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Thomas Krieg

Publications and source records attributed to Thomas Krieg.

At least 19 recordsLinked to original sources
PubMed2006

Identification of susceptibility loci for skin disease in a murine psoriasis model.

Psoriasis is a frequently occurring inflammatory skin disease characterized by thickened erythematous skin that is covered with silvery scales. It is a complex genetic disease with both heritable and environmental factors contributing to onset and severity. The CD18 hypomorphic PL/J mouse reveals reduced expression of the common chain of beta(2) integrins (CD11/CD18) and spontaneously develops a skin disease that closely resembles human psoriasis. In contrast, CD18 hypomorphic C57BL/6J mice do not demonstrate this phenotype. In this study, we have performed a genome-wide scan to identify loci involved in psoriasiform dermatitis under the condition of low CD18 expression. Backcross analysis of a segregating cross between susceptible CD18 hypomorphic PL/J mice and the resistant CD18 hypomorphic C57BL/6J strain was performed. A genome-wide linkage analysis of 94 phenotypically extreme mice of the backcross was undertaken. Thereafter, a complementary analysis of the regions of interest from the genome-wide screen was done using higher marker density and further mice. We found two loci on chromosome 10 that were significantly linked to the disease and interacted in an additive fashion in its development. In addition, a locus on chromosome 6 that promoted earlier onset of the disease was identified in the most severely affected mice. For the first time, we have identified genetic regions associated with psoriasis in a mouse model resembling human psoriasis. The identification of gene regions associated with psoriasis in this mouse model might contribute to the understanding of genetic causes of psoriasis in patients and pathological mechanisms involved in development of disease.

Animals↗
PubMed2006

Integrin alpha2beta1 is required for regulation of murine wound angiogenesis but is dispensable for reepithelialization.

The alpha2beta1 integrin functions as the major receptor for collagen type I on a large number of different cell types, including keratinocytes, fibroblasts, endothelial cells, and a variety of inflammatory cells. Recently, we demonstrated that adhesion of keratinocytes to collagen critically depends on alpha2beta1, whereas fibroblasts can partly compensate for loss of alpha2beta1 in simple adhesion to collagen. However, in three-dimensional collagen matrices, alpha2beta1-null fibroblasts are hampered in generating mechanical forces. These data suggested a pivotal role for alpha2beta1 during wound healing in vivo. Unexpectedly, reepithelialization of excisional wounds of alpha2beta1-null mice was not impaired, indicating that keratinocytes do not require adhesion to or migration on collagen for wound closure. Whereas wound contraction and myofibroblast differentiation were similar, wound tensile strain was reduced in alpha2beta1-null mice, suggesting subtle changes in organization of the extracellular matrix. In addition, we observed reduced influx of mast cells into the granulation tissue, whereas infiltration of other inflammatory cells was not impaired. Interestingly, ablation of alpha2beta1 resulted in strong enhancement of neovascularization of granulation tissue and sponge implants. Both ultrastructurally and functionally, these new blood vessels appeared intact. In conclusion, our data show unique and overlapping functions of alpha2beta1 integrin during murine cutaneous wound healing.

Animals↗
PubMed2006

Enhanced expression levels of IL-31 correlate with IL-4 and IL-13 in atopic and allergic contact dermatitis.

BACKGROUND: IL-31 is produced by activated T lymphocytes, preferentially by TH2 cells. Transgenic mice overexpressing IL-31 have a phenotype resembling allergic dermatitis in human subjects. OBJECTIVE: We sought to evaluate the potential importance of IL-31 in the pathogenesis of human T cell-mediated skin diseases. METHODS: We analyzed total RNA taken from 149 skin biopsy specimens from patients with atopic dermatitis (AD), allergic contact dermatitis (ACD), or psoriasis in comparison with specimens taken from patients with healthy skin (n = 13) by using quantitative real-time PCR for the expression of TH1/TH2 cytokines. RESULTS: We found statistically increased mRNA levels of IL-31 in biopsy specimens taken from patients with AD, irrespective of the severity of the disease and serum IgE levels. Moreover, IL-31 mRNA levels were strongly increased in many biopsy specimens taken from patients with ACD. However, no increased transcription of IL-31 could be detected in biopsy specimens taken from psoriatic plaques. A comparison of mRNA levels of IL-31 with TH1 or TH2 cytokines demonstrates a correlation of the expression of IL-31 with IL-4 and IL-13 but not with IFN-gamma. No significant increase of IL-31 receptor mRNA could be detected in any disease, whereas the second receptor subunit of IL-31, the oncostatin M receptor, seems to be enhanced transcribed in patients with psoriasis. CONCLUSION: IL-31 expression is not only increased in patients with AD but also in those with ACD, 2 pruritic skin disorders. In both types of eczema, expression of IL-31 is associated with the expression of the TH2 cytokines IL-4 and IL-13. CLINICAL IMPLICATIONS: IL-31 might contribute not only to the development of AD but also to ACD-provoked skin inflammation.

