Systemic administration of quality- and quantity-controlled PBMNCs reduces bisphosphonate-related osteonecrosis of jaw-like lesions in mice

Medication-related osteonecrosis of the jaw: evolving research for multimodality medical management

PURPOSE

Medication-related osteonecrosis of the jaw (MRONJ) is a debilitating side effect of antiresorptive and antiangiogenic agents that can lead to progressive bone destruction in the maxillofacial region. Dental surgery, including tooth extractions, commonly trigger the onset of MRONJ. While guidelines suggest avoiding extraction when possible, complete avoidance is not always feasible, as necrosis can develop from dental and periodontal disease without dental procedures. The goal of this article is to provide an update review of current preventive and therapeutic approaches for MRONJ.

METHODS

A comprehensive electronic search was conducted on PubMed/MEDLINE, Embase, and Scopus databases. All English articles encompassing randomized controlled trials, systematic reviews, observational studies, and case studies were reviewed. The current medical treatments and adjuvant therapies for managing MRONJ patients were critically assessed and summarized.

RESULTS

Pentoxifylline and alpha tocopherol (PENT-E), teriparatide, photobiomodulation (PBM), photodynamic therapy (PDT), and the use of growth factors have shown to enhance healing in MRONJ patients. Implementing these methods alone or in conjunction with surgical treatment has been linked to reduced discomfort and improved wound healing and increased new bone formation.

DISCUSSION

While several adjuvant treatment modalities exhibit promising results in facilitating the healing process, current clinical practice guidelines predominantly recommend antibiotic therapy as a non-surgical approach, primarily addressing secondary infections in necrotic areas. However, this mainly addresses the potential infectious complication of MRONJ. Medical approaches including PENT-E, teriparatide, PBM, and PDT can result in successful management and should be considered prior to taking a surgical approach. Combined medical management for both preventing and managing MRONJ holds potential for achieving optimal clinical outcomes and avoiding surgical intervention, requiring further validation through larger studies and controlled trials.

Medication-related osteonecrosis of the jaw in a paediatric patient taking denosumab: a case report

Medication-related osteonecrosis of the jaw (MRONJ) is a known complication of antiresorptive and anti-angiogenic therapies in adults. Increasingly, these drugs are being prescribed for children with a variety of conditions, such as osteogenesis imperfecta and cancers of the bone. Review of the literature, however, reveals no reported paediatric MRONJ cases to date. We present such a case in a nine-year-old female patient with a vertebral aneurysmal bone cyst, who received dental extractions subsequent to denosumab therapy.

Depletion of macrophages deteriorates bisphosphonate-related osteonecrosis of the jaw-like lesions in mice

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a potentially intractable disease with no definitive pathophysiology and no treatment and prevention strategies. This study aimed to investigate whether time-selective depletion of macrophages worsens BRONJ-like lesions in mice. A murine model of high-prevalence BRONJ-like lesions in combination with zoledronate/chemotherapeutic drug administration and tooth extraction was created according to the methods of our previous studies. Daily intra-oral submucosal administration of clodronate-loaded liposomes, which temporarily depletes systemic macrophages, was performed immediately after tooth extraction. Spleens, femora, tibiae, and maxillae were dissected 2 weeks after extraction to evaluate BRONJ-like lesions and systemic conditions by micro-computed tomography analysis, histomorphometric and immunofluorescent analyses, and serum chemistry with ELISA. Depletion of macrophages significantly decreased the numbers of local and systemic macrophages and osteoclasts on the bone surface, which markedly worsened osseous healing, with increased necrotic bone and empty lacunae in the existing alveolar bone and newly formed bone in the extraction sockets, and soft tissue healing, with decreased collagen production and increased infiltration of polymorphonuclear cells. Interestingly, the depletion of macrophages significantly shifted macrophage polarization to M1 macrophages through an increase in F4/80+CD38+ M1 macrophages and a decrease in F4/80+CD163+ M2 macrophages, with decreases in the total number of F4/80+ macrophages. These data demonstrated that severe inhibition of osteoclasts in bone tissue and polarization shifting of macrophages in soft tissue are essential factors associated with BRONJ.

