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.     

Late-onset inversa recessive dystrophic epidermolysis bullosa caused by glycine substitutions in collagen type VII

Dystrophic epidermolysis bullosa (DEB) is a rare hereditary skin disorder caused by mutations in COL7A1, encoding collagen type VII.1 Clinical manifestations of COL7A1 mutations range from generalized skin blistering to mild localized blistering or nail dystrophy.2 The investigation of the molecular basis of DEB has revealed more than 540 different mutations that cannot entirely explain phenotypic variations (HGMD Professional 2010.3, https://portal.biobase-international. com/hgmd/). Inversa recessive DEB (RDEB-I) is a subtype characterized by generalized blistering in the neonatal period. The condition improves with age, and in adults blistering is restricted to intertriginous areas, and severe lesions of the oral and genital mucosa and nail changes occur in the majority of described patients.2 Recent data suggested that amino-acid substitutions affecting arginines or glycines at borders of collagenic subdomains might cause this phenotype.3 We report a German patient with an unusually mild RDEB-I harbouring compound heterozygous mutations in COL7A1.     

Anchoring fibrils and type VII collagen are absent from skin in severe recessive dystrophic epidermolysis bullosa

Skin of patients with severe generalized recessive dystrophic epidermolysis bullosa (SGRDEB) was studied by immunoelectron microscopy and immunoblotting with antibodies to type VII collagen, a major structural component of anchoring fibrils. In normal skin, the protein was localized to the dermoepidermal junction zone below the basement membrane and was extractable from the papillary dermis after artificial epidermolysis. In SGRDEB skin, neither immunoreactive material below the basement membrane nor identifiable anchoring fibrils could be recognized and neither the tissue form nor the specific proteolytic fragments of type VII collagen were found in extracts of SGRDEB skin. Very low amounts of type VII collagen alpha-chains could be detected in cultures of SGRDEB-fibroblasts, whereas normal fibroblasts synthesized more of this collagen. These results suggest that a genetic defect in the correct synthesis, secretion, or in the molecular assembly of type VII collagen may underlie SGRDEB.     

Evidence for a structural abnormality of collagen VII in a patient with dystrophic epidermolysis bullosa inversa.

Recent studies indicate that in skin of patients with dystrophic epidermolysis bullosa (EB) inversa, anchoring fibrils have an abnormal ultrastructure, but the major protein of these fibrils, collagen VII, is expressed and detectable with antibodies at the dermo-epidermal junction. For molecular characterization of this rare EB phenotype, skin biopsies from a patient with dystrophic EB inversa were investigated with indirect immunofluorescence, immunoelectron microscopy, and immunoblotting. Ultrastructural analysis of clinically uninvolved skin showed sublamina densa splitting. In unblistered areas, focal groups of anchoring fibrils that appeared loosely polymerized and without a distinct crossbanding pattern were observed. Indirect immunofluorescence staining with antibodies to collagen VII exhibited a linear fluorescence at the dermo-epidermal junction and at the roof of a spontaneous blister. Immunoelectron microscopy demonstrated staining of the poorly assembled anchoring fibrils, but no significant reaction in areas where no fibrillar structures could be discerned. In contrast to normal control skin, immunoblotting showed immunoreactive collagen VII in both epidermal and dermal extracts. Moreover, the dermis-associated collagen VII appeared as a distinct doubleband that contained the tissue form of collagen VII (250-300 kD) and an additional band with a slightly smaller molecular weight. In epidermal extracts one band, of the size of the tissue form, was detected. The studies on the present patient suggest that a structural abnormality of collagen VII that prevents its aggregation to stable dimers or polymerization to distinct anchoring fibrils may contribute to the etiopathogenesis of dystrophic EB inversa.     

Dermolytic (dystrophic) epidermolysis bullosa inversa

We treated four patients with an inverse form of recessive dermolytic (dystrophic) epidermolysis bullosa. The distinguishing features of the disease are (1) early generalized skin involvement with blisters and erosions that heal with superficial, atrophic scars; (2) persistence into adulthood, although milder; (3) severity in flexural areas, especially the inguinal folds, perineum, axillae, submammary area, posterior and lateral aspects of the neck, and often the lower parts of the abdomen and back; (4) normal stature and general development; (5) severe oral and esophageal mucosal involvement; (6) normal teeth; (7) normal or minimally involved fingernails, but mild to moderately dystrophic or atrophic toenail changes; and (8) microscopic findings similar to those of the Hallopeau-Siemens form of epidermolysis bullosa.     

