Interleukin-6 messenger RNA expression and interleukin-6 protein secretion in cells isolated from normal human bone: regulation by interleukin-1

Genetics and pediatric hospital admissions, 1985 to 2017

PURPOSE

To determine the prevalence and sociodemographic and hospitalization history of genetic conditions in a sample of inpatients in a pediatric hospital in 2017, and to compare results with unpublished studies from 1985, 1995, and 2007.

METHODS

Two weeks of admissions were classified according to a pre-existing categorization, based on genetic etiology, encompassing chromosomal and monogenic conditions, multifactorial (MF) conditions, and no known genetic cause.

RESULTS

In 2017, 299 (16%) patients had chromosomal or monogenic conditions, 6-7% more than 2007 and 1995, but similar to 1985. Autosomal dominant (AD) conditions increased from <2% previously to 6% in 2017 (p < 0.001). MF conditions comprised the majority throughout, increasing from 45% to 54%. Age at admission was highest in autosomal recessive (AR) and X-linked categories in 1995, 2007, and 2017, reflected in their high number of previous admissions, while the AD, MF, and nongenetic categories were the youngest with similar lengths of stay and previous admissions.

CONCLUSION

Conditions with a genetic contribution account for over half of pediatric inpatients. Since 1985, there have been many changes in age at admission and length of stay, but it is the increasing prevalence of AR, AD, and MF conditions that is important when considering future service provision.

Cytokines and Bone: Osteoimmunology

Cytokines and hematopoietic growth factors have traditionally been thought of as regulators of the development and function of immune and blood cells. However, an ever-expanding number of these factors have been discovered to have major effects on bone cells and the development of the skeleton in health and disease (Table 1). In addition, several cytokines have been directly linked to the development of osteoporosis in both animal models and in patients. In order to understand the mechanisms regulating bone cells and how this may be dysregulated in disease states, it is necessary to appreciate the diverse effects that cytokines and inflammation have on osteoblasts, osteoclasts, and bone mass. This chapter provides a broad overview of this topic with extensive references so that, if desired, readers can access specific references to delve into individual topics in greater detail.

Age Dependence of Systemic Bone Loss and Recovery Following Femur Fracture in Mice

The most reliable predictor of future fracture risk is a previous fracture of any kind. The etiology of this increased fracture risk is not fully known, but it is possible that fracture initiates systemic bone loss, leading to greater fracture risk at all skeletal sites. In this study, we investigated systemic bone loss and recovery after femoral fracture in young (3-month-old) and middle-aged (12-month-old) mice. Transverse femur fractures were created using a controlled impact, and whole-body bone mineral density (BMD), trabecular and cortical microstructure, bone mechanical properties, bone formation and resorption rates, mouse voluntary movement, and systemic inflammation were quantified at multiple time points post-fracture. We found that fracture led to decreased whole-body BMD in both young and middle-aged mice 2 weeks post-fracture; this bone loss was recovered by 6 weeks in young but not middle-aged mice. Similarly, trabecular bone volume fraction (BV/TV) of the L5 vertebral body was significantly reduced in fractured mice relative to control mice 2 weeks post-fracture (-11% for young mice, -18% for middle-aged mice); no significant differences were observed 6 weeks post-fracture. At 3 days post-fracture, we observed significant increases in serum levels of interleukin-6 and significant decreases in voluntary movement in fractured mice compared with control mice, with considerably greater changes in middle-aged mice than in young mice. At this time point, we also observed increased osteoclast number on L5 vertebral body trabecular bone of fractured mice compared with control mice. These data show that systemic bone loss occurs after fracture in both young and middle-aged mice, and recovery from this bone loss may vary with age. This systemic response could contribute to increased future fracture risk after fracture; these data may inform clinical treatment of fractures with respect to improving long-term skeletal health. © 2018 American Society for Bone and Mineral Research.

Gingival Crevicular Fluid Turnover Markers in Premenopausal vs Postmenopausal Women receiving Orthodontic Treatment

BACKGROUND

Orthodontic treatment is one of the commonly used dental treatments. Orthodontic forces act on the bone by modulating the biomolecules, chiefly the osteoprotegerin (OPG), osteopontin (OPN), receptor activator of nuclear factor kappa-B (RANK), and RANK ligand (RANKL) (OPG ligand). Hormonal changes are known to cause marked alteration in the levels of these biomolecules. Hence, we planned this study to evaluate the response of bone biomarkers in the gingival crevicular fluid (GCF) in postmenopausal women undergoing fixed orthodontic therapy.

MATERIALS AND METHODS

This study included assessment of 50 subjects who underwent orthodontic treatment from June 2012 to July 2016. All the patients were divided into two study groups with 25 patients in each group: premenopausal group and postmenopausal group. Similar orthodontic wires were used for controlling the forces applied in subjects of both the study groups and their GCF levels of RANKL, and OPN was assessed at baseline and 24 hours after the activation of orthodontic forces. All the results were compiled, assessed, and analyzed by Statistical Package for the Social Sciences software version 16.0. Chi-square test, Student's t-test, and Mann-Whitney U test were used for the assessment of the level of significance.

RESULTS

The mean values of RANKL and OPN in the premenopausal and postmenopausal groups were found to be 241.52 and 317.15 pg/μL respectively. The mean values of RANKL at baseline in the premenopausal and postmenopausal groups were found to be 7.15 and 3.84 pg/μL respectively. Nonsignificant results were obtained while comparing mean OPN and RANKL level alteration in between the two study groups.

CONCLUSION

The mean alterations in the GCF levels of bone biomarkers are similar for both premenopausal and postmeno-pausal women.

CLINICAL SIGNIFICANCE

For women with either premenopausal or postmenopausal status, orthodontic treatment appears to be equally safer.

Gingival crevicular fluid bone turnover biomarkers: How postmenopausal women respond to orthodontic activation

INTRODUCTION

Bone turnover associated with orthodontic tooth movement is evidenced by increased bone turnover markers in gingival crevicular fluid (GCF). Postmenopausal women have an increased concentration of serum bone turnover markers. The filtrate of this serum makes up GCF, but little is known of the bone turnover around teeth in this cohort. The objective of this investigation was to compare the GCF bone turnover markers in premenopausal vs postmenopausal women receiving orthodontic treatment at baseline and at orthodontic activation.

METHODS

Twenty-eight women were enrolled in the study and separated into 2 groups: premenopausal (16) and postmenopausal (12). Bone turnover was evaluated by GCF at baseline and 24 hours after orthodontic appliance activation. GCF concentrations of RANKL and OPN were measured using ELISA. Baseline and change in concentrations were compared between groups.

RESULTS

Baseline RANKL and OPN were significantly different between the premenopausal and postmenopausal groups (P <0.05). Both markers increased significantly from baseline to 24 hours after orthodontic appliance activation in both groups (P <0.05). However, the response to orthodontic activation was not significantly different between groups.

CONCLUSIONS

Although postmenopausal women have a different bone turnover profile at baseline than do their premenopausal counterparts, there is no difference in their response to orthodontic activation. This confers a level of security associated with orthodontic activation. Future studies are warranted to construct biomarker curves throughout orthodontic therapy.

Duffy antigen receptor for chemokines regulates post-fracture inflammation

There is now considerable experimental data to suggest that inflammatory cells collaborate in the healing of skeletal fractures. In terms of mechanisms that contribute to the recruitment of inflammatory cells to the fracture site, chemokines and their receptors have received considerable attention. Our previous findings have shown that Duffy antigen receptor for chemokines (Darc), the non-classical chemokine receptor that does not signal, but rather acts as a scavenger of chemokines that regulate cell migration, is a negative regulator of peak bone density in mice. Furthermore, because Darc is expressed by inflammatory and endothelial cells, we hypothesized that disruption of Darc action will affect post-fracture inflammation and consequently will affect fracture healing. To test this hypothesis, we evaluated fracture healing in mice with targeted disruption of Darc and corresponding wild type (WT) control mice. We found that fracture callus cartilage formation was significantly greater (33%) at 7 days post-surgery in Darc-KO compared to WT mice. The increased cartilage was associated with greater Collagen (Col) II expression at 3 days post-fracture and Col-X at 7 days post-fracture compared to WT mice, suggesting that Darc deficiency led to early fracture cartilage formation and differentiation. We then compared the expression of cytokine and chemokine genes known to be induced during inflammation. Interleukin (Il)-1β, Il-6, and monocyte chemotactic protein 1 were all down regulated in the fractures derived from Darc-KO mice at one day post-fracture, consistent with an altered inflammatory response. Furthermore, the number of macrophages was significantly reduced around the fractures in Darc-KO compared to WT mice. Based on these data, we concluded that Darc plays a role in modulating the early inflammatory response to bone fracture and subsequent cartilage formation. However, the early cartilage formation was not translated with an early bone formation at the fracture site in Darc-KO compared to WT mice.

