Comparison of calcitonin, alendronate and fluorophosphate effects on ovariectomized rat bone

Triphasic calcium-based implant material resorbs and is replaced with bone in ovariectomized rats with or without bisphosphonate treatment

This study evaluated the effects of AGN1, a triphasic calcium-based material, and alendronate (A) on distal femoral defect bone repair in ovariectomized (OVX) rats. Of 106 rats, 92 were OVX'ed at 12 weeks old and underwent a 12-week induction period. Animals were randomized into five groups: OVX Control, OVX Alendronate Control, Normal Control, OVX Implantation, OVX Alendronate + Implantation. OVX Alendronate Control and OVX Alendronate + Implantation groups received alendronate injection twice weekly (0.015 mg/kg) from 6 weeks until sacrifice. Twelve weeks after OVX, 2.5 mm diameter by 4.0 mm long cylindrical, bilateral distal femoral defects were created in experimental animals. One defect was left empty, and one filled with AGN1. Dual-energy X-ray absorptiometry, microcomputed tomography, and histomorphometry were performed 0-, 6-, 12-, and 18-week postdefect/implantation surgery (N = 6-8/group). Results showed OVX induced significant and progressive bone loss which alendronate prevented. Histomorphometry demonstrated rapid AGN1 resorption: AGN1 resorbed from 95.1 ± 0.7% filling of the implant site (week 0) to 1.3 ± 1.0% (18 weeks) with no significant alendronate effect (1.6 ± 1.1%, 18 weeks). Bone formation in empty defects consisted primarily of cortical wall healing, whereas AGN1 implants demonstrated cortical wall healing with new trabecular bone filling the subcortical space. Alendronate dramatically increased bone formation in empty and AGN1 defects. We conclude AGN1 is resorbed and replaced by new cortical and trabecular bone in this OVX model, and alendronate did not compromise these effects.

Early effects of ovariectomy on bone microstructure, bone turnover markers and mechanical properties in rats

Background

Fragility fracture is one of the most serious consequences of female aging, which can increase the risk of death. Therefore, paying attention to the pathogenesis of postmenopausal osteoporosis (PMOP) is very important for elderly women.

Methods and materials

Forty 12-week-old female rats were divided into two groups including the ovariectomy (OVX) group and the control group. Four rats in each group were selected at 1, 4, 8, 12 and 16 weeks after operation. Vertebral bones and femurs were dissected completely for micro-Computed Tomography (micro-CT) scanning, biological modulus detection and histomorphological observation.

Results

In OVX group, bone volume/total volume (BV/TV), bone trabecular connection density (Conn.D) and trabecular bone number (Tb.N) decreased significantly with time (P < 0.05). The elastic modulus of femur in OVX group was lower than that in control group, but there was no significant difference between them (P > 0.05). Over time, the tartrate resistant acid phosphatase (TRAP), osteocalcin (BGP), type I procollagen amino terminal propeptide (PINP) and type I collagen carboxy terminal peptide (CTX-I) in OVX group increased significantly (P < 0.05). The micrographs of the OVX group showed sparse loss of the trabecular interconnectivity and widening intertrabecular spaces with time.

Conclusion

The bone loss patterns of vertebral body and femur were different in the early stage of estrogen deficiency. The bone turnover rate of OVX rats increased, however the changes of biomechanical properties weren’t obvious.

Recent development of drugs for osteoporosis and anti-cancer agents: a patent analysis

Osteoporosis and cancer are becoming a major public health problem. Some studies have shown that osteoporosis drugs may have anti-cancer effects. To better understand the relationship between drugs for osteoporosis and antineoplastic agents, and to better demonstrate recent developments for patents concerning drugs for osteoporosis, we conducted an analysis of US patents. The results indicated that there was a good correlation between agents for osteoporosis and antineoplastic agents, which indicated that numerous anti-osteoporosis agents displayed antineoplastic activities. Our study was the first one to provide new evidence, through comprehensive analysis, for a correlation between anti-osteoporosis agents and anticancer agents. The present study may open new avenues for developing anticancer drugs and expanding the application role of anti-osteoporosis agents.

