Ultrastructural localization of lectin-binding sites in normal skin

Concanavalin A promotes angiogenesis and proliferation in endothelial cells through the Akt/ERK/Cyclin D1 axis

CONTEXT

Concanavalin A (Con A) exhibited multiple roles in cancer cells. However, the role of Con A in endothelial cells was not reported.

OBJECTIVE

Our present study investigated the potential angiogenic role of Con A in endothelial cells and ischaemic hind-limb mice.

MATERIALS AND METHODS

Human umbilical vein endothelial cells and Ea.hy926 cells were employed to determine the effect of Con A (0.3, 1, and 3 μg/mL) or vehicle on angiogenesis and cell proliferation with tube formation, ELISA, flow cytometry, EdU, and western blot. Hind-limb ischaemic mice were conducted to determine the pro-angiogenic effect of Con A (10 mg/kg) for 7 days.

RESULTS

Con A promoted tube formation to about three-fold higher than the control group and increased the secretion of VEGFa, PDGFaa, and bFGF in the medium. The cell viability was promoted to 1.3-fold by Con A 3 μg/mL, and cell cycle progression of G0G1 phase was decreased from 77% in the vehicle group to 70% in Con A 3 μg/mL, G2M was promoted from 15 to 19%, and S-phase was from 7 to 10%. Con A significantly stimulated phosphorylation of Akt and ERK1/2 and expression of cyclin D1 and decreased the expression of p27. These effects of Con A were antagonised by the PI3K inhibitor LY294002 (10 μM) and MEK pathway antagonist PD98059 (10 μM). Moreover, Con A (10 mg/kg) exhibited a repair effect in ischaemic hind-limb mice.

DISCUSSION AND CONCLUSIONS

This study will provide a new option for treating ischaemic disease by local injection with Con A.

Concanavalin A for in vivo glucose sensing: a biotoxicity review

Over the last two decades there as has been surging scientific interest in employing the glucose- and mannose-specific lectin Concanavalin A (ConA) in affinity biosensors for in vivo glucose monitoring in diabetics. Numerous research groups have successfully shown in in vitro and in vivo studies that ConA-based affinity sensors can monitor glucose very accurately and reproducibly over many months, making ConA-based sensors an extremely interesting prospect for long-term implantation in humans. Despite this progress, there remains concern over the safety of ConA, which has widely been reported as a toxin in the literature. In this article, we review in vitro and in vivo studies related to ConA toxicity in order to assess the health risks posed by ConA in the context of an implantable biosensor. Based on the wealth of information available and on data from our own studies, we can conclude that the site of implantation (subcutaneous skin tissue) and the small amount of ConA (<10 microg/microl) being used in implantable glucose-sensitive detector devices like those proposed by various research groups would pose little or no health risk to its bearer even in the event of unexpected sensor rupture.

Mannosides as crucial part of bioactive supports for cultivation of human epidermal keratinocytes without feeder cells

Large-scale production of keratinocytes by cell culture is of interest for medical applications. Long-term cultivation of epidermal cells is presently possible with feeder cells, i.e. 3T3 fibroblasts with arrested mitosis, or with specially formulated culture medium. To define refinements for in vitro conditions, the analysis of the natural environment with growth-maintaining/stimulating factors can provide important clues. Cells with proliferative activity are located in the basal layer of the epidermis in close contact with a basement membrane. Employing lectin and reverse lectin histochemistry of skin, muscle fibers and feeder cells, we assumed that the interplay of mannose-binding sites of epidermal cells, detected by a labeled neoglycoprotein, with glycoligands in the feeder cell layer or basement membrane could trigger signaling with relevance for adhesion and growth regulation. Indeed, coating of polystyrene with mannose-containing neoglycoprotein mimicking a mannose-rich cell matrix enabled the cultivation of keratinocytes without feeder cells in a Ca(2+)-dependent manner in serum-containing culture medium. Following this experimental demonstration of specific binding of mannose residues as part of a neoglycoprotein controlled by testing sugar-free carrier protein and other substances, we next synthesized and tested biocompatible polymers. Attachment and proliferation of keratinocytes on the surface of these polymers compared favorably to control experiments using feeder cells. In conclusion, we suggest that these polymers are bioactive offering a perspective for keratinocyte cultivation without feeder cells.

