Induction of collagenase secretion in human fibroblast cultures by growth promoting factors

EGF receptor in neoplasia and metastasis

EGFR is a member of the tyrosine kinase family of cell surface receptors with a wide range of expression throughout development and in a variety of different cell types. The receptor can transmit signals to cells: i) upon interaction with ligands such as EGF, TGF alpha, amphiregulin or heparin binding EGF, ii) upon truncation or mutation of extracellular and/or intracellular domains, iii) upon amplification of a basal receptor activity (in the absence of ligand) through cooperation with other cellular signaling pathways or nuclear events (e.g. expression of v-erbA). The activated EGFR can exert pleiotropic functions on cells, depending on their tissue origin and state of differentiation. Under certain conditions it can also contribute to neoplasia and development of metastases. Such conditions can exist upon aberrant receptor/ligand expression and activation (e.g. in the wrong cell; at the wrong time; in the wrong amounts). Aberrant signalling can also occur through constitutive EGFR activation. Oncogenic potential of EGFR has been demonstrated in a wide range of experimental animals. EGFR is also implicated in human cancer, where it may contribute both to the initiation (glioblastoma) and progression (epithelial tumors) of the disease. EGFR may influence key steps in the processes of tumor invasion and dissemination. Involvement of EGFR in tumor spread may indicate a potential use of this receptor as a target for antimetastatic therapy.

Interleukin-1 alpha and epidermal growth factor synergistically enhance the release of collagenase by periosteal connective tissue in vitro

The effects of recombinant human interleukin-1 alpha (IL-1 alpha) and murine epidermal growth factor (EGF) on the release of collagenase were studied in an in vitro model system using periosteal explants from rabbit calvariae. Following an incubation period of 72 h it was shown that IL-1 alpha in combination with EGF (IL-1 alpha + EGF) induced a synergistic increase in the amount of collagenase released by periosteal explants. This increase appeared to be at least 10-fold. Most of the enzyme was present in a latent form since the increase in enzyme activity was only detectable after activation by APMA and the molecular weight as determined in immunoblots corresponded to the latent form of this enzyme. Incubations carried out with IL-1 alpha alone resulted in a 2- to 4-fold increase of total enzyme activity, whereas the amount of collagenase in media of EGF-treated periosteal did not surpass control values. A neutralizing anti-IL-1 alpha antibody completely blocked the enhanced release of collagenase as induced both by IL-1 alpha and by IL-1 alpha + EGF. Indomethacin partially prevented the IL-1 alpha + EGF-induced increase in enzyme release, suggesting the involvement of prostaglandins. The amount of tissue inhibitor of metalloproteinases (TIMP) as determined by ELISA was slightly elevated in culture media obtained from all cytokine-treated explants. Comparable results were obtained by Western blot analysis as well as by a functional bioassay. It is suggested that the concomitant presence of the cytokines IL-1 alpha and EGF may play an important role in collagenase-mediated degradation of collagen.

Vascular endothelial growth factor induces interstitial collagenase expression in human endothelial cells

Vascular endothelial growth factor (VEGF) is a 45kDa secreted peptide that has potent mitogenic activity specific for endothelial cells in vitro and the ability to induce a strong angiogenic response in vivo. In the present study, 24 h treatment with VEGF resulted in a stimulation of expression of the metalloproteinase, interstitial collagenase, at the protein and mRNA levels 2.5-3.0-fold in human umbilical vein endothelial cells but not in human dermal fibroblasts. The dose response curve for collagenase induction was biphasic with the peak stimulatory response obtained by treatment of cells with 10-100 ng/ml (0.2-2 nM) VEGF. The dose response curve for collagenase induction overlapped with, but was not identical to, the response curve for proliferation, which showed VEGF mitogenic activity between < or = 0.1-50 ng/ml (< or = 0.002-1 nM). There was no induction seen in expression of other members of the matrix metalloproteinase family, including the 72kDa type IV collagenase, the 92kDa type V collagenase, or stromelysin. Expression of transcripts for the major metalloproteinase inhibitor, tissue inhibitor of metalloproteinases, was also unaltered by treatment with VEGF (1-200 ng/ml). These studies demonstrate that in addition to stimulating proliferation of endothelial cells, VEGF can also induce the expression of the only metalloproteinase that can initiate degradation of interstitial collagen types I-III under normal physiological conditions. Both responses are likely to contribute to the angiogenic potential of this peptide.

Differential expression of metalloproteinase and tissue inhibitor of metalloproteinase genes in aged human fibroblasts

The basal levels of mRNAs encoding two metalloproteinases, collagenase and stromelysin, were increased as a function of in vitro serial subcultivation (cellular aging) of human fibroblasts. Procollagenase and prostromelysin synthesis and secretion were also greater in the old cultures (late passage). In contrast, the steady-state expression of mRNA for an inhibitor of metalloproteinases, tissue inhibitor of metalloproteinase-1 (TIMP-1), in late-passage cultures was lower than that in young cell cultures (early passage). Each mRNA was analyzed using total RNA preparations isolated from normal fibroblast cultures at different phases of the in vitro life span and from cultures derived from donors with the premature senescence syndromes characterized as Werner syndrome, progeria (Hutchinson-Gilford) syndrome, or Cockayne syndrome. In normal cell cultures expression of metalloproteinase mRNAs was increased after the culture had completed greater than 90% of the in vitro life span, and the reduction in TIMP-1 mRNA expression occurred after the culture had completed greater than 74% of the in vitro lifespan. In Werner syndrome cultures expression of metalloproteinase and TIMP-1 mRNAs was similar to the level of expression observed in late-passage cell cultures. Levels of metalloproteinase and TIMP-1 mRNA expression in progeria and Cockayne syndromes were similar to those of early-passage cell cultures. To determine if young and old cells were each responsive to mediators of metalloproteinase synthesis, cultures were treated with phorbol ester or cytokines. 12-O-tetradecanoylphorbol-13-acetate treatment increased the steady-state levels of all three mRNAs in young, old, and Werner syndrome cultures and increased procollagenase levels in all cultures. Early- and late-passage cell cultures also responded to cytokines. Interleukin-1 alpha treatment increased collagenase and stromelysin mRNA levels while transforming growth factor-beta reduced the steady-state levels of both transcripts. Neither cytokine affected the steady-state level of TIMP-1 mRNA. The results indicate that in vitro cellular aging is associated with changes in expression of mRNAs encoding proteins that mediate inflammatory responses and connective tissue remodeling.

