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Biomedical subjects

E A Bauer

Publications and source records attributed to E A Bauer.

At least 37 records · Page 2Linked to original sources
PubMed1993

Labeling of fractured human skin with antibodies to BM 600/nicein, epiligrin, kalinin and other matrix components.

A variety of methods were used to fracture the dermal-epidermal junction (DEJ) of human skin. These included warm and hot phosphate buffered saline, trypsin, cold 1 M salt, potassium bromide and proteolytic digestion with dispase. The localization and sensitivity of basement membrane components (bullous pemphigoid antigen, BM 600/nicein, epiligrin, kalinin, laminin, collagens IV and VII (EBA antigen) and linkin) were determined after the DEJ was fractured by each method. We found that the basement membrane zone proteins, BM 600/nicein, epiligrin and kalinin remained with the dermal side of the DEJ fractured through the lamina lucida by cold salt, phosphate buffered saline and potassium bromide. BM 600/nicein, epiligrin and kalinin were not detected after treatment with trypsin. In contrast, laminin, another glycoprotein in the lamina lucida, was insensitive to all of the procedures, but co-localized to the dermal side of DEJ-fractured skin. We also found that separation of the DEJ with brief exposure of skin to 56 degrees C provided a useful substrate for testing the autoantibodies in the sera of patients with epidermolysis bullosa acquisita (EBA). Heat-separated skin can be prepared in a significantly shorter period of time than salt-separated skin.

Antibodies↗
PubMed1993

Human relaxin decreases collagen accumulation in vivo in two rodent models of fibrosis.

The reproductive hormone, relaxin, inhibits collagen synthesis in vitro by normal human dermal fibroblast. In the present study, recombinant human relaxin is shown to modulate collagen accumulation and organization by mesenchymal cells in vivo in two rodent models of fibrosis: 1) fibrotic infiltration of polyvinyl alcohol sponge implants in rats, and 2) capsule formation around implanted osmotic pumps in mice. In the sponge, relaxin inhibits collagen accumulation, a measured by hydroxyproline content, in a dose-responsive manner by up to 25-29% in animals receiving 30 ng/ml relaxin, a finding supported by a decrease in collagen-specific trichrome staining in sections of sponges from relaxin-treated animals. In mice, the capsules surrounding relaxin-containing pumps are thinner and less dense than are capsules from control pumps. Ultrastructurally, control capsules are composed of densely packed parallel arrays of collagen fibrils, whereas fibrils more frequently are not packed in parallel arrays and are less abundant in treated capsules.

Animals↗
PubMed1993

Desipramine-induced blue-gray photosensitive pigmentation.

BACKGROUND: Blue-gray pigmentation of the skin can be elicited by several medications. We report the first case (to our knowledge) of desipramine-induced photosensitive blue-gray pigmentation. OBSERVATIONS: Diffuse blue-gray pigmentation on sun-exposed surfaces was noted in a healthy 48-year-old woman who had been taking desipramine hydrochloride for 8 years. Ultrastructural studies demonstrated the presence of melanin and homogeneous electron-dense material in the dermis. CONCLUSIONS: We conclude that tricyclic antidepressant agents represent another class of medications responsible for blue-gray cutaneous pigmentation.

Desipramine↗
PubMed1992

Vascular endothelial growth factor induces interstitial collagenase expression in human endothelial cells.

