Isolation of a collagenase cDNA clone and measurement of changing collagenase mRNA levels during induction in rabbit synovial fibroblasts

A personal journey with matrix metalloproteinases

I was given the honor of delivering the 2015 Lifetime Membership Award lecture at the International Proteolysis Society's annual meeting held in Penang, Malaysia in October 2015. It gave me an opportunity to look back on how I started my research on matrix metalloproteinases (MMPs) and how I continued to work on these proteinases for the next 42 years. This is a series of sketches from the personal journey that I took with MMPs, starting from the purification of metalloproteinases, cloning, structural studies, then to a more recent encounter, endocytic regulation of matrix-degrading metalloproteinases.

Effect of retinoids on rheumatoid arthritis, a proliferative and invasive non-malignant disease

In rheumatoid arthritis synovial tissue proliferates and destroys articular cartilage, bone and tendons. Collagenase is a major mediator of the connective tissue degradation. This enzyme is produced in large quantities by rheumatoid tissue and its synthesis can be inhibited by retinoids. However, knowledge of mechanisms controlling retinoid inhibition of collagenase production and of factors possibly controlling synovial cell proliferation is limited. We found that transforming growth factor beta in combination with epidermal growth factor, epidermal growth factor alone and immune interferon increased proliferation of cultured human and rabbit synovial fibroblasts. Only transforming growth factor beta caused a piling up of cells into foci resembling those seen in primary cultures of human rheumatoid tissue. All the factors were antagonized by retinoids but not by glucocorticoids or indomethacin. Adding retinoids or glucocorticoids to collagenase-producing cells decreased hybridizable collagenase mRNA by 50% within 24 h. Oral administration of retinoids to rats with experimental arthritis decreased clinical disease without toxicity, and inhibited collagenase synthesis by synovial cells taken from treated animals. Retinoids are both antiproliferative and anti-invasive, and therefore may be potential therapeutic agents in the treatment of rheumatoid arthritis.

The turnover and degradation of collagen

The interstitial collagens are degraded predominantly extracellularly, by specific collagenases (metalloproteinases) capable of cleaving the helical region across the three chains at a similar locus, solubilizing the cleaved products from the fibril. Other neutral proteinases may also function in this role by cleaving near cross-links in the fibril. Collagen type, molecular aggregation and small changes in temperature all markedly affect rates of collagenolysis in the fibril. Regulation of collagenolysis is also modulated at the levels of (1) cellular production of latent collagenase (procollagenase), (2) activation of latent collagenase, and (3) production of collagenase inhibitors. Fibroblastic cells and certain macrophages are probably the predominant sources of collagenases in inflammation; an enzyme in polymorphonuclear leucocytes (neutrophils) is distinct from the tissue enzyme. Molecules such as mononuclear cell factor (MCF), homologous with interleukin 1, which augment cellular collagenase production in inflammation, are derived from monocytes. The mechanisms of augmented collagenase production involve new protein synthesis and, if this augmentation is analogous to that produced by urate crystals, it is probably associated with increased levels of procollagenase mRNA. MCF production is itself controlled by products of lymphocytes as well as by interactions of monocytes with the Fc portion of immunoglobulins and components of the extracellular matrix. Activation of latent (pro)collagenase probably occurs in vivo through the action of neutral proteinases such as plasmin (through plasminogen activator). These effects may be indirect and exerted through proteolytic activation of a procollagenase activator. Tissue inhibitors act to regulate the active collagenase.

Tadpole collagenase, the single parent of such a large family

This editorial review comments the development of the field of the matrix metalloproteinases that was initiated by the demonstration of the tadpole collagenase in 1962.

Bcl-3 is an interleukin-1-responsive gene in chondrocytes and synovial fibroblasts that activates transcription of the matrix metalloproteinase 1 gene

OBJECTIVE

To define the role of Bcl-3, a member of the inhibitor of nuclear factor kappaB (NF-kappaB) family and a known regulator of NF-kappaB, in interleukin-1 (IL-1)-induced matrix metalloproteinase 1 (MMP-1) transcription in chondrocytes and synovial fibroblasts.

METHODS

SW-1353 cells, a human chondrosarcoma cell line, were stimulated with IL-1beta, and the harvested RNA was subjected to microarray analysis and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). The SW-1353 cells were stimulated with IL-1 or transfected with a plasmid that constitutively expressed Bcl-3, and then MMP-1 messenger RNA (mRNA) expression was assayed by quantitative real-time RT-PCR. SW-1353 cells were transfected with antisense oligonucleotides to Bcl-3, and IL-1-induced MMP-1 mRNA expression was assayed by quantitative RT-PCR. SW-1353 cells and rabbit synovial fibroblasts were transfected with a 4.3-kb human MMP-1 promoter construct along with Bcl-3 and NF-kappaB1 expression constructs, and MMP-1 transcription was assayed.

RESULTS

Microarray analysis and real-time RT-PCR showed Bcl-3 to be an IL-1beta-responsive gene in SW-1353 cells. Exogenous expression of Bcl-3 in SW-1353 cells activated MMP-1 transcription. Endogenous Bcl-3 expression was required for IL-1beta induction of MMP-1 gene expression. Bcl-3 also activated MMP-1 transcription in primary synovial fibroblasts. We showed previously that NF-kappaB1 contributes to IL-1beta induction of MMP-1 transcription in stromal cells. We showed here that Bcl-3 can cooperate with NF-kappaB1 to activate MMP-1 transcription in SW-1353 cells.

CONCLUSION

These data define a new role for Bcl-3 in joint cells as an IL-1beta-responsive early gene involved in cell-mediated cartilage remodeling. Our findings implicate Bcl-3 as an important contributor to chronic inflammatory disease states, such as osteoarthritis and rheumatoid arthritis.

