Zoledronic acid enhances bone-implant osseointegration more than alendronate and strontium ranelate in ovariectomized rats

Summary

This study was designed to compare the effects of alendronate (ALN), strontium ranelate (SR), and zoledronic acid (ZOL) on bone-implant osseointegration in ovariectomized rats. Histological examination and biomechanical tests show that ZOL, ALN, and SR enhance bone-implant osseointegration; ALN and SR have similar effects, while ZOL enhances bone-implant osseointegration more than ALN and SR

Introduction

This study aims to compare the effects of ALN, SR, and ZOL on bone-implant osseointegration in ovariectomized rats.

Methods

Sixty female Sprague–Dawley rats were included in this study. Of them, 48 rats were ovariectomized (OVX) and assigned to four groups: OVX (OVX?+?Veh), ALN (OVX?+?ALN), SR (OVX?+?SR), and ZOL (OVX?+?ZOL). And another 12 rats were sham-operated as a control group (Sham). Four weeks after ovariectomy, HA-coated titanium implants were inserted into the tibias bilaterally in all rats. Then the rats in groups ALN, SR, and ZOL were systemically administrated with alendronate (7 mg/kg/week, orally), strontium ranelate (500 mg/kg/day, orally), or a single injection of zoledronic acid (0.1 mg/kg, iv), respectively. Twelve weeks after implantation, all rats were sacrificed to get the femurs and tibias. Histological examination and biomechanical tests were used to evaluate bone-implant osseointegration in all groups.

Results

ALN, SR, and ZOL significantly increased distal femoral BMD when compared with group OVX; ZOL increased BMD significantly more than ALN and SR (P?<?0.05). Significant increase of bone-to-implant contact and peri-implant bone fraction were observed in groups ALN, SR, and ZOL when compared with group OVX (P?<?0.05). Groups ALN and SR were inferior to groups ZOL and Sham (P?<?0.05) in bone-to-implant contact and peri-implant bone fraction. Similar results were found in biomechanical testing (max pushout force).

Conclusions

In rats losing bone rapidly after ovariectomy, systemic administration of ZOL, ALN, and SR causes better bone-implant osseointegration when compared to OVX; ALN and SR have similar positive effects on osseointegration, while ZOL, that was given in a dose with more positive BMD effect than that of ALN or SR, causes better osseointegration than either ALN or SR.     

Effects of combined elcatonin and alendronate treatment on the architecture and strength of bone in ovariectomized rats

We examined the combined effects of elcatonin (ECT) and alendronate (ALN) on bone mass, architecture, and strength in ovariectomized (OVX) rats. Fifty female Sprague Dawley rats, aged 13 weeks, were divided into Sham, OVX, OVX+ECT, OVX+ALN, and OVX+ECT+ALN groups (n = 10). Immediately after ovariectomy, ECT was administered at a dose of 15 units (U)/kg three times a week, and ALN was administered daily at a dose of 2.0 µg/kg, subcutaneously for 12 weeks. The three-dimensional architecture of the bone in the distal femoral metaphysis was analyzed using a microfocus X-ray computed tomography system (µCT), and bone strength was measured using a material-testing machine. Trabe-cular bone volume (BV/TV) and number (Tb.N) were significantly greater in the OVX+ECT and OVX+ALN groups than in the OVX group. In the OVX+ECT+ALN group, BV/TV and Tb.N were significantly greater when compared with those in the OVX+ECT and OVX+ALN groups. Trabecular thickness (Tb.Th) was significantly greater in the OVX+ECT+ALN group than in the OVX+ALN group. With regard to bone strength, the compression strength in the femoral metaphysis was significantly lower in the OVX group than in the Sham group. The reduction of compression strength was slightly lower in the OVX+ECT and OVX+ALN groups. In the OVX+ECT+ALN group, the compression strength in the femoral metaphysis significantly increased when compared with the OVX and OVX+ECT groups. These results suggest that the combined treatment of ECT and ALN does not alter the individual effects of each drug and that it exerts an additive effect on trabecular architecture and bone strength in OVX rats.     

