Macrophage miR-149-5p induction is a key driver and therapeutic target for BRONJ

Chinese expert consensus on the diagnosis and clinical management of medication-related osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a side effect that occurs after treatment for systemic diseases. However, most institutions currently rely on empirical methods to make diagnosis and treatment plans, and there is a lack of consensus or guidelines for the classification, staging and treatment of MRONJ in China. To address this gap and improve prognosis, an expert panel representing 11 renowned domestic medical colleges and affiliated hospitals in China was convened. The panel made a comprehensive literature review of previous treatment experiences and research findings to address issues of definitions, etiology and risk factors, diagnosis, treatment and prevention methods. The panel concluded that the diagnosis of MRONJ can be made on the basis of a history of related medications and typical clinical manifestations, with either typical radiographic manifestations or histopathological manifestations, after excluding jaw metastasis. Surgical treatment should be considered for symptomatic patients with sequestrum or bone abnormalities accompanied by recurrent infections, and He's classification was considered a practical clinical MRONJ staging system. Multidisciplinary comprehensive treatment should be proposed to achieve optimal treatment outcomes.

Targeting endoplasmic reticulum stress-induced lymphatic dysfunction for mitigating bisphosphonate-related osteonecrosis

BACKGROUND

Bisphosphonates (BPs) are the first-line treatment to stop bone resorption in diseases, including osteoporosis, Paget's disease, multiple myeloma and bone metastases of cancer. However, BPs-related osteonecrosis of the jaw (BRONJ), characterized by local inflammation and jawbone necrosis, is a severe intractable complication. The cumulative inflammatory burden often accompanies impaired lymphatic drainage, but its specific impact on BRONJ and the underlying mechanisms remain unclear.

METHODS

The mouse BRONJ model was established to assess the integrity and drainage function of lymphatic vessels by tissue clearing techniques, injected indocyanine green lymphatic clearance assay, flow cytometry analysis and histopathological staining. RNA sequencing, metabolome analysis, transmission electron microscopy and Western blotting were utilized to analyze the impacts of Zoledronate acid (ZA) on endoplasmic reticulum stress (ERS) and function of lymphatic endothelial cells (LECs). By constructing Lyve1creERT; SIRT6f/f and Lyve1creERT; ATG5f/f mice, we evaluated the role of ERS-induced LECs apoptosis in the progression of BRONJ. Additionally, we developed a nanoparticle-loaded ZA and rapamycin (ZDPR) to enhance autophagy and evaluated its potential in mitigating BRONJ.

RESULTS

The mouse BRONJ model displayed impaired lymphatic drainage, accompanied by significant local inflammation and bone necrosis. The prolonged stimulation of ZA resulted in the extension of ERS and the inhibition of autophagy in LECs, ultimately leading to apoptosis. Mechanistically, ZA activated XBP1s through the NAD+/SIRT6 pathway, initiating ERS-induced apoptosis in LECs. The conditional knockout mouse models demonstrated that the deletion of SIRT6 or ATG5 significantly worsened lymphatic drainage and inflammatory infiltration in BRONJ. Additionally, the innovative nanoparticle ZDPR alleviated ERS-apoptosis in LECs and enhanced lymphatic function, facilitating inflammation resolution.

CONCLUSION

Our study has elucidated the role of the NAD+/SIRT6/XBP1s pathway in ERS-induced apoptosis in ZA-treated LECs, and further confirmed the therapeutic potential of ZDPR in restoring endothelial function and improving lymphatic drainage, thereby effectively mitigating BRONJ.

KEY POINTS

Bisphosphonate-induced lymphatic drainage impairment exacerbates bone necrosis. Zoledronate acid triggers endoplasmic reticulum stress and apoptosis in lymphatic endothelial cells via the NAD+/SIRT6/XBP1s pathway. Novel nanoparticle-loaded Zoledronate acid and rapamycin enhances autophagy, restores lymphatic function, and mitigates bisphosphonates-related osteonecrosis of the jaw progression.

