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

Synthetic peptides of IL-1Ra and HSP70 have anti-inflammatory activity on human primary monocytes and macrophages: Potential treatments for inflammatory diseases

Chronic inflammatory diseases are increasing in developed societies, thus new anti-inflammatory approaches are needed in the clinic. Synthetic peptides complexes can be designed to mimic the activity of anti-inflammatory mediators, in order to alleviate inflammation. Here, we evaluated the anti-inflammatory efficacy of tethered peptides mimicking the interleukin-1 receptor antagonist (IL-1Ra) and the heat-shock protein 70 (HSP70). We tested their biocompatibility and anti-inflammatory activity in vitro in primary human monocytes and differentiated macrophages activated with two different stimuli: the TLR agonists (LPS + IFN-γ) or Pam3CSK4. Our results demonstrate that IL-1Ra and HSP70 synthetic peptides present a satisfactory biocompatible profile and significantly inhibit the secretion of several pro-inflammatory cytokines (IL-6, IL-8, IL-1β and TNFα). We further confirmed their anti-inflammatory activity when peptides were coated on a biocompatible material commonly employed in surgical implants. Overall, our findings support the potential use of IL-1Ra and HSP70 synthetic peptides for the treatment of inflammatory conditions.

Nano wear particles and the periprosthetic microenvironment in aseptic loosening induced osteolysis following joint arthroplasty

Joint arthroplasty is an option for end-stage septic arthritis due to joint infection after effective control of infection. However, complications such as osteolysis and aseptic loosening can arise afterwards due to wear and tear caused by high joint activity after surgery, necessitating joint revision. Some studies on tissue pathology after prosthesis implantation have identified various cell populations involved in the process. However, these studies have often overlooked the complexity of the altered periprosthetic microenvironment, especially the role of nano wear particles in the etiology of osteolysis and aseptic loosening. To address this gap, we propose the concept of the "prosthetic microenvironment". In this perspective, we first summarize the histological changes in the periprosthetic tissue from prosthetic implantation to aseptic loosening, then analyze the cellular components in the periprosthetic microenvironment post prosthetic implantation. We further elucidate the interactions among cells within periprosthetic tissues, and display the impact of wear particles on the disturbed periprosthetic microenvironments. Moreover, we explore the origins of disease states arising from imbalances in the homeostasis of the periprosthetic microenvironment. The aim of this review is to summarize the role of relevant factors in the microenvironment of the periprosthetic tissues, in an attempt to contribute to the development of innovative treatments to manage this common complication of joint replacement surgery.

The gut microbiota may be a novel pathogenic mechanism in loosening of orthopedic implants in rats

Particles released from implants cause inflammatory bone loss, which is a key factor in aseptic loosening, the most common reason for joint replacement failure. With the anticipated increased incidence of total joint replacement in the next decade, implant failure will continue to burden patients. The gut microbiome is increasingly recognized as an important factor in bone physiology, however, its role in implant loosening is currently unknown. We tested the hypothesis that implant loosening is associated with changes in the gut microbiota in a preclinical model. When the particle challenge caused local joint inflammation, decreased peri-implant bone volume, and decreased implant fixation, the gut microbiota was affected. When the particle challenge did not cause this triad of local effects, the gut microbiota was not affected. Our results suggest that cross-talk between these compartments is a previously unrecognized mechanism of failure following total joint replacement.

Early changes in serum osteocalcin and body weight are predictive of implant fixation in a rat model of implant loosening

