Production of both 92- and 72-kDa gelatinases by bone cells

Bone demineralization improves onlay graft consolidation: A histological study in rat calvaria

BACKGROUND

Previous data suggest that bone demineralization may promote bone graft consolidation as well as proliferation and differentiation of pre-osteoblasts, but the biological mechanisms involved in this process need to be clarified. This study investigated the effects of bone demineralization with citric acid (CA) and tetracycline (TCN) on the repair of onlay bone grafts.

METHODS

Onlay bone grafts were performed on the calvaria of 126 Wistar rats. The contacting surfaces between bone graft and receptor bone bed were demineralized for 15, 30, and 60 seconds with TCN (50 mg/mL), or 10% CA, (pH 1), constituting the following test groups (n = 18): TCN15, TCN30, TCN60, CA15, CA30, and CA60. Control grafts (C) were performed without demineralization (n = 18). After 7, 30, and 60 days, biopsies were obtained for quantitative and qualitative histological analysis (a = 6).

RESULTS

Demineralization accelerated the bone repair early from 7 days of healing. Higher percentage area of newly formed bone was observed in CA15 and TCN60 groups when compared to C in all evaluation periods (P = 0.02). At 30 days, C specimens had lower percentage of consolidated surfaces than TCN60, TCN30 and CA15 (P = 0.0015). At 60 days, CA15, CA60, and TCN60 presented bone surfaces almost completely filled by newly formed bone, against about 75% in C specimens (P = 0.0015).

CONCLUSIONS

Both CA and TCN were effective in accelerating osteogenesis at the interface between bone grafts and receptor bone beds, especially when applied for 15 seconds and 60 seconds, respectively.

A single-nucleotide polymorphism in MMP9 is associated with decreased risk of steroid-induced osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a common hip joint disease, and steroid-induced ONFH accounts for a large number of cases. Here, we examined eight previously-identified single-nucleotide polymorphisms (SNPs) in the MPP2 and MPP9 genes of 285 steroid-induced ONFH patients and 507 healthy controls from northern China to determine whether these SNPs were associated with the risk of developing steroid-induced ONFH. Chi-squared tests and genetic model and haplotype analyses were used to evaluate associations. The rs2274755 SNP in MMP9 was associated with a decreased risk of steroid-induced ONFH in the allele, dominant, and additive models. Additionally, the “CGC” MMP9 haplotype was associated with a 0.69-fold decrease in the risk of steroid-induced ONFH. Although additional, larger population-based studies are needed to confirm these findings, our results reveal for the first time an association between a MMP9 SNP at the rs2274755 locus and a decreased risk of steroid-induced ONFH in a northern Chinese population.

Glycogen synthase kinase-3β mediated regulation of matrix metalloproteinase-9 and its involvement in oral squamous cell carcinoma progression and invasion

PURPOSE

Oral squamous cell carcinoma (OSCC)-related deaths mainly result from invasion of the tumor cells into local cervical lymph nodes. It has been reported that progressive basement membrane loss promotes the metastatic and invasive capacities of OSCCs. Matrix metalloproteinase-9 (MMP-9) is known to play a central role in tumor progression and invasion. However, the role of MMP-9 in OSCC invasion has so far remained paradoxical and little is known about its regulation. Here, we aimed to assess MMP-9 expression regulation and its activation by glycogen synthase kinase-3β during human OSCC progression and invasion.

METHODS

In the present study, 178 human OSCC samples, including 118 fresh samples (18 adjacent normal, 42 noninvasive and 58 invasive tumor samples) and 60 archival human tissue microarray (TMA) tongue cancer samples, were included. mRNA expression, protein expression, MMP-9/-2 activity, protein-protein interaction and Snail, c-Myc, β-catenin and TIMP1 expression were assessed using RT-PCR, immunohistochemistry, Western blotting, co-immunoprecipitation and gelatin zymography analyses, respectively. Wnt5a and LPA mediated MMP-9 regulation was assessed in OCSCC-derived SCC-9 cells exogenously expressing GSK3β (WT) or non phosphoryable GSK3β (S9A).

RESULTS

We observed a progressive up-regulation/activation of MMP-9 at various stages of oral tumor progression/invasion. Positive correlations were observed between MMP-9 and c-Myc expression, MMP-9 and MMP-2 activity, MMP-9 and TIMP1 expression and MMP-9 activity and TIMP1-MMP-9 interaction. In contrast, a negative correlation between phosphorylated β-catenin and MMP-9 expression was observed. Conversely, we found that in oral tongue SCC MMP-9 expression was positively correlated with inactivation of GSK3 signaling. Finally, we found that Wnt5a and LPA mediated increased MMP-9 and decreased GSK3β activities in tongue SCC-derived SCC-9 cells. MMP-9 regulation by GSK3β was confirmed by using phosphoryable/regulatory GSK3β (WT construct) and not by non-phosphoryable GSK3β (S9A construct).

CONCLUSIONS

Collectively, our results show that MMP-9 overexpression and activation are important events occurring during OSCC progression/invasion and that this overexpression/activation is regulated by c-Myc, active MMP-2 and inactive GSK3β mediated pathways.

MMP9 polymorphism is associated with susceptibility to non-traumatic osteonecrosis of femoral head in a Chinese Han population

Non-traumatic osteonecrosis of femoral head (ONFH) is an orthopedic refractory disease with escalating morbidity in Chinese Han population. In our case-control study, we examined eight previously identified MMP9 single-nucleotide polymorphisms (SNPs) in 585 non-traumatic ONFH patients and 507 healthy individuals from northern China to determine whether these SNPs associated with the risk of developing non-traumatic ONFH. Genetic model and haplotype analyses were used to evaluate the association between SNPs and non-traumatic ONFH. MMP9 rs2274755 (OR, 0.740; 95% CI, 0.578-0.949; p = 0.017) was associated with a reduced risk of non-traumatic ONFH. After adjusting for age and gender, the logistic regression results showed that rs2274755 associated with a lower risk of non-traumatic ONFH in the dominant (OR=0.71, 95% CI: 0.54-0.94, p=0.016), overdominant (OR=0.73, 95% CI: 0.55-0.96, p=0.026) and log-additive (OR=0.74740; 95% CI, 0.578-0.949; p=0.017) models. In addition, the “TGC” haplotype of rs2274755 was associated with a 0.79-fold decrease in risk while the “CTC” haplotype associated with a 0.65-fold decrease risk of the non-traumatic ONFH. These results provide evidence that the MMP9 SNP at the rs2274755 locus is associated with a decreased risk of non-traumatic ONFH in a Chinese Han population.

Expression of metalloproteases by cardiac myocytes and fibroblasts in vitro

Regulation of the turnover of extracellular matrix (ECM) components has been attributed in part to matrix metalloproteases (MMP). Isolated cardiac myocytes and fibroblasts from different developmental stages express different patterns of MMPs in vitro. Zymography of media and cell extracts of fibroblasts and myocytes indicated several apparent molecular weights (Mr) with gelatinolytic activity with prominent bands at 92 and 72 kDa. No caseinolytic activity was detected. These MMPs were characteristic of known MMP-2 and MMP-9. Fibroblasts predominantly expressed the latent 72-kDa MMP, whereas myocytes expressed a latent 92-kDa MMP. Expression of these MMPs was not affected by density of culture or the type of ECM substrate on which the cells were grown. Sodium dodecyl sulfate (SDS)-activated MMP-2 showed specific cleavage patterns on collagen types I and III but not on fibronectin, collagen type IV, or laminin. The reaction of SDS-activated MMP-2 produced a 140-kDa fragment from collagen types I and III. No specific substrate patterns were observed with activated MMP-9. MMP-2 from fibroblasts could also be activated by mechanical tension developed by fibroblasts within collagen gels or by cyclically stretching Silastic membranes on which the fibroblasts were grown. When mechanical tension was inhibited in collagen gels by antibodies against the β1 integrin, the 72-kDa MMP, or cytochalasin D, the activated band at 62 kDa was not detected. Immunocytochemical localization with antibodies against MMP-2 showed a weak reaction on cardiac myocytes, but intense staining around the focal adhesions of migrating fibroblasts. In collagen gels, staining was localized to the leading pseudopodia of the fibroblasts. Together, these data indicate that the rat MMP-2 is a collagenase primarily associated with cardiac fibroblasts, activated by mechanical tension, and may be important in cellular ECM interactions.