Skin flap-induced regression of granulation tissue correlates with reduced growth factor and increased metalloproteinase expression

Previous studies have shown that covering granulation tissue of a full-thickness skin wound by a vascularized skin flap induces tissue remodeling, with a rapid loss of granulation tissue cells by apoptosis. In the present study, in situ hybridization has been used to examine mRNA expression for several factors that may be implicated in the apoptosis seen in this tissue. Skin wounds were made on the dorsal skin of 8-week-old rats. Ten days after wounding, skin flaps were created surgically and sutured over the granulation tissue. Tissue sections of granulation tissue from various times after addition of the skin flap were hybridized with 33P-labelled cRNA probes for transforming growth factor-beta1 (TGF-beta1), beta-inducible gene H3 (beta-ig-h3), alpha1 (1) procollagen, alpha-smooth muscle actin, matrix metalloproteinase-13 (MMP-13) and -2 (MMP-2), tissue inhibitor of metalloproteinase-1 (TIMP-1), and inducible nitric oxide synthase (iNOS). Control granulation tissue prior to addition of the skin flap showed high levels of TGF-beta1, beta-ig-h3, alpha1 (1) procollagen, alpha-smooth muscle actin, and TIMP-1 expression. MMP-13, MMP-2, and iNOS mRNA were low in 10-day granulation tissue. Addition of a skin flap resulted in a decrease in the expression of TGF-beta1, beta-ig-h3, alpha1 (I) procollagen, alpha-smooth muscle actin, and TIMP-1, but increased expression of MMP-13 and MMP-2. Similarly, an increase in iNOS mRNA expression was observed in the granulation tissue after addition of the skin flap. Addition of a vascularized skin flap may result in rapid remodelling of granulation tissue due to a decrease in expression of the trophic growth factor TGF-beta1 and increased degradation of extracellular matrix due to an alteration in the balance between MMPs and their inhibitor, TIMP-1. Additionally, increased iNOS expression may also favour apoptosis through the generation of free radicals. The additive effect of reduced growth factor expression, increased extracellular matrix turnover, and nitric oxide generation may result in the fibroblast and vascular cell apoptosis seen during the rapid remodelling of this tissue.

Matrix metalloproteinases: a tail of a frog that became a prince

It is 40 years since the first member of what came to be known as the matrix metalloproteinase (MMP) family was described. Structural, molecular and biochemical approaches have subsequently contributed to piecing together the puzzle of how MMPs work, and how they contribute to various disease processes.

Integration of the NF-kappaB and mitogen-activated protein kinase/AP-1 pathways at the collagenase-1 promoter: divergence of IL-1 and TNF-dependent signal transduction in rabbit primary synovial fibroblasts

Collagenase-1 (MMP-1) is a protease that is expressed by stromal cells and that is involved in remodeling of the extracellular matrix. IL-1 and TNF-alpha enhance collagenase secretion by stromal cells, and chronic exposure of cells to these cytokines can contribute to connective tissue disease. In this study, we show that the NF-kappaB pathway is required for activation of collagenase-1 transcription in rabbit primary synovial fibroblasts (RSF). Although both IL-1 and TNF activate NF-kappaB in these cells, only IL-1 induces collagenase-1 transcription. We have reported previously that NF-kappaB and AP-1 cooperate to mediate IL-1-induced MMP-1 transcription. Here, we show that IL-1 is superior to TNF at inducing c-Jun synthesis, phosphorylation and binding activity in RSF. Similarly, IL-1 is more effective at activating the mitogen-activated protein kinases (MAPK), including the extracellular signal-regulated kinases (ERK), which are required for IL-1-induced MMP-1 transcription. Thus stimulation of the ERK and AP-1 pathways is an essential component of MMP-1 transcriptional activation, which is deficient in TNF-treated cells. These studies demonstrate cooperation between the MAPK and NF-kappaB signaling pathways for IL-1-dependent collagenase-1 transcription, and they define a dichotomy of IL-1- and TNF-elicited signaling that is relevant to cytokine-mediated connective tissue disease.

Cloning of the gene for interstitial collagenase-3 (matrix metalloproteinase-13) from rabbit synovial fibroblasts: differential expression with collagenase-1 (matrix metalloproteinase-1)

Cartilage, bone and the interstitial stroma, composed largely of the interstitial collagens, types I, II and III, are remodelled by three members of the metalloproteinase (MMP) family, collagenase-1 (MMP-1), collagenase-2 (MMP-8) and collagenase-3 (MMP-13). MMP-1 and MMP-13 may contribute directly to disease progression, since they are induced in patients with rheumatoid arthritis and osteoarthritis. The study of MMP-1 and MMP-13 gene regulation in models of arthritic disease has been problematic because mice and rats, which are typically used, only possess a homologue of MMP-13. Here we show that in contrast with mice and rats, rabbits possess distinct genes homologous to human MMP-1 and MMP-13. Furthermore, rabbit MMP-13 is expressed simultaneously with MMP-1 in chondrocytes and synovial fibroblasts in response to the cytokines interleukin-1 and tumour necrosis factor-alpha, or the phorbol ester PMA. The time course of MMP-13 induction is more rapid and transient than that of MMP-1, suggesting that distinct mechanisms regulate the expression of these two collagenases. We have cloned the rabbit MMP-13 gene from synovial fibroblasts and demonstrated that the rabbit gene shares greater homology with human MMP-13 than does the mouse interstitial collagenase. Together with the fact that mice and rats do not possess a homologue to human MMP-1, our data suggest that the rabbit provides an appropriate model for studying the roles of interstitial collagenases in connective-tissue diseases, such as rheumatoid arthritis and osteoarthritis.

Role of serum amyloid A as an intermediate in the IL-1 and PMA-stimulated signaling pathways regulating expression of rabbit fibroblast collagenase

The matrix metalloproteinase collagenase is expressed by resident tissue cells only when needed for biological remodeling. Exogenous addition of inflammatory and growth-promoting cytokines stimulates collagenase expression in early passage fibroblast cultures. In addition, the signal for collagenase expression in response to phorbol-12 myristate-13 acetate (PMA) or to agents which alter cell shape in early passage fibroblast cultures is routed extracellularly to an autocrine cytokine intermediate, IL-1 alpha. Importantly, fibroblasts, when freshly isolated from the tissue, are not competent for IL-1 alpha gene expression and, therefore, cannot produce collagenase in response to shape change agents. However, they do make a small amount of collagenase in response to PMA via an IL-1-independent pathway that has not been further characterized. In this paper, we investigate the role of a second autocrine, serum amyloid A3 (SAA3), in IL-1-dependent and -independent collagenase gene expression. We demonstrate that SAA3 is required for effective stimulation of collagenase expression by either exogenous or endogenous IL-1. Furthermore, while freshly isolated fibroblasts cannot express IL-1 alpha they can express SAA3, and this autocrine mediator acts independently of IL-1 alpha to control the low level of collagenase expression that can be stimulated by PMA. These results provide further evidence for a newly emerging paradigm of collagenase regulation which emphasizes the requirement for extracellular routing of signals. They also suggest that SAA3 might be utilized independently of IL-1 alpha to control tissue remodeling in vivo.

