Upregulation of matrix metalloproteinase (MMP)-1 and its activator MMP-3 of human osteoblast by uniaxial cyclic stimulation

Decisive gene strategy on osteoarthritis: a comprehensive whole-literature based approach for conclusive gene targets

BACKGROUND

Previous meta-analyses only examined the association between single or several gene polymorphisms and osteoarthritis (OA), whereas no studies have concluded that there are existing all gene loci that associate with OA.

OBJECTIVE

To assess whether a definite conclusion of the association between the gene loci and OA can be drawn.

METHODS

Decisive gene strategy (DGS), a literature-based approach, was used to search PubMed, Embase, and Cochrane databases for all meta-analyses that associated gene polymorphisms and OA. Trial Sequential Analysis (TSA) examined the sufficiency of the cumulative sample size. Finally, we assessed the importance of gene loci in OA based on whether there were enough sample sizes and the heterogeneity of the literatures with I2 value.

RESULTS

After excluding 179 irrelevant publications, 80 meta-analysis papers were recruited. Among Caucasians, SMAD3 rs12901499 (OR = 1.20, 95% CI: 1.12-1.29) was a risk factor with validation of sufficient sample sizes through TSA model. Among Asians, there were 3 gene loci risk factors with validation of sufficient sample sizes through TSA model: ESR1 rs2228480, SMAD3 rs12901499, and MMP-1 rs1799750 (OR = 1.35, 95% CI: 1.08-1.69; OR = 1.34, 95% CI: 1.07-1.69; OR = 1.43, 95% CI: 1.18-1.74, respectively). Besides, 3 gene loci, DVWA rs7639618, GDF5 rs143383, and VDR rs7975232 (OR = 0.78, 95% CI: 0.67-0.90; OR = 0.74, 95% CI: 0.67-0.81; OR = 0.56, 95% CI: 0.35-0.90, respectively) were identified as protective factors through TSA model.

CONCLUSIONS

We used DGS to identify conclusive gene loci associated with OA. These findings provide implications of precision medicine in OA and may potentially advance genetic therapy.

Adeno-Associated Virus-Delivered Fibroblast Growth Factor 18 Gene Therapy Promotes Cartilage Anabolism

OBJECTIVE

To determine the characterization of chondrogenic properties of adeno-associated virus type 2 (AAV2)-delivered hFGF18, via analysis of effects on primary human chondrocyte proliferation, gene expression, and in vivo cartilage thickness changes in the tibia and meniscus.

DESIGN

Chondrogenic properties of AAV2-FGF18 were compared with recombinant human FGF18 (rhFGF18) in vitro relative to phosphate-buffered saline (PBS) and AAV2-GFP negative controls. Transcriptome analysis was performed using RNA-seq on primary human chondrocytes treated with rhFGF18 and AAV2-FGF18, relative to PBS. Durability of gene expression was assessed using AAV2-nLuc and in vivo imaging. Chondrogenesis was evaluated by measuring weight-normalized thickness in the tibial plateau and the white zone of the anterior horn of the medial meniscus in Sprague-Dawley rats.

RESULTS

AAV2-FGF18 elicits chondrogenesis by promoting proliferation and upregulation of hyaline cartilage-associated genes, including COL2A1 and HAS2, while downregulating fibrocartilage-associated COL1A1. This activity translates to statistically significant, dose-dependent increases in cartilage thickness in vivo within the area of the tibial plateau, following a single intra-articular injection of the AAV2-FGF18 or a regimen of 6 twice-weekly injections of rhFGF18 protein relative to AAV2-GFP. In addition, we observed AAV2-FGF18-induced and rhFGF18-induced increases in cartilage thickness of the anterior horn of the medial meniscus. Finally, the single-injection AAV2-delivered hFGF18 offers a potential safety advantage over the multi-injection protein treatment as evidenced by reduced joint swelling over the study period.

CONCLUSION

AAV2-delivered hFGF18 represents a promising strategy for the restoration of hyaline cartilage by promoting extracellular matrix production, chondrocyte proliferation, and increasing articular and meniscal cartilage thickness in vivo after a single intra-articular injection.

The application of mechanical load onto mouse tendons by magnetic restraining represses Mmp-3 expression

OBJECTIVES

Mechanical loading is crucial for tendon matrix homeostasis. Under-stimulation of tendon tissue promotes matrix degradation and ultimately tendon failure. In this study, we examined the expression of tendon matrix molecules and matrix-degrading enzymes (matrix metalloproteinases) in stress-deprived tail tendons and compared to tendons that were mechanically loaded by a simple restraining method.

DATA DESCRIPTION

Isolated mouse tail fascicles were either floated or restrained by magnets in cell culture media for 24 h. The gene expression of tendon matrix molecules and matrix metalloproteinases in the tendon fascicles of mouse tails were examined by real-time RT-PCR. Stress deprivation of tail tendons increase Mmp3 mRNA levels. Restraining tendons represses these increases in Mmp3. The gene expression response to restraining was specific to Mmp3 at 24 h as we did not observe mRNA level changes in other matrix related genes that we examined (Col1, Col3, Tnc, Acan, and Mmp13). To elucidate, the mechanisms that may regulate load transmission in tendon tissue, we examined filamentous (F-)actin staining and nuclear morphology. As compared to stress deprived tendons, restrained tendons had greater staining for F-actin. The nuclei of restrained tendons are smaller and more elongated. These results indicate that mechanical loading regulates specific gene expression potentially through F-actin regulation of nuclear morphology. A further understanding on the mechanisms involved in regulating Mmp3 gene expression may lead to new strategies to prevent tendon degeneration.

External stimulation: A potential therapeutic strategy for tendon-bone healing

Injuries at the tendon-bone interface are very common in the field of sports medicine, and healing at the tendon-bone interface is complex. Injuries to the tendon-bone interface can seriously affect a patient’s quality of life, so it is essential to restore stability and promote healing of the tendon-bone interface. In addition to surgical treatment, the healing of tendons and bones can also be properly combined with extracorporeal stimulation therapy during the recovery process. In this review, we discuss the effects of extracorporeal shock waves (ESWs), low-intensity pulsed ultrasound (LIPUS), and mechanical stress on tendon-bone healing, focusing on the possible mechanisms of action of mechanical stress on tendon-bone healing in terms of transcription factors and biomolecules. The aim is to provide possible therapeutic approaches for subsequent clinical treatment.