Dermcidin: a novel human antibiotic peptide secreted by sweat glands

Antimicrobial peptides are an important component of the innate response in many species. Here we describe the isolation of the gene Dermcidin, which encodes an antimicrobial peptide that has a broad spectrum of activity and no homology to other known antimicrobial peptides. This protein was specifically and constitutively expressed in the sweat glands, secreted into the sweat and transported to the epidermal surface. In sweat, a proteolytically processed 47-amino acid peptide was generated that showed antimicrobial activity in response to a variety of pathogenic microorganisms. The activity of the peptide was maintained over a broad pH range and in high salt concentrations that resembled the conditions in human sweat. This indicated that sweat plays a role in the regulation of human skin flora through the presence of an antimicrobial peptide. This peptide may help limit infection by potential pathogens in the first few hours following bacterial colonization.

Lectin histochemistry of glycoconjugates in the feline hair follicle and hair

The distribution of glycoconjugate in the feline hair follicle and hair was studied by light and electron microscopic histochemical methods. The hair apparatus was found to contain considerable amounts of complex carbohydrates with different saccharide residues (alpha-D-mannose, beta-D-glucose, alpha-L-fucose, beta-N-acetyl-D-glucosamine). Variations of those were detected in the plasma membrane of the hair follicle cells during the course of their differentiation and keratinization, namely, alph-D-glucose, alpha-L-fucose and beta-N-acetyl-D-glucosamine in the suprabulbar and bulbar regions. The reaction level of sialic acid residues in the plasma membrane decreased in some cell layers during the course of differentiation. The results obtained from the present study indicated that interaction between saccharide residues of neutral carbohydrates and sialyl groups during the anagen phase might contribute to cell keratinization in hair follicles and hairs. It is discussed whether the existence of glycogen in outer root sheath cells might enable these cells to provide other hair apparatus cells with energy when necessary. Moreover, it became obvious from variations in sialyl residue distribution that cell differentiation processes terminate first of all in Huxley's and Henle's layers within the suprabulbar region of the hair follicle, as followed by the hair cortex.

Ultrastructural localization of alpha-3 integrin subunit in malignant melanoma and adjacent epidermis

Eight cases of malignant melanoma were studied by immunohistopathology and immunoelectron microscopy. Alpha3 integrin localization was documented in malignant melanoma cells, basal and suprabasal keratinocytes, melanocytes, blood vessels and in basement membrane material. In melanoma cell membranes and, to a lesser extent, the interior of melanosomal vesicles were labeled. In addition, neighbouring cells such as basal and suprabasal keratinocytes and melanocytes showed strong alpha3-integrin expression. The labeling was much stronger in the plasma membrane than in the cytoplasm. Endothelial cells showed stronger labeling of the cytoplasm than of the plasma membrane. In some cases we found increased flocculent material surrounding melanoma cells or nests that seems to contain basement membrane protein components, specifically alpha3-integrin subunits. Compared to normal epidermis alpha3-labeling was stronger in tissues of malignant melanoma.

Presence of human papillomavirus DNA and expression of L-fucose moiety in some vulvar intraepithelial lesions and vulvar squamous cell carcinoma

BACKGROUND

Human papillomavirus could reside and play an etiological role in some vulvar epithelial lesions. Human papillomavirus-infected keratinocytes might have certain biochemical changes that could be of significance in helping clinical diagnosis or elucidating the pathogenesis of some vulvar epithelial diseases.

OBJECTIVE

To detect the presence of human papillomavirus DNA and observe the expression pattern of L-fucose moiety in some vulvar intraepithelial lesions and vulvar squamous cell carcinoma.