应用原子力显微镜观察脉冲电磁场对大鼠骨质疏松的治疗后骨组织表面超微结构的变化

目的观察实验性大鼠骨质疏松模型股骨颈超微结构的变化特点,并探讨利用原子力显微镜观察的可行性。方法清洁级雌性SD大鼠(鼠龄3个月)60只,体重(200±20)g。随机将其分成对照组(Sham组)、去卵巢组(OVX组)、阿伦膦酸钠治疗组(ALN组)、PEMFs治疗组(PEMFs组),每组大鼠15只。除Sham组外,对其他各组行双侧卵巢切除术,造模后第30天开始分组干预。ALN组给予阿伦膦酸钠灌胃,PEMFs组给予脉冲电磁场治疗。Sham组和OVX组手术后正常喂养,不予任何处理。治疗后30d取大鼠股骨头切片,通过AFM观察大鼠股骨颈的表面超微结构。结果 Sham组原子力显微镜扫描可显示骨组织的骨陷窝、骨小管及其表面的钙磷晶体沉积,骨组织表面粗糙度为(2.59±0.645)μm。OVX组可见骨陷窝的大小变化及其钙磷晶体的排列紊乱,模型组骨组织表面粗糙度明显高于对照组(P0.01),提示造模成功;ALN组表面粗糙度明显低于OVX组(P0.05),PEMFs组的表面粗糙度与OVX组相比,有明显降低,差异具有统计学意义(P0.05);而PEMFs组与ALN组比较,其表面粗糙度无明显差异(P0.05)。结论通过原子力显微镜能清晰观察到脉冲电磁场对大鼠骨质疏松治疗后的骨组织表面超微结构的变化,其疗效与阿仑膦酸钠相当,为脉冲电磁场治疗骨质疏松提供了一定的理论依据。     

Effects of the combination treatment of raloxifene and alendronate on the biomechanical properties of vertebral bone

Raloxifene (RAL) and alendronate (ALN) improve the biomechanical properties of bone by different mechanisms. The goal here was to investigate the effects of combination treatment of RAL and ALN on the biomechanical properties of vertebral bone. Six‐month‐old Sprague‐Dawley rats (n = 80) were randomized into five experimental groups (sham, OVX, OVX + RAL, OVX + ALN, and OVX + RAL + ALN; n = 16/group). Following euthanization, structural and derived material biomechanical properties of vertebral bodies were assessed. Density and dynamic histomorphometric measurements were made on cancellous bone. The results demonstrate that the structural biomechanical properties of vertebral bone are improved with the combination treatment. Stiffness and ultimate load of the OVX + RAL and OVX + ALN groups were significantly lower than those of sham animals, but the combination treatment with RAL + ALN was not significantly different from sham. Furthermore, the OVX + RAL + ALN group was the only agent‐treated group in which the ultimate load was significantly higher than that in OVX animals (p < .05). Cancellous bone fractional volume (BV/TV_canc) and bone mineral density (aBMD) also were improved with the combination treatment. BV/TV_canc of the OVX + RAL + ALN group was 6.7% and 8.7% greater than that of the OVX + RAL (p < .05) and OVX + ALN (p < .05) groups, respectively. Areal BMD of the OVX + RAL or OVX + ALN groups was not significantly different from that in OVX animals, but the value in animals undergoing combination treatment was significantly higher than that in OVX or OVX + RAL animals alone and not significantly different from that in sham‐operated animals. Turnover rates of both the RAL + ALN and ALN alone groups were lower than in the RAL‐treated alone group (p < .05). We conclude that the combination treatment of raloxifene and alendronate has beneficial effects on bone volume, resulting in improvement in the structural properties of vertebral bone. © 2011 American Society for Bone and Mineral Research.     

