Correlations between macrophage polarizing cytokines, inflammatory mediators, osteoclast activity, and toll-like receptors in tissues around aseptically loosened hip implants.
Journal of biomedical materials research. Part A
NF-?B decoy oligodeoxynucleotide mitigates wear particle-associated bone loss in the murine continuous infusion model.
2016; 41: 273-281
Aseptic loosening and osteolysis of joint replacements are driven by macrophage-mediated inflammatory reactions to implant-derived wear debris, but many aspects of these events remain poorly characterized. To better understand the relationships among inflammatory and chemotactic mediators, macrophage phenotype and polarizing cytokines, osteoclast activity, and Toll-like receptors (TLRs) in the pathogenesis of aseptic loosening, we determined how the relative expressions of these factors in the peri-implant tissues correlate to each other and to the life span of the implants using Pearson correlation. The expression of pro-inflammatory mediators and chemokines showed positive correlations among themselves, and with TLR4. Furthermore, M1-polarizing IFN-? showed positive correlations with a number of pro-inflammatory and chemotactic mediators, whereas M2-polarizing IL-4 showed no such association. IL-8 expression significantly correlated with early time to revision. Similar trends were observed for TNF-?, IFN-? and CCL3, while the opposite was detected for IL-4. However, none of the inflammatory mediators correlated with the markers of osteoclast activity or the RANKL/OPG ratio. The results highlight the importance of the inflammatory mediators, IFN-? and TLR4 in the pathogenesis of aseptic loosening; increased pro-inflammatory status was associated with early time to revision, whereas IL-4 correlated with longer implant survival. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jbm.a.35913
View details for PubMedID 27669374
The effect of local IL-4 delivery or CCL2 blockade on implant fixation and bone structural properties in a mouse model of wear particle induced osteolysis.
Journal of biomedical materials research. Part A
2016; 104 (9): 2255-2262
Total joint replacement is a cost-effective surgical procedure for patients with end-stage arthritis. Wear particle-induced chronic inflammation is associated with the development of periprosthetic osteolysis. Modulation of NF-?B signaling in macrophages, osteoclasts, and mesenchymal stem cells could potentially mitigate this disease. In the current study, we examined the effects of local delivery of decoy NF-?B oligo-deoxynucleotide (ODN) on wear particle-induced bone loss in a murine continuous femoral particle infusion model. Ultra-high molecular weight polyethylene particles (UHMWPE) with or without lipopolysaccharide (LPS) were infused via osmotic pumps into hollow titanium rods placed in the distal femur of mice for 4 weeks. Particle-induced bone loss was evaluated by ?CT, and immunohistochemical analysis of sections from the femur. Particle infusion alone resulted in reduced bone mineral density and trabecular bone volume fraction in the distal femur. The decoy ODN reversed the particle-associated bone volume fraction loss around the implant, irrespective of the presence of LPS. Particle-infusion with LPS increased bone mineral density in the distal femur compared with particle-infusion alone. NF-?B decoy ODN reversed or further increased the bone mineral density in the femur (3-6mm from the distal end) exposed to particles alone or particles plus LPS. NF-?B decoy ODN also inhibited macrophage infiltration and osteoclast number, but had no significant effects on osteoblast numbers in femurs exposed to wear particles and LPS. Our study suggests that targeting NF-?B activity via local delivery of decoy ODN has great potential to mitigate wear particle-induced osteolysis.Total joint replacement is a cost-effective surgical procedure for patients with end-stage arthritis. Chronic inflammation is crucial for the development of wear particle-associated bone loss. Modulation of NF-?B signaling in macrophages (pro-inflammatory cells), osteoclasts (bone-resorbing cells), and osteoblasts (bone-forming cells) could potentially mitigate this disease. Here we demonstrated that local delivery of decoy NF-?B oligo-deoxynucleotide (ODN) mitigated ultra-high molecular weight polyethylene (UHMWPE) wear particleinduced bone loss in a clinically relevant murine model. The protective effects of decoy ODN was associated with reduced macrophage infiltration and osteoclast activation, but had no significant effects on osteoblast numbers. Our study suggests that targeting NF-?B activity via local delivery of decoy ODN has great potential to mitigate wear particle-induced bone loss.
View details for DOI 10.1016/j.actbio.2016.05.038
View details for PubMedID 27260104
Mutant CCL2 protein coating mitigates wear particle-induced bone loss in a murine continuous polyethylene infusion model.
2016; 117: 1?9
Modulation of macrophage polarization and prevention of CCL2-induced macrophage chemotaxis are emerging strategies to reduce wear particle induced osteolysis and aseptic total joint replacement loosening. In this study, the effect of continuous IL-4 delivery or bioactive implant coating that constitutively releases a protein inhibitor of CCL2 signaling (7ND) on particle induced osteolysis were studied in the murine continuous femoral intramedullary particle infusion model. Polyethylene particles with or without IL-4 were infused into mouse distal femurs implanted with hollow titanium rods using subcutaneous infusion pumps. In another experimental group, particles were infused into the femur through a 7ND coated rod. After four weeks, fixation of the implant was assessed using a pullout test. The volume of trabecular bone and the geometry of the local cortical bone were assessed by µCT and the corresponding structural properties of the cortical bone determined by torsional testing. Continuous IL-4 delivery led to increased trabecular bone volume as well as enhanced local bone geometry and structural properties, while 7ND implant coating did not have effect on these parameters. The results suggest that local IL-4 treatment is a promising strategy to mitigate wear particle induced osteolysis. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jbm.a.35759
View details for PubMedID 27114284
Mesenchymal Stem Cells in the Aseptic Loosening of Total Joint Replacements.
Journal of biomedical materials research. Part A
Wear particle-induced osteolysis limits the long-term survivorship of total joint replacement (TJR). Monocyte/macrophages are the key cells of this adverse reaction. Monocyte Chemoattractant Protein-1 (MCP-1/CCL2) is the most important chemokine regulating trafficking of monocyte/macrophages in particle-induced inflammation. 7ND recombinant protein is a mutant of CCL2 that inhibits CCL2 signaling. We have recently developed a layer-by-layer (LBL) coating platform on implant surfaces that can release biologically active 7ND. In this study, we investigated the effect of 7ND on wear particle-induced bone loss using the murine continuous polyethylene (PE) particle infusion model with 7ND coating of a titanium rod as a local drug delivery device. PE particles were infused into hollow titanium rods with or without 7ND coating implanted in the distal femur for 4 weeks. Specific groups were also injected with RAW 264.7 as the reporter macrophages. Wear particle-induced bone loss and the effects of 7ND were evaluated by microCT, immunohistochemical staining, and bioluminescence imaging. Local delivery of 7ND using the LBL coating decreased systemic macrophage recruitment, the number of osteoclasts and wear particle-induced bone loss. The development of a novel orthopaedic implant coating with anti-CCL2 protein may be a promising strategy to mitigate peri-prosthetic osteolysis.