METHODS

Nineteen cases of vulvar intraepithelial lesions and 13 cases of vulvar squamous cell carcinoma from the inner aspect of labia majora or the outer aspect of labia minora were selected. Polymerase chain reaction was employed to detect the presence of human papillomavirus DNA in lesional skin. Ulex europeaus agglutinin-1 histochemistry was used to observe the L-fucose expression pattern.

RESULTS

A large proportion of vulvar intraepithelial lesions had the presence of human papillomavirus DNA, but the positive rate was low in vulvar squamous cell carcinoma and squamous cell hyperplasia. L-Fucose expression was much more pronounced in human papillomavirus DNA-positive lesions than those negative ones.

CONCLUSIONS

Human papillomavirus had an important impact on some vulvar intraepithelial lesions in this Oriental population. The expression pattern of L-fucose may be used as an indicator for vulvar keratinocyte transformation by human papillomavirus.

A comparison of methods for heat-mediated antigen retrieval for immunoelectron microscopy: demonstration of cytokeratin No. 18 in normal and neoplastic hepatocytes

Postembedding antigen retrieval is a well established technique for immunoelectron microscopy; however, many antigens cannot be detected without additional unmasking procedures. This study was undertaken to determine whether microwave oven heating, autoclaving, and pressurized boiling, which are well recognized methods of antigen retrieval for light microscopy, and simple boiling can also be used in electron microscopy. We investigated neoplastic and normal hepatocytes using a commercially available mouse monoclonal antibody against cytokeratin NO. 18 (CK 18). The tissue was fixed in paraformaldehyde/glutaraldehyde and embedded in Lowicryl K4M at -40 C. Ultrathin sections in various buffers were exposed to heat using one of four methods or to pronase at 37 C before incubation with the primary antibody. The secondary antibody was gold-labeled goat anti-mouse antibody. Sections that were not heat-treated remained unlabeled, but heat-treated sections showed immunoreactivity located mainly at the cytoplasmic periphery. Some of the gold particles lay in direct or loose association with intermediate filaments, some were seen in the area of desmosomes, and some did not appear related to any structures. No difference in immunostaining was found among the four methods of heat treatment. The citrate buffer, pH 6.0, and 10 mM EDTA, pH 8.0, generated the best labeling results.

New applications of electron microscopy techniques in dermatopathology

The application of immunostaining techniques to electron microscopy specimens has led to a renewal of interest in electron microscopy in biological research in general, as well as in dermatopathology. Refinements in the preparative procedures have made easier the immunolocalization of antigens both in chemically-fixed and frozen unfixed tissues, embedded in plastic and sectioned. Application of these methods has led to the demonstration of the bullous pemphigoid antigen inside basal keratinocytes. HMB-45 antigen has been found to be present in premelanosomes. Recently, Factor XIIIa has been localized not only in dermal dendrocytes but also in endothelial cells and mast cells.

Localization of anionic sites in normal and psoriatic epidermis: the effect of enzyme digestion on these anionic sites

Cell surface anionic charge is known to be related to various cellular functions. Therefore, we ultrastructurally localized anionic sites in normal and psoriatic human epidermis, using poly-L-lysine-gold complex (cationic gold), to assess their possible participation in the differentiation of keratinocytes and the pathogenesis of psoriasis. In normal and psoriatic epidermis, the cell membrane of keratinocytes showed positive staining at pH 2.0. At pH 7.4 the cytoplasm and nucleus were diffusely stained, in addition to the cell membrane. In normal epidermis, the intensity of labelling on the cell membrane at pH 2.0 was strong in the basal layer and lower stratum spinosum, and decreased in parallel with differentiation of keratinocytes. In psoriatic epidermis, the intensity of labelling on the cell membrane at pH 2.0 was stronger than in normal epidermis. In normal epidermis, heparitinase digested 63% and chondroitinase ABC digested 80% of cationic labelling. This suggests that heparan sulphate and chondroitin sulphate (and/or dermatan sulphate) constitute anionic sites in normal epidermis. In psoriatic epidermis, chondroitinase ABC-sensitive anionic sites were greatly increased, whereas heparitinase-sensitive anionic sites were the same, when compared with normal epidermis. This suggests that chondroitin sulphate and/or dermatan sulphate constitute anionic sites which are increased in psoriatic epidermis.

