Chondroitin 6-sulfate proteoglycan but not heparan sulfate proteoglycan is abnormally expressed in skin basement membrane from patients with dominant and recessive dystrophic epidermolysis bullosa

Immunohistopathologic diagnosis of epidermolysis bullosa

Routine histologic study usually is insufficient to subclassify epidermolysis bullosa (EB); currently, electron microscopic evaluation has been the gold standard. A major advance recently has been made in elucidating the molecular basis of several major forms of EB. Concomitantly, immunoreagents have been developed to map antigens in the basement membrane zone. Some of these reagents facilitate the classification of EB into types and subtypes and can be used as an adjunct informative screening procedure to direct mutation identification efforts using DNA technologies. The current review provides an overview of these recent developments and a more detailed account of the immunohistopathologic diagnosis of EB.

cDNA cloning of the basement membrane chondroitin sulfate proteoglycan core protein, bamacan: a five domain structure including coiled-coil motifs

Basement membranes contain several proteoglycans, and those bearing heparan sulfate glycosaminoglycans such as perlecan and agrin usually predominate. Most mammalian basement membranes also contain chondroitin sulfate, and a core protein, bamacan, has been partially characterized. We have now obtained cDNA clones encoding the entire bamacan core protein of Mr = 138 kD, which reveal a five domain, head-rod-tail configuration. The head and tail are potentially globular, while the central large rod probably forms coiled-coil structures, with one large central and several very short interruptions. This molecular architecture is novel for an extracellular matrix molecule, but it resembles that of a group of intracellular proteins, including some proposed to stabilize the mitotic chromosome scaffold. We have previously proposed a similar stabilizing role for bamacan in the basement membrane matrix. The protein sequence has low overall homology, apart from very small NH2- and COOH-terminal motifs. At the junctions between the distal globular domains and the coiled-coil regions lie glycosylation sites, with up to three N-linked oligosaccharides and probably three chondroitin chains. Three other Ser-Gly dipeptides are unfavorable for substitution. Fusion protein antibodies stained basement membranes in a pattern commensurate with bamacan, and they also Western blotted bamacan core protein from rat L2 cell cultures. The antibodies could also specifically immunoprecipitate an in vitro transcription/translation product from a full-length bamacan cDNA. The unusual structure of this proteoglycan is indicative of specific functional roles in basement membrane physiology, commensurate with its distinct expression in development and changes in disease models.

Perlecan and basement membrane-chondroitin sulfate proteoglycan (bamacan) are two basement membrane chondroitin/dermatan sulfate proteoglycans in the Engelbreth-Holm-Swarm tumor matrix

The presence of proteoglycans bearing galactosaminoglycan chains has been reported, but none has been identified previously in the matrix of the Engelbreth-Holm-Swarm tumor, which is a source of several basement membrane components. This tumor matrix contains perlecan, a large, low buoyant density heparan sulfate proteoglycan, widespread in many basement membranes and connective tissues. We now identify two distinct proteoglycan species from this tumor source, which are substituted with galactosaminoglycans and which show basement membrane localization by immunohistochemistry. One species is perlecan but, in addition to being present as a heparan sulfate proteoglycan, it is also present as a hybrid molecule, with dermatan sulfate chains. A minor population of perlecan apparently lacks heparan sulfate chains totally, and some of this is substituted with chondroitin sulfate. The second species is immunologically related to basement membrane-chondroitin sulfate proteoglycan (BM-CSPG) and bears chondroitin sulfate chains. No BM-CSPG was detectable which was substituted with heparan sulfate chains. A combination of immunological and molecular approaches, including cDNA cloning, showed that perlecan and BM-CSPG are distinct in core protein structure. Both are, however, basement membrane components, although there are tissue-specific differences in their distribution.

