Synthesis of PGE2, collagenase and tissue factor by fibroblast substrains: substrains are differentially activated for different metabolic products

Dermal fibroblasts from different layers of human skin are heterogeneous in expression of collagenase and types I and III procollagen mRNA

Patients with diabetic neuropathy have reduced numbers of cutaneous nerves, which may contribute to an increased incidence of nonhealing wounds. Nerve growth factor (NGF) has been reported to augment wound closure. We hypothesized that topical 2.5S NGF, a biologically active subunit of the NGF polymer, would accelerate wound repair, augment nerve regeneration, and increase inflammation in excisional wounds in diabetic mice. A full-thickness 6-mm punch biopsy wound was created on the dorsum of C57BL/6J-m+ Leprdb mice (db/db) and heterozygous (db/-) littermates and treated daily with normal saline or 2.5S NGF (1 microg/day or 10 microg/day) on post-injury days 0-6. Time to closure, wound epithelialization, and degree of inflammation were compared using a Student's t-test. Color subtractive-computer-assisted image analysis was used to quantify immunolocalized nerves in wounds. Non-overlapping (20x) digital images of the wound were analyzed for nerve profile counts, area density (number of protein gene product 9.5 positive profiles per unit dermal area) and area fraction (protein gene product 9.5 positive area per unit dermal area). Healing times in db/db mice decreased from 30 days in normal saline-treated mice to 26 days in mice treated with 1 microg/day NGF (p<0.05) and 24 days in mice treated with 10 microg/day NGF (p<0.02). A similar trend in db/- mice was not significant. NGF treatment augmented epithelialization in the db/db mice (p<0.05). Histological evaluation of inflammation in healed wounds showed no statistical difference between treatment groups. Total nerve number, area density, and area fraction were increased in NGF-treated wounds at 14, 21, and 35 days (p<0.05). The 2.5 NGF subunit may improve wound closure kinetics by promoting epithelialization and nerve regeneration. Further studies to determine the role of nerves in wound repair are warranted.

Current perspective on the pathogenesis of Graves' disease and ophthalmopathy

Graves' disease (GD) is a very common autoimmune disorder of the thyroid in which stimulatory antibodies bind to the thyrotropin receptor and activate glandular function, resulting in hyperthyroidism. In addition, some patients with GD develop localized manifestations including ophthalmopathy (GO) and dermopathy. Since the cloning of the receptor cDNA, significant progress has been made in understanding the structure-function relationship of the receptor, which has been discussed in a number of earlier reviews. In this paper, we have focused our discussion on studies related to the molecular mechanisms of the disease pathogenesis and the development of animal models for GD. It has become apparent that multiple factors contribute to the etiology of GD, including host genetic as well as environmental factors. Studies in experimental animals indicate that GD is a slowly progressing disease that involves activation and recruitment of thyrotropin receptor-specific T and B cells. This activation eventually results in the production of stimulatory antibodies that can cause hyperthyroidism. Similarly, significant new insights have been gained in our understanding of GO that occurs in a subset of patients with GD. As in GD, both environmental and genetic factors play important roles in the development of GO. Although a number of putative ocular autoantigens have been identified, their role in the pathogenesis of GO awaits confirmation. Extensive analyses of orbital tissues obtained from patients with GO have provided a clearer understanding of the roles of T and B cells, cytokines and chemokines, and various ocular tissues including ocular muscles and fibroblasts. Equally impressive is the progress made in understanding why connective tissues of the orbit and the skin in GO are singled out for activation and undergo extensive remodeling. Results to date indicate that fibroblasts can act as sentinel cells and initiate lymphocyte recruitment and tissue remodeling. Moreover, these fibroblasts can be readily activated by Ig in the sera of patients with GD, suggesting a central role for them in the pathogenesis. Collectively, recent studies have led to a better understanding of the pathogenesis of GD and GO and have opened up potential new avenues for developing novel treatments for GD and GO.