Excessive mechanical stretch‑mediated osteoblasts promote the catabolism and apoptosis of chondrocytes via the Wnt/β‑catenin signaling pathway

Excessive biomechanical loading is considered an important cause of osteoarthritis. Although the mechanical responses of chondrocytes and osteoblasts have been investigated, their communication during mechanical loading and the underlying molecular mechanisms are not yet fully known. The present study investigated the effects of excessive mechanically stretched osteoblasts on the metabolism and apoptosis of chondrocytes, and also assessed the involvement of the Wnt/β‑catenin signaling pathway. In the present study, rat chondrocytes and osteoblasts were subjected to mechanical tensile strain, and an indirect chondrocyte‑osteoblast co‑culture model was established. Reverse transcription‑quantitative PCR and western blotting were performed to determine the expression levels of genes and proteins of interest. An ELISA was performed to investigate the levels of cytokines, including matrix metalloproteinase (MMP) 13, MMP 3, interleukin‑6 (IL‑6) and prostaglandin E2 (PG E2), released from osteoblasts. Flow cytometry was performed to detect the apoptosis of chondrocytes exposed to stretched osteoblast conditioned culture medium. The levels of MMP 13, IL‑6 and PG E2 increased significantly in the supernatants of stretched osteoblasts compared with the un‑stretched group. By contrast, the mRNA expression levels of Collagen 1a and alkaline phosphatase were significantly decreased in osteoblasts subjected to mechanical stretch compared with the un‑stretched group. The mRNA expression level of Collagen 2a was significantly decreased, whereas the expression levels of MMP 13 and a disintegrin and metalloproteinase with thrombospondin‑like motifs 5 were significantly increased in chondrocytes subjected to mechanical stretch compared with the un‑stretched group. In the co‑culture model, the results indicated that excessive mechanically stretched osteoblasts induced the catabolism and apoptosis of chondrocytes, which was partly inhibited by Wnt inhibitor XAV‑939. The results of the present study demonstrated that excessive mechanical stretch led to chondrocyte degradation and inhibited osteoblast osteogenic differentiation; furthermore, excessive mechanically stretched osteoblasts induced the catabolism and apoptosis of chondrocytes via the Wnt/β‑catenin signaling pathway.

Bursa-Derived Cells Show a Distinct Mechano-Response to Physiological and Pathological Loading in vitro

The mechano-response of highly loaded tissues such as bones or tendons is well investigated, but knowledge regarding the mechano-responsiveness of adjacent tissues such as the subacromial bursa is missing. For a better understanding of the physiological role of the bursa as a friction-reducing structure in the joint, the study aimed to analyze whether and how bursa-derived cells respond to physiological and pathological mechanical loading. This might help to overcome some of the controversies in the field regarding the role of the bursa in the development and healing of shoulder pathologies. Cells of six donors seeded on collagen-coated silicon dishes were stimulated over 3 days for 1 or 4 h with 1, 5, or 10% strain. Orientation of the actin cytoskeleton, YAP nuclear translocation, and activation of non-muscle myosin II (NMM-II) were evaluated for 4 h stimulations to get a deeper insight into mechano-transduction processes. To investigate the potential of bursa-derived cells to adapt their matrix formation and remodeling according to mechanical loading, outcome measures included cell viability, gene expression of extracellular matrix and remodeling markers, and protein secretions. The orientation angle of the actin cytoskeleton increased toward a more perpendicular direction with increased loading and lowest variations for the 5% loading group. With 10% tension load, cells were visibly stressed, indicated by loss in actin density and slightly reduced cell viability. A significantly increased YAP nuclear translocation occurred for the 1% loading group with a similar trend for the 5% group. NMM-II activation was weak for all stimulation conditions. On the gene expression level, only the expression of TIMP2 was down-regulated in the 1 h group compared to control. On the protein level, collagen type I and MMP2 increased with higher/longer straining, respectively, whereas TIMP1 secretion was reduced, resulting in an MMP/TIMP imbalance. In conclusion, this study documents for the first time a clear mechano-responsiveness in bursa-derived cells with activation of mechano-transduction pathways and thus hint to a physiological function of mechanical loading in bursa-derived cells. This study represents the basis for further investigations, which might lead to improved treatment options of subacromial bursa-related pathologies in the future.

Notch3 promotes prostate cancer-induced bone lesion development via MMP-3

Prostate cancer metastases primarily localize in the bone where they induce a unique osteoblastic response. Elevated Notch activity is associated with high-grade disease and metastasis. To address how Notch affects prostate cancer bone lesions, we manipulated Notch expression in mouse tibia xenografts and monitored tumor growth, lesion phenotype, and the bone microenvironment. Prostate cancer cell lines that induce mixed osteoblastic lesions in bone expressed 5–6 times more Notch3, than tumor cells that produce osteolytic lesions. Expression of active Notch3 (NICD3) in osteolytic tumors reduced osteolytic lesion area and enhanced osteoblastogenesis, while loss of Notch3 in osteoblastic tumors enhanced osteolytic lesion area and decreased osteoblastogensis. This was accompanied by a respective decrease and increase in the number of active osteoclasts and osteoblasts at the tumor-bone interface, without any effect on tumor proliferation. Conditioned medium from NICD3-expressing cells enhanced osteoblast differentiation and proliferation in vitro, while simultaneously inhibiting osteoclastogenesis. MMP-3 was specifically elevated and secreted by NICD3-expressing tumors, and inhibition of MMP-3 rescued the NICD3-induced osteoblastic phenotypes. Clinical osteoblastic bone metastasis samples had higher levels of Notch3 and MMP-3 compared to patient matched visceral metastases or osteolytic metastasis samples. We identified a Notch3-MMP-3 axis in human prostate cancer bone metastases that contributes to osteoblastic lesion formation by blocking osteoclast differentiation, while also contributing to osteoblastogenesis. These studies define a new role for Notch3 in manipulating the tumor microenvironment in bone metastases.

Lack of association between matrix metalloproteinase-1 gene rs1799750 polymorphism and osteoarthritis susceptibility: a meta-analysis

Background. A relationship between matrix metalloproteinase-1 (MMP-1)-1607 (rs1799750) gene polymorphism and osteoarthritis (OA) susceptibility was reported in the Bioscience Reports journal; however, these results were inconsistent. To evaluate the specific relationship, we used a meta-analysis study to clarify the controversy. Methods. The relevant articles were retrieved on 20 October 2018 from PubMed, Elsevier, Springer, Ebase (Ovid), and Google Scholar. The number of alleles and genotypes for MMP-1 was obtained. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to estimate the association between MMP-1-1607 (rs1799750) 1G/2G promoter polymorphism and OA, while the Egger’s test was used to assess heterogeneity among studies and publication bias. All statistical analyses were conducted using STATA 12.0 software. Results. A total of six case–control studies covering 1133 cases and 1119 controls were included in the final meta-analysis. There was no significant association between MMP-1-1607 1G/2G promoter polymorphism and OA in all genetic models (2G versus 1G: OR = 1.12, 95% CI = 0.78–1.60; 1G/2G versus 1G/1G: OR  = 0.73, 95% CI = 0.32–1.67; 2G/2G versus 1G/1G: OR  =  1.31, 95% CI = 0.57–2.98; the recessive model: OR  =  1.23, 95% CI = 0.63-2.41; and the dominant model: OR  =  1.25, 95% CI = 0.79–1.97). We obtained similar results for the subgroup analysis using ethnicity and type of disease. Conclusion. We systematically investigated the association between MMP-1-1607 (rs1799750) 1G/2G polymorphism and OA susceptibility; however, the results show no correlation.