Biomarkers of periodontal tissue remodeling during orthodontic tooth movement in mice and men: overview and clinical relevance

Biologically active substances are expressed by cells within the periodontium in response to mechanical stimuli from orthodontic appliances. Several possible biomarkers representing biological modifications during specific phenomena as simile-inflammatory process, bone resorption and formation, periodontal ligament changes, and vascular and neural responses are proposed. Citations to potentially published trials were conducted by searching PubMed, Cochrane databases, and scientific textbooks. Additionally, hand searching and contact with experts in the area were undertaken to identify potentially relevant published and unpublished studies. Selection criteria were as follows: animal models involving only mice and rats undergoing orthodontic treatment; collection of gingival crevicular fluid (GCF) as a noninvasively procedure for humans; no other simultaneous treatment that could affect experimental orthodontic movement. The data suggest that knowledge of the remodeling process occurring in periodontal tissues during orthodontic and orthopedic therapies may be a clinical usefulness procedure leading to proper choice of mechanical stress to improve and to shorten the period of treatment, avoiding adverse consequences. The relevance for clinicians of evaluating the rate of some substances as valid biomarkers of periodontal effects during orthodontic movement, by means of two models of study, mice and men, is underlined.

Effects of interleukin-6 ablation on fracture healing in mice

This study examined the impact of an interleukin-6 (IL-6) knockout on fracture healing in terms of histological and biomechanical responses. Following IACUC approval, tibial fractures were produced in 4- to 6-week-old IL-6 knockouts (n = 35) and wild-type mice (n = 36) and harvested along with contralateral limbs at 2 and 6 weeks postsurgery. Histology quantified stage of healing, lymphocyte infiltration, TRAP+ cells, and osteocalcin deposition. Bend testing established maximum load and stiffness. Based on normality assessments, Mann-Whitney U or independent t-tests were used for data analysis using a p-value threshold of 0.05. Stage of healing, lymphocyte infiltration, and osteocalcin deposition were similar for all time points (p ≥ 0.243). TRAP+ cell counts were reduced approximately 10-fold in the knockout at 2 weeks (p = 0.015) but were similar at 6 weeks (p = 0.689). Force-to-failure in knockouts was approximately 40% that of wild-type mice at 2 weeks (p = 0.040) but similar at 6 weeks (p = 0.735). Knockout bone was about 25% less stiff at 2 weeks but approximately 60% stiffer at 6 weeks (p ≥ 0.110). The absence of IL-6 during early fracture healing significantly reduced osteoclastogenesis and impaired callus strength. By 6 weeks, most histological and biomechanical parameters were similar to fractures in wild-type bone.

Osteoimmunology: interactions of the bone and immune system

Bone and the immune system are both complex tissues that respectively regulate the skeleton and the body's response to invading pathogens. It has now become clear that these organ systems often interact in their function. This is particularly true for the development of immune cells in the bone marrow and for the function of bone cells in health and disease. Because these two disciplines developed independently, investigators in each don't always fully appreciate the significance that the other system has on the function of the tissue they are studying. This review is meant to provide a broad overview of the many ways that bone and immune cells interact so that a better understanding of the role that each plays in the development and function of the other can develop. It is hoped that an appreciation of the interactions of these two organ systems will lead to better therapeutics for diseases that affect either or both.

The bone microenvironment in metastasis; what is special about bone?

The skeleton is a common destination for many cancer metastases including breast and prostate cancer. There are many characteristics of bone that make it an ideal environment for cancer cell migration and colonization. Metaphyseal bone, found at the ends of long bone, in ribs, and in vertebrae, is comprised of trabecular bone interspersed with marrow and rich vasculature. The specialized microvasculature is adapted for the easy passage of cells in and out of the bone marrow. Moreover, the metasphyseal regions of bone are constantly undergoing remodeling, a process that releases growth factors from the matrix. Bone turnover also involves the production of numerous cytokines and chemokines that provide a means of communication between osteoblasts and osteoclasts, but co-incidentally can also attract and support metastatic cells. Once in the marrow, cancer cells can interact directly and indirectly with osteoblasts and osteclasts, as well as hematopoietic and stromal cells. Cancer cells secrete factors that affect the network of cells in the bone microenvironment as well as interact with other cytokines. Additionally, transient cells of the immune system may join the local mileau to ultimately support cancer cell growth. However, most metastasized cells that enter the bone marrow are transient; a few may remain in a dormant state for many years. Advances in understanding the bone cell-tumor cell interactions are key to controlling, if not preventing metastasis to bone.

Sex steroids, cytokines and the bone marrow: new concepts on the pathogenesis of osteoporosis

Osteoclasts and osteoblasts, originating in the bone marrow from haemopoietic progenitors and mesenchymal stromal cells, respectively, are responsible for the remodelling of the skeleton throughout adult life. Upon loss of sex steroids, the production of osteoclasts in the bone marrow is increased. This is mediated by an increase in the production of interleukin 6 (IL-6), as well as an increase in the sensitivity of the osteoclastic precursors to the action of cytokines such as IL-6, owing to an up-regulation of the gp130 signal transduction pathway. Consistent with this, oestrogens as well as androgens inhibit IL-6 production through an indirect effect of their specific receptors on the transcriptional activity of the IL-6 gene promoter, and inhibit the expression of the gp130 gene. With advancing age, the ability of the marrow to maintain the high rate of osteoclastogenesis caused by the acute loss of sex steroids is diminished. This is probably the result of the negative effect of senescence on the ability of the marrow to produce stromal/osteoblastic cells, which provide the essential support for osteoclastogenesis. These observations suggest that inappropriate production of osteoclasts or inadequate production of osteoblasts in the bone marrow are fundamental cellular changes in the pathogenesis of postmenopausal and senescence-associated osteoporosis, respectively.

Cytokines regulating osteoclast formation and function

PURPOSE OF REVIEW

The osteoclast is the principal bone-resorbing cell. Because of its unique ability to efficiently remove both the mineral and the organic matrix of bone, the osteoclast is an important element of the homeostatic mechanisms that maintain skeletal integrity and serum calcium levels. Over the past 30 years, a number of immune cell modulators have been shown to have effects on osteoclast formation and function. This review will briefly summarize the roles that cytokines have in osteoclast regulation.

RECENT FINDINGS

A large number of cytokines have been shown to regulate osteoclast formation and function. In addition, a number of additional cytokines are now known to have a major influence on the ability of osteoclasts to resorb bone. Interactions of the immune system with bone, which has been recently labeled 'osteoimmunology', appear to be mediated mainly by cytokine signals. Cytokines are known to regulate many of the responses of bone to inflammatory conditions; however, they also may regulate physiologic responses of bone.

SUMMARY

In the future it is hoped that therapies that target cytokine actions may be used to reduce the effects of inflammatory diseases on bone, as well as to regulate normal bone physiology.

Identification and characterization of novel IGFBP5 interacting protein: evidence IGFBP5-IP is a potential regulator of osteoblast cell proliferation

Insulin-like growth factor binding protein-5 (IGFBP5) is a multifunctional protein, which acts not only as a traditional binding protein, but also functions as a growth factor independent of IGFs to stimulate bone formation. It has been predicted that the intrinsic growth factor action of IGFBP5 involves binding of IGFBP5 to a putative receptor to induce downstream signaling pathways and/or nuclear translocation of IGFBP5 to influence transcription of genes involved in osteoblast cell proliferation/differentiation. Our study indentified proteins that bound to IGFBP5 using IGFBP5 as bait in a yeast two-hybrid screen of the U2 human osteosarcoma cell cDNA library. One of the clones that interacted strongly with the bait under high-stringency conditions corresponded to a novel IGFBP5 interacting protein (IGFBP5-IP) encoded by a gene that resides in mouse chromosome 10. The interaction between IGFBP5-IP and IGFBP5 is confirmed by in vitro coimmunoprecipitation studies that used pFlag and IGFBP5 polyclonal antibody, and cell lysates overexpressing both IGFBP5-IP and IGFBP5. Northern blot and RT-PCR analysis showed that the IGFBP-IP is expressed in both untransformed normal human osteoblasts and in osteosarcoma cell lines, which are known to produce IGFBP5. To determine the roles of IGFBP5-IP, we evaluated the effect of blocking the expression of IGFBP5-IP on osteoblast proliferation. We found that using a IGFBP5-IP-specific small interfering-hairpin plasmid resulted in a decrease in both basal and IGFBP5-induced osteoblast cell proliferation. On the basis of these findings, we predict that IGFBP5-IP may act as intracellular mediator of growth promoting actions of IGFBP5 and perhaps other osteoregulatory agents in bone cells.

