Effects of polyethylene and TiAIV wear particles on expression of RANK, RANKL and OPG mRNA

Melittin Treats Periprosthetic Osteolysis in a Rat Model by Inhibiting the NF-kB Pathway and Regulating the Ratio of Receptor Activator of Nuclear Factor Kappa B Ligand/Osteoprotegerin

BACKGROUND

Aseptic loosening around the prosthesis is a common cause of failure in total joint arthroplasty. Polyethylene wear particles trigger the release of inflammatory factors by macrophages. Key mediators involved in osteoclastogenesis include interleukin-6, tumor necrosis factor-α, receptor activator of nuclear factor kappa B (RANK), RANK ligand (RANKL), and bone protection hormone (Osteoprotegerin [OPG]). The purpose of our experiment was to see whether melittin can slow down the release of inflammatory mediators through the NF-kB pathway, regulate the RANKL/OPG ratio, reduce osteoclast formation, and delay the onset of arthritis in rats.

METHODS

A total of 20 male Sprague-Dawley rats (10 months, Specific Pathogen Free, 350 g ± 20 g) were randomly divided into 5 groups: sham group, model group, melittin concentration 1 group (0.2 mg/kg), concentration 2 group (0.4 mg/kg), and concentration 3 group (0.6 mg/kg). All rats were implanted with TA2 high-purity titanium rods. A drill was used to create a bone canal along the long axis of the femur in the intercondylar notch. The model group and experimental groups were exposed to polyethylene particles, while the sham group did not receive any particles.

RESULTS

The melittin group exhibited significantly increased serum levels of serum P, calcium-phosphorus product, OPG, PINP, PINP/CTX-I, and OPG/RANKKL (P < .05). In the experimental group, micro computed tomography scanning results revealed a decrease in the amount of bone defect around the prosthesis. Immunofluorescence analysis demonstrated a decrease in the expression of IKKα and P65, while the expression of OPG showed an upward trend. Both Hematoxylin-Eosin and Tartrate-Resistant Acid Phosphatase staining revealed less osteoclast and inflammatory cell infiltration in bone resorption pits.

CONCLUSIONS

Our study demonstrates that melittin has the ability to inhibit the NF-kB pathway in a rat model, and reduce the impact of RANKL/OPG, thereby delaying osteoclast activity and alleviating periprosthetic osteolysis.

Quercetin inhibits macrophage polarization through the p-38α/β signalling pathway and regulates OPG/RANKL balance in a mouse skull model

Aseptic loosening caused by wear particles is a common complication after total hip arthroplasty. We investigated the effect of the quercetin on wear particle‐mediated macrophage polarization, inflammatory response and osteolysis. In vitro, we verified that Ti particles promoted the differentiation of RAW264.7 cells into M1 macrophages through p‐38α/β signalling pathway by using flow cytometry, immunofluorescence assay and small interfering p‐38α/β RNA. We used enzyme‐linked immunosorbent assays to confirm that the protein expression of M1 macrophages increased in the presence of Ti particles and that these pro‐inflammatory factors further regulated the imbalance of OPG/RANKL and promoted the differentiation of osteoclasts. However, this could be suppressed, and the protein expression of M2 macrophages was increased by the presence of the quercetin. In vivo, we revealed similar results in the mouse skull by μ‐CT, H&E staining, immunohistochemistry and immunofluorescence assay. We obtained samples from patients with osteolytic tissue. Immunofluorescence analysis indicated that most of the macrophages surrounding the wear particles were M1 macrophages and that pro‐inflammatory factors were released. Titanium particle‐mediated M1 macrophage polarization, which caused the release of pro‐inflammatory factors through the p‐38α/β signalling pathway, regulated OPG/RANKL balance. Macrophage polarization is expected to become a new clinical drug therapeutic target.

Targeting Anion Exchange of Osteoclast, a New Strategy for Preventing Wear Particles Induced- Osteolysis

Joint replacement is essential for the treatment of serious joint disease. However, prosthetic failure remains an important clinical issue, with periprosthesis osteolysis (PO), caused by osteoclastic bone resorption induced by wear particles, being the leading cause of failure. Nuclear factor of activated T cells c1 (NFATc1) appears to play an important role in wear particle-induced osteoclastogenesis, with bicarbonate/chloride exchanger, solute carrier family 4, anion exchanger, member 2, (SLC4A2) being upregulated during osteoclastogenesis in an NFATc1-dependent manner. Anion exchange mediated by SLC4A2 in osteoclasts could affect the bone resorption activity by regulating pHi. This study investigated the role and mechanism of SLC4A2 in wear particle-induced osteoclast differentiation and function in vitro. The use of 4, 4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS), an anion exchange inhibitor, suppressed wear particle-induced PO in vivo. Furthermore, controlled release of DIDS from chitosan microspheres can strengthen the PO therapy effect. Therefore, anion exchange mediated by osteoclastic SLC4A2 may be a potential therapeutic target for the treatment of aseptic loosening of artificial joints.

Inhibition of osteoclastogenesis for periprosthetic osteolysis therapy through the suppression of p38 signaling by fraxetin

Periprosthetic osteolysis belongs to osteolytic diseases, which often occur due to an imbalance between osteoclast and osteoblast number or activity. Fraxetin, a natural plant extract, inhibits osteoblast apoptosis and has therapeutic potential for treating osteolytic diseases. However, data pertaining to the effects of fraxetin on osteoclasts are limited. In the present study, it was demonstrated that the inhibition of osteoclastogenesis by fraxetin had an important role on the therapy of titanium particle-induced osteolysis in vivo. In addition, fraxetin was demonstrated to suppress receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclast differentiation and bone resorption in vitro in a dose-dependent manner. Fraxetin inhibited osteoclast differentiation and function through the suppression of p38 signaling and subsequently, the suppression of osteoclast-specific gene expression, including tartrate-resistant acid phosphatase, nuclear factor of activated T-cells, cytoplasmic 1, and cathepsin K. In conclusion, fraxetin administration may have potential as a treatment method for periprosthetic osteolysis and other osteolytic diseases.

