Macrophage colony-stimulating factor suppresses osteoblast formation

Shark protein improves bone mineral density in ovariectomized rats and inhibits osteoclast differentiation

OBJECTIVES

Fish proteins are potential sources of natural medicines and food additives. There are many studies being performed to develop underutilized fish proteins. Therefore, the aim of this study was to determine how shark protein functions as a dietary supplement for bone health.

METHODS

Three groups of ovariectomized (OVX) rats were fed different diets containing 20% casein protein, 20% shark protein, or 20% cod protein for 4 wk. Bone mineral density of the right femur was measured by dual-energy x-ray absorptiometry and quantitative computed tomography. Furthermore, we prepared low-molecular-weight peptides from shark protein using protease for in vitro studies. Calcitriol was added to bone marrow cells and the receptor activator of the nuclear factor-κB ligand was added to RAW264 cells. After 7 d, the number of tartrate-resistant acid phosphatase-positive cells was counted.

RESULTS

In the shark protein-fed group, bone mineral density of the femur epiphysis was higher than that of the casein protein-fed group. In particular, the shark protein-fed group showed an increase in bone mineral density, represented mainly by trabecular bone. Shark protein hydrolysates inhibited osteoclast formation in bone marrow cells and RAW264 cells.

CONCLUSIONS

These results suggest that shark protein might suppress the bone loss caused by estrogen deficiency through the suppression of osteoclast formation.

Colony-stimulating factor-1 (CSF-1) directly inhibits receptor activator of nuclear factor-{kappa}B ligand (RANKL) expression by osteoblasts

Colony-stimulating factor-1 (CSF-1), released by osteoblasts, stimulates the proliferation of osteoclast progenitors via the c-fms receptor (CSF-1R) and, in combination with receptor activator of nuclear factor-kappaB ligand (RANKL), leads to the formation of mature osteoclasts. Whether the CSF-1R is expressed by osteoblasts and mediates specific biological effects in osteoblasts has not been explored. Wild-type primary calvaria osteoblasts (OB) were analyzed for CSF-1R expression (RT-PCR and Western blot) and functionality (immunocomplex kinase assay). OB were serum starved for 24 h, and the effect of CSF-1 (0-100 ng/ml) on OB biological activities was determined at 48 h. In wild-type mouse bone marrow cultures, CSF-1 was tested for its effect on RANKL mRNA and osteoclast formation. Because ROS influence osteoblast RANKL expression, studies analyzed the effect of CSF-1 on reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and Nox1 and Nox4 proteins. Results indicate that OB express CSF-1R mRNA and protein and that CSF-1R could be phosphorylated in the presence of CSF-1. In osteoblasts, CSF-1 decreased RANKL mRNA in a dose- and time-dependent manner. Incubation of bone marrow cultures with CSF-1 resulted in a significant decline in tartrate-resistant acid phosphatase (TRACP) activity and CTR expression. RANKL-decreased expression by CSF-1 was correlated with a decrease of NADPH oxidase activity as well as Nox1 and Nox4 protein levels. These findings provide the first evidence that osteoblasts express CSF-1R and are a target for CSF-1 ligand. CSF-1-mediated inhibition of RANKL expression on osteoblasts may provide an important mechanism for coupling bone formation/resorption and preventing excessive osteoclastogenesis during normal skeletal growth.

Suppressive effects of Anoectochilus formosanus extract on osteoclast formation in vitro and bone resorption in vivo

Anoectochilus formosanus, a plant native to Taiwan, is used as a folk medicine. It was found that oral administration of A. formosanus extract (AFE) (500 mg/kg) for 4 weeks suppressed bone weight loss and trabecular bone loss in ovariectomized mice, an experimental model of osteoporosis. Although AFE at 12.5 and 25 mug/ml inhibited osteoclast formation in co-culture of osteoblasts and bone marrow cells, AFE did not inhibit the formation of osteoclast progenitor cells and preosteoclast cells in bone marrow cells and RAW264 cells. However, AFE (at 12.5 and 25 microg/ml) decreased RANKL expression. These results suggested that AFE might suppress the bone loss caused by estrogen deficiency through suppression of RANKL expression required for osteoclast formation.

The role of dental pulp cells in resorption of deciduous teeth

OBJECTIVE

To address the question whether dental pulp cells of exfoliating human deciduous teeth have some roles for controlling or regulating the root resorption via secreting key molecules (OPG, RANKL, CSF-1, TGFbeta, MCP-1 and Cbfa-1) in osteoclastogenesis, we used a sensitive reverse transcriptase polymerase chain reaction (RT-PCR) method for detection of mRNA expressions for the cytokines listed.