The effect of alendronate sodium on trabecular bone structure in an osteoporotic rat model

Objectives

TObjectives: This study aims to investigate the effect of alendronate sodium on trabecular bone structure in an osteoporotic rat model.

Materials and methods

Between May 2006 and July 2006, 60 female Wistar Albino rats aged three months were randomly allocated to three groups: sham operated receiving no treatment (Shm); ovariectomized-alendronate receiving 1 mg/kg/day alendronate sodium (Ovx-A), and ovariectomized-vehicle receiving 1 mL/kg/day physiological saline (Ovx-PS). Both Ovx groups received treatment through gastric gavage for 56 days.

Results

Densitometric measurements showed that bone mineral density decreased in the Ovx-PS and increased in Ovx-A groups (p<0.05). Biomechanical measurements showed a decrease in the breaking force in the Ovx-PS group and an increase in the Ovx-A group (p<0.05). Histomorphometric measurements showed that the Shm group had normal trabecular structure, while the Ovx-PS group had a less well- formed trabecular structure with a loss in the trabecular number and thickness and a corresponding increase in the trabecular spacing (p<0.05). In the Ovx-A group, there was an improvement in the trabecular structure with an increase in the trabecular number and thickness and a loss in the trabecular space (p<0.05).

Conclusion

Our study results suggest that alendronate sodium is a valuable treatment agent for osteoporosis in postmenopausal women.

Study on in vitro release and cell response to alendronate sodium-loaded ultrahigh molecular weight polyethylene loaded with alendronate sodium wear particles to treat the particles-induced osteolysis

The aim of this study is to investigate in vitro release and cell response to wear particles of ultrahigh molecular weight polyethylene loaded with alendronate sodium (UHMWPE-ALN), a potent bone resorption inhibitor. Wear particles of UHMWPE-ALN with different ALN contents (0.5 wt % or 1.0 wt %) and size ranges (<45 μm or 45-75 μm) were cocultured with macrophages (RAW264.7) and osteoblasts (MC3T3-E1), respectively. The in vitro ALN release was divided into three stages: an initial burst release, subsequent rapid release, and final slow release. The particle size and ALN content of UHMWPE-ALN wear particles affected the in vitro release mainly during initial burst and rapid release. Compared with the control cells, UHMWPE-ALN wear particles stimulated a significant elevation of tumor necrosis factor-alpha (TNF-α) release from macrophages but had no obvious effect on interleukin-6 release. However, this stimulation of TNF-α release could be reduced by ALN released from UHMWPE-ALN wear particles. The wear particle size had stronger effect of on the macrophages compared with the ALN concentration. After coculture with UHMWPE-ALN wear particles, osteoblast proliferation and alkaline phosphatase activities increased moderately with the increase in particle sizes and ALN concentrations. These results suggest that incorporation of ALN in UHMWPE-ALN may be an effective approach to prevent or reduce particles-induced osteolysis.

Ultra-short echo-time MRI detects changes in bone mineralization and water content in OVX rat bone in response to alendronate treatment