Zoledronic Acid Accelerates ER Stress-Mediated Inflammation by Increasing PDE4B Expression in Bisphosphonate-Related Osteonecrosis of the Jaw

Long-term administration of bisphosphonates can lead to a significant side effect known as bisphosphonate-related osteonecrosis of the jaw (BRONJ). Although macrophage-mediated inflammation has been established as an important factor in BRONJ, the underlying mechanism remains elusive. In the current study, the roles of endoplasmic reticulum (ER) stress in zoledronic acid (ZOL)-induced inflammation were analyzed in macrophages, and the regulatory mechanism of ER stress activation was next investigated. An in vitro model of BRONJ was established by treating RAW264.7 cells with ZOL. The activation of ER stress was analyzed by western blotting and transmission electron microscopy, and inflammation was assessed by quantitative real-time PCR and enzyme-linked immunosorbent assay. ER stress was significantly activated in ZOL-treated macrophages, and inhibition of ER stress by TUDCA, an ER stress inhibitor, suppressed ZOL-induced inflammation in macrophages. Mechanistically, phosphodiesterase 4B (PDE4B) was significantly increased in ZOL-treated macrophages. Forced expression of PDE4B promoted ER stress and inflammation, whereas PDE4B knockdown decreased ZOL-induced ER stress and inflammation in macrophages. More importantly, PDE4B inhibitor could improve ZOL-induced BRONJ in vivo. These data suggest that ZOL accelerates ER stress-mediated inflammation in BRONJ by increasing PDE4B expression. PDE4B inhibition may represent a potential therapeutic strategy for BRONJ. Subsequent research should concentrate on formulating medications that selectively target PDE4B, thereby mitigating the risk of BRONJ in patients undergoing bisphosphonate treatment.

Genetic Background of Medication-Related Osteonecrosis of the Jaw: Current Evidence and Future Perspectives

Medication-related osteonecrosis of the jaw (MRONJ) is a rare side effect of antiresorptive drugs that significantly hinders the quality of life of affected patients. The disease develops in the presence of a combination of factors. Important pathogenetic factors include inflammation, inhibition of bone remodeling, or genetic predisposition. Since the first description of this rare side effect in 2003, a growing body of data has suggested a possible role for genetic factors in the disease. Several genes have been suggested to play an important role in the pathogenesis of MRONJ such as SIRT1, VEGFA, and CYP2C8. With the development of molecular biology, newer methods such as miRNA and gene expression studies have been introduced in MRONJ, in addition to methods that can examine the base sequence of the DNA. Describing the complex genetic background of MRONJ can help further understand its pathophysiology as well as identify new therapeutic targets to better manage this adverse drug reaction.

Medication-related osteonecrosis of the jaw: a retrospective single center study of recurrence-related factors after surgical treatment

OBJECTIVES

To provide an overview of the features of patients with medication-related osteonecrosis of the jaw (MRONJ) and explore recurrence-related factors after surgery.

MATERIALS AND METHODS

All pathological records of patients diagnosed with osteonecrosis or osteomyelitis of the jaw were reviewed. Only patients who had a history of use of medication related to bone turnover were included. All demographic and clinical characteristics were collected during review. Univariate and logistic regression analyses were performed to evaluate the associations between risk factors and recurrence. A p value < 0.05 was considered to indicate statistical significance in all analyses.

RESULTS

A total of 313 patients were ultimately included. Most patients (89.14%) underwent bone turnover-related treatment due to malignancy. The breast and prostate were the most common locations of primary tumors in females and males, respectively. Almost all MRONJ patients experienced inflammatory symptoms. Recurrence occurred in 55 patients at 60 locations. The total recurrence rate was 16.85%, with no significant differences between the maxilla and mandible. Extensive surgery and flap transfer were strongly related to a lower recurrence risk. Nearly 80% of patients had recurrence-related symptoms within 6 months.

CONCLUSION

When MRONJ is treated with surgical methods, extensive resection and flap transfer can reduce recurrence risk. Six-month follow-up is needed to exclude recurrence after surgery.

CLINICAL RELEVANCE

This study revealed the surgical-related risk factors, such as extensive surgery and flap transfer, when treating MRONJ patients, and 6-month follow-up is needed to detect recurrence. This could provide clinical guidance for head and neck surgeons.