Basement membrane proteoglycans are of epithelial origin in rodent skin

Basement membrane proteoglycans in mammalian skin comprise at least one chondroitin sulfate proteoglycan and heparan sulfate proteoglycans, including perlecan. In this study, the origins of basement membrane chondroitin sulfate proteoglycan and perlecan were investigated both in vivo and in vitro. For in vivo experiments, pieces of newborn rat epidermis obtained by dispase treatment were grafted onto athymic nude mice. Three and six weeks after grafting, immunofluorescence analysis of the grafted skin was carried out, using monoclonal antibodies specific for rat basement membrane chondroitin sulfate proteoglycan and rat and mouse perlecan. While the isolated rat epidermis was shown to completely lack rat basement membrane chondroitin sulfate proteoglycan and rat basement membrane heparan sulfate proteoglycans, including perlecan, immunofluorescence staining of tissue sections from the grafted sites on mice demonstrated the presence of rat basement membrane chondroitin sulfate proteoglycan and rat perlecan on interfollicular and follicular basement membranes including that separating dermal papillae from adjacent hair follicle epithelium. In contrast, the basement membranes of all dermal capillaries were positive for mouse perlecan, but negative for rat basement membrane chondroitin sulfate proteoglycan and rat perlecan, including the basement membranes of papillary dermal capillaries beneath the rat epidermis. These data suggest that basement membrane proteoglycans of the dermal-epidermal junction and hair follicle epithelium are of epidermal (epithelial) origin in vivo. Stratified rat keratinocytes cultured on a collagen matrix at the air-liquid interface showed the synthesis of perlecan, laminin 1, and type IV collagen in basement membranes, but not clearly detectable basement membrane chondroitin sulfate proteoglycan.

Defective in vivo expression and apparently normal in vitro expression of a newly identified 105-kDa lower lamina lucida protein in dystrophic epidermolysis bullosa

We have previously identified a novel 105-kDa lower lamina lucida protein detected by the autoantibodies from a group of patients who developed a unique immune-mediated subepidermal bullous dermatosis. We sought to determine if this novel basement membrane zone (BMZ) protein is normally expressed in the skin of patients with various subsets of epidermolysis bullosa (EB). Indirect immunofluorescence microscopy performed on non-lesional skin sections from patients with three major EB subsets revealed absence or significantly reduced expression of this novel BMZ protein in 20 out of 23 skin sections from patients with generalized dominant and recessive dystrophic EB. However, immunoblot analyses with the autoantibodies on Western-blotted proteins revealed that a comigrating 105-kDa protein is present in both cytosol extracts (n = 6) and conditioned media (n = 3) of cultured dermal fibroblasts derived from patients with dystrophic EB, as well as those cultured from two healthy individuals. Although the reason for such disparate findings is not known, the defective in vivo expression of this novel 105-kDa protein in dystrophic EB is presumably not due to a failure of fibroblasts to synthesize or secrete the protein. It is possible, however, that the 105-kDa protein may be unable to incorporate into the BMZ because it is produced in a dysfunctional form, or its BMZ binding site is missing. It is also possible that other structural alterations in skin BMZ, which occur in dystrophic EB, result in masking of the antigenic binding by the autoantibody when intact BMZ is probed.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel antigen of the dermal-epidermal junction defined by an anti-CD1b monoclonal antibody (NU-T2)

NU-T2 is a mouse monoclonal IgG1 antibody to the CD1b molecule, (cross-)reacting with an antigen of the dermal-epidermal junction (NU-T2 DEJ AG). Further immunohistochemical characterization of the NU-T2 DEJ AG showed it to display unique properties that differentiate it from other known antigens of the dermal-epidermal junction. Indeed, the NU-T2 DEJ AG is primate-specific and present only in epithelial basement membranes. In normal human skin it is expressed within the lowermost lamina lucida of the dermal-epidermal junction but not in the deep part of epidermal appendages nor in the deep part of epidermal appendages nor in the basement membrane of dermal vessels, smooth muscles or nerves. In diseases with intraepidermal or intradermal cleavage, NU-T2 reactivity was observed at the floor of the blister. In various skin specimens with a cleavage through the lamina lucida (NaCl--or dispase-split skin, bullous pemphigoid, junctional epidermolysis bullosa), NU-T2 immunoreactivity seemed reduced, being localized at the dermal side of the cleavage. These results suggest that the antigen recognized by NU-T2 is a novel component of the lamina lucida of the dermal-epidermal junction, that seems to be important for dermal-epidermal adhesion.

