Nitrogen-containing bisphosphonate therapy: assessment of the alveolar bone structure in rats - a blind randomized controlled trial

Ozone therapy effect in medication-related osteonecrosis of the jaw as prevention or treatment: microtomographic, confocal laser microscopy and histomorphometric analysis

OBJECTIVE

This study aimed to evaluate the efficacy of ozone therapy in the preoperative (prevention) and/or postoperative (treatment) of MRONJ.

MATERIAL AND METHODS

Forty male Wistar rats were caudally treated with zoledronic acid (ZOL) and to ozone therapy before extraction (prevention, POG), after extraction (treatment, TOG), or both (prevention and treatment, TPOG), and treated with saline (SAL). The animals received intramuscular fluorochrome (calcein and alizarin), and 28 days postoperatively, they were euthanized, and the tissues were subjected to microtomographic computed tomography (microCT), LASER confocal, and histomorphometric analyses.

RESULTS

Micro-CT showed a higher bone volume fraction average in all groups than that in the ZOL group (P < 0.001), the ZOL group showed high porosity (P = 0.03), and trabecular separation was greater in the TOG group than in the POG group (P < 0.05). The mineral apposition rate of the POG group was high (20.46 ± 6.31) (P < 0.001), followed by the TOG group (20.32 ± 7.4). The TOG group presented the highest mean newly formed bone area (68.322 ± 25.296) compared with the ZOL group (P < 0.05), followed by the SAL group (66.039 ± 28.379) and ZOL groups (60.856 ± 28.425).

CONCLUSIONS

Ozone therapy modulated alveolar bone repair in animals treated with ZOL, mainly after surgery trauma, leading to bone formation as healing tissue.

CLINICAL RELEVANCE

Osteonecrosis has been a challenge in dentistry, and owing to the lack of a consensus regarding therapy, studies presenting new therapies are important, and ozone has been one of the therapies explored empirically.

Medication-related osteonecrosis of the jaw using periodontitis-induced rat before tooth extraction

OBJECTIVE

This study aimed to investigate the occurrence of medication-related osteonecrosis of the jaw (MRONJ) after tooth extraction due to periodontitis in ovariectomized rats.

METHODS

Twenty-four osteoporosis-induced rats were administered with zoledronic acid (ZA; ZA group) or saline (CONT group). In both groups, tooth extraction was performed after inducing periodontitis, and all animals were sacrificed 8-week after tooth extraction.

RESULTS

Micro-CT of the tibia showed that the bone volume fraction, bone surface density, trabecular number, and bone mineral density were significantly higher in the ZA group than in the CONT group. Histologically, the proliferative zone on the growth plate was thicker in the ZA group than in the CONT group. Micro-CT of the extraction sites revealed that the bone volume fraction was significantly higher in the ZA group than in the CONT group. Radiologically, the ZA group showed partial healing and delayed healing. Histological analysis revealed normal bone healing status with completely healed epithelium in the extraction sites of the CONT group, whereas abnormal empty osteocytes in the necrotic bone and inflammatory infiltration were observed in the ZA group.

CONCLUSION

The incidence of MRONJ increased in the rats administered with ZA.

Beta tricalcium phosphate, either alone or in combination with antimicrobial photodynamic therapy or doxycycline, prevents medication-related osteonecrosis of the jaw

Surgical trauma in those under a prolonged use of bisphosphonates, can lead to mediation-related osteonecrosis of the jaw (MRONJ). This study aimed to evaluate the preventive therapies for MRONJ. Following four cycles of zoledronic acid administration, Wistar rats had their molar extracted, and were organized into nine treatment groups: negative control group (NCG), treated with saline solution and blood-clot in the alveolus; positive control group (PCG), with blood-clot in the alveolus; BG, β-tricalcium phosphate-based biomaterial; DG, 10% doxycycline gel; aG, antimicrobial photodynamic therapy; and DBG, aBG, aDG, and aDBG, using combination therapy. After 28 days, the lowest bone volume (BV/TV) was reported in PCG (42.17% ± 2.65), and the highest in aDBG (69.85% ± 6.25) (p < 0.05). The higher values of daily mineral apposition rate were recorded in aDBG (2.64 ± 0.48) and DBG (2.30 ± 0.37) (p < 0.001). Moreover, aDBG presented with the highest neoformed bone area (82.44% ± 2.69) (p < 0.05). Non-vital bone was reported only in the PCG (37.94 ± 18.70%). Owing to the key role of the biomaterial, the combination approach (aDBG) was the most effective in preventing MRONJ following tooth extraction.

