Intracellular accumulation of collagen VII in cultured keratinocytes from a patient with dominant dystrophic epidermolysis bullosa

Cartilage regeneration by selected chondrogenic clonal mesenchymal stem cells in the collagenase-induced monkey osteoarthritis model

Osteoarthritis (OA) is the most common form of arthritis, in which cartilage is irreversibly degraded, causing severe pain and disability. Current therapeutic strategies cannot repair damaged cartilage. We evaluated the repair potential of selected chondrogenic clonal MSCs (sC-MSCs) by delivering them into the injured cartilage site in a collagenase-induced OA model in Cynomolgus monkeys. In vitro characterization showed that the isolated monkey sC-MSCs and polyclonal MSCs (P-MSCs) expressed mesenchymal stem cell markers and could differentiate into chondrocytes. The articular cartilage lesions in animals were treated with normal saline (NS), autologous P-MSCs and sC-MSCs, respectively, by direct delivery. The clinical parameters, radiographic images, histological and immunohistochemical examinations at weeks 8, 16 and 24 post-treatment demonstrated that the abrasions of articular cartilage were significantly improved and repaired by MSC-based treatment, particularly in the sC-MSC-treated group, which displayed consistently higher histological scores than those of other groups. In summary, treatment with sC-MSCs can effectively improve the healing of cartilage lesions in the Cynomolgus monkey collagenase-induced OA model. Due to the genetic proximity of monkey and human, the therapeutic strategy presented in this study will have broad applications in clinical practice.

Epidermolysis Bullosa Acquisita following Bullous Pemphigoid, Successfully Treated with the Anti-CD20 Monoclonal Antibody Rituximab

Epidermolysis bullosa acquisita is a rare autoimmune subepidermal blistering disease, often resisting current treatments, especially systemic corticosteroids. We report a patient having a bullous pemphigoid who relapsed with clinical and immunological features of inflammatory epidermolysis bullosa acquisita. An anti-CD20 monoclonal antibody (rituximab) was proposed because of resistance to high-dose steroids and other immunosuppressive agents. The disease dramatically improved within a few weeks following rituximab infusion allowing the decrease in steroid therapy. Our case illustrates also the possible evolution from bullous pemphigoid to epidermolysis bullosa acquisita that should be suspected when clinical atypia occurs or in case of corticosteroid resistance.

Transient bullous dermolysis of the newborn in three generations

Transient bullous dermolysis of the newborn (TBDN) is a rare form of dystrophic epidermolysis bullosa (DEB) that presents with neonatal skin blistering but which usually improves markedly during early life or even remits completely. Skin biopsies reveal abnormal intraepidermal accumulation of type VII collagen which results in poorly constructed anchoring fibrils and a sublamina densa plane of blister formation. The reason for the spontaneous clinical improvement is not known, but there is a gradual recovery in type VII collagen secretion from basal keratinocytes to the dermal-epidermal junction, with subsequent improvement or correction of anchoring fibril morphology. In this report, we describe TBDN occurring in three generations of the same family. Blistering occurred only during the first few months after birth, and all affected individuals were found to have a heterozygous glycine substitution mutation in exon 45 of the type VII collagen gene, COL7A1, designated G1522E. This mutation represents the third report of a pathogenic COL7A1 mutation in TBDN. Despite limited understanding of the disease mechanism in TBDN, this distinct form of DEB is important to recognize as it typically has a benign and self-limiting course. However, not all cases of DEB associated with intraepidermal type VII collagen are 'transient'. Genetic counselling in such patients therefore should be guarded until the pathophysiology of TBDN is better understood.