Activation of protein kinase C stimulates collagenase production by cultured cells of the cervix of the pregnant guinea pig

OBJECTIVE

Dilatation of the uterine cervix at parturition is achieved by an estrogen-induced, collagenase-mediated degradation of type I collagen in the cervix. The objective was to test the hypothesis that collagenase production in the cervix of pregnant guinea pig in culture is mediated by activation of protein kinase C.

STUDY DESIGN

The effects of 17 beta-estradiol, prostaglandin F2 alpha, or activation of protein kinase C by phorbol-12-myristate-13-acetate, 1-stearoyl-2-arachidonyl-sn-glycerol and phospholipase C on collagenase production was studied with primary monolayer cultures of cervical cells from Hartley guinea pigs at 50 days' gestation. Results are analyzed for statistical significance with analysis of variance.

RESULTS

Collagenase production is increased twofold to threefold by 17 beta-estradiol, prostaglandin F2 alpha, or activation of protein kinase C. The observed stimulation of collagenase production by 17 beta-estradiol and prostaglandin F2 alpha was blocked by the protein kinase C inhibitor 1-(5-isoquinoline sulfonyl) 2-methylpiperazine dihydrochloride.

CONCLUSION

Collagenase production in cultured cervical cells of pregnant guinea pig is stimulated by activation of protein kinase C.

Secretion of stromelysin by cultured dermal papilla cells: differential regulation by growth factors and functional role in mitogen-induced cell proliferation

To understand better the molecular nature of the epithelial-mesenchymal interactions that govern folliculogenesis and hair growth, we have studied the behavior of cultured rat dermal papilla cells (rDP), the mesenchymal component of the hair follicle. Basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) both potentiated the growth of rDP in culture, and transforming growth factor-beta (TGF-beta) inhibited rDP proliferation. Biosynthetic labeling studies demonstrated that both PDGF and bFGF induced synthesis of a major secreted protein(s) with Mr = 55-60 kD. It was noted that PDGF and bFGF differentially regulated synthesis of this major secreted protein; PDGF-mediated induction was found to be transient, while bFGF allowed prolonged synthesis of the protein. Sodium dodecyl sulfate (SDS)-substrate gel analysis of rDP-conditioned media revealed that this protein is a metalloproteinase with casienolytic activity and Mr approximately 51 kD (unreduced). We have identified the growth factor-regulated rDP protein as the matrix metalloproteinase stromelysin by immunoprecipitation. Northern analysis established that increased secretion of stromelysin was accompanied by an increased expression of stromelysin-specific mRNA. Remarkably, stromelysin antisera interfere with stimulation of dermal papilla cell growth, demonstrating that stromelysin production serves a functional role in mitogen-induced proliferation in these cells. These findings provide insight into the mechanism by which the connective tissue remodeling required for formation of hair embryonically and the postembryonic hair cycle may be regulated.

Effects of acetate dialysate on transforming growth factor beta 1, interleukin, and beta 2-microglobulin plasma levels

To evaluate potential adverse effects of acetate use in hemodialysis (HD), we measured plasma interleukin (IL-1 alpha, IL-1 beta, IL-6), TNF alpha, TGF beta 1, and beta 2-microglobulin levels with ELISA assays in normal (N = 9), CRF (N = 6), CAPD (N = 7) and HD (N = 8) subjects and compared the effects of acetate (Ac) and acetate-free (Ac-free) dialysate. TGF beta 1 was the only cytokine consistently detected. Compared to normals (median 57, range 53 to 68 pg/ml, one undetected; N = 8), TGF beta 1 was higher in the CRF (75, 70 to 97 pg/ml, one undetected) and CAPD (75.5, 66 to 116 pg/ml, N = 6) groups (P less than 0.05), and was somewhat higher in the HD (68, 52 to 88 pg/ml) group (P less than 0.10). Acutely, TGF beta 1 pre-HD (70, 63 to 88 pg/ml) increased above normals post AcHD [79.5, 65 to 140 pg/ml uncorrected for ultrafiltration (UF)] and was higher after AcHD versus Ac-free HD both uncorrected (79.5, 65 to 140 pg/ml vs. 70, 52 to 86 pg/ml) and corrected for UF (68, 51 to 115 pg/ml vs. 57, 43 to 69 pg/ml; P less than 0.05). beta 2-microglobulin was not different after AcHD (81.2 +/- 8.0 mg/ml) versus Ac-free HD (72.5 +/- 6.9 mg/ml). Significantly lower serum inorganic phosphorus was also found four hours post-AcHD compared to four hours post-Ac-free HD (0.87 mmol +/- 0.10 SEM vs. 1.05 mmol +/- 0.07 SEM; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Orthotopic implantation of human colon carcinomas into nude mice provides a valuable model for the biology and therapy of metastasis

Human colon carcinomas (HCC) are heterogeneous for a variety of biological properties that include invasion and metastasis. The presence of a small subpopulation of cells with a highly metastatic phenotype has important clinical implications for diagnosis and therapy of cancer. For this reason, it is important to develop animal models for the selection and isolation of metastatic variants from human colon cancers and for testing the metastatic potential of these cells. We have implanted cells from more than 100 HCC (obtained from surgical specimens) into different organs of nude mice. Regardless of their malignant potential in the patient, the HCC did not metastasize unless they were implanted orthotopically. Only when they were injected into the cecum or spleen of nude mice did they yield hepatic metastases. These metastases consisted of highly metastatic cells. The invasive phenotype was influenced by the organ environment. HCC cells in the subcutis did not produce degradative enzymes and the cells did not metastasize. In contrast, HCC cells in the cecum did both. Collectively, the results demonstrate that the orthotopic implantation of HCC cells can yield metastatic subpopulations of cells suitable for the study of metastasis.

