Alendronate (ALN) combined with osteoprotegerin (OPG) significantly improves mechanical properties of long bone than the single use of ALN or OPG in the ovariectomized rats

A narrative review of the effects of vitamin D3 on orthodontic tooth movement: Focus on molecular and cellular mechanisms

Orthodontic tooth movement (OTM) is a critical process in dental alignment, driven by the application of calibrated orthodontic forces. This study delves into the intricate molecular and cellular mechanisms by which vitamin D3 influences OTM. Vitamin D3 is identified as a critical regulator in bone metabolism, enhancing osteoblast activity and bone formation while also modulating osteoclast quantity and RANKL expression, essential for the remodeling of the alveolar bone. The precise mechanisms through which vitamin D3 facilitates these processes are explored, highlighting its potential in accelerating bone remodeling and, consequently, tooth alignment. This comprehensive review underscores vitamin D3's anabolic impact on bone metabolism and its pivotal role in the synthesis and mineralization processes governed by osteoblasts. The findings illuminate vitamin D3's promise in augmenting orthodontic therapy, suggesting its utility in improving treatment efficiency and reducing duration. However, the need for further research into the optimal application of vitamin D3 in orthodontics is emphasized, particularly concerning dosage, timing, and delivery methods.

Effect of recombinant human bone morphogenetic protein-2 and osteoprotegerin-Fc in MC3T3-E1 cells

Objective

We compared the osteoblastogenesis by serially administrating recombinant human bone morphogenetic protein-2 (rhBMP-2) and osteoprotegerin-immunoglobulin Fc segment complex (OPG-Fc).

Methods

The MC3T3-E1 preosteoblast cell line was differentiated for 1, 3, and 7 days with a treatment of OPG-Fc in 10~200 ng/mL concentration and the cell viability was evaluated by Cell Counting Kit-8 analysis. The level of differentiation from MC3T3-E1 cells to osteoblasts was determined by alkaline phosphatase activity. The level of runt domain-containing transcription factor 2 (Runx2) and osteopontin (OPN) manifestation, involved in osteoblast differentiation, was examined by real-time polymerase chain reaction and western blotting.

Results

During MC3T3-E1 cell differentiation, the differentiation level was high with 1-day treatment using 100 ng/mL OPG-Fc. The treatment with 50 ng/mL rhBMP-2 for 7 days, followed by 1-day treatment with 100 ng/mL OPG-Fc produced the highest differentiation level, which was approximately 5.3 times that of the control group (p<0.05). The expression of Runx2 mRNA significantly increased, reaching 2.5 times the level of the control group under the condition of 7-day treatment with rhBMP-2 and 1-day treatment with OPG-Fc (p<0.001). The expression of Runx2 protein significantly increased to approximately 5.7 times that of the control group under the condition of 7-day treatment with rhBMP-2, followed by 1-day treatment with OPG-Fc (p<0.01). The expression of OPN protein showed no change from that of the control group under various conditions of rhBMP-2 and OPG-Fc combinations.

Conclusion

These results imply that the treating preosteoblasts with rhBMP-2 first and then with OPG-Fc increased osteoblast differentiation efficacy.

Gleditsiae fructus regulates osteoclastogenesis by inhibiting the c‑Fos/NFATc1 pathway and alleviating bone loss in an ovariectomy model