Differential maintenance of cortical and cancellous bone strength following discontinuation of bone‐active agents

Osteoporotic patients treated with antiresorptive or anabolic agents experience an increase in bone mass and a reduction in incident fractures. However, the effects of these medications on bone quality and strength after a prolonged discontinuation of treatment are not known. We evaluated these effects in an osteoporotic rat model. Six‐month‐old ovariectomized (OVX) rats were treated with placebo, alendronate (ALN, 2 µg/kg), parathyroid hormone [PTH(1–34); 20 µg/kg], or raloxifene (RAL, 2 mg/kg) three times a week for 4 months and withdrawn from the treatments for 8 months. Treatment with ALN, PTH, and RAL increased the vertebral trabecular bone volume (BV/TV) by 47%, 53%, and 31%, with corresponding increases in vertebral compression load by 27%, 51%, and 31%, respectively (p < .001). The resulting bone strength was similar to that of the sham‐OVX control group with ALN and RAL and higher (p < .001) with PTH treatment. After 4 months of withdrawal, bone turnover (BFR/BS) remained suppressed in the ALN group versus the OVX controls (p < .001). The vertebral strength was higher than in the OVX group only in ALN‐treated group (p < .05), whereas only the PTH‐treated animals showed a higher maximum load in tibial bending versus the OVX controls (p < .05). The vertebral BV/TV returned to the OVX group level in both the PTH and RAL groups 4 months after withdrawal but remained 25% higher than the OVX controls up to 8 months after withdrawal of ALN (p < .05). Interestingly, cortical bone mineral density increased only with PTH treatment (p < .05) but was not different among the experimental groups after withdrawal. At 8 months after treatment withdrawal, none of the treatment groups was different from the OVX control group for cortical or cancellous bone strength. In summary, both ALN and PTH maintained bone strength (maximum load) 4 months after discontinuation of treatment despite changes in bone mass and bone turnover; however, PTH maintained cortical bone strength, whereas ALN maintained cancellous bone strength. Additional studies on the long‐term effects on bone strength after discontinuation and with combination of osteoporosis medications are needed to improve our treatment of osteoporosis. © 2011 American Society for Bone and Mineral Research.     

Effects of vibration treatment on tibial bone of ovariectomized rats analyzed by in vivo micro‐CT

Daily low‐amplitude, high‐frequency whole‐body vibration (WBV) treatment can increase bone formation rates and bone volume in rodents. Its effects vary, however, with vibration characteristics and study design, and effects on 3D bone microstructure of ovariectomized animals over time have not been documented. Our goal was to determine the effects of WBV on tibial bone of ovariectomized, mature rats over time using an in vivo micro‐CT scanner. Adult rats were divided into: ovariectomy (OVX) (n = 8), SHAM‐OVX (n = 8), OVX and WBV treatment (n = 7). Eight weeks after OVX, rats in the vibration group were placed on a vibrating platform for 20 min at 0.3 g and 90 Hertz. This was done 5 days a week for six weeks, twice a day. Zero, 8, 10, 12 and 14 weeks after OVX, in vivo micro‐CT scans were made (vivaCT 40, Scanco Medical AG) of the proximal and diaphyseal tibia. After sacrifice, all tibiae were dissected and tested in three‐point bending. In the metaphysis between 8 to 12 weeks after OVX, WBV treatment did not alter structural parameters compared to the OVX group and both groups continued to show deterioration of bone structure. In the epiphysis, structural parameters were not altered. WBV also did not affect cortical bone and its bending properties. To summarize, no substantial effects of 6 weeks of low‐magnitude, high‐frequency vibration treatment on tibial bone microstructure and strength in ovariectomized rats were found. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:62–69, 2010     