Therapeutic application of regeneration-associated cells: a novel source of regenerative medicine

Chronic diseases with comorbidities or associated risk factors may impair the function of regenerative cells and the regenerative microenvironment. Following this consideration, the vasculogenic conditioning culture (VCC) method was developed to boost the regenerative microenvironment to achieve regeneration-associated cells (RACs), which contain vasculogenic endothelial progenitor cells (EPCs) and anti-inflammatory/anti-immunity cells. Preclinical and clinical studies demonstrate that RAC transplantation is a safe and convenient cell population for promoting ischemic tissue recovery based on its strong vasculogenicity and functionality. The outputs of the scientific reports reviewed in the present study shed light on the fact that RAC transplantation is efficient in curing various diseases. Here, we compactly highlight the universal features of RACs and the latest progress in their translation toward clinics.

Zoledronate/Anti-VEGF Neutralizing Antibody Combination Administration Increases Osteal Macrophages in a Murine Model of MRONJ Stage 0-like Lesions

The pathophysiology, pathogenesis, histopathology, and immunopathology of medication-related osteonecrosis of the jaw (MRONJ) Stage 0 remain unclear, although 50% of MRONJ Stage 0 cases could progress to higher stages. The aim of this study was to investigate the effects of zoledronate (Zol) and anti-vascular endothelial cell growth factor A (VEGFA) neutralizing antibody (Vab) administration on polarization shifting of macrophage subsets in tooth extraction sockets by creating a murine model of MRONJ Stage 0-like lesions. Eight-week-old, female C57BL/6J mice were randomly divided into 4 groups: Zol, Vab, Zol/Vab combination, and vehicle control (VC). Subcutaneous Zol and intraperitoneal Vab administration were performed for 5 weeks with extraction of both maxillary first molars 3 weeks after drug administration. Euthanasia was conducted 2 weeks after tooth extraction. Maxillae, tibiae, femora, tongues, and sera were collected. Structural, histological, immunohistochemical, and biochemical analyses were comprehensively performed. Tooth extraction sites appeared to be completely healed in all groups. However, osseous healing and soft tissue healing of tooth extraction sites were quite different. The Zol/Vab combination significantly induced abnormal epithelial healing, and delayed connective tissue healing due to decreased rete ridge length and thickness of the stratum granulosum and due to decreased collagen production, respectively. Moreover, Zol/Vab significantly increased necrotic bone area with increased numbers of empty lacunae compared with Vab and VC. Most interestingly, Zol/Vab significantly increased the number of CD169⁺ osteal macrophages (osteomacs) in the bone marrow and decreased F4/80+ macrophages, with a slightly increased ratio of F4/80⁺CD38⁺ M1 macrophages compared to VC. These findings are the first to provide new evidence of the involvement of osteal macrophages in the immunopathology of MRONJ Stage 0-like lesions.

Effective-mononuclear cell (E-MNC) therapy alleviates salivary gland damage by suppressing lymphocyte infiltration in Sjögren-like disease

Introduction: Sjögren syndrome (SS) is an autoimmune disease characterized by salivary gland (SG) destruction leading to loss of secretory function. A hallmark of the disease is the presence of focal lymphocyte infiltration in SGs, which is predominantly composed of T cells. Currently, there are no effective therapies for SS. Recently, we demonstrated that a newly developed therapy using effective-mononuclear cells (E-MNCs) improved the function of radiation-injured SGs due to anti-inflammatory and regenerative effects. In this study, we investigated whether E-MNCs could ameliorate disease development in non-obese diabetic (NOD) mice as a model for primary SS. Methods: E-MNCs were obtained from peripheral blood mononuclear cells (PBMNCs) cultured for 7 days in serum-free medium supplemented with five specific recombinant proteins (5G culture). The anti-inflammatory characteristics of E-MNCs were then analyzed using a co-culture system with CD3/CD28-stimulated PBMNCs. To evaluate the therapeutic efficacy of E-MNCs against SS onset, E-MNCs were transplanted into SGs of NOD mice. Subsequently, saliva secretion, histological, and gene expression analyses of harvested SG were performed to investigate if E-MNCs therapy delays disease development. Results: First, we characterized that both human and mouse E-MNCs exhibited induction of CD11b/CD206-positive cells (M2 macrophages) and that human E-MNCs could inhibit inflammatory gene expressions in CD3/CD28- stimulated PBMNCs. Further analyses revealed that Msr1-and galectin3-positive macrophages (immunomodulatory M2c phenotype) were specifically induced in E-MNCs of both NOD and MHC class I-matched mice. Transplanted E-MNCs induced M2 macrophages and reduced the expression of T cell-derived chemokine-related and inflammatory genes in SG tissue of NOD mice at SS-onset. Then, E-MNCs suppressed the infiltration of CD4-positive T cells and facilitated the maintenance of saliva secretion for up to 12 weeks after E-MNC administration. Discussion: Thus, the immunomodulatory actions of E-MNCs could be part of a therapeutic strategy targeting the early stage of primary SS.

