Cellular proliferation and cytokine responses to polymethylmethacrylate particles in patients with a cemented total joint arthroplasty

Nanoplastics affect the inflammatory cytokine release by primary human monocytes and dendritic cells

So far, the human health impacts of nano- and microplastics are poorly understood. Thus, we investigated whether nanoplastics exposure induces inflammatory processes in primary human monocytes and monocyte-derived dendritic cells. We exposed these cells in vitro to nanoplastics of different shapes (irregular vs. spherical), sizes (50-310 nm and polydisperse mixtures) and polymer types (polystyrene; polymethyl methacrylate; polyvinyl chloride, PVC) using concentrations of 30-300 particles cell^-1. Our results show that irregular PVC particles induce the strongest cytokine release of these nanoplastics. Irregular polystyrene triggered a significantly higher pro-inflammatory response compared to spherical nanoplastics. The contribution of chemicals leaching from the particles was minor. The effects were concentration-dependent but varied markedly between cell donors. We conclude that nanoplastics exposure can provoke human immune cells to secrete cytokines as key initiators of inflammation. This response is specific to certain polymers (PVC) and particle shapes (fragments). Accordingly, nanoplastics cannot be considered one homogenous entity when assessing their health implications and the use of spherical polystyrene nanoplastics may underestimate their inflammatory effects.

Identification of biological risk factors for persistent postoperative pain after total knee arthroplasty

BACKGROUND

There is growing evidence that cytokines and adipokines are associated with osteoarthritis (OA) severity, progression, and severity of associated pain. However, the cytokine response to total knee arthroplasty (TKA) and its association with persistent postoperative pain is not well understood. This study aims to describe the perioperative systemic (plasma) and local (synovial fluid) cytokine profiles of patients who do and do not develop persistent pain after TKA.

METHODS

Patients undergoing primary unilateral TKA for end-stage OA were prospectively enrolled. Demographic and clinical data were gathered preoperatively and postoperatively. Synovial fluid was collected pre arthrotomy and plasma was collected at multiple time points before and after surgery. Persistent postoperative pain (PPP) was defined as Numerical Rating Score≥4 at 6 months. Cytokine levels were measured using the V-Plex Human Cytokine 30-Plex Panel (Mesoscale-Rockville, Maryland, USA). Cytokine levels were compared between PPP and minimal pain groups. Given that the study outcomes are exploratory, no adjustment was performed for multiple testing.

RESULTS

Incidence of persistent pain at 6 months post TKA was 15/162 (9.3%). Postoperative plasma levels of four cytokines were significantly different in patients who developed persistent postoperative pain: interleukin (IL)-10, IL-1β, vascular endothelial growth factor, and IL12/IL23p40. Significantly lower IL-10 levels in the prearthrotomy synovial fluid were associated with development of postoperative persistent pain.

CONCLUSIONS

This prospective cohort study described a distinct acute perioperative inflammatory response profile in patients who developed persistent post-TKA pain, characterized by significant differences in four cytokines over the first 2 postoperative days. These results support the growing evidence that the patient-specific biologic response to surgery may influence longer-term clinical outcomes after TKA.

TRIAL REGISTRATION NUMBER

Clinicaltrials.gov NCT02626533.

Cytokine and neuropeptide levels are associated with pain relief in patients with chronically painful total knee arthroplasty: a pilot study

Background

There are few studies with an assessment of the levels of cytokines or neuropeptides as correlates of pain and pain relief in patients with painful joint diseases. Our objective was to assess whether improvements from baseline to 2-months in serum cytokine, chemokine and substance P levels were associated with clinically meaningful pain relief at 2-months post-injection in patients with painful total knee arthroplasty (TKA).

Methods

Using data from randomized trial of 60 TKAs, we assessed the association of change in cytokine/chemokine/Substance P levels with primary study outcome, clinically important improvement in Western Ontario McMaster Osteoarthritis Index (WOMAC) pain subscale at 2-months post-injection using Student’s t-tests and Spearman’s correlation coefficient (non-parametric). Patients were categorized as pain responders (20-point reduction or more on 0-100 WOMAC pain) vs. pain non-responders. Sensitivity analysis used 0–10 daytime pain numeric rating scale (NRS) instead of WOMAC pain subscale.