Recovery of low volumes of wear debris from rat stifle joint tissues using a novel particle isolation method

Less than optimal particle isolation techniques have impeded analysis of orthopaedic wear debris in vivo. The purpose of this research was to develop and test an improved method for particle isolation from tissue. A volume of 0.018 mm³ of clinically relevant CoCrMo, Ti-6Al-4V or Si₃N₄ particles was injected into rat stifle joints for seven days of in vivo exposure. Following sacrifice, particles were located within tissues using histology. The particles were recovered by enzymatic digestion of periarticular tissue with papain and proteinase K, followed by ultracentrifugation using a sodium polytungstate density gradient. Particles were recovered from all samples, observed using SEM and the particle composition was verified using EDX, which demonstrated that all isolated particles were free from contamination. Particle size, aspect ratio and circularity were measured using image analysis software. There were no significant changes to the measured parameters of CoCrMo or Si₃N₄ particles before and after the recovery process (KS tests, p > 0.05). Titanium particles were too few before and after isolation to analyse statistically, though size and morphologies were similar. Overall the method demonstrated a significant improvement to current particle isolation methods from tissue in terms of sensitivity and efficacy at removal of protein, and has the potential to be used for the isolation of ultra-low wearing total joint replacement materials from periprosthetic tissues.

STATEMENT OF SIGNIFICANCE

This research presents a novel method for the isolation of wear particles from tissue. Methodology outlined in this work would be a valuable resource for future researchers wishing to isolate particles from tissues, either as part of preclinical testing, or from explants from patients for diagnostic purposes. It is increasingly recognised that analysis of wear particles is critical to evaluating the safety of an orthopaedic device.

The influence of calcitonin gene-related peptide on markers of bone metabolism in MG-63 osteoblast-like cells co-cultured with THP-1 macrophage-like cells under virtually osteolytic conditions

Background

The neuropeptide calcitonin gene-related peptide (CGRP) has been described to have an inhibitory effect on endotoxin- and wear particle-induced inflammation in the early stages of periprosthetic osteolysis. In the present study, the crosstalk between immune cells and osteoblasts in osteolytic conditions treated with CGRP has been analyzed to evaluate whether the anti-inflammatory properties of the peptide also have a beneficial, i.e. an anti-resorptive and osteo-anabolic impact on bone metabolism.

Methods

MG-63 osteoblast-like cells were co-cultured with THP-1 macrophage-like cells stimulated with either ultra-high molecular weight polyethylene (UHMWPE) particles or different concentrations of bacterial lipopolysaccharides (LPS) and simultaneously treated with CGRP. Inflammation was monitored in terms of measuring the levels of tumor necrosis factor (TNF)-α secretion. Furthermore, the production of the osteoblast markers osteoprotegerin (OPG), receptor activator of nuclear factor κB ligand (RANKL), alkaline phosphatase (ALP) and osteopontin (OPN) was quantified. Also, ALP enzymatic activity was measured.

Results

Stimulation of co-cultured THP-1 macrophages with either high levels of LPS or UHMWPE induced the secretion of TNF-α which could be inhibited by CGRP to a great extent. However, no remarkable changes in the OPG/RANKL ratio or bone ALP activity were observed. Interestingly, OPN was exclusively produced by THP-1 cells, thus acting as a marker of inflammation. In addition, TNF-α production in THP-1 single cell cultures was found to be considerably higher than in co-cultured cells.

Conclusions

In the co-culture system used in the present study, no obvious relation between inflammation, its mitigation by CGRP, and the modulation of bone metabolism became evident. Nonetheless, the results suggest that during the onset of periprosthetic osteolysis the focus might lie on the modulation of inflammatory reactions. Possibly, implant-related inflammation might merely have an impact on osteoclast differentiation rather than on the regulation of osteoblast activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1044-5) contains supplementary material, which is available to authorized users.

Innate immunity sensors participating in pathophysiology of joint diseases: a brief overview

The innate immune system consists of functionally specialized "modules" that are activated in response to a particular set of stimuli via sensors located on the surface or inside the tissue cells. These cells screen tissues for a wide range of exogenous and endogenous danger/damage-induced signals with the aim to reject or tolerate them and maintain tissue integrity. In this line of thinking, inflammation evolved as an adaptive tool for restoring tissue homeostasis. A number of diseases are mediated by a maladaptation of the innate immune response, perpetuating chronic inflammation and tissue damage. Here, we review recent evidence on the cross talk between innate immune sensors and development of rheumatoid arthritis, osteoarthritis, and aseptic loosening of total joint replacements. In relation to the latter topic, there is a growing body of evidence that aseptic loosening and periprosthetic osteolysis results from long-term maladaptation of periprosthetic tissues to the presence of by-products continuously released from an artificial joint.

Endoplasmic reticulum stress-mediated inflammatory signaling pathways within the osteolytic periosteum and interface membrane in particle-induced osteolysis

Aseptic loosening secondary to periprosthetic inflammatory osteolysis results from the biological response to wear particles and is a leading cause of arthroplasty failure. The origin of this inflammatory response remains unclear. We aim to validate the definite link between endoplasmic reticulum (ER) stress and particle-induced inflammatory signaling pathways in periprosthetic osteolysis. We examine the histopathologic changes of osteolysis and the expression of specific biomarkers for ER-stress-mediated inflammatory signaling pathways (IRE1α, GRP78/Bip, c-Fos, NF-κB, ROS and Ca(2+)). Moreover, pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and osteoclastogenic molecules (VEGF, OPG, RANKL and M-CSF) were assessed in clinical interface membranes and murine periosteum tissues. We found wear particles to be capable of inducing ER stress in macrophages within clinical osteolytic interface membranes and murine osteolytic periosteum tissues and to be associated with the inflammatory response and osteoclastogenesis. Blocking ER stress with sodium 4-phenylbutyrate (4-PBA) results in a dramatic amelioration of particle-induced osteolysis and a significant reduction of ER-stress intensity. Simultaneously, this ER-stress blocker also lessens inflammatory cell infiltration, diminishes the capability of osteoclastogenesis and reduces the inflammatory response by lowering IRE1α, GRP78/Bip, c-Fos, NF-κB, ROS and Ca(2+) levels. Thus, ER stress plays an important role in particle-induced inflammatory osteolysis and osteoclastogenic reactions. The pharmacological targeting of ER-stress-mediated inflammatory signaling pathways might be an appealing approach for alleviating or preventing particle-induced osteolysis in at-risk patients.

