Macrophages in aseptic loosening: Characteristics, functions, and mechanisms

Anti-tumor effect of dandelion flavone on multiple myeloma cells and its mechanism

BACKGROUND

Multiple myeloma (MM) is a prevalent hematologic malignancy characterized by the uncontrolled proliferation of monoclonal plasma cells in the bone marrow and excessive monoclonal immunoglobulin production, leading to organ damage. Despite therapeutic advancements, recurrence and drug resistance remain significant challenges.

OBJECTIVE

This study investigates the effects of dandelion flavone (DF) on MM cell proliferation, migration, and invasion, aiming to elucidate the mechanisms involved in MM metastasis and to explore the potential of traditional Chinese medicine in MM therapy.

METHODS

DF's impact on myeloma cell viability was evaluated using the CCK-8 and colony formation assays. Cell mobility and invasiveness were assessed through wound healing and transwell assays, respectively. RT-PCR was employed to quantify mRNA levels of MMP-2, MMP-9, TIMP-1, and TIMP-2. Apoptotic rates and molecular markers were analyzed via flow cytometry and RT-PCR. The PI3K/AKT signaling pathway was studied using Western blot and ELISA, with IGF-1 and the PI3K inhibitor LY294002 used to validate the findings.

RESULTS

DF demonstrated dose-dependent inhibitory effects on MM cell proliferation, migration, and invasion. It reduced mRNA levels of MMP-2 and MMP-9 while increasing those of TIMP-1 and TIMP-2. Furthermore, DF enhanced the expression of pro-apoptotic proteins and inhibited M2 macrophage polarization by targeting key molecules and enzymes. The anti-myeloma activity of DF was mediated through the inhibition of the PI3K/AKT pathway, as evidenced by diminished phosphorylation and differential effects in the presence of IGF-1 and LY294002.

CONCLUSION

By modulating the PI3K/AKT pathway, DF effectively inhibits MM cell proliferation, migration, and invasion, and induces apoptosis, establishing a novel therapeutic strategy for MM based on traditional Chinese medicine.

Wogonin induces apoptosis in macrophages by exhibiting cytotoxic and genotoxic effects

Macrophages play an important role in defending the body against invading pathogens. In the face of pathogens, macrophages become activated and release toxic materials that disrupt the pathogens. Macrophage overactivation can lead to severe illness and inflammation. Wogonin has several therapeutic effects, including anti-inflammatory, anticancer, antioxidant, and neuroprotective effects. No studies have investigated the cytotoxic effects of wogonin at concentrations of more than 0.1 mM in RAW264.7 cells. In this study, RAW 264.7 cells were treated with wogonin, which, at concentrations of more than 0.1 mM, had cytotoxic and genotoxic effects in the RAW264.7 cells, leading to apoptosis and necrosis. Further, wogonin at concentrations of more than 0.1 mM induced caspase-3, caspase-8, and caspase-9 activation and mitochondrial dysfunction and death receptor expression. These results suggest that wogonin induces apoptosis through upstream intrinsic and extrinsic pathways by exhibiting cytotoxic and genotoxic effects.

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.

The Microbial Revolution in the World of Joint Replacement Surgery

Background

The prevalence of revision surgery due to aseptic loosening and periprosthetic joint infection (PJI) following total hip and knee arthroplasty is growing. Strategies to prevent the need for revision surgery and its associated health-care costs and patient morbidity are needed. Therapies that modulate the gut microbiota to influence bone health and systemic inflammation are a novel area of research.

Methods

A literature review of preclinical and clinical peer-reviewed articles relating to the role of the gut microbiota in bone health and PJI was performed.

Results

There is evidence that the gut microbiota plays a role in maintaining bone mineral density, which can contribute to osseointegration, osteolysis, aseptic loosening, and periprosthetic fractures. Similarly, the gut microbiota influences gut permeability and the potential for bacterial translocation to the bloodstream, increasing susceptibility to PJI.

Conclusions

Emerging evidence supports the role of the gut microbiota in the development of complications such as aseptic loosening and PJI after total hip or knee arthroplasty. There is a potential for microbial therapies such as probiotics or fecal microbial transplantation to moderate the risk of developing these complications. However, further investigation is required.

Clinical Relevance

Modulation of the gut microbiota may influence patient outcomes following total joint arthroplasty.

