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PubMed1995

Three patterns of cytokine expression potentially involved in epithelial-fibroblast interactions of human ocular surface.

Signals transmitted from mesenchyme to epithelia or vice versa constitute the basis of reciprocal epithelial-mesenchymal interactions. As a first step toward understanding epithelial-mesenchymal interactions on the ocular surface where the transit amplifying cell-containing corneal epithelium is anatomically separated from the stem cell-containing limbal epithelium, we sought to characterize the expression patterns of cytokines and their receptors by primary epithelial and early-passaged fibroblast cultures of human cornea and limbus. Northern hybridization with oligonucleotide and cDNA probes to a total of 25 cytokines and 12 of their receptors revealed that the positively expressed cytokines could be divided into the following four patterns. Type I: TGF-alpha, IL-1 beta, and PDGF-B were expressed exclusively by epithelial cells but their respective receptors EGFR and IL-1R were predominantly and PDGFR-beta was exclusively expressed by fibroblasts. Type II: IGF-I, TGF-beta 1, -beta 2, LIF, and bFGF, and their receptors were expressed by both epithelial cells and fibroblasts. FGFR-1 (flg) and FGFR-2 (bek) were expressed more by fibroblasts and bFGF was expressed more by corneal than limbal epithelial cells. Type III: keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) were expressed exclusively by fibroblasts and their respective receptors, KGFR and c-met, were predominantly expressed by epithelial cells. Combined with RT-PCR, the quantity of KGF and KGFR transcripts was highest in limbal fibroblasts and epithelial cells, respectively. In contrast, the quantity of HGF and HGFR (c-met) transcripts was highest in corneal fibroblasts and epithelial cells, respectively. Type IV: M-CSF and IL-8 were expressed by fibroblasts and/or epithelial cells but their receptors were not expressed by epithelial cells nor fibroblasts, but by immune or inflammatory cells. In addition to these potential paracrine actions, autocrine actions mediated by TGF-alpha/EGFR, IL-1 beta/IL1-R, and bFGF/FGFR-1 were more expressed by corneal than limbal epithelial cells. Immunofluorescence staining on human corneoscleral cryosections confirmed that EGFR and bFGF were not expressed by the limbal basal epithelium, but expressed strongly by the corneal epithelium, a pattern consistent with Northern hybridization. These results indicate that ocular surface epithelial cells and fibroblasts can express a myriad of cytokines, among which the first three patterns constitute the network of potential epithelial-mesenchymal cytokine dialogues. The difference of certain cytokine expression between corneal and limbal regions suggests that this network participates in normal epithelial growth and differentiation, and plays an important role in wound healing.

Adult↗
PubMed1987

Alveolar macrophage/peripheral blood monocyte-derived factors modulate proliferation of primary lines of human lung fibroblasts.

Pulmonary fibrosis is characterized by an alteration in lung collagen synthesis and deposition, as well as by increased fibroblast proliferation. It is also characterized by an intermittent influx of immune and inflammatory cells in the lung. To investigate the nature of the target cell in this disorder, we established a series of primary lines of human adult lung fibroblasts and studied the effect of mediators released from activated normal human alveolar macrophages (AM) and peripheral blood monocytes (PBM) on the proliferation of both normal lung fibroblasts and fibroblasts established from lung tissue of patients with active fibrosis. Our data show that monocyte supernatants containing a 15-18 kD monokine from either AM or PBM inhibits growth of logarithmic phase proliferating lung fibroblasts in a dose-dependent manner. This effect can be entirely abrogated by treating the fibroblasts with indomethacin and is reconstituted by adding exogenous PGE2. A study of the kinetics of this interaction shows that exposure to monocyte supernatant for 30 min to 1 hr is sufficient to cause significant inhibition of fibroblast proliferation and that this effect can be halted, but not reversed, at any stage by incubation with indomethacin. We also show that fibroblasts derived from patients with pulmonary fibrosis are affected more quickly by exposure to the mediators, although the final extent of inhibition seen at each concentration of mediators is similar in normal and "fibrotic" fibroblasts. These studies indicate that activated AM or PBM release cytokines (including IL-1) which inhibit the growth of proliferating normal and fibrotic fibroblasts through activation of the intrinsic arachidonic acid pathway of this cell and also that this effect requires a continuous activation of this pathway to be fully expressed.