Vascular endothelial growth factor (VEGF) is a 45kDa secreted peptide that has potent mitogenic activity specific for endothelial cells in vitro and the ability to induce a strong angiogenic response in vivo. In the present study, 24 h treatment with VEGF resulted in a stimulation of expression of the metalloproteinase, interstitial collagenase, at the protein and mRNA levels 2.5-3.0-fold in human umbilical vein endothelial cells but not in human dermal fibroblasts. The dose response curve for collagenase induction was biphasic with the peak stimulatory response obtained by treatment of cells with 10-100 ng/ml (0.2-2 nM) VEGF. The dose response curve for collagenase induction overlapped with, but was not identical to, the response curve for proliferation, which showed VEGF mitogenic activity between < or = 0.1-50 ng/ml (< or = 0.002-1 nM). There was no induction seen in expression of other members of the matrix metalloproteinase family, including the 72kDa type IV collagenase, the 92kDa type V collagenase, or stromelysin. Expression of transcripts for the major metalloproteinase inhibitor, tissue inhibitor of metalloproteinases, was also unaltered by treatment with VEGF (1-200 ng/ml). These studies demonstrate that in addition to stimulating proliferation of endothelial cells, VEGF can also induce the expression of the only metalloproteinase that can initiate degradation of interstitial collagen types I-III under normal physiological conditions. Both responses are likely to contribute to the angiogenic potential of this peptide.

Cells, Cultured↗
PubMed1992

Dermal mast cell granules bind interstitial procollagenase and collagenase.

In order to identify structures in human skin that bind collagenase, sections from frozen or paraffin-embedded skin were incubated with either procollagenase or activated collagenase. After washing, bound procollagenase or collagenase was detected by immunofluorescence microscopy. In normal skin, procollagenase bound only to isolated granular dermal cells that were identified as mast cells on the basis of staining with fluoresceinated avidin and pinacyanol erythrosinate. When mast cells were degranulated by exposure to the ionophore A23187, extracellular granules bound procollagenase. Of various pathologic conditions examined, the highest binding of procollagenase occurred in specimens of urticaria pigmentosa. Procollagenase bound to granular cells and to abundant granules scattered throughout the dermis. Binding could be abolished by pre-treatment of tissue sections with heparinase or by pre-incubation of procollagenase with soluble heparin, suggesting that heparin is the binding agent in the granules. Activated collagenase also bound to dermal mast cells but in addition bound strongly to the dermal collagen. Enzymatic activity of activated collagenase was not inhibited by heparin in concentrations up to 10 mg/ml. There is evidence that mast cell tryptase can contribute to procollagenase activation. This study further supports a role for mast cells in collagenolysis by demonstrating that heparin from mast cells binds procollagenase and possibly serves as a reservoir for procollagenase, which may then subsequently be activated.

Animals↗
PubMed1992

Recessive dystrophic epidermolysis bullosa phenotype is preserved in xenografts using SCID mice: development of an experimental in vivo model.

Recessive dystrophic epidermolysis bullosa (RDEB) is a subgroup of hereditary blistering diseases characterized by repetitive wounding and healing with subsequent extensive scarring. The purpose of this study was to establish a xenograft model that retains the RDEB phenotype and thus might be used as an experimental in vivo model to explore the molecular and biochemical mechanisms of the chronically wounded phenotype of RDEB. Full-thickness, tumor-free RDEB skin tissues were grafted onto the dorsum of severe combined immunodeficiency (SCID) mice. At 4, 8, 12, and 24 weeks after grafting, the xenografts were removed for examination. Immunofluorescence studies were performed using species-specific antibodies to human class I antigen, mouse class I antigen, human type IV and VII collagens and with cross-reacting antibody against bullous pemphigoid antigen (BPA). Staining with the antibody to human class I antigen, W6/32, and with the antibody to mouse class I antigen, 20.8.4s, confirmed the species-specific results obtained with the type IV and type VII collagen and laminin antibodies. The RDEB grafts showed essentially no staining with the type VII collagen antibody. Antibodies against laminin and BPA showed normal staining patterns in RDEB grafts. There was an overall paucity of anchoring fibrils in the grafts when examined with electron microscopy. Blisters could be induced in these grafts with minor trauma and showed a sublamina densa separation by immunomapping and electron microscopy. As late as 24 weeks post-transplantation, the RDEB grafts remain human, are not significantly replaced by mouse cells, and retain the RDEB disease phenotype.

Adolescent↗
PubMed1992

Relaxin alone and in conjunction with interferon-gamma decreases collagen synthesis by cultured human scleroderma fibroblasts.