Medical and economic developments have allowed the human lifespan to extend and, as a result, the elderly population has increased worldwide. Osteoporosis is a common geriatric disease that has no symptoms and even a small impact can cause fractures in patients, leading to a serious deterioration in the quality of life. Osteoporosis treatment typically involves bisphosphonates and selective estrogen receptor modulators. However, these treatments are known to cause severe side effects, such as mandibular osteonecrosis and breast cancer, if used for an extended period of time. Therefore, it is essential to develop therapeutic agents from natural products that have fewer side effects. Gleditsiae fructus (GF) is a dried or immature fruit of Gleditsia sinensis Lam. and is composed of various triterpenoid saponins. The anti‑inflammatory effect of GF has been confirmed in various diseases, and since the anti‑inflammatory effect plays a major role in inhibiting osteoclast differentiation, GF was expected to be effective in osteoclast differentiation and menopausal osteoporosis; however, to the best of our knowledge, it has not yet been studied. Therefore, the present study was designed to examine the effect of GF on osteoclastogenesis and to investigate the mechanism underlying inhibition of osteoclast differentiation. The effects of GF on osteoclastogenesis were determined in vitro by tartrate‑resistant acid phosphatase (TRAP) staining, pit formation assays, filamentous actin (F‑actin) ring formation assays, western blotting and reverse transcription‑quantitative PCR analyses. Furthermore, the administration of GF to an animal model exhibiting menopausal osteoporosis allowed for the analysis of alterations in the bone microstructure of the femur using micro‑CT. Additionally, assessments of femoral tissue and serum were conducted. The present study revealed that the administration of GF resulted in a reduction in osteoclast levels, F‑actin rings, TRAP activity and pit area. Furthermore, GF showed a dose‑dependent suppression of nuclear factor of activated T‑cells cytoplasmic, c‑Fos and other osteoclastogenesis‑related markers.

Effect of osteoporosis treatment agents on the cortical bone osteocyte microenvironment in adult estrogen-deficient, osteopenic rats

Though osteoporosis is a significant cause of disability worldwide, treatment with pharmacologic agents decreases risk of fragility fracture. Though these treatments act through the bone remodeling system to improve bone mass, it is unclear if they alter the response of bone to mechanical loading at the level of the osteocyte. This pre-clinical study determined the relationship between microstructural bone tissue properties and osteocyte lacunar size and density to strain around osteocytes with standard osteoporosis treatment or sequential therapies. Six-month-old female ovariectomized (OVX) Sprague-Dawley rats were cycled through various sequences of pharmacological treatments [alendronate (Aln), raloxifene (Ral) and human parathyroid hormone-1,34 (PTH)] for three month intervals, over nine months. Linear nanoindentation mapping was used to determine Young's modulus in perilacunar and bone matrix regions around cortical bone osteocyte lacunae. Measurements of lacunar diameter and density were completed. Treatment-related differences in Young's modulus in the perilacunar and bone matrix regions were not observed. We confirmed previous data that showed that the bone matrix region was stiffer than the perilacunar matrix region. Whole bone material properties were correlated to perilacunar matrix stiffness. Finite element models predicted a range of mechanical strain amplification factors estimated at the osteocyte across treatment groups. In summary, though the perilacunar matrix near cortical osteocyte lacuna is not as stiff as bone matrix further away, osteoporosis treatment agents do not affect the stiffness of bone tissue near osteocyte lacunae.

•

Monotherapy with osteoporosis treatment agents does not affect the stiffness of bone tissue around osteocyte lacunae.

•

Sequential use of osteoporosis treatment agents does not affect bone tissue stiffness around osteocyte lacunae.

•

Perilacunar cortical bone tissue is not as stiff as bone matrix further from osteocyte lacunae.

•

Whole bone material properties are negatively correlated to the stiffness of perilacunar bone tissue.

Evaluation of the effects of two different bone resorption inhibitors on osteoclast numbers and activity: An animal study

Background:

The aim of this study was to evaluate the effects of bone resorption inhibitors, doxycycline (DOX) and erythromycin (EM), on osseous wound healing in rat alveolar socket.

Materials and Methods:

In this randomized controlled trial, 45 8–10-week-old male Wistar rats had their maxillary right molar extracted. They were divided into three groups of 15. In Group 1 normal saline, Group 2 DOX, and Group 3 EM were administered at the doses of 5 ml/kg/day, 5 mg/kg/day, and 2 mg/kg/day, respectively, for 7 consecutive days. The rats were sacrificed 7, 14, and 21 days after surgery. Real-time polymerase chain reaction was employed to evaluate the mRNA expression of receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG) and immunohistochemical staining for tartrate-resistant acid phosphatase (TRAP) to determine osteoclasts. The data were analyzed by one-way analysis of variance followed by Tukey's post hoc test using SPSS version 20. Significant level was set at 0.05.

