Chloride channel activity in human lung fibroblasts and myofibroblasts

It is well established that transforming growth factor (TGF)-beta stimulates human lung fibroblasts (HLF) to differentiate into myofibroblasts. We characterized lysophosphatidic acid (LPA)-activated Cl- channel current (I(Cl-LPA)) in cultured human lung fibroblasts and myofibroblasts and investigated the influence of I(Cl-LPA) on fibroblast-to-myofibroblast differentiation. We recorded I(Cl-LPA) using the amphotericin perforated-patch technique. We activated I(Cl-LPA) using LPA or sphingosine-1-phosphate. We determined phenotype by Western blotting and immunohistochemistry using an anti-alpha-smooth muscle actin (SMA) antibody. RT-PCR was performed to determine which phospholipid growth factor receptors are present in HLF. We found that HLF cultured in TGF-beta (myofibroblasts) had significantly elevated alpha-SMA levels and I(Cl-LPA) current density compared with control fibroblasts. I(Cl-LPA) activation was blocked by DIDS, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and the LPA receptor-specific antagonist dioctyl-glycerol pyrophosphate (1 microM). DIDS and NPPB, in a dose-dependent manner, significantly reduced alpha-SMA levels in HLF stimulated with TGF-beta. These results demonstrate the receptor-mediated activation of I(Cl-LPA) by LPA and sphingosine-1-phosphate in cultured human lung myofibroblasts, with only minimal I(Cl-LPA) activity in fibroblasts. This Cl- channel activity appears to play a critical role in the differentiation of human lung fibroblasts to myofibroblasts.     

Pirfenidone attenuates the profibrotic contractile phenotype of differentiated human dermal myofibroblasts

Dysregulated wound healing after burn injury frequently results in debilitating hypertrophic scarring and contractures. Myofibroblasts, the main effector cells for dermal fibrosis, develop from normal fibroblasts via transforming growth factor beta 1 (TGF-β1). During wound healing, myofibroblasts produce extracellular matrix (ECM) proteins, modulate ECM stability, and contract the ECM using alpha smooth muscle actin (α-SMA) in contractile stress fibers. The antifibrotic pirfenidone has previously been shown to inhibit the initial differentiation of fibroblasts into myofibroblasts in vitro and act as a prophylactic measure against hypertrophic scar development in a mouse burn model. To test whether pirfenidone affects differentiated myofibroblasts, we investigated the in vitro effects of pirfenidone treatment after three to five days of stimulation with TGF-β1. In assays for morphology, protein and gene expression, and contractility, pirfenidone treatment produced significant effects. Profibrotic gene expression returned to near-normal levels, further α-SMA protein expression was prevented, and cell contraction within a stressed collagen matrix was reduced. These in vitro results promote pirfenidone as a promising antifibrotic agent to treat existing scars and healing wounds by mitigating the effects of differentiated myofibroblasts.     

Natural killer cells activate human dermal fibroblasts

Human dermal fibroblasts (HDF) undergo activation and secrete cytokines when cocultured with T cells. Here, we identify potent activators of HDF among human peripheral CD2(+)-lymphocytes. Populations with strong HDF activating capacity consisted essentially of cells with a natural killer (NK) surface marker phenotype (CD3(-), CD4(-), CD8(-), CD56(+)). Addition of these cells to HDF resulted in rapid increase of intracellular free calcium concentrations as an early rapid cell activation signal. Upregulation of mRNA encoding for the inflammatory cytokines IL-1 beta and IL-6 as well as for chemokines IL-8 and MCP-1 was detected after cells were cocultured. Elevated concentrations of IL-6 and IL-8 were found in coculture supernatants of HDF and NK-cells. Skin-homing NK cells leaving the blood-stream during an inflammatory skin reaction might therefore represent potent activators of local inflammatory cytokine and chemokine production.     