Fibroblasts derived from the involved skin of scleroderma patients frequently display a phenotype of supernormal collagen expression when cultured. Fibroblasts displaying this phenotype derived from seven patients were treated with relaxin (1-100 ng/ml) and interferon-gamma (1-100 U/ml), individually and in combination, to assess the relative abilities of these cytokines to down-modulate collagen synthesis and secretion. Scleroderma fibroblasts displayed varying sensitivities to both relaxin and interferon-gamma. Relaxin (100 ng/ml) decreased expression of collagen by six of seven lines tested from 8 to 59% compared to untreated cultures. Interferon-gamma (100 U/ml) depressed collagen secretion by all seven lines in a range from 7 to 89%. When relaxin and interferon-gamma were used in combination, relaxin augmented IFN-gamma-induced decreases in collagen secretion in four of seven lines. In three of these lines, the use of relaxin in conjunction with suboptimal doses of interferon-gamma resulted in decreases equivalent to or greater than that seen with a tenfold higher concentration of interferon-gamma. This study demonstrates the ability of relaxin to directly alter the excessive collagen-producing phenotype of scleroderma fibroblasts. In addition, in some cases, combining relaxin and interferon-gamma resulted in a cooperative effect in decreasing collagen expression by scleroderma cells in vitro.

Cells, Cultured↗
PubMed1991

Stromelysin expression regulates collagenase activation in human fibroblasts. Dissociable control of two metalloproteinases by interferon-gamma.

The expression of collagenolytic activity by cells represents the rate-limiting step in the turnover of collagen during remodeling. The collagenase gene is transcriptionally activated in normal dermal or rheumatoid synovial fibroblasts by interleukin-1 beta (IL-1 beta), resulting in secretion of trypsin-activatable procollagenase measuring in the range of 2.0-5.0 units/10(6) cells/48 h in the 14C-fibril assay. The addition of interferon-gamma (IFN-gamma; 50-100 units/ml) inhibits the expression of collagenase activity by 45-80% in these cells. The IL-1 beta induction of procollagenase protein was not altered by IFN-gamma, as judged by Western blot analysis using a monoclonal antibody to collagenase and by gelatin zymography, and procollagenase mRNA was also unaltered, as assessed by Northern blot analysis. Because collagenolytic activity is also controlled by the quantity of tissue inhibitor of metalloproteinases present, its expression was examined by Western blot analysis using a polyclonal antibody to tissue inhibitor of metalloproteinases and by reverse gelatin zymography. Tissue inhibitor of metalloproteinase protein was found to be unaltered or slightly less abundant in conditioned media from cultures treated with IL-1 beta and IFN-gamma when compared with that from cultures treated with IL-1 beta alone. However, the expression of the metalloproteinase activator of procollagenase, stromelysin, was found to be significantly inhibited by the addition of IFN-gamma. Addition of purified activated stromelysin to these conditioned media completely reconstituted collagenolytic activity. These observations demonstrate in an intact system that stromelysin is a specific activator necessary for the development of collagenolytic activity. Despite stromelysin's lack of catalytic activity against collagen, its expression can serve as a control point in the regulation of collagenolysis.

Cells, Cultured↗
PubMed1991

Human type VII collagen: cDNA cloning and chromosomal mapping of the gene.