Tumor necrosis factor alpha and epidermal growth factor regulation of collagenase and stromelysin in adult porcine articular chondrocytes

Chondrocyte-derived metalloproteases have been postulated to play a role in the degradation of articular cartilage during the development of chronic arthritic disorders. TNF alpha (tumor necrosis factor alpha), an inflammatory mediator released by activated macrophages, has been detected in the synovial fluid of patients with rheumatoid diseases. We have found that TNF alpha is a potent stimulator of collagenase and stromelysin mRNA accumulation, collagenase activity, and immunoprecipitable stromelysin in monolayer cultures of adult porcine articular chondrocytes. In contrast EGF (epidermal growth factor), which stimulates collagenase and/or stromelysin synthesis in fibroblast systems, stimulated minimal amounts of these enzymes at both the message and protein levels. Nuclear run-on transcription analysis demonstrated that the TNF alpha-stimulated increase in stromelysin and collagenase message levels was, at least partially, due to increased transcription. Elevated transcription of these genes, in response to TNF alpha, was apparent by at least 2 hours post-stimulation. The degree of c-fos and c-jun stimulation by TNF alpha or EGF did not correlate with the levels of collagenase and stromelysin message stimulated by these factors. EGF stimulated significant accumulation of both c-fos and c-jun mRNAs while only very low amounts of these messages were stimulated by TNF alpha. Our data suggests that TNF alpha may contribute to articular cartilage degradation by stimulating chondrocyte-derived matrix metalloproteases. In addition the regulation of metalloprotease genes in chondrocytes may be different from their regulation in fibroblasts.

Growth hormone and insulin-like growth factor I regulate collagen gene expression and extracellular collagen in cultures of avian skin fibroblasts

Avian skin fibroblasts were isolated, cultured and incubated with [3H]proline for 24 h. The cells exported radiolabeled collagenase-digestible (CDP) and non-collagenase-digestible (NCDP) proteins into the medium. Human, bovine and avian growth hormone (GH) as well as insulin-like growth factor I (IGF-I) attenuated the appearance of [3H]CDP in the medium without affecting [3H]NCDP. The appearance of [3H]CDP was not affected by prolactin. The effects of GH and IGF-I were enhanced by increasing concentrations of fetal calf serum (FCS). A synergism was observed between GH and IGF-I in their effect on CDP. Each peptide, at an ineffective concentration, increased the sensitivity of the cells to the other peptide. Collagenase activity in the medium was enhanced by IGF-I, but not modified by GH, FCS, or by their interaction with IGF-I. GH and IGF-I inhibition of type I procollagen gene expression was demonstrated with the aid of probes containing sequences corresponding to the mRNAs for avian alpha I and alpha II chains. The results suggest that GH and IGF-I cooperate in regulating collagen synthesis, but collagen degradation is affected by IGF-I and not by GH.

The mitogenic response to stimulation with basic calcium phosphate crystals is accompanied by induction and secretion of collagenase in human fibroblasts

Synovial fluid basic calcium phosphate (BCP) crystals are associated with severe destructive arthropathies that are characterized by synovial proliferation and digestion of articular collagenous structures. BCP crystals are potent mitogens, which may account for this proliferation. The role of collagenase in articular degradation is controversial because, despite the massive loss of collagen, no studies have confirmed collagenolytic activity in synovial fluid, as originally reported. We investigated collagenase messenger RNA induction and enzyme activity in human foreskin fibroblasts proliferating in response to stimulation with BCP crystals, and analyzed the associated secreted proteins. Northern blots revealed a dose-dependent accumulation of collagenase message, evident by 4 hours and continuing to at least 36 hours, in BCP-stimulated cultures. One- and 2-dimensional polyacrylamide gel electrophoresis of conditioned media from BCP crystal-stimulated cultures revealed the selective induction of 2 proteins with molecular weight and pI values consistent with those of collagenase. Increased enzyme activity was also found. Thus, the mitogenic response of fibroblasts to BCP crystals is accompanied by collagenase induction and secretion, supporting the hypothesis that they act as a mediator of joint destruction in BCP crystal-associated arthropathies.

Porcine collagenase from synovial fibroblasts: cDNA sequence and modulation of expression of RNA in vitro by various cytokines

Collagenase is a metalloproteinase that is important in extracellular matrix turnover and is produced by synovial fibroblasts in response to various cytokines and growth factors. Porcine collagenase cDNA was cloned and the sequence shows a 469-amino acid (AA) peptide with high homology to the human and rabbit enzyme (84% and 83.4% respectively). Predicted amino acid sequence from position #99-114 agree well with previously obtained NH2-terminal AA sequence data of purified mature, active pig collagenase. Using the cloned porcine cDNA as a probe in Northern analysis, it was found that IL-1, TNF and EGF enhanced 24-hour steady state mRNA levels while TGF-beta inhibited basal expression of collagenase. When added 10 hours previously, TGF-beta partially inhibited the induction of collagenase by TNF and EGF, but did not affect induction by IL-1.

Platelet-derived growth factor potentiates cellular responses of articular chondrocytes to interleukin-1

Recombinant human interleukin-1 alpha (IL-1 alpha) induced a time-dependent (0-72 hours) and concentration-dependent (0.01-10 ng/ml) production of metalloproteinases (collagenase, gelatinase, stromelysin) and prostaglandin E2 (PGE2) in rabbit articular chondrocytes (RAC). Exposure of RAC to recombinant human platelet-derived growth factor homodimer BB (PDGF-BB; 2-200 ng/ml) in the presence of stimulatory and substimulatory concentrations of IL-1 alpha resulted in a marked augmentation of metalloproteinase and PGE2 production. PDGF-BB exerted no agonist effects on RAC responsiveness. PDGF-BB up-regulated the number of IL-1 receptors per chondrocyte but had no effect on receptor affinity. Cycloheximide and actinomycin D caused a concentration-dependent suppression of the PDGF-BB-mediated potentiation of radiolabeled IL-1 alpha binding to RAC and cell responsiveness to IL-1 alpha. Similarly, IL-1 increased the number of PDGF receptors on RAC without changing receptor affinity. These data are discussed within the context of cytokine-growth factor interactions as components of the pathogenesis of arthritic diseases.

