Epithelial-stromal interface in normal and neoplastic human bladder epithelium

Role of Hemidesmosomes in Oral Carcinogenesis: A Systematic Review

BACKGROUND

Oral cancers have limited diagnostic tools to aid clinical management. Current evidence indicates that alterations in hemidesmosomes, the adhesion complexes primarily involved in epithelial attachment to the basement membrane, are correlated to cancer phenotype for multiple cancers. This systematic review aimed to assess the experimental evidence for hemidesmosomal alterations, specifically in relation to oral potentially malignant disorders and oral squamous cell carcinomas.

METHODS

We conducted a systemic review to summarise the available literature on hemidesmosomal components and their role in oral pre-cancer and cancer. Relevant studies were retrieved from a comprehensive search of Scopus, Ovid MEDLINE, Ovid Embase and Web of Science.

RESULTS

26 articles met the inclusion criteria, of which 19 were in vitro studies, 4 in vivo studies, 1 in vitro and in vivo study, and 2 in vitro and cohort studies. Among them, 15 studies discussed individual alpha-6 and/or beta-4 subunits, 12 studies discussed the alpha-6 beta-4 heterodimers, 6 studies discussed the entire hemidesmosome complex, 5 studies discussed bullous pemphigoid-180, 3 studies discussed plectin, 3 studies discussed bullous pemphigoid antigen-1 and 1 study discussed tetraspanin.

CONCLUSION

Heterogeneity in cell type, experimental models, and methods were observed. Alterations in hemidesmosomal components were shown to contribute to oral pre-cancer and cancer. We conclude that there is sufficient evidence for hemidesmosomes and their components to be potential biomarkers for evaluating oral carcinogenesis.

Junctional complexes in epithelial cells: sentinels for extracellular insults and intracellular homeostasis

The cell-cell and cell-ECM junctions within the epithelial tissues are crucial anchoring structures that provide architectural stability, mechanical resistance, and permeability control. Their indispensable role as signaling hubs orchestrating cell shape-related changes such as proliferation, differentiation, migration, and apoptosis has also been well recognized. However, growing amount of evidence now suggests that the multitasking nature of epithelial junctions extends well beyond anchorage-dependent or cell shape change-related biological processes. In this review, we discuss the emerging roles of junctional complexes in regulating innate immune defense, stress resistance, and intracellular proteostasis of the epithelial cells, with emphasis on the upstream regulation of epithelial junctions on various aspects of the epithelial barrier.

Development, regeneration and tumorigenesis of the urothelium

The urothelium of the bladder functions as a waterproof barrier between tissue and outflowing urine. Largely quiescent during homeostasis, this unique epithelium rapidly regenerates in response to bacterial or chemical injury. The specification of the proper cell types during development and injury repair is crucial for tissue function. This Review surveys the current understanding of urothelial progenitor populations in the contexts of organogenesis, regeneration and tumorigenesis. Furthermore, we discuss pathways and signaling mechanisms involved in urothelial differentiation, and consider the relevance of this knowledge to stem cell biology and tissue regeneration.

The Urothelium: Life in a Liquid Environment

The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.

Gliding Basal Cell Migration of the Urothelium during Wound Healing

Collective cell migration during wound healing has been extensively studied in the epidermis. However, it remains unknown whether the urothelium repairs wounds in a manner similar to the epidermis. By in vivo two-photon excitation microscopy of transgenic mice that express fluorescent biosensors, we studied the collective cell migration of the urothelium in comparison with that of the epidermis. In vivo time-lapse imaging revealed that, even in the absence of a wound, urothelial cells continuously moved and sometimes glided as a sheet over the underlying lamina propria. On abrasion of the epithelium, the migration speed of each epidermal cell was inversely correlated with the distance to the wound edge. Repetitive activation waves of extracellular signal-regulated kinase (ERK) were generated at and propagated away from the wound edge. In contrast, urothelial cells glided as a sheet over the lamina propria without any ERK activation waves. Accordingly, the mitogen-activated protein kinase/ERK kinase inhibitor PD0325901 decreased the migration velocity of the epidermis but not the urothelium. Interestingly, the tyrosine kinase inhibitor dasatinib inhibited migration of the urothelium as well as the epidermis, suggesting that the gliding migration of the urothelium is an active, not a passive, migration. In conclusion, the urothelium glides over the lamina propria to fill wounds in an ERK-independent manner, whereas the epidermis crawls to cover wounds in an ERK-dependent manner.

Evolving concepts and use of immunohistochemical biomarkers in flat non-neoplastic urothelial lesions: WHO 2016 classification update with diagnostic algorithm

CONTEXT

The classification of flat non-neoplastic urothelial lesions has been evolved through the years in the attempt to better define a spectrum of morphologic entities with somewhat overlapping features. Differentiating these lesions is important because of differences in patient management and clinical outcome. Materials and methods and objective: A systematic review of the literature has been carried out in order to (1) assess the most striking clinical features of each lesion and (2) identify those morphological traits and immunophenotypical markers which may aid in the differential diagnosis.

