Species-specific differences in the mitogenic activity of heparin-binding growth factors in the sera of various mammals

Levels of fibroblast growth factor 2 in synovial fluids in human patients with internal derangement of the temporomandibular joint

OBJECTIVE

We sought to elucidate the levels of fibroblast growth factor 2 (FGF-2) in synovial fluid taken from internally deranged human temporomandibular joints (TMJs) and to discuss the role of FGF-2 in the pathogenesis of internal derangement.

STUDY DESIGN

Through the use of a pumping procedure, diluted synovial fluid was collected from the upper joint compartment of 22 TMJs with evidence of internal derangement (21 patients) and 8 TMJs with no such evidence (5 control subjects). Two of the control subjects were patients who had habitual dislocation, and three were healthy volunteers. The level of FGF-2 in the synovial fluid was assessed by means of an enzyme-linked immunosorbent assay.

RESULTS

FGF-2 levels were at detectable levels in 15 of the 22 TMJs (68%) with internal derangement. The mean concentration of FGF-2 was 24 pg/mL. In the control group, FGF-2 levels were detectable in only 1 of 8 joints (13%), for a concentration of 3 pg/mL. The mean concentration of FGF-2 in the synovial fluid was significantly higher in the internal derangement group than in the control group (P =.02).

CONCLUSIONS

FGF-2 levels are elevated in the human synovial fluid of TMJs with internal derangement.

Inhibitory effects of human serum on human fetal skin fibroblast migration: migration-inhibitory activity and substances in serum, and its age-related changes

In order to clarify the environmental factors modulating cell migration, we investigated the effects of human serum on cell migration, and found that serum from adult donors strongly (by 48%) suppressed the migration of human fetal skin fibroblasts into a denuded area in a cell monolayer. Human serum from old donors inhibited cell migration more strongly than that from adult donors. Next, we investigated the properties of migration-inhibitory activity of human serum and serum proteins in order to identify migration-inhibitory substances. Human serum from adult donors strongly suppressed the migration of human fetal skin fibroblasts, although it stimulated cell proliferation more strongly than fetal bovine serum (FBS), indicating that the inhibitory effects of human serum on cell migration was not due to its toxic effects. The inhibition of cell migration by human serum was concentration dependent. It was demonstrated that the inhibition did not depend on the inhibitory effects of human serum on collagen synthesis. The migration-inhibitory activity was seen in fractions over 100 kDa, as determined by an ultrafiltration membrane, and no inhibitory activity was observed in fractions under 100 kDa. On the other hand, it was not detected either in fractions over 100 kDa or under 100 kDa in FBS. Among the over 100 kDa human serum proteins examined, gamma-globulin, alpha2-macroglobulin, and low density lipoprotein (LDL) suppressed fibroblast migration in a concentration-dependent manner. However, among the three, cell migration-inhibiting activity of gamma-globulin almost disappeared when cell migration was conducted in 10% FBS-supplemented medium. These results indicated that alplha2-macroglobulin and LDL were candidate substances for cell migration-inhibiting activity in human serum.

Expression and localization of basic fibroblast growth factor (bFGF) in the repair process of rat liver injury

BACKGROUND/AIMS

To clarify the expression and localization of basic fibroblast growth factor in the repair process of liver injury, acute liver injury was induced by administration of carbon tetrachloride, D-glactosamine hydrochloride, or dimethylnitrosamine to rats.

METHODS

We measured basic fibroblast growth factor protein in the liver tissue by radioimmunoassay, evaluated the expression of basic fibroblast growth factor mRNA by the reverse transcriptase polymerase chain reaction, and identified basic fibroblast growth factor-positive cells by immunostaining.

RESULTS

In the carbon tetrachloride injured liver, the basic fibroblast growth factor protein contents began to increase 2 days after administration when liver injury was most marked, and reached a peak after 4 days, decreasing thereafter. In the carbon tetrachloride-injured liver, basic fibroblast growth factor mRNA expression was observed from 12 h after administration, prior to an increase in the protein content. In the D-galactosamine hydrochloride-injured liver, basic fibroblast growth factor protein also increased. On the other hand, in the dimethylnitrosamine-injured liver, the basic fibroblast growth factor protein content decreased 2 days after administration when liver injury was marked, but increased after 7 days. In the regenerating liver after partial hepatectomy, the basic fibroblast growth factor protein content did not increase. Among cell fractions, the Ito cell fraction obtained from the carbon tetrachloride-injured liver after 4 days showed expression of basic fibroblast growth factor mRNA. In cells cultured for 24 h, this fraction was immunopositive for basic fibroblast growth factor. Ito cells in the liver tissue markedly increased in the carbon tetrachloride-injured liver and increased after 7 days in the dimethylnitrosamine-injured liver.