Techniques in immuno-electron microscopy. I. Cryosubstitution

Normal skin was cryoprotected by submerging it in a mixture of 30% dimethylformamide (DMF) in PBS or RPMI. Subsequently it was frozen in liquid propane gas. Cryosubstitution was carried out at -90 degrees C by using methanol to which uranyl acetate or osmium tetroxide were added. The tissue was embedded in either Lowicryl K4M at -40 degrees C or in Epon at +60 degrees C. The tissue was evaluated by its overall preservation of ultrastructural details and by its labeling intensity after incubation with either anti-desmoglein or anti-type VII collagen monoclonal antibodies. The mixture of DMF and PBS caused an electron-dense precipitate within the cell. The overall morphology was better in Epon-embedded material than in K4M-embedded material. However, the labeling was best in K4M material. Regardless of whether the tissue was embedded in Epon or K4M, the addition of osmium tetroxide markedly reduced the degree of labeling.

Ultrastructural localization of factor XIIIa

Thin sections of dermatofibromas, of a basal cell epithelioma, a patch stage lesion of Kaposi's sarcoma, a case of angiolymphoid hyperplasia with eosinophilia, and one case of malignant mastocytosis were incubated with antibody to factor XIIIa (FXIIIa). Regardless whether the tissue had been embedded in Lowicryl K4M, Epon, or Araldite, labeling was found in dermal dendrocytes, mast cells, and endothelial cells. In dermal dendrocytes, the reaction product was seen in dilated cisternae of the rough endoplasmic reticulum as well as free within the cytoplasm. In endothelial cells, FXIIIa was localized within Weibel Palade bodies, free within the cytoplasm, and in villous projections into the vasucular lumen. In mast cells, the reaction was found in mast cell granules exclusively. Mast cells, dermal dendrocytes, and endothelial cells have in common that all three express FXIIIa, belong to the microvascular unit, and are increased in number during angiogenesis and in fibrovascular processes. It thus seems that these cells are functionally related.

Congenital self-healing reticulohistiocytosis--a benign Langerhans cell disease

An-11-day old girl was seen with brownish nodular lesions scattered over the body with emphasis on the face and scalp. Several lesions had started to involute. Tissue was studied by histopathology, immunohistopathology, routine electron microscopy, and immuno-electron microscopy using cryosubstitution and embedding in K4M. Immunohistopathology revealed that the cells of the dermal infiltrate were Langerhans cells. They expressed Leu 6 and HLA-DR. On routine electron microscopy no Birbeck granules were found in the dermal cells. Birbeck granules in epidermal Langerhans cells were deformed and often situated next to laminated dense bodies. The latter expressed Leu 6 and lysozyme on immuno-electron microscopy. It was concluded that congenital self-healing reticulohistiocytosis is a benign Langerhans cell disease in which Birbeck granules are transformed to laminated dense bodies and possibly degraded by lysosomal enzymes.

Cantharidin-induced acantholysis: adhesion molecules, proteases, and related proteins

