Simple Epithelial Cells Research Articles

Characterisation of maturation of photoreceptor cell subtypes during zebrafish retinal development.

ABSTRACTPhotoreceptor cells (PRCs) mature from simple epithelial cells, a process characterised by growth and compartmentalisation of the apical membrane into an inner and an outer segment. So far, a PRC subtype-specific description of morphological and cellular changes in the developing zebrafish retina is missing. Here, we performed an in-depth characterisation of four of the five PRC subtypes of the zebrafish retina between 51 and 120 h post fertilisation, including quantification of the size of different compartments, localisation of polarity proteins and positioning of organelles. One of the major findings was the anisotropic and subtype-specific growth of the different PRC compartments. In addition, a transient accumulation of endoplasmic reticulum in rod PRCs, changes in chromatin organisation in UV sensitive cones and differential expression of polarity proteins during the initial stages of PRC maturation were observed. The results obtained provide a developmental timeline that can be used as a platform for future studies on PRC maturation and function. This platform was applied to document that increased exposure to light leads to smaller apical domains of PRCs.

Limbal stem cell transplants and amniotic membrane grafts in ocular surface disease: current perspectives.

Limbal stem cells (LSC) play pivotal role in corneal epithelial cell homeostasis and corneal epithelial healing. In addition to corneal epithelial cell regeneration, LSC act as barrier, preventing conjunctival epithelial cells to grow on to the cornea. Limbal stem cell deficiency (LSCD) may occur following trauma, immune mediated diseases, repeated surgical procedures at limbus and genetic diseases. Chemical eye injury remains the most frequent cause of LSCD. LSCD leads to conjunctivilization, corneal vascularization, recurrent erosions and corneal opacification. LSCD is best addressed with surgical procedure, limbal stem cell transplantation (LSCT). Uniocular LSCD is treated with autologus LSCT and bilateral LSCD with live-related LSCT or cadaveric LSCT. Recently cultivated limbal stem cell transplants (CLSCT) have been used to rehabilitate damaged ocular surface. Cultivated oral mucosal epithelial cell have also been used successfully to reconstruct the ocular surface. More recently, simple limbal epithelial cell transplantation (SLET) has been introduced to treat LSCD. The technique is simple, inexpensive and does not require elaborate laboratory set up. Following LSCT dry eye, glaucoma, eyelid abnormalities and ocular surface inflammation should be addressed. Inflammation is detrimental to the survival of LSC. Thus ocular surface inflammation should be kept minimum using topical or systemic corticosteroid or immune suppressants. Results of LSCT in inflammatory disorders including Stevens-Johnson syndrome and ocular cicatricial pemphigoid are less favorable. AMG and LSCT have revolutionized the ocular surface disease management.

Histological Organization of Thyroid and Interrenal Glands of the Pearl Mullet, Alburnus tarichi (Cypriniformes: Cyprinidae) from Lake Van Basin of Turkey

In this study, histological organizations of the thyroid and interrenal glands were first investigated in pearl mullet (Alburnus tarichi Guldenstadt, 1814), living in the Lake Van basin in Turkey. The serial sections taken from the subpharyngeal region and kidney were stained with hematoxylin and eosin, Mallory’s trichrome and periodic acid-Schiff/hematoxylin and then examined. The histological examinations showed that the thyroid gland of pearl mullet was unencapsulated and the thyroid follicles were scattered diffusely in the subpharyngeal region, located at the dorsal and lateral aspects of the ventral aorta. The follicles had colloid-filled lumens and were surrounded by simple follicular epithelial cells varying in shapes (squamose, cuboidal and cylindrical). Thyroid follicles were not found in any areas of the kidney. The interrenal and chromaffin tissue were observed to be associated with postcardinal vein with its branches in the head of the kidney. The interrenal cells having a deeply eosinophilic cytoplasm were determined adjacent to branches in the head kidney. The eosinophobic chromaffin cells were found to show two different distributions. They were observed as being intermingled with the interrenal cells and formed separate groups surrounded by a thin connective tissue in the walls of the major veins. Both interrenal and chromaffin cells displayed a negative periodic acid-Schiff reaction.

