The effects of recombinant human interleukin-1 beta on cellular proliferation and the production of prostaglandin E2, plasminogen activator, osteocalcin and alkaline phosphatase by osteoblast-like cells derived from human bone

MicroRNA-125a-3p participates in odontoblastic differentiation of dental pulp stem cells by targeting Fyn

Fyn is a member of the protein tyrosine kinase family and its overexpression is associated with various types of inflammation. MicroRNAs can regulate the expression of target genes and play an important role in varied physiological and pathological processes. Based on the important role of Fyn and microRNA-125a-3p (miR-125a-3p) in inflammation, and combined with the bioinformatics studies, we performed in this study and chose miR-125a-3p as the focus of our research. During the progression of inflammation, we found that the expression of miR-125a-3p was decreased while the expression of Fyn was up-regulated. Fyn formed a complex with Neuropilin-1, which inhibited odontoblastic differentiation and expanded inflammatory responses through nuclear factor-κB signal pathways in dental pulp stem cells (DPSCs). These findings suggested that miR-125a-3p plays an important role in odontoblastic differentiation of DPSCs by targeting Fyn, implying its therapeutic potential in dental caries.

Interleukin-1β signaling in osteoarthritis - chondrocytes in focus

Osteoarthritis (OA) can be regarded as a chronic, painful and degenerative disease that affects all tissues of a joint and one of the major endpoints being loss of articular cartilage. In most cases, OA is associated with a variable degree of synovial inflammation. A variety of different cell types including chondrocytes, synovial fibroblasts, adipocytes, osteoblasts and osteoclasts as well as stem and immune cells are involved in catabolic and inflammatory processes but also in attempts to counteract the cartilage loss. At the molecular level, these changes are regulated by a complex network of proteolytic enzymes, chemokines and cytokines (for review: [1]). Here, interleukin-1 signaling (IL-1) plays a central role and its effects on the different cell types involved in OA are discussed in this review with a special focus on the chondrocyte.

The Role of Neuropilin-1-FYN Interaction in Odontoblast Differentiation of Dental Pulp Stem Cells

Abnormal odontoblast differentiation of dental pulp stem cells (DPSCs) caused by inflammation is closely related to the development of dental caries. Neuropilin-1 (NRP1) is one of the members of neuropilin family. It can combine with disparate ligands involved in regulating cell differentiation. FYN belongs to the protein-tyrosine kinase family, which has been implicated in the control of cell growth, and the effect can be further strengthened by inflammatory factors. In our studies, we verified that NRP1 can form complexes with FYN and have the correlation changes in odontoblast differentiation of DPSCs. Therefore, we surmise that in the progress of dental caries, NRP1 interacts with FYN, by expanding inflammation and inhibition of odontoblast differentiation of DPSCs through nuclear factor kappa B (NF-κB) signaling pathway. In this subject, we first investigated the expression and interaction of NRP1 and FYN in DPSCs. And then, we researched the effect of this complex controlling downstream signal pathway in normal or inflammation stimulated DPSCs. Finally, we analyzed the relationship between this role and odontoblast differentiation of DPSCs. This research will provide the molecular mechanism of inflammation factors of dental caries through activating NF-κB signal regulating odontoblast differentiation in DPSCs for finding new potential drug targets for the clinical treatment of dental caries.

Antiosteoporotic effect of icariin in ovariectomized rats is mediated via the Wnt/β-catenin pathway

Icariin (ICA), the main active flavonoid glucoside isolated from Herba Epimedii, has been shown to prevent postmenopausal bone loss in vitro. However, the mechanisms by which ICA prevents bone loss in vivo remain poorly understood. In the present study, the effect of ICA in an ovariectomized (OVX) rat model of osteoporosis was evaluated. Sprague-Dawley rats were divided into sham-operated and OVX groups. The OVX rats were randomly divided into five groups: OVX group (water only), Fosamax (positive) group (5.04 mg/kg, weekly, administered orally), and OVX-ICA groups (125, 250 or 500 mg/kg, daily, administered orally) and treated for 12 weeks. The 125, 250 and 500 mg/kg doses of ICA were designated as low (L-ICA), medium (M-ICA) and high (H-ICA), respectively. Compared with the sham-operated group, the OVX rats had significantly decreased bone mineral density (BMD), reduced serum osteoprotegerin (OPG) and increased serum bone gla protein (BGP) concentrations. ICA significantly increased BMD, biomechanical strength, trabecular bone number and trabecular bone thickness, and reduced lumbar trabecular bone separation. Treatment with ICA also completely normalized the expression of osteoblast markers by increasing serum concentrations of OPG and BGP. Enhanced mineralization was demonstrated by increased expression of differentiation markers. Although further in vivo studies are required to investigate the efficacy of ICA in improving bone mass, this study demonstrates that ICA has strong osteogenic activity, inducing osteogenic differentiation and inhibiting resorption by osteoclasts. It also demonstrates an antiosteoporotic effect for ICA on the basis of BMD, biochemical markers, biomechanical tests and histopathological parameters. Compared with L-ICA and H-ICA, M-ICA was more effective and caused no liver or kidney damage.

Anti-osteoporotic effects of Angelica sinensis (Oliv.) Diels extract on ovariectomized rats and its oral toxicity in rats

Angelica sinensis root is one of the herbs most commonly used in China; it is also often included in dietary supplements for menopause in Europe and North America. In the present study, we examined the anti-osteoporotic effects of A. sinensis extract in an ovariectomized (OVX) rat model of osteoporosis as well as toxicity of the extract after repeated oral administration. The OVX rats were treated with 17β-estradiol (10 μg/kg i.p. once daily) or A. sinensis extract (30, 100, and 300 mg/kg, p.o. once daily) for four weeks. The bone (femur) mineral density (BMD) of rats treated with the extract (300 mg/kg) was significantly higher than that of the OVX-control, reaching BMD of the estradiol group. Markers of bone turnover in osteoporosis, serum alkaline phosphatase, collagen type I C-telopeptide and osteocalcin, were significantly decreased in the extract group. The body and uterus weight and serum estradiol concentration were not affected, and no treatment-related toxicity was observed during extract administration in rats. The results obtained indicate that A. sinensis extract can prevent the OVX-induced bone loss in rats via estrogen-independent mechanism.

Role of flavonoids on oxidative stress and mineral contents in the retinoic acid-induced bone loss model of rat

PURPOSE

Reactive oxygen species play a role in a number of degenerative conditions including osteoporosis. Flavonoids as phyto-oestrogens exert physiological effects against oxidative stress diseases. We developed a retinoic acid-induced bone loss model of rats to assess whether flavonoids and alendronate as positive control have role against oxidative stress and mineral contents in osteoporosis in vivo.

METHODS

Three-month-old female rats of the Y59 strain were given quercetin, chrysin, naringenin (100 mg kg(-1)) or alendronate (40 mg kg(-1), a positive control) immediately before retinoic acid treatment (80 mg kg(-1)) once daily for 14 days by a single intragastric (i.g.) application. In the second part of the study, we assessed the effect of those flavonoids on the skeletal system of healthy rats using single i.g. application on the respective flavonoids during 14 days. Twenty-four hours after the treatment, we analysed bone mineral density and the total content of bone calcium and phosphorus in the femur, the geometric and physical characteristics of thigh bones and lipid peroxidation and glutathione levels of liver and kidney cells.