Calcitonin gene-related peptide modulates the production of pro-inflammatory cytokines associated with periprosthetic osteolysis by THP-1 macrophage-like cells

OBJECTIVE

An anti-resorptive impact of the neuropeptide calcitonin gene-related peptide (CGRP) on periprosthetic osteolysis, the leading cause of early prosthesis loosening, has been shown previously. In this study, the impact of CGRP on pro-inflammatory cytokine production associated with periprosthetic osteolysis was analysed using THP-1 macrophage-like cells.

METHODS

Cells were stimulated with ultra-high-molecular-weight polyethylene (UHMWPE) particles (cell-to-particle ratios of 1:100 and 1:500) and lipopolysaccharides (LPS; 1 µg/ml) to establish osteolytic conditions, and simultaneously treated with CGRP (10(-8)M). Receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNF)-α mRNA expression were measured by quantitative RT-PCR. RANK protein was detected by Western blot. Secreted protein levels of TNF-α as well as interleukin (IL)-1β and IL-6 were quantified in cell culture supernatants by ELISA and Bio-Plex cytokine assay, respectively.

RESULTS

Activation of macrophage-like cells failed to enhance the production of RANK but led to a dose- and time-dependent increase of TNF-α mRNA and secreted protein levels of TNF-α, IL-1β and IL-6. Application of CGRP time-dependently suppressed TNF-α mRNA expression induced by low-particle concentrations and LPS, while both particle- and LPS-induced secretion of TNF-α was inhibited. A pronounced inhibitory effect of CGRP on LPS-induced cytokine production at 24 h of incubation was also observed with IL-1β and IL-6.

CONCLUSIONS

CGRP shows a time-dependent inhibitory effect on the secretion of osteolysis-associated pro-inflammatory cytokines, indicating an indirect anti-resorptive influence of the neuropeptide on both aseptic prosthesis loosening and bacterially induced bone resorption which might enhance the life time of total joint replacements.

AKILE™ total ankle arthroplasty: Clinical and CT scan analysis of periprosthetic cysts

INTRODUCTION

Despite good clinical results following total ankle replacement (TAR), the development of large periprosthetic cysts (>400 mm(2)) in the medium-term is a source of concern.

OBJECTIVE

The primary objective of this study was to detect any large periprosthetic cysts in a cohort of AKILE™ patients using radiographs and CT scans, and then to compare these findings to published ones.

MATERIAL AND METHODS

A total of 127 TAR procedures were performed between June 1995 and January 2012. We retrospectively reviewed 68 cases with the newest AKILE™ implant design that had a minimum follow-up of 36 months. The average follow-up was 81 ± 33 months; eight patients were lost to follow-up. The outcomes consisted of analyzing radiographs (A/P and lateral weight bearing views, Meary view and lateral views of flexion/extension) and helical CT scans, performing clinical evaluations (range of motion, AOFAS score, Foot Function Index, pain levels) and determining the survivorship of TAR implants.

RESULTS

TAR survival at 5 years was 79% for in situ implants and 62% for revision-free implants. The AOFAS score improved from 33.7 ± 14.7 to 77.1 ± 15.1 (out of 100) and the pain sub-score was 30.2 ± 9.7 (out of 40) at the last follow-up. The average ankle range of motion was 32.3° ± 12.7° on the radiographs. CT scan revealed Type A cysts (<200 mm(2)) under the talar implant in 52% of cases and in the tibia in 50% of cases; these cysts were smaller than 100 mm(2) in 80% of cases and had no effect on the implants. No periprosthetic cysts larger than 400 mm(2) in size were identified.

DISCUSSION

The medium-term functional results and survivorship are comparable to those reported for other TAR designs. The incidence of cysts was low overall and there were no large-diameter cysts, which should improve long-term survival. The implant's design and materials likely played a role in preserving the periprosthetic bone stock. The AKILE™ TAR has distinctive features related to the low rate of large periprosthetic cysts in the medium-term.

LEVEL OF EVIDENCE

IV (retrospective case series).

The inhibition of RANKL-induced osteoclastogenesis through the suppression of p38 signaling pathway by naringenin and attenuation of titanium-particle-induced osteolysis

The aim of this study was to assess the effect of naringenin on osteoclastogenesis and titanium particle-induced osteolysis. Osteolysis from wear-induced particles and aseptic loosening are the most frequent late complications of total joint arthroplasty leading to revision of the prosthesis. Osteolysis during aseptic loosening is most likely due to increased bone resorption by osteoclasts. Through in vitro studies, we demonstrated that naringenin, a naturally occurring flavanone in grapefruit and tomatoes, exerts potent inhibitory effects on the ligand of the receptor activator of nuclear factor-κB (RANKL)-induced osteoclastogenesis and revealed that the mechanism of action of naringenin, which inhibited osteoclastogenesis by suppression of the p38 signaling pathway. Through in vivo studies, we proved that naringenin attenuated titanium particle-induced osteolysis in a mouse calvarial model. In general, we demonstrated that naringenin inhibited osteoclastogenesis via suppression of p38 signaling in vitro and attenuated titanium particle-induced osteolysis in vivo. This study also suggested that naringenin has significant potential for the treatment of osteolysis-related diseases caused by excessive osteoclast formation and activity.