Type VII collagen and 19-DEJ-1 antigen. Comparison of expression in inversa and generalized variants of recessive dystrophic epidermolysis bullosa

The expression of type VII collagen and 19-DEJ-1 antigen was examined in 73 and 71 patients, respectively, with recessive dystrophic epidermolysis bullosa (RDEB), comprising gravis, mitis, inversa, and indeterminant subsets, to better determine the specificity and sensitivity of two monoclonal antibodies directed against these dermoepidermal junction-specific epitopes. Type VII collagen (LH 7:2 epitope) was usually absent (in 90%) in patients with the gravis variant of RDEB, whereas its expression was most often diminished (in 67%) in those with the mitis form of the disease. Only 2% and 5% of patients with gravis and mitis variants, respectively, had apparent normal amounts of type VII collagen within their skin. In contrast, six (86%) of seven patients with the inversa variant had normal expression of the antigen. Only 25% of all patients with RDEB lacked the 19-DEJ-1 antigen; of these, however, most had the gravis variant, although absence or diminution was also infrequently observed in those with the mitis and inversa forms. Intermediate findings were noted in patients classified as having indeterminant forms of RDEB. Some variability in antigen expression was also noted among affected siblings. We conclude that assessment of expression of the LH 7:2 epitope of type VII collagen may be diagnostically useful, although considerable overlap does exist between individual patients with gravis and mitis forms. 19-DEJ-1 expression is a far less sensitive probe in RDEB, although such data may prove useful in the assessment of newborns lacking the characteristic features of gravis disease. In addition, based on our experience with inversa RDEB, it would appear that altered expression of type VII collagen cannot be attributed to blister formation in this latter rare subset, since this antigen is usually strongly detected along the dermoepidermal junction, even in perilesional skin sites.     

Epidermal aspects of type VII collagen: Implications for dystrophic epidermolysis bullosa and epidermolysis bullosa acquisita

Type VII collagen (COL7), a major component of anchoring fibrils in the epidermal basement membrane zone, has been characterized as a defective protein in dystrophic epidermolysis bullosa and as an autoantigen in epidermolysis bullosa acquisita. Although COL7 is produced and secreted by both epidermal keratinocytes and dermal fibroblasts, the role of COL7 with regard to the epidermis is rarely discussed. This review focuses on COL7 physiology and pathology as it pertains to epidermal keratinocytes. We summarize the current knowledge of COL7 production and trafficking, its involvement in keratinocyte dynamics, and epidermal carcinogenesis in COL7 deficiency and propose possible solutions to unsolved issues in this field.     

Intraepidermal collagen type VII in dystrophic epidermolysis bullosa: report of five new cases

The presence of intraepidermal collagen type VII has recently been used to define a subgroup of patients with mild dystrophic epidermolysis bullosa (DEB). This subgroup demonstrates virtual resolution of blistering during infancy despite often severe neonatal blistering. Using the antibody LH7.2, we have detected intraepidermal collagen type VII in five cases with DEB. These represent a much wider spectrum of clinical features and of intraepidermal and basement membrane zone (BMZ) staining patterns. Only one of our cases had features consistent with reported cases. Sequential skin biopsies from this case showed a marked change towards normal within 6 months of birth, paralleling the clinical improvement. The other four cases had sparse epidermal deposits of collagen type VII and included an affected foetus with autosomal recessive DEB. These findings suggest that the frequency of intraepidermal LH7.2 in DEB may be much higher than previously thought. The presence of abundant intraepidermal collagen type VII is of prognostic significance and can disappear over months. We recommend that biopsies of infants suspected of having EB are taken during the neonatal period.     

Spontaneous disappearance of intraepidermal type VII collagen in a patient with dystrophic epidermolysis bullosa

Summary Recently, a peculiar self-healing neonatal blistering disease has been reported, which is characterized by perinuclear stellate inclusions within basilar keratinocytes, representing abnormal retention of type VII collagen. We report a Japanese patient with this condition, in whom we studied the expression of a variety of basement membrane zone (BMZ)-related antigens. Skin biopsy specimens at 5 days of age showed abundant accumulation of both the NC-1 domain and the collagenous part of type VII collagen within the basal and suprabasal keratinocytes, in addition to patchy and weak staining along the BMZ. In contrast, at 4 years of age, when the disease activity was markedly attenuated, a second biopsy showed complete linear staining of type VII collagen along the BMZ, with no detectable intracytoplasmic deposits. Expression of other BMZ-related antigens, including laminin 5, α6 and ß4 integrins, bullous pemphigoid antigens 1 and 2. and type IV collagen, was normal in both the biopsy specimens. Our observations further confirm that the perinuclear stellate bodies seen in this peculiar condition are composed of both collagenous and non-collagenous domains of type VII collagen retained within the epidermis, and that these bodies disappear when the disease activity remits.     