Results

In a pilot study, compared to non-responders (n = 23) on WOMAC pain scale at 2-months, pain responders (n = 12) had significantly greater increase in serum levels of IL-7, IL-10, IL-12, eotaxin, interferon gamma and TNF-α from baseline to 2-months post-injection (p < 0.05 for all). Change in several cytokine/chemokine and substance P levels from pre-injection to 2-month follow-up correlated significantly with change in WOMAC pain with correlation coefficients ranging −0.37 to −0.51: IL-2, IL-7, IL-8, IL-9, IL-16, IL-12p, GCSF, IFN gamma, IP-10, MCP, MIP1b, TNF-α and VEGF (n = 35). Sensitivity analysis showed that substance P decreased significantly more from baseline to 2-months in the pain responders (0.54 ± 0.53; n = 10) than in the pain non-responders (0.48 ± 1.18; n = 9; p = 0.023) and that this change in serum substance P correlated significantly with change in daytime NRS pain, correlation coefficient was 0.53 (p = 0.021; n = 19). Findings should be interpreted with caution, since cytokine analyses were performed for a sub-group of the entire trial population.

Conclusion

Serum cytokine, chemokine and Substance P levels correlated with pain response in patients with painful TKA after an intra-articular injection in a randomized trial.

Murine model of prosthesis failure for the long-term study of aseptic loosening

We examined a novel mouse model of wear debris-induced prosthesis instability and osteolysis, and its application for the evaluation of therapy. A stainless steel or titanium-alloy pin was implanted into the proximal tibia to form a contiguous surface with the articular cartilage. In some mice, titanium particles were injected into the tibial canal during the surgery, followed by monthly intraarticular injection. MicroCT scans revealed that the implants without particle challenge were stable without bone mineral density changes for 6 months. Histological analysis showed new bone formation around the implant at 6 weeks postsurgery. Periprosthetic soft tissue with inflammatory cells was a ubiquitous finding at the interface between the implant and surrounding bone in samples exposed to titanium particles, and expression of IL-1beta, TNFalpha, and CD68 was common in these joints. Pullout tests indicated that an average 5N load was required to pull out stable implants from surrounding bone. However, particle stimulation dramatically reduced the pullout force to less than 0.4 N. The feasibility of in vivo gene transfer on this model was confirmed by X-gal staining of synovial membrane and periprosthetic tissue after injection of AAV-LacZ in the prosthetic joint. This murine model of weight-bearing knee prosthesis provides an economical, reproducible, and easily obtained means to study joint arthroplasty failure. The ability to evaluate the biomechanical properties of the prosthetic joint, in addition to histological and biochemical examination, results in a useful model to investigate many of the properties of prosthetic joint components during the response to debris-associated osteolysis.

Inhibition of particulate debris-induced osteolysis by alendronate in a rat model

A rat model was used to study the efficacy of alendronate therapy in inhibition of particle-induced periprosthetic osteolysis. A prosthesis was simulated by inserting a cylindrical polymethylmethacrylate plug into the distal femur of 24 rats allowing the plug to communicate with the joint space. Intra-articular injections of irregularly-shaped ultra-high molecular weight polyethylene particles of 20-200 pm in diameter were administered at 2-week intervals. The rats were randomized into two groups (n=12 each). Group A rats received twice weekly subcutaneous injections of alendronate sodium while group B rats received injections of saline vehicle only. At 10 weeks all rats were sacrificed. The distal femurs were harvested and axial sections were prepared for histologic analysis. Each section was graded on a scale of 1-4, quantifying the degree of osteolysis surrounding the polymethylmethacrylate plug. Microscopic examination showed a significant (P<.0001) difference in the amount of periprosthetic bone. Femurs from group A treated with alendronate demonstrated mostly normal or near-normal periprosthetic trabeculations, whereas femurs from group B treated with saline showed extensive bone resorption. There was no qualitative difference in the inflammatory cellular response between the groups. This study established the ability of alendronate to inhibit the osteoclastic-mediated osteolysis around joint implants.