Mechanical Stretching of Mouse Calvarial Osteoblasts In Vitro Models Changes in MMP-2 and MMP-9 Expression at the Bone-Implant Interface

Bone to mechanical loading elicits a biological response that has clinical significance for several areas in dental medicine, including orthodontic tooth movement, tempromandibular joint disease, and endosseous dental implant osseointegration. Human orthopedic studies of failed hip implant sites have identified increased mRNA expression of several collagen-degrading matrix metalloproteinases (MMPs), while in vitro experiments have shown increases in MMP secretion after exposure to inflammatory mediators. This investigation evaluates the effects of mechanical deformation on in vitro osteoblasts by assessing changes in MMP gene expression and enzyme activity. We seeded mouse neonatal calvarial osteoblasts onto flexible 6-well plates and subjected to continuous cyclic mechanical stretching. The expression and activity of mRNA for several MMPs (2, 3, 9, and 10) was assessed. When subjected to mechanical stress in culture, only mRNA specific for MMP-9 was significantly increased compared to nonstretched controls (P < .005). Measurement of MMP activity by gelatin zymography demonstrated that none of the MMPs showed increased activity with stretching; however, MMP-2 activity decreased. Our results suggest that in response to stretch, MMP-2 responds rapidly by inhibiting conversion of a MMP-2 to the active form, while a slower up-regulation of MMP-9 may play a role in the long-term remodeling of extracellular matrix in response to continuous mechanical loading. This study suggests that the regulation of metalloproteinases at both the mRNA and protein level are important in the response of bone to mechanical stress.

Protection against T1DM-Induced Bone Loss by Zinc Supplementation: Biomechanical, Histomorphometric, and Molecular Analyses in STZ-Induced Diabetic Rats

Several studies have established an association between diabetes and alterations in bone metabolism; however, the underlying mechanism is not well established. Although zinc is recognized as a potential preventive agent against diabetes-induced bone loss, there is no evidence demonstrating its effect in chronic diabetic conditions. This study evaluated the effects of zinc supplementation in a chronic (90 days) type 1 diabetes-induced bone-loss model. Male Wistar rats were distributed in three groups: control, type 1 diabetes mellitus (T1DM), and T1DM plus zinc supplementation (T1DMS). Serum biochemical analysis; tibia histomorphometric, biomechanical, and collagen-content analyses; and femur mRNA expression were evaluated. Relative to T1DM, the zinc-supplemented group showed increased histomorphometric parameters such as TbWi and BAr and decreased TbSp, increased biomechanical parameters (maximum load, stiffness, ultimate strain, and Young's modulus), and increased type I collagen content. Interestingly, similar values for these parameters were observed between the T1DMS and control groups. These results demonstrate the protective effect of zinc on the maintenance of bone strength and flexibility. In addition, downregulation of OPG, COL1A, and MMP-9 genes was observed in T1DMS, and the anabolic effects of zinc were evidenced by increased OC expression and serum ALP activity, both related to osteoblastogenesis, demonstrating a positive effect on bone formation. In contrast, T1DM showed excessive bone loss, observed through reduced histomorphometric and biomechanical parameters, characterizing diabetes-associated bone loss. The bone loss was also observed through upregulation of OPG, COL1A, and MMP-9 genes. In conclusion, zinc showed a positive effect on the maintenance of bone architecture and biomechanical parameters. Indeed, OC upregulation and control of expression of OPG, COL1A, and MMP-9 mRNAs, even in chronic hyperglycemia, support an anabolic and protective effect of zinc under chronic diabetic conditions. Furthermore, these results indicate that zinc supplementation could act as a complementary therapy in chronic T1DM.

Matrix metalloproteinases and their inhibitors: correlation with invasion and metastasis in oral cancer

Matrix metalloproteinases (MMPs) have been implicated in invasion and metastasis of various malignancies. The study evaluated a comprehensive profile of MMP-2 and MMP-9 and their inhibitors, tissue inhibitor of metalloproteinases-2 (TIMP-2) and tissue inhibitor of metalloproteinases-1 (TIMP-1), respectively in 50 controls and 75 patients with oral squamous cell carcinoma (OSCC). Blood samples from controls and patients as well as malignant and adjacent normal tissues from the patients were collected. The study examined pro, active and total forms of MMP-2 and MMP-9 using zymography. Enzyme-linked immunoassay (ELISA) and reverse transcription polymerase chain reaction were carried out to evaluate protein levels and mRNA expression; respectively, for the MMPs and TIMPs. Plasma pro, active and total MMP-2, MMP-9 as well as TIMP-1 and TIMP-2 levels were significantly higher in oral cancer patients as compared to the controls. mRNA expression of the MMPs and TIMPs was significantly higher in malignant tissues as compared to adjacent normal tissues. A significant positive correlation was observed between levels of proMMP-9 and active MMP-9 with differentiation, stage and infiltration. ProMMP-2 and active MMP-2 exhibited significant positive correlation with differentiation and lymph node involvement. The multivariate analysis of ELISA results revealed a significant positive correlation between MMP-2, TIMP-1 and TIMP-2 levels with lymph node involvement, stage and differentiation. The receiver operating characteristic curve (ROC) analysis showed that the levels of MMPs and TIMPs have significant discriminatory efficacy to differentiate between controls and patients. The results indicate that MMP-2, MMP-9, TIMP-1 and TIMP-2 have significant clinical usefulness for oral cancer patients. Zymographic analysis is a simple, cost effective, rapid and sensitive alternative assay.

Proteinase-activated receptor (PAR)-2 activation impacts bone resorptive properties of human osteoarthritic subchondral bone osteoblasts

INTRODUCTION

In osteoarthritis (OA), the subchondral bone undergoes a remodelling process involving several factors synthesized by osteoblasts. In this study, we investigated the expression, production, modulation, and role of PAR-2 in human OA subchondral bone osteoblasts.

MATERIALS AND METHODS

PAR-2 expression and production were determined by real-time PCR and flow cytometry, respectively. PAR-2 modulation was investigated in OA subchondral bone osteoblasts treated with IL-1 beta (100 pg/ml), TNF-alpha (5 ng/ml), TGF-beta1 (10 ng/ml), PGE(2) (500 nM), IL-6 (10 ng/ml) and IL-17 (10 ng/ml). Membranous RANKL protein was assessed by flow cytometry, and OPG, MMP-1, MMP-9, MMP-13, IL-6 and intracellular signalling pathways by specific ELISAs. Bone resorptive activity was measured by using a co-culture model of human PBMC and OA subchondral bone osteoblasts.

RESULTS

PAR-2 expression and production (p<0.05) were markedly increased when human OA subchondral bone osteoblasts were compared to normal. On OA osteoblasts, PAR-2 production was significantly increased by IL-1 beta, TNF-alpha and PGE(2). Activation of PAR-2 with a specific agonist, SLIGKV-NH(2), induced a significant up-regulation of MMP-1, MMP-9, IL-6, and membranous RANKL, but had no effect on MMP-13 or OPG production. Interestingly, bone resorptive activity was also significantly enhanced following PAR-2 activation. The PAR-2 effect was mediated by activation of the MAP kinases Erk1/2 and JNK.

CONCLUSION

This study is the first to demonstrate that PAR-2 activation plays a role in OA subchondral bone resorption via an up-regulation of major bone remodelling factors. These results shed new light on the potential of PAR-2 as a therapeutic target in OA.

Avaliação das metaloproteinases de matriz -2 e -9 em gatos com desmineralização óssea secundária à tirotoxicose induzida

Observou-se significativo aumento de atividade das formas ativas das metaloproteinases -2 e -9 em gatos com tirotoxicose induzida e desmineralização óssea. As formas pró e intermediária da metaloproteinase -2 elevaram-se com 14 dias de administração hormonal, porém, posteriormente, houve uma tendência de queda. Observou-se correlação negativa entre a forma ativa das metaloproteinases de matriz -2 e -9 e a densidade mineral óssea da extremidade distal do rádio. Os resultados sugerem aumento da degradação da matriz colágena secundária com a elevação dos hormônios tiroidianos.

The roles of proteolytic enzymes in the development of tumour-induced bone disease in breast and prostate cancer

Tumour-induced bone disease is a common clinical feature of advanced breast and prostate cancer and is associated with considerable morbidity for the affected patients. Our understanding of the molecular mechanisms underlying the development of bone metastases is incomplete, but proteolytic enzymes are implicated in a number of processes involved in both bone metastasis and in normal bone turnover, including matrix degradation, cell migration, angiogenesis, tumour promotion and growth factor activation. Malignant as well as non-malignant cells in the primary and secondary sites express these enzymes, the activity of which may be regulated by soluble factors, cell- or matrix-associated components, as well as a number of cell signalling pathways. A number of secreted and cell surface-associated proteolytic enzymes are implicated in tumour-induced bone disease, including the matrix metalloproteinases, lysosomal cysteine proteinases and plasminogen activators. This review will introduce the role of proteolytic enzymes in normal bone turnover and give an overview of the studies in which their involvement and regulation in the development of bone metastases in breast and prostate cancer has been described. The results from trials involving protease inhibitors in clinical development will also be briefly discussed.

