Biological response to prosthetic debris

Characterisation of porous knitted titanium for replacement of intervertebral disc nucleus pulposus

Effective restoration of human intervertebral disc degeneration is challenged by numerous limitations of the currently available spinal fusion and arthroplasty treatment strategies. Consequently, use of artificial biomaterial implant is gaining attention as a potential therapeutic strategy. Our study is aimed at investigating and characterizing a novel knitted titanium (Ti6Al4V) implant for the replacement of nucleus pulposus to treat early stages of chronic intervertebral disc degeneration. Specific knitted geometry of the scaffold with a porosity of 67.67 ± 0.824% was used to overcome tissue integration failures. Furthermore, to improve the wear resistance without impairing original mechanical strength, electro-polishing step was employed. Electro-polishing treatment changed a surface roughness from 15.22 ± 3.28 to 4.35 ± 0.87 µm without affecting its wettability which remained at 81.03 ± 8.5°. Subsequently, cellular responses of human mesenchymal stem cells (SCP1 cell line) and human primary chondrocytes were investigated which showed positive responses in terms of adherence and viability. Surface wettability was further enhanced to super hydrophilic nature by oxygen plasma treatment, which eventually caused substantial increase in the proliferation of SCP1 cells and primary chondrocytes. Our study implies that owing to scaffolds physicochemical and biocompatible properties, it could improve the clinical performance of nucleus pulposus replacement.

Is Metal Particle Release Associated with Peri-implant Bone Destruction? An Emerging Concept

Peri-implant diseases affecting the surrounding structures of endosseous dental implants include peri-implant mucositis and peri-implantitis. The prevalence of peri-implantitis ranges between 15% and 20% after 10 y, highlighting the major challenge in clinical practice in the rehabilitation of dental implant patients. The widespread nature of peri-implant bone loss poses difficulties in the management of biological complications affecting the long-term success of osseointegrated implant reconstructions. Metal and titanium particles have been detected in peri-implant supporting tissues. However, it remains unclear what mechanisms could be responsible for the elicitation of particle and ion release and whether these released implant-associated materials have a local and/or systemic impact on the peri-implant soft and hard tissues. Metal particle release as a potential etiologic factor has been intensively studied in the field of orthopedics and is known to provoke aseptic loosening around arthroplasties and is associated with implant failures. In dental medicine, emerging information about metal/titanium particle release suggests that the potential impact of biomaterials at the abutment or bone interfaces may have an influence on the pathogenesis of peri-implant bone loss. This mini-review highlights current evidence of metal particle release around dental implants and future areas for research.

Effects of low-dose X-ray irradiation on activated macrophages and their possible signal pathways

Low-dose irradiation (LDI) has been used in clinics to treat human diseases, including chronic inflammation. This study assessed the effects of LDI on the inflammatory response of activated mouse primary peritoneal macrophages, and the underlying signal pathways. Primary peritoneal macrophages were isolated from mice and then incubated with lipopolysaccharide (LPS)-coated Ti microparticles (Ti-positive control) with or without brief exposure to LDI (X-ray, 0.5 Gy) 1 h later (Ti-LDI group) or left untreated in culture medium (Ti-negative control). The macrophages were then subjected to qRT-PCR, Western blot, cell viability CCK-8 assay, and ELISA. qRT-PCR analysis revealed the Ti-LDI group expressed significantly lower levels of IL-1β, IL-6, and TNF-α mRNA than those of the Ti-positive control group, while the ELISA data showed that Ti-LDI group had significantly lower secretion of IL-1β, IL-6, and TNF-α proteins. The most significant reduction associated with LDI was the secretion TNF-α protein, which barely increased from 13 to 25 h after treatment. Western blot data demonstrated that phosphorylation of p65 and ERK was much lower in the Ti-LDI group than in the controls. The data from the current study suggests that LDI of activated mouse macrophages was associated with significantly lower inflammation responses, compared with non-exposed activated macrophages, which was possibly through inhibition of the NF-κB and ERK pathways.

