Aseptic and septic prosthetic joint loosening: Impact of biomaterial wear on immune cell function, inflammation, and infection

Graphene oxide-decorated microporous sulfonated polyetheretherketone for guiding osteoporotic bone regeneration

Recent studies have indicated that the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is an ideal therapeutic target for osteoporosis because it affects the differentiation of osteoblasts and osteoclasts. RNA sequencing utilizing multifunctional graphene oxide (GO) nanosheets revealed a correlation between GO nanomaterials and the NLRP3 inflammasome, as well as osteogenic genes in macrophages. This study aimed to construct a bone microenvironment-responsive multifunctional two-dimensional GO coating on the surface of microporous sulfonated polyetheretherketone (SPEEK) via polydopamine modification (SPEEK@PDA-GO). In vitro analysis showed that the SPEEK@PDA-GO implants weakened the STAT3-mediated NLRP3/caspase-1/IL-1β signaling pathway in macrophages and subsequently prevented the formation of an extracellular inflammatory microenvironment, which is crucial for osteoclastogenesis. SPEEK@PDA-GO displayed significantly higher expression of M2 macrophage markers and osteogenic genes, indicating that the multifunctional GO nanosheets could facilitate bone regeneration via their immunomodulatory properties. The ability of SPEEK@PDA-GO to stimulate new bone formation and block bone loss caused by estrogen loss due to ovariectomy was also analyzed. The findings of this study offer valuable information on the possible involvement of the NLRP3 inflammasome in the interaction between the immune system and bone health in patients with osteoporosis.

Friend or foe? Inflammation and the foreign body response to orthopedic biomaterials

The use of biomaterials and implants for joint replacement, fracture fixation, spinal stabilization and other orthopedic indications has revolutionized patient care by reliably decreasing pain and improving function. These surgical procedures always invoke an acute inflammatory reaction initially, that in most cases, readily subsides. Occasionally, chronic inflammation around the implant develops and persists; this results in unremitting pain and compromises function. The etiology of chronic inflammation may be specific, such as with infection, or be unknown. The histological hallmarks of chronic inflammation include activated macrophages, fibroblasts, T cell subsets, and other cells of the innate immune system. The presence of cells of the adaptive immune system usually indicates allergic reactions to metallic haptens. A foreign body reaction is composed of activated macrophages, giant cells, fibroblasts, and other cells often distributed in a characteristic histological arrangement; this reaction is usually due to particulate debris and other byproducts from the biomaterials used in the implant. Both chronic inflammation and the foreign body response have adverse biological effects on the integration of the implant with the surrounding tissues. Strategies to mitigate chronic inflammation and the foreign body response will enhance the initial incorporation and longevity of the implant, and thereby, improve long-term pain relief and overall function for the patient. The seminal research performed in the laboratory of Dr. James Anderson and co-workers has provided an inspirational and driving force for our laboratory's work on the interactions and crosstalk among cells of the mesenchymal, immune, and vascular lineages, and orthopedic biomaterials. Dr. Anderson's delineation of the fundamental biologic processes and mechanisms underlying acute and chronic inflammation, the foreign body response, resolution, and eventual functional integration of implants in different organ systems has provided researchers with a strategic approach to the use of biomaterials to improve health in numerous clinical scenarios.

Hecogenin alleviates LPS-induced osteolysis via regulating pyroptosis and ROS involved Nrf2 activation

Reactive oxidative species (ROS) generation triggers pyroptosis and induces development of inflammatory osteolysis. Hecogenin (HG) has anti-inflammatory and antioxidative property, but its effects on inflammatory osteolysis remains unclear. In our study, we investigated the mechanism of HG on pyroptosis and its effect on inflammatory osteolysis in vitro and in vivo. The impact of HG on osteoclastogenesis was evaluated using cytotoxicity, TRAcP staining and bone resorption assays. The RNA-sequencing was employed to identify potential signaling pathways, and then RT-qPCR, western blot, immunofluorescence, and ELISA were used to verify. To determine the protective effect of HG in vivo, Lipopolysaccharide (LPS)-induced animal models were utilized, along with micro-CT and histological examination. HG suppressed RANKL-induced osteoclast differentiation, bone resorption, NFATc1 activity and downstream factors. RNA-sequencing results showed that HG inhibited osteoclastogenesis by modulating the inflammatory response and macrophage polarization. Furthermore, HG inhibited the NF-κB pathway, and deactivated the NLRP3 inflammasome. HG activated the expression of nuclear factor E2-related factor 2 (Nrf2) to eliminate ROS generation. Importantly, the inhibitory effect of HG on NLRP3 inflammasome could be reversed by treatment with the Nrf2 inhibitor ML385. In vivo, HG prevented the mice against LPS-induced osteolysis by suppressing osteoclastogenesis and inflammatory factors. In conclusion, HG could activate Nrf2 to eliminate ROS generation, inactivate NLRP3 inflammasome and inhibit pyroptosis, thereby suppressing osteoclastogenesis in vitro and alleviating inflammatory osteolysis in vivo, which indicating that HG might be a promising candidate to treat inflammatory osteolysis.

Bioinspired Hybrid Nanostructured PEEK Implant with Enhanced Antibacterial and Anti-inflammatory Synergy

Implant-associated infections and excessive immune responses are two major postsurgical issues for successful implantation. However, conventional strategies including antibiotic treatment and inflammatory regulation are always compromised due to the comodification of various biochemical agents and instances of functional interference. It is imperative to provide implant surfaces with satisfactory antibacterial and anti-inflammatory properties. Here, a dual-effect nanostructured polyetheretherketone (PEEK) surface (NP@PDA/Zn) with bionic mechano-bactericidal nanopillars and immobilized immunomodulatory Zn2+ is designed. The constructed hybrid nanopillars display remarkable antibacterial performance against Gram-negative and Gram-positive strains through the synergy of physical and chemical bactericidal effects imposed by nanopillars and Zn2+. Meanwhile, the immunoregulatory property is evaluated through the investigation of macrophage polarization both in vitro and in vivo, and the results reveal that NP@PDA/Zn could downregulate the expression of M1-related cytokines and decrease the M1 macrophage recruitment to lower the inflammatory response. Notably, the surface exhibited exceptional biocompatibility with discerning biocidal activity between bacterial and mammalian cells and antioxidant performance that effectively scavenges ROS, minimizing potential cytotoxicity. Taken together, NP@PDA/Zn presents a convenient and promising strategy of combining synergistic bactericidal activity and inflammatory regulation without any mutual interference, which can support the development of multifunctional implant-associated materials.

Piezoelectric biomaterials with embedded ionic liquids for improved orthopedic interfaces through osseointegration and antibacterial dual characteristics

Orthopedic implant failures, primarily attributed to aseptic loosening and implant site infections, pose significant challenges to patient recovery and lead to revision surgeries. Combining piezoelectric materials with ionic liquids as interfaces for orthopedic implants presents an innovative approach to addressing both issues simultaneously. In this study, films of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) incorporated with 1-ethyl-3-methylimidazolium hydrogen sulfate ([Emim][HSO4]) ionic liquid were developed. These films exhibited strong antibacterial properties, effectively reducing biofilm formation, thereby addressing implant-related infections. Furthermore, stem cell-based differentiation assays exposed the potential of the composite materials to induce osteogenesis. Interestingly, our findings also revealed the upregulation of calcium channel expression as a result of electromechanical stimulation, pointing to a mechanistic basis for the observed biological effects. This work highlights the potential of piezoelectric materials with ionic liquids to improve the longevity and biocompatibility of orthopedic implants. Offering dual-functionality for infection prevention and bone integration, these advancements hold significant potential for advancing orthopedic implant technologies and improving patient outcomes.

Engineered Niobium Carbide MXenzyme-Integrated Self-Adaptive Coatings Inhibiting Periprosthetic Osteolysis by Orchestrating Osteogenesis-Osteoclastogenesis Balance

Periprosthetic osteolysis induced by the ultrahigh-molecular-weight polyethylene (UHMWPE) wear particles is a major complication associated with the sustained service of artificial joint prostheses and often necessitates revision surgery. Therefore, a smart implant with direct prevention and repair abilities is urgently developed to avoid painful revision surgery. Herein, we fabricate a phosphatidylserine- and polyethylenimine-engineered niobium carbide (Nb2C) MXenzyme-coated micro/nanostructured titanium implant (PPN@MNTi) that inhibits UHMWPE particle-induced periprosthetic osteolysis. The specific mechanism by which PPN@MNTi operates involves the bioresponsive release of nanosheets from the MNTi substrate within an osteolysis microenvironment, initiated by the cleavage of a thioketal-dopamine molecule sensitive to reactive oxygen species (ROS). Subsequently, functionalized Nb2C MXenzyme could target macrophages and escape from lysosomes, effectively scavenging intracellular ROS through its antioxidant nanozyme-mimicking activities. This further achieves the suppression of osteoclastogenesis by inhibiting NF-κB/MAPK and autophagy signaling pathways. Simultaneously, based on the synergistic effect of MXenzyme-integrated coatings and micro/nanostructured topography, the designed implant promotes the osteogenic differentiation of bone mesenchymal stem cells to regulate bone homeostasis, further achieving advanced osseointegration and alleviable periprosthetic osteolysis in vivo. This study provides a precise prevention and repair strategy of periprosthetic osteolysis, offering a paradigm for the development of smart orthopedic implants.