STUDY DESIGN

The dental pulps were retrieved from incisor and molar teeth in the late stage of shedding (n = 30) and from sound premolar teeth extracted for orthodontic reasons (control group; n = 30). The RT-PCR assays were used to identify targeted gene expression.

RESULTS

Of the cytokines examined, RANKL and CSF-1 expressions showed significantly higher occurrence in deciduous dental pulps than in permanent teeth pulpal tissues (P < .040).

CONCLUSIONS

The findings may suggest an interactive role for pulp tissue cells in the physiologic root resorption process. The cells of dental pulp may have some cytokine-producing cells which mediate monocyte-macrophage lineage to form osteo/odontoclasts, and the RANKL/RANK system might be involved in human deciduous teeth resorption.

Human cytomegalovirus, Epstein-Barr virus and bone resorption-inducing cytokines in periapical lesions of deciduous teeth

BACKGROUND

A connection of herpesvirus periapical infection with symptomatic and large-size periapical lesions has been recognized in adult patients, but no data exist about a possible involvement of herpesviruses in severe periapical pathosis in children. Herpesviruses have the potential to elicit potent bone resorption-inducing cytokines in mammalian cells.

AIM

This study aimed to determine the occurrence of human cytomegalovirus and Epstein-Barr virus DNA, and mRNA transcripts of receptor activator of nuclear kappa B ligand (RANKL), osteoprotegerin, core binding factor alpha-1, colony stimulating factor-1, transforming growth factor-beta, and monocyte chemoattractant protein-1 in periapical symptomatic pathosis of deciduous teeth.

MATERIAL AND METHODS

Twelve deciduous molar teeth from patients aged 2-8 years were extracted due to severe periapical infection, and granulomatous tissue adherent to the root tip of the extracted teeth was collected using a surgical knife. Non-diseased pulpal tissue, obtained from 12 teeth extracted for orthodontic reasons, served as negative control. Polymerase chain reaction assays were employed to identify herpesvirus DNA and cytokine gene expression, using established polymerase chain reaction primers and procedures.

RESULTS

Seven (58%) of the periapical lesions yielded human cytomegalovirus and eight (67%) Epstein-Barr virus. Only one (8%) periapical lesion showed neither human cytomegalovirus nor Epstein-Barr virus. In healthy pulpal tissue, one (8%) specimen demonstrated human cytomegalovirus and another (8%) specimen revealed Epstein-Barr virus. Of the cytokines examined, RANKL expression showed significantly higher occurrence in periapical pathosis than in healthy pulpal tissue (P < 0.040). No relationship was identified between the type of herpesvirus and cytokine expression in the periapical lesions studied.

CONCLUSIONS

The present findings provide evidence of a putative role of human cytomegalovirus and Epstein-Barr virus in the pathogenesis of symptomatic periapical pathosis in deciduous teeth. Increased RANKL expression in periapical lesions may be of pathogenetic significance.

Osteoblast dysfunction in male idiopathic osteoporosis

The etiology of primary osteoporosis in young and middle-aged men is unknown. We have studied osteoblast function in cells derived from men with idiopathic osteoporosis and in control cells from age-matched men with osteoarthrosis. Osteoblasts were isolated from transiliac bone biopsies. Osteoblast function was measured as vitamin D-stimulated osteocalcin production and production of cytokines and factors involved in osteoclast activation and bone formation. Cell proliferation was measured as (3)H-thymidine incorporation. Parathyroid hormone-related peptide (PTHrP) mRNA was measured using reverse-transcriptase polymerase chain reaction. In osteoporotic men, bone mineral density at the femoral neck was correlated to in vitro production of osteocalcin. Osteoblasts from osteoporotic men produced significantly less osteocalcin after vitamin D stimulation but had increased production of macrophage colony-stimulating factor (M-CSF) compared to controls. The osteocalcin response was negatively correlated to production of M-CSF, interleukin-6, and C-terminal propeptide of type I collagen. Basal (3)H-thymidine incorporation was similar in cells from osteoporotic patients and controls. PTHrP (10(-9 )M) significantly increased cell proliferation in control cells but not in osteoporotic cells. Basal PTHrP mRNA levels were significantly higher in osteoporotic cells than in cells from controls. The results are in agreement with previous histomorphologic studies indicating that men with idiopathic osteoporosis have an osteoblast dysfunction with decreased osteocalcin production and increased production of factors stimulating osteoclast activation. This indicates a catabolic cellular metabolic balance leading to negative bone turnover, resulting in osteoporosis. The cause of such cellular dysfunction needs further evaluation.