Clinical significance of MMP-2 and MMP-9 in patients with oral cancer

BACKGROUND

Factors that represent the potential for invasion and metastasis, such as matrix metalloproteinases (MMPs), could predict prognosis of cancer. Therefore, the authors studied plasma and tissue levels of MMP-2 and MMP-9 in oral cancer, the leading malignancy in India.

METHODS

Enzyme-linked immunosorbent assay and gelatin zymography were used for the MMP analysis from plasma and tissue samples, respectively.

RESULTS

Latent, active, and total forms and activation ratio of MMP-2 and MMP-9 were significantly elevated in malignant tissues as compared with adjacent normal tissues. Activation of MMP-2 was higher than MMP-9 in malignant tissues. Activation ratio was significantly higher in malignant tissues of the patients with lymph node metastasis as compared with those without lymph node metastasis (p = .005). Plasma MMP-9 levels were significantly lower in responders as compared with pretreatment levels (p = .002).

CONCLUSION

The data indicate that MMP-2 and MMP-9 can be useful to identify metastatic phenotype as well as for treatment monitoring in oral cancer.

Galanin treatment offsets the inhibition of bone formation and downregulates the increase in mouse calvarial expression of TNFalpha and GalR2 mRNA induced by chronic daily injections of an injurious vehicle

We have previously shown that after bone fracture, galanin (GAL) and GAL receptor expression is increased in osteoblast-like cells of callus; however, the role of elevated GAL/GAL receptors in this instance of bone injury is not known. We hypothesize that in injury, GAL may facilitate bone formation by suppressing the production of cytokines such as TNFalpha and IL-1alpha, thereby affecting bone collagen formation and collagenolysis by key matrix metalloproteinases (MMPs). In studies to explore this hypothesis, we used a mouse calvarial injection model to (1) investigate whether mild injury caused by a daily subcutaneous injection of a glycerol-containing vehicle onto calvaria affected osteoblast/bone formation-associated histomorphometric parameters and gene expression (mRNA encoding GAL, GAL receptors, TNFalpha, IL-1beta, collagen type I, MMP-2 and -13) compared to non-injected, control mice and (2) determine the effect of GAL+vehicle treatment on these entities. Five groups of 4-week-old mice were used: a non-injected control group; a vehicle (50/50 solution of 10 mM PBS+0.025% BSA/5.4 M glycerol)-treated group; and 3 GAL-treated groups (0.2, 2 and 20 ng doses). Solutions were injected subcutaneously onto calvaria in a 10 mul volume, every day for 2 weeks. Vehicle injection reduced calvarial periosteal osteoblast cell height (P<0.001), osteoblast number (P<0.001) and osteoid thickness (P<0.01), relative to values in non-injected animals at 2 weeks. Vehicle injection also inhibited BFR in this periosteal bone relative to values in non-injected animals at both 1 and 2 weeks (P<0.05 and P<0.001, respectively). Increasing concentrations of GAL reversed the above-listed inhibitory effects caused by vehicle. This reversal was demonstrated by a dose-dependent effect of GAL on osteoblast cell height (Pearson's r=0.330; P<0.05), osteoblast number (Pearson's r=0.715; P=0.000), osteoid thickness (Pearson's r=0.516; P=0.000) and BFR (Pearson's r=0.525; P<0.05) after 2 weeks of GAL+vehicle treatment; with the 20 ng/day GAL+vehicle injection schedule returning these measured parameters toward non-injected control values. All GAL+vehicle treatments had no effect on calvarial expression of GAL, GALR1, GALR3, collagen type 1 and MMP-2 mRNAs compared to levels in vehicle-injected controls. GAL treatment did, however, produce dose-dependent effects on calvarial expression of GALR2 (Pearson's r=0.763; P=0.000), MMP-13 (Pearson's r=0.806; P=0.000), IL-1beta (Pearson's r=0.807; P=0.000) and TNFalpha (Pearson's r=0.542; P=0.000) mRNAs with 20 ng/day of GAL+vehicle producing the strongest reversal of vehicle-associated changes. Thus, the 20 ng/day GAL+vehicle regimen offset the inhibition of osteoblastic activity, and therefore bone formation caused by daily glycerol-containing vehicle injection. This effect on bone formation may be due in part to the peptide suppressing the formation and associated activity of TNFalpha, IL-1beta and MMP-13, as TNFalpha and IL-1beta are known inhibitors of bone formation and MMP-13 is involved in collagenolysis. Furthermore, these effects may be due to the action of GAL via GALR2, as it was the only GAL receptor affected by this GAL treatment regimen. These results indicate that GAL can facilitate bone formation associated with injury and reveal potential efficacy for GAL in treating osseous conditions where bone formation may be inhibited due to excess TNFalpha and IL-1beta production.

Activation of MMP-2 and MMP-9 in patients with oral squamous cell carcinoma

BACKGROUND AND OBJECTIVES

Oral cancer accounts for one third of all malignancies in India where habit of tobacco consumption is the major etiologic factor, which causes field cancerization in oral mucosa. Multiple molecular events in oral mucosa due to field cancerization may be the cause of local and regional lymph node involvement in oral cancer resulting into low overall survival, high recurrence rate, and poor prognosis. Several matrix metalloproteinases (MMPs) have been shown to play an important role in the invasion and metastasis of oral squamous cell carcinoma (SCC). MMP-2 and MMP-9 are capable of degrading type-IV collagen, which is a major component of basement membrane. Therefore, we studied MMP-2 and MMP-9 activation by gelatin zymography, which is cost effective alternate to ELISA method, in patients with oral SCCs to predict their role in metastatic potentials.

MATERIALS AND METHODS

Thirty-nine patients of oral SCCs were classified as non-metastatic (n = 28), and metastatic (n = 11) according to regional lymph node involvement. Malignant and adjacent normal tissues of the patients were collected at the time of surgery. Gelatin zymography was carried out using 7.5% polyacrylamide gel under non-denaturing and non-reducing conditions. Zymograms were analyzed densitometrically. Latent and active forms of MMP-2 and MMP-9 were expressed as ng/50 microg of protein.

RESULTS

Latent and active forms of MMP-2 and MMP-9 were significantly elevated in malignant tissues as compared to their adjacent normal tissues (P < 0.05). Total MMP-2 and MMP-9 activities were also significantly elevated in malignant tissues as compared to adjacent normal tissues (P = 0.005 and P = 0.028, respectively). Activation ratio of MMP-2 and MMP-9 were significantly elevated in malignant tissues as compared to adjacent normal tissues. Activation of MMP-2 was prominent (11%) than MMP-9 (5%) in malignant tissues. Activation ratio of MMP-2 was significantly elevated in patients with lymph node metastasis than patients without lymph node metastasis (P = 0.005). Receiver's operating characteristic (ROC) curve analysis revealed that activation ratio of MMP-2 discriminate better than and activation ratio of MMP-9 between patients with and without lymph node metastasis. Activation ratio of MMP-2 could predict risk of lymph node metastasis development in patients without lymph node involvement.

CONCLUSION

The study concluded that activation of MMP-2 and MMP-9 was significantly higher in malignant tissues as compared to adjacent normal tissues. Further, activation ratio of MMP-2 was significantly elevated in patients with lymph node metastasis as compared to patients without lymph node metastasis, which could predict risk of lymph node metastasis development in node negative patients.

Matrix metalloproteinases MMP-2, -9 and tissue inhibitors TIMP-1, -2 expression and secretion by primary human osteoblast cells in response to titanium, zirconia, and alumina ceramics

Osteogenic properties of bone cells are a key parameter governing osseointegration of implant devices. In this context, osteoblasts have a central role via extracellular matrix synthesis and remodeling that they regulate through different protease activity. In this study, we have analyzed the expression of two matrix metalloproteinases (MMPs): MMP-2 (72 kDa) and MMP-9 (92 kDa) and their specific tissue inhibitors TIMP-1 and TIMP-2 in primary human osteoblastic cells. The effect of titanium, zirconia, and alumina ceramics on the synthesis of these proteases was assessed using reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, and zymographic analysis. Our results showed that osteoblasts express MMP-2 and -9 mRNA. Furthermore, MMP-2 mRNA expression was decreased by titanium and increased by alumina whereas zirconia did not have any significant effect. Conversely, MMP-9 mRNA expression was stimulated by titanium but decreased with zirconia, whereas alumina induced no significant changes. Zymographic analysis has evidenced pro-MMP-2 gelatinolytic activity in all cell populations with time-dependent increase profile; pro-MMP-9, however, was not detected. Enzyme-linked immunosorbent assay data confirmed the production of MMP-2 and very low levels of MMP-9. In addition, TIMP-1 was secreted in 24-h-cultured cells and increased to maximal level at 48-72 h whereas TIMP-2 levels were very low. The interactions between human osteoblasts and the studied biomaterials altered both MMP-2, -9 and TIMP-1expression indicating that biomaterials may influence osseointegration and bone remodeling.