Biological Products↗
PubMed1995

Unique patterns of regulation of nitric oxide production in fibroblasts.

The pathways regulating rat and mouse embryonic and lung fibroblast nitric oxide production were analyzed in an attempt to evaluate the potential role of these cells in nonspecific host defense and inflammation. Interleukin-1 beta (IL-1 beta) was found to be the strongest single activator in all types of fibroblasts examined. In addition, lipopolysaccharide (LPS) was synergistic with IL-1 beta or tumor necrosis factor-alpha (TNF-alpha) in induction of nitric oxide synthesis. These patterns of responsiveness are not observed in macrophages and may be significant in initiation of early host defense processes, before specific interferon-gamma (IFN-gamma)-mediated immune responses have become operative. Rat and mouse fibroblasts were also found to produce nitric oxide when primed with IFN-gamma and simultaneously treated with IL-1, TNF-alpha, or LPS. The doses of IFN-gamma effective in priming fibroblasts for nitric oxide production were as low as 1-10 U/ml. Furthermore, effective triggering doses of LPS, TNF-alpha, and IL-1 were 10 ng/ml, 100 U/ml, and 0.2 ng/ml, respectively. These results demonstrate that fibroblasts are activated more readily to produce nitric oxide than interstitial macrophages and may be the major source of this mediator in tissues. Immunohistochemical studies demonstrated that fibroblasts are heterogeneous with respect to inducible nitric oxide synthase expression with the majority of cells not involved in the response. Fibroblasts were also found to be distinct from macrophages in their sensitivity to the suppressive effects of transforming growth factor-beta, which in fibroblasts inhibited both IFN-gamma plus LPS- and IFN-gamma plus TNF-alpha-induced nitric oxide production. At the stage of growth crisis, a dramatic increase in nitric oxide production was observed in rat fibroblasts in response to IFN-gamma or TNF-alpha that may be directly correlated with cellular senescence. Taken together, our data suggest that mouse and rat fibroblasts are potential effectors in both IFN-gamma-dependent and -independent nitric oxide-mediated processes and that the patterns regulating nitric oxide metabolism in these cells are distinct from those of macrophages.

Animals↗
PubMed2004

Gene expression profiles from hypertrophic scar fibroblasts before and after IL-6 stimulation.

The structural rearrangement of collagen fibres in hypertrophic scar causes abnormal contracture, low tensile strength, and raised scars, which cause functional impairment and disfigurement. It is hypothesized that changes in the genes of cytokines, extracellular matrix proteins, and proteins regulating programmed cell death are related to hypertrophic scar formation. To test this hypothesis, fibroblasts were cultured from hypertrophic scars and their response to interleukin-6 (IL-6) stimulation was studied by defining their gene expression profiles. Affymetrix gene chip analysis was used to identify up- or down-regulation in the 12 625 genes present in the affymetrix array. RT-PCR and ELISA assays were used to validate microarray expression profiles further. Comparison of gene profiles showed an increase of 12 genes in hypertrophic scar fibroblasts compared with normal skin fibroblasts, while the expression of 14 genes decreased. Thirty-three genes were affected by IL-6 treatment in the hypertrophic scar fibroblasts, while 57 genes were affected in normal skin fibroblasts. Messenger RNA to beta-actin ratios for matrix metalloproteinase-1 (MMP-1) and MMP-3 were increased with IL-6 in normal skin fibroblasts from 2.43 +/- 0.06 to 5.50 +/- 0.45 and from 0.75 +/- 0.09 to 1.98 +/- 0.01, respectively. No change in these matrix metalloproteinases could be shown with IL-6 stimulation in hypertrophic scar fibroblasts. Secreted protein levels of pro-MMP-1 and MMP-3 were elevated in the supernatants from normal skin fibroblasts from 2.00 +/- 0.09 and 1.72 +/- 0.10 ng/ml to 4.60 +/- 0.12 and 3.41 +/- 0.20 ng/ml, respectively, after treatment with IL-6 (p < 0.05). No changes were observed in hypertrophic scar fibroblasts treated with IL-6. Values are means +/- SEM. The absence of any up-regulation of MMP-1 and MMP-3 in hypertrophic scar fibroblasts, in response to IL-6, suggests that suppression of matrix metalloproteinases may play a role in the excessive accumulation of collagen formed in hypertrophic scars. While the pathogenesis of abnormal hypertrophic scars remains poorly understood, the use of gene expression arrays may prove helpful in identifying the mechanisms responsible for this type of abnormal scar formation and in formulating an effective therapeutic protocol.