View details for DOI 10.1016/j.biomaterials.2016.11.039
View details for PubMedID 27918885
Establishment of Green Fluorescent Protein and Firefly Luciferase Expressing Mouse Primary Macrophages for In Vivo Bioluminescence Imaging
2015; 10 (11)
Characterization of macrophage polarizing cytokines in the aseptic loosening of total hip replacements.
Journal of orthopaedic research
2014; 32 (9): 1241-1246
Periprosthetic osteolysis remains as the main long-term complication of total joint replacement surgery. Research over four decades has established implant wear as the main culprit for chronic inflammation in the peri-implant tissues and macrophages as the key cells mediating the host reaction to implant-derived wear particles. Wear debris activated macrophages secrete inflammatory mediators that stimulate bone resorbing osteoclasts; thus bone loss in the peri-implant tissues is increased. However, the balance of bone turnover is not only dictated by osteoclast-mediated bone resorption but also by the formation of new bone by osteoblasts; under physiological conditions these two processes are tightly coupled. Increasing interest has been placed on the effects of wear debris on the cells of the bone-forming lineage. These cells are derived primarily from multipotent mesenchymal stem cells (MSCs) residing in bone marrow and the walls of the microvasculature. Accumulating evidence indicates that wear debris significantly impairs MSC-to-osteoblast differentiation and subsequent bone formation. In this review, we summarize the current understanding of the effects of biomaterial implant wear debris on MSCs. MSCs have several properties that make them attractive candidates for cell-based therapy. Emerging treatment options to improve initial implant integration and treat developing osteolytic lesions are also discussed. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jbm.a.35978
View details for PubMedID 27977880
Interaction of Materials and Biology in Total Joint Replacement - Successes, Challenges and Future Directions.
Journal of materials chemistry. B, Materials for biology and medicine
2014; 2 (41): 7094-7108
Aseptic loosening of hip replacements is driven by the macrophage reaction to wear particles. The extent of particle-induced macrophage activation is dependent on the state of macrophage polarization, which is dictated by the local cytokine microenvironment. The aim of the study was to characterize cytokine microenvironment surrounding failed, loose hip replacements with an emphasis on identification of cytokines that regulate macrophage polarization. Using qRT-PCR, the expression of interferon gamma (IFN-?), interleukin-4 (IL-4), granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-13, and IL-17A was low and similar to the expression in control synovial tissues of patients undergoing primary hip replacement. Using immunostaining, no definite source of IFN-? or IL-4 could be identified. IL-17A positive cells, identified as mast cells by double staining, were detected but their number was significantly reduced in interface tissues compared to the controls. Significant up-regulation of IL-10, M-CSF, IL-8, CCL2-4, CXCL9-10, CCL22, TRAP, cathepsin K, and down regulation of OPG was seen in the interface tissues, while expression of TNF-?, IL-1?, and CD206 were similar between the conditions. It is concluded that at the time of the revision surgery the peri-implant macrophage phenotype has both M1 and M2 characteristics and that the phenotype is regulated by other local and systemic factors than traditional macrophage polarizing cytokines. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
View details for DOI 10.1002/jor.22658
View details for PubMedID 24897980
Innate Immune Reactions in Septic and Aseptic Osteolysis around Hip Implants.
Journal of long-term effects of medical implants
2014; 24 (4): 283-296
Total joint replacement (TJR) has revolutionized the treatment of end-stage arthritic disorders. This success is due, in large part, to a clear understanding of the important interaction between the artificial implant and the biology of the host. All surgical procedures in which implants are placed in the body evoke an initial inflammatory reaction, which generally subsides over several weeks. Thereafter, a series of homeostatic events occur leading to progressive integration of the implant within bone and the surrounding musculoskeletal tissues. The eventual outcome of the operation is dependent on the characteristics of the implant, the precision of the surgical technique and operative environment, and the biological milieu of the host. If these factors and events are not optimal, adverse events can occur such as the development of chronic inflammation, progressive bone loss due to increased production of degradation products from the implant (periprosthetic osteolysis), implant loosening or infection. These complications can lead to chronic pain and poor function of the joint reconstruction, and may necessitate revision surgery or removal of the prosthesis entirely. Recent advances in engineering, materials science, and the immunological aspects associated with orthopaedic implants have fostered intense research with the hope that joint replacements will last a lifetime, and facilitate pain-free, normal function.
View details for DOI 10.1039/C4TB01005A
View details for PubMedID 25541591
The response of macrophages to titanium particles is determined by macrophage polarization
2013; 9 (11): 9229-9240
According to the long-standing definition, septic and aseptic total joint replacement loosening are two distinct conditions with little in common. Septic joint replacement loosening is driven by bacterial infection whereas aseptic loosening is caused by biomaterial wear debris released from the bearing surfaces. However, recently it has been recognized that the mechanisms that drive macrophage activation in septic and aseptic total joint replacement loosening resemble each other. In particular, accumulating evidence indicates that in addition to mediating bacterial recognition and the subsequent inflammatory reaction, toll-like receptors (TLRs) and their ligands, pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPS), play a key role in wear debris-induced inflammation and macrophage activation. In addition, subclinical bacterial biofilms have been identified from some cases of seemingly aseptic implant loosening. Furthermore, metal ions released from some total joint replacements can activate TLR signaling similar to bacterial derived PAMPs. Likewise, metal ions can function as haptens activating the adaptive immune system similar to bacterial derived antigens. Thus, it appears that aseptic and septic joint replacement loosening share similar underlying pathomechanisms and that this strict dichotomy to sterile aseptic and bacterial-caused septic implant loosening is somewhat questionable. Indeed, rather than being two, well-defined clinical entities, peri-implant osteolysis is, in fact, a spectrum of conditions in which the specific clinical picture is determined by complex interactions of multiple local and systemic factors.
View details for PubMedID 25747031
SURGERY Adverse reactions to metal-on-metal implants
NATURE REVIEWS RHEUMATOLOGY
2013; 9 (1): 5-6
NF-?B as a Therapeutic Target in Inflammatory-Associated Bone Diseases.
