Opposite effects of tumour necrosis factor-alpha on type I and III collagen gene expression by human dermal fibroblasts in monolayer and three-dimensional cultures

Chronic exposure of interleukin-13 suppress the induction of matrix metalloproteinase-1 by tumour necrosis factor α in normal and scleroderma dermal fibroblasts through protein kinase B/Akt

Peripheral blood mononuclear cells taken from patients with scleroderma express increased levels of interleukin (IL)-13. Moreover, the expression of matrix metalloproteinase-1 (MMP-1) from involved scleroderma skin fibroblasts is refractory to stimulation by tumour necrosis factor (TNF)-α. To elucidate the mechanism(s) involved, we examined the effect of IL-13 on TNF-α-induced MMP-1 expression in normal and scleroderma human dermal fibroblast lines and studied the involvement of serine/threonine kinase B/protein kinase B (Akt) in this response. Dermal fibroblast lines were stimulated with TNF-α in the presence of varying concentrations of IL-13. Total Akt and pAkt were quantitated using Western blot analyses. Fibroblasts were treated with or without Akt inhibitor VIII in the presence of IL-13 followed by TNF-α stimulation. MMP-1 expression was analysed by real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA). Statistical analysis was performed using analysis of variance (anova) or Student's t-test. Upon TNF-α stimulation, normal dermal fibroblasts secrete more MMP-1 than systemic sclerosis (SSc) fibroblasts. This increase in MMP-1 is lost when fibroblasts are co-incubated with IL-13 and TNF-α. IL-13 induced a significant increase in levels of pAkt in dermal fibroblasts, while Akt inhibitor VIII reversed the suppressive effects of IL-13 on the response of cultured fibroblasts to TNF-α, increasing their expression of MMP-1. We show that IL-13 suppresses MMP-1 in TNF-α-stimulated normal and scleroderma dermal fibroblast. Akt inhibitor VIII is able to reverse the suppressive effect of IL-13 on MMP-1 expression and protein synthesis. Our data suggest that IL-13 regulates MMP-1 expression in response to TNF-α through an Akt-mediated pathway and may play a role in fibrotic diseases such as scleroderma.

Novel tuberculosis susceptibility candidate genes revealed by the reconstruction and analysis of associative networks

Tuberculosis (TB) is a common infectious disease caused by M. tuberculosis. The risk of the disease is dependent on complex interactions between host genetics and environmental factors. Accumulated genomic data, along with novel methodological approaches such as associative networks, facilitate studies into the inherited basis of TB. In the current study, we carried out the reconstruction and analysis of an associative network representing molecular interactions between proteins and genes associated with TB. The network predominantly comprises of well-studied key proteins and genes which are able to govern the immune response against M. tuberculosis. However, this approach also allowed us to reveal 12 proteins encoded by genes, the polymorphisms of which have never been studied in relation to M. tuberculosis infection. These proteins include surface antigens (CD4, CD69, CD79, CD80, MUC16) and other important components of the immune response, inflammation, pathogen recognition, cell migration and activation (HCST, ADA, CP, SPP1, CXCR4, AGER, PACRG). Thus, the associative network approach enables the discovery of new candidate genes for TB susceptibility.

Evaluation of anti-inflammatory and atrophogenic effects of glucocorticoids on reconstructed human skin

Topical glucocorticoids (GCs) are extensively used in the treatment of inflammatory skin diseases. However, their long-term use is often accompanied by severe and eventually irreversible adverse effects, with atrophy being the most important limitation. Currently, most non-clinical studies involve animal testing, so the results are not always representative of the situation in humans. The aim of this project was to establish an in vitro test protocol for the evaluation of the anti-inflammatory and atrophic potential of topically applied GCs in reconstructed human skin. Initial studies with fibroblasts and keratinocytes confirmed the anti-inflammatory and atrophogenic effects of GCs, as evidenced by decreased cytokine production and collagen mRNA expression. In non-pretreated reconstructed human skin (EpiDermFT™), the topical application of GCs for seven days strongly reduced the secretion of interleukin (IL)-6. GC-induced skin atrophy, known to appear only after prolonged treatment, was not detected by the analysis of epidermal thickness and collagen mRNA expression. However, reproducible epidermal inflammation was established for the first time in reconstructed human skin. Topical treatment with tumour necrosis factor (TNF) increased IL-6 release and strongly reduced epidermal thickness accompanied by severe parakeratosis. GC treatment of reconstructed human skin reduced IL-6 levels and completely resolved parakeratosis, leading to the normalisation of epidermal thickness. These induced inflammatory conditions mimic more closely the clinical situations in which GCs are used, and therefore appear to be more suitable for future investigations for the establishment of a human-based in vitro test protocol for evaluating wanted and unwanted GC effects.

Hypoxia-induced increase of matrix metalloproteinase-1 synthesis is not restored by reoxygenation in a three-dimensional culture of human dermal fibroblasts

BACKGROUND

Delayed wound healing is multi-factorial. Although ischemic change is considered to be crucial, little is known about the effects of hypoxia or reoxygenation on the connective tissue metabolism by human dermal fibroblasts.

OBJECTIVE

The aim of this study is to determine whether or not hypoxia (2% O(2)) or reoxygenation (20% O(2)) affects mRNA expression and production of matrix metalloproteinase-1 (MMP-1), type I collagen, tissue inhibitors of metalloproteinase-1 (TIMP-1), and transforming growth factor-beta1 (TGF-beta1) by human dermal fibroblasts in a three-dimensional culture.