A serum factor promotes collagenase synthesis by an osteoblastic cell line

Regulation of the synthesis of collagenase was investigated in the osteoblastic cell line, UMR 106-01. The cells were stained by the avidin-biotin-complex technique for the presence of the enzyme. By this method, it was possible to identify cells producing collagenase. Synthesis, but not secretion, was found to be constitutive in these cells with the enzyme located intracellularly in cytoplasmic vesicles and the Golgi apparatus. The amount of collagenase contained within UMR cells and the number of cells synthesizing the enzyme were proportional to the concentration of fetal bovine serum in the incubating medium. When serum was withdrawn from the osteosarcoma cells, the content of collagenase decreased with time and the enzyme became undetectable by 48 h of serum depletion. The decrease in collagenase content could be completely reversed by resupplying serum to the cells. The collagenase promoting activity of serum could not be eliminated by adsorption on activated charcoal but was retained by a dialysis membrane with a 12,000 mol wt cutoff. A range of bone-seeking hormones or agents known to affect collagenase secretion was added to the medium in an attempt to mimic the effect of serum on collagenase accumulation. None of these agonists, including parathyroid hormone, could reproduce the effect of serum on these cells, although parathyroid hormone could act as a collagenase secretagogue in the presence or absence of serum. It is concluded that fetal bovine serum contains a yet unidentified factor or factors greater than 12,000 mol wt responsible for the continued synthesis of collagenase by UMR 106-01 cells.

New insights into the causes of cancer

Recent advances in molecular biologic analysis have led to major new insights concerning the genetic mechanisms underlying the development of cancer. This article examines the current state of our understanding of the genetic basis underlying the possible mechanisms of carcinogenesis and metastasis. The nature of the genetic lesions found in some cancer-causing genes, cancer-inhibiting genes, growth factor genes, and metastasis genes is discussed, as is the impact that these may have on clinical oncology.

Continuous EGF application impairs long-term collagen accumulation during wound healing in rats

Continuous topical application of epidermal growth factor (EGF) to granulation tissue has been demonstrated to increase the rate of collagen accumulation in wounds. Studies from this laboratory have indicated that a single topical application of EGF leads to a short period of elevated wound collagen content, followed by a rapid breakdown of this newly acquired collagen. In light of recent clinical trials of EGF as an aid to wound healing, we studied the long-term effects of continuous EGF injection. Standard polytetrafluoroethylene (PTFE) wound cylinders were surgically placed in the dorsal midline of 40 male Sprague-Dawley rats. Rats received EGF daily for 14 days, at which time all injections ceased. Wound cylinders were removed for analysis from five test animals and five controls on study days 14, 21, 28, and 35. Wound collagen content in EGF-treated animals was significantly higher than in controls on the 14th day of the study (330% higher, P less than .002), but dropped to lower levels on each succeeding day (day 21: 97% of control, NS; day 28: 63% of control, NS; day 35: 72% of control, P less than .03). There was a significant increase in wound collagenase activity only on days 14 and 21, but not on days 28 and 35. We demonstrated that continuous application of EGF may artificially elevate wound collagen content, thereby leading to increased wound catabolism on cessation of treatment.

Partial sequencing and characterization of the tumor cell-derived collagenase stimulatory factor

A tumor cell-derived, collagenase stimulatory factor (TCSF), previously isolated and purified from LX-1 human lung carcinoma cells and judged by immunoblotting and SDS-PAGE to contain a single protein of approximately 58 kDa, has been further analyzed for its biological activity and composition. Three significant new findings have been made. First, the biological activity of TCSF preparations was shown definitively to reside in the 58-kDa protein. This was achieved in two ways: (a) a polyclonal antibody was raised against the 58-kDa protein, after excision from an SDS-PAGE gel, and shown to inhibit the stimulation of fibroblast collagenase production by TCSF preparations; (b) the 58-kDa protein was eluted from a transblot of purified TCSF and shown to stimulate fibroblast collagenase production. Second, partial sequencing of the 58-kDa protein revealed no significant homologies with other known collagenase stimulatory factors. Third, purified TCSF was found, on transblotting to Immobilon, to contain a doublet of 58 kDa (TCSF1) and 54 kDa (TCSF2) proteins; the former was present in higher concentration than the latter. N-terminal amino acid sequencing of the two intact proteins and of four corresponding pairs of tryptic peptides derived from the two proteins showed identity in each case, indicating that TCSF1 and TCSF2 are very similar in composition. However, TCSF1 but not TCSF2 stimulated fibroblast collagenase production, confirming that the 58-kDa protein is the major active component of TCSF preparations.

Estrone modulates the EGF receptor in the liver of db/db mouse

The genetically diabetic db/db mouse is an excellent model to study the effect of diabetes on hormone receptors. The decrease of EGF binding sites could be detected in the hepatic microsomes of diabetic mice as early as 3 weeks of age. In addition, there was an age-related decrease in the autophosphorylating activity of EGF receptor isolated from the liver of diabetic mice. Estrone feeding (0.005%) partially restored this autophosphorylating activity. Northern blot analysis showed that the hepatic EGF receptor transcripts were dramatically decreased during the progression of diabetes and could be reversed by estrone feeding. Transfection experiments carried out on HepG2 cells using EGF receptor promoter (pERCAT-6) demonstrated that addition of 2 x 10(-8) M estrone stimulated chloramphenicol acetyltransferase activity. Our results suggest that estrone modulates EGF receptor by enhancing EGF receptor transcripts and the promoter activity of this gene.

Effect of growth factors on collagen metabolism in cultured human heart fibroblasts

Using human heart fibroblasts (HHF), we studied the effect of basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta) on the gene expression of type I collagen, collagenase and tissue inhibitor of metalloproteinases (TIMP). Initially, treatment of HHF with bFGF alone (10 ng/ml) resulted in elevated secretion of collagenase into the culture medium. Subsequent treatment of HHF with TGF-beta in combination with bFGF suppressed collagenase secretion. Northern blot analysis reinforced this observation by revealing an enhancement of the steady-state mRNA level of collagenase in response to bFGF. In order to examine if the collagenase gene was affected by bFGF at the transcriptional level, transfection experiments were carried out with a plasmid containing collagenase promoter linked to chloramphenicol acetyltransferase gene (CAT). Basic FGF stimulated CAT activity by four-fold, indicating increased promoter activity whereas the combination of TGF-beta and bFGF resulted in decreased CAT activity. TGF-beta was shown to increase type I collagen and TIMP mRNA levels by 2.5- and 2.1-fold, respectively. These results suggest that TGF-beta and bFGF may play a pivotal role in regulating collagen metabolism in HHF.

