Osteonecrosis of the Jaws: An Update and Review of Literature

Pathophysiology of the Effects of Oxidative Stress on the Skeletal System

Reactive oxygen species (ROS) are molecules that are generated primarily during energy production in cells. ROS are involved in critical biological functions such as signal transduction; when the production of ROS is imbalanced, excessive ROS causes oxidative stress, and subsequent cellular damage. Oxidative stress is linked to numerous pathological disorders in major organs including the skeletal system. In an aging society, understanding the role of ROS in skeletal health is critical to developing preventative and therapeutic interventions. Oxidative stress causes defects in cellular differentiation, apoptosis, mitochondrial dysfunction, and inflammation. The effects of oxidative stress on the skeletal system have been implicated in the development of osteoporosis, knee osteoarthritis, and osteonecrosis by inhibiting bone remodeling, increasing osteoclast activity, and decreasing osteoblast function. ROS are also involved in many signaling pathways that regulate immune defense, cell proliferation, and inflammation. This underscores the importance of maintaining a balance between ROS and antioxidants to prevent oxidative stress and related diseases. Targeting ROS and oxidative stress mechanisms may offer new treatments for diseases affecting the skeletal system and other organs, potentially improving health outcomes, and extending healthy lifespans. This review highlights the significant impact of oxidative stress on skeletal health and explores potential preventative and therapeutic strategies to mitigate the adverse effects of ROS.

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.

Association between genetically plasma proteins and osteonecrosis: a proteome-wide Mendelian randomization analysis

Background

Previous studies have explored the role of plasma proteins on osteonecrosis. This Mendelian randomization (MR) study further assessed plasma proteins on osteonecrosis whether a causal relationship exists and provides some evidence of causality.

Methods

Summary-level data of 4,907 circulating protein levels were extracted from a large-scale protein quantitative trait loci study including 35,559 individuals by the deCODE Genetics Consortium. The outcome data for osteonecrosis were sourced from the FinnGen study, comprising 1,543 cases and 391,037 controls. MR analysis was conducted to estimate the associations between protein and osteonecrosis risk. Additionally, Phenome-wide MR analysis, and candidate drug prediction were employed to identify potential causal circulating proteins and novel drug targets.

Results

We totally assessed the effect of 1,676 plasma proteins on osteonecrosis risk, of which 71 plasma proteins had a suggestive association with outcome risk (P < 0.05). Notably, Heme-binding protein 1 (HEBP1) was significant positively associated with osteonecrosis risk with convening evidence (OR, 1.40, 95% CI, 1.19 to 1.65, P = 3.96 × 10-5, P FDR = 0.044). This association was further confirmed in other MR analysis methods and did not detect heterogeneity and pleiotropy (all P > 0.05). To comprehensively explore the health effect of HEBP1, the phenome-wide MR analysis found it was associated with 136 phenotypes excluding osteonecrosis (P < 0.05). However, no significant association was observed after the false discovery rate adjustment.

Conclusion

This comprehensive MR study identifies 71 plasma proteins associated with osteonecrosis, with HEBP1, ITIH1, SMOC1, and CREG1 showing potential as biomarkers of osteonecrosis. Nonetheless, further studies are needed to validate this candidate plasma protein.

Bisphosphonate-Related Osteonecrosis of the Jaw and Oral Microbiome: Clinical Risk Factors, Pathophysiology and Treatment Options

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) represents a serious health condition, impacting the lives of many patients worldwide. The condition challenges clinical care due to its complex etiology and limited therapeutic options. A thorough understanding of the pathophysiological and patient-related factors that promote disease development is essential. Recently, the oral microbiome has been implicated as a potential driver and modulating factor of BRONJ by several studies. Modern genomic sequencing methods have provided a wealth of data on the microbial composition of BRONJ lesions; however, the role of individual species in the process of disease development remains elusive. A comprehensive PubMed search was conducted to identify relevant studies on the microbiome of BRONJ patients using the terms "microbiome", "osteonecrosis of the jaws", and "bisphosphonates". Studies focusing on symptoms, epidemiology, pathophysiology, risk factors, and treatment options were included. The principal risk factors for BRONJ are tooth extraction, surgical procedures, and the administration of high doses of bisphosphonates. Importantly, the oral microbiome plays a significant role in the progression of the disease. Several studies have identified alterations of microbial composition in BRONJ lesions. However, there is no consensus regarding bacterial species that are associated with BRONJ across studies. The bacterial genera typically found include Actinomyces, Fusobacterium, and Streptococcus. It is postulated that these microbes contribute to the pathogenesis of BRONJ by promoting inflammation and disrupting normal bone remodeling processes. Current therapeutic approaches are disease-stage-specific and the necessity for more effective treatment strategies remains. This review examines the potential causes of and therapeutic approaches to BRONJ, highlighting the link between microbial colonization and BRONJ development. Future research should seek to more thoroughly investigate the interactions between bisphosphonates, the oral microbiome, and the immune system in order to develop targeted therapies.

Denosumab-Induced Maxillary Osteonecrosis: A Case Study on Long-Term Complications in Multiple Myeloma Treatment

Background: Targeted therapies like denosumab have revolutionized multiple myeloma (MM) treatment, improved patient outcomes while introducing long-term complications. This study explores a rare instance of delayed maxillary osteonecrosis post-denosumab therapy, delving into its pathophysiology and management. Methods: A 40-year-old male MM patient who developed a painful palatal lesion post denosumab treatment and diagnosed of maxillary osteonecrosis by computed tomography scan and surgical biopsy is presented. Treatment history, symptom progression, and response to the PENTOCLO protocol were analyzed. Results: Post-denosumab discontinuation osteonecrosis highlights its prolonged impact on bone metabolism. PENTOCLO treatment protocol led to significant improvement. Genetic factors influencing osteonecrosis susceptibility have been discussed and considered. Conclusions: This case underscores the need for vigilance regarding long-term complications in MM survivors, preventive strategies, including regular dental evaluations and reducing invasive dental procedures, are crucial. We advocate for an interdisciplinary approach and further research into tailored prevention and management of osteonecrosis in cancer survivors.

Highlights on the Effects of Non-Coding RNAs in the Osteonecrosis of the Jaw

Osteonecrosis of the jaw is the progressive loss and destruction of bone affecting the maxilla or mandible in patients treated with antiresorptive and antiangiogenic agents without receiving prior radiation therapy. The pathogenesis involves the inflammatory pathway of receptor activator of nuclear factor NF-kB ligand and the macrophage colony-stimulating factor, essential for osteoclast precursors survival and proliferation and acting through its receptor c-Fms. Evidence has shown the role of non-coding RNAs in the pathogenesis of osteonecrosis of the jaw and this finding might be useful in diagnosis since these small RNAs could be considered as biomarkers of apoptotic activity in bone. Interestingly, it has been proved that miR-29 and miR-31-5p, acting on specific targets such as CALCR and RhoA, promote programmed-cell death and consequently the necrosis of bone tissue. Specific long non-coding RNAs, instead, have been detected both at reduced levels in patients with multiple myeloma and osteonecrosis, and associated with suppression of osteoblast differentiation, with consequences in the progression of mandible lesions. Among non-coding genic material, circular RNAs have the capability to modify the expression of specific mRNAs responsible for the inhibition of bisphosphonates activity on osteoclastogenesis.