Coxsackievirus and adenovirus receptor-positive cells compose the putative stem/progenitor cell niches in the marginal cell layer and parenchyma of the rat anterior pituitary

Abstract

The pituitary gland is a slow generative tissue but actively responds to demands by changing homeostasis. The marginal cell layer (MCL) facing the residual lumen has long been indicated as a stem/progenitor cell niche of the pituitary. On the other hand, the coxsackievirus and adenovirus receptor (CAR), which localizes at the tight-junction of the polarized epithelium, is known to participate in the development, differentiation and regeneration of specified tissues. The present study attempts to characterize the cells lining the MCL during pituitary development by immunohistochemistry of CAR. Consequently, we found that CAR localizes in an apical surface of the single cell layer facing the oral cavity in the invaginating oral epithelium on rat embryonic day (E) 11.5. On E13.5, when this single layer constructs the MCL in the pituitary primordium Rathke's pouch, CAR-positive cells occupied the MCL and this localization pattern of CAR was persistently maintained throughout life. Moreover, clusters of CAR-positive cells were also found in the parenchyma. CAR-positive cells were positive for stem/progenitor cell markers sex-determining region Y-box 2 (SOX2) and epithelial calcium-dependent adhesion (E-cadherin). However, prior to the postnatal growth wave, cells positive for CAR in the basolateral surface constructed multiple cell layers beneath the MCL and cell-type transition to a putative migratory cell phenotype by fading of SOX2 and E-cadherin occurred, suggesting the composition of new putative niches in the parenchyma. These data, together with our previous reports, suggest that CAR-positive cells are pituitary stem/progenitor cells and compose putative stem/progenitor cell niches in the MCL and parenchyma.

Pituitary stem cell regulation: who is pulling the strings?

“…These and other markers (including E-cadherin, glial cell line derived neurotrophic factor family receptor alpha 2 or GFRA2, nestin and PROP1) were found in the cells of the marginal zone bordering the cleft (Fauquier et al 2008, Gleiberman et al 2008, GarciaLavandeira et al 2009, Yoshida et al 2011, with a similar expression and organization picture in human pituitary (Garcia-Lavandeira et al 2009. In addition, SOX2 + cells were also found within the gland's parenchyma, mostly occurring in clusters and also expressing SOX9 and E-cadherin (Fauquier et al 2008, Chen et al 2013, Nantie et al 2014, Zhu et al 2015. The marginal zone and parenchymal clusters are proposed to represent plural stem cell niches in the pituitary to enable swift adaptation during (subtle) cell remodeling processes (Vankelecom 2012, Vankelecom & Chen 2014.…”

“…In contrast, PRRX2 only emerges after birth from P30 in a subset of the SOX2 + cells . Another mesenchymal marker, VIM, is found co-localized with coxsackie and adenovirus receptor (CAR) in some cells just beneath the marginal cell layer, particularly at neonatal age (Chen et al 2013). CAR has been identified as an additional marker of the (rat) pituitary stem cells in the marginal zone as well as the parenchymal clusters throughout life (Chen et al 2013).…”

Pituitary Stem Cells: Quest for Hidden Functions

“…Finally, a battery of new candidate markers has emerged from recent studies (extensively reviewed in Vankelecom 2010 andChen 2014), including the retinoic acid-producing retinal aldehyde dehydrogenase 1 (Raldh1; Fujiwara et al 2007) and the retinoic acid receptor Rarb (Vankelecom 2010;Vankelecom and Chen 2014); the transcription factors PRRX1 and PRRX2 (expressed in proliferating RP progenitor cells until cell-cycle exit and start of differentiation; Susa et al 2012); the cell-adhesion molecule cadherin-18 (expressed in the MZ in a different pattern than CDH1; Chauvet et al 2009); the coxsackievirus and adenovirus receptor (CAR; Chen et al 2013); the Kr€ uppel-like factor 6 (KLF6; Ueharu et al 2014); and the juxtacrine signaling molecule ephrin-B2 (Yoshida et al 2015). A number of the pituitary stem cell markers identified may be involved in constructing and maintaining the 3D network, in particular the cadherins, ephrins and CAR.…”

Pituitary Stem Cells During Normal Physiology and Disease

“…We isolated SOX2 cells expressing GFP from these two regions by microdissection, and demonstrated that their in vitro clonogenic potential did not differ between the two locations (Andoniadou et al 2012). Recent studies from rat have revealed that double-positive SOX2 + /S100β + cells may be further refined through in vivo expression of the gene Cxadr, which codes for coxsackievirus and adenovirus receptor (CAR; Chen et al 2013). Furthermore, expression of E-cadherin and the juxtacrine factor ephrin-B2 reportedly define SOX2 + /S100β + /CAR + cells, both in the marginal epithelium and throughout the parenchyma (Chen et al 2013;Yoshida et al 2015).…”

“…Recent studies from rat have revealed that double-positive SOX2 + /S100β + cells may be further refined through in vivo expression of the gene Cxadr, which codes for coxsackievirus and adenovirus receptor (CAR; Chen et al 2013). Furthermore, expression of E-cadherin and the juxtacrine factor ephrin-B2 reportedly define SOX2 + /S100β + /CAR + cells, both in the marginal epithelium and throughout the parenchyma (Chen et al 2013;Yoshida et al 2015). Analysing the side population, the Vankelecom group (2010) also reported enrichment in ephrin-B expression in this stem cell-rich compartment; together the data suggested that ephrin-B expression was a hallmark of the population containing PSCs.…”