Kaempferol attenuates particle-induced osteogenic impairment by regulating ER stress via the IRE1α-XBP1s pathway

Periprosthetic osteolysis and subsequent aseptic loosening are the primary causes of failure following total joint arthroplasty. Wear particle-induced osteogenic impairment is recognized as an important contributing factor in the development of osteolysis, with endoplasmic reticulum (ER) stress emerging as a pivotal underlying mechanism. Hence, searching for potential therapeutic targets and agents capable of modulating ER stress in osteoblasts is crucial for preventing aseptic loosening. Kaempferol (KAE), a natural flavonol compound, has shown promising osteoprotective effects and anti-ER stress properties in diverse diseases. However, the influence of KAE on ER stress-mediated osteogenic impairment induced by wear particles remains unclear. In this study, we observed that KAE effectively relieved TiAl6V4 particles-induced osteolysis by improving osteogenesis in a mouse calvarial model. Furthermore, we demonstrated that KAE could attenuate ER stress-mediated apoptosis in osteoblasts exposed to TiAl6V4 particles, both in vitro and in vivo. Mechanistically, our results revealed that KAE mitigated ER stress-mediated apoptosis by upregulating the IRE1α-XBP1s pathway while concurrently partially inhibiting the IRE1α-regulated RIDD and JNK activation. Collectively, our findings suggest that KAE is a prospective therapeutic agent for treating wear particle-induced osteolysis and highlight the IRE1α-XBP1s pathway as a potential therapeutic target for preventing aseptic loosening.

Multifunctional Prosthesis Surface: Modification of Titanium with Cinnamaldehyde-Loaded Hierarchical Titanium Dioxide Nanotubes

Orthopedic prostheses are the ultimate therapeutic solution for various end-stage orthopedic conditions. However, aseptic loosening and pyogenic infections remain as primary complications associated with these devices. In this study, a hierarchical titanium dioxide (TiO2) nanotube drug delivery system loaded with cinnamaldehyde for the surface modification of titanium implants, is constructed. These specially designed dual-layer TiO2 nanotubes enhance material reactivity and provide an extensive drug-loading platform within a short time. The introduction of cinnamaldehyde enhances the bone integration performance of the scaffold (simultaneously promoting bone formation and inhibiting bone resorption), anti-inflammatory capacity, and antibacterial properties. In vitro experiments have demonstrated that this system promoted osteogenesis by upregulating both Wnt/β-catenin and MAPK signaling pathways. Furthermore, it inhibits osteoclast formation, suppresses macrophage-mediated inflammatory responses, and impedes the proliferation of Staphylococcus aureus and Escherichia coli. In vivo experiments shows that this material enhances bone integration in a rat model of femoral defects. In addition, it effectively enhances the antibacterial and anti-inflammatory properties in a subcutaneous implant in a rat model. This study provides a straightforward and highly effective surface modification strategy for orthopedic Ti implants.

Impact of fixation method on femoral bone loss: a retrospective evaluation of stem loosening in first-time revision total hip arthroplasty among two hundred and fifty five patients

PURPOSE

Implant loosening represent the most common indication for stem revision in hip revision arthroplasty. This study compares femoral bone loss and the risk of initial revisions between cemented and uncemented loosened primary stems, investigating the impact of fixation method at primary implantation on femoral bone defects.

METHODS

This retrospective study reviewed 255 patients who underwent their first revision for stem loosening from 2010 to 2022, receiving either cemented or uncemented stem implants. Femoral bone loss was preoperatively measured using the Paprosky classification through radiographic evaluations. Kaplan-Meier analysis estimated the survival probability of the original stem, and the hazard ratio assessed the relative risk of revision for uncemented versus cemented stems in the first postoperative year and the following two to ten years.

RESULTS

Cemented stems showed a higher prevalence of significant bone loss (type 3b and 4 defects: 32.39% vs. 2.72%, p < .001) compared to uncemented stems, which more commonly had type 1 and 2 defects (82.07% vs. 47.89%, p < .001). In our analysis of revision cases, primary uncemented stems demonstrated a 20% lower incidence of stem loosening in the first year post-implantation compared to cemented stems (HR 0.8; 95%-CI 0.3-2.0). However, the incidence in uncemented stems increased by 20% during the subsequent years two to ten (HR 1.2; 95%-CI 0.7-1.8). Septic loosening was more common in cemented stems (28.17% vs. 10.87% in uncemented stems, p = .001). Kaplan-Meier analysis indicated a modestly longer revision-free period for cemented stems within the first ten years post-implantation (p < .022).

CONCLUSION

During first-time revision, cemented stems show significantly larger femoral bone defects than uncemented stems. Septic stem loosening occurred 17.30% more in cemented stems.

Fundamental, mechanism and development of hydration lubrication: From bio-inspiration to artificial manufacturing

Friction and lubrication are ubiquitous in all kinds of movements and play a vital role in the smooth operation of production machinery. Water is indispensable both in the lubrication systems of natural organisms and in hydration lubrication systems. There exists a high degree of similarity between these systems, which has driven the development of hydration lubrication from biomimetic to artificial manufacturing. In particular, significant advancements have been made in the understanding of the mechanisms of hydration lubrication over the past 30 years. This enhanced understanding has further stimulated the exploration of biomimetic inspiration from natural hydration lubrication systems, to develop novel artificial hydration lubrication systems that are cost-effective, easily transportable, and possess excellent capability. This review summarizes the recent experimental and theoretical advances in the understanding of hydration-lubrication processes. The entire paper is divided into three parts. Firstly, surface interactions relevant to hydration lubrication are discussed, encompassing topics such as hydrogen bonding, hydration layer, electric double layer force, hydration force, and Stribeck curve. The second part begins with an introduction to articular cartilage in biomaterial lubrication, discussing its compositional structure and lubrication mechanisms. Subsequently, three major categories of bio-inspired artificial manufacturing lubricating material systems are presented, including hydrogels, polymer brushes (e.g., neutral, positive, negative and zwitterionic brushes), hydration lubricant additives (e.g., nano-particles, polymers, ionic liquids), and their related lubrication mechanism is also described. Finally, the challenges and perspectives for hydration lubrication research and materials development are presented.

Influence of metallic particles and TNF on the transcriptional regulation of NLRP3 inflammasome-associated genes in human osteoblasts

Introduction

The release of mature interleukin (IL-) 1β from osteoblasts in response to danger signals is tightly regulated by the nucleotide-binding oligomerization domain leucine-rich repeat and pyrin-containing protein 3 (NLRP3) inflammasome. These danger signals include wear products resulting from aseptic loosening of joint arthroplasty. However, inflammasome activation requires two different signals: a nuclear factor-kappa B (NF-κB)-activating priming signal and an actual inflammasome-activating signal. Since human osteoblasts react to wear particles via Toll-like receptors (TLR), particles may represent an inflammasome activator that can induce both signals.

Methods

Temporal gene expression profiles of TLRs and associated intracellular signaling pathways were determined to investigate the period when human osteoblasts take up metallic wear particles after initial contact and initiate a molecular response. For this purpose, human osteoblasts were treated with metallic particles derived from cobalt-chromium alloy (CoCr), lipopolysaccharides (LPS), and tumor necrosis factor-alpha (TNF) alone or in combination for incubation times ranging from one hour to three days. Shortly after adding the particles, their uptake was observed by the change in cell morphology and spectral data.

Results

Exposure of osteoblasts to particles alone increased NLRP3 inflammasome-associated genes. The response was not significantly enhanced when cells were treated with CoCr + LPS or CoCr + TNF, whereas inflammation markers were induced. Despite an increase in genes related to the NLRP3 inflammasome, the release of IL-1β was unaffected after contact with CoCr particles.

Discussion

Although CoCr particles affect the expression of NLRP3 inflammasome-associated genes, a single stimulus was not sufficient to prime and activate the inflammasome. TNF was able to prime the NLRP3 inflammasome of human osteoblasts.

