Implant Wear Debris Research Articles

Early failure of a polyvinyl alcohol hydrogel implant with foreign body reaction and osteolysis in an ovine model of cartilage repair

Purpose: Hemiarthroplasty with polyvinyl alcohol hydrogel (PVA) cartilage implants in the treatment of hallux rigidus showed initial promise with a 90% success rate. However, recent studies suggest that the implant may shrink and subside, leading to higher than anticipated failure rates. The purpose of this study was to characterize the healing response to polyvinyl implantation by using an ovine model. Methods: An osteochondral defect was created unilaterally in the medial femoral condyle of six sheep and filled with a PVA implant (Cartiva, Wright Medical) (n=4) or left empty (n=2). Sheep were followed for six months. Post-mortem quantitative CT (qCT) evaluations were performed to measure bone density using 5mm-wide ROI delineated in 3D reconstruction around the defect/implant area. Joints were then dissected and evaluated using a modified International Cartilage Repair Society (ICRS) macroscopic score (I=best, IV=worst). Osteochondral sections were assessed using a modified Osteoarthritis Research Society International (OARSI) histopathology net score (0=best, 20=worst). Synovial membrane histology was scored using the aseptic lymphocyte-dominated vasculitis-associated lesions (ALVAL) scoring system for soft tissue reaction (0=best, 19=worst). Both the synovial membrane and osteochondral sections underwent immunohistochemistry with anti-ionized calcium-binding adapter molecule 1 antibody (Iba1) to identify macrophages. Results: Two of four sheep with the PVA implant showed unrelenting pain and lameness necessitating early euthanasia. These were considered failed implants. qCT scans revealed 2-fold more osteolysis around failed implants than the other two (successful) implants or empty defects (Figure 1A). Grossly, failed implant sheep had ICRS scores of III and IV/V. The two successful implant sheep had ICRS scores of II/V and both empty defect sheep had scores of III/V. Osteochondral histology of failed implants had a mean OARSI score of 13/20 with extensive GAG loss and a stromal inflammatory reaction surrounding the implant that was up to 5-fold wider than successful implants (Figure 1B). This reaction contained abundant fibrovascular tissue with aggregates of lymphocytes and plasma cells. Failed implants revealed strong and diffuse Iba1 staining of macrophages along the implant/bone interface with cells densely packed in multiple rows (Figure 1C). Multinucleated giant cells and macrophages were identified surrounding presumptive implant debris in one failed implant (Figure 1C, red arrow and X). Successful implants and empty defects had few Iba1 positive cells randomly distributed (Figure 1C). Mean synovial membrane ALVAL score for failed implants was 11/19 with presence of an adverse local tissue reaction with lymphocytes and macrophages, vascular reactivity, and synovial hyperplasia (Figure 1D, E). In contrast, synovial membrane in successful implants and empty defects were normal (ALVAL 0/19). Conclusions: Polyvinyl alcohol hydrogel implants had a 50% early failure rate with uncontrollable pain, severe osteolysis, inflammation and an adverse local tissue reaction. Furthermore, the recruitment of macrophages and multinucleated giant cells are evidence of a foreign body reaction typically associated with implant wear debris. Non-degradable biomaterials such as PVA will result in continuous infiltration by macrophages and secretion of proinflammatory cytokines, leading to periprosthetic osteolysis and ultimately implant failure. These Results suggest that the use of this PVA implant should not be continued in human patients without further in vivo safety studies.

The Effects of Biomaterial Implant Wear Debris on Osteoblasts.

Aseptic loosening subsequent to periprosthetic osteolysis is the leading cause for the revision of arthroplasty failure. The biological response of macrophages to wear debris has been well established, however, the equilibrium of bone remodeling is not only dictated by osteoclastic bone resorption but also by osteoblast-mediated bone formation. Increasing evidence shows that wear debris significantly impair osteoblastic physiology and subsequent bone formation. In the present review, we update the current state of knowledge regarding the effect of biomaterial implant wear debris on osteoblasts. The interaction of osteoblasts with osteoclasts and macrophages under wear debris challenge, and potential treatment options targeting osteoblasts are also presented.