Cells, Cultured↗
PubMed1997

Increased expression of caveolin-1 in heterozygous Niemann-Pick type II human fibroblasts.

Human Niemann-Pick type II fibroblasts, which encompass the panethnic type C (NPC) and Nova Scotia Acadian type D (NPD) variants, exhibit altered expression of caveolin-1 protein when examined by immunoblotting using an anti-caveolin-1 monoclonal antibody. Unexpectedly, caveolin-1 in heterozygous fibroblasts was significantly elevated as much as 10-fold compared to caveolin-1 in normal and homozygous affected fibroblasts. Homozygous NPC fibroblasts expressed caveolin-1 levels similar to those in normal fibroblasts, while the expression of caveolin-1 in homozygous NPD fibroblasts was slightly elevated. Northern analysis indicates that normal fibroblasts and NPC heterozygous fibroblasts have similar amounts of caveolin-1 mRNA, while NPC homozygous fibroblasts have significantly less caveolin-1 mRNA. In contrast, heterozygous and homozygous NPD fibroblasts exhibit increased levels of caveolin-1 mRNA. These novel findings suggest that caveolin-1 containing subcellular structures are involved in the pathophysiology of Niemann-Pick type II disease. Furthermore, altered caveolin-1 protein expression may serve as a useful marker for the diagnosis of carriers of NPC or NPD.

Caveolin 1↗
PubMed1993

Copper effects on metal regulatory factors of cultured human fibroblasts.

The effects of copper on metal regulatory factors were studied in cultured human fibroblasts using mobility shift assays and protein blotting. A mobility shift was apparent on polyacrylamide gels when fibroblast whole cell extracts were reacted with a 32P-labeled 14-base-pair MREa sequence of the hMT IIA gene. Binding was specific, since the shifted band was not competed away by MREa analogs containing two base changes. Known transcription factors SP1, AP1, AP2, and OCT1 did not compete with the fibroblast metal regulatory element binding protein (MREBP) for binding to the MREa probe. When fibroblasts were grown in 200 or 800 microM copper, binding of the MREBP was enhanced. Protein blotting experiments were performed by electrophoresing cell extracts, blotting onto nitrocellulose, and probing with the 32P-labeled MREa 14-mer. A 112-kDa band, apparent in HeLa cell nuclear extract as well as fibroblast whole cell extract, was not influenced by the presence of copper in the growing fibroblasts. A 34-kDa protein, also present in both HeLa cells and fibroblasts, appeared to correspond with the protein causing the mobility shift. Copper added to the fibroblast growth media enhanced binding of the 34-kDa protein to MREa using the blotting procedure. We conclude that the fibroblast 34-kDa MREBP is a positive regulatory factor influenced by copper. Human fibroblasts can be employed to further study metal regulatory factors whose binding to metal regulatory elements is influenced by copper and other heavy metals.