Intelligent and Bioactive Osseointegration of the Implanted Piezoelectric Bone Cement with the Host Bone Is Realized by Biomechanical Energy

Poly methyl methacrylate (PMMA) bone cement is widely used in orthopedic surgeries, including total hip/knee arthroplasty and vertebral compression fracture treatment. However, loosening due to bone resorption is a common mid-to-late complication. Therefore, developing bioactive bone cement that promotes bone growth and integration is key to reducing aseptic loosening. In this study, we developed a piezoelectric bone cement comprising PMMA and BaTiO3 with excellent electrobioactivity and further analyzed its ability to promote bone integration. Experiments demonstrate that the PMMA and 15 wt % BaTiO3 cement generated an open-circuit voltage of 37.109 V under biomimetic mechanical stress, which effectively promoted bone regeneration and interfacial bone integration. In vitro experiments showed that the protein expression levels of ALP and RUNX-2 in the 0.65 Hz and 20 min group increased by 1.74 times and 2.31 times. In vivo experiments confirmed the osteogenic ability of PMMA and 15 wt % BaTiO3, with the increment of bone growth in the non-movement and movement groups being 4.67 and 4.64 times, respectively, at the second month after surgery. Additionally, Fluo-4 AM fluorescence staining and protein blotting experiments verified that PMMA and 15 wt % BaTiO3 electrical stimulation promoted osteogenic differentiation of BMSCs by activating calcium-sensitive receptors and increasing calcium ion inflow by 1.41 times when the stimulation reached 30 min. Therefore, piezoelectric bioactive PMMA and 15 wt % BaTiO3 cement has excellent application value in orthopedic surgery systems where stress transmission is prevalent.

Proposal for a classification system of radiographic bone changes after cervical disc replacement

BACKGROUND

The goal of this study is to propose a classification system with a common nomenclature for radiographic observations of periprosthetic bone changes following cTDR.

METHODS

Aided by serial plain radiographs from recent cTDR cases (34 patients; 44 devices), a panel of experts assembled for the purpose of creating a classification system to aid in reproducibly and accurately identifying bony changes and assessing cTDR radiographic appearance. Subdividing the superior and inferior vertebral bodies into 3 equal sections, observed bone loss such as endplate rounding, cystic erosion adjacent to the endplate, and cystic erosion not adjacent to the endplate, is recorded. Determining if bone loss is progressive, based on serial radiographs, and estimating severity of bone loss (measured by the percentage of end plate involved) is recorded. Additional relevant bony changes and device observations include radiolucent lines, heterotopic ossification, vertebral body olisthesis, loss of core implant height, and presence of device migration, and subsidence.

RESULTS

Serial radiographs from 19 patients (25 devices) implanted with a variety of cTDR designs were assessed by 6 investigators including clinicians and scientists experienced in cTDR or appendicular skeleton joint replacement. The overall agreement of assessments ranged from 49.9% (95% bootstrap confidence interval 45.1-73.1%) to 94.7% (95% CI 86.9-100.0%). There was reasonable agreement on the presence or absence of bone loss or radiolucencies (range: 58.4% (95% CI 51.5-82.7%) to 94.7% (95% CI 86.9-100.0%), as well as in the progression of radiolucent lines (82.9% (95% CI 74.4-96.5%)).

CONCLUSIONS

The novel classification system proposed demonstrated good concordance among experienced investigators in this field and represents a useful advancement for improving reporting in cTDR studies.

Material-Intrinsic NIR-Fluorescence Enables Image-Guided Surgery for Ceramic Fracture Removal

Hip arthroplasty effectively treats advanced osteoarthritis and is therefore entitled as "operation of the 20th century." With demographic shifts, the USA alone is projected to perform up to 850 000 arthroplasties annually by 2030. Many implants now feature a ceramic head, valued for strength and wear resistance. Nonetheless, a fraction, up to 0.03% may fracture during their lifespan, demanding complex removal procedures. To address this, a radiation-free, fluorescence-based image-guided surgical technique is presented. The method uses the inherent fluorescence of ceramic implant materials, demonstrated through chemical and optical analysis of prevalent implant types. Specifically, Biolox delta implants exhibited strong fluorescence around 700 nm with a 74% photoluminescence quantum yield. Emission tails are identified extending into the near-infrared (NIR-I) biological transparency range, forming a vital prerequisite for the label-free visualization of fragments. This ruby-like fluorescence could be attributed to Cr within the zirconia-toughened alumina matrix, enabling the detection of even deep-seated millimeter-sized fragments via camera-assisted techniques. Additionally, fluorescence microscopy allowed detection of µm-sized ceramic particles, enabling debris visualization in synovial fluid as well as histological samples. This label-free optical imaging approach employs readily accessible equipment and can seamlessly transition to clinical settings without significant regulatory barriers, thereby enhancing the safety, efficiency, and minimally invasive nature of fractured ceramic implant removal procedures.

Calycosin alleviates titanium particle-induced osteolysis by modulating macrophage polarization and subsequent osteogenic differentiation

Periprosthetic osteolysis (PPO) caused by wear particles is one of the leading causes of implant failure after arthroplasty. Macrophage polarization imbalance and subsequent osteogenic inhibition play a crucial role in PPO. Calycosin (CA) is a compound with anti-inflammatory and osteoprotective properties. This study aimed to evaluate the effects of CA on titanium (Ti) particle-induced osteolysis, Ti particle-induced macrophage polarization and subsequent osteogenic deficits, and explore the associated signalling pathways in a Ti particle-stimulated calvarial osteolysis mouse model using micro-CT, ELISA, qRT-PCR, immunofluorescence and western blot techniques. The results showed that CA alleviated inflammation, osteogenic inhibition and osteolysis in the Ti particle-induced calvarial osteolysis mouse model in vivo. In vitro experiments showed that CA suppressed Ti-induced M1 macrophage polarization, promoted M2 macrophage polarization and ultimately enhanced osteogenic differentiation of MC3T3-E1 cells. In addition, CA alleviated osteogenic deficits by regulating macrophage polarization homeostasis via the NF-κB signalling pathway both in vivo and in vitro. All these findings suggest that CA may prove to be an effective therapeutic agent for wear particle-induced osteolysis.

A Polished Cobalt-Chrome Baseplate is not Associated With a Lower Revision Rate Than Matt Titanium in a Single Total Knee Arthroplasty Implant System With Identical Baseplate Design

BACKGROUND

Polished baseplates were introduced into total knee arthroplasty (TKA) systems to reduce the incidence of backside wear. In 2004, a fixed-bearing knee arthroplasty system underwent a change in baseplate material from matt titanium to polished cobalt-chrome (CoCr) with the intention to reduce backside wear. Other design aspects were left unchanged. The aim of this study was to compare these implants with each baseplate using data from the Australian Orthopaedic Association National Joint Replacement Registry.

METHODS

Primary TKA procedures performed between January 2010 and December 2021 for osteoarthritis, using a single design with cross-linked polyethylene inserts and matt titanium or polished CoCr baseplates, were analyzed. The primary outcome was all-cause revision, summarized using Kaplan-Meier estimates, with age- and sex-adjusted hazard ratios estimated from Cox proportional hazards models. In total, there were 2,091 procedures with matt titanium and 2,519 procedures with polished CoCr baseplates.

RESULTS

The 9-year cumulative percent revision was 2.5% (95% confidence interval [CI] 1.8 to 3.5%) and 4.2% (95% CI 3.1 to 5.6%) for the matt titanium and CoCr groups, respectively. Compared to matt titanium, the revision rate of CoCr baseplates was not significantly higher (hazard ratio 1.44; 95% CI 0.96 to 2.15; P = .076).

CONCLUSIONS

Polished CoCr baseplates in a single TKA system were not associated with reduced all-cause revision rates compared to matt titanium up to 11 years post-TKA. Our results suggest that the predicted reduction in wear particle debris production from polished CoCr baseplates may not correlate with reduced revision rates in vivo, but further evaluation is required.

Brush-Like Coatings Provide a Cloak of Invisibility to Titanium Implants

Orthopedic implants such as knee and hip implants are one of the most important types of medical devices. Currently, the surface of the most advanced implants consists of titanium or titanium-alloys with high porosity at the bone-contacting surface leading to superior mechanical properties, excellent biocompatibility, and the capability of inducing osseointegration. However, the increased surface area of porous titanium provides a nidus for bacteria colonization leading to implant-related infections, one of the main reasons for implant failure. Here, two readily applicable titanium-coatings based on hydrophilic carboxybetaine polymers that turn the surface stealth thereby preventing bacterial adhesion and colonization are developed. These coatings are biocompatible, do not affect cell functionality, exhibit great antifouling properties, and do not cause additional inflammation during the healing process. In this way, the coatings can prevent implant-related infections, while at the same time being completely innocuous to its biological environment. Thus, these coating strategies are a promising route to enhance the biocompatibility of orthopedic implants and have a high potential for clinical use, while being easy to implement in the implant manufacturing process.

