Antigenic Profile of Osteoblasts Present in Human Bone Tissue Sections

Effect of NSAIDs on the aminopeptidase activity of cultured human osteoblasts

Aminopeptidases (APs) are involved in various physiological and pathological processes. In tumor tissues the expression of APs, cyclooxygenase-2 and its metabolites are increased. The objective was to determine the effect of certain NSAIDs on the AP activity of osteoblasts. Primary cultures of osteoblast were treated with different concentrations of indomethacin, meloxicam, naproxen, nimesulide, and piroxicam. The AP activity was fluorimetrically determined using aminoacyl-β-naphthylamides (aa-βNAs) as substrates: Ala-βNA, Arg-βNA, Gly-βNA, Leu-βNA, Lys-βNA, Met-βNA, and Phe-βNA. The five NSAIDs showed an inhibitory effect of AP activity against the study substrates depending on the dose tested. Meloxicam and piroxicam had the highest inhibitory effect on enzymatic activity, with an IC50 of around 70 μM. Our results suggest that the physiological alteration of osteoblasts in the presence of NSAIDs may be a consequence of AP inhibition, suggesting a potential clinical role for these drugs against cancer in combination with chemotherapeutic agents.

Dioscin promotes osteoblastic proliferation and differentiation via Lrp5 and ER pathway in mouse and human osteoblast-like cell lines

Background

Dioscin, a typical steroid saponin, is isolated from Dioscorea nipponica Makino and Dioscorea zingiberensis Wright. It has estrogenic activity and many studies have also reported that dioscorea plants have an effect in preventing and treating osteoporosis. However, the molecular mechanisms underlying their effect on osteoporosis treatment are poorly understood. Therefore, the present study aims to investigate the mechanism (s) by which dioscin promotes osteoblastic proliferation and differentiation in mouse pre-osteoblast like MC3T3-E1 cells and human osteoblast-like MG-63 cells.

Results

We found that dioscin (0.25 μg/ml, 0.5 μg/ml, and 1.0 μg/ml) promoted MC3T3-E1 cells and MG-63 cells proliferation and differentiation dose dependently. Western blot analysis results showed that estrogen receptor α (ER-α), estrogen receptor β (ER-β), β-catenin and Bcl-2 protein expression increased after MC3T3-E1 cells were treated with dioscin. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that dioscin could increase the ratio of osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) and up-regulate the level of Lrp5 and β-catenin. And by RNA interference analysis, we proved that the effect of dioscin increasing the ratio of OPG/RANKL was dependent on Lrp5 pathway. In addition, we also found that these effects of dioscin were abolished by ICI 182, 780 (100 nM), an antagonist of ER, indicating that an ER signaling pathway was also involved. We also found that dioscin (0.25 μg/ml, 0.5 μg/ml, and 1.0 μg/ml) induced MG-63 cells proliferation and differentiation in a dose-dependent manner. Western blot analysis results indicated that ER-α, ER-β and β-catenin protein expression increased after MG-63 cells were treated with dioscin.

Conclusions

The current study is the first to reveal that dioscin can promote osteoblasts proliferation and differentiation via Lrp5 and ER pathway.

High molecular weight hyaluronic acid regulates osteoclast formation by inhibiting receptor activator of NF-κB ligand through Rho kinase

OBJECTIVE

To determine the effects of high molecular weight hyaluronic acid (HMW-HA) on osteoclast differentiation by monocytes co-cultured with stromal cells.

METHODS

Mouse bone marrow stromal cell line ST2 cells were incubated with HMW-HA or 4-methylunbeliferone (4-MU) for various times. In some experiments, cells were pre-treated with the anti-CD44 monoclonal antibody (CD44 mAb) or Rho kinase pathway inhibitors (simvastatin or Y27632), then treated with HMW-HA. The expression of receptor activator of NF-κB ligand (RANKL) was determined using real-time reverse transcription polymerase chain reaction (RT-PCR), western blotting, and immunofluorescence microscopy, while the amount of active RhoA was measured by a pull-down assay. To further clarify the role of HMW-HA in osteoclastogenesis, mouse monocyte RAW 264.7 cells were co-cultured with ST2 cells pre-stimulated with 1,25(OH)2D3. Osteoclast-like cells were detected by staining with tartrate-resistant acid phosphatase (TRAP).