Establishment and assessment of rodent models of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is primarily associated with administering antiresorptive or antiangiogenic drugs. Despite significant research on MRONJ, its pathogenesis and effective treatments are still not fully understood. Animal models can be used to simulate the pathophysiological features of MRONJ, serving as standardized in vivo experimental platforms to explore the pathogenesis and therapies of MRONJ. Rodent models exhibit excellent effectiveness and high reproducibility in mimicking human MRONJ, but classical methods cannot achieve a complete replica of the pathogenesis of MRONJ. Modified rodent models have been reported with improvements for better mimicking of MRONJ onset in clinic. This review summarizes representative classical and modified rodent models of MRONJ created through various combinations of systemic drug induction and local stimulation and discusses their effectiveness and efficiency. Currently, there is a lack of a unified assessment system for MRONJ models, which hinders a standard definition of MRONJ-like lesions in rodents. Therefore, this review comprehensively summarizes assessment systems based on published peer-review articles, including new approaches in gross observation, histological assessments, radiographic assessments, and serological assessments. This review can serve as a reference for model establishment and evaluation in future preclinical studies on MRONJ.

Porphyromonas gingivalis Induces Bisphosphonate-Related Osteonecrosis of the Femur in Mice

One of the most prominent characteristics of bisphosphonate-related osteonecrosis of the jaw(BRONJ) is its site-specificity. Osteonecrosis tends to occur specifically in maxillofacial bones, in spite of a systemic administration of the medicine. Previous studies suggested rich blood supply and fast bone turnover might be reasons for BRONJ. Yet, a sound scientific basis explaining its occurrence is still lacking. The present study aimed to explore the role of Porphyromonas gingivalis (P. gingivalis), an important oral pathogen, on the site-specificity of bisphosphonate-induced osteonecrosis and to elucidate its underlying mechanism. Mice were intraperitoneally injected with zoledronic acid (ZA) or saline for 3 weeks. In the third week, the right mandibular first molars were extracted and circular bone defects with a diameter of 1 mm were created in right femurs. After the operation, drug administration was continued, and P. gingivalis suspension was applied to the oral cavities and femur defects. The mice were killed after four or eight weeks postoperatively. The right mandibles and femurs were harvested for micro-CT and histological analyses. A poor healing of bone defects of both jaws and femurs was noted in mice injected with both ZA and P. gingivalis. Micro-CT analysis showed a decreased bone volume, and histological staining showed an increased number of empty osteocyte lacunae, a decreased collagen regeneration, an increased inflammatory infiltration and a decreased number of osteoclasts. In addition, the left femurs were collected for isolation of osteoclast precursors (OCPs). The osteoclastogenesis potential of OCPs was analyzed in vitro. OCPs extracted from mice of ZA-treated groups were shown to have a lower osteoclast differentiation potential and the expression level of related genes and proteins was declined. In conclusion, we established a mouse model of bisphosphonate-related osteonecrosis of both the jaw and femur. P. gingivalis could inhibit the healing of femur defects under the administration of ZA. These findings suggest that P. gingivalis in the oral cavity might be one of the steering compounds for BRONJ to occur.