RESULTS AND CONCLUSION

Our results point out the importance of a proper definition of flat non-neoplastic urothelial lesions in order to predict clinical behaviour and allow tailored patient management; therefore, we attempted to construct a novel and "easy to use" algorithm for a clear, standardized and evidence-based pathological diagnosis.

Association of Therapeutic Radiation with Golgi Complex Hypertrophy in Human Urinary Bladder Carcinomas: Quantitative Electron Microscopy Studies

The volume (Vv) and surface area (surface density; Sv) of the Golgi complex were measured by electron microscopy stereologic techniques in 17 patients with urinary bladder transitional cell carcinomas. Seven patients were irradiated prior to surgical removal, 4 had recurrent carcinomas that arose from previously irradiated bladder urothelium, and the remaining 6 patients had bladder carcinoma but no prior history of therapeutic irradiation. There were significant differences in the Vv and Sv of Golgi complexes per unit of cytoplasmic volume in carcinomas from irradiated and nonirradiated patients (p < 0.01). In carcinomas obtained from irradiated urinary bladders, the Vv was 3.45 +/- 0.24% (mean +/- SE). In contrast, the Vv was 0.98 +/- 0.15% for tumors in the nonirradiated group. Sv values were 1.51 +/- 0.09 microm2/microm3 in carcinomas from irradiated bladders, and in the nonirradiated group, the mean Sv was 0.76 +/- 0.07 microm2/microm3. These results support the hypothesis that therapeutic irradiation to the urinary bladder induces hyperplasia of Golgi complexes.

Basement membrane and extracellular interstitial matrix components in bladder neoplasia--evidence of angiogenesis

Immunohistochemical studies to localise collagen IV, laminin, fibronectin and tenascin were undertaken in 59 bladder biopsies. These were non-neoplastic or contained foci of flat dysplasia or of transitional cell neoplasia. Collagen IV and laminin were reliably demonstrated in basement membranes but focal loss of reactivity for collagen IV was found in the urothelial basement membrane in some cases of inflammation, dysplasia, and non-invasive papillary transitional cell tumour. Basement membranes were rarely demonstrated around invasive transitional cell carcinomas. Fibronectin and tenascin were found in the sub-urothelial lamina propria and in some urothelial basement membranes. The stroma of invasive tumours reacted strongly for both. Increased numbers of sub-urothelial capillaries were present in association with some cases of cystitis, flat dysplasia or non-invasive transitional cell neoplasia suggesting an angiogenic stimulus in these circumstances. Immunohistochemical staining of basement membrane components is unlikely to be of value in the routine histopathological assessment of transitional cell neoplasms of the bladder.

What's new in the ultrastructure of tumor invasion in vivo?

An important point emerging from the literature on tumor invasion in vivo is the great variability of nearly all aspects studied. It seems that there is neither one particular morphologic change which renders a cell invasive, nor one particular mechanism by which a cell crosses the boundaries of its original tissue compartment to occupy another. Nevertheless, some general trends are demonstrable. The majority of invasive tumor cells appear to be characterized by prominent surface protrusions, decreased junctional contacts and, in the case of epithelium-derived tumor cells, an incomplete basement membrane. The fact that some tumors can invade foreign tissues without loosing their basement membrane is emphasized. Invasive cells frequently form organized associations with preexistent non-neoplastic cells without damaging them. Apparently, the eventual disappearance of the preexistent cells in most invaded tissues is not necessarily due to a direct action on the part of the tumor cells. It rather seems a secondary phenomenon caused by, e.g., the insertion of invasive tumor cells between the preexistent cells and their original stroma. Very often, this seems to be due to the affinity of malignant cells for basement membranes. In addition, the adhesion of tumor cells to basement membranes frequently seems to determine their pattern of spread through a tissue. A process which may turn out to be a key factor in tumor invasion is desmoplasia, the series of host reactions which creates a new environment for the tumor cells which may favor their survival, proliferation, and locomotion. With the rapid development of new techniques, electron microscopy will probably contribute to the elucidation of the exact nature, the degree of similarity to granulation tissue, and the influence on invasion of desmoplastic tumor stroma.