The Effect of RANKL/OPG Balance on Reducing Implant Complications

Despite the phenomenal success of implants particularly in the realms of dentistry and orthopaedics, there are still challenges to overcome. The failure of implants resulting from infection, prosthetic loosening, and non-union continue to be the most notorious examples. The cascade of fracture healing and bone repair, especially with the presence of an implant, is complex because it involves a multifaceted immune response alongside the intricate process of bone formation and remodelling. Bone loss is a serious clinical problem that is frequently accompanied by chronic inflammation, illustrating that there is a convoluted relationship between inflammation and bone erosion. The effects of pro-inflammatory factors play a significant role in initiating and maintaining osteoclastogenesis that results in bone resorption by osteoclasts. This is because there is a disruption of the relative ratio between Receptor Activator of Nuclear Factor κB-Ligand (RANKL) and osteoprotegerin (OPG), which is central to modulating bone repair and remodelling. This review aims to provide a background to the bone remodelling process, the bone repair cascade post-implantation, and the associated complications. Furthermore, current clinical solutions that can influence bone formation via either internal or extrinsic mechanisms will be described. These efficacious treatments for osteolysis via targeting the RANKL/OPG ratio may be crucial to reducing the incidence of related implant failures in the future.

Effects of pulsed electromagnetic fields and platelet rich plasma in preventing osteoclastogenesis in an in vitro model of osteolysis

Osteolysis is the main limiting cause for the survival of an orthopedic prosthesis and is accompanied by an enhancement in osteoclastogenesis and inflammation, due by wear debris formation. Unfortunately therapeutic treatments, besides revision surgery, are not available. The aim of the present study was to evaluate the effects of Pulsed Electro Magnetic Fields (PEMFs) and platelet rich plasma (PRP), alone or in combination, in an in vitro model of osteolysis. Rats peripheral blood mononuclear cells were cultured on Ultra High Molecular Weight Polyethylene particles and divided into four groups of treatments: (1) PEMF stimulation (12 hr/day, 2.5 mT, 75 Hz, 1.3 ms pulse duration); (2) 10% PRP; (3) combination of PEMFs, and PRP; (4) no treatment. Treatments were performed for 3 days and cell viability, osteoclast number, expression of genes related to osteoclastogenesis and inflammation and production of pro-inflammatory cytokines were assessed up to 14 days. PEMF stimulation exerted best results because it increased cell viability at early time points and counteracted osteoclastogenesis at 14 days. On the contrary, PRP increased osteoclastogenesis and reduced cell viability in comparison to PEMFs alone. The combination of PEMFs and PRP increased cell viability over time and reduced osteoclastogenesis in comparison to PRP alone. However, these positive results did not exceed the level achieved by PEMF alone. At longer time points PEMF could not counteract osteoclastogenesis increased by PRP. Regarding inflammation, all treatments maintained the production of pro-inflammatory cytokines at low level, although PRP increased the level of interleukin 1 beta.

Toward the development of biomimetic injectable and macroporous biohydrogels for regenerative medicine

Repairing or replacing damaged human tissues has been the ambitious goal of regenerative medicine for over 25years. One promising approach is the use of hydrated three-dimensional scaffolds, known as hydrogels, which have had good results repairing tissues in pre-clinical trials. Benefiting from breakthrough advances in the field of biology, and more particularly regarding cell/matrix interactions, these hydrogels are now designed to recapitulate some of the fundamental cues of native environments to drive the local tissue regeneration. We highlight the key parameters that are required for the development of smart and biomimetic hydrogels. We also review the wide variety of polymers, crosslinking methods, and manufacturing processes that have been developed over the years. Of particular interest is the emergence of supramolecular chemistries, allowing for the development of highly functional and reversible biohydrogels. Moreover, advances in computer assisted design and three-dimensional printing have revolutionized the production of macroporous hydrogels and allowed for more complex designs than ever before with the opportunity to develop fully reconstituted organs. Today, the field of biohydrogels for regenerative medicine is a prolific area of research with applications for most bodily tissues. On top of these applications, injectable hydrogels and macroporous hydrogels (foams) were found to be the most successful. While commonly associated with cells or biologics as drug delivery systems to increase therapeutic outcomes, they are steadily being used in the emerging fields of organs-on-chip and hydrogel-assisted cell therapy. To highlight these advances, we review some of the recent developments that have been achieved for the regeneration of tissues, focusing on the articular cartilage, bone, cardiac, and neural tissues. These biohydrogels are associated with improved cartilage and bone defects regeneration, reduced left ventricular dilation upon myocardial infarction and display promising results repairing neural lesions. Combining the benefits from each of these areas reviewed above, we envision that an injectable biohydrogel foam loaded with either stem cells or their secretome is the most promising hydrogel solution to trigger tissue regeneration. A paradigm shift is occurring where the combined efforts of fundamental and applied sciences head toward the development of hydrogels restoring tissue functions, serving as drug screening platforms or recreating complex organs.