Acantholysis is a feature of disorders such as Hailey-Hailey disease and Darier's disease. Immunocytochemical studies have shown internalization of desmosomal components after acantholysis. Basal cytokeratins show suprabasal expression in lesional Darier's disease. The exact mechanisms of acantholysis are still unclear. Cantharidin induces blistering, with suprabasal keratinocyte acantholysis, possibly by protease activation. Plasmin has been implicated in the pathogenesis of acantholysis in Darier's disease and Hailey-Hailey disease. We examined the distribution of desmosomal components, proteases and cytokeratins in cantharidin blisters, to compare them with those previously found in Darier's disease and Hailey-Hailey disease. Two drops of cantharidin collodion were applied to the skin of five normal volunteers. A 4-mm punch biopsy of the blister was taken, and snap frozen. Sections were stained with antibodies to desmosomal proteins (dp) 1/2, dp 3, desmosomal glycoproteins (dg) 1, 2/3, extracellular carbohydrate residues, using the lectins peanut agglutinin (PNA) and soybean agglutinin (SBA), proteases and cytokeratins. Acantholytic cells were stained diffusely with dp1/2; there was markedly reduced or absent peripheral staining for dp3, dg1, dg2/3, PNA and SBA. There was no clumping of stain. Plasminogen, fibrinogen and urokinase were expressed in some acantholytic cells. Basal keratin markers were expressed suprabasally in acantholytic cells. These results are similar to those previously obtained in Darier's disease, but different from the staining obtained in Hailey-Hailey disease. Extracellular glycosylated portions of adhesion molecules may be lost after acantholysis, perhaps as a result of conformational changes, internalization of extracellular domains, or proteolysis. The changes in the expression of plasminogen, fibrinogen, urokinase and cytokeratins in acantholytic cells in cantharidin-induced blisters are, as in Darier's disease and Hailey-Hailey disease, probably secondary to acantholysis, and changes in the shape of cells. We conclude that cantharidin blisters may be a useful model for the study of acantholysis in Darier's disease.

Immunohistochemical study of cell proliferation and differentiation in epidermis of mice after administration of cholera toxin

Cholera toxin causes reversible epidermal hyperplasia. We observed maximal thickness of the epidermis on the fourth day after treatment and a return to pretreatment values by day 7. The increase in thickness occurred in the basal and intermediate layers, with these layers becoming two to three times thicker than those of normal epidermis. The time sequence of epidermal proliferation was studied using bromodeoxyuridine (BrdU) labelling. We observed a maximum number of labelled basal cells within the first 24 h. Only a few cells were labelled 7 days after toxin injection. Griffonia simplicifolia-IB4 (GSA-IB4), Ulex europaeus-I (UEA-I) and Griffonia simplicifolia-II (GSA-II) lectins were used for the analysis of epidermal cell differentiation in the tissue sections. To study keratinocyte differentiation, further immunological staining was performed using two anticytokeratin antibodies, PKK2 and PKK3 mouse monoclonal antibodies. From the immunocytochemical results, we conclude that synchronous differentiation of the epidermis occurs after cholera toxin administration.

C32 human melanoma cell endogenous lectins: characterization and implication in vesicle-mediated melanin transfer to keratinocytes

To optimize skin pigmentation in order to help body prevention against UV radiation, the mechanism of melanin pigment transfer from melanocytes to keratinocytes must be elucidated. Melanin transfer to keratinocytes requires specific recognition between keratinocytes and melanocytes or melanosomes. Cell surface sugar-specific receptor (membrane lectin) expression was studied in human C32 melanoma cells, an amelanotic melanoma, by flow cytometry analysis of neoglycoprotein binding as an approach to the molecular specificity. Sugar receptors on melanocytes are mainly specific for alpha-L-fucose. Their expression is enhanced upon treatment by the diacylglycerol analogue 1-oleoyl-2-acetylglycerol, which can induce melanin synthesis in amelanotic human melanoma cells in a dose-dependent manner. Flow cytometry analyses showed a small-sized population of vesicles distinguishable from large cells by their fluorescence properties upon neoglycoprotein binding. Sorting indicated that the small-sized subpopulation is composed of vesicles produced by melanocytic cells. Upon vesicle formation, a selective concentration of sugar receptors specific for 6-phospho-beta-D-galactosides appears in the resulting melanocytic vesicles. Vesicles are recognized and taken up by cultured keratinocytes and a partial inhibitory effect was obtained upon cell incubation in the presence of neoglycoproteins, indicating a possible participation of sugar receptors in this recognition. The validity for such a model to help in understanding the natural melanin transfer by melanosomes is confirmed by electron microscopy, which demonstrates the presence of melanin inside keratinocytic cells upon incubation with melanocytic vesicles.