Basement membrane zone remodeling during appendageal development in human fetal skin. The absence of type VII collagen is associated with gelatinase-A (MMP2) activity

Epithelial cell adhesion, migration, and differentiation are controlled by interactions at the basement membrane zone (BMZ). Type VII collagen is the major collagenous component of anchoring fibrils that are essential for the attachment of the epidermis to the dermis. Gelatinase A (MMP-2) is believed to be necessary for the degradation of type VII collagen. In this study we have examined the in vivo distribution of type VII collagen and gelatinase A (Gel A) in the developing human epidermis and its appendages. At 13-15 wk of gestation a marked decrease in type VII collagen immunoreactivity was seen in the BMZ surrounding invading appendageal buds; however, type VII collagen mRNA was strongly expressed in the budding epidermal keratinocytes adjacent to the BMZ. At these stages, Gel A-positive mesenchymal-like cells were found scattered throughout the stroma with numerous Gel A-containing cells in direct contact with the developing appendageal buds. In situ zymography was used to show Gel A-activity in vivo. Gel A-mediated lysis was present at the interface between the appendageal buds and the underlying BMZ. By 20-25 wk of gestational age, immunostaining for type VII collagen protein was absent from the BMZ surrounding the distal portion of invading appendageal epithelial cords of both hair follicles and sweat glands. In contrast, type VII collagen mRNA was present in the basal keratinocytes adjacent to the BMZ surrounding the distal portion of these invading appendageal epithelial cords. At these stages Gel A-positive cells were present in the stroma directly adjacent to the distal portion of developing appendageal cords that lacked type VII collagen. In situ zymography showed zones of Gel A-mediated stromal lysis at the distal portion of developing appendageal cords. Interestingly, no differences were seen in the distribution of type IV collagen in the BMZ of both budding and resting fetal epidermis. These observations suggest that the absence of type VII collagen protein correlates directly with the presence of Gel A-activity at the BMZ. Gel A appears to play a major role in appendageal development and contributes to remodeling of the BMZ during fetal skin morphogenesis.

Three new cases of transient bullous dermolysis of the newborn

We present 3 new patients with transient bullous dermolysis of the newborn (TBDN), which is a form of dystrophic epidermolysis bullosa. TBDN may be diagnosed by electron microscopy showing a sublamina densa cleavage; immunofluorescence antigenic mapping demonstrating bullous pemphigoid antigen, laminin- 1, and type IV collagen along the epidermal roof of subepidermal clefts; and indirect immunofluorescence with monoclonal antibodies revealing intraepidermal type VII collagen. Although intraepidermal type VII collagen has been reported in other forms of dystrophic epidermolysis bullosa, we believe that the presence of type VII collagen in a striking intraepidermal granular array is a finding unique to TBDN. Our cases demonstrate the importance of immunodermatologic studies in the diagnosis of bullous disorders that are seen at birth because accurate diagnosis carries prognostic implications. This variant of epidermolysis bullosa, in contrast to other forms of dystrophic epidermolysis bullosa, is a benign, self-limited disease.

Intraepidermal expression of basement membrane components in the lesional skin of a patient with dystrophic epidermolysis bullosa

The patient was a 15-year-old male. Since birth, he had developed blistering and erosion of the skin. Biopsy skin specimen of the bullous lesions showed subepidermal blister formation. Electron microscopic examination revealed that tissue separation had occurred at the sublamina densa level. By indirect immunofluorescence using antibodies specific for alpha 6 integrin, laminin 5, type IV collagen, and type VII collagen, all of these basement membrane components were detected as coarse granular intracytoplasmic deposits only in the basal and suprabasal cells of the blister roof. In the non-blistered regions, these basement membrane components showed a linear pattern similar to that seen in normal skin. These findings suggest that intraepidermal expression of basement membrane components was closely related to the blister formation. The biological meaning of intraepidermal expression of basement membrane components were also discussed.

Transient bullous dermolysis of the newborn associated with compound heterozygosity for recessive and dominant COL7A1 mutations