Lack of co-ordinate expression of the alpha1(I) and alpha1(III) procollagen genes in fibroblast clonal cultures

BACKGROUND

Several extracellular matrix genes, most notably alpha1(I) and alpha1(III) procollagen, are reported to be co-ordinately expressed in cultures of dermal fibroblasts. However, it remains unclear whether the expression of these genes is truly co-ordinate or whether it may be the result of averaging the phenotypic expression of different fibroblast subpopulations present within each culture. Objectives To determine by Northern analysis the correlation between alpha1(I) and alpha1(III) procollagen mRNA levels in clonal populations of human dermal fibroblasts.

METHODS

As previously described, clonal cultures were derived from parent strains of human dermal fibroblasts by a microscopically controlled dilution technique and by stimulation of single cells with low oxygen tension in the early phases of clonal growth.

RESULTS

In agreement with previous reports, we found that baseline steady-state levels of alpha1(I) procollagen mRNA were co-ordinately regulated with the alpha1(III) procollagen mRNA in 26 parent strains (r = 0. 9003; P < 0.0001). However, this close correlation between the expression of these two procollagen chains was absent in a total of 40 unselected clonal strains derived from four of the parent cultures (r = 0.5745; P < 0.0001). Moreover, this intrachain heterogeneity in alpha1(I) and alpha1(III) procollagen mRNA levels in clonal cultures was statistically significant from that measured in parent strains (P = 0.0016).

CONCLUSIONS

alpha1(I) and alpha1(III) procollagen mRNA levels in clonal cultures do not show the tight co-ordinate regulation observed in non-clonal cultures, suggesting that these two genes operate under different sets of regulatory controls. This clonal heterogeneity may provide additional flexibility to the process of tissue repair and fibroblast clonal expansion.

Physiology of wound healing and surgical wound care

Wound healing is a systemic process, which occurs stepwise and involves the stages of hemostasis, inflammation, and repair. Hemostasis with fibrin formation creates a protective wound scab. The scab provides a surface beneath which cell migration and movement of the wound edges can occur. Inflammation brings nutrients to the area of the wound, removes debris and bacteria, and provides chemical stimuli for wound repair. Repair begins immediately after wounding and proceeds rapidly through the processes of epithelialization, fibroplasia, and capillary proliferation into the healing area. Different tissues have their own normal rates of growth during the process of healing. The optimal rate of healing is approached when factors advantageous to healing are present and factors having the ability to disturb or retard the healing processes are controlled or absent. These factors are discussed.

Basic biology and clinical application of specific cyclooxygenase-2 inhibitors

In summary, COX-2 is a highly regulated gene product that catalyzes the local production of PGs in pathologic and physiologic situations (Figure 1). It is clear that COX-2 is the isoform responsible for production of the PGs that mediate inflammation, pain, and fever. However, the role for COX-2 in normal physiology is still being defined. Specific COX-2 inhibitors represent a significant conceptual advance in therapy for patients with arthritis. Although there is no expectation of superior efficacy, clinical trials suggest that efficacy will be comparable with that of nonselective NSAIDs. Clinical trials demonstrate the potential for clinically meaningful reductions in the incidence of the most serious GI complications found with nonselective NSAIDs, i.e., ulcer, perforation, and GI bleeding. Over the next several years, treatment of large numbers of patients with specific COX-2 inhibitors will help to define the biology of COX-2. The magnitude of this advance in the therapy of rheumatic diseases is yet to be accurately determined, but the development of specific COX-2 inhibitors may afford significant new treatment options for many patients.

Is fibroblast heterogeneity relevant to the health, diseases, and treatments of periodontal tissues?