RESULTS

HMW-HA decreased RANKL mRNA and protein expressions, whereas inhibition of hyaluronic acid (HA) synthesis by 4-MU enhanced RANKL expression. Blockage of HA-CD44 binding by CD44 mAb suppressed HMW-HA-mediated inhibition of RANKL. Pull-down assay findings also revealed that HMW-HA transiently activated RhoA in ST2 cells and pre-treatment with CD44 mAb inhibited the activation of RhoA protein mediated by HMW-HA. Moreover pre-treatment with Rho kinase pathway inhibitors also blocked the inhibition of RANKL by HMW-HA. Co-culture system results showed that HMW-HA down-regulated differentiation into osteoclast-like cells by RAW 264.7 cells induced by 1,25(OH)2D3-stimulated ST2 cells.

CONCLUSIONS

These results indicated that HA-CD44 interactions down-regulate RANKL expression and osteoclastogenesis via activation of the Rho kinase pathway.

Therapeutic doses of nonsteroidal anti-inflammatory drugs inhibit osteosarcoma MG-63 osteoblast-like cells maturation, viability, and biomineralization potential

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used to reduce pain and inflammation. However, their effect on bone metabolisms is not well known, and results in the literature are contradictory. The present study focusses on the effect of dexketoprofen, ketorolac, metamizole, and acetylsalicylic acid, at therapeutic doses, on different biochemical and phenotypic pathways in human osteoblast-like cells. Osteoblasts (MG-63 cell line) were incubated in culture medium with 1-10 μM of dexketoprofen, ketorolac, metamizole, and acetylsalicylic acid. Flow cytometry was used to study antigenic profile and phagocytic activity. The osteoblastic differentiation was evaluated by mineralization and synthesis of collagen fibers by microscopy and alkaline phosphatase activity (ALP) by spectrophotometric assay. Short-term treatment with therapeutic doses of NSAIDs modulated differentiation, antigenic profile, and phagocyte activity of osteoblast-like cells. The treatment reduced ALP synthesis and matrix mineralization. However, nonsignificant differences were observed on collagen syntheses after treatments. The percentage of CD54 expression was increased with all treatments. CD80, CD86, and HLA-DR showed a decreased expression, which depended on NSAID and the dose applied. The treatments also decreased phagocyte activity in this cellular population. The results of this paper provide evidences that NSAIDs inhibit the osteoblast differentiation process thus reducing their ability to produce new bone mineralized extracellular matrix.

Effect of ibuprofen on proliferation, differentiation, antigenic expression, and phagocytic capacity of osteoblasts

Ibuprofen is a nonselective nonsteroidal antiinflammatory drug commonly prescribed for acute postsurgical and posttraumatic pain. However, little known is about the effect of this drug on osteoblasts. In this study, we aimed to investigate the effect of ibuprofen on cell proliferation, differentiation, antigenic profile, and phagocytic activity, in a human MG-63 osteosarcoma cell line, as a model of osteoblasts. Flow cytometry was used to study proliferation, antigenic profile, and phagocytic activity, and radioimmunoassay was used to determine osteocalcin synthesis as a cell differentiation marker. Our results showed that therapeutic doses of ibuprofen (5 and 25 μM) did not modify cell proliferation and osteocalcin synthesis in the MG-63 cellular line. However, treatment with a higher dose (25 μM) increased the expression of antigens CD21, CD44, CD80, CD86, and HLA-DR and decreased phagocytic activity. The results indicate that a therapeutic dose of ibuprofen has no adverse effects on growth of the osteoblast-like cells. Treatment with ibuprofen alone may produce some cell activation, which would explain the increase in expression of membrane markers and decrease in phagocytic capacity.