Induced cumulus expansion of poor quality buffalo cumulus oocyte complexes by Interleukin-1beta improves their developmental ability

The present study was conceived with the aim of modulating the cumulus expansion characteristics of poor quality (BCB-) buffalo oocyte complexes (COCs) in order to improve their fertilization outcomes. BCB- COCs were subjected to in vitro maturation (IVM) in presence of Interleukin-1 beta (IL-1β) along with BCB- (control) and good quality (BCB+) COCs. Results were assessed morphologically, by scanning electron microscopy (SEM) and by expression analysis of cumulus expansion related genes. Also, numbers of zona pellucida bound spermatozoa were counted and development rates of oocytes were monitored under different groups. Expression of versican isoforms and ADAMTS-1 was observed to be significantly different between cumulus cells of BCB+ and BCB- COCs. Upon IL-1β supplementation, ADAMTS-1 expression increased in BCB- COCs along with corresponding cumulus expansion rates. SEM analysis also revealed improved cumulus expansion in IL-1β supplemented BCB- COCs. HAS2 and TNFAIP-6 were significantly up-regulated after IL-1β supplementation while PTGS2 expression remained unaffected. Significantly more numbers of sperms crossed the cumulus barrier, especially in 100 ng/mL IL-1β supplemented COCs. Besides, cleavage and blastocyst development rates were also improved upon IL-1β addition. We concluded that IL-1β supplementation in IVM medium can improve cumulus expansion and development ability of poor quality buffalo oocytes.

[Research progress on protease-activated receptor 2 in pathogenesis of osteoarthritis]

Objective

To review the research progress on protease-activated receptor 2 (PAR-2) in the pathogenesis of osteoarthritis (OA).

Methods

The relevant literature about the mechanism of PAR-2 in the occurrence and development of OA in recent years was extensively reviewed and comprehensively analyzed.

Results

Abnormal activation of PAR-2 plays an important role in responses to occurrence and development of OA. Through regulating production and releasing of a variety of cytokines (such as inflammatory factors, metabolic factors, pain factors, etc.), the PAR-2 can involve in pathophysiological progression of OA articular cartilage, subchondral bone, and synovial membrane, as well as occurrence and transmission of pain.

Conclusion

PAR-2 participation in the development of OA has been confirmed. However, since PAR-2 is complicated and widespread, it is necessary to study the specific role of PAR-2 and the interaction between various signal pathways in the progression of OA, and to elucidate the potential pathophysiological mechanisms of PAR-2 participating in the process of OA, in the hope of exploring the new targets for the effective control of OA.

Examining the association of MMP-1 gene -1607 (2G/1G) and -519 (A/G) polymorphisms with the risk of osteomyelitis: A case-control study

To investigate the effects of matrix metalloproteinase-1 (MMP-1) gene polymorphisms on the onset of osteomyelitis in Chinese Han population.In all, 80 osteomyelitis patients (case group) and 81 healthy people (control group) were recruited into this case-control study. Polymerase chain reaction-restriction fragment length polymorphism method was utilized to examine the genotypes of MMP-1 polymorphisms (-1607 2G/1G and -519A/G) in the 2 groups. Genotype and allele differences between the case and control groups were analyzed by chi-square test. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to present the association strength between MMP-1 gene polymorphisms and osteomyelitis.Frequencies of -1607 2G/2G genotype between the case and control groups were statistically significant (P = .025). Compared with 1G/1G genotype carriers, the 2G/2G genotype carriers had 1.605 times risk of developing osteomyelitis (OR 2.605, 95% CI 1.116-6.082). Meanwhile, the 2G allele significantly associated with the risk of osteomyelitis (OR 1.735, 95% CI 1.115-2.701). In addition, frequency of -519GG genotype was obviously higher in case group than that in control group (P = .024), and GG genotype related to an increased risk of osteomyelitis (OR 2.792, 95% CI 1.127-6.917). Whereas, the -519G allele may be a susceptible factor for osteomyelitis (OR 1.622, 95% CI 1.038-2.536).The MMP-1 -1607 (2G/1G) and -519 (A/G) polymorphisms may contribute to the onset of osteomyelitis.

Production of a Self-Aligned Scaffold, Free of Exogenous Material, from Dermal Fibroblasts Using the Self-Assembly Technique

Many pathologies of skin, especially ageing and cancer, involve modifications in the matrix alignment. Such tissue reorganization could have impact on cell behaviour and/or more global biological processes. Tissue engineering provides accurate study model by mimicking the skin and it allows the construction of versatile tridimensional models using human cells. It also avoids the use of animals, which gave sometimes nontranslatable results. Among the various techniques existing, the self-assembly method allows production of a near native skin, free of exogenous material. After cultivating human dermal fibroblasts in the presence of ascorbate during two weeks, a reseeding of these cells takes place after elevation of the resulting stroma on a permeable ring and culture pursued for another two weeks. This protocol induces a clear realignment of matrix fibres and cells parallel to the horizon. The thickness of this stretched reconstructed tissue is reduced compared to the stroma produced by the standard technique. Cell count is also reduced. In conclusion, a new, easy, and inexpensive method to produce aligned tissue free of exogenous material could be used for fundamental research applications in dermatology.

Mechanical stimulation of human tendon stem/progenitor cells results in upregulation of matrix proteins, integrins and MMPs, and activation of p38 and ERK1/2 kinases

Background

Tendons are dense connective tissues subjected periodically to mechanical stress upon which complex responsive mechanisms are activated. These mechanisms affect not only the development of these tissues but also their healing. Despite of the acknowledged importance of the mechanical stress for tendon function and repair, the mechanotransduction mechanisms in tendon cells are still unclear and the elucidation of these mechanisms is a key goal in tendon research. Tendon stem/progenitor cells (TSPC) possess common adult stem cell characteristics, and are suggested to actively participate in tendon development, tissue homeostasis as well as repair. This makes them an important cell population for tendon repair, and also an interesting research target for various open questions in tendon cell biology. Therefore, in our study we focused on TSPC, subjected them to five different mechanical protocols, and investigated the gene expression changes by using semi-quantitative, quantitative PCR and western blotting technologies.