Dermatitis, Allergic Contact↗
PubMed2006

Integrin alpha2beta1 deficiency does not affect contact hypersensitivity.

Collagens in the extracellular matrix are thought to play an important role in regulating inflammatory responses by affecting cell adhesion and migration. The contact between collagens and cells is established mainly by alpha1beta1, alpha2beta1 and alpha11beta1integrin receptors. Here, we analyzed the contact hypersensitivity (CHS) reaction in mice that were genetically deficient in the collagen receptor alpha2beta1. Integrin alpha2beta1 is widely expressed and has been suggested to play an important role in mediating inflammatory responses. CHS was induced by applying dinitrofluorobenzene to abdominal skin and challenging with the same reagent on ear skin. Macroscopically and histologically, ear swelling in alpha2beta1-deficient mice did not differ from that in wild-type control mice. Immunohistological detection of infiltrated T lymphocytes, neutrophils and mast cells in inflamed ear skin revealed similar numbers in controls and integrin alpha2beta1-deficient animals. Our results suggest that the adhesive functions of integrin alpha2beta1 are dispensable for the CHS response; they may be compensated for by the collagen receptor alpha1beta1 or other collagen receptors.

Animals↗
PubMed2006

Terminal B cell differentiation is skewed by deregulated interleukin-6 secretion in beta2 integrin-deficient mice.

Absence of the common beta chain (CD18) of beta(2) integrins leads to leukocyte-adhesion deficiency type-1 (LAD1) in humans. Mice with a CD18 null mutation suffer from recurrent bacterial infections, impaired wound healing, and skin ulcers, closely resembling human LAD1. Previous findings in CD18(-/-) mice demonstrated a skewed terminal B cell differentiation with plasmacytosis and elevated serum immunoglobulin G (IgG). As interleukin-6 (IL-6) is a potent enhancer of plasma cell formation and Ig secretion, we assessed IL-6 serum levels of CD18(-/-) and wild-type (WT) mice kept under a conventional or barrier facility or specific pathogen-free (SPF) conditions. We detected an up to 20-fold increase in IL-6 in serum of CD18(-/-) mice compared with WT controls when kept under conventional or barrier facility conditions, respectively. Under SPF conditions, no significant differences in terms of IL-6 serum levels were found between CD18(-/-) and WT mice. However, histological alterations of secondary lymphoid tissues, plasmacytosis, abnormal plasmacytoid cells (Mott cells), and hypergammaglobulinemia persisted. To further analyze the role of IL-6 in these pathological alterations, we established a CD18(-/-) IL-6(-/-) double-deficient mouse mutant. In these mice, serum IgG levels were normal, and the altered plasma cell phenotype, including Mott cells, was no longer detectable. The CD18(-/-) IL-6(-/-) double-deficient mouse model thus demonstrated that IL-6 is responsible for parts of the phenotype seen in the CD18(-/-) mouse mutants. It may be of interest to examine human leukocyte-adhesion deficiency type-1 patients closer and search for pathological changes possibly induced via overproduction of IL-6.

Animals↗
PubMed2006

Contact of high-invasive, but not low-invasive, melanoma cells to native collagen I induces the release of mature cathepsin B.

Metastasis of malignant tumor cells involves cell-cell and cell-matrix interactions, which regulate the expression and localization of proteolytic enzymes. In the present study, we investigated the expression and localization of the lysosomal cysteine proteinase cathepsin B and its natural inhibitors cystatin A, B and C in high- (MV3), intermediate- (SKmel28) and low-invasive (SKmel23, WM164) human melanoma cell lines grown on plastic or in contact with monomeric or fibrillar collagen type I. Neither the transcript levels of cathepsin B nor those of the natural inhibitors, cystatin B and C, were altered by the interaction of melanoma cells with collagen type I. However, protein expression and cellular localization of cathepsin B and its inhibitors were markedly affected. In contrast to low-invasive cells, high-invasive cells constitutively released procathepsin B when cultured on plastic. In addition, contact of invasive cells with fibrillar collagen type I resulted in the release of both mature forms of the protease. Perturbation studies using inhibitory antibodies against the beta1 subunit of the integrin receptor indicated a role for the beta1 integrin receptor family in the regulation of cathepsin B release. Cystatin B protein expression was much lower in high-invasive cells in both culture conditions, when compared to low-invasive cells. Cystatin C expression was comparable in all cells, but cell contact to fibrillar collagen type I induced its expression. These results strongly implicate a pivotal role of cell-matrix interactions for the regulation of cathepsin B localization and activity in melanoma cells.