Inhibition of rabbit collagenase (matrix metalloproteinase-1; MMP-1) transcription by retinoid receptors: evidence for binding of RARs/RXRs to the -77 AP-1 site through interactions with c-Jun

Treatment of synovial fibroblasts with retinoic acid (RA) decreases their expression of collagenase (matrix metalloproteinase-1 or MMP-1), an enzyme that degrades interstitial collagens and contributes to the pathology of rheumatoid arthritis. This inhibition results, at least in part, from RA-induced decreases in the mRNA for the transactivators Fos and Jun (with concominant increases in RAR mRNA) and by sequestration of Fos/Jun by RARs/RXRs. Previously, we provided evidence that retinoid receptors are also present in complexes that bind to fragments of rabbit MMP-1 promoter DNA containing an AP-1 site at -77 (Pan et al., 1995, J. Cell. Biochem., 57:575-589). However, it was unclear whether RARs and retinoid X receptors (RXRs) were binding directly to the DNA or indirectly through another protein. We now use a sensitive MMP-1 promoter/luciferase reporter construct to confirm the transcriptional role of the AP-1 site at -77. In addition, with electrophoretic mobility shift analyses (EMSAs), antibody "supershifts" and DNAase 1 footprinting, we examine the interaction of retinoid receptors and AP-1 protein on the MMP-1 promoter. We demonstrate that RARs, RXRs, and c-Jun form a complex at the AP-1 site in which c-Jun binds directly to the DNA and apparently tethers the retinoid receptors to the complex. We conclude that retinoid receptors/AP-1 protein interactions at the DNA may provide an additional means of controlling collagenase gene transcription by retinoids.

Inhibition of the induction of collagenase by interleukin-1 beta in cultured rabbit synovial fibroblasts after treatment with the poly(ADP-ribose)-polymerase inhibitor 3-aminobenzamide

3-Aminobenzamide is an inhibitor of poly-(ADP-ribosyl)ation. In concentrations from 3 to 10 mM it reduced the collagenase activity in culture supernatants of interleukin-1 beta-stimulated rabbit synovial fibroblasts. 3-Aminobenzoate, not an inhibiter of poly(ADP-ribosyl)ation, had no effect on collagenase activity at a concentration of 10 mM. We concluded that poly(ADP-ribosyl)ation plays a role in the induction of the expression of collagenase and that 3-aminobenzamide can inhibit this process.

Induction and activation of procollagenase in rabbit synovial fibroblasts after treatment with active oxygen released by xanthine/xanthine oxidase

Treatment of rabbit synovial fibroblasts with active oxygen (AO) released by xanthine/xanthine oxidase resulted in an induction of procollagenase in these cells in concentrations ranging from 12.5 micrograms/ml xanthine plus 0.0025 U/ml xanthine oxidase to 50 micrograms/ml xanthine plus 0.01 U/ml xanthine oxidase. Preceding this there was an accumulation of poly(ADP-ribose) for the same concentration range of xanthine/xanthine oxidase. Furthermore, it was found that AO caused activation of the latent procollagenase to the active enzyme in concentrations ranging from 0.1 micrograms/ml xanthine plus 0.00002 U/ml xanthine oxidase to 1 microgram/ml xanthine plus 0.0002 U/ml xanthine oxidase. It is suggested that poly(ADP-ribosyl)ation participates in the induction of procollagenase by relaxing chromatin. Furthermore, it is proposed that AO activates latent procollagenase under physiological conditions.

Competence for collagenase gene expression by tissue fibroblasts requires activation of an interleukin 1 alpha autocrine loop

The enzyme collagenase (EC 3.4.24.7), a key mediator in biological remodeling, can be induced in early-passage fibroblasts by a wide variety of agents and conditions. In contrast, at least some primary tissue fibroblasts are incompetent to synthesize collagenase in response to many of these stimulators. In this study, we investigate mechanisms controlling response to two of the conditions in question: (i) trypsin or cytochalasin B, which disrupt actin stress fibers, or (ii) phorbol 12-myristate 13-acetate (PMA), which activates growth factor signaling pathways. We demonstrate that collagenase expression stimulated by trypsin or cytochalasin B is regulated entirely through an autocrine cytokine, interleukin 1 alpha (IL-1 alpha). The IL-1 alpha intermediate also constitutes the major mechanism by which PMA stimulates collagenase expression, although a second signaling pathway(s) contributes to a minor extent. Elevation of the IL-1 alpha level in response to stimulators is found to be sustained by means of an autocrine feedback loop in early-passage fibroblast cultures. In contrast, fibroblasts freshly isolated from the tissue are incompetent to activate and sustain the IL-1 alpha feedback loop, even though they synthesize collagenase in response to exogenous IL-1. We conclude that this is the reason why tissue fibroblasts are limited, in comparison with subcultured fibroblasts, in their capacity to synthesize collagenase. Activation of the IL-1 alpha feedback loop, therefore, seems likely to be an important mechanism by which resident tissue cells adopt the remodeling phenotype.

Heat shock of human synovial and dermal fibroblasts induces delayed up-regulation of collagenase-gene expression

We investigated the effect of heat shock on the expression of the collagenase gene in normal human synovial and dermal fibroblasts. Heat shock (42-44 degrees C for 1 h) caused a marked increase in heat-shock protein 70 (HSP-70) mRNA levels, followed by a delayed increase in collagenase mRNA levels, in both cell types. Pretreatment with cycloheximide had no effect on the heat-shock-induced increase in HSP-70 mRNA expression, but abrogated the induction of collagenase mRNA during the recovery. To study the mechanisms of collagenase-gene induction by heat shock, the transcriptional activity of a collagenase-promoter-driven chloramphenicol acetyltransferase (CAT) reporter gene was examined in transient transfection experiments. Heat shock was followed by a > 2-fold increase in CAT activity driven by a 3.8 kb fragment of the collagenase promoter, or by a construct containing an AP-1 binding site. A mutation in the AP-1 binding site abolished the effect of heat shock. Electrophoretic-mobility-shift assays revealed a marked increase in DNA-binding activity specific for the AP-1 binding site in nuclear extracts prepared from synovial fibroblasts recovering from heat shock. These results indicate that heat shock causes a delayed increase in collagenase-gene expression in human fibroblasts, and suggests that this stimulation involves, at least in part, transcriptional activation through an AP-1 binding site. Heat shock appears to initiate a programme of cellular events resulting in collagenase-gene expression, and therefore may contribute to connective-tissue degradation in disease states.