Bone-derived growth factors modulate collagenase and TIMP (tissue inhibitor of metalloproteinases) activity and type I collagen degradation by mouse calvarial osteoblasts

The finding that osteoblasts synthesize collagenase has led to the hypothesis that bone cells play a major role in bone resorption by degrading the surface osteoid layer, thereby preparing the underlying mineralized bone for osteoclastic action. To further understand the mechanisms regulating osteoid removal, mouse calvarial osteoblasts were cultured on 14C-labelled type I collagen films and the abilities of (i) bovine bone matrix extracts and (ii) purified or recombinant human growth factors, to modify their collagenolytic behaviour were investigated. EDTA/Tris-HCl extracts of bone matrix containing growth factor activity, exerted a dose-dependent inhibition of type I collagenolysis by osteoblasts stimulated with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3, 10 ng/ml). Inhibition was accompanied by a reduction in collagenase activity and an increase in free TIMP (tissue inhibitor of metalloproteinases) in the culture medium. Transforming growth factor-beta, epidermal growth factor, platelet-derived growth factor and the acidic and basic fibroblast growth factors all mimicked these effects. In contrast, insulin-like growth factors-I and -II did not inhibit type I collagenolysis, only partially inhibited collagenase activity, and did not stimulate TIMP production by either 1,25(OH)2D3-treated or untreated cells. These findings provide additional evidence for the tight control exerted on the proteolytic activity of osteoblasts and the importance of TIMP in its regulation. They suggest strongly that the conversion (coupling) of the initial resorptive phase of the bone remodelling cycle to one of deposition, may be mediated by polypeptide growth factors either produced locally by osteoblasts, or released by proteolysis from the bone matrix.

Growth factors specifically alter hair follicle cell proliferation and collagenolytic activity alone or in combination

A three-dimensional culture model for isolated murine pelage hair follicles in a type I collagen gel has been utilized to study the effects of selected growth factors on follicle cell proliferation and release of collagenolytic factors. Cultured follicle organoids differentially express cytokeratins 6 and 14 in a pattern suggesting they contain cells of the outer root sheath, inner root sheath and follicle matrix. Using incorporation of [3H]thymidine as a measure of proliferation, follicle organoids show a peak of DNA synthesis between day 1 and 5 of culture, depending on plating density, and then have a low rate of DNA synthesis. Thymidine incorporation is stimulated by transforming growth factor-alpha (TGF-alpha) in a dose-dependent response. Only peripheral cells presumably of the outer root sheath, incorporate thymidine in basal or stimulated conditions. TGF-beta 1 and TGF-beta 2 inhibit constitutive cell proliferation and oppose growth stimulation by TGF-alpha. Hair follicles lyse the collagen gel matrix when exposed to certain cytokines. Epidermal growth factor (EGF) and TGF-alpha stimulate gel lysis, but TGF-beta 1, TGF-beta 2 and cholera toxin do not. Other skin-derived cells, such as interfollicular epidermal cells, dermal fibroblasts, or combinations thereof, do not lyse gels in this culture model even when exposed to growth factors. Combinations of EGF or TGF-alpha with TGF-beta 1 or TGF-beta 2 are synergistic for collagenase release. These cytokines stimulate release of multiple species of matrix metalloproteinases, but the 92-kDa and 72 kDa type IV procollagenases and their activated derivatives predominate on zymograms. In cytokine-stimulated follicles, both peripheral and centrally located cells in the organoids express the 72-kDa type IV collagenase and a similar immunostaining pattern is present in developing follicles in vivo. Thus growth factors appear to work in concert for certain hair follicle responses and in opposition for others. These combined actions may play a role in different phases of hair follicle development that require cell replication and invasion into the deeper dermis.

Induction and stimulation of 92-kDa gelatinase/type IV collagenase production in osteosarcoma and fibrosarcoma cell lines by tumor necrosis factor alpha

Production of a 92-kDa gelatinase/type IV collagenase and tissue inhibitor of metalloproteinases (TIMP) was investigated with human sarcoma cell lines. Among the cytokines and growth factors examined, only human recombinant tumor necrosis factor alpha (TNF alpha) induced and stimulated the proteinase with concomitant increase in TIMP expression, but matrix metalloproteinase 2 (72-kDa gelatinase/type IV collagenase) expression was unchanged. These data suggest that gene expression of the two metalloproteinases is regulated in a different fashion and TNF alpha may be important to allow cancer cells to be more invasive and metastatic.

Tumor necrosis factor-alpha induces mRNA for collagenase and TIMP in human skin fibroblasts

We demonstrated previously that growth promoting factors in general could induce the secretion of interstitial collagenase into the medium of human fibroblast cells (HF). In this study, the effect of tumor necrosis factor-alpha (TNF-alpha) on the induction of collagenase and tissue inhibitor of metalloproteinases (TIMP) was examined. Stimulation of quiescent HF cells with 10 ng/ml TNF-alpha induced the secretion of Mr 57,000, 52,000 procollagenases into the medium. The collagenase activity was elevated 2.8-fold after TNF-alpha treatment. Northern blot analysis of the steady-state mRNA indicated a tenfold elevation of collagenase transcript after 24 h treatment with 10 ng/ml TNF-alpha. The increase in collagenase mRNA was due to transcriptional activation of collagenase gene activity. TIMP mRNA level increased three-fold after TNF-alpha treatment. The activity of TNF-alpha on collagenase and TIMP induction may play an important role in tissue inflammatory, repair and remodeling processes after wound and injury.