In this work we hypothesize that bisphosphonate treatment following ovariectomy manifests in increased phosphorus and decreased water concentration, both quantifiable nondestructively with ultra-short echo-time (UTE) (31)P and (1)H-MRI techniques. We evaluated this hypothesis in ovariectomized (OVX) rats undergoing treatment with two regimens of alendronate. Sixty female four-month-old rats were divided into four groups of 15 animals each: ovariectomized (OVX), OVX treatment groups ALN1 and ALN2, receiving 5 microg/kg/day and 25 microg/kg/day of alendronate, and a sham-operated group (NO) serving as control. Treatment, starting 1 week post-surgery, lasted for 50 days at which time animals were sacrificed. Whole bones from the left and right femora were extracted from all the animals. (31)P and (1)H water concentration were measured by UTE MRI at 162 and 400 MHz in the femoral shaft and the results compared with other measures of mineral and matrix properties obtained by (31)P solution NMR, CT density, ash weight, and water measured by dehydration. Mechanical parameters (elastic modulus, EM, and ultimate strength, US) were obtained by three-point bending. The following quantities were lower in OVX relative to NO: phosphorus concentration measured by (31)P-MRI (-8%; 11.4+/-0.9 vs. 12.4+/-0.8%, p<0.005), (31)P-NMR (-4%; 12.8+/-0.4 vs. 13.3+/-0.8 %, p<0.05) and micro-CT density (-2.5%; 1316+/-34 vs. 1349+/-32 mg/cm(3), p=0.005). In contrast, water concentration by (1)H-MRI was elevated in OVX relative to NO (+6%; 15.5+/-1.7 vs. 14.6+/-1.4 %, p<0.05). Alendronate treatment increased phosphorus concentration and decreased water concentration in a dose-dependent manner, the higher dose yielding significant changes relative to values found in OVX animals: (31)P-MRI (+14%; p<0.0001), (31)P-NMR (+9%; p<0.0001), ash content (+1.5%; p<0.005), micro-CT mineralization density (+2.8%; p<0.05), and (1)H-MRI, (-19%, p<0.0001). The higher dose raised phosphorus concentration above and water concentration below NO levels: (31)P-MRI (+6%; p<0.05), (31)P-NMR (+5%; p=0.01), ash content (+1.5%; p=0.005), (1)H-MRI (-14%; p<0.0001), and drying water (-10%; p<0.0005). Finally, the group means of phosphorus concentration were positively correlated with EM and US (R(2)> or =0.98, p<0.001 to p<0.05) even though the pooled data from individual animals were not. The results highlight the implications of estrogen depletion and bisphosphonate treatment on mineral composition and mechanical properties and the potential of solid-state MR imaging to detect these changes in situ in an animal model of rat ovariectomy.

Determination of rat vertebral bone compressive fatigue properties in untreated intact rats and zoledronic-acid-treated, ovariectomized rats

SUMMARY

Compressive fatigue properties of whole vertebrae, which may be clinically relevant for osteoporotic vertebral fractures, were determined in untreated, intact rats and zoledronic-acid-treated, ovariectomized rats. Typical fatigue behavior was found and was similar to that seen in other species. Fatigue properties were comparable between both groups.

INTRODUCTION

Osteoporosis is often treated with bisphosphonates, which reduce fracture risk. Effects of bisphosphonates on fatigue strength, which may be clinically relevant for vertebral fractures, are unknown. We determined vertebral, compressive fatigue properties in normal and zoledronic acid (ZOL)-treated, OVX rats.

METHODS

Thirty-five-week old Wistar rats were divided into SHAM-OVX (n = 7) and OVX with ZOL treatment (n = 5; single injection, 20 microg/kg b.w. s.c.). After 16 weeks, vertebral trabecular microarchitecture and cortical thickness were determined using micro-CT. Vertebrae were cyclically compressed in load-control at 2 Hz starting at 0.75% apparent strain. A line parallel to the apparent strain curve was drawn at 0.5% higher offset, after which the intersection was defined as the time to failure and the apparent strain at failure. Data were compared using Student's t test.

RESULTS

Morphology and fatigue properties were the same in both groups. Samples failed between 10 min and 15 h. Force-displacement curves displayed typical fatigue behavior. Displacement increased over time due to mostly creep and to decreasing secant stiffness.

CONCLUSIONS

We established a technique to determine compressive fatigue properties in the rat vertebral body. Our initial results indicate that ZOL-treated OVX rats have similar vertebral fatigue properties as SHAM-OVX controls.

Calcitonin directly attenuates collagen type II degradation by inhibition of matrix metalloproteinase expression and activity in articular chondrocytes

OBJECTIVE

Calcitonin was recently reported to counter progression of cartilage degradation in an experimental model of osteoarthritis, and the effects were primarily suggested to be mediated by inhibition of subchondral bone resorption. We investigated direct effects of calcitonin on chondrocytes by assessing expression of the receptor and pharmacological effects on collagen type II degradation under ex vivo and in vivo conditions.

METHODS

Localization of the calcitonin receptor on articular chondrocytes was investigated by immunohistochemistry, and the expression by reverse transcriptase polymerase chain reaction (RT-PCR). In bovine articular cartilage explants, cartilage degradation was investigated by release of C-terminal telopeptides of collagen type II (CTX-II), induced by tumor necrosis factor-alpha (TNF-alpha) [20 ng/ml] and oncostatin M (OSM) [10 ng/ml], with salmon calcitonin [0.0001-1 microM]. In vivo, cartilage degradation was investigated in ovariectomized (OVX) rats administered with oral calcitonin [2 mg/kg calcitonin] for 9 weeks.