The neonatal skin blistering disorder transient bullous dermolysis of the newborn (TBDN) heals spontaneously or improves dramatically within the first months and years of life. TBDN is characterized by subepidermal blisters, reduced or abnormal anchoring fibrils at the dermo-epidermal junction, and electron-dense inclusions in keratinocytes. These features are partly similar to those in dystrophic epidermolysis bullosa, which is caused by defects in COL7A1 gene encoding collagen VII, the main anchoring fibril protein. TBDN has been grouped separately from dystrophic epidermolysis bullosa based on the pronounced morphologic features and the self-limiting course of the disorder; however, it remains unclear whether it represents a distinct clinical entity with a single etiology. We now report a TBDN patient who is compound heterozygous for a recessive and a dominant glycine substitution mutation in COL7A1. Two point mutations caused amino acid substitutions G1519D and G2251E in the triple helical domain of collagen VII. In the heterozygous state G1519D was silent, and G2251E led to nail dystrophy, but not to skin blistering. In the proband, compound heterozygosity for the mutations caused massive, transitory retention of collagen VII in the epidermis, its reduced deposition at the basement membrane zone, and extensive dermo-epidermal separation at birth. Accordingly, TBDN keratinocytes in vitro accumulated collagen VII intracellularly in the rough endoplasmic reticulum.

Some, but not all, glycine substitution mutations in COL7A1 result in intracellular accumulation of collagen VII, loss of anchoring fibrils, and skin blistering

COL7A1 gene mutations cause dystrophic epidermolysis bullosa, a skin blistering disorder. The phenotypes result from defects of collagen VII, the major component of the anchoring fibrils at the dermo-epidermal junction; however, the molecular mechanisms underlying the phenotypes remain elusive. We investigated naturally occurring COL7A1 mutations and showed that some, but not all, glycine substitutions in collagen VII interfered with biosynthesis of the protein in a dominant-negative manner. Three point mutations in exon 73 caused glycine substitutions G2006D, G2034R, and G2015E in the triple helical domain of collagen VII and interfered with its folding and secretion. Confocal laser scanning studies and semiquantitative immunoblotting determined that dystrophic epidermolysis bullosa keratinocytes retained up to 2.5-fold more procollagen VII within the rough endoplasmic reticulum than controls. Limited proteolytic digestions of mutant procollagen VII produced aberrant fragments and revealed reduced stability of the triple helix. In contrast, the glycine substitution G1519D in another segment of the triple helix affected neither procollagen VII secretion nor anchoring fibril function and remained phenotypically silent. These data demonstrate that collagen VII presents a remarkable exception among collagens in that not all glycine substitutions within the triple helix exert dominant-negative interference and that the biological consequences of the substitutions probably depend on their position within the triple helix.

A combination of a common splice site mutation and a frameshift mutation in the COL7A1 gene: absence of functional collagen VII in keratinocytes and skin

We describe a patient with severe generalized dystrophic epidermolysis bullosa (EBD) and a novel combination of compound heterozygous mutations in the COL7A1 gene. The maternal mutation was an A-to-G transition (425-A --> G) at position -2 of the donor splice site within exon 3 that causes aberrant splicing of two abnormal transcripts. One includes intron 3, and one excludes both exon 3 and intron 3. Both splice variants contained a premature termination of the translation. The paternal mutation is a 25-bp deletion in exon 20 (2638de125) that leads to a frameshift and a premature termination codon 133 bp downstream from the site of deletion. This combination of mutations allowed expression of collagen VII mRNA. Immunofluorescence staining of the patient's skin and cultured keratinocytes with domain-specific collagen VII antibodies, however, demonstrated markedly reduced levels of alpha1(VII) polypeptides, and no stable collagen VII protein could be extracted from the patient's cells. Electron microscopy showed severely hypoplastic fibrils below the lamina densa, without evidence of normal anchoring fibrils. The clinically unaffected parents were heterozygous for the mutations, suggesting that both COL7A1 gene defects were recessively inherited disease-causing mutations that are "silent" in heterozygous carriers but in combination can severely interfere with the dermal-epidermal adhesion and lead to severe EBD.