Differentiation of human dermal fibroblasts towards endothelial cells

The ultimate goal of vascular tissue engineering is the production of functional grafts for clinical use. Difficulties acquiring autologous endothelial cells have motivated the search for alternative cell sources. Differentiation of dermal fibroblasts towards several mesenchymal lineages as well as endothelial cells has been proposed. The aim of the present study was to investigate the endothelial differentiation capacity of human dermal fibroblasts on a gene expression, protein expression and functional physiological level. Endothelial differentiation of fibroblasts was induced by culturing cells in 30% human serum, but not in fetal calf serum. Expression of proteins and genes relevant for endothelial function and differentiation was increased after induction. Furthermore, fibroblasts exposed to 30% human serum displayed increased uptake of low-density lipoprotein and formation of capillary-like networks. The results of this study may have an impact on cell sourcing for vascular tissue engineering, and the development of methods for vascularization of autologous tissue engineered constructs.     

Specific age-associated DNA methylation changes in human dermal fibroblasts

Epigenetic modifications of cytosine residues in the DNA play a critical role for cellular differentiation and potentially also for aging. In mesenchymal stromal cells (MSC) from human bone marrow we have previously demonstrated age-associated methylation changes at specific CpG-sites of developmental genes. In continuation of this work, we have now isolated human dermal fibroblasts from young (<23 years) and elderly donors (>60 years) for comparison of their DNA methylation profiles using the Infinium HumanMethylation27 assay. In contrast to MSC, fibroblasts could not be induced towards adipogenic, osteogenic and chondrogenic lineage and this is reflected by highly significant differences between the two cell types: 766 CpG sites were hyper-methylated and 752 CpG sites were hypo-methylated in fibroblasts in comparison to MSC. Strikingly, global DNA methylation profiles of fibroblasts from the same dermal region clustered closely together indicating that fibroblasts maintain positional memory even after in vitro culture. 75 CpG sites were more than 15% differentially methylated in fibroblasts upon aging. Very high hyper-methylation was observed in the aged group within the INK4A/ARF/INK4b locus and this was validated by pyrosequencing. Age-associated DNA methylation changes were related in fibroblasts and MSC but they were often regulated in opposite directions between the two cell types. In contrast, long-term culture associated changes were very consistent in fibroblasts and MSC. Epigenetic modifications at specific CpG sites support the notion that aging represents a coordinated developmental mechanism that seems to be regulated in a cell type specific manner.     

Heterogeneity of dimer excision in young and senescent human dermal fibroblasts

We have examined the relationship between nucleotide excision of the main UV-induced photoproduct, the cyclobutane pyrimidine dimer and in vitro cellular senescence. An in situ semiquantitative immunocytochemical assay has demonstrated that, following a UV-C dose of 15 J m-2, young human dermal fibroblasts maintained in a high level of serum are more efficient than senescent fibroblasts in the removal of dimers. However, in G0-arrested cultures (serum-starved), young fibroblasts are compromised in their ability to remove dimers and are significantly less efficient than senescent cells in this process. Supplementation of the culture medium with 0.1 mm deoxyribonucleosides enhances the removal of dimers in both young and senescent fibroblasts in proliferating or serum-starved cells. These data indicate that overall there is a modest but significant reduction in nucleotide excision of dimer photoproducts in cells as they age in vitro. In addition, G0-arrested young cells exhibit reduced removal of dimers, although this can be complemented by deoxyribonucleoside addition. In addition, this in situ assay has revealed heterogeneity in both susceptibility to UV-C-induced damage and excision. Overall, we provide evidence of reduced UV-induced damage excision in senescent compared with young fibroblasts, and demonstrate modulation of these processes in young and senescent cells under specific growth conditions.     

Microgravity and hypergravity effects on collagen biosynthesis of human dermal fibroblasts

Astronauts experiencing long periods of space flight suffer from severe loss of bone tissue, particularly in those bones that carry the body weight under normal gravity. It is assumed that the lack of mechanical load decreases connective tissue biosynthesis in bone-forming cells. To test this assumption, quantitative and qualitative aspects of collagen synthesis under microgravity, normal gravity, and hypergravity conditions were investigated by incubating human fibroblast cultures with [³H]-proline for 4, 7, 10, and 20 h during the Spacelab D2-mission in 1993. Quantitative analysis revealed an increase of collagen synthesis under microgravity conditions, being up to 143% higher than in 1 g controls. In contrast, hypergravity samples showed a decrease in collagen synthesis with increasing g, being at the 13% level at 10 g. The relative proportion of collagen in total synthesized protein showed a slight decrease with increasing g. The secretion of collagen by the cells, proline hydroxylation of individual collagen -chains, and the relative proportions of synthesized collagens I, III, and V were not affected under any of the applied conditions.Our research was supported financially by Dara GmbH Bonn (grant. no. 01QV 8866), the Deutsche Forschungsgemeinschaft (SFB A1/367) and BMFT grant. no. 01 KM 9303/8.     