Inhibitory effects of norcantharidin on titanium particle-induced osteolysis, osteoclast activation and bone resorption via MAPK pathways

Wear particles generated from the surface of implanted prostheses can lead to peri-implant osteolysis and subsequent aseptic loosening. In the inflammatory environment, extensive formation and activation of osteoclasts are considered the underlying cause of peri-implant osteolysis. Current medications targeting osteoclasts for the treatment of particle-induced bone resorption are not ideal due to significant side effects. Therefore, there is an urgent need to develop more effective drugs with fewer side effects. Norcantharidin (NCTD), a derivative of cantharidin extracted from blister beetles, is currently primarily used for the treatment of solid tumors in clinical settings. However, the potential role of NCTD in treating aseptic loosening of the prosthesis has not been reported. In this study, the in vitro results demonstrated that NCTD could effectively inhibit the formation of osteoclasts and bone resorption induced by the RANKL. Consistently, NCTD strongly inhibited RANKL-induced mRNA and protein levels of c-Fos and NFATc1, concomitant with reduced expression of osteoclast specific genes including TRAP, CTR and CTSK. The in vivo data showed that NCTD exerted significant protective actions against titanium particle-induced inflammation and subsequent osteolysis. The molecular mechanism investigation revealed that NCTD could suppress the activations of RANKL-induced MAPK (p38, ERK). Overall, these findings support the potential use of NCTD for the treatment of aseptic loosening following total joint arthroplasty.

Mettl3‑mediated m6A RNA methylation regulates osteolysis induced by titanium particles

Peri‑prosthetic osteolysis (PPO) induced by wear particles is considered the primary cause of titanium prosthesis failure and revision surgery. The specific molecular mechanisms involve titanium particles inducing multiple intracellular pathways, which impact disease prevention and the targeted therapy of PPO. Notably, N6‑methyladenosine (m6A) serves critical roles in epigenetic regulation, particularly in bone metabolism and inflammatory responses. Thus, the present study aimed to determine the role of RNA methylation in titanium particle‑induced osteolysis. Results of reverse transcription‑quantitative PCR (RT‑qPCR), western blotting, ELISA and RNA dot blot assays revealed that titanium particles induced osteogenic inhibition and proinflammatory responses, accompanied by the reduced expression of methyltransferase‑like (Mettl) 3, a key component of m6A methyltransferase. Specific lentiviruses vectors were employed for Mettl3 knockdown and overexpression experiments. RT‑qPCR, western blotting and ELISA revealed that the knockdown of Mettl3 induced osteogenic inhibition and proinflammatory responses comparable with that induced by titanium particle, while Mettl3 overexpression attenuated titanium particle‑induced cellular reactions. Methylated RNA immunoprecipitation‑qPCR results revealed that titanium particles mediated the methylation of two inhibitory molecules, namely Smad7 and SMAD specific E3 ubiquitin protein ligase 1, via Mettl3 in bone morphogenetic protein signaling, leading to osteogenic inhibition. Furthermore, titanium particles induced activation of the nucleotide binding oligomerization domain 1 signaling pathway through methylation regulation, and the subsequent activation of the MAPK and NF‑κB pathways. Collectively, the results of the present study indicated that titanium particles utilized Mettl3 as an upstream regulatory molecule to induce osteogenic inhibition and inflammatory responses. Thus, the present study may provide novel insights into potential therapeutic targets for aseptic loosening in titanium prostheses.

Microsporidia (Encephalitozoon cuniculi) in Patients with Degenerative Hip and Knee Disease, Czech Republic

Total joint arthroplasty is a commonly used surgical procedure in orthopedics. Revision surgeries are required in >10% of patients mainly because of prosthetic joint infection caused by bacteria or aseptic implant loosening caused by chronic inflammation. Encephalitozoon cuniculi is a microsporidium, an obligate intracellular parasite, capable of exploiting migrating proinflammatory immune cells for dissemination within the host. We used molecular detection methods to evaluate the incidence of E. cuniculi among patients who had total hip or knee arthroplasty revision. Out of 49 patients, E. cuniculi genotypes I, II, or III were confirmed in joint samples from 3 men and 2 women who had implant loosening. Understanding the risks associated with the presence of microsporidia in periprosthetic joint infections is essential for proper management of arthroplasty. Furthermore, E. cuniculi should be considered a potential contributing cause of joint inflammation and arthrosis.

Polysaccharide-Based Coating with Excellent Antibiofilm and Repeatable Antifouling-Bactericidal Properties for Treating Infected Hernia

In recent years, the utilization of medical devices has gradually increased and implantation procedures have become common treatments. However, patients are susceptible to the risk of implant infections. This study utilized chemical grafting to immobilize polyethylenimine (QPEI) and hyaluronic acid (HA) on the surface of the mesh to improve biocompatibility while being able to achieve antifouling antimicrobial effects. From the in vitro testing, PP-PDA-Q-HA exhibited a high antibacterial ratio of 93% against S. aureus, 93% against E. coli, and 85% against C. albicans. In addition, after five rounds of antimicrobial testing, the coating continued to exhibit excellent antimicrobial properties; PP-PDA-Q-HA also inhibits the formation of bacterial biofilms. In addition, PP-PDA-Q-HA has good hemocompatibility and cytocompatibility. In vivo studies in animal implantation infection models also demonstrated the excellent antimicrobial properties of PP-PDA-Q-HA. Our study provides a promising strategy for the development of antimicrobial surface medical materials with excellent biocompatibility.

Risk factors for early septic failure after two-stage exchange total knee arthroplasty for treatment of periprosthetic joint infection

BACKGROUND

The cause of early septic failure after two-stage exchange revision total knee arthroplasty (TKA) for chronic periprosthetic joint infection (PJI) and the factors affecting it are not well known. The purpose of this study was to determine the surgical outcomes and the risk factors for early septic failure after two-stage revision TKA for chronic PJI.

METHODS

We identified a total of 246 adult patients who met the Musculoskeletal Infection Society (MSIS) diagnostic criteria for chronic PJI at two academic tertiary hospitals from March 2012 to December 2018. Finally, 151 patients who consecutively received two-stage exchange revision TKA for chronic PJI and who had a minimum 3-year follow-up were enrolled and retrospectively reviewed. Successful surgical treatment was evaluated for two-stage revision TKA and risk factors for early septic failure were identified.

RESULTS

Early septic failures occurred within 3 years after reimplantation in 48 patients (31.8%). After accounting for potentially confounding variables, we found that male patient [odds ratio (OR): 2.753, 95% confidence interval (CI) 1.099-6.893, p = 0.031], fungus or mycobacterial infection (OR: 5.224, 95% CI 1.481-18.433, p = 0.01), and positive culture at reimplantation (OR: 4.407, 95% CI 1.255-15.480, p = 0.021) were independently associated with early septic failure after two-stage exchange revision TKA.

CONCLUSION

Male patients, fungus or mycobacterial infection, and positive culture at reimplantation were independently associated with an increased risk of early septic failure after two-stage exchange revision TKA despite normal C-reactive protein values prior to reimplantation. Further prospective and high-quality studies are needed to determine the risk factors of two-stage exchange revision TKA for chronic PJI.

LEVEL OF EVIDENCE

level IV; retrospective comparison; treatment study.

How good are surgeons at disclosing periprosthetic joint infection at the time of revision, based on pre- and intra-operative assessment? A study on 16,922 primary total hip arthroplasties reported to the Norwegian Arthroplasty Register

BACKGROUND AND PURPOSE

Revision due to infection, as reported to the Norwegian Arthroplasty Register (NAR), is a surrogate endpoint to periprosthetic joint infection (PJI). We aimed to find the accuracy of the reported causes of revision after primary total hip arthroplasty (THA) compared with PJI to see how good surgeons were at disclosing infection, based on pre- and intraoperative assessment.

PATIENTS AND METHODS

We investigated the reasons for revision potentially caused by PJI following primary THA: infection, aseptic loosening, prolonged wound drainage, and pain only, reported to the NAR from surgeons in the region of Western Norway during the period 2010-2020. The electronic patient charts were investigated for information on clinical assessment, treatment, biochemistry, and microbiological findings. PJI was defined in accordance with the Musculoskeletal Infection Society (MSIS) definition. Sensitivity, specificity, and accuracy were calculated.

RESULTS

363 revisions in the NAR were eligible for analyses. Causes of revision were (reported/validated): infection (153/177), aseptic loosening (139/133), prolonged wound drainage (37/13), and pain only (34/40). The sensitivity for reported revision due to infection compared with PJI was 80%, specificity was 94%, and accuracy-the surgeons' ability to disclose PJI or non-septic revision at time of revision-was 87%. The accuracy for the specific revision causes was highest for revision due to aseptic loosening (95%) and pain only (95%), and lowest for revision due to prolonged wound drainage (86%).

CONCLUSION

The accuracy of surgeon-reported revisions due to infection as representing PJI was 87% in the NAR. Our study shows the importance of systematic correction of the reported cause of revision in arthroplasty registers, after results from adequately taken bacterial samples.

