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T Krieg

Publications and source records attributed to T Krieg.

At least 127 records · Page 7Linked to original sources
PubMed1996

Decreased expression of alpha 2 beta 1 integrin in scleroderma fibroblasts.

Systemic scleroderma (SSc) is a complex connective tissue disorder of unknown etiology. In early stages of the disease, fibroblasts are activated to produce large amounts of collagen with subsequent fibrosis. Collagen metabolism of fibroblasts is modulated by their contact with the extracellular matrix (ECM), which involves distinct receptors on the cell surface, mainly belonging to the integrins. We investigated the expression of collagen receptor alpha 2 beta 1 in SSc and normal fibroblasts, since this receptor has been shown to be utilized by fibroblasts for adhesion to and reorganization of collagen I. 9 strains of scleroderma fibroblasts grown as monolayer cultures were first analyzed with respect to their collagen I expression. 6 of these strains were similar to controls "low" producers) and 3 strains showed up to 2-3 x higher levels of collage I mRNA expression ("high" producers). Northern hybridization using a cDNA probe specific for the alpha 2 integrin subunit revealed a decrease of the corresponding mRNA in SSc fibroblasts as compared to controls (75% versus 100%). "High" collagen producing cell strains displayed the lowest values for alpha 2 integrin mRNA. The decrease of alpha 2 integrin subunit expression at the mRNA level in selected fibroblasts was further substantiated by radioimmunoprecipitation using specific mAbs directed against alpha 2 integrin subunit. No significant changes in beta 1 integrin expression could be observed - neither at mRNA nor at the protein level. Our data indicate a correlation between excessive synthesis of collagen and low levels of alpha 2 integrin subunit expression in SSc fibroblasts. Further experiments should clarify whether this observation is a phenomenon specific for scleroderma or whether it reflects an "activated" state of fibroblasts.

Cells, Cultured↗
PubMed1996

New aspects in scleroderma research.

Systemic sclerosis (SSc) still is a disease of unknown origin. However, in the past few years, progress has been made in elucidating some features of SSc. In this review we summarize recently established data that center around genetics, immunology, and animal models of SSc as well as around the important role of cytokines, endothelial cells, fibroblasts and the extracellular matrix in this disease.

Animals↗
PubMed1996

Glycosaminoglycans modulate cell-matrix interactions of human fibroblasts and endothelial cells in vitro.

Contact of various cells with extracellular matrix molecules modulates their cellular functions and phenotype. Most investigations have employed dishes coated with purified matrix constituents or plain collagen I lattices omitting the effects of other important matrix components such as proteoglycans. In this study we analyze the effect of purified glycosaminoglycans (GAGs) on human fibroblasts and human umbilical vein endothelial cells (HUVEC) embedded within collagen I/III lattices. HUVEC contracted collagen I/III gels far less efficiently than fibroblasts and addition of heparan sulfate and heparin almost completely inhibited contraction. In collagen gels HUVEC down-regulated collagenase mRNA while increasing collagen I, IV mRNA expression. Addition of heparin and heparan sulfate reversed the collagen IV mRNA induction whereas hyaluronic acid and chondroitin sulfate enhanced fibronectin and collagenase transcripts. Fibroblasts readily contracted collagen gels, and mRNA levels for fibronectin, collagenase and interleukin-6 were stimulated. Gel contraction was mostly unaffected by the different glycosaminoglycans. Fibroblasts responded to the addition of dermatan sulfate, heparan sulfate and heparin with a decrease in fibronectin, collagenase and interleukin-6 mRNA. Binding studies revealed saturable binding sites on fibroblasts and HUVEC for 35S-labelled heparin, demonstrating specificity for heparin and heparan sulfate over other GAGs in competition experiments. This study implies that glycosaminoglycans participate in cell-matrix interactions by effectively modulating the cellular phenotype via high affinity binding sites.

Animals↗
PubMed1996

Regulation of collagen expression by interleukin-1 beta is dependent on donor age.