Base Sequence↗
PubMed1996

Effects of interleukins on Crouzon fibroblast phenotype in vitro. Release of cytokines and IL-6 mRNA expression.

In Crouzon's syndrome, the cranial morphogenic processes are altered due to the early fusion of the facial and basal cranial bones. Evidence that Crouzon fibroblasts have an altered phenotype which is modulated by interleukin 1 (IL-1) and interleukin 6 (IL-6) is provided. [3H]Thymidine incorporation and cell count studies showed that Crouzon fibroblasts have an accelerated proliferation rate. [3H]Glucosamine incorporation studies, followed by chromatography analysis of culture medium samples, revealed that the various classes of glycosaminoglycans (GAG) secreted into the medium were differently distributed in Crouzon and normal fibroblasts. Crouzon fibroblasts secreted less total GAG, particularly hyaluronic acid (HA) and heparan sulfate (HS), but a relatively greater quantity of chondroitin sulfate. Type I and III collagen were raised in Crouzon fibroblast medium whereas the concentration of fibronectin was lower than in normal cells. Interleukin treatment induced changes in cell growth and neosynthesis of extracellular matrix macromolecules. Both IL-1 and IL-6 stimulated proliferation of Crouzon fibroblasts, whereas only IL-6 increased [3H]thymidine incorporation in normal cells. IL-1 provided a drop in HA and a rise in GAG sulfates in normal fibroblasts, but caused an opposite effect in Crouzon fibroblasts. Type I collagen and fibronectin secretions are differently modulated by the cytokines in the two populations. Moreover, level of IL-1 able to stimulate [3H] thymidine incorporation into mouse thymocytes, and level of IL-1 receptor antagonist (IL-1ra), as determined by ELISA, were higher in pathological than in normal fibroblasts. Also evidence that levels of IL-1 alpha and IL-6 proteins measured by ELISA and also IL-6 mRNA expression are enhanced in Crouzon fibroblasts is provided. These novel data suggested that, in Crouzon's syndrome, the modifications in the relative concentrations of the extracellular matrix (ECM) components associated with the abnormal cytokine networks may alter the balance of the microenvironment where the morphogenic events take place.

Adolescent↗
PubMed1997

Transforming growth factor-beta 1 modulates myofibroblastic phenotype of rat palatal fibroblasts in vitro.

The effects of transforming growth factor-beta 1 (TGF-beta 1) on normal rat palatal fibroblasts in vitro were investigated in the present study in order to unravel the precise mechanisms by which the phenotypic modulation of fibroblasts occurs during the scar formation process. TGF-beta 1 dramatically changed the morphology of normal palatal fibroblasts from polygonal into an elongated shape, which was very similar to that of fibroblasts derived from experimental immature scar tissue in rat palatal mucosa. This morphological transition was concomitant with an increase in the expression of alpha-smooth muscle (alpha-SM) actin protein, a marker for myofibroblasts, when determined by immunocytochemistry. An immunoblot study also revealed that alpha-SM actin expression in palatal fibroblasts became evident after 24 h of TGF-beta 1 treatment and increased time-dependently up to 72 h. Northern blot analysis showed that TGF-beta 1 stimulated endogenous TGF-beta 1 mRNA expression in palatal fibroblasts within 24 h. Neither epidermal growth factor nor basic fibroblast growth factor had any effect on either alpha-SM actin expression or TGF-beta 1 mRNA expression. Pretreatment of palatal fibroblasts with TGF-beta 1 significantly increased the contractile capacity in a three-dimensional collagen gel culture, even when the culture medium was deprived of TGF-beta 1 for 72 h of the experimental period. Moreover, the contractility of scar fibroblasts, which highly expressed alpha-SM actin protein and TGF-beta 1 mRNA, was significantly lowered by a neutralizing antibody to TGF-beta 1. These data strongly suggest that TGF-beta 1 is a potential inducer of phenotypic expression of myofibroblasts in palatal fibroblasts and that auto-induction of TGF-beta 1 mRNA expression may play an important role in the scar formation process in palatal mucosa.