Generation of a large volume of clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles for cell culture studies

It has recently been shown that the wear of ultra-high-molecular-weight polyethylene in hip and knee prostheses leads to the generation of nanometre-sized particles, in addition to micron-sized particles. The biological activity of nanometre-sized ultra-high-molecular-weight polyethylene wear particles has not, however, previously been studied due to difficulties in generating sufficient volumes of nanometre-sized ultra-high-molecular-weight polyethylene wear particles suitable for cell culture studies. In this study, wear simulation methods were investigated to generate a large volume of endotoxin-free clinically relevant nanometre-sized ultra-high-molecular-weight polyethylene wear particles. Both single-station and six-station multidirectional pin-on-plate wear simulators were used to generate ultra-high-molecular-weight polyethylene wear particles under sterile and non-sterile conditions. Microbial contamination and endotoxin levels in the lubricants were determined. The results indicated that microbial contamination was absent and endotoxin levels were low and within acceptable limits for the pharmaceutical industry, when a six-station pin-on-plate wear simulator was used to generate ultra-high-molecular-weight polyethylene wear particles in a non-sterile environment. Different pore-sized polycarbonate filters were investigated to isolate nanometre-sized ultra-high-molecular-weight polyethylene wear particles from the wear test lubricants. The use of the filter sequence of 10, 1, 0.1, 0.1 and 0.015 µm pore sizes allowed successful isolation of ultra-high-molecular-weight polyethylene wear particles with a size range of < 100 nm, which was suitable for cell culture studies.

Calcineurin/NFAT pathway mediates wear particle-induced TNF-α release and osteoclastogenesis from mice bone marrow macrophages in vitro

AIM

To investigate the roles of the calcineurin/nuclear factor of activated T cells (NFAT) pathway in regulation of wear particles-induced cytokine release and osteoclastogenesis from mouse bone marrow macrophages in vitro.

METHODS

Osteoclasts were induced from mouse bone marrow macrophages (BMMs) in the presence of 100 ng/mL receptor activator of NF-κB ligand (RANKL). Acridine orange staining and MTT assay were used to detect the cell viability. Osteoclastogenesis was determined using TRAP staining and RT-PCR. Bone pit resorption assay was used to examine osteoclast phenotype. The expression and cellular localization of NFATc1 were examined using RT-PCR and immunofluorescent staining. The production of TNFα was analyzed with ELISA.

RESULTS

Titanium (Ti) or polymethylmethacrylate (PMMA) particles (0.1 mg/mL) did not significantly change the viability of BMMs, but twice increased the differentiation of BMMs into mature osteoclasts, and markedly increased TNF-α production. The TNF-α level in the PMMA group was significantly higher than in the Ti group (96 h). The expression of NFATc1 was found in BMMs in the presence of the wear particles and RANKL. In bone pit resorption assay, the wear particles significantly increased the resorption area and total number of resorption pits in BMMs-seeded ivory slices. Addition of 11R-VIVIT peptide (a specific inhibitor of calcineurin-mediated NFAT activation, 2.0 μmol/L) did not significantly affect the viability of BMMs, but abolished almost all the wear particle-induced alterations in BMMs. Furthermore, VIVIT reduced TNF-α production much more efficiently in the PMMA group than in the Ti group (96 h).

CONCLUSION

Calcineurin/NFAT pathway mediates wear particles-induced TNF-α release and osteoclastogenesis from BMMs. Blockade of this signaling pathway with VIVIT may provide a promising therapeutic modality for the treatment of periprosthetic osteolysis.

Protection against titanium particle-induced inflammatory osteolysis by the proteasome inhibitor bortezomib in vivo

Wear particle-induced vascularized granulomatous inflammation and subsequent inflammatory osteolysis is the most common cause of aseptic loosening after total joint replacement (TJR); however, the precise mechanism by which this occurs is unclear. This study investigates the effects of the proteasome inhibitor bortezomib (Bzb) on the expression of key biochemical markers of bone metabolism and vascularised granulomatous tissues, such as receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), vascular endothelial growth factor (VEGF) and tumor necrosis factor receptor-associated factor 6 (TRAF6). In addition, the effect of Bzb on apoptosis of CD68+ cells was examined. A total of 32 female BALB/C mice were randomly divided into four groups. After implantation of calvaria bone from syngeneic littermates, titanium (Ti) particles were injected into established air pouches for all mice (excluding negative controls) to provoke inflammatory osteolysis. Subsequently, Bzb was administered at a ratio of 0, 0.1, or 0.5 mg/kg on day 1, 4, 8, and 11 post-surgery to alleviate this response. All of the air pouches were harvested 14 days after the surgical procedure and were processed for molecular and histological analysis. The results demonstrated that Ti injection elevated the expression of RANKL, OPG, VEGF, and TRAF6 at both the gene and protein levels, increased counts of infiltrated cells and thickness of air pouch membranes, and elevated the apoptosis index (AI) of CD68+ cells. Bzb treatment significantly improved Ti particle-induced implanted bone osteolysis, attenuated vascularised granulomatous tissues and elevated AI of CD68+ cells. Therefore, the proteasome pathway may represent an effective therapeutic target for the prevention and treatment of aseptic loosening.

Inhibiting wear particles-induced osteolysis with naringin

PURPOSE

The purpose of this study was to determine the effects of naringin on osteoclastogenesis and osteolysis both in vitro and in vivo.

METHODS

In this research osteoclasts were generated from mouse bone marrow monocytes with the receptor activator of NF-КB ligand and the macrophage colony stimulating factor. Naringin, at a concentration of 1, 10, 50, and 100 μg/mL, was respectively added to the medium. Seven days later, the osteoclasts were determined through tartrate-resistant acid phosphatase (TRAP) staining. Mature osteoclasts were isolated from newborn rabbits and cultured for three days on bone slices. Naringin at a concentration of 1, 10, 50, and 100 μg/mL was respectively added to the medium. The resorption bone slices were quantified, and the area was calculated after toluidine blue and Mayer-hematoxylin staining. Polymethyl methacrylate (PMMA) particles were implanted on the calvariae of C57BL/J6 mice. Naringin, at a dose of 50 μg/kg and 100 μg/kg, was respectively given intraperitoneally for seven. Seven days later, the calvariae were removed and processed for pathological analysis.