Novel Cell Therapy Using Mesenchymal Stromal Cell Sheets for Medication-Related Osteonecrosis of the Jaw

Despite medication-related osteonecrosis of the jaw (MRONJ) being first reported in 2003, the optimal treatment and prevention modalities for MRONJ are not clear. As a result, dentistry, oral surgery, and departments involved in the treatment of cancer and bone diseases are struggling with the management of MRONJ. Several cases of MRONJ cannot be managed by conventional treatment strategies recommended in various position papers. Therefore, studies have been conducted to investigate the efficacy of novel therapies for MRONJ. However, the optimal treatment is unknown. Several cell therapies including autologous cell transplantation have been reported for MRONJ. Although the efficacy of cell therapy for MRONJ has been demonstrated, large, statistically accurate clinical trials are lacking. We have been investigating the efficacy of MRONJ treatment using mesenchymal stromal cell (MSC) sheets since 2013 and confirmed its efficacy through various experiments, wherein MSC sheets were transplanted in model rats and beagle dogs with MRONJ-like lesions. Based on these results, we are planning to conduct a clinical trial of MRONJ therapy using periodontal ligament-derived MSC sheets.

American Association of Oral and Maxillofacial Surgeons' Position Paper on Medication-Related Osteonecrosis of the Jaws-2022 Update

Strategies for management of patients with, or at risk for, medication-related osteonecrosis of the jaws (MRONJ) - formerly referred to as bisphosphonate-related osteonecrosis of the jaws (BRONJ)-were set forth in the American Association of Oral and Maxillofacial Surgeons (AAOMS) position papers in 2007, 2009 and 2014. The position papers were developed by a committee appointed by the AAOMS Board of Trustees and comprising clinicians with extensive experience in caring for these patients, as well as clinical and basic science researchers. The knowledge base and experience in addressing MRONJ continues to evolve and expand, necessitating modifications and refinements to the previous position papers. Three members of the AAOMS Committee on Oral, Head, and Neck Oncologic and Reconstructive Surgery (COHNORS) and three authors of the 2014 position paper were appointed to serve as a working group to analyze the current literature and revise the guidance as indicated to reflect current knowledge in this field. This update contains revisions to diagnosis and management strategies and highlights the current research status. AAOMS maintains that it is vitally important for this information to be disseminated to other relevant healthcare professionals and organizations.

Tetrahedral framework nucleic acid carrying angiogenic peptide prevents bisphosphonate-related osteonecrosis of the jaw by promoting angiogenesis

The significant clinical feature of bisphosphonate-related osteonecrosis of the jaw (BRONJ) is the exposure of the necrotic jaw. Other clinical manifestations include jaw pain, swelling, abscess, and skin fistula, which seriously affect the patients’ life, and there is no radical cure. Thus, new methods need to be found to prevent the occurrence of BRONJ. Here, a novel nanoparticle, tFNA-KLT, was successfully synthesized by us, in which the nanoparticle tetrahedral framework nucleic acid (tFNA) was used for carrying angiogenic peptide, KLT, and then further enhanced angiogenesis. TFNA-KLT possessed the same characteristics as tFNA, such as simple synthesis, stable structure, and good biocompatibility. Meanwhile, tFNA enhanced the stability of KLT and carried more KLT to interact with endothelial cells. First, it was confirmed that tFNA-KLT had the superior angiogenic ability to tFNA and KLT both in vitro and in vivo. Then we apply tFNA-KLT to the prevention of BRONJ. The results showed that tFNA-KLT can effectively prevent the occurrence of BRONJ by accelerating angiogenesis. In summary, the prepared novel nanoparticle, tFNA-KLT, was firstly synthesized by us. It was also firstly confirmed by us that tFNA-KLT significantly enhanced angiogenesis and can effectively prevent the occurrence of BRONJ by accelerating angiogenesis, thus providing a new avenue for the prevention of BRONJ and a new choice for therapeutic angiogenesis.