Actins↗
PubMed1997

Fibroblasts can modulate the phenotype of malignant epithelial cells in vitro.

An organotypic, tridimensional cell culture, also called a raft system, was used to study the influence of fibroblasts on epithelial carcinogenesis in a cell line derived from laryngeal squamous cell carcinoma and harboring a mutated p53. Differences between the effects of normal fibroblasts and those of tumor-derived fibroblasts were compared by means of fibroblasts taken from the normal skin and from the tumor of a cancer patient and cultivated with epithelial carcinoma cells in an organotypic culture. To study cell contact-mediated changes, the fibroblasts were either simply embedded in collagen matrix or additionally brought into direct contact with epithelial cells. Control epithelial cells were cultivated without any fibroblasts in an organotypic model. A protein panel [p53, p21, PCNA, bcl-2, Ki67, total cytokeratin (CK), CK 8, CK 10, CK 17, CK 18, CK 19, vimentin] involved in cell cycling and epithelial differentiation was assessed immunocytochemically in all organotypic cultures with fibroblasts, in tumor cells cultivated as a monolayer, and in the original tumor sample. The most dysplastic phenotype was obtained when tumor-derived fibroblasts were used in direct contact with epithelial cells, whereas the most benign phenotype was seen when skin fibroblasts had no contact with them. The intensive staining seen for p53 can be explained by p53 mutations also reflecting the weak expression of p21 and abundant expression of PCNA. The intensive Ki67 staining seen in all sections paralleled that of PCNA and marked active cellular proliferation. The CK staining pattern seen in cultured epithelia toward embryonic CKs, CK 8 and CK 18, suggested a simple epithelial phenotype. CK 19 was found only in the epithelium where no direct contacts had occurred. Vimentin expression increased when the raft epithelium was shifting toward a more benign phenotype. The results stress the importance of the origin of fibroblasts as well as the role of direct cellular contacts in modifying the epithelial phenotype even when the epithelial cells are malignant.

Adult↗
PubMed2002

Tamoxifen decreases fibroblast function and downregulates TGF(beta2) in dupuytren's affected palmar fascia.

BACKGROUND: Dupuytren's contracture is a fibroproliferative disorder that is associated with increased collagen deposition. Isoforms of transforming growth factor beta (TGF(beta)), normally TGF(beta1) and TGF(beta2), are involved in the progressive fibrosis of Dupuytren's disease. It has been suggested that downregulation of TGF(beta) may be useful in the treatment of the condition. Tamoxifen, a synthetic nonsteroidal antiestrogen, is known to modulate the production of TGF(beta). This study examined the role of tamoxifen in decreasing fibroblast function and downregulating TGF(beta2). METHODS: Primary cultures of fibroblasts were obtained from Dupuytren's affected fascia and carpal tunnel affected fascia as a control. Collagen lattices were prepared and populated with the fibroblasts. The fibroblast-populated collagen lattices (FPCL) were then measured for contraction every 24 h for 5 days. Supernatant was obtained from the culture medium following completion of the FPCL portion of the experiment and used for a TGF(beta2) immunoassay. RESULTS: Dupuytren's affected fibroblasts contracted the FPCLs significantly more than carpal tunnel control fibroblasts. Treating the fibroblasts with tamoxifen caused a decreased contraction rate in both Dupuytren's affected fibroblasts and carpal tunnel controls. There was increased TGF(beta2) expression in the Dupuytren's affected fascia group compared to the carpal tunnel control group. Tamoxifen decreased TGF(beta2) expression in Dupuytren's affected fascia group but not in the carpal tunnel control group. CONCLUSION: TGF(beta) appears to be the key cytokine in the fibrogenic nature of Dupuytren's disease. Tamoxifen treatment has been demonstrated to decrease the function of fibroblasts derived from Dupuytren's affected fascia and downregulated TGF(beta2) production in these same fibroblasts. These data suggest a method to manipulate and control Dupuytren's contracture in the clinical setting.