Growth-altering effects of sodium hypochlorite in cultured human dermal fibroblasts

Sodium hypochlorite, the most widely used antimicrobial active chlorine compound in chemical disinfection, is little used as an antiseptic in clinical practice. This study aimed to assess the capacity of hypochlorite to alter human dermal fibroblast growth in vitro in relation to the concentration and exposure time. Effects of decreasing concentrations of hypochlorite (0.5%-0.00025%) on fibroblast adherence capacity and proliferation, according to varying exposure times and fetal calf serum (FCS) concentrations were investigated combining XTT assay, which provides cytochemical quantification of metabolically-active cell number, and total cell protein content, an indirect method for assessing substrate-adhered cell number. Initial cytotoxicity was produced at 0.0075% hypochlorite within contact time of two hours, provoking concentration-dependent cell detachment. From 0.1% upwards, NaOCl exerted a profound cytotoxic effect on fibroblasts. At later stages (4 h) and concentrations > or = 0.01% hypochlorite produced dose-dependent mitochondrial dysfunction: cell survival progressively diminished from 71% to 10%. Cytotoxic effects were not significantly affected by exposure-time periods, probably because maximum chlorine is released within the first four hours. Hypochlorite concentrations from 0.005% to 0.00025% were found to have no inhibitory effects on cell growth; in fact, they appear to exhibit the opposite effect. Increments in protein content found after 24 h exposure ranged from 30% to 120% above control values. Hypochlorite is highly cytotoxic for fibroblasts at concentrations > or = 0.01% provoking concentration-dependent loss of cell adherence capacity and mitochondrial dysfunction. In contrast, a mitogenic effect was observed with concentrations < or = 0.005% which supports NaOCl as a source growth-promoting activity in cultured human fibroblasts. Hypochlorite proved to be a highly reactive molecule which inhibits or stimulates cell division according to the concentration.     

Differentiation of human multipotent dermal fibroblasts into islet-like cell clusters

Background  

We have previously obtained a clonal population of cells from human foreskin that is able to differentiate into mesodermal, ectodermal and endodermal progenies. It is of great interest to know whether these cells could be further differentiated into functional insulin-producing cells.     

Membrane interleukin 1 induction on human endothelial cells and dermal fibroblasts

Human endothelial cells and dermal fibroblasts both expressed a membrane-associated interleukin 1 (IL-1) activity when stimulated with either recombinant tumor necrosis factor (TNF) or recombinant lymphotoxin but stimulated endothelial cells expressed significantly more membrane IL-1 per cell than did fibroblasts. Lipopolysaccharide induced membrane IL-1 activity on endothelial cells but not fibroblasts. Interferon-gamma treatment of endothelial cells and fibroblasts had no direct effect on membrane IL-1 expression and little effect when used as a pretreatment for TNF or lipopolysaccharide stimulation. Endothelial cell membrane IL-1 activity was induced within 24 hr of culture with TNF or lipopolysaccharide, and increased up to 72 hr of incubation. Antibodies raised against human monocyte-derived IL-1 species neutralized the membrane IL-1 activity of TNF-stimulated endothelial cells. Both absorption studies and neutralization with specific sera indicated that endothelial cell membrane IL-1 is structurally related to IL-1 alpha. Endothelial cells expressed both IL-1 beta mRNA in response to TNF, lymphotoxin, and recombinant IL-1 species, as detected by Northern blot analysis. These studies demonstrate that endothelial cells can be activated to express a cell-surface IL-1 activity which is structurally, as well as functionally, related to the secreted form of IL-1.     