Effect of platelet-rich plasma on growth and antigenic profile of human osteoblasts and its clinical impact

PURPOSE

In recent years, there has been widespread clinical use of platelet-rich plasma (PRP) to facilitate the regeneration of different tissues. However, few data are available on the effect of PRP on parameters other than cell growth. The aim of the present study was to evaluate the effect of PRP on the cell cycle, antigenic profile, and proliferation of primary cultured human osteoblasts.

MATERIALS AND METHODS

The cells in the present study were derived from human bone sections obtained from healthy volunteers during third molar surgery. PRP was prepared from human venous blood and used to culture the cell line obtained from the same patient. Flow cytometry was used to study the cell cycle, antigenic profile, and proliferation.

RESULTS

The treatment of osteoblasts with PRP modified the expression of CD54, CD80, CD86, and HLA-DR antigens. PRP treatment increased cell proliferation in the short term, but the cell proliferation capacity diminished in the long term, perhaps owing to cell exhaustion. No change in the cell cycle profile was observed in the PRP-cultured cells.

CONCLUSIONS

These results suggest that PRP treatment accelerates bone neoformation with no cell cycle changes that might carry a risk of malignant transformation.

Aminopeptidase activity profile in cultured human osteoblasts

Aminopeptidases (APs) are enzymes involved in a wide variety of biological processes and present in a variety of different cell populations. The authors studied these enzymes in primary cultured human osteoblasts in order to establish an activity profile and thereby contribute to knowledge of bone tissue. The authors used 13 different substrates (N-terminal amino acids) and a fluorimetric assay to examine AP activity associated with the membranes of cultured osteoblasts. The authors demonstrated activity > 10 pmol/min/10(4) cells when glycine, alanine, leucine, arginine, phenylalanine, methionine, and lysine were used as substrates. The activity was markedly lower (<1.6 pmol/min/10(4) cells) when the other N-terminal amino acids were used. Puromycin and bestatin inhibited AP activity, though not completely, when we used AlaNA or LeuNA as substrates. Further studies are warranted to determine the role of these enzymes in bone tissue physiology.

Effects of Indomethacin, Nimesulide, and Diclofenac on Human MG-63 Osteosarcoma Cell Line

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most widely prescribed drugs worldwide and serve as treatment of some degenerative inflammatory joint diseases. The aim of the present study was to investigate the influence of different concentrations of three NSAIDs on cell proliferation, differentiation, antigenic profile, and cell cycle in the human MG-63 osteosarcoma cell line, incubated for 24 hr. All NSAIDs had an inhibiting effect on osteoblastic proliferation. Treatments for 24 hr had small but significant effects on the antigenic profile. No treatment altered osteocalcin synthesis. Indomethacin and nimesulide treatments arrested the cell cycle at G0/G1. These results suggest that indomethacin, nimesulide, and diclofenac appear to have no effects on osteocalcin synthesis and a slight effect on the antigenic profile. They may delay bone regeneration due to their inhibiting effect on osteoblast growth. Therefore, these drugs should only be used in situations that do not require rapid bone healing.

Effect of acetaminophen (paracetamol) on human osteosarcoma cell line MG63

AIM

To examine the effects of acetaminophen (paracetamol), a nonsteroidal anti-inflammatory drug (NSAID), on different cellular and functional parameters of the human osteosarcoma cell line MG63.

METHODS

Flow cytometry was used to study proliferation, antigenic profile, and phagocytic activity, and radioimmunoassay was used to determine osteocalcin synthesis as a cell differentiation marker.

RESULTS

Short-term treatment with therapeutic doses of paracetamol(5 or 25 μmol/L) reduced cell proliferation, osteocalcin synthesis, and phagocyte activity, and increased the expression of antigens involved in antigen presentation to T lymphocytes (CD80, CD86, HLA-DR).

CONCLUSION

These findings suggest that paracetamol activates the osteoblast, inducing its immunogenic action to the detriment of its bone formation capacity.