Proteoglycans in cultures of skin fibroblasts in recessive dystrophic epidermolysis bullosa

The proteoglycans of cultured fibroblasts from the skin of three patients with recessive dystrophic epidermolysis bullosa and three normals were compared after labeling with [35S]sulfate and [3H]leucine. The behavior in gel chromatography of the intact proteoglycans and several properties of their component glycosaminoglycans (size, content of iduronic acid, and content of 4- and 6-sulfate) showed no statistical differences. In addition, the binding of intact proteoglycans and of their constituent proteins and glycosaminoglycans to type I collagen were measured by affinity chromatography. No differences were found that could account for the skin lesions in recessive dystrophic epidermolysis bullosa.

Basement membrane proteoglycans and development

Basement membranes contain distinct collagen, glycoprotein and proteoglycan species, and these exhibit considerable heterogeneity in isoform or type when different tissue types are compared. Additionally, many components are differentially expressed in organogenesis. We have considered the distributions in glomerulogenesis of two distinct basement membrane proteoglycans, a small heparan sulfate proteoglycan and a chondroitin sulfate proteoglycan (BM-CSPG). While the former was present in all kidney basement membranes through development, the latter was apparently regulated in distribution. BM-CSPG was only strongly expressed in the vasculature invading late comma stage glomeruli, and later in presumptive and mature Bowman's capsule. Over the first six to eight weeks, the capillary basement membranes contained BM-CSPG, but in gradually decreasing amounts until it became completely undetectable. The basement membrane of the adult rat glomerulus is unique in its lack of BM-CSPG. However, in diabetic rats, BM-CSPG is apparently re-expressed in the glomerular basement membrane, a potential marker for pathological changes in glomerular structure. While its function awaits elucidation, BM-CSPG may be essential for basement membrane integrity or stability and have important roles in kidney development.

Epitopes for CD1a, CD1b, and CD1c antigens are differentially mapped on Langerhans cells, dermal dendritic cells, keratinocytes, and basement membrane zone in human skin

BACKGROUND

CD1 antigens are classified serologically into at least three groups, CD1a, CD1b, and CD1c, and many kinds of monoclonal antibodies are available for each subgroup of CD1 antigens. CD1a, CD1b, and CD1c antigens have been shown to be selectively and differentially expressed on epidermal Langerhans cells and dermal dendritic cells in normal human skin.

OBJECTIVE

The objective was to further delineate the localization of epitopes of CD1 antigens in human skin.

METHODS

We examined the immunoreactivity of 14 different CD1 antibodies (seven CD1a, five CD1b, and two CD1c antibodies) with the immunoperoxidase technique. We also studied the reactivity of NU-T2 (CD1b) antibody by immunogold electron microscopy.

RESULTS

The epitopes for CD1a, CD1b, and CD1c antigens were differentially mapped on epidermal Langerhans cells, dermal dendritic cells, keratinocytes, the luminal portion of eccrine gland ducts, and the basement membrane zone in human skin.

CONCLUSION

These CD1 antibodies may be useful to analyze the phenotypic alteration of immune and nonimmune cells in various skin diseases.

Patterns of glycosaminoglycan/proteoglycan immunostaining in human skin during aging

Proteoglycans and their component glycosaminoglycans are involved in such cell-cell and cell-matrix interactions as cell adhesion and migration, processes that are essential for embryonic and fetal development. As definitive organs such as skin emerge, structurally different proteoglycans partition into highly defined compartments. In skin, these compartments correspond to morphologically and functionally distinct layers. However, during the normal aging process, the relative amounts of structurally distinct proteoglycans apparently varies independently in each of these layers. This was demonstrated, in an indirect immunocytochemical study, through the use of monoclonal antibodies that detect structurally distinct domains in glycosaminoglycan chains of proteoglycans. Using samples of normal human skin obtained from individuals ranging in age from 20 weeks of gestation to 98 years of age, we determined that a common distribution pattern existed in skin. The epidermis contained chondroitin 4- and keratan sulfates, the basal lamina was the only layer that contained chondroitin 6-sulfate, the papillary and reticular dermis contained principally dermatan sulfate. In addition, antibodies that recognize native domains in chondroitin sulfates identified proteoglycan subsets that partitioned into distinct layers. An important new finding was that the relative amounts of specific types of glycosaminoglycans varied in an age- and layer-dependent manner. In the epidermis there was a notable increase in keratan sulfate beginning at age 50. Chondroitin 6-sulfate, found principally in the basal lamina, decreased after age 60. In the papillary dermis, the amount of dermatan sulfate increased after age 50, whereas the amount of novel chondroitin sulfate epitope, detected by antibody 4C3, decreased with age. Thus, age-related changes in proteoglycan distribution exist and correlate with morphologic and functional changes that occur in the intrinsic process of aging in human skin.