Biomarkers are of interest to identify patients at risk for peri-implant osteolysis and aseptic loosening. We used a rat model of particle-induced peri-implant osteolysis to investigate if early changes in biomarkers were associated with subsequent implant fixation strength. Implants were placed in rat femora, which were then challenged with intra-articular knee injections of either clean polyethylene, lipopolysaccharide-doped polyethylene, or cobalt-chromium alloy particles, with particle-free vehicle serving as control (n ≥ 8 per group). Rats were weighed weekly, blood was collected at weeks 0, 3, 5, and 6, and locomotor behavior was assessed 4 days before study conclusion. Rats were euthanized 6 weeks post surgery. Week 6 serum was analyzed for five bone remodeling markers, while longitudinal serum was assessed for osteocalcin. Bone-implant contact, peri-implant trabecular architecture, and implant fixation strength were measured. Rats challenged with cobalt-chromium particles had a significant reduction in implant fixation strength compared with the vehicle-control group (P = .034). This group also had elevated serum osteocalcin (P = .005), depressed weight gain (P = .001) and less frequent rearing behavior (P = .029). Regardless of group, change in serum osteocalcin at week 3 (r = -.368; P = .046), change in weight at week 2 (r = .586; P < .001), as well as weight change at all other time intervals were associated with fixation strength. The finding that early alterations in serum osteocalcin and body weight were predictive of subsequent implant fixation strength supports continued investigation of biomarkers for early detection of peri-implant osteolysis and implant loosening. Further, change in biomarker levels was found to be more indicative of implant fixation status than any single measurement.

Sophocarpine attenuates wear particle-induced implant loosening by inhibiting osteoclastogenesis and bone resorption via suppression of the NF-κB signalling pathway in a rat model

BACKGROUND AND PURPOSE

Aseptic prosthesis loosening, caused by wear particles, is one of the most common causes of arthroplasty failure. Extensive and over-activated osteoclast formation and physiological functioning are regarded as the mechanism of prosthesis loosening. Therapeutic modalities based on inhibiting osteoclast formation and bone resorption have been confirmed to be an effective way of preventing aseptic prosthesis loosening. In this study, we have investigated the effects of sophocarpine (SPC, derived from Sophora flavescens) on preventing implant loosening and further explored the underlying mechanisms.

EXPERIMENTAL APPROACH

The effects of SPC in inhibiting osteoclastogenesis and bone resorption were evaluated in osteoclast formation, induced in vitro by the receptor activator of NF-κB ligand (RANKL). A rat femoral particle-induced peri-implant osteolysis model was established. Subsequently, micro-CT, histology, mechanical testing and bone turnover were used to assess the effects of SPC in preventing implant loosening.

KEY RESULTS

In vitro, we found that SPC suppressed osteoclast formation, bone resorption, F-actin ring formation and osteoclast-associated gene expression by inhibiting NF-κB signalling, specifically by targeting IκB kinases. Our in vivo study showed that SPC prevented particle-induced prosthesis loosening by inhibiting osteoclast formation, resulting in reduced periprosthetic bone loss, diminished pseudomembrane formation, improved bone-implant contact, reduced bone resorption-related turnover and enhanced stability of implants. Inhibition of NF-κB signalling by SPC was confirmed in vivo.

CONCLUSION AND IMPLICATIONS

SPC can prevent implant loosening through inhibiting osteoclast formation and bone resorption. Thus, SPC might be a novel therapeutic agent to prevent prosthesis loosening and for osteolytic diseases.

Arthrotomy-based preclinical models of particle-induced osteolysis: A systematic review

We completed a systematic literature review of in vivo animal models that use arthrotomy-based methods to study particle-induced peri-implant osteolysis. The purpose of the review was to characterize the models developed to date, to determine the questions addressed, to assess scientific rigor and transparency, and to identify gaps in knowledge. We probed three literature databases (Medline, Embase, and Scopus) and found 77 manuscripts that fit the search parameters. In the most recent 10 years, researchers mainly used rat and mouse models, whereas in the previous 20 years, large animal, canine, and rabbit models were more common. The studies have demonstrated several pathophysiology pathways, including macrophage migration, particle phagocytosis, increased local production of cytokines and lysosomal enzymes, elevated bone resorption, and suppressed bone formation. The effect of variation in particle characteristics and concentration received limited attention with somewhat mixed findings. Particle contamination by endotoxin was shown to exacerbate peri-implant osteolysis. The possibility of early diagnosis was demonstrated through imaging and biomarker approaches. Several studies showed that both local and systemic delivery of bisphosphonates inhibits the development of particle-induced osteolysis. Other methods of inhibiting osteolysis include the use of anabolic agents and altering the implant design. Few studies examined non-surgical rescue of loosened implants, with conflicting results with alendronate. We found that the manuscripts often lacked the methodological detail now advocated by the ARRIVE guidelines, suggesting that improvement in reporting would be useful to maximize rigor and transparency. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2595-2605, 2017.