Absence of medication-related jaw osteonecrosis after treatment with strontium ranelate in ovariectomized rats

This study aimed to evaluate the potential of strontium ranelate (SR) in medication-related jaw osteonecrosis (MRONJ) after tooth extraction in ovariectomized rats. Thirty ovariectomized rats were divided into three groups (n = 10): bisphophonate (BP) group (zoledronic acid; 0.4 mg/kg/week), SR group (625 mg/kg/day), and control group (saline solution). The lower first molars were extracted after 60 days of drug therapy. Drug administration was continued for another 30 days after tooth extraction. The mandibles were subjected to clinical, histological, radiographic, and microtomographic evaluations. Only the BP group showed clinical changes, characterized by the presence of 70% (n = 7) and 20% (n = 2) of ulcers and extraoral fistulas. Radiographic evaluation demonstrated bone sequestration only in the BP group (n = 7, 70%). Microtomographic analysis revealed increased bone porosity after ovariectomy, particularly in the the control group (p < 0.05). The BP group showed a higher bone surface density, bone volume, and trabecular number than SR and control groups, but with less trabecular separation (p < 0.05). All the animals in the BP group demonstrated histological osteonecrosis. There was no evidence of osteonecrosis in the control and SR groups, which was characterized by the absence of empty osteocyte gaps and associated with the gradual healing of the extraction area. Also, an increased number of blood vessels and a reduced number of osteoclasts were observed in the SR group (p < 0.05). Therefore, SR treatment increased angiogenesis and osteoclastogenesis in the healing socket and was not associated with MRONJ development after tooth extraction in ovariectomized rats.

The Severity of Interstitial Inflammation in the Renal Parenchyma of Albino Rats Is Subjected to the Dose of Heavy Metals

Aim

This study aimed to determine the relationship between irreversible morphological changes in the renal interstitium and the duration of exposure to heavy metals such as copper in albino rats.

Materials and methods

An experimental research design was used to conduct this study from November 2019 to May 2020. All experiments were performed in the Department of Pathology of the Services Institute of Medical Sciences, University of Health Sciences (UHS) (animal house), Lahore, Pakistan. A total of 30 albino rats equally divided into three groups were included in the study. Group I (control) was given tap water and a typical rodent pellet diet. Groups II and III (experimental) were fed with copper (heavy metal) at a dose of 0.15 and 0.30 mg/kg body weight, respectively, for 18 weeks on alternate days. At the end of the experiment, the kidneys were extracted from the rats, stained with hematoxylin and eosin, and processed for histological observation. Renal histopathological changes were evaluated in terms of edema, inflammation, and fibrosis.

Results

The collected data were analyzed using the Chi-square test, with p < 0.05 considered significant. Renal histopathology in terms of interstitium showed that edema, inflammation, and fibrosis were significantly different in all groups. In Group I, none of the rats had edema, inflammation, and fibrosis, while in Groups II and III, these characteristics were observed; the difference was significant between the experimental and control groups.

Conclusions

Heavy metals, such as copper, can induce renal parenchymal changes in a dose-dependent manner, resulting in edema, fibrosis, and inflammation.

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.

Bone mineralization and vascularization in bisphosphonate-related osteonecrosis of the jaw: an experimental study in the rat

OBJECTIVES

Pathogenesis of bisphosphonate-related osteonecrosis of the jaws (BRONJ) is not fully explained. An antiangiogenic effect of bisphosphonates (BPs) or an altered bone quality have been advocated. The aims of the present study were to analyze alveolar mandibular vascularization and bone quality in rats with BRONJ.