Cultured skin fibroblasts derived from old (> 60 years) donors differ in various morphological and functional aspects from cells obtained from young (< 20 years) donors. We were interested in whether fibroblasts obtained from old and young donors differ in their cellular response to interleukin-1 beta, a cytokine which has been shown to affect the synthesis of extracellular matrix proteins in human dermal fibroblasts. Therefore the expression of interstitial collagen (type I), minor collagen (type VI) and interstitial collagenase genes was investigated, using fibroblasts derived from either old or young donors. Fibroblasts were incubated in the absence or presence of interleukin-1 beta (5 units/ml, 50 units/ml, 500 units/ml) for 48 h. Total RNA was isolated and mRNA levels were determined by Northern and dot blot analysis. Comparing the synthetic response of fibroblasts obtained from young and old donors, we observed a marked increase of the inhibition of type I and type VI collagen expression and the stimulation of interstitial collagenase in the aged fibroblasts. These results suggest that physiological ageing in human fibroblasts is associated with an altered responsiveness to interleukin-1 beta.

Adolescent↗
PubMed1996

Co-ordinate induction of collagen type I and biglycan expression in keloids.

Proteoglycans are macromolecules displaying structural roles as well as regulatory functions in the maintenance of the extracellular matrix. Biglycan/PG-I and decorin/PG-II are two small proteoglycans that are structurally related but differ considerably in their localization in vivo and behaviour in vitro. Decorin and, to a minor extent, biglycan, can be located at the surface of type I collagen fibrils and have been shown to influence collagen fibrillogenesis. However, the physiological role of biglycan in the dermis is not known. Biopsies obtained from keloids were bisected and processed for total RNA extraction and immunohistochemistry. Northern blot analysis of total RNA obtained from keloids with high growth tendency in vivo showed a marked induction of biglycan and collagen alpha 1(I)mRNA expression in comparison with total RNA obtained from normal skin or keloids with little growth tendency. In contrast, decorin mRNA expression remained largely unaltered. Studying these biopsies by immunohistochemistry, decorin expression in the dermis was unaltered comparing normal and keloid tissue, whereas a markedly increased staining for biglycan was observed in the keloid tissue, which was most pronounced in the nodular formations, and was a characteristic feature of keloids. The altered expression of biglycan in keloid tissue might be involved in the abnormal regulation of extracellular matrix deposition either through the binding of growth factors or by influencing the three-dimensional organization of collagen fibres or associated molecules.

Biglycan↗
PubMed1995

Sequence data and chromosomal localization of human type I and type II hair keratin genes.

A cDNA library constructed with poly(A)+ RNA from human scalp was screened with selected fragments of both murine type I and type II hair keratin cDNAs. Two keratin clones, one type I, phKI-2, and one type II, phKII-1, were isolated and sequenced. In Northern blots, cDNA probes containing the 3'-noncoding sequences of the clones specifically hybridized to scalp mRNA species. Based on sequence homology comparisons with the four known murine type I hair keratins mHa1-4, the phKI-2 encoded keratin could be identified as human hair keratin hHa2. Similarly, sequence comparison with the four type II sheep wool keratins K2.9-12 revealed an orthologous relationship between the largest member of the type II wool keratin subfamily, K2.9 (i.e., sHb1) and the phKII-1 encoded human hair keratin (hHb1). The specific 3'-noncoding sequences of hHa2 and hHb1 were also used to isolate genomic fragments for both keratins from human genomic libraries which were than used for fluorescence in situ hybridization to human metaphase chromosomes. The hHa2 gene could be mapped to the long arm of chromosome 17, whereas the hHb1 gene was found on the long arm of chromosome 12. DAPI banding of the chromosomes allowed sublocalization of the hHa2 gene to 17q12-q21 and the hHb1 gene to 12q13, i.e., gene loci that have also been previously determined for human type I and type II epithelial keratins.

Amino Acid Sequence↗
PubMed1995

A purine-rich sequence in the human BM-40 gene promoter region is a prerequisite for maximum transcription.

