Elektronenmikroskopische Untersuchungen des Keratoakanthoms

AN ULTRASTRUCTURAL OBSERVATION OF INTRACYTOPLASMIC DESMOSOMES IN DARIER'S DISEASE

In a typical case of Darier's disease, intracytoplasmic desmosomes, gap junctions and many vesicles were observed in the cytoplasm of epidermal keratinocytes. Intracytoplasmic desmosomes were found in the cytoplasm of the excessively keratinized cells, vacuolated cells and acantholytic cells. They were not associated with tonofilaments as much as with ordinal intercellular desmosome-tonofilament complexes, and some of them lacked a central strip and looked similar to the denatured intercellular desmosomes in the morphology of the abnormal keratinocytes of Darier's disease. These intracytoplasmic desmosomes were long and undulating and some of the showed a "tennis racket" image (Caputo). Furthermore, some were combined with the gap junction and the intermediate junction, forming a bounded vesicle in the cytoplasm.

H-7 stimulates desmosome formation and inhibits growth in KB oral carcinoma cells

Protein kinase inhibitor H-7 was reported to stimulate desmosome formation in normal keratinocytes and to inhibit proliferation of neural cell lines. In the present study, the effects of this inhibitor on adhesion and growth of KB human oral carcinoma cells were investigated. H-7 was found to enhance desmosome assembly, as evidenced by an increased punctate labeling for the major desmosomal markers. Immunogold labeling confirmed the formation of desmosomes both at the cell surface and in the cytoplasm. In order to assess cell proliferation and possible correlation with adhesion, confluent cultures were treated and both adherert and detached cell fractions were counted. Under serum-free conditions, H-7 significantly reduced cell detachment. In contrast, EGF stimulated cell detachment, and this effect was abolished when cells were simultaneously treated with both EGF and H-7. Total cell counts were also significantly reduced by H-7, both in the presence and absence of EGF. Using the TUNEL technique, labeled cells were increased after H-7 treatment, thus implicating protein kinase inhibition in cell death. These results indicate that H-7 inhibits growth and stimulates adhesion of KB carcinoma cells.

Cytoplasmic desmosome formation by H-7 and EGF treatment in cultured fetal rat keratinocytes

Cytoplasmic desmosomes (CD) are classically found in dyskeratotic cells of many epithelial tumors. Their significance and mechanism of formation remain largely speculative. Recently, we have reported the induction of these structures in rat keratinocytes following a brief treatment with acrylamide, and proposed that protein kinase inhibition may be implicated in their formation. In the present study, we show that protein kinase inhibitor H-7 in the presence of EGF is able to induce CD in rat keratinocytes within half an hour. In serum free medium containing 20 ng/ml of EGF, desmosomal structures at different stages of assembly were obtained using H-7 at concentrations ranging between 20 and 80 microM. No such structures were found at lower concentrations. The plaque diameters were significantly small in comparison with plasma membrane plaques. EGF induced plakoglobin positive membrane invaginations and in the presence of H-7, desmosomal plaques assembled on these membranes as either half desmosomes or as symmetric ones. The present results implicate protein kinase inhibition in CD formation and suggest that EGF provides tubular membrane structures in the cytoplasm on which desmosomes may assemble.

An immunohistological study of desmosomes in Darier's disease and Hailey-Hailey disease