Preclinical models of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). pARs, including nitrogen-containing bisphosphonates (N-BPs; e.g., zoledronic acid, alendronate) and anti-RANKL antibodies (e.g., denosumab), are used to manage bone metastases in patients with cancer or to prevent fragility fractures in patients with osteoporosis. Though significant advances have been made in understanding MRONJ, its pathophysiology is still not fully elucidated. Multiple species have been used in preclinical MRONJ research, including the rat, mouse, rice rat, rabbit, dog, sheep, and pig. Animal research has contributed immensely to advancing the MRONJ field, particularly, but not limited to, in developing models and investigating risk factors that were first observed in humans. MRONJ models have been developed using clinically relevant doses of systemic risk factors, like N-BPs, anti-RANKL antibodies, or AgIs. Specific local oral risk factors first noted in humans, including tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection, etc.), were then added. Research in rodents, particularly the rat, and, to some extent, the mouse, across multiple laboratories, has contributed to establishing multiple relevant and complementary preclinical models. Models in larger species produced accurate clinical and histopathologic outcomes suggesting a potential role for confirming specific crucial findings from rodent research. We view the current state of animal models for MRONJ as good. The rodent models are now reliable enough to produce large numbers of MRONJ cases that could be applied in experiments testing treatment modalities. The course of MRONJ, including stage 0 MRONJ, is characterized well enough that basic studies of the molecular or enzyme-level findings in different MRONJ stages are possible. This review provides a current overview of the existing models of MRONJ, their more significant features and findings, and important instances of their application in preclinical research.

Small Extracellular Vesicles Derived from Adipose Tissue Prevent Bisphosphonate-Related Osteonecrosis of the Jaw by Promoting Angiogenesis

Purpose

There is no definitive treatment for bisphosphonate-related osteonecrosis of the jaw (BRONJ). Small extracellular vesicles derived from adipose tissue (sEV-AT) have been proved efficient at promoting tissue regeneration. The aim of this study was to evaluate the effects of sEV-AT administration on BRONJ-like lesions in rats.

Methods

Zoledronate (Zol) and dexamethasone (Dex) were subcutaneously administered to create a BRONJ rat model. Rats were randomly divided into three groups: 1) Control; 2) Zol+Dex; 3) sEV-AT. The maxillary left first molars were extracted two weeks after the first administration. In the sEV-AT group, sEV-AT were given intravenously every three days right after tooth extraction. We preformed occlusal view images, microcomputed tomography (µCT) and histological analysis to measure the regeneration of osseous and soft tissue in extraction sockets. Human umbilical vein endothelial cells (HUVECs) were isolated and cultured with endothelial cell medium (ECM). HUVECs were then divided into three groups: 1) Control: ECM; 2) Zol: ECM+Zol; 3) sEV-AT: ECM+Zol+sEV-AT. We evaluated the proliferation, tube formation and migration of HUVECs in each group.

Results

Rats treated with Zol+Dex showed BRONJ-like lesions including open wounds, necrotic bones, empty osteocyte lacunae and reduced osteoclasts. sEV-AT administration reduced BRONJ-like lesions by promoting soft tissue healing. µCT results showed that bone volume in extraction sockets in the sEV-AT group was larger than the Zol+Dex group. Histological analysis showed less necrotic bones and empty osteocyte lacunae in the sEV-AT group compared to the Zol+Dex group. Histological analysis also showed more osteoclasts, collagen fibers and blood vessels in the sEV-AT group compared to the Zol+Dex group. Furthermore, sEV-AT enhanced the proliferation, migration and tube formation of HUVECs which were inhibited by Zol.

Conclusion

Our findings indicate that sEV-AT prevent BRONJ in rats. Angiogenesis promotion contributes to the prevention of BRONJ.

M2-like macrophage infiltration and transforming growth factor-β secretion during socket healing process in mice

OBJECTIVE

Macrophages are involved in tissue inflammation and repair through cytokine secretion. However, the contribution of macrophages to healing and osteogenesis after tooth extraction remains unclear. Therefore, we investigated the distribution of osteoblastic cells and macrophages in the early healing process after tooth extraction.

METHODS

The maxillary first molars of 6-week-old male mice were extracted. The maxilla was collected 1, 3, and 7 days after extraction. The states of socket healing, localization of osteoblastic markers, and macrophage infiltration were sequentially observed by micro-CT imaging and immunohistochemistry.