Ras-association domain family 1 protein, RASSF1C, is an IGFBP-5 binding partner and a potential regulator of osteoblast cell proliferation

The goal of this study was to identify downstream signaling molecules involved in mediating the IGF-independent effects of IGFBP-5 in osteoblasts. We identified RASSF1C, a member of the RASSF1 gene products, as a IGFBP-5 binding partner and as a potential mediator of IGFBP-5 effects on ERK phosphorylation and cell proliferation.

INTRODUCTION

It has been predicted that the intrinsic growth factor action of insulin-like growth factor binding protein (IGFBP)-5 involves either the binding of IGFBP-5 to a putative receptor to induce downstream signaling pathways and/or intracellular translocation of IGFBP-5 to bind to potential signaling molecules involved in osteoblast cell regulation. This study reports the characterization of isoform C of the Ras association family 1 (RASSF1C) gene as an interacting partner of IGFBP-5.

MATERIALS AND METHODS

IGFBP-5 was used as bait in a yeast two-hybrid screen of a human osteosarcoma cDNA library. Expression levels of RASSF1C were measured by RT-PCR and/or Northern blot. IGFBP-5 effects on ERK phosphorylation were evaluated by immunoblot analysis. The effect of RASSF1C siRNA on cell proliferation was measured by the AlamarBlue assay.

RESULTS

One of the clones that interacted strongly with the bait under high stringency conditions corresponded to RASSF1C. The interaction between RASSF1C and IGFBP-5 was confirmed by in vitro co-immunoprecipitation studies. Northern blot and RT-PCR analysis showed that RASSF1C was expressed in a variety of osteoblast cell types that produce IGFBP-5. Addition of synthetic RASSF1C-specific small interfering (si) RNA duplex or use of a RASSF1C-specific si-hairpin plasmid caused a decrease in cell number and abolished IGFBP-5-induced extracellular signal-regulated kinase (ERK)-1/2 phosphorylation but had no effect on IGFBP-5-induced increases in alkaline phosphatase (ALP) activity.

CONCLUSIONS

We have shown a novel interaction between IGFBP-5 and RASSF1C. Our findings that silencing of RASSF1C results in the reduction of osteoblast cell proliferation and that IGFBP-5 treatment increases phosphorylation of ERK-1/2 raise the possibility that RASSF1C, a Ras effector, could, in part, contribute to mediating the effects of IGFBP-5 on ERK phosphorylation and, consequently, cell proliferation.

Glucocorticoids inhibit the transcriptional activity of LEF/TCF in differentiating osteoblasts in a glycogen synthase kinase-3beta-dependent and -independent manner

Glucocorticoids, widely used as immune suppressors, cause osteoporosis by inhibiting bone formation. In MC3T3-E1 osteoblast-like cultures, dexamethasone (DEX) activates glycogen synthase kinase-3beta (GSK3beta) and inhibits a differentiation-related cell cycle that occurs at a commitment stage immediately after confluence. Here we show that DEX inhibition of the differentiation-related cell cycle is associated with a decrease in beta-catenin levels and inhibition of LEF/TCF-mediated transcription. These inhibitory activities are no longer observed in the presence of lithium, a GSK3beta inhibitor. DEX decreased the serum-responsive phosphorylation of protein kinase B/Akt-Ser(473) within minutes, and this inhibition was also observed after 12 h. When the phosphatidylinositol 3-kinase (PI3K)/Akt pathway was inhibited by wortmannin, DEX no longer inhibited beta-catenin levels. Furthermore, DEX-mediated inhibition of LEF/TCF transcriptional activity was attenuated in the presence of dominant negative forms of either PI3K or protein kinase B/Akt. These results suggest cross-talk between the PI3K/Akt and Wnt signaling pathways. Consistent with a role for Wnt signaling in the osteoblast differentiation-related cell cycle, wortmannin partially negated the DEX inhibition of this cell cycle. DEX also induced histone deacetylase (HDAC) 1, which is known to inhibit LEF/TCF transcriptional activity. Overexpression of HDAC1 negated the inhibitory effect of DEX on LEF/TCF transcriptional activity. In the presence of trichostatin A, a deacetylase inhibitor, DEX-mediated inhibition of the differentiation-related cell cycle was partially negated. When administered together, wortmannin and trichostatin A completely negated the inhibitory effect of DEX on the differentiation-related cell cycle. These results suggest that inhibition of a PI3K/Akt/GSK3beta/beta-catenin/LEF axis and stimulation of HDAC1 cooperate to mediate the inhibitory effect of DEX on Wnt signaling and the osteoblast differentiation-related cell cycle.

IL-6, RANKL, TNF-alpha/IL-1: interrelations in bone resorption pathophysiology

All osteogenic cells (osteoclasts, osteoblasts) contribute individually to bone remodeling. Their cellular interactions control their cellular activities and the bone remodeling intensity. These interactions can be established either through a cell-cell contact, involving molecules of the integrin family, or by the release of many polypeptidic factors and/or their soluble receptor chains. These factors can act directly on osteogenic cells and their precursors to control differentiation, formation and functions (matrix formation, mineralization, resorption...). Here, we present the involvement of three groups of cytokines which seem to be of particular importance in bone physiology: interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) (TNF-alpha)/IL-1, and the more recently known triad osteoprotegerin (OPG)/receptor activator of NF-kappaB (RANK)/RANK ligand (RANKL). The interactions between these three groups are presented within the framework of bone resorption pathophysiology such as tumor associated osteolysis. The central role of the OPG/RANK/RANKL triad is pointed out.

Increased expression of IL-6 and RANK mRNA in human trabecular bone from fragility fracture of the femoral neck

Previous studies have implicated pro-inflammatory cytokines in the bone loss of estrogen deficiency. The aim of this study was to investigate the expression of key regulatory molecules of bone remodeling in the trabecular bone microenvironment in osteoporosis. Bone samples were taken from the intertrochanteric region of the proximal femur of patients undergoing total hip arthroplasty for a subcapital fragility fracture of the femoral neck (#NOF). For comparison, samples were taken from age-matched control individuals at routine autopsy. Expression of RANKL, RANK, osteoprotegerin (OPG), IL-6, IL-11, osteocalcin (OCN), and calcitonin receptor (CTR) messenger RNA (mRNA) species were analyzed and the data were nonparametrically distributed. The median expression of the proresorptive genes, RANK and IL-6, were significantly elevated in the fracture group compared to an age-matched control group (2.2 [1.9-2.9; 25th-75th percentiles] > 1.0 [0.4-2.1], P < 0.03; 3.9 [1.8-6.2] > 0.8 [0.7-1.5], P < 0.002, respectively). In contrast, there were no significant differences in expression of RANKL, OPG, CTR, or OCN mRNA between the #NOF and control groups. The median RANKL/OPG mRNA ratio was significantly greater in hip fracture bone than in bone from controls (4.8 [3.8-7.6] > 3.2 [2.1-4.0], P < 0.05). IL-6 mRNA levels associated strongly with RANKL mRNA levels in the #NOF group (r = 0.77, P < 0.001), but not in the control group. A strong positive association was found between IL-11 mRNA levels and RANKL mRNA levels in the #NOF group (r = 0.81, P < 0.001), consistent with the apparent coordinated regulation of IL-6 and IL-11 in bone samples from the #NOF group (r = 0.93, P < 0.0001). These data suggest a relative increase in the expression of the molecular promoters of osteoclast formation and activity in #NOF bone, which may lead to the imbalance between bone formation and resorption associated with fragility fracture.

Chemically modified tetracyclines selectively inhibit IL-6 expression in osteoblasts by decreasing mRNA stability

In bone biology, interleukin (IL)-6 is an autocrine/paracrine cytokine which can induce osteoclasts formation and activation to help mediate inflammatory bone destruction. Previous studies have shown that tetracycline and its derivatives have potentially beneficial therapeutic effects in the prevention and treatment of metabolic bone diseases by modulating osteoblast and osteoclast activities. Our previous studies indicated that non-antimicrobial chemically modified tetracyclines (CMTs) can dose-dependently inhibit IL-1 beta-induced IL-6 secretion in osteoblastic cells. In the present study, we explored the molecular mechanisms underlying the ability of doxycycline analogs CMT-8 and its non-chelating pyrazole derivative, CMT-5 to affect IL-6 gene expression in murine osteoblasts. Steady-state IL-6 mRNA was decreased with CMT-8 (ca. 50%) but not by CMT-5 when stimulated by IL-1 beta. CMT-8 regulation of IL-1 beta-induced IL-6 gene expression was further explored. CMT-8 did not affect IL-6 promoter activity in reporter gene assays. However, the IL-6 mRNA stability was decreased in the presence of CMT-8. These effects require de novo protein synthesis as they were inhibited by cycloheximide. Western blot analysis indicated that CMT-8 did not affect p38 mitogen-activated protein kinase, c-jun NH(2)-terminal kinases, or extracellular signal-regulated kinases (1 and 2) phosphorylation in response to IL-1 beta. These data suggest that CMT-8 can modulate inhibit IL-1 beta-induced IL-6 expression in MC3T3-E1 cells at the post-transcriptional level affecting IL-6 mRNA stability. These observations may offer a novel molecular basis for this treatment of metabolic bone diseases that are mediated by IL-6.

