Effects of risedronate on cortical and trabecular bone of the mandible in glucocorticoid-treated growing rats

Influence of risedronate on orthodontic tooth movement in rodents: a systematic review and case report

INTRODUCTION

Bisphosphonates have an inhibitory impact on osteoclastic activity, reducing bone resorption. However, the influence of risedronate on tooth movement is not well-defined.

OBJECTIVE

This systematic review assessed the effect of risedronate intake on orthodontic tooth movement. A case report was also provided.

METHODS

Two independent reviewers searched six databases (PubMed, Web of Science, Ovid, Lilacs, Scopus, and Open Grey). The searches were carried out in April/2020, and an update was set in place in June/2023. Therefore, the searches considered a timeline from the databases' inception date until June/2023, with no publication date and/or language restrictions. The clinical question focused on evaluating the orthodontic tooth movement and relapse movement (Outcome) in animals (Population) exposed to risedronate (Exposure), compared to control groups (Comparison). The Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines were applied, and the protocol was registered in PROSPERO (CRD42020168581). The risk of bias was determined using the Systematic Review Centre for Laboratory Animal Experimentation protocol (SYRCLE).

RESULTS

Two studies in rats and one in guinea pigs were included in the systematic review. The studies reported a decrease in orthodontic tooth movement, a reduction in the relapse movement, and a reduced number of positive tartrate-resistant acid phosphatase (TRAP) cells, with a significantly reduced number of bone gaps after the administration of risedronate in rats. A case report illustrated the effects of risedronate administration in one patient.

CONCLUSION

Based on the systematic review, risedronate seems to impair orthodontic tooth movement and relapse due to a decrease in bone resorption cells.

Biomechanical and histomorphological analysis of the mandible in rats with chronic kidney disease

The present study aimed to investigate the biomechanical and histomorphological features of mandibles in an adenine-induced chronic kidney disease-mineral and bone disorder (CKD-MBD) rat model of CKD. A total of 14 Sprague-Dawley rats were randomized into the following two groups: control group and CKD group. At the end of the sixth week, all rats were euthanized, and serum was collected for biochemical marker tests. Macroscopic bone growth and biomechanical parameters were measured in the right hemimandible, while the left hemimandible was used for bone histomorphometric analysis. Compared to the control group, the CKD group showed a significant increase in serum creatinine, blood urea nitrogen, and serum parathyroid hormone at the end of the sixth week. The biomechanical structural properties significantly decreased in the CKD group compared to the control group. Bone histomorphometric analysis indicated that the trabecular bone volume of rats in the CKD group was significantly lower than that of the control group. In the CKD groups, the bone formation parameters of the trabecular bone were significantly increased, while the bone mineralization apposition rates of both the trabecular bone and periosteal cortical bone were significantly increased. The rat CKD model showed deteriorated structural mechanics, low trabecular bone volume, high trabecular bone formation, increased trabecular bone mineralization apposition rate, and increased cortical bone mineralization apposition rate, which met the characteristics of osteitis fibrosa, indicating that this model is a useful tool for the study of mandible diseases in CKD patients.

Glucocorticoid-induced dose-related and site-specific bone remodelling, microstructure, and mechanical changes in cancellous and cortical bones

The study investigated the effects of long-term glucocorticoid (GC) administration on bone remodelling, microstructure, and biomechanical strength in cortical and cancellous (trabecular) bones. Thirty-one female Sprague-Dawley rats were randomly divided into three dexamethasone (Dex) dosage groups, 1.0, 2.5, and 5.0 mg/kg twice a week for 8 weeks, and one control group treated with saline. At the end of the experiment, the tibia of one side and the fourth lumbar vertebrae were processed into sections for a histomorphometric analysis, while the femur of the same side and the fifth vertebrae were isolated for a biomechanical test. A dose-dependent decline in bone formation was observed in both trabecular and cortical (periosteal and endosteal) bones. In contrast, bone resorption was inhibited only in cancellous bone in the two higher dose groups and not dose-related. The ratio of Node/Termini increased, while marrow star volume (MSV) decreased in all Dex groups in metaphyseal trabecular bones, both of which were dose-dependent. Subendosteal cortex porosity increased in parallel with non-uniform trabecular distribution, but cortical thickness remained unchanged. Interestingly, there were no significant changes in microstructure or mechanical strength in lumbar trabecular bone. The cortical elastic load was dose-independently reduced in all three Dex groups when compared with the control group. In summary, bone remodelling was dose-dependently inhibited in cancellous bones but enhanced in intracortical bones. The non-uniform distribution of trabecular bone and increased porosity in the inner edge of cortical bone were both in parallel with GC dosage, and the porosity increase was more likely to occur, leading to reduced cortical mechanical strength.