Advances in protein chemistry and structural biology
2017; 107: 117?54
Aseptic loosening of total joint replacements is driven by the reaction of macrophages to foreign body particles released from the implant. It was hypothesized that the macrophages' response to these particles is dependent, in addition to particle characteristics and contaminating biomolecules, on the state of macrophage polarization as determined by the local cytokine microenvironment. To test this hypothesis we differentiated M1 and M2 macrophages from human peripheral blood monocytes and compared their responses to titanium particles using genome-wide microarray analysis and a multiplex cytokine assay. In comparison to non-activated M0 macrophages, the overall chemotactic and inflammatory responses to titanium particles were greatly enhanced in M1 macrophages and effectively suppressed in M2 macrophages. In addition, the genome-wide approach revealed several novel, potentially osteolytic, particle-induced mediators, and signaling pathway analysis suggested the involvement of toll-like and nod-like receptor signaling in particle recognition. It is concluded that the magnitude of foreign body reaction caused by titanium particles is dependent on the state of macrophage polarization. Thus, by limiting the action of M1 polarizing factors, e.g. bacterial biofilm formation, in peri-implant tissues and promoting M2 macrophage polarization by biomaterial solutions or pharmacologically, it might be possible to restrict wear-particle-induced inflammation and osteolysis.
View details for DOI 10.1016/j.actbio.2013.06.027
View details for Web of Science ID 000326902500044
View details for PubMedID 23827094
Iron oxide nanoparticles inhibit tumour growth by inducing pro-inflammatory macrophage polarization in tumour tissues.
2016; 11 (11): 986-994
Inflammation is a defensive mechanism for pathogen clearance and maintaining tissue homeostasis. In the skeletal system, inflammation is closely associated with many bone disorders including fractures, nonunions, periprosthetic osteolysis (bone loss around orthopedic implants), and osteoporosis. Acute inflammation is a critical step for proper bone-healing and bone-remodeling processes. On the other hand, chronic inflammation with excessive proinflammatory cytokines disrupts the balance of skeletal homeostasis involving osteoblastic (bone formation) and osteoclastic (bone resorption) activities. NF-?B is a transcriptional factor that regulates the inflammatory response and bone-remodeling processes in both bone-forming and bone-resorption cells. In vitro and in vivo evidences suggest that NF-?B is an important potential therapeutic target for inflammation-associated bone disorders by modulating inflammation and bone-remodeling process simultaneously. The challenges of NF-?B-targeting therapy in bone disorders include: (1) the complexity of canonical and noncanonical NF-?B pathways; (2) the fundamental roles of NF-?B-mediated signaling for bone regeneration at earlier phases of tissue damage and acute inflammation; and (3) the potential toxic effects on nontargeted cells such as lymphocytes. Recent developments of novel inhibitors with differential approaches to modulate NF-?B activity, and the controlled release (local) or bone-targeting drug delivery (systemic) strategies, have largely increased the translational application of NF-?B therapy in bone disorders. Taken together, temporal modulation of NF-?B pathways with the combination of recent advanced bone-targeting drug delivery techniques is a highly translational strategy to reestablish homeostasis in the skeletal system.
View details for DOI 10.1016/bs.apcsb.2016.11.002
View details for PubMedID 28215222
Inflammation, fracture and bone repair.
2016; 86: 119-130
Until now, the Food and Drug Administration (FDA)-approved iron supplement ferumoxytol and other iron oxide nanoparticles have been used for treating iron deficiency, as contrast agents for magnetic resonance imaging and as drug carriers. Here, we show an intrinsic therapeutic effect of ferumoxytol on the growth of early mammary cancers, and lung cancer metastases in liver and lungs. In vitro, adenocarcinoma cells co-incubated with ferumoxytol and macrophages showed increased caspase-3 activity. Macrophages exposed to ferumoxytol displayed increased mRNA associated with pro-inflammatory Th1-type responses. In vivo, ferumoxytol significantly inhibited growth of subcutaneous adenocarcinomas in mice. In addition, intravenous ferumoxytol treatment before intravenous tumour cell challenge prevented development of liver metastasis. Fluorescence-activated cell sorting (FACS) and histopathology studies showed that the observed tumour growth inhibition was accompanied by increased presence of pro-inflammatory M1 macrophages in the tumour tissues. Our results suggest that ferumoxytol could be applied 'off label' to protect the liver from metastatic seeds and potentiate macrophage-modulating cancer immunotherapies.
View details for DOI 10.1038/nnano.2016.168
View details for PubMedID 27668795
Engineered protein coatings to improve the osseointegration of dental and orthopaedic implants.
2016; 83: 269-282
The reconstitution of lost bone is a subject that is germane to many orthopaedic conditions including fractures and non-unions, infection, inflammatory arthritis, osteoporosis, osteonecrosis, metabolic bone disease, tumors, and periprosthetic particle-associated osteolysis. In this regard, the processes of acute and chronic inflammation play an integral role. Acute inflammation is initiated by endogenous or exogenous adverse stimuli, and can become chronic in nature if not resolved by normal homeostatic mechanisms. Dysregulated inflammation leads to increased bone resorption and suppressed bone formation. Crosstalk amongst inflammatory cells (polymorphonuclear leukocytes and cells of the monocyte-macrophage-osteoclast lineage) and cells related to bone healing (cells of the mesenchymal stem cell-osteoblast lineage and vascular lineage) is essential to the formation, repair and remodeling of bone. In this review, the authors provide a comprehensive summary of the literature related to inflammation and bone repair. Special emphasis is placed on the underlying cellular and molecular mechanisms, and potential interventions that can favorably modulate the outcome of clinical conditions that involve bone repair.
View details for DOI 10.1016/j.bone.2016.02.020
View details for PubMedID 26946132
Lipoteichoic acid modulates inflammatory response in macrophages after phagocytosis of titanium particles through Toll-like receptor 2 cascade and inflammasomes
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2016; 104 (2): 435-444
The effects of immunomodulation by macrophage subsets on osteogenesis in vitro
STEM CELL RESEARCH & THERAPY
Aging Affects Bone Marrow Macrophage Polarization: Relevance to Bone Healing.