Carcinogenesis in mammalian urothelium: changes induced by non-carcinogenic substances and chronic indwelling catheters

Carcinogenesis in urinary bladders may not be represented by a continuum of pathological lesions beginning with papillary tumors or flat dysplasias/atypias. In a previous experiment, sterile water and saline continuously infused via catheters connected to ALZA mini-pumps were shown to induce papillary urothelial lesions indistinguishable from tumors considered to be carcinomas in most histological classification schemes. The animals in the initial experiment were followed for relatively brief periods which did not allow for determination of potential reversibility of the process and did not distinguish the effects of the catheters versus those of the infused substances. The present study was designed to control for these variables. Rats were divided into seven groups to examine the urothelial changes after: surgery alone, continuous infusion of the sterile water and mitomycin C, and chronic indwelling catheters with and without infusion. The results indicated that chronic irritation with indwelling catheters was a strong stimulus for the induction of urothelial neoplasms and that continuous infusion of certain substances, even sterile water, might play a small role in the process of carcinogenesis. Comparing the frequencies of papillary urothelial tumors appearing after brief exposure to sterile water and catheters in the initial experiment (75 per cent) and papillary lesions appearing long after removal of the sterile water and catheters in the current study (0 per cent) indicates that these lesions are reversible and probably not neoplastic.

Junctions between intraepithelial carcinoma and non-neoplastic tissue of the esophagus. Light and electron microscopic studies

This report describes light and electron microscopic observations in 11 patients with intraepithelial carcinomas concomitant with invasive squamous cell carcinomas of the esophagus. The junctions between the intraepithelial carcinomas and non-neoplastic tissues were examined using an electron microscope. Vertical sections through the basal laminae revealed intraepithelial carcinomas with bulky outgrowths and simple replacement histological patterns. The bulky outgrowths contained many pseudopodial cytoplasmic projections from the tumor cells through the basal laminae, while the simple replacement patterns included rare small breaks in the basal laminae. Horizontal sections parallel to the basal laminae showed that the cells of the poorly differentiated squamous cell carcinoma were readily distinguishable from the non-neoplastic cells in the surface layer of the esophageal epithelia and distinctly smaller and darker than the normal prickle cells. At most of the junctions, mesenchymal cells, degenerated cells, and amorphous material separated the tumor cells from the non-neoplastic epithelial cells. However, tumor cells were occasionally attached directly to normal epithelial cells with well-developed desmosomes. Ductal involvement of the carcinomas was found in the submucosal esophageal gland proper. The tumor cells invaded between the ductal cells and basal laminae, and neoplastic cells were also directly attached to the benign ductal cells by poorly-developed desmosomes. The host-tumor junctions in the intraepithelial carcinomas of the human esophagus consisted of basal laminae with hemidesmosomes and pseudopodial projections, mesenchymal cell accumulations and direct attachments with desmosomes.

Ultrastructural morphometry of collagen from lamina propria during experimental oral carcinogenesis and chronic inflammation

Stereological point-counting methods were used to determine the volumetric alterations in collagen from the lamina propria immediately beneath the epithelial-connective tissue junction in hamster check-pouch mucosa treated with the chemical carcinogen DMBA. In addition, a non-neoplastic inflammatory control was evaluated in which a delayed hypersensitivity reaction was induced by the contact-sensitising agent DNCB. DMBA-treated tissues were assigned to histopathologically defined hyperplasia, dysplasia and carcinoma stages. The volume densities of collagen present in unit volume of extracellular lamina propria were found to decrease progressively and significantly in DMBA-treated tissues when compared with values obtained from normal untreated mucosa. Values from the inflammatory control were comparable with those from the dysplasia stage of carcinogenesis. The mechanisms responsible for these decreases in collagen volume density are unknown, but contributory factors might include collagen destruction by enzymes originating in either the epithelium or the cells of the inflammatory infiltrate, dilution of collagen produced by inflammatory oedema or alterations in the synthetic capabilities of fibroblasts.

Invasiveness of transformed bladder epithelial cells

The invasiveness of bladder tumors has been studied in man, experimental animals, and in tissue culture by numerous authors. The prognostic importance of cellular markers for invasiveness is stressed, and the usefulness of histopathological and cytologic grading, cytogenetic studies, antigenic investigations, and enzymatic characterization is discussed. The invasiveness of bladder cells has frequently been examined in transplantation and explantation experiments. In human urothelial cell cultures three grades of transformation are defined, and a correlation has been established between the invasiveness of these cell lines in a three-dimensional in vitro model and their tumorigenicity in nude mice. The mechanism of tumor invasion is discussed, and it is recommended in future research to make a distinction between invasion en bloc and cellular infiltration.

