Ultrastructural features of normal epithelium and 4-nitroquinoline 1-oxide-induced carcinomas of the rat tongue

Quantitative and Qualitative Analysis of Mast Cells in Oral Lichen Planus and Its Effect on Basement Membrane Using Special Stains

Background:

Oral lichen planus (OLP) is characterized histologically by epithelial basal cell destruction and a dense subepithelial lymphocytic infiltrate. Mast cells (MCs) play a role in the pathogenesis and progression of the disease causing changes in the basement membrane (BM). BM is seen as continuous or fragmented, distinct or indistinct, and afibrillar or fibrillar extensions.

Aims and Objectives:

This study was done to demonstrate the BM using acriflavine stain in addition to hematoxylin and eosin (H-E) stain. An attempt was also made to study MC using Azure A stain and assess the degree of changes in the thickness of BM associated with degranulated MC in patients with OLP.

Materials and Methods:

A total of 66 paraffin-embedded tissue sections which included 30 inflamed gingival mucosa (IGM) and 36 OLP were stained with H-E stain, Azure A, and fluorescent periodic acid–acriflavine stain.

Results:

MC density was higher in OLP when compared with MC in IGM. Degranulated MCs were found in abundance in OLP. Thickness of BM was significantly less in OLP when compared with IGM. Significant fragmentation was seen in OLP when compared with BM of IGM.

Conclusion:

Degranulated MC in OLP may or may not alter the quality of BM but definitely seems to influence the thickness of the BM both directly and indirectly.

Comparing The Efficacy of Hematoxylin and Eosin, Periodic Acid Schiff and Fluorescent Periodic Acid Schiff-Acriflavine Techniques for Demonstration of Basement Membrane in Oral Lichen Planus: A Histochemical Study

BACKGROUND

Basement membrane (BM) is a thick sheet of extracellular matrix molecules, upon which epithelial cells attach. Various immunohistochemical studies in the past have been carried out but these advanced staining techniques are expensive and not feasible in routine laboratories. Although hematoxylin and eosin (H-E) is very popular among pathologists for looking at biopsies, the method has some limitations. This is where special stains come handy.

AIMS AND OBJECTIVES

The aim of the present study was to demonstrate and compare the efficacy of H-E, periodic acid Schiff (PAS) and fluorescent periodic acid-acriflavine staining techniques for the basement membrane and to establish a histochemical stain which could be cost effective, less time consuming, and unambiguous for observation of the basement membrane zone.

MATERIALS AND METHODS

A total number of 40 paraffin-embedded tissue sections of known basement membrane containing tissues including 10 - Normal oral mucosa (NOM) and 30 - oral lichen planus (OLP) were considered in the study. Four-micron-thick sections of each block were cut and stained with H-E stain, PAS and fluorescent periodic acid-acriflavine stain. Sections were evaluated by three oral pathologists independently for continuity, contrast and pattern.

RESULTS

Though all the three stains showed favorable features at different levels, acriflavine stain was better than the other stains in demonstrating BM continuity, contrast and also the pattern followed by PAS stain. Acriflavine stain was the better in demonstrating a fibrillar pattern of a BM. Acriflavine stains a BM distinctly and is less time consuming and easy to carry out using readily available dyes as compared to other stains.

CONCLUSION

The continuity and contrast along with the homogenous pattern and the afibrillar pattern of the BM was better demonstrated by acriflavine followed by the PAS stain.

Animal models for the study of squamous cell carcinoma of the upper aerodigestive tract: a historical perspective with review of their utility and limitations. Part A. Chemically-induced de novo cancer, syngeneic animal models of HNSCC, animal models of transplanted xenogeneic human tumors

Understanding the complex histological, genetic and molecular changes that lead to malignant transformation of squamous epithelia of the head and neck will likely guide the development of methods for improved diagnosis, monitoring and treatment of head and neck squamous cell carcinoma (HNSCC). The development and use of animal models that closely mimic the histopathology and molecular pathogenesis of HNSCC in humans would greatly expand the research possibilities and provide a means of testing potential therapeutic agents. However, many available animal models of HNSCC fall short of this objective. In order for investigators to select the appropriate model to answer scientific questions, it is important to understand the benefits and limitations of available animal models for the study of HNSCC. The purpose of this work is to give an overview of the most pertinent animal models of HNSCC, and to discuss future directions of research in this field.

Ultrastructural changes of the palatal mucosa following application of 4-nitroquinoline-l-oxide (4NQO) in rats subjected to major salivary gland excision

OBJECTIVE

It has been suggested that saliva exerts a protective role against the carcinogenic effect of various substances in the oral cavity. The objective of this study was to examine the ultrastructural changes of the palatal mucosa caused by the application of 4-nitroquinoline-l-oxide (4NQO) in the presence or absence of saliva.