Immunoelectron microscopy and immunofluorescence antigenic mapping: diagnostic applications

In selected situations, direct and indirect IEM may provide important diagnostic information for the clinician, as pertains to the diagnosis and therefore prognosis in a given patient. As discussed, however, all of the more conventional approaches should be pursued before consideration is given to the performance of IEM, knowing its relative cost and technical difficulty. In contrast, we consider immunofluorescence antigenic mapping to be the diagnostic method of choice for the determination of the type of inherited EB present in affected individuals. When additional ultrastructural or morphometric data is required, then TEM can be performed as an adjunct study once it is determined by mapping technique that additional useful information may be derived.

Immunohistochemical staining for chondroitin sulphate and keratan sulphate. An evaluation of two monoclonal antibodies

Immunohistochemical staining with commercially available antibodies against chondroitin sulphate (clone CS-56) and keratan sulphate (clone 1/20/5-D-4) was compared with two conventional histochemical methods for the demonstration of glycosaminoglycans, namely Alcian Blue with varying pH and critical electrolyte concentrations, and a modified PAS stain. The antibodies were tested on sections from both frozen and fixed, paraffin embedded human material from umbilical cord, skin, and bronchus. The results showed immunostaining to function equally well on frozen and routine sections, and to be superior to Alcian Blue and PAS with regard to morphological detail. Thus, reactivity with anti-chondroitin sulphate was demonstrated in vessel walls, in small nerves, in the basal membrane zone of the skin, in perichondrium, and in and around chondrocytes. Reactivity with anti-keratan sulphate occurred in chondroid matrix and in perichondrial tissue; however, some cells of the bronchial epithelium and mucous glands also exhibited positivity.

Immunohistochemical alterations in basement membrane components of squamous cell carcinoma

To investigate alterations in the basement membrane (BM) in squamous cell carcinoma (SCC), we investigated 20 tumors. Four had the cytologic characteristics of Bowen's disease (SCC-BD) and 16 did not have them (SCC-NB). Tumors were studied immunohistochemically by double immunofluorescent staining by using mouse monoclonal antibodies to the core protein of heparan sulfate proteoglycan (HSPG) and chondroitin 6-sulfate glycosaminoglycan (Ch6S) as well as rabbit antiserum to laminin (LN) and type IV collagen (C-4). In well-differentiated and highly keratinized SCC-NB, LN, C-4, and HSPG could be detected in the tumor nest BM and showed no loss of continuity, but they were largely lost in poorly differentiated and poorly keratinized SCC-NB. This suggests that poorly differentiated SCC-NB cause greater enzymatic degradation of BM components than well-differentiated SCC-NB. Ch6S was detected in parts of the BM of SCC-BD, but it was absent in all SCC-NB examined. It appears that SCC-NB have lost the ability to synthesize Ch6S, and that SCC-BD degrade Ch6S although they continue to produce it. Thus, it appears that in SCC the BM is qualitatively different from that of normal epidermis, and that SCC-BD can be distinguished from SCC-NB by the Ch6S content of the BM.