Suppression of collagenase gene expression by all-trans and 9-cis retinoic acid is ligand dependent and requires both RARs and RXRs

Retinoic acids (RA) are active metabolites of vitamin A which affect the expression of many genes involved in embryonic development, cell differentiation, and homeostasis. One important target gene for RA is matrix metalloproteinase (MMP-1, collagenase), the only enzyme active at neutral pH that can degrade interstitial collagen, a major component of extracellular matrix. Using a cell line of normal rabbit synovial fibroblasts, HIG82 cells, as a model, we report that both all-trans- and 9-cis-RA inhibit collagenase synthesis. This inhibition occurs at a transcriptional level and is ligand-dependent. Constitutive levels of retinoic acid receptor (RAR) mRNA levels are low, but are increased by all-trans and by 9-cis RA. In contrast, constitutive levels of retinoid X receptor (RXR) mRNA are higher and are not affected by RA. To measure DNA/protein interactions, we used a gel mobility shift assay with oligonucleotides containing either an AP-1 site or a 40 bp region between -182/-141, nuclear extracts from RT-treated cells, and antibodies to RARs and RXRs. We found that both RARs and RXRs interact with these regions of the collagenase promoter, perhaps as part of a complex with other proteins. Our results suggest that heterodimers between RARs and RXRs mediate suppression of the collagenase gene by RA, and that RAR is a limiting factor in this negative regulation.

Regulation of collagenase gene expression by IL-1 beta requires transcriptional and post-transcriptional mechanisms

Interleukin-1 beta is believed to contribute to the pathophysiology of rheumatoid arthritis by activating collagenase gene expression. We have used a cell culture model of rabbit synovial fibroblasts to examine the molecular mechanisms of IL-1 beta-mediated collagenase gene expression. Stimulation of rabbit synovial fibroblasts with 10 ng/ml recombinant human IL-1 beta resulted in a 20-fold increase in collagenase mRNA by 12 h. Transient transfection studies using collagenase promoter-CAT constructs demonstrated that proximal sequences responded poorly to IL-1 beta, possibly due to insufficient activation of AP-1 by this cytokine. More distal sequences were required for IL-1 beta responsiveness, with a 4700 bp construct showing approximately 5-fold induction above control. To examine post-transcriptional mechanisms, transcript from a human collagenase cDNA was constitutively produced by the simian virus 40 early promoter. IL-1 beta stabilized the constitutively expressed human transcript. Furthermore, mutation of the ATTTA motifs in the 3' untranslated region of the human gene also stabilized the transcript. Finally, the rabbit collagenase 3' untranslated region destabilized a constitutively transcribed chloramphenicol acetyltransferase transcript. These data indicate that in addition to activating transcription, IL-1 beta increases collagenase transcript stability by reversing the destabilizing effects of sequences in the 3' untranslated region.

The tumor suppressor p53 regulates its own transcription

The ability of p53 to suppress transformation correlates with its ability to activate transcription. To identify targets of p53 transactivation, we examined the p53 promoter itself. Northern (RNA) analysis and transient transfection experiments showed that p53 transcriptionally regulated itself. A functionally inactive mutant p53 could not regulate the p53 promoter. Deletion analysis of the p53 promoter delineated sequences between +22 and +67 as being critical for regulation. Electrophoretic mobility shift analysis and methylation interference pinpointed the p53 DNA responsive element. When oligomerized in front of a heterologous minimal promoter, this element was regulated by wild-type p53 and not by mutant p53. Point mutations in the DNA element that eliminated protein-DNA interactions also resulted in a nonresponsive p53 promoter. The DNA element in the p53 promoter responsive to p53 regulation is similar to the p53 consensus sequence. However, we have been unable to detect a direct interaction of p53 with its promoter.

The tumor suppressor p53 regulates its own transcription

The ability of p53 to suppress transformation correlates with its ability to activate transcription. To identify targets of p53 transactivation, we examined the p53 promoter itself. Northern (RNA) analysis and transient transfection experiments showed that p53 transcriptionally regulated itself. A functionally inactive mutant p53 could not regulate the p53 promoter. Deletion analysis of the p53 promoter delineated sequences between +22 and +67 as being critical for regulation. Electrophoretic mobility shift analysis and methylation interference pinpointed the p53 DNA responsive element. When oligomerized in front of a heterologous minimal promoter, this element was regulated by wild-type p53 and not by mutant p53. Point mutations in the DNA element that eliminated protein-DNA interactions also resulted in a nonresponsive p53 promoter. The DNA element in the p53 promoter responsive to p53 regulation is similar to the p53 consensus sequence. However, we have been unable to detect a direct interaction of p53 with its promoter.

Multiple levels of post-transcriptional regulation of collagenase (matrix metalloproteinase 1) in an epithelial cell line

Multiple levels of regulation of collagenase (matrix metalloproteinase 1; MMP-1), have been demonstrated in a clonal rat epithelial cell line (A5P/B10). Secreted enzyme could not be demonstrated in culture medium from A5P/B10 cells but, using antibodies specific for collagenase, the enzyme was detected within the cytoplasm and on the surface of the cells. A probe for rat collagenase could not detect a signal for mRNA in the cytoplasm while nuclear run-on data demonstrated that the gene for collagenase was being transcribed. Incubating the cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) significantly increased cytoplasmic mRNA levels and slightly increased the intensity of staining in permeabilized cells, but collagenase activity was still not detected in the conditioned medium. This indicated that the protein was being synthesized by the TPA-treated cells but was not being secreted into the medium. These data suggest that the secretion of collagenase may be regulated both following transcription and after the completion of translation and it is suggested that multiple levels of control may be operating to determine the rate of collagenase release and hence, the rate of collagen turnover.