CONCLUSIONS

This study confirmed basic fibroblast growth factor production in the liver tissue in the repair process of liver injury. Our results suggest that basic fibroblast growth factor is primarily produced in Ito cells, acts on sinusoidal wall cells including Ito cells by the autocrine and paracrine mechanisms, and promotes extracellular matrix production and vascularization, involving the repair process of liver injury.

Proliferation and progesterone production of ovine luteal cells from several stages of the estrous cycle: effects of fibroblast growth factors and luteinizing hormone

This study was conducted to evaluate the effects of fibroblast growth factor 1 (FGF-1), fibroblast growth factor 2 (FGF-2), or luteinizing hormone (LH) on proliferation and progesterone secretion of ovine luteal cells from days 5, 10, or 15 after estrus (estrus = day 0; n = 4 or 5 ewes/day). After enzymatic dispersion, luteal cells were incubated in the presence or absence of various doses of FGF-1, FGF-2, LH, or fetal bovine serum (FBS) (positive control) in serum-free media for 7 days in 24-well plates. Cells were counted on day 7 of culture and media analyzed for progesterone concentration. For all treatments, maximal effects (Emax) and dissociation constants (KD) were calculated. In addition, luteal cells were cultured in eight-chamber slides and treated as above, but on day 7 of culture cells were fixed and stained for the presence of 3beta-hydroxy-delta 5-steroid dehydrogenase (3beta HSD). The number of steroidogenic (3beta HSD positive) cells per unit area was counted for control cultures (no treatment) and cultures treated with the most effective doses of FGF-1, FGF-2, LH, OR FBS in proliferation and (or) progesterone assays. FGF-1, FGF-2, AND FBS stimulated (p < 0.05) proliferation of luteal cells from all stages of luteal development in a dose-dependent manner. In addition, LH increased (p < 0.01) the number of 3beta HSD-positive cells across all stages of luteal development. Moreover, LH and FBS increased (p < 0.05) progesterone secretion by luteal cells from all stages in a dose-responsive manner, but the effects of FGF-1 and FGF-2 were variable. For proliferation, the Emax of all factors was greatest (p < 0.01) on day 5, whereas the KD values were similar across days of the estrous cycle. For progesterone production, the Emax and KD of LH and FBS were similar and did not differ across the estrous cycle. These data demonstrate the luteal cells from the early luteal phase of the estrous cycle exhibit the greatest ability to proliferate and (or) increase their progesterone secretion in response to FGF-1, FGF-2, LH, or FBS. In addition, although LH does not affect the total number of luteal cells in culture, it does increase the number of steroidogenic cells. These data indicate that in addition to LH, fibroblast growth factors may be involved in regulation of luteal growth and differentiation in ewes.

Initial characterization of mitogenic activity of ovine corpora lutea from early pregnancy

To characterize angiogenic factors produced by ovine corpora lutea (CL) during early pregnancy, two experiments were performed. In Experiment 1, luteal explants from days 12, 18, 24, and 30 (n=4 ewes/day) after mating were incubated in serum-free medium for 6 h. Luteal-conditioned media (LCM) were evaluated for their ability to stimulate proliferation of endothelial and 3T3 cells, as well as migration of endothelial cells. Pools of the LCM (one pool/day) then were characterized biochemically. In Experiment 2, two pools of LCM from days 24 of pregnancy were evaluated for their effects on endothelial cell, 3T3 cell, and ovine luteal cell proliferation. These pools of LCM then were concentrated by ultrafiltration and subjected to heparin-agarose affinity chromatography with salt gradient (0-4 M NaCl in buffer) elution, and fractions were evaluated for mitogenic activity for endothelial and 3T3 cells. The resulting five peaks of mitogenic activity from heparin-agarose chromatography were characterized biochemically. The five peaks of mitogenic activity were further purified by using chromatography, then were concentrated and subjected to SDS-PAGE and Western analysis for FGF-2. Ovine CL from each day of early pregnancy secreted mitogens (P<0.05) for endothelial (285 +/- 8% of unconditioned media controls) and 3T3 (142 +/- 7%) cells as well as factors which stimulated migration of endothelial cell (153 +/- 8% of controls). LCM pool from day 24 of pregnancy also stimulated (P<0.05) proliferation of ovine luteal cells in a dose-dependent manner. In Experiment 1, mitogenic activity for endothelial cells was greater than 100 kDa, heat-labile, trypsin-sensitive and bound to DEAE-Sephacel and heparin-agarose columns, but not to a CM-Sepharose column. Antibody against FGF-1 did not affect mitogenic activity of LCM for endothelial and 3T3 cells, whereas treatment with FGF-2 antibody decreased (P<0.05) mitogenic activity of LCM for both endothelial and 3T3 cells. In Experiment 2, heparin-agarose affinity chromatography resolved five peaks of mitogenic activity: a non-heparin-binding peak that was specific for 3T3 cells, three heparin-binding peaks that were specific for endothelial cells, and one heparin-binding peak that was specific for 3T3 cells. In Experiment 2, heparin-, heat-, or trypsin-treatment and immunoneutralization with FGF-1 or FGF-2 antibodies influenced mitogenic activity of all of the peaks. Whereas SDS-PAGE demonstrated several bands of protein within each peak, Western analysis was unable to detect the presence of FGF-2 in any of the heparin-binding peaks. These data demonstrate that ovine CL from early pregnancy produce mitogenic factors that can be resolved into 5 separate peaks of activity with differing affinities for heparin. These data also indicate that the endothelial mitogens produced by CL of early pregnancy are immunologically related to, but biochemically distinct from FGF-2. Mitogens for endothelial and other cells likely play a role in regulation of luteal function during early pregnancy in sheep.