A cytotoxicity and wear analysis of trapeziometacarpal total joint replacement implant consisting of DLC-coated Co-Cr-Mo alloy with the use of titanium gradient interlayer

Diamond-like carbon (DLC) coatings exhibit excellent mechanical properties and improve the smoothness and the wear characteristic of the metallic component of total joint replacements. Although DLC is considered to be highly biocompatible, the effect of implant wear debris must be carefully analyzed. Simulated loading can help to mimic the wear of the implant in the human body over time. The purpose of the study presented here is to observe the wear of trapeziometacarpal (TMC) total joint arthroplasty implant consisting of DLC-coated Co-Cr-Mo alloy with the use of titanium gradient interlayer (Ti/Ti-C:H), and to analyze the potential cytotoxicity of the wear particles generated by simulated loading. No visible wear or delamination of the DLC coating was observed after 3 million cycles of increasing loading force up to 2.5 kN. Accordingly, no correlation was observed between increasing number of loading cycles (with increasing loading force) and decreasing proliferation of human osteoblast-like cells incubated in the wear suspension. We can therefore conclude that no cytotoxic wear debris was formed during the simulated loading of TMC total joint replacement implant composed of DLC-coated Co-Cr-Mo alloy with Ti/Ti-C:H gradient interlayer.

Effects of proteasome inhibitors on cytokines, metalloproteinases and their inhibitors and collagen type-I expression in periprosthetic tissues and fibroblasts from loose arthroplasty endoprostheses

ABSTRACTObjective: Aseptic loosening is a major problem in total joint replacement. Implant wear debris provokes a foreign body host response and activates cells to produce a variety of mediators and ROS, leading to periprosthetic osteolysis. Elevated ROS levels can harm proteasome function. Proteasome inhibitors have been reported to alter the secretory profile of cells involved in inflammation and also to induce ROS production. In this work, we aimed to document the effects of proteasome inhibitors MG-132 and Epoxomicin, on the production of factors involved in aseptic loosening, in periprosthetic tissues and fibroblasts, and investigate the role of proteasome impairment in periprosthetic osteolysis.Materials and methods: IL-6 levels in tissue cultures were determined by sandwich ELISA. MMP-1, -3, -13, -14 and TIMP-1 levels in tissue or cell cultures were determined by indirect ELISA. Results for MMP-1 and TIMP-1 in tissue cultures were confirmed by Western blotting. MMP-2 and MMP-9 levels were determined by gelatin zymography. Gene expression of IL-6, MMP-1,-3,-14, TIMP-1 and collagen type-I was determined by RT-PCR.Results: Results show that proteasome inhibition induces the expression of ΜΜΡ-1, -2, -3, -9 and suppresses that of IL-6, MMP-14, -13, TIMP-1 and collagen type I, enhancing the collagenolytic and gelatinolytic activity already present in periprosthetic tissues, as documented in various studies.Conclusions: These findings suggest that proteasome impairment could be a contributing factor to aseptic loosening. Protection and enhancement of proteasome efficacy could thus be considered as an alternative strategy toward disease treatment.

Metallic wear debris collected from patients induces apoptosis in rat primary osteoblasts via reactive oxygen species‑mediated mitochondrial dysfunction and endoplasmic reticulum stress.

Although total hip arthroplasty is considered to be an effective surgical procedure for treating hip joint diseases, it is hindered by implant wear debris, which induces aseptic loosening. Various cell types are involved in this pathogenesis; however, the interactions between wear debris and osteoblasts, which serve a crucial role in bone formation, have not been clearly illustrated. In the present study, minor metallic wear particles were collected from the interfacial membrane around loosened implants of patients, and the biological effects of these particles on rat primary osteoblasts were then explored. The results demonstrated that metallic wear debris was able to induce the apoptosis of treated cells in a concentration- and time-dependent manner. Furthermore, it was identified that reactive oxygen species (ROS) generation increased, the mitochondrial membrane potential collapsed, and the mitochondria-caspase-dependent and endoplasmic reticulum (ER) stress apoptotic pathways were activated following metallic wear debris application. In addition, apoptosis and associated pathways were inhibited by the use of N-acetyl-L-cysteine, an antioxidant that suppresses ROS production, indicating that the ROS generation triggered ER stress, mitochondrial dysfunction and downstream cascades that contributed to cell apoptosis. These findings suggest that metallic wear debris-induced ROS serve an important role in the apoptosis of osteoblasts. This provides a valuable insight, not only into understanding the mechanisms underlying the involvement of osteoblasts in osteolysis, but also into a potential novel therapeutic approach to treat implant aseptic loosening.