Inflammatory responses to orthopaedic biomaterials in the murine air pouch

An in vivo model of the inflammatory response to orthopaedic biomaterials was used to examine cellular and cytokine responses to polymer particles of ultra high molecular weight polyethylene (UHMWPE) and polymethylmethacrylate (PMMA), and metal particles of cobalt-chrome (Co-Cr) and titanium alloy (Ti-6Al-4V). Responses were determined separately and in combinations, to examine interactions between different forms of biomaterials. Murine air pouches were injected with particle suspensions, and reactions evaluated using histological, immunological, and molecular techniques. All particulate biomaterials caused significant increases in membrane thickness compared with control (saline) air pouches, with the highest reaction seen in response to Ti-6Al-4V particles. A synergistic increase in membrane thickness was observed when PMMA was combined with UHMWPE, suggesting that multiple biomaterial stimuli markedly increase the inflammatory reaction. Cellular analysis indicated that all particles increased the absolute number and the percentage of macrophages in the membrane over the control level, with the most pronounced increase due to individual biomaterial occurring with UHMWPE particles. Cytokine analysis revealed that biomaterials provoked a strong IL-1 response. Ti-6Al-4V stimulated the highest IL-6 gene transcription and the lowest IL-1 gene transcription. The data suggest that synergism in the inflammatory response to biomaterials may be important in adverse responses to orthopaedic wear debris.

No lymphokines in T-cells around loosened hip prostheses

Research results have been contradictory about the role of lymphocytes and immune response in aseptic loosening of total hip replacement (THR). Conclusive evidence is still lacking in spite of extensive in vivo and in vitro studies. Our study was designed to check whether T-cells were activated and if they produced lymphokines in synovial membrane-like interface tissue around loosened THRs. Tissue sections were stabilized and permeabilized to allow the cytokine-specific antibodies to penetrate through the cell membrane and the membranes of intracellular organelles. This technique, combined with computer-assisted image analysis, permits the detection and quantitation of lymphokine-producing cells. We found that the number of T-cells was low, and none of the T-cells was activated, as shown by the absence of interleukin-2 receptor (IL-2R) immunoreactivity. There was no cell producing lymphokines, such as interleukin-2 (IL-2), interferon-gamma (IFN-gamma), and tumor necrosis factor-beta (TNF-beta). Our results suggest that T-cell-mediated immune response is not actively involved in aseptic loosening of THR.

Expression of the CD69 activation antigen on lymphocytes of patients with hip prosthesis

The aim of the study was to evaluate the sensitization to metals in patients with Co-Cr hip prosthesis. Peripheral blood mononuclear cells (PBMC) were collected from 14 healthy donors and three groups of patients: 10 candidates for primary total joint replacements, 11 patients with well-fixed implant and 13 patients with aseptic loosening of the hip prosthesis. PBMCs were cultured with the metal ions employed for implant manufacturing and the expression of CD69 activation antigen on CD3/T lymphocytes was detected by flow cytometry. Chromium extract increased significantly the expression of CD3/CD69 phenotype in patients with loosening of hip prosthesis. The chromium-induced 'activation index' was higher in patients with loosening of hip prosthesis than in healthy donors and in pre-implant patients. The cobalt-stimulated PBMC of patients with either well-fixed or loosened prosthesis had an 'activation index' significantly higher than healthy donors. The activation index values were used to graduate the PBMC-response as 'normal' (> or = 0.9 and < 2), 'low' (< 0.9) and 'high' (> or = 2): an high-activation index was observed only in chromium-exposed PBMC of patients with prosthesis. Our data show that chromium released from orthopedic implants could be responsible for the lymphocyte sensitization and flow cytometry is an easy and reliable method for monitoring the hypersensitivity state in patients with metal prostheses. Activated lymphocytes in the peri-implant tissue are likely to elicit a localized immune response and contribute to maintain the inflammatory process evolving in the implant failure.

