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Thomas Krieg

Publications and source records attributed to Thomas Krieg.

At least 37 records · Page 2Linked to original sources
PubMed2006

Immunoadsorption in dilated cardiomyopathy: 6-month results from a randomized study.

BACKGROUND: Various randomized studies evidenced that immunoadsorption (IA) repeated at monthly intervals induced acute and prolonged hemodynamic benefit in patients with severe heart failure due to dilated cardiomyopathy. Some findings indicate that the use of only one course of IA therapy may also induce prolonged beneficial effects. METHODS: This randomized study included 22 patients suffering from severe heart failure (left ventricular ejection fraction [LVEF] <35%) due to dilated cardiomyopathy. The first group (11 patients) was treated with four IA courses at monthly intervals. The second group (11 patients) received one IA course only without repetition. In all patients of the 2 groups, each course was performed in one IA session on 5 consecutive days. At 3 and 6 months after the beginning of this study, left ventricular function and hemodynamics were reevaluated in both groups. RESULTS: Immunoadsorption treatment repeated at monthly intervals induced improvement in LVEF after 6 months, that is, from 28.1% +/- 1.5% to 37.0% +/- 1.6% (+/-SEM; P < .01 vs baseline). Patients treated in only one IA course experienced comparable improvement of LVEF after 6 months, that is, from 26.5% +/- 2.2% to 34.8% +/- 2.9% (P < .01 vs baseline). In the group with repeated IA courses, cardiac index increased from baseline 2.2 +/- 0.1 to 2.8 +/- 0.2 L min(-1) m(-2) after 6 months (P < .01 vs baseline). In comparison, during the 6 months of this study in the group with one IA course, cardiac index increased from 2.1 +/- 0.1 to 2.7 +/- 0.2 L min(-1) m(-2). After 3 and 6 months, there were no significant differences between the 2 groups with respect to LVEF and all measured hemodynamic parameters. CONCLUSIONS: One course of IA treatment may induce improvement of left ventricular function over a period of 6 months, with results comparable to those received by IA treatment repeated at monthly intervals.

Cardiac Output↗
PubMed2006

Localized inflammatory skin disease following inducible ablation of I kappa B kinase 2 in murine epidermis.

Skin inflammation is a complex process that involves interactions between various cell types residing in different skin compartments. Using mice with conditionally targeted I kappa B kinase 2 (IKK2) alleles, we have previously shown that epidermal keratinocytes can play a dominant role in the initiation of an inflammatory reaction. In order to investigate long-term consequences of IKK2 deletion in adult skin, we have generated mice with floxed IKK2 alleles in which expression of a Tamoxifen-inducible Cre recombinase construct is targeted to epidermal keratinocytes (K14-Cre-ER(T2)IKK2(fl/fl) mice). K14-Cre-ER(T2)IKK2(fl/fl) mice are born normally and do not show signs of a skin disease until the age of 6 months. Deletion of IKK2 can be observed after Tamoxifen application to the back skin or spontaneously, without Tamoxifen application, in mice older than 6 months. This deletion is accompanied by dramatic, localized skin changes that are characterized by invasion of inflammatory cells, hair follicle disruption, and pseudoepitheliomatous hyperplasia of the epidermis, but not by tumor formation. The hyperplastic epithelium shows increased phosphorylation of signal transducer and activator of transcription 3 and extracellular signal-regulated protein kinase 1/2, typical features of psoriatic epidermis. Our results identify a primary role for IKK2 in the development of skin inflammation and confirm its requirement for the maintenance of skin homeostasis.

Animals↗
PubMed2006

Mechanical tension and integrin alpha 2 beta 1 regulate fibroblast functions.

The extracellular matrix (ECM) environment in connective tissues provides fibroblasts with a structural scaffold and modulates cell shape, but it also profoundly influences the fibroblast phenotype. Here we studied fibroblasts cultured in a three-dimensional network of native collagen, which was either mechanically stressed or relaxed. Mechanical load induces fibroblasts that synthesize abundant ECM and a characteristic array of cytokines/chemokines. This phenotype is reminiscent of late granulation tissue or scleroderma fibroblasts. By contrast, relaxed fibroblasts are characterized by induction of proteases and a subset of cytokines that does not overlap with that of mechanically stimulated cells. Thus, the biochemical composition and physical nature of the ECM exert powerful control over the phenotypes of fibroblasts, ranging from "synthetic" to "inflammatory" phenotypes. Interactions between fibroblasts and collagen fibrils are mostly mediated by a subset of beta 1 integrin receptors. Fibroblasts utilize alpha 1 beta 1, alpha 2 beta 1, and alpha 11 beta 1 integrins for establishing collagen contacts and transducing signals. In vitro assays and mouse genetics have demonstrated individual tasks served by each receptor, but also functional redundancy. Unraveling the integrated functions of fibroblasts, collagen integrin receptors, collagen fibrils, and mechanical tension will be important to understand the molecular mechanisms underlying tissue repair and fibrosis.

