Immune function of epithelial cells
Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald in Principles of Mucosal Immunology, 2020
In general, there are two broad histological types of epithelia that line mucosal surfaces: stratified squamous epithelia and simple epithelia, which can be columnar or cuboidal (Figure 5.1). Stratified refers to the presence of multiple epithelial layers that are composed of squamous cells in the vagina, urethra, rectal canal, mouth, esophagus, pharynx, and nasal surfaces. Most often, the stratified squamous mucosa immediately abuts the skin, or is located close to it, and these surfaces do not participate in large-scale selective transport of materials necessary for life. The stratified squamous epithelium that is associated with mucosal tissues is distinguished from the squamous epithelium of the skin by the fact that the former is noncornified, i.e., there is not typically a dense layer of acellular keratin on the apical, i.e., luminal, surface. This can, however, develop in squamous mucosa as a response to chronic injury and is present in some neoplasms, e.g., esophageal verrucous (squamous cell) carcinomas.
Experimental Oral Carcinogenesis
Samuel Dreizen, Barnet M. Levy in Handbook of Experimental Stomatology, 2020
Most of the research on chemical carcinogenesis utilized the polycyclic hydrocarbons in the skin of mice. As indicated earlier, the mouse became one of the animals of choice for the exploration of the pathogenesis of malignant change in epithelial cells. It was only natural, then, that when the field of oral oncology started to develop, the oral cancer researchers would apply the known skin carcinogens to the oral mucosa. If malignant disease developed, its pathogenesis could be studied. There are obvious similarities as well as differences between skin and oral mucosa. All epithelial surfaces or membranes are said to be protective, but the amount of protection they provide differs in different anatomical locations and is reflected in differences in structure. In some sites, the epithelial membranes perform additional functions, such as secretion and/or absorption. In these sites the structures are modified further. All epithelial coverings, however, do have features in common. They consist almost entirely of cells fitted closely together. Epithelial membranes contain no blood vessels, so the cells obtain nourishment from the tissue fluids of the underlying connective tissue. Almost all epithelial membranes possess a great capacity for multiplication, since almost all are subjected to some degree of “wear and tear” during their normal function, and they must therefore be capable of regeneration.
Identifying Nanotoxicity at the Cellular Level Using Electron Microscopy
Suresh C. Pillai, Yvonne Lang in Toxicity of Nanomaterials, 2019
Epithelial tissue, or epithelium (which comes from the Latin meaning ‘upon sheets’) is found covering surfaces of the body that either come into contact with the exterior or line the internal tubes and cavities. The initial interaction of nanoparticles with cells in an in vivo system tend to be primarily with epithelial cells. Moreover, many nanotoxicological studies at the ultrastructural level using EM will use epithelial cells in culture to classify and investigate the interaction at the bio-nano interface (Muhlfeld et al., 2007b, Ye et al., 2015). All epithelia are avascular but adhere to a vascularised bed of connective tissue, with the two layers being separated by an intermediate layer known as the basement membrane, which is generally manufactured by and secreted from the epithelial cells themselves. Epithelial cells display three key characteristics: cells are tightly bound together to form these sheet-like structures through junctional complexes; there are functionally different membrane domains within the cell (apical, basal, and lateral), and cells adhere to the underlying basement membrane (Gray et al., 1995, Ross, 1995, Young and Wheater, 2006). Therefore, they present the ideal model system for studying nanoparticle uptake.
Critical roles of adherens junctions in diseases of the oral mucosa
Published in Tissue Barriers, 2023
Christina Kingsley, Antonis Kourtidis
The oral epithelium is a stratified human tissue responsible for protection from direct exposure to the environment and to numerous pathogens. This renders cellular components that regulate integrity of the epithelium, such as the AJs, critical for the health and homeostasis of the tissue. Although there has been significant research in this field, including the studies we discuss in this review, the role of AJs in diseases of the oral epithelium is far from being fully explored, especially when compared to similar research in other epithelial tissues, which have been more extensively studied. For example, the full breadth of the ways that the hundreds of oral microbial species modulate AJ composition, as well as the mechanisms through which they can tamper with AJs to infiltrate host cells, is still not known. More importantly, little is known on the impact that the microbial-AJ crosstalk in intracellular cadherin signaling and eventually in cell behavior. Such signaling could include, for example, investigation of JNK and RhoA activity, which have been specifically associated with intercellular E-cadherin junctions in human gingival epithelial cells.137 Therefore, further investigation of the microbial-AJ interaction could provide novel insights in the regulation of the diseases of the oral epithelium and can be a future field of therapeutic intervention of pathologies that are caused by external pathogens, both bacterial and viral.
A comprehensive overview of advanced dynamic in vitro intestinal and hepatic cell culture models
Published in Tissue Barriers, 2023
Filipa Leal, Scarlett Zeiringer, Ramona Jeitler, Pedro F. Costa, Eva Roblegg
The small intestine is the main location where absorption occurs. Because of the formation of villi and microvilli, the surface area is rather large and well supplied with blood vessels. The epithelium is composed of different cell types with columnar shapes and tight cell-cell junctions, covered by a mucus layer. The columnar shape is established by the formation of the typical crypt-villus units (Figure 1). Crypts are invaginations of the intestinal epithelium that primarily accommodate proliferating cells, enabling the renewal of the epithelial cells.19 In addition, villi are finger-like structures whose functions include lumen sensing, digestion, absorption, secretion, and immune defense.20 The epithelial cells themselves form microvilli, which are actin-based membrane features. Their functions include absorption, secretion, mechano-transduction and increase of the surface area leading to a greater interaction with nutrients and drugs.21
Congenital Pouch Colon: Further Histopathological Perspectives
Published in Fetal and Pediatric Pathology, 2022
Neha Singh, Suravi Mohanty, Inchara Yeliur Kalegowda, Pritilata Rout
Case 1 showed lining of pseudostratified columnar epithelium and transitional epithelium with foci of squamous metaplasia. The epithelial lining represents a histological transition from the hindgut into the urinary bladder in ano-urogenital communications. Since the colovesical fistula opens at the dome of the bladder, high on its posterior wall or occasionally in the vesicourethral territory, it bears the lining epithelium of the urinary bladder or anal canal [10,20]. In our case, the flattened areas adjacent to the fistulous orifice in the pouch displayed these features. The cystitis glandularis with intestinal metaplasia in Case 1 is believed to develop from the Von Brunn’s nests. The intestinal subtype of cystitis glandularis has been described as premalignant, but progression to cancer may be a long-term process [21]. The squamous metaplasia and intestinal metaplasia due to irritation of the native tissue illustrates early changes in a nine-month infant.Though there is no documentation of an adenocarcinoma developing in a CPC till date, retaining the pouch has a potential risk of metaplasia and malignant transformation.