología, Instituto Multidisciplinario de Biología Celular (IMBICE)
Hypothalamic tanycytes are polarized ependymoglial cells that line the ventral part of the third ventricle (V3) and emit processes through the hypothalamic parenchyma and median eminence contacting blood vessels, neurons and other glial cells. We recently described that tanycytes internalize the orexigenic hormone ghrelin trough clathrin-mediated endocytosis. Here, we study its uptake and transport direction in these cells with a fluorescent ghrelin tracer (Fr-ghr) using in vivo, ex vivo and in vitro strategies.
First, we centrally injected mice with Fr-ghr and observed a fluorescent signal in tanycytes 15 min post-injection that was reduced by 87% at 30 min and returned to control values at 60 min. We then studied mouse hypothalamic explants incubated with Fr-ghrelin on their outer side (contacting terminals) or within the V3 (contacting soma), and observed fluorescence within tanycytes only in the second condition. Finally, we used primary cultures of rat hypothalamic tanycytes incubated with a 5-min pulse of Fr-ghr to quantify the intracellular redistribution of fluorescent signal over time. We observed that the signal was mostly found in somas after the 5 min pulse, and significantly increased in processes and terminals after 10 min. After 30 min, fluorescence decreased in the whole cell.
This evidence shows that tanycytes internalize ghrelin in their CSF-contacting soma and transport it to their terminals, possibly playing a role in CSF ghrelin clearance.