An extract from cultured human keratinocytes that contains the major autoantigens related to autoimmune bullous skin diseases

Autoantibodies characteristic of autoimmune bullous skin diseases (AIBDs) can be detected by immunoblotting on epidermal, dermal, or bovine muzzle extracts. However, none of those substrates contain all the autoantigens involved in AIBDs, and the diagnosis requires the use of various substrates. Human keratinocytes were cultured under such conditions that they expressed the major autoantigens associated with AIBDs. Forty-two sera with antiepidermal antibodies were immunoblotted on the keratinocyte extract. Bands corresponding to desmoglein III, desmoglein I, BPAg2, BPAg1, and type VII collagen were found in 38 sera. Desmoplakins I and II were revealed by specific monoclonal antibodies. A review of the patients' charts showed a perfect correlation between the blots and the diagnoses of pemphigus vulgaris, pemphigus foliaceus, bullous pemphigoid, cicatricial pemphigoid, and epidermolysis bullosa acquisita. Four sera revealing no band typical of AIBD were from patients with no autoimmune skin disease. Therefore, a single extract of keratinocytes can be used for the differential diagnosis of AIBDs.

Cross-linking of the dermo-epidermal junction of skin regenerating from keratinocyte autografts. Anchoring fibrils are a target for tissue transglutaminase

Since transglutaminases create covalent gamma-glutamyl-epsilon-lysine cross-links between extracellular matrix proteins they are prime candidates for stabilizing tissue during wound healing. Therefore, we studied the temporo-spatial expression of transglutaminase activity in skin regenerating from cultured epithelial autografts in severely burned children by the specific incorporation of monodansylcadaverine into cryostat sections from skin biopsies obtained between 5 d to 17 mo after grafting. The dansyl label was subsequently immunolocalized in the epidermis, dermal connective tissue, and along the basement membrane. Incubation of cryosections of normal and regenerating skin with purified tissue transglutaminase confirmed the dermo-epidermal junction and the papillary dermis as targets for this enzyme and revealed that in regenerating skin transamidation of the basement membrane zone was completed only 4-5 mo after grafting. Immunoelectron microscopy revealed that three distinct regions on the central portion of anchoring fibrils were positive for monodansylcadaverine in normal skin which were negative during the initial phase of de novo formation of anchoring fibrils in regenerating skin. Biochemically, we identified collagen VII as potential substrate for tissue transglutaminase. Thus, tissue transglutaminase appears to play an important role not only in cross-linking of the papillary dermis but also of the dermo-epidermal junction in particular.

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

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 3 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, alpha 6 and beta 4 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.

Nail changes in epidermolysis bullosa: clinical and pathogenetic considerations

Nail changes in epidermolysis bullosa (EB) are common, but although they are highly suggestive of the disease, they are not pathognomonic. They are the result of abnormalities of the nail matrix and nail bed, associated with the pathogenetic alterations of the dermo-epidermal junction which occur in EB. In addition, secondary trauma in the areas of epidermal-dermal separation, and chronic inflammation of the nail matrix, are probable contributory factors, even in non-scarring forms of EB. Recent developments in the molecular and cell biology of the cutaneous basement membrane zone have greatly advanced our understanding of the pathomechanisms underlying different subtypes of EB. Defects in genes coding for the structural proteins of the basement membrane zone have been defined in some EB subtypes, and abnormal expression of structural proteins in others. The data accumulated from study of these genetic disorders will contribute to knowledge of the role of the dermo-epidermal junction in the normal physiology and differentiation of the nails, and be of value in discerning the aetiopathogenesis of acquired nail diseases.

Epidermolysis bullosa: pathogenetic pathways from mutations to symptoms

Recent developments of the molecular and cell biology of the cutaneous basement membrane zone have greatly advanced our understanding of the pathomechanisms underlying skin blistering disorders. The heritable blistering diseases, the epidermolysis bullosa group, have been investigated as model diseases. Defects in genes coding for the structural proteins of the basement membrane zone have been defined in some EB subtypes and abnormal expression of the structural proteins in others. In vitro studies utilizing cutaneous cells derived from epidermolysis bullosa skin have helped to understand the pathogenetic pathways that lead from the mutation to the symptom, skin blistering. The data accumulated from analyses of the genetic disorders will yield indirect information on the normal physiology of the skin and be highly relevant for discerning the etiopathogenesis of acquired blistering diseases and for dermal-epidermal interactions required for reparative processes, such as wound healing.