Onion decreases the ovariectomy-induced osteopenia in young adult rats

It has been suggested that fruit and vegetable consumption are associated with good bone health. Onion, in particular, has been verified in its efficacy in bone resorption activity. In this study, we further investigated the effects of an onion-containing diet on ovariectomy-induced bone loss using methods of serum marker assay, histomorphometric analysis and biomechanical tests. Sixty-four female Wistar rats (14-week-old) with sham operations or ovariectomy were assigned to 6 groups: CON, sham-operated control group; OVX, ovariectomized group; ALN, ovariectomized rats treated with alendronate (1 mg/kg/day, p.o.); and 3% ON, 7% ON and 14% ON, ovariectomized rats fed with diets containing 3%, 7% and 14% (wt/wt) onion powder, respectively. Animals were sacrificed after a six-week treatment course. In the serum marker assay, alendronate and all three onion-enriched diets significantly decreased serum calcium level (p<0.05). Both 14% ON group and the ALN group even showed similarly lower level of serum osteocalcin (p<0.05), suggesting a down-regulation of bone turnover. The histomorphometric analysis showed that ovariectomy markedly decrease bone trabeculae. The ALN and 14% ON rats were 80% and 46% higher, respectively, in BV/TV than the OVX rats (p<0.05), and the rats fed with onion-enriched food showed a lesser ovariectomy-induced bone loss in a dose-dependent manner. Additionally, both ALN and 14% ON groups had significantly more trabecular number, less separated trabeculae, and fewer osteoclasts (p<0.05), but the protective efficacy from the 14% onion-enriched diet was slightly inferior to that of alendronate. Ovariectomy also significantly decreased tissue weight and biomechanical strength in the OVX group (p<0.05). The ALN and 14% ON groups equivalently showed a lesser decrease in tissue weight, though the difference was not significant. On the other hand, both the ALN and 14% ON groups represented similar biomaterial properties of femurs, and both reduced the ovariectomy-induced decrease in bending load and bending energy (p<0.05). The present study further verified that an onion-enriched diet could counteract ovariectomy-induced bone loss and deterioration of biomechanical properties.     

The bisphosphonate ibandronate improves implant integration in osteopenic ovariectomized rats

Osteoporosis is known to impair the process of implant osseointegration. Bisphosphonates are drugs that inhibit osteoclast-mediated bone resorption and normalize the high rate of bone turnover that characterizes this disease. Consequently, there is a rationale for using bisphosphonates to enhance the early stabilization of implants in subjects with low bone mass. In this study, 84 rats received titanium-only or hydroxyapatite (HA)-coated titanium femoral implants, 3 months after being ovariectomized (OVX) or sham operated. They were then treated for 4 weeks. The OVX rats were randomly assigned to daily subcutaneous injections of either saline or the bisphosphonate ibandronate (at a dose of 1 microg/kg or 25 microg/kg), while the sham-operated animals received saline throughout. The 1 microg/kg or 25 microg/kg ibandronate doses are considered translatable to doses used to treat osteoporosis and metastatic bone disease (MBD), respectively, in rats, and roughly reflect those used in humans. At the end of the treatment period, bone mineral density (BMD) at the lumbar spine increased in both of the ibandronate-treated groups when compared with the OVX control animals and to a level similar to that of the sham-operated control group. Osseointegration, determined by histomorphometric analysis and expressed as percentage of osseointegration implant surface (OIS), did not differ between groups for the titanium-only implants. For the HA-coated implants, however, OIS was 113.5% and 185% higher in the groups receiving 1 microg/kg or 25 microg/kg ibandronate, respectively, relative to the OVX controls. In turn, the OIS of the HA-coated implants was 56.5% lower in the OVX control group than in the sham control group. These findings clearly demonstrate that OVX-induced osteopenia impairs the osseointegration of HA-coated titanium implants and that ibandronate, administered at doses analogous to those used to clinically treat osteoporosis and MBD, counters this harmful effect. Ibandronate may, therefore, have a role in improving the osseointegration of implants in patients with osteoporosis and MBD.     