RESULTS

The result indicated that naringin treatment effectively inhibited in vitro osteoclastogenesis and inhibited mature osteoclasts. In vivo data indicated that naringin strongly inhibited PMMA-induced osteolysis.

CONCLUSION

Naringin can effectively inhibit osteoclastogenesis and suppress wear particles-induced osteolysis and might be useful in the treatment or prevention of wear particles-induced osteolysis and aseptic loosening for its effect on osteoclast generation and function.

Significance of nano- and microtopography for cell-surface interactions in orthopaedic implants

Cell-surface interactions play a crucial role for biomaterial application in orthopaedics. It is evident that not only the chemical composition of solid substances influence cellular adherence, migration, proliferation and differentiation but also the surface topography of a biomaterial. The progressive application of nanostructured surfaces in medicine has gained increasing interest to improve the cytocompatibility and osteointegration of orthopaedic implants. Therefore, the understanding of cell-surface interactions is of major interest for these substances. In this review, we elucidate the principle mechanisms of nano- and microscale cell-surface interactions in vitro for different cell types onto typical orthopaedic biomaterials such as titanium (Ti), cobalt-chrome-molybdenum (CoCrMo) alloys, stainless steel (SS), as well as synthetic polymers (UHMWPE, XLPE, PEEK, PLLA). In addition, effects of nano- and microscaled particles and their significance in orthopaedics were reviewed. The significance for the cytocompatibility of nanobiomaterials is discussed critically.

Kineflex lumbar artificial disc versus Charité lumbar total disc replacement for the treatment of degenerative disc disease: A randomized non-inferiority trial with minimum of 2 years' follow-up

Background

The Kineflex lumbar artificial disc replacement device (SpinalMotion, Mountain View, California) is a semiconstrained, posterior center of rotation, metal-on-metal intervertebral disc prosthesis. We performed a prospective, randomized, non-inferiority trial comparing the Kineflex Disc with the Food and Drug Administration (FDA)–approved Charité device (DePuy Spine, Raynham, Massachusetts). Our objective was to evaluate the Kineflex Disc's safety and efficacy using validated outcomes measures—the visual analog scale (VAS) and the Oswestry Disability Index (ODI).

Methods

Sixty-four patients were randomized to receive either the Kineflex Disc or Charité device and were then followed up for up to 3 years. Patients completed VAS and ODI questionnaires and were evaluated clinically and radiologically for complication or device failure. Results were analyzed in terms of change in mean VAS score and ODI from baseline, as well as with a comparison of clinical success as defined by FDA investigational device exemption criteria. Non-inferiority was defined as a difference of less than 18 points in the VAS score and difference of less than 10 units on the ODI scale, in keeping with a previously established minimum clinically important difference.

Results

The mean improvement for the Kineflex Disc group at 24 months was 56.80 for the VAS score and 37.30 for the ODI. Similarly, the mean improvement in the Charité group was 54.43 for the VAS score and 38.40 for the ODI. At 2 years of follow-up, no difference was found in VAS scores between the two groups. The Kineflex Disc group was therefore found to be non-inferior (mean difference, 2.37; 95% confidence interval, −12.5 to 17.3; P = .004). In addition, at 24 months, 83% of patients in the Kineflex Disc group and 85% of patients in the Charité group met FDA-defined criteria for clinical success, with no difference between groups (P = .802).

Conclusions

This level I evidence shows the Kineflex Disc to be non-inferior to the Charité device in terms of pain reduction (VAS score) and FDA-defined clinical success at 24 months’ follow-up. Both devices showed a high degree of safety.

In vivo response to cross-linked polyethylene and polycarbonate-urethane particles

This study was undertaken to examine macrophage response to polycarbonate-urethane, a proposed alternative material to polyethylene in acetabular components of total hip arthroplasty. Polyethylene wear debris from total joint replacements has been linked to osteolysis and implant lifespan. It has been shown in vitro, that polyethylene particles cleaned of endotoxin generate less of an inflammatory cytokine response than endotoxin bound particles. Comparative particle induced effects on implant fixation were tested using endotoxin free cross-linked ultra-high molecular weight polyethylene (x-UHMWPE) and polycarbonate-urethane (PCU) particles with and without intraperitoneal injection (IP) of lipopolysaccharide (LPS) using a Ti-alloy femoral intramedullary nail rat model. MicroCT and mechanical testing assessment of peri-implant bone indicated significantly less bone and lower fixation strength, respectively, when the implant was surrounded by xUHMWPE particles compared to PCU particles (with and without LPS IP). This indicates particles of PCU may be less disruptive to bone-implant fixation than x-UHMWPE in vivo, under both LPS free and challenged conditions.

A review of the biologic effects of spine implant debris: Fact from fiction

BACKGROUND

Biologic-reactivity to implant-debris is the primary determinant of long-term clinical performance. The following reviews: 1) the physical aspects of spinal-implant debris and 2) the local and systemic biologic responses to implant debris.

METHODS

Methods included are: 1) gravimetric wear analysis; 2) SEM and LALLS; 3) metal-ion analysis; 4) ELISA, toxicity testing, patch testing; and 5) metal-lymphocyte transformation testing (metal-LTT).