The immunocytochemical distribution of desmosomal components was determined in involved skin from eight patients with Darier's disease, five patients with Hailey-Hailey disease and two patients with transient acantholytic dermatosis as well as skin from four normal controls. Sections were stained using monoclonal antibodies to the desmosomal proteins dp1 and dp2 (desmoplakins) and the desmosomal glycoproteins dg1 (desmoglein), and dg2 and dg3 (desmocollins). There was normal expression of desmosomal proteins and glycoproteins at the periphery of the keratinocytes in the perilesional skin in Darier's disease, in Hailey-Hailey disease and in transient acantholytic dermatosis. In the lesional skin there was reduced expression of desmosomal proteins and glycoproteins in the basaloid 'buds' at the base of the lesions, but there was bright diffuse staining of the acantholytic cells. Focal intracellular staining was detected within many of the acantholytic keratinocytes in Hailey-Hailey disease and within some of these cells in Darier's disease. Suction blisters were used to induce fresh acantholysis in lesional skin in Darier's disease and clinically uninvolved skin in Hailey-Hailey disease. The results indicated that acantholysis precedes the development of intracellular staining. Although there are immunopathological abnormalities in the distribution of desmosomal proteins and glycoproteins in both Darier's disease and Hailey-Hailey disease, the changes are probably secondary to internalization of desmosomal components with breakdown and redistribution of antigens rather than a primary deficiency in the synthesis of these proteins. Focal internalization was more widespread in Hailey-Hailey disease than in Darier's disease and the differences in the distribution of desmosomal components in these diseases confirm that they are distinct entities.

Buschke-Loewenstein tumour. A histologic and ultrastructural study of six cases

Results on the light- and electron microscopic studies of six cases of Buschke-Loewenstein tumour are presented. The role of chronic irritation is emphasized in the aetiology of the tumour. Fistulas and abscesses arising in the tumour are dangerous as they give rise to chronic sepsis. In two perianal tumours, in situ or invasive carcinoma developed. Electron microscopy revealed varying degrees of differentiation of keratinocytes. As a result of the defective desmosomes, the tumour cell underwent segregation, with widened intercellular spaces containing oedema, erythrocytes and leucocytes. This phenomenon is probably responsible for frequent bleeding and fistula formation. The investigations disclosed that the Buschke-Loewenstein tumour is a special form of squamous carcinoma and therefore, radical surgical excision must be attempted even in case of a benign histological picture.

Domain turnover of junctional membrane areas in the epidermis

To investigate the turnover of complete junctional membrane areas ("domain turnover"), psoriatic epidermis, keratoacanthoma, and squamous cell carcinoma were studied with an electron microscope and compared with the normal epidermis. Three types of domain turnover of junctions were observed. First, the uptake of intact intercellular junctions, which occurred as complete or incomplete annular junctions in the cytoplasm. Mainly gap junctions were involved. Second, the formation of autojunctions bridging an infolding at the surface of a cell, which is then incorporated and occurs partly with an attached saccule in the cytoplasm. This type was confined to desmosomes. Finally, the loss of intercellular desmosomes into the intercellular space was observed. Proliferating epidermis was associated with an increased domain turnover of gap junctional membrane areas. Domain turnover of desmosomes prevailed in tumors.

Unilateral central corneal epithelial dysplasia

A unilateral, apparently nonfamilial disease process affecting the interpalpebral portion of the corneal epithelium is reported. The patient, a 62-year-old man, was in good general health; he had no disease of the skin or mucous membranes and no history of trauma. Severe intermittent discomfort of the left eye had been present for several months. Corneal epithelial scrapings were performed on two occasions with a one-year interval, the condition having recurred during the intervening months. Material from both biopsy specimens showed dysplasia of the epithelium with foci of acantholysis and dyskeratosis and features of apoptosis. Transmission electron microscopic findings included intracytoplasmic desmosomes, conspicuous thickened tonofibrils, irregular convoluted cytoplasmic membranes, and dyskeratotic bodies.

Clinical, histological and ultrastructural features of a possibly virus-induced oral leukoplakia

Two male patients with oral leukoplakias exhibiting a peculiar type of apparent dysplastic changes have been followed for 4 and 6 years, and a series of biopsies have been examined by light and electron microscopy. The apparent lack of normal epithelial stratification below the keratinized cell layers was mainly caused by the frequent appearance of large ballooned cells and multinuclear giant cells. The centre of the large ballooned cells contained aggregations of chromatin and evenly-dispersed microtubulus surrounded by a thick rim of tonofibril bundles. In the peripheral cytoplasm large numbers of smooth-surfaced endoplasmic reticulum were found, but no Golgi apparatus was observed. In addition, several autophagocytic bodies were recorded. Along the cell membrane only a few desmosomes were present, whereas aggregations of digested desmosomes were found in the cytoplasm. On the basis of the ultrastructural findings, it is suggested that the large ballooned cells represented epithelial cells arrested in early stages of mitotic division. The epithelial cells in interphase exhibited a normal ultrastructure except for large nucleoli with varying degrees of condensation of nucleolonema and vacuolization. Further, atypical dense granular aggregations and strands of fine fibrillar material were recorded in the nuclei. It is suggested that this new type of oral leukoplakia has a viral etiology.