Causal effects of autoimmune diseases on temporomandibular disorders and the mediating pathways: a Mendelian randomization study

Background

The role of autoimmune diseases (ADs) in temporomandibular disorders (TMDs) has been emphasized in observational studies. However, whether the causation exists is unclear, and controversy remains about which specific disorder is destructive in TMDs. This Mendelian randomization (MR) study aims to estimate the causal effect of common ADs on TMDs.

Methods

Genetic data from published genome-wide association studies for fourteen common ADs, specifically multiple sclerosis (MS, N = 15,283), ankylosing spondylitis (AS, N = 22,647), asthma (N = 408,422), celiac disease (N = 15,283), Graves' disease (N = 458,620), Hashimoto thyroiditis (N = 395,640), primary biliary cirrhosis (PBC, N = 11,375), primary sclerosing cholangitis (PSC, N = 14,890), psoriasis vulgaris (N = 483,174), rheumatoid arthritis (RA, N = 417,256), systemic lupus erythematosus (SLE, N = 23,210), Type 1 diabetes (T1D, N = 520,580), inflammatory bowel disease (IBD, N = 34,652), and Sjogren's syndrome (SS, N = 407,746) were collected. Additionally, the latest summary-level data for TMDs (N = 228,812) were extracted from the FinnGen database. The overall effects of each immune traits were assessed via inverse-variance weighted (IVW), weighted median, and MR-Egger methods, and performed extensive sensitivity analyses. Finally, 731 immune cell phenotypes (N = 3,757) were analyzed for their mediating role in the significant causality.

Results

Univariable MR analyses revealed that genetically predicted RA (IVW OR: 1.12, 95% CI: 1.05-1.19, p < 0.001) and MS (IVW OR: 1.06, 95% CI: 1.03-1.10, p = 0.001) were associated with increased risk of TMDs. Two out of 731 immune cell phenotypes were identified as causal mediators in the associations of RA with TMDs, including "CD25++ CD8+ T cell % CD8+ T cell" (mediation proportion: 6.2%) and "CD3 on activated CD4 regulatory T cell" (5.4%). Additionally, "CD127 on granulocyte" mediated 10.6% of the total effect of MS on TMDs. No reverse directions, heterogeneity, and pleiotropy were detected in the analyses (p > 0.05).

Conclusion

This MR study provides new evidence regarding the causal impact of genetic predisposition to RA or MS on the increased risk of TMDs, potentially mediated by the modulation of immune cells. These findings highlight the importance for clinicians to pay more attention to patients with RA or MS when consulting for temporomandibular discomfort. The mediating role of specific immune cells is proposed but needs further investigation.

Role of miRNA-regulated type H vessel formation in osteoporosis

Osteoporosis (OP) is a chronic systemic bone metabolism disease characterized by decreased bone mass, microarchitectural deterioration, and fragility fractures. With the demographic change caused by long lifespans and population aging, OP is a growing health problem. The role of miRNA in the pathogenesis of OP has also attracted widespread attention from scholars in recent years. Type H vessels are unique microvessels of the bone and have become a new focus in the pathogenesis of OP because they play an essential role in osteogenesis-angiogenesis coupling. Previous studies found some miRNAs regulate type H vessel formation through the regulatory factors, including platelet-derived growth factor-BB (PDGF-BB), hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor (VEGF), and so on. These findings help us gain a more in-depth understanding of the relationship among miRNAs, type H vessels, and OP to find a new perspective on treating OP. In the present mini-review, we will introduce the role of type H vessels in the pathogenesis of OP and the regulation of miRNAs on type H vessel formation by affecting regulatory factors to provide some valuable insights for future studies of OP treatment.

Rodents as an animal model for studying tooth extraction-related medication-related osteonecrosis of the jaw: assessment of outcomes

OBJECTIVE

To assess the outcomes of several rodent animal models for studying tooth extraction-related medication-related osteonecrosis of the jaw (MRONJ).

DESIGN

After a search of the databases, 2004 articles were located, and 118 corroborated the inclusion factors (in vivo studies in rodents evaluating tooth extraction as a risk factor for the development of MRONJ).