BM-40 (osteonectin, SPARC [secreted protein, acidic, rich in cysteine]) is a highly conserved, matrix-associated protein that is found in basement membranes, bones and remodeling tissues throughout vertebrate evolution. We are reporting the characterization of the 5' end of the human BM-40 gene. Sequence comparison of the 5' region revealed significant homologies with the bovine and murine genes, including a purine-rich stretch composed of two boxes, GGA-box 1 and 2, separated by a pyrimidine-rich spacer element. Transfection analyses of the human BM-40 promoter provide strong evidence that this region comprises several distinct regulatory domains, to which different functions can be assigned. GGA-box 1 is thereby absolutely required and sufficient by itself for maximal BM-40 transcriptional activity, whereas the spacer element has a down-regulatory effect. Comparative transfection analyses in human cell lines, positive or negative for BM-40 transcripts, indicate that the GGA-box sequences in the human promoter, in contrast to the bovine promoter, do not significantly contribute to cell-type specific expression in human cells.

Adenosine↗
PubMed1995

Collagen and collagenase gene expression in three-dimensional collagen lattices are differentially regulated by alpha 1 beta 1 and alpha 2 beta 1 integrins.

The reorganization of extracellular matrix (ECM) is an important function in many biological and pathophysiological processes. Culture of fibroblasts in a three-dimensional collagenous environment represents a suitable system to study the underlying mechanisms resulting from cell-ECM interaction, which leads to reprogramming of fibroblast biosynthetic capacity. The aim of this study was to identify receptors that transduce ECM signals into cellular events, resulting in reprogramming of connective tissue metabolism. Our data demonstrate that in human skin fibroblasts alpha 1 beta 1 and alpha 2 beta 1 integrins are the major receptors responsible for regulating ECM remodeling: alpha 1 beta 1 mediates the signals inducing downregulation of collagen gene expression, whereas the alpha 2 beta 1 integrin mediates induction of collagenase (MMP-1). Applying mAb directed against different integrin subunits resulted in triggering the heterodimeric receptors and enhancing the normal biochemical response to receptor ligation. Different signal transduction inhibitors were tested for their influence on gel contraction, expression of alpha 1(I) collagen and MMP-1 in fibroblasts within collagen gels. Ortho-vanadate and herbimycin A displayed no significant effect on any of these three processes. In contrast, genistein reduced lattice contraction, and completely inhibited induction of MMP-1, whereas type I collagen down-regulation was unaltered. Calphostin C inhibited only lattice contraction. Taken together, these data indicate a role of tyrosine-specific protein kinases in mediating gel contraction and induction of MMP-1, as well as an involvement of protein kinase C in the contraction process. The data presented here indicate that different signaling pathways exist leading to the three events discussed here, and that these pathways do not per se depend upon each other.

Antibodies, Monoclonal↗
PubMed1995

Altered immunohistochemical expression of small proteoglycans in the tumor tissue and stroma of basal cell carcinoma.

Small proteoglycans have been shown to act as receptors for matrix molecules or growth factors and to influence the attachment and the migration of cells. We therefore report here on the immunocytochemical expression of three small proteoglycans, i.e., decorin, biglycan, and the recently described PG-100, in normal human skin and in basal cell carcinoma. In normal human skin, staining for decorin revealed expression throughout the dermis with an increased signal in the papillary dermis, whereas no expression was observed in the epidermis. Biglycan and PG-100 were mainly detected in the epidermis, with biglycan being expressed only in suprabasal layers. In addition, biglycan could be detected in a narrow zone below the basement membrane. In tissue specimens obtained from 12 basal cell carcinomas, the expression of biglycan and PG-100 was absent or strongly down-regulated in the tumor tissue. Tumor cells thus displayed a staining pattern similar to that found on the basal cells of normal human skin. In the stroma surrounding the tumor, however, the expression of biglycan and to a lesser degree decorin was increased when compared with normal human dermis. The increased deposition appears to be due to an increased synthesis of these molecules, as total RNA extracted from basal cell carcinoma tissue revealed an induction of biglycan and decorin mRNA. This study indicates that the expression of proteoglycans in basal cell carcinoma tumor cells and in tumor stroma is altered from that in normal skin.

Animals↗
PubMed1995

Up-regulation of keratin 17 expression in human HaCaT keratinocytes by interferon-gamma.