Cathepsin K inhibitors prevent bone loss in estrogen‐deficient rabbits

Two cathepsin K inhibitors (CatKIs) were compared with alendronate (ALN) for their effects on bone resorption and formation in ovariectomized (OVX) rabbits. The OVX model was validated by demonstrating significant loss (9.8% to 12.8%) in lumbar vertebral bone mineral density (LV BMD) in rabbits at 13‐weeks after surgery, which was prevented by estrogen or ALN. A potent CatKI, L‐006235 (L‐235), dosed at 10 mg/kg per day for 27 weeks, significantly decreased LV BMD loss (p < .01) versus OVX‐vehicle control. ALN reduced spine cancellous mineralizing surface by 70%, whereas L‐235 had no effect. Similarly, endocortical bone‐formation rate and the number of double‐labeled Haversian canals in the femoral diaphysis were not affected by L‐235. To confirm the sparing effects of CatKI on bone formation, odanacatib (ODN) was dosed in food to achieve steady‐state exposures of 4 or 9 µM/day in OVX rabbits for 27 weeks. ODN at both doses prevented LV BMD loss (p < .05 and p < .001, respectively) versus OVX‐vehicle control to levels comparable with sham or ALN. ODN also dose‐dependently increased BMD at the proximal femur, femoral neck, and trochanter. Similar to L‐235, ODN did not reduce bone formation at any bone sites studied. The positive and highly correlative relationship of peak load to bone mineral content in the central femur and spine suggested that ODN treatment preserved normal biomechanical properties of relevant skeletal sites. Although CatKIs had similar efficacy to ALN in preventing bone loss in adult OVX rabbits, this novel class of antiresorptives differs from ALN by sparing bone formation, potentially via uncoupling bone formation from resorption. © 2011 American Society for Bone and Mineral Research.     

Strontium ranelate treatment enhances hydroxyapatite‐coated titanium screws fixation in osteoporotic rats

Increased bone turnover with excessive bone resorption and decreased bone formation is known to impair implant fixation. Strontium ranelate is well known as an effective antiosteoporotic agent by its dual effect of antiresorbing and bone‐forming activity. This study was designed to evaluate the effect of systemic strontium ranelate (SR) treatment on fixation of hydroxyapatite (HA)‐coated titanium screws in ovariectomized (OVX) rats. Twelve weeks after being OVX (n = 30) or sham (n = 10) operated, 40 female Sprague–Dawley rats received unilateral implants in the proximal tibiae. The OVX rats were randomly divided into the following groups: OVX, OVX + SR_L (“_L” refers to low SR dose of 500 mg/kg/day), OVX + SR_H (“_H” refers to high SR dose of 1000 mg/kg/day).Twelve weeks after treatment, bone blocks with implants were evaluated with micro‐CT and biomechanical push‐out tests. Compared to OVX animals, SR treatment increased the bone volume ratio by 51.5% and 1.1‐fold, the percentage osteointegration by 1.0‐fold and 1.9‐fold in micro‐CT evaluation, and the maximal force by 1.9‐fold and 3.3‐fold in biomechanical push‐out test, for the low and high dose of SR, respectively. Significant correlation between micro‐CT and biomechanical properties demonstrated that trabecular parameters played an important role in predicting the biomechanical properties of implant fixation. Our findings suggest that SR treatment can dose‐dependently improve HA‐coated screw fixation in OVX rats and facilitate the stability of the implant in the osteoporotic bone. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:578–582, 2010     

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.     

曲古抑菌素A促进去卵巢大鼠钛植入物骨整合

目的 探讨TSA对去卵巢大鼠TI骨整合的影响。方法 将30只健康3月龄雌性SD大鼠随机分为Sham组（n=5）和OVX组（n=25）。正常饲养3个月后,两组各选取5只大鼠处死,取股骨远端样本行Micro-CT和HE染色以鉴定是否成功建立骨质疏松模型。随后在OVX组剩余大鼠双侧股骨干骺端植入直径1.5 mm TI,并将其分为2组：Control组（n=10）和TSA组（n=10）。连续给药4周。给药结束后处死全部大鼠并取股骨样本行Micro-CT扫描、HE染色以及Masson染色,ELISA法检测,拔钉实验。结果 与Sham组对比,Micro-CT显示OVX组BMD、BV/TV、Tb.Th、Tb.N降低（P<0.05）,而Tb.Sp、SMI升高（P<0.05）,HE染色显示OVX组骨小梁数量明显降低。与Control组对比,Micro-CT显示TSA组BMD、BV/TV、Tb.Th、Tb.N 、Conn.D均升高（P<0.05）,而Tb.Sp、SMI降低（P<0.05）,HE染色、Masson染色显示TSA组骨小梁数量、新生骨数量均升高,ELISA法检测结果显示TSA组OCN、BMP2均升高,拔钉实验显示TSA组TI轴向拔出力增大。结论 TSA通过上调OCN、BMP2等成骨相关蛋白,促进骨小梁形成和新骨形成,进而改善去卵巢大鼠TI骨整合。     