There are wide variations of gene expression and strikingly different responses to extracellular signals among different fibroblast populations. This has prompted a large number of in vitro studies which suggest that fibroblasts are not homogeneous but instead comprise multiple subpopulations with extensive site-to-site and intra-site variations. Conceivably, either fibroblasts are not all created equal, or, alternatively, discrete subpopulations may emerge in development, inflammatory lesions, or wound healing. While the heterogeneous nature of cultured fibroblasts has been known for some time, are these variations relevant to our understanding of the biology of oral tissues, their involvement in disease, and their response to therapy? Since fibroblasts are the predominant cell type in soft connective tissue matrices, the regulation of their proliferative, synthetic, and degradative behavior is likely to be important in tissue physiology and pathology. In this review, we use the current literature to assess whether fibroblast subpopulations really make a difference in the health and disease of periodontal tissues. We address the following questions: (1) Is fibroblast heterogeneity a real in vivo phenomenon? (2) How can we advance our knowledge of phenotypic variations and the regulation of fibroblast differentiation? (3) Could a knowledge of fibroblast heterogeneity have an impact on the development of new approaches to pathogenesis and the treatment of periodontal tissues?

Biochemical alterations in inflammatory periodontal diseases I. Poly (ADP-ribose) synthetase activity in gingiva and gingival fibroblasts from humans with periodontitis

Periodontal diseases are characterized in part by generation of oxygen free radicals, which can cause breaks in cellular DNA strands. Repair of damaged DNA is dependent upon the synthesis of poly (ADP-ribose)(PADPR) catalyzed by PADPR synthetase, an enzyme known to be activated by the broken ends of DNA strands. We measured the activities of PADPR synthetase and of PADPR glycohydrolase, which degrades PADPRS, in gingival biopsy specimens from 16 sites with adult periodontitis and 12 clinically healthy control sites. The results indicated that sites with periodontitis displayed markedly reduced PADPR synthetase activity compared with healthy control sites, whereas PADPR glycohydrolase activity was not changed. The mean specific activity of PADPR synthetase for the diseased specimens was one-sixth of that of the healthy specimens (p < 0.001). The PADPR synthetase activity was negatively correlated with the Gingival Index (rs = -0.60), pocket depth (rs = -0.70) and bleeding upon probing (rs = -0.72). Cultured fibroblasts derived from clinically characterized healthy and diseased gingival sites reflected similar patterns of enzyme activity. The mean specific activity of PADPR synthetase for the diseased-site cultures (n = 9) was 56 +/- 7% (p < 0.001) of the cultures from healthy control sites (n = 6). These results suggest that a reduced level of PADPR synthetase activity is associated with increased inflammation and periodontal destruction, and that the ability to synthesize PADPR is compromised in adult periodontitis.

Heterogeneity of collagen synthesis in normal and systemic sclerosis skin fibroblasts. Increased proportion of high collagen-producing cells in systemic sclerosis fibroblasts

OBJECTIVE

The goal of this study was to quantitatively analyze the distribution of collagen synthesis in normal and systemic sclerosis (SSc) fibroblast populations in order to determine the extent of activation in SSc populations.

METHODS

We used quantitative in situ hybridization to assess the population distribution of type I collagen synthesis. Fibroblast cultures were derived from both clinically involved and uninvolved skin regions of patients with SSc, and from healthy adults, and assessed for levels of alpha 1(I) procollagen messenger RNA (mRNA).

RESULTS

Dermal fibroblasts from both patients with SSc and normal adults were heterogeneous for distribution of alpha 1(I) procollagen mRNA when assessed by in situ hybridization, with a wide range of grains per cell. In contrast, clones of neonatal fibroblasts showed a relatively homogeneous distribution of grain counts. Involved SSc skin fibroblasts had a larger proportion of cells in the high collagen-producing mRNA subpopulation (mean +/- SEM 28.4 +/- 6.85%), compared with normal fibroblasts (1.75 +/- 1.44%) and uninvolved fibroblasts (9.6 +/- 6.73%). Conversely, within the low collagen-producing mRNA subpopulation, involved fibroblasts had a smaller proportion of cells (mean +/- SEM 14.0 +/- 5.63%) than did uninvolved fibroblasts (37.8 +/- 13.69%), while normal fibroblasts had a majority of the cells in this subpopulation (53.5 +/- 8.68%).