Revised clinical and laboratory criteria for subtypes of inherited epidermolysis bullosa. A consensus report by the Subcommittee on Diagnosis and Classification of the National Epidermolysis Bullosa Registry

Inherited epidermolysis bullosa encompasses a number of diseases, with the common finding of blister formation after minor mechanical trauma to the skin. In some forms significant, if not eventually fatal, extracutaneous disease activity may occur. In recent years application of newer technologies has contributed substantially to an overall understanding of this collection of inherited diseases. Concurrently, many new phenotypes have been recognized, in part the result of ongoing prospective patient registries in the United States and abroad. Unfortunately, this has resulted in a massive literature that may appear to be confounded by seemingly excessive or arbitrary subdivision of epidermolysis bullosa variants. With these concerns in mind a subcommittee was established by the National Epidermolysis Bullosa Registry to summarize the current literature and to make recommendations as to the best clinical and laboratory criteria for the practical diagnosis and subclassification of patients with inherited epidermolysis bullosa.

Expression of extracellular matrix in hair follicle mesenchyme in alopecia areata

Human hair follicle mesenchyme contains a distinctive extracellular matrix which varies in volume and composition in concert with the hair growth cycle. To investigate the possibility that mesenchymal function is disturbed in alopecia areata we have studied the expression of extracellular matrix constituents in scalp biopsies from 14 patients by immunohistochemical staining for basement membrane proteins, proteoglycans and interstitial collagens. The staining patterns in follicles from non-lesional scalp were normal. Miniature anagen follicles from bald patches also showed relatively normal expression of basement membrane proteins and proteoglycans. However, in some large anagen follicles from lesional sites, there was loss of the normal staining pattern for chondroitin-6-sulphate in the dermal papilla. In lesional catagen follicles, the glassy membranes showed marked convolution and thickening. These structures stained strongly for laminin and type IV collagen but only weakly for interstitial collagens.

Ultrastructural localization of the core protein of a basement membrane-specific chondroitin sulfate proteoglycan in adult rat skin

Basement membranes are complex extracellular matrices present at epithelial/mesenchymal interfaces of tissues. The dermal-epidermal junction has been shown to contain numerous components, some of the most well known being laminin, types IV and VII collagens, heparan sulfate proteoglycan, fibronectin, and entactin/nidogen. IN this paper we show, using core protein-specific antibodies, the presence of a newly described basement membrane-specific chondroitin sulfate proteoglycan at the epithelial/mesenchymal interface of adult rat skin. Ultrastructurally, this antigen was proven to reside primarily within the basal lamina, apparently concentrated in the lamina densa. In addition, some of the proteoglycan was also present beneath the lamina densa, associated with the reticular lamina collagen fibrils.

Applicability of 19-DEJ-1 monoclonal antibody for the prenatal diagnosis or exclusion of junctional epidermolysis bullosa

Recently a monoclonal antibody (19-DEJ-1) was produced with binding specificity for the mid-lamina lucida of the skin dermo-epidermal junction, in very close association with overlying hemidesmosomes. Since skin cleavage occurs within the lamina lucida in the inherited blistering disorder, junctional epidermolysis bullosa (EB), and is associated with aberrations in the morphology and/or number of hemidesmosomes in such tissue, we have sought to determine whether this monoclonal antibody could be used for prenatal diagnosis. Fetoscopy-directed skin biopsies were obtained from two fetuses at risk for junctional EB and post-mortem samples from two other fetuses with the Herlitz type of junctional EB, the latter after prenatal diagnosis by electron microscopy and termination of each pregnancy. Specimens were examined in part by light and electron microscopy for evidence of skin cleavage or other alterations in morphology, and in part by indirect immunofluorescence for altered basement membrane antigenicity. Three of four fetuses were shown to have intra-lamina lucida blister formation indicative of, and hemidesmosome hypoplasia proving, junctional EB. Each was also shown to lack expression of GB3 and 19-DEJ-1 antigens, consistent with findings noted postnatally in junctional EB; diagnosis was confirmed in each at the time of therapeutic abortion. A fourth fetus had no abnormalities detected; lack of disease involvement was confirmed at the time of delivery, and subsequently over 8 months of careful serial evaluation. We conclude that 19-DEJ-1 monoclonal antibody is an accurate and sensitive immunohistochemical probe for junctional EB, and may be employed in the prenatal diagnostic evaluation of fetuses at risk for this disorder.