Mesenchymal stem cells in the aseptic loosening of total joint replacements.

Peri-prosthetic 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. Emerging treatment options to improve initial implant integration and treat developing osteolytic lesions by utilizing or targeting MSCs are also discussed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1195-1207, 2017.

Biologic Responses to Orthopedic Implants: Innate and Adaptive Immune Responses to Implant Debris.

Almost 20% of joint replacement implants fail at 15 to 20 years. Reports suggest that systemic effects of metal-on-metal implants and local effects of total joint arthroplasty implants contributing to implant failure are immune system based. Sometimes implant wear debris can cause implant failure resulting from bone fracture, infection, or implant fracture/failure; most often, aseptic osteolysis or loosening leads to wear debris. Debris is produced by wear (primary) or by corrosion. Corrosion-chemical oxidation comprising reduction reactions involving electron transport-produces electrochemical degradation. Metallic implant degradation occurs when electrochemical dissolution and mechanical/physical wear are combined (i.e., tribocorrosion). With metal-on-metal implants, even with relatively low levels of wear and particle release, pathology caused by metal debris such as pseudotumor/fibrous tissue growth can lead to early implant failure.

Resveratrol Protects against Titanium Particle-Induced Aseptic Loosening Through Reduction of Oxidative Stress and Inactivation of NF-κB.

Aseptic implant loosening is closely associated with chronic inflammation induced by implant wear debris, and reactive oxygen species (ROS) play an important role in this process. Resveratrol, a plant compound, has been reported to act as an antioxidant in many inflammatory conditions; however, its protective effect and mechanism against wear particle-induced oxidative stress remain unknown. In this study, we evaluated resveratrol's protective effects against wear particle-induced oxidative stress in RAW 264.7 macrophages. At non-toxic concentrations, resveratrol showed dose-dependent inhibition of nitric oxide (NO) production, ROS generation, and lipid peroxidation. It also downregulated the gene expression of oxidative enzymes, including inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX)-1 and NOX-2, and promoted the gene expression and activities of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and glutathione peroxidase (GPx). This protective effect against wear particle-induced oxidative stress was accompanied by a reduction of gene expression and release of tumor necrosis factor-α (TNF-α), and decreased gene expression and phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). These findings demonstrate that resveratrol can inhibit wear particle-induced oxidative stress in macrophages, and may exert its antioxidant effect and protect against aseptic implant loosening.

Ultrasonic welding in orthopedic implants

A critical event in hip replacement is the occurrence of osteolysis. Cemented hip replacements most commonly use polymethylmethacrylate (PMMA), not as an adhesive but rather a filler to limit micromotion and provide stability. PMMA, however, contributes to osteolysis through both a thermal response during curing and implant wear debris. In order to mitigate the occurrence of osteolysis, we are exploring ultrasonic welding as a means of attachment. Weld strength was assessed using ex vivo bovine rib and femur bones. A flat end mill provided 20 site locations for insertion of an acrylonitrile butadiene styrene, ABS pin. Each location was characterized on topography, porosity, discoloration, and any other notable features. Each site was welded using a Branson Ultrasonic Welder 2000iw; 20 kHz, 1100 W. Machine parameters include weld force, weld time, and hold time. The bond strength was determined using a tensile tester. Tensile testing showed a negative correlation between porosity and bond strength. Further evaluation and characterization of bone properties to bond strength will enable appropriate selection of welding properties to ensure a superior bond.

Effects of gelsolin on macrophage inflammatory responses to orthopaedic implant wear debris.

The local effects of implant wear debris on surrounding tissue has been a major focus of many investigators. Although there have been improvements in implants, significant numbers of revision surgeries are performed to address these issues. Gelsolin (GSN) is a protein in the cytoplasm and circulating serum involved in actin breakdown as well as anti-inflammatory processes. In this study, we tested the hypothesis that GSN in the presence of wear debris in vitro decreases the inflammatory response of a human monocyte cell line. We utilized titanium-, polyethylene-, and cobalt-characterized wear particles in a 1:100 and a 1:500 cell-to-particle ratios in the presence of a low (0.2 µM) and normal (2.0 µM) concentrations of GSN and compared the inflammatory response to cells without GSN exposure. The results show that IL-6, IL-1, TNF-α, and PGE₂ all increased with higher concentrations of GSN. Although the anti-inflammatory properties of GSN were not seen in this in vitro experiment, it has previously been shown that GSN does affect the inflammatory response of monocytes to orthopedic implant wear debris. The dose-response curve for GSN may have a bimodal profile, which should be further investigated.