Results

Among the 25 different genes analyzed, we can convincingly report that the tendon-related genes - fibromodulin, lumican and versican, the collagen I-binding integrins - α1, α2 and α11, the matrix metalloproteinases - MMP9, 13 and 14 were strongly upregulated in TSPC after 3 days of mechanical stimulation with 8% amplitude. Molecular signaling analyses of five key integrin downstream kinases suggested that mechanical stimuli are mediated through ERK1/2 and p38, which were significantly activated in 8% biaxial-loaded TSPC.

Conclusions

Our results demonstrate the positive effect of 8% mechanical loading on the gene expression of matrix proteins, integrins and matrix metalloproteinases, and activation of integrin downstream kinases p38 and ERK1/2 in TSPC. Taken together, our study contributes to better understanding of mechanotransduction mechanisms in TPSC, which in long term, after further translational research between tendon cell biology and orthopedics, can be beneficial to the management of tendon repair.

Electronic supplementary material

The online version of this article (doi:10.1186/s12867-015-0036-6) contains supplementary material, which is available to authorized users.

Estrogen receptor beta and truncated variants enhance the expression of transfected MMP-1 promoter constructs in response to specific mechanical loading

Background

Joint diseases such as osteoarthritis (OA) predominantly afflict post-menopausal women, suggesting a pertinent role for female hormones. Estrogen receptor beta (ER-β) has been detected in connective tissues of the knee joint suggesting that these tissues are responsive to the hormone estrogen. Matrix metalloproteinase-1 (MMP-1) activity contributes to cartilage degradation, a key factor leading to OA development in synovial joints. Two polymorphic forms of MMP-1 exist due to a deletion/insertion of the guanine residue in the promoter, and the 2G allelic variant of MMP-1 exhibits more activity than the 1G allele. Previous studies have demonstrated that the polymorphic forms of the human MMP-1 are influenced by the modulating effects of estrogen receptor isoforms. In addition to hormonal influences, physiological factors such as altered mechanical loading are also contributory features of OA. In the present study, the combined influence of biomechanical and hormonal variables on the activity of MMP-1 isoforms was evaluated. We hypothesized that the combined effects of ER-β and sheer stress will differentially activate the two allelic forms of MMP-1 in a hormone-independent manner.

Methods

HIG-82 synoviocytes were transiently transfected with 1G or 2G alleles (±) ER-β and subjected to either shear or equibiaxial stress. Next, 1G/2G promoter activity was measured to determine the combined influence of physiological stimuli. Truncated ER-β constructs were used to determine the importance of different domains of ER-β on 1G/2G activation.

Results

The 2G allele exhibited a constitutively higher activity than the 1G allele, which was further increased when the transfected cells were subject to shear stress, but not equibiaxial stress. Moreover, the combination of ER-β and shear stress further increased the activity levels of the 1G/2G allelic variants. Additionally, select AF-2 truncated ER-β variants led to increased activity levels for the 2G allele, indicating the AF-1 domain was likely involved in the response to mechanical stimulation.

Conclusions

These results suggest that the 1G/2G alleles of MMP-1 are influenced by specific mechanical stimuli like shear stress, as well as the ER-β receptor. These findings contribute to the potential allelic involvement in connective tissue diseases such as OA in females compared to males.

A single blunt impact on cartilage promotes fibronectin fragmentation and upregulates cartilage degrading stromelysin-1/matrix metalloproteinase-3 in a bovine ex vivo model

Post-traumatic osteoarthritis (PTOA) is characterized by progressive cartilage degeneration in injured joints. Since fibronectin-fragments (Fn-fs) degrade cartilage mainly through up-regulating matrix metalloproteinases (MMPs) and pro-inflammatory cytokines, we hypothesized that Fn-fs play a key role in PTOA by promoting chondrolysis in and around injured cartilage. To test this hypothesis, we profiled the catabolic events focusing on fibronectin fragmentation and proteinase expression in bovine osteochondral explants following a single blunt impact on cartilage with a drop tower device which created partial-thickness tissue damage. Injured and control explants were cultured for up to 14 days. The presence of Fn-fs, MMPs (-1, -3, -13), ADAMTS-5 in culture media and in cartilage was determined with immunoblotting. The daily proteoglycan (PG) depletion of cartilage matrix was assessed with DMMB assay. The effect of explant-conditioned media on chondrocytes was also examined with immunoblotting. Impacted cartilage released significantly higher amount of native Fn, three chondrolytic Fn-fs and PG than non-impacted controls did. Those increases coincided with up-regulation of MMP-3 both in culture media and in impacted cartilage. These findings support our hypothesis that PTOA may be propelled by Fn-fs which act as catabolic mediators through up-regulating cartilage-damaging proteinases.

IL-1β-induced matrix metalloproteinase-13 is activated by a disintegrin and metalloprotease-28-regulated proliferation of human osteoblast-like cells

We reported previously that matrix metalloproteinase (MMP)-13 accelerates bone remodeling in oral periradicular lesions, and indicated a potentially unique role for MMP-13 in wound healing and regeneration of alveolar bone. The ADAM (a disintegrin and metalloprotease) family is a set of multifunctional cell surface and secreted glycoproteins, of which ADAM-28 has been localized in bone and bone-like tissues. In this study, we show that interleukin (IL)-1β induces the expression of MMP-13 and ADAM-28 in homogeneous α7 integrin-positive human skeletal muscle stem cell (α7(+)hSMSC)-derived osteoblast-like (α7(+)hSMSC-OB) cells, and promotes proliferation while inhibiting apoptosis in these cells. At higher concentrations, however, IL-1β failed to induce the expression of these genes and caused an increase in apoptosis. We further employed ADAM-28 small interfering RNA (siRNA) to investigate whether IL-1β-induced MMP-13 expression is linked to this IL-1β-mediated changes in cell proliferation and apoptosis. Silencing ADAM-28 expression potently suppressed IL-1β-induced MMP-13 expression and activity, decreased cell proliferation and increased apoptosis in α7(+)hSMSC-OB cells. In contrast, MMP-13 siRNA had no effect on ADAM-28 expression, suggesting ADAM-28 regulates MMP-13. Exogenous MMP-13 induced α7(+)hSMSC-OB cell proliferation and could rescue ADAM-28 siRNA-induced apoptosis, and we found that proMMP-13 is partially cleaved into its active form by ADAM-28 in vitro. Overall, our results suggest that IL-1β-induced MMP-13 expression and changes in cell proliferation and apoptosis in α7(+)hSMSC-OB cells are regulated by ADAM-28.

Subchondral cyst development and MMP-1 expression during progression of osteoarthritis: an immunohistochemical study

BACKGROUND

Subchondral bone cyst (SBC) formation is often identified in patients with osteoarthritis. Furthermore, several studies have shown that expression of matrix metalloproteinases (MMPs) is elevated in patients with OA.