Type VII collagen is a normal component of epidermal basement membrane, which shows altered expression in recessive dystrophic epidermolysis bullosa

The murine monoclonal antibody LH 7:2, which reacts with the basement membrane of stratified squamous epithelia including epidermis, has been characterized biochemically and shown to bind to part of the type VII collagen molecule. Immunoblotting reveals that the antibody binding site lies in the non-helical carboxy terminal region of the type VII collagen dimer and immunoelectron microscopy shows that the epitope is within the lamina densa of the basement membrane. Loss of LH 7:2 binding in the hereditary blistering disease recessive dystrophic epidermolysis bullosa suggests that inadequate synthesis or excessive breakdown of type VII collagen may form the biologic basis for the disease.     

Intra-epidermal retention of type VII collagen in a patient with recessive dystrophic epidermolysis bullosa

An infant born with severe blisters on the limbs, face, trunk, and oral mucosa was diagnosed by light and electron microscopy to have recessive dystrophic epidermolysis bullosa. Transmission electron microscopy showed that the basal lamina remained with the epidermis and that the floor of the blister was exposed collagen of the papillary dermis. No banded anchoring fibrils were observed along either the roof or the floor of the blister; however, small filamentous structures, possibly immature anchoring fibrils, extended down from the lamina densa along the blister roof. Some basal and suprabasal keratinocytes contained large vesicles filled with filamentous matrix of variable electron density. Immunofluorescent staining of skin for type VII collagen showed sparse and irregular staining of type VII collagen along the blister roof, and intense intracellular labeling for type VII collagen in clusters of epidermal cells in basal and suprabasal layers. Type VII collagen appeared to be synthesized by keratinocytes but not secreted.     

The carboxyl-terminal domain of type VII collagen is present at the basement membrane in recessive dystrophic epidermolysis bullosa

Recent studies showing that type VII collagen is a component of anchoring fibrils suggests that the absence of anchoring fibrils in recessive dystrophic epidermolysis bullosa may be due to a defect in the synthesis, secretion, and deposition of type VII collagen. That hypothesis is further supported by recent studies suggesting that monoclonal antibodies to type VII collagen do not react with the basement membrane in most patients. To investigate further, we examined skin from 12 patients by electron microscopy and by immunohistology and immunoelectron microscopy using a concentrated and purified monoclonal antibody to the carboxy-terminal domain of Type VII collagen. Although anchoring fibrils were not detected by electron microscopy, the results of immunohistology showed definite, but reduced, binding of the monoclonal antibody to type VII collagen at the basement membrane in a linear pattern in 11 of 12 patients. By immunoelectron microscopy, reduced deposition of anti-type VII collagen antibody was detected beneath the lamina densa. The results of this study show that the carboxyl-terminal domain of type VII collagen is synthesized, secreted, and deposited at the basement membrane zone in 11 of 12 patients with recessive dystrophic epidermolysis bullosa and suggest that the absence of anchoring fibrils may be due either to deposition of abnormal type VII collagen, reduced levels of normal type VII collagen, defective assembly of type VII collagen into anchoring fibrils, or destruction of the collagenous domain of type VII collagen.     

Recurrent molecular abnormalities in type VII collagen in southern Italian patients with recessive dystrophic epidermolysis bullosa

In this study we searched for mutations in the type VII collagen gene (COL7A1) in 10 families from Southern Italy with severe generalised recessive dystrophic epidermolysis bullosa using PCR amplification of genomic DNA, heteroduplex analysis and direct nucleotide sequencing. Our principal aim was to identify any recurrent mutations in COL7A1 that might facilitate future mutation detection strategies in this population. Three recurrent COL7A1 mutations were delineated in six of the 10 families: a frameshift mutation in exon 4, 497insA, was detected in three affected individuals from three families, a deletion mutation at the acceptor splice site of intron 114/exon 115, 8441-14del21, was found in five patients in three of the families, and an intron 49 acceptor splice site mutation, 4783-1 G-to-A, was identified in three subjects in two families (GenBank accession no, L02870). Haplotype analyses showed evidence for propagation of common ancestral mutant COL7A1 alleles for each of these recurrent mutations. These results contribute significantly to understanding the nature of COL7A1 pathology in patients from Southern Italy and in designing future approaches to mutation detection.     