Regulation of collagen deposition and lysyl oxidase by tumor necrosis factor-alpha in osteoblasts

Tumor necrosis factor-alpha (TNF-alpha) inhibits osteoblast function in vitro by inhibiting collagen deposition. Studies generally support that TNF-alpha does not inhibit collagen biosynthesis by osteoblasts but that collagen deposition is in some way diminished. The study investigated TNF-alpha regulation of biosynthetic enzymes and proteins crucial for posttranslational extracellular collagen maturation in osteoblasts including procollagen C-proteinases, procollagen C-proteinase enhancer, and lysyl oxidase. The working hypothesis is that such regulation could inhibit collagen deposition by osteoblasts. We report that in phenotypically normal MC3T3-E1 osteoblasts, TNF-alpha decreases collagen deposition without decreasing collagen mRNA levels or procollagen protein synthesis. Analyses of the cell layers revealed that TNF-alpha diminished the levels of mature collagen cross-links, pyridinoline and deoxypyridinoline. Further analyses revealed that the mRNA expression for lysyl oxidase, the determining enzyme required for collagen cross-linking, is down-regulated by TNF-alpha in a concentration- and time-dependent manner by up to 50%. The decrease was accompanied by a significant reduction of lysyl oxidase protein levels and enzyme activity. By contrast, Northern and Western blotting studies revealed that procollagen C-proteinases bone morphogenic protein-1 and mammalians Tolloid and procollagen C-proteinase enhancer were expressed in MC3T3-E1 cells and not down-regulated. The data together demonstrate that TNF-alpha does not inhibit collagen synthesis but does inhibit the expression and activity of lysyl oxidase in osteoblasts, thereby contributing to perturbed collagen cross-linking and accumulation. These studies identify a novel mechanism in which proinflammatory cytokine modulation of an extracellular biosynthetic enzyme plays a determining role in the control of collagen accumulation by osteoblasts.

Regulation of monocyte chemokine and MMP-9 secretion by proinflammatory cytokines in tuberculous osteomyelitis

Tuberculous osteomyelitis causes bony destruction as a result of interactions among the pathogen, resident bone cells, and influxing leukocytes. Recruitment of monocytes and T cells is critical for antimycobacterial granuloma formation, but little is known about mechanisms regulating this in bone. We investigated the role of tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-1, key cytokines in granuloma formation, in networks involving human osteoblasts and monocytes. Experiments focused on CXC ligand (CXCL)8, CCL2, and matrix metalloproteinase (MMP)-9, human monocyte-derived mediators involved in control of leukocyte influx. TNF-alpha but not IL-1 has a key role stimulating CXCL8 secretion in Mycobacterium tuberculosis-infected human osteoblast MG-63 cells. Conditioned medium from M. tuberculosis-infected osteoblasts (COBTB) drives CXCL8 and some CCL2 gene expression and secretion from primary human monocytes. IL-1 receptor antagonist and to a lesser extent anti-TNF-alpha inhibited COBTB-induced CXCL8 secretion (P<0.01) but did not affect gene expression. IL-1 blockade had a comparatively lesser effect on CCL2 secretion, whereas anti-TNF decreased CCL2 concentrations from 7840 +/- 140 to 360 +/- 80 pg/ml/4 x 10(5) cells. Neither proinflammatory mediator affects MMP-9 secretion from COBTB-stimulated human monocytes. In summary, in a paracrine network, M. tuberculosis-infected osteoblasts drive high-level CXCL8, comparatively less CCL2, but do not alter MMP-9 secretion from uninfected human monocytes. This network is, in part, regulated by IL-1 and TNF-alpha.

Simvastatin, an HMG-CoA Reductase Inhibitor, Reduced the Expression of Matrix Metalloproteinase-9 (Gelatinase B) in Osteoblastic Cells and HT1080 Fibrosarcoma Cells

MMP-9 or Gelatinase B, a member of the matrix metalloproteinase family (MMPs), plays important roles in physiological events such as tissue remodeling and in pathological processes that lead to destructive bone diseases, including osteoarthritis and periodontitis. In addition to its effect on the increase of total bone mass, statin (an HMG-CoA reductase inhibitor) suppresses the expression of MMPs. In this study, we proposed that simvastatin reduces MMP-9 expression in osteoblasts and HT1080 fibrosarcoma cell line. Gelatin zymography, Western blot analysis and reverse transcriptase-PCR were used to investigate the effects of simvastatin on MMP-9 in primary calvaria cells, U2-OS osteosarcoma cells, and HT1080 fibrosarcoma cells. The results from gelatin zymography and Western blot analysis revealed that simvastatin suppressed MMP-9 activity in these cells in concentration- and time-dependent manners. The effective concentrations of simvastatin were 100 - 500 nM, 5 - 15 microM, and 2.5 - 10 microM in primary calvaria, U2-OS, and HT1080 cells, respectively. Collectively, these results suggest that simvastatin is a potent drug for inhibition of MMP-9 expression in osteoblastic cells and HT1080 fibrosarcoma cells.

Tumor necrosis factor-α: molecular and cellular mechanisms in skeletal pathology

Tumor necrosis factor-alpha (TNF) is one member of a large family of inflammatory cytokines that share common signal pathways, including activation of the transcription factor nuclear factor kappa B (Nf-kappa B) and stimulation of the apoptotic pathway. Data derived from early work supported a role for TNF as a skeletal catabolic agent that stimulates osteoclastogenesis while simultaneously inhibiting osteoblast function. The finding that estrogen deficiency was associated with increased production of cytokines led to a barrage of studies and lively debate on the relative contributions of TNF and other cytokines on bone loss, on the potential cell sources of TNF in the bone microenvironment, and on the mechanism of TNF action. TNF has a central role in bone pathophysiology. TNF is necessary for stimulation of osteoclastogenesis along with the receptor activator of Nf-kappa B ligand (RANKL). TNF also stimulates osteoblasts in a manner that hinders their bone-formative action. TNF suppresses recruitment of osteoblasts from progenitor cells, inhibits the expression of matrix protein genes, and stimulates expression of genes that amplify osteoclastogenesis. TNF may also affect skeletal metabolism by inducing resistance to 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) by a mechanism that extends to other members of the steroid hormone nuclear receptor family. Thus, TNF assails bone at many levels. This review will focus on the cellular and molecular mechanisms of TNF action in the skeleton that result in increased bone resorption and impaired formation. TNF and its signal pathway remains an important target for the development of new therapies for bone loss from osteoporosis and inflammatory arthritis.

Functional roles of the tissue inhibitor of metalloproteinase 3 (TIMP-3) during ascorbate-induced differentiation of osteoblastic MC3T3-E1 cells

The tissue inhibitor of the metalloproteinase-3 (TIMP-3) gene was isolated as a gene involved in the process of ascorbate-induced differentiation of mouse MC3T3-E1 cells by the differential display method. The functional roles of TIMP-3 were characterized by establishing stable cell lines, which constitutively expressed the TIMP-3 gene. The TIMP-3 transfectants produced type I collagen at the same level as that of normal cells in response to ascorbic acid 2-phosphate (AscP). However, the expression of the other osteoblastic marker proteins such as alkaline phosphatase (ALPase), osteopontin (OP), osteocalcin (OC), osteonectin (ON) and matrix metalloproteinases (MMPs) remained at a low level even in the presence of AscP. Furthermore, no mineralization of the extracellular matrix (ECM) occurred with the transfectants. Remodeling ECM through TIMPs and MMPs is concluded to be required for osteoblastic differentiation.

The effects of enamel matrix derivative (EMD) on osteoblastic cells in culture and bone regeneration in a rat skull defect

OBJECTIVE

Enamel matrix derivative (EMD) has been clinically used to promote periodontal tissue regeneration. The purpose of the present study is to clarify EMD affects on osteoblastic cells and bone regeneration.

MATERIALS AND METHODS

Mouse osteoblastic cells (ST2 cells and KUSA/A1 cells) are used in culture experiments. After cells were treated with EMD, cell growth was evaluated with DNA measurement, 5-bromo-2'-deoxyurydine (BrdU) incorporation assay. Measurement of alkaline phosphatase (ALP) activity and mineralized-nodule (MN) formation, Northern blotting analysis and zymography are also performed. In addition, EMD was applied to a rat skull defect and the defect was radiographically and histologically evaluated 2 weeks after the application.