Adhesion molecules and related proteins in Darier's disease and Hailey-Hailey disease

We have used antibodies to plakoglobin and E-cadherin: the lectins, peanut agglutinin (PNA) and soybean agglutinin (SBA); and sera from patients with the autoimmune diseases pemphigus vulgaris (PV) or pemphigus foliaceus (PF), in an immunohistological study of Darier's disease and Hailey-Hailey disease. There was normal expression of plakoglobin, E-cadherin, lectins and pemphigus antigens at the periphery of keratinocytes in uninvolved skin. Clumps of plakoglobin were detected within acantholytic cells in Hailey-Hailey disease, whereas expression was diffuse in acantholytic cells in Darier's disease. This difference may reflect differences in the pathogenesis of acantholysis. E-cadherin expression was weak or absent at the periphery of some acantholytic cells; lectin binding was sometimes reduced around acantholytic cells, and pemphigus antibodies did not bind to the acantholytic cells involved skin in either disease. Internalization, conformational changes or proteolysis may alter the expression of extracellular epitopes by acantholytic cells.

Ultrastructural localization of HMB-45 binding sites

Three malignant melanomas, two melanoma metastases, two junctional dysplastic nevi, and normal skin were embedded in Lowicryl. Ultrathin sections were incubated with HMB-45 and a gold-labeled anti-mouse antibody. Gold particles indicating the presence of HMB-45 were found in melanosomes Stage 1 and 2 and in the non-melanized portion of melanosomes Stage 3. Melanosomes Stage 4 and melanosome complexes in keratinocytes, as well as in melanophages, were consistently negative. No specific labelling with HMB-45 was seen in eccrine glands of normal skin.

Ultrastructural localization of lectin-binding sites in normal human eccrine and apocrine glands

The distribution of carbohydrate residues in eccrine and apocrine glands of normal human skin was studied using a post-embedding technique with Lowicryl K4M. Thin sections were incubated with Ulex europaeus agglutinin I (UEA I), wheat germ agglutinin (WGA), peanut agglutinin (PNA), concanavalin A (Con A), soybean agglutinin (SBA), and dolichos biflorus agglutinin (DBA). All lectins except for PNA showed labeling of the plasma membranes of dark cells, clear cells, and apocrine cells. The granules of the eccrine gland were labeled with all lectins except for DBA. The mitochondrial granules of the apocrine gland were not labeled with any lectin, whereas the lysosomal granules showed a positive reaction with all lectins except for PNA. After incubation with PNA, in eccrine glands the granules were the only structure labeled, whereas in apocrine glands the luminal side of the plasma membrane and cytoplasmic vesicles beneath it were the only structures labeled.

Ultrastructural localization of lectin binding sites in human melanocytes

The ultrastructural localization of carbohydrate residues in human melanocytes of normal epidermis and of one compound naevus was studied. The following lectins were used in a post-embedding technique: 1. peanut agglutinin (PNA), which reacts specifically with N-acetylgalactosamine; 2. Concanavalia ensiformis (Con A) indicating alpha-D-glucose and alpha-D-mannose binding sites; 3. Ulex europaeus agglutinin (UEA I) specific for alpha-L-fucose; 4. Wheat germ agglutinin (WGA), reacting specifically with N-acetyl-glucosamine and neuraminic acid (sialic acid); and 5. Limax flavus agglutinin (LFA), also specific for sialic acid (Neu5Ac-alpha-2,3-Gal and Neu5Ac-alpha-2,6-Gal). When incubated with WGA, Con A and LFA strong labelling was seen within the cytoplasm and in the plasma membrane of melanocytes, whereas incubations with PNA and UEA I revealed an occasional gold particle only. The determination of the distribution of carbohydrate residues in normal melanocytes is a prerequisite for future studies of abnormal melanocytes.