Regenerative engineering and translational medicine
2016; 2 (2): 98?104
Here we present the design of an engineered, elastin-like protein (ELP) that is chemically modified to enable stable coatings on the surfaces of titanium-based dental and orthopaedic implants by novel photocrosslinking and solution processing steps. The ELP includes an extended RGD sequence to confer bio-signaling and an elastin-like sequence for mechanical stability. ELP thin films were fabricated on cp-Ti and Ti6Al4V surfaces using scalable spin and dip coating processes with photoactive covalent crosslinking through a carbene insertion mechanism. The coatings withstood procedures mimicking dental screw and hip replacement stem implantations, a key metric for clinical translation. They promoted rapid adhesion of MG63 osteoblast-like cells, with over 80% adhesion after 24 h, compared to 38% adhesion on uncoated Ti6Al4V. MG63 cells produced significantly more mineralization on ELP coatings compared to uncoated Ti6Al4V. Human bone marrow mesenchymal stem cells (hMSCs) had an earlier increase in alkaline phosphatase activity, indicating more rapid osteogenic differentiation and mineral deposition on adhesive ELP coatings. Rat tibia and femur in vivo studies demonstrated that cell-adhesive ELP-coated implants increased bone-implant contact area and interfacial strength after one week. These results suggest that ELP coatings withstand surgical implantation and promote rapid osseointegration, enabling earlier implant loading and potentially preventing micromotion that leads to aseptic loosening and premature implant failure.
View details for DOI 10.1016/j.biomaterials.2015.12.030
View details for PubMedID 26790146
The biological response to orthopaedic implants for joint replacement: Part I: Metals.
Journal of biomedical materials research. Part B, Applied biomaterials
Macrophages are an important component of the inflammatory cascade by initiating and modulating the processes leading to tissue regeneration and bone healing. Depending on the local environment, macrophages can be polarized into M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotypes. In order to assess the effects of aging on macrophage function, bone marrow macrophage polarization using primary bone marrow macrophages (BMMs) from young (8 weeks old) and aged (72 weeks old) wild-type male C57BL/6J mice was analyzed. Fluorescence-activated cell sorting (FACS) analysis (CD11b, iNOS, CD206), qRT-PCR (iNOS, TNF-?, CD206, Arginase 1), and ELISA (TNF-?, IL-1ra) were performed to compare the M1 and M2 phenotypic markers in young and aged mouse macrophages. Once M1 and M2 macrophage phenotypes were confirmed, the results showed that TNF-? mRNA was significantly upregulated in aged M1s after interferon gamma (INF-?) exposure. Arginase 1 and CD206 mRNA expression were still upregulated with IL4 stimulation in aged macrophages, but to a lesser extend than those from younger animals. TNF-? secretion was also significantly increased in aged M1s compared to young M1s, following lipopolysaccharide (LPS) exposure. However, the IL-1ra secretion did not increase accordingly in aged mice. The results demonstrate that, compared to younger animals, aging of bone marrow derived macrophages increases the resting levels of oxidative stress, and the ratios of pro- to anti-inflammatory markers. These age-related changes in macrophage polarization may explain in part the attenuated response to adverse stimuli and delay in processes such as fracture healing seen in the elderly.Bone healing is a complex process that involves both biological and mechanical factors. Macrophages are key cells that regulate the events involved in bone healing, especially the initial inflammatory phase. In this biological cascade of events, macrophages present as different functional phenotypes including uncommitted (M0), pro-inflammatory (M1), and anti-inflammatory (M2), a process called macrophage polarization. A clear understanding of the effects of aging on macrophage polarization is critical to modulating adverse events such as fractures, atraumatic bone loss, and tissue regeneration in an aging population.
View details for DOI 10.1007/s40883-016-0016-5
View details for PubMedID 28138512
Decreased osteogenesis in mesenchymal stem cells derived from the aged mouse is associated with enhanced NF-?B activity.
Journal of orthopaedic research : official publication of the Orthopaedic Research Society
Joint replacement is a commonly performed, highly successful orthopaedic procedure, for which surgeons have a large choice of different materials and implant designs. The materials used for joint replacement must be both biologically acceptable to minimize adverse local tissue reactions, and robust enough to support weight bearing during common activities of daily living. Modern joint replacements are made from metals and their alloys, polymers, ceramics, and composites. This review focuses on the biological response to the different biomaterials used for joint replacement. In general, modern materials for joint replacement are well tolerated by the body as long as they are in bulk (rather than in particulate or ionic) form, are mechanically stable and noninfected. If the latter conditions are not met, the prosthesis will be associated with an acute/chronic inflammatory reaction, peri-prosthetic osteolysis, loosening and failure. This article (Part 1 of 2) is dedicated to the use of metallic devices in orthopaedic surgery including the associated biological response to metallic byproducts is a review of the basic science literature regarding this topic. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.
View details for DOI 10.1002/jbm.b.33734
View details for PubMedID 27328111
Local delivery of mutant CCL2 protein-reduced orthopaedic implant wear particle-induced osteolysis and inflammation in vivo.