RESULTS

All flavonoids improved the decrease in bone weight coefficient, the length and the diameter of the bone, the content of bone ash and calcium and phosphorus content induced by retinoic acid. Chrysin and quercetin showed promise as preventive agents. Flavonoids were superior to alendronate according to some criteria.

CONCLUSIONS

These results suggest that the dietary flavonoids could reduce retinoic acid-induced oxidative stress and bone loss and that flavonoids may be useful therapeutics for prevention of skeletal diseases.

Preventive effects of Eleutherococcus senticosus bark extract in OVX-induced osteoporosis in rats

Eleutherococcus senticosus (Siberian ginseng), has been used as a powerful tonic herb with an impressive range of health benefits. This medicinal herb has been commonly used to treat bone metabolism diseases due to its traditional Korean medicine use to strengthen muscle and bone. This study was conducted to investigate prevention of bone loss by a standardized extract of dried E. senticosus stem bark in an ovariectomized (OVX) rat model of osteoporosis. The OVX groups were divided into five groups treated with distilled water, 17β-estradiol (E2 10 μg/kg, once daily, i.p) and dried stem bark of E. senticosus extracts (DES 10, 30, and 100 mg/kg, once daily, p.o) for eight weeks, respectively. After eight weeks of treatments, the femur bone mineral density of the 100 mg/kg DES-treated group was significantly higher than that of the OVX-control group (16.7%, p < 0.01) without affecting the body, organs, and uterus weights, and serum estradiol levels. Additionally, bone markers such as serum ALP, CTx, and OC levels were significantly decreased in the DES 100 mg/kg treated group. These results show that DES is able to prevent OVX-induced in bone loss without the influence of hormones such as estrogen.

Dried root of Rehmannia glutinosa prevents bone loss in ovariectomized rats

Dried root of Rehmannia glutinosa is a kidney-tonifying herbal medicine with a long history of safe use in traditional folk medicine for the treatment of joint diseases. This study was conducted to investigate prevention of bone loss by a standardized dried root of R. glutinosa in an ovariectomized (OVX) rat model of osteoporosis. The OVX groups were divided into five groups treated with distilled water, 17β-estradiol (E2 10 µg/kg, once daily, i.p) and dried root of R. glutinosa extracts (DRGE 30, 100, and 300 mg/kg, twice daily, p.o) for eight weeks. We measured the body, organs, and uterus weights, and femur and lumbar vertebrae bone mineral density (BMD), serum alkaline phosphatase (ALP), estradiol levels. The treatments with DRGE 300 mg/kg significantly inhibited BMD decrease in the femur and lumbar (17.5% and 16.4%, p < 0.05, respectively) by OVX without affecting the body, organs, and uterus weights. Also, serum ALP level in the DRGE 300 mg/kg treated group was significantly decreased, but the estradiol level did not change in serum of the DRGE 300 mg/kg treated group. These results show that DRGE is able to prevent OVX-induced bone loss without influencing hormones such as estrogen.

Interleukin-1β promotes skeletal colonization and progression of metastatic prostate cancer cells with neuroendocrine features

Despite the progress made in the early detection and treatment of prostate adenocarcinoma, the metastatic lesions from this tumor are incurable. We used genome-wide expression analysis of human prostate cancer cells with different metastatic behavior in animal models to reveal that bone-tropic phenotypes upregulate three genes encoding for the cytokine interleukin-1β (IL-1β), the chemokine CXCL6 (GCP-2), and the protease inhibitor elafin (PI3). The Oncomine database revealed that these three genes are significantly upregulated in human prostate cancer versus normal tissue and correlate with Gleason scores ≥7. This correlation was further validated for IL-1β by immunodetection in prostate tissue arrays. Our study also shows that the exogenous overexpression of IL-1β in nonmetastatic cancer cells promotes their growth into large skeletal lesions in mice, whereas its knockdown significantly impairs the bone progression of highly metastatic cells. In addition, IL-1β secreted by metastatic cells induced the overexpression of COX-2 (PTGS2) in human bone mesenchymal cells treated with conditioned media from bone metastatic prostate cancer cells. Finally, we inspected human tissue specimens from skeletal metastases and detected prostate cancer cells positive for both IL-1β and synaptophysin while concurrently lacking prostate-specific antigen (PSA, KLK3) expression. Collectively, these findings indicate that IL-1β supports the skeletal colonization and metastatic progression of prostate cancer cells with an acquired neuroendocrine phenotype.

Expression and stability of hypoxia inducible factor 1α in osteosarcoma

BACKGROUND

Hypoxia contributes to both physiological and pathological processes and its effects are mainly mediated through the transcription factors hypoxia-inducible factor 1α and 2α (HIF1α and HIF2α). The purpose of this study was to examine the role of these proteins in osteosarcoma progression.

PROCEDURES

We developed a method to isolate primary human osteoblast cell lines. HIF1α and HIF2α expression were then compared in osteoblast and osteosarcoma cell lines under 21% oxygen (normoxia) and 1% oxygen (hypoxia). We also used hypoxia-responsive element (HRE)-driven reporter constructs in conjunction with siRNAs specific to HIF1α or HIF2α to determine the contribution of each protein to HRE-mediated transcription. Finally, we measured HIF1α expression in primary osteosarcoma tumors by immunohistochemistry.

RESULTS

We found that mainly HIF1α transcript was significantly higher in osteosarcoma cell lines compared to normal osteoblasts under both normoxia and hypoxia. At the protein level, HIF1α was preferentially stabilized in osteosarcoma cell lines under both conditions. HIF1α expression was required for the observed increases in HRE activity. Finally, nuclear or nucleocytoplasmic HIF1α staining in osteosarcoma cases was associated with high-grade tumors.

CONCLUSIONS

These findings point to a role for HIF1α in osteosarcoma progression and suggest that the observed differences in HIF1α oxygen dependent degradation may play an important pathophysiological role in this disease. Pediatr Blood Cancer 2012; 59: 1215-1222. © 2012 Wiley Periodicals, Inc.

The effect of polyunsaturated fatty acids on bone health

The essential polyunsaturated fatty acids (PUFAs) are divided into two classes, n-3 (ω-3) and n-6 (ω-6) and their dietary precursors are α-linolenic (ALA) and linoleic acid (LA), respectively. PUFAs are precursors of a wide range of metabolites, for example eicosanoids like prostaglandins and leukotrienes, which play critical roles in the regulation of a variety of biological processes, including bone metabolism.

A large body of evidence supports an effect of PUFA on bone metabolism which may be mediated by regulation of osteoblastogenesis and osteoclast activity, change of membrane function, decrease in inflammatory cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-α), modulation of peroxisome proliferators-activated receptor γ (PPARγ) and influence in NO secretion and NO synthase.

Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. Human studies conducted in elderly subjects suggest that omega-3 instead of omega-6 has a positive effect on bone metabolism. In spite of increasing evidence, studies conducted in humans do not allow us to draw a definitive conclusion on the usefulness of PUFAs in clinical practice.