Osteoconductivity of an injectable and bioresorbable poly(propylene glycol-co-fumaric acid) bone cement

We have investigated an injectable form of a resorbable bone cement based on in situ crosslinking of the unsaturated polyester, poly(propylene glycol-co-fumaric acid) (PPF). This material, filled with calcium gluconate/hydroxyapatite (CG/HA), cures to a hard cement degradable by hydrolysis. The purpose of this study was to evaluate the osteoconductive properties of this injectable cement. The cement was used as an adjunct to fixation with an intramedullary rod in the rat femoral osteotomy model. Ingrowth of new bone into the cement was examined in vivo. Negative and positive controls with rigid and loose internal fixation were included for comparison. Animals were evaluated histologically and histomorphometrically at 4 weeks postoperatively. Results of this study showed osteoblastic activity and new bone formation at the interface between the femoral bone and the cement in the experimental group. However, there was little bone remodeling at the endosteal surface in positive and negative controls. Histologic evaluation of the cement revealed the formation of cavitations, which likely resulted from leaching of the highly soluble calcium gluconate portion of the filler from the cement. These cavitations were sites of ingrowth of vascular and bony tissues. Intimate contact between the bone cement and the endosteal surface of the cortex was found. Quantitative histomorphometric analysis corroborated these observations. Findings of this study demonstrated the osteoconductivity of this type of injectable PPF-based bone cement.

Experimental acute hematogenous osteomyelitis in mice. II. Influence of Staphylococcus aureus infection on T-cell immunity

A murine model of acute hematogenous osteomyelitis was used to study the immune response following Staphylococcus aureus infection and to examine the hypothesis that the bacteria may modify T-cell responses due to the production of bacterial enterotoxins with mitogenic or superantigenic activity. Lymph-node T cell-receptor expression was assessed with use of flow cytometry and reverse transcription-polymerase chain reaction techniques, and increased apoptosis (programmed cell death) in T-cell subsets was monitored. The expression and levels of circulating cytokines and T-cell cytokines within tissues surrounding the damaged area of the proximal tibia were also investigated. Analysis of T-cell receptors in experimental osteomyelitis revealed two distinct patterns of T-cell evolution during the disease. Certain T-cell subsets (Vbeta2, Vbeta3, Vbeta9, and Vbeta10) were activated and expanded during the first 24 hours after infection; they reached maximum levels 6 days after infection, followed by a return to pre-infection levels. In contrast, other T-cell subsets (Vbeta11, Vbeta12, Vbeta13, Vbeta14, and Vbeta16) contracted during the first 24 hours after infection, followed by expansion to a maximum level 9 days after infection. Activation and proliferation of T-cell subsets (notably Vbeta14 T cells) was followed by apoptosis, suggesting that staphylococcal bone infection caused superantigenic-like effects on the mouse immune system. Analysis of cytokine responses in local tissue revealed that the T-cell cytokines interleukin-2 and interferon-gamma showed a late and relatively short activation pattern compared with the inflammatory cytokines interleukin-1, interleukin-6, and tumor necrosis factor-alpha. The results suggest that Staphylococcus aureus bone infection may undermine the antibacterial immune response through downregulation of T-cell immunity and immune-cytokine production, which could increase the severity of the systemic infection and local osseous destruction that occur with acute hematogenous osteomyelitis.

Cellular proliferation and cytokine responses of murine macrophage cell line J774A.1 to polymethylmethacrylate and cobalt-chrome alloy particles

Wear debris from orthopedic joint implants have been postulated to initiate a cascade of complex cellular events that results in aseptic loosening of the prosthesis and eventually in loss of function of the device. The impact of biomaterials used in these devices on host inflammatory response has not been examined extensively. Polymethylmethacrylate (PMMA) and cobalt-chrome alloy (CoCr) are biomaterials widely used in orthopedic implant devices. Macrophages are an important component of the host inflammatory response, and we have examined the effect of PMMA and CoCr particles on the murine macrophage cell line J774A.1. Our objective was to obtain a comprehensive analysis of the particle-macrophage interaction, and we examined a number of basic biological responses of the J774A.1 cell line, including cell proliferation, apoptosis, cytokines secreted into the culture supernatant (TNFalpha, IL-1alpha, IL-6, and IL-12) and mRNA expression of the cytokines (TNFalpha, IL-1alpha, IL-6, IFN-alpha, M-CSF, and TGF-beta) in response to PMMA and CoCr particles. Our results indicate that the relative contribution of PMMA and CoCr particles in J774A.1 activation is negligible, and we observed a change in metabolic activity of J774A.1 cells only at higher concentrations of CoCr particles.