Results:

The results showed that when drug-treated groups compared to control groups, RANKL gene expression significantly decreased, TRAP⁺ cells decreased on day 7. The RANKL/OPG ratios in the first two weeks in the test groups were significantly lower than the control group. There was no significant difference in the studied indices between DOX and EM groups.

Conclusion:

Following administration of DOX and EM, the number of osteoclasts and RANKL/OPG ratio decreased suggesting their anti-osteoclastogenesis activity. These two drugs have no advantage over each other in increasing the bone formation.

Recombinant receptor activator of nuclear factor κB exhibits more marked inhibitory effects on osteoclasts compared with recombinant osteoprotegerin in vitro and in vivo

The aim of the present study was to compare the osteoclast-inhibiting ability of recombinant osteoprotegerin (OPG) protein (rhOPG-Fc) and recombinant receptor activator of nuclear factor κB (rhRANK) in vitro and in vivo. Osteoclasts were cultured with either rhOPG-Fc or rhRANK for 9 days. The number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and resorption pits in bone slices were then counted. In the in vivo investigation, female mice were bilaterally ovariectomized (OVX) and intraperitoneally injected with 3 mg/kg rhOPG-Fc or rhRANK for 12 weeks, respectively. Bone metabolism, bone mineral density and microstructure changes were then evaluated. The number of TRAP-positive cells and bone resorption pits decreased significantly following culture with either rhOPG-Fc or rhRANK, and this was more marked following culture with rhRANK compared with rhOPG-Fc. The levels of calcium and alkaline phosphatase in the serum were similar pre-OVX and after 12 weeks of treatment, while the levels of phosphorus in the serum were higher following treatment with rhRANK compared with rhOPG. The bone mineral density (BMD) of the whole body, femoral neck and L4 lumbar vertebral body in the mice treated with either rhOPG-Fc or rhRANK increased markedly. In addition, the mice treated with rhRANK exhibited significantly higher BMD in the femoral neck and lumbar vertebral body compared with those treated with rhOPG-Fc. Microcomputed tomography analysis demonstrated that the mice treated with rhRANK exhibited an increased bone volume and structure model index, and decreased trabecular spacing compared with those treated with rhOPG-Fc. rhRANK increased the inhibition of osteoclast differentiation and bone resorption, and rescued OVX-induced osteoporosis more effectively compared with rhOPG-Fc.

Comparable effects of alendronate and strontium ranelate on femur in ovariectomized rats

This study compared the effects of alendronate (ALN) and strontium ranelate (SR) on bone mineral density (BMD), bone histomorphometry, and biomechanics in ovariectomized (OVX) rats. We randomly assigned 48 3-month-old female Sprague-Dawley rats to four groups: sham, OVX, ALN, and SR. Rats in the OVX, ALN, and SR groups received bilateral OVX. Rats in the ALN and SR groups were orally administrated ALN (7 mg/kg/week) and SR (500 mg/kg/day). Rats in the sham and OVX groups were treated with saline. All treatments continued for 12 weeks. Femoral BMD examination, distal femoral bone histomorphometry analysis, and biomechanical tests at the femoral diaphysis and metaphysis were performed to evaluate the effects of treatments in OVX rats. Results showed that both ALN and SR significantly increased femoral BMD (total femur, diaphyseal BMD, and distal metaphyseal BMD), distal femoral bone histomorphometric parameters (BV/TV, Tb.N, and Tb.Th), and femoral biomechanical parameters (maximum load, failure load, stiffness) compared with the OVX group (P < 0.05). No differences were found between ALN and SR in increasing femoral BMD, distal femoral bone histomorphometric parameters (BV/TV, Tb.N, and Tb.Th), and femoral diaphysis biomechanical parameters (maximum load, failure load, stiffness) (P > 0.05). The SR group was inferior to the ALN group in femoral metaphysis biomechanical parameters (P < 0.05). In conclusion, ALN (7 mg/kg/week) and SR (500 mg/kg/day) have similar effects by increasing BMD, distal femoral bone histomorphometric parameters, and femoral metaphysis biomechanical properties. Although ALN has greater effects than SR on distal femoral metaphysis biomechanical properties, in general, ALN and SR have comparable effects on the femur in OVX rats.