RESULTS

Numerous studies attempting to establish an optimal protocol to induce MRONJ were found. Zoledronic acid (ZA) was the most used drug, followed by alendronate (ALN). Even when ZA did not lead to the development of MRONJ, its effect compromised the homeostasis of the bone and soft tissue. The association of other risk factors (dexamethasone, diabetes, and tooth-related inflammatory dental disease) besides tooth extraction also played a role in the development of MRONJ. In addition, studies demonstrated a relationship between cumulative dose and MRONJ.

CONCLUSIONS

Both ZA and ALN can lead to MRONJ in rodents when equivalent human doses (in osteoporosis or cancer treatment) are used. Local oral risk factors and tooth-related inflammatory dental disease increase the incidence of MRONJ in a tooth extraction-related rodent model.

Type H vessels in osteogenesis, homeostasis, and related disorders

The vascular system plays a crucial role in bone tissue. Angiogenic and osteogenic processes are coupled through a spatial-temporal connection. Recent studies have identified three types of capillaries in the skeletal system. Compared with type L and E vessels, type H vessels express high levels of CD31 and endomucin, and function to couple angiogenesis and osteogenesis. Endothelial cells in type H vessels interact with osteolineage cells (e.g., osteoblasts, osteoclasts, and osteocytes) through cytokines or signaling pathways to maintain bone growth and homeostasis. In imbalanced bone homeostases, such as osteoporosis and osteoarthritis, it may be a new therapeutic strategy to regulate the endothelial cell activity in type H vessels to repair the imbalance. Here, we reviewed the latest progress in relevant factors or signaling pathways in coupling angiogenesis and osteogenesis. This review would contribute to further understanding the role and mechanisms of type H vessels in coupling angiogenic and osteogenic processes. Furthermore, it will facilitate the development of therapeutic approaches for bone disorders by targeting type H vessels.

[Regulation of non-coding RNA in type H vessels angiogenesis of bone]

Objective

To summarize the regulatory effect of non-coding RNA (ncRNA) on type H vessels angiogenesis of bone.

Methods

Recent domestic and foreign related literature about the regulation of ncRNA in type H vessels angiogenesis was widely reviewed and summarized.

Results

Type H vessels is a special subtype of bone vessels with the ability to couple bone formation. At present, the research on ncRNA regulating type H vessels angiogenesis in bone diseases mainly focuses on microRNA, long ncRNA, and small interfering RNA, which can affect the expressions of hypoxia inducible factor 1α, platelet derived growth factor BB, slit guidance ligand 3, and other factors through their own unique ways of action, thus regulating type H vessels angiogenesis and participating in the occurrence and development of bone diseases.

Conclusion

At present, the mechanism of ncRNA regulating bone type H vessels angiogenesis has been preliminarily explored. With the deepening of research, ncRNA is expected to be a new target for the diagnosis and treatment of vascular related bone diseases.

Molecular events in the jaw vascular unit: A traditional review of the mechanisms involved in inflammatory jaw bone diseases

Inflammatory jaw bone diseases are common in stomatology, including periodontitis, peri-implantitis, medication-related osteonecrosis of the jaw, radiation osteomyelitis of the jaw, age-related osteoporosis, and other specific infections. These diseases may lead to tooth loss and maxillofacial deformities, severely affecting patients' quality of life. Over the years, the reconstruction of jaw bone deficiency caused by inflammatory diseases has emerged as a medical and socioeconomic challenge. Therefore, exploring the pathogenesis of inflammatory diseases associated with jaw bones is crucial for improving prognosis and developing new targeted therapies. Accumulating evidence indicates that the integrated bone formation and dysfunction arise from complex interactions among a network of multiple cell types, including osteoblast-associated cells, immune cells, blood vessels, and lymphatic vessels. However, the role of these different cells in the inflammatory process and the 'rules' with which they interact are still not fully understood. Although many investigations have focused on specific pathological processes and molecular events in inflammatory jaw diseases, few articles offer a perspective of integration. Here, we review the changes and mechanisms of various cell types in inflammatory jaw diseases, with the hope of providing insights to drive future research in this field.