Distribution of two basement membrane proteoglycans through hair follicle development and the hair growth cycle in the rat

The distribution of two distinct populations of basement membrane proteoglycans has been monitored through hair growth development in the rat embryo and subsequent hair growth cycle. An antiserum against a small heparan sulfate proteoglycan uniformly stained the dermal-epidermal junction of embryonic rats throughout the period of hair follicle formation. On the other hand, monoclonal antibodies recognizing a basement membrane-specific chondroitin sulfate proteoglycan only weakly stained 16-d embryo dermal-epidermal junction, but strong staining was associated with hair follicle buds as they developed. Through the hair growth cycle, it was found that the heparan sulfate proteoglycan persisted around the follicles, while the chondroitin sulfate proteoglycan decreased in amount through catagen until it was undetectable at the base and dermal papilla of the telogen follicle. As anagen commenced, expression of the chondroitin sulfate proteoglycan was again demonstrated. It therefore appears that a basement membrane-specific proteoglycan shows variation in its distribution in rat skin, expression correlating with morphogenetic activity in hair follicles. It is possible that this newly described basement membrane component is involved in the complex processes of dermal-epidermal interaction that lead to skin appendage formation and growth.

Effect of enzyme digestion on anionic sites and charge-selective permeability of dermo-epidermal junction

To study components of anionic sites on the lamina densa of the dermo-epidermal junction (DEJ) and to assess the effect of removal of sialic acid or glycosaminoglycans on its charge-selective permeability, epidermal sheets, whose dermis had been removed by treatment with dithiothreitol, were digested with heparitinase, chondroitinase ABC, hyaluronidase, or neuraminidase. They were then stained with polyethyleneimine for demonstration of the anionic sites or incubated in a medium containing native anionic ferritin for tracer experiments. The anionic sites were completely removed after heparitinase digestion. Although the numerical density of the sites was not altered, their electron density was decreased after chondroitinase ABC digestion. The other enzymes had no effect on the sites. In the tracer experiments, heparitinase or neuraminidase increased the number of tracer molecules penetrating into the lamina lucida of the epidermal sheet, while the other enzymes had no effect on it. These data indicate that heparan sulfate, which is a main component of the anionic sites, plays an important role in the charge-selective permeability of the DEJ, whereas chondroitin sulfate, which seems to be contained in the sites, does not, probably because of its small amount. These data also indicate that sialic acid, which is not a main component of the anionic sites demonstrated with the cationic probe, has a role in the permeability function.

Tenascin/hexabrachion in human skin: biochemical identification and localization by light and electron microscopy

Tenascin/hexabrachion is a large glycoprotein of the extracellular matrix. Previous reports have demonstrated that tenascin is associated with epithelial-mesenchymal interfaces during embryogenesis and is prominent in the matrix of many tumors. However, the distribution of tenascin is more restricted in adult tissues. We have found tenascin to be present in normal human skin in a distribution distinct from other matrix proteins. Immunohistochemical studies showed staining of the papillary dermis immediately beneath the basal lamina. Examination of skin that had been split within the lamina lucida of the basement membrane suggested a localization of tenascin beneath the lamina lucida. In addition, there was finely localized staining within the walls of blood vessels and in the smooth muscle bundles of the arrectori pilorem. Very prominent staining was seen around the cuboidal cells that formed the basal layer of sweat gland ducts. The sweat glands themselves did not stain. The distribution of tenascin in the papillary dermis was studied at high resolution by immunoelectron microscopy. Staining was concentrated in small amorphous patches scattered amongst the collagen fibers beneath the basal lamina. These patches were not associated with cell structures, collagen, or elastic fibers. Tenascin could be partially extracted from the papillary dermis by urea, guanidine hydrochloride, or high pH solution. The extracted protein showed a 320-kD subunit similar to that purified from fibroblast or glioma cell cultures. We have developed a sensitive ELISA assay that can quantitate tenascin at concentrations as low as 5 ng/ml. Tests on extracts of the papillary dermis showed tenascin constituted about 0.02-0.05% of the protein extracted.