Animals↗
PubMed2006

Molecular mechanisms of VEGF-A action during tissue repair.

Vascular endothelial growth factor-A (VEGF-A) is a crucial mediator of vascular hyperpermeability, angiogenesis, and inflammation, processes intimately involved in tissue repair. Although much emphasis has been placed on understanding the synthesis and stability of VEGF-A mRNA, relatively little attention has been given to the study of the stability and processing of VEGF-A proteins themselves. In recent years, several studies indicated that VEGF-A protein activity is highly controlled through interaction with angiogenic or non-angiogenic mediators. We analyzed mechanisms that might control extracellular VEGF-A processing during wound repair. First, our studies provide evidence that VEGF-A protein is a target of proteases present in the microenvironment of human chronic non-healing wounds. Serine proteases, in particular plasmin cleave VEGF165 and digested VEGF fragments, showed decreased mitogenic activity. Inactivation of the plasmin cleavage site Arg110/Ala111 preserved the structural integrity and increased the angiogenic potency of VEGF165 when tested in an impaired healing mouse model. Secondly, we identified significantly increased levels of the potent VEGF-A inhibitor, the soluble form of the VEGF receptor VEGFR-1 (sVEGFR-1) in non-healing wounds when compared to healing wounds. Wound closure in healing and non-healing wounds correlated significantly with a decline in sVEGFR-1 levels. These observations support the concept that VEGF-A and VEGF-A receptors are important mediators in tissue repair. Further, our data provide mechanisms how VEGF-A-mediated interactions are disturbed during impaired healing.

Animals↗
PubMed2006

Expression of matrix metalloproteinase (MMP)-2, MMP-9, MMP-13, and MT1-MMP in skin tumors of human papillomavirus type 8 transgenic mice.

Human papillomaviruses (HPV) are small DNA viruses that induce a wide variety of hyperproliferative lesions in cutaneous and mucosal epithelia. It is proposed that HPV is involved in non-melanoma skin cancer development. We have previously shown that HPV8 transgenic mice spontaneously develop papillomatous skin tumors. Histology revealed epidermal hyperplasia, acanthosis and hypergranulosis and in some cases squamous cell carcinomas (SCC). Zymographic and immunoblot analysis of normal skin extracts identified increased amounts of matrix metalloproteinase (MMP)-9, MMP-13 and MT1-MMP in HPV8-positive mice compared with HPV8-negative animals. In situ gelatin zymography of tumor specimens displayed a strong proteolytic activity in papillomas, and SCC putatively attributed to the increased amounts of activated MMP-9 found in tissue extracts. In addition, immunoblot analysis revealed increased amounts of active MMP-13 and MT1-MMP in tumor extracts as compared with control extracts. Immunohistochemical stainings of SCC specimens depicted MMP-13 to be specifically expressed in stromal fibroblasts neighboring the tumor islands, whereas MT1-MMP was detected both in tumor cells and in stromal cells. Taken together, these results implicate a role for MMPs in the development of HPV8-induced cutaneous tumors.

Animals↗
PubMed2006

Pathogenic role for skin macrophages in a mouse model of keratinocyte-induced psoriasis-like skin inflammation.

Psoriasis is a common skin disease, the pathogenesis of which has not yet been resolved. In mice, epidermis-specific deletion of inhibitor of NF-kappaB (IkappaB) kinase 2 (IKK2) results in a skin phenotype that mimics human psoriasis in several aspects. Like psoriasis, this skin disease shows pronounced improvement when mice are treated with a TNF-neutralizing agent. We have found previously that this phenotype does not depend on the presence of alphabeta T lymphocytes. In order to evaluate contributions of other immune cell populations to the skin disease, we selectively eliminated macrophages and granulocytes from the skin of mice with epidermis-specific deletion of IKK2 (K14-Cre-IKK2fl/fl mice). Elimination of skin macrophages by subcutaneous injection of clodronate liposomes was accompanied by inhibition of granulocyte migration into the skin and resulted in a dramatic attenuation of psoriasis-like skin changes. The hyperproliferative, inflammatory skin disease in K14-Cre-IKK2fl/fl mice was a direct consequence of the presence of macrophages in the skin, as targeted deletion of CD18, which prevented accumulation of granulocytes but not macrophages, did not lead to major changes in the phenotype. Targeted deletion of the receptor for IFN-gamma revealed that the pathogenesis of the skin disease does not depend on classical IFN-gamma-mediated macrophage activation. Our results demonstrate that in mice epidermal keratinocytes can initiate a hyperproliferative, inflammatory, IFN-gamma-independent, psoriasis-like skin disease whose development requires essential contributions from skin macrophages but not from granulocytes or alphabeta T lymphocytes.