Correlation between tumor necrosis factor-alpha (TNF-alpha)-induced cytoskeletal changes and human collagenase gene induction

Tumor necrosis factor-alpha (TNF-alpha) has been shown not only to induce the biosynthesis and secretion of collagenase but also to change the organization of cytoskeletal components. In the present study we explore the correlation between the biosynthesis of collagenase (by mRNA hybridization, indirect immunofluorescence and collagenolytic activity), and cytoskeletal reorganization (by rhodamine-phalloidin staining of F-actin) induced in fibroblasts by recombinant TNF (rTNF). In the concentration range of 1-100 ng/ml, rTNF increased extracellular collagenase activity 8-fold and collagenase mRNA 4-fold. In addition, whereas the collagenase mRNA was detected as early as 24 h posttreatment, the appearance of extracellular collagenase activity required 48 h. Using phalloidin to follow the organization of the cytoskeleton we observed that rTNF disrupted the parallel array of stress fibers normally observed in the perinuclear region. In contrast to the time required to affect collagenase synthesis, the effect of rTNF on stress fiber organization occurred as early as 6 h post-treatment. Finally, while the number of cells exhibiting this change increased with increasing concentrations of rTNF, a maximum of about 30% of the cells showed this effect. Interestingly, double staining studies demonstrated that both stress fiber changes and procollagenase production occurred in the same cells. This finding, together with the observation that the cytoskeletal disorganization preceded collagenase gene induction by at least 18 h is consistent with the conclusion that the organizational status of the microfilaments may have a role as a regulator of procollagenase gene expression.

Differential regulation of collagenase gene expression by retinoic acid receptors--alpha, beta and gamma

The mechanisms involved in retinoic acid (RA)-mediated regulation of the collagenase gene in a rabbit synovial fibroblast cell line (HIG82) were investigated. When HIG82 cells are cotransfected with expression vectors containing cDNAs for retinoic acid receptor (RAR) alpha 1, beta 2, or gamma 1 and collagenase promoter-driven CAT reporter constructs, only RAR-gamma 1 represses basal CAT expression upon RA treatment, while RAR-alpha 1, beta 2, and gamma 1 all suppress phorbol-induced CAT expression. Thus, transcriptional regulation of collagenase by RA is mediated by RARs in an RAR-type specific manner. Using mutational and deletional analysis, we find that interaction between elements within 182 bp collagenase promoter plays an important role in this process. In addition, cotreatment with RA results in a decrease of phorbol-induced mRNA levels of fos and jun, and binding of nuclear proteins to an AP-1 oligonucleotide. Furthermore, RA-induced nuclear protein(s) specifically bind to a 22 bp sequence (-182 to -161) of the collagenase promoter. We propose that RA-mediated regulation of the collagenase gene depends on the availability and interaction of specific RARs with multiple DNA elements within the promoter and with transcription factors, including AP-1 related proteins.

Serum amyloid A (SAA3) produced by rabbit synovial fibroblasts treated with phorbol esters or interleukin 1 induces synthesis of collagenase and is neutralized with specific antiserum

We report that nucleic acid sequence analysis of a full-length cDNA clone for a rabbit serum amyloid A (SAA)-like protein has identified this protein as more closely related to SAA3 than to SAA1. SAA3 induced collagenase synthesis in rabbit synovial fibroblasts, and immune IgG raised against this SAA protein abrogated the induction. Using antisera to immunoprecipitate biosynthetically labeled 3H-SAA and 3H-collagenase from culture medium, we compared the levels of SAA and collagenase synthesized by cultures of rabbit fibroblasts at early passage (passages 3-6) with those synthesized by late passage cells (passage 16). Comparatively high levels of both proteins were produced constitutively by fibroblasts at low passage. With increasing passage, levels of both proteins drop so that by passage 16, constitutive production of SAA and collagenase was only approximately 15-20% that of passage 3 cells. Cells at low passage could be readily stimulated with phorbol myristate acetate (PMA) or interleukin 1 (IL-1) to synthesize increased amounts of both SAA and collagenase. In passage 5 cells treated with PMA, we detected increased SAA mRNA by 1.5 h and collagenase mRNA by 5 h. However, older passage cells were more refractory to stimulation and required longer induction times. We suggest that SAA3 may be expressed by fibroblasts at sites of acute inflammation or injury, and that elevated levels of SAA3 may signify "activated" fibroblasts which are already producing increased amounts of collagenase constitutively and which are predisposed to further stimulation.

The role of proteinases in cartilage destruction

Most of the organic, extracellular matrix of articular cartilage consists of collagens and proteoglycans. Their degradation is initiated extra- or peri-cellularly by proteinases produced locally by cells in and around the joint. Although enzymes from all four classes of proteinases can degrade the cartilagenous matrix, serine proteinases, particularly plasmin, and various neutral metalloproteinases (NMPs) are likely to be the key enzymes in this process. Much attention has been paid to members of the latter group, which are synthesised both by the resident, mesenchymal cells of the joint and by various types of white blood cells which colonise it during inflammation. NMPs can be conveniently grouped into three classes, the collagenases, the stromelysins and the gelatinases. Two members are known for each class, with the recently identified "pump" (Putative Metalloproteinase) probably constituting a third member of the stromelysin group. Regulation of these enzymes is complex. Cells normally synthesise NMPs at low rates, but their production increases markedly following cellular activation by cytokines or certain other stimuli. Major control points for enzyme synthesis occur at the levels of transcription and the conversion of proenzyme to active enzyme; enzyme activity is further regulated through the action of inhibitors. Alpha-2 macroglobulin is the major systemic inhibitor, while a number of tissue inhibitors act as local regulators. These include at least two TIMPs and several IMPs. Pharmacologic manipulation of NMP activity holds promise as an approach to anti-erosive therapy in arthritis.

Effects of capsaicin on the metabolism of rheumatoid arthritis synoviocytes in vitro

The effects of capsaicin, the ingredient of hot pepper, on rheumatoid arthritis synoviocytes have been studied. Capsaicin was shown to have a direct action on the metabolism of synovial cells. Thus at 10(-6) mol/l and at higher doses DNA synthesis was restored to the control level. Capsaicin at both doses induced an increase in the synthesis of collagenase and at the lower concentration (10(-8) mol/l) only of prostaglandins. These results indicate that the different effects of capsaicin on cellular proliferation and on metabolic activities are dependent on dose. The responses seen in rheumatoid arthritis synoviocytes in vitro might not be mediated by tachykinins if the synovial tissue is still able to produce neuropeptides in the absence of neuronal afferents. These results suggest that capsaicin, in addition to its direct action on the afferent nervous fibres and the consequent release of tachykinins, may also have a direct action on the cells. The mechanisms by which capsaicin stimulates DNA synthesis and production of collagenase and prostaglandin E2, in a manner dependent on dose, remain to be determined.