Cathepsin B↗
PubMed2006

Interactions of primary fibroblasts and keratinocytes with extracellular matrix proteins: contribution of alpha2beta1 integrin.

The alpha2beta1 integrin is a collagen-binding protein with very high affinity for collagen I. It also binds several other collagens and laminins and it is expressed by many cells, including keratinocytes and fibroblasts in the skin. In the past, alpha2beta1 integrin was suggested to be responsible for cell attachment, spreading and migration on monomeric collagen I and contraction of three-dimensional collagen lattices. In view of these functions, normal development and fertility in integrin alpha2-deficient mice, which we generated by targeting the integrin alpha2 gene, came as a surprise. This suggested the existence of compensatory mechanisms that we investigate here using primary fibroblasts and keratinocytes isolated from wild-type and alpha2-deficient mice, antibodies blocking integrin function and downregulation of integrin alpha2 expression. The results show that the alpha2beta1 integrin is absolutely required for keratinocyte adhesion to collagens whereas for fibroblasts other collagen-binding integrins partially back-up the lack of alpha2beta1 in simple adhesion to collagen monomers. A prominent requirement for alpha2beta1 integrins became apparent when fibroblasts executed mechanical tasks of high complexity in three-dimensional surroundings, such as contracting free-floating collagen gels and developing isometric forces in tethered lattices. The deficits observed for alpha2-deficient fibroblasts appeared to be linked to alterations in the distribution of force-bearing focal adhesions and deregulation of Rho-GTPase activation.

Animals↗
PubMed2006

NECA at reperfusion limits infarction and inhibits formation of the mitochondrial permeability transition pore by activating p70S6 kinase.

The A1/A2 adenosine agonist 5'-(N-ethylcarboxamido) adenosine (NECA) limits infarction when administered at reperfusion. The present study investigated whether p70S6 kinase is involved in this anti-infarct effect. Adult rat ventricular myocytes were isolated and incubated in tetramethylrhodamine ethyl ester (TMRE, 100 nM), which causes cells to fluoresce in proportion to their mitochondrial membrane potential. A reduction in TMRE fluorescence serves as an indicator of collapse of the mitochondrial transmembrane potential. Cells were subjected to H2O2 (200 microM), which like ischemia induces loss of mitochondrial membrane potential. Fluorescence was measured every 3 min and to facilitate quantification membrane potential was arbitrarily considered as collapsed when fluorescence reached less than 60% of the starting value. Adding NECA (1 mM) to the cells prolonged the time to fluorescence loss (48.0+/-3.2 min in the NECA group versus 29.5+/-2.2 min in untreated cells, P<0.001) and the mTOR/p70S6 kinase inhibitor rapamycin (5 nM) abolished this protection (31.3+/-3.4 min). Since cyclosporine A offered similar protection, mitochondrial permeability transition pore formation is a likely cause of the H2O2-induced loss of potential. The direct GSK-3beta inhibitor SB216763 (3 microM) also prolonged the time to fluorescence loss (49.2+/-2.1 min, P<0.001 versus control), and its protection could not be blocked by rapamycin (42.2+/-2.3 min, P<0.001 versus control). NECA treatment (100 nM) of intact isolated rabbit hearts at reperfusion after 30 min of regional ischemia decreased infarct size from 33.0+/-3.8% of the risk zone in control hearts to 11.8+/-2.0% (P<0.001), and rapamycin blocked this NECA-induced protection (38.3+/-3.7%). A comparable protective effect was seen for SB216763 (1 microM) with infarct size reduction to 13.5+/-2.3% (P<0.001). NECA treatment (200 nM) of intact rabbit hearts at reperfusion also resulted in phosphorylation of p70S6 kinase more than that seen in untreated hearts. This NECA-induced phosphorylation was blocked by rapamycin. These experiments reveal a critical role for p70S6 kinase in the signaling pathway of NECA's cardioprotection at reperfusion.

Adenosine-5'-(N-ethylcarboxamide)↗
PubMed2006

A human keratin 10 knockout causes recessive epidermolytic hyperkeratosis.