Animals↗
PubMed2006

Plasmin modulates vascular endothelial growth factor-A-mediated angiogenesis during wound repair.

Plasmin-catalyzed cleavage of the vascular endothelial growth factor (VEGF)-A isoform VEGF165 results in loss of its carboxyl-terminal heparin-binding domain and significant loss in its bioactivity. Little is known about the in vivo significance of this process. To investigate the biological relevance of the protease sensitivity of VEGF165 in wound healing we assessed the activity of a VEGF165 mutant resistant to plasmin proteolysis (VEGF165(A111P)) in a genetic mouse model of impaired wound healing (db/db mouse). In the present study we demonstrate that in this mouse model plasmin activity is increased at the wound site. The stability of the mutant VEGF165 was substantially increased in wound tissue lysates in comparison to wild-type VEGF165, thus indicating a prolonged activity of the plasmin-resistant VEGF165 mutant. The db/db delayed healing phenotype could be reversed by topical application of wild-type VEGF165 or VEGF165(A111P). However, resistance of VEGF165 to plasmin cleavage resulted in the increased stability of vascular structures during the late phase of healing due to increased recruitment of perivascular cells and delayed and reduced endothelial cell apoptosis. Our data provide the first indication that plasmin-catalyzed cleavage regulates VEGF165-mediated angiogenesis in vivo. Inactivation of the plasmin cleavage site Arg110/Ala111 may preserve the biological function of VEGF165 in therapeutic angiogenesis under conditions in which proteases are highly active, such as wound repair and inflammation.

Animals↗
PubMed2005

Ras-induced spreading and wound closure in human epidermal keratinocytes.

Although it is known that growth factor signaling cascades are active during epithelial wound healing, signals that regulate reepithelialization after wounding are not very well characterized. The small GTP binding protein Ras is a molecular switch involved in the regulation of signals originating from different growth factor receptors. We have investigated consequences of its activation in primary human keratinocytes. We provide evidence that activation of Ras can lead to shape changes of keratinocytes caused by rearrangements of the actin cytoskeleton that result in membrane protrusion and ruffling. Similar shape changes were found in the migrating tip of newly formed epithelium in mouse wounds. These cytoskeletal changes occur independently of keratinocyte terminal differentiation, and they can determine the speed of wound epithelialization in vitro. Using various mutant constructs and specific pharmacological inhibitors, we found that the effects of activated Ras on the cytoskeleton of keratinocytes are mediated by a phosphatidylinositol 3 kinase-independent activation of Rac. Our results suggest that growth factor-induced, Ras-mediated changes of keratinocyte shape may be an important mechanism that determines the speed of wound epithelialization.

Actins↗
PubMed2005

Wound-healing defect of CD18(-/-) mice due to a decrease in TGF-beta1 and myofibroblast differentiation.

We studied the mechanisms underlying the severely impaired wound healing associated with human leukocyte-adhesion deficiency syndrome-1 (LAD1) using a murine disease model. In CD18(-/-) mice, healing of full-thickness wounds was severely delayed during granulation-tissue contraction, a phase where myofibroblasts play a major role. Interestingly, expression levels of myofibroblast markers alpha-smooth muscle actin and ED-A fibronectin were substantially reduced in wounds of CD18(-/-) mice, suggesting an impaired myofibroblast differentiation. TGF-beta signalling was clearly involved since TGF-beta1 and TGF-beta receptor type-II protein levels were decreased, while TGF-beta(1) injections into wound margins fully re-established wound closure. Since, in CD18(-/-) mice, defective migration leads to a severe reduction of neutrophils in wounds, infiltrating macrophages might not phagocytose apoptotic CD18(-/-) neutrophils. Macrophages would thus be lacking their main stimulus to secrete TGF-beta1. Indeed, in neutrophil-macrophage cocultures, lack of CD18 on either cell type leads to dramatically reduced TGF-beta1 release by macrophages due to defective adhesion to, and subsequent impaired phagocytic clearance of, neutrophils. Our data demonstrates that the paracrine secretion of growth factors is essential for cellular differentiation in wound healing.

Actins↗
PubMed2005

Absence of autoantibodies against correctly folded recombinant fibrillin-1 protein in systemic sclerosis patients.