RESULTS

Wear and corrosion of spine-implants produce particles and ions. Particles (0.01-1000 μm) are generally submicron ( <1 µm). Wear rates of metal-on-polymer and metal-on-metal disc arthroplasties are approximately 2-20 and 1 mm(3)/yr, respectively. Metal-on-metal total disc replacement components have significant increases in circulating metal (less than 10-fold that of controls at 4 ppb-Co and 3 ppb-Cr or ng/mL). Debris reactivity is local and systemic. Local inflammation is caused primarily by ingestion of debris by local macrophages, which produce pro-inflammatory cytokines TNFα, IL-1β, IL-6, and PGE2. Systemic responses associated with implant-debris have been limited to hypersensitivity reactions. Elevated amounts of in the liver, spleen, etc of patients with failed TJA have not been associated with remote toxicological or carcinogenic pathology to date. Implant debris are differentially bioreactive. Greater numbers are pro-inflammatory; the smaller-sized debris are more bioreactive by virtue of their greater numbers (dose) for a given amount of implant mass loss (one 100-μm-diameter particle is equivalent in mass to 1 million 1-μm-diameter particles). Elongated particles are pro-inflammatory (ie, aspect ratio of greater than 3). Metal particles are more proinflammatory than polymers, ceteris paribus.

CONCLUSION

Spinal arthroplasty designs have been in use for more than 20 years internationally; therefore, concerns about neuropathology, toxicity, and carcinogenicity are mitigated. Debris-induced inflammation still depends on the individual and the type of debris. The consequence of debris-induced inflammation is continued; vigilance by physicians is recommended monitoring of spinal implants using physical exams and testing of metal content and bioreactivity, as is planning for the likelihood of revision in younger individuals.

Alumina ceramic particles, in comparison with titanium particles, hardly affect the expression of RANK-, TNF-alpha-, and OPG-mRNA in the THP-1 human monocytic cell line

Particle-induced osteolysis is the most frequent cause of aseptic loosening after total joint replacement. We performed a study to illuminate the effect of ceramic particles with different diameters and concentrations on the mRNA expression of certain key regulators in particle-induced aseptic osteolysis (RANK, RANKL, OPG, and TNF-alpha) in THP-1 macrophage-like cells. Titanium particles were used as a positive control. RNA was analyzed by quantitative RTPCR. Our results demonstrate that alumina ceramic particles, regardless of particle size, caused only slight upregulations of RANK, TNF-alpha, and OPG mRNA, whose levels were significantly lower in comparison with those of titanium particles (p < 0.05). The continuous increasing tendency to time and particle-dependent mRNA expression of all the parameters stimulated by titanium particles was not found after stimulation with ceramic materials. Even after the concentration of ceramic particles was increased, only a mild upregulation of mRNA expression was found. Furthermore, we observed that the bioinert properties of ceramic particles did not change much in diameters ranging from 0.5 to 1.5 microm. At most of the measuring time points, there was no significant difference between the reactions of the large and small particles in this range. Our results support the theory about the relative bioinert properties of alumina ceramic particles.

Inhibiting wear particles-induced osteolysis with doxycycline

AIM

To study the effect of doxycycline (DOX) on osteoclastogenesis, mature osteoclast fate and function, wear particles-induced osteoeolysis, and to provide some foundation for treating aseptic loosening and osteolysis after joint arthroplasty.

METHODS

Osteoclasts were generated from mouse bone marrow monocytes with the receptor activator of NF-kappaB ligand and the macrophage colony stimulating factor. DOX at a concentration of 5, 10, 15, and 20 microg/mL was respectively added to the medium. Seven days later, the osteoclasts were determined through tartrate-resistant acid phosphatase (TRAP) staining. Mature osteoclasts were isolated from newborn rabbits and cultured for 3 d in 24-well plates or on bone slices. DOX at a concentration of 5, 10, 15, and 20 microg/mL was respectively added to the medium. After TRAP staining, the osteoclasts were counted, resorption on bone slices was quantified, and the area was calculated after toluidine blue and Mayer-hematoxylin staining. Polymethyl methacrylate (PMMA) or ultra-high molecular weight polyethylene (UHMWPE) particles were implanted on the calvariae of C57BL/J6 mice. DOX, at a dose of 2 and 10 mg x kg(-1) x d(-1), was respectively given intraperitoneally for 7 d. Seven days later, the calvariae were removed and processed for pathological analysis.

RESULTS

DOX treatment effectively inhibited in vitro osteoclastogenesis, affected the fate of mature osteoclasts, and inhibited mature osteoclasts, causing bone resorption. In vivo data indicated that DOX strongly inhibited PMMA or UHMWPE-induced osteolysis and osteoclastogenesis.

CONCLUSION

DOX can effectively inhibit osteoclastogenesis and affect mature osteoclast fate and suppress wear particles induced by osteolysis and osteoclastogenesis. DOX might be useful in the treatment or prevention of wear particles-induced osteolysis and aseptic loosening for its effect on osteoclast generation and mature osteoclast fate and function.

The biology of aseptic osteolysis

Total hip arthroplasty is one of the most commonly performed and successful elective orthopaedic procedures. However, numerous failure mechanisms limit the long-term success including aseptic osteolysis, aseptic loosening, infection, and implant instability. Aseptic osteolysis and subsequent implant failure occur because of a chronic inflammatory response to implant-derived wear particles. To reduce particulate debris and their consequences, implants have had numerous design modifications including high-molecular-weight polyethylene sockets and noncemented implants that rely on bone ingrowth for fixation. Surgical techniques have improved cementation with the use of medullary plugs, cement guns, lavage of the canal, pressurization, centralization of the stem, and reduction in cement porosity. Despite these advances, aseptic osteolysis continues to limit implant longevity. Numerous proinflammatory cytokines, such as interleukin-1, interleukin-6, tumor necrosis factor-alpha, and prostaglandin E2, have proosteoclastogenic effects in response to implant-derived wear particles. However, none of these cytokines represents a final common pathway for the process of particle-induced osteoclast differentiation and maturation. Recent work has identified the fundamental role of the RANKL-RANK-NF-kappaB pathway not only in osteoclastogenesis but also in the development and function the immune system. Thus, the immune system and skeletal homeostasis may be linked in the process of osteoclastogenesis and osteolysis.