The Impact of Metal Ion Exposure on the Cellular Behavior of Human Osteoblasts and PBMCs: In Vitro Analyses of Osteolytic Processes

Osteolysis in the periprosthetic tissue can be caused by metallic wear particles and ions that can originate from implant surface corrosion. These products influence cellular behavior and stimulate the expression of proinflammatory cytokines. The purpose of this study was to evaluate the impact of CoCr29Mo6 ions on cell survival, differentiation, and cytokine expression in human osteoblasts and peripheral blood mononuclear cells (PBMCs). Thus, we exposed cells with a mixture of 200 µg/L ion solution and determined cell viability and apoptosis/necrosis. Gene expression analyses of osteoblastic and osteoclastic differentiation markers as well as pro-osteolytic mediators (IL-6, IL-8, TNF-α, MCP-1, MMP1, TIMP1) were performed. These markers were also investigated in mixed cultures of adherent and non-adherent PBMCs as well as in co-cultures of human osteoblasts and PBMCs. The ion solution induced necrosis in osteoblasts and PBMCs in single cultures. All examined mediators were highly expressed in the co-culture of osteoblasts and PBMCs whereas in the single cell cultures only IL-6, IL-8, and MMP1 were found to be stimulated. While the applied concentration of the CoCr29Mo6 ion solutions had only marginal effects on human osteoblasts and PBMCs alone, the co-culture may provide a comprehensive model to study osteolytic processes in response to Co and Cr ions.

Direct influence of titanium and zirconia particles on the morphology and functionality of mature human osteoclasts

Within the last ten years of biomedical implants, the focus is increasingly on bioceramics, specifically on zirconia (ZrO₂ ). Hence, we analyzed the impact of ZrO₂ particles in comparison to titanium particles on mature human osteoclasts (OCs) as little is known about the direct effect of wear particles on mature OCs and their role in the osteolytic process during aseptic endoprosthesis loosening. Changes in cell morphology and functionality of OCs incubated with particles in different concentrations were investigated in vitro. OCs tend to be enlarged after three days of cultivation with both types of particles, especially with high concentrations of ZrO₂ , suggesting increased cell fusion. Further, we identified significantly increased expression of OC specific and bone matrix related genes: VNR, RANK, TRAP, and CTSK pointing on a direct stimulatory particle effect on the functionality of mature OCs. In completion, we quantified the bone resorption activity of particle treated mature OCs but could not detect a significant difference in bone resorption compared to OCs cultivated without particles. However, we could identify significantly higher gene expression of MMP-1 in particle treated OCs compared to untreated control OCs after three days of incubation. We also detected an impaired production of the tissue inhibitor of metalloproteinase, especially for OCs treated with high ZrO₂ concentrations. In conclusion, our in vitro data show that abrasion particles could have a direct influence on mature OCs and therefore could promote increased OC-mediated bone resorption during aseptic loosening of total joint replacements. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2608-2615, 2017.

Macrophages and bone inflammation

Bone metabolism is tightly regulated by the immune system. Accelerated bone destruction is observed in many bone diseases, such as rheumatoid arthritis, fracture, and particle-induced osteolysis. These pathological conditions are associated with inflammatory responses, suggesting the contribution of inflammation to bone destruction. Macrophages are heterogeneous immune cells and are polarized into the proinflammatory M1 and antiinflammatory M2 phenotypes in different microenvironments. The cytokines produced by macrophages depend on the macrophage activation and polarization. Macrophages and macrophage-derived cytokines are important to bone loss in inflammatory bone disease. Recent studies have shown that macrophages can be detected in bone tissue and interact with bone cells. The interplay between macrophages and bone cells is critical to bone formation and repair. In this article, we focus on the role of macrophages in inflammatory bone diseases, as well as discuss the latest studies about macrophages and bone formation, which will provide new insights into the therapeutic strategy for bone disease.

Histological Analysis of Early Osteolysis in Total Ankle Arthroplasty

BACKGROUND

The purpose of this study was to perform a histological comparative analysis of tibiotalar joint samples taken from areas of osteolysis adjacent to total ankle arthroplasties vs control synovial specimens to determine the reaction to and presence of polyethylene (PE) particles.

