Adiponectin attenuates osteolysis in aseptic loosening of total hip replacements

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.

Cortistatin attenuates titanium particle-induced osteolysis through regulation of TNFR1-ROS-caspase-3 signaling in osteoblasts

Aseptic loosening is a major complication of prosthetic joint surgery and is associated with impaired osteoblast homeostasis. Cortistatin (CST) is a neuropeptide that protects against inflammatory conditions. In this study, we found that expression of CST was diminished in patients with prosthetic joint loosening and in titanium (Ti) particle-induced animal models. A Ti particle-induced calvarial osteolysis model was established in wild-type and CST gene knockout mice; CST deficiency enhanced, while exogenously added CST attenuated, the severity of Ti particle-mediated osteolysis. CST protected against inflammation as well as apoptosis and maintained the osteogenic function of MC3T3-E1 osteoblasts upon stimulation with Ti particles. Furthermore, CST antagonized reactive oxygen species production and suppressed caspase-3-associated apoptosis mediated by Ti particles in osteoblasts. Additionally, CST protects against Ti particle-induced osteolysis through tumor necrosis factor receptor 1. Taken together, CST might provide a therapeutic strategy for wear debris-induced inflammatory osteolysis.

The TiO2-μ implant residual is more toxic than the Al2O3-n implant residual via blocking LAP and inducing macrophage polarization

Medical device residuals cause harmful effects and diseases in the human body, such as Particle Disease (PD), but the biological interaction of different types of particles is unclear. In this study, after a biological interaction screen between different particles, we aimed to explore the mechanism of the biological interaction between different types of particles, and the effect of a proteasome inhibitor on PD. Our studies showed that the titanium oxide microscale particle (Ti-μ) was more toxic than the aluminum oxide nanoscale particle (Al-n). Al-n activated LAP, attenuated the macrophage M1 polarization, inhibited the activator of the NF-κB pathway, and blocked the secretion of inflammatory factors and apoptosis in vitro, and also prevented the inflammation tissue disorder and aseptic loosening in vivo induced by Ti-μ. What is more, Bortezomib blocked apoptosis, secretion of inflammatory factors and the activation of the NF-κB pathway induced by TiO2 micro particles. Al-n-induced autophagy could play the function in the efficient clearance of dying cells by phagocytosis, and serves in dampening M1 polarization-related pro-inflammatory responses. While the Ti alloy medical implant and devices are applied worldwide, the toxicity of Ti-μ and its interaction with Al-n could be considered in the implant design, and Bortezomib was a potential therapeutic for PD.

Adipokines: New Therapeutic Target for Osteoarthritis?

PURPOSE OF THE REVIEW

Osteoarthritis (OA) is an aging-associated and injury-induced joint disease characterized by cartilage degradation, bone sclerosis, and persistent low-grade inflammation in the joint. Aging and injury are triggers of joint pathological changes mediated by pro-inflammatory factors, some of which are secreted by white adipose tissue. Adipokines including adiponectin, leptin, resistin, chemerin, IL-6, and TNF-α are major players not only during inflammation but also in metabolic regulation of joint cells including chondrocytes, osteoblasts, osteoclasts as well as mesenchymal stem cells. The purpose of this review is to summarize the signal transduction pathways of adipokines in the articular joint to provide new information on potential targets for intervention of OA.

RECENT FINDINGS

The risk of knee osteoarthritis is associated with adipokine gene polymorphism. While the infrapatellar fat pad is a major source of adipokines in knee synovial fluid, adipocytes also accumulate in the bone marrow during aging and obesity. Adipokines can act as SASPs (senescence associated secretory phenotype factors) that participate in cellular senescence of chondrocytes, but they also regulate energy metabolism impacting bone remodeling. Thus, adipokines are closely related to the metabolic syndrome and degenerative pathological changes in cartilage and bone during OA. Modulating the effects of adipokines on different cell types in the intra-articular joint will be a promising new option for OA intervention.

