Plasminogen activator inhibitor-2 expression in inflamed appendix

Mesothelial cells: their structure, function and role in serosal repair

The mesothelium is composed of an extensive monolayer of specialized cells (mesothelial cells) that line the body's serous cavities and internal organs. Traditionally, this layer was thought to be a simple tissue with the sole function of providing a slippery, non-adhesive and protective surface to facilitate intracoelomic movement. However, with the gradual accumulation of information about serosal tissues over the years, the mesothelium is now recognized as a dynamic cellular membrane with many important functions. These include transport and movement of fluid and particulate matter across the serosal cavities, leucocyte migration in response to inflammatory mediators, synthesis of pro-inflammatory cytokines, growth factors and extracellular matrix proteins to aid in serosal repair, release of factors to promote both the deposition and clearance of fibrin, and antigen presentation. Furthermore, the secretion of molecules, such as glycosaminoglycans and lubricants, not only protects tissues from abrasion, but also from infection and possibly tumour dissemination. Mesothelium is also unlike other epithelial-like surfaces because healing appears diffusely across the denuded surface, whereas in true epithelia, healing occurs solely at the wound edges as sheets of cells. Although controversial, recent studies have begun to shed light on the mechanisms involved in mesothelial regeneration. In the present review, the current understanding of the structure and function of the mesothelium and the biology of mesothelial cells is discussed, together with recent insights into the mechanisms regulating its repair.

Peritoneal sclerosis: one or two nosological entities?

The frequency, pathology, animal models, pathogenesis, clinical manifestations, diagnostic criteria, therapy and prevention of peritoneal sclerosis are reviewed. Many of these aspects have a bimodal configuration which suggests that peritoneal sclerosis, usually considered a single pathology in peritoneal dialysis, is actually two distinct nosological entities: simple sclerosis and sclerosing peritonitis. The former is very frequent, with minor anatomical alterations and low clinical impact; it is reproducible in animals by means of peritoneal dialysis, and is clearly due to the poor biocompatibility of peritoneal dialysis solutions. The latter is rare, with radical anatomical alterations and high mortality requiring valid methods of diagnosis, therapy and prevention; it can only be reproduced in animal models by means other than peritoneal dialysis and seems to be due to factors both related and unrelated to peritoneal dialysis.

Immunohistochemical demonstration of the plasminogen activator system in human gingival tissues and gingival fibroblasts

The relative distribution of urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1) and plasminogen activator inhibitor-2 (PAI-2) was studied in cultured human gingival fibroblasts, healthy gingival tissues and inflamed gingival tissues by immunohistochemistry. In cultured gingival fibroblasts t-PA, u-PA and PAI-1 were expressed in cytoplasm; u-PA and PAI-1 were more intensely stained than t-PA; PAI-2 was not detectable in gingival fibroblasts. Following interleukin 1 beta (IL-1 beta) stimulation, the intensity of intracellular staining for t-PA was increased and a number of cells staining strongly for PAI-2 were seen; no difference in the intensity of immunostaining level was noted for the expression of u-PA and PAI-1 between IL-1 beta stimulated cells and unstimulated cells. In healthy gingival tissues, u-PA and PAI-1 displayed a wide distribution throughout all the connective tissue and epithelium; t-PA localized mainly in the connective tissue while PAI-2 showed little association with the connective tissue but did faintly stain in the epithelial layer. In inflamed gingival tissues, staining for t-PA was significantly increased in the extracellular matrix of the connective tissue, whereas staining for u-PA, PAI-1 and PAI-2 was found to be slightly increased, but no significant difference was noted for staining when compared with the healthy gingival tissues. A granular distribution of t-PA, u-PA, PAI-1 and PAI-2 was noted around areas of inflammatory cell infiltration. These immunohistochemical findings indicate that the plasminogen activator system produced by fibroblasts may be influenced by the presence of the inflammatory mediator IL-1 beta. In addition, the significant increase of t-PA in inflamed connective tissue and the wide expression of these components around inflamed cells may contribute to connective tissue degradation and may relate to the migration and localization of monocytes/macrophages in inflamed tissue.