Osteoblast physiology in normal and pathological conditions

Osteoblasts are mononucleated cells that are derived from mesenchymal stem cells and that are responsible for the synthesis and mineralization of bone during initial bone formation and later bone remodelling. Osteoblasts also have a role in the regulation of osteoclast activity through the receptor activator of nuclear factor κ-B ligand and osteoprotegerin. Abnormalities in osteoblast differentiation and activity occur in some common human diseases such as osteoporosis and osteoarthritis. Recent studies also suggest that osteoblast functions are compromised at sites of focal bone erosion in rheumatoid arthritis.

Biphasic effects of interleukin-1beta on osteoblast differentiation in vitro

A rat calvarial cell model of osteoblast differentiation using the formation of bone nodules in vitro as an endpoint was used to assess the effects of IL-1beta on osteoblast differentiation. Short-term treatment (2 days) with IL-1beta early in culture resulted in increased nodule number and size as well as calcium content in contrast to long-term treatment (6 days) in cultures assessed at 10-12 days. This increase in bone formation was blocked by IL-1 receptor antagonists. Short-term treatment increased COX-2, prostaglandin (PGE(2)), and iNOS production. Exogenous PGE(2) with IL-1beta enhanced this effect. COX-2 inhibitors, indomethacin and N-39, blocked 50% of nodule formation. NO donor did not modify effects of IL-1beta, but iNOS inhibitor (1400W) partially blocked the effects. However, PGE(2) and NO donors could not rescue the decreased nodule number resulting from long-term IL-1beta treatment. The results of this study suggest a biphasic effect of IL-1beta on bone nodule formation activated by IL-1beta binding with IL-1 receptors, and the anabolic effect of early short-term treatment with IL-1beta is likely mediated by PGE without ruling out nitric oxide.

Influence of ferutinin on bone metabolism in ovariectomized rats. II: role in recovering osteoporosis

The aim of the present investigation, which represents an extension of a previous study, was to investigate the effect of ferutinin in recovering severe osteoporosis due to estrogen deficiency after rat ovariectomy and to compare phytoestrogen effects with those of estrogens commonly used in hormone replacement therapy (HRT) by women with postmenopausal osteoporosis. The animal model used was the Sprague-Dawley ovariectomized rat. Ferutinin was orally administered (2 mg kg(-1) per day) for 30 or 60 days starting from 2 months after ovariectomy (i.e. when osteoporosis was clearly evident) and its effects were compared with those of estradiol benzoate (1.5 microg per rat twice a week, subcutaneously injected) vs. vehicle-treated ovariectomized (OVX) and sham-operated (SHAM) rats. Histomorphometric analyses were performed on trabecular bone of lumbar vertebrae (4th and 5th) and distal femoral epiphysis, as well as on cortical bone of femoral diaphysis. Bone histomorphometric analyses showed that ferutinin seems to display the same effects on bone mass recorded with estradiol benzoate, thus suggesting that it could enhance the recovery of bone loss due to severe estrogen deficiency in OVX rats. On this basis, the authors propose listing ferutinin among the substances representing a potential alternative for the treatment of postmenopausal osteoporosis, which occurs as a result of estrogen deficiency.

Platelet rich plasma to facilitate wound healing following tooth extraction

Following tooth removal bone formation normally takes 16 weeks and may result in less than adequate volume for the necessary reconstruction. Platelet rich plasma (PRP) has been promoted as an effective method for improving bone formation. Its use is often expensive, time consuming, or not clinically convenient for the patient and/or clinician. This study examines a simple method for obtaining a "Buffy Coat"-PRP (BC-PRP) and its effect on bone healing following the removal of bilateral mandibular 3rd molars. Subtraction digital radiography and CT scan analysis were used to track changes in radiographic density at PRP treated sites in comparison to ipsilateral non-PRP treated sites. PRP treated sites demonstrated early and significant increased radiographic density over baseline measurements following tooth removal. The greatest benefit of PRP is during the initial 2-week postoperative healing time period (P < .001). During weeks 3 though 12, BC-PRP treatment resulted in significant (P < .0001) increases in bone density compared to control, but there was no significant interaction between time and treatment (P > .05). For the entire time period (0-25 weeks) PRP treatment was significant (P < .0001) and time was significant (P < .0001) but there was no significant interaction (P > .05) between the effect of PRP treatment and time. It required 6 weeks for control extraction sites to reach comparable bone density that PRP treated sites achieved at week 1. Postoperative pain, bleeding, and numbness were not significantly affected by BC-PRP application. Results suggest that this simple technique may be of value to clinicians performing oral surgery by facilitating bone regeneration following tooth extraction.

Effects of volatile components and ethanolic extract from Eclipta prostrata on proliferation and differentiation of primary osteoblasts

Eclipta prostrata, an aromatic plant, is known in Chinese herbal medicine for the treatment of various kidney diseases. In the present study, the volatile components were isolated from the aerial parts of this plant by hydrodistillation and analysed by GC-MS. A total of 55 compounds, which were the major part (91.7%) of the volatiles, were identified by matching mass spectra with a mass spectrum library (NIST 05.L). The main components were as follows: heptadecane (14.78%), 6,10,14-trimethyl-2-pentadecanone (12.80%), n-hexadecanoic acid (8.98%), pentadecane (8.68%), eudesma-4(14),11-diene (5.86%), phytol (3.77%), octadec-9-enoic acid (3.35%), 1,2-benzenedicarboxylic acid diisooctyl ester (2.74%), (Z,Z)-9,12-octadecadienoic acid (2.36%), (Z)-7,11-dimethyl-3-methylene-1,6,10-dodecatriene (2.08%) and (Z,Z,Z)-1,5,9,9-tetramethyl-1,4,7-cycloundecatriene (2.07%). The effects of volatile components and ethanolic extract from the aerial parts of this plant on the proliferation and differentiation of primary osteoblasts were evaluated by the MTT method and measuring the activity of alkaline phosphatase (ALP activity). Both volatile components and ethanolic extract (1 microg/mL to 100 microg/mL) significantly (p < 0.01) stimulated the proliferation and increased the ALP activity of primary osteoblasts. These results propose that E. prostrata can play an important role in osteoblastic bone formation, and may possibly lead to the development of bone-forming drugs.

Follicle-stimulating hormone, interleukin-1, and bone density in adult women

Recent studies have indicated that follicle-stimulating hormone (FSH) promotes bone loss. The present study tested the hypothesis that FSH enhances the activity of bone-resorbing cytokines [interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, and IL-6], either by inducing their secretion or by altering their receptor expression. Thirty-six women between the ages of 20 and 50 were assessed for bone mineral density (BMD), reproductive hormone, cytokine ligand and soluble receptor concentrations, and surface expression of cytokine receptors on monocytes. In addition, isolated mononuclear cells were incubated in vitro with exogenous FSH. Univariate regression analyses indicated that BMD was inversely related to serum FSH (r = -0.29 to -0.51, P = 0.03-0.001, depending upon the skeletal site). Physical activity and body composition were also identified as significant factors by multiple regressions. Exogenous FSH induced isolated cells to secrete IL-1beta, TNF-alpha, and IL-6 in proportion to the surface expression of FSH receptors on the monocytes. Endogenous (serum) FSH concentrations correlated with the circulating concentrations of these cytokines. None of these individual cytokines was related to BMD, but the IL-1beta to IL-1 receptor antagonist (IL-1Ra) ratio was inversely related to BMD (r = -0.53, P = 0.002) in all but the most physically active women, who had significantly lower expression of IL-1 type I receptors relative to type II (decoy receptors, P = 0.01). Physical activity also correlated positively with secretion of inhibitory soluble IL-1 receptors (r = 0.53, P = 0.003). Moreover, IL-1Ra correlated strongly with percent body fat (r = 0.66, P < 0.0001). These results indicate that BMD is related to FSH concentration, physical activity, and body composition. Although each of these factors likely has direct effects on bone, the present study suggests that each may also influence BMD by modulating the activity of the osteoresorptive cytokine IL-1beta.