Insulin-like growth factor-binding protein 5 (IGFBP-5) interacts with a four and a half LIM protein 2 (FHL2)

Recent studies using insulin-like growth factor I (IGF-I) knockout mice demonstrate that IGF-binding protein (IGFBP)-5, an important bone formation regulator, itself is a growth factor with cellular effects not dependent on IGFs. Because IGFBP-5 contains a nuclear localization sequence that mediates transport of IGFBP-5 into the nucleus, we propose that IGFBP-5 interacts with nuclear proteins to affect transcription of genes involved in bone formation. We therefore undertook studies to identify proteins that bind to IGFBP-5 using IGFBP-5 as bait in a yeast two-hybrid screen of a U2 human osteosarcoma cDNA library. Five related clones that interacted strongly with the bait corresponded to the FHL2 gene, which contains four and a half LIM domains. Co-immunoprecipitation studies with lysates from U2 cells overexpressing FHL2 and IGFBP-5 confirmed that interaction between IGFBP-5 and FHL2 occurs in whole cells. In vitro interaction studies revealed that purified FHL2 interacted with IGFBP-5 but not with IGFBP-3, -4, or -6. Northern blot analysis showed that FHL2 was strongly expressed in human osteoblasts. Nuclear localization of both FHL2 and IGFBP-5 was evident from Western immunoblot analysis and immunofluorescence. The role of FHL2 as an intracellular mediator of the effects of IGFBP-5 and other osteoregulatory agents in osteoblasts will need to be verified in future studies.

Changes in proinflammatory cytokine activity after menopause

There is now a large body of evidence suggesting that the decline in ovarian function with menopause is associated with spontaneous increases in proinflammatory cytokines. The cytokines that have obtained the most attention are IL-1, IL-6, and TNF-alpha. The exact mechanisms by which estrogen interferes with cytokine activity are still incompletely known but may potentially include interactions of the ER with other transcription factors, modulation of nitric oxide activity, antioxidative effects, plasma membrane actions, and changes in immune cell function. Experimental and clinical studies strongly support a link between the increased state of proinflammatory cytokine activity and postmenopausal bone loss. Preliminary evidence suggests that these changes also might be relevant to vascular homeostasis and the development of atherosclerosis. Better knowledge of the mechanisms and the time course of these interactions may open new avenues for the prevention and treatment of some of the most prevalent and important disorders in postmenopausal women.

Effect of MPC-11 myeloma and MPC-11 + IL-1 receptor antagonist treatment on mouse bone properties

This study examines the effects of an IL-6-producing murine multiple myeloma cell line on trabecular and cortical mouse bone, and evaluates the efficacy of interleukin-1 receptor antagonist (IL-1ra) in mitigating bone destruction. Six-week-old BALB/c mice were assigned to two groups: normal controls and myeloma animals (5 x 10(7) MPC-11 cells on day 0). Myeloma animals were further assigned to three unique groups: MPC-11 only; MPC-11 treated with hyaluronic acid (HA); and MPC-11 + IL-1ra/HA (100 mg/kg). Disease development was assessed at 14 and 21 days via spleen, liver, and proximal tibia histology; histomorphometry at the femoral middiaphysis; and long bone composition and mechanical testing. Histologic analysis revealed marked myeloma infiltration into organs and bone marrow and gross bone resorption of the proximal tibia. IL-1ra tended to decrease bone resorption at the proximal tibia; however, it had no effect on quantitatively measured bone parameters. Whole femur and tibia, and tibial epiphysis, percent mineralization was decreased (3.0%, 2.9%, and 6.3%, respectively) in all MPC-11 groups. The presence of myeloma did not affect long bone stiffness, strength, or length over the 3 week study. The percent of the femoral endosteal perimeter showing excessive resorption ( approximately 60%) in the MPC-11 groups increased significantly after 21 days. MPC-11 cell presence caused no change in bone formation or morphology. Normal growth mechanisms were not impacted, as the bones lengthened and increased in size and mass despite the presence of myeloma. IL-1 does not appear to be a primary factor in in vivo bone destruction caused by the MPC-11 cell line. These findings reveal the stochastic nature of bone lesions in multiple myeloma and suggest that IL-1 is not a cytokine critical to this disease pathology.

Mastocytosis

Mastocytosis represents a heterogeneous group of clinical disorders resulting from the infiltration of mast cells in the skin and other organs. Although mastocytosis was first described over 130 years ago, the pathophysiologic mechanisms responsible for this disease have been identified only recently. This article discusses the salient clinical features of the disease, the mechanisms responsible for its development, and provides treatment approaches that have proven useful for managing patients with this disorder.

Hypercalcemia in a patient with B-cell acute lymphoblastic leukemia: a role of proinflammatory cytokine

The complication of hypercalcemia is reported to occur only in 2.5-4.8% of patients with acute lymphoblastic leukemia (ALL). We herein report a 53-year-old female patient with early B-cell ALL, complicated with extreme hypercalcemia (15.2 mg/dL). Bone X-ray revealed osteolytic changes in many locations. Serum 1,25(OH)2vitaminD3 and parathyroid hormone (PTH) levels were suppressed below normal ranges on admission. The circulating parathyroid hormone-related protein (PTHrP) value was within a normal range (< 1.1 pmol/L). Serum concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and soluble IL-2 receptor were increased to 72 pg/ml, 25.3 pg/ml, and 1469 U/ml, respectively. Following the induction chemotherapy, the serum calcium level was promptly normalized accompanied with decreases in serum TNF-alpha, IL-6 and soluble IL-2 receptor values to 34 pg/ml, 6.35 pg/ml, and 737 U/ml, respectively. Serum PTHrP values remained within detectable levels. To our knowledge, this is the first case of B-cell ALL in a patient who developed hypercalcemia with elevated concentrations of TNF-alpha, IL-6, and soluble IL-2 receptor, but not related to PTHrP. High circulating proinflammatory cytokines may have contributed to development of ALL-induced osteolysis and hypercalcemia in the present case.

Increased mRNA expression and protein secretion of interleukin-6 in primary human osteoblasts differentiated in vitro from rheumatoid and osteoarthritic bone

We have investigated the expression and synthesis of potential bone-resorbing cytokines, interleukin-6 (IL-6), interleukin-1 (IL-1), and tumor necrosis factor (TNF) in rheumatoid arthritic (RA) and osteoarthritic (OA) bone, two common diseases which are associated with bone loss. Primary human osteoblast (hOB) cultures were established to determine the temporal mRNA expression of IL-6, IL-1 (alpha and beta), and TNF (alpha and beta) in relation to osteoblast growth and phenotypic genes. IL-6 mRNA levels were found to be significantly higher (P < 0.04) in both OA hOB (17 patients) and RA hOB (10 patients) compared to normal (NO) hOB (9 patients) and reached five-fold increases in OA hOB and 13-fold increases in RA hOB. Maximal levels of IL-6 are expressed at Day 21 which corresponds to the mineralization stage reflected by decreasing collagen I (alpha(1)), osteopontin, bone sialoprotein, alkaline phosphatase mRNA levels, while osteocalcin (OC) mRNA levels increased. IL-6 protein levels also were significantly higher (P < 0.05) in OA hOB and RA hOB compared to NO hOB. These increases were not attributable to sex or age of the donor bone. Neither the mRNA encoding IL-1(alpha and beta) and TNF(alpha and beta) nor the related proteins were detectable. These results indicate that differentiated OA hOB and RA hOB within a bone tissue-like matrix constitutively express and secrete high levels of IL-6. This inherent property suggests that these osteoblasts, independent of local inflammatory parameters, can contribute to enhanced recruitment of osteoclast progenitors and thereby bone resorption.