Hemidesmosomal dimensions and frequency in experimental oral carcinogenesis: a stereological investigation

Connective tissue invasion by carcinomas results in a variety of morphological changes at the epithelial-connective tissue junction. In this report, hemidesmosomal size (-delta) and frequency (Ns) were quantified using established stereological methods. Following treatment of hamster cheek pouches with the chemical carcinogen DMBA, lesions defined as hyperplasias, dysplasias and carcinomas were evaluated using electron microscopical techniques. Untreated pouches served as controls. Stereological intersection counting procedures were used to quantify hemidesmosomes at the epithelial-connective tissue junction. During carcinogenesis, hemidesmosomal diameter decreased progressively, although the reductions were not statistically significant. Hemidesmosomal frequency also decreased progressively between control and carcinoma groups. Normal basal plasma membranes possessed approximately 8 hemidesmosomes/micron 2 whereas values were reduced to approximately 3/micron 2 in the carcinoma group. The reductions in hemidesmosomal frequency during carcinogenesis may reflect an increased motility of basal epithelial cells and a decreased adherence of basal cells to the adjacent lamina propria. The specificity of this alteration in the pathogenesis of malignancy can be readily determined by the application of stereological methods to various neoplastic and non-neoplastic lesions.

Invasion of chicken caecal and intestinal lamina propria by crypt epithelial cells infected with coccidia

The development of second generation schizonts of Eimeria necatrix and E. tenella was studied with the electron microscope. Invasion of the crypt epithelial cells by merozoites of the first generation schizonts caused changes in the morphology of the infected cells and stimulated their migration into the lamina propria through breaks which appeared in the basement membrane of the crypts. Second generation schizonts developed in the lamina propria within these crypt cells whose epithelial origin was confirmed by their interconnection by desmosomes and tight junctions and by their possession of characteristic microvilli. A comparison is made between this invasion of the lamina propria by parasitized cells and invasion of connective tissue by malignant epithelial cells; the possible mechanisms involved are discussed.

Growth and characterization of normal human urothelium in vitro

A method for initiating rapidly growing cultures of normal human transitional cells from ureter and embryonic bladder specimens has been developed and quantified. A new microdissection technique was used to nonenzymatically separate the urothelium. The use of enriched medium containing 10 micrograms/ml insulin, 5 micrograms/ml transferrin, and 1 microgram/ml hydrocortisone resulted in improved growth. The use of thin collagen gel substrates (0.6 ml/60 mm petri dish) resulted in 97% attachment of explants compared to 77% attachment on plastic. Explants grown on thicker collagen (2 ml/60 mm petri dish) showed, in addition to better attachment, enhanced growth of cells as determined both by measurements of colony size and cell density. Cultures of transitional cells that were initiated using explants could be passed three to five times using 0.1% EDTA for dispersion. Autoradiography of [3H]thymidine-labeled cells showed an initial phase of rapid cell division in primary explant cultures and restimulation of cell division in passaged cultures. Transmission electron microscopy showed that the cells growing out from the explants were continuous with the stratified urothelium maintained in the original explant. Stratification of transitional cells occurred in cultures of both ureter and embryonic bladder cells. Surface cells were joined near their apices by junctional complexes. Desmosomes and Golgi vesicles were present in all cells. Passage in culture did not alter the morphological characteristics of cells.

Inverted papillomas of nasal cavity and paranasal sinuses. Ultrastructural investigations on epithelial-stromal interface

10 cases of inverted papillomas of nasal cavity and paranasal sinuses were examined electron microscopically with particular regard to the epithelial-stromal interface. The papilloma cells were clearly demarcated from the stromal tissue by a basement membrane-like material. However, this structure mainly consisted of two or more layers, occasional breaks in the basement membrane were visible. Within the basal epithelial cells resting on the basement membrane accumulations of actin-like microfilaments could sometimes be observed. Furthermore, in the stromal tissue some myofibroblasts were present in the vicinity of the papillomatous cell complexes and capillary vessels also demonstrated several layers of basement membrane. All the changes presented here are considered to be the result of a permanent interaction between aggressive forces of papilloma cells and the defence mechanism of stromal tissue. The results allow the conclusion that inverted papillomas of nasal cavity and paranasal sinuses are true neoplasms with very low malignancy.

Primary adenocarcinomas of the human urinary bladder: histochemical, immunological and ultrastructural studies

Neoplastic and non-neoplastic tissue specimens from ten patients with primary adenocarcinoma of the urinary bladder were examined. Most of these tumors were associated with either foci of transitional cell carcinoma and/or with glandular metaplasia of the bladder epithelium. The mucin produced by the neoplastic cells was PAS, alcian blue, mucicarmine, PB/KOH/PAS, and RPB/KOH/PAS-positive. ABH isoantigens of these tumors were not always deleted. Ultrastructurally, the neoplastic cells resembled goblet cells. Their plasma membrane had numerous microvilli with prominent glycocalyx. Proliferation and attenuation of tight junctions were noted. The gap junctions were few and small. Two types of desmosomes were found. The ultrastructural features of the neoplastic cells were attributed in part to the malignant transformation and in part to the direction of their differentiation. We have not observed any distinctive morphologic, histochemical, immunologic or ultrastructural features that might be diagnostic for these adenocarcinomas.