Inhibition of Protein Disulfide Isomerase Attenuates Osteoclast Differentiation and Function via the Readjustment of Cellular Redox State in Postmenopausal Osteoporosis

Due to the accumulation of reactive oxygen species (ROS) and heightened activity of osteoclasts, postmenopausal osteoporosis could cause severe pathological bone destruction. Protein disulfide isomerase (PDI), an endoplasmic prototypic thiol isomerase, plays a central role in affecting cellular redox state. To test whether suppression of PDI could inhibit osteoclastogenesis through cellular redox regulation, bioinformatics network analysis was performed on the causative genes, followed by biological validation on the osteoclastogenesis in vitro and ovariectomy (OVX) mice model in vivo. The analysis identified PDI as one of gene targets for postmenopausal osteoporosis, which was positively expressed during osteoclastogenesis. Therefore, PDI expression inhibitor and chaperone activity inhibitor were used to verify the effects of PDI inhibitors on osteoclastogenesis. Results demonstrated that PDI inhibitors could reduce osteoclast number and inhibit resorption function via suppression on osteoclast marker genes. The mechanisms behind the scenes were the PDI inhibitors-caused intracellular ROS reduction via enhancement of the antioxidant system. Micro-CT and histological results indicated PDI inhibitors could effectively alleviate or even prevent bone loss in OVX mice. In conclusion, our findings unveiled the suppressive effects of PDI inhibitors on osteoclastogenesis by reducing intracellular ROS, providing new therapeutic options for postmenopausal osteoporosis.

Modelling of macrophage responses to biomaterials in vitro: state-of-the-art and the need for the improvement

The increasing use of medical implants in various areas of medicine, particularly in orthopedic surgery, oncology, cardiology and dentistry, displayed the limitations in long-term integration of available biomaterials. The effective functioning and successful integration of implants requires not only technical excellence of materials but also consideration of the dynamics of biomaterial interaction with the immune system throughout the entire duration of implant use. The acute as well as long-term decisions about the efficiency of implant integration are done by local resident tissue macrophages and monocyte-derived macrophages that start to be recruited during tissue damage, when implant is installed, and are continuously recruited during the healing phase. Our review summarized the knowledge about the currently used macrophages-based in vitro cells system that include murine and human cells lines and primary ex vivo differentiated macrophages. We provided the information about most frequently examined biomarkers for acute inflammation, chronic inflammation, foreign body response and fibrosis, indicating the benefits and limitations of the model systems. Particular attention is given to the scavenging function of macrophages that controls dynamic composition of peri-implant microenvironment and ensures timely clearance of microorganisms, cytokines, metabolites, extracellular matrix components, dying cells as well as implant debris. We outline the perspective for the application of 3D systems for modelling implant interaction with the immune system in human tissue-specific microenvironment avoiding animal experimentation.

Changes in serum inflammatory factors after hip arthroplasty and analysis of risk factors for prosthesis loosening

OBJECTIVE

To explore the relationship of serum levels of IL-1β, IL-6, and TNF-α with prosthesis loosening after hip arthroplasty, and to establish a predictive model for prosthesis loosening.

METHODS

We retrospectively analyzed the data of 501 patients who underwent hip arthroplasty in Xi'an International Medical Center Hospital from January 2020 to August 2022. Based on radiological diagnosis, the patients were divided into a prosthesis loosening group and a non-loosening group. Clinical data including postoperative serum levels of inflammatory cytokines were collected. Univariant analysis, Lasso regression, decision tree, and random forest models were used to screen feature variables. Based on the screening results, a nomogram model for predicting the risk of prosthesis loosening was established and then validated using ROC curve, and calibration curve, and other methods.

RESULTS

There were 50 cases in the loosening group and 451 cases in the non-loosening group. Postoperative levels of IL-1β, IL-6, and TNF-α were found to be significantly higher in the loosening group (P<0.0001). Univariant analysis showed that osteoporosis and postoperative infection were risk factors for prosthesis loosening (P<0.001). The machine learning algorithm identified osteoporosis, postoperative infection, IL-1β, IL-6, and TNF-α as 5 relevant variables. The predictive model based on these 5 variables exhibited an area under the ROC curve of 0.763. The calibration curve and DCA curve verified the accuracy and practicality of the model.

CONCLUSION

Serum levels of IL-1β, IL-6, and TNF-α were significantly elevated in patients with postoperative prosthesis loosening. Osteoporosis, postoperative infection, and inflammatory cytokines are independent risk factors for prosthesis loosening. The predictive model we established through machine learning can effectively determine the risk of prosthesis loosening. Monitoring inflammatory cytokines and postoperative infections, combined with prevention of osteoporosis, can help reduce the risk of prosthesis loosening.