Pamidronate increases markers of bone formation in patients with multiple myeloma in plateau phase under interferon-alpha treatment

Bisphosphonates are potent inhibitors of osteoclastic activity and reduce the disease-related skeletal complications when they are used in combination with chemotherapy in patients with multiple myeloma (MM). Pamidronate also inhibits apoptosis of primary osteoblastic cells and probably induces apoptosis on human MM cells and osteoclasts. It has been reported that interferon-alpha (IFN-alpha) decreases bone resorption and that low doses of IFN-alpha result in a significant increase in serum osteocalcin (OSC). The aim of this study was to determine the effects of pamidronate treatment on biochemical markers of bone resorption [cross-linked N-telopeptides of type I collagen (NTx)], bone formation [bone alkaline phosphatase (BAP) and OSC], disease activity [beta2-microglobulin, CRP, paraprotein], and interleukin-6 (IL-6) in patients with MM in plateau phase under IFN-alpha maintenance. The above parameters were evaluated in 28 patients (13 M, 15 F, median age 70 years) during maintenance treatment, before the addition of pamidronate and after 1, 3, 6, 9, 12, and 14 months of the combined therapy. The addition of pamidronate to maintenance treatment resulted in a significant reduction of NTx, IL-6, beta2-microglobulin, CRP from the 3rd month and paraprotein from the 6th month of treatment, whereas BAP and OSC were significantly increased from the 6th month. These changes continued during the 14-month follow-up of the combined treatment. Multivariate analysis showed a significant negative correlation between changes of BAP and OSC and the patients' age. The greater increase of the bone formation markers was observed in younger patients. These results suggest that, in addition to the inhibition of osteoclastic activity, pamidronate in combination with IFN-alpha was shown to induce bone formation in patients with MM in the plateau phase.

Inactivation of NF-kappaB involved in osteoblast development through interleukin-6

Osteoblasts undergo a process of proliferation and differentiation and are responsible for bone formation. In this study, we examined the relation between NF-kappaB, a key transcription factor in bone metabolism, and osteoblast maturation. NF-kappaB activity and expression of p50, a subunit of NF-kappaB, decreased during development of osteoblastic MC3T3-E1 cells. The secretion of IL-6 by osteoblast, which in combination with soluble IL-6 receptor induces conversion of fibroblasts to alkaline phosphatase-positive cells, also increased. p50 antisense oligonucleotide increased IL-6 mRNA expression. These results suggest that p50 regulates transcription of IL-6 and indirectly controls osteoblast maturation.

Orthodontic tooth movement and de novo synthesis of proinflammatory cytokines

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) are proinflammatory cytokines that are thought to play a role in bone remodeling, bone resorption, and new bone deposition. In the present work, in situ hybridization was performed to measure the messenger RNA expression of IL-1beta, IL-6, and TNF-alpha at 3, 7, and 10 days after the application of orthodontic force on the maxillary first molars of 12 rats. The contralateral side and 3 untreated rats served as controls. Measurements of the messenger RNA expression were selected as the means to investigate the role of orthodontic force in de novo synthesis of proinflammatory cytokines. After the application of force, the induction of IL-1beta and IL-6 was observed to reach a maximum on day 3 and to decline thereafter. No messenger RNA induction of either cytokine was measured in the control teeth. The messenger RNA expression of TNF-alpha was not detected at any time point of this study in the experimental or contralateral sides or in the control animals. Our data support the hypothesis that these proinflammatory cytokines may play important roles in bone resorption after the application of orthodontic force.

Upregulation of mRNA of interleukin-1 and -6 in subchondral cystic lesions of four horses

This study investigated the potential association of interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) in subchondral cystic lesions (SCL) in horses. With the technique of in situ hybridisation in paraffin sections of fibrous tissue of SCL and quantitative real-time PCR in fresh frozen fibrous tissue and undecalcified bone sections of SCL embedded in acrylic resin, upregulation of mRNA of both cytokines could be demonstrated. mRNA of IL-1beta was upregulated at the periphery of the cystic lesion adjacent to normal bone, whereas IL-6 mRNA was upregulated within the fibrous tissue found within the centre of the SCL. It was concluded that both cytokines are associated in pathological bone resorption observed in SCL and, in combination with increased production of prostaglandin E2, may be responsible for the slow healing, maintenance or further expansion of the cystic lesions.

Human marrow-derived mesenchymal stem cells (MSCs) express hematopoietic cytokines and support long-term hematopoiesis when differentiated toward stromal and osteogenic lineages

Human mesenchymal stem cells (MSCs), bone marrow-derived pluripotent adherent cells of mesenchymal origin can differentiate along the osteogenic, chondrogenic, adipogenic, and tendonogenic lineages. In this report we characterize cytokine and growth factor gene expression by MSCs and investigate the modulation of cytokine expression that occurs during osteogenic and stromal differentiation. MSCs constitutively expressed mRNA for interleukin (IL)-6, IL-11, leukemia inhibitory factor (LIF), macrophage colony-stimulating factor (M-CSF), and stem cell factor (SCF). MSCs treated with IL-1alpha upregulated mRNA levels of IL-6, IL-11, and LIF, and began to express detectable levels of granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF). mRNA levels of M-CSF and SCF did not change. MSCs cultured in osteogenic medium differentiated along the osteogenic lineage and downregulated mRNA levels of IL-6, IL-11 and LIF whereas, M-CSF and SCF expression were unchanged and G-CSF and GM-CSF remained undetectable. IL-3 was not detected in MSC culture under any conditions. MSCs precultured in control medium, IL-1alpha, or osteogenic medium maintained similar capacity to support long-term culture initiating cell (LT-CIC). Thus, primary and osteogenic differentiated MSCs produce important hematopoietic cytokines and support hematopoiesis in long-term cultures, suggesting that these cells may provide an excellent ex vivo environment for hematopoiesis during progenitor cell expansion and may be important for in vivo cell therapy.

Interleukin-6 modulates trabecular and endochondral bone turnover in the nude mouse by stimulating osteoclast differentiation

A great deal of evidence has been accumulating that implicates the immune system in normal and pathological bone turnover. The objective of the present study was to examine the possible involvement of cytokines produced by T lymphocytes in bone metabolism. We have chosen the immunologically compromised athymic mouse, which demonstrate sclerotic features in its trabecular bone, as the animal model for assessment of possible modulation effects of interleukin-1alpha (IL-1alpha) and interleukin-6 (IL-6) on bone and cartilage metabolism. The cytokines were applied by daily subcutaneous injections for 3 consecutive days. Histomorphometry, measuring epiphyseal trabecular bone volume (ETBV), metaphyseal trabecular bone volume (MTBV), and the width of the growth plate, and tartrate-resistant acid phosphatase (TRAP) histochemistry were used to assess parameters of bone turnover in the proximal tibia. IL-6, but not IL-1alpha, reduced ETBV and MTBV. Both IL-6 and IL-1alpha reduced the width of the growth plate. IL-6, but not IL-1alpha, increased the number of chondroclasts and osteoclasts in the primary spongiosa of the proximal tibia, as well as the number of nuclei. The resultant bone resembled that of the wild-type mouse. The results point to IL-6 as a possible regulator of bone turnover in vivo. It is suggested that the athymic mouse has a deficiency somewhere in the cascade of events leading to the production of IL-6 or, alternatively, that IL-6 replaces other factors that are supplied by T lymphocytes directly or indirectly. As T lymphocytes interact with B lymphocytes it is suggested that the athymic mouse might be appropriate for studying the in vivo effects of the immune system on normal bone metabolism.

Enhanced expression of osteocalcin mRNA in human osteoarthritic trabecular bone of the proximal femur is associated with decreased expression of interleukin-6 and interleukin-11 mRNA

Few studies have investigated the factors or mechanisms that may lead to structural changes in OA bone. This study examines the in vivo expression of messenger RNA encoding the osteoclastogenic cytokines interleukin-6 (IL-6) and interleukin-11 (IL-11), together with the osteoblastic marker osteocalcin (OCN) and the calcitonin receptor (CTR), which in bone is exclusively expressed by osteoclasts. Total RNA was isolated from intertrochanteric trabecular bone from OA patients, and from controls taken at autopsy. The patterns of mRNA expression of IL-6, IL-11, OCN, and CTR were examined using reverse-transcription polymerase chain reaction (RT-PCR) by determining the relative ratios of the amplified products with respect to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Both IL-6 and IL-11 mRNA were significantly less abundant in OA than in the control group. Expression of IL-11 mRNA decreased significantly with age for both groups. OCN mRNA expression was significantly more abundant in OA, and there was no significant difference for CTR mRNA between the two groups. For both OCN and CTR in OA, expression increased significantly with increasing age. These differences in expression between the OA and control groups are consistent with an hypothesis that biochemical and genetic factors in bone can contribute or perhaps underlie the degenerative joint changes seen in OA.