Antiosteoporotic activity of icariin in ovariectomized rats

Icariin was evaluated for its antiosteoporotic activity in an ovariectomized rat model of osteoporosis. The rats were divided into sham and OVX groups. The OVX rats were then subdivided into five groups treated with water, nylestriol (1 mg/kg body weight, weekly, orally) or icariin (ICA) (5, 25, and 125 mg/kg body weight, daily, orally) for 12 weeks. In OVX rats, the increases of body weight, serum BGP and ALP were significantly decreased by ICA treatment. In OVX rats, atrophy of uterus and descent of BMD were suppressed by treatment with ICA. In addition, ICA (125 mg/kg body weight) completely corrected the decreased serum concentration of Calcium, Phosphorus, and E(2) observed in OVX rats. ICA (125 mg/kg body weight) increased biomechanical strength significantly in comparison to the sham group. Histological results also showed its protective action through promotion of bone formation. The findings, assessed on the basis of biochemical, bone mineral density, biomechanical, and histopathological parameters, showed that ICA has a definite antiosteoporotic effect, similar to estrogen, especially effective for prevention bone fracture induced by estrogen deficiency.

Influence of ferutinin on bone metabolism in ovariectomized rats. I: role in preventing osteoporosis

Phytoestrogens play a role in maintaining bone mass in the post-menopausal period for their putative function as osteoprotective agents. The aim of the present study was to investigate the influence of Ferutinin, a phytoestrogen found in the plants of Ferula genus, on bone loss in ovariectomized rats. Such an animal model can simulate the various clinical syndromes deriving from osteoporosis. The effect of the daily oral administration of ferutinin to ovariectomized rats (dosed at 2 mg/kg per day for 30 and 60 days) was compared to that of estradiol benzoate (subcutaneously administered at the dose of 1.5 microg/rat twice a week). After the sacrifice, histomorphometrical analyses were performed on trabecular bone of L4-L5 vertebrae and distal femoral metaphysis, as well as on cortical bone of femoral diaphysis; biochemical parameters (bone mineral components and markers) were also evaluated from the rat serum. The histomorphometrical analyses of trabecular and cortical bone from lumbar vertebrae and femur showed that ferutinin has the same antiosteoporotic effect of estradiol benzoate on bone mass, and in some cases is even stronger. This fact suggests that it could prevent osteoporosis caused by severe estrogen deficiency in ovariectomized rats. The possibility of using ferutinin as an alternative to the commonly employed hormonal replacing therapy in post-menopausal women is discussed.

Inhibition of Ulmus davidiana Planch (Ulmaceae) on bone resorption mediated by processing of cathepsin K in cultured mouse osteoclasts

Ulmus davidiana Planch (Ulmaceae) (UD) has long been known to be antiinflammatory in traditional Korean medicine. This experiment investigated the effects of UD on bone resorption using bone cell culture. Different concentrations of crude extract of UD were added to mouse bone cell culture. The mitochondrial activity of the bone cells after exposure of UD was determined by colorimetric 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT). It was demonstrated that UD has potential effects on bone cell culture without cytotoxicity. The most effective concentration of UD in bone cells was 100 microg/mL. Cathepsin K (Cat K) is the major cysteine protease expressed in osteoclasts and is thought to play a key role in matrix degradation during bone resorption. When mouse long bone cells including osteoclasts and osteoblasts were treated with UD, UD prevented the osteoclast-mediated intracellular processing of Cat K, suggesting that UD may disrupt the intracellular transport of pro Cat K. Since secreted proenzymes have the potential to reenter the cell via the mannose-6-phosphate (M6P) receptor, to prevent this possibility, UD was tested in the absence or presence of M6P. Inhibition of Cat K processing by UD was observed in a dose-dependent manner. Furthermore, the addition of M6P resulted in enhanced potency of UD. UD dose-dependently inhibited in vitro bone resorption with a potency similar to that observed for inhibition of Cat K processing.

Effect of safflower seeds supplementation on stimulation of the proliferation, differentiation and mineralization of osteoblastic MC3T3-E1 cells

Anti-bone resorption properties of the Korean herbal formulation, Gami-Honghwain (HJ), which comprises Carthamus tinctorius L. seed and hominis placenta, were investigated. We demonstrate that the production of PGE2 is inhibited by 20-100 microg/ml HJ in nontransformed osteoblastic cells (MC3T3-E1 cells), indicating that HJ inhibits PGE2 production. The effect of HJ on the proliferation and osteoblastic differentiation in MC3T3-E1 was also studied. HJ dose-dependently increased DNA synthesis (significant at 20-100 microg/ml), and increased alkaline phosphatase (ALP) and prolyl hydroxylase activities of MC3T3-E1 cells (20-100 microg/ml), while anti-estrogen tamoxifen eliminated the stimulation of proliferation and ALP activity of MC3T3-E1 which was induced by HJ. These results indicate that HJ directly stimulates cell proliferation and differentiation of osteoblasts. Also, when we assessed the effects of HJ on osteoblastic differentiation in MC3T3-E1, HJ enhanced ALP activity and mineralization in a dose- and time-dependent fashion. This stimulatory effect of the HJ was observed at relatively low doses (significant at 20-100 microg/ml and maximal at 100 microg/ml). Northern blot analysis showed that the HJ (60 microg/ml) increased in bone morphogenetic protein-2 as well as ALP mRNA concentrations in MC3T3-E1 cells. HJ (100 microg/ml) slightly increased in type I collagen mRNA abundance throughout the culture period, whereas it markedly inhibited the gene expression of collagenase-1 between days 15 and 20 of culture. These results indicate that HJ has anabolic effect on bone through the promotion of osteoblastic differentiation, suggesting that it could be used for the treatment of common metabolic bone diseases.

Antiosteoporotic activity of Er-Xian Decoction, a traditional Chinese herbal formula, in ovariectomized rats

The antiosteoporotic effect of a herbal formula, Er-Xian Decoction (EXD), in ovariectomized (OVX) rats model of osteoporosis was investigated. The rats were divided into Sham and OVX groups. The OVX rats were further sub-divided into four groups administered orally with water, nylestriol (1 mg/kg, weekly) or EXD (300, 600 mg/kg, daily) for 12 weeks. In OVX rats, the increases of body weight, serum BGP and ALP were significantly decreased by EXD treatment. In OVX rats, atrophy of uterus and descent of BMD were suppressed by treatment with EXD and nylestriol. In addition, EXD completely corrected the decreased concentration of calcium, phosphorus, and estradiol in serum observed in OVX rats. EXD also significantly increased biomechanical strength comparable to the Sham group. This was also confirmed by histological results that showed its protective action. The findings assessed on the basis of biochemical, bone mineral density, biomechanical, and histopathological parameters strongly suggested that EXD had a definite antiosteoporotic effect, which is similar to estrogen.

