Babes, blisters and basement membranes: from sticky molecules to epidermolysis bullosa

The Ocular Signs and Complications of Epidermolysis Bullosa

Eleven patients with the dystrophic form of epidermolysis bullosa underwent ophthalmic assessment to establish the presence, characteristics, and extent of any ocular involvement. Eight patients were found to have eye changes: these included varying degrees of Symblepharon, broadening of the limbus, and corneal opacities. Taken as a group, these changes formed a characteristic pattern. The majority of patients were asymptomatic and the ocular changes appear to be only slowly progressive. Recurrent corneal abrasion and Symblepharon are the most important complications.

Molecular genetics of the skin: the implications of understanding

During recent decades, discoveries in genetic skin disease have produced insights into the biology of the skin, and in some cases permitted preventive prenatal diagnosis, but application of this knowledge in palliation or cure remains a tantalising prospect.

Sulphur mustard injuries of the skin. Pathophysiology and management

Sulphur mustard is a vesicant (blistering agent), which produces chemical burns with widespread blistering. It was used extensively as a chemical warfare agent in the First World War, and has allegedly been employed in a number of conflicts since then, most recently by Iraq against Iran (1984-1987). The potential further use of mustard in military conflicts and by terrorists remains a significant threat that if realised in practice would result in a large number of casualties with severely incapacitating, partial thickness burns. Such injuries clearly present a huge potential wound care problem. The development and healing of mustard-induced cutaneous injuries has not only been observed in human casualties, but has been studied recently at the microscopic and ultrastructural levels in several animal models. Vesication generally begins on the second day after exposure, and may progress for up to 2 weeks. Wound healing is considerably slower than for a comparable thermal burn, and patients often require extended hospital treatment. The current management strategy is essentially symptomatic and supportive. Recently, two techniques for removing damaged tissue and improving wound healing have been investigated. Mechanical dermabrasion and laser debridement ('lasablation') both produced an increased rate of wound healing in animal models, and may be of benefit in a clinical context.

The role of laminins in basement membrane function

Laminins are a family of multifunctional macromolecules, ubiquitous in basement membranes, and represent the most abundant structural noncollagenous glycoproteins of these highly specialised extracellular matrices. Their discovery started with the difficult task of isolating molecules produced by cultivated cells or extracted from tissues. The development of molecular biology techniques has facilitated and accelerated the identification and the characterisation of new laminin variants making it feasible to identify full-length polypeptides which have not been purified. Further, genetically engineered laminin fragments can be generated for studies of their structure-function relationship, permitting the demonstration that laminins are involved in multiple interactions with themselves, with other components of the basal lamina, and with cells. It endows laminins with a central role in the formation, the architecture, and the stability of basement membranes. In addition, laminins may both separate and connect different tissues, i.e. the parenchymal and the interstitial connective tissues. Laminins also provide adjacent cells with a mechanical scaffold and biological information either directly by interacting with cell surface components, or indirectly by trapping growth factors. In doing so they trigger and control cellular functions. Recently, the structural and biological diversity of the laminins has started to be elucidated by gene targeting and by the identification of laminin defects in acquired or inherited human diseases. The consequent phenotypes highlight the pivotal role of laminins in determining heterogeneity in basement membrane functions.

Production of basement membrane components by a reconstructed epidermis cultured in the absence of serum and dermal factors

A fully differentiated epithelium displaying features of human epidermis was obtained in vitro by culturing second-passage normal human keratinocytes for 14 days in defined medium and on an inert polycarbonate filter substratum at the air-liquid interface. Vertical sections stained for histology and indirect immunofluorescence studies showed that the 'basal' cells synthesize and secrete all major markers of hemidesmosomes and the lamina lucida. Components of the lamina densa are also expressed. Collagen VII is synthesized, but not secreted. Ultrastructural studies showed the presence of hemidesmosomes with major dense plaques and anchoring filaments, and a basement membrane-like structure was clearly identified. These results show that epidermal cells are able to produce hemidesmosomes and to secrete the major components of the dermo-epidermal junction in the absence of serum and dermal factors, suggesting that basement membrane synthesis and hemidesmosome assembly are not dependent on the presence of dermis.