Human myeloma cells promote the production of interleukin 6 by primary human osteoblasts

Interleukin-6 (IL-6) is an important growth and survival factor for myeloma cells. However, the identity of the cells producing IL-6 in vivo remains unclear. Myeloma cells are found closely associated with sites of active bone turnover, and cells of the osteogenic lineage, including bone marrow osteoprogenitors, osteoblasts and bone lining cells, may therefore be ideally placed to synthesize IL-6. We have examined the possibility that human osteogenic cells may produce IL-6 in response to stimulation by myeloma cells. Primary human osteoblasts (hOBs) were isolated from normal donors, co-cultured with the human myeloma cell lines, JJN-3, RPMI-8226 and NCI-H929, and the amount of IL-6 released was determined by enzyme-linked immunosorbent assay (ELISA). All myeloma cells stimulated a significant increase in the production of IL-6 when cultured with hOBs (P < 0.05). Prior fixation of hOBs completely abrogated release of IL-6 in the co-cultures. In contrast, fixed myeloma cells retained the ability to induce IL-6 production, suggesting that hOBs were the principal source of IL-6. Physical separation of myeloma cells from hOBs using transwell inserts caused a partial inhibition of IL-6 release (P < 0.05), whereas the addition of media conditioned by myeloma cells to cultures of hOBs stimulated a significant increase in IL-6 production (P < 0.05). hOBs secreted greater amounts of IL-6 than human bone marrow stromal cells (hBMSCs) (2.2- to 3.5-fold, P < 0.05), but incubating hBMSCs with dexamethasone to stimulate osteoblastic differentiation resulted in an increase in their ability to produce IL-6 (1.7- to 4. 8-fold, P < 0.05) and to respond to myeloma cells (P < 0.05). These data clearly indicate that cells of the osteoblast lineage release significant amounts of IL-6 in response to stimulation by myeloma cells and may contribute to the IL-6 that promotes the proliferation and survival of myeloma cells in vivo.

Human osteoblast-like cells and osteosarcoma cell lines synthesize macrophage inhibitory protein 1alpha in response to interleukin 1beta and tumour necrosis factor alpha stimulation in vitro

Recent investigations have demonstrated that macrophage inhibitory protein 1alpha (MIP-1alpha) plays a critical role in haematopoiesis. In part, MIP-1alpha limits the differentiation of early haematopoietic cells, thereby ensuring that sufficient quantities of blood precursors are available to meet haematopoietic demands. MIP-1alpha is produced by cells of the marrow microenvironment (marrow stromal cells) in response to a variety of stimuli, including interleukin 1beta (IL-1beta) and tumour necrosis factor alpha (TNF-alpha). Our recent investigations demonstrated that normal human osteoblast-like cells (HOBs) maintain the early phenotype of haematopoietic precursors, like other members of the bone marrow stroma. Although the precise molecular mechanisms for these observations have not been determined, the production of MIP-1alpha remains one such possibility. In the present study, we investigated whether cells of the osteoblast lineage under basal, IL-1beta and/or TNF-alpha stimulation produce MIP-1alpha. We observed that IL-1beta and TNF-alpha stimulated HOBs and human osteosarcoma cells to rapidly express MIP-1alpha mRNA and to secrete large quantities of the protein. MIP-1alpha mRNA and protein was not, however, detected under basal conditions. Perhaps more importantly, enriched human CD34+ bone marrow cells in co-culture may be capable of stimulating the expression of MIP-1alpha mRNA by HOBs in vitro. These findings suggest that human osteoblast-like cells may produce MIP-1alpha in vivo to support haematopoiesis at sites where osteoblasts and haematopoietic cells are closely associated.

Multiple Myeloma: New Insights and Therapeutic Approaches

This review discusses the evolution of novel diagnostic and treatment strategies for multiple myeloma based upon increased understanding of basic disease pathogenesis. Although myeloma has remained an incurable illness to date, these new developments will derive treatments to improve outcome and achieve eventual cure.

In Section I, Dr. Kyle reviews the results of current therapy for multiple myeloma, including high dose therapy and stem cell transplantation which have proven to achieve improved response rates, event-free, and overall survival. Supportive therapy, such as erythropoietin to treat disease-related anemia, and methods of prophylaxis against infection, which both lessen toxicities of treatment and improve quality of life for patients, are also addressed.

In Section II, Dr. Dalton with Drs. Landowski, Shain, Jove and Hazlehurst discusses mechanisms of drug resistance in myeloma, with emphasis on novel treatment approaches to prevent development of drug resistance and to overcome drug resistance. Laboratory studies delineating mechanisms whereby myeloma cells resist drug-induced apoptosis provide the framework for related treatment protocols for patients with refractory disease.

In Section III, Dr. Berenson reviews the management of complications in bone, which occur in the majority of patients with myeloma and are the major cause of decreased quality of life. New insights into the mediators of bone resorption and new bone formation in the marrow milieu have already derived effective bisphosphonate therapy. These drugs not only reduce bone complications and related pain, thereby improving quality of life, but also may have intrinsic anti-tumor activity by virtue of inducing tumor cell adherence to marrow, reducing interleukin-6 secretion, inducing tumor cell apoptosis, or inhibiting angiogenesis.

In the last section, Dr. Anderson explores the potential for future therapies which offer great promise to improve patient outcomes. First, drugs which alter the marrow microenvironment include thalidomide and its derivative immunomodulatory drugs, which act directly on tumor cells to induce apoptosis or G1 growth arrest, alter tumor cell adhesion to marrow stroma, inhibit angiogenesis, and trigger a cellular anti-tumor response. The proteasome inhibitors both act directly on tumor cells and also inhibit the transcription factor NFκB-dependent upregulation of IL-6 secretion triggered by tumor cell adhesion. Second, delineation of both growth and apoptotic pathways has derived novel treatment strategies. Third, the preclinical basis and early clinical trial results using vaccination and adoptive immunotherapy to harness autoimmune and alloimmune anti-myeloma responses are presented. This review sets the stage for an evolving new biologically based treatment paradigm in myeloma targeting both the tumor and its microenvironment to improve outcome and achieve eventual cure.

Multiple Myeloma: New Insights and Therapeutic Approaches

This review discusses the evolution of novel diagnostic and treatment strategies for multiple myeloma based upon increased understanding of basic disease pathogenesis. Although myeloma has remained an incurable illness to date, these new developments will derive treatments to improve outcome and achieve eventual cure.

In Section I, Dr. Kyle reviews the results of current therapy for multiple myeloma, including high dose therapy and stem cell transplantation which have proven to achieve improved response rates, event-free, and overall survival. Supportive therapy, such as erythropoietin to treat disease-related anemia, and methods of prophylaxis against infection, which both lessen toxicities of treatment and improve quality of life for patients, are also addressed.

In Section II, Dr. Dalton with Drs. Landowski, Shain, Jove and Hazlehurst discusses mechanisms of drug resistance in myeloma, with emphasis on novel treatment approaches to prevent development of drug resistance and to overcome drug resistance. Laboratory studies delineating mechanisms whereby myeloma cells resist drug-induced apoptosis provide the framework for related treatment protocols for patients with refractory disease.

In Section III, Dr. Berenson reviews the management of complications in bone, which occur in the majority of patients with myeloma and are the major cause of decreased quality of life. New insights into the mediators of bone resorption and new bone formation in the marrow milieu have already derived effective bisphosphonate therapy. These drugs not only reduce bone complications and related pain, thereby improving quality of life, but also may have intrinsic anti-tumor activity by virtue of inducing tumor cell adherence to marrow, reducing interleukin-6 secretion, inducing tumor cell apoptosis, or inhibiting angiogenesis.

In the last section, Dr. Anderson explores the potential for future therapies which offer great promise to improve patient outcomes. First, drugs which alter the marrow microenvironment include thalidomide and its derivative immunomodulatory drugs, which act directly on tumor cells to induce apoptosis or G1 growth arrest, alter tumor cell adhesion to marrow stroma, inhibit angiogenesis, and trigger a cellular anti-tumor response. The proteasome inhibitors both act directly on tumor cells and also inhibit the transcription factor NFκB-dependent upregulation of IL-6 secretion triggered by tumor cell adhesion. Second, delineation of both growth and apoptotic pathways has derived novel treatment strategies. Third, the preclinical basis and early clinical trial results using vaccination and adoptive immunotherapy to harness autoimmune and alloimmune anti-myeloma responses are presented. This review sets the stage for an evolving new biologically based treatment paradigm in myeloma targeting both the tumor and its microenvironment to improve outcome and achieve eventual cure.