STUDY DESIGN

Wistar-Furth rats subjected and not subjected to total bilateral excision of the major salivary glands were either painted with an aqueous solution of 4NQO or with propylene glycol only (controls). Two animals of each group were humanely killed periodically. The areas of the palatal lesions were immediately sliced and processed for TEM examination.

RESULTS

Ultrastructurally, the progressive changes to squamous cell carcinoma were observed in the animals painted with 4NQO. In the desalivated animals group, the ultrastructural alterations appeared earlier than in the group with salivary glands.

CONCLUSIONS

Saliva appeared to delay but not hinder tumor induction by 4NQO.

Occurrence of mast cells within bundles of myelinated and unmyelinated nerves in the rat tongue

The rat tongue has been the subject of many cytological studies, both purely descriptive and experimental. To assess the suitability of the organ for additional cytological and histological senior research thesis projects, light and transmission electron microscope studies of thin and ultrathin sections, respectively, were conducted. Several samples from the anterior dorsal surface of the tongue of a male rat (Sprague-Dawley) were processed conventionally for light and electron microscope study. About 170 sections, each approximately 1 x 1 mm in area and 1.0 microm thick, collected from 12 adjacent areas, all including the mucosa, of a tongue were studied in the light microscope. Numerous mast cells were observed scattered throughout the submucosal region, adjacent to nerve bundles, blood vessels, and skeletal muscle, and up to six bundles each consisting of many myelinated and unmyelinated nerve processes were seen per section. Single, double, and quadruple myelinated nerve processes were also seen. Several of the multiple, mixed nerve bundles contained a mast cell. Mast cells were not found within the endoneurium or perineurium of exclusively myelinated processes. Ultrathin sections adjacent to the thin sections containing mast cells within the nerve bundles were sought and studied in the transmission electron microscope to confirm the identification of these mast cells. Mast cells occur within bundles containing both myelinated and unmyelinated nerves in the rat tongue, and this is an apparently previously unreported event. Furthermore, no clear evidence has been found in the literature of such specific mast cell distribution in other parts of the animal body. Single, double, and quadruple myelinated nerve processes were noted, but none contained a mast cell.

Oral cancer: role of the basement membrane in invasion

Invasive growth of cancer cells is a complex process involving specific interactions between tumour cells and the orderly, integrated complexes of the extracellular matrix. Basement membranes have been proposed as one constituent of extracellular matrix which carries responsibility for regulating invasion and metastasis. Using a chemically induced rat tongue carcinoma model, it has been shown that components of the basement membrane and its overall structure are altered during tumour invasion, and methods have been developed to quantitate some of these differences. Since the basement membrane can be specifically characterized by its fibrous protein network of Type IV collagen and laminin, which is embedded in a heparan sulphate-rich proteoglycan matrix, these components have been targeted. In particular, the current paper presents results in the context of current concepts of early changes in neoplastic invasion of underlying connective tissues. In consequence, further elaboration of the underlying mechanisms of epithelial migration in oral cancer may allow an exploration of the use of alterations in expression of basement membrane components as prognostic indicators.

Distribution of basal lamina type IV collagen and laminin in normal rat tongue mucosa and experimental oral carcinoma: ultrastructural immunolocalization and immunogold quantitation

The relationship of basal lamina, a form of specialised extracellular matrix which separates epithelial cells and other cell types from adjacent stroma, to the behaviour of malignant neoplasms of epithelial origin is not well understood. However, it is widely acknowledged that the properties of local invasion and metastasis of carcinomas are linked to extracellular matrix (including basal lamina) changes. In the present study, the distribution of the major basal lamina components, type IV collagen and laminin, in normal rat tongue mucosa and experimentally induced oral carcinomas was investigated using post-embedding immunogold techniques and electron microscopy. The expression of these components was also quantitatively analysed using morphometry and immunocytochemistry. Results indicated that type IV collagen and laminin were confined to the lamina densa of normal oral epithelial basal lamina, and that both components were also detected in the lamina densa of basal lamina associated with carcinomas, and in the extracellular matrix of tumours. Furthermore, laminin was detected within stromal fibroblasts in normal tissues and experimental carcinomas. Quantitative analysis indicated that expression of laminin was significantly increased in carcinomas. In contrast, type IV collagen expression was significantly decreased. The quantitative changes observed in the two basal lamina constituents may be related to the process of tumour invasion, reflecting altered metabolic activities of tumour and stromal cells. These observations may be of use in understanding the architectural characteristics of oral mucosa basal lamina and in assessing the malignant potential of epithelial dysplasias or "premalignant" lesions.

Laminin and type IV collagen in experimental rat oral carcinomas

The pattern of staining and the distribution of laminin and type IV collagen in normal rat tongue mucosa and induced tongue carcinomas were investigated by immunohistochemical techniques. Both normal and neoplastic epithelial basement membrane revealed positive staining for laminin and type IV collagen. However, compared with normal tissue, carcinomas exhibited areas of increased density and thickness for laminin. Focal tumour basement membrane discontinuities were observed in some specimens stained for type IV collagen.