In vitro characterization of immune-related properties of human fetal bone cells for potential tissue engineering applications

We describe herein some immunological properties of human fetal bone cells recently tested for bone tissue-engineering applications. Adult mesenchymal stem cells (MSCs) and osteoblasts were included in the study for comparison. Surface markers involved in bone metabolism and immune recognition were analyzed using flow cytometry before and after differentiation or treatment with cytokines. Immunomodulatory properties were studied on activated peripheral blood mononuclear cells (PBMCs). The immuno-profile of fetal bone cells was further investigated at the gene expression level. Fetal bone cells and adult MSCs were positive for Stro-1, alkaline phosphatase, CD10, CD44, CD54, and beta2-microglobulin, but human leukocyte antigen (HLA)-I and CD80 were less present than on adult osteoblasts. All cells were negative for HLA-II. Treatment with recombinant human interferon gamma increased the presence of HLA-I in adult cells much more than in fetal cells. In the presence of activated PBMCs, fetal cells had antiproliferative effects, although with patterns not always comparable with those of adult MSCs and osteoblasts. Because of the immunological profile, and with their more-differentiated phenotype than of stem cells, fetal bone cells present an interesting potential for allogeneic cell source in tissue-engineering applications.

Transcriptional profiling of immune system-related genes in postmenopausal osteoporotic versus non-osteoporotic human bone tissue

The functional interaction between the immune system and bone metabolism has been established at both molecular and cellular levels. We have used non-parametric and multidimensional expression pattern analyses to determine significantly changed mRNA profile of immune system-associated genes in postmenopausal osteoporotic (OP) vs. non-osteoporotic (NOP) bone tissue. Seven bone tissue samples from OP patients and ten bone tissue samples from NOP women were examined in our study. The transcription differences of selected 44 genes were analyzed in Taqman probe-based quantitative real-time RT-PCR system. Mann-Whitney test indicated significantly down-regulated transcription activity of 3 genes (FCGR2A, NFKB1 and SCARA3) in OP bone tissue which have prominent role in (antibody) clearance, phagocytosis, pathogen recognition and inflammatory response. According to the canonical variates analysis results, the groups of postmenopausal OP and NOP women are separable by genes coding for cytokines, co-stimulators and cell surface receptors affected in innate immunity which have high discriminatory power. Based on the complex gene expression patterns in human bone cells, we could distinguish OP and NOP states from an immunological aspect. Our data may provide further insights into the changes of the intersystem crosstalk between the immune and skeletal systems, as well as into the local immune response in the altered microenvironment of OP bone.

Expression of cytokines IL-4, IL-12, IL-15, IL-18, and IFNgamma and modulation by different growth factors in cultured human osteoblast-like cells

The antigenic phenotype of cultured human osteoblast-like cells, their ability to phagocytose particles of different nature and size, and their capacity to stimulate allogeneic T cells suggest that they are related to other cell populations with which they may also have immunological functions in common. The objective of this study was to investigate the intracytoplasmatic presence of cytokines and their modulation by different biomolecules. Immunocytochemistry and flow cytometry were used to study the expression of IL-4, IL-12, IL-15, IL-18, and IFNgamma cytokines. To investigate whether FGF, TGF, PDGF, IL-1, and IFNgamma modulate expression of these cytokines in cultured human osteoblast-like cells we used flow cytometry. IL-4, IL-12, IL-15, IL-18, and IFNgamma cytokines were expressed by all the cultured human osteoblast-like cells studied. Treatment with FGF and TGFbeta1 reduced the percentage expression and fluorescence intensity of the cytokines. PDGF treatment enhanced their fluorescence intensity but did not modify their expression. IL-1 treatment produced a small reduction in expression and fluorescence intensity of IL-12 and IL-15, but did not produce major changes in the expression of IL-4, IL-18, or IFNgamma. IFNgamma markedly increased the fluorescence intensity of the cytokines. The results indicate that human osteoblast-like cells may perform immunological functions (e.g., synthesizing cytokines with immune regulator function) that can be modulated by different biomolecules related to bone tissue and/or immune response.