Transforming growth factor-ßs as modulators of pericellular proteolytic events

Since the discovery of transforming growth factor-ß:s an increasing number of different biological effects have been attributed to this group of proteins. Analysis of the cellular responses to TGFß stimulation at the molecular level has indicated that TGFß acts as an activator of transcription of several genes. This may in part explain the plethora of various functions that have been ascribed to TGFß. In addition to the TGFß family of polypeptides there is an increasing number of related factors, whose major roles appear to be involved in developmental processes. A distinct feature of TGFß is its ability to regulate pericellular proteolysis of cultured cells. As yet this property has not been associated with other members of this group of polypeptides. Depending on the target cell type TGFß may either increase or decrease pericellular proteolytic activity. Proteolytic activation of latent TGFß and its possible inhibition by TGFß-induced protease inhibitors could be a physiological feed-back mechanism in the control of proteolytic activity in the vicinity of cells.

Identification and characterization of calcium-dependent metalloproteases in rat brain

We have begun to identify and characterize brain protease activities separated by and assayed in substrate-containing polyacrylamide gels. In the present report, we focus on four proteolytic activities identified from rat brain that are dependent on micromolar and millimolar Ca2+ concentrations for activity. In contrast to the previously described Ca2+-dependent neutral cysteine proteases (calpains), all four activities appear to be metalloproteases based on their inhibition by EDTA, EGTA, and 1,10-o-phenanthroline, but not by blockers of serine, cysteine, or aspartic proteases. In the presence of excess Ca2+ and the Zn2+-chelating inhibitor 1,10-o-phenanthroline, activity of the enzymes was reconstituted by addition of lower concentrations of Zn2+, and inhibited by higher Zn2+ concentrations. The four metalloproteases were designated MP-112, MP-92, MP-70, and MP-65 on the basis of their apparent molecular masses in kilodaltons. MP-70, the major activity detected, had an apparent kact for Ca2+ greater than 100 microM versus 10-25 microM for MP-65 and 50-100 microM for MP-92. MP-112 was a minor activity for which Ca2+ activation levels were not determined. MP-112, MP-70, and MP-65 were similar in being most active in the soluble fraction of 7-day neonate forebrain. In contrast, MP-92 activity was highest in the particulate fraction of adult forebrain. About half of the MP-92 activity and lower levels of the other three activities were still detectable in particulate fractions after detergent extraction of membrane, suggesting an association with cytoskeletal or other structural proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine-mediated proteolysis in tissue remodelling

Proteolytic enzymes play a key role in a variety of physiological processes in which the degradation of macromolecules is essential: angiogenesis, embryogenesis, bone and tissue remodelling, blood hemostasis and cell migration. The action of these enzymes is also crucial in the development of many pathological conditions such as wound healing, neoplasia, inflammation and arthritic disorders. The activity of proteases is negatively affected by specific protease-inhibitors. Various growth factors and other cytokines modulate the synthesis and secretion of both proteases and protease-inhibitors. The study of this regulation results in a better insight into (patho)physiology at the molecular level and promises to result in alternative treatment strategies.

Differential effects of interleukin-1 alpha, tumor necrosis factor alpha, and transforming growth factor beta 1 on cell proliferation and collagen formation by cultured fat-storing cells

Fat-storing cells (FSCs), perisinusoidal cells which normally participate in metabolism of vitamin A, have been suggested to participate in collagen synthesis in fibrotic liver. However, key mediators which regulate collagen metabolism in FSCs are yet to be elucidated. In fibroblasts, Interleukin-1 (IL-1), Tumor Necrosis Factor alpha (TNF alpha), and Transforming Growth Factor beta (TGF beta) have been shown to induce diverse modulations of collagen metabolism and cell proliferation. In the present study, these cytokines were tested for their abilities to regulate collagen formation and proliferation by cultured rat FSCs. FSCs primary culture was established and incubated in the absence or presence of various concentrations of IL-1 alpha, TNF alpha, and TGF beta 1. Tritiated proline and thymidine were used to examine collagen formation and cell proliferation. IL-1 alpha (2.5-10 U/ml) had a concentration-dependent stimulatory effect on FSC proliferation with a maximal response of 160% compared to that of untreated FSCs. This mitogenic effect resulted in slight but significant increases (15-20%) in the net collagen formation. However, when this parameter was standardized relative to DNA content, significant inhibition of both collagen and noncollagen protein formation by IL-1 alpha was demonstrated. TNF alpha also exhibited a similar mitogenic effect but induced a more selective inhibition of collagen formation. In contrast, TGF beta 1 (0.01-1 ng/ml) specifically enhanced collagen formation by 60-80%, as also evidenced by significant increases in the ratio of [3H]hydroxyproline to [3H]proline incorporated in newly formed proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of collagenase and collagenase mRNA production in early- and late-passage human diploid fibroblasts

The levels of collagenase and collagenase mRNA produced by early-passage (less than 40% of lifespan completed) and late-passage (greater than 80% of lifespan completed) cultures of human fibroblasts were analyzed. The constitutive levels of collagenase and collagenase mRNA produced by the late-passage cultures were 10-30 x greater than the levels observed in similarly treated early-passage cultures. Immunofluorescence analysis established that the percentage of collagenase-positive cells was also greater (77% vs. 4%) in the late-passage cultures. To determine whether the difference in collagenase production resulted from cell-derived regulatory factors, collagenase production was examined in cultures plated onto substrates coated with fibroblast extracellular matrix (ECM). Collagenase and collagenase mRNA production was enhanced in both types of cultures, although amounts produced by ECM-induced early-passage cultures was significantly less than that produced by similarly treated late-passage cultures. Collagen-coated substrates also induced collagenase synthesis.

Neutral metalloprotease from tendons

Tendon repair following trauma, rupture, or surgery involves both synthesis and degradation of collagen in order to reweave new collagen bundles in with the old. Using an in situ assay on polyacrylamide gels containing gelatin, we have identified protease activity from tendon tissue and from tendon cells in culture. A population of synovial cells from the epitenon surrounding the tendon as well as the tendon fibroblasts themselves were examined. The cells and the conditioned medium from both cell populations exhibited a major band of gelatin-degrading activity at 70 kdaltons and a minor band of activity at 60 kdaltons. When preparations were reacted with p-aminophenylmercuric acetate (APMA) before electrophoresis, a third band appeared at 63 kdaltons. The main band at 70 kdaltons comigrated with a [35S]methionine-radiolabeled protein band. Inhibitor and pH studies identified the enzymes as neutral metalloproteases requiring disulfide bonds for activity. No proteolytic activity was detected on casein-containing gels, ruling out the presence of stromelysin. Since electrophoresis in the presence of SDS would separate the metalloprotease from the smaller molecular weight inhibitor (TIMP), these in situ assays provide a sensitive screening system for gelatin-degrading enzymes present in tendon without prior removal of TIMP.

