Histological defects of chronic benign familial pemphigus expressed in tissue culture

Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy

The rapid proliferation of many different engineered nanomaterials (defined as materials designed and produced to have structural features with at least one dimension of 100 nanometers or less) presents a dilemma to regulators regarding hazard identification. The International Life Sciences Institute Research Foundation/Risk Science Institute convened an expert working group to develop a screening strategy for the hazard identification of engineered nanomaterials. The working group report presents the elements of a screening strategy rather than a detailed testing protocol. Based on an evaluation of the limited data currently available, the report presents a broad data gathering strategy applicable to this early stage in the development of a risk assessment process for nanomaterials. Oral, dermal, inhalation, and injection routes of exposure are included recognizing that, depending on use patterns, exposure to nanomaterials may occur by any of these routes. The three key elements of the toxicity screening strategy are: Physicochemical Characteristics, In Vitro Assays (cellular and non-cellular), and In Vivo Assays. There is a strong likelihood that biological activity of nanoparticles will depend on physicochemical parameters not routinely considered in toxicity screening studies. Physicochemical properties that may be important in understanding the toxic effects of test materials include particle size and size distribution, agglomeration state, shape, crystal structure, chemical composition, surface area, surface chemistry, surface charge, and porosity. In vitro techniques allow specific biological and mechanistic pathways to be isolated and tested under controlled conditions, in ways that are not feasible in in vivo tests. Tests are suggested for portal-of-entry toxicity for lungs, skin, and the mucosal membranes, and target organ toxicity for endothelium, blood, spleen, liver, nervous system, heart, and kidney. Non-cellular assessment of nanoparticle durability, protein interactions, complement activation, and pro-oxidant activity is also considered. Tier 1 in vivo assays are proposed for pulmonary, oral, skin and injection exposures, and Tier 2 evaluations for pulmonary exposures are also proposed. Tier 1 evaluations include markers of inflammation, oxidant stress, and cell proliferation in portal-of-entry and selected remote organs and tissues. Tier 2 evaluations for pulmonary exposures could include deposition, translocation, and toxicokinetics and biopersistence studies; effects of multiple exposures; potential effects on the reproductive system, placenta, and fetus; alternative animal models; and mechanistic studies.

Hailey-Hailey disease keratinocytes: normal assembly of cell-cell junctions in vitro

The blisters in the inherited disorder, Hailey-Hailey disease, may be caused by defective epidermal junctional complexes. We evaluated these structural complexes in vivo and in vitro. We induced a vesicular lesion in the apparently normal skin of a patient with Hailey-Hailey disease and studied a biopsy of this lesion by transmission electron microscopy. To determine whether acantholysis was related to a defect in the number or assembly of intercellular junctions, we cultured Hailey-Hailey disease keratinocytes in medium containing 0.1 mM Ca2+ and increased the [Ca2+] to 1.1 mM in order to induce assembly of cell-cell junctions. Keratinocytes were examined by double immunofluorescence with antibodies to the desmosome protein, desmoplakin, and the adherens junction protein, vinculin, at intervals after the increase in [Ca2+]. Characteristic Hailey-Hailey disease histopathology was observed by electron microscopy of the patient's skin after trauma, but we found no splitting of desmosomes. Based on the location, intensity, and rate of change of immunofluorescent staining, Hailey-Hailey and normal keratinocytes did not differ in their ability to assemble desmosomes and adherens junctions. Furthermore, we observed no significant morphologic differences between normal and Hailey-Hailey keratinocytes cultured in low and high [Ca2+]-containing media; Hailey-Hailey cells contained abundant normal-appearing desmosomes in 1.1 mM [Ca2+]. Since Hailey-Hailey disease keratinocytes can assemble normal-appearing adherens junctions and desmosomes in vitro, the functional defect may not lie in assembly of cell-cell adhering junctions, or additional perturbation may be required to expose the defect.