A new in vitro wound model based on the co-culture of human dermal microvascular endothelial cells and human dermal fibroblasts

BACKGROUND INFORMATION: Different in vitro models, based on co-culturing techniques, can be used to investigate the behaviour of cell types, which are relevant for human wound and soft-tissue healing. Currently, no model exists to describe the behaviour of fibroblasts and microvascular endothelial cells under wound-specific conditions. In order to develop a suitable in vitro model, we characterized co-cultures comprising NHDFs (normal human dermal fibroblasts) and HDMECs (human dermal microvascular endothelial cells). The CCSWMA (co-culture scratch wound migration assay) developed was supported by direct visualization techniques in order to investigate a broad spectrum of cellular parameters, such as migration and proliferation activity, the differentiation of NHDFs into MFs (myofibroblasts) and the expression of endothelin-1 and ED-A-fibronectin (extra domain A fibronectin). The cellular response to hypoxia treatment, as one of the crucial conditions in wound healing, was monitored. RESULTS: The comparison of the HDMEC-NHDF co-culture with the respective mono-cultures revealed that HDMECs showed a lower proliferation activity when co-cultured, but their number was stable throughout a period of 48 h. NHDFs in co-culture were slightly slower at proliferating than in the mono-culture. The MF population was stable for 48 h in the co-culture, as well as in NHDF mono-culture. Co-cultures and HDMEC mono-cultures were characterized by a slower migration rate than NHDF mono-cultures. Hypoxia decreased both cell proliferation and migration in the mono-cultures, as well as in the co-cultures, indicating the general suitability of the assay. Exclusively, in co-cultures well-defined cell clusters comprising HDMECs and MFs formed at the edges of the in vitro wounds. CONCLUSIONS: On the basis of these results, the CCSWMA developed using co-cultures, including HDMECs, NHDFs and MFs, proved to be an effective tool to directly visualize cellular interaction. Therefore, it will serve in the future to evaluate the influence of wound-healing-related factors in vitro, as shown for hypoxia in the present study.     

Anti-fas induces apoptosis and proliferation in human dermal fibroblasts: Differences between foreskin and adult fibroblasts

Apoptosis, or programmed cell death, is a naturally occurring process mediated by extracellular signals. We studied anti-Fas (CD95/Apo-1) antibody-induced apoptosis in cultured human foreskin and adult dermal fibroblasts. Induction of apoptosis was identified by fluorescence in situ DNA end-labeling. Anti-Fas antibody induced apoptosis in fibroblasts in a dose- and time-dependent manner. Adult dermal skin fibroblasts were more susceptible to anti-Fas antibody-induced apoptosis than foreskin fibroblasts, with 21–52% dead cells in different strains. In foreskin fibroblasts, anti-Fas antibody (1.0 μg/ml) predominantly induced proliferation ([³H]thymidine incorporation increased to 115–165% of control level) and only low levels of apoptotic cell death after 48 hours of treatment. No induction of proliferation by anti-Fas was found in the adult fibroblasts. Addition of tumor necrosis factor-α (TNF-α) slightly augmented the anti-Fas antibody-induced apoptosis in both cell types. When we examined the levels of Fas expression using flow cytometry, we found two- to threefold higher Fas expression in adult fibroblasts. C6-ceramide treatment, which induces Fas-independent apoptosis, gave similar levels of cell death in both foreskin and adult fibroblasts. No proliferation was observed in C6-ceramide-treated fibroblasts. Thus, this difference in apoptosis between adult dermal and foreskin fibroblasts appears to be related to the level of Fas expression. When clones of foreskin fibroblasts were examined, there was heterogeneity of anti-Fas antibody-induced apoptosis and proliferation in the cloned fibroblast subpopulations, but this was not correlated with differences in Fas expression. Alterations in fibroblast populations during the process of differentiation and aging may result from selective loss of apoptosis-susceptible populations. J. Cell. Physiol. 175:19–29, 1998. © 1998 Wiley-Liss, Inc.     