RESULTS

On day 3 after tooth extraction, α-smooth muscle actin (SMA)-positive cells, osteoprogenitor cells at fracture healing, were observed in the socket. Several α-SMA-positive cells also expressed Runx2, the early osteoblast differentiation marker. The infiltration of F4/80-positive, mature macrophages and CD206-positive, M2-like macrophages was noted in the socket. However, CD169-positive macrophages (Osteomac), which are involved in fracture healing, were not detected in the socket. F4/80-positive and CD206-positive macrophages also showed the localization of transforming growth factor-β (TGF-β), which promotes osteoprogenitor cell proliferation and early differentiation. Phosphorylated Smad3, a downstream mediator of the signal activity of TGF-β, was detected in α-SMA-positive cells. On day 7, the extracted socket contained a large amount of new bone. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts were detected on bone surfaces.

CONCLUSION

Our data indicate that M2-like macrophages regulate the proliferation and differentiation of α-SMA-positive cells by secreting TGF-β at the early stage of socket healing, and also suggest the importance of macrophages in healing and bone formation after tooth extraction.

Effects of metformin on the prevention of bisphosphonate-related osteonecrosis of the jaw-like lesions in rats

PURPOSE

In this study, we aimed to investigate the effect of glucose metabolism on bone healing after tooth extraction in an osteoporosis rat model administered zoledronic acid (ZA) and dexamethasone (DX).

METHODS

In total, 24 male Wistar rats (4 weeks old) were randomly assigned to four groups: Control (subcutaneous physiological saline), ZD (subcutaneous ZA and DX twice a week), Ins+ZD (subcutaneous insulin followed by ZD treatment), and Met+ZD (oral metformin followed by ZD treatment). Blood was collected every two weeks . Two weeks after treatment initiation, the first molar tooth on the right maxilla was extracted from all rats. Four weeks later, the rats were sacrificed, and bone healing was assessed. Maxillae samples were fixed and scanned using micro-computed tomography for quantifying areas of bone defects. Hematoxylin-eosin and tartrate-resistant acid phosphatase (TRAP) staining were performed to evaluate bone apoptosis and osteoclast number.

RESULTS

In all experimental groups, body weight was statistically lower than that in the Control group, with no changes observed in uncarboxylated osteocalcin concentrations. The radiological analysis revealed that insulin or metformin administration improved healing in the tooth extraction socket (p < 0.01). Histological examination revealed that the osteonecrosis area was reduced in the Ins+ZD and Met+ZD groups (p < 0.01). TRAP staining presented increased osteoclast numbers in the ZD group when compared with that observed in the Control.

CONCLUSIONS

Tooth extraction with long-term ZA and DX administration inhibited bone remodeling and induced bisphosphonate-related osteonecrosis of the jaw-like lesions. Metformin exerted protective effects ag ainst osteonecrosis of the jaw.

Intermittent administration of parathyroid hormone improves bone quality and quantity around implants in rat tibiae

OBJECTIVES

Intermittent injection of parathyroid hormone (PTH) is used to treat osteoporosis. The concept of bone quality was updated 20 years ago; however, these updates have not been adopted in implant dentistry. This study aimed to investigate the effects of intermittent administration of PTH on bone quality around implants in rat tibiae.

METHODS

Grade IV-titanium-threaded implants that were 3.5 mm long and 2.0 mm wide were placed in a randomly selected side of the proximal tibiae of 12-week-old female Wistar rats. Three weeks after implant placement, the rats were randomly divided into PTH-administration and saline-injection groups (PTH and VC, respectively; n = 7 per group). Micro-computed tomographical, histomorphometric, and immunohistochemical analyses were performed to evaluate bone quality and quantity surrounding the implants.

RESULTS

PTH significantly increased bone volume and bone mineral density in bones not associated with the implants as compared to these values in the VC group. PTH significantly increased bone area and the amount of collagen within the total inside areas of all implant threads compared to that observed in VC. Moreover, PTH significantly increased the number of osteoblasts, osteocytes, and osteoclasts in the total inside and/or outside areas of all implant threads and altered the ratio of type I and III collagen to total collagen fibers.

CONCLUSIONS

Within the limitations of this study, intermittent administration of PTH improved both bone quantity and bone quality based on the types and numbers of bone cells and the types of collagen fibers surrounding implants placed into rat tibiae.