Star-shaped poly(oligoethylene glycol) copolymer-based gels: Thermo-responsive behaviour and bioapplicability for risedronate intranasal delivery

The aim of this work was to obtain an intranasal delivery system with improved mechanical and mucoadhesive properties that could provide prolonged retention time for the delivery of risedronate (RS). For this, novel in situ forming gels comprising thermo-responsive star-shaped polymers, utilizing either polyethylene glycol methyl ether (PEGMA-ME 188, Mn 188) or polyethylene glycol ethyl ether (PEGMA-EE 246, Mn 246), with polyethylene glycol methyl ether (PEGMA-ME 475, Mn 475), were synthesized and characterized. RS was trapped in the selected gel-forming solutions at a concentration of 0.2% w/v. The pH, rheological properties, in vitro drug release, ex vivo permeation as well as mucoadhesion were also examined. MTT assays were conducted to verify nasal tolerability of the developed formulations. Initial in vivo studies were carried out to evaluate anti-osteoporotic activity in a glucocorticoid induced osteoporosis model in rats. The results showed successful development of thermo-sensitive formulations with favorable mechanical properties at 37 °C, which formed non-irritant, mucoadhesive porous networks, facilitating nasal RS delivery. Moreover, sustained release of RS, augmented permeability and marked anti-osteoporotic efficacy as compared to intranasal (IN) and intravenous (IV) RS solutions were realized. The combined results show that the in situ gels should have promising application as nasal drug delivery systems.

Effects of short-term glucocorticoid administration on bone mineral density, biomechanics and microstructure in rats’ femur

The effects of short-term use of oral glucocorticoid (GC) on the skeleton are not well defined. To address this gap, the influences of 7 days, 21 days of GC administration on femurs of intact rats were investigated. Forty 4-month-old female Sprague–Dawley rats were randomly divided into control group (Cont) and prednisone-treated group (Pre) and administered either distilled water or prednisone acetate at doses of 3.5 mg/kg/day for 0, 7 and 21 days, respectively. All the femurs were harvested for dual-energy X-ray absorptiometry scan, biomechanical testing and micro computed tomography scan. The whole body weight, femur bone mineral density (BMD), all three-point bending test parameters, microstructural parameters increased or improved significantly in Cont at day 21 when compared to day 0. The whole body weight, distal femur BMD, Young’s modulus, bending stiffness, density of tissue volume and trabecular thickness (Tb.Th) decreased, while structure model index and trabecular separation (Tb.Sp) increased significantly in Pre at day 21 when compared to age-matched control but had no significant differences between day 7 and day 21. Our data demonstrate that 7-day use of prednisone does not influence on rats’ femur, and 21-day use of prednisone slows in rate of whole body weight gain, decreases femur metaphysis BMD and bone stiffness which mainly due to the deteriorated bone microstructure.

