Mesothelial cells and peritoneal homeostasis.

The mesothelium was traditionally thought to be a simple tissue with the sole function of providing a slippery, nonadhesive, and protective surface to allow easy movement of organs within their body cavities. However, our knowledge of mesothelial cell physiology is rapidly expanding, and the mesothelium is now recognized as a dynamic cellular membrane with many other important functions. When injured, mesothelial cells initiate a cascade of processes leading either to complete regeneration of the mesothelium or the development of pathologies such as adhesions. Normal mesothelial healing is unique in that, unlike with other epithelial-like surfaces, healing appears diffusely across the denuded surface, whereas for epithelium healing occurs solely at the wound edges. This is because of a free-floating population of mesothelial cells which attach to the injured serosa. Taking advantage of this phenomenon, intraperitoneal injections of mesothelial cells have been assessed for their ability to prevent adhesion formation. This review discusses some of the functions of mesothelial cells regarding maintenance of serosal integrity and outlines the mechanisms involved in mesothelial healing. In addition, the pathogenesis of adhesion formation is discussed with particular attention to the potential role of mesothelial cells in both preventing and inducing their development.

Quantification of total and perfused blood vessels in murine skin autografts using a fluorescent double-labeling technique.

BACKGROUND: Two theories exist regarding the revascularization of skin autografts: direct anastomosis between graft vessels and bed vessels, and ingrowth of bed vessels (angiogenesis) into the graft. This study characterizes revascularization, spatially and chronologically, in a murine skin autograft model using a double-labeling technique. METHODS: Full-thickness (1 cm2) skin grafts were performed on adult male C57/Bl6 mice. After 48 hours, 60 hours, 3 days, 5 days, and 14 days (n = 3 mice per time point) terminal intracardiac perfusion with a fluorescein/dextran dye demonstrated vascular filling of graft blood vessels. Fluorescence immunohistochemistry of CD31+ endothelial cells allowed counting of total vessels and fluorescein perfusion quantification of patent vessels in the lateral graft area, central graft area, graft bed, and wound margins. RESULTS: Initial filling of graft vessels was seen after 48 hours. This included vessels in the papillary dermis of the graft, and there was no significant difference in the percentage of filled vessels in the deep dermis of the graft compared with the papillary dermis of the graft. A rapid increase in vessel filling was seen between 48 and 60 hours in all areas of the graft. Vessel filling occurred mainly in the central area of the graft rather than in the lateral areas. CONCLUSIONS: The short time course of vessel filling indicates that the initial onset of revascularization is attributable to early anastomoses between graft and bed vessels, mainly in the central area of the graft. These findings have implications for both autograft revascularization in a clinical setting and in the development of tissue-engineered skin substitutes.