METHODS

We introduced the three-dimensional culture of human dermal fibroblasts with experimental wound. After wounding, cells were incubated under hypoxic (2%) or normoxic (20%) condition, and harvested at 24, 36, 48, and 72 h (n=8). In the reoxygenation study (n=4), cells were first exposed to a hypoxic condition for 72 h and further incubated under a normoxic condition for 72 h.

RESULTS

The relative ratio (hypoxia/normoxia) of MMP-1 mRNA expressions were significantly elevated at 36 and 48 h compared with those at 12 h (P<0.05). The relative ratio of proMMP-1 was also significantly increased at 48 and 72 h compared with that at 12 h (P<0.001 and P<0.05, respectively). There were no significant changes in mRNA and protein levels of type I collagen, TGF-beta1, and TIMP-1. In a reoxygenic condition, 72 h reoxygenation after 72 h hypoxia, the hypoxia-induced alterations of MMP-1 and carboxyterminal propeptide of type I procollagen (PIP) were not restored.

CONCLUSION

Our results indicate that hypoxia may be responsible for delayed wound healing by inducing an increase of MMP-1 synthesis.

Hypoxic conditions decrease the mRNA expression of proalpha1(I) and (III) collagens and increase matrix metalloproteinases-1 of dermal fibroblasts in three-dimensional cultures

The effect of hypoxia on the expression of extracellular matrix-related genes by human dermal fibroblasts was investigated using a novel three-dimensional culture supplemented with L-ascorbic acid 2-phosphate. Experiments were performed by placing replicate dishes in either hypoxic (2%) or in normoxic (20%) condition for various periods of time ranging up to 72 h. The mRNA expression levels of proalpha1(I), proalpha1(III) collagens and MMP-1 were analyzed using Northern blotting. Hypoxia transiently increased proalpha1(I) and proalpha1(III) collagen gene expression at 24 h, but a prolonged exposure to hypoxia decreased them. A slight increase in MMP-1 mRNA was observed at 24 h and prolonged exposure for up 72 h resulted in significantly increased expression of MMP-1 gene. Our results suggest that enhanced degradation as well as decreased synthesis of collagens induced by hypoxia may account for the delayed wound healing associated with circulatory disturbances.

Differential effect of etretinate on proliferation and extracellular matrix metabolism of human dermal fibroblasts from elderly and young individuals in a novel three-dimensional culture

The effect of etretinate on proliferation and biosynthesis of collagens and glycosaminoglycans (GAGs) were investigated using human dermal fibroblasts in a novel three-dimensional culture supplemented with L-ascorbic acid 2-phosphate. Fibroblasts from two young and two elderly individuals were studied at different concentrations of etretinate, 0.25, 1.0 and 2.5 microg/ml. Collagens (hydroxyproline) and GAGs (disaccharide units) extracted from the cell layer were analyzed and quantified biochemically by high-performance liquid chromatography (HPLC). Etretinate showed no significant effect on fibroblast proliferation either in the monolayer or the three-dimensional culture. Etretinate increased the collagen or GAGs content in the cell layer, which was prominent at etretinate concentrations of 1.0 and 2.5 or 0.25 microg/ml, respectively in fibroblasts from the elderly (P < 0.05). This effect was not seen in dermal fibroblast from the young. These results suggest that etretinate may have the differential effect on collagen and GAG metabolisms depending on the donor age of the cultured fibroblasts.

Topical tamoxifen--a potential therapeutic regime in treating excessive dermal scarring?

Abnormal dermal scarring which affects a large number of people is aesthetically disfiguring and can be functionally disabling. Existing medical and surgical strategies to prevent or to treat scars are frequently disappointing and more effective therapies are needed. Tamoxifen, which has been used extensively in the treatment of breast cancer over the last 20 years has recently been shown to inhibit the proliferation of fibroblasts cultured from keloid biopsies. Successful treatment of retroperitoneal fibrosis and desmoid tumours with tamoxifen has also been reported. We have investigated the potential of tamoxifen as an inhibitor of wound contraction, using fibroblast-populated collagen lattices as an in vitro model. From these studies we postulate that tamoxifen may have potential clinical significance in the treatment of abnormal scarring. Normal adult human skin fibroblasts were embedded within type I collagen, then medium either with or without addition of tamoxifen was added to the collagen lattices. Lattice diameters were measured at intervals to assess the influence of tamoxifen on the lattice contraction. The reversibility of the inhibitory effect of tamoxifen on lattice contraction was investigated by 'washing out the tamoxifen' at different time-points. To visualise changes in the morphology of fibroblasts MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] was added to the lattices. Tamoxifen at 1 and 5 microM had no significant influence on lattice contraction but higher concentrations of 50 and 100 microM completely inhibited contraction. At intermediate concentrations from 10 to 20 microM the degree of lattice contraction was dose-dependent. The reversibility of the inhibition was both dose- and time-dependent. Both the inhibition of contraction and the reversibility of inhibition appeared to correlate with changes in fibroblast morphology. The dose- and time-dependent inhibition of contraction by fibroblasts suggests that tamoxifen could be investigated as a novel potential therapeutic agent in treating abnormal dermal scarring.