OBJECTIVES

The aim of our study is to correlate the presence of SBCs and MMP-1 expression with the osteochondral alterations during OA progression.

METHODS

We studied the cartilage and subchondral bone of 15 patients who had undergone total knee or hip replacement due to primary OA. As controls, we used the femoral heads of three patients without macroscopic OA changes. We evaluated three specimens per patient.

RESULTS

Specimens were divided in four groups based on the Mankin histological severity score. Using immunohistochemistry, we noted SBCs at the site of greatest disease severity. Specifically, these were present more frequently in group III (Mankin score: 6-7) and IV (Mankin: ≥ 8), compared with group I (Mankin: 1-3) and II (Mankin: 4-5). Mild OA stages (Mankin: 1-6) were characterized by degeneration and thinning of the cartilage, followed by increased osteoblast and osteoclast activity of the subjacent bone and the subsequent appearance of SBCs. Simultaneously, we observed expression of MMP-1 in groups I and II in the cartilage and III and IV in both the cartilage and the subchondral bone. Moreover, osteoblast-like cells in the lining of the SBCs showed an increased expression of MMP-1 in stages III and IV.

CONCLUSION

Our study provides immunohistological evidence that SBCs accumulate in advanced OA and contain activated cells, which express MMP-1, suggesting that they may thus participate in the osteochondral changes of OA.

LEVEL OF EVIDENCE

Level III; prospective comparative study.

Regulation of subchondral bone osteoblast metabolism by cyclic compression

OBJECTIVE

Recent data have shown that abnormal subchondral bone remodeling plays an important role in osteoarthritis (OA) onset and progression, and it was suggested that abnormal mechanical pressure applied to the articulation was responsible for these metabolic changes. This study was undertaken to evaluate the effects of cyclic compression on osteoblasts from OA subchondral bone.

METHODS

Osteoblasts were isolated from sclerotic and nonsclerotic areas of human OA subchondral bone. After 28 days, the osteoblasts were surrounded by an abundant extracellular matrix and formed a resistant membrane, which was submitted to cyclic compression (1 MPa at 1 Hz) for 4 hours. Gene expression was evaluated by reverse transcription-polymerase chain reaction. Protein production in culture supernatants was quantified by enzyme-linked immunosorbent assay or visualized by immunohistochemistry.

RESULTS

Compression increased the expression of genes coding for interleukin-6 (IL-6), cyclooxygenase 2, RANKL, fibroblast growth factor 2, IL-8, matrix metalloproteinase 3 (MMP-3), MMP-9, and MMP-13 but reduced the expression of osteoprotegerin in osteoblasts in both sclerotic and nonsclerotic areas. Colα1(I) and MMP-2 were not significantly affected by mechanical stimuli. Nonsclerotic osteoblasts were significantly more sensitive to compression than sclerotic ones, but after compression, differences in messenger RNA levels between nonsclerotic and sclerotic osteoblasts were largely reduced or even abolished. Under basal conditions, sclerotic osteoblasts expressed similar levels of α5, αv, β1, and β3 integrins and CD44 as nonsclerotic osteoblasts but 30% less connexin 43, an important mechanoreceptor.

CONCLUSION

Genes involved in subchondral bone sclerosis are mechanosensitive. After compression, nonsclerotic and sclerotic osteoblasts expressed a similar phenotype, suggesting that compression could be responsible for the phenotype changes in OA subchondral osteoblasts.

The effect of smoking on the mRNA expression of MMPs and TIMP-1 in untreated chronic periodontitis patients: a cross-sectional study

BACKGROUND AND OBJECTIVE

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are important for extracellular matrix. Expression of MMPs has been evaluated in gingiva without studying smoking. The aim of this study was to explore the effect of smoking on mRNA expression of MMP-1, -3, -8, -9 and -13 and TIMP-1 in untreated chronic periodontitis and in periodontal health.

MATERIAL AND METHODS

Gingival samples were harvested from 30 subjects with untreated chronic periodontitis (15 nonsmokers and 15 smokers) and 30 periodontally healthy subjects (15 nonsmokers and 15 smokers). Full-mouth plaque score, gingival index, bleeding on probing, probing depth and clinical attachment level were recorded. Total RNA was isolated, and the mRNA expression of MMPs and TIMP-1 was assessed by RT-PCR.

RESULTS

Periodontitis groups were comparable in clinical measurements. Nonsmoker subjects with periodontitis had statistically significantly higher MMP-1, lower MMP-9 and TIMP-1 expression and higher MMP-1/TIMP-1 ratio than smokers; and higher MMP-8 expression and MMP-8/TIMP-1 and MMP-1/TIMP-1 ratios than healthy nonsmokers. Healthy nonsmokers had statistically significantly higher MMP-13 expression than healthy smokers. Smoker periodontitis and healthy subjects had similar expression levels of MMPs and TIMP-1 and MMPs/TIMP-1 ratios. There was correlation among the MMPs only for smoker periodontitis subjects. Expression of MMP-13 was correlated with mean clinical attachment level.

CONCLUSION

Within its limits, this study demonstrated that smoking affected mRNA expression of MMPs and TIMP-1, MMPs/TIMP-1 ratios and relationships among MMPs in untreated chronic periodontitis and expression of MMPs in health. In the absence of smoking, chronic periodontitis affected expression of MMPs and MMPs/TIMP-1 ratios.

Toll-like receptors and their adaptors are regulated in macrophages after phagocytosis of lipopolysaccharide-coated titanium particles

Macrophages phagocytose metallic wear particles and produce mediators, which can induce cellular host response and aseptic implant loosening. Lipopolysaccharide (LPS) on the wear debris can stimulate macrophages via Toll-like receptor 4 (TLR4) and enhance the response. However, the precise functional role and interaction of TLRs and their adaptor molecules is still unclear. Rat bone marrow macrophages were stimulated with titanium particle (Ti) coated by LPS (Ti/LPS+) and LPS-free Ti (Ti/LPS-). mRNA levels of cytokines, TLRs and their adaptor molecules were measured using real time PCR. mRNA levels of TNF-α, IL-1β, and IL-6 increased in Ti/LPS+ than Ti/LPS-. In contrast, mRNA levels of TLR4, TLR5, and TLR9 decreased in Ti/LPS+ compared to Ti/LPS-. mRNA levels of MyD88, IRAK1, IRAK4 decreased gradually, and TRAF6 underwent an initial transient increase, followed by suppression in Ti/LPS+. However, mRNA levels of TLR2 and IRAK2 increased after phagocytosis of Ti/LPS+ than Ti/LPS-. The increased expressions of proinflammatory cytokines found in Ti/LPS+ indicated that their productions cytokines could be enhanced by phagocytosis of LPS-coated particles. Subsequent down-regulation of TLR4, TLR5, TLR9, MyD88, IRAK1, and IRAK4 suggests that self-protective mechanisms to regulate excessive host responses are activated in macrophages. Increase of TLR2 and IRAK2 and a transient increase of TRAF6 in Ti/LPS+ suggest that another possible pathway to modulate TLR-mediated cellular response to prolong inflammatory response in foreign body reaction of aseptic loosening. This down- and/or up-regulation of the potential TLR-mediated responses to LPS-coated particles reflects the proactive behavior of effector cells.