Histologic study of periprosthetic osteolytic lesions after AES total ankle replacement. A 22 case series

Medium-term results for total ankle replacement (TAR) are in general satisfactory, but there is a high redo rate for periprosthetic osteolysis associated with the AES implant. Comparing radioclinical findings and histologic analysis of implant revision procedure specimens can account for the elevated rate of osteolysis associated with the AES TAR implant. In a prospective series of 84 AES TAR implants (2003-2008), 25 underwent revision for osteolysis (including three undergoing revision twice) at a mean 59.8 months. Eight patients had hydroxyapatite (HA) coated models and the others had titanium-hydroxyapatite (Ti-HA) coatings. Radiographs were systematically analyzed on Besse's protocol and evolution was monitored on AOFAS scores. The 94 specimens taken for histologic analysis during revision were re-examined, focusing specifically on foreign bodies. Macroscopically, no metallosis or polyethylene wear was found at revision. AOFAS global and pain scores fell respectively from 89.7/100 at 1 year postoperatively to 72.9 before revision and from 32.5/40 to 20.6/40, although global scores were unchanged in 25% of patients. Radiologically, all patients showed tibial and talar osteolytic lesions, 45% showed cortical lysis and in 25% the implant had collapsed into the cysts. All specimens showed macrophagic granulomatous inflammatory reactions in contact with a foreign body; the cysts showed necrotic remodeling. Some of the foreign bodies could be identified on optical histologic examination with polyethylene in 95% of the specimens and metal in 60% (100% of HA-coated models and 33.3% of Ti-HA-coated models). Unidentifiable material was associated: a brownish pigment in Ti-HA-coated models (33.3%) and flakey bodies in 44.4% of the HA-coated models and 18.2% of the Ti-HA-coated models. The phenomenon of periprosthetic osteolysis is still poorly understood, although implant wear debris seems to be implicated. All the patients with HA-coated implants with modular tibial stem had metal particles in the tissue around the implant, although their exact nature could not be determined. The double-layer Ti-HA coating may induce delamination by fretting while the biological bone anchorage is forming. Prospective cohort study - Level IV.

Toll-like receptor 4 signaling pathway mediates proinflammatory immune response to cobalt-alloy particles

Metal orthopedic implant debris-induced osteolysis of hip bone is a major problem in patients with prosthetic-hips. Although macrophages are the principal targets for implant-wear debris, the receptor(s) and mechanisms underlying these responses are not fully elucidated. We examined whether the TLR4 pathway mediates immune response to metal-on-metal (MoM) implant-generated wear particles. Human monocytes (THP-1) were exposed to Co-alloy particles at increasing particle:cell ratio for 24h. Challenge with particles caused up-regulation of IL-1β, TNF-α and IL-8, and mediated degradation of cytosolic I-κB and nuclear translocation of NF-κB. Blocking antibodies against TLR4 or gene silencing of MyD88 and IRAK-1 prevented particle-induced I-κB/NF-κB activation response and markedly inhibited IL-8 release. Particle-mediated IL-8 response was not observed in TLR4-negative HEK293T cells; whereas transfection-based TLR4-overexpression in HEK293T enabled particle-sensitivity, as observed by I-κB degradation and IL-8 expression in response to particles. Results demonstrate that Co-alloy particles trigger immune response via the TLR4-MyD88-dependent signaling pathway.

Cellular response to prosthetic wear debris differs in patients with and without rheumatoid arthritis