From drugs to biomaterials: a review of emerging therapeutic strategies for intervertebral disc inflammation

Chronic low back pain (LBP) is an increasingly prevalent issue, especially among aging populations. A major underlying cause of LBP is intervertebral disc degeneration (IDD), often triggered by intervertebral disc (IVD) inflammation. Inflammation of the IVD is divided into Septic and Aseptic inflammation. Conservative therapy and surgical treatment often fail to address the root cause of IDD. Recent advances in the treatment of IVD infection and inflammation range from antibiotics and small-molecule drugs to cellular therapies, biological agents, and innovative biomaterials. This review sheds light on the complex mechanisms of IVD inflammation and physiological and biochemical processes of IDD. Furthermore, it provides an overview of recent research developments in this area, intending to identify novel therapeutic targets and guide future clinical strategies for effectively treating IVD-related conditions.

Kaempferol attenuates wear particle-induced inflammatory osteolysis via JNK and p38-MAPK signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Wear particle-induced inflammatory osteoclast activation is a master contributor to periprosthetic osteolysis, which can cause pathological bone loss and destruction. Hence, inhibiting inflammation and osteoclastogenesis is an important strategy for preventing wear particle-induced osteolysis. To date, there are no FDA-approved non-surgical pharmacotherapies for arresting periprosthetic osteolysis. Kaempferol (KAE), a natural flavonol abundant in many traditional Chinese herbal medicines, has been shown to have protective effects against inflammatory bone diseases such as rheumatoid arthritis, but no previous study has evaluated the effects of KAE on wear particle-induced osteolysis.

AIM OF THE STUDY

The study aimed to investigate the effects of KAE on wear particle-induced inflammatory osteolysis and osteoclast activation, and further explore the underlying mechanisms.

MATERIALS AND METHODS

TiAl6V4 metal particles (TiPs) were retrieved from the prosthesis of patients who underwent revision hip arthroplasty due to aseptic loosening. A mouse calvarial osteolysis model was used to investigate the effects of KAE on wear particle-induced inflammatory osteolysis in vivo. Primary bone marrow-derived macrophages (BMMs) were used to explore the effects of KAE on osteoclast differentiation and bone-resorbing activity as well as the underlying mechanisms in vitro.

RESULTS

In the present study, we found that KAE alleviated wear particle-induced inflammatory bone loss in vivo and inhibited osteoclast differentiation and function in vitro. Furthermore, we revealed that KAE exerted anti-osteoclastogenic effects by downregulating JNK and p38-MAPK signaling as well as the downstream NFATc1 expression.

CONCLUSIONS

KAE is an alternative therapeutic agent for preventing and treating periprosthetic osteolysis and aseptic loosening.

Cytocompatibility, antibacterial, and corrosion properties of chitosan/polymethacrylates and chitosan/poly(4-vinylpyridine) smart coatings, electrophoretically deposited on nanosilver-decorated titania nanotubes

The development of novel implants subjected to surface modification to achieve high osteointegration properties at simultaneous antimicrobial activity is a highly current problem. This study involved different surface treatments of titanium surface, mainly by electrochemical oxidation to produce a nanotubular oxide layer (TNTs), a subsequent electrochemical reduction of silver nitrate and decoration of a nanotubular surface with silver nanoparticles (AgNPs), and finally electrophoretic deposition (EPD) of a composite of chitosan (CS) and either polymethacrylate-based copolymer Eudragit E 100 (EE100) or poly(4-vinylpyridine) (P4VP) coating. The effects of each stage of this multi-step modification were examined in terms of morphology, roughness, wettability, corrosion resistance, coating-substrate adhesion, antibacterial properties, and osteoblast cell adhesion and proliferation. The results showed that the titanium surface formed nanotubes (inner diameter of 97 ± 12 nm, length of 342 ± 36 nm) subsequently covered with silver nanoparticles (with a diameter of 88 ± 8 nm). Further, the silver-decorated nanotubes were tightly coated with biopolymer films. Most of the applied modifications increased both the roughness and the surface contact angle of the samples. The deposition of biopolymer coatings resulted in reduced burst release of silver. The coated samples revealed potent antimicrobial activity against both Gram-positive and Gram-negative bacteria. Total elimination (99.9%) of E. coli was recorded for a sample with CS/P4VP coating. Cytotoxicity results using hFOB 1.19, a human osteoblast cell line, showed that after 3 days the tested modifications did not affect the cellular growth according to the titanium control. The proposed innovative multilayer antibacterial coatings can be successful for titanium implants as effective postoperative anti-inflammation protection.

Isolation of TiNbN wear particles from a coated metal-on-metal bearing: Morphological characterization and in vitro evaluation of cytotoxicity in human osteoblasts

To improve the wear resistance of articulating metallic joint endoprostheses, the surfaces can be coated with titanium niobium nitride (TiNbN). Under poor tribological conditions or malalignment, wear can occur on these implant surfaces in situ. This study investigated the biological response of human osteoblasts to wear particles generated from TiNbN-coated hip implants. Abrasive particles were generated in a hip simulator according to ISO 14242-1/-2 and extracted with Proteinase K. Particle characteristics were evaluated by electron microscopy and energy dispersive x-ray spectroscopy (EDS), inductively coupled plasma mass spectrometry (ICP-MS) and dynamic light scattering (DLS) measurements. Human osteoblasts were exposed to different particle dilutions (1:20, 1:50, and 1:100), and cell viability and gene expression levels of osteogenic markers and inflammatory mediators were analyzed after 4 and 7 days. Using ICP-MS, EDS, and DLS measurements, ~70% of the particles were identified as TiNbN, ranging from 39 to 94 nm. The particles exhibited a flat and subangular morphology. Exposure to particles did not influence cell viability and osteoblastic differentiation capacity. Protein levels of collagen type 1, osteoprotegerin, and receptor activator of nuclear factor κB ligand were almost unaffected. Moreover, the pro-inflammatory response via interleukins 6 and 8 was minor induced after particle contact. A high number of TiNbN wear particles only slightly affected osteoblasts' differentiation ability and inflammatory response compared to metallic particles. Nevertheless, further studies should investigate the role of these particles in peri-implant bone tissue, especially concerning other cell types.

Roles of inflammatory cell infiltrate in periprosthetic osteolysis

Classically, particle-induced periprosthetic osteolysis at the implant-bone interface has explained the aseptic loosening of joint replacement. This response is preceded by triggering both the innate and acquired immune response with subsequent activation of osteoclasts, the bone-resorbing cells. Although particle-induced periprosthetic osteolysis has been considered a foreign body chronic inflammation mediated by myelomonocytic-derived cells, current reports describe wide heterogeneous inflammatory cells infiltrating the periprosthetic tissues. This review aims to discuss the role of those non-myelomonocytic cells in periprosthetic tissues exposed to wear particles by showing original data. Specifically, we discuss the role of T cells (CD3+, CD4+, and CD8+) and B cells (CD20+) coexisting with CD68+/TRAP- multinucleated giant cells associated with both polyethylene and metallic particles infiltrating retrieved periprosthetic membranes. This review contributes valuable insight to support the complex cell and molecular mechanisms behind the aseptic loosening theories of orthopedic implants.

CXCL chemokines-mediated communication between macrophages and BMSCs on titanium surface promotes osteogenesis via the actin cytoskeleton pathway

The refined functional cell subtypes in the immune microenvironment of specific titanium (Ti) surface and their collaborative role in promoting bone marrow mesenchymal stem cells (BMSCs) driven bone integration need to be comprehensively characterized. This study employed a simplified co-culture system to investigate the dynamic, temporal crosstalk between macrophages and BMSCs on the Ti surface. The M2-like sub-phenotype of macrophages, characterized by secretion of CXCL chemokines, emerges as a crucial mediator for promoting BMSC osteogenic differentiation and bone integration in the Ti surface microenvironment. Importantly, these two cells maintain their distinct functional phenotypes through a mutually regulatory interplay. The secretion of CXCL3, CXCL6, and CXCL14 by M2-like macrophages plays a pivotal role. The process activates CXCR2 and CCR1 receptors, triggering downstream regulatory effects on the actin cytoskeleton pathway within BMSCs, ultimately fostering osteogenic differentiation. Reciprocally, BMSCs secrete pleiotrophin (PTN), a key player in regulating macrophage differentiation. This secretion maintains the M2-like phenotype via the Sdc3 receptor-mediated cell adhesion molecules pathway. Our findings provide a novel insight into the intricate communication and mutual regulatory mechanisms operating between BMSCs and macrophages on the Ti surface, highlight specific molecular events governing cell-cell interactions in the osteointegration, inform the surface design of orthopedic implants, and advance our understanding of osteointegration.