RESULTS

EMD did not stimulate ST2 cell growth; however, it enhanced KUSA/A1 cell proliferation. Although EMD stimulated ALP activity in both the cells, ALP activity in KUSA/A1 cells was affected to a much greater degree. Corresponding to the increase in ALP activity, MN formation in KUSA/A1 cells was enhanced by EMD. EMD stimulated osteoblastic phenotype expression of KUSA/A1 cells such as type I collagen, osteopontin, transforming growth factor beta 1 and osteocalcin. EMD treatment also stimulated matrix metalloproteinase production in KUSA/A1 cells. Although the effects of EMD on osteoblastic cells depend on cell type, the overall effect of EMD on osteoblastic cells is stimulatory rather than inhibitory. Finally, EMD application to a rat skull defect accelerated new bone formation.

CONCLUSION

These results indicate that EMD affects osteoblastic cells and has potential as a therapeutic material for bone healing.

Effects of lipopolysaccharide extracted from Prevotella intermedia on bone formation and on the release of osteolytic mediators by fetal mouse osteoblasts in vitro

Prevotella intermedia, a Gram-negative obligate anaerobic black-pigmented oral bacterium, belongs to a small group of microorganisms that is closely associated with the initiation of periodontal diseases. Lipopolysaccharide (LPS), an outer membrane component, is one of the main virulence factors of this bacterium. The aim of this study was to examine the effects of Prev. intermedia lipopolysaccharide, extracted by the hot-phenol-water method, on differentiation (alkaline phosphatase activity) and mineralisation (calcium incorporation) of fetal mouse calvarial cells in vitro and to determine the release of the important osteolytic factors nitric oxide, interleukin-6 (IL-6) and matrix metalloproteinases by these cells after treatment with different concentrations of Prev. intermedia lipopolysaccharide (0.2-25 microg/ml). By gelatin zymography, we also characterized the matrix metalloproteinases released by these osteoblasts. Treatment with Prev. intermedia lipopolysaccharide dose-dependently inhibited bone formation by reducing alkaline phosphatase activity and calcium incorporation and induced the release of nitric oxide, IL-6 and the latent proforms of MMP-2 and MMP-9 by fetal mouse osteoblasts in organoid culture. These results indicate that the lipopolysaccharide from Prev. intermedia not only participates in periodontal tissue destruction and alveolar bone resorption, but also inhibits bone formation.

Expression of matrix metalloproteinase-9 mRNA and protein during deciduous tooth resorption in bovine odontoclasts

Matrix metalloproteinase-9 (MMP-9, or gelatinase B) is an extracellular proteinase that is highly expressed in osteoclasts and has been postulated to play an important role in their resorptive activity. Although MMP-9 has been reported to play a role in bone resorption, the association of this enzyme during deciduous tooth resorption has not yet been clarified. The purpose of the present study was to increase our understanding of the role of MMP-9 during deciduous tooth resorption. Reverse transcription-polymerase chain reaction (RT-PCR) and northern blot analysis of total RNAs extracted from bovine root-resorbing tissues, which lie between the root of a deciduous tooth and its permanent successor, revealed the expression of mRNA for MMP-9 in the tissue. These results indicate that MMP-9 may be involved in the process of deciduous tooth resorption. In addition, in situ hybridization and immunohistochemistry were also performed to identify the cells that produced MMP-9 in bovine root-resorbing tissue. MMP-9 mRNA was highly expressed in odontoclasts that were aligned along the surface of the tissue. Immunohistochemistry confirmed the predominant localization of MMP-9 in odontoclasts. The present data demonstrate that odontoclasts in deciduous root resorption express MMP-9, which may participate in proteolysis during root resorption of deciduous tooth.

Expression of matrix metalloproteinases during ascorbate-induced differentiation of osteoblastic MC3T3-E1 cells

The mouse calvarial osteoblast MC3T3-E1 cells released 92 kDa and 68 kDa of gelatinase activities into the conditioned media (CMs) from undifferentiated cells. When differentiation was induced by cultivating cells with ascorbate-2-phosphate (AscP), 68-kDa activity increased significantly in parallel with production of 60-kDa activity. These enzymes required Ca2+ and Zn2+ ions for their proteolytic activities. The 68-kDa activity was immunologically identified as latent matrix metalloproteinase 2 (MMP-2). The 92-kDa activity was deduced to be latent MMP-9 based on its molecular mass. The 60-kDa activity band was found to possess both gelatin and beta-casein hydrolyzing activities, indicating that this activity band might comprise the active form of MMP-2 and latent MMP-13. MC3T3-E1 cells were found to express MMP-2, MMP-13, and membrane type (MT)1-MMP genes by Northern blotting. MMP-2 was expressed constitutively. MMP-13 was up-regulated during the growth with AscP. MT1-MMP expression also was modulated by AscP; at the early stage of differentiation, its messenger RNA (mRNA) level increased and then decreased gradually to the control level. These changes in the profiles of MMPs observed here could be attributed to the maturation of collagenous extracellular matrix (ECM) induced by AscP.

Immunolocalization of matrix metalloproteinases and their inhibitors in clinical specimens of bone metastasis from breast carcinoma

Matrix metalloproteinases (MMPs) are essential in several stages of the metastatic process, and in normal bone development and remodeling. We explored whether the interaction between tumor cells and bone leads to changes in MMP and tissue inhibitor of MMP (TIMP) expression thus affecting osteolysis in metastatic bone disease. Using immunohistochemistry we have investigated the MMP/TIMP expression in tumor cells, fibroblasts, osteoblasts and osteoclasts. Thirty one specimens of bone metastasis from breast carcinoma were stained for MMP-1, -2, -9, MT1-MMP and TIMP-1, and -2 and compared with staining in normal breast tissue, primary breast carcinoma and normal bone. Specimens came from patients in three clinical scenarios: from open biopsies without or with pathological fracture, or bone marrow biopsies containing tumor from patients with pancytopenia but without clinical evidence of osteolysis. By bone histomorphometry the latter group showed a heavy tumor load not different from the open biopsy groups but displayed little active bone resorption and low numbers of osteoclasts. Cell type-specific MMP/TIMP expression was observed and the staining patterns were comparable between the three groups of patients. Though no major differences in the MMP/TIMP staining of tumor cells and fibroblasts were observed between bone metastasis and primary tumor, we showed that tumor cells do express MMPs capable of degrading bone matrix collagen. The number and activity of osteoclasts and osteoblasts was increased dramatically in bone metastases, their MMP/TIMP profiles, however, were not different from normal bone, suggesting that the mechanism of bone degradation by osteoclasts is not different from normal bone remodelling.

Fluorescence polarization assay and SDS-PAGE confirms matrilysin degrades fibronectin and collagen IV whereas gelatinase A degrades collagen IV but not fibronectin

Matrilysin and gelatinase A are hypothesized to have significant roles in uterine and ovarian function. However, proteolytic activity assays for these enzymes are limited. We describe the development of simple and rapid assays for the proteolysis of fluorescein-labeled full-length substrates, collagen IV (Col-IV) and fibronectin (FN), and demonstrate the selectivity of matrilysin (MMP-7) compared to gelatinase A (MMP-2) for fibronectin. Changes in fluorescence intensity (FIU) and fluorescence polarization (mP) resulting from the protease activity of matrilysin and gelatinase A were measured. These studies show that the fluorescently labeled substrates, Col-IV and FN, are as reliable and amenable to rapid in vitro assay as peptide substrates. In addition, they are easier to use than previously described, non-fluorescent methods. The results demonstrate that assays using full-length, biological matrix proteins are more sensitive indicators of MMP-specific substrate activity than peptide based assays.

Suppression of chronic streptococcal cell wall-induced arthritis in Lewis rats by liposomal clodronate

OBJECTIVES

To investigate the role of macrophages in the pathogenesis of chronic streptococcal cell wall (SCW)-induced arthritis using liposomal clodronate.

METHODS

Female Lewis rats with SCW-induced arthritis received a single intravenous injection of 20 mg of clodronate encapsulated within small unilamellar vesicles (SUVc) 10 days post-arthritis induction.

RESULTS

SUVc significantly suppressed the development of chronic SCW-induced arthritis for up to 26 days after treatment. At this time point, ED1(+) macrophages were significantly depleted in the liver and ankle joints, although splenic macrophage numbers were not significantly different from control groups. Macrophage elimination induced a significant reduction in local levels of interleukin (IL)-1beta, IL-6, tumour necrosis factor-alpha (TNFalpha) and matrix metalloproteinase-9 (MMP-9) from ankle joints.

CONCLUSIONS

Macrophage elimination by SUVc inhibits local production of IL-1beta, IL-6, TNFalpha and MMP-9, and the pathogenesis of inflammatory arthritis.