Autoantibodies against short recombinant fragments of fibrillin-1 produced in bacterial expression systems have been found in tight-skin mouse, systemic sclerosis, mixed connective tissue disease, and primary pulmonary hypertension syndrome. In patients with scleroderma, the frequency of anti-fibrillin-1 antibodies was 42% in Caucasians. Until now it has been unclear whether this immune response has a primary function in disease pathogenesis or is a secondary phenomenon. In the present study we analyzed the frequency of autoantibodies against two overlapping recombinant polypeptides spanning the N-terminal and C-terminal halves of human fibrillin-1, which were produced in human embryonic kidney (HEK-293) cells. Correct three-dimensional structures of the recombinant fibrillin-1 polypeptides were shown by electron microscopy and immunoreactivity with antibodies. Screening of fibrillin-1 antibodies was performed in 41 sera from systemic sclerosis patients and in 44 healthy controls with a Caucasian background. Microtiter plates were coated with the recombinant polypeptides of fibrillin-1 and incubated with 1:100 diluted sera. Positive binding was defined as being more than 2 SD above the mean of the control group. ELISAs showed that none of the sera of patients with systemic sclerosis contained autoantibodies against the N-terminal or C-terminal recombinant fibrillin-1 polypeptide. The data show the absence of autoantibodies against recombinant fibrillin-1 protein in Caucasian systemic sclerosis patients. Because the correct three-dimensional folding of the recombinant proteins has been substantiated by several independent methods, we conclude that autoantibodies against correctly folded fibrillin are not a primary phenomenon in the pathogenesis of systemic sclerosis.

Autoantibodies↗
PubMed2005

Human scalp dermal papilla and fibrous sheath cells have a different expression profile of matrix metalloproteinases in vitro when compared to scalp dermal fibroblasts.

The dermal papilla is a cluster of specialised mesenchymal cells at the bottom of the mammalian hair follicle, embedded in a loose extracellular matrix. These cells have the capability to induce and support hair growth via close epithelial-mesenchymal interactions with the keratinocytes surrounding the hair matrix. The extracellular matrix of the dermal papilla differs markedly from the interfollicular matrix and plays a key role in the maintenance of hair growth. In this study we investigated the expression pattern and activity of matrix metalloproteinases (MMP) and their tissue inhibitor in in vitro cultures of cells derived from scalp dermal papilla and fibrous sheath. Expression and activity of MMP-1, MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2 and MT1-MMP were analysed in those cells cultured in contact with one of the relevant protein component of the dermal matrix, collagen type I as well as in monolayer. Zymographic analysis showed activation of MMP-2 in all cells grown in three-dimensional collagen lattices whereas MMP-9 was activated only in three-dimensional collagen cultures of dermal fibroblasts and weakly in follicular cells. Expression of MMP-1, TIMP-1, TIMP-2 and MT1-MMP was similar in all cells, in both culture conditions, whereas expression of MMP-3 was absent in dermal papilla cells. In addition to a series of reported morphological and functional differences between dermal fibroblasts and the dermal mesenchyme-derived cells of the hair follicle, we reported differences in MMP expression in dermal papilla and fibrous sheath cells within the mesenchymal population of the hair follicle.

Cells, Cultured↗
PubMed2005

Heterozygous deficiency of manganese superoxide dismutase results in severe lipid peroxidation and spontaneous apoptosis in murine myocardium in vivo.

To circumvent the early lethality of manganese superoxide dismutase (SOD2)-deficient mice, we have used a skin-specific strategy with introduction of loxP sites flanking exon 3 of the SOD2 gene. To our surprise, when breeding a female keratin 14 Cre transgenic mouse to a SOD2 "floxed" male mouse, due to keratin 14 promoter-driven Cre expression in the oocytes, all offspring were heterozygous for SOD2. In sharp contrast to initial publications on SOD2(+/-) mice, the herein reported mice on a mixed genetic background (C57BL/6 x 129/Ola) in their heterozygous state (SOD(+/-)) revealed distinct ultrastructural damage of the myocard, with swelling and disruption of mitochondria and accumulation of lipid droplets, increased nitrotyrosine formation, and lipid peroxidation as well as activation of apoptosis signaling pathways in the heart in vivo. Strikingly, and so far unreported, we found a substantial decrease in the activity of the cytosolic copper, zinc superoxide dismutase (SOD1) in the heart tissue of SOD2(+/-) mice, suggesting that the breakdown of mitochondrial membranes in the heart of SOD2(+/-) mice results in the enhanced release of superoxide anion radicals or derivatives thereof with subsequent inactivation of cytosolic SOD1. This model may be particularly suited to long-term studies on age-related heart failure as well as other age-related diseases and the polygenic base of tissue-specific responses to oxidative injury.