Strontium ranelate reduces the progression of titanium particle-induced osteolysis by increasing the ratio of osteoprotegerin to receptor activator of nuclear factor-κB ligand in vivo

The present study aimed to investigate the effects of strontium ranelate (SR), an anti‑osteoporotic drug, on osteolysis in an experimental mouse model of aseptic loosening. A total of 45 female C57BL/6J mice each received implantation of one titanium alloy pin into the tibia, followed by intraarticular injection of titanium particles. One week following surgery, mice were randomly divided into three groups: Control group (no additional treatment), SR625 group (treated with SR at a dose of 625 mg/kg/day), and SR1800 group (treated with SR at a dose of 1,800 mg/kg/day). SR was administered via oral gavage once every day for 12 weeks. Micro‑computed tomography scanning and hematoxylin/eosin staining were used to assess osteolysis around the prosthesis. Immunohistochemistry and reverse transcription-quantitative polymerase chain reaction analysis were used to measure the expression of receptor activator of nuclear factor‑κB ligand (RANKL) and osteoprotegerin (OPG). Compared with the control, the SR625 and SR1800 groups exhibited a significantly increased pulling force of the titanium alloy pin. Bone volume and the bone surface/volume ratio in the periprosthetic tissue were significantly increased in the SR‑treated groups. Significant differences were observed between the SR1800 group and control group with respect to trabecular thickness and trabecular number. Mechanistically, SR downregulated the expression of RANKL and upregulated the expression of OPG in the periprosthetic tissue. In addition, SR was observed to inhibit wear particle‑associated osteolysis in a dose‑dependent manner. In conclusion, the present data illustrated that SR inhibited titanium particle‑induced osteolysis in vivo.

Adiponectin improves the osteointegration of titanium implant under diabetic conditions by reversing mitochondrial dysfunction via the AMPK pathway in vivo and in vitro

Diabetes-induced reactive oxygen species (ROS) overproduction would result in compromised osteointegration of titanium implant (TI) and high rate of implant failure, yet the underlying mechanisms remain elusive. Adiponectin (APN) is a fat-derived adipocytokine with strong antioxidant, mitochondrial-protective and anti-diabetic efficacies. We hypothesized that mitochondrial dysfunction under diabetes may account for the oxidative stress in osteoblasts and titanium-bone interface (TBI) instability, which could be ameliorated by APN. To test this hypothesis, we incubated primary rat osteoblasts on TI and tested the cellular behaviors when subjected to normal milieu (NM), diabetic milieu (DM), DM+APN, DM+AICAR (AMPK activator) and DM+APN+Compound C (AMPK inhibitor). In vivo, APN or APN+Compound C were administered to diabetic db/db mice with TI implanted in their femurs. Results showed that diabetes induced structural damage, dysfunction and content decrease of mitochondria in osteoblasts, which led to ROS overproduction, dysfunction and apoptosis of osteoblasts accompanied by the inhibition of AMPK signaling. APN alleviated the mitochondrial damage by activating AMPK, thus reversing osteoblast impairment and improving the osteointegration of TI evidenced by Micro-CT and histological analysis. Furthermore, AICAR showed beneficial effects similar to APN treatment, while the protective effects of APN were abolished when AMPK activation was blocked by Compound C. This study clarifies mitochondrial dysfunction as a crucial mechanism in the impaired bone healing and implant loosening in diabetes, and provides APN as a novel promising active component for biomaterial-engineering to improve clinical performance of TI in diabetic patients.

STATEMENT OF SIGNIFICANCE

The loosening rate of titanium implants in diabetic patients is high. The underlying mechanisms remain elusive and, with the rapid increase of diabetic morbility, efficacious strategies to mitigate this problem have become increasingly important. Our study showed that the mitochondrial impairment and the consequent oxidative stress in osteoblasts at the titanium-bone interface (TBI) play a critical role in the diabetes-induced poor bone repair and implant destabilization, which could become therapeutic targets. Furthermore, adiponectin, a cytokine, promotes the bio-functional recovery of osteoblasts and bone regeneration at the TBI in diabetes. This provides APN as a novel bioactive component used in material-engineering to promote the osteointegration of implants, which could reduce implant failure, especially for diabetic patients.