To examine whether patients with rheumatoid arthritis (RA) demonstrate patterns of prosthetic wear or cellular responses to implant wear debris different from those demonstrated by patients without inflammatory joint disease. Thirty-eight patients who had undergone a primary revision of a total elbow arthroplasty for aseptic loosening between 1996 and 2008 were identified. Twenty-five of these patients had RA, and 13 did not have inflammatory arthritis. Clinical data, gross wear patterns of the removed prostheses, and histopathologic analyses of peri-implant tissue were compared between the patients with RA and those without RA. Evaluation of the retrieved prostheses showed that conformational change of the humeral polyethylene bushing was associated with the generation of polyethylene and metal particles. The amount and type of wear debris in periprosthetic tissues were similar in patients with and those without RA. Patients with RA who were not receiving anti-tumor necrosis factor (anti-TNF) therapy exhibited a histologic pattern of interstitial and sheet-like lymphocytic infiltrates associated with a high plasma cell composition, which was different from the predominantly perivascular infiltrates with few plasma cells seen in non-RA patients (P = 0.04). Patients with RA who were receiving anti-TNF therapy showed a mixed perivascular and interstitial pattern of infiltrates with variable cell composition. Patients with RA exhibited a distinct cellular response to implant wear debris compared with patients without RA. This reaction was unrelated to differences in the type or amount of wear debris and was mitigated by anti-TNF therapy. These results suggest an intrinsic alteration in immunoregulation in RA and have implications for potential immunologic treatment of osteolysis in these patients.

Distinct immunohistomorphologic changes in periprosthetic hip tissues from historical and highly crosslinked UHMWPE implant retrievals

Assessment of immune response to implant wear debris in periprosthetic tissue following total hip arthroplasty suggests that multiple factors are involved in the loss implant function. The current study investigated wear debris and the associated immunohistomorphologic changes in tissues from nine patients with historical (gamma air-sterilized) and nine highly crosslinked UHMWPE implant components. Paraffin embedded tissue sections were evaluated for the presence of histiocytes, giant cells, fibrocartilage/bone, and necrosis. To determine the incidence, degree and co-localization of immunohistomorphologic changes and wear, overlapping full-field tissue arrays were collected in brightfield and polarized light. The historical cohort tissues predominantly showed histiocytes associated with significant accumulations of small wear (0.5-2 microm), and giant cells associated with large wear (> or =2 microm). Frequently, focal regions of necrosis were observed in association with wear debris. For the highly crosslinked cohort, inflammation and associated wear debris were limited, but in tissues from patients revised after implantation times of >2 years a response was observed. Whereas significant amounts of fibrocartilage/bone were observed in patients at earlier implantation times. In both cohorts, tissue responses were more extensive in the retroacetabular or proximal femoral regions. The current findings suggest that wear debris-induced inflammation may be a major contributor to the loss of implant function for both the historical and highly crosslinked cohorts, but it is not the primary cause of early implant loosening. This study highlights the importance of using a more quantitative and standardized assessment of immunohistomorphologic responses in periprosthetic tissues, and emphasizes differences in specific anatomical regions of individual patient tissues.

A Quantitative Evaluation of Inflammatory Cells in Human Temporomandibular Joint Tissues From Patients With and Without Implants

Previous studies made only qualitative assessments of immune cell responses to temporomandibular joint (TMJ) implant wear debris. The aim of this study was to perform a quantitative comparison of inflammatory cell types in TMJ tissues with implant wear debris, TMJ tissues with a history of disc pathology without implant debris, and TMJ tissues from normal control subjects. TMJ tissues were collected from the following 3 groups of subjects: 1) individuals with failed TMJ implants (implant group, n = 10), 2) patients with TMJ disc pathology but no history of implant placement (nonimplant surgery group, n = 10), and normal cadaveric tissues with no history of surgery (control group, n = 10). Tissue sections (5 microm) from all subjects were stained with hematoxylin-eosin, after which cell counts were done for 2 types of inflammatory cells: multinucleated giant cells and lymphocytes. Mean inflammatory cell counts from the 3 groups were compared by use of a 1-way analysis of variance procedure and Bonferroni adjustment to maintain an overall type I error rate of .05. Implant group tissues contained significantly more inflammatory cells than tissues from the nonimplant surgery and control groups (P < .0001). Multinucleated giant cells were only present in implant group tissues. Although the high number of multinucleated giant cells present in the implant group obscured a total count of lymphocytes for that group, lymphocyte cell counts were still significantly greater (P < .005) in implant group tissues than in tissues from the other 2 groups. Our data provide quantitative confirmation that the presence of Proplast-Teflon implant (Vitek, Houston, TX) wear debris is associated with a significant increase in the number of local multinucleated giant cells and lymphocytes.