Local immunomodulation with CD4 and CD8 antibodies, but not cyclosporine A, improves osteogenesis induced by ADhBMP9 gene therapy

This study was designed to see if immunosuppression achieved using local application of cyclosporine A (Cs. A) or CD4 and CD8 antibodies would improve bone formation following intramuscular injections of human BMP-4 and BMP-9 adenoviral vectors (ADhBMP4 and ADhBMP9) in Sprague-Dawley rats. Cs. A was injected into the thigh muscle. After 2 days, ADhBMP4, ADhBMP9, and the antibodies were separately injected into the left and right rear legs. At this time, the number of CD4+/CD3+ cells was significantly lower and the number of CD8+/CD3+ cells higher in the Cs. A group than in the control group (P < 0.01). The total number of white blood cells 3 days following injection of CD4 and CD8 antibodies was significantly lower than that before the injection (P < 0.01). At 4 weeks after the viral and antibody injections, mean bone volumes at the ADhBMP9 treatment sites were 0.29 +/- 0.01 cm3 in the viral control group, 0.17 +/- 0.03 cm3 in the Cs. A-ADhBMPs group, and 0.59 +/- 0.07 cm3 in the antibodies-ADhBMPs group. ADhBMP4 did not induce new bone formation in any group. This study demonstrates that local immunomodulation may improve the osteogenic potential of bone morphogenetic protein gene therapy in the clinical setting.

cAMP-PKA signaling pathway regulates bone resorption mediated by processing of cathepsin K in cultured mouse osteoclasts

Cathepsin K (Cat K) is the major cysteine protease expressed in osteoclast and is thought to play a key role in matrix degradation during bone resorption. It is shown that the intracellular maturation of Cat K was prevented by the cAMP antagonist, Rp-cAMP, and the protein kinase A (PKA) inhibitors of KT5720 and H89. In contrast, forskolin, an adenylate cyclase agonist, rather induced Cat K processing and maturation in osteoclast. Furthermore, to determine whether Cat K processing and maturation signaling involves protein kinase C (PKC), mouse total bone cells were treated with calphostin C, a specific inhibitor of PKC, however, no effect was observed, indicating that PKC calphostin C did not affect to osteoclast-mediated Cat K processing and maturation in osteoclast. Thus, it is indicated that the cAMP-PKA signaling pathway regulate Cat K maturation in osteoclast. Since secreted proenzymes have the potential to reenter the cell via M6P receptor, to prevent this possibility, we tested cAMP antagonist Rp-cAMP and the PKA inhibitors KT5720 and H89 in the absence or presence of M6P. Inhibition of Cat K processing by Rp-cAMP, KT5720 or H89 was observed in a dose-dependent manner. Furthermore, the addition of M6P resulted in enhanced potency of Rp-cAMP, KT5720 and H89, which dose-dependently inhibited in vitro bone resorption with potency similar to that observed for inhibition of Cat K processing.

Graded Doses of Recombinant Interleukin-1β Induce Generalized Osteopenia in Rats without Altering Skeletal Growth and Joint Integrity

BACKGROUND

Whereas a primary role of interleukin-1beta (IL-1beta) in local bone remodelling and articular inflammation has been well established, the effect of prolonged systemic administration of this cytokine on total skeletal Ca, somatic growth and joint tissue has not yet been investigated.

METHODS

Five groups of 14 rats each, aged 7-8 weeks, had miniosmotic pumps (Alzet 200 microl) implanted and primed to release 100, 200, 500, 1,000 and 2,000 ng/kg/24 h of human recombinant IL-1beta (rIL-1beta) daily for 14 days. On days 0 and 14 total skeletal mineral content (BMC) was assessed by means of X-ray absorptiometry and vertebral and tibial growth was measured by computer-assisted radiometry. On the same days, blood was drawn and analyzed for rat growth hormone (rGH), insulin-like growth factor (IGF-1), and osteocalcin. Also 24-hour urine was collected for d-pyridinoline (dpd) determinations. Hind- and forepaw diameter as a parameter of joint inflammation was assessed using a micrometric calliper. Subsequently the animals were sacrificed and one tibia dissected for measurement of trabecular volume by computerized histomorphometry.

RESULTS

BMC decreased in a dose-dependent manner reaching significance at 1,000 and 2,000 ng/kg (p < 0.03 and 0.04) in close correlation with tibial trabecular volumes (r = 0.84; p < 0.02). Normal vertebral and tibial growth was recorded at all dosages. There was no evidence of joint involvement. Blood rGH and IGF-1 remained normal as did osteocalcin, the latter reflecting lack of osteoblast activation. In contrast dpd increased in a dose-dependent manner indicating enhanced bone matrix turnover.

CONCLUSION

It is concluded that graded infusions of supraphysiological doses of rIL-1beta capable of inducing osteopenia did not affect skeletal growth in the absence of articular reaction. This is in contrast with the experience recorded in experimental arthritis in which growth retardation, in addition to osteopenia, may be caused by factors other than circulating IL-1beta.

Dietary ratio of n-6/n-3 PUFAs and docosahexaenoic acid: actions on bone mineral and serum biomarkers in ovariectomized rats

Hypoestrogenic states escalate bone loss in animals and humans. This study evaluated the effects of the amount and ratio of dietary n-6 and n-3 polyunsaturated fatty acids (PUFAs) on bone mineral in 3-month-old sexually mature ovariectomized (OVX) Sprague-Dawley rats. For 12 weeks, the rats were fed either a high-PUFA (HP) or a low-PUFA (LP) diet with a ratio of n-6/n-3 PUFAs of 5:1 (HP5 and LP5) or 10:1 (HP10 and LP10). All diets (modified AIN-93G) provided 110.4 g/kg of fat from safflower oil and/or high-oleate safflower oil blended with n-3 PUFAs (DHASCO oil) as a source of docosahexaenoic acid (DHA). Fatty acid analyses confirmed that the dietary ratio of 5:1 significantly elevated the amount of DHA in the periosteum, marrow and cortical and trabecular bones of the femur. Dual-energy X-ray absorptiometry measurements for femur and tibia bone mineral content (BMC) and bone mineral density showed that the DHA-rich diets (HP5 and LP5) resulted in a significantly lower bone loss among the OVX rats at 12 weeks. Rats fed the LP diets displayed the lowest overall serum concentrations of the bone resorption biomarkers pyridinoline (Pyd) and deoxypyridinoline, whereas the bone formation marker osteocalcin was lowest in the HP groups. Regardless of the dietary PUFA content, DHA in the 5:1 diets (HP5 and LP5) preserved rat femur BMC in the absence of estrogen. This study indicates that the dietary ratio of n-6/n-3 PUFAs (LP5 and HP5) and bone tissue concentration of total long-chain n-3 PUFAs (DHA) minimize femur bone loss as evidenced by a higher BMC in OVX rats. These findings show that dietary DHA lowers the ratio of 18:2n-6 (linoleic acid)/n-3 in bone compartments and that this ratio in tissue correlates with reduced Pyd but higher bone alkaline phosphatase activity and BMC values that favor bone conservation in OVX rats.

