Yangchun Zhang

Decision making regarding spinal osteotomy and total hip replacement for ankylosing spondylitis: experience with 28 patients

Few studies have examined the order in which a spinal osteotomy and total hip replacement (THR) are to be performed for patients with ankylosing spondylitis. We have retrospectively reviewed 28 consecutive patients with ankylosing spondylitis who underwent both a spinal osteotomy and a THR from September 2004 to November 2012. In the cohort 22 patients had a spinal osteotomy before a THR (group 1), and six patients had a THR before a spinal osteotomy (group 2). The mean duration of follow-up was 3.5 years (2 to 9). The spinal sagittal Cobb angle of the vertebral osteotomy segment was corrected from a pre-operative kyphosis angle of 32.4 (SD 15.5°) to a post-operative lordosis 29.6 (SD 11.2°) (p < 0.001). Significant improvements in pain, function and range of movement were observed following THR. In group 2, two of six patients had an early anterior dislocation. The spinal osteotomy was performed two weeks after the THR. At follow-up, no hip has required revision in either group. Although this non-comparative study only involved a small number of patients, given our experience, we believe a spinal osteotomy should be performed prior to a THR, unless the deformity is so severe that the procedure cannot be performed.

IRAK-M in macrophages around septically and aseptically loosened hip implants†

The most common long-term complication of joint arthroplasty is loosening, which is mediated by chronic inflammatory cytokines produced by macrophages stimulated by implant-derived debris and eventually bacterial components adherent to such debris. In this study, antiinflammatory interleukin-1 receptor-associated kinase-M (IRAK-M) was studied in macrophages in interface membranes in vivo using immunohistochemical staining and in titanium particle-stimulated macrophages in vitro using reverse transcriptase-polymerase chain reaction. Results show that the interface membranes of septically and aseptically loosened prosthesis express more IRAK-M protein than control membranes from osteoarthritic patient and that IRAK-M mRNA-levels increase upon particle stimulation. These findings suggest that, the upregulation of IRAK-M in macrophages is involved in the local immunosuppression around implants, and may contribute to septic and aseptic implant loosening.

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

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

Wear Particles Promote Reactive Oxygen Species-Mediated Inflammation via the Nicotinamide Adenine Dinucleotide Phosphate Oxidase Pathway in Macrophages Surrounding Loosened Implants

Background/Aims: Prosthesis loosening is closely associated with chronic inflammatory cytokine secretion by macrophages, which are activated by wear particles or inflammatory stimulants such as lipopolysaccharide (LPS). Reactive oxygen species (ROS) are critical regulators of inflammation, but their enzymatic sources in response to wear particles and their effects on peri-implant LPS-tolerance remain unclear. Methods: Three ROS-related enzymes—nicotinamide adenine dinucleotide phosphate oxidase (NOX)-1 and -2 and catalase—were investigated in interface membrane tissues and in titanium (Ti) particle-stimulated macrophages in vitro. The generation of ROS and downstream inflammatory effects were measured with or without pre-incubation with apocynin, an NOX inhibitor. Results: Pre-exposure to Ti particles attenuated NF-κB activation in LPS-stimulated macrophages, indicating that wear particles suppress immune response, which may lead to chronic inflammation. NOX-1 and -2 were highly expressed in aseptically loosened interface membranes and in macrophages stimulated with Ti particles; the particles induced a moderate amount of ROS generation, NF-κB activation, and TNF-a secretion in macrophages, and these effects were suppressed by apocynin. Conclusion: Wear particles induce ROS generation through the NOX signaling pathway, resulting in persistent inflammation and delayed loosening. Thus, the suppression of NOX activity may be a useful strategy for preventing prosthesis loosening.

Wear particles promote endotoxin tolerance in macrophages by inducing interleukin‐1 receptor‐associated kinase‐M expression

Toll-like receptors (TLRs) recognizing pathogen-associated molecular patterns (PAMP) play a role in local immunity and participate in implant-associated loosening. TLRs-mediated signaling is regulated by interleukin-1 receptor-associated kinase-M (IRAK-M). Our previous studies have proved that IRAK-M is induced by wear particles in macrophages from periprosthetic tissues. In this study, the IRAK-M-related mechanisms were further explored by lipopolysaccharide (LPS) and/or titanium (Ti) particles stimulations and small interfering RNAs (siRNAs). The protein level of IRAK-M was studied using western blotting and tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) levels were measured using ELISA. Results showed that in RAW264.7 cells stimulated by LPS after Ti particle pre-exposure, IRAK-M was slightly changed, compared with LPS stimulation. And levels of TNF-α and IL-1β in cultures stimulated by LPS first after Ti particle pre-exposure were lower than in the other two groups which were stimulated by LPS with or without Ti particles (p < 0.001), whereas there were no statistic differences between the later two (p > 0.05). The cytokines were lowest in Ti particles alone stimulation. After siRNAs silenced, IRAK-M-deficient cells exhibited increased expression of the cytokines in LPS stimulation after Ti particle pre-exposure and when stimulated with Ti particles alone. Our findings suggest that debris-induced IRAK-M decreases foreign body reactions, but at the same time, the over-expression of IRAK-M may also be detrimental on local intrusion of PAMPs or bacteria, negatively regulates the LPS-induced and TLRs-mediated inflammation and results in immunosuppression in periprosthetic tissue, which may predispose to implant-associated infections.