Effect of alendronate and intermittent parathyroid hormone on implant fixation in ovariectomized rats

Background  Intermittent administration of parathyroid hormone (PTH) leads to bone formation by increasing osteoblast numbers and activity levels. Animal studies have shown that intermittent PTH administration increases implant fixation in normal rats. The purpose of this study was to analyze the osseous incorporation of an implant in osteoporotic rats while treating them with intermittent PTH (1–34) or alendronate. Methods  A total of 36 ovariectomized (OVX) Wistar rats were randomized into three groups. Polymethylmethacrylate cement rods were implanted in one tibia in each rat. The three groups received daily PTH (60 μg/kg body weight [BW]), alendronate (200 μg/kg BW), or saline (0.5 ml/kg BW). A sham-ovariectomized group (n = 12) was treated with saline. After 2 weeks, the area around the implants was analyzed by histomorphometry for bone volume density (BVD) and implant bone contact. Bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry. Results  The BVD was higher in the specimens treated with PTH than in the other groups. PTH improved the BVD, BMD, and implant bone contact. Alendronate doubled the implant bone contact compared to the OVX and sham groups but did not improve BVD or BMD. Conclusions  These findings confirm that intermittent PTH enhances implant fixation in osteoporotic bone. The clinical significance of these findings is that application of intermittent PTH may be beneficial for early implant fixation in fractures, nonunions, and prosthetic replacements when bone density is decreased.     

Whole body vibration improves osseointegration by up-regulating osteoblastic activity but down-regulating osteoblast-mediated osteoclastogenesis via ERK1/2 pathway

Due to the reduction in bone mass and deterioration in bone microarchitecture, osteoporosis is an important risk factor for impairing implant osseointegration. Recently, low-magnitude, high-frequency (LMHF) vibration (LM: < 1 ×g; HF: 20–90 Hz) has been shown to exhibit anabolic, but anti-resorptive effects on skeletal homeostasis. Therefore, we hypothesized that LMHF loading, in terms of whole body vibration (WBV), may improve implant fixation under osteoporotic status. In the in vivo study, WBV treatment (magnitude: 0.3 g, frequency: 40 Hz, time: 30 min/12 h, 5 days/week) was applied after hydroxyapatite-coated titanium implants were inserted in the bilateral tibiae of ovariectomized rats. The bone mass and the osteospecific gene expressions were measured at 12 weeks post implantation. In the in vitro study, the cellular and molecular mechanisms underlying osteoblastic and osteoclastic activities were fully investigated using various experimental assays. Micro-CT examination showed that WBV could enhance osseointegration by improving microstructure parameters surrounding implants. WBV-regulated gene levels in favor of bone formation over resorption may be the reason for the favorable adaptive bone remolding on bone-implant surface. The in vitro study showed that vibration (magnitude: 0.3 g, frequency: 40 Hz, time: 30 min/12 h) up-regulated osteoblast differentiation, matrix synthesis and mineralization. However, mechanically regulated osteoclastic activity was mainly through the effect on osteoblastic cells producing osteoclastogenesis-associated key soluble factors, including RANKL and M-CSF. Osteoblasts were therefore the direct target cells during the mechanotransduction process. The ERK1/2 pathway was demonstrated to play an essential role in vibration-induced enhancement of bone formation and decreased bone resorption. Our data suggests that WBV was a helpful non-pharmacological intervention for improving osseointegration under osteoporosis.     