Erdr1 Drives Macrophage Programming via Dynamic Interplay with YAP1 and Mid1

Erythroid differentiation regulator 1 (Erdr1) is a stress-induced, widely expressed, highly conserved secreted factor found in both humans and mice. Erdr1 is linked with the Hippo-YAP1 signaling. Initially identified as an inducer of hemoglobin synthesis, Erdr1 emerged as a multifunctional protein, especially in immune cells. Although Erdr1 has been implicated in regulating T cells and NK cell function, its role in macrophage remains unclear. This study explored the function and mechanism of Erdr1 in macrophage inflammatory response. The data demonstrated that Erdr1 could promote anti-inflammatory cytokine production, a function that also has been reported by previous research. However, I found Erdr1 also could play a proinflammatory role. The function of Erdr1 in macrophages depends on its dose and cell density. I observed that Erdr1 expression was inhibited in M1 macrophages but was upregulated in M2 macrophages compared with unpolarized macrophages. I hypothesized that Erdr1 balances the inflammatory response by binding with distinct adaptors dependent on varying concentrations. Mechanistically, I demonstrated YAP1 and Mid1 as the two adaptor proteins of Erdr1. The Erdr1-YAP1 interaction promotes anti-inflammatory cytokine production when Erdr1 levels are elevated, whereas the Erdr1-Mid1 interaction induces proinflammatory cytokine production when Erdr1 levels are decreased. This study highlights the effects of Erdr1 on regulating cytokine production from polarized macrophages potentially by regulating YAP1 in the nonclassical Hippo pathway.

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

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.

Erdr1 orchestrates macrophage polarization and determines cell fate via dynamic interplay with YAP1 and Mid1

Erythroid differentiation regulator 1 (Erdr1) is a stress-induced, widely distributed, extremely conserved secreted factor found in both humans and mice. Erdr1 is highly linked with the Hippo-YAP1 signaling. Initially identified as an inducer of hemoglobin synthesis, it has emerged as a multifunctional protein, especially in immune cells. Although Erdr1 has been implicated in T cells and NK cell function, its role in macrophage remains unclear. This study aims to explore the function and mechanism of Erdr1 in IL-1β production in macrophages. Data manifest Erdr1 could play an inhibition role in IL-1β production, which also has been reported by previous research. What significance is we discovered Erdr1 can promote IL-1β production which is associated with Erdr1 dose and cell density. We observed that Erdr1 was inhibited in pro-inflammatory (M1) macrophages but was upregulated in anti-inflammatory (M2) macrophages compared to naive macrophages. We hypothesized that Erdr1 dual drives and modulates IL-1β production by binding with distinct adaptors via concentration change. Mechanistically, we demonstrated that Erdr1 dual regulates IL-1β production by dynamic interaction with YAP1 and Mid1 by distinct domains. Erdr1-YAP1 interplay mediates macrophage M2 polarization by promoting an anti-inflammatory response, enhancing catabolic metabolism, and leading to sterile cell death. Whereas, Erdr1-Mid1 interplay mediates macrophage M1 polarization by initiating a pro-inflammatory response, facilitating anabolic metabolism, and causing inflammatory cell death. This study highlights Erdr1 orchestrates macrophage polarization and determines cell date by regulating YAP1 through non-classical Hippo pathway.

Byakangelicol suppresses TiPs-stimulated osteoclastogenesis and bone destruction via COX-2/NF-κB signaling pathway

Aseptic loosening (AL) is considered a significant cause of prosthesis revision after arthroplasty and a crucial factor in the longevity of an artificial joint prosthesis. The development of AL is primarily attributed to a series of biological reactions, such as peri-prosthetic osteolysis (PPO) induced by wear particles around the prosthesis. Chronic inflammation of the peri-prosthetic border tissue and hyperactivation of osteoclasts are key factors in this process, which are induced by metallic wear particles like Ti particles (TiPs). In our in vitro study, we observed that TiPs significantly enhanced the expression of inflammation-related genes, including COX-2, IL-1β and IL-6. Through screening a traditional Chinese medicine database, we identified byakangelicol, a traditional Chinese medicine molecule that targets COX-2. Our results demonstrated that byakangelicol effectively inhibited TiPs-stimulated osteoclast activation. Mechanistically, we found that byakangelicol suppressed the expression of COX-2 and related pro-inflammatory factors by modulating macrophage polarization status and NF-κB signaling pathway. The in vivo results also demonstrated that byakangelicol effectively inhibited the expression of inflammation-related factors, thereby significantly alleviating TiPs-induced cranial osteolysis. These findings suggested that byakangelicol could potentially be a promising therapeutic approach for preventing PPO.