Advanced glycation end products biphasically modulate bone resorption in osteoclast-like cells

Advanced glycation end products (AGEs) disturb bone remodeling during aging, and this process is accelerated in diabetes. However, their role in modulation of osteoclast-induced bone resorption is controversial, with some studies indicating that AGEs enhance bone resorption and others showing the opposite effect. We determined whether AGEs present at different stages of osteoclast differentiation affect bone resorption differently. Based on increased levels of tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CTSK), we identified day 4 of induction as the dividing time of cell fusion stage and mature stage in RAW264.7 cell-derived osteoclast-like cells (OCLs). AGE-modified BSA (50-400 μg/ml) or control BSA (100 μg/ml) was then added at the beginning of each stage. Results showed that the presence of AGEs at the cell fusion stage reduced pit numbers, resorption area, and CTSK expression. Moreover, expression of receptor activator of nuclear factor-κB (RANK) as well as the number of TRAP-positive cells, nuclei per OCL, actin rings, and podosomes also decreased. However, the presence of AGEs at the mature stage enlarged the resorption area markedly and increased pit numbers slightly. Intriguingly, only the number of nuclei per OCL and podosomes increased. These data indicate that AGEs biphasically modulate bone resorption activity of OCLs in a differentiation stage-dependent manner. AGEs at the cell fusion stage reduce bone resorption dramatically, mainly via suppression of RANK expression in osteoclast precursors, whereas AGEs at the mature stage enhance bone resorption slightly, most likely by increasing the number of podosomes in mature OCLs.

Wear Particles Impair Antimicrobial Activity Via Suppression of Reactive Oxygen Species Generation and ERK1/2 Phosphorylation in Activated Macrophages.

Implant-related infection (IRI) is closely related to the local immunity of peri-implant tissues. The generation of reactive oxygen species (ROS) in activated macrophages plays a prominent role in the innate immune response. In previous studies, we indicated that implant wear particles promote endotoxin tolerance by decreasing the release of proinflammatory cytokines. However, it is unclear whether ROS are involved in the damage of the local immunity of peri-implant tissues. In the present study, we assessed the mechanism of local immunosuppression using titanium (Ti) particles and/or lipopolysaccharide (LPS) to stimulate RAW 264.7 cells. The results indicate that the Ti particles induced the generation of a moderate amount of ROS through nicotinamide adenine dinucleotide phosphate oxidase-1, but not through catalase. Pre-exposure to Ti particles inhibited ROS generation and extracellular-regulated protein kinase activation in LPS-stimulated macrophages. These findings indicate that chronic stimulation by Ti particles may lead to a state of oxidative stress and persistent inflammation, which may result in the attenuation of the immune response of macrophages to bacterial components such as LPS. Eventually, immunosuppression develops in peri-implant tissues, which may be a risk factor for IRI.

Presence of interleukin-17C in the tissue around aseptic loosened implants.

PurposeThe most common long-term complication of joint arthroplasty is aseptic loosening. The proinflammatory cytokines secreted by macrophages are involved in aseptic loosening. Recently, a novel proinflammatory cytokine IL-17C was reported to participate in inflammatory diseases by synergising with proinflammatory cytokines. However, the relationship between IL-17C and the aseptic loosening is unclear.MethodsThe tissues around aseptic loosened implants were collected during revision surgery and handled by formalin fixation and embedded in paraffin. The presence of IL-17C in the tissues around the aseptic loosened implants was investigated in 12 aseptic loosening patients using immunofluorescence.ResultsThe presence of IL-17C protein in the tissues around aseptic loosened implants was detected by immunofluorescence. There are no statistical differences between optical density of IL-17C in aseptic loosening samples and in rheumatoid arthritis samples (positive control).ConclusionsThese results suggest the presence of IL-17C in aseptic loosening. Interleukin-17C was related to the inflammation of aseptic loosening, possibly by contributing to the inflammation and osteolysis in the tissues surrounding aseptic loosened implants.

Protein Disulfide Isomerase Silence Inhibits Inflammatory Functions of Macrophages by Suppressing Reactive Oxygen Species and NF-κB Pathway

Macrophages play an essential role in inflammation. Protein disulfide isomerase (PDI) is central to the redox system, which is closely linked with the inflammatory function of macrophages. However, the relationship between PDI and inflammation is still unknown. In this study, we tested the effects of PDI on inflammatory responses in RAW 264.7 macrophages stimulated with lipopolysaccharide (LPS). Using CRISPR/Cas9 system, we found that PDI knockout suppressed migration, M1 polarization, and secretion of tumor necrosis factor-α (TNF-α) and interluekin-6 (IL-6). The repression of these inflammatory processes was accompanied by decreased production of reactive oxygen species (ROS). PDI ablation also inactivated the phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and activated the phosphorylation of NF-κB inhibitor alpha (IκBα). These findings demonstrate that PDI knockout inhibits the inflammatory function of macrophages by decreasing ROS production and inactivating NF-κB pathway.