Stromelysin (MMP-3) synthesis is up-regulated in estrogen-deficient mouse osteoblasts in vivo and in vitro

Sex steroids are important regulators of bone cell function and osteoblast-derived matrix metalloproteinases (MMPs) are key mediators of bone resorption during the initial stage of osteoid removal prior to osteoclast attachment. To investigate the mechanism of bone loss following estrogen deficiency, we examined the effects of estrogen on osteoblast synthesis of MMPs and tissue inhibitor of metalloproteinases (TIMPs). Immunolocalization in mouse bone samples ex vivo and primary mouse osteoblast (MOB) cultures was used to document the synthesis of mouse interstitial collagenase (MMP-13), stromelysin-1 (MMP-3), gelatinase-A (MMP-2), and gelatinase-B (MMP-9). Endosteal bone lining cells from distal femoral head and lumbar vertebral body showed an increase in the pattern of synthesis of stromelysin-1 following ovariectomy, compared with sham-operated controls; the synthesis of other MMPs was unaffected. The expression of all classes of MMPs and TIMP-1 and TIMP-2 by MOB in culture was demonstrated by reverse transcriptase-polymerase chain reaction. Following the withdrawal of 17beta-estradiol, MOB cultures showed a significant increase in the number of cells synthesizing stromelysin-1; this effect was enhanced by stimulation with either interleukin-1 or interleukin-6. Northern blot analysis showed only a slight increase in stromelysin-1 mRNA message following the withdrawal of 17beta-estradiol. Our data show an unexpected up-regulation of stromelysin-1 synthesis by osteoblasts both in vivo and in vitro following estrogen withdrawal. Although this effect was not reflected in a significant change in stromelysin-1 mRNA expression in vitro, there is evidence to suggest a role for this enzyme in the early stages of bone loss during the pathogenesis of osteoporosis.

Regulation of osteoclast activity

Osteoclasts are the primary cell type responsible for bone resorption. This paper reviews many of the known regulators of osteoclast activity, including hormones, cytokines, ions, and arachidonic acid metabolites. Most of the hormones and cytokines that inhibit osteoclast activity act directly on the osteoclasts. In contrast, most of the hormones and cytokines that stimulate osteoclast activity act indirectly through osteoblasts. Particularly interesting in this regard are agents that directly inhibit activity of highly purified osteoclasts yet stimulate activity of osteoclasts that are co-cultured with osteoblasts. Recent studies have demonstrated that the primary mechanism by which bone resorptive agents stimulate osteoclast activity indirectly is likely to be up-regulation of production of osteoclast differentiation factor/osteoprotegerin ligand (ODF/OPGL) by the osteoblasts. In addition to discussing regulators of osteoclast activity per se, this paper also reviews the role of osteoclast apoptosis to limit the extent of bone resorption.

Arginine increases insulin-like growth factor-I production and collagen synthesis in osteoblast-like cells

Protein-energy malnutrition, which is common in elderly patients with osteoporotic hip fractures, is associated with reduced plasma levels of insulin-like growth factor-I (IGF-I). IGF-I is an important regulator of bone metabolism, particularly of osteoblastic bone formation both in vivo and in vitro. Pharmacological doses of arginine (Arg) increase growth hormone (GH) and IGF-I serum levels. Whether amino acids, particularly Arg, can directly modulate the production of IGF-I by osteoblasts is not known. We investigated the effects of increasing concentrations of Arg on IGF-I expression and production, alpha1(I) collagen expression and collagen synthesis, and cell proliferation and cell differentiation, as assessed by alkaline phosphatase (ALP) activity and osteocalcin (OC) release, in confluent mouse osteoblast-like MC3T3-E1 cells. The addition of Arg (7.5-7500 micromol/L, equivalent to 0.1- to 100-fold human plasma concentration) for 48 h increased IGF-I production (adjusted for cell number) in a concentration-dependent manner with a maximum of 2.3 +/- 0.3-fold at 7500 micromol/L Arg [x +/- standard error of the mean (SEM), n = 3 experiments, p < 0.01]. Arg (7.5-7500 micromol/L) increased the percentage of de novo collagen synthesis in a concentration-dependent manner (2.1 +/- 0.4-fold with 7500 micromol/L Arg, p < 0.001) and ALP activity with a maximal stimulation of 144% +/- 13% plateauing at 750 micromol/l Arg (p = 0.002). The steady state level of IGF-I messenger ribonucleic acid (mRNA) and alpha1(I) collagen mRNA (both normalized to cyclophilin mRNA) of cells incubated with Arg at high (100-fold) or low (0.1-fold) human plasma concentrations, was 1.4 +/- 0.2, 1.2 +/- 0.2, and 1.1 +/- 0.2 after 24 h for the 7.5, 1.8, and 0.9 kb IGF-I mRNA transcripts, respectively (n = 3 experiments) and 1.5 +/- 0.2 and 3.1 +/- 0.7 after 24 and 48 h, respectively, for the combined analysis of the 5.6 and 4.7 kb alpha1(I) collagen mRNA transcripts (n = 3 experiments). A maximal mitogenic effect (cell number) of +21% +/- 3% (p < 0.01) was obtained with 1000 micromol/L Arg. In contrast, Arg (7.5-7500 micromol/L) induced a reduction of OC production, which reached 30% +/- 3% with 7500 micromol/L Arg (p = 0.02). In conclusion, Arg stimulated IGF-I production and collagen synthesis in osteoblast-like cells. Thus, Arg may influence bone formation by enhancing local IGF-I production.

Combination of interleukin-6 and soluble interleukin-6 receptors induces differentiation and activation of JAK-STAT and MAP kinase pathways in MG-63 human osteoblastic cells

Studies on the role of interleukin-6 (IL-6) in bone metabolism have been accumulating. However, its effects on osteoblasts are still unclear because the results are conflicting depending on the study models employed. We reasoned that these conflicting data are due to variable expression levels of membrane-bound IL-6 receptors (IL-6Rs). In the present study, we found that IL-6 in combination with soluble IL-6R (sIL-6R) consistently caused a marked elevation of alkaline phosphatase and a decrease in proliferation in the human osteoblastic cell line MG-63, which expressed no detectable membrane-bound IL-6R and failed to respond to IL-6. These effects of IL-6/sIL-6R were blocked by neutralizing antibodies to the IL-6 signal transducer gp130, suggesting an involvement of IL-6 signaling in the elicitation of the effects of IL-6/sIL-6R. Upon stimulation with IL-6/sIL-6R, the gp130, cytoplasmic Janus kinases JAK1 and JAK2 were tyrosine phosphorylated. Moreover, signal transducers and activators of transcription STAT1 and STAT3 were also tyrosine phosphorylated, translocated to the nucleus, and bound to the putative STAT-binding DNA elements. In addition, mitogen-activated protein (MAP) kinase was also activated in response to IL-6/sIL-6R These data demonstrate that sIL-6R may enhance the responsiveness of MG-63 cells to IL-6. Thus, IL-6 in collaboration with sIL-6R may modulate differentiation and proliferation of osteoblastic cells, presumably by activating two distinct signaling pathways of JAK-STAT and MAP kinase.

Severe hypercalcaemia and extensive osteolytic lesions in an adult patient with T cell acute lymphoblastic leukaemia

Hypercalcaemia is a rare feature of acute lymphoblastic leukaemia (ALL) in adults, particularly of the T cell type. We report on a 24-year-old patient with T-ALL, who presented with symptoms of hypercalcaemia (vomitus, acute renal failure), bone pain, extensive osteolytic lesions and normal white cell count without circulating blasts. An increased serum tumor necrosis factor (TNF-alpha) concentration of 35 pg/ml was found; it remained elevated at 52 pg/ml four weeks later, after having achieved haematological remission. Serum concentrations of IL-1beta, IL-6 and IL-2 were within the control range. The pathophysiology of hypercalcaemia in malignancy and possible mediators of bone resorption, in particular TNF-alpha, are discussed.