METHODS

A total of 57 pathology samples were identified in the osteolysis group, while 11 were identified in the control group. For each sample, hematoxylin and eosin, Oil Red O (ORO), and macrophage marker CD163-stained slides were created. Polarized light and ORO stain were used to identify PE particles. The presence of metal particles and giant cell reaction to PE particles were also scored.

RESULTS

Macrophages, PE particles, metallosis, and foreign body giant cell reaction scores were significantly higher in the osteolysis group compared with the control group. In the osteolysis group, ORO staining was positive in 93% (53/57), birefringent material was present in 96.5% (55/57), and macrophage infiltrates were present in 96.5% (55/57). Foreign body giant cell reaction with giant cells surrounding PE particles was present in 49.1% (28/57) of osteolytic specimens. The presence of foreign body giant cell reaction was associated with significantly higher macrophage, ORO, and polarizable material scores. The average time to surgery for osteolysis from the index ankle replacement was 6.0 (range, 0-15) years for the 57 patients in the osteolysis group.

CONCLUSION

This study is the largest ankle arthroplasty histological analysis to show that areas of osteolysis consist of abundant polyethylene wear particles, present both intracellularly and extracellularly. Furthermore, these areas were associated with a CD163⁺ macrophage infiltrate and frequently a foreign body reaction with giant cells engulfing PE particles. It is likely that implant wear particles play a significant role in osteolysis based on the histopathology.

LEVEL OF EVIDENCE

Level III, retrospective comparative series.

Influence of different grained powders and pellets made of Niobium and Ti-42Nb on human cell viability

Nowadays, biomaterials can be used to maintain or replace several functions of the human body if necessary. Titanium and its alloys, i.e. Ti6Al4V are the most common materials (70 to 80%) used for structural orthopedic implants due to their unique combination of good mechanical properties, corrosion resistance and biocompatibility. Addition of β-stabilizers, e.g. niobium, can improve the mechanical properties of such titanium alloys further, simultaneously offering excellent biocompatibility. In this in vitro study, human osteoblasts and fibroblasts were cultured on different niobium specimens (Nb Amperit, Nb Ampertec), Nb sheets and Ti-42Nb (sintered and 3D-printed by selective laser melting, SLM) and compared with forged Ti6Al4V specimens. Furthermore, human osteoblasts were incubated with particulates of the Nb and Ti-42Nb specimens in three concentrations over four and seven days to imitate influence of wear debris. Thereby, the specimens with the roughest surfaces, i.e. Ti-42Nb and Nb Ampertec, revealed excellent and similar results for both cell types concerning cell viability and collagen synthesis superior to forged Ti6Al4V. Examinations with particulate debris disclosed a dose-dependent influence of all powders with Nb Ampertec showing the highest decrease of cell viability and collagen synthesis. Furthermore, interleukin synthesis was only slightly increased for all powders. In summary, Nb Ampertec (sintered Nb) and Ti-42Nb materials seem to be promising alternatives for medical applications compared to common materials like forged or melted Ti6Al4V.

RAW 264.7 co-cultured with ultra-high molecular weight polyethylene particles spontaneously differentiate into osteoclasts: an in vitro model of periprosthetic osteolysis

Wear-particle osteolysis affects prosthesis survival leading to implant loosening up to 70% of revisions. Therapeutic strategies are increasing, however alternative testing methods to experimentally evaluate such treatments are lacking. The aim of this study was to reproduce an in vitro osteolysis model recapitulating the events that, starting from the exposure of macrophages to polyethylene, lead to the establishment of osteoclastogenesis and inflammation. Responses to polyethylene, at 3 and 7 days, in a macrophage cell line, RAW 264.7, were determined by DNA quantification, immunofluorescence, pit assay, gene expression, cytokine production and NF-kB activation. Results showed that 3 days exposure to particles could induce a significant production of Tumor Necrosis Factor alpha (p < 0.0005) and Prostaglandin E₂ (p < 0.005) compared to controls. Particles also induced macrophages to spontaneously differentiate into mature and active osteoclasts, in terms of identification of multinucleated cells by Phalloidin staining and by the analysis of osteoclast-specific gene markers. In particular, at 3 days polyethylene induced a significant up-regulation of Nuclear Factor of Activated T-cells, cytoplasmic 1, Receptor Activator of Nuclear factor Kappa-B and Receptor Activator of Nuclear Factor Kappa-B Ligand genes (p < 0.0005) compared to controls. At protein level, the particles induced a significant increase of Receptor Activator of Nuclear Factor Kappa-B Ligand at day 7 over controls (p < 0.0005). Osteoclasts were capable to resorb bone even in absence of differentiating factors. The possible mechanism, beside spontaneous osteoclastogenesis mediated by wear debris, was identified in an autocrine up-regulation of Receptor activator of nuclear factor kappa-B ligand gene expression and protein synthesis. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 510-520, 2017.