Fixed drug eruption: ultrastructural study of dyskeratotic cells

Electron microscopic studies have been carried out on three cases of fixed drug eruption, with particular regard to the dyskeratotic cells. The authors have tried to show the sequence of events leading from a normal basal keratinocyte to a dyskeratotic body. Ribosomes were first increased in number; then the tonofibrillar system looked thicker, cytoplasmic organelles degenerated and numerous melanosomes appeared. Many dyskeratotic bodies were later found in epidermal macrophages and in the intercellular space. Several intra-cytoplasmic desmosomes were found in the dyskeratotic cells and their evolution is discussed. The increased number of melanosomes seen in the dyskeratotic bodies could be due to injury to epidermal lysosomal catabolism or it could be due to an apparent increase in melanosome numbers, within cells whose volume has been reduced.

Trends in electron microscopy of skin

Some trends in electron microscopy of skin have emerged and should be pursued in the future. The fine structure and some basic cellular reaction patterns of epidermal cells are discussed to illustrate the interplay of morphologic, cytochemical, and tracer studies. Intracytoplasmic membranes and secretory granules, lysosomes and endocytic mechanisms, cytomembranes and cell surface specialization are discussed to show how these can be used to arrive at a more meaningful interpretation of structure. Despite all advances, however, a great deal more needs to be done before the details of skin structure are completely elucidated.

Desmosome-like structures in the cytoplasm of normal human keratinocyte

Desmosome-like structures in the cytoplasm which have so far been described in tumoral and acantholytic epidermal cells were observed on two occasions in morphologically normal basal and prickle cells. It seems that under specific conditions a normal epidermal cell can lose contact with the surrounding cell during cell division and forms intracytoplasmic desmosomes.

Ultrastructural changes in bovine lingual epithelium infected with vesicular stomatitis virus

Vesicular stomatitis virus was inoculated into the dorsal lingual epithelium of three cows. The reaction that developed in 72 h was characterized by severe acute diffuse glossitis with intercellular edema and necrosis of keratinocytes. Virions budded from the plasma membrane and were in the intercellular spaces. Reduplication of desmosomes was a prominent alteration, and normal desmosomes were within the cytoplasm. Intracytoplasmic desmosomes appeared to be formed by endocytosis after breaks occurred in the plasma membrane of one cell; endocytosis of loops of plasma membrane containing desmosomes; and formation of desmosomes on invagination of the plasma membrane.

[Desmosomal structures in the cytoplasm of normal and abnormal keratinocytes (author's transl)]

The occurrence of intracytoplasmic desmosomes in normal, hyperplastic, and hyperkeratotic epithelia, in carcinoma-in-situ and in invasive carcinoma of the human oral cavity is demonstrated by electron microscopy. The mechanism for formation of these structures by invagination, separation and by intracytoplasmic incorporation of plasma membrane-desmosome-complexes are described in various oral epithelia, and other possible mechanisms are discussed. Intracytoplasmic desmosomes may occur in normal and pathological keratinocytes of all layers of the oral epithelium. Their ultrastructure in the peripheral cytoplasm is similar to that of the regular desmosomes on the cell surface. However, as they migrate centripetally, they show signs of degeneration, suggesting dissolution by lysosomal enzyme systems. Various surface membrane alterations involved in the formation of intracytoplasmic desmosomes may lead to a reduction of plasma membrane material and of desmosome structures and to defective intercellular adhesion. The intracytoplasmic incorporation of desmosome structures is a ubiquitous phenomenon exhibited by epithelial keratinocytes under certain physiological or pathological conditions.