Patients with recessive dystrophic epidermolysis bullosa develop squamous-cell carcinoma regardless of type VII collagen expression

Recent data suggest that individuals with recessive dystrophic epidermolysis bullosa (RDEB) only develop squamous-cell carcinoma (SCC) in the presence of the NC1 domain of type VII collagen. This conclusion was based on experimental work in which cryosections of SCCs from 10 people with RDEB all showed positive type VII collagen immunostaining and observations in a murine model of SCC development in which tumors only occurred using keratinocytes from RDEB subjects that expressed detectable levels of the NC1 domain of the type VII collagen protein. To assess whether the clinical interpretation was valid in another cohort of RDEB patients, we examined expression of type VII collagen in 17 SCC tumors excised from 11 patients. Indirect immunofluorescent staining of SCC cryosections and Western blotting of cultured keratinocyte lysates identified two RDEB individuals who did not express detectable levels of type VII collagen. Mutation analysis revealed that these two patients harbor compound heterozygous nonsense mutations within the region of the COL7A1 gene encoding the NC1 domain. These data suggest that individuals with RDEB can develop SCC regardless of type VII collagen expression and that additional factors have a role in explaining the high incidence of tumors complicating this genodermatosis.     

Murine type VII collagen distorts outcome in human skin graft mouse model for dystrophic epidermolysis bullosa

Human skin graft mouse models are widely used to investigate and develop therapeutic strategies for the severe generalized form of recessive dystrophic epidermolysis bullosa (RDEB), which is caused by biallelic null mutations in COL7A1 and the complete absence of type VII collagen (C7). Most therapeutic approaches are focused on reintroducing C7. Therefore, C7 and anchoring fibrils are widely used as readouts in therapeutic research with skin graft models. In this study, we investigated the expression pattern of human and murine C7 in a grafting model, in which human skin is reconstituted out of in vitro cultured keratinocytes and fibroblasts. The model revealed that murine C7 was deposited in both human healthy control and RDEB skin grafts. Moreover, we found that murine C7 is able to form anchoring fibrils in human grafts. Therefore, we advocate the use of human‐specific antibodies when assessing the reintroduction of C7 using RDEB skin graft mouse models.     

Lack of type VII collagen in unaffected skin of patients with severe recessive dystrophic epidermolysis bullosa

Type VII collagen, the major structural component of the anchoring fibrils, was assayed in normal unaffected skin of patients with different forms of hereditary epidermolysis bullosa. Immunofluorescence staining with affinity-purified polyclonal antibodies to type VII collagen revealed a complete absence of staining in the skin of patients with severe dystrophic recessive epidermolysis bullosa. In all other forms, localized recessive dystrophic, dominant dystrophic, junctional and simplex forms there was an intense continuous linear staining of type VII collagen at the dermoepidermal junction. Also, obligate heterozygote carriers of the gene for severe dystrophic recessive form showed a normal pattern of staining. As internal controls and to define the clinical diagnosis, staining with antibodies to type IV collagen, laminin and bullous pemphigoid antigen was also performed. All these antibodies showed a normal staining pattern indicating an intact general morphology of the dermoepidermal junction zone. These results suggest that there is a defect of type VII collagen in patients with severe recessive dystrophic epidermolysis bullosa. The data also suggest that the group of recessive dystrophic epidermolysis bullosa may be heterogeneous not only clinically, but also at the molecular level.     

Proteases are responsible for blister formation in recessive dystrophic epidermolysis bullosa and epidermolysis bullosa simplex

The specific factors which induce blister formation in recessive dystrophic epidermolysis bullosa (RDEB) and epidermolysis bullosa simplex (EBS) were studied by culturing normal human skin with blister fluid from patients with RDEB and EBS. When skin from a healthy person was cultured with RDEB blister fluid, it developed a clean subepidermal blister with histology similar to that of a RDEB blister. The specific factor(s) which induced this subepidermal blister was inactivated by heat (60 degrees C, 30 min), trypsin digestion and by treating with EDTA, EGTA, alpha 2-macroglobulin, soybean trypsin inhibitor (SBTI) or N-ethylmaleimide (NEM), but was not affected by dialysis. These findings suggest that the active factor(s) in the blister fluid from patients with RDEB might include collagenase, neutral thiol protease and trypsin-like protease. By contrast, when normal skin was cultured with EBS blister fluid, this produced a clean intra-epidermal blister with histology similar to that of an EBS blister. The specific factor(s) inducing the intra-epidermal blister was inactivated by heat (60 degrees C, 30 min), trypsin digestion and by treating with NEM, but was not affected by dialysis, divalent cation chelators (EGTA, EDTA), alpha 2-macroglobulin, SBTI and pepstatin. These results suggest that the active factor(s) inducing the intra-epidermal blister in EBS might be a neutral SH-protease.