Particle Disease: A Current Review of the Biological Mechanisms in Periprosthetic Osteolysis After Hip Arthroplasty

Background:

Inflammatory responses to wear debris cause osteolysis that leads to aseptic prosthesis loosening and hip arthroplasty failure. Although osteolysis is usually associated with aseptic loosening, it is rarely seen around stable implants. Aseptic implant loosening is a simple radiologic phenomenon, but a complex immunological process. Particulate debris produced by implants most commonly causes osteolysis, and this is called particle-associated periprosthetic osteolysis (PPO).

Objective:

The objective of this review is to outline the features of particle-associated periprosthetic osteolysis to allow the physician to recognise this condition and commence early treatment, thereby optimizing patient outcome.

Methods:

A thorough literature search was performed using available databases, including Pubmed, to cover important research published covering particle-associated PPO.

Results:

Although osteolysis causes bone resorption, clinical, animal, and in vitro studies of particle bioreactivity suggest that particle-associated PPO represents the culmination of several biological reactions of many cell types, rather than being caused solely by the osteoclasts. The biological activity is highly dependent on the characteristics and quantity of the wear particles.

Conclusion:

Despite advances in total hip arthroplasty (THA), particle-associated PPO and aseptic loosening continue to be major factors that affect prosthetic joint longevity. Biomarkers could be exploited as easy and objective diagnostic and prognostic targets that would enable testing for osteolysis after THA. Further research is needed to identify new biomarkers in PPO. A comprehensive understanding of the underlying biological mechanisms is crucial for developing new therapeutic interventions to reverse or suppress biological responses to wear particles.

Contribution of human osteoblasts and macrophages to bone matrix degradation and proinflammatory cytokine release after exposure to abrasive endoprosthetic wear particles

One of the major reasons for failure after total joint arthroplasty is aseptic loosening of the implant. At articulating surfaces, defined as the interface between implant and surrounding bone cement, wear particles can be generated and released into the periprosthetic tissue, resulting in inflammation and osteolysis. The aim of the present study was to evaluate the extent to which osteoblasts and macrophages are responsible for the osteolytic and inflammatory reactions following contact with generated wear particles from Ti-6Al-7Nb and Co-28Cr-6Mo hip stems. To this end, human osteoblasts and THP-1 monocytic cells were incubated with the experimentally generated wear particles as well as reference particles (0.01 and 0.1 mg/ml) for 48 h under standard culture conditions. To evaluate the impact of these particles on the two cell types, the release of different bone matrix degrading matrix metalloproteinases (MMPs), tissue inhibitors of MMPs (TIMPs), and relevant cytokines were determined by multiplex enzyme-linked immunosorbent assays. Following incubation with wear particles, human osteoblasts showed a significant upregulation of MMP1 and MMP8, whereas macrophages reacted with enhanced MMP3, MMP8 and MMP10 production. Moreover, the synthesis of TIMPs 1 and 2 was inhibited. The osteoblasts and macrophages also responded with modified expression of the inflammatory mediators interleukin (IL)-6, IL-8, monocyte chemoattractant protein-1 and vascular endothelial growth factor. These results demonstrate that the release of wear particles affects the release of proinflammatory cytokines and has a negative impact on bone matrix formation during the first 48 h of particle exposure. Human osteoblasts are directly involved in the proinflammatory cascade of bone matrix degradation. The simultaneous activation and recruitment of monocytes/macrophages boosted osteolytic processes in the periprosthetic tissue. By the downregulation of TIMP production and the concomitant upregulation of MMPs as a response to particle exposure, bone formation around implants may be suppressed, resulting in implant failure.