Regulation of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) by bone resorptive factors in osteoblastic cells

In addition to their stimulating function on osteoclastic bone resorption, bone resorptive factors may regulate proteinases and related factors in osteoblastic cells to degrade bone matrix proteins. This study investigated the regulation of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) by bone resorptive factors in the cultures of mouse osteoblastic MC3T3-E1 cells, mouse primary osteoblastic (POB) cells, and neonatal mouse calvariae. Expression of either MMP-2, -3, -9, -11, -13, and -14 or TIMP-1, -2, and -3 was detected in MC3T3-E1 cells and POB cells. When the bone resorptive factors parathyroid hormone, 1,25-dihydroxyvitamin D(3), prostaglandin E(2), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha) were added to the cell cultures, MMP-13 mRNA levels were found predominantly to increase by all resorptive factors in the three cultures. mRNA levels of either MMP-3 and -9 or TIMP-1 and -3 were found to increase mainly by the cytokines IL-1beta and TNF-alpha. BB94, a nonselective MMP inhibitor, neutralized the (45)Ca release stimulated by these resorptive factors to an extent similar to that of calcitonin, strongly suggesting that bone resorptive factors function at least partly through MMP formation. We propose that MMP-13 mRNA expression in osteoblastic cells may play an important role in stimulating matrix degradation by both systemic and local resorptive factors, whereas either MMP-3 and -9 or TIMP-1 and -3 might modulate matrix degradation by local cytokines only.

Osteopenia and decreased bone formation in osteonectin-deficient mice

Bone continuously remodels in response to mechanical and physiological stresses, allowing vertebrates to renew bone as adults. Bone remodeling consists of the cycled synthesis and resorption of collagenous and noncollagenous extracellular matrix proteins, and an imbalance in this process can lead to disease states such as osteoporosis, or more rarely, osteopetrosis. There is evidence that the extracellular matrix glycoprotein osteonectin or secreted protein acidic and rich in cysteine (BM-40) may be important in bone remodeling. Osteonectin is abundant in bone and is expressed in areas of active remodeling outside the skeleton. In vitro studies indicate that osteonectin can bind collagen and regulate angiogenesis, metalloproteinase expression, cell proliferation, and cell-matrix interactions. In some osteopenic states, such as osteogenesis imperfecta and selected animal models for bone fragility, osteonectin expression is decreased. To determine the function of osteonectin in bone, we used contact x-ray, histomorphometry, and Northern blot analysis to characterize the skeletal phenotype of osteonectin-null mice. We found that osteonectin-null mice have decreased bone formation and decreased osteoblast and osteoclast surface and number, leading to decreased bone remodeling with a negative bone balance and causing profound osteopenia. These data indicate that osteonectin supports bone remodeling and the maintenance of bone mass in vertebrates.

Human growth hormone stimulates proteinase activities of rabbit bone cells via IGF-I

Human growth hormone (hGH) and human insulin-like growth factor-I (hIGF-I) are known to have a marked influence on osteoclastic formation and bone resorption in an unfractionated rabbit bone cell model. This study investigated the effects of both of these factors on the induction of cysteine-proteinases and matrix metalloproteinase-2 (MMP-2) and MMP-9. After 4 days of rabbit bone cell culture, hGH and hIGF-I significantly modulated cathepsin, MMP-9 (latent form) and MMP-2 (active form) activities. Similar studies were performed in the presence of parathyroid hormone (hPTH). hPTH increased MMP-2 and MMP-9 activities whereas it had no effect on the production of cathepsins by bone cells. When neutralizing anti-hIGF-1 antiserum was added to the culture, the stimulatory effects of hGH were totally abolished, indicating that hGH-modulated cathepsin and metalloproteinase activities were partly mediated by local hIGF-I secretion. Cysteine-proteinase activities released by purified osteoclasts were very low and were not modulated by hGH and h-IGF-I. However, hIGF-I but not hGH increased MMP-2 and MMP-9 activities released by purified osteoclasts. It may be concluded that hGH markedly stimulates the expression of proteinases in total rabbit bone cells via local hIGF-I production by stromal cells. Cysteine-proteinase activities are mainly produced by non-osteoclastic cells, while MMP-2 and MMP-9 modulated by hIGF-I are mainly expressed by osteoclastic cells.

Collagenase-3 binds to a specific receptor and requires the low density lipoprotein receptor-related protein for internalization

We have previously identified a specific receptor for collagenase-3 that mediates the binding, internalization, and degradation of this ligand in UMR 106-01 rat osteoblastic osteosarcoma cells. In the present study, we show that collagenase-3 binding is calcium-dependent and occurs in a variety of cell types, including osteoblastic and fibroblastic cells. We also present evidence supporting a two-step mechanism of collagenase-3 binding and internalization involving both a specific collagenase-3 receptor and the low density lipoprotein receptor-related protein. Ligand blot analysis shows that (125)I-collagenase-3 binds specifically to two proteins ( approximately 170 kDa and approximately 600 kDa) present in UMR 106-01 cells. Western blotting identified the 600-kDa protein as the low density lipoprotein receptor-related protein. Our data suggest that the 170-kDa protein is a specific collagenase-3 receptor. Low density lipoprotein receptor-related protein-null mouse embryo fibroblasts bind but fail to internalize collagenase-3, whereas UMR 106-01 and wild-type mouse embryo fibroblasts bind and internalize collagenase-3. Internalization, but not binding, is inhibited by the 39-kDa receptor-associated protein. We conclude that the internalization of collagenase-3 requires the participation of the low density lipoprotein receptor-related protein and propose a model in which the cell surface interaction of this ligand requires a sequential contribution from two receptors, with the collagenase-3 receptor acting as a high affinity primary binding site and the low density lipoprotein receptor-related protein mediating internalization.

Triiodothyronine induces collagenase-3 and gelatinase B expression in murine osteoblasts

Triiodothyronine (T3) increases bone resorption, but its effects on matrix metalloprotease (MMP) expression in bone are unknown. We tested the effects of T3 on collagenase-3 and gelatinase A and B expression in MC3T3 osteoblastic cells. T3 at 1 nM to 1 microM for 24-72 h increased collagenase-3 and gelatinase B mRNA levels, but it did not increase gelatinase A transcripts. In addition, T3 increased immunoreactive collagenase and gelatinase activity. Cycloheximide prevented the stimulatory effect of T3 on collagenase-3 but not on gelatinase B transcripts. Indomethacin did not prevent the effect of T3 on either MMP. T3 did not alter the decay of collagenase-3 or gelatinase B mRNA in transcriptionally arrested MC3T3 cells, and it increased the rate of collagenase-3 and gelatinase B gene transcription. Although T3 enhanced the expression of the tissue inhibitor of metalloproteinase-1 in MC3T3 cells, it increased collagen degradation in cultured intact rat calvariae. In conclusion, T3 increases collagenase-3 and gelatinase B synthesis in osteoblasts by transcriptional mechanisms. This effect may contribute to the actions of T3 on bone matrix remodeling.

Matrix metalloproteinase-2 and -9 are activated in joint diseases

A study was performed to identify the activation status of the gelatinase MMPs, MMP-2 and -9, in both normal and diseased equine articular tissues. In addition, the production and activation status of equine MMP-2 and -9 by equine articular cells and tissues in response to increasing IL-1beta concentrations was assessed. The study was performed to test the hypothesis that activation of MMPs is a fundamental step in the pathogenesis of joint diseases; and that this activation is mediated by the cytokine IL-1. Using purified equine MMP-2 and -9, the molecular weights of the zymogen and activated form of equine MMP-2 and -9 were identified by a combination of gelatin zymography and a gelatin degradation assay using aminophenylmercuric acetate as a chemical activator of the molecules. Normal equine articular tissues (cartilage and synovial membrane) maintained in short-term tissue culture produced MMP-2 zymogen alone, while similar tissues obtained from a variety of pathological conditions produce both zymogen and active MMP-2, as well as MMP-9 monomer and dimer. Activated MMP-9 was an inconsistent finding. Normal equine synovial fibroblasts in monolayer culture produced zymogen MMP-2 alone under basal conditions. A mild increase in active and zymogen MMP-2 levels occurred with IL-1beta treatment. Equine synovial membrane explants demonstrated a dose-dependent increase in active and zymogen MMP-2 and MMP-9 levels following IL-1beta treatment. Monolayer chondrocyte cell cultures demonstrated a dose-dependent mild increase in active and zymogen MMP-2 following IL-1beta treatment. Explant cartilage cultures demonstrated a dose-dependent mild increase in zymogen MMP-2 alone following IL-1beta treatment. This study supports the hypothesis that activation of MMPs is occurring in joint disease, and that in vitro stimulation of equine articular cells and tissues causes not only an increase in MMP production, but also an increase in amount of activated enzyme released. Further research is required to investigate the role of MMP activation in joint diseases, and to investigate the potential use of therapeutic agents, which inhibit MMP activation, in the treatment and prevention of joint diseases.