Decreased cell proliferation and PGE2 production by fibroblasts treated with a modified hexose sugar, amiprilose hydrochloride

Amiprilose hydrochloride, a modified hexose sugar effectively decreases proliferation of human skin and synovial fibroblasts and of rabbit synovial fibroblasts. It also decreases production of the inflammatory mediator prostaglandin E2 (PGE2) by these cells. Cell proliferation, measured by incorporation of 3H-thymidine and by cell number, is decreased by concentrations of amiprilose hydrochloride of 1 mg/ml, while PGE2 synthesis is decreased by concentrations as low as 10 micrograms/ml. Concentrations of 1 mg/ml are not cytotoxic, as measured by protein synthesis. The anti-proliferate and anti-inflammatory effects of amiprilose hydrochloride, combined with its lack of cytotoxicity, suggest that this compound may be useful in the treatment of rheumatoid arthritis, a chronic autoimmune proliferate and inflammatory disease of connective tissue.

Chondrocyte activation by interleukin-1: synergism with fibroblast growth factor and phorbol myristate acetate

Exposure to synovial factors or purified interleukin-1 (IL-1) induces the production of prostaglandin E2 (PGE2) and the neutral proteinases (NP) collagenase, gelatinase and stromelysin by lapine articular chondrocytes. Having frequently found our partially purified synovial preparations to elicit this process of chondrocyte activation more strongly than recombinant IL-1, Phadke's report of synergism between IL-1 and fibroblast growth factor (FGF) intrigued us. In our hands, basic FGF (1 ng/ml-1 micrograms/ml) did not activate chondrocytes but, in a dose-dependent manner, enhanced the production of PGE2 and NP by chondrocytes exposed to IL-1 alpha or IL-1 beta (1-10 U/ml). Further examination determined that the basic FGF was a better synergist than acidic FGF. In view of reports that FGF activates protein kinase C, we tested whether phorbol myristate acetate (PMA) could substitute for FGF as a synergist. Not only did it do so, but PMA alone (0.1 ng/ml-100 ng/ml), unlike FGF, provoked the production of PGE2 by chondrocytes. The Ca2+ ionophore A23187 could not substitute for FGF in enhancing induction of the NP. Using a cDNA probe, we confirmed that the synergistic effects of both FGF and PMA upon IL-1 mediated collagenase induction, were associated with an increased abundance of collagenase mRNA.

Heat shock of rabbit synovial fibroblasts increases expression of mRNAs for two metalloproteinases, collagenase and stromelysin

Two metalloproteinases, collagenase and stromelysin, are produced in large quantities by synovial fibroblasts in individuals with rheumatoid arthritis. These enzymes play a major role in the extensive destruction of connective tissue seen in this disease. In this study, we show that heat shock of monolayer cultures of rabbit synovial fibroblasts increases expression of mRNA for heat shock protein 70 (HSP-70), and for collagenase and stromelysin. We found that after heat shock for 1 h at 45 degrees C, the mRNA expression for HSP-70 peaks at 1 h and returns to control levels by 3 h. Collagenase and stromelysin mRNA expression is coordinate, reaching peak levels at 3 h and returning to control levels by 10 h. The increase in mRNA is paralleled by an increase in the corresponding protein in the culture medium. 3 h of heat shock at a lower temperature (42 degrees C) is also effective in inducing collagenase and stromelysin mRNAs. Concomitant treatment with phorbol myristate acetate (PMA; 10(-8) or 10(-9) M) and heat shock is not additive or synergistic. In addition, all-trans-retinoic acid, added just before heat shock, prevents the increase in mRNAs for collagenase and stromelysin. Our data suggest that heat shock may be an additional mechanism whereby collagenase and stromelysin are increased during rheumatoid arthritis and perhaps in other chronic inflammatory stress conditions.

Cycloheximide inhibits the induction of collagenase mRNA in chondrocytes exposed to synovial factors or recombinant interleukin-1

Synoviocytes secrete "chondrocyte activating factors" (CAF) which, like recombinant interleukin-1 (IL-1), induce the synthesis of collagenase by cultures of articular chondrocytes. Enzyme synthesis is preceded by the appearance of collagenase mRNA some 3-5 hours after exposure of the chondrocytes to CAF or IL-1. Cycloheximide (CX) inhibits the appearance of this message in a dose-dependent manner. At a concentration of 5 micrograms/ml inhibition by CX is completely reversible, with superinduction being observed in certain experiments. Identification of the newly synthesised proteins which are required for collagenase mRNA induction would greatly advance our understanding of collagenase gene expression.

Plasminogen activator inhibitor-type I is a major biosynthetic product of retinal microvascular endothelial cells and pericytes in culture

Previous studies have shown that a glycoprotein of Mr 47,000 (designated Gp47) is a major biosynthetic product of retinal endothelial cells in vitro (Canfield, Schor, West, Schor & Grant (1987) Biochem. J. 246, 121-129). We now present data indicating that (a) an identical protein is secreted by bovine retinal pericytes, (b) this protein is plasminogen activator inhibitor-type I (PAI-1), as revealed by immunoprecipitation with specific antibodies and reverse fibrin zymography, and (c) retinal endothelial cells and pericytes synthesize different species of matrix macromolecules, that is: type IV collagen is the major collagen secreted by endothelial cells, whereas pericytes produce predominantly type I collagen; fibronectin and thrombospondin are synthesized by both cell types. Our studies also indicate that PAI-1 is produced, albeit at considerably lower levels, by large vessel vascular cells (aortic endothelial and smooth muscle cells) and human skin fibroblasts. PAI-1 produced by human skin fibroblasts appears to be a distinct molecular species compared to its bovine counterpart as assessed by its slower mobility on SDS/polyacrylamide-gel electrophoresis. The potential significance of elevated PAI-1 production by retinal endothelial cells and pericytes, as well as their distinctive patterns of matrix biosynthesis, is discussed in terms of the involvement of these cells in the maintenance and remodelling of microvessel basement membrane.