Mucous Cell Prosoplasia in Oral Pathologies: A Brief Review.

One of the enigmas in cell differentiation process is prosoplasia, which is contemplated as forward differentiation. A well-known example of prosoplastic switch is mucous cell prosoplasia, which is the transformation of a simple squamous epithelial cell into mucous secreting cell. Numerous theories have been proposed for histogenesis of this phenomenon, which are comprehensively discussed in the present paper. Oral pathologies like odontogenic cysts and salivary gland tumours show mucous prosoplasia quite often; sometimes leading to diagnostic difficulties. In the present paper, efforts have been made to comprehensively discuss diverse aspects of mucous prosoplasia like histogenesis, theories and diagnostic importance in various oral pathologies.

Expression of Ccdc85C, a causative protein for murine hydrocephalus, in the mammary gland tumors of dogs.

Coiled-coil domain containing 85c (Ccdc85c) is a causative gene for hemorrhagic hydrocephalus mouse which shows hydrocephalus with frequent brain hemorrhage and formation of subcortical band heterotopia. A previous study revealed that Ccdc85C protein is expressed in the systemic simple epithelial cells with proliferative activity in rats and suggested that Ccdc85C expression may be related to the cell proliferation of simple epithelial cells. To reveal the roles of Ccdc85C in the proliferative lesion, we examined the expression patterns of Ccdc85C in the mammary gland tumor of dogs, a common representative tumor derived from simple epithelial cells. In canine mammary gland tumors, Ccdc85C was expressed at the apical junctions of the luminal epithelial cells. Ccdc85C was also distributed throughout the entire cytoplasm of the myoepithelial cells. Ccdc85C expression was observed at the epithelial cells with luminal structures, but was not observed at the epithelial cells forming sheet growth pattern without luminal structure. In carcinomas, Ccdc85C expression in mammary tumor tissue tended to be weaker than that in surrounding normal mammary gland tissue. Ccdc85C is known to cause neurological diseases such as hydrocephalus, and subcortical heterotopia, and the present study is the first to demonstrate Ccdc85C expression in canine mammary tumors and a relationship between Ccdc85C expression and tumor malignancy.

Remodeling the zonula adherens in response to tension and the role of afadin in this response.

Morphogenesis requires dynamic coordination between cell-cell adhesion and the cytoskeleton to allow cells to change shape and move without losing tissue integrity. We used genetic tools and superresolution microscopy in a simple model epithelial cell line to define how the molecular architecture of cell-cell zonula adherens (ZA) is modified in response to elevated contractility, and how these cells maintain tissue integrity. We previously found that depleting zonula occludens 1 (ZO-1) family proteins in MDCK cells induces a highly organized contractile actomyosin array at the ZA. We find that ZO knockdown elevates contractility via a Shroom3/Rho-associated, coiled-coil containing protein kinase (ROCK) pathway. Our data suggest that each bicellular border is an independent contractile unit, with actin cables anchored end-on to cadherin complexes at tricellular junctions. Cells respond to elevated contractility by increasing junctional afadin. Although ZO/afadin knockdown did not prevent contractile array assembly, it dramatically altered cell shape and barrier function in response to elevated contractility. We propose that afadin acts as a robust protein scaffold that maintains ZA architecture at tricellular junctions.

Analysis of distinct molecular assembly complexes of keratin K8 and K18 by hydrogen-deuterium exchange.