Carpal Tunnel Syndrome↗
PubMed1994

Nicotine regulates collagen gene expression, collagenase activity, and DNA synthesis in cultured cardiac fibroblasts.

Cardiac fibroblasts that reside in the interstitium are the cellular origin of collagen and other proteins of the extracellular matrix in the heart. We have previously shown that in vitro gene expression, proliferation and even phenotypic features of cardiac fibroblasts are subject to regulation by biological factors such as hormones, growth factors and neurotransmitters. The influence of nicotine, the active ingredient of tobacco, on risk factors for cardiac diseases is well known. In vivo adverse effects of nicotine are as the result of its direct and indirect effects. The cellular and molecular mechanisms of direct effects of nicotine in the heart are widely unknown. The objective of this study was to investigate if nicotine has direct influence on cardiac fibroblasts. To this end, we studied the effects of nicotine on cultured cardiac fibroblasts. Northern hybridization analysis of RNA extracted from cardiac fibroblasts, enzymography of conditioned medium of cardiac fibroblasts and [3H]-thymidine incorporation into DNA of cardiac fibroblasts were used to examine the effects of nicotine on collagen gene expression, collagenase activity and DNA synthesis respectively. Treatment of cardiac fibroblasts with nicotine (10 micrograms/ml) led to a 31% (P < 0.05) decrease in the abundance of mRNA for pro alpha 1(I) but not pro alpha 2(I) collagen compared with control untreated cells. Nicotine treatment of cardiac fibroblasts also led to decreased collagenase activity (62%, P < 0.001) in the conditioned medium of those cells in culture. Studies with [3H]-thymidine incorporation into DNA of cardiac fibroblasts showed a nicotine-induced decrease (39%, P < 0.001) in DNA synthesis in those cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Mechanism of action of the migration stimulating factor produced by fetal and cancer patient fibroblasts: effect on hyaluronic and synthesis.

We have previously demonstrated that confluent fetal fibroblasts migrate into three-dimensional collagen gels to a significantly greater extent than their normal adult counterparts. Recent studies have revealed that this behavioral difference results from the secretion by fetal fibroblasts of a soluble migration-stimulating factor (MSF) which acts on these cells in an autocrine fashion. Adult fibroblasts do not produce MSF but remain responsive to it. Skin fibroblasts from cancer patients resemble fetal fibroblasts (rather than normal adult cells) with respect to their migratory behavior on collagen gels and continued production of MSF. This communication is concerned with elucidating the biochemical basis of MSF activity. Data are presented indicating that a) hyaluronic acid is required for the elevated migratory activity displayed by confluent fetal and breast cancer patient skin fibroblast; b) adult fibroblasts exhibit a bell-shaped dose-response to MSF, with maximal stimulation of migration observed at a concentration of 10 ng/ml; c) the migratory activity of adult fibroblasts pre-incubated with MSF remains high in the absence of additional factor: and d) MSF affects both the quantity and size class distribution of hyaluronic acid synthesized by adult fibroblasts. We have previously speculated that the persistent fetal-like fibroblasts of breast cancer patients play a direct role in disease pathogenesis by perturbing normal epithelial-mesenchymal interactions. The observations reported here suggest that MSF-induced alterations in hyaluronic acid synthesis may contribute to the molecular basis of such perturbations.

Cell Line↗
PubMed1997

[Chloride conduction of nasal fibroblasts in polyposis patients with cystic fibrosis and in patients without cystic fibrosis. Relevance for the ENT physician].