HIG-82: an established cell line from rabbit periarticular soft tissue, which retains the "activatable" phenotype

We have isolated a continuous cell line from soft tissue lining the knee joints of rabbits. Designated HIG-82, this line was produced by spontaneous establishment of an aging, late-passage culture of primary cells. Like unpassaged, primary cells, HIG-82 cells can be activated by a number of stimuli, including phorbol myristate acetate (PMA), interleukin-1 (IL-1), and the endocytosis of latex beads. Activated cells secrete collagenase, gelatinase, caseinase (stromelysin), and prostaglandin E2 (PGE2) into their culture medium. Pseudodiploid, HIG-82 cells combine a high plating efficiency with a doubling time of approximately 24 h. As primary tissue of this origin is difficult to obtain in large quantities and shows cellular heterogeneity, the HIG-82 cell line should facilitate research into the biology and biochemistry of the fibroblastic cells that line the diarthrodial joints of mammals. Such cells are likely to be important in the pathophysiology of various arthritides.

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.

Cloning of a complementary DNA for rabbit proactivator. A metalloproteinase that activates synovial cell collagenase, shares homology with stromelysin and transin, and is coordinately regulated with collagenase

Rabbit proactivator is a neutral metalloproteinase that activates another metalloproteinase, procollagenase, and degrades noncollagenous matrix. We describe the construction of an activator complementary DNA (cDNA) clone, which is 1.9 kb, that selects a 2.1-kb messenger RNA (mRNA) in Northern blot hybridizations. Nucleic acid sequence studies of the activator cDNA indicate 1) that it encodes protein Mr 53,881, 2) that this protein exhibits approximately 80% homology with rat transin, an oncogene-induced protein with a previously unknown function, and 3) that, in the first 172 residues, it is virtually identical to the rabbit metalloproteinase, stromelysin. Homology between rabbit activator and human skin collagenase is approximately 50%. Activator and collagenase mRNA are coordinately regulated; untreated cultures of rabbit synovial fibroblasts produce low levels of each protein, but addition of phorbol myristate acetate (10(-8)M) results in an increase in mRNA for both proteins by 2.5-5 hours. Adding all-trans-retinoic acid (10(-6)M) or dexamethasone (10(-7)M) to phorbol-stimulated cells coordinately suppresses both activator and collagenase mRNA. Our data suggest the existence of coordinately regulated metalloproteinases that are important in the modulation of connective tissue metabolism.

12-O-tetradecanoyl-phorbol-13-acetate induction of the human collagenase gene is mediated by an inducible enhancer element located in the 5'-flanking region

Genomic clones coding for human fibroblast collagenase were isolated. By constructing and transfecting mutants with 5' and 3' deletion mutations of the 5' control region of the gene into human or murine cells, we delimited a 32-base-pair sequence at positions -73 to -42 which is required for the induction of transcription by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. The DNA element behaves as a 12-O-tetradecanoyl-phorbol-13-acetate-inducible enhancer: it mediates the stimulation of transcription to the heterologous herpes simplex virus thymidine kinase promoter and acts in a position- and orientation-independent manner. Differences in enhancer efficiency in different cell lines are interpreted to indicate differences in the activity of a trans-acting factor.

12-O-tetradecanoyl-phorbol-13-acetate induction of the human collagenase gene is mediated by an inducible enhancer element located in the 5'-flanking region

Genomic clones coding for human fibroblast collagenase were isolated. By constructing and transfecting mutants with 5' and 3' deletion mutations of the 5' control region of the gene into human or murine cells, we delimited a 32-base-pair sequence at positions -73 to -42 which is required for the induction of transcription by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate. The DNA element behaves as a 12-O-tetradecanoyl-phorbol-13-acetate-inducible enhancer: it mediates the stimulation of transcription to the heterologous herpes simplex virus thymidine kinase promoter and acts in a position- and orientation-independent manner. Differences in enhancer efficiency in different cell lines are interpreted to indicate differences in the activity of a trans-acting factor.

The immunologic relationship of human neutrophil and skin collagenases

An understanding of the immunologic relationships between collagenases of various cellular origins is necessary to define the roles of various cell types in the pathologic tissue destruction seen in chronic inflammatory diseases, such as rheumatoid arthritis. We compared the immunologic cross-reactivity of human neutrophil and skin fibroblast collagenases, utilizing polyclonal antisera prepared to purified enzymes. Polyclonal antisera from rabbits immunized with neutrophil collagenase recognized fibroblast collagenase, as well as the neutrophil enzyme, when analyzed by immunoblot techniques. The cross-reactive epitopes constituted a major proportion of the antibody population, as shown by competitive inhibition enzyme-linked immunosorbent assay; 50% of the antibody to neutrophil collagenase was inhibited by skin collagenase. Paradoxically, antisera to fibroblast collagenase failed to recognize the neutrophil enzyme, either by immunoblot techniques or competitive inhibition enzyme-linked immunosorbent assay, an observation which supports the notion that there are unique immunodominant epitopes. The cross-reactivity with skin fibroblast collagenase shown by the neutrophil antibody suggests a conservation of epitopes between collagenases of different cellular origins. The presence of epitopes unique for each enzyme, however, could lead to a feasible approach for investigating the differential contribution of various cell types to collagenolytic activity in inflamed tissues.

Coordinate regulation of stromelysin and collagenase genes determined with cDNA probes

Secreted proteinases are required for tumor metastasis, angiogenesis, and tissue remodeling during wound healing and embryonic growth. Thus, the regulation of the genes of secreted proteinases may serve as an interesting model for growth-controlled genes in general. We studied the genes of the secreted proteinases stromelysin and collagenase by using molecularly cloned cDNAs from each proteinase. Stromelysin cDNA was cloned by differential screening of a total cDNA library from rabbit synovial cells treated with phorbol 12-myristate 13-acetate, which yielded a clone of 1.2 kilobase pairs; collagenase cDNA was obtained by cloning reverse transcripts of anti-collagenase-immunoadsorbed polysomal mRNA, which yielded a clone of 0.8 kilobase pairs. Stromelysin and collagenase mRNA species of 2.2 and 2.4 kilobases, respectively, were detected on hybridization blots of RNA from phorbol 12-myristate 13-acetate-treated but not untreated rabbit synovial cells. Expression of stromelysin mRNA was also induced in rabbit alveolar macrophages and rabbit brain capillary endothelial cells treated with phorbol 12-myristate 13-acetate. Stromelysin and collagenase mRNA were both induced by phorbol 12-myristate 13-acetate and cytochalasin B at a constant ratio of the two gene products; this suggests coordinate regulation. The fact that induction was blocked after inhibition of protein synthesis by cycloheximide implicates an indirect signal transduction pathway that requires new protein synthesis.

