Mesothelial lamellar bodies in norm and experimental conditions. Transmission and scanning electron microscopic observations on the peritoneum, pleura and pericardium

Abstract

The ultrastructural characteristics of the mesothelial intracellular and extracellular lamellar bodies (LB) in norm, and especially in pathological conditions are still unknown. After routine fixation procedure, material from organs in the three serous cavities of Wistar rats, as control group were compared with animals following experimental hemothorax (EH) and experimental peritonitis (EP), using transmission and scanning electron microscopy (TEM, SEM). Different membrane-bound profiles, short strip-like structures and single LB characterize the control group. Five days after EH small groups of LB were observed. Single balloon-like profiles, numerous particles and larger groups of LB with wide varieties in size, form and membrane structure characterize the 8th day after EH. Thin and concentric membranes build single LB the 5th day of EP. Eight days after the same treatment, groups of LB, complex structures with several multilamellar centers, strip-like structures with rough granulo-filamentous material and uninterrupted covering over wide areas were observed. We conclude that constant components in the untreated rats are different membrane profiles, as initial lamellar formations and single typical LB with predominant intracellular position. The preferable sites for exocytosis of LB are the intercellular spaces. The present data demonstrate simultaneous findings of the two main groups of formations by using routine fixation in the control group and in the treated animals. The first represent LB as well as other round profiles, observed by TEM and particles, observed by SEM, which are widespread and probably have a basic role. The second ones are strip-like structures and its SEM-equivalents, i.e. uninterrupted covering. TEM-profiles and their SEM-images show significant organ differences and in some cases lack of correspondence between both electron microscopic techniques in the same treatment. Significant enlargement of the number of LB and the length of the strip-like structures characterize the mesothelium after pathologic conditions. LB with considerable differences in the structure and larger particles over the microvillous border predominate after EH. Strip-like profiles, continuous covering and smaller groups of LB with similar morphology and preferable submesothelial position characterize the mesothelium after EP.

Transforming growth factor β1 produced in autocrine/paracrine manner affects the morphology and function of mesothelial cells and promotes peritoneal carcinomatosis

“…It has been previously reported that healthy mesothelial cells can prevent tumor cell invasion and metastasis by providing an intact barrier. Interestingly, tumor cells are also known to secrete various factors to induce damage or apoptosis in mesothelial cells and the disrupted mesothelial cells will then promote tumor cells invasion (17)(18)(19). We hypothesize that the damaged peritoneum may provide such a microenvironment for scirrhoid gastric cancer cell metastasis.…”

Pericardium: structure and function in health and disease

“…There are numerous vesicles, vacuoles and multivesicular bodies, as well as the signs of the robust vesicle formation at the cell membranes in the form of either coated or uncoated vesicles being in the process of internalization from or budding of the cell membranes ( Figure 1). In addition, the cytoplasm of cuboidal cells contains numerous vesicles/vacuoles filled entirely or partially with an electron-dense material, sometimes displaying a multilamellar appearance, often described as dense bodies [8] (Figure 1). These structures are believed to contain surfactant-like substances, similar to those produced by type II pneumocytes [8].…”

“…In addition, the cytoplasm of cuboidal cells contains numerous vesicles/vacuoles filled entirely or partially with an electron-dense material, sometimes displaying a multilamellar appearance, often described as dense bodies [8] (Figure 1). These structures are believed to contain surfactant-like substances, similar to those produced by type II pneumocytes [8]. The apical surface of cuboidal cells is covered by abundant microvilli, having the length of up to 3 μm [3][4][5][6][7]; some of the microvilli bifurcate near their ends.…”

Pleural Lubrication

“…Their presence has been later suggested also on pleura, peritoneal and pericardial mesothelium [12,[30][31][32][33]. Actually, by transmission electron microscopy, Wang [12] and Ohtsuka [32] found that colloidal iron stain of mesothelial glycocalyx is removed by neuraminidase treatment, which cleaves sialic acid from sialomucin.…”

“…Moreover, in samples of human and rat peritoneum, Dobbie and Anderson [49], and Michailova [33] provided electron microscopy evidence of several lamellar bodies among the microvilli, and of some superficial lamellar membranes. Unfortunately, no information is available on the spatial and functional relationships between these phospholipids layers and the mucopolysaccharides coat of the mesothelial surface glycocalyx under physiological conditions.…”