CONCLUSION

These results suggest that only a specific subset of fibroblasts are activated in SSc, as evidence by an increased proportion of cells with high levels of alpha 1(I) procollagen mRNA. Differences between the SSc and normal fibroblast populations appeared to be quantitative rather than qualitative. This may be a result of either clonal selection or selective activation in the pathogenesis of SSc.

Altered collagen metabolism in nifedipine-induced gingival overgrowth

Fibroblasts from nifedipine-induced fibrotic gingiva (NFG) have been characterized with respect to several cellular functions which could contribute to the characteristic clinical overgrowth of the gingiva: collagen synthesis and breakdown, glycosaminoglycan production, fibronectin synthesis, and proliferation. Histologic examination of NFG tissue revealed a hyperplastic epithelium with elongated, branched rete pegs. The connective tissue consisted of densely-packed collagen fibers and numerous enlarged fibroblasts, as well as regions of thinner, disorganized collagen fibers in the vicinity of scattered inflammatory and mast cells. Results of in vitro experiments showed that the fibroblast strains from the fibrotic gingiva (NFG) produced significantly greater amounts of collagen and lower levels of collagenase activity when compared to age- and sex-matched normal human gingival fibroblast strains. The NFG fibroblasts did not produce significantly greater amounts of fibronectin, and their level of glycosaminoglycan production was less than that of the normal fibroblasts. The NFG fibroblasts did not proliferate significantly more rapidly than the normal fibroblast strains. These findings therefore show that there are defects in the regulation of collagen production by NFG fibroblasts in vitro, and suggest that these alterations in collagen metabolism contribute to the over-deposition of collagen in this tissue, rather than hyperproliferation of the fibroblasts or through the production of increased amounts of fibronectin and glycosaminoglycans.

Inter- and intra-site heterogeneity in the expression of fetal-like phenotypic characteristics by gingival fibroblasts: potential significance for wound healing

We have previously reported that fetal and adult skin fibroblasts display distinctive migratory phenotypes on 3-D collagen substrata and that these behavioural characteristics may be quantified by a function defined as the cell density migration index (CDMI). Subsequent work indicated that this difference in migratory phenotype was due to the production by fetal fibroblasts of a migration stimulating factor (MSF) that is not produced by normal adult skin fibroblasts. We now present data indicating that: (a) unselected fibroblasts obtained from 14/14 (100%) of adult gingival explants expressed fetal-like CDMI values compared to only 1/10 (10%) of similarly explanted paired skin cells; (b) 12/12 (100%) of these gingival fibroblast lines also produced detectable quantities of MSF compared to 0/9 (0%) of the tested skin cells; (c) by microdissection studies, gingival fibroblasts obtained from different anatomical microdomains consisted of behaviourally distinct subpopulations, with cells derived from the papillary tips (PAP fibroblasts) displaying fetal-like CDMI values and persistent MSF production, whilst cells obtained from the deeper reticular tissue (RET fibroblasts) were adult-like with respect to these two criteria; (d) PAP fibroblasts were also smaller and achieved higher saturation cell densities compared to paired RET cells; (e) PAP fibroblasts passaged in vitro underwent a fetal-to-adult phenotypic transition characterized by the adoption of various RET cell characteristics, including the acquisition of CDMI values falling within the adult range and cessation in MSF production; and (f) early passage PAP fibroblasts incubated in the presence of an affinity-purified anti-MSF rabbit polyclonal antibody were induced to alter their migratory phenotype and exhibited CDMI values falling within the adult range. Statistical analysis indicated a highly significant correlation between the expression of a fetal-like CDMI and production of MSF (P &lt; 0.00001, using the Fisher exact contingency test). Taken together, these observations suggest that the production of MSF by PAP fibroblasts is responsible for their characteristically fetal-like migratory behaviour. The existence of such inter- and intra-site phenotypic heterogeneity in populations of skin and gingival fibroblasts is discussed in the context of fibroblast lineage relationships and the possible contribution of persistently fetal-like fibroblast subpopulations to connective tissue function in wound healing.