Collagenase production by human mononuclear cells in culture: inhibition by gold containing compounds and other antirheumatic agents

Human peripheral blood mononuclear cells in adherent cultures have been shown to synthesise and secrete collagenase. In the present study we have examined the modulation of collagenase production in these cultures by several antirheumatic agents. Incubation of monocytes in serum free medium with sodium aurothiomalate in concentrations varying from 7.7 X 10(-7) to 7.7 X 10(-3) mol/l resulted in marked dose dependent inhibition of the collagenase production. This inhibition was apparently selective in that total protein synthesis or the viability of the cells were not affected. Similar inhibition of the collagenase production was also noted with auranofin, aurothioglucose, and chloroauric acid. The inhibition with auranofin was achieved with a concentration as low as 7.4 X 10(-8) mol/l. To examine the mechanisms of the inhibition of the collagenase activity induced by sodium aurothiomalate the production of prostaglandin E2 was also measured in the same cell cultures. Sodium aurothiomalate in concentrations greater than 7.7 X 10(-4) mol/l significantly inhibited the prostaglandin E2 production; the prostaglandin E2 production was not inhibited, however, in 7.7 X 10(-5) mol/l concentration, while the collagenase production was reduced by 51.0%. Also, exogenous prostaglandin E2 added to the cultures only slightly reversed the inhibition of the collagenase production by sodium aurothiomalate. Thus the inhibition of collagenase production by sodium aurothiomalate in human adherent mononuclear cell cultures appears to be independent of the inhibition of prostaglandin E2 production. The inhibition of collagenase produced by monocyte-macrophages, as shown here in vitro, may contribute to the clinical efficacy of the compounds tested in the treatment of rheumatoid arthritis.

Characterization of rabbit genes for synovial cell collagenase

To provide tools for understanding collagenase gene expression in rheumatoid arthritis, we have isolated and characterized genomic clones for rabbit synovial cell collagenase. These clones represent 2 types of collagenase gene, at least 1 of which is transcribed in synovial fibroblasts. By examining the rabbit genome in situ, we provide evidence that there are only 2 different synovial cell collagenase genes found in a haploid genome. Amplification of these genes is not a mechanism for collagenase messenger RNA induction by phorbol esters.

Half-life of synovial cell collagenase mRNA is modulated by phorbol myristate acetate but not by all-trans-retinoic acid or dexamethasone

As part of our studies on the mechanisms controlling the synthesis of the neutral proteinase collagenase by rabbit synovial cells, we used a cDNA clone to measure total collagenase mRNA levels and to determine mRNA half-life. Phorbol myristate acetate was used to induce collagenase synthesis while all-trans-retinoic acid and dexamethasone were used to inhibit it. Cells stimulated with phorbol myristate acetate contained substantial amounts of collagenase mRNA, but cells treated with all-trans-retinoic acid or dexamethasone contained decreased amounts of collagenase mRNA which correlated well with levels of collagenase protein. Studies on mRNA half-life showed that the t1/2 for total poly(A+) RNA was about 25 h, while that of collagenase varied from as short as 12 h to as long as 36 h. The half-life was not affected by treatment with all-trans-retinoic acid or dexamethasone but was affected by the level of induction of collagenase mRNA: the greater the amount of collagenase mRNA induced, the longer the t1/2. We conclude that our data are consistent with the hypothesis that retinoic acid and dexamethasone act at the level of transcription to decrease collagenase production and the increased level of collagenase mRNA resulting from stimulation with phorbol esters is, in part, due to increased stability of the induced collagenase mRNA.

Reorganization of polymerized actin: a possible trigger for induction of procollagenase in fibroblasts cultured in and on collagen gels

Changes in cell shape are postulated to modulate gene expression during differentiation of a number of cell types, including rabbit synovial fibroblasts, which are inducible for expression of the zymogen form of the metalloendopeptidase, collagenase. In the work presented here, fibroblasts cultured on and within hydrated collagen gels were allowed to contract by release of the gels from the sides of the culture dish. Within 24 h of cell release, synthesis and secretion of procollagenase was initiated in the absence of any chemical manipulation. Fibroblasts grown in and on collagen also responded to 12-O-tetradecanoylphorbol-13-acetate and cytochalasin B with morphologic change and induced procollagenase. However, colchicine, which altered morphology to varying degrees in cells on plastic, on collagen, and within collagen gels, did not induce procollagenase expression. In all cases, the enzyme was induced only after reorganization of polymerized actin, rather than after a change in cellular morphology per se. As a first approach to identifying other aspects of the stimulated phenotype that could affect collagen turnover, the expression of collagen and endogenous metalloproteinase inhibitors in relation to procollagenase secretion was investigated. Collagen secretion by fibroblasts decreased when procollagenase secretion was induced by the pharmacologic agents, but not when cells were stimulated by contraction on or within collagen gels. The expression of two endogenous inhibitors was not coordinately regulated with induction of procollagenase. Therefore, the extracellular matrix and the cellular actin cytoskeleton may transduce signals that modulate the tissue remodeling phenotype of fibroblasts.

Homology between exon-containing portions of rabbit genomic clones for synovial cell collagenase and human foreskin and synovial cell mRNAs

Portions of rabbit genomic clones containing exons cross-hybridize with human synovial cell and human foreskin fibroblast mRNAs. These cross-hybridizing genomic fragments have been subcloned into pBR328 and may be useful probes in isolating cDNA and genomic clones from human tissue, and perhaps from other species as well. In addition, DNA sequence data on a 530 bp cDNA clone for rabbit synovial-cell collagenase indicate that this clone is composed primarily of 3'-untranslated region. As such, it is probably not useful in cross-species hybridizations.