Inhibition of Drynariae Rhizoma extracts on bone resorption mediated by processing of cathepsin K in cultured mouse osteoclasts

In the traditional Korean medicine, Drynariae Rhizoma (DR) [Drynaria fortunei (kunze) J. Sm] has been reported as a good enhancer for bone healing. In this experiment, we investigate the effects of DR on bone resorption using the bone cells culture. Different concentrations of crude extract of DR were added to mouse bone cells culture. The mitochondria activity of the bone cells after exposure was determined by colorimetric MTT assay. It was demonstrated that DR has potential effects on the bone cells culture without any cytotoxicity. The most effective concentration of DR on bone cells was 100 micro g/ml. On the other hand, cathepsin K (Cat K) is the major cysteine protease expressed in osteoclasts and is thought to play a key role in matrix degradation during bone resorption. In this study, Mouse long bone cells including osteoclasts and osteoblast were treated with the PI3-kinase inhibitor, wortmannin (WT), and a specific inhibitor of protein kinase C (PKC), calphostin C. Although WT prevented the osteoclast-mediated intracellular processing of Cat K, calphostin C did not. Similarly, treatment of osteoclasts-containing long bone cells with Drynariae Rhizoma (DR) extracts prevented the intracellular maturation of Cat K, suggesting that DR may disrupt the intracellular trafficking of pro Cat K. This is similar to that of WT. Since secreted proenzymes have the potential to reenter the cell via mannose-6-phosphate (M6P) receptor, to prevent this possibility, we tested WT and DR in the absence or presence of M6P. Inhibition of Cat K processing by WT or DR was observed in a dose-dependent manner. Furthermore, the addition of M6P resulted in enhanced potency of WT and DR. DR dose-dependently inhibited in vitro bone resorption with a potency similar to that observed for inhibition of Cat K processing.

IL-1beta induces and TGF-beta reduces vitamin D3-induced bone resorption in mouse calvarial bone cells

Bone cells produce multiple growth factors and cytokines that have effects on bone metabolism and can be incorporated into the bone matrix. The present study was designed to extend these observations by examining the interactions between transforming growth factor-beta (TGF-beta) or interleukin-1beta (IL-1beta) and bone cells in a rat long bone culture model. IL-1beta regulates several activities of the osteoblast cells derived from rat long bone explants in vitro. IL-1beta stimulated cellular proliferation and the synthesis of prostaglandin E2 and plasminogen activator activity in the cultured cells in a dose-dependent manner. TGF-B is present in the bone matrix and potentially can be released during bone resorption. TGF-beta reduced basal bone resorption and inhibited vitamin D3 [1,25(OH)2D3]-induced bone resorption in rat long bone cells. These studies support the role of IL-1beta in the pathological modulation of bone cell metabolism, with regard to implication in the pathogenesis of osteoporosis by IL-1beta, and that TGF-beta is positively inhibiting the bone resorption.

Modulatory effect of omega-3 polyunsaturated fatty acids on osteoblast function and bone metabolism

Recent investigations indicate that the type and amount of polyunsaturated fatty acids (PUFA) influence bone formation in animal models and osteoblastic cell functions in culture. In growing rats, supplementing the diet with omega-3 PUFA results in greater bone formation rates and moderates ex vivo prostaglandin E(2) production in bone organ cultures. A protective effect of omega-3 PUFA on minimizing bone mineral loss in ovariectomized rats has also been reported. The actions of omega-3 fatty acids on bone formation appear to be linked to altering osteoblast functions. Herein we describe experiments with MC3T3-E1 osteoblast-like cells that support findings in vivo where omega-3 PUFA modulated COX-2 protein expression, reduced prostaglandin E(2) production, and increased alkaline phosphatase activity. Other studies indicate that the dietary source of PUFA may affect protein expression of Cbfa1 and nodule formation in fetal rat calvarial cells.

Cathepsin B in osteoblasts

Active cathepsin B has been found in cell extract and medium of human osteoblast-like cells and MG-63 cells. The released form is stable at neutral and alkaline pH and, in both cell types, intracellular and extracellular cathepsin B activities are increased by interleukin-1 beta (IL-1beta) and parathyroid hormone (PTH). To evaluate the physiological role of cathepsin B in osteoblasts, we investigated the production and secretion of this enzyme in normal human synovial fibroblasts and modulation by IL-1beta and PTH. Lactate secretion concurrent with release of cathepsin B and comparable responses in osteoblasts were also examined. Our data show that synovial fibroblasts respond differently to treatment with the two agents, suggesting a cell-specific regulation of cathepsin B and possible involvement in osteoblast physiology. Cathepsin B involvement was then evaluated in the activation of plasminogen activator (PA) in MG-63 cells using two specific inhibitors of cathepsin B, CA074 and CA074-Me, in constitutive conditions and after treatment with IL-1beta. As results of PA activity obtained in the presence of IL-beta were in contrast with previous reports, we examined the activities of PA, pro-PA activated with trypsin, and plasmin in cell extract and media of MG-63 cells after 24-h treatment with IL-1beta. Results show that in normal conditions and in the presence of IL-1beta, cathepsin B is involved in the activation of PA. Moreover, IL-1beta stimulates PA, pro-PA activated by trypsin, and plasmin activity in medium, whereas in cell extract it stimulates pro-PA activated by trypsin and plasmin activity. IL-1beta has no effect on cell extract-associated PA.

IL-1beta regulates cellular proliferation, prostaglandin E2 synthesis, plasminogen activator activity, osteocalcin production, and bone resorptive activity of the mouse calvarial bone cells

Interleukin-1beta (IL-1beta) regulates several activities of the osteoblast cells derived from mouse calvarial bone explants in vitro. IL-1beta stimulated cellular proliferation and the synthesis of prostaglandin E2 in the cultured cells in a dose-dependent manner. Furthermore, plasminogen activator activity of the mouse osteoblast was positively affected by IL-1beta in a dose-dependent manner over the dosage range of 0.01 ng-2 ng/mL with a maximal effect being observed at 2 ng/mL. However, the induction of osteocalcin synthesis and alkaline phosphatase activity in response to vitamin D, two characteristics of the osteoblast phenotype, were significantly antagonized by IL-1beta over a similar dose range. Treatment of mouse calvarial bone cells with IL-1beta resulted in a dose dependent stimulation of bone resorption and the bone resorption induced by IL-1beta was strongly inhibited by calcitonin treatment, indicating osteoclast-mediated bone resorption, suggesting that the bone resorption induced by IL-1beta appears to be osteoclast-mediated. This study supports the role of IL-1beta in the pathological modulation of bone cell metabolism, with regard to implication of the pathogenesis of osteoporosis by IL-1beta.