Alendronate protects against articular cartilage erosion by inhibiting subchondral bone loss in ovariectomized rats

Osteoporosis (OP) and osteoarthritis (OA) are major health problems in the increasing elderly population, particularly in postmenopausal women, but their relationship remains unclear. The present study investigated whether alendronate (ALN), a potent inhibitor of bone resorption, could protect articular cartilage from degeneration in a combined animal model of OP and OA induced by ovariectomy (OVX). Seventy-eight seven-month-old female Sprague-Dawley rats were assigned into five experimental groups: (1) sham-operated with vehicle treatment, (2) sham-operated with ALN treatment, (3) OVX with vehicle treatment, (4) ALN treatment starting at OVX, and (5) ALN treatment starting at eight weeks after OVX. Histological and micro-CT analyses, together with urine collagen degradation markers, indicated that early ALN treatment completely prevented both subchondral bone loss and cartilage surface erosion induced by OVX. Although late ALN treatment also inhibited subchondral bone loss and significantly reduced cartilage erosion in the OVX rats, these tissues did not completely recover even after 10-weeks of ALN treatment. Quantitative RT-PCR analyses showed that the protective effect of ALN correlated with increased ratio of OPG/RANKL in both subchondral bone and cartilage. Moreover, whereas OVX caused upregulation of expression of matrix metalloproteinases MMP-13 and MMP-9 in the articular cartilage and chondrocytes in the interface between the articular cartilage and subchondral bone, respectively, early ALN treatment blocked whereas late ALN treatment attenuated the upregulation of these catabolic enzymes in the corresponding tissues. Together, these data indicate that the subchondral bone loss plays an important role in OA pathogenesis in the combined OP and OA model and suggest that treatment timing is an important factor for the effectiveness of anti-resorptive drug therapy of combined OP and OA.

Establishment of OPG Transgenic Mice and the Effect of OPG on Bone Microarchitecture

Osteoprotegerin (OPG) plays a determinant role in regulating bone metabolism, but the effect of OPG on bone microarchitecture needs to be further elucidated. We attempted to construct pCI-hOPGp-mOPG vector containing human OPG promoter and FLAG tag and to microinject vector into fertilized zygotes from C57BL/6J × CBA mice to prepare transgenic mice. The OPG transgenic positive mice were identified by PCR and western blotting. Twelve-week-old OPG transgenic mice (OPG-Tg mice) and wild-type mice (WT mice) were utilized in the study of bone microarchitecture. Microcomputed tomography (micro-CT) data showed that compared with WT mice, the tibia of OPG-Tg mice showed an increased volumetric BMD (vBMD), tissue BMD (tBMD), trabecular thickness (Tb.Th), and trabecular number (Tb.N), and a decreased trabecular separation (Th.Sp) (P < 0.05) . The cortical bone microarchitecture parameters, such as cortical area (Ct.Ar), cortical thickness (Ct.Th), cortical BMD (Ct.BMD), cortical BMC (Ct.BMC), BMD, and BMC of femur, were increased, and the inner perimeter (In.Pm) was decreased, in OPG-Tg mice, compared to those in WT mice (P < 0.05). The established OPG transgenic mouse model could be valuable for further studying the biological significance and gene regulation of OPG in vivo.