Cellular immune responses to orthopaedic implant materials following cemented total joint replacement

In vitro cellular immune responses to metallic and polymeric implant materials in particulate form were measured preoperatively in 185 patients. The patients were candidates for either primary total joint replacement (n = 65) or revision arthroplasty (n = 120). Proliferative cellular responses to polymethylmethacrylate particles in patients with osteoarthritis at revision surgery for aseptic loosening were significantly higher than the responses of patients with osteoarthritis at either primary surgery or surgical revision for mechanical failure of the prosthesis or sepsis. The responses to particles of cobalt-chromium alloy at revision surgery were also higher than the responses at primary surgery. The responses were reevaluated in 32 patients after a minimum of 10 months following surgery to correlate individual changes in the biological responses with clinical progress. Reevaluation at early follow-up of patients who had undergone primary surgery revealed significantly elevated proliferative responses and in vitro cytokine production in response to polymethylmethacrylate and cobalt-chromium alloy particles compared with their preoperative responses. In contrast, the response at follow-up to polymethylmethacrylate was significantly reduced in patients who had undergone revision surgery, and this reduction corresponded with a marked improvement in pain, joint motion, and function following revision surgery. These data suggest that specific cellular responses to polymethylmethacrylate or cobalt-chromium alloy particles, or both, may be associated with loose or painful prostheses.

Techniques to investigate cellular and molecular interactions in the host response to implanted biomaterials

Evaluation of the host response to implanted materials requires systematic, objective investigations of responses at both the cellular and molecular levels. This article explains the basis behind two technologies: antibody and molecular techniques, which will give valuable information when applied to investigations of cells and molecules involved in the host biomaterial interaction. Such investigations are well underway, and a number of groups are now studying well characterised cell markers or molecules to evaluate the host response to biomaterials. Here we outline current technologies for the development of antibodies as tools to study cell markers or molecules, including those for which reagents are not yet available and DNA based technologies, whose continued application should prove an invaluable adjunct to existing approaches. These technologies may be particularly valuable to investigations focusing on newly characterised cytokines, receptors or cell adhesion molecules and subsequently provide a way forward for the production of advanced biomaterials.

Total joint arthroplasty and the immune response

Total joint replacement arthroplasty has proved highly successful in the management of osteoarthritis and rheumatoid arthritis. The cause of aseptic loosening of prosthetic joint replacement components is unclear. Early experience with total joint arthroplasty was plagued by a number of problems that no longer exist as major impediments to long-term success. Improvement in the operating room environment and the use of prophylactic antibiotics have substantially reduced the high incidence of infection to less than 1%. Implant materials have long been considered biologically inert, but recent studies indicate that inflammatory reactions directed against the implanted materials may contribute to aseptic loosening. Currently, particulate debris from cement or polyethylene causing loosening of the prosthesis is the major problem in total joint arthroplasty. Significant data suggest a progression from a simple inflammatory reaction to complex immune responses against the biomaterials. The cellular responses to particles of polymethylmethacrylate, ultra-high-molecular-weight polyethylene, and alloys of cobalt-chromium and titanium have been assayed in vitro in patients with osteoarthritis, rheumatoid arthritis, and avascular necrosis who had total joint replacement. Elevated immunologic cell proliferation responses to both acrylic and cobalt chromium were observed in patients with aseptically loosened prostheses. These findings suggest that the development of a cellular response to particulate debris may be significant in the pathogenesis of aseptic loosening.

The immune response to implant materials in humans

The etiology of aseptic loosening of prosthetic joint replacement components is unclear. Implant materials have been considered biologically inert, but recently studies indicate that inflammatory reactions directed against the implanted materials may contribute to aseptic loosening. Data suggesting a progression from a simple inflammatory reaction to complex immune responses against the biomaterials are reviewed. The cellular responses to particles of polymethylmethacrylate, ultrahigh molecular weight polyethylene, and alloys of cobalt-chromium and titanium were assayed in vitro to determine cell proliferation in patients with underlying diagnoses of osteoarthrosis, rheumatoid arthritis, and avascular necrosis who had joint replacement. Control populations were provided by patients with similar diagnoses who were preoperative surgical candidates. The underlying diagnoses did not seem to influence responses to particle stimulation. Elevated responses to both acrylic and cobalt-chromium were observed in patients with aseptically loosened prostheses. These findings suggest that the development of a cellular response to particulate debris may be significant in the pathogenesis of aseptic loosening.