Transforming growth factor-beta1 to the bone

TGF-beta1 is a ubiquitous growth factor that is implicated in the control of proliferation, migration, differentiation, and survival of many different cell types. It influences such diverse processes as embryogenesis, angiogenesis, inflammation, and wound healing. In skeletal tissue, TGF-beta1 plays a major role in development and maintenance, affecting both cartilage and bone metabolism, the latter being the subject of this review. Because it affects both cells of the osteoblast and osteoclast lineage, TGF-beta1 is one of the most important factors in the bone environment, helping to retain the balance between the dynamic processes of bone resorption and bone formation. Many seemingly contradictory reports have been published on the exact functioning of TGF-beta1 in the bone milieu. This review provides an overall picture of the bone-specific actions of TGF-beta1 and reconciles experimental discrepancies that have been reported for this multifunctional cytokine.

Molecular mechanisms underlying osteoclast formation and activation

Osteoporosis is one of the leading causes of morbidity in the elderly and is characterized by a progressive loss of total bone mass and bone density. Bone loss in osteoporosis is due to the persistent excess of osteoclastic bone resorption over osteoblastic bone formation. Receptor activator of NFkappaB ligand (RANKL) critically regulates both osteoclast differentiation and activation. TRAFs appear to be central coupling molecules in the signal transduction pathways that regulate osteoclastogenesis, cathepsin K is the major mediator of osteoclastic bone resorption, and sex steroids and aging also affect osteoclastogenesis and osteoclast activity. However, bone homeostasis depends upon the intimate coupling of bone formation and bone resorption, wherein both osteoclasts and osteoblasts exert vital stimulatory and inhibitory effects upon each other via molecules such as RANKL, TGFbeta, PDGF, BMP2, and Mim-1. This review will highlight some of the major features of the complex circuit of cytokines, growth factors, and hormones that underlies the formation and function of osteoclasts and the dynamic equilibrium that marks the interaction between osteoclasts and osteoblasts.

Osteoclast stimulating and differentiating factors in human cholesteatoma

OBJECTIVES

To investigate the expression of osteoclast-activating and differentiating factors and to study the occurrence of osteoclast precursor cells and osteoclasts in acquired human cholesteatoma tissue.

METHODS

We examined 21 cholesteatoma samples versus 18 normal auditory canal skin specimens for the expression of osteoprotegerin ligand (OPGL), osteoprotegerin (OPG), and macrophage-colony stimulating factor (M-CSF) using reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. Immunohistochemistry and computer-assisted microscopy using markers CD4, CD11a, CD11b, CD14, CD51, CD68, and TRAP obtained the detection of osteoclast cell lineage.

RESULTS

An increased expression of the investigated cytokines M-CSF, OPG, and OPGL was demonstrated by immunohistochemistry and RT-PCR in cholesteatoma tissue compared with normal external meatal skin. Several CD4-positive cells exhibited a co-expression for OPGL within the perimatrix of cholesteatoma. The presence of osteoclast precursor cells was confirmed in all samples of cholesteatoma tissue.

CONCLUSIONS

This study reveals that the number of osteoclast precursor cells is markedly increased in the perimatrix of cholesteatoma tissue. Our results support a concept described for inflammatory arthritis: the inflammation related to cholesteatoma induces bone resorption by release of OPGL from activated T-cells and triggers osteoclastogenesis. This could be a major target for drugs to inhibit osteoclast formation and bone resorption and may be an adjunct in cholesteatoma management.

New insights into the regulation of cathepsin K gene expression by osteoprotegerin ligand

Cathepsin K plays a key role in bone resorption. We provide the first evidence that osteoprotegerin ligand (OPGL), a critical pro-resorptive cytokine, acutely stimulates the expression of cathepsin K in osteoclasts. We used in situ RT-PCR and real time quantitative RT-PCR to analyze cathepsin K gene expression. OPGL enhanced cathepsin K mRNA levels in mature osteoclasts isolated from rat neonatal long bones. OPGL together with macrophage colony-stimulating factor (M-CSF) also stimulated cathepsin K gene expression in monocytic cells and multinucleate osteoclasts in bone marrow cultures. Real time quantitative RT-PCR demonstrated high levels of cathepsin K mRNA in bone marrow cultures, paralleling the degree of osteoclastogenesis. We therefore suggest that OPGL enhances bone resorption, at least in part, by inducing cathepsin K gene expression.