Novel EP4 Receptor Agonist‐Bisphosphonate Conjugate Drug (C1) Promotes Bone Formation and Improves Vertebral Mechanical Properties in the Ovariectomized Rat Model of Postmenopausal Bone Loss

Current treatments for postmenopausal osteoporosis aim to either promote bone formation or inhibit bone resorption. The C1 conjugate drug represents a new treatment approach by chemically linking the antiresorptive compound alendronate (ALN) with the anabolic agent prostanoid EP4 receptor agonist (EP4a) through a linker molecule (LK) to form a conjugate compound. This enables the bone‐targeting ability of ALN to deliver EP4a to bone sites and mitigate the systemic side effects of EP4a, while also facilitating dual antiresorptive and anabolic effects. In vivo hydrolysis is required to release the EP4a and ALN components for pharmacological activity. Our study investigated the in vivo efficacy of this drug in treating established bone loss using an ovariectomized (OVX) rat model of postmenopausal osteopenia. In a curative experiment, 3‐month‐old female Sprague‐Dawley rats were OVX, allowed to lose bone for 7 weeks, then treated for 6 weeks. Treatment groups consisted of C1 conjugate at low and high doses, vehicle‐treated OVX and sham, prostaglandin E₂ (PGE₂), and mixture of unconjugated ALN‐LK and EP4a to assess the effect of conjugation. Results showed that weekly administration of C1 conjugate dose‐dependently increased bone volume in trabecular bone, which partially or completely reversed OVX‐induced bone loss in the lumbar vertebra and improved vertebral mechanical strength. The conjugate also dose‐dependently stimulated endocortical woven bone formation and intracortical resorption in cortical bone, with high‐dose treatment increasing the mechanical strength but compromising the material properties. Conjugation between the EP4a and ALN‐LK components was crucial to the drug's anabolic efficacy. To our knowledge, the C1 conjugate represents the first time that a combined therapy using an anabolic agent and the antiresorptive compound ALN has shown significant anabolic effects which reversed established osteopenia. © 2014 American Society for Bone and Mineral Research.     

Relationship between age,skeletal site,and time post‐ovariectomy on bone mineral and trabecular microarchitecture in rats

The ovariectomized (OVX) rat is widely used in osteoporosis research, but no standard model exists. The individual effects of rat age, skeletal site, and time post‐ovariectomy (post‐OVX) on bone have been examined. However, the relationship between them is not yet fully explored. This study examined how various combinations of rat age, skeletal site, and time post‐OVX affect bone mineral and microarchitecture. The rats used were 12 (n = 28), 24 (n = 28), and 44 (n = 31) weeks old. In each age group, approximately half underwent OVX and other half underwent Sham surgeries. Bone mineral (content and density) and trabecular morphology was assessed at 2, 5, 10, 15, 20, 25, and 30 weeks post‐surgery. Sites examined included the proximal tibia, spine, distal femur, and proximal femur. Overall, the proximal tibia showed the earliest and greatest differences between OVX and Sham groups. The 24‐week‐old group showed the best osteoporotic response. The 12‐week‐old group showed growth effects, whilst the 44‐week‐old group showed aging effects. The response of certain sites to OVX was also found to depend on the rat age used. These findings may aid in explaining discrepancies reported in the literature as well as synergistic combinations that may signify advanced conditions. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:189–196, 2011     

Preventive effects of sequential treatment with alendronate and 1 alpha-hydroxyvitamin D3 on bone mass and strength in ovariectomized rats

