![]() 1A), who found that cells resembling the embryonic radial glial cells, by virtue of their retaining their embryonic connection with the surface of the central nervous system, were abundant in the brains of adult fish, amphibians, and reptiles, but were restricted to specific brain areas in birds and mammals ( 2). These elongated ependymoglial cells had already been described in 1909 by Santiago Ramón y Cajal ( Fig. Historically, the term tanycytes, after τανύς (tanus) for “stretched” in Greek, was first used in 1954 by Ernst Horstmann to describe a group of cells bridging the cerebrospinal fluid (CSF) and the pial surface of the brain in cartilaginous fishes ( 1). Tanycyte–endothelial cell interactions tightly control the direct access of bloodborne signals to select hypothalamic neurons involved in the adaptive response to metabolic changes Tanycytes shuttle circulating metabolic hormones into the brain Tanycytes lie at a nodal point in the hypothalamus, from which they man the dialogue between the brain and the peripheryĭynamic tanycyte-neuron interactions are part of the physiology of several neuroendocrine axes Tanycytes are highly plastic elements in the adult central nervous system We will also discuss the putative involvement and therapeutic potential of hypothalamic tanycytes in metabolic and fertility disorders. In this article, we will examine these recent advances in the understanding of tanycytic plasticity and function in the hypothalamus and the underlying molecular mechanisms. Tanycytes could thus constitute the missing link in the loop connecting behavior, hormonal changes, signal transduction, central neuronal activation and, finally, behavior again. Moreover, accumulating data suggest that, in keeping with their putative descent from radial glial cells, tanycytes are endowed with neural stem cell properties and may respond to dietary or reproductive cues by modulating hypothalamic neurogenesis. In addition to their barrier properties, tanycytes possess the ability to sense blood glucose levels, and play a fundamental and active role in shuttling circulating metabolic signals to hypothalamic neurons that control food intake. Tanycytes, a specialized glial cell type lining the wall of the third ventricle in the median eminence of the hypothalamus, appear to act as the linchpin of these processes by dynamically controlling the secretion of neuropeptides into the portal vasculature by hypothalamic neurons and regulating blood-brain and blood–cerebrospinal fluid exchanges, both processes that depend on the ability of these cells to adapt their morphology to the physiological state of the individual. The fertility and survival of an individual rely on the ability of the periphery to promptly, effectively, and reproducibly communicate with brain neural networks that control reproduction, food intake, and energy homeostasis. ![]()
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