VEGF-dependent and PDGF-dependent dynamic neurovascular reconstruction in the neurohypophysis of adult mice

Abstract

Hypothalamo-neurohypophysial system (HNS) releases arginine vasopressin (AVP) and oxytocin (OXT) from axonal terminals of the neurohypophysis (NH) into blood circulation for controlling body fluid homeostasis and lactation. Chronic osmotic and suckling stimulations have been shown to cause neurovascular and neuroglial reconstruction in the NH of adult mammals and no study has been reported for vascular dynamics. The aim of this study was to elucidate the occurrence of continuous angiogenesis and growth factor-dependent neurovascular reconstruction in the NH of adult mice. Active proliferation of endothelial cells and oligodendrocyte progenitor cells (OPCs) was observed using the immunohistochemistry of bromodeoxyuridine and Ki-67. Vascular endothelial growth factor A (VEGFA) and VEGF receptor 2 (VEGFR2 (KDR)) were highly expressed at pituicytes and endothelial cells respectively. Moreover, prominent expression of platelet-derived growth factor B (PDGFB) and PDGF receptor beta was observed at OXT-containing axonal terminals and pericytes respectively. Administration of the selective tyrosine kinase inhibitor AZD2171 for VEGFRs and STI571 for PDGFRs significantly decreased proliferation of endothelial cells and OPCs. Moreover, AZD2171 treatment decreased vascular density by facilitating apoptosis of endothelial cells and the withdrawal of its treatment led to remarkable rebound proliferation of endothelial cells, so that vascular density rapidly returned to normal levels. AZD2171 decreased the density of both AVP-and OXT-containing axonal terminals, whereas STI571 selectively decreased the density of AVP-containing ones. Thus, this study demonstrates that the signaling pathways of VEGF and PDGF are crucial mediators for determining proliferation of endothelial cells and OPCs and the density of AVP-and OXT-containing axonal terminals in the HNS.

Single-cell molecular and cellular architecture of the mouse neurohypophysis

“…Among them, Mest, Srebf1, Adm and Col25a1 were not reported to be expressed by pituicyte before. Vegfa was reported as pituicyte marker in both mice and zebrafish (Anbalagan et al, 2018;Furube et al, 2014). Another prominent pituicyte marker we identified, namely Rax, is a known hypothalamic tanycyte marker which is also expressed in the NH Pak et al, 2014).…”

“…The identified differentially expressed gene clusters revealed by scRNA-Seq correspond to previously characterized cell types. Thus, previous studies reported the appearance of pituicyte (Anbalagan et al, 2018;Furube et al, 2014;Seyama et al, 1980;Wittkowski, 1986;Yamamoto and Nagy, 1993), macrophage/microglia (Kindt et al, 2007;Pow et al, 1989;Sasaki and Nakazato, 1992), and fenestrated endothelia (Stan et al, 1999) in the NH. The identification of IL and epithelial-like cells in the present study is in agreement with other reports of these cells in the mammalian pituitary (Hudson, 2002;Moran et al, 2010) and also matches recent scRNA-Seq analyses of whole mouse pituitary (Cheung et al, 2018;Ho et al, 2018;Mayran et al, 2018).…”

“…Furthermore, Apoe, which is often used as pituicyte and astrocyte marker displayed low cell-type specificity, as it was detected in all neurohypophyseal types except for T-cell like. The other three reported pituicyte markers Gja1/Cx43, Vegfa and Vim (Yamamoto and Nagy, 1993;Furube et al, 2014;Marin et al, 1989;) displayed higher normalized pituicyte expression and were somewhat more specific than Apoe (Fig. 4B).…”

Robust increase of microglia proliferation in the fornix of hippocampal axonal pathway after a single LPS stimulation

“…The experimental procedure was performed according to our previous study (Furube et al, 2014). For the detection of new-born cells, animals received BrdU via intraperitoneal administration (200 mg/kg) or in the drinking water (1 mg/ml).…”

Structural Reconstruction of the Perivascular Space in the Adult Mouse Neurohypophysis During an Osmotic Stimulation

“…We recently reported continuous angiogenesis, which accompanies the proliferation and apoptosis in endothelial cells, in the ME , NH and sensory CVOs . Angiogenesis starts at the embryonic period, persists until the early postnatal period, and then becomes quiescent along with the formation of the BBB .…”