Involvement of the adherens junction-actin filament system in acantholytic dyskeratosis of Hailey-Hailey disease. A histological, ultrastructural, and histochemical study of lesional and non-lesional skin

Hailey-Hailey disease is a blistering genodermatosis that shows acantholytic dyskeratosis throughout the epidermis. The aim of our study was to investigate the involvement of adherens structures and cytofilaments in this particular type of acantholysis. Both lesional and non-lesional skin from 18 patients was studied histologically and ultrastructurally. Additionally, the samples were stained for desmosomes, adherens junctions, keratin filaments, actin filaments, and actin-associated proteins, and finally investigated with an electron and a confocal laser scanning microscope (CLSM), respectively. Acantholytic dyskeratosis was not only confined to lesions, but was also focally detectable in clinically unaffected skin. Despite disruption and internalization of the desmosomes, keratinocytes remained linked together by well-preserved adherens junctions. Staining for actin filaments with fluorochrome-labeled phalloidin showed a remarkable formation of actin stress fibers in these keratinocytes. Thus, incomplete acantholysis, as demonstrable in both lesional and non-lesional skin of Hailey-Hailey patients, may be due to a cohesive function of the adherens junction-actin system succeeding the dissolution of desmosomes. Most remarkably, none of the adnexal epithelia expressed the intrinsic defect of cell adhesion. This finding offers an explanation for the successful treatment of Hailey-Hailey disease by dermabrasion, which after complete removal of the involved epidermis results in reepithelialization from skin appendages.

Modified epidermal lipid composition in air-exposed culture of non-bullous congenital ichthyotic erythroderma (NBCIE) keratinocytes

Emerged epidermal cultures on dead de-epidermized dermis (DED) constitute an excellent model for in vitro reproduction of dermatoses linked to a keratinocyte defect. We used such cultures for studies of non-bullous congenital ichthyotic erythroderma (NBCIE). Keratinocytes of normal and pathological origin were expanded in submerged cell cultures and frozen keratinocytes from the resulting cell bank were subsequently used for seeding on DED. Lipid extracts from 14 day emerged cell cultures were assayed qualitatively and quantitatively using thin layer chromatography and compared with the neutral and non-polar lipid profiles obtained from normal epidermis extracts and with those from the plantar stratum corneum of healthy donors and untreated NBCIE patients. The ichthyotic cultures were found to contain significantly elevated levels of n-alkanes, as were the lipid extracts from the patients' plantar horny layer. Our results demonstrate that a major marker of the NBCIE epidermis can be reproduced under the emerged culture conditions. They also indicate that the characteristic n-alkane increase in NBCIE is indeed endogenous and not merely related to possible contamination from topical treatments.

Hailey-Hailey disease: the clinical features, response to treatment and prognosis

Fifty-eight individuals with Hailey-Hailey disease were studied to delineate the clinical features, response to treatment and prognosis. The disease generally presented between the second and fourth decades, but the morphology of lesions was varied and a delay in diagnosis was common. Nail changes have not been documented in previous studies of Hailey-Hailey disease, but asymptomatic longitudinal white bands were present in the fingernails in 71% of 38 patients examined and are a helpful physical sign. The disease is predominantly flexural. Friction and heat or sweating exacerbate the lesions and pain may limit physical activities. The prognosis was assessed in 27 patients with longstanding disease and the long-term outlook is generally good. Seventeen patients had improved and the disease was static in seven patients. Three patients deteriorated with age. Topical corticosteroids with or without added antibiotics were an effective treatment.

Cell adhesion in Hailey-Hailey disease and Darier's disease: immunocytological and explant-tissue-culture studies

The pathogenesis of Hailey-Hailey disease and Darier's disease was investigated using immunocytological and explant-tissue-culture techniques. There was breakdown of the intercellular adhesions between keratinocytes in explants from clinically uninvolved skin of patients with Hailey-Hailey disease or Darier's disease. The major desmosomal components were present in the cultures and were expressed in a punctate peripheral pattern at cell-cell contact sites, but there was diffuse staining of acantholytic cells. Plasminogen, which is expressed by basal keratinocytes in normal skin, was detected in association with suprabasal acantholytic cells in skin biopsies from these diseases. Plasminogen was reversibly displaced from the cells by 6-aminohexanoic acid, suggesting that binding is mediated by a reaction with the lysine receptor on the plasminogen molecule. Plasminogen was also detected in separating cells in explant cultures and there was cytoplasmic expression of the plasminogen activator urokinase by these cells. These abnormalities are not unique to either disease and do not account for the phenotypic differences between Darier's disease and Hailey-Hailey disease, but plasmin generation may have a role in perpetuating cell separation.