RESULTS

The calcitonin receptor was identified in articular chondrocytes by immunohistochemistry and RT-PCR. Calcitonin concentration-dependently increased cAMP levels in isolated chondrocytes. Explants cultured with TNF-alpha and OSM showed a 100-fold increase in CTX-II release compared to vehicle-treated controls (P<0.001). The degradation of type II collagen in these explants was concentration-dependently inhibited by calcitonin, 65% protection at 10 nM calcitonin (P<0.01). TNF-alpha and OSM induced a pronounced increase in matrix metalloproteinase (MMP) activity, which was strongly inhibited by calcitonin. In vivo, administration of salmon calcitonin to OVX rats resulted in significant (P<0.001) decrease in CTX-II levels.

CONCLUSION

These results are the first evidence of calcitonin receptor expression on articular chondrocytes and that the chondroprotective effects of calcitonin might involve the inhibition of MMP expression.

Comparative Effects of Alendronate and Alfacalcidol on Cancellous and Cortical Bone Mass and Bone Mechanical Properties in Ovariectomized Rats

The purpose of the present study was to compare the effects of alendronate and alfacalcidol on cancellous and cortical bone mass and bone mechanical properties in ovariectomized rats. Twenty-six female Sprague-Dawley rats, 7 months of age, were randomized by the stratified weight method into four groups: the sham-operated control (Sham) group and the three ovariectomy (OVX) groups, namely, OVX + vehicle, OVX + alendronate (2.5 mg/kg, p.o., daily), and OVX + alfacalcidol (0.5 mug/kg, p.o., daily). At the end of the 8-week experimental period, bone histomorphometric analyses of cancellous bone at the proximal tibial metaphysis and cortical bone at the tibial diaphysis were performed, and the mechanical properties of the femoral distal metaphysis and femoral diaphysis were evaluated. OVX decreased cancellous bone volume per total tissue volume (BV/TV), and the maximum load of the femoral distal metaphysis, as a result of increases in serum osteocalcin (OC) levels, and also the number of osteoclasts (N.Oc), osteoclast surface (OcS) and bone formation rate (BFR) per bone surface (BS), and BFR/BV, without any effect on cortical area (Ct Ar), or maximum load of the femoral diaphysis. Alendronate prevented this decrease in cancellous BV/TV by suppressing increases in N.Oc/BS, OcS/BS, BFR/BS, and BFR/BV, without any apparent effect on Ct Ar, or maximum load of the femoral distal metaphysis and femoral diaphysis. On the other hand, alfacalcidol increased cancellous BV/TV, Ct Ar, and the maximum load of the femoral distal metaphysis and femoral diaphysis, by mildly decreasing trabecular BFR/BV, maintaining trabecular mineral apposition rate and osteoblast surface per BS, increasing periosteal and endocortical BFR/BS, and preventing an increase in endocortical eroded surface per BS. The present study clearly showed the differential skeletal effects of alendronate and alfacalcidol in ovariectomized rats. Alendronate prevented OVX-induced cancellous bone loss by suppressing bone turnover, while alfacalcidol improved cancellous and cortical bone mass and bone strength by suppressing bone resorption and maintaining or even increasing bone formation.

Alendronate inhibits bone resorption at the bone-screw interface

In the current study, we investigated whether the systemic administration of alendronate, a third-generation bisphosphonate, suppressed the loosening of screws at the bone-screw interface. We systemically administered alendronate to rats fitted with external fixators. External fixators with two half pins were applied to the right femurs of rats, and alendronate was administrated once a week during a 5-week postoperative period. Radiographic, histologic, and immunohistochemical findings subsequently were analyzed. Treatment with alendronate reduced the width of the fibrous loosening membrane and the number of osteoclasts at the bone-screw interface. These findings indicate that systemic treatment with alendronate exerts an inhibitory effect on local bone resorption at the bone-screw interface.