Keratins are intermediate filament (IF) proteins that form complex filament systems in epithelial cells, thus serving as scaffolding elements and mechanical stress absorbers. The building blocks of keratin IFs are parallel coiled-coil dimers of two distinct sequence-related proteins distinguished as type I and type II keratins. To gain more insight into their structural dynamics, we resorted to hydrogen-deuterium exchange mass spectrometry of keratins K8 and K18, which are characteristic for simple epithelial cells. Using this powerful technique not employed with IFs before, we mapped patterns of protected versus unprotected regions in keratin complexes at various assembly levels. In particular, we localized protein segments exhibiting different hydrogen exchange patterns in tetramers versus filaments. We observed a general pattern of precisely positioned regions of stability intertwining with flexible regions, mostly represented by the non-α-helical segments. Notably, some regions within the coiled-coil domains are significantly more dynamic than others, while the IF-consensus motifs at the end domains of the central α-helical "rod" segment, which mediate the "head-to-tail" dimer-dimer interaction in the filament elongation process, become distinctly more protected upon formation of filaments. Moreover, to gain more insight into the dynamics of the individual keratins, we investigated the properties of homomeric preparations of K8 and K18. The physiological importance of keratins without a partner is encountered in both pathological and experimental situations when one of the two species is present in robust excess or completely absent, such as in gene-targeted mice.

Assembly of Simple Epithelial Keratin Filaments: Deciphering the Ion Dependence in Filament Organization.

The intermediate filament proteins keratin K8 and K18 constitute an essential part of the cytoskeleton in simple epithelial cell layers, structurally enforcing their mechanical resistance. K8/K18 heterodimers form extended filaments and higher-order structures including bundles and networks that bind to cell junctions. We study the assembly of these proteins in the presence of monovalent or divalent ions by small-angle X-ray scattering. We find that both ion species cause an increase of the filament diameter when their concentration is increased; albeit, much higher values are needed for the monovalent compared to the divalent ions for the same effect. Bundling occurs also for monovalent ions and at comparatively low concentrations of divalent ions, very different from vimentin intermediate filaments, a fibroblast-specific cytoskeleton component. We explain these differences by variations in charge and hydrophobicity patterns of the proteins. These differences may reflect the respective physiological situation in stationary cell layers versus single migrating fibroblasts.

Histological and Histochemical studies of Esophagus in Mabuya aurata septemaeniata

The wall of the esophagus in Mabuya aurata septemaeniata as in high vertebrates consists of four layers, mucosa, submucosa,muscularis and serosa. Mucosa forms many unorganized short and long folds penetrate inside the esophageal cavity. Mucosa contains two sub layers, first one is lining epithelium which includes two types of cells, simple ciliated columnar epithelial cells and goblet cells, second one is lamina properia. Mucosa does not have muscularis mucosa. There is no esophageal glands within esophagus. Many special stains were used as (Periodic Acid Schiff (PAS)) to detect Carbohydrates in goblet cells. Alcian blue were used to detect the amount of goblet cells within lining epithelium. Alcian blue + PAS together confirm that the secreted mucin from goblet cells was acidic.

Histological and Histochemical studies of Esophagus in Mabuya aurata septemaeniata

The wall of the esophagus in Mabuya aurata septemaeniata as in high vertebrates consists of four layers, mucosa, submucosa,muscularis and serosa. Mucosa forms many unorganized short and long folds penetrate inside the esophageal cavity. Mucosa contains two sub layers, first one is lining epithelium which includes two types of cells, simple ciliated columnar epithelial cells and goblet cells, second one is lamina properia. Mucosa does not have muscularis mucosa. There is no esophageal glands within esophagus. Many special stains were used as (Periodic Acid Schiff (PAS)) to detect Carbohydrates in goblet cells. Alcian blue were used to detect the amount of goblet cells within lining epithelium. Alcian blue + PAS together confirm that the secreted mucin from goblet cells was acidic.

Cryosectioning Method for Microdissection of Murine Colonic Mucosa

The colonic mucosal tissue provides a vital barrier to luminal antigens. This barrier is composed of a monolayer of simple columnar epithelial cells. The colonic epithelium is dynamically turned over and epithelial cells are generated in the stem cell containing crypts of Lieberkühn. Progenitor cells produced in the crypt-bases migrate toward the luminal surface, undergoing a process of cellular differentiation before being shed into the gut lumen. In order to study these processes at the molecular level, we have developed a simple method for the microdissection of two spatially distinct regions of the colonic mucosa; the proliferative crypt zone, and the differentiated surface epithelial cells. Our objective is to isolate specific crypt and surface epithelial cell populations from mouse colonic mucosa for the isolation of RNA and protein.