Differential stimulation of collagenase and chemotactic activity in fibroblasts derived from rat wound repair tissue and human skin by growth factors

Epidermal growth factor and cartilage-derived basic fibroblast growth factor (EGF and CD-bFGF) are mitogens shown to increase the rate of wound repair in animal models. In addition to being a mitogen for granulation tissue, CD-bFGF stimulates the recruitment of cells to the wound site. CD-bFGF and a closely-related chondrosarcoma-derived fibroblast growth factor stimulated chemotaxis of granulation tissue cells in vitro, each factor having a maximum activity at a concentration of 55 pM. Epidermal growth factor was also a potent chemoattractant for rat granulation tissue fibroblasts; however, maximum activity was obtained at 1.7 nM. Cells from all stages of wound repair were chemotactically responsive to these factors, but there was some attenuation of the response to bFGF in cells derived from fully-organized day 28 granulation tissue. Collagenase-catalyzed restructuring of collagen, an additional significant feature of wound repair, is probably critical to cell movement in an extracellular matrix. Cells derived from organizing (6-day old) sponge granulation tissue secreted latent collagenase constitutively in vitro. In the presence of serum, the production of collagenase was stimulated three-four fold by 1.8 nM bFGF derived either from cartilage or chondrosarcoma. When serum was present, as at a wound site, collagenase production was not enhanced by the addition of EGF. Cells from fully organized, day 21 sponge granulation tissue did not secrete latent collagenase constitutively and could not be stimulated to do so by the addition of EGF, bFGF, or phorbol ester. Human skin fibroblast collagenase production was also stimulated by bFGF and was refractory to EGF. While both classes of growth factor have the ability to promote wound healing, the varying responses they elicit in cell populations from the wound site emphasize the different pathways of cellular activation.

Collagenase production by early and late passage cultures of human fibroblasts

Comparison of the proteins secreted by early and late passage cell cultures of human fibroblasts revealed a high level of immunoreactive collagenase (Mr = 55,000 Da and 58,000 Da) in the late passage cell culture conditioned medium. Both molecular weight species reacted with a monoclonal anticollagenase antibody and were apparently glycosylation varaents of the same protein. The question of whether the apparent age-dependent differences in collagenase synthesis reflected changes in protein synthesis or secretion was addressed by assaying immunoreactive collagenase and collagenase mRNA. Immunofluorescence microscopy of cellular collagenase revealed that the percentage of collagenase positive cells ranged from 1 to 6% (early passage) to 35 to 46% (late passage) indicating that the late passage cells had higher basal levels of collagenase synthesis. Later passage cultures also secreted higher levels of immunoprecipitable collagenase into the culture medium and Northern analysis established that the basal level of collagenase mRNA was also 10 times greater in late passage cells. High basal levels of collagenase were also observed in fibroblasts cultured from an in vivo aged donor and from donors with Werner's syndrome. Collagenase production was induced in both early and late passage cell cultures by exposure to fibroblast extracellular matrix, fibroblast conditioned media, polypeptide growth factors, or phorbol esters. The induced levels were always greater in the late passage cell cultures than in the early passage cell cultures.

Increased chemotactic and mitogenic response of psoriatic fibroblasts to platelet-derived growth factor

The effect of increasing doses from 1.25 to 10 ng/ml of PDGF was tested for chemotactic and mitogenic activity on psoriatic fibroblasts cultured from involved and uninvolved skin of five patients compared to normal fibroblasts from five matched control subjects. The chemotactic response of psoriatic fibroblasts from involved skin (p less than 0.05) and uninvolved skin (p less than 0.005) is significantly enhanced compared to normal fibroblasts. Similarly, PDGF in the presence of platelet poor human plasma is a more potent mitogenic agent in psoriatic fibroblasts than in normal fibroblasts. This increased sensitivity of psoriatic fibroblasts to PDGF may be related to the inflammatory and vascularization processes involved in psoriatic dermis.

Expression of platelet-derived growth factor receptors is induced on connective tissue cells during chronic synovial inflammation

The tissue distribution of the receptor for platelet-derived growth factor (PDGF) was investigated by immunohistochemistry on frozen sections from normal and inflamed synovial tissue using monoclonal antibodies to the receptor. Non-inflamed synovial tissue showed no staining, indicating that PDGF receptor expression is low or absent in normal tissue. In contrast, tissue from synovitis with prominent neovascularization showed a strong staining in the tunica media of the proliferating blood vessels as well as on connective tissue cells in the stroma. Tissue from synovitis with prominent proliferation of synovial lining showed intense staining for PDGF receptors in fibroblast-like cells of the lining and a less intense staining on vascular and connective tissue cells deeper in the stroma. Staining for PDGF receptors was also intense in the pannus tissue close to infiltrated bone and cartilage. In all these forms of synovitis, PDGF receptor staining was associated with increased HLA-DR staining and infiltration of macrophages and T lymphocytes. The finding that PDGF receptor expression is induced in conjunction with the chronic synovial inflammation associated with rheumatoid arthritis and some other forms of arthritides suggests that PDGF may play a role in the stimulation of mesenchymal cell proliferation that often accompanies chronic inflammatory disease.

Serum and growth factors regulate expression of a 43 kDa protein in smooth muscle cell cultures

Smooth muscle cells respond to injury and the presence of serum factors by modulating from a quiescent contractile cell to a motile synthetic phenotype. To evaluate the biochemical response to serum exposure, we examined the proteins synthesized and secreted in response to serum. The most prominent effect of serum was the rapid production of a protein with an apparent molecular weight of 43 kDa. Removal of serum from the culture environment led to a cessation of 43 kDa protein production. The effect of exogenous heparin on 43 kDa protein production was also evaluated. Neither the 43 kDa protein nor a previously described 38 kDa protein was induced by heparin. Further, heparin treatment did not counteract the effects of serum. These studies demonstrate that an early response of vascular smooth muscle cells to serum is the production of this previously undescribed protein and that other modifications of the culture conditions did not affect its synthesis.