Parathyroid hormone (1-34)-mediated interleukin-6 induction

Parathyroid hormone (PTH) functions in part by regulating osteoblast cytokine expression. We recently demonstrated that PTH induced a rapid and transient increase in interleukin-6 (IL-6) mRNA expression in rat bones in vivo. To determine the molecular basis of this effect, we analyzed the human IL-6 promoter fused (-1,179 to +9) with the chloramphenicol acetyltransferase (CAT) reporter gene in stable transfections into human osteoblast-like osteosarcoma SaOS-2 cells. We compared the effects of PTH on IL-6 expression with adenylate cyclase activator forskolin, PKC activator phorbol 12-myristate 13-acetate (PMA), calcium ionophore A23187, interleukin-1 alpha (IL-1 alpha), prostaglandin E-2 (PGE-2), RS-66271 (a parathyroid hormone-related peptide analog), and platelet-derived growth factor-BB (PDGF-BB). Analyses of cell clones showed that IL-6 promoter expression was extremely low in the unstimulated state. Exposure to PTH (0.001-100 nM) for 12 h stimulated CAT expression in a dose-dependent manner (200-500% of control). Treatment with IL-1 alpha was more potent than PTH in inducing transcription of the IL-6 promoter (900-1,000%). Activation of the cAMP-PKA pathway by treatment with forskolin induced a comparable level of induction with PTH. Together, the effects of PTH and forskolin were additive. RS-66271, previously shown to have PTH-like effects, induced a comparable level of IL-6 promoter expression. When examined together, PTH+RS-66271 effects were comparable to PTH effects alone. Exposure to PGE-2, PMA, PDGF-BB, or A23187 for 12 h did not significantly alter IL-6 promoter expression. These results demonstrate PTH, forskolin, the PTHrP analog RS-66271, and IL-1 alpha stimulate IL-6 expression by stimulating gene transcription. The response to forskolin suggests that the messenger system mediated by PKA is sufficient to induce IL-6 expression.

Human osteosarcomas inhibit hematopoietic colony formation: partial reversal by antibody to transforming growth factor-beta 1

Recently we found that primary human osteoblast-like cells (HOBs) support hematopoietic progenitor cells (assayed by colony formation in methylcellulose) and long-term culture initiating (LTC-IC) activity in vitro. In the present investigation, we evaluate whether human osteosarcoma cells share in these activities. We observed that relative to controls, significantly fewer hematopoietic colonies were formed in the presence of HOS TE85, MG-63, SaOS-2, or U2-OS human osteosarcomas. In addition, neither MG-63 or SaOS-2 cells supported hematopoietic progenitor cell activity or LTC-IC activity in vitro. We established that the suppressive activity produced by the osteosarcomas is soluble, correlated with osteosarcoma cell number and is partially neutralized with antibody to TGF-beta 1,2,3. While it is clear that the osteosarcomas express several phenotypic characteristics of primary human osteoblasts, these data suggest that they may be functionally disregulated with regard to their ability to support normal hematopoiesis. For these reasons, caution should be exercised when evaluating osteoblastic and hematopoietic cell interactions based purely on the use of osteosarcoma cell lines.

Pathogenesis and management of bone lesions in multiple myeloma

Osteolytic lesions are among the hallmarks of multiple myeloma (MM). On the other hand, they are rare in B cell malignancies other than MM. Data have shown a close relationship between myeloma cell growth factors and factors involved in the occurrence of bone lesions in MM. Biophosphonates, which are potent inhibitors of bone resorption to control MM-induced hypercalcemia, are of interest due to their ability to slow the progression of MM bone disease.

Augmented Production of Interleukin-6 by Normal Human Osteoblasts in Response to CD34+ Hematopoietic Bone Marrow Cells In Vitro

Based on anatomic and developmental findings characterizing hematopoietic cells in close approximation with endosteal cells, we have begun an analysis of osteoblast/hematopoietic cell interactions. We explore here the functional interdependence between these two cell types from the standpoint of de novo cytokine secretion. We determined that, over a 96-hour period, CD34+ bone marrow cells had no significant effect on osteoblast secretion of granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, or transforming growth factor-β1 , but in some experiments minor increases in leukemia inhibitory factor levels were observed. However, when CD34+ bone marrow cells were cocultured in direct contact with osteoblasts, a 222% ± 55% (range, 153% to 288%) augmentation in interleukin-6 (IL-6) synthesis was observed. The accumulation of IL-6 protein was most rapid during the initial 24-hour period, accounting for nearly 55% of the total IL-6 produced by osteoblasts in the absence of blood cells and 77% of the total in the presence of the CD34+ cells. Cell-to-cell contact does not appear to be required for this activity, as determined by coculturing the two cell types separated by porous micromembranes. The identity of the soluble activity produced by the CD34+ cells remains unknown, but is not likely due to IL-1β or tumor necrosis factor-α, as determined with neutralizing antibodies. To our knowledge, these data represent the first demonstration that early hematopoietic cells induce the production of molecules required for the function of normal bone marrow microenvironments, in this case through the induction of hematopoietic cytokine (IL-6) secretion by osteoblasts.

In vitro senescence enhances IL-6 production in human gingival fibroblasts induced by lipopolysaccharide from Campylobacter rectus

The production of interleukin-6 (IL-6) in human gingival fibroblasts (Gin cells) is increased by lipopolysaccharide (LPS) from Campylobacter rectus (C. rectus), which is associated with adult periodontitis; however, the age-related changes in the susceptibility of Gin cells to C. rectus LPS remain unclear. We examined the influence of in vitro senescence on C. rectus LPS-stimulated IL-6 production in Gin cells. LPS was prepared from C. rectus ATCC 33238 using hot phenol-water. The Gin cells were established from healthy gingival tissue removed from three patients, aged 10-12 years. The cells were cultured until confluence then stimulated with LPS (0.01, 0.1, 1.0 and 10.0 micrograms/ml). Levels of IL-6 released in the medium were measured after incubation for 3, 6, 9, 12, and 24 h. In both young (5-6 population doublings) and senescent (17-20 population doublings) cells, LPS stimulated IL-6 production in a dose- and time-dependent manner. In response to 0.01-10.0 micrograms/ml of LPS, IL-6 production in the senescent cells was higher than that in the young cells. Using cells from each of the three donors, we found that this phenomenon of higher LPS-stimulated IL-6 production in senescent cells was reproducible. The greater capacity of the senescent cells to synthesize IL-6 in response to LPS was a higher production of mRNA for IL-6. This increase of IL-6 production induced by C. rectus LPS in senescent Gin cells could help to explain the increased susceptibility to periodontal diseases shown by aged individuals.

Effect of size, concentration, surface area, and volume of polymethylmethacrylate particles on human macrophages in vitro

This study investigated effects of different sizes, concentrations, volumes, and surface areas of polymethylmethacrylate (PMMA) particles on human macrophages. Adherent peripheral blood monocytes isolated from five healthy individuals were exposed for 48 h to phagocytosable (0.325 micron and 5.5 microns) and nonphagocytosable (200 microns) spherical particles. Each particle size was tested over a range of concentrations (10(4)-10(11) particles per milliliter [0.325 micron], 10(2)-10(7) particles per milliliter [5.5 microns], 10(1)-10(4) particles per milliliter [200 microns]) to provide overlap in number, volume, and surface area. Primary human monocyte/macrophages were cultured in macrophage serum-free medium and 5% fetal calf serum. Macrophage viability was assessed by 3H-thymidine uptake and activation was quantified by release of interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, prostaglandin E2 (PGE2), and the lysosomal enzyme hexosaminidase. Medium alone served as a negative control; lipopolysaccharide (10 micrograms/mL) was also tested. PMMA particles were not toxic to human macrophages at any concentration tested. The smallest phagocytosable particles (0.325 micron) stimulated the release of interleukin-1 beta, interleukin-6, prostaglandin E2, and hexosaminidase at concentrations of 10(10)-10(11) particles/mL. The release of cytokines, PGE2, and hexosaminidase depended on the size, concentration, surface area, and volume of the phagocytosable particles. This study demonstrates that PMMA particle load Mi.e., the concentration of phagocytosable particles per tissue volume, characterized by size, surface area, and volume, rather than simply particle number-determines the degree of macrophage activation.

Osteoclasts are not the major source of interleukin-6 in mouse parietal bones

Interleukin-6 (IL-6) is produced by bone cells and has been shown to stimulate the proliferation of osteoclast progenitors. Which cells in bone produce IL-6 is controversial. This article tests the hypothesis that tartrate-resistant acid phosphatase-positive osteoclasts (TRAP + OC) in neonatal mouse parietal bones are the major source of IL-6. Bones were preincubated with indomethacin to decrease the number of TRAP + OC and the amount of IL-6 produced. Incubation with parathyroid hormone or prostaglandin E2 increased the number of TRAP + OC and the amount of IL-6 produced. Calcitonin and 17 beta-estradiol inhibited this increase in TRAP + OC but had no effect on IL-6 production. 1,25-dihydroxy-vitamin D3 also stimulated an increase in TRAP + OC number but did not cause increased IL-6 production. Both the endocranial and ectocranial membranes of these bones produced large amounts of IL-6. TRAP activity in extracts of endocranial membranes was 14-fold that of the ectocranial membrane and, histochemically, some TRAP + cells could be detected here. However, the ectocranial membranes produced more IL-6 than the endocranial membranes. We conclude that TRAP + OC are not a major source of IL-6 in this system.