Evaluation of Surgically Retrieved Temporomandibular Joint Alloplastic Implants: Pilot Study

The purpose of this study was to perform a retrieval analysis of temporomandibular joint (TMJ) alloplastic interpositional implants and test possible correlation between implant failure features and patient clinical outcomes. In addition, we investigated the implants' surface and examined the foreign body reaction associated with different types of alloplastic materials. Twelve implants (Proplast/Teflon [Vitek, Houston, TX] and Silastic [Dow Corning, Midland, MI]) were surgically removed from the patients' TMJs. Implant surface failure features (fracture length, perforation of the implants) were observed using stereomicroscopy and recorded for description of the failure mechanisms and to statistically compare with clinical outcomes. Patients' clinical data (pain symptoms and mandibular function) were collected and examined. Clinical outcomes were obtained relative to symptom severity (Symptom Severity Index [SSI]) and jaw function (modified Mandibular Function Impairment Questionnaire [mMFIQ]). Peri-implant soft tissues and implants were analyzed with light microscopy and stereo zoom microscopy. Electron microprobe analysis of implant fragments and peri-implant tissues was performed. The statistical results showed that only the presence of implant perforation was statistically associated with the SSI, specifically with the pain tolerability dimension. No statistical association was seen between any of the other implant failure predictors and the SSI and between the predictors and the mMFIQ. Stereo zoom microscopy suggested that Proplast/Teflon implants (n = 7) were susceptible to perforation, layer tearing, fracture and fiber extrusion. The Silastic implants (n = 3) revealed a possible center perforation with fracture lines towards the periphery and fiber extrusion. Teflon implant wear debris particles appear to trigger a multinucleated giant cell foreign body reaction. Facial pain was a significant correlate to perforation and breakdown of the alloplastic TMJ interpositional implants, and most likely was the reason for implant removal.

Microstimulation at the bone–implant interface upregulates osteoclast activation pathways

Peri-implant bone resorption after total joint arthroplasty is a key parameter in aseptic loosening. Implant wear debris and biomechanical aspects have both been demonstrated to be part of the bone resorption process. However, neither of these two parameters has been clearly identified as the primary initiator of peri-implant bone resorption. For the biomechanical parameters, micromotions were measured at the bone–implant interface during normal gait cycles. The amplitude of the micromotions was shown to trigger differentiation of bone tissues. So far no data exists directly quantifying the effect of micromotion and compression on human bone. We hypothesize that micromotion and compression at the bone–implant interface may induce direct activation of bone resorption around the implant through osteoblasts–osteoclasts cell signaling in human bone. This hypothesis was tested with an ex vivo loading system developed to stimulate trabecular bone cores and mimic the micromotions arising at the bone–implant interface. Gene expression of RANKL, OPG, TGFB2, IFNG and CSF-1 was analyzed after no mechanical stimulation (control), exposure to compression or exposure to micromotions. We observed an 8-fold upregulation of RANKL after exposure to micromotions, and downregulation of OPG, IFNG and TGFB2. The RANKL:OPG ratio was upregulated 24-fold after micromotions. This suggests that the micromotions arising at the bone–implant interface during normal gait cycles induce a bone resorption response after only 1 h, which occurs before any wear debris particles enter the system.

Kinetics of polymethylmethacrylate particle‐induced inhibition of osteoprogenitor differentiation and proliferation

Periprosthetic bone loss induced by implant wear debris may be a combined effect of osteolysis and reduced bone formation resulting from particle-induced suppression of osteoprogenitor differentiation. This study investigated the time-dependent effects of polymethylmethacrylate (PMMA) particles on the osteogenic capability of bone marrow osteoprogenitor cells during the early phase of differentiation. Murine bone marrow cells were challenged with PMMA particles (0.30% v/v) on the first day of growth in osteogenic medium. Particles were removed from culture after 1, 3, and 5 days, respectively, after which cell growth in osteogenic medium was continued until the 15th day. Bone marrow osteoprogenitor cells exposed to particles during the first 5 days of differentiation showed complete, irreversible inhibition of proliferation, alkaline phosphatase expression, and mineralization. Osteoprogenitors exposed to particles for more than 5 days showed the same degree of inhibition, while those exposed to particles for less than 5 days showed a diminished inhibitory response. Conditioned medium from particle-treated cells did not suppress osteogenic development, demonstrating that suppression of osteogenesis was not due to secreted inhibitory factors. This study has shown that the early phase of osteoprogenitor differentiation is a crucial time period during which exposure to PMMA particles causes irreversible inhibition of osteogenesis.