Expression of matrix metalloproteinase-1 (MMP-1) in Wistar rat's intervertebral disc after experimentally induced scoliotic deformity

Introduction

A scoliotic deformity on intervertebral discs may accelerate degeneration at a molecular level with the production of metalloproteinases (MMPs). In the present experimental study we evaluated the presence of MMP-1 immunohistochemically after application of asymmetric forces in a rat intervertebral disc and the impact of the degree of the deformity on MMP-1 expression.

Material-Method

Thirty female Wistar rats (aged 2 months old, weighted 200 ± 10 grams) were used. All animals were age, weight and height matched. A mini Ilizarov external fixator was applied at the base of a rat tail under anaesthesia in order to create a scoliotic deformity of the intervertebral disc between the 9^th and 10^th vertebrae. Rats were divided into three groups according to the degree of the deformity. In group I, the deformity was 10°, in group II 30° and in group III 50°. The rats were killed 35 days after surgery. The discs were removed along with the neighbouring vertebral bodies, prepared histologically and stained immunohistochemically. Immunopositivity of disc's cells for MMP-1 was determined using a semi-quantitative scored system.

Results

MMP-1 immunopositivity was detected in disc cells of annulus fibrosus of all intervertebral disc specimens examined. The percentage of MMP-1 positive disc cells in annulus fibrosus in group I, II and III were 20%, 43% and 75%, respectively. MMP-1 positivity was significantly correlated with the degree of the deformity (p < 0,001). An increase of chondrocyte-like disc cells was observed in the outer annulus fibrosus and at the margin of the intervertebral disc adjacent to the vertebral end plates. The difference in the proportion of MMP-1 positive disc cells between the convex and the concave side was statistically not significant in group I (p = 0,6), in group II this difference was statistically significant (p < 0,01). In group III the concave side showed a remarkable reduction in the number of disc's cells and a severe degeneration of matrix microstructure.

Conclusion

The present study showed that an experimentally induced scoliotic deformity on a rat tail intervertebral disc results in over-expression of MMP-1, which is dependent on the degree of the deformity and follows a dissimilar distribution between the convex and the concave side.

Bone regeneration and stem cells

This invited review covers research areas of central importance for orthopaedic and maxillofacial bone tissue repair, including normal fracture healing and healing problems, biomaterial scaffolds for tissue engineering, mesenchymal and foetal stem cells, effects of sex steroids on mesenchymal stem cells, use of platelet-rich plasma for tissue repair, osteogenesis and its molecular markers. A variety of cells in addition to stem cells, as well as advances in materials science to meet specific requirements for bone and soft tissue regeneration by addition of bioactive molecules, are discussed.

Molecular and mechano-biology of collagen gel contraction mediated by human MG-63 cells: involvement of specific intracellular signaling pathways and the cytoskeleton

Culture of human osteoblast-like MG-63 cells within collagen gels results in the generation of intrinsic stress. Release of such collagen gels from attachment results in gel contraction and enhanced MMP-1, MMP-3, and alpha2 integrin mRNA levels. To understand the potential role of microtubules and signaling pathways involved in MG-63 cell-mediated contraction and gene expression, cells were cultured in collagen gels. After 24 h collagen gels were released, then immediately treated with nocodazole or specific protein kinase inhibitors. Contraction was assessed, RNA isolated, and real-time PCR analysis performed. Treatment with high concentrations of a microtubule depolymerization agent, nocodazole, enhanced early contraction and led to elevated mRNA levels for MMP-3, whereas low concentrations inhibited contraction at later time points and did not affect mRNA levels. ROCK inhibitor treatment (Y27632) inhibited collagen gel contraction and led to depressed mRNA levels. The ERK1/2 inhibitor U0126 did not affect contraction, but treatment led to depressed MMP-1, MMP-3, and alpha2 mRNA levels. The p38MAPK inhibitor SB203580 modestly affected contraction, but did not affect mRNA levels. These results suggest the potential role of cytoskeletal integrity and multiple kinase signaling pathways in specific bone-remodeling events.

Upregulation of MMP-13 via Runx2 in the stromal cell of Giant Cell Tumor of bone

Giant Cell Tumor of bone (GCT) is an aggressively osteolytic and cytokine-rich bone tumor. Previous work in our lab has shown that matrix metalloproteinase-13 (MMP-13) is the principal proteinase expressed by the mesenchymal stromal cells of GCT. The Runx2 transcription factor is known to have a binding site in the MMP-13 promoter region, and we have previously found this transcription factor to be constitutively expressed in GCT stromal cells. The purpose of this study was to determine the role of Runx2 in MMP-13 regulation in GCT stromal cells. Following in vitro stimulation of GCT stromal cells with incremental concentrations of cytokine IL-1beta or TNF-alpha, the level of MMP-13 mRNA expression increased dramatically over 100-fold with a concomitant increase in MMP-13 protein expression. Inhibition of the ERK and JNK signaling pathways inhibited the upregulation of MMP-13 in these cells. Runx2 siRNA knockdown resulted in MMP-13 knockdown, and this effect was amplified following cytokine stimulation. Our study provides the first evidence that Runx2 may play a crucial role in cytokine-mediated MMP-13 expression in GCT stromal cells.

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.

Mechanical loading highly increases IL-6 production and decreases OPG expression by osteoblasts

OBJECTIVES

In osteoarthritis (OA), mechanical factors play a key role, not only in cartilage degradation, but also in subchondral bone sclerosis. The aim of this study was to develop on original compression model for studying the effect of mechanical stress on osteoblasts.

MATERIALS AND METHODS

We investigate the effects of compression on primary calvaria osteoblasts isolated from newborn mice and cultured for 28 days in monolayer. At the end of this period, osteoblasts were embedded in a newly synthesized extracellular matrix which formed a three-dimensional membrane. This membrane was then submitted to compression in Biopress Flexercell plates (1-1.7 MPa compressions at 1 Hz frequency) during 1-8h. The expression of 20 genes was investigated by real time reverse transcriptase polymerase chain reaction. Interleukin (IL)-6, matrix metalloproteinase (MMP)-3 and prostaglandin (PG)E(2) were assayed in the culture medium by specific immunoassays.