The immortalized human keratinocyte cell line HaCaT was used to assess the effect of interferon-gamma (IFN-gamma) on expression of keratin K17. Both IFN-gamma and K17 have been implicated in the pathophysiology of psoriasis. Western and quantitative enzyme-linked immunosorbent assay analyses demonstrated increasing induction of K17 protein by 48 h exposure to IFN-gamma at concentrations of 10, 50, and 250 U/ml. At 50 U/ml IFN-gamma, immunohistochemical analysis revealed numerous K17-positive foci, whereas in situ hybridization demonstrated K17 message in the majority of cells. In addition, at low (5 U/ml) concentrations of IFN-gamma, cell proliferation and protein synthesis decreased, as determined by 3H-thymidine labeling and 14C-amino acid uptake. These data suggest that aberrant K17 expression observed in psoriatic lesions may be a consequence of IFN-gamma overexpression, and that the HaCaT cell line may be a useful in vitro model system to elucidate the underlying mechanisms.

Antigens, Differentiation↗
PubMed1994

The function of KGF in morphogenesis of epithelium and reepithelialization of wounds.

The function of keratinocyte growth factor (KGF) in normal and wounded skin was assessed by expression of a dominant-negative KGF receptor transgene in basal keratinocytes. The skin of transgenic mice was characterized by epidermal atrophy, abnormalities in the hair follicles, and dermal hyperthickening. Upon skin injury, inhibition of KGF receptor signaling reduced the proliferation rate of epidermal keratinocytes at the wound edge, resulting in substantially delayed reepithelialization of the wound.

Aging↗
PubMed1994

Changes in calcium and collagen IV binding caused by mutations in the EF hand and other domains of extracellular matrix protein BM-40 (SPARC, osteonectin).

Recombinant expression in a human kidney cell-line was used to prepare mutant human BM-40 with deletions including the N-terminal acidic domain, a central alpha-helical domain and the C-terminal EF hand domain. Two putative EF hand motifs were altered by point mutations. Only elimination of the whole EF hand domain or its single disulfide bond decreased production and secretion indicating that the C-terminal region of BM-40 is essential for correct folding. Deletions in the alpha-helical domain changed a single disulfide bond in this domain and caused oligomerization. Several mutations resulted in significant conformational changes as shown by CD spectroscopy and epitope analysis. Fluorescence titration demonstrated a single high-affinity (Kd = 0.08 microM) calcium-binding site with a low dissociation rate constant. A Glu to Lys mutation in the -Z position of the C-terminal EF hand motif and lack of a stabilizing disulfide bridge caused a 30 to 100-fold reduction in calcium affinity, while an Asp to Lys mutation in the X position had only a small effect. Deletions in the alpha-helical domain caused an even more dramatic reduction in calcium binding and abolished calcium-dependent binding of BM-40 to collagen IV. Both binding properties are critically dependent on a conformational interaction between the EF hand and the alpha-helical domain, which contains the collagen-binding site.

Amino Acid Sequence↗
PubMed1994

Three-dimensional contact with type I collagen mediates tyrosine phosphorylation in primary human fibroblasts.

By applying Western blot analysis using anti-phosphotyrosine antibodies, primary human dermal fibroblasts were examined after having been cultured on type I collagen-coated surfaces or in free-floating type I collagen gels. In both systems cells showed enhanced tyrosine phosphorylation of a M(r) 120,000 protein (pp120) and of a M(r) 42,000 protein (pp42). Phosphorylation was apparent 6 h at the latest after initiation of the culture and was only slightly induced on polylysine or on plastic. In contrast to pp42, pp120 was rapidly dephosphorylated in cells suspended by trypsinization or released from collagen gels by collagenase treatment, but regained phosphorylation in cells cultured in/on type I collagen. Two human sarcoma cell lines (HT-1080 and RD) exhibited identical tyrosine phosphorylation of pp120 but not of pp42. pp120 is identical with pp125FAK, a novel tyrosine kinase localized in focal adhesions, as proved by immunological cross-reactivity with anti-pp125FAK antibodies. Our results suggest that tyrosine phosphorylation is involved in signal transduction triggered by two- and three-dimensional type I collagen-fibroblast contact.