Cystic fibrosis (CF) is a complex systemic disease that has pathological alterations in the upper airways, including the recurrent formation of nasal polyps. Although the fibroblast is the predominant cell type in nasal stroma and nasal polyps, little is known about the electrophysiological properties of nasal fibroblasts. We investigated whether fibroblasts possess a cAMP-regulated chloride conductance which is impaired in patients with CF. Thus far the few studies concerning conductance in fibroblasts have been performed on skin fibroblasts using indirect methods and have yielded conflicting results. Therefore we studied chloride conductance in fused nasal fibroblasts by employing conventional microelectrodes. We have demonstrated that a cAMP-regulated chloride conductance is present in fibroblasts. However, this chloride conductance cannot be activated in fibroblasts from CF-patients. Thus, we present direct evidence that the impairment of the cAMP-regulated chloride conductance in CF is not confined to epithelial cells but also affects the fibroblast. We discuss how this conductance might modulate fibroblast proliferation to produce polyp formation.

Child↗
PubMed2003

Cathepsin K deficiency in pycnodysostosis results in accumulation of non-digested phagocytosed collagen in fibroblasts.

The rare osteosclerotic disease, pycnodysostosis, is characterized by decreased osteoclastic bone collagen degradation due to the absence of active cathepsin K. Although this enzyme is primarily expressed by osteoclasts, there is increasing evidence that it may also be present in other cells, including fibroblasts. Since fibroblasts are known to degrade collagen intracellularly following phagocytosis, we analyzed various soft connective tissues (periosteum, perichondrium, tendon, and synovial membrane) from a 13-week-old human fetus with pycnodysostosis for changes in this collagen digestion pathway. In addition, the same tissues from cathepsin K-deficient and control mice were analyzed. Microscopic examination of the human fetal tissues showed that cross-banded collagen fibrils had accumulated in lysosomal vacuoles of fibroblasts. Morphometric analysis of periosteal fibroblasts revealed that the volume density of collagen-containing vacuoles was 18 times higher than in fibroblasts of control patients. A similar accumulation was seen in periosteal fibroblasts of three children with pycnodysostosis. In contrast to the findings in humans, an accumulation of internalized collagen was not apparent in fibroblasts of mice with cathepsin K deficiency. Our observations indicate that the intracellular digestion of phagocytosed collagen by fibroblasts is inhibited in humans with pycnodysostosis, but probably not in the mouse model mimicking this disease. The data strongly suggest that cathepsin K is a crucial protease for this process in human fibroblasts. Murine fibroblasts may have other proteolytic activities that are expressed constitutively or up regulated in response to a deficiency of cathepsin K. This may explain why cathepsin K-deficient mice lack the dysostotic features that are prominent in patients with pycnodysostosis.

Animals↗
PubMed1998

Reduced expression of mRNA for transforming growth factor beta (TGF beta) and TGF beta receptors I and II and decreased TGF beta binding to the receptors in in vitro-aged fibroblasts.

Previous studies have demonstrated that the expression of type I collagen, the most abundant protein in the dermis, is reduced in in vitro-aging fibroblast cultures, but the mechanism controlling the reduction of type I collagen expression is not understood. Recent studies, however, have demonstrated that transforming growth factor beta (TGF beta) plays an important role in the regulation of type I collagen expression. The purpose of this study was to investigate the role of TGF beta in downregulation of type I collagen expression in in vitro-aged fibroblasts. We compared the expression of mRNA for alpha 1 (I) collagen, TGF beta, TGF beta type I receptor and TGF beta type II receptor in early and late-passage fibroblasts by Northern blot hybridizations. The mRNA levels of alpha 1(I) collagen, TGF beta, and TGF beta receptors I and II in late-passage fibroblasts were reduced to 62%, 62%, 59% and 59%, respectively, of those in early-passage fibroblasts. We also compared TGF beta receptor binding in early- and late-passage fibroblasts using receptor binding assays. The affinity of 125I-TGF beta in late-passage fibroblasts was lower than that in early-passage fibroblasts. These results suggest that the reduction of type I collagen expression in in vitro-aged fibroblasts is regulated by reduced expression of TGF beta and TGF beta receptors I and II and by decreased TGF beta receptor binding ability of the fibroblasts.