Experimental development of bisphosphonate-related osteonecrosis of the jaws in rodents

Osteonecrosis of the jaw (ONJ) following the use of bisphosphonates has become of increased interest in the scientific community, due in particular to its as-yet-unsolved pathogenesis. An experimental model of ONJ was induced in normal male rats [alendronate (ALN); 1 mg/Kg/day; n = 10] and matched controls (saline solution; n = 10). After 60 days of drug treatment, all animals were subjected to extractions of the left first lower molars and were euthanized at 3 and 28 days postsurgery. The following analyses were performed: (i) descriptive and quantitative (scores) histological evaluation, (ii) stereometry of distal sockets and (iii) biochemical measurement of C-telopeptide cross-linked collagen type I (CTX) and bone-specific alkaline phosphatase (BALP). The results showed that 28 days postsurgery the animals treated with ALN had areas of exposed and necrotic bone, associated with significant infection, especially in the interalveolar septum area and crestal regions, compared with controls. The levels of CTX, BALP and bone volume, as well as the degrees of inflammation and vascularization, were significantly reduced in these animals. Therefore, analysis of the data presented suggests that ALN therapy is associated with the development of osteonecrosis in the jaws of rodents after tooth extraction.

A higher dosage of oral alendronate will increase the subsequent cancer risk of osteoporosis patients in Taiwan: a population-based cohort study

BACKGROUND

Controversy still exists regarding whether alendronate (ALN) use increases the risk of esophageal cancer or breast cancer.

METHODS

This paper explores the possible association between the use of oral ALN in osteoporosis patients and subsequent cancer risk using the National Health Insurance (NHI) system database of Taiwan with a Cox proportional-hazard regression analysis. The exposure cohort contained 5,624 osteoporosis patients used ALN and randomly frequency-matched by age and gender of 3 osteoporosis patients without any kind of anti-osteoporosis drugs in the same period.

RESULTS

For a dose ≥ 1.0 g/year, the risk of developing overall cancer was significantly higher (hazard ratio: 1.69, 95% confidence ratio: 1.39-2.04) than in osteoporosis patients without any anti-osteoporosis drugs. The risks for developing liver, lung, and prostate cancers and lymphoma were also significantly higher than in the control group.

CONCLUSIONS

This population-based retrospective cohort study did not find a relationship between ALN use and either esophageal or breast cancer, but unexpectedly discovered that use of ALN with dose ≥ 1.0 g/year significantly increased risks of overall cancer incidence, as well as liver, lung, and prostate cancers and lymphoma. Further large population-based unbiased studies to enforce our findings are required before any confirmatory conclusion can be made.

Bisphosphonate- and statin-induced enhancement of OPG expression and inhibition of CD9, M-CSF, and RANKL expressions via inhibition of the Ras/MEK/ERK pathway and activation of p38MAPK in mouse bone marrow stromal cell line ST2

Osteoclast differentiation is influenced by receptor activator of the NF-κB ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and CD9, which are expressed on bone marrow stromal cells and osteoblasts. In addition, osteoprotegerin (OPG) is known as an osteoclastogenesis inhibitory factor. In this study, we investigated whether bisphosphonates and statins increase OPG expression and inhibit the expression of CD9, M-CSF, and RANKL in the bone marrow-derived stromal cell line ST2. We found that bisphosphonates and statins enhanced OPG mRNA expression and inhibited the expression of CD9, M-CSF, and RANKL mRNA. Futhermore, bisphosphonates and statins decreased the membrane localization of Ras and phosphorylated ERK1/2, and activated the p38MAPK. This indicates that bisphosphonates and statins enhanced OPG expression, and inhibited the expression of CD9, M-CSF, and RANKL through blocking the Ras/ERK pathway and activating p38MAPK. Accordingly, we believe that its clinical applications will be investigated in the future for the development of osteoporosis therapy.