Anchoring fibrils, collagen VII, and neutral metalloproteases in recessive dystrophic epidermolysis bullosa inversa

Structure of the anchoring fibrils, expression of collagen VII, and gelatinolytic activity in skin fibroblasts were assessed in six patients with epidermolysis bullosa dystrophica (EBD) inversa and in control groups consisting of probands with other EBD subtypes and healthy individuals. All six patients with EBD inversa, as well as the patients with generalized non-mutilating and localized EBD, showed positive staining with antibodies to collagen VII, the major anchoring fibril protein. Four patients with severe generalized mutilating EBD exhibited negative staining. Ultrastructurally, normal anchoring fibrils were demonstrable in uninvolved skin of patients with localized, inversa, and generalized non-mutilating subtypes. At the same time, a high degree of variability was observed in the amount and quality of anchoring fibrils in the various stages of lesional skin, including co-existence of normal and partially degraded anchoring fibrils. Of all 12 patients only one localized and two inversa cases showed an increased gelatinolytic activity in vitro. However, the high activity was associated with neither the severity of the disease nor the inversa subtype. In addition, intact collagen VII could be extracted from the dermis of one inversa patient. The present data show no correlation between increased in vitro gelatinolytic activity and abnormalities of the anchoring fibrils or collagen VII in skin of patients with recessive EBD, and therefore suggest molecular heterogeneity of the causative pathogenetic mechanisms.

The surgical management of dystrophic epidermolysis bullosa (excluding the hand)

Fifty patients with Dystrophic Epidermolysis Bullosa (DEB) underwent surgery including release of limb, oral, anal, eye and penile contractures and treatment of chronic skin ulceration or skin tumours. Correction of contractures involves extensive release of skin and underlying tissues, with split skin grafting of secondary defects. Specific regions are discussed. Recurrence is inevitable due to ongoing disease; however, functional improvement is obtained for several years. Management of chronic skin ulceration with split skin grafting has failed to produce long term healing, with local flaps successful but limited by the problem of donor site instability. Nine of the 17 patients over 20 years of age developed squamous cell carcinomas (29 lesions), benign hyperkeratosis (9) or malignant melanoma (1) requiring excision and skin grafting or amputation of digits. Local recurrence was infrequent (3 squamous cell carcinomas), with distant metastatic spread occurring in 1 patient.

Kalinin: an epithelium-specific basement membrane adhesion molecule that is a component of anchoring filaments

Basal keratinocytes attach to the underlying dermal stroma through an ultrastructurally unique and complex basement membrane zone. Electron-dense plaques along the basal surface plasma membrane, termed hemidesmosomes, appear to attach directly to the lamina densa of the basement membrane through fine strands, called anchoring filaments. The lamina densa is secured to the stroma through a complex of type VII collagen containing anchoring fibrils and anchoring plaques. We have identified what we believe is a novel antigen unique to this tissue region. The mAbs to this antigen localize to the anchoring filaments, just below the basal-dense plate of the hemidesmosomes. In cell culture, the antigen is deposited upon the culture substate by growing and migrating human keratinocytes. Addition of mAb to the cultures causes the cells to round and detach, but does not impair them metabolically. Skin fragments incubated with antibody extensively de-epithelialize. These findings strongly suggest that this antigen is intimately involved in attachment of keratinocytes to the basement membrane. This antigen was isolated from keratinocyte cultures by immunoaffinity chromatography. Two molecules are observed. The most intact species contains three nonidentical chains, 165, 155, and 140 kD linked by interchain disulfide bonds. The second and more abundant species contains the 165- and 140-kD chains, but the 155-kD chain has been proteolytically cleaved to 105 kD. Likewise, two rotary-shadowed images are observed. The larger of the two, presumably corresponding to the most intact form, appears as an asymmetric 107-nm-long rod, with a single globule at one end and two smaller globules at the other. The more abundant species, presumably the proteolytically cleaved form, lacks the distal small globule. We propose the name "kalinin" for this new molecule.

Immunohistochemical studies on the localization of fetal antigen 2 (FA2), laminin, and collagen type 4 in basal cell carcinoma

The localization of fetal antigen 2 (FA2), a recently described basement membrane (BM) associated antigen, was studied by immunohistochemical techniques in 21 basal cell carcinomas (BCC). In both superficial and infiltrating BCC, FA2 was located in a broad diffuse band around the tumor elements and in close contact with the BM. Compared to normal skin, a more extensive distribution of FA2 was seen in BCC. In the infiltrating BCC, FA2 staining was also present in the interstitial stroma between the tumor islands. FA2 was absent in areas with inflammatory cell infiltrates and elastoid degeneration. Epithelial and tumor cells were FA2 negative. The distribution of FA2 was clearly different from that of laminin and collagen type 4. Collagen type 4 and laminin were present as a continuous linear band corresponding to the BM surrounding the tumors. The close contact to the BM and the increased content of FA2 in the reactive stroma around BCC suggest that FA2 is involved in the matrix and/or BM changes taking place during tumor growth and invasion.