Leukemia inhibitory factor and oncostatin M stimulate collagenase-3 expression in osteoblasts

Leukemia inhibitory factor (LIF) and oncostatin M (OSM) have multiple effects on skeletal remodeling. Although these cytokines modestly regulate collagen synthesis in osteoblasts, their effects on collagenase expression and collagen degradation are not known. We tested whether LIF and OSM regulate the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in osteoblast-enriched cells isolated from fetal rat calvariae. LIF and OSM increased collagenase-3 (MMP-13) mRNA and immunoreactive protein levels in a time- and dose-dependent manner. LIF and OSM enhanced the rate of transcription of the collagenase gene and stabilized collagenase mRNA in transcriptionally arrested cells. LIF and OSM failed to regulate the expression of gelatinase A (MMP-2) and B (MMP-9). LIF and OSM modestly stimulated the expression of TIMP-1 but did not alter the expression of TIMP-2 and -3. In conclusion, LIF and OSM stimulate collagenase-3 and TIMP-1 expression in osteoblasts, and these effects may be involved in mediating the bone remodeling actions of these cytokines.

Alendronate blocks metalloproteinase secretion and bone collagen I release by PC-3 ML cells in SCID mice

We have previously shown that alendronate, a potent bisphosphonate compound, can prevent human PC-3 ML tumor cell metastasis to the bone (Stearns and Stearns, 1996, Oncol Res, 8, 69-75). In this paper, tumor cells were injected into the bone medullary cavity of SCID mice femurs both in vivo and following isolation in vitro. ELISAs showed that the amount of collagen I released in the bone marrow (i.e. in in vitro experiments) and the blood plasma (i.e. in in vivo experiments) was a function of the time of incubation or the number of cells injected in the femurs. ELISAs also showed that the levels of matrix metalloproteinase (MMP-2 and MMP-9) secreted in the bone medullary cavity of the femurs directly correlated with the extent of collagen 1 release. In vitro experiments carried out with 'live' and 'devitalized bone' yielded similar results suggesting that the tumor cells (not the osteoclasts) were primarily responsible for the bone solubilization observed. Alendronate pretreatment of the SCID mice (0.1 mg/kg biweekly for 3 weeks) (or the tumor cells) blocked both MMP production by the tumor cells (and the osteoclasts) and collagen I release, providing direct evidence that alendronate might be utilized to prevent bone destruction by metastatic tumor cells. Zymography indicated that MMP-2 activation might be responsible for bone solubilization. In addition, the data suggest that the plasma levels of collagen I might be a marker of bone metastasis and osteolysis.

Differential regulation of MMP-13 (collagenase-3) and MMP-3 (stromelysin-1) in mouse calvariae

Bone resorption in mice involves the degradation of extracellular matrix. Whereas several proteases seem to be implicated in this process, it becomes increasingly clear that matrix metalloproteinases (MMPs), amongst them especially MMP-13 and MMP-3, play an essential role. We have purified MMP-13 and MMP-3 from mouse calvariae-conditioned media by differential fractionation and analyzed their collagenolytic, caseinolytic, gelatinolytic and proteoglycanolytic activities. It could be shown that in mouse calvariae-conditioned media most of the measured enzyme activities were due to MMP-13, although zymographies revealed that MMP-3, MMP-2, MMP-9 as well as TIMPs were present too. MMP-13 and MMP-3 proteins were detected and their enzyme activities were neutralized by specific polyclonal antisera. Furthermore, it was demonstrated that in cultures of mouse calvariae the production of MMP-13 was induced by the potent MMP-stimulator heparin and by parathyroid hormone (PTH), whereas the levels of MMP-3 remained unchanged. Although PTH-induced bone resorption was inhibited by calcitonin treatment, MMP-13 mRNA and protein expression were not significantly altered by this hormone. Together with previous observations, these results indicate that PTH regulates bone resorption through MMP-13, but not by MMP-3, and that its reversion by calcitonin involves neither of the two enzymes.

Matrix metalloproteinase (MMP)-9 type IV collagenase/gelatinase implicated in the pathogenesis of Sjögren's syndrome

Type IV collagenases/gelatinases (matrix metalloproteinases MMP-2 and MMP-9) in labial salivary glands (LSG) and saliva in Sjögren's syndrome (SS) and healthy controls were studied. Zymograms and Western blots disclosed that SS saliva contained 92/82 kD MMP-9/type IV collagenase duplex. Specific activity measurement disclosed 53.1+/-9.8 U/mg protein MMP-9 in SS compared to 16.5+/-2.6 U/mg in healthy controls (p=0.01). MMP-2 did not differ between SS and controls. In SS salivary glands, MMP-2 and MMP-9 were also expressed, in addition to stromal fibroblasts and occasional infiltrating neutrophils, respectively, in acinar end piece cells. In addition, an effective proMMP-9 activator, human trypsin-2 (also known as tumor-associated trypsin-2 or TAT-2), was found in acinar end piece cells and in saliva. Interestingly, proteolytically processed MMP-9 was found in saliva (vide supra), and in vivo activated MMP-9 was significantly higher in SS than in controls (p=0.002). LSGs, particularly in SS, were characterized ultrastructurally by areas containing small cytoplasmic vesicles in the basal parts of the epithelial cells associated with areas of disordered and thickened basal lamina. Based on our results, we conclude here that SS saliva contains increased concentrations of MMP-9, which is of glandular origin in part. Pro MMP-9 is to a large extent proteolytically activated. This is probably mediated by the most potent pro MMP-9 activator found in vivo thus far, namely trypsin-2. Therefore, the MMP 9/trypsin-2 cascade may be responsible for the increased remodelling and/or structural destruction of the basement membrane scaffolding in salivary glands in SS. Due to the role of basal lamina as an important molecular sieve and extracellular matrix-cell signal, these pathological changes may contribute to the pathogenesis of the syndrome.

Expression of matrix metalloproteinase-9 mRNA in osteoporotic bone tissues

Matrix metalloproteinases (MMPs), a sort of important enzymes involved in extracellular matrix metabolism, play critical roles in the process of tissues remodeling, wound healing and metastasis of tumors. Dot blot and in situ hybridization were used in this study to detect the expression and localization of MMP-9, an important proteolytic enzyme implicated in bone resorption in bone tissues. The results showed that the level of MMP-9 mRNA expression in osteoporotic bone tissues was significantly higher than that in normal control group and the cell types that expressed MMP-9 mRNA included mono- and multi-nuclear osteoclasts and some lining cells on the surface of bone matrix. It was suggested that MMP-9 play a key role in the development of bone loss in osteoporosis.

72-kDa and 92-kDa gelatinases in saliva of patients with human immunodeficiency virus infection

Human immunodeficiency virus (HIV) infection has been associated with periodontal diseases in HIV-seropositive patients. In periodontal diseases, matrix metalloproteinases (MMPs) may play key roles in the extracellular matrix, basement membrane, serpin degradation, and modification of cytokine action. We characterized the 72 kDa type IV collagenase (gelatinase A, MMP-2) and 92 kDa type IV collagenase (gelatinase B, MMP-9) in the saliva of HIV-seropositive patients and seronegative healthy controls by activity measurements and quantitative immunoblotting. Immunoblot analysis with specific antibodies against MMP-2 and MMP-9 and their tissue inhibitors (TIMP-1, TIMP-2) disclosed that, independent of the phase of the patients' HIV infection, their salivary samples contained higher amounts of MMP-2 and MMP-9 immunoreactivities in pro- and active forms and the TIMP-1 and TIMP-2 inhibitors than did the control samples. Healthy control saliva contained only slight immunoreactivities for gelatinases and TIMPs. However, as judged by the studied clinical and microbiologic indicators, HIV-seropositive patients showed only a slight tendency to develop periodontitis. Overall, an increased amount of gelatinases in saliva may reflect increased host response and defense activities in HIV infection.