A human keratinocyte cDNA expression library in bacteriophage lambda gt11 was screened with the purified IgG fraction of serum from a patient with epidermolysis bullosa acquisita, which had a high titer of anti-type VII collagen antibodies. Screening of approximately 3 x 10(5) plaques identified 8 positive clones, the largest one (K-131) being approximately 1.9 kilobases in size. Dideoxynucleotide sequencing of K-131 indicated that it consisted of 1875 base pairs and contained an open reading frame coding for a putative N-terminal noncollagenous domain of 439 amino acids and a collagenous C-terminal segment of 186 amino acids. The collagenous domain was characterized by repeating Gly-Xaa-Yaa sequences that were interrupted in several positions by insertions or deletions of 1-3 amino acids. The deduced amino acid sequence also revealed a peptide segment that had a high degree of identity with a published type VII collagen protein sequence. Northern hybridization of the K-131 cDNA with human epidermal keratinocyte and skin fibroblast RNA revealed an mRNA of approximately 8.5 kilobases. The fusion protein produced by the K-131 cDNA, when incubated with epidermolysis bullosa acquisita serum, bound to antibodies that reacted in Western blots with type VII collagen. The genomic location of the type VII collagen gene (COL7A1) was determined by chromosomal in situ hybridization with the K-131 cDNA. The results mapped the COL7A1 to the locus 3p21. The cDNA clones characterized in this study will be valuable for understanding the protein structure and gene expression of type VII collagen present in anchoring fibrils and its aberrations in the dystrophic forms of heritable epidermolysis bullosa.

Amino Acid Sequence↗
PubMed1991

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.

Epidermolysis Bullosa↗
PubMed1989

Cleavage of type VII collagen by interstitial collagenase and type IV collagenase (gelatinase) derived from human skin.

Type VII collagen is the major structural protein of anchoring fibrils, which are believed to be critical for epidermal-dermal adhesion in the basement membrane zone of the skin. To elucidate possible mechanisms for the turnover of this protein, we examined the capacities of two proteases, human skin collagenase, which degrades interstitial collagens, and a protease with gelatinolytic and type IV collagenase activities, to cleave type VII collagen. At temperatures below the denaturation temperature, pepsin cleaves type VII collagen into products of approximately 95 and approximately 75 kDa. Human skin collagenase cleaved type VII collagen into two stable fragments of approximately 83 and approximately 80 kDa, and the type IV collagenase (gelatinase) produced a broad band of approximately 80 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cleavage of type VII collagen was linear with time and enzyme concentration for both enzymes. Although the Km values were similar for both enzymes, the catalytic rate of cleavage by type IV collagenase is much faster than by interstitial collagenase, and shows a greater rate of increase with increasing temperature. Sequence analysis of the cleavage products from both enzymes showed typical collagenous sequences, indicating a relaxation in the helical part of the type VII collagen molecule at physiological temperature which makes it susceptible to gelatinolytic degradation. Interstitial collagenase from both normal skin cells and cells from patients with recessive dystrophic epidermolysis bullosa, a severe hereditary blistering disease in which both an anchoring fibril defect and excessive production of collagenase can be observed, produced identical cleavage products from type VII collagen. These data suggest a pathophysiological link between increased enzyme levels and the observed decrease or absence of anchoring fibrils.

Amino Acid Sequence↗
PubMed1989

Collagenase expression in skin fibroblasts from families with recessive dystrophic epidermolysis bullosa.

The collagenase production of cultured skin fibroblasts from Scandinavian families with dominant (D-EBD) and recessive (R-EBD) epidermolysis bullosa dystrophica has been investigated. Heterogeneity as a result of body location origin has been ruled out as fibroblasts obtained from predilection sites produce the same amount of immunoreactive collagenase as those obtained from non-predilection sites of the same subjects. Large variations in in vitro collagenase production were found between individuals and families. Within the R-EBD group, four out of eighteen patients showed an in vitro elevated level of immunoreactive collagenase compared to their healthy relatives, other EB types, and the control group. This shows that an in vitro elevated collagenase production is not a marker for the entire disease group and that the disease denoted as R-EBD probably is etiologically and pathogenetically heterogeneous.

Biopsy↗
PubMed1988

The structure of the human skin fibroblast collagenase gene.