A comparative multi-parametric in vitro model identifies the power of test conditions to predict the fibrotic tendency of a biomaterial

Despite growing effort to advance materials towards a low fibrotic progression, all implants elicit adverse tissue responses. Pre-clinical biomaterial assessment relies on animals testing, which can be complemented by in vitro tests to address the Russell and Burch’s 3R aspect of reducing animal burden. However, a poor correlation between in vitro and in vivo biomaterial assessments confirms a need for suitable in vitro biomaterial tests. The aim of the study was to identify a test setting, which is predictive and might be time- and cost-efficient. We demonstrated how sensitive in vitro biomaterial assessment based on human primary macrophages depends on test conditions. Moreover, possible clinical scenarios such as lipopolysaccharide contamination, contact to autologous blood plasma, and presence of IL-4 in an immune niche influence the outcome of a biomaterial ranking. Nevertheless, by using glass, titanium, polytetrafluorethylene, silicone, and polyethylene representing a specific material-induced fibrotic response and by comparison to literature data, we were able to identify a test condition that provides a high correlation to state-of-the-art in vivo studies. Most important, biomaterial ranking obtained under native plasma test conditions showed a high predictive accuracy compared to in vivo assessments, strengthening a biomimetic three-dimensional in vitro test platform.

Study of the polycarbonate-urethane/metal contact in different positions during gait cycle

Nowadays, a growing number of young and more active patients receive hip replacement. More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients.

Bone turnover markers correlate with implant fixation in a rat model using LPS-doped particles to induced implant loosening

Revision surgery for particle-induced implant loosening in total joint replacement is expected to increase dramatically over the next few decades. This study was designed to investigate if local tissue and serum markers of bone remodeling reflect implant fixation following administration of lipopolysaccharide (LPS)-doped polyethylene (PE) particles in a rat model. Twenty-four rats received bilateral implantation of intramedullary titanium rods in the distal femur, followed by weekly bilateral intra-articular injection of either LPS-doped PE particles (n = 12) or vehicle that contained no particles (n = 12) for 12 weeks. The group in which the particles were injected had increased serum C-terminal telopeptide of type I collagen (CTX-I), decreased serum osteocalcin (OC), increased peri-implant eroded surface, decreased peri-implant bone volume, and decreased mechanical pull-out strength compared to the controls. Implant fixation strength was positively correlated with peri-implant bone volume and serum OC and inversely correlated with serum CTX-I, while energy to yield was positively correlated with serum OC and inversely correlated with the number of tartrate-resistant acid phosphatase positive cells at the interface and the amount of peri-implant eroded surface. There was no effect on trabecular bone volume at a remote site. Thus, the particle-induced impaired fixation in this rat model was directly associated with local and serum markers of elevated bone resorption and depressed bone formation, supporting the rationale of exploring both anticatabolic and anabolic strategies to treat and prevent particle-related implant osteolysis and loosening, and indicating that serum markers may prove useful in tracking implant fixation.

Mediators of the inflammatory response to joint replacement devices

Joint replacement surgery is one of the success stories of modern medicine, restoring mobility, diminishing pain and improving the overall quality of life for millions of people. Unfortunately, wear of these prostheses over time generates debris, which activates an innate immune response that can ultimately lead to periprosthetic resorption of bone (osteolysis) and failure of the implant. Over the past decade, the biological interactions between the particulate debris from various implant materials and the immune system have begun to be better understood. The wear debris induces a multifaceted immune response encompassing the generation of reactive oxygen species and damage-associated molecular patterns, Toll-like receptor signaling and NALP3 inflammasome activation. Acting alone or in concert, these events generate chronic inflammation, periprosthetic bone loss and decreased osteointegration that ultimately leads to implant failure.