RESULTS

The compression highly increased IL-6 and cyclooxygenase (COX)-2 mRNA levels in osteoblasts. In parallel, increased amount of IL-6 and PGE(2) was found in the supernatant of loaded osteoblasts. This stimulation reached a maximum after 4h of 10% compression. MMP-2, MMP-3, and MMP-13 mRNA levels were also increased by compressive stress, while 15-hydroxyprostaglandin-dehydrogenase and osteoprotegerin (OPG) start to decrease at hour 4. COX-1, microsomial PG E synthase-1 (mPGES1), mPGES2 and cytosolic PGES and receptor activator of nuclear factor ligand (RANKL) were unmodified. Finally, we observed that alpha 5 beta 1 integrin, intracellular Ca(++), nuclear factor-kappaB and extracellular signal-regulated kinase 1/2 pathways were involved in the compression-induced IL-6 and PGE(2) production. IL-6 neutralizing antibodies and piroxicam inhibited the decrease OPG expression, but did not modify RANKL mRNA level, indicating that IL-6 and PGE(2) induce a decrease of the OPG/RANKL ratio.

CONCLUSION

This work demonstrates that IL-6 is mechano-sensitive cytokine and probably a key factor in the biomechanical control of bone remodeling in OA.

Osteoarthritis and obesity: experimental models

Osteoarthritis (OA) is a multifactorial disease. Different risk factors have been identified such as aging and obesity and different models have been used to study the impact of obesity and overweight in this pathology. The field the more studied is in vitro cartilage submitted to mechanical stresses. Four different stresses can be applied on this tissue: shear stress, loading, tensile stress (stretching) and hydrostatic pressure. The signal transduction to the chondrocyte and to the nucleus of the cell is a large field of investigation named mechano-transduction. The response of cartilage depends on quality of subchondral bone as well. So, more and more teams are studying the impact of mechanical stresses on bone, mainly by stretching osteoblasts or by submitting them to a fluid shear stress. Recently, a new model of bone compression has been set up, with osteoblasts in their own extracellular matrix. Finally the third field studied is the role of adipokines, mediators playing a key role in obesity, on the aetiology of OA. Adipokines like leptin, resistin, adiponectin and visfatin, seems to play a pro-inflammatory role in arthritis. Studying the role of obesity in OA could be more complex than expected. The link between OA and obesity may not simply be due to high mechanical stresses applied on the tissues, but soluble mediators may play an important role in the onset of OA in obese patients.

Emdogain stimulates matrix degradation by osteoblasts

Emdogain has been used clinically for periodontal regeneration, although the underlying molecular mechanisms are not clear at present. In this study, we hypothesized that Emdogain stimulated degradation of type I collagen via osteoblasts. We showed that Emdogain enhanced cell-mediated degradation of type I collagen in an MMP-dependent manner. Although MG-63 cells spontaneously produced a zymogen form of MMP-1, treatment with Emdogain significantly induced the generation of the active form of this enzyme. We demonstrated that MMP-3 was produced from MG63 cells in response to Emdogain in a MEK1/2-dependent manner. Concomitantly, blocking of MEK1/2 activation by U0126 significantly inhibited the generation of the active form of MMP-1 without affecting the total production of this collagenase. These results suggest that Emdogain facilitates tissue regeneration through the activation of the collagenase, MMP-1, that degrades matrix proteins in bone tissue microenvironments.

Matrix metalloproteinase levels in children with aggressive periodontitis

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of host-derived proteinases reported to mediate multiple functions associated with periodontal destruction and inflammation. Most of the existing data have been gathered from adults with chronic periodontitis. The purpose of this study was to determine the MMP levels in a cohort of African American children with and without aggressive periodontitis.

METHODS

Gingival crevicular fluid (GCF) was collected in a cohort of 44 African American children, 7 to 19 years of age, with and without aggressive periodontitis (AgP) and compared to healthy unrelated children and to adults with chronic periodontitis (CP). GCF volume was determined with a calibrated gingival fluid meter. The samples were assayed for MMP-1, -2, -3, -8, -9, -12, and -13 using fluorimetric substrates.

RESULTS

The MMP levels from diseased sites in the subjects with AgP were statistically higher (P <0.05) in almost all instances than those associated with the unrelated controls or with the subjects with CP. MMP-8 was significantly elevated in the diseased sites of the children with AgP relative to non-diseased sites in the same children (P = 0.002), as well as the siblings, non-diseased controls, and subjects with CP (P < or =0.0001). There was no positive correlation between probing depth and any MMP level.

CONCLUSIONS

MMP levels were elevated in AgP sites relative to non-diseased sites in the same subjects, in siblings, and in unrelated controls. MMPs associated with the AgP sites in children were generally elevated compared to an adult cohort with a history of CP.

Nutrigenomic analysis of diet-gene interactions on functional supplements for weight management

Recent advances in molecular biology combined with the wealth of information generated by the Human Genome Project have fostered the emergence of nutrigenomics, a new discipline in the field of nutritional research. Nutrigenomics may provide the strategies for the development of safe and effective dietary interventions against the obesity epidemic. According to the World Health Organization, more than 60% of the global disease burden will be attributed to chronic disorders associated with obesity by 2020. Meanwhile in the US, the prevalence of obesity has doubled in adults and tripled in children during the past three decades. In this regard, a number of natural dietary supplements and micronutrients have been studied for their potential in weight management. Among these supplements, (-)-hydroxycitric acid (HCA), a natural extract isolated from the dried fruit rind of Garcinia cambogia, and the micronutrient niacin-bound chromium(III) (NBC) have been shown to be safe and efficacious for weight loss. Utilizing cDNA microarrays, we demonstrated for the first time that HCA-supplementation altered the expression of genes involved in lipolytic and adipogenic pathways in adipocytes from obese women and up-regulated the expression of serotonin receptor gene in the abdominal fat of rats. Similarly, we showed that NBC-supplementation up-regulated the expression of myogenic genes while suppressed the expression of genes that are highly expressed in brown adipose tissue in diabetic obese mice. The potential biological mechanisms underlying the observed beneficial effects of these supplements as elucidated by the state-of-the-art nutrigenomic technologies will be systematically discussed in this review.

Plasmin-matrix metalloproteinase cascades in spinal response to an experimental disc lesion in pig

STUDY DESIGN

Proteinases were immunohistochemically stained to analyze degenerated discs and paradiscal tissues in comparison to contiguous control tissues in an experimental porcine model of intervertebral disc degeneration.

OBJECTIVE

The aim was to analyze plasmin and metalloproteinases known to participate in mutual activation cascades.