Epidermolytic hyperkeratosis (EHK) is a blistering skin disease inherited as an autosomal-dominant trait. The disease is caused by genetic defects of the epidermal keratin K1 or K10, leading to an impaired tonofilament network of differentiating epidermal cells. Here, we describe for the first time a kindred with recessive inheritance of EHK. Sequence analysis revealed a homozygous nonsense mutation of the KRT10 gene in the affected family members, leading to a premature termination codon (p.Q434X), whereas the clinically unaffected consanguineous parents were both heterozygous carriers of the mutation. Semi-quantitative RT-PCR and western blot analysis demonstrated degradation of the KRT10 transcript, resulting in complete absence of keratin K10 protein in the epidermis and cultured keratinocytes of homozygous patients. This K10 null mutation leads to a severe phenotype, clinically resembling autosomal-dominant EHK, but differing in form and distribution of keratin aggregates on ultrastructural analysis. Strong induction of the wound-healing keratins K6, K16 and K17 was found in the suprabasal epidermis, which are not able to compensate for the lack of keratin 10. We demonstrate that a recessive mutation in KRT10 leading to a complete human K10 knockout can cause EHK. Identification of the heterogeneity of this disorder has a major impact for the accurate genetic counseling of patients and their families and also has implications for gene-therapy approaches.

3T3 Cells↗
PubMed2006

Expression of laminin 5 by parental and c-Ha-ras-transformed HaCaT keratinocytes in organotypic cultures.

Tumor cells traverse the basement membrane zone and gain access to the underlying mesenchyme to eventually form metastases. Laminin 5 is a major component of the basement membrane and connects keratinocytes at the level of hemidesmosomes to the mesenchyme. Underneath invading tumor cells anti-laminin 5 staining is diminished, and laminin 5 degradation products can stimulate cell migration and epidermal growth factor (EGF) receptor signaling. To investigate laminin 5 expression in parental HaCaT and tumorigenic c-Ha-ras-transformed HaCaT II-4rt keratinocytes, the cells were cultivated under monolayer and organotypic culture conditions. In monolayer cultures, HaCaT and c-Ha-ras-transformed HaCaT II-4rt keratinocytes secreted comparable amounts of laminin 5. After 7 days of organotypic cultures, collagen IV, beta4-integrin, nidogen and laminin 5 were detected along the epithelial-mesenchymal interface of parental HaCaT keratinocytes, while staining for these proteins was patchy or absent in the organotypic cultures with c-Ha-ras-transformed HaCaT II-4rt cells. Immunoblotting analysis confirmed absence of laminin 5 deposition in organotypic cultures of c-Ha-ras-transformed HaCaT II-4rt while the protein was detected in organotypic cultures of HaCaT keratinocytes. Surprisingly, however, the alpha3 and gamma2 laminin chain transcripts were strongly induced in c-Ha-ras-transformed HaCaT II-4rt cells by organotypic culture conditions, indicating that invasive epidermal tumor cells retain high mRNA levels for laminin 5 chains and suggesting an autocrine/paracrine induction of the laminin chain mRNAs. Moreover, as laminin 5 was absent in organotypic cultures of c-Ha-ras-transformed HaCaT II-4rt cells, it suggests immediate degradation of the protein. Degradation products may further contribute to the malignant phenotype by enhancing cellular migration and EGF-receptor activation.

Cell Adhesion Molecules↗
PubMed2006

Senescence of human fibroblasts after psoralen photoactivation is mediated by ATR kinase and persistent DNA damage foci at telomeres.

Cellular senescence is a phenotype that is likely linked with aging. Recent concepts view different forms of senescence as permanently maintained DNA damage responses partially characterized by the presence of senescence-associated DNA damage foci at dysfunctional telomeres. Irradiation of primary human dermal fibroblasts with the photosensitizer 8-methoxypsoralen and ultraviolet A radiation (PUVA) induces senescence. In the present study, we demonstrate that senescence after PUVA depends on DNA interstrand cross-link (ICL) formation that activates ATR kinase. ATR is necessary for the manifestation and maintenance of the senescent phenotype, because depletion of ATR expression before PUVA prevents induction of senescence, and reduction of ATR expression in PUVA-senesced fibroblasts releases cells from growth arrest. We find an ATR-dependent phosphorylation of the histone H2AX (gamma-H2AX). After PUVA, ATR and gamma-H2AX colocalize in multiple nuclear foci. After several days, only few predominantly telomere-localized foci persist and telomeric DNA can be coimmunoprecipitated with ATR from PUVA-senesced fibroblasts. We thus identify ATR as a novel mediator of telomere-dependent senescence in response to ICL induced by photoactivated psoralens.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2006

Phosphodiesterase type 5 inhibition is a novel therapeutic option in Raynaud disease.

