Human skin basement membrane-associated heparan sulphate proteoglycan: distinctive differences in ultrastructural localization as a function of developmental age

An immunohistochemical study of basement membrane heparan sulfate proteoglycan (perlecan) in oral epithelial dysplasia and squamous cell carcinoma

BACKGROUND

Basement membrane heparan sulfate proteoglycan (perlecan) has been demonstrated in precancer lesions and carcinomas of oral cavity. It helps in malignant transformation of epithelial cells. The aim of our study was to understand the immuno-localization of perlecan in oral dysplastic epithelium and oral carcinomas.

MATERIALS AND METHODS

A total of 50 cases comprising 10 normal mucosa, 20 dysplastic mucosa, and 20 oral squamous cell carcinomas (OSCC) were included in the retrospective study. They were examined for the presence of perlecan protein core by immunohistochemistry using monoclonal antibody. Interpretation of the pattern of staining was done, and majority of the observations were taken for statistical analysis.

RESULTS

In normal epithelium, perlecan was found to be present in basal layer at the cell border. In dysplastic epithelium, it was present in suprabasal layers also. With the increase in severity of dysplasia, its expression was more in suprabasal layers, and the immuno-localization was found to be at cell border and cytoplasm. In OSCC cases, perlecan was present in stroma and tumor islands.

CONCLUSION

It was deduced from the above results that perlecan helps potentially in dysplastic changes of epithelial cells. It gets accumulated within the cell and intercellular spaces and serves as a reservoir for various growth factors. In OSCC, it breaks down and releases growth factors, which help in tumor progression, angiogenesis, and metastasis of the carcinoma.

Basement membrane proteoglycans are of epithelial origin in rodent skin

Basement membrane proteoglycans in mammalian skin comprise at least one chondroitin sulfate proteoglycan and heparan sulfate proteoglycans, including perlecan. In this study, the origins of basement membrane chondroitin sulfate proteoglycan and perlecan were investigated both in vivo and in vitro. For in vivo experiments, pieces of newborn rat epidermis obtained by dispase treatment were grafted onto athymic nude mice. Three and six weeks after grafting, immunofluorescence analysis of the grafted skin was carried out, using monoclonal antibodies specific for rat basement membrane chondroitin sulfate proteoglycan and rat and mouse perlecan. While the isolated rat epidermis was shown to completely lack rat basement membrane chondroitin sulfate proteoglycan and rat basement membrane heparan sulfate proteoglycans, including perlecan, immunofluorescence staining of tissue sections from the grafted sites on mice demonstrated the presence of rat basement membrane chondroitin sulfate proteoglycan and rat perlecan on interfollicular and follicular basement membranes including that separating dermal papillae from adjacent hair follicle epithelium. In contrast, the basement membranes of all dermal capillaries were positive for mouse perlecan, but negative for rat basement membrane chondroitin sulfate proteoglycan and rat perlecan, including the basement membranes of papillary dermal capillaries beneath the rat epidermis. These data suggest that basement membrane proteoglycans of the dermal-epidermal junction and hair follicle epithelium are of epidermal (epithelial) origin in vivo. Stratified rat keratinocytes cultured on a collagen matrix at the air-liquid interface showed the synthesis of perlecan, laminin 1, and type IV collagen in basement membranes, but not clearly detectable basement membrane chondroitin sulfate proteoglycan.

Identification of basal lamina acidic glycoconjugates, particularly heparan sulphate proteoglycans, using a poly-L-lysine-gold probe in induced oral carcinomas

Acidic glycoconjugates represent the major non-fibrous macromolecular components that form the extracellular and cell-associated matrices of all animal tissues. The constituent molecules are principally structural glycoproteins and proteoglycans. While their protein component is determined by gene pools, it is the polyanionic (acidic) nature of the polysaccharides, determined by their degrees of carboxylation and sulphation, which confers both functional and diagnostic status on these molecules. Sulphated glycoconjugates in the basal laminae have been reported to play a role in tumour invasion and metastasis. In this study, we used cationic colloidal gold together with transmission electron microscopic methods to compare the expression of acidic glyconconjugates in the basal lamina of both normal rat tongue mucosa and experimentally induced oral carcinomas. Results indicated that heparan sulphate rich glycoconjugates were predominant and were mostly confined to the lamina lucida of the basal lamina in normal oral mucosa. Conversely, observation of basal laminae associated with induced carcinomas showed less intense and more widely dispersed gold labelling for heparan sulphate. The observed differences in gold labelling may reflect modified metabolism of sulphated glycoconjugates or result from the action of degradative enzymes in the induced tumours.