Cryosectioning Method for Microdissection of Murine Colonic Mucosa.

The colonic mucosal tissue provides a vital barrier to luminal antigens. This barrier is composed of a monolayer of simple columnar epithelial cells. The colonic epithelium is dynamically turned over and epithelial cells are generated in the stem cell containing crypts of Lieberkühn. Progenitor cells produced in the crypt-bases migrate toward the luminal surface, undergoing a process of cellular differentiation before being shed into the gut lumen. In order to study these processes at the molecular level, we have developed a simple method for the microdissection of two spatially distinct regions of the colonic mucosa; the proliferative crypt zone, and the differentiated surface epithelial cells. Our objective is to isolate specific crypt and surface epithelial cell populations from mouse colonic mucosa for the isolation of RNA and protein.

Ontogeny of digestive organs during early developmental stages of the tropical whitespotted bamboo shark, Chiloscyllium plagiosum – a histological study

This study was undertaken to address a lack of understanding of the early developmental stages of the tropical elasmobranch whitespotted bamboo shark, Chiloscyllium plagiosum, to assist with advancement of its aquaculture. It is the first report of the histological and ultrastructural characteristics of its developing digestive tract. The study was carried out from hatching to 60 days after hatching (DAH). Embryos for this study were maintained in the laboratory. Histological investigations yielded the following data. At hatching, the gut of an embryo consisted of an undifferentiated straight tube that lay over the yolk sac. The digestive tract was differentiated into buccopharynx, esophagus, stomach, and intestine by 8 DAH. During the preflexion phase (within 16 DAH), the mucous cells of the esophagus were differentiated. Gastric glands were present at 60 DAH, indicating the transition from the embryonic to the juvenile stage and the acquisition of an adult mode of digestion. The lumen of the intestine appeared on 6 DAH; the intestinal valve appeared and divided the intestine into anterior and posterior sections on 20 DAH. The liver and the pancreas were formed on 8 DAH. The yolk sac was partially depleted by 80 DAH. In terms of ultrastructure, on 30 DAH, the anterior section of the esophagus was lined by a stratified epithelium, whereas the posterior section was lined by simple tall columnar epithelial cells. Goblet cells and oxynticopeptic cells were found in the stomach. The pancreatic acinar cells were strongly elongated and of two types: one with a pale and the other with a more opaque cytoplasm.

Cryosectioning method for microdissection of murine colonic mucosa

The barrier function of mucosal tissues is a vital component of innate immunity in the colon. This barrier is provided by a monolayer of simple columnar epithelial cells. It is a highly regenerative tissue, with resident stem cells replenishing the epithelium every few days. This process of regeneration requires the maintenance of a proliferative stem cell compartment within structures called the crypts of lieberkuhn. Over time, the newly produced daughter cells lose their proliferative potential, migrate toward the surface of the gut, and are finally shed into the lumen. Failure of this differentiation program is thought to contribute to diseases such as inflammatory bowel disease and colon cancer. In order to study these processes at the molecular level, we have developed a simple method for the microdissection of two spatially distinct regions of the colon; the proliferative crypt zone, and the differentiated surface cells. Our objective is to isolate specific crypt and surface cell epithelial populations from mouse colonic mucosa for the isolation of mRNA and protein. Colonic tissue was harvested from wild-type mice, cleaned and bisected. The tissue was then frozen between two metal plates and sectioned on a cryotome. Isolation of spatial distinct epithelial layers was confirmed by examining serial sections histologically, for protein content, and mRNA. In conclusion, we have developed a simple method for isolating crypt and surface epithelial cells from murine colonic tissue.