Inhibitory effect of a Korean traditional medicine, Honghwain-Jahage (water extracts of Carthamus tinctorius L. seed and Hominis placenta) on interleukin-1-mediated bone resorption

A Korean herbal formulation, Honghwain-Jahage (HJ), which is comprised of a herb of Carthamus tinctorius L. seed and Hominis Placenta, was investigated for inhibiting effects on IL-1 beta-stimulated bone resorption in the fetal mouse bone culture system. Results of in vitro cytotoxicities showed that HJ extracts have no any cytotoxicities in concentrations of 1-200 microg/ml on the cultured osteoblast cells derived from mouse calvarial bone explants. Cell viability was not significantly affected by treatment with the indicated concentration of the extracts. The HJ extracts were shown to have inhibitory effects against the synthesis of PGE(2). We also examined the effect of the pretreatment with various concentrations of the HJ extracts then treated by the PGE(2)-induction agents. Pretreatment of the HJ extracts for 1 h, which by itself had little effect on cell survival, reduced the synthesis of PGE(2). Furthermore, the HJ extracts were shown to have protective effects against plasminogen dependent fibrinolysis induced by IL-1 beta. Pretreatment of the HJ extracts for 1 h did not enhance the plasminogen dependent fibrinolysis. Finally, co-treatment of HJ with calcitonin showed significant inhibitory activity on the IL-1 beta-stimulated bone resorption. From these results, it was found that HJ extracts inhibited IL-1 beta-induced bone resorption.

Activities of plasminogen activator, plasmin and kallikrein in synovial fluid from patients with temporomandibular joint disorders

To measure the activities of plasminogen activator (PA), plasmin and kallikrein, multiple synovial fluid samples were taken from 32 patients with internal derangement (ID) and osteoarthrosis (OA), and nine asymptomatic volunteers. The enzyme activity in synovial fluid from the temporomandibular joint (TMJ) was quantitated by a fluorogenic substrate assay using an enzyme substrate. In fluid samples from the patient group, PA was detected in 24 (31.5%), plasmin in 20 (26.3%) and kallikrein in 53 (96.4%), while none of these enzymes were found in the synovial fluid samples from the control group. There were positive correlations found among PA, plasmin and kallikrein. These results clearly demonstrated increased levels of PA, plasmin and kallikrein activities in the synovial fluid of patients with ID and OA, and suggest that these enzymes may be involved in the pathogenesis of synovitis, as well as the resorption of cartilage and bone in TMJ.

Omega-3 polyunsaturated fatty acids and skeletal health

This minireview on skeletal biology describes the actions of prostaglandins and cytokines involved in the local regulation of bone metabolism, it documents the role of lipids in bone biology, and it presents relationships between fatty acids and other factors that impact skeletal metabolism. The data presented herein show consistent and reproducible beneficial effects of omega-3 (n-3) fatty acids on bone metabolism and bone/joint diseases. Polyunsaturated fatty acids modulate eicosanoid biosynthesis in numerous tissues and cell types, alter signal transduction, and influence gene expression. These effects have not been explored in the skeletal system. Future research on n-3 fatty acids in bone biology should focus on the following two aspects. First, the further elucidation of how n-3 fatty acids alter biochemical and molecular processes involved in bone modeling and bone cell differentiation, and second, the evaluation of the potential pharmaceutical applications of these nutraceutical fatty acids in maintaining bone mineral status and controlling inflammatory bone/joint diseases.

Increased expression of protein kinase Calpha, interleukin-1alpha, and RhoA guanosine 5'-triphosphatase in osteoblasts expressing the Ser252Trp fibroblast growth factor 2 receptor Apert mutation: identification by analysis of complementary DNA microarray

Apert (Ap) syndrome is a craniofacial malformation characterized by premature fusion of cranial sutures (craniosynostosis). We previously showed that the Ser252Trp fibroblast growth factor receptor 2 (FGFR-2) mutation in Ap syndrome increases osteoblast differentiation and subperiosteal bone matrix formation, leading to premature calvaria ossification. In this study, we used the emerging technology of complementary DNA (cDNA) microarray to identify genes that are involved in osteoblast abnormalities induced by the Ser252Trp FGFR-2 mutation. To identify the signaling pathways involved in this syndrome, we used radioactively labeled cDNAs derived from two sources of cellular messenger RNAs (mRNAs) for hybridization: control (Co) and mutant Ap immortalized osteoblastic cells. Among genes that were differentially expressed, protein kinase Ca (PKC-alpha), interleukin-1alpha (IL-1alpha), and the small guanosine-5'-triphosphatase (GTPase) RhoA were increased in FGFR-2 mutant Ap cells compared with Co cells. The validity of the hybridization array was confirmed by Northern blot analysis using mRNAs derived from different cultures. Furthermore, immunochemical and Western blot analyses showed that mutant Ap cells displayed increased PKC-alpha, IL-1alpha, and RhoA protein levels compared with Co cells. Treatment of Co and Ap cells with the PKC inhibitor calphostin C decreased IL-1alpha and RhoA mRNA and protein levels in Ap cells, indicating that PKC is upstream of IL-1alpha and RhoA. Moreover, SB203580, a specific inhibitor of p38 mitogen-activated protein kinase (MAPK), and PD-98059, a specific inhibitor of MAPK kinase (MEKK), also reduced IL-1alpha and RhoA expression in Ap cells. These data show that the Ser252Trp FGFR-2 mutation in Ap syndrome induces constitutive overexpression of PKC-alpha, IL-1alpha, and small GTPase RhoA, suggesting a role for these effectors in osteoblast alterations induced by the mutation. The cDNA microarray technology appears to be a useful tool to gain information on abnormal gene expression and molecular pathways induced by genetic mutations in bone cells.

Human bone cell hyperpolarization response to cyclical mechanical strain is mediated by an interleukin-1beta autocrine/paracrine loop

Mechanical stimuli imparted by stretch, pressure, tension, fluid flow, and shear stress result in a variety of biochemical responses important in bone (re)modeling. The molecules involved in the recognition and transduction of mechanical stimuli that lead to modulation of bone cell function are not yet fully characterized. Cyclical pressure-induced strain (PIS) induces a rapid change in membrane potential of human bone cells (HBC) because of opening of membrane ion channels. This response is mediated via integrins and requires tyrosine kinase activity and an intact actin cytoskeleton. We have used this electrophysiological response to further study the signaling events occurring early after mechanical stimulation of HBC. Stimulation of HBC at 0.33 Hz PIS, but not 0.104 Hz PIS, results in the production of a transferable factor that induces membrane hyperpolarization of unstimulated HBC. The production of this factor is inhibited by antibodies to beta1-integrin. Interleukin-1beta (IL-1beta and prostaglandin E2 (PGE2) were identified as candidate molecules for the transferable factor as both were shown to induce HBC hyperpolarization by opening of small conductance calcium-activated potassium channels, the means by which 0.33 Hz PIS causes HBC hyperpolarization. Antibodies to IL-1beta, but not other cytokines studied, inhibit the hyperpolarization response of HBC to 0.33 Hz PIS. Comparison of the signaling pathways required for 0.33 Hz PIS and IL-1beta-induced membrane hyperpolarization shows that both involve the phospholipase C/inositol triphosphate pathway, protein kinase C (PKC), and prostaglandin synthesis. Unlike 0.33 Hz PIS-induced membrane hyperpolarization, IL-1beta-induced hyperpolarization does not require tyrosine kinase activity or an intact actin cytoskeleton. These studies suggest that 0.33 Hz PIS of HBC induces a rapid, integrin-mediated, release of IL-1beta with a subsequent autocrine/paracrine loop resulting in membrane hyperpolarization. IL-1beta production in response to mechanical stimuli is potentially of importance in regulation of bone (re)modeling.

