Organisation of basement membrane components in the human adult and fetal pituitary gland and in pituitary adenomas

Abstract

Cell-matrix interactions undoubtedly have a role in the development and maintenance of the complex nonrandom structure of the human pituitary gland. We have extended previous studies by documenting the patterns of immunoreactivity for type IV collagen, laminin and fibronectin in the fetal gland, comparing these with the adult patterns. In both we have examined the differences between the anterior lobe and intermediate zone in an attempt to elucidate the apparent differences in functional response between corticotrophs in the two areas. We have also examined expression of these proteins in a series of pituitary adenomas. Finally, we have immunolocalised beta 4 integrin, a component of the alpha 6 beta 4 laminin receptor, in the adult gland and in adenomas. In the anterior lobe of the adult gland, type IV collagen and laminin were present in both epithelial and vascular basement membrane. Fibronectin was related to the basement membrane but showed a less continuous distribution. beta 4 Integrin was expressed on the basal aspects of pituitary cells, in association with laminin, suggesting that this did identify the alpha 6 beta 4 laminin receptor. In addition, immunoreactivity was present on the lateral margins of some pituitary cells, which might indicate a role in cell-cell adhesion. None of the proteins showed specific association with any particular cell type, suggesting that these specific interactions do not regulate differentiation. This pattern of expression had developed in the fetal gland by the second trimester, with expression relating to vessels preceding that in epithelial basement membrane. Type IV collagen, laminin and fibronectin were also expressed in epithelial and vascular basement membrane in the intermediate zone of the adult gland, and around Rathke's cleft in the fetal gland. However, the organisation differed, with larger groups of cells enclosed within a single basement membrane. Possible vascular connections demonstrated between the posterior lobe and the intermediate zone would permit access of posterior lobe hormones to this zone. Our data confirmed disruption of expression in pituitary adenomas, type IV collagen, laminin and beta 4 integrin having a mainly perivascular distribution, with more variable immunoreactivity for fibronectin.

Age-Related Changes in Nestin Immunoreactivity in the Rat Pituitary Gland

“…In one case, nestin was also induced in what were likely to be hyperplastic thyrotrophs. Our observations are consistent with the well-documented remodeling of the vasculature and the perivascular space that occurs during hyperplasia and tumorigenesis of the pituitary gland [50,51,52]. Meanwhile, pericytes migrate, divide and change their morphology in order to facilitate vascular remodeling.…”

Deficiency of cathepsin S reduces atherosclerosis in LDL receptor–deficient mice

“…We observed a similar pattern of Cat S expression in fatty streaks of LDLR -/-mice (Figure 5a). To enter the intima during early atherogenesis, leukocytes must penetrate the arterial basement membrane, which contains type IV and type I collagen, laminin, and fibronectin (46). This study monitored monocyte transmigration in vitro through layers of SMCs, collagen matrix, and ECs.…”

Cathepsin L Deficiency Reduces Diet-Induced Atherosclerosis in Low-Density Lipoprotein Receptor–Knockout Mice

“…Leukocyte migration across the endothelium and subjacent basement membrane may involve degradation of matrix proteins, including type I and type IV collagens. 22 At 12 weeks, lesion characterization demonstrated that the absence of Cat L activity significantly reduced macrophage contents in lesions (Figure 2A). Decreased expression of Cat L also reduced lesion lymphocyte accumulation in a genedose-dependent manner ( Figure 2B), suggesting that Cat L participates in blood-borne leukocyte infiltration during atherosclerosis development, a hypothesis supported by our in vitro transwell chemotaxis assay.…”