Adult↗
PubMed1994

Mg2+ and Ca2+ differentially regulate beta 1 integrin-mediated adhesion of dermal fibroblasts and keratinocytes to various extracellular matrix proteins.

The specific requirements for divalent cations in the integrin-dependent adhesion and deadhesion of human dermal fibroblasts and human epidermal keratinocytes to various extracellular matrix proteins have been studied in vitro. The adhesion of both cell types to collagen type I and to laminin was enhanced by Mg2+ in a concentration-dependent manner, while Ca2+ dose-dependently antagonized this effect, thus promoting deadhesion. The cation-dependent conversion between adhesion and deadhesion occurred already at 2 to 10 min after addition of the alternate cation and was almost completed at 20 min. Interestingly, Ca2+ could not reverse the Mg(2+)-enhanced adhesion of both cell types to fibronectin. Inhibition studies with function-blocking antibodies directed against distinct beta 1 integrins showed that the Mg(2+)-enhanced fibroblast adhesion to collagen type I was mediated by the alpha 1 beta 1 and the alpha 2 beta 1 integrins, whereas keratinocyte adhesion to collagen type I was mediated by the alpha 2 beta 1 integrin. Both cell types utilized the alpha 2 beta 1 and the alpha 6 beta 1 integrins for Mg(2+)-dependent adhesion to laminin and the alpha 5 beta 1 integrin for the adhesion to fibronectin. Integrin expression at the cell surface was not altered, indicating that divalent cation-dependent conformational changes of beta 1 integrins most likely regulate their functional activity.

Calcium↗
PubMed1994

Role of the extracellular matrix in the degradation of connective tissue.

Cell-matrix interactions have an important impact on regulating connective tissue degradation during physiological and pathological processes, e.g., development, wound healing and tissue remodeling and tumor invasion and metastasis. Connective tissue breakdown is initiated by a specific class of enzymes, the matrix metalloproteinases, which include the type I collagenases, the type IV collagenases/gelatinases and the stromelysins and which vary with respect to their substrate specificities. The activity of the metalloproteinases is regulated by de novo synthesis of the proenzymes, the activation of the zymogens and by the presence of the inhibitors, TIMPs. This tight control is required in order to guarantee normal functioning of connective tissue.

Animals↗
PubMed1994

[Simultaneous occurrence of extra-abdominal fibromatosis and post-traumatic keloid].

The report deals with the clinical features of a 26-year-old man with the extraabdominal form of deep fibromatosis, which became manifest at the age of 18 years as acute ileus caused by diffuse intraabdominal fibromatous tumours. In the later course of the disease extensive fibromatous lesions developed, mainly at the skin. In addition, multiple keloids occurred after excision or after negligible traumas. The pathogenetic events of the clinical picture described may be linked to the activation of mesenchymal cells leading to the generation of either fibromatous tumours or posttraumatic keloids.

Adult↗
PubMed1994

Pathomorphological and biochemical alterations in Ehlers-Danlos-syndrome type IV.

We are reporting the morphological and biochemical data of a patient with the characteristic features of the Ehlers-Danlos-Syndrome Type IV (Sack-Barabas Type) who died acutely after an episode of recurrent ruptures of the bowel with subsequent septic peritonitis. Morphologically, the connective tissue of the vessel walls, the dermis and the connective tissue of internal organs, particularly that of liver and lung, showed a distinct hypoplasia of the collagenous scaffold. Collagen fibers were irregularly arranged which was also corroborated by ultrastructural examination of the collagen fibrils of the dermis and of intervertebral disc material. Immunohistochemically, a loss in the staining intensity for collagen III could be observed in all locations. In contrast, the localization of collagen I, IV, V and VI appeared normal, although with some reduced staining intensity which particularly held true for collagen I in the dermis and vessel wall. The biochemical content of collagen III in lung and liver tissue was significantly reduced when compared to control tissues. Accordingly, in the pool of newly synthesized collagen from skin fibroblasts, only minute amounts of collagen III could be found which was normally secreted and had a normal electrophoretic migration.

Cells, Cultured↗