Autonomous migration of human fetal skin fibroblasts into a denuded area in a cell monolayer is mediated by basic fibroblast growth factor and collagen

Human fetal skin fibroblasts (TIG-3S) were found to migrate into a denuded area in a cell monolayer when cultured in both serum-depleted and serum-supplemented media, unlike adult-donor skin fibroblasts which migrated well only when cultured in serum-supplemented medium. Therefore, a series of experiments was carried out to determine whether autocrine factors are involved in their migration. The migration of TIG-3S cells in serum-depleted medium was suppressed by the addition of suramin, a factor with growth factor antagonist properties, which suggests that growth factors are important for cell migration. The suramin-induced inhibition was reversed completely by adding excess basic fibroblast growth factor (bFGF) to the culture medium and partially by platelet-derived growth factor (PDGF). Treatment with neutralizing anti-PDGF antibody did not suppress TIG-3S cell migration, whereas neutralizing anti-bFGF antibody did, which indicates that bFGF is an autocrine and PDGF a paracrine factor involved in cell migration. Next, an experiment was performed to ascertain whether the extracellular matrix is involved in TIG-3S cell migration. Monensin, an inhibitor of extracellular matrix secretion, inhibited cell migration, which was reversed by adding excess type I collagen, but not excess plasma fibronectin. In addition, further evidence for the involvement of collagen was provided by the observation that ethyl-3,4-dihydroxybenzoate, a specific inhibitor of collagen synthesis, suppressed cell migration. These results suggest that the autonomous migration of TIG-3S human fetal skin fibroblasts is mediated by bFGF and type I collagen, which they produce and secrete.

Age-related changes in the mitogenic activity of heparin-binding growth factors in rat sera

Sera from rats of either sex and different ages were examined for their ability to stimulate DNA synthesis in BALB/c 3T3 cells. The activity levels of sera from male and female rats were almost the same, with age-related changes in activity also being quite similar. Activity was considerably higher in infant rats (1-month-old), but then, at a young age (6-7 months), decreased drastically for male rats, but not significantly for female rats. It increased again in middle-aged rats (12-13 months old) and was maintained at the same level toward old age (24-26 months old) for both sexes. In order to determine what kinds of growth factors were responsible for these changes, we carried out heparin affinity chromatography on the sera of male rats. Four peaks were obtained for all sera, with individual peaks exhibiting specific age-related changes in activity. Among them a peak which was eluted at 1.1 M NaCl had very high activity. It showed a similar age-related change to that of the whole sera, except for a significant increase at old age, and the factor(s) included in the peak was found to be derived from platelets. These results suggested that the factor(s) in the peak was responsible for maintaining serum mitogenic activity at an old age. The experiments undertaken to characterize this factor suggested that it is a novel one.

Platelet-derived growth factor in combination with collagen promotes the migration of human skin fibroblasts into a denuded area of a cell monolayer

Since we have found previously that adult donor skin fibroblasts (TIG-114) migrated more slowly in serum-depleted medium than in medium supplemented with 10% FBS, we tried to identify a factor(s) which promotes fibroblast migration from the edge of a denuded area in a monolayer. In medium supplemented with 10% FBS, the effects of both suramin, a competitor of growth factors at the receptor level, and monensin, an inhibitor of the secretion of extracellular matrix, were examined. Both substances suppressed cell migration, suggesting that growth factors and matrix substances are important for cell migration. Then, we examined the effects of growth factors and extracellular matrix on fibroblast migration in serum-free medium. Platelet-derived growth factor (PDGF), basic fibroblast growth factor, acidic fibroblast growth factor, and transforming growth factor-beta did not stimulate cell migration. Type I collagen, plasma fibronectin, and heparin also did not promote cell migration. However, the combination of PDGF and type I collagen did promote cell migration. Addition of anti-PDGF antibody reduced the stimulatory effect induced by the combination of PDGF and type I collagen. These results suggest that the copresence of growth factors and extracellular matrix regulates fibroblast migration into a denuded area in a monolayer.