Phenotypic differences in cytokine responsiveness of hypertrophic scar versus normal dermal fibroblasts

The alteration of normal dermal fibroblast function that leads to the development of hypertrophic scar after thermal injury is unknown. To determine functional differences that might explain this process, fibroblasts were cultured from biopsies of post-thermal injury mature hypertrophic scars and patient-matched normal skin. The mitogenic responses of scar cells to fetal bovine serum, epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and tumor necrosis factor alpha (TNF alpha) were determined and compared to normal skin cells. Collagen synthetic rate was also compared in the presence and absence of transforming growth factor beta 1 (TGF beta 1). Whereas both scar and normal cells responded with increased thymidine uptake to serum and cytokines, the stimulation to EGF and serum was significantly lower in scar cells. In contrast, synthesis of collagen, but not of non-collagenous proteins, was increased in scar relative to normal cells, both basally and when stimulated with low doses of TGF beta 1. Additionally, the fraction of protein synthesized as collagen was significantly higher in scar fibroblasts. These results suggest that fibroblasts from hypertrophic scars demonstrate stable phenotypic differences in cytokine responsiveness in comparison to cells from unaffected skin. The increased rate of collagen synthesis and decreased responsiveness to mitogens are consistent with the increased extracellular matrix content and decreased cellularity of hypertrophic scars.

Deficiencies in collagen phagocytosis by human fibroblasts in vitro: a mechanism for fibrosis?

Degradation of collagen by fibroblast phagocytosis is an important pathway for physiological remodelling of soft connective tissues. Perturbations of this pathway may provide a mechanism for the development of fibrotic lesions. As collagen phagocytosis may be regulated by either a change of the proportions or the activity of phagocytic cells, we quantified phagocytosis with an in vitro model system. Collagen-coated fluorescent latex beads were incubated with human gingival fibroblasts and the fluorescence associated with internalized beads was measured by flow cytometry. Cells from normal tissues that had been incubated with beads for 3 hours contained a mean of 64% phagocytic cells; however, a small subpopulation (10% of phagocytic cells) contained more than threefold higher numbers of beads per cell than the mean. In contrast, cells from fibrotic lesions exhibited a large reduction of the proportions of phagocytic cells (mean = 13.8%) and there were no cells with high numbers of beads. On the basis of 3H-Tdr labeling, cells from fibrotic lesions that had internalized beads failed to proliferate, in contrast to phagocytic cells from normal tissues, which underwent repeated cell divisions. This result was not due to variations of cell cycle phase as there was no preferential internalization of beads during different phases of the cell cycle. The low phagocytic rate of cells from fibrotic lesions was also not due to asymmetric partitioning of phagosomes at mitosis as videocinemicrography of bead-labeled phagosomes in single, pre-mitotic cells demonstrated that > 90% of phagocytic cells equally partitioned beads to daughter cells. To investigate if inhibition of phagocytosis could be replicated in vitro, cells were incubated with the fibrosis-inducing drugs nifedipine or dilantin. These cultures exhibited marked (15-75%), dose-dependent reductions in the proportions of phagocytic cells, but there was no reduction in bead number per cell. Fibrotic lesions appear to contain fibroblasts with marked deficiencies in phagocytosis and the reduced phagocytic activity of these cells may contribute to unbalanced degradation and fibrosis.

Burn wound healing: James Ellsworth Laing memorial essay for 1991

This essay has concentrated on the basic processes, clinical techniques involved in burn wound healing and how the two relate to each other. The achievement of early, sound, durable burn wound healing is one of the fundamental aims of burn care in order to minimize subsequent morbidity and mortality. It must be remembered that all patients with burns are individuals. There is no standard way to treat a burn and treatment must be tailored to suit the needs and requirements of both the patient and the burn wound. Burn wound healing is not the specific domain of any one specialist. It requires input from all disciplines and can be best achieved by the burn team approach.