Effect of glucocorticoid withdrawal on glucocorticoid inducing bone impairment

Glucocorticoid (GC) withdrawal after a short-term use was common in clinical practice like immediate post-transplant period. However, previous studies without setting age-control group failed to determine whether the BMD recovery was sufficient and whether it is necessary to accept anti-osteoporosis therapy after GC withdrawal. The aim of this study was to investigate the effect of GC withdrawal on bone impairment in glucocorticoid-induced osteoporosis (GIOP) rats. Twenty-four female Sprague-Dawley rats (3 months' old) were randomly divided into two treatment groups: an untreated age-control group (Con, n = 12); another group receiving a dexamethasone injection (DEXA, n = 12). Animals in the Con group were euthanized at 3rd month (M3) and 6th month (M6), respectively. Six rats in the DEXA group were euthanized at 3rd month (M3), whereas GC intervention was withdrew in the remaining animals of DEXA group, which were euthanized at the end of 6th month (M6). Bone mass, bone microarchitecture, biomechanical properties of vertebrae, morphology, serum levels of PINP and β-CTX were evaluated. Compared with the Con(M3) group, the Con(M6) group showed significantly better bone quantity, morphology and quality. Compared with the Con(M3) group, the DEXA (M3) group showed significantly lower BMC, BMD, BS/TV, BV/TV, Tb.N, Tb.Th, vBMD, bone strength, compressive displacement, energy absorption capacity, PINP levels, β-CTX levels, and damaged trabecular morphology. And the same change trend was observed in the comparison between the Con(M6) group and DEXA (M6) group. Compared with the DEXA (M3) group, the DEXA (M6) group showed significantly higher BMC, BMD and AREA, but no significant difference in BS/TV, BV/TV, SMI, Tb.N, Tb.Th, Tb.Sp, vBMD, bone strength, bone stiffness, compressive displacement, energy absorption capacity, PINP levels, β-CTX levels, and improvement in trabecular morphology was observed. These results indicate that the reverse effect of GC withdrawal for 3 months on bone impairment in GIOP rats was insufficient, which implied that related anti-osteoporosis treatment might be still necessitated after GC withdrawal in clinical setting.

Effect of Pulsed Electromagnetic Field on Bone Formation and Lipid Metabolism of Glucocorticoid-Induced Osteoporosis Rats through Canonical Wnt Signaling Pathway

Pulsed electromagnetic field (PEMF) has been suggested as a promising method alternative to drug-based therapies for treating osteoporosis (OP), but the role of PEMF in GIOP animal models still remains unknown. This study was performed to investigate the effect of PEMF on bone formation and lipid metabolism and further explored the several important components and targets of canonical Wnt signaling pathway in GIOP rats. After 12 weeks of intervention, bone mineral density (BMD) level of the whole body increased significantly, serum lipid levels decreased significantly, and trabeculae were thicker in GIOP rats of PEMF group. PEMF stimulation upregulated the mRNA and protein expression of Wnt10b, LRP5, β-catenin, OPG, and Runx2 and downregulated Axin2, PPAR-γ, C/EBPα, FABP4, and Dkk-1. The results of this study suggested that PEMF stimulation can prevent bone loss and improve lipid metabolism disorders in GIOP rats. Canonical Wnt signaling pathway plays an important role in bone formation and lipid metabolism during PEMF stimulation.

Histomorphometry of the tibia and mandible of healthy female Wistar rats at different stages of growth

Female Wistar rats are frequently used in experimental models to study hormone and bone pathologies and treatments. Most experimental studies involving histomorphometric evaluation assessed long bones, and few reports also studied mandibular bone. The aim of this work was to clarify and distinguish the age-related histomorphometric changes that occur in the tibia (subchondral bone) and in the mandible (interradicular bone), and thus obtain reference histomorphometric data of healthy female Wistar rats at different growth stages. Three groups of 8 healthy female Wistar rats were euthanized at 6 (GI), 10 (GII), and 14 (GIII) weeks. The tibiae and mandible were resected and histologically processed to obtain H&E stained sections of the tibia and the lower first molar to analyze the following histomorphometric parameters: Bone volume, trabecular width, trabecular number (Th.N)(1/mm), growth cartilage width, hypertrophic cartilage width and number of osteoclasts per area in the tibiae, and bone volume and number of osteoclasts per area N.Oc/mm² in the interradicular bone of the first lower molar. A significant decrease in subchondral bone volume as a result of a decrease in trabecular number and growth cartilage width was observed in 14-week-old rats. Conversely, interradicular bone volume was found to increase with age. The results highlight the importance of analyzing both types of bone to better understand the response of two different trabecular bones, contributing in turn to decision making regarding treatment strategies and disease management.