MATERIALS AND METHODS

Thirty-eight Sprague-Dawley rats were randomized into two groups: zoledronic acid (ZA), n = 27, and control (CTRL) n = 11. The ZA group received a weekly IV injection of ZA (100 μg/kg) during 10 weeks. The CTRL group received saline. After 6 weeks, extraction of the right mandibular molars was performed. Rats were sacrificed after 14 weeks. Microtomography characterized bone lesions and vascularization after injection of a radio-opaque material. Raman microspectroscopy evaluated bone mineralization.

RESULTS

Fifty-five percent of ZA rats presented bone exposure and signs of BRONJ. None sign was found at the left hemimandible in the ZA group and in the CTRL group. Vascular density appeared significantly increased in the right hemimandibles of the CTRL group compared to the left hemimandibles. Vascularization was reduced in the ZA group. A significantly increased of the mineral-to-amide ratio was found in the alveolar bone of ZA rats by Raman microspectroscopy.

CONCLUSIONS

In a rat model of BRONJ, microtomography evidenced osteonecrosis in BRONJ. Raman spectroscopy showed an increased mineralization. Vascularization after tooth extraction was impaired by ZA.

CLINICAL RELEVANCE

Prolonged BP administration caused an increase in the mineralization and a quantitative reduction of the vascularization in the alveolar bone; both factors might be involved concomitantly in the BRONJ pathophysiology.

Nitrogen-containing bisphosphonate therapy-Part II: Assessment of alveolar bone tissue inflammatory response in rats-A blind randomized controlled trial

This study aimed to evaluate the alveolar bone tissue inflammatory response in rats undergoing zoledronic acid therapy. The study sample was composed of 28 Wistar rats. Animals from the test group GTa received a weekly intraperitoneal dose of 0.2 mg/kg of zoledronic acid for 3 weeks, while test group GTb received the same dose for 8 weeks. A physiological saline dose, equivalent to that of the medication, was administered to the controls in groups GCa and GCb. A defect was created in the dental crown of the lower first molars using a drill to simulate pulp and periapical injury. Data were evaluated regarding image grey levels by cone-beam computed tomography and histologically by assigning scores for the presence of inflammatory infiltrate, type of infiltrate, vascularization, bone necrosis and dental resorption. Grey levels in the 3-week therapy group (GTa) showed more pronounced changes in comparison with those seen in the GCa group (P < 0.05). Evaluation of the scores demonstrated no association between any of the variables amongst the groups (>0.05). However, bone remodelling decreased in the groups receiving the medication. Bone necrosis was present more frequently in group GTb than in the control group GCb. The results suggest that the drug interfered in the reaction capacity of the alveolar bone tissue as test group GTa showed higher grey levels in comparison to the control group GCa. In addition, there was less bone remodelling activity, with the appearance of bone necrosis zones and intense acute inflammatory infiltrate associated with the 8-week therapy group GTb.

Dental extraction following zoledronate, induces osteonecrosis in rat's jaw

BACKGROUND

Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ) is clinically characterized by the presence of exposed bone in the oral cavity that persists for more than eight weeks. Previous attempts to establish an animal model have not sufficiently considered disease features. Our aim was to establish an inexpensive and replicable animal model that develops BRONJ in a short time.

MATERIAL AND METHODS

Thirty-two male Wistar rats were randomly divided into two groups: control and experimental. In the experimental group, we administered 0.06mg/kg intraperitoneal dose of zoledronic acid (ZA) 7 and 14 days prior to maxillary second molar extraction. At two, four and six weeks after tooth extraction, the animals were euthanized, and we dissected the maxilla following histological procedures. We stained serial slides with hematoxylin and eosin and Masson's trichrome. The samples were harvested for macroscopic, radiologic and histological evaluation of bone changes.

RESULTS

At two weeks postextraction, we observed exposed necrotic bone in dental socket areas in experimental groups. Radiological analysis revealed osteolytic lesions accompanied by extensive destruction and sequestrum formation in the same group. Histological examination confirmed the absence of necrotic bone in control groups in contrast with the experimental groups. The percentage of empty lacunae and the number of osteoclasts and the necrotic bone area were significantly increased (p<0.05) in the experimental groups.

CONCLUSIONS

The animal model using ZA administration to prior dental extraction successfully mimicked human BRONJ lesions. Also, the model was easily replicated, inexpensive and showed different features than other previous BRONJ models.