Effect of gamma-interferon on collagen synthesis by normal and fibrotic human lung fibroblasts

Increased lung collagen and increased collagen synthesis by lung fibroblasts is well recognized in pulmonary fibrosis. gamma-Interferon has been shown to inhibit collagen synthesis by fibroblasts. To understand its effect on lung fibroblasts we compared how this lymphokine affects the growth and collagen synthesis of normal and fibrotic human lung fibroblasts. The results showed that gamma-IFN inhibited DNA synthesis in all fibroblast strains examined. Both collagen production and type 1 mRNA levels were reduced in three normal and two fibrotic cell strains exposed to gamma-IFN, while they were not affected in one strain from fibrotic lung. Even though an occasional cell was unaffected by the gamma-IFN, collagen mRNA level was reduced in most cells and it remained reduced for 48 h after removing the gamma-IFN. These results show that gamma-IFN inhibits the growth of fibroblast cultures derived from normal and fibrotic human lungs and suppresses collagen synthesis in most of these cells.

Human lung fibroblast subpopulations with different C1q binding and functional properties

Human lung fibroblasts differing in C1q binding, steady-state levels of collagen synthesis, and other functional properties were isolated. Explants of normal human lung specimens were cultured in medium containing complement-inactivated plasma-derived human serum or complete human serum. Cells obtained were treated with C1q and fluorescein isothiocyanate-anti-C1q antibody and separated based on fluorescence intensity in a fluorescence-activated cell sorter (FACS). FACS profiles showed that fibroblasts obtained in the presence of plasma-derived serum (HF cells) displayed higher fluorescence intensity than those obtained in complete serum (LF cells). The unsorted and sorted HF and LF fibroblasts retained their respective fluorescence phenotypes after subculture. The LF fibroblasts proliferated faster than HF cells and contained more cycling cells. However, whereas the sorted HF cells grew normally, sorted LF cells grew poorly. Collagen production and pro alpha l[I] mRNA levels in HF cells were 2.6 +/- 0.7 and 2.1 +/- 0.6 times as high as LF cells (n = 4). Collagen synthesis in both HF and LF cells was stimulated by transforming growth factor-beta and inhibited by interferon-gamma, but the stimulation was greater and inhibition less in LF cells. Our results indicate that C1q binding and the type of C1q receptors can serve as markers for fibroblast subpopulations differing in collagen synthesis, and that selection of subpopulations and their differential sensitivity to regulatory molecules can contribute to collagen alterations associated with inflammation, fibrosis, and other acquired diseases.

Heterogeneity in hormone responses and patterns of collagen synthesis in cloned dermal fibroblasts

Fibroblasts cultured from normal human dermis are heterogeneous with respect to growth kinetics, synthetic function, and morphologic features. There are many examples of clonal heterogeneity in apparently homogeneous connective tissue cell populations, and it has been suggested that selection of cell populations with particular phenotypic features is the basis for the development of pathologic connective tissue changes in inflammatory disorders. In these studies we report characterization of the pattern of matrix biosynthesis and responses to hormones in cells cloned from normal human dermis. The results indicate that cloned dermal fibroblasts are heterogeneous with respect to synthesis of collagens as well as their responses to prostaglandin E2 and parathyroid hormone. Selective expansion of clonal populations with unique patterns of matrix synthesis and cell surface receptors could provide the basis for abnormal connective tissue remodeling in certain pathologic states.

Characterization of fibroblasts derived from human periodontal ligament and gingiva

Growth characteristics and macromolecular synthesis of fibroblasts derived from human periodontal ligament (PDLF) and gingiva (GF) have been compared in cell culture. Cells were isolated from explants and plated at 500,000 cells/100 mm culture dish (day 0) with daily changes of culture medium. DNA histograms were obtained by flow microfluorimetric analysis to confirm the growth state of the cell cultures. Human PDLF cultures became confluent at day 6 as determined by cell number and cell cycle analysis while GF were confluent by day 4. Initially, DNA content of logarithmically growing cells was significantly greater in GF cultures; however, when confluent, DNA content and cell number was greater in PDLF cultures. Total protein content in GF was slightly greater than PDLF until day 7 but this difference was not significant. Analysis of collagen and noncollagen protein synthesis revealed a greater trend in noncollagen protein synthesis in the GF cultures compared to PDLF cultures. Analysis of glycosaminoglycans in the culture medium of GF and PDLF revealed similar distributions of components. In the cellular fraction, GF had greater amounts of hyaluronic acid and heparin and lesser amounts of chondroitin sulfates A and C than PDLF cultures. The results indicate that the growth characteristics of PDLF and GF, although similar in many respects, do exhibit specific differences in proliferative rates and macromolecular synthesis. The differences observed in these parameters may be important during in vivo events, such as guided tissue regeneration, where significant functional differences are observed between gingival connective tissue and periodontal ligament connective tissue.