Upregulation of LITAF mRNA expression upon exposure to TiAlV and polyethylene wear particles in THP-1 macrophages

Tumor necrosis factor alpha (TNFalpha) plays a fundamental role in the pathogenesis of wear particle-induced periprosthetic osteolysis. However, particle-induced mechanisms that control TNFalpha gene expression are not yet well characterized. LITAF [lipopolysaccharide (LPS)-induced TNFalpha factor] is a novel transcription factor that regulates expression of the TNFalpha gene, but nothing is known about its role in wear particle-induced osteolysis. We evaluated the effect of titanium aluminum vanadium (TiAlV) and polyethylene particles on mRNA expression of LITAF. A human monocytic leukemia cell line (THP-1) was used in this in vitro study. THP-1 monocytes were differentiated to macrophage-like cells and exposed to LPS-detoxified polyethylene particles and prosthesis-derived TiAlV particles. Supernatant was used for TNFalpha protein measurement and total RNA was extracted from cells. LITAF was analyzed at the mRNA level using semiquantitative RT-PCR. Both polyethylene and TiAlV particles induced significant upregulation of LITAF mRNA that was followed by a significant TNFalpha response. These effects were dependent on the particle dose. Low particle concentrations exhibited no significant effect on expression of TNFalpha and LITAF mRNA. In comparison to exposure to polyethylene and TiAlV particles, LPS stimulation exhibited similar upregulation of LITAF mRNA, but led to an overwhelming TNFalpha response. Our findings provide evidence that LITAF is implicated in the pathogenesis of wear particle-induced osteolysis.

Polyethylene wear debris and long-term clinical failure of the Charité disc prosthesis: a study of 4 patients

STUDY DESIGN

A clinical case series of 4 patients undergoing anterior lumbar revision due to failure of total disc replacement surgery.

OBJECTIVES

To assess the clinical significance of polyethylene wear debris in salvage surgery after initial total disc replacement, the pattern and the mechanisms of polyethylene wear in the retrieved cores, and the extent of polyethylene debris in the periprosthetic tissues obtained from 4 patients.

SUMMARY OF BACKGROUND DATA

Previous in vitro wear tests have demonstrated low wear rates for lumbar artificial discs, suggesting that implant wear may not be a clinically relevant issue with total disc replacement. However, only long-term clinical investigations with analysis of retrieved implants and periprosthetic tissue can ultimately establish the significance of polyethylene wear debris for total disc arthroplasty.

METHODS

Starting in 2004, we began routinely performing salvage procedures in patients with failed total disc replacements. We report on the short-term outcomes of 4 patients at our institution who were revised with a Charité prosthesis (DePuy Spine, Raynham, MA). Wear analysis of the retrieved prosthesis and histologic examination of the periprosthetic tissue were also performed.

RESULTS

All of the retrieved polyethylene cores showed evidence of wear, but the extent and severity varied among the 4 patients. Wear and fracture of the core were associated with osteolysis of the underlying sacrum in 1 patient. Histologic examination of the periprosthetic tissues confirmed the presence of wear debris lying in inflammatory fibrous tissue. In 3 of the 4 patients, implant wear was associated with an unfavorable biomechanical environment (e.g., subsidence, migration, undersizing, and adjacent fusion). The mechanisms of wear included adhesive/abrasive wear of the central domed region of the polyethylene core, as well as chronic rim impingement, resulting in rim fatigue and fracture.

CONCLUSIONS

This study demonstrates the clinical significance of polyethylene wear debris and the potential for osteolysis with total disc replacements. The authors recommend that patients undergoing lumbar disc arthroplasty receive long-term follow-up to monitor the wear and functional status of their implants.

Synergistic effects of mixed TiAlV and polyethylene wear particles on TNFα response in THP-1 macrophages / Synergistische Effekte gemischter TiAlV- und Polyethylen-Abriebpartikel auf die TNFα-Antwort in THP-1 Makrophagen

TNFalpha is a potent osteoclastogenic cytokine that has a fundamental role in the pathogenesis of wear particle-induced osteolysis. Wear particles of one composition and their biological effects are well characterised. In contrast, little is known about the effects of mixed particles with respect to mix ratio and particle concentration. We evaluated the effects of different mix ratios of polyethylene and TiAlV particles on TNFalpha response. We used a human monocytic cell line (THP-1) in this in vitro study. THP-1 monocytes were differentiated to macrophage-like cells and exposed to different mixtures of lipopolysaccharide-detoxified polyethylene and TiAlV particles. TNFalpha was analysed in culture supernatants using ELISAs. Both polyethylene and TiAlV particles induced a dose- and time-related release of TNFalpha, with maximum levels after 6 h. A PE/TiAlV mix ratio of 36:1 at 10(8) particles/ml induced significantly higher TNFalpha concentrations compared to equal particle concentrations of isolated TiAlV (p=0.047) or PE (p=0.044), indicating the synergistic effect of mixed particles. These results provide evidence that TiAlV and polyethylene particles have significant synergistic effects, depending on the mix ratio and particle concentrations. This supra-additive effect can contribute substantially to the pathogenesis of implant particle-induced osteolysis.

The correlation of RANK, RANKL and TNFα expression with bone loss volume and polyethylene wear debris around hip implants

This study investigates receptor activator NF-kappaB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNFalpha), key factors regulating bone turnover, present in the tissues near peri-prosthetic osteolysis. Tissue was obtained from zones of peri-prosthetic osteolysis from 11 patients undergoing revision of total hip prostheses, analysed preoperatively by high-resolution spiral multislice CT using a metal artefact suppression protocol. Synovial tissue from 10 patients with osteoarthritis undergoing primary hip replacement was used as control tissue. Immunohistochemical analysis of formalin fixed tissue sections demonstrated that RANK, RANKL and TNFalpha were strongly expressed by large multinucleated cells containing polyethylene wear debris in revision tissues. Control tissue stained weakly for RANK, RANKL and TNFalpha. A strong statistical correlation (p<0.02) was found between the five parameters, volume of bone loss, polyethylene wear debris, RANK, RANKL and TNFalpha expression. Importantly, in vitro studies revealed that RANKL and TNFalpha synergise to increase the volume of bone resorbed, by more than seven fold, when compared to the effect of either cytokine treatment alone. This suggests that the interaction of TNFalpha and RANKL promotes osteoclast activity associated with polyethylene wear and therapies targeting TNF activity may be useful to treat peri-implant osteolysis.