The regulation of PGE(2) biosynthesis in MG-63 osteosarcoma cells by IL-1 and FGF is cell density-dependent

We investigated the molecular mechanisms by which treatment of the human osteoblast-like cell line MG-63 with interleukin 1beta (IL-1) and/or fibroblast growth factor 1 (FGF-1) elicited prostaglandin biosynthesis. IL-1 induced a 5-fold increase in PGE(2) production compared to controls. While treatment with FGF-1 alone did not affect PGE(2) biosynthesis, it enhanced the formation of PGE(2) by IL-1 by an additional 3- to 5-fold. IL-1-induced PGE(2) biosynthesis accompanied increases in steady-state levels of mRNAs encoding cPLA(2) (10- to 15-fold) and PGHS-2 (>3-fold) and concomitant increases in cPLA(2) protein (>3-fold) and PGHS-2 protein (>1. 5-fold). FGF-1 treatment did not affect PGHS-2 gene expression, but enhanced the effect of IL-1 on PGHS-2 expression by an additional 2- to 3-fold. FGF-1 alone enhanced cPLA(2) expression (5-fold), and the combined effects of FGF-1 and IL-1 on cPLA(2) expression were additive. There was no measurable effect of either agonist on PGHS-1 expression. We also discovered that induction of PGE(2) biosynthesis in response to IL-1 or IL-1/FGF-1 was affected by the density of MG-63 cells in culture. Subconfluent cultures displayed a 3- to 10-fold greater response to IL-1 or IL-1/FGF-1 than confluent cultures. The decreased PGE(2) induction by IL-1 in confluent cultures was associated with reduced IL-1 receptor expression. We conclude that the signaling pathways resulting in PGE(2) biosynthesis in response to proinflammatory agents like IL-1 are subject to complex regulation by additional soluble mediators as well as cell-cell or cell-extracellular matrix interactions.

Low-energy diode laser irradiation reduced plasminogen activator activity in human periodontal ligament cells

BACKGROUND AND OBJECTIVE

The plasminogen activator (PA)-plasmin proteolytic system is implicated in the degradation of the extracellular matrix in inflammation. Since human periodontal ligament (PDL) cells produced high PA activity in response to mechanical stress, excessive mechanical stress to PDL cells such as occlusal trauma may induce collagen breakdown through activation of the PA-plasmin system. As low-energy laser irradiation has anti-inflammatory effects, we examined the effects of low-energy laser irradiation on the PA-plasmin system in stretched PDL cells in vitro.

STUDY DESIGN/MATERIALS AND METHODS

Human PDL cells obtained from healthy premolars were mechanically stretched and Ga-Al-As low-energy laser was irradiated (830 nm, 3.95 to 7.90 J/cm2) to the stretched cells.

RESULTS

PDL cells showed a marked elevation in PA activity in response to stretching, which was significantly inhibited by a laser irradiation in a dose-dependent manner (55-86%, p < 0.001). This effect could involve transcriptional events of tissue type (t) PA gene.

CONCLUSION

These results suggests that laser irradiation may reduce collagen breakdown around the PDL associated with traumatic occlusion.

No effect of immunosuppression with cyclosporin A detected on bone ingrowth into cancellous allo- and xenografts in the rat

We studied the effects of the immunosuppressant cyclosporin A on bone ingrowth into allo- and xenografts in the rat using titanium bone chambers. The bone chambers were implanted bilaterally in the tibia. Each rat had one allograft and one xenograft. At 6 weeks the distance of soft tissue and bone ingrowth was measured on histological slides. In xenografts, soft-tissue ingrowth was only slightly less than in allografts, but the ingrown tissue became much less ossified. These differences were unaffected by cyclosporin A treatment, suggesting that the lesser amount of bone formation in xenografts is only weakly associated with T-cell-dependent immune reactions.

Involvement of nitric oxide and biopterin in proinflammatory cytokine-induced apoptotic cell death in mouse osteoblastic cell line MC3T3-E1

We previously demonstrated that the addition of proinflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma) caused induction of mRNAs for inducible nitric oxide (NO) synthase and GTP cyclohydrolase I, a rate-limiting enzyme for 5,6,7,8-tetrahydrobiopterin (BH4) biosynthesis, and produced their end-products, NO and BH4, in osteoblastic cells. In the present study, we examined whether NO and BH4, biologically active substances produced in response to proinflammatory cytokines, are involved in the effect of these cytokines on cell viability and apoptotic cell death involving DNA fragmentation. Cytokines as well as S-nitroso-N-acetyl-d,l-penicillamine, an NO generator, decreased cell viability, whereas sepiapterin, which was converted intracellularly to BH4, increased it. The examination of cytotoxicity measured in terms of lactate dehydrogenase release and apoptotic cell death assessed by flow cytometric analysis showed that cytokine-induced reduction of cell viability may be based upon cell death by apoptosis, but not lytic death as in necrosis. In the presence of sepiapterin, cytokine treatment resulted in a statistically pronounced reduction in the amount of DNA fragmentation. Furthermore, this fragmentation could be blocked by 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide, an NO scavenger. These results suggest that cytokine-induced apoptotic cell death is attributed to NO and is protected by BH4, and that osteoblastic cells in response to proinflammatory cytokines operate both a stimulatory process resulting in NO production and an inhibitory one resulting in BH4 production for apoptotic cell death. Cytokine-induced apoptotic cell death may be a consequence of the predominance of the stimulatory process over the inhibitory process.

Inhibition of osteoblastic cell differentiation by lipopolysaccharide extract from Porphyromonas gingivalis

Lipopolysaccharide from Porphyromonas gingivalis (P-LPS), an important pathogenic bacterium, is closely associated with inflammatory destruction of periodontal tissues. P-LPS induces the release of cytokines and local factors from inflammatory cells, stimulates osteoclastic-cell differentiation, and causes alveolar bone resorption. However, the effect of P-LPS on osteoblastic-cell differentiation remains unclear. In this study, we investigated the effect of P-LPS extract prepared by the hot-phenol-water method, on the differentiation of primary fetal rat calvaria (RC) cells, which contain a subpopulation of osteoprogenitor cells, into osteoblastic cells. P-LPS extract significantly inhibited bone nodule (BN) formation and the activity of alkaline phosphatase (ALPase), an osteoblastic marker, in a dose-dependent manner (0 to 100 ng of P-LPS extract per ml). P-LPS extract (100 ng/ml) significantly decreased BN formation to 27% of the control value and inhibited ALPase activity to approximately 60% of the control level on days 10 to 21 but did not affect RC cell proliferation and viability. P-LPS extract time-dependently suppressed the expression of ALPase mRNA, with an inhibitory pattern similar to that of enzyme activity. The expression of mRNAs for osteocalcin and osteopontin, matrix proteins related to bone metabolism, was markedly suppressed by P-LPS extract. Furthermore, P-LPS extract increased the expression of mRNAs for CD14, LPS receptor, and interleukin-1beta in RC cells. These results indicate that P-LPS inhibits osteoblastic-cell differentiation and suggest that LPS-induced bone resorption in periodontal disease may be mediated by effects on osteoblastic as well as osteoclastic cells.