The induction of specific metabolic alterations in mouse calvarial organ cultures by glycosaminoglycans

Glycosaminoglycans specifically regulate the amount of calcium released from bone cultures; the mechanisms responsible for this regulation are not known. Media from glycosaminoglycan-stimulated bone organ cultures were analysed to determine (1) if specific calcium-releasing substances were selectively produced, and (2) if protein synthesis was differentially affected by glycosaminoglycans. Chondroitin sulphate B, hyaluronic acid and keratan sulphate at 100 micrograms/ml significantly increased prostaglandin release when compared with control cultures. In combination with suboptimal concentrations of PTH, chondroitin sulphate B, heparin and keratan sulphate significantly stimulated prostaglandin release. When indomethacin was included in the test assays, the stimulated prostaglandin release was abolished. Heparin-treated cultures released the greatest percentage of latent collagenase activity followed by hyaluronic acid-treated cultures. Organ cultures treated with heparin and PTH amount of active collagenase. Stimulation increased interleukin-1 above control levels but with no significant difference among the glycosaminoglycans except for keratan sulphate cultures with which had the greatest amount of interleukin-1. Collagen protein decreased between 48 and 72 h under both control and experimental conditions. Examination of the predominant [35S]-methionine labelled proteins revealed that prostaglandin E2 treatment resulted in a relative shift in labelling to higher molecular-weight proteins as time in culture increased (up to 144 h). After 48 h, when equal amounts of labelled protein were analysed, there was a predominance in labelling of a 200,000 Da protein in the prostaglandin-treated cultures. These findings demonstrate that modulation of calcium release by glycosaminoglycans results in the selective release of molecules capable of stimulating calcium release.(ABSTRACT TRUNCATED AT 250 WORDS)

Clonal interactions in fibroblast proliferation: recognition of self vs. non-self

The proliferation and aging of fibroblast populations has been postulated to include a process of clonal selection. Using carbocyanine dyes to label clonal fibroblast populations, we were able to follow their growth in mixed cultures. Individual fibroblast clones seeded as the minority population (20%) with either another clone or the parent line (differentially labeled) always demonstrated increase relative growth so that, by the end of 4 weeks, approximately equal numbers of both populations were present. Labeled cells of the same clone mixed as the minority population with differentially labeled cells of the same clone maintained their minority status. The results indicate that clonal populations of fibroblasts are able to recognize "self" as different from "non-self" and that this recognition leads to alterations in cellular proliferation.

Autocrine control of collagenase synthesis by synovial fibroblasts

Fibroblasts respond to exogenous stimuli, such as Interleukin 1, phorbol esters, or crystals of monosodium urate monohydrate, by synthesizing and secreting large quantities of collagenase. Here we show that addition of exogenous stimuli results in the production of an autologous protein that is, itself, capable of inducing collagenase. This autocrine has been partially purified. Activity resides in a protein(s) with a pl of 5 or 8 and with Mr of approximately 15K. Conversely, conditioned medium taken from unstimulated cultures contains an inhibitor of collagenase synthesis. This protein, which has a Mr approximately 20-25k by HPLC gel filtration antagonizes collagenase synthesis induced by phorbol esters, exogenous parallel 1, and the autologous inducer. We conclude that synovial fibroblasts regulate collagenase synthesis via an autocrine mechanism that includes the synthesis of both an inducer and inhibitor. Both proteins are active at nanomolar amounts and may function as polypeptide hormones in regulating collagenase synthesis and, hence, connective tissue remodeling.