Gross and Microanatomical Studies on the Uterus of Japanese Quail (Coturnix japonica) During the Post-hatching Period with Special Emphasis on Sperm Host Gland

The quail acts as a model for recent experimental studies and its oviduct development is of special interest. This study was carried out on 61 adult female Japanese Quail (Coturnix japonica) collected from quail farms in Assiut and South Valley Universities in order to characterize the morphological features of the uterus during the post-hatching life. The process of development was consisted of three stages: undifferentiated, differentiated and adult stage. The undifferentiated stage began from day of hatching till 25-days old age and the oviduct was divided into cranial, middle and caudal parts. The caudal part (the future uterus and vagina) was represented by a simple wall of a single layer of simple columnar epithelial cells resting on subepithelial undifferentiated mesenchymal cells with many mitotic divisions. At 20 days old, the mucosa is thrown into distinct mucosal folds as well as the ciliated and secretory epithelial cells were first appeared at this age. At differentiated stage (from 30-40 days), the tubular glands began to develop and opened between the epithelial cells. The adult stage began from 50 days old and the luminal surface of the uterus was characterized by numerous long leaf-like folds. Also, the apical part of the cells showed positive reaction with PAS and Alcian blue. The tubular glands are filled with the secretion, which give positive reaction with PAS and Alcian blue. The uterovaginal junction lies between the uterus and the cranial part of the vagina, and contains the sperm host gland. This area showed transition of the mucosal folds from longitudinal folds of the uterus to complex interconnecting folds of the vagina. Many typical sperms with oval head and tail were inserted between the ciliated and microvillous surface epithelial cells of sperm host glands. This detailed anatomical and histological study of post-hatching development of uterus in quail will not only help to evaluate changes occurs during this critical period, but also will assist in understanding clearly the physiology of reproduction in quail.

Harderian gland in Canadian ostrich (Struthio camelus): a morphological and histochemical study.

Heads of ten healthy adult ostrich obtained from slaughter house were the constituted materials of the study. The Harderian gland (HG) was dissected out, and all of the gross morphometrical parameters including length, width and thickness as well as weight of left and right glands were recorded. Tissue sections were stained, using haematoxylin and eosin, Masson trichrome, periodic acid-Schiff and Alcian blue (pH 2.5) techniques. In ostrich, HG was an orbital organ located ventromedially around the posterior part of the eyeball. It was an oval flatted shape, light pink colour with irregular outline and was pointed in the dorsal end. Its mean length was 35.30±2.84mm and 35.55±3.58mm in left and right sides, respectively, and mean width 15.30±1.20mm and 15.65±1.18mm in left and right sides, respectively. There was no significant difference between length, thickness, weight and width of left and right glands. Histological results showed that the glandular epithelium was multilobular and compound tubuloalveolar. The gland was surrounded by a connective tissue capsule, and the epithelium was lined by simple columnar epithelial cells of varying height. The secretion of HG was mucous and the secretion type was apocrine. Mucosubstance analysis revealed that secretory units contained acidic and neutral glycoproteins. The granules within the epithelial cells lining the intralobular and inter-lobular excretory ducts of the gland were positive for periodic acid-Schiff and Alcian blue (pH 2.5).

Unwrapping the origins and roles of the renal endothelium

The renal vasculature, like all vessels, is lined by a thin layer of simple squamous epithelial cells called an endothelium. These endothelial-lined vessels can be subdivided into four major compartments: arteries, veins, capillaries and lymphatics. The renal vasculature is a highly integrated network that forms through the active processes of angiogenesis and vasculogenesis. Determination of the precise contribution of these two processes and of the molecular signaling that governs the differentiation, specification and maturation of these critical cell populations is the focus of an actively evolving field of research. Although much of the focus has concentrated on the origin of the glomerular capillaries, in this review we extend the investigation to the origins of the endothelial cells throughout the entire kidney and the signaling events that cause their distinct functional and molecular profiles. A thorough understanding of endothelial cell biology may play a critical role in a better understanding of renal vascular diseases.