Inhibitory effect of quercetin on titanium particle-induced endoplasmic reticulum stress (ERS)-related apoptosis and in vivoosteolysis

Wear particle induced periprosthetic osteolysis is the main cause of aseptic loosening of orthopedic implants. The aim of the present study is to determine the protective effect of quercetin (QUE) against titanium (Ti) particle induced endoplasmic reticulum stress (ERS) related apoptosis and osteolysis. In the present study, RAW264.7 cells were pretreated with different concentrations (40, 80, and 160 μmol/l) of QUE for 30 min and then treated with Ti particle (5 mg/ml) for 24 h. Cell viability and apoptosis were determined using MTT assay and Annexin V-FITC Apoptosis Detection Kit, respectively. Protein and mRNA expressions of ERS-related genes were examined by Western blot and real-time PCR, respectively. The release of inflammatory cytokines was detected by ELISA. Then, a mouse calvarial osteolysis model was established. Histological sections of calvaria were stained with Hematoxylin-Eosin (H&E) or tartrate-resistant acid phosphatase (TRAP). The results showed that Ti particle reduced cell viability and induced apoptosis in RAW264.7 macrophages. The cytotoxic effects of Ti particle were dramatically inhibited by QUE pretreatment. Interestingly, we found that QUE also significantly reduced Ti particle induced up-regulation of the expression levels of protein kinase RNA-like ER kinase (PERK), inositol-requiring enzyme-1 (IRE1), glucose-regulated protein (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, and caspase-3 and enhanced the down-regulation of Bcl-2. In addition, QUE decreased Ti particle-induced inflammatory cytokines release from RAW264.7 cells. Moreover, treatment with QUE markedly decreased osteoclast number. In a mouse calvarial osteolysis model, QUE inhibited Ti particle induced osteolysis in vivo by inhibiting osteoclast formation and expressions of ERS-related genes. In conclusion, QUE can protect RAW264.7 cells from Ti particle induced ERS-related apoptosis and suppress calvarial osteolysis in vivo.

Apoptotic pathways of macrophages within osteolytic interface membrane in periprosthestic osteolysis after total hip replacement

Macrophage apoptosis in interface membrane, which occurs through either death receptor, mitochondrion, or endoplasmic reticulum (ER) stress pathways, has been suggested to play an important role in promoting osteolysis. However, how and why macrophage apoptosis originates and the correlation among these apoptotic pathways is not yet clear. The objective of this study was to identify the apoptotic mechanism of macrophages, and to explore the relationship between the apoptotic pathways and progression of osteolysis. Transmission electron microscopy (TEM) was utilized to analyze the tissue ultrastructure of wear particles, and in situ apoptotic macrophage identification was performed by TUNEL staining. We analyzed the expression of the key biomarkers of apoptotic pathways via immunohistochemistry and Western blotting. Our results demonstrated that the majority of wear particles within osteolytic interface membrane was in the 30-60 nm range, and that macrophage apoptotic ratio increased along with osteolysis progression. Normal hip dysplasia and mechanical loosening of tissues showed low expression levels of biomarkers for ER stress (Ca²⁺ , JNK, cleaved Caspase-4, IRE1-α, Grp78/Bip, and CHOP), mitochondrion (Bcl-2, Bax, and Cytochrome c), and death receptor (Fas and cleaved Caspase-8) pathways, while osteolytic interface membrane tissues expressed high levels of these biomarkers. In addition, we found that the ER stress intensity was in complete conformity with mitochondrial dysfunction and was consistent with the results of death receptor activation. Thus, our findings suggested that wear particles generated at implant interface can accelerate macrophage apoptosis through changes in apoptotic pathways and ultimately aggravate the symptom of osteolysis. These data represent a preferential apoptotic signaling pathway of macrophages as specific target points for the prevention and therapeutic modulation of periprosthetic osteolysis.

Inhibitory Effects of Lanthanum Chloride on Wear Particle-Induced Osteolysis in a Mouse Calvarial Model

Osteolysis is a bone disorder associated with progressive destruction of bone tissues. However, the effects of lanthanum chloride (LaCl3) on osteolysis remain unknown. Therefore, the aim of this study was to determine the effects of LaCl3 on osteolysis in vivo. In a mouse calvarial model, C57BL/6J mice were injected with wear particles with or without LaCl3. Microcomputed tomography, hematoxylin and eosin staining, and tartrate-resistant acid phosphatase staining were performed for the pathological characterization of calvariae, and eight calvariae per group were prepared for the assay of TNF-α, IL-1β, and RANKL secretion using quantitative enzyme-linked immunosorbent assay (ELISA). In mice treated with high-dose LaCl3, particle-induced osteolysis and inflammatory reaction were reduced compared with that in the vehicle-treated control. Moreover, treatment with high-dose LaCl3 suppressed the wear particle-induced decrease in bone mineral content, bone mineral density, and bone volume fraction. Bone destruction and resorption were higher in the LaCl3-treated group than in the saline-treated group but lower than those in the wear particle group. Finally, our results showed that treatment with a high dose of LaCl3 suppressed osteoclastogenesis. Thus, LaCl3 may represent a novel therapeutic agent for the treatment or prevention of wear particle-induced osteolysis and aseptic loosening.