Because accumulating evidence has shown that bisphosphonates are unable to maintain their bone-sparing effects after the withdrawal of the drug, a replacement treatment is needed when bisphosphonate treatment cannot be continued for some reason. The present study investigated the preventive effects of alendronate followed by 1alpha(OH)D3 on the mass and mechanical strength of trabecular and cortical bones in ovariectomized rats. Sprague-Dawley rats were ovariectomized or sham-operated at 48 weeks of age. Ovariectomized rats treated with vehicle alone (OVX group) showed significant decreases in bone mineral density (BMD) and mechanical strength of the lumbar vertebra and the midfemur during a 20-week period after the operation as compared with sham-operated rats. These decreases were prevented by continuous treatment with alendronate (0.5 mg/kg/day, po) for 20 weeks (ALN-C group), whereas the values reverted to those of the OVX group when alendronate was withdrawn at 10 weeks (ALN-W group). The sequential treatment with alendronate and 1alpha(OH)D3 (0.05 microg/kg/day, po) for 10 weeks each (ALN --> 1alpha group) resulted in higher BMD and mechanical strength of the lumbar vertebra and the midfemur in this group than in the OVX and ALN-W groups. The increase in mechanical strength was proportional to that in BMD at both sites, suggesting that the stimulatory effects of these treatments on bone strength were due to those on bone mass. Analyses of histology, computed tomography, and biochemical markers confirmed the preventive effects of the sequential treatment. Therefore, we propose that 1alpha(OH)D3 may be a good choice to replace alendronate when alendronate treatment cannot be continued for some reason.     

Effects of alendronate on lumbar intervertebral disc degeneration with bone loss in ovariectomized rats

Background Context

Osteoporosis adversely affects disc degeneration cascades, and prophylactic alendronate (ALN) helps delay intervertebral disc degeneration (IDD) in ovariectomized (OVX) rats. However, there remains no information regarding whether ALN affects IDD with bone loss.

阿仑膦酸钠对0VX大鼠体外培养的破骨细胞的作用

目的研究第三代双膦酸盐类药物阿仑膦酸钠（alendronate，固邦）对体外培养的破骨细胞的作用。方法建立骨质疏松大鼠模型，于0、2、4、8W进行体外骨髓破骨细胞样细胞（OLC）的培养，并进行阿仑膦酸钠干预，观察OLC数量和形态的变化。结果OVX组大鼠OLC数量高于C组和Sham组；在所有组中，阿仑膦酸钠均能使OLC显著减少（P〈0．01）。结论大鼠去卵巢后OLC形成增加；阿仑膦酸钠能显著抑制OVX大鼠体外培养的OLC的形成。     

Intermittent Parathyroid Hormone After Prolonged Alendronate Treatment Induces Substantial New Bone Formation and Increases Bone Tissue Heterogeneity in Ovariectomized Rats

Postmenopausal osteoporosis is often treated with bisphosphonates (eg, alendronate, [ALN]), but oversuppression of bone turnover by long‐term bisphosphonate treatment may decrease bone tissue heterogeneity. Thus, alternate treatment strategies after long‐term bisphosphonates are of great clinical interest. The objective of the current study was to determine the effect of intermittent parathyroid hormone (PTH) following 12 weeks of ALN (a bisphosphonate) treatment in 6‐month‐old, ovariectomized (OVX) rats on bone microarchitecture, bone remodeling dynamics, and bone mechanical properties at multiple length scales. By using in vivo μCT and 3D in vivo dynamic bone histomorphometry techniques, we demonstrated the efficacy of PTH following ALN therapy for stimulating new bone formation, and increasing trabecular thickness and bone volume fraction. In healthy bone, resorption and formation are coupled and balanced to sustain bone mass. OVX results in resorption outpacing formation, and subsequent bone loss and reduction in bone tissue modulus and tissue heterogeneity. We showed that ALN treatment effectively reduced bone resorption activity and regained the balance with bone formation, preventing additional bone loss. However, ALN treatment also resulted in significant reductions in the heterogeneity of bone tissue mineral density and tissue modulus. On the other hand, PTH treatment was able to shift the bone remodeling balance in favor of formation, with or without a prior treatment with ALN. Moreover, by altering the tissue mineralization, PTH alleviated the reduction in heterogeneity of tissue material properties induced by prolonged ALN treatment. Furthermore, switching to PTH treatment from ALN improved bone's postyield mechanical properties at both the whole bone and apparent level compared to ALN alone. The current findings suggest that intermittent PTH treatment should be considered as a viable treatment option for patients with prior treatment with bisphosphonates. © 2017 American Society for Bone and Mineral Research.