Journal of orthopaedic research
2016; 34 (1): 58-64
Aging is associated with significant bone loss and delayed fracture healing. NF-?B activation is highly correlated with inflammatory-associated bone diseases including infection, wear particle exposure, and chronic inflammation during natural aging processes. The critical roles of NF-?B in both the pro-inflammatory response and osteoclast-mediated bone resorption have been well defined. However, the biological effects of NF-?B activation in mesenchymal stem cell (MSC)-mediated bone formation remain largely unknown. In the current study, bone marrow-MSCs were isolated from young (8 weeks old) and aged (72 weeks old) mice. NF-?B activity in MSCs at basal levels and under different biological conditions were determined by our recently established lentiviral vector-based luciferase reporter assay. We found that NF-?B activity was increased in aged MSCs at basal levels or when exposed to low dose (10ng/ml or 100ng/ml) lipopolysaccharide (LPS); this effect was not seen when the cells were exposed to higher dose (1?g/ml) LPS. During osteogenesis, NF-?B activity was increased in aged MSCs at week 1 and 2, but showed no significant difference at week 3. Both Smurf2 and TAZ, the NF-?B target genes that regulate osteogenic differentiation, were increased in aged MSCs. In addition, the expression of RANKL was dramatically increased, and OPG was decreased in aged MSCs. Our findings suggest that targeting NF-?B activity in MSCs has the potential to modulate aging-associated bone loss, or enhance bone-healing in aged patients. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jor.23270
View details for PubMedID 27105133
NF-B decoy oligodeoxynucleotide inhibits wear particle-induced inflammation in a murine calvarial model
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2015; 103 (12): 3872-3878
Total joint replacement (TJR) has been widely used as a standard treatment for late-stage arthritis. One challenge for long-term efficacy of TJR is the generation of ultra-high molecular weight polyethylene wear particles from the implant surface that activates an inflammatory cascade that may lead to bone loss, prosthetic loosening and eventual failure of the procedure. Here we investigate the efficacy of local administration of mutant CCL2 proteins, such as 7ND, on reducing wear particle-induced inflammation and osteolysis in vivo using a mouse calvarial model. Mice were treated with local injection of 7ND or phosphate buffered saline (PBS) every other day for up to 14 days. Wear particle-induced osteolysis and the effects of 7ND treatment were evaluated using micro-CT, histology and immunofluorescence staining. Compared with the PBS control, 7ND treatment significantly decreased wear particle-induced osteolysis, which led to a higher bone volume fraction and bone mineral density. Furthermore, immunofluorescence staining showed 7ND treatment decreased the number of recruited inflammatory cells and osteoclasts. Together, our results support the feasibility of local delivery of 7ND for mitigating wear particle-induced inflammation and osteolysis, which may offer a promising strategy for extending the life time of TJRs. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jor.22977
View details for PubMedID 26174978
Modulation of mouse macrophage polarization in vitro using IL-4 delivery by osmotic pumps
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2015; 103 (4): 1339-1345
Wear particles induce periprosthetic inflammation and osteolysis through activation of Nuclear Factor kappa B (NF-?B) in macrophages, which up-regulates the downstream target gene expression for pro-inflammatory cytokines. It is hypothesized that direct suppression of NF-?B activity in the early phases of this disorder is a therapeutic strategy for mitigating the inflammatory response to wear particles, potentially mitigating osteolysis. NF-?B activity can be suppressed via competitive binding with double stranded NF-?B decoy oligodeoxynucleotides (ODNs) that block this transcription factor from binding to the promoter regions of targeted genes. In this murine calvarial study, clinically relevant polyethylene particles (PEs) with/without ODN were subcutaneously injected over the calvarial bone. In the presence of PE particles, macrophages migrated to the inflammatory site and induced tumor necrosis factor alpha (TNF-?) and Receptor Activator of Nuclear Factor kappa-B Ligand (RANKL) expression, resulting in an increase in the number of osteoclasts. Local injections of ODN mitigated the expression of TNF-?, RANKL, and induced the expression of two anti-inflammatory, anti-resorptive cytokines: Interleukin-1 receptor antagonist (IL-1ra) and Osteoprotegerin (OPG). Local intervention with NF-?B decoy ODN in early cases of particle-induced inflammation in which the prosthesis is still salvageable may potentially preserve periprosthetic bone stock. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jbm.a.35532
View details for Web of Science ID 000363879200018
NF-kappa B Decoy Oligodeoxynucleotide Enhanced Osteogenesis in Mesenchymal Stem Cells Exposed to Polyethylene Particle
TISSUE ENGINEERING PART A
2015; 21 (5-6): 875-883
Modulation of macrophage polarization is emerging as promising means to mitigate wear particle-induced inflammation and periprosthetic osteolysis. As a model for continuous local drug delivery, we used miniature osmotic pumps to deliver IL-4 in order to modulate macrophage polarization in vitro from nonactivated M0 and inflammatory M1 phenotypes towards a tissue regenerative M2 phenotype. Pumps delivered IL-4 into vials containing mouse bone marrow macrophage (mBMM) media. This conditioned media (CM) was collected at seven day intervals up to four weeks (week 1 to week 4 samples). IL-4 concentration in the CM was determined by ELISA and its biological activity was assayed by exposing M0 and M1 mBMMs to week 1 or week 4 CM. The IL-4 concentration in the CM approximated the mathematically calculated amount, and its biological activity was well retained, as both M0 and M1 macrophages exposed to either the week 1 or week 4 CM assumed M2-like phenotype as determined by qRT-PCR, ELISA, and immunocytochemistry. The results show that IL-4 can be delivered using osmotic pumps and that IL-4 delivered can modulate macrophage phenotype. Results build a foundation for in vivo studies using our previously validated animal models and provide possible strategies to locally mitigate wear particle-induced macrophage activation and periprosthetic osteolysis. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014.
View details for DOI 10.1002/jbm.a.35278
View details for Web of Science ID 000350395300006
Exposure of polyethylene particles induces interferon-gamma expression in a natural killer T lymphocyte and dendritic cell coculture system in vitro: A preliminary study
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2015; 103 (1): 71-75
Mutant monocyte chemoattractant protein 1 protein attenuates migration of and inflammatory cytokine release by macrophages exposed to orthopedic implant wear particles
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2014; 102 (9): 3291-3297
Excessive generation of wear particles after total joint replacement may lead to local inflammation and periprosthetic osteolysis. Modulation of the key transcription factor NF-?B in immune cells could potentially mitigate the osteolytic process. We previously showed that local delivery of ultra-high molecular weight polyethylene (UHMWPE) particles recruited osteoprogenitor cells and reduced osteolysis. However, the biological effects of modulating the NF-?B signaling pathway on osteoprogenitor/mesenchymal stem cells (MSCs) remain unclear. Here we showed that decoy oligodeoxynucleotide (ODN) increased cell viability when primary murine MSCs were exposed to UHMWPE particles, but had no effects on cellular apoptosis. Decoy ODN increased TGF-?1 and osteoprotegerin in MSCs exposed to UHMWPE particles. Mechanistic studies showed that decoy ODN up-regulated osteoprotegerin expression through a TGF-?1 dependent pathway. By measuring alkaline phosphatase activity, osteocalcin levels, Runx2 and osteopontin expression, and performing a bone mineralization assay, we found that decoy ODN increased MSC osteogenic ability when the cells were exposed to UHMWPE particles. Furthermore, the cellular response to decoy ODN and UHMWPE particles with regards to cell phenotype, cell viability and osteogenic ability were confirmed using primary human MSCs. Our results suggest that modulation of wear particle induced inflammation by NF-?B decoy ODN had no adverse effects on MSCs, and may potentially further mitigate peri-prosthetic osteolysis by protecting MSC viability and osteogenic ability.