Alendronate blocks TGF-beta1 stimulated collagen 1 degradation by human prostate PC-3 ML cells

We have previously shown that alendronate can prevent human PC-3 ML tumor cell metastasis to the bone (Wang and Stearns, 1991, Differentiation, 48, 115-25). In this paper, ELISAs and Western blots showed that TGF-beta1 stimulated the secretion of a 72 kDa matrix metalloproteinase 2 (MMP-2) to enhance the solubilization of radiolabeled collagen 1 by metastatic human prostate PC-3 ML cells. A potent bisphosphonate compound, alendronate, inhibited MMP-2 secretion to block solubilization of collagen 1. Alendronate failed to inhibit MMP-2 activity directly, but instead appeared to block cellular secretion of MMP-2. Alendronate failed to inhibit secretion of tissue inhibitor of metalloproteinase-2 (TIMP-2; the inhibitor of MMP-2) and the decrease in collagen 1 solubilization observed may occur, in part, from changes in the molar stoichiometry of TIMP-2 to MMP-2. We conclude that alendronate may be a potent inhibitor of bone resorption based on its ability to block MMP-2 secretion by tumor cells.

Regulation of matrix metalloproteinases (MMP-2, -3, -9, and -13) by interleukin-1 and interleukin-6 in mouse calvaria: association of MMP induction with bone resorption

Interleukin-1 (IL-1) greatly induces osteoclast formation and stimulates bone resorption of mouse calvaria in culture. In the presence of soluble IL-6 receptor (sIL-6R), IL-6 similarly induces osteoclast formation, but the potency of IL-6 in inducing bone resorption in organ culture is weaker than that of IL-1. To study the differences in bone-resorbing activity between IL-1 and IL-6, we examined the effects of the two cytokines on the induction of matrix metalloproteinases (MMPs). In mouse calvarial cultures, IL-1 markedly enhanced the messenger RNA (mRNA) expression of MMP-13 (collagenase 3), MMP-2 (gelatinase A), MMP-9 (gelatinase B), and MMP-3 (stromelysin 1), which associated with increases in bone matrix degradation. A hydroxamate inhibitor of MMPs significantly suppressed bone-resorbing activity induced by IL-1. Gelatin zymography showed that both pro- and active-forms of MMP-2 and MMP-9 were detected in the conditioned medium collected from calvarial cultures, and IL-1 markedly stimulated both pro- and active-forms of the two gelatinases. IL-6 with sIL-6R also stimulated mRNA expression and biological activities of these MMPs, but the potency was much weaker than that of IL-1. Conditioned medium collected from IL-1-treated calvariae degraded native type I collagen, but 3/4- and 1/4-length collagen fragments were not detected, suggesting that both collagenases and gelatinases synergistically degraded type I collagen into smaller fragments. In mouse osteoblastic cells, the expression ofMMP-2, MMP-3, and MMP-13 mRNAs could be detected, and they were markedly enhanced by IL-1alpha on days 2 and 5. IL-6 with sIL-6R also induced expression of MMP-13 and MMP-2 mRNAs on day 2, but the expression was rather transient. These results demonstrate that the potency of induction of MMPs by IL-1 and IL-6 is closely linked to the respective bone-resorbing activity, suggesting that MMP-dependent degradation of bone matrix plays a key role in bone resorption induced by these cytokines.

Further characterization of the murine collagenase (type IVB) gene promoter and analysis of mRNA expression in murine tissues

The collagenase B type IV (Col4B) gene is highly expressed in the osteoclast, the primary bone-resorbing cell. However, factors that regulate expression of the Col4B gene are not well characterized. A murine P1 genomic clone containing a 94 kb sequence insert which contains the Col4B gene was isolated. A 4 kb EcoR1 DNA fragment containing the 5' flanking sequence of the gene was further subcloned and restriction mapped. Putative transcription factors such as SRY, Lyf-1, and GATA1 and 2, binding motifs were identified by sequence analysis in this promoter region. Enhancer and suppressor regions were mapped by transient expression of Col4B gene promoter deletion mutant-luciferase reporter gene constructs in HepG2 cells. Col4B mRNA expression in different murine tissues was analyzed by reverse transcription-polymerase chain reaction and demonstrated high levels of expression in bone, clavaria, spleen and thymus. This promoter provides a valuable tool for targeting gene expression to the osteoclast.

Cytokines stimulate matrix metalloproteinase production by human pulp cells during long-term culture

Interleukin-1 and tumor necrosis factor-alpha are inflammatory cytokines that are known to be potent stimulators of mineralized tissue resorption. One of the mechanisms by which these cytokines induce this loss is through the stimulation of matrix metalloproteinase (MMP) production and secretion by the host cells present at the inflammatory site. We have previously shown that these cytokines have little effect on MMP production by human pulp cells in short-term culture (24 to 48 h). In this study, we examined the production of MMPs by human pulp cells in the presence and absence of interleukin-1 and tumor necrosis factor-alpha in long-term cultures (2 to 16 days) using substrate gel zymography. The major band present in all samples examined migrated at 68 kDa, corresponding to the migration pattern of MMP-2, whereas a minor band migrated at 90 kDa, corresponding to the migration pattern of MMP-9. In the presence of cytokines, elevated levels of MMP-2 and MMP-9 were apparent at days 9 through 16. In addition, a band migrating at 110 kDa was present. This study demonstrates that cytokines stimulate the production of elevated levels of MMPs by human pulp cells in long-term cultures and that these MMPs may play a role in pulpal inflammation.

EGF and IL-1 alpha modulate the release of collagenase, gelatinase and TIMP-1 as well as the release of calcium by rabbit calvarial bone explants

Matrix metalloproteinases (MMPs), among which is collagenase (MMP-1), are likely to be involved in various steps of the bone resorption process. As both production of these enzymes and bone resorption appear to be mediated by cytokines, we investigated the effects of two cytokines, IL-1 alpha and EGF, on the release of collagenase, gelatinase A (MMP-2), gelatinase B (MMP-9), TIMP-1 and calcium by rabbit calvariae. It was found that all these parameters increased under the influence of these cytokines. The release of calcium--used as a parameter of bone resorption--was highest in the combined presence of the cytokines. Although the absolute and relative enhancement by a combination of IL-1 alpha and EGF was most pronounced for collagenase (7-fold), both gelatinase A (5-fold) and gelatinase B (1.5-fold) had increased simultaneously. Calvariae produced a high level of MMP inhibitor (TIMP-1), especially under the influence of the cytokines; periosteum released little inhibitor. It is concluded that IL-1 alpha and EGF are likely to play a modulating role in the process of bone resorption.

Expression of gelatinases within the trabecular bone compartment of ovariectomized and parathyroidectomized adult female rats

Ovariectomized (ovx) and parathyroidectomized (ptx) rat models of disturbed bone metabolism have been widely used in evaluating bone changes resulting from hormonal depletion, and are characterized by elevated and depressed bone turnover, respectively. We report here the expression of gelatinases extracted from native trabecular bone in these models. Nine-month-old female Sprague-Dawley rats were sacrificed after 3 weeks following ovx or 10 days post ptx to determine the influence of these procedures on the levels of proximal tibial bone tissue gelatinases. Identification and quantitation of these enzymes were performed via gelatin gel zymography of native tissue extracts and laser densitometry of developed gels, respectively. In the ptx model, a reduction in tissue levels of pro- and active-MMP-2 and a 45 kDa activated fragment was seen, whereas ovx exhibited significant increases in these enzymes. The MMPs are therefore clearly under the influence of factors known to modulate bone remodeling in vivo. The study of MMP levels directly extracted from bone using these experimental models may assist in developing management regimes for metabolic bone diseases through the use of drugs aimed at controlling turnover.

Interleukin-6 and its soluble receptor cause a marked induction of collagenase 3 expression in rat osteoblast cultures

Interleukin-6 (IL-6), a cytokine produced by skeletal cells, increases bone resorption, but its effects on collagenase expression are unknown. We tested the effects of IL-6 and its soluble receptor on collagenase 3 expression in osteoblast-enriched cells from fetal rat calvariae (Ob cells). IL-6 caused a small increase in collagenase mRNA levels, but in the presence of IL-6-soluble receptor (IL-6sR), IL-6 caused a marked increase in collagenase transcripts after 2-24 h. In addition, IL-6sR increased collagenase mRNA when tested alone. IL-6 and IL-6sR increased immunoreactive collagenase levels. Cycloheximide and indomethacin did not prevent the effect of IL-6 and IL-6sR on collagenase mRNA levels. IL-6 and IL-6sR did not alter the decay of collagenase mRNA in transcriptionally arrested Ob cells and increased the levels of collagenase heterogeneous nuclear RNA and the rate of collagenase gene transcription in Ob cells. IL-6 and IL-6sR increased collagenase 3 mRNA in MC3T3 cells but only modestly in skin fibroblasts. IL-6 and IL-6sR enhanced the expression of tissue inhibitor of metalloproteinases 1. In conclusion, IL-6, in the presence of IL-6sR, increases collagenase 3 synthesis in osteoblasts by transcriptional mechanisms. This effect may contribute to the action of IL-6 on bone matrix degradation and bone resorption.