The biology of perlecan: the multifaceted heparan sulphate proteoglycan of basement membranes and pericellular matrices

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Identification and partial characterization of a novel 105-kDalton lower lamina lucida autoantigen associated with a novel immune-mediated subepidermal blistering disease

Certain skin basement membrane components, such as bullous pemphigoid antigens and epidermolysis bullosa acquisita antigen, were discovered as a result of an autoimmune reaction. In this report, we describe a unique lamina lucida determinant associated with a novel immune-mediated subepidermal bullous dermatosis. This unique bullous dermatosis resembled severe toxic epidermal necrolysis clinically. The histologic findings resemble dermatitis herpetiformis. Direct immunofluorescence microscopy detected linear immunoglobulin G (IgG) and C3 deposition at the cutaneous basement membrane zone of lesional and perilesional skin. Direct and indirect immunoelectron microscopy localized the IgG deposits to the lowest portion of the lamina lucida. The patient's autoantibodies, belonging to the IgG1 subclass, labeled basement membrane zone of normal intact human skin, oral mucosa, and conjunctiva, and localized to the dermal side of salt-split normal adult and neonatal human skin, but failed to react with human fetal skin up to 142 gestational days. The patient's autoantibodies failed to react with bullous pemphigoid antigens or epidermolysis bullosa acquisita antigen (type VII collagen) by immunoblotting. Instead, the patient's autoantibodies unequivocally labeled a 105-kilodalton (kD) protein in cellular extracts and conditioned media of human cultured keratinocytes and dermal fibroblasts. The titer of the patient's antibody against the cutaneous basement membrane zone and the intensity of the antibody reactivity against the 105-kD protein paralleled the patient's disease activity. Thus, this 105-kD lower lamina lucida protein represents a novel autoantigen and this patient's disease represents a novel autoantigen and this patient's disease represents a deep lamina lucida pemphigoid, distinguishable from all other known autoimmune bullous dermatoses.

Cellular origin of the dermal-epidermal basement membrane

The basement membrane underlying epithelium of skin is generally believed to be of epithelial origin, but a mesenchymal contribution to the basement membrane has not been directly examined. The purpose of this study was to directly evaluate both epithelial and mesenchymal contributions to the basement membrane. Fetal bovine keratinocytes cultured on the surface of collagen gels in the absence of fibroblasts did not produce an ultrastructurally recognizable basement membrane; however, when these cells were cultured in the presence of dermal fibroblasts a basement membrane at the keratinocyte-fibroblast interface was produced after 1 week which was very similar in biochemical composition and ultrastructural appearance to dermal-epidermal basement membrane in human skin. When dual species cultures of bovine keratinocytes and human fibroblasts were analyzed by indirect immunofluorescent microscopy (IF)1 with human specific antibodies against basement membrane components, dermal fibroblasts were shown to synthesize and deposit type IV collagen, type VII collagen, and laminin in a linear manner into the basement membrane zone. Fetal bovine keratinocytes cultured in the presence or absence of fibroblasts synthesized and deposited type IV collagen, type VII collagen, laminin, K-laminin, kalinin, and basement membrane associated heparan sulfate proteoglycan (HSPG) into the underlying basement membrane zone. In organ culture, a subpopulation of fibroblasts initially migrating from human foreskin explants was found to stain strongly for types VII and IV collagen and laminin by IF whereas after subculture all cells showed a uniform low staining. Based on these observations we propose that differentiated fibroblasts exist adjacent to epithelial tissues in vivo which produce basement membrane components and assist in basement membrane assembly.

Structure and antigenicity of the skin basement membrane zone

The skin basement membrane zone is comprised of two major ultrastructural regions, four associated structures, and at least 17 different antigens. In this brief review, the ultrastructure, antigenicity, and ontogeny of normal human skin will be discussed in detail, as will alterations in expression or immune response to selected basement membrane components in specific mechanobullous and autoimmune diseases.