View details for DOI 10.1089/ten.tea.2014.0144
View details for Web of Science ID 000350549500002
Suppression of wear-particle-induced pro-inflammatory cytokine and chemokine production in macrophages via NF-kappa B decoy oligodeoxynucleotide: A preliminary report
2014; 10 (8): 3747-3755
Wear particles generated from total joint replacements can stimulate macrophages to release chemokines, such as monocyte chemoattractant protein 1 (MCP-1), which is the most important chemokine regulating systemic and local cell trafficking and infiltration of monocyte/macrophages in chronic inflammation. One possible strategy to curtail the adverse events associated with wear particles is to mitigate migration and activation of monocyte/macrophages. The purpose of this study is to modulate the adverse effects of particulate biomaterials and inflammatory stimuli such as endotoxin by interfering with the biological effects of the chemokine MCP-1. In the current study, the function of MCP-1 was inhibited by the mutant MCP-1 protein called 7ND, which blocks its receptor, the C-C chemokine receptor type 2 (CCR2) on macrophages. Addition of 7ND decreased MCP-1-induced migration of THP-1 cells in cell migration experiments in a dose-dependent manner. Conditioned media from murine macrophages exposed to clinically relevant polymethylmethacrylate (PMMA) particles with/without endotoxin [lipopolysaccharide (LPS)] had a chemotactic effect on human macrophages, which was decreased dramatically by 7ND. 7ND demonstrated no adverse effects on the viability of macrophages, and the capability of mesenchymal stem cells (MSCs) to form bone at the doses tested. Finally, proinflammatory cytokine production was mitigated when macrophages were exposed to PMMA particles with/without LPS in the presence of 7ND. Our studies confirm that the MCP-1 mutant protein 7ND can decrease macrophage migration and inflammatory cytokine release without adverse effects at the doses tested. Local delivery of 7ND at the implant site may provide a therapeutic strategy to diminish particle-associated periprosthetic inflammation and osteolysis. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
View details for DOI 10.1002/jbm.a.34981
View details for Web of Science ID 000339965200040
Chronic inflammation in biomaterial-induced periprosthetic osteolysis: NF-?B as a therapeutic target.
2014; 10 (1): 1-10
Total joint replacement (TJR) is a very cost-effective surgery for end-stage arthritis. One important goal is to decrease the revision rate especially because TJR has been extended to younger patients. Continuous production of ultra-high molecular weight polyethylene (UHMWPE) wear particles induces macrophage infiltration and chronic inflammation, which can lead to peri-prosthetic osteolysis. Targeting individual pro-inflammatory cytokines directly has not reversed the osteolytic process in clinical trials, due to compensatory upregulation of other pro-inflammatory factors. We hypothesized that targeting the important transcription factor NF-?B could mitigate the inflammatory response to wear particles, potentially diminishing osteolysis. In the current study, we suppressed NF-?B activity in mouse RAW264.7 and human THP1 macrophage cell lines, as well as primary mouse and human macrophages, via competitive binding with double strand decoy oligodeoxynucleotide (ODN) containing an NF-?B binding element. We found that macrophage exposure to UHMWPE particles induced multiple pro-inflammatory cytokine and chemokine expression including TNF-?, MCP1, MIP1? and others. Importantly, the decoy ODN significantly suppressed the induced cytokine and chemokine expression in both murine and human macrophages, and resulted in suppression of macrophage recruitment. The strategic use of decoy NF-?B ODN, delivered locally, could potentially diminish particle-induced peri-prosthetic osteolysis.
View details for DOI 10.1016/j.actbio.2014.04.034
View details for Web of Science ID 000339459500037
Macrophage polarization and activation in response to implant debris: influence by "particle disease" and "ion disease".
Journal of long-term effects of medical implants
2014; 24 (4): 267-281
Biomaterial-induced tissue responses in patients with total joint replacement are associated with the generation of wear particles, which may lead to chronic inflammation and local bone destruction (periprosthetic osteolysis). Inflammatory reactions associated with wear particles are mediated by several important signaling pathways, the most important of which involves the transcription factor NF-?B. NF-?B activation is essential for macrophage recruitment and maturation, as well as the production of pro-inflammatory cytokines and chemokines such as TNF-?, IL-1?, IL-6 and MCP1. In addition, NF-?B activation contributes to osteoclast differentiation and maturation via RANK/RANKL signaling, which increases bone destruction and reduces bone formation. Targeting individual downstream cytokines directly (such as TNF-? or IL-1?) may not effectively prevent wear particle induced osteolysis. A more logical upstream therapeutic approach may be provided by direct modulation of the core I?B/IKK?/?/NF-?B signaling pathway in the local environment. However, the timing, dose and strategy for administration should be considered. Suppression of chronic inflammation via inhibition of NF-?B activity in patients with malfunctioning joint replacements may be an effective strategy to mitigate wear particle induced periprosthetic osteolysis.
View details for DOI 10.1016/j.actbio.2013.09.034
View details for PubMedID 24090989
Novel biological strategies for treatment of wear particle-induced periprosthetic osteolysis of orthopaedic implants for joint replacement.
Journal of the Royal Society, Interface / the Royal Society
2014; 11 (93): 20130962-?
Macrophages derive from human embryonic and fetal stem cells and from human bone marrow-derived blood monocytes. They play a major homeostatic role in tissue remodeling and maintenance facilitated by apoptotic "eat me" opsonins like CRP, serum amyloid P, C1q, C3b, IgM, ficolin, and surfactant proteins. Three subsets of monocytes, classic, intermediate, and nonclassic, are mobilized and transmigrate to tissues. Implant-derived wear particles opsonized by danger signals regulate macrophage priming, polarization (M1, M2, M17, and Mreg), and activation. CD14+ monocytes in healthy controls and CD16+ monocytes in inflammation differentiate/polarize to foreign body giant cells/osteoclasts or inflammatory dendritic cells (infDC). These danger signal opsonins can be pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs), but in aseptic loosening, usually are damage-associated molecular patterns (DAMPs). Danger signal-opsonized particles elicit "particle disease" and aseptic loosening. They provide soluble and cell membrane-bound co-stimulatory signals that can lead to cell-mediated immune reactions to metal ions. Metal-on-metal implant failure has disclosed that quite like Ni2+, its neighbor in the periodic table Co2+ can directly activate toll-like receptor 4 (TLR4) as a lipopolysaccharide-mimic. "Ion disease" concept needs to be incorporated into the "particle disease" concept, due to the toxic, immune, and inflammatory potential of metal ions.
