Effects of green tea and bisphosphonate association on dental socket repair of rats

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.

Is the Bacterial Cellulose Membrane Feasible for Osteopromotive Property?

Guided bone regeneration was studied to establish protocols and develop new biomaterials that revealed satisfactory results. The present study aimed to comparatively evaluate the efficiency of the bacterial cellulose membrane (Nanoskin^®) and collagen membrane Bio-Gide^® in the bone repair of 8-mm critical size defects in rat calvaria. Seventy-two adult male rats were divided into three experimental groups (n = 24): the CG—membrane-free control group (only blood clot, negative control), BG—porcine collagen membrane group (Bio-Guide^®, positive control), and BC—bacterial cellulose membrane group (experimental group). The comparison periods were 7, 15, 30, and 60 days postoperatively. Histological, histometric, and immunohistochemical analyses were performed. The quantitative data were subjected to 2-way ANOVA and Tukey’s post-test, and p < 0.05 was considered significant. At 30 and 60 days postoperatively, the BG group showed more healing of the surgical wound than the other groups, with a high amount of newly formed bone (p < 0.001), while the BC group showed mature connective tissue filling the defect. The inflammatory cell count at postoperative days 7 and 15 was higher in the BC group than in the BG group (Tukey’s test, p = 0.006). At postoperative days 30 and 60, the area of new bone formed was greater in the BG group than in the other groups (p < 0.001). Immunohistochemical analysis showed moderate and intense immunolabeling of osteocalcin and osteopontin at postoperative day 60 in the BG and BC groups. Thus, despite the promising application of the BC membrane in soft-tissue repair, it did not induce bone repair in rat calvaria.

Nephroprotective and antioxidant effect of green tea (Camellia sinensis) against nicotine-induced nephrotoxicity in rats and characterization of its bioactive compounds by HPLC-DAD

Nicotine is a potential inducer of oxidative stress, through which it can damage numerous biological molecules. Natural antioxidants that prevent or slow the progression and severity of nicotine toxicity may have a significant health impact. The purpose of this study, conducted on Wistar rats, was to evaluate the beneficial effects of green tea (Camellia sinensis) extract on nicotine treatment-induced damage on kidney. Our results showed that nicotine significantly (p < 0.01) increased serum and kidney malondialdehyde, the serum contents of urea, creatinine, and uric acid. In addition, nicotine intoxication significantly (p < 0.01) decreased the levels of vitamins E and C in serum and kidney tissue as well as the activities of superoxide dismutase, catalase, and glutathione peroxidase. Interestingly, animals that were pretreated with green tea, prior to nicotine administration, showed a significant nephroprotection, revealed by a significant reduction-induced oxidative damage for all tested markers. The nephroprotective activity of green tea is mediated, at least in part, by the antioxidant effect of its constituents.

Collagen sponge and rhBMP-2 improve socket healing in rats treated with zoledronic acid

The aim of the present study was to evaluate the possible use of a commercial absorbed collagen sponge and bone morphogenetic protein (BMP) for the prevention of bisphosphonate-related osteonecrosis of the jaw (BRONJ) in rats. Twenty rats received intraperitoneal injections of 0.1-mg/kg of zoledronic acid three times a week for eight weeks before the extraction of both maxillary first molars after eight weeks. A collagen sponge (experimental group 1) and a collagen sponge with recombinant human BMP-2 (experimental group 2) were applied to the right extraction sockets of ten rats each. The 20 left extraction sockets (control groups 1 and 2) were left unprotected. After eight weeks, all rats were euthanized. Macroscopic analysis, micro-computed tomography (CT) analysis, and histological analysis were performed. There was a significant difference in the bone density between the control and experimental groups on micro-CT analysis. Impaired healing of the extraction sockets, indicating BRONJ, was observed in 80% of control group 1, 90% of control group 2, 30% of experimental group 1, and 20% of experimental group 2. The collagen sponge with/without BMP used for protecting the extraction socket had the potential for a positive effect in reducing the incidence of bisphosphonate-related osteonecrosis of the jaw in rats.