Animal model for dermolytic mechanobullous disease: sheep with recessive dystrophic epidermolysis bullosa lack collagen VII

A severe congenital mechanobullous disease with dermolytic blistering and recessive inheritance is described in sheep. The affected animals of wild and inbred flocks of the breed Weisses Alpenschaf (WAS) have blisters of skin, oral mucosa, tongue, and esophagus at birth or within the first week of life. Exungulation occurs early, and severe erosions in the mouth lead to difficulty in feeding. Electron microscopic examination revealed sub-lamina densa splitting in natural or fresh friction blisters and absence of identifiable anchoring fibrils in clinically uninvolved skin. Antigen mapping localized laminin and collagen IV to the blister roof. Indirect immunofluorescence staining with antibodies to collagen VII, the major structural component of the anchoring fibrils, demonstrated a complete absence of reaction in clinically uninvolved tissues of the affected sheep, whereas in normal sheep a strong linear fluorescence was seen at the epithelial-mesenchymal basement membrane zone. Dermal extracts of normal sheep contained intact collagen VII, but epidermal and dermal extracts from the affected sheep lacked this collagen or its fragments in immunoblotting experiments. Based on genetic, clinical, ultrastructural, and immunochemical findings, the sheep disorder corresponds to the severe mutilating subtype of recessive dystrophic epidermolysis bullosa in humans and can be used as an animal model to investigate the human disorder.

Localization of foetal antigen 2 (FA-2) in foetal and adult human skin

Foetal antigen 2 (FA-2) is a connective-tissue-associated antigen isolated from second trimester human amniotic fluid. FA-2 has an alpha-electrophoretic mobility and is a single-chain molecule with a molecular weight of 26 kDa as determined by polyacrylamide gel electrophoresis (PAGE). Using indirect immunofluorescence and the immunoperoxidase technique, FA-2 was found to be in the lamina densa/sublamina densa region of the basement membrane zone (BMZ) in adult as well as in foetal skin. FA-2 was found throughout the dermis in foetal skin, whereas in adult skin it was found to be associated with the BMZ and around the blood vessels, hair follicles and eccrine glands. Intracellular FA-2 antigen was demonstrated in proliferating fibroblasts by the indirect immunoperoxidase technique and immunoelectron microscopy of the fibroblasts revealed staining of the antigen in the cisternae of the rough endoplasmatic reticulum at the trans-side of the Golgi complex as well as in vesicles close to the plasma membranes. FA-2, a hitherto undescribed antigen associated with human BMZ, is probably being synthesized by proliferating fibroblasts.

Epidermolysis bullosa simplex with mottled pigmentation

A patient with epidermolysis bullosa simplex with mottled pigmentation is described. Clinical features include blistering of the skin, especially of the extremities; healing without scars; slight atrophy of the skin; and striking mottled pigmentation of the trunk. Histologic examination of a biopsy specimen from freshly frictioned, clinically uninvolved skin indicated a split inside the basal keratinocytes, focal hyperpigmentation of the basal cells, and pigment incontinence without an inflammatory infiltrate. Indirect immunofluorescence demonstrated focal discontinuity of the basement membrane zone. Electron microscopic examination revealed basal keratinocytes with few intact intracellular organelles, aggregated tonofilaments, and subnuclear splitting with the basal parts of the cells adhering to the basement membrane. Both normal basement membrane and zones of irregular and interrupted structures were seen. Hemidesmosomes and anchoring fibrils appeared to be normal.

Prenatal diagnosis and prevention of inherited abnormalities of collagen

There is now strong evidence for the implication of collagen alpha 1(I), alpha 2(I) and alpha 1(III) mutations in many forms of osteogenesis imperfecta and inherited arterial aneurysms (Ehlers Danlos syndrome type IV). A sizeable proportion of these disorders have detectable abnormalities by conventional protein chemistry, immunofluorescence, or more sophisticated DNA analysis. Everyone of them with specific defects or with linkage to appropriate gene markers is therefore amenable to prevention using conventional prenatal diagnosis by chorionic villus biopsy (with fibroblast culture), fetoscopic biopsy (with fibroblast culture), ultrasound diagnosis of the severely deformed fetus, or gene linkage studies by chorionic villus biopsy or amniocentesis. Already many collagen alpha 1(I), alpha 2(I) and alpha 1(III) mutations have been characterized including point mutations, small and large deletions and regulatory mutations. Many others are likely to be rapidly studied by exploiting recent advances in DNA technology, and other strong candidate genes include collagen II (some chondrodystrophies), collagen VI (certain arterial and cardiovascular diseases) and collagen VII (dystrophic epidermolysis bullosa). Other important common diseases are likely to include osteoporosis, osteoarthritis and cerebral aneurysms. A detailed review is provided of collagen interstitial genes and proteins, together with a description of the various forms of osteogenesis imperfecta and Ehlers Danlos syndrome in which either collagen alpha 1(I), alpha 2(I) or alpha 1(III) mutations have been identified. Appropriate restriction length polymorphisms (RFLPs) useful in identifying carriers of these mutant genes are also described.