The effects of interleukin 1 on collagenolytic activity and prostaglandin-E secretion by human periodontal-ligament and gingival fibroblast

Fibroblasts of the periodontium may be involved in extracellular matrix degradation in response to inflammatory cytokines produced by mononuclear phagocytes. Interleukin 1 (IL1), one of these biologically-active agents, is produced by such cells when stimulated by lipopolysaccharide (LPS). Periodontal-ligament (PLF) and gingival fibroblasts responded to recombinant human IL1 beta and to media conditioned by LPS-stimulated mononuclear phagocytes by secreting prostaglandin E (PGE). This response was dose- and time-dependent. Stimulated gingival fibroblasts also produced about five- to ten-fold as much collagenolytic activity when compared to controls but PLF produced no more activity. On mixing the conditioned media from both fibroblast types, inhibitory activity was found in the PLF-culture medium. Thus gingival fibroblasts in particular may be involved in the pathogenesis of periodontal disease by responding to factors produced by inflammatory phagocytes.

Molecular cloning of human synovial cell collagenase and selection of a single gene from genomic DNA

We used a subclone of a rabbit genomic clone for collagenase that cross-hybridizes with human synovial cell messenger RNA (mRNA) to identify a human collagenase complementary DNA (cDNA) clone. The human cDNA clone is 2.1 kilobases (kb) and selects a mRNA transcript of approximately the same size from primary cultures of rheumatoid synovial cells that produce collagenase, but no mRNA is selected from control (nonproducing) synovial fibroblasts. Restriction enzyme analysis and DNA sequence data indicate that our cDNA clone is full length and that it is identical to that recently described for human skin fibroblast collagenase. The cDNA clone identified a single collagenase gene of approximately 17 kb from blots of human genomic DNA. The identity of human skin and synovial cell collagenase and the ubiquity of this enzyme and of its substrates, the interstitial collagens types I, II, and III, imply that common mechanisms controlling collagenolysis throughout the human body may be operative in both normal and disease states.

An in-vitro comparison of human fibroblasts from normal and oral submucous fibrosis tissue

Fibroblasts cultured in vitro from normal buccal tissue and from tissue from oral submucous fibrosis (OSF) associated with betel-nut chewing showed no significant difference in their rates of proliferation in culture, nor in the rate at which they hydrolysed the betel nut alkaloid arecoline to arecaidine. Basal rates of collagen synthesis were slightly higher in the OSF cells but, on addition of arecoline, the rate of collagen synthesis in normal and OSF cells was stimulated to the same level.

Structure and expression of cDNA and genes for human interferon-beta-2, a distinct species inducible by growth-stimulatory cytokines

Induced human fibroblasts produce several mRNAs encoding interferon (IFN) activity. We previously cloned cDNA for a 1.3-kb RNA designated IFN-beta 2 and distinct from the 0.9-kb IFN-beta 1 mRNA. In vitro transcription--translation mapping of the full-length IFN-beta 2 cDNA sequence, shows that it encodes a 23.7-kd protein of 212 amino acids. This cDNA, fused to the SV40 early gene promoter, was transfected and amplified in Chinese hamster ovary cells and clones were obtained which constitutively produce human interferon activity. Two IFN-beta 2 genomic clones were isolated and their expression in hamster and mouse cells also produces biologically active rIFN-beta 2. Specific immunoassays show that IFN-beta 2 secreted by DNA-transformed rodent cells is a processed 21-kd protein, whose activity is cross-neutralized by antibodies to human IFN-beta 1 but not to IFN-alpha or gamma. The immunoassay also demonstrates the induction of IFN-beta 2 secretion by fibroblasts in response to growth-regulatory cytokines, such as interleukin-1 and tumor necrosis factor. The function of this IFN-beta 2 as an autoregulatory inhibitor of cell growth is discussed.