Modulation of fibroblast proliferation by postsurgical macrophages

Macrophages and fibroblasts are major components of postsurgical peritoneal repair. In order to understand the interaction between these two cell types, we studied the effects of spent macrophage culture media on fibroblast proliferation. Rabbits underwent resection and reanastomosis of their small intestine. Peritoneal exudative cells (PEC) were then collected from these animals on postoperative Days 4, 7, and 28 and from nonsurgical controls. PEC (5 X 10(5) cells/ml) were cultured in M-199 with 3% fetal calf serum. After 48 hr the spent media from the cultured PEC were harvested, centrifuged (200g for 10 min), and stored (medium: M-D0, D4, D7, D28). A second group of rabbits underwent peritoneal wall abrasion followed by collection of fibroblasts directly from the site of injury on postoperative Days 1, 4, and 7. After Day 7 of culture, fibroblasts were resuspended and seeded into dishes (1 X 10(5) cells in 1 ml medium), to which was added 1 ml of spent PEC culture medium. After 24 hr of incubation, 1 muCi [3H]thymidine was added for an additional 18 hr. Fibroblasts were then collected and the amount of [3H]thymidine incorporated into trichloroacetic acid-precipitable material was quantitated. In one protocol, fresh M-199 with 3% fetal calf serum was used, and in another protocol, "U-medium" (which was previously incubated for 48 hr with fibroblasts) was used. The cytology of the PEC was determined by Wright's staining, nonspecific esterase activity, and phagocytosis. At least 80% of the peritoneal exudative cells were identified as macrophages. Postsurgical Day 7 fibroblasts demonstrated greater [3H]thymidine incorporation compared to fibroblasts from postoperative Days 1 and 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Membrane association of collagenase stimulatory factor(s) from B-16 melanoma cells

Past studies have shown that contact between tumor cells and fibroblasts results in stimulation of collagenase production by the fibroblasts. Membrane fractions prepared by differential centrifugation of sonicated B-16 melanoma cells were shown here to contain a collagenase stimulatory factor(s) (CSF). Trypsin treatment of intact B-16 cells prior to membrane fractionation led to loss of 90% of the total activity, indicating that CSF is localized on the outer surface of the cells. Stimulation of fibroblast collagenase production was also observed with dialyzed octylglucoside extracts of the B-16 membranes. Additional of exogenous lipid, ie, a mixture of phosphatidylcholine and phosphatidylserine, to the detergent extract of the membranes followed by dialysis and centrifugation at 100,000g resulted in 80% recovery of the factor activity in the pellet containing reconstituted lipid vesicles. Fractionation of tritium-labeled, reconstituted lipid vesicles on a Sephacryl S-300 column revealed that the collagenase stimulatory factor coeluted with the radioactive lipid vesicles. The fractionated lipid vesicles lost stimulatory activity completely after trypsin treatment or heating at 65 degrees C, indicating that the factor is a protein.

Insulin stimulates secretion of a collagenase inhibitor by Swarm rat chondrosarcoma chondrocytes

Swarm rat chondrosarcoma chondrocytes produce an inhibitor of collagenase similar to that found in bovine articular chondrocytes and extracts of bovine scapular cartilage. These cells synthesize normal levels of cartilage type proteoglycans when cultured in serum free medium with insulin. Collagen synthesis is also increased when insulin is added to chondrosarcoma chondrocytes. We have demonstrated that insulin stimulates collagenase inhibitor production by these chondrocytes. Enhancement of inhibitory activity occurs over the range of 10 to 1000 ng/ml. A 3.2 fold stimulation was observed at a concentration of 1 microgram/ml. There was a lag period of 24 to 48 hours before the insulin effect became evident. Latent or active collagenase was not detectable under these conditions. These results suggest that the hormone insulin controls the levels of collagen in this tumor by stimulating synthesis of collagen and inhibitors of collagenase.

Induction and suppression of type I collagenase in cultured human cells

A number of peptide growth factors have been shown to induce the secretion of type I collagenase into the medium of human fibroblast cultures (Chua et al., 1985). In this study the ability of eye-derived growth factor, lectin and tumor-promoting agents on collagenase induction in human fibroblast cells were examined. These agents were found to be able to induce collagenase production to a similar extent as epidermal growth factor. Dexamethasone at 10-100 nM was found to suppress collagenase induction in human fibroblast cells. The cell-type specificity of this enzyme induction by growth factors was studied by using a human epidermoid carcinoma cell line, A-431. An Mr 55,000 band appeared in the medium of A-431 cells upon 22 h exposure to EGF. Two-dimensional peptide pattern of the Mr 55,000 band in A-431 cells was identical to the counterpart in HF cells. Our results indicated that the induction of collagenase was not unique to human fibroblast cultures.

Effect of tunicamycin on the biosynthesis of human fibroblast collagenase

It is generally accepted that collagenase from human fibroblast cultures consists of two proenzymes (Mr 60,000 and 55,000) and two active forms (Mr 50,000 and 43,000). We demonstrated previously that epidermal growth factor (EGF) as well as a number of other growth factors induced the secretion of procollagenase (Mr 60,000, Mr 55,000) into the medium of human fibroblast cultures (Chua et al., 1985). In the presence of tunicamycin and EGF, the secretion of the larger form of procollagenase was suppressed preferentially with concomitant appearance of a new band, Mr 40,000. This Mr 40,000 band could be specifically immunoprecipitated by antibody raised against human collagenase. By two-dimensional peptide mapping, the Mr 40,000 material appeared to have similar composition as the Mr 60,000 band. In a time course study, the Mr 55,000 procollagenase band was the earliest protein to appear in the medium after 1 hour labeling with [35S]-methionine. The Mr 60,000, 50,000 and 43,000 bands appeared after a 2 hour labeling period. Our results indicate that human collagenases are glycosylated proteins and are synthesized via the dolichol phosphate pathway.