Genomic clones containing the complete gene encoding human fibroblast interstitial collagenase were isolated from a lambda phage human DNA library. The gene is comprised from 10 exons and spans 8.2 kilobase pairs. We have mapped the relative positions and determined the DNA sequence of all the exon/intron borders of the gene. The organization of the human interstitial collagenase gene is very similar to that of rabbit collagenase and of two other extracellular matrix (ECM) metalloproteases: rat stromelysin (transin) and rat transin 2. All four genes are organized into 10 exons of virtually identical size while the length of the 3' proximal introns is subject to variation. The protein sequence comprising the putative active center is coded for by exon 5 of all four genes and contains a strongly conserved zinc binding site. This observation suggests that the organization of the ECM metalloprotease genes reflect the structure of the functional domains of the enzyme proteins. The structural data accumulated so far provides evidence for the existence of a gene family coding for secreted ECM metalloproteases and suggests that gene duplication played an important role in its formation.

Animals↗
PubMed1988

H-ras oncogene-transformed human bronchial epithelial cells (TBE-1) secrete a single metalloprotease capable of degrading basement membrane collagen.

H-ras-transformed human bronchial epithelial cells (TBE-1) secrete a single major extracellular matrix metalloprotease which is not found in the normal parental cells. The enzyme is secreted in a latent form of 72 kDa, which can be activated to catalyze the cleavage of the basement membrane macromolecule type IV collagen. The substrates in their order of preference are: gelatin, type IV collagen, type V collagen, fibronectin, and type VII collagen; but the enzyme does not cleave the interstitial collagens or laminin. This protease is identical to gelatinase isolated from normal human skin explants, normal human skin fibroblasts, and SV40-transformed human lung fibroblasts. Based on its ability to initiate the degradation of type IV collagen in a pepsin-resistant portion of the molecule, it will be referred to as type IV collagenase. This enzyme is most likely the human analog of type IV collagenase detected in several rodent tumors, which has the same molecular mass and has been linked to their metastatic potential. Type IV collagenase consists of three domains. Two of them, the amino-terminal domain and the carboxyl-terminal domain, are homologous to interstitial collagenase and human and rat stromelysin. The middle domain, of 175 residues, is organized into three 58-residue head-to-tail repeats which are homologous to the type II motif of the collagen-binding domain of fibronectin. Type IV collagenase represents the third member of a newly recognized gene family coding for secreted extracellular matrix metalloproteases, which includes interstitial fibroblast collagenase and stromelysin.

Amino Acid Sequence↗
PubMed1988

Werner's syndrome. Evidence for preferential regional expression of a generalized mesenchymal cell defect.

We describe a patient with Werner's syndrome from whom skin biopsy specimens were sampled for histology and electron microscopy and fibroblasts were cultured. Tissue sampled from five sites that varied in clinical presentation revealed striking changes in the dermoepidermal junction, elastic fibers of the papillary and reticular dermis, and adipose tissue of the hypodermis. The density and organization of the collagenous connective tissue was altered variably depending on the biopsy site. Changes noted in the epidermis were indicative of tissue regeneration and repair. Cells derived from acral areas grew poorly and could not be passed. Collagen synthesis in these cells was enhanced approximately 50%, and collagenase expression was decreased to a similar degree. Cells derived from the skin of the trunk could be passed but had an abbreviated in vitro life span. Collagen synthesis in these cells was unaltered. Serum from the patient with Werner's syndrome or from his obligate heterozygote offspring stimulated collagen synthesis in low-passage normal human skin fibroblast target cells. Sequential passage of these normal cells resulted in a blunting of the stimulatory effect. These observations suggest that a stimulator of collagen synthesis exists in the serum of patients with Werner's syndrome and that as cells (either normal or Werner's syndrome) "age" in vitro they may become hyporesponsive to this as yet undefined stimulatory factor in serum.

Collagen↗
PubMed1988

A perspective on the role of collagenase in recessive dystrophic epidermolysis bullosa.

The pathophysiology of tissue fragility in recessive dystrophic epidermolysis bullosa may be due in part to excessive destruction of interstitial collagens by a structurally altered, but catalytically active, form of human skin collagenase. Therapeutic attempts directed toward reducing the expression of this enzyme have resulted in clinical improvement in some patients with the disease.

Epidermolysis Bullosa↗