BACKGROUND: Raynaud disease (RD) is a common disorder affecting 3% to 5% of the healthy population, and occurs in more than 90% of patients with connective tissue diseases. The therapeutic options remain limited, particularly in patients with secondary RD due to connective tissue disease. Theoretical considerations lead to the expectation that phosphodiesterase type 5 inhibitors may improve clinical symptoms and digital blood flow in patients with RD. METHODS: We conducted an open-label pilot study in 40 patients with RD, 33 (82%) of whom had secondary and 7 (18%) of whom had primary RD. Digital blood flow was measured by laser-Doppler flowmetry at room temperature and during the cold-exposure test before medical treatment, 1 hour after the initial intake, and after 2 weeks of continuous treatment (10 mg twice a day) with the novel phosphodiesterase type 5 inhibitor vardenafil. Clinical symptoms were recorded by a patient questionnaire and summarized as the Raynaud condition score. RESULTS: Laser-Doppler flowmetry revealed that vardenafil improved digital blood flow in 28 (70%) patients, whereas 12 (30%) did not respond. In individuals responding, digital blood flow significantly increased by a mean +/- SEM of 21.0% +/- 4.9% and 30.0% +/- 5.7% at 1 hour and 2 weeks of treatment at room temperature, respectively, and by 18.8% +/- 4.4% and 35.1% +/- 7.5% at 1 hour and 2 weeks during the cold-exposure test, respectively (P < .01 for all). Consistently, clinical symptoms improved in 27 (68%) of the 40 patients, and the Raynaud condition score declined from a mean +/- SEM of 5.05 +/- 0.38 to 3.54 +/- 0.31 (P < .001). CONCLUSION: Our data indicate that phosphodiesterase type 5 inhibition significantly improves peripheral blood flow and clinical symptoms in a large subset of patients with RD and, thus, may provide a novel therapeutic approach in such individuals.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2006

Skin lesion development in a mouse model of incontinentia pigmenti is triggered by NEMO deficiency in epidermal keratinocytes and requires TNF signaling.

NF-kappaB essential modulator (NEMO), the regulatory subunit of the IkappaB kinase, is essential for NF-kappaB activation. Mutations disrupting the X-linked NEMO gene cause incontinentia pigmenti (IP), a human genetic disease characterized by male embryonic lethality and by a complex pathology affecting primarily the skin in heterozygous females. The cellular and molecular mechanisms leading to skin lesion pathogenesis in IP patients remain elusive. Here we used epidermis-specific deletion of NEMO in mice to investigate the mechanisms causing the skin pathology in IP. NEMO deletion completely inhibited NF-kappaB activation and sensitized keratinocytes to tumor necrosis factor (TNF)-induced death but did not affect epidermal development. Keratinocyte-restricted NEMO deletion, either constitutive or induced in adult skin, caused inflammatory skin lesions, identifying the NEMO-deficient keratinocyte as the initiating cell type that triggers the skin pathology in IP. Furthermore, genetic ablation of tumor necrosis factor receptor 1 (TNFRI) rescued the skin phenotype demonstrating that TNF signaling is essential for skin lesion pathogenesis in IP. These results identify the NEMO-deficient keratinocyte as a potent initiator of skin inflammation and provide novel insights into the mechanism leading to the pathogenesis of IP.

Animals↗
PubMed2006

Novel and recurrent mutations in keratin KRT5 and KRT14 genes in epidermolysis bullosa simplex: implications for disease phenotype and keratin filament assembly.

Epidermolysis bullosa simplex (EBS) is a group of autosomal dominant genetic skin disorders caused by mutations of the keratin genes KRT5 and KRT14. It is characterised by lysis of basal keratinocytes leading to the development of intraepidermal blisters upon minor mechanical trauma. We investigated 27 EBS patients and families of mainly German origin by sequence analysis of the entire coding sequences of KRT5 and KRT14 and identified 12 novel and seven previously reported mutations within the KRT5 and KRT14 genes. The study discusses possible implications of the novel mutations on protein structure, keratin intermediate filament (KIF) formation and the corresponding phenotype, and summarises the spectrum of mutations reported so far in EBS. Detailed knowledge of the spectrum of EBS mutations and their genotype-phenotype correlation is essential for accurate genetic counselling and prenatal diagnosis.

DNA Mutational Analysis↗
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↗