SUMMARY OF BACKGROUND DATA

Comparison of the degenerated discs and paradiscal structures with control tissues disclosed accumulation of plasmin and induction of matrix metalloproteinases (MMP), MMP-1 and MMP-2 in the discs, but some other MMPs in reactive and remodeling tissues.

MATERIAL AND METHODS

In 6 domestic pigs, the cranial L4 endplate was perforated to penetrate the nucleus pulposus. Three months later, the animals were killed and the experimental and the contiguous control vertebrae, complete with their intervertebral discs, were excised and subjected to histologic and immunohistochemical examinations.

RESULTS

Immunohistochemical analysis disclosed increased expression of MMP-1 and MMP-2 in the traumatized and degenerated intervertebral discs. Some MMPs were also induced in all paradiscal structures (bone marrow, vertebral bone, and spinal ligaments), or decreased in already scarred areas. The common denominator for all the anatomic sites studied was accumulation of plasmin.

CONCLUSION

Fibroblast collagenase (MMP-1) and gelatinase A (MMP-2), capable of degrading native and denatured collagen, were induced in degenerating intervertebral discs. Use of an experimental model enabled demonstration that biomechanical destabilization and degeneration of the disc also affects all other paradiscal structures, which are subjected to proteolysis and/or reparative fibrosis apparently representing remodeling of the spine subjected to pathologic stress. Profiling of various MMPs and plasmin, known to participate in mutual activation cascades, suggests that plasmin could activate pro-MMP-1, pro-MMP-2, pro-MMP-3, pro-MMP-7, pro-MMP-9, and pro-MMP-13 and alone or/and in cooperation with MMP-3 initiate at least 2 mutual MMPs activation cascades driven by activated MMP-3 and MMP-7.

Enhanced osteolytic potential of monocytes/macrophages derived from bone marrow after particle stimulation

BACKGROUND

Total hip replacement can be complicated by periprosthetic osteolysis. Monocytes/macrophages play a major role in the formation of the foreign body granulomas induced by wear debris. We hypothesized that periprosthetic monocytes/macrophages do not only accelerate inflammatory and osteoclast-mediated osteolytic processes, but also resorb periprosthetic bone directly by themselves. This study was designed to evaluate the osteolytic potential in vitro of monocytes/macrophages derived from bone marrow.

METHODS

Monocytes/macrophages were produced by filtration of rat bone marrow cells, followed by culture in the presence of macrophage-colony stimulating factor (M-CSF). Monocyte/macrophage properties were ascertained using immunocytochemistry and phagocytic activity. Osteolytic cytokines and extracellular matrix degrading proteinases were quantified at the mRNA level.

RESULTS

Adherent cell fraction was immunoreactive for the monocyte/macrophage specific marker CD68 and active in the phagocytosis of carbon particles up to 72 h. They also showed immunoreactivity to cathepsin K, IL-1beta, IL-6, and M-CSF, but mostly did not react to TRAP. mRNA levels of osteolytic cytokines and extracellular matrix degrading proteinases were enhanced, but that of RANKL were not. Monocytes/macrophages resorbed dentine discs and carbonated calcium phosphate was very actively resorbed after stimulation with titanium particles.

DISCUSSION

Harvested bone marrow cells expressed monocyte/macrophage phenotype, but not osteoclastic markers. The capacity of these cathepsin-K-positive phagocytic cells to resorb dentine discs and carbonated calcium phosphate in vitro suggests a direct role of monocytes/macrophages in bone resorption and periprosthetic osteolysis. The finding supports our hypothesis and previous histomorphometric observations on the presence of such osteolytic macrophages in vivo around loosening prosthesis.

Osteoactivin promotes breast cancer metastasis to bone

The skeleton is a preferred site of metastasis in patients with disseminated breast cancer. We have used 4T1 mouse mammary carcinoma cells, which metastasize to bone from the mammary fat pads of immunocompetent mice, to identify novel genes involved in this process. In vivo selection of parental cells resulted in the isolation of independent, aggressively bone metastatic breast cancer populations with reduced metastasis to the lung. Gene expression profiling identified osteoactivin as a candidate that is highly and selectively expressed in aggressively bone metastatic breast cancer cells. These cells displayed enhanced migratory and invasive characteristics in vitro, the latter requiring sustained osteoactivin expression. Osteoactivin depletion in these cells, by small interfering RNA, also lead to a loss of matrix metalloproteinase-3 expression, whereas forced osteoactivin expression in parental 4T1 cells was sufficient to elevate matrix metalloproteinase-3 levels, suggesting that this matrix metalloproteinase may be an important mediator of osteoactivin function. Overexpression of osteoactivin in an independent, weakly bone metastatic breast cancer cell model significantly enhanced the formation of osteolytic bone metastases in vivo. Finally, high levels of osteoactivin expression in primary human breast cancers correlate with estrogen receptor-negative status and increasing tumor grade. Thus, we have identified osteoactivin as a protein that is expressed in aggressive human breast cancers and is capable of promoting breast cancer metastasis to bone.

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.

Transcriptome of primary adipocytes from obese women in response to a novel hydroxycitric acid-based dietary supplement

BACKGROUND

Obesity is a global public health problem. Traditional herbal medicines may have some potential in managing obesity. The dried fruit rind of Garcinia cambogia, also known as Malabar tamarind, is a unique source of (-)-hydroxycitric acid (HCA), which exhibits a distinct sour taste and has been safely used for centuries in Southeastern Asia to make meals more filling. Recently it has been demonstrated that when taken orally, a novel, highly soluble calcium/potassium salt of HCA (HCA-SX) is safe and bioavailable in the human plasma. Although HCA-SX seems to be conditionally effective in weight management in experimental animals and in humans, its mechanism of action remains unclear.

METHODS

In this study, subcutaneous preadipocytes collected from obese women with body mass index>25 kg/m2 were differentiated to adipocytes for 2 weeks in culture. The effects of low-dose HCA-SX on lipid metabolism and on the adipocyte transcriptome were tested. HCA-SX augmented isoproterenol- and 3-isobutyryl-1-methylxanthine-induced lipolysis. Using oil red O, the production of lipid storage droplets by the cultured mature human adipocytes was visualized and enumerated.

RESULTS

HCA-SX caused droplet dispersion facilitating lipase action on the lipids. HCA-SX markedly induced leptin expression in the adipocytes. In the microarray analyses, a total of 54,676 probe sets were screened. HCA-SX resulted in significant down-regulation of 348, and induction of 366 fat- and obesity-related genes. HCA-SX induced transactivation of hypoxia inducible factor (HIF), a novel approach in the management of obesity.

CONCLUSION

Taken together, the net effects support the antilipolytic and antiadipogenic effects of HCA-SX. Further human studies are warranted.