Chronic Periodontal Infection and Not Iatrogenic Interference Is the Trigger of Medication-Related Osteonecrosis of the Jaw: Insights from a Large Animal Study (PerioBRONJ Pig Model)

Next-generation sequencing analysis of bacterial species present in the sequestrum of medication-related osteonecrosis of the jaw patients

OBJECTIVE

Antiresorptives cases of adverse reactions to highly effective drugs used to treat skeletal-related events that occur during treatment of osteoporosis or malignancy have been reported in the jaw. To date, there is no clear pathophysiology for medication-related osteonecrosis of the jaw (MRONJ), but the role of inflammation or infection has been proposed as one of several possible pathogenesis theories. This study was designed to investigate the role of infection in the pathogenesis of MRONJ by analyzing the microbial communities observed in the bone samples from MRONJ patients.

DESIGN

Oral microbial samples were collected from 39 MRONJ patients and 45 healthy patients and subjected to next generation sequencing analysis. Alpha diversity, beta diversity, linear discriminant analysis and effect size, and network analysis were applied to compare the microbiome features.

RESULTS

The 10 predominant microbial strains observed in MRONJ patients were Streptococcus spp. S. constellatus, Tannerella forsythia, Parvimonas micra, Granulicatella adiacens, Bacteroidaceae G-1 bacterium HMT 272, Treponema socranskii, T. maltophilum, Pyramidobacter piscolens, and Fretibacterium fastidiosum. Network analysis revealed a significant correlation between T. forsythia and P. gingivalis. T. socranskii was closely related to T. maltophilum, Fretibacterium fastidiosum, and Peptostreptococcaceae nodatum. G. adiacens was closely related to Streptococcus parasanguinis, S. sanguinis, and Prevotella buccae.

CONCLUSIONS

In conclusion, this study sheds light on the potential role of infection in the pathogenesis of MRONJ. A distinct microbial profile was identified in MRONJ patients, with notable predominance of S. constellatus, T. forsythia, P. micra and G. adiacens among others. Network analysis further revealed significant correlations between certain microbial strains, suggesting possible synergistic interactions in MRONJ pathogenesis. These findings contribute to a deeper understanding of the complex microbial dynamics underlying MRONJ and may inform future therapeutic strategies aimed at targeting specific bacterial species implicated in this condition.

A retrospective case series on bisphosphonate related osteonecrosis of the jaw in 20 cats

Introduction

This retrospective study highlights the salient aspects of a series of feline patients affected with bisphosphonate related osteonecrosis of the jaw. Though more commonly published in human literature, this presentation is rare in cats. The authors hope that this study will assist in making this a more globally known entity with subsequent improved prognosis.

Methods

Data was retrospectively obtained from the medical records between 2015 and 2021 of 20 cats with Medication Related Osteonecrosis of the Jaw. Data included patient information, clinical history, presenting complaint, systemic diseases, details referable to hypercalcemia and treatment thereof, bisphosphonate specifics (dose and duration), clinical presentation of the lesion, diagnostic testing including radiographic and histopathologic descriptions, treatment, and outcome.

Results

Pertinent results include that all 20 cats who developed Medication Related Osteonecrosis of the Jaw had been treated for idiopathic hypercalcemia with the bisphosphonate medication alendronate. Eighty-five percent of the cases had prior dental extractions at the site of MRONJ lesion. Ninety-five percent of the affected cats required a surgical procedure to control the disease. Thirty-five percent of cases required at least one revision surgery after the initial procedure was performed. Diagnosis of MRONJ was made by a correlation of diagnostic findings and patient history. No single diagnostic, or combination was pathognomonic for lesion diagnosis. As well, there were no statistically significant associations between patient variables assessed and the overall patient outcome.

Discussion

The case series reveals that cats with feline idiopathic hypercalcemia treated with alendronate may be at a risk for development of MRONJ, a serious oral condition with significant morbidity. Prior dental extraction sites in patients concurrently treated with bisphosphonate medications were often associated with MRONJ lesions. Therefore, any needed dental surgery should be performed prior to the use of bisphosphonates where possible. The authors have also included a relevant comparative literature review.

Inflammation Can Be a High-Risk Factor for Mucosal Nonunion of MRONJ by Regulating SIRT1 Signaling When Treated with an Oncologic Dose of Zoledronate

Purpose

Zoledronate (ZA) stands as a highly effective antiresorptive agent known to trigger medication-related osteonecrosis of the jaw (MRONJ). Its clinical dosages primarily encompass those used for oncologic and osteoporosis treatments. While inflammation is recognized as a potential disruptor of mucosal healing processes associated with ZA, prior research has overlooked the influence of varying ZA dosages on tissue adaptability. Therefore, a deeper understanding of the specific mechanisms by which inflammation exacerbates ZA-induced MRONJ, particularly when inflammation acts as a risk factor, remains crucial.

Methods

Cell proliferation and migration of human oral keratinocytes (HOK) was analyzed after treatment with different doses of ZA and/or lipopolysaccharide (LPS) to assess their possible effect on mucosal healing of extraction wounds. Mouse periodontitis models were established using LPS, and histological changes in extraction wounds were observed after the administration of oncologic dose ZA. Hematoxylin and eosin (HE) staining and immunofluorescence were used to evaluate mucosal healing.

Results

In vitro, LPS did not exacerbate the effects of osteoporosis therapeutic dose of ZA on the proliferation and migration of HOK cells, while aggravated these with the oncologic dose of ZA treatment by inducing mitochondrial dysfunction and oxidative stress via regulating SIRT1 expression. Furthermore, SIRT1 overexpression can alleviate this process. In vivo, local injection of LPS increased the nonunion of mucous membranes in MRONJ and decreased the expression of SIRT1, PGC-1α, and MnSOD.

Conclusion

Inflammation aggravates oncologic dose of ZA-induced mitochondrial dysfunction and oxidative stress via a SIRT1-dependent pathway, enhancing the risk of impaired mucosal healing in MRONJ. Our study implies that inflammation becomes a critical risk factor for MRONJ development at higher ZA concentrations. Elucidating the mechanisms of inflammation as a risk factor for mucosal non-healing in MRONJ could inform the development of SIRT1-targeted therapies.

Etiopathogenesis of medication-related osteonecrosis of the jaws: a review

This study compiles the main hypotheses involved in the etiopathogenesis of medication-related osteonecrosis of the jaw (MRONJ). A narrative review of the literature was performed. The etiopathogenesis of MRONJ is multifactorial and not fully understood. The main hypothesis considers the disturbance of bone turnover caused by anti-resorptive drugs. Bisphosphonates and denosumab inhibit osteoclast activity through different action mechanisms, accumulating bone microfracture. Other hypotheses also consider oral infection and inflammation, the antiangiogenic effect and soft tissue toxicity of bisphosphonates, and the inhibition of lymphangiogenesis. Knowledge of the current theories for MRONJ is necessary to define future studies and protocols to minimize the incidence of this severe condition.