Survivability of Titanium Implant Materials: In Vitro Simulated Inflammatory and Infectious Environment

Titanium-based implants utilized in total joint arthroplasties could restore primary musculoskeletal function to patients suffering from osteoarthritis and other conditions. Implants are susceptible to failure stemming from aseptic loosening and infection at the joint site, eventually requiring revision surgery. We hypothesized that there might be a feedback loop by which metal degradation particles and ions released from the implant decrease cell viability and increase immune response, thereby creating biochemical conditions that increase the corrosion rate and release more metal ions. This study focused on the synergistic process through cell viability assays and electrochemical tests. From the results, inflammatory conditions from ion release resulting in cell death would further increase the corrosion rate at the metal implant site. The synergistic interaction in the implant surroundings in which infectious conditions produce Ti ions that contribute to more infection, creating a potential cycle of accelerating corrosion.

Increased local bone turnover in patients with chronic periprosthetic joint infection

Aims

The management of periprosthetic joint infection (PJI) remains a major challenge in orthopaedic surgery. In this study, we aimed to characterize the local bone microstructure and metabolism in a clinical cohort of patients with chronic PJI.

Methods

Periprosthetic femoral trabecular bone specimens were obtained from patients suffering from chronic PJI of the hip and knee (n = 20). Microbiological analysis was performed on preoperative joint aspirates and tissue specimens obtained during revision surgery. Microstructural and cellular bone parameters were analyzed in bone specimens by histomorphometry on undecalcified sections complemented by tartrate-resistant acid phosphatase immunohistochemistry. Data were compared with control specimens obtained during primary arthroplasty (n = 20) and aseptic revision (n = 20).

Results

PJI specimens exhibited a higher bone volume, thickened trabeculae, and increased osteoid parameters compared to both control groups, suggesting an accelerated bone turnover with sclerotic microstructure. On the cellular level, osteoblast and osteoclast parameters were markedly increased in the PJI cohort. Furthermore, a positive association between serum (CRP) but not synovial (white blood cell (WBC) count) inflammatory markers and osteoclast indices could be detected. Comparison between different pathogens revealed increased osteoclastic bone resorption parameters without a concomitant increase in osteoblasts in bone specimens from patients with Staphylococcus aureus infection, compared to those with detection of Staphylococcus epidermidis and Cutibacterium spp.

Conclusion

This study provides insights into the local bone metabolism in chronic PJI, demonstrating osteosclerosis with high bone turnover. The fact that Staphylococcus aureus was associated with distinctly increased osteoclast indices strongly suggests early surgical treatment to prevent periprosthetic bone alterations.

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.

A finite element study on the interactive effect between the damage of the cup-bone interface and the bone strain of hip implants under various fixation conditions

Interfacial damage has a high impact on the loosening of the acetabular cup. However, monitoring this damage induced by the variations in loading conditions, such as the angle, amplitude, and frequency in vivo, is challenging. In this study, we evaluated the risk of loosening of the acetabular cup due to interfacial damages induced by the deviation in loading conditions and amplitudes. A three-dimensional model of the acetabular cup component was developed, and the interfacial crack growth between the cup and the bone was modeled using a fracture mechanics approach, which simulated the extent of interfacial damage and associated cup displacement. The interfacial delamination mechanism changed with the increasing inclination angle, wherein a fixation angle of 60° exhibited the largest area of contact loss. The compressive strain of embedding the simulated bone at the remaining bonding area accumulated as the lost contact area widened. Such interfacial damages, namely, the growth of the lost contact area and accumulated compressive strain in the simulated bone, promoted both embedding and rotational displacement of the acetabular cup. In the worst case of a fixation angle of 60°, the total displacement of the acetabular cup exceeded the limit of the modified safe zone, suggesting a quantitative risk of dislocation of the acetabular cup induced by the accumulated interfacial damage. Furthermore, nonlinear regression analyses between the degree of displacement of the acetabular cup and the extent of the two types of interfacial damage demonstrated that the interactive effect of the fixation angle with the loading amplitude showed a significant effect on increasing cup displacement. These findings suggest that proper control of the fixation angle during operation is useful in preventing the loosening of the hip joint.

Nanosurface Texturing for Enhancing the Antibacterial Effect of Biodegradable Metal Zinc: Surface Modifications

Zinc (Zn) as a biodegradable metal has attracted research interest for bone reconstruction, with the aim of eliminating the need for a second removal surgery and minimizing the implant-to-bone transfer of stress-shielding to maintain bone regeneration. In addition, Zn has been shown to have antibacterial properties, particularly against Gram-negative bacteria, and is often used as a surface coating to inhibit bacterial growth and biofilm formation. However, the antibacterial property of Zn is still suboptimal in part due to low Zn ion release during degradation that has to be further improved in order to meet clinical requirements. This work aims to perform an innovative one-step surface modification using a nitric acid treatment to accelerate Zn ion release by increasing surface roughness, thereby endowing an effective antimicrobial property and biofilm formation inhibition. The antibacterial performance against Staphylococci aureus was evaluated by assessing biofilm formation and adhesion using quantitative assays. The surface roughness of acid-treated Zn (Ra ~ 30 nm) was significantly higher than polished Zn (Ra ~ 3 nm) and corresponded with the marked inhibition of bacterial biofilm, and this is likely due to the increased surface contact area and Zn ion accumulation. Overall, surface modification due to nitric acid etching appears to be an effective technique that can produce unique morphological surface structures and enhance the antibacterial properties of biodegradable Zn-based materials, thus increasing the translation potential toward multiple biomedical applications.

Insight on the in vivo wear characteristics of goat artificial cervical disc implanted for 6 months

Since the prosthesis may suffer overload or extreme motion during the daily activities, some special failure modes may be found in service. In order to give an insight on the in vivo stability of artificial cervical disc, the wear characteristics of goat prosthesis were studied after implanted in goat animal for 6 months. The prosthesis was designed with a ball-on-socket structure under the material combination of PE-on-TC4. The X-ray examination was performed to monitor the in vivo wear process. The worn morphology and wear debris were analyzed in detail by EDX and SEM. The result indicated that goat prosthesis revealed good safety and effectiveness during 6-month in vivo wear test. The wear damage occurred only on nucleus pulposus component with the dominant failure mode of surface fatigue and deformation. The damage distribution and wear severity was seriously uneven with a trend that the closer to the edge, the more severe the wear. For example, slippage phenomenon caused a wide and curved severe ploughing damage on the edge. Three kinds of debris were found including bone debris, carbon-oxygen compound debris and PE wear debris. Both bone debris and carbon-oxygen compound debris came from superior endplate while PE wear debris came from nucleus pulposus. The debris proportion for endplate was 82% for bone debris, 15% for carbon-oxygen compound debris and 3% for PE debris while for nucleus pulposus it was 8% for carbon-oxygen compound debris and 92% for PE debris. The size range of PE debris for nucleus pulposus was 0.1-100 μm, with an average size of 9.58 ± 16.34 μm. For the bone debris of endplate components, the size range was 0.1-600 μm, with an average size of 49.18 ± 94.54 μm. After wear test, the equivalent elastic modulus of nucleus pulposus increased from 28.55 MPa to 38.25 MPa. The results of FT-IR spectrum showed that the functional groups on the surface of polyethylene have not changed significantly after wear test. The results indicated that there were some differences in wear characteristics of wear morphology and wear debris between in vivo wear and in vitro wear.

Glycolytic reprogramming underlies immune cell activation by polyethylene wear particles

Primary total joint arthroplasties (TJAs) are widely and successfully applied reconstructive procedures to treat end-stage arthritis. Nearly 50 % of TJAs are now performed in young patients, posing a new challenge: performing TJAs which last a lifetime. The urgency is justified because subsequent TJAs are costlier and fraught with higher complication rates, not to mention the toll taken on patients and their families. Polyethylene particles, generated by wear at joint articulations, drive aseptic loosening by inciting insidious inflammation associated with surrounding bone loss. Down modulating polyethylene particle-induced inflammation enhances integration of implants to bone (osseointegration), preventing loosening. A promising immunomodulation strategy could leverage immune cell metabolism, however, the role of immunometabolism in polyethylene particle-induced inflammation is unknown. Our findings reveal that immune cells exposed to sterile or contaminated polyethylene particles show fundamentally altered metabolism, resulting in glycolytic reprogramming. Inhibiting glycolysis controlled inflammation, inducing a pro-regenerative phenotype that could enhance osseointegration.