Endoplasmic reticulum stress-mediated inflammatory signaling pathways within the osteolytic periosteum and interface membrane in particle-induced osteolysis

Aseptic loosening secondary to periprosthetic inflammatory osteolysis results from the biological response to wear particles and is a leading cause of arthroplasty failure. The origin of this inflammatory response remains unclear. We aim to validate the definite link between endoplasmic reticulum (ER) stress and particle-induced inflammatory signaling pathways in periprosthetic osteolysis. We examine the histopathologic changes of osteolysis and the expression of specific biomarkers for ER-stress-mediated inflammatory signaling pathways (IRE1α, GRP78/Bip, c-Fos, NF-κB, ROS and Ca(2+)). Moreover, pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) and osteoclastogenic molecules (VEGF, OPG, RANKL and M-CSF) were assessed in clinical interface membranes and murine periosteum tissues. We found wear particles to be capable of inducing ER stress in macrophages within clinical osteolytic interface membranes and murine osteolytic periosteum tissues and to be associated with the inflammatory response and osteoclastogenesis. Blocking ER stress with sodium 4-phenylbutyrate (4-PBA) results in a dramatic amelioration of particle-induced osteolysis and a significant reduction of ER-stress intensity. Simultaneously, this ER-stress blocker also lessens inflammatory cell infiltration, diminishes the capability of osteoclastogenesis and reduces the inflammatory response by lowering IRE1α, GRP78/Bip, c-Fos, NF-κB, ROS and Ca(2+) levels. Thus, ER stress plays an important role in particle-induced inflammatory osteolysis and osteoclastogenic reactions. The pharmacological targeting of ER-stress-mediated inflammatory signaling pathways might be an appealing approach for alleviating or preventing particle-induced osteolysis in at-risk patients.

Calcitonin gene-related peptide modulates the production of pro-inflammatory cytokines associated with periprosthetic osteolysis by THP-1 macrophage-like cells

OBJECTIVE

An anti-resorptive impact of the neuropeptide calcitonin gene-related peptide (CGRP) on periprosthetic osteolysis, the leading cause of early prosthesis loosening, has been shown previously. In this study, the impact of CGRP on pro-inflammatory cytokine production associated with periprosthetic osteolysis was analysed using THP-1 macrophage-like cells.

METHODS

Cells were stimulated with ultra-high-molecular-weight polyethylene (UHMWPE) particles (cell-to-particle ratios of 1:100 and 1:500) and lipopolysaccharides (LPS; 1 µg/ml) to establish osteolytic conditions, and simultaneously treated with CGRP (10(-8)M). Receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNF)-α mRNA expression were measured by quantitative RT-PCR. RANK protein was detected by Western blot. Secreted protein levels of TNF-α as well as interleukin (IL)-1β and IL-6 were quantified in cell culture supernatants by ELISA and Bio-Plex cytokine assay, respectively.

RESULTS

Activation of macrophage-like cells failed to enhance the production of RANK but led to a dose- and time-dependent increase of TNF-α mRNA and secreted protein levels of TNF-α, IL-1β and IL-6. Application of CGRP time-dependently suppressed TNF-α mRNA expression induced by low-particle concentrations and LPS, while both particle- and LPS-induced secretion of TNF-α was inhibited. A pronounced inhibitory effect of CGRP on LPS-induced cytokine production at 24 h of incubation was also observed with IL-1β and IL-6.

CONCLUSIONS

CGRP shows a time-dependent inhibitory effect on the secretion of osteolysis-associated pro-inflammatory cytokines, indicating an indirect anti-resorptive influence of the neuropeptide on both aseptic prosthesis loosening and bacterially induced bone resorption which might enhance the life time of total joint replacements.