Activin Receptors, Type I↗
PubMed2006

Healing and normal fibroblasts exhibit differential proliferation, collagen production, alpha-SMA expression, and contraction.

This study determines the differences in proliferation, collagen production, alpha-smooth muscle actin (alpha-SMA) expression, and contraction between healing and normal fibroblasts. Transected and sham-operated rat medial collateral ligaments (MCL) were used to obtain healing and normal fibroblasts, respectively. It was found that healing fibroblasts in monolayer culture proliferated 1.4-fold faster at 48 h and had 1.7-fold greater protein expression of alpha-SMA than normal fibroblasts. In addition, it was noted that the proliferation of healing fibroblasts in collagen gels was not significantly different from that of normal fibroblasts at 24 h, but it was at 48 h. Furthermore, in collagen gels, healing fibroblasts produced more type I collagen than normal fibroblasts and generated 1.6- and 1.7-fold larger contractile forces at 15 and 20 h, respectively, than their normal counterparts. Taken together, the results of this study show that healing fibroblasts possess a differential proliferation, alpha-SMA protein expression, and contraction than normal fibroblasts.

Actins↗
PubMed1989

The interaction of human papillary and reticular fibroblasts and human keratinocytes in the contraction of three-dimensional floating collagen lattices.

Fibroblasts derived from the papillary and reticular dermis of human skin and human keratinocytes show differences in their abilities to contract floating three-dimensional gels constructed from type I collagen. Reticular fibroblasts produce greater gel contraction than papillary fibroblasts. When equal numbers of papillary and reticular fibroblasts are mixed in the gels, papillary fibroblasts consistently inhibit gel contraction by reticular fibroblasts indicating interaction between these cell types in the contraction process. Surprisingly, keratinocytes alone produce greater gel contraction than that produced by either fibroblast type. Cooperativity in the gel contraction process is observed when fibroblasts are incorporated into the collagen matrix and keratinocytes are seeded onto the gel surface. Keratinocytes and dermal fibroblasts adhere to the collagen fibril to induce gel contraction by different mechanisms. Fibroblast contraction of collagen gels does not require fibronectin but is a serum-dependent reaction. In contrast, keratinocyte contraction of collagen gels occurs in a serum-free environment. Polyclonal, affinity-purified antibodies to human plasma fibronectin at high concentrations do not inhibit gel contraction by keratinocytes, making unlikely the possibility that fibronectin synthesized by the keratinocyte is a significant factor in the gel contraction process. We are currently examining the possibilities either that keratinocytes are synthesizing other adhesion proteins or that receptors on the cell surface can interact directly with the collagen fiber.

Cell Adhesion↗
PubMed1992

Changes in the migratory ability of human lung and skin fibroblasts during in vitro aging and in vivo cellular senescence.

The migration of human lung and skin fibroblasts was determined during in vitro aging and in vivo cellular senescence by measuring their migration from the edge of a denuded area of a monolayer. The migration of human fetal lung fibroblasts (TIG-1 and TIG-3) decreased only very slightly with increasing passage, whereas the migration of human fetal skin fibroblasts (TIG-3S) declined gradually: the difference in cell migratory ability between early and late passages was significant (P less than 0.05). The migratory patterns of skin fibroblasts from adult and elderly donors were also similar to that of fetal skin fibroblasts. Next, the migratory abilities of fibroblast lines from adult and elderly donor groups were compared, using relatively early passaged cells. The migratory ability of the elderly-donor skin fibroblast lines was significantly lower (P less than 0.05) than that of the adult-donor skin fibroblast lines. Addition of suramin and monensin suppressed the migration of fibroblasts from fetal, adult and elderly donors, which implies that fibroblast migration is regulated by growth factors and matrix substances. The relationships between the age-dependent decline of migratory ability, growth factors and the extracellular matrix are discussed.

Adult↗