STING/TBK1 Regulates Inflammation in Macrophages and Titanium Particles-Induced Osteolysis

Inflammatory response in macrophages on account of prostheses-derived wear particles is the leading cause of artificial joint failure. However, the mechanism by which wear particles initiate macrophage inflammation has not been fully elucidated. Previous research studies have identified TANK-binding kinase 1 (TBK1) and stimulator of interferon genes (STING) as potential factors in inflammation and autoimmune diseases. Here, we found that both TBK1 and STING were increased in synovium from aseptic loosening (AL) patients and were activated in titanium particles (TiPs)-stimulated macrophages. Lentivirus-mediated knockdown of TBK or STING significantly inhibited the inflammatory effects of macrophages, while overexpression of TBK or STING exerted opposite results. In concrete, STING/TBK1 promoted the activation of NF-κB and IRF3 pathways and macrophage M1 polarization. For further validation, a mice cranial osteolysis model was constructed for in vivo assays, and we found that STING-overexpressed lentivirus injection exacerbated osteolysis and inflammation, which was counteracted by TBK1-knockdown injection. In conclusion, STING/TBK1 enhanced TiP-induced macrophage inflammation and osteolysis via orchestrating the activation of NF-κB and IRF3 pathways and M1 polarization, which suggested STING/TBK1 as potential therapeutic targets for preventing AL of prostheses.

Hydrophilic surface-modified 3D printed flexible scaffolds with high ceramic particle concentrations for immunopolarization-regulation and bone regeneration

Bioceramic scaffolds used in bone tissue engineering suffer from a low concentration of ceramic particles (<50 wt%), because the high concentration of ceramic particles increases the brittleness of the composite. 3D printed flexible PCL/HA scaffolds with high ceramic particle concentrations (84 wt%) were successfully fabricated in this study. However, the hydrophobicity of PCL weakens the composite scaffold hydrophilicity, which may limit the osteogenic ability to some extent. Thus, as a less time-consuming, less labour intensive, and more cost-effective treatment method, alkali treatment (AT) was employed to modify the surface hydrophilicity of the PCL/HA scaffold, and its regulation of immune responses and bone regeneration were investigated in vivo and in vitro. Initially, several concentrations of NaOH (0.5, 1, 1.5, 2, 2.5, and 5 mol L^-1) were employed in tests to determine the appropriate concentration for AT. Based on the comprehensive consideration of the results of mechanical experiments and hydrophilicity, 2 mol L^-1 and 2.5 mol L^-1 of NaOH were selected for further investigation in this study. The PCL/HA-AT-2 scaffold dramatically reduced foreign body reactions as compared to the PCL/HA and PCL/HA-AT-2.5 scaffolds, promoted macrophage polarization towards the M2 phenotype and enhanced new bone formation. The Wnt/β-catenin pathway might participate in the signal transduction underlying hydrophilic surface-modified 3D printed scaffold-regulated osteogenesis, according to the results of immunohistochemical staining. In conclusion, hydrophilic surface-modified 3D printed flexible scaffolds with high ceramic particle concentrations can regulate the immune reactions and macrophage polarization to promote bone regeneration, and the PCL/HA-AT-2 scaffold is a potential candidate for bone tissue repair.

Combined photothermal and sonodynamic therapy using a 2D black phosphorus nanosheets loaded coating for efficient bacterial inhibition and bone-implant integration

Surgical site infection (SSI) remains a major threat for implant failure in orthopedics. Herein, we report a dual-functional coating on Ti implants (named Ti/PDA/BP) with the integration of two-dimensional (2D) photo-sono sensitive black phosphorus nanosheets (BPNSs) and polydopamine (PDA) for efficient bacterial inhibition and bone-implant integration. For the first time, we employ BPNSs as generators of reactive radicals (ROS) under ultrasound (US) stimuli for implant associated infection. Additionally, the application of PDA improves the stability of BPNSs, the biocompatibility and photothermal performance of this hybrid coating. The as-prepared Ti/PDA/BP coating exhibits superior biocompatibility, bioactivity, photothermal and sonodynamic conversion abilities. Owing to the synergistic effect of hyperthermia and ·OH, Ti/PDA/BP damages the membrane and antioxidant system of Staphylococcus aureus, reaching a high antibacterial activity of 96.6% in vitro and 97.3% in vivo with rapid 10 min NIR irradiation and 20 min US treatment. In addition, we firstly unveil the significant effect of Ti/PDA/BP-based sonodynamic therapy (SDT) on bacterial membrane and oxidative stress at the transcriptome level. Moreover, the Ti/PDA/BP coating remarkably promotes osteogenesis in vitro and bone-implant osseointegration in vivo. Overall, development of Ti/PDA/BP bioactive coating provides a new strategy for combating the implant associated infection.

Mussel-inspired alkaline phosphatase-specific coating on orthopedic implants for spatiotemporal modulating local osteoimmune microenvironment to facilitate osseointegration

Inadequate initial osseointegration and consequent prosthesis loosening are the most severe complications after artificial arthroplasty. Proper immune responses are crucial for the successful implantation of artificial prostheses. Macrophages are central in osteoimmunomodulation because they exert distinct functions with highly plasticity. Herein, we developed an alkaline phosphatase (ALP) sensitive mussel-inspired coating on orthopedic implants for promoting osseointegration. First, the resveratrol-alendronate complexes were deposited on titanium implant surface through mussel-inspired interfacial interactions. Upon prosthesis implantation, macrophages first polarized towards M1 type to initiate inflammatory responses and bone regeneration. As osteogenesis progresses, increasing amounts of ALP secreted by osteoblasts was cleaved the resveratrol-alendronate complexes. Then, the released resveratrol further promoted osteogenic differentiation of BMSCs and induced locoregional macrophages M2 polarization. Our results demonstrated that the bioinspired osteoimmunomodulation coating remarkably facilitated the prosthesis-bone integration by spatiotemporally modulating macrophages switching from M1 to M2 polarization in response to a real-time healing signal during osteogenesis. In summary, the mussel-inspired osteoimmunomodulation coating technology may provide a new approach for promoting osseointegration after artificial arthroplasty.

A dual functional Ti-Ga alloy: inhibiting biofilm formation and osteoclastogenesis differentiation via disturbing iron metabolism

BACKGROUND

Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic loosening-prevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component.

METHODS

A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga³⁺ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation.

RESULTS

The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga³⁺ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening.

CONCLUSION

This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga³⁺ ions to inhibit biofilm formation and osteoclast differentiation.

Macrophages in aseptic loosening: Characteristics, functions, and mechanisms

Aseptic loosening (AL) is the most common complication of total joint arthroplasty (TJA). Both local inflammatory response and subsequent osteolysis around the prosthesis are the fundamental causes of disease pathology. As the earliest change of cell behavior, polarizations of macrophages play an essential role in the pathogenesis of AL, including regulating inflammatory responses and related pathological bone remodeling. The direction of macrophage polarization is closely dependent on the microenvironment of the periprosthetic tissue. When the classically activated macrophages (M1) are characterized by the augmented ability to produce proinflammatory cytokines, the primary functions of alternatively activated macrophages (M2) are related to inflammatory relief and tissue repair. Yet, both M1 macrophages and M2 macrophages are involved in the occurrence and development of AL, and a comprehensive understanding of polarized behaviors and inducing factors would help in identifying specific therapies. In recent years, studies have witnessed novel discoveries regarding the role of macrophages in AL pathology, the shifts between polarized phenotype during disease progression, as well as local mediators and signaling pathways responsible for regulations in macrophages and subsequent osteoclasts (OCs). In this review, we summarize recent progress on macrophage polarization and related mechanisms during the development of AL and discuss new findings and concepts in the context of existing work.

The immunomodulatory effects of RNA-based biomaterials on bone regeneration

The use of RNA as therapeutic agents is a visionary idea in contemporary medicine. Some forms of RNA can modulate the immune response of the host to enhance tissue regeneration events such as osteogenesis. Herein, RNA molecules commercially available for immunomodulatory applications (imRNA) were used to prepare biomaterials for bone regeneration. The polyanionic imRNA stabilized calcium phosphate ionic clusters to produce imRNA-ACP that had the capacity to mineralize the intrafibrillar compartments of collagen fibrils. For the first time, it was shown that incorporating imRNA-ACP into collagen scaffolds resulted in rapid new bone formation in cranial defects of mice. Both in vivo and in vitro results demonstrated that macrophage polarization was highly-sensitive to the imRNA-ACP containing collagen scaffolds. Macrophages were polarized into the anti-inflammatory M2 phenotype that produced anti-inflammation cytokines and growth factors. The favorable osteoimmunological microenvironment created by the scaffolds prevented their immunorejection and facilitated osteogenesis. The potential of RNA in creating immunomodulatory biomaterials has been underestimated in the past. The overall aim of this study was to explore the potential application of imRNA-based biomaterials in bone tissue engineering, with the competitive edge of facile synthesis and excellent biocompatibility. STATEMENT OF SIGNIFICANCE: In this work, commercially available RNA extracted from bovine spleens for immunomodulatory applications (imRNA) were used to stabilize amorphous calcium phosphate (ACP) and induce mineralization within collagen fibrils. Incorporation of imRNA-ACP into collagen scaffolds regenerated new bone in-situ. Because of its immunomodulatory effects, the imRNA-ACP that was incorporated into collagen scaffolds modulated the local immune environment of murine cranial defects by altering the macrophage phenotype through JAK2/STAT3 signaling pathway. The novelty of this work existed in the discovery of RNA's potential in creating immunomodulatory biomaterials. With the competitive edge of facile synthesis and excellent biocompatibility, the imRNA-based biomaterials are potentially useful for future bone tissue engineering applications.

