Abstract
The anterior and intermediate lobes of the pituitary are composed of endocrine cells, as well as vasculature and supporting cells, such as folliculostellate cells. Folliculostellate cells form a network with several postulated roles in the pituitary, including production of paracrine signalling molecules and cytokines, coordination of endocrine cell hormone release, phagocytosis, and structural support. Folliculostellate cells in rats are characterised by expression of S100B protein, and in humans by glial fibrillary acid protein. However, there is evidence for another network of supporting cells in the anterior pituitary that has properties of mural cells, such as vascular smooth muscle cells and pericytes. The present study aims to characterise the distribution of cells that express the mural cell marker platelet derived growth factor receptor beta (PDGFRβ) in the mouse pituitary and establish whether these cells are folliculostellate. By immunohistochemical localisation, we determine that approximately 80% of PDGFRβ+ cells in the mouse pituitary have a non-perivascular location and 20% are pericytes. Investigation of gene expression in a magnetic cell sorted population of PDGFRβ+ cells shows that, despite a mostly non-perivascular location, this population is enriched for mural cell markers but not enriched for rat or human folliculostellate cell markers. This is confirmed by immunohistochemistry. The present study concludes that a mural cell network is present throughout the anterior pituitary of the mouse and that this population does not express well-characterised human or rat folliculostellate cell markers.
Highlights
The pituitary is an endocrine gland located underneath the brain that produces and releases circulating hormones in response to signals from the hypothalamus
To visualise whether PDGFRβ+ cells are found only in a perivascular location in the anterior pituitary, we immunostained for PDGFRβ in sections of pituitary from adult mice that had been intravascularly perfused with an opaque resin at termination 19
20% of PDGFRβ+ cells were seen to be either contacting or surrounding anterior pituitary blood vessels in a location characteristic of pericytes, 80% were located in the pituitary parenchyma in a location and distribution characteristic of folliculostellate cells (Figure 1C)
Summary
The pituitary is an endocrine gland located underneath the brain that produces and releases circulating hormones in response to signals from the hypothalamus Folliculostellate cells are named after their appearance in electron micrographs: they have a distinctive stellate shape and surround follicular structures 1 Their long cytoplasmic processes connect to form a three-dimensional network 2 that is thought to perform multiple roles in the pituitary including production of paracrine signalling molecules and cytokines 1, coordination of endocrine cell hormone release 3, phagocytosis 4 and structural support 5. There is evidence that folliculostellate cells in rats are composed of multiple subpopulations that may arise from different precursors 6 Mural cells such as vascular smooth muscle cells and pericytes are required for the formation and stability of the vasculature and the support of endothelial cells. This study aims to characterise the distribution of PDGFRβ+ cells in the mouse pituitary and establish whether these cells have folliculostellate cells and/or mural-like properties
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