Effects of bone cement particles on the function of pseudocapsule-derived fibroblasts

BACKGROUND

Despite the wide clinical use of bone cement, little is known about cellular responses to the debris from this material. We thus investigated the effects of bone cement particles on the secretion of soluble osteotropic factors in prosthetic pseudomembrane-derived fibroblasts.

METHODS

Bone cement particles were added to fibroblasts maintained in tissue culture. The secretions of soluble receptor activator for nuclear factor kappa B ligand and osteoprotegerin together with interleukin-6 and tumor necrosis factor-alpha were assessed by enzyme-linked immunosorbent assays. The fibroblasts were also co-cultured with osteoclast precursors in the presence and absence of particles, and we assessed osteoclast formation and bone resorption.

RESULTS

The particles produced an increase in the secretion of soluble receptor activator for nuclear factor kappa B ligand, interleukin-6 and tumor necrosis factor-alpha, but not osteoprotegerin. At a concentration of 88 particles/cell, bone cement particles yielded a 2-fold increase (327 pg/mL) in soluble receptor activator for nuclear factor kappa B ligand secretion, a 5-fold (239 pg/mL) increase in interleukin-6 secretion and 4-fold (129 pg/mL) increase in tumor necrosis factor-alpha secretion. The particles also enhanced bone resorption in the co-culture group. Both the increase in soluble receptor activator for nuclear factor kappa B ligand secretion and the increase in bone resorption were inhibited by the addition of neutralizing antibodies to the proinflammatory cytokines.

INTERPRETATION

Our findings show that bone cement particles are capable of stimulating the secretion of soluble receptor activator for nuclear factor kappa B ligand in pseudocapsule-derived fibroblasts by increasing the secretion of proinflammatory cytokines, and may also promote implant loosening.

The effects of titanium and polymethylmethacrylate particles on osteoblast phenotypic stability

Wear particles generated following total joint arthroplasty interact with cells at the periprosthetic margin and induce an inflammatory response that contributes to osteolysis, aseptic loosening, and implant failure. This study examined the long-term effects of particles from two commonly implanted materials, titanium (Ti) and polymethylmethacrylate (PMMA), on cell viability and metabolism over a 21-day time course, using the human osteoblast-like cell line MG-63. Addition of particles was not associated with increased cell death or nitric oxide production at the particle concentration chosen. Collagen production was increased with exposure to titanium particles, whereas alkaline phosphatase and osteocalcin expression remained unchanged following exposure to both types of particles. The data show that titanium but not PMMA particles shifts bone cell metabolism to preferentially produce fibrous tissue rather than bone.

Suppression of polyethylene particle-induced osteolysis by exogenous osteoprotegerin

Alterations of the key regulators of osteoclastogenesis, receptor activator of NF-kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) have been implicated in wear particle-induced osteolysis, the most common cause for implant failure in total joint replacements. This study investigated the effect of exogenous OPG on ultra-high-molecular-weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 28 C57BL/6J mice randomized to four groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III and IV particles and subcutaneous OPG starting from day 0 (group III) or day 5 (group IV) until sacrifice. After 2 weeks, calvaria were prepared for histology and histomorphometry. Bone resorption was measured within the midline suture using Giemsa staining and osteoclast numbers were determined using TRAP staining. UHMWPE particle implantation resulted in grossly pronounced osteoclastogenesis and bone resorption. Both immediate and delayed treatment with OPG counteracted these particle-induced effects significantly, suppressing osteoclast formation and bone resorption (p < 0.001 and p < 0.001, respectively). In conclusion, exogenous OPG markedly suppressed UHMWPE particle-induced osteolysis in a murine calvarial model. This important finding underscores the crucial significance of the OPG-RANKL-RANK signaling in wear particle-induced osteolysis. Exogenous OPG may prove an effective treatment modality for wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.

Activation of NF-kappaB signalling and TNFalpha-expression in THP-1 macrophages by TiAlV- and polyethylene-wear particles

Wear particles are believed to induce periprosthetic inflammation which contributes to periprosthetic osteolysis. TNFalpha plays a pivotal role in the pathogenesis of this process. The molecular mechanisms leading to the development of periprosthetic inflammation with upregulated TNFalpha expression in monocytic cells in response to different wear particles have yet to be defined. In this study we evaluated the effects of polyethylene- and TiAlV-particles on activation of NF-kappaB signalling pathways and TNFalpha biosynthesis and release in monocytic cells with respect to periprosthetic osteoclastogenesis. THP-1 monocytic cells were differentiated to macrophage-like cells and exposed to LPS-detoxified polyethylene and prosthesis-derived TiAlV-particles. TNFalpha release was analyzed in culture supernatant by ELISA. NF-kappaB activation was examined by electrophoretic mobility shift assay (EMSA), and NF-kappaB target promoter activities including transactivation of the TNFalpha promoter were determined by luciferase reporter gene assays. Differentiated THP-1 macrophages were exposed to increasing numbers of particles for 0, 60, 180 and 360 min. Both, polyethylene- and TiAlV-particles induced a significant activation of both NF-kappaB and TNFalpha promoters at 180 min. A significant TNFalpha release was detected after 360 min exposure to polyethylene- and TiAlV-particles in a dose dependent manner. In comparison, LPS induced a much greater activation of NF-kappaB and TNFalpha promoters, and TNFalpha secretion into the supernatant was strongly induced. These results provide evidence that induction of the NF-kappaB signal transduction pathway in macrophages plays a major role in initiating and mediating the inflammatory response leading to periprosthetic osteolysis.