Interaction of Ceramic Implant Materials with Immune System

The immuno-compatibility of implant materials is a key issue for both initial and long-term implant integration. Ceramic implants have several advantages that make them highly promising for long-term medical solutions. These beneficial characteristics include such things as the material availability, possibility to manufacture various shapes and surface structures, osteo-inductivity and osteo-conductivity, low level of corrosion and general biocompatibility. The immuno-compatibility of an implant essentially depends on the interaction with local resident immune cells and, first of all, macrophages. However, in the case of ceramics, these interactions are insufficiently understood and require intensive experimental examinations. Our review summarizes the state of the art in variants of ceramic implants: mechanical properties, different chemical modifications of the basic material, surface structures and modifications, implant shapes and porosity. We collected the available information about the interaction of ceramics with the immune system and highlighted the studies that reported ceramic-specific local or systemic effects on the immune system. We disclosed the gaps in knowledge and outlined the perspectives for the identification to ceramic-specific interactions with the immune system using advanced quantitative technologies. We discussed the approaches for ceramic implant modification and pointed out the need for data integration using mathematic modelling of the multiple ceramic implant characteristics and their contribution for long-term implant bio- and immuno-compatibility.

Insight into the Molecule Impact of Critical-Sized UHMWPE-ALN Wear Particles on Cells by the Alginate-Encapsulated Cell Reactor

Wear particles of ultra-high molecular weight polyethylene (UHMWPE) are inevitable during service as joint prosthesis, and particles ≤ 10 μm with critical size could cause serious osteolysis and aseptic loosening of joint prosthesis. The aim of this study is to adopt the alginate-encapsulated cell reactor to investigate the molecular impact of critical-sized wear particles of UHMWPE loaded with alendronate sodium (UHMWPE-ALN) on cells. Results showed that compared with UHMWPE wear particles, UHMWPE-ALN wear particles inhibited the proliferation of macrophages significantly after being co-cultured for 1, 4, 7, and 14 d. Furthermore, the released ALN promoted early apoptosis, suppressed the secretion of TNF-α and IL-6 of macrophages, and down-regulated relative gene expressions of TNF-α, IL-6, and IL-1β and RANK. In addition, compared with UHMWPE wear particles, UHMWPE-ALN wear particles promoted the ALP activity of osteoblasts, down-regulated the gene expression of RANKL, and up-regulated gene expression of osteoprotegerin. There were mainly two approaches of the effects of critical-sized UHMWPE-ALN wear particles on cells, one of which was cytology and the other was cytokine signal pathway. The former mainly affected the proliferation and activity of macrophages and osteoblasts. The latter would inhibit osteoclasts via cytokine and RANKL/RANK signal pathway. Thus, UHMWPE-ALN had the potential application in clinics to treat osteolysis induced by wear particles.

Zingerone attenuates Ti particle-induced inflammatory osteolysis by suppressing the NF-κB signaling pathway in osteoclasts

Aseptic loosening caused by inflammatory osteolysis is one of the most frequent and serious long-term complications after total joint arthroplasty (TJA). Development of a new therapeutic drug is required due to the lack of effective therapy and serious adverse effects. This study aimed to explore the pharmacological properties of zingerone (ZO) in attenuating osteoclast-mediated periprosthetic osteolysis and how ZO modulates osteoclastogenesis. The nontoxic concentration of ZO was clarified by the CCK-8 method. Then, we explored the efficacy of ZO on suppressing osteoclast differentiation, F-actin ring formation, bone resorption, and NF-κB luciferase activity in vitro as well as osteoprotection in vivo. Polymerase chain reaction and western blotting were applied to detect the underlying mechanisms involved in osteoclastogenesis. ZO showed an obvious inhibitory effect on osteoclastogenesis and bone resorption in a dose-dependent manner by mainly suppressing the activation of NF-κB signaling pathways. Furthermore, ZO administration successfully attenuated titanium (Ti) particle-stimulated periprosthetic osteolysis and osteoporosis by regulating osteoclast formation. Our findings demonstrated the pharmacological properties of ZO in inhibiting osteoclast formation and function by downregulation of NF-κB signaling activation. As a result, these findings could be expected to provide a novel reagent for regulating inflammatory osteolysis caused by prosthetic loosening.

Electrical stimulation of piezoelectric BaTiO3 coated Ti6Al4V scaffolds promotes anti-inflammatory polarization of macrophages and bone repair via MAPK/JNK inhibition and OXPHOS activation

Bone regeneration is a highly synchronized process that requires multiple biochemical, bioelectrical, mechanical, and other physiological cues. The restoration and delivery of electrical cues locally through piezoelectric materials have been demonstrated to facilitate osteogenesis in vitro and bone repair in vivo. However, the underlying mechanism by which piezoelectric stimulation promotes osteogenesis and bone repair remains unclear yet, limiting the design and clinical application of piezoelectric materials for bone repair. Herein, a piezoelectric BaTiO3/Ti6Al4V (BT/Ti) scaffold was prepared by hydrothermal synthesis of a uniform BaTiO3 layer on three dimensionally printed Ti6Al4V scaffold. The BT/Ti scaffolds exhibited piezoelectricity and favorable biocompatibility with RAW264.7 macrophages after polarization. In vitro results demonstrated that the piezoelectric effects of the poled BT/Ti scaffolds promoted M2 polarization of macrophages and immunoregulatory osteogenesis of MC-3T3 osteoblasts. In a subcutaneous implantation model, a higher proportion of CD68⁺ CD206⁺ M2 macrophages was observed in the tissues around the poled BT/Ti scaffolds under low intensity pulsed ultrasound (LIPUS) stimulation. Improvements in macrophage M2 polarization and bone regeneration were further identified in a sheep cervical corpectomy model. RNA sequencing and mechanistic investigation revealed that the piezoelectric BT/Ti (poled) scaffolds inhibited the inflammatory MAPK/JNK signaling cascade and activated oxidative phosphorylation (OXPHOS) and ATP synthesis in macrophages. Collectively, our study provides a promising method for regulating the immune microenvironment and enhancing bone regeneration using polarized piezoelectric BT/Ti scaffolds.

Osteoimmune Interactions and Therapeutic Potential of Macrophage-Derived Small Extracellular Vesicles in Bone-Related Diseases

Due to the aging of the global population, the burden of bone-related diseases has increased sharply. Macrophage, as indispensable components of both innate immune responses and adaptive immunity, plays a considerable role in maintaining bone homeostasis and promoting bone establishment. Small extracellular vesicles (sEVs) have attracted increasing attention because they participate in cell cross-talk in pathological environments and can serve as drug delivery systems. In recent years, an increasing number of studies have expanded our knowledge about the effects of macrophage-derived sEVs (M-sEVs) in bone diseases via different forms of polarization and their biological functions. In this review, we comprehensively describe on the application and mechanisms of M-sEVs in various bone diseases and drug delivery, which may provide new perspectives for treating and diagnosing human bone disorders, especially osteoporosis, arthritis, osteolysis, and bone defects.

Biofunctionalization of 3D Printed Porous Tantalum Using a Vancomycin-Carboxymethyl Chitosan Composite Coating to Improve Osteogenesis and Antibiofilm Properties

3D-printed porous tantalum scaffold has been increasingly used in arthroplasty due to its bone-matching elastic modulus and good osteoinductive ability. However, the lack of antibacterial ability makes it difficult for tantalum to prevent the occurrence and development of periprosthetic joint infection. The difficulty and high cost of curing periprosthetic joint infection (PJI) and revision surgery limit the further clinical application of tantalum. Therefore, we fabricated vancomycin-loaded porous tantalum scaffolds by combining the chemical grafting of (3-aminopropyl)triethoxysilane (APTES) and the electrostatic assembly of carboxymethyl chitosan and vancomycin for the first time. Our in vitro experiments show that the scaffold achieves rapid killing of initially adherent bacteria and effectively prevents biofilm formation. In addition, our modification preserves the original excellent structure and biocompatibility of porous tantalum and promotes the generation of mineralized matrix and osteogenesis-related gene expression by mesenchymal stem cells on the surface of scaffolds. Through a rat subcutaneous infection model, the composite bioscaffold shows efficient bacterial clearance and inflammation control in soft tissue and creates an immune microenvironment suitable for tissue repair at an early stage. Combined with the economic friendliness and practicality of its preparation, this scaffold has great clinical application potential in the treatment of periprosthetic joint infection.