Expression of ZO1, vimentin, pan-cadherin and AGTR1 in tanycyte-like cells of the sulcus medianus organum

Abstract

Tanycytes are a specialized ependymal lining of brain ventricles with exceptional features of having long basal processes and junctional complexes between cell bodies. These tanycytes are present at the regions of circumventricular organs (CVOs) which possess common morphological and functional features enabling them to be described as the brain windows where the barrier systems have special properties. Previous studies detailed seven of these CVOs but little information is available regarding another putative site at the rostral part of the median sulcus of the 4th ventricle, or the sulcus medianus organum (SMO). Here we performed a pilot immunohistochemical study to support earlier observations suggesting the SMO as a novel CVO. We labeled rat brain with ZO1, vimentin, pan-cadherin and angiotensin II type 1 receptors markers which showed a morphologically distinct population of cells at the region of the SMO similar to tanycytes present in the median eminence, a known CVO. These cells had basal processes reaching the deeply seated blood vessels while the caudal part of the median sulcus did not show similar long cellular extensions. We concluded that tanycyte-like cells are present in the SMO in a pattern resembling that of other CVOs where the strategic location of the SMO is probably for signal integration between brainstem nuclei and the rostrally located neuronal centers.

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“…PR-A may also suppress the transcriptional activity of PR-B, which is the main receptor for the nuclear signal transduction of progesterone (31,32) . Apart from myometrial contractions, the functional progesterone withdrawal due to the altered expression of PR-A, PR-B isoforms may also contribute to the cervical changes during labor (33,34) . While the exact mechanism of action of progestogens in preventing preterm labor is unknown, several possibilities have been proposed; in summary by two mechanisms; either anti-inflammatory effect, or local increase in progesterone in gestational tissues (35)(36)(37)(38)(39)(40)(41) as it may act on prevention of gap junctions formation which inhibits myometrial contractions and prevent spontaneous early miscarriage and preterm labor (PTL) (42) .…”

“…Rare studies have been done to describe the ECs of the SMO region using H&E stains under light microscope. SMO region with H&E staining appears as median longitudinal cleft in the floor of the 4 th ventricle lined by single layer of ECs while in its deepest part it is lined by more than one layer of ECs (33) . In this study we reported that the SMO region was located in the rostral part of the of the median sulcus region at the floor of the 4 th ventricle and when we stained with H&E we noted that SMO region lined by multilayer of ECs at the deepest part low columnar or cuboidal in shape (Figures 1-2).…”

“…The ME forms the lower part of the brain extending caudal to the optic chiasm up to the hypophyseal stalk (35) . The ventricular surface of ME is formed by a single layer of ECs (33) . Horstmann (11) first used the word "tanycyte" when he described the ECs lining the infundibular recess of the 3rd ventricle because of their shape.…”

“…Tanycytes in the CVOs were investigated by examining vemintin positive ECs lining the walls of the ventricles (37) . Al-Kaabi et al (33) observed that vimentin-labeled ECs of the 3rd ventricle have basal processes extending toward the deeper capillaries. expression in the rat during a search of the EST database for novel members of the MCT family.…”