View details for PubMedID 25747030
Mutant MCP-1 protein delivery from layer-by-layer coatings on orthopedic implants to modulate inflammatory response
2013; 34 (38): 10287-10295
Wear particles and by-products from joint replacements and other orthopaedic implants may result in a local chronic inflammatory and foreign body reaction. This may lead to persistent synovitis resulting in joint pain and swelling, periprosthetic osteolysis, implant loosening and pathologic fracture. Strategies to modulate the adverse effects of wear debris may improve the function and longevity of joint replacements and other orthopaedic implants, potentially delaying or avoiding complex revision surgical procedures. Three novel biological strategies to mitigate the chronic inflammatory reaction to orthopaedic wear particles are reported. These include (i) interference with systemic macrophage trafficking to the local implant site, (ii) modulation of macrophages from an M1 (pro-inflammatory) to an M2 (anti-inflammatory, pro-tissue healing) phenotype in the periprosthetic tissues, and (iii) local inhibition of the transcription factor nuclear factor kappa B (NF-?B) by delivery of an NF-?B decoy oligodeoxynucleotide, thereby interfering with the production of pro-inflammatory mediators. These three approaches have been shown to be viable strategies for mitigating the undesirable effects of wear particles in preclinical studies. Targeted local delivery of specific biologics may potentially extend the lifetime of orthopaedic implants.
View details for DOI 10.1098/rsif.2013.0962
View details for PubMedID 24478281
Toll-like receptors in human chondrocytes and osteoarthritic cartilage
2013; 84 (6): 585-592
Total joint replacement (TJR) is a common and effective surgical procedure for hip or knee joint reconstruction. However, the production of wear particles is inevitable for all TJRs, which activates macrophages and initiates an inflammatory cascade often resulting in bone loss, prosthetic loosening and eventual TJR failure. Macrophage Chemoattractant Protein-1 (MCP-1) is one of the most potent cytokines responsible for macrophage cell recruitment, and previous studies suggest that mutant MCP-1 proteins such as 7ND may be used as a decoy drug to block the receptor and reduce inflammatory cell recruitment. Here we report the development of a biodegradable, layer-by-layer (LBL) coating platform that allows efficient loading and controlled release of 7ND proteins from the surface of orthopedic implants using as few as 14 layers. Scanning electron microscopy and fluorescence imaging confirmed effective coating using the LBL procedure on titanium rods. 7ND protein loading concentration and release kinetics can be modulated by varying the polyelectrolytes of choice, the polymer chemistry, the pH of the polyelectrolyte solution, and the degradation rate of the LBL assembly. The released 7ND from LBL coating retained its bioactivity and effectively reduced macrophage migration towards MCP-1. Finally, the LBL coating remained intact following a femoral rod implantation procedure as determined by immunostaining of the 7ND coating. The LBL platform reported herein may be applied for in situ controlled release of 7ND protein from orthopedic implants, to reduce wear particle-induced inflammatory responses in an effort to prolong the lifetime of implants.
View details for DOI 10.1016/j.biomaterials.2013.09.028
View details for Web of Science ID 000328094600054
Macrophages-Key cells in the response to wear debris from joint replacements
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2013; 101 (10): 3033-3045
RANKL in the osteolysis of AES total ankle replacement implants
2012; 51 (3): 546-552
Degenerating cartilage releases potential danger signals that react with Toll-like receptor (TLR) type danger receptors. We investigated the presence and regulation of TLR1, TLR2, and TLR9 in human chondrocytes.We studied TLR1, TLR2, TLR4, and TLR9 mRNA (qRT-PCR) and receptor proteins (by immunostaining) in primary mature healthy chondrocytes, developing chondrocytes, and degenerated chondrocytes in osteoarthritis (OA) tissue sections of different OARSI grades. Effects of a danger signal and of a pro-inflammatory cytokine on TLRs were also studied.In primary 2D-chondrocytes, TLR1 and TLR2 were strongly expressed. Stimulation of 2D and 3D chondrocytes with a TLR1/2-specific danger signal increased expression of TLR1 mRNA 1.3- to 1.8-fold, TLR2 mRNA 2.6- to 2.8-fold, and TNF-? mRNA 4.5- to 9-fold. On the other hand, TNF-? increased TLR1 mRNA] expression 16-fold, TLR2 mRNA expression 143- to 201-fold, and TNF-? mRNA expression 131- to 265-fold. TLR4 and TLR9 mRNA expression was not upregulated. There was a correlation between worsening of OA and increased TLR immunostaining in the superficial and middle cartilage zones, while chondrocytes assumed a CD166(×) progenitor phenotype. Correspondingly, TLR expression was high soon after differentiation of mesenchymal stem cells to chondrocytes. With maturation, it declined (TLR2, TLR9).Mature chondrocytes express TLR1 and TLR2 and may react to cartilage matrix/chondrocyte-derived danger signals or degradation products. This leads to synthesis of pro-inflammatory cytokines, which stimulate further TLR and cytokine expression, establishing a vicious circle. This suggests that OA can act as an autoinflammatory disease and links the old mechanical wear-and-tear concept with modern biochemical views of OA. These findings suggest that the chondrocyte itself is the earliest and most important inflammatory cell in OA.
View details for DOI 10.3109/17453674.2013.854666
View details for Web of Science ID 000328281100014
View details for PubMedID 24237425
Profile of toll-like receptor-positive cells in septic and aseptic loosening of total hip arthroplasty implants.
Journal of biomedical materials research. Part A
2010; 94 (1): 84-92
Peri-implant tissue reactions in failed total ankle replacement (TAR) are characterized by early developing peri-implant osteolysis. The hypothesis of the study was that this reaction is mediated by receptor activator of nuclear factor kappa B ligand (RANKL). Samples of peri-prosthetic tissues from failed TAR implants were stained for macrophages, RANKL, its receptor RANK and osteoprotegerin (OPG), and compared to control samples. The failed TAR implants were surrounded by implant capsule, synovial lining-like interface membrane or necrotic tissues. Infiltrating scavenger receptor I positive CD163(+) macrophages were frequent, in particular around necrotic soft tissues or bone sequestrate, and possibly in part formed due to ischemia and mechanical factors. In contrast, implant-derived wear debris was scanty. Still many RANK(+) macrophages were often seen in close contact with RANKL(+) mesenchymal cells, whereas OPG was mostly located at a distance in vascular endothelial cells. Foreign body giant cells were frequent. RANKL seems to stimulate locally accumulated CD163(+) RANK-expressing cells to fusion, which leads to the local formation of multinuclear foreign body giant cells (and probably of osteoclasts). Therefore, peri-implant osteolysis in early TAR implant failure seems to be caused by the RANKL-driven chronic foreign body inflammation directed against, not implant-derived particles, but against necrotic autologous tissues.