以人皮肤成纤维细胞作为饲养层细胞培养人胚胎干细胞

目的：比较人皮肤成纤维细胞（humandermalfibroblasts,HDFs）与小鼠胚胎成纤维细胞（Mouseembryonicfibroblasts,MEFs）的增殖能力及研究人皮肤成纤维细胞作为饲养层支持人胚胎干细胞（humanembryonicstemcells,hESCs）未分化生长的能力。方法：利用组织贴壁法从人皮肤中分离出HDFs,通过细胞形态的观察和生长曲线的绘制比较HDFs与MEFs的体外增殖能力。将HDFs作为饲养层细胞与hESCs共培养,传代12代后,检测hESCs碱性磷酸酶（AKP）、表面特异性标志及胚胎干细胞特异性转录因子。结果：HDFs可连续传代培养15代以上,10代以下的HDFs增殖迅速,而MEFs自第4代起,增殖能力就明显下降;hESCs在HDFs饲养层上可传代培养12代以上,克隆边界清晰,细胞排列紧密,碱性磷酸酶、表面标志物检测均呈阳性,表达了hESCs特异性转录因子。结论：HDFs比MEFs具有更强的增殖能力;HDFs可作为培养hEscs的饲养层细胞。     

Elaboration of biodegradable polymer substrate for cultivation of human dermal fibroblasts

The influence of polylactic acid (PLA) surface films on the pattern of cell behavior was studied. The human dermal fibroblasts were cultivated on PLA covered glasses. The hydrophobic nature of PLA films depends on the availability of polymer solvent in the film preparation. PLA films obtained from a more polar solvent--aceton--appeared to be more hydrophilic than those obtained from methylene chloride. More hydrophilic polymer films also appeared to be more preferable for cell cultivation, and human dermal fibroblasts demonstrated a better adhesion and proliferation on hydrophilic rather than on hydrophobic PLA films.     

Induction of telomerase activity increase reprogramming efficiency of human dermal fibroblasts

Reprogramming of human cells is a perspective direction of development of Cell Biology with the distant prospect of using these methods for cellular-replacing therapy in clinical practice. One of the problems rising in this regard is low reprogramming efficiency and application of undesirable oncogenes in initial techniques. In this research, we had offered the alternative modified method of reprogramming human skin fibroblasts. It has been shown that the telomerase induction increases an exit of reprogrammed cells and allows excluding oncogene c-Myc from a used set of genes.     

Relaxin modulates synthesis and secretion of procollagenase and collagen by human dermal fibroblasts

Relaxin is believed to play a role in connective tissue remodeling during pregnancy (Bell, R.J., Eddie, L. W., Lester, A. R., Wood, E. C., Johnston, P.D., and Niall, H. D. (1987) Obstet. Gynecol. 69, 585-589; MacLennan, A. H. (1983) Clin. Reprod. Fertil. 2, 77-95). In the present study, normal human fibroblasts exposed to concentrations of a synthetic bioactive relaxin peptide from 0.1 to 10 ng/ml synthesized and secreted the metalloproteinase procollagenase, which was immunoprecipitable as a doublet of 52 and 57 kDa by a monoclonal antibody to human collagenase. The stimulation in procollagenase protein expression was reflected in an elevation in procollagenase mRNA levels. Media conditioned for 48 h by relaxin-treated fibroblasts (0.1 ng/ml) contained 1.7 units/ml activatable collagenase compared with 0.2 units/ml by untreated fibroblasts. In addition, relaxin caused a modest decrease in the levels of tissue inhibitor of metalloproteinases, as detected by reverse zymography and Northern analysis. Relaxin was also a potent modulator of the collagen secretory phenotype of these fibroblasts. Relaxin at 100 ng/ml down-regulated collagen secretion by 40%. When fibroblasts were treated simultaneously with cytokines such as transforming growth factor beta or interleukin 1 beta, which stimulated collagen synthesis to at least 9-fold of basal levels, relaxin at 100 ng/ml was able to down-regulate collagen expression by up to 88%. This decrease was reflected by changes at the mRNA level. These results indicate that relaxin can cause significant collagen turnover both by stimulating collagenase expression and by down-modulating collagen synthesis and secretion.