Immunolocalization of laminin, heparan‐sulfate proteoglycan, entactin and type IV collagen in the rat anterior pituitary. II. An in vitro study on primary cultures

Abstract

The distribution of four basement membrane components: laminin (LAM), type IV collagen (Coll. IV), heparan-sulfate proteoglycan (HSPG), and entactin (ENT), was studied by immunocytochemistry in primary cultures of adult rat anterior pituitaries. In such cultures, the pituitary cells are deprived of their normal environment of adjacent cells and basement membranes (BM), and of the connectivo-vascular system of the hypophysis. In this dissociated system, pituitary cells grow as small clusters upon a monolayer of fibroblasts. LAM was found highly expressed in endocrine and in folliculo-stellate cells. Very small amounts of Coll. IV, but neither HSPG nor ENT, could be detected in endocrine cells. In contrast, in fibroblasts, very large amounts of Coll. IV, HSPG, and ENT, and a lower quantity of LAM were detected. At the ultrastructural level, the immunoreactive components present within the cells were located in the subcellular compartments involved in the elaboration of exported products. In addition to that intracellular distribution, the four constituents were observed in an extracellular matrix which appeared between the cultured cells, either as an amorphous material, or as a more or less dense reticular network, weakly stained with anti-LAM, but strongly stained with the other antibodies. Thus, the present immunocytochemical data support the implication of pituitary endocrine cells, at least for LAM secretion, in the elaboration of a novel extracellular matrix in primary cultures. In addition, a cooperation with non-endocrine cells seemed to be required for the production of the four BM components.

Human anterior pituitary adenoma cell attachment in vitro

“…Collagen IV appeared to be superior to collagen I for the attachment of adenoma cells, which may reflect the reports of rat endocrine epithelial cells and Rathke's pouch expressing collagen IV rather than collagen I (8,13). However, neither attached the 3 prolactinomas studied and collagen I attached only 6 of 13 tumors, while collagen IV attached only 12 of 13 tumors; there was no difference in viability between collagen I and collagen IV for attached tumors.…”

“…The poor attachment of adenoma cel~s to fibronectin (attaching 6 of 13 tumors) and laminin (attaching 5 of 13 tumors) was unexpected because both of these components have been found in the basement membrane in rat endocrine cells and Rathke's pouch (8,13), suggesting that a combination of extracellular components may be required for attachment of pituitary adenoma cells in vitro. No adhesion to the commercial HEM preparation occurred; however, this preparation is composed of a high percentage of laminin to which pituitary cells were seen to attach poorly.…”

Extracellular Matrix Proteins in the Anterior Pituitary Gland

“…They influenced the organisation of the endocrine cells and their secretory activity. Basement membranes of endothelial and perivascular connective tissue cells express many ECMassociated components, such as different isoforms of laminin and fibronectin, collagen-IV, entactin, and heparan sulphate proteoglycans, associated with the corresponding integrin subunits on cell membranes [40][41][42][43][44][45]. The presence of the traditional molecules that are involved in ECM activities were reported in the pituitary almost three decades ago.…”

Contribution of french electron microscopists to the immunocytochemical analysis of the secretory process

“…The major component of basement membrane, laminin, was also detected by Vila-Porcile et al [25] in most anterior pituitary cell types, in all intracellular compartments, albeit with different intensity depending on cell types. Its distribution was then compared to that of three other components of the basement membrane (heparan-sulfate proteoglycan, entactin and type IV collagen) [26,27]. Localization of membrane antigens.…”