An alternative promoter of the human plakophilin-3 gene controls the expression of the new isoform PKP3b

The plakophilin family (PKP1 to PKP3) is an essential component of the desmosomal adhesion complex with differentiation-dependent and partially overlapping expression and possible participation of the corresponding genes in malignant transformation. Here, we describe a new protein variant of the human PKP3 gene, namely PKP3b, which differs from the published PKP3a only at the amino-terminus by the splicing in of the newly identified exon 1b. Specific antibodies have demonstrated differential expression patterns of the two variants. Whereas PKP3a is broadly expressed among epithelial cells, PKP3b is abundant in the desmosomes of stratified epithelial cells, such as HaCaT but absent or heterogeneous in simple epithelial cells such as CaCo2 or MCF7. The differential expression of the PKP3 variants has been observed in a similar manner in selected normal human tissues and carcinomas derived thereof. Both variants are localized to the desmosomes of all cells of stratified tissues, whereas the new PKP3b is heterogeneously expressed in the colon and its tumors. Therefore, we assume that both variants are controlled by alternative promoters. Reporter gene assays have confirmed that a fragment upstream of exon 1b exhibits transcriptional activity only in HaCaT cells but not in CaCo2 cells and thus has been identified as an alternative promoter driving the expression of PKP3b. Finally, by using electromobility shift assays, we found a potential binding site in the PKP3b promoter for transcription factor C/EBP regulating keratinocyte differentiation and probably also PKP3b expression. We discuss the properties of the new variant PKP3b as a possible marker protein for the analyses of differentiation and malignant transformation.

Human Embryonic Stem Cell-Derived Epithelial Cells in a Novel In Vitro Model of Vocal Mucosa

A satisfactory in vitro model of vocal fold mucosa does not exist, thus precluding a systematic, controlled study of vocal fold biology and biomechanics. We sought to create a valid, reproducible three-dimensional (3D) in vitro model of human origin of vocal fold mucosa of human origin. We hypothesized that coculture of human embryonic stem cell (hESC)-derived simple epithelial cells with primary vocal fold fibroblasts under appropriate conditions would elicit morphogenesis of progenitor cells into vocal fold epithelial-like cells and creation of a basement membrane. Using an in vitro prospective study design, hESCs were differentiated into cells that coexpressed the simple epithelial cell marker, keratin 18 (K18), and the transcription factor, p63. These simple epithelial cells were cocultured with primary vocal fold fibroblasts seeded in a collagen gel scaffold. The cells were cultured for 3 weeks in a keratinocyte medium at an air-liquid interface. After that time, the engineered mucosa demonstrated a stratified, squamous epithelium and a continuous basement membrane recapitulating the key morphologic and phenotypic characteristics of native vocal fold mucosa. hESC-derived epithelial cells exhibited positive staining for vocal fold stratified, squamous epithelial markers, keratin 13 (K13) and 14 (K14), as well as tight junctions, adherens junctions, gap junctions, and desmosomes. Despite the presence of components critical for epithelial structural integrity, the epithelium demonstrated greater permeability than native tissue indicating compromised functional integrity. While further work is warranted to improve functional barrier integrity, this study demonstrates that hESC-derived epithelial progenitor cells can be engineered to create a replicable 3D in vitro model of vocal fold mucosa featuring a multilayered, terminally differentiated epithelium.

E-cadherin supports steady-state Rho signaling at the epithelial zonula adherens

In simple polarized epithelial cells, the Rho GTPase commonly localizes to E-cadherin-based cell–cell junctions, such as the zonula adherens (ZA), where it regulates the actomyosin cytoskeleton to support junctional integrity and tension. An important question is how E-cadherin contributes to Rho signaling, notably whether junctional Rho may depend on cadherin adhesion. We sought to investigate this by assessing Rho localization and activity in epithelial monolayers depleted of E-cadherin by RNAi. We report that E-cadherin depletion reduced both Rho and Rho-GTP at the ZA, an effect that was rescued by expressing a RNAi-resistant full-length E-cadherin transgene. This impact on Rho signaling was accompanied by reduced junctional localization of the Rho GEF ECT2 and the centralspindlin complex that recruits ECT2. Further, the Rho signaling pathway contributes to the selective stabilization of E-cadherin molecules in the apical zone of the cells compared with E-cadherin at the lateral surface, thereby creating a more defined and restricted pool of E-cadherin that forms the ZA. Thus, E-cadherin and Rho signaling cooperate to ensure proper ZA architecture and function.