Single nucleotide polymorphisms in the interleukin-6 gene promoter, tumor necrosis factor-α gene promoter, and transforming growth factor-β1 gene signal sequence as predictors of time to onset of aseptic loosening after total hip arthroplasty: preliminary study

BackgroundAseptic loosening resulting from inflammatory response to the implant wear debris is the major cause of late total hip arthroplasty (THA) failure. We examined single nucleotide polymorphisms in genes encoding for three involved cytokines — interleukin-6 (IL-6), tumor necrosis factor-a (TNF-α), and transforming growth factor-β1 (TGF-β1) — as potential predictors of time to onset of aseptic instability. MethodsA total of 41 patients/45 total hip endoprostheses (same type, same surgeon) were followed up for as long as 18years. They were genotyped for the IL-6 promoter (−597G→A) and (−572G→C), TNF-α promoter (−308G→A), and TGF→β1 signal sequence (29T→C) transitions. Cox regression was performed on the prosthesis survival. ResultsOverall, 22 of 45 prostheses developed aseptic instability. Cumulative survivals at 10 and 15years after THA were 95.6% and 66.6%, respectively. The effect of a particular polymorphic site was estimated with adjustment for sex, age at THA, reason for THA, and the effects of other analyzed sites. The hazard ratio (HR) for genotype T/T versus “C-allele carriage” at the TGF-β1 site was 8.23 [95% confidence interval (CI) 1.45–46.8] (P=0.017) or 5.70 (1.39–23.4) (P=0.016) when the IL-6 promoter sites were considered as a “combination of genotypes (−597) | (−572).” The most prevalent combination of genotypes at IL-6 sites was G/A (−597) | C/C (−572). HR for this combination (versus other combinations) was 5.43 (1.73–17.0) (P=0.004) when “TGF-/31 (29T→C)” was considered as a three-level factor (three possible genotypes), and 4.92 (1.71-14.1) (P=0.003) when TGF-β1 site was considered as a two-level factor (T/T and “C-allele carriage”). The HR for the “A-allele carriage” at TNF-α (−308G→A) could not be determined (only two patients had the G/G genotype). ConclusionsThis preliminary study is the first to suggest that the TGF-β1 signal sequence (29T→C) and IL-6 promoter (−597G→A) | (−572G→C) transitions are predictive for the time to onset of aseptic instability after THA.

Human Periprosthetic Tissues Implanted in Severe Combined Immunodeficient Mice Respond to Gene Transfer of a Cytokine Inhibitor

Periprosthetic tissue formation and local inflammation that are associated with wear debris contribute to the pathogenesis of aseptic loosening of a prosthesis. This study evaluated a retrovirus-mediated gene therapy with use of a novel xenograft-based animal model. Human periprosthetic tissues obtained from patients during revision arthroplasty performed because of aseptic loosening of a prosthetic joint were transplanted into the left quadriceps and paravertebral muscles of severe combined immunodeficient (SCID) mice. The engrafted tissues were recovered seven, fifteen, or thirty days after implantation for histological and molecular analyses. The periprosthetic tissues were incubated with retroviruses encoding for human interleukin-1 receptor antagonist (hIL-1Ra) or bacteria beta-galactosidase (LacZ) at 37 degrees C for three hours prior to implantation to evaluate their responses to gene modification. The human periprosthetic tissues were well accepted in SCID mice for up to thirty days, with angiogenesis occurring in the majority of the implanted tissue sections. The histological appearance was consistent between the recovered graft tissue and the original donor tissue. Strong expression of interleukin-1, tumor necrosis factor, and interleukin-6 was detected in the xenografts with use of immunohistochemical stains. Histological analysis revealed that interleukin-1 receptor antagonist gene modification significantly decreased the total number of inflammatory cells (p < 0.01) in engrafted human tissue containing implant wear debris. Real-time reverse transcription-polymerase chain reaction and immunohistochemical staining showed declining expression levels of interleukin-1 and tumor necrosis factor following interleukin-1 receptor antagonist gene transfer in comparison with LacZ-transduced or virus-free controls. Human periprosthetic tissue can survive in the SCID mouse host for up to thirty days and responds to the interleukin-1 receptor antagonist gene transfer with the amelioration of inflammation.