Animals↗
PubMed2005

E-cadherin is essential for in vivo epidermal barrier function by regulating tight junctions.

Cadherin adhesion molecules are key determinants of morphogenesis and tissue architecture. Nevertheless, the molecular mechanisms responsible for the morphogenetic contributions of cadherins remain poorly understood in vivo. Besides supporting cell-cell adhesion, cadherins can affect a wide range of cellular functions that include activation of cell signalling pathways, regulation of the cytoskeleton and control of cell polarity. To determine the role of E-cadherin in stratified epithelium of the epidermis, we have conditionally inactivated its gene in mice. Here we show that loss of E-cadherin in the epidermis in vivo results in perinatal death of mice due to the inability to retain a functional epidermal water barrier. Absence of E-cadherin leads to improper localization of key tight junctional proteins, resulting in permeable tight junctions and thus altered epidermal resistance. In addition, both Rac and activated atypical PKC, crucial for tight junction formation, are mislocalized. Surprisingly, our results indicate that E-cadherin is specifically required for tight junction, but not desmosome, formation and this appears to involve signalling rather than cell contact formation.

Animals↗
PubMed2005

Silicone granuloma of the face treated with minocycline.

Siliconoma represents a granulomatous foreign body reaction to silicone, which is often used for soft tissue augmentation. Although considered as biologically inert for a long time, silicone has been implicated in various undesirable local and systemic reactions, sometimes with a latency period of up to several decades. Treatment of siliconomas is difficult and granulomas involving the face are a therapeutic challenge. We present a 43-year-old woman with a severely disfiguring facial silicone granuloma who was successfully treated with minocycline.

Adult↗
PubMed2005

High invasive melanoma cells induce matrix metalloproteinase-1 synthesis in fibroblasts by interleukin-1alpha and basic fibroblast growth factor-mediated mechanisms.

Tumor invasion and metastasis of melanoma have been shown to require proteolytic degradation of the extracellular environment, achieved primarily by enzymes of the matrix metalloproteinases (MMP) family. Increased enzyme activity is localized at the border of tumor cells and the adjacent peritumoral connective tissue, emphasizing the crucial role of tumor-stroma interactions in the regulation of MMP activity. To analyze whether direct cell-cell contacts of melanoma cells and stromal fibroblasts or whether soluble factors, secreted by melanoma cells are involved in the regulation of MMP, we used different in vitro co-culture systems. Both direct and indirect co-cultures of high invasive BLM melanoma cells and human dermal fibroblasts resulted in an induction of pro-MMP-1 synthesis. Medium conditioned by BLM cells strongly induced pro-MMP-1 synthesis in fibroblasts, indicating the importance of diffusible factors for this induction. Competition by recombinant human interleukin (IL)-1 receptor antagonist, neutralizing IL-1alpha and basic fibroblast growth factor (bFGF) antibodies, resulted in a concentration-dependent reduction of pro-MMP-1 synthesis. Taken together, our results indicate an essential role for soluble factors, mainly IL-1alpha and bFGF, in the stimulation of dermal fibroblasts by human melanoma cells to secrete MMP-1.

Antibodies↗
PubMed2005

[The clinical spectrum of dermatomyositis].

Dermatomyositis is characterized by marked clinical heterogeneity. Many classification schemes are available, based on internal organ involvement, presence of circulating autoantibodies and additional symptoms characteristic for other connective tissue diseases. Viral infections and underlying malignancies are possible mechanisms to trigger this autoimmune disease. Intensive clinical investigations to detect such malignancies are therefore required. The prognosis of the individual patient depends on the involvement of internal organs and the characterization of circulating autoantibodies. There are patients with rapidly developing subsets of dermatomyositis and those with slowly progressive disease. Therefore treatment has to be adjusted for the disease severity. Sometimes high dosages of corticosteroids in combination with immunosuppressive agents or immunoglobulins are required.

Adult↗
PubMed2005

[Treatment of chronic actinic dermatitis with mycophenolate mofetil].

A 63-year-old man presented in the summer of 1999 with eczematous skin lesions predominantly in sun-exposed areas. Based on the history, clinical picture and results of the diagnostic procedures, he was diagnosed with chronic actinic dermatitis. Therapy with sunscreens, topical and oral corticosteroids and systemic PUVA was unsuccessful. Initiation of immunosuppression with mycophenolate mofetil (500 mg b.i.d.) led to complete resolution of the skin lesions within several weeks.

Chronic Disease↗