View details for DOI 10.1016/j.bone.2012.05.007
View details for Web of Science ID 000307617400029
View details for PubMedID 22627031
Titanium particles modulate expression of Toll-like receptor proteins
JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A
2010; 92A (4): 1528-1537
Toll-Like Receptors and Aseptic Loosening of Hip Endoprosthesis-A Potential to Respond against Danger Signals?
JOURNAL OF ORTHOPAEDIC RESEARCH
2010; 28 (2): 184-190
Distinction between the two major complications of total hip replacement surgery, septic bacterial culture-positive and aseptic bacterial culture-negative osteolysis and loosening, is difficult due to the eventual role of bacterial remnants and biofilms, which are recognized by cells provided by toll-like receptors (TLRs) of the innate immune system. It was hypothesized that cell typing and TLR mapping might provide new information on the pathomechanisms of loosening. To test this hypothesis, septic (n = 10) and aseptic (n = 5) interface tissue as well as mildly inflamed osteoarthritic synovial membrane (n = 5) samples were characterized and compared using antibodies against several cell line-specific markers, including fibroblast, monocyte/macrophage, T cell, B cell, plasma cell and neutrophil markers, and TLRs. In osteoarthritic synovium, TLR-positive cells were restricted to surface tissues and only few inflammatory cells were detected, whereas aseptic interface was heavily infiltrated with monocyte/macrophages, which were also the major TLR-positive cell type rendering the tissue reactive to TLR ligands. Interestingly, septic cases contained also neutrophil and lymphocyte infiltrates of which especially B-cell infiltrates might be clinically useful in discriminating the two major complications of the joint replacement surgery. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.
View details for DOI 10.1002/jbm.a.32674
View details for PubMedID 20127718
Microbial antigens mediate HLA-B27 diseases via TLRs
JOURNAL OF AUTOIMMUNITY
2009; 32 (3-4): 172-177
Bacterial remnants and subclinical biofilms residing on prosthesis surfaces have been speculated to play a role in hip implant loosening by opsonizing otherwise relatively inert wear particles. The innate immune system recognizes these microbial pathogen-associated molecular patterns (PAMPs) using Toll-like receptors (TLRs). Our objective was to evaluate the possible presence of TLRs in aseptic synovial membrane-like interface tissue. Bacterial culture-negative, aseptic (n = 4) periprosthetic synovial membrane-like tissue was compared to osteoarthritis synovial membrane (n = 5) for the presence of cells positive for all known human functional TLRs, stained using specific antibodies by immunohistochemistry, and evaluated using morphometry. In comparison to osteoarthtritic synovium, the number of TLR-positive cells was found to be increased in the aseptic setting, reflecting the considerable macrophage infiltration to the tissues investigated. Thus aseptic periprosthetic tissue seems to be very reactive to PAMPs. It has been recently recognized that TLR do not only respond to traditional PAMPs, but also to endogenous alarmings or danger signals released from necrotic and activated cells. Alarming-TLR interaction in the periprosthetic tissue might be a novel mechanism of aseptic loosening of endoprosthesis.
View details for DOI 10.1002/jor.20979
View details for Web of Science ID 000273675700007
View details for PubMedID 19725103
Receptor activator of nuclear factor kappa B ligand in an experimental intervertebral disc degeneration
CLINICAL AND EXPERIMENTAL RHEUMATOLOGY
2009; 27 (2): 299-306
HLA-B27 positive individuals are predisposed to reactive arthritis developing 1-3 weeks after urogenital and gastrointestinal infections. Also ankylosing spondylitis (AS) associates strongly to HLA-B27, but no specific infection, Klebsiella pneumoniae excluded, has been linked to it. Before the discovery of its HLA-B27 association there were many reports suggesting a link between chronic prostatitis in men or pelvic inflammatory disease in women and AS. They have since been forgotten although HLA-B27 did not help to understand, why this disease has an axial and ascending nature. It is proposed that the urogenital organs form a source of damage (or danger)-associated molecular patterns (DAMPs), either exogenous pathogen-associated molecular patterns (PAMPs) from microbes or endogenous alarmins, such as uric acid, released from necrotic cells or urate deposits. DAMPs are slowly seeded from low-down upwards via the pelvic and spinal lymphatic pathways. They reach Toll-like receptors (TLRs) in their target mesenchymal stem cells, which are stimulated to ectopic enchondral bone formation leading to syndesmophytes and bamboo spine. At the same time inflammatory cytokines induce secondary osteoporosis of the spine. This new paradigm places microbes, HLA-B27 and TLRs in the pathogenic centre stage, but without pinpointing any (one) specific pathogen; instead, shared microbial patterns are indicated.
View details for DOI 10.1016/j.jaut.2009.02.010
View details for Web of Science ID 000266510300004
View details for PubMedID 19299108
This study was designed to clarify the role of the receptor activator of nuclear factor kappa B ligand (RANKL) in the process of discus degeneration and spondylarthrosis. It was hypothesized that experimental discus lesion would initiate not only local bone remodelling but also increased osteoclast formation on a location remote to the injury site due to altered spinal biomechanics. It was speculated that these changes in vertebral bone remodelling could be reflected in an increased RANKL expression.The presence of RANKL in the spine was studied in an experimental perforating lesion of the cranial endplate of L4 and the adjoining disc in six domestic pigs and in one human herniated disc. After three months, the experimental and contiguous control vertebrae, complete with intervertebral discs, were subjected for immunohistochemistry.This is the first study to show that RANKL was locally seen (produced) in osteoblasts, fibroblasts replacing annulocytes and mesenchymal bone marrow cells and, in part, apparently bound to the surface of osteoclasts and macrophage-like prefusion macrophages. Such RANKL induction was also seen at sites remote from the experimental lesion driving the whole process. More RANKL-positive cells were found in close proximity to the endplate than in the central parts of the vertebrae. Osteocytes in bone matrix and most bone marrow cells in the marrow microenvironment showed no RANKL staining. Human annulus fibrosus also contained RANKL, RANK and OPG.We have demonstrated that RANKL is produced locally, also in soluble form, at the site of injury and also in intact vertebrae and bony structures likely due to altered biomechanics. It seems to be engaged in bone healing and remodelling, essentially proving our working hypothesis. These secondary bone changes could represent part of the degenerative spine disease (spondylarthrosis). RANKL inhibitors, like recombinant human osteoprotegerin (OPG), could be interesting drugs to test